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Sample records for assinaturas temporais ndvi

  1. Séries temporais de NDVI do sensor SPOT Vegetation e algoritmo SAM aplicados ao mapeamento de cana‑de‑açúcar

    Directory of Open Access Journals (Sweden)

    Luiz Eduardo Vicente

    2012-09-01

    Full Text Available O objetivo deste trabalho foi avaliar o mapeamento de área de cana‑de‑açúcar por meio de série temporal, de seis anos de dados do índice de vegetação por diferença normalizada (NDVI, oriundos do sensor Vegetation, a bordo do satélite "système pour l'observation de la Terre" (SPOT. Três classes de cobertura do solo (cana‑de‑açúcar, pasto e floresta, do Estado de São Paulo, foram selecionadas como assinaturas espectro‑temporais de referência, que serviram como membros extremos ("endmembers" para classificação com o algoritmo "spectral angle mapper" (SAM. A partir desta classificação, o mapeamento da área de cana‑de‑açúcar foi realizado com uso de limiares na imagem-regra do SAM, gerados a partir dos valores dos espectros de referência. Os resultados mostram que o algoritmo SAM pode ser aplicado a séries de dados multitemporais de resolução moderada, o que permite eficiente mapeamento de alvo agrícola em escala mesorregional. Dados oficiais de áreas de cana‑de‑açúcar, para as microrregiões paulistas, apresentam boa correlação (r² = 0,8 com os dados obtidos pelo método avaliado. A aplicação do algoritmo SAM mostrou ser útil em análises temporais. As séries temporais de NDVI do sensor SPOT Vegetation podem ser utilizadas para mapeamento da área de cana‑de‑açúcar em baixa resolução.

  2. Perfis temporais NDVI MODIS, na cana-soca, de maturação tardia NDVI MODIS temporal profiles, in sugarcane, late maturation

    OpenAIRE

    Fernando L. P. Ramme; Rubens A. C. Lamparelli; Jansle V. Rocha

    2010-01-01

    Este artigo descreve o desenvolvimento de um banco de dados relacional e de uma ferramenta para a visualização de perfis temporais do NDVI MODIS, a partir dos dados do produto MOD09Q1, referente ao fator de refletância bidirecional de superfície relativa ao comprimento de onda do vermelho e do infravermelho-próximo, composição temporal em mosaicos de 8 dias, e a banda de controle de qualidade, dos talhões de cana-de-açúcar no Estado de São Paulo, para analisar a maturação da cana-soca Tardia....

  3. Inferências sobre o calendário agrícola a partir de perfis temporais de NDVI/MODIS

    Directory of Open Access Journals (Sweden)

    Denise Cybis Fontana

    2015-01-01

    Full Text Available Um dos maiores desafios para a modelagem de rendimentos de grãos, no contexto das estimativas de safras feitas de forma operacional para grandes áreas, está relacionado à identificação no tempo dos períodos em que as culturas anuais apresentam maior suscetibilidade a estresses ambientais. Para a cultura da soja, cultivada no período de primavera-verão no sul do Brasil, o principal fator de risco é a ocorrência de estresse hídrico no florescimento e enchimento de grãos. Esses subperíodos ocorrem em períodos distintos ao longo da região de produção como consequência de práticas de manejo diferenciadas dos produtores. Este trabalho teve como objetivo relacionar o calendário agrícola da cultura da soja a perfis temporais do índice de vegetação por diferença normalizada (NDVI/MODIS, com intuito de apresentar/validar uma tecnologia de baixo custo e adequada acurácia para fins de monitoramento e previsão de safras. Para tanto, foram analisados os dados de calendário agrícola (subperíodos de floração, enchimento de grãos e maturação da cultura da soja em regionais da EMATER (RS e imagens NDVI do sensor MODIS. Os resultados mostraram que os perfis temporais de NDVI permitem acompanhar a evolução temporal da biomassa da cultura da soja e determinar a ocorrência dos subperíodos do ciclo. As diferenças no valor do NDVI entre safras, regionais e subperíodos do ciclo da cultura demonstram a sensibilidade deste índice em detectar as respostas das plantas de soja às condições ambientais. Como consequência dos dados de NDVI serem gerados a partir das imagens MODIS, é possível a espacialização da informação acerca dos subperíodos para todas as safras e em todo o Estado, o que permite maior detalhamento temporal e espacial comparativamente à atual disponibilidade dos dados.

  4. NDVI

    Data.gov (United States)

    U.S. Environmental Protection Agency — Normalized Difference Vegetation Index (NDVI) This dataset is associated with the following publication: Shao, Y., R. Lunetta , B. Wheeler, J. Iiames , and J....

  5. Votação online para iniciativas populares na Califórnia: coleta eletrônica de assinaturas

    Directory of Open Access Journals (Sweden)

    Walter S. Baer

    2012-05-01

    Full Text Available Este artigo discute o processo de coleta online de assinaturas para proposições legislativas, tendo por ponto de partida o processo vigente para iniciativa popular na Califórnia. Nele, descreve-se como a assinatura online de petições de iniciativa popular funcionaria, bem assim como questões de segurança e outras objeções à coleta de assinaturas via internet poderiam ser abordadas e, finalmente, os prós e contras de se aplicar este método de coleta de assinaturas às iniciativas populares.

  6. Redes neurais temporais aplicadas ao monitoramento de barragens

    OpenAIRE

    Janaina Veiga Carvalho; Celso Romanel

    2007-01-01

    O monitoramento do desempenho de barragem é realizado pela revisão e análise de dados coletados pela instrumentação que medem indicadores críticos do comportamento da barragem. Neste trabalho emprega-se a técnica de redes neurais temporais (RNT) para análise, modelagem e previsão dos valores de vazão na barragem Funil, do sistema Furnas Centrais Elétricas, a partir dos dados de instrumentações disponíveis no período compreendido entre 02/09/1985 e 25/02/2002. As redes neurais temporais empreg...

  7. Desenvolvimento das culturas de cereais de inverno no Rio Grande do Sul por meio de perfis temporais do índice de vegetação por diferença normalizada Winter cereal crop development in Rio Grande do Sul, Brazil, throughout the temporal profiles of normalized difference vegetation index

    Directory of Open Access Journals (Sweden)

    Amanda Heemann Junges

    2009-08-01

    Full Text Available Os objetivos deste trabalho foram elaborar perfis temporais de NDVI/MODIS, mediante a construção de máscaras de cultivo, verificando as variações interanuais dos perfis associadas à variação do rendimento de grãos de trigo no Rio Grande do Sul. Foram utilizadas imagens MOD13 dos meses de maio a novembro para os anos 2000 a 2006, pontos de controle na superfície (coletados em lavouras de trigo, aveia e cevada e dados oficiais de rendimento médio de grãos de trigo (IBGE e Cotrijal. Os resultados mostraram que, por meio da metodologia de construção de máscaras de cultivo, é possível gerar perfis temporais de NDVI que permitem monitorar o desenvolvimento das lavouras de cereais de inverno e que podem ser empregados no estudo das variações interanuais de rendimento de grãos de trigo. Os maiores rendimentos de grãos estão relacionados à manutenção de altos valores de NDVI (acima de 0,7 por um período maior de tempo. Porém, a metodologia não permitiu a distinção de lavouras de trigo, aveia e cevada, sendo necessários estudos subseqüentes.This research aimed to elaborate temporal NDVI profiles through the crop masks building, and find the interannual variations of profiles associated with variation of wheat grain yield in Rio Grande do Sul, Brazil. The data set were composed by MODIS13 images (NDVI product from May to November, 2000 to 2006, ground control points (collected in wheat, oat and barley fields and official wheat grain yield (IBGE and Cotrijal. The results showed that using the proposed methodology for crop masking it is possible to generate consistent NDVI temporal profiles, which allows monitoring the development of winter cereal crops and can be used to evaluate the interannual variations of grain yield. The profiles showed that wheat grain yield was related to the maintenance of high NDVI values (above 0.7 for a larger period of time. However, the methodology did not allow the wheat, oats and barley

  8. Modelling critical NDVI curves in perennial ryegrass

    DEFF Research Database (Denmark)

    Gislum, R; Boelt, B

    2010-01-01

      The use of optical sensors to measure canopy reflectance and calculate crop index as e.g. normalized difference vegetation index (NDVI) is widely used in agricultural crops, but has so far not been implemented in herbage seed production. The present study has the purpose to develop a critical N...

  9. Cereal Production Ratio and NDVI in Spain

    Science.gov (United States)

    Saa-Requejo, Antonio; Recuero, Laura; Palacios, Alicia; Díaz-Ambrona, Carlos G. H.; Tarquis, Ana M.

    2014-05-01

    Droughts are long-term phenomena affecting large regions causing significant damages both in human lives and economic losses. The use of remote sensing has proved to be very important in monitoring the growth of agricultural crops and trying to asses weather impact on crop loss. Several indices has been developed based in remote sensing data being one of them the normalized difference vegetation index (NDVI). In this study we have focus to know the correlation between NDVI data and the looses of rain fed cereal in the Spanish area where this crop is majority. For this propose data from drought damage in cereal come from the pool of agricultural insurance in Spain (AGROSEGURO) including 2007/2008 to 2011/2012 (five agricultural campaigns). This data is given as a ratio between drought party claims against the insured value of production aggregated at the agrarian region level. Medium resolution (500x500 m2) MODIS images were used during the same campaigns to estimate the eight-day composites NDVI at these locations. The NDVI values are accumulated following the normal cycle of the cereal taking in account the sowing date at different sites. At the same time, CORINE Land Cover (2006) was used to classify the pixels belonging to rain fed cereal use including a set of conditions such as pixels showing dry during summer, area in which there has been no change of use. Fallow presence is studied with particular attention as it imposes an inter annual variation between crop and bare soil and causes decreases in greenness in a pixel and mix both situations. This is more complex in the situation in which the avoid fallow and a continuous monoculture is performed. The results shown that around 40% of the area is subject to the regime of fallow while 60% have growing every year. In addition, another variation is detected if the year is humid (decrease of fallow) or dry (increase of fallow). The level of correlation between the drought damage ratios and cumulative NDVI for the

  10. Repercussões temporais da ligadura do ducto biliar principal em ratos Wistar

    Directory of Open Access Journals (Sweden)

    Maia Eugenio Lincoln Campos

    2003-01-01

    Full Text Available OBJETIVO: Objetivou-se investigar os efeitos temporais da ligadura do ducto biliar principal, em ratos Wistar. MÉTODOS: Utilizaram-se 48 ratos machos distribuídos em 2 grupos e redistribuídos em 4 subgrupos (n=06, identificados pelo tempo estipulado para a coleta das amostras (12, 24, 48 e 168 horas. Após laparotomia, os animais foram submetidos à dissecção e passagem de dois fios circundando o ducto biliar principal, sem ligadura (Grupo 1 e com ligadura (Grupo 2. RESULTADOS: As concentrações das bilirrubinas séricas (total, direte e indireta quando comparadas ao repectivo grupo controle, aumentaram (p<0,05 nos animais do grupo 2, nos tempos 24, 48 e 168 horas. As concentrações de proteína C reativa e fosfatase alcalina aumentaram (p<0,05 no grupo 2 no tempo 24 horas e nos tempos 24 e 48 horas, respectivamente. Concentrações de albumina e gamaglutamil transferase, não apresentaram diferenças significantes nos dois grupos. Foram observadas, no exame histopatológico, hiperplasia ductal, pericolangite e colangite no grupo 2 e pericolangite no grupo 1. CONCLUSÕES: A ligadura do ducto biliar principal induz aumento das concentrações séricas de bilirrubinas, proteína C reativa e fosfatase alcalina. Hiperplasia ductal, pericolangite e colangite são as principais alterações histológicas encontradas nos fígados dos ratos submetidos à ligadura do ducto biliar principal.

  11. Temporal variations of NDVI and correlations between NDVI and hydro-climatological variables at Lake Baiyangdian, China

    Science.gov (United States)

    Wang, Fei; Wang, Xuan; Zhao, Ying; Yang, Zhifeng

    2014-09-01

    In this paper, correlations between vegetation dynamics (represented by the normalized difference vegetation index (NDVI)) and hydro-climatological factors were systematically studied in Lake Baiyangdian during the period from April 1998 to July 2008. Six hydro-climatological variables including lake volume, water level, air temperature, precipitation, evaporation, and sunshine duration were used, as well as extracted NDVI series data representing vegetation dynamics. Mann-Kendall tests were used to detect trends in NDVI and hydro-climatological variation, and a Bayesian information criterion method was used to detect their abrupt changes. A redundancy analysis (RDA) was used to determine the major hydro-climatological factors contributing to NDVI variation at monthly, seasonal, and yearly scales. The results were as follows: (1) the trend analysis revealed that only sunshine duration significantly increased over the study period, with an inter-annual increase of 3.6 h/year ( p RDA showed that evaporation and temperature were highly correlated with monthly changes in NDVI. At larger time scales, however, water level and lake volume gradually became more important than evaporation and precipitation in terms of their influence on NDVI. These results suggest that water availability is the most important factor in vegetation restoration. In this paper, we recommend a practical strategy for lake ecosystem restoration that takes into account changes in NDVI.

  12. Monitoring Forest Fire with MODIS-NDVI Images in Beijing

    Institute of Scientific and Technical Information of China (English)

    TIAN Xiaorui; SHU Lifu; WANG Mingyu; ZHAO Fengjun

    2006-01-01

    Fuel moisture monitoring is an important component of fire danger rating system in fire management This paper describes the application of NDVI images in monitoring potential fire danger and analyses the relationship between MODIS-NDVI and fire weather index.The series of weather data in Beijing are used in this analysis including fire seasons in spring during 2004 to 2005.Canadian Fire Weather Index (FWI) is selected in this study, because it can properly estimate moisture conditions of live fuel.Fine fuel moisture, drought code and FWI values are generated by using the squared inverse distance algorithm.Strong correlations have previously been observed between FWI variables and NDVI data.The MODIS-NDVI images can be used in fire management as component related with live fuel moisture and fire danger.

  13. NDVI Short-Term Forecasting Using Recurrent Neural Networks

    OpenAIRE

    Stepčenko, A; Čižovs, J

    2015-01-01

    In this paper predictions of the Normalized Difference Vegetation Index (NDVI) data recorded by satellites over Ventspils Municipality in Courland, Latvia are discussed. NDVI is an important variable for vegetation forecasting and management of various problems, such as climate change monitoring, energy usage monitoring, managing the consumption of natural resources, agricultural productivity monitoring, drought monitoring and forest fire detection. Artificial Neural Networks (ANN) are comput...

  14. Correlation between NDVI and the annual groundnut yield in Senegal

    Science.gov (United States)

    Martin, Samuel; Borondo, Javier; Morales, Alfredo; Losada, Juan Carlos; Tarquis, Ana M.; Benito, Rosa M.

    2016-04-01

    A key strategy to assert and minimize risk in agriculture is to gather information about the factors that may affect the production. That is why remote sensing measurements have become a fundamental tool in this area. Between all the existing measurements, the Normalized Difference Vegetation Index (NDVI) is one of the most useful. The NDVI, which is computed using satellite images, takes into account the physicochemical mechanism of the photosynthesis in order to quantify the photosynthetic activity of a an area. A natural question that arises from the risk and hazard management point of view is if this index can help us estimate or even forecast the yield of a given harvest. Intuitively, this should be possible if a correlation between NDVI and yield is found. We have focused our study in the country of Senegal, where more than 70% of the work force is employed in the agricultural sector. Since Senegal is also one of the most important peanut oil producer and exporter, the crop we have chosen for this research is the peanut. The economic relevance of this product guarantees that a significant fraction of the soil will be used for this crop. We have worked with NDVI data computed from satellite images taken with the MODIS instrument of the Terra satellite launched by NASA on 1999. In order to explore the correlations with agricultural yield, we have also retrieved production data from the Food and Agriculture Organization (FAO) of the United Nations. The results we have obtained suggest that a linear correlation between NDVI and yield do exist; moreover, this correlation can be enhanced if, instead of yearly averages of NDVI, the NDVI corresponding to a smaller time period -which lies within the growing season - is taken. Acknowledgements First author acknowledges the Research Grant obtained from CEIGRAM in 2015

  15. Estimating agricultural yield gap in Africa using MODIS NDVI dataset

    Science.gov (United States)

    Luan, Y.; Zhu, W.; Luo, X.; Liu, J.; Cui, X.

    2013-12-01

    Global agriculture has undergone a period of rapid intensification characterized as 'Green Revolution', except for Africa, which is the region most affected by unreliable food access and undernourishment. Increasing crop production will be one of the most challenges and most effectual way to mitigate food insecurity there, as Africa's agricultural yield is on a much lower level comparing to global average. In this study we characterize cropland vegetation phenology in Africa based on MODIS NDVI time series between 2000 and 2012. Cumulated NDVI is a proxy for net primary productivity and used as an indicator for evaluating the potential yield gap in Africa. It is achieved via translating the gap between optimum attainable productivity level in each classification of cropping systems and actual productivity level by the relationship of cumulated NDVI and cereal-equivalent production. The results show most of cropland area in Africa have decreasing trend in cumulated NDVI, distributing in the Nile Delta, Eastern Africa and central of semi-arid to arid savanna area, except significant positive cumulated NDVI trends are mainly found between Senegal and Benin. Using cumulated NDVI and statistics of cereal equivalent production, we find remarkable potential yield gap at the Horn of East Africa (especially in Somalia), Northern Africa (Morocco, Algeria and Tunisia). Meanwhile, countries locating at the savanna area near Sahel desert and South Africa also show significant potential, though they already have a relatively high level of productivity. Our results can help provide policy recommendation for local government or NGO to tackle food security problems by identifying zones with high potential of yield improvement.

  16. METODOLOGIA PARA CARACTERIZAÇÃO DE ASSINATURA GEOQUÍMICA DE TRAJETOS DE ÁGUA EM ZONAS DE RECARGA DE INTERFLÚVIOS (Methodology for geochemical signature characterization of water paths in interfluves recharge zones)

    OpenAIRE

    MARTINS JUNIOR, Paulo Pereira; VASCONCELOS, Vitor Vieira; Scherrer, Luciano Rios; MORAIS, Maria Carolina de; SANTA CECÍLIA, Vinícius Coutinho; GOMES, Lawrence de Andrade Magalhães; NOVAES, Leandro Arb D`Abreu

    2013-01-01

    Apresenta-se uma metodologia para caracterização de assinaturas hidrogeoquímicas de partilha de aquífero entre bacias e de trajetos de água comuns em zonas de recarga de interflúvios. O método baseia-se na coleta e análise de características químicas de águas subterrâneas a partir de fontes. As Bacias de Paracatu, São Marcos, Alto Paranaíba e São Mateus foram investigadas. Palavras-chave: hidrogeoquímica; aqüíferos; recarga; Noroeste de Minas Gerais. ABSTRACT This a proposal of a m...

  17. Using NDVI to measure precipitation in semi-arid landscapes

    Science.gov (United States)

    Birtwhistle, Amy N.; Laituri, Melinda; Bledsoe, Brian; Friedman, Jonathan M.

    2016-01-01

    Measuring precipitation in semi-arid landscapes is important for understanding the processes related to rainfall and run-off; however, measuring precipitation accurately can often be challenging especially within remote regions where precipitation instruments are scarce. Typically, rain-gauges are sparsely distributed and research comparing rain-gauge and RADAR precipitation estimates reveal that RADAR data are often misleading, especially for monsoon season convective storms. This study investigates an alternative way to map the spatial and temporal variation of precipitation inputs along ephemeral stream channels using Normalized Difference Vegetation Index (NDVI) derived from Landsat Thematic Mapper imagery. NDVI values from 26 years of pre- and post-monsoon season Landsat imagery were derived across Yuma Proving Ground (YPG), a region covering 3,367 km2 of semiarid landscapes in southwestern Arizona, USA. The change in NDVI from a pre-to post-monsoon season image along ephemeral stream channels explained 73% of the variance in annual monsoonal precipitation totals from a nearby rain-gauge. In addition, large seasonal changes in NDVI along channels were useful in determining when and where flow events have occurred.

  18. The relationship between phytomass, NDVI and vegetation communities on Svalbard

    Science.gov (United States)

    Johansen, Bernt; Tømmervik, Hans

    2014-04-01

    Several studies have shown a close relationship between vegetation fertility and different vegetation indices extracted from satellite data. The vegetation fertility in Arctic is at overall scales highly related to temperature. At lower scales surface material, snow cover, hydrology and anthropogenic effects (geese, reindeer) are determinant in constituting the different vegetation communities. The extent and occurrence of different vegetation communities are expressed in vegetation maps. On Svalbard a vegetation map covering the entire archipelago has recently been developed. The map is differentiated into 18 map units showing large areas of non- and sparsely vegetated ground. The most favorable vegetation is seen as productive marshes and moss tundra communities in the lowland. Various mathematical combinations of spectral channels in satellite images have been applied as sensitive indicators of the presence and condition of green vegetation. Today the normalized difference vegetation index (NDVI) is mostly used to display this information. NDVI is an indicator of the density of chlorophyll in leaf tissue calculated from the red and near infrared bands: NDVI = (NIR - RED)/(NIR + RED). NDVI gives values between -1 and +1 where vegetated areas in general yield high positive values, while non-vegetated ground is found on the negative side.

  19. An Improved Method for Producing High Spatial-Resolution NDVI Time Series Datasets with Multi-Temporal MODIS NDVI Data and Landsat TM/ETM+ Images

    Directory of Open Access Journals (Sweden)

    Yuhan Rao

    2015-06-01

    Full Text Available Due to technical limitations, it is impossible to have high resolution in both spatial and temporal dimensions for current NDVI datasets. Therefore, several methods are developed to produce high resolution (spatial and temporal NDVI time-series datasets, which face some limitations including high computation loads and unreasonable assumptions. In this study, an unmixing-based method, NDVI Linear Mixing Growth Model (NDVI-LMGM, is proposed to achieve the goal of accurately and efficiently blending MODIS NDVI time-series data and multi-temporal Landsat TM/ETM+ images. This method firstly unmixes the NDVI temporal changes in MODIS time-series to different land cover types and then uses unmixed NDVI temporal changes to predict Landsat-like NDVI dataset. The test over a forest site shows high accuracy (average difference: −0.0070; average absolute difference: 0.0228; and average absolute relative difference: 4.02% and computation efficiency of NDVI-LMGM (31 seconds using a personal computer. Experiments over more complex landscape and long-term time-series demonstrated that NDVI-LMGM performs well in each stage of vegetation growing season and is robust in regions with contrasting spatial and spatial variations. Comparisons between NDVI-LMGM and current methods (i.e., Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM, Enhanced STARFM (ESTARFM and Weighted Linear Model (WLM show that NDVI-LMGM is more accurate and efficient than current methods. The proposed method will benefit land surface process research, which requires a dense NDVI time-series dataset with high spatial resolution.

  20. Differences between MODIS NDVI and AVHRR NDVI in monitoring grasslands change%MODIS NDVI和AVHRR NDVI对草原植被变化监测差异

    Institute of Scientific and Technical Information of China (English)

    陈燕丽; 龙步菊; 潘学标; 钟仕全; 莫伟华

    2011-01-01

    以草地作为研究载体,对比分析草原植被AVHRR NDVI和MODIS NDVI两种NDVI序列的年内、年际变化特征,讨论两种NDVI序列对降水量、平均气温和水汽压3种气候因子的响应差异,为合理选择NDVI序列对植被进行监测研究提供参考.结果表明:(1)两种NDVI序列所反映的草原植被年内变化趋势相似,但MODIS NDVI对各类草原的区分度优于AVHRR NDVI; (2)两种NDVI序列所反映的2000年—2003年草原植被年际变化差异明显.较之于MODISNDVI,AVHRR NDVI变化趋势分类图表现出更强的植被改善趋势,植被改善面积在AVHRR NDVI变化趋势分类图中占94.25%,在MODIS NDVI中为83.33%;两种NDVI变化趋势分类图反映的植被变化趋势吻合度为52.88%.(3)两种NDVI序列与水汽压、降水量相关性差异显著.MODlSNDVI与各站点平均气温的相关系数均大于GIMMS NDVI;而MODIS NDVI与水汽压的相关系数83%(10个站点)小于G1MMS NDVI,与降水量的相关系数67%(8个站点)小于GIMMSNDVI.%In this paper,with grassland of Xilingol as the research site,the average method,unary linear regression model,correlation analysis are used to compare the annual and interannual characteristics of NDVI series,including the MODIS NDVI and the AVHRR NDVI.The precipitation,mean temperature,vapor pressure are taken as climatic variables to compare the relationship between NDVI series and climatic factors over different types of grasslands.The objective is to provide references for reasonable use of NDVI series to monitor vegetation changes.The results show that,(1) Annual characteristics of the MODIS NDVI and the GIMMS NDVI are similar,yet the MODIS NDVI can distinguish each steppe better than that of the GIMMS NDVI.(2) Different interannual characteristics are observed between MODIS NDVI and GIMMS NDVI of grassland vegetation during 2000 to 2003.Compared with MODIS NDVI,vegetation increase trend is stronger in GIMMS NDVI change trend classification image,with a

  1. AÇÃO ANTRÓPICA SOBRE AS ESCALAS TEMPORAIS DOS FENÔMENOS GEOMORFOLÓGICOS

    Directory of Open Access Journals (Sweden)

    Archimedes Perez Filho

    2012-02-01

    Full Text Available Formas e processos da superfície terrestre possuem manifestação espacial e temporal. Com relação ao tempo, definimos no presente artigo pelo menos quatro escalas de importância na compreensão do objeto de estudo da geomorfologia, a saber: tempo da natureza, histórico do homem, presente e futuro. A verificação da reativação da rede de drenagem e intensificação de processos erosivos relacionados às alterações no nível de base local, devido à construção de represas de usinas hidrelétricas, bem como do fenômeno de desertificação antrópica, ocasionado pela remoção da cobertura vegetal natural em áreas de Neossolos Quartzarênicos são indicadores da capacidade do sistema antrópico de influenciar processos geomorfológicos, impondo-lhes ritmos diferentes, com consequente alteração de suas escalas temporais de ocorrência. Deste modo, comprova-se que processos e formas que se manifestariam na escala de tempo geológico, passam a ocorrer nas escalas do tempo histórico do homem e presente, evidenciando que as formas variadas, rápidas e agressivas com que o homem tem interferido na dinâmica natural da Terra resultam em processos geomorfológicos com gênese antrópica.

  2. Aspectos prosódicos temporais da leitura de escolares com dislexia do desenvolvimento Temporal prosodic aspects of reading in students with developmental dyslexia

    OpenAIRE

    Luciana Mendonça Alves; César Augusto da Conceição Reis; Ângela Maria Vieira Pinheiro; Simone Aparecida Capellini

    2009-01-01

    OBJETIVO: Analisar, do ponto de vista fonético, por meio de medidas acústicas e perceptivas, os aspectos prosódicos temporais presentes na leitura em voz alta de escolares com e sem dislexia, a fim de identificar diferenças de desempenho entre os dois tipos de leitores que possam apontar para características peculiares da dislexia. MÉTODOS: Gravação da leitura de um texto por 40 escolares (entre nove e 14 anos, cursando da 3ª à 5ª série), sendo 10 disléxicos (grupo clínico) e 30 escolares sem...

  3. UAV-based NDVI calculation over grassland: An alternative approach

    Science.gov (United States)

    Mejia-Aguilar, Abraham; Tomelleri, Enrico; Asam, Sarah; Zebisch, Marc

    2016-04-01

    The Normalised Difference Vegetation Index (NDVI) is one of the most widely used indicators for monitoring and assessing vegetation in remote sensing. The index relies on the reflectance difference between the near infrared (NIR) and red light and is thus able to track variations of structural, phenological, and biophysical parameters for seasonal and long-term monitoring. Conventionally, NDVI is inferred from space-borne spectroradiometers, such as MODIS, with moderate resolution up to 250 m ground resolution. In recent years, a new generation of miniaturized radiometers and integrated hyperspectral sensors with high resolution became available. Such small and light instruments are particularly adequate to be mounted on airborne unmanned aerial vehicles (UAV) used for monitoring services reaching ground sampling resolution in the order of centimetres. Nevertheless, such miniaturized radiometers and hyperspectral sensors are still very expensive and require high upfront capital costs. Therefore, we propose an alternative, mainly cheaper method to calculate NDVI using a camera constellation consisting of two conventional consumer-grade cameras: (i) a Ricoh GR modified camera that acquires the NIR spectrum by removing the internal infrared filter. A mounted optical filter additionally obstructs all wavelengths below 700 nm. (ii) A Ricoh GR in RGB configuration using two optical filters for blocking wavelengths below 600 nm as well as NIR and ultraviolet (UV) light. To assess the merit of the proposed method, we carry out two comparisons: First, reflectance maps generated by the consumer-grade camera constellation are compared to reflectance maps produced with a hyperspectral camera (Rikola). All imaging data and reflectance maps are processed using the PIX4D software. In the second test, the NDVI at specific points of interest (POI) generated by the consumer-grade camera constellation is compared to NDVI values obtained by ground spectral measurements using a

  4. Normalization of NDVI from Different Sensor System using MODIS Products as Reference

    International Nuclear Information System (INIS)

    Medium Resolution NDVI(Normalized Difference Vegetation Index) from different sensor systems such as Landsat, SPOT, ASTER, CBERS and HJ-1A/1B satellites provide detailed spatial information for studies of ecosystems, vegetation biophysics, and land cover. Limitation of sensor designs, cloud contamination, and sensor failure highlighted the need to normalize and integrate NDVI from multiple sensor system in order to create a consistent, long-term NDVI data set. In this paper, we used a reference-based method for NDVI normalization. And present an application of this approach which covert Landsat ETM+ NDVI calculated by digital number (NDVIDN) to NDVI calculated by surface reflectance (NDVISR) using MODIS products as reference, and different cluster was treated differently. Result shows that this approach can produce NDVI with highly agreement to NDVI calculated by surface reflectance from physical approaches based on 6S (Second Simulation of the satellite Signal in the Solar Spectrum). Although some variability exists, the cluster specified reference based approach shows considerable potential for NDVI normalization. Therefore, NDVI products in MODIS era from different sources can be combined for time-series analysis, biophysical parameter retrievals, and other downstream analysis

  5. Comparison of Different Ground-Based NDVI Measurement Methodologies to Evaluate Crop Biophysical Properties

    Directory of Open Access Journals (Sweden)

    Rossana Monica Ferrara

    2010-06-01

    Full Text Available The usage of vegetation indices such as the Normalized Difference Vegetation Index (NDVI calculated by means of remote sensing data is widely spread for describing vegetation status on large space scale. However, a big limitation of these indices is their inadequate time resolution for agricultural purposes. This limitation could be overcome by the ground-based vegetation indices that could provide an interesting tool for integrating satellite-based value. In this work, three techniques to calculate the ground-NDVI have been evaluated for sugar beet cultivated in South Italy in all its phenological phases: the NDVI1 based on hand made reflectance measurements, the NDVI2 calculated on automatically reflectance measurements and the broadband NDVIb based on Photosynthetically Active Radiation (PAR and global radiation measurements. The best performance was obtained by the NDVIb. Moreover, crop-microclimate-NDVI relations were investigated. In particular, the relationship between NDVI and the Leaf Area Index (LAI was found logarithmic with a saturation of NDVI at LAI around 1.5 m2 m-2. A clear relation was found between NDVI and crop coefficient Kc experimentally determined by the ratio between actual and reference measured or modelled evapotranspirations, while the relation between NDVI and crop actual evapotranspiration was very weak and not usable for practical purposes. Lastly, no relationship between the microclimate and the NDVI was found.

  6. The temporal and spatial relationship between NDVI and climatological parameters in Colorado

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper describes the spatial and temporal relationship between AVHRR/NDVI (Normalized Difference Vegetation Index) and climatological parameters (temperature and precipitation), which, in some sense, is influenced by topographical factors and land-cover types in Colorado. The correlation coefficients and partial correlation coefficients have been computed pixel by pixel over Colorado in order to analyze the relationship. The temporal variation and correlation of AVHRR/NDVI, temperature and precipitation were analyzed with a sampling method. The study reveals that there exists a close correspondence between monthly NDVI and temperature, which has strong impact from temperature on the changes of NDVI in Colorado. The spatial changes of NDVI are not influenced obviously by the precipitation since these two variables are different from each other in time series in Colorado. The study clearly revealed the spatial variation and its distribution patterns of relationship between NDVI and climatic parameters (temperature and precipitation) in Colorado.

  7. Dynamic LiDAR-NDVI classification of fluvial landscape units

    Science.gov (United States)

    Ramírez-Núñez, Carolina; Parrot, Jean-François

    2015-04-01

    The lower basin of the Coatzacoalcos River is a wide floodplain in which, during the wet season, local and major flooding are distinguished. Both types of floods, intermittent and regional, are important in terms of resources; the regional flood sediments enrich the soils of the plains and intermittent floods allow obtaining aquatic resources for subsistence during the heatwave. In the floodplain different abandoned meanders and intermittent streams are quickly colonized by aquatic vegetation. However, from the 1990s, the Coatzacoalcos River floodplain has important topographic changes due to mining, road and bridges construction; erosion and sedimentation requires continuous parcel boundaries along with the increasing demand of channel reparation, embankments, levees and bridges associated to tributaries. NDVI data, LiDAR point cloud and various types of flood simulations taking into account the DTM are used to classify the dynamic landscape units. These units are associated to floods in relation with water resources, agriculture and livestock. In the study area, the first returns of the point cloud allow extracting vegetation strata. The last returns correspond to the bare earth surface, especially in this area with few human settlements. The surface that is not covered by trees or by aquatic vegetation, correspond to crops, pastures and bare soils. The classification is obtained by using the NDVI index coupled with vegetation strata and water bodies. The result shows that 47.96% of the area does not present active vegetation and it includes 31.53% of bare soils. Concerning the active vegetation, pastures, bushes and trees represent respectively 25.59%, 11.14% and 13.25%. The remaining 1.25% is distributed between water bodies with aquatic vegetation, trees and shrubs. Dynamic landscape units' classification represents a tool for monitoring water resources in a fluvial plain. This approach can be also applied to forest management, environmental services and

  8. Analysis of the Relationship Between Climate and NDVI Variability at Global Scales

    Science.gov (United States)

    Zeng, Fan-Wei; Collatz, G. James; Pinzon, Jorge; Ivanoff, Alvaro

    2011-01-01

    interannual variability in modeled (CASA) C flux is in part caused by interannual variability in Normalized Difference Vegetation Index (NDVI) Fraction of Photosynthetically Active Radiation (FPAR). This study confirms a mechanism producing variability in modeled NPP: -- NDVI (FPAR) interannual variability is strongly driven by climate; -- The climate driven variability in NDVI (FPAR) can lead to much larger fluctuation in NPP vs. the NPP computed from FPAR climatology

  9. Relationships between tree-ring width index and NDVI of grassland in Delingha

    Institute of Scientific and Technical Information of China (English)

    HE Jicheng; SHAO Xuemei

    2006-01-01

    Using five well-replicated Qilian juniper (Sabina przewalskii Kom.) tree-ring width index series, monthly normalized difference vegetation index (NDVI) of grassland, and climatic data from 1982 to 2001, the relationships between tree-ring width index, NDVI of grassland, and climatic data were analyzed firstly. Then, the relationship between tree-ring width index and NDVI of grassland was explored. The results showed that: (1) Temperature and precipitation in June influenced tree-ring width index and NDVI of grassland deeply in Delingha. (2) There were significant relationships between five tree-ring width index series (DLH1-DLH5) and monthly NDVI of grassland from June to September, with the most significant relationship being between tree-ring width index series and NDVI of grassland in August. (3) The PC1 (the first principal component derived from DLH1-DLH5 series) exhibited good agreement with monthly NDVI of grassland in the grass growth season (from June to September) and the averaged NDVI in the growth season, which was attributed to their common responses to water-supply limit in Delingha. This study may allow an increase in studying the past dynamics of grassland in Delingha in that the variation of grassland NDVI during the last millennium has been reconstructed from PC1.

  10. Study on NDVI-Ts space by combining LAI and evapotranspiration

    Institute of Scientific and Technical Information of China (English)

    HAN; Lijuan; WANG; Pengxin; YANG; Hua; LIU; Shaomin; WANG; Jindi

    2006-01-01

    This paper focuses on interpreting the different spatial relationships between NDVI and Ts, a triangular or a trapezoid, and on analyzing transformation conditions, the physical and ecological meanings of the vegetation index-surface temperature space as well. Further, we use the Temperature-Vegetation Dryness Index (TVDI) to explain the existent meaning of a triangular space after NDVI reaches its saturated state by employing the relationships between NDVI, LAI and evapotranspiration.The specific relations between NDVI and Ts are useful for describing, validating and updating land surface models.

  11. STUDY ON THE INTERACTION BETWEEN NDVI PROFILE AND THE GROWING STATUS OF CROPS

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Daily and ten-day Normalized Difference Vegetation Index( NDVI) of crops were retrieved from meteorological satellite NOAA AVHRR images. The temporal variations of the NDVI were analyzed during the whole growing season, and thus the principle of the interaction between NDVI profile and the growing status of crops was discussed. As a case in point, the relationship between integral NDVI and winter wheat yield of Henan Province in 1999 had been analyzed. By putting integral NDVI values of 60 sample counties into the winter wheat yield-integral NDVI coordination, scattering map was plotted. It demonstrated that integral NDVI had a close relation with winter wheat yield. These relation could be described with linear, cubic polynomial, and exponential regression, and the cubic polynomial regression was the best way. In general, NDVI reflects growing status of green vegetation, so crop monitoring and crop yield estimation could be realized by using remote sensing technique on the basis of time serial NDVI data together with agriculture calendars.

  12. Spatiotemporal variability and predictability of Normalized Difference Vegetation Index (NDVI) in Alberta, Canada

    Science.gov (United States)

    Jiang, Rengui; Xie, Jiancang; He, Hailong; Kuo, Chun-Chao; Zhu, Jiwei; Yang, Mingxiang

    2016-09-01

    As one of the most popular vegetation indices to monitor terrestrial vegetation productivity, Normalized Difference Vegetation Index (NDVI) has been widely used to study the plant growth and vegetation productivity around the world, especially the dynamic response of vegetation to climate change in terms of precipitation and temperature. Alberta is the most important agricultural and forestry province and with the best climatic observation systems in Canada. However, few studies pertaining to climate change and vegetation productivity are found. The objectives of this paper therefore were to better understand impacts of climate change on vegetation productivity in Alberta using the NDVI and provide reference for policy makers and stakeholders. We investigated the following: (1) the variations of Alberta's smoothed NDVI (sNDVI, eliminated noise compared to NDVI) and two climatic variables (precipitation and temperature) using non-parametric Mann-Kendall monotonic test and Thiel-Sen's slope; (2) the relationships between sNDVI and climatic variables, and the potential predictability of sNDVI using climatic variables as predictors based on two predicted models; and (3) the use of a linear regression model and an artificial neural network calibrated by the genetic algorithm (ANN-GA) to estimate Alberta's sNDVI using precipitation and temperature as predictors. The results showed that (1) the monthly sNDVI has increased during the past 30 years and a lengthened growing season was detected; (2) vegetation productivity in northern Alberta was mainly temperature driven and the vegetation in southern Alberta was predominantly precipitation driven for the period of 1982-2011; and (3) better performances of the sNDVI-climate relationships were obtained by nonlinear model (ANN-GA) than using linear (regression) model. Similar results detected in both monthly and summer sNDVI prediction using climatic variables as predictors revealed the applicability of two models for

  13. Aspectos temporais auditivos em adolescentes do 6º ano do Ensino Fundamental Temporal aspects of hearing in adolescents from the 6th year of elementary education

    Directory of Open Access Journals (Sweden)

    Sulamita da Silva Marcelino Terto

    2012-01-01

    Full Text Available OBJETIVO: esclarecer a relação entre desempenho escolar e aspectos temporais auditivos. MÉTODO: estudo descritivo-transversal com amostra de conveniência, composta por 82 estudantes, na faixa etária de 11 a 13 anos, sendo 43 do sexo feminino e 38 do sexo masculino do 6º ano de uma escola de financiamento privado na Região Metropolitana de Belo Horizonte. Cada estudante respondeu a um formulário de caracterização da amostra, realizou o Teste de Desempenho Escolar e foi submetido aos testes que avaliam os aspectos temporais auditivos: Teste Padrão de Duração, Teste Padrão de Frequência e Teste Gap-in-Noise. RESULTADOS: os testes que avaliam os aspectos temporais auditivos não sofreram influência relacionada às variáveis sexo, idade, realização de atividades de musicalização e preferência manual. Com exceção da variável "acompanhamento fonoaudiológico" que apresentou significância estatística no teste Gap-in-Noise. Os subtestes do Teste de Desempenho Escolar que exerceram maior influencia no desempenho nos testes Padrão de Duração e Padrão de Frequência foram Escrita, seguida de Leitura e Aritmética. CONCLUSÃO: a análise dos dados revelou que há correlação entre desempenho escolar e aspectos temporais auditivos. Cabe ressaltar que os testes que avaliam a ordenação temporal complexa (Teste Padrão de Frequência e Teste Padrão de Duração são influenciados pelo desempenho no Teste de Desempenho Escolar. Porém o mesmo não ocorre com o teste que avalia resolução temporal (Gap-in-Noise.PURPOSE: to elucidate the relationship between school performance and temporal aspects of hearing. METHOD: a descriptive cross-sectional convenience sample composed of 82 students, aged 11-13 years, 43 females, and 38 males in the 6th grade at a private funding school in the Metropolitan Region of Belo Horizonte. Each student responded to one form of sample characterization, performed the Academic Performance Test and was

  14. Aspectos temporais auditivos em adolescentes do 6º ano do ensino fundamental Temporal aspects of hearing in adolescents from the 6th year of elementary education

    Directory of Open Access Journals (Sweden)

    Sulamita da Silva Marcelino Terto

    2013-04-01

    Full Text Available OBJETIVO: esclarecer a relação entre desempenho escolar e aspectos temporais auditivos. MÉTODO: estudo descritivo-transversal com amostra de conveniência, composta por 82 estudantes, na faixa etária de 11 a 13 anos, sendo 43 do sexo feminino e 38 do sexo masculino do 6º ano de uma escola de financiamento privado na Região Metropolitana de Belo Horizonte. Cada estudante respondeu a um formulário de caracterização da amostra, realizou o Teste de Desempenho Escolar e foi submetido aos testes que avaliam os aspectos temporais auditivos: Teste Padrão de Duração, Teste Padrão de Frequência e Teste Gap-in-Noise. RESULTADOS: os testes que avaliam os aspectos temporais auditivos não sofreram influência relacionada às variáveis sexo, idade, realização de atividades de musicalização e preferência manual. Com exceção da variável "acompanhamento fonoaudiológico" que apresentou significância estatística no teste Gap-in-Noise. Os subtestes do Teste de Desempenho Escolar que exerceram maior influencia no desempenho nos testes Padrão de Duração e Padrão de Frequência foram Escrita, seguida de Leitura e Aritmética. CONCLUSÃO: a análise dos dados revelou que há correlação entre desempenho escolar e aspectos temporais auditivos. Cabe ressaltar que os testes que avaliam a ordenação temporal complexa (Teste Padrão de Frequência e Teste Padrão de Duração são influenciados pelo desempenho no Teste de Desempenho Escolar. Porém o mesmo não ocorre com o teste que avalia resolução temporal (Gap-in-Noise.PURPOSE: to elucidate the relationship between school performance and temporal aspects of hearing. METHOD: a descriptive cross-sectional convenience sample composed of 82 students, aged 11-13 years, 43 females, and 38 males in the 6th grade at a private funding school in the Metropolitan Region of Belo Horizonte. Each student responded to one form of sample characterization, performed the Academic Performance Test and was

  15. Trauma dos ossos temporais e suas complicações: aspectos na tomografia computadorizada Temporal bone trauma and complications: computed tomography findings

    Directory of Open Access Journals (Sweden)

    Ana Maria Doffémond Costa

    2013-04-01

    Full Text Available A maioria das fraturas dos ossos temporais resulta de traumas cranianos bruscos, de alta energia, estando muitas vezes relacionadas a outras fraturas cranianas ou a politraumatismo. As fraturas e os deslocamentos da cadeia ossicular, na orelha média, representam umas das principais complicações das injúrias nos ossos temporais e, por isso, serão abordadas de maneira mais profunda neste artigo. Os outros tipos de injúrias englobam as fraturas labirínticas, fístula dural, paralisia facial e extensão da linha de fratura ao canal carotídeo. A tomografia computadorizada tem papel fundamental na avaliação inicial dos pacientes politraumatizados, pois é capaz de identificar injúrias em importantes estruturas que podem causar graves complicações, como perda auditiva de condução ou neurossensorial, tonturas e disfunções do equilíbrio, fístulas perilinfáticas, paralisia do nervo facial, lesões vasculares, entre outras.Most temporal bone fractures result from high-energy blunt head trauma, and are frequently related to other skull fractures or to polytrauma. Fractures and displacements of ossicular chain in the middle ear represent some of the main complications of temporal bone injury, and hence they will be more deeply approached in the present article. Other types of injuries include labyrinthine fractures, dural fistula, facial nerve paralysis and extension into the carotid canal. Computed tomography plays a fundamental role in the initial evaluation of polytrauma patients, as it can help to identify important structural injuries that may lead to severe complications such as sensorineural hearing loss, conductive hearing loss, dizziness and balance dysfunction, perilymphatic fistulas, facial nerve paralysis, vascular injury and others.

  16. Evaluating temporal consistency of long-term global NDVI datasets for trend analysis

    DEFF Research Database (Denmark)

    Tian, Feng; Fensholt, Rasmus; Verbesselt, Jan;

    2015-01-01

    As a way to understand vegetation changes, trend analysis on NDVI (normalized difference vegetation index) time series data have been widely performed at regional to global scales. However, most long-term NDVI datasets are based upon multiple sensor systems and unsuccessful corrections related to...

  17. Quantitative Analysis of Relationship Between HJ-1 NDVI and MODIS NDVI%环境一号卫星与 MODIS NDVI 的定量关系分析

    Institute of Scientific and Technical Information of China (English)

    陈星; 刘智华

    2015-01-01

    不同遥感器由于波段设置和光谱响应函数差异导致其在红光和近红外波段所接收的地物反射信号不同,产生了 NDVI 的不一致性问题,针对这一问题,该文研究了 HJ-1 NDVI 和 MODIS NDVI 的定量关系。采用高光谱 Hyperion 数据进行光谱卷积和空间卷积,模拟 HJ-1与 MODIS 两遥感器波段反射率数据。通过计算 NDVI,进行回归分析求出两者之间的定量关系。分别基于单一覆盖类型和混合覆盖类型建立 HJ-1与 MODIS 的转换方程,排除其定量关系可能受不同土地覆盖类型的影响。定量分析与精度验证表明:HJ-1 NDVI 与 MODIS NDVI有很高的线性正相关性(R 2>0.99);单一覆盖类型转换精度高于混合覆盖类型转换精度,均能满足定量应用要求,但单一覆盖类型转换在实际应用中较为复杂,可采用混合覆盖类型转换方程进行 HJ-1 NDVI 与 MODIS NDVI 的转换。%Quantitative relationship between NDVI of HJ-1 and MODIS was acquired using Hyperion hyperspectral data. Hyperion scenes were processed to simulate NDVI of the two sensors.To study the effect of land cover on the relationship of NDVI of HJ-1 and MODIS,regression models were derived both for land cover-dependent and land cover-independent situation. The conversion models were directly validated by comparison of HJ-1 and MODIS image data.The result indicated that HJ-1 NDVI was highly correlated with MODIS NDVI (R2 >0.99);Regression models under both situations worked well.The land cover-dependent model worked slightly better than the land cover-independent,but it was more complicated when used.So it was suggested to use a single equation to convert HJ-1 NDVI to MODIS NDVI.

  18. Comportamento do NDVI obtido por sensor ótico ativo em cereais Behavior of NDVI obtained from an active optical sensor in cereals

    Directory of Open Access Journals (Sweden)

    Fabrício Pinheiro Povh

    2008-08-01

    Full Text Available O objetivo deste trabalho foi avaliar, com um sensor ótico ativo, o comportamento do índice de vegetação por diferença normalizada (NDVI - "normalized difference vegetation index", nas culturas de trigo, triticale, cevada e milho. Cinco experimentos foram conduzidos no Paraná e São Paulo, com variação de classes de solo, doses e fontes de N, e variedades de trigo. As seguintes variáveis foram avaliadas: NDVI, teor de N foliar, matéria seca e produtividade das culturas. Análises de regressões foram realizadas entre as doses de N aplicadas e NDVI, teor de N foliar, matéria seca e produtividade. Análises de correlação entre as variáveis foram realizadas. O trigo, triticale e cevada apresentaram resposta às aplicações de doses crescentes de N, pelo aumento nas leituras do NDVI, no teor de N foliar e na produtividade. Medido pelo sensor ótico ativo utilizado, o NDVI apresenta alto potencial para manejo do N nas culturas do trigo, triticale e cevada, e baixo potencial para a cultura do milho. Há interferência das variedades de trigo nas leituras do sensor ótico ativo.The objective of this work was to evaluate the behavior of the normalized difference vegetation index (NDVI, with an active optical sensor, in wheat, triticale, barley and corn crops. Experiments were conducted in Paraná and São Paulo, comparing different soil classes, N rates and sources, and wheat varieties. The following variables were determined: NDVI, N foliar content, dry mass and crop yield. Regression analyses were performed between NDVI and applied N rates, N foliar content, dry mass and yield. Correlation analyses among the variables were performed. Wheat, triticale and barley crops showed response to increasing N rates by the increase in the NDVI readings, to N foliar content and to yield. Measured by the used active optical sensor the NDVI shows high potential for N management wheat, triticale and barley crops, and low potential for corn crops. There

  19. NDVI Variation and Its Responses to Climate Change on the Northern Loess Plateau of China from 1998 to 2012

    OpenAIRE

    Tingting Ning; Wenzhao Liu; Wen Lin; Xiaoqiang Song

    2015-01-01

    This study analyzed temporal and spatial changes of normalized difference vegetation index (NDVI) on the northern Loess Plateau and their correlation with climatic factors from 1998 to 2012. The possible impacts of human activities on the NDVI changes were also explored. The results showed that (1) the annual maximum NDVI showed an upward trend. The significantly increased NDVI and decreasing severe desertification areas demonstrate that the vegetation condition improved in this area. (2) Ove...

  20. Vegetation dynamics using AVHRR/NDVI: Regional climate, carbon dioxide fertilization and crop yield relations

    Science.gov (United States)

    Lim, Chai Kyung

    Vegetation development is closely related to climate factors, and, therefore, it is important to understand how it responds to global climate changes. For the last two decades it has been possible to monitor vegetation development at continental or global scales utilizing remote sensing Normalized Difference Vegetation Index (NDVI) data. We have developed a frequency analysis method to investigate land's vegetation greenness change and its response to the El Nino Southern Oscillation (ENSO). We found an ENSO influence on a tropical forest, southern semi-deciduous forest and a northeastern mixed forest. Our analysis shows the annual trends in vegetation greenness respond more sensitively than averaging methods. Atmospheric CO2 increase is another concern for climate change, for which fertilization effect on land vegetation has been suggested. Atmospheric CO2 and NDVI have a seasonal pattern of negative correlation, which makes it difficult to discern any positive influence of CO2 on vegetation. We adopted the concept of the rate of change in atmospheric CO2 concentration and NDVI to overcome this set pattern, and to reveal undergoing fluctuations. We found evidence that suggests a CO2 fertilization effect in some arctic and sub arctic regions and northern and inland parts of the eastern humid temperate zones in North America. Although NDVI reveals the vegetation greenness only at a fixed time and location, we have transformed NDVI effectively to describe the vegetation growth dynamics in the form of a new index, Normalized Growth Index (NGI). Utilizing NGI, we found the vegetation growth during the growing season is highly negatively correlated with the initial minimum vegetation greenness. One needs to be careful when comparing Net Primary Production (NPP) using NDVI between different types of vegetation, because the same NDVI value can imply the existence of different biomass due to different Leaf Area Index (LAI). To overcome this difficulty we have developed

  1. Remote sensing of interannual boreal forest NDVI in relation to climatic conditions in interior Alaska

    Science.gov (United States)

    Verbyla, David

    2015-12-01

    Climate has warmed substantially in interior Alaska and several remote sensing studies have documented a decadal-scale decline in the normalized difference vegetation index (NDVI) termed a ‘browning trend’. Reduced summer soil moisture due to changing climatic factors such as earlier springs, less snowpack, and summer drought may reduce boreal productivity and NDVI. However, the relative importance of these climatic factors is poorly understood in boreal interior Alaska. In this study, I used the remotely sensed peak summer NDVI as an index of boreal productivity at 250 m pixel size from 2000 to 2014. Maximum summer NDVI was related to last day of spring snow, early spring snow water equivalent (SWE), and a summer moisture index. There was no significant correlation between early spring SWE and peak summer NDVI. There was a significant correlation between the last day of spring snow and peak summer NDVI, but only for a few higher elevation stations. This was likely due to snowmelt occurring later at higher elevations, thus having a greater effect on summer soil moisture relative to lower elevation sites. For most of boreal interior Alaska, summer drought was likely the dominant control on peak summer NDVI and this effect may persist for several years. Peak summer NDVI declined at all 26 stations after the 2004 drought, and the decline persisted for 2 years at all stations. Due to the shallow rooting zone of most boreal plants, even cool and moist sites at lower elevations are likely vulnerable to drought. For example the peak summer NDVI response following the 2004 drought was similar for adjacent cold and warm watershed basins. Thus, if frequent and severe summer droughts continue, moisture stress effects are likely to be widespread and prolonged throughout most of interior boreal Alaska, including relatively cool, moist sites regardless of spring snowpack conditions or spring phenology.

  2. Effect of Temporal Resolution of NDVI on Potential Evapotranspiration Estimation and Hydrological Model Performance

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Normalized difference vegetation index (NDVI) data, obtained from remote sensing information, are essential in the Shuttleworth-Wallace(S-W) model for estimation of evapotranspiration. In order to study the effect of temporal resolution of NDVI on potential evapotranspiration (PET) estimation and hydrological model performance,monthly and 10-day NDVI data set were used to estimate potential evapotranspiration from January 1985 to December 1987 in Huangnizhuang catchment, Anhui Province, China. The differences of the two calculation results were analyzed and used to drive the block-wise use of the TOPMODEL with the Muskingum-Cunge routing (BTOPMC) model to test the effect on model performance. The results show that both annual and monthly PETs estimated by 10-day NDVI are lower than those estimated by monthly NDVI. Annual PET from the vegetation root zone (PETr) lowers 9.77%-13.64% and monthly PETr lowers 3.28%-17.44% in the whole basin. PET from the vegetation interception (PETi) shows the same trend as PETr. In addition, temporal resolution of NDVI has more effect on PETr in summer and on PETi in winter. The correlation between PETr as estimated by 10-day NDVI and pan measurement (R2= 0.835)is better than that between monthly NDVI and pan measurement (R2 = 0.775). The two potential evapotranspiration estimates were used to drive the BTOPMC model and calibrate parameters, and model performance was found to be similar. In summary, the effect of temporal resolution of NDVI on potential evapotranspiration estimation is significant,but trivial on hydrological model performance.

  3. A Non-Stationary 1981–2012 AVHRR NDVI3g Time Series

    Directory of Open Access Journals (Sweden)

    Jorge E. Pinzon

    2014-07-01

    Full Text Available The NDVI3g time series is an improved 8-km normalized difference vegetation index (NDVI data set produced from Advanced Very High Resolution Radiometer (AVHRR instruments that extends from 1981 to the present. The AVHRR instruments have flown or are flying on fourteen polar-orbiting meteorological satellites operated by the National Oceanic and Atmospheric Administration (NOAA and are currently flying on two European Organization for the Exploitation of Meteorological Satellites (EUMETSAT polar-orbiting meteorological satellites, MetOp-A and MetOp-B. This long AVHRR record is comprised of data from two different sensors: the AVHRR/2 instrument that spans July 1981 to November 2000 and the AVHRR/3 instrument that continues these measurements from November 2000 to the present. The main difficulty in processing AVHRR NDVI data is to properly deal with limitations of the AVHRR instruments. Complicating among-instrument AVHRR inter-calibration of channels one and two is the dual gain introduced in late 2000 on the AVHRR/3 instruments for both these channels. We have processed NDVI data derived from the Sea-Viewing Wide Field-of-view Sensor (SeaWiFS from 1997 to 2010 to overcome among-instrument AVHRR calibration difficulties. We use Bayesian methods with high quality well-calibrated SeaWiFS NDVI data for deriving AVHRR NDVI calibration parameters. Evaluation of the uncertainties of our resulting NDVI values gives an error of ± 0.005 NDVI units for our 1981 to present data set that is independent of time within our AVHRR NDVI continuum and has resulted in a non-stationary climate data set.

  4. FFT analysis on NDVI annual cycle and climatic regionality in Northeast Brazil

    Science.gov (United States)

    Negrón Juárez, Robinson I.; Liu, William T.

    2001-11-01

    By considering that the climate of Northeast Brazil (NEB) has distinct wet and dry seasons, the mixed radix fast Fourier transform (mrFFT) algorithm, developed at the National Aerospace Centre of the Netherlands, was applied to a monthly Normalized Difference Vegetation Index (NDVI) time series from July 1981 to June 1993, to generate phase, amplitude and mean NDVI data using a 1-year frequency in order to improve the analysis of its spatial variation.The NDVI mean values varied from >0.7, which occurred in northwest and southeast regions, to 0.25 in the northeast region. By using spatial variations of phase, amplitude and mean NDVI values, 15 climate types were delineated for the NEB.The spatial distribution of climate types in the NEB delineated by the NDVI FFT analysis agreed mostly with the climatic types presented by Hargreaves (Precipitation dependability and potentials for agricultural production in Northeast Brazil. Empresa Brasileira de Pesquisa Agropecuária-EMBRAPA, Brazil, 1974), except regions with higher spatial variability and limited surface meteorological data. Among the three components: phase, amplitude and mean NDVI, the phase image, informing the initiation and duration of rainy season, was the most important component for climate-type delineation. Nevertheless, while the extreme values of amplitude, inferring a high wet-dry rainfall regime contrast, and mean NDVI, inferring annual rainfall total, occurred in the same phase area, amplitude and mean NDVI images were used for further delineation. It is concluded that the application of the mrFFT algorithm to NDVI time series analysis is an effective method for identifying vegetation phenology and hence to delineate the transit spatial change of climate types. Our further study is to construct and validate the alternative El Niño-Southern Oscillation (ENSO) drought onset model for each of the 15 climate types delineated for the NEB.

  5. Detecção de mudança de nível em séries temporais não lineares usando Descritores de Hjorth

    Directory of Open Access Journals (Sweden)

    Gabriela da Fonseca de Amorim

    2015-12-01

    Full Text Available Resumo O propósito deste artigo é apresentar um método de detecção de mudança de nível na dinâmica de séries temporais não lineares que consiste no uso de um gráfico de Controle Multivariado T2 de Hotelling monitorando a variação de três descritores normalizados: os Descritores de Hjorth de atividade, mobilidade e complexidade. Esta abordagem foi aplicada em diferentes séries temporais não lineares criadas artificialmente e é ilustrada neste artigo por um exemplo detalhado. Também foi feito um estudo de caso com seis séries reais do consumo de energia elétrica no meio industrial, confirmando a eficácia do método.

  6. NOAA Climate Data Record (CDR) of Normalized Difference Vegetation Index (NDVI), Version 4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains gridded daily Normalized Difference Vegetation Index (NDVI) derived from the NOAA Climate Data Record (CDR) of Advanced Very High Resolution...

  7. NDVI-based vegetation responses to climate change in an arid area of China

    Science.gov (United States)

    Xu, Yufeng; Yang, Jing; Chen, Yaning

    2016-10-01

    Warming of the climate system is unequivocal, and the change of climate variables will eventually have a great impact on vegetation cover and agricultural practices, especially in the arid area Xinjiang in China, whose agriculture and ecosystems are heavily vulnerable to climate change. In this paper, normalized difference vegetation index (NDVI) was used to study the vegetation growth and its response to climate change in Xinjiang. Firstly, two NDVI datasets (Global Inventory Modeling and Mapping Studies (GIMMS) and Moderate Resolution Imaging Spectroradiometer (MODIS)) were merged through a pixel-wise regression analysis to obtain a long time series of NDVI data, and then, relationships between yearly NDVI and yearly climate variables, and monthly NDVI and monthly climate variables were extensively investigated for grassland and cropland in northern and southern Xinjiang, respectively. Results show the following: (1) there was an increasing trend in NDVI for both grassland and cropland in both northern and southern Xinjiang over the past decades and trends were significant except that for grassland in northern Xinjiang; (2) precipitation and evaporation were more important than temperature for grassland in northern Xinjiang, while precipitation and temperature were more important than evaporation for grassland in southern Xinjiang and cropland in both northern and southern Xinjiang; (3) NDVI was highly correlated with accumulated monthly precipitation instead of monthly precipitation, and there was a lagged effect of precipitation, temperature, and evaporation on NDVI change. However, lagged effects were only significant in specific months. The results could be helpful to agricultural practices; e.g., based on lagged effect of precipitation, irrigation in July is very important for crop growth.

  8. Phenologically-tuned MODIS NDVI-based production anomaly estimates for Zimbabwe

    Science.gov (United States)

    Funk, C.; Budde, M.E.

    2009-01-01

    For thirty years, simple crop water balance models have been used by the early warning community to monitor agricultural drought. These models estimate and accumulate actual crop evapotranspiration, evaluating environmental conditions based on crop water requirements. Unlike seasonal rainfall totals, these models take into account the phenology of the crop, emphasizing conditions during the peak grain filling phase of crop growth. In this paper we describe an analogous metric of crop performance based on time series of Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) imagery. A special temporal filter is used to screen for cloud contamination. Regional NDVI time series are then composited for cultivated areas, and adjusted temporally according to the timing of the rainy season. This adjustment standardizes the NDVI response vis-??-vis the expected phenological response of maize. A national time series index is then created by taking the cropped-area weighted average of the regional series. This national time series provides an effective summary of vegetation response in agricultural areas, and allows for the identification of NDVI green-up during grain filling. Onset-adjusted NDVI values following the grain filling period are well correlated with U.S. Department of Agriculture production figures, possess desirable linear characteristics, and perform better than more common indices such as maximum seasonal NDVI or seasonally averaged NDVI. Thus, just as appropriately calibrated crop water balance models can provide more information than seasonal rainfall totals, the appropriate agro-phenological filtering of NDVI can improve the utility and accuracy of space-based agricultural monitoring.

  9. Using MODIS NDVI products for vegetation state monitoring on the oil production territory in Western Siberia

    OpenAIRE

    Kovalev Anton; Tokareva Olga

    2016-01-01

    Article describes the results of using remote sensing data for vegetation state monitoring on the oil field territories in Western Siberia. We used MODIS data product providing the normalized difference vegetation index (NDVI) values. Average NDVI values of each studied area were calculated for the period from 2010 to 2015 with one year interval for June, July and August. Analysis was carried out via an open tool of geographic information system QGIS used for spatial analysis and calculation ...

  10. NDVI-based vegetation responses to climate change in an arid area of China

    Science.gov (United States)

    Xu, Yufeng; Yang, Jing; Chen, Yaning

    2015-07-01

    Warming of the climate system is unequivocal, and the change of climate variables will eventually have a great impact on vegetation cover and agricultural practices, especially in the arid area Xinjiang in China, whose agriculture and ecosystems are heavily vulnerable to climate change. In this paper, normalized difference vegetation index (NDVI) was used to study the vegetation growth and its response to climate change in Xinjiang. Firstly, two NDVI datasets (Global Inventory Modeling and Mapping Studies (GIMMS) and Moderate Resolution Imaging Spectroradiometer (MODIS)) were merged through a pixel-wise regression analysis to obtain a long time series of NDVI data, and then, relationships between yearly NDVI and yearly climate variables, and monthly NDVI and monthly climate variables were extensively investigated for grassland and cropland in northern and southern Xinjiang, respectively. Results show the following: (1) there was an increasing trend in NDVI for both grassland and cropland in both northern and southern Xinjiang over the past decades and trends were significant except that for grassland in northern Xinjiang; (2) precipitation and evaporation were more important than temperature for grassland in northern Xinjiang, while precipitation and temperature were more important than evaporation for grassland in southern Xinjiang and cropland in both northern and southern Xinjiang; (3) NDVI was highly correlated with accumulated monthly precipitation instead of monthly precipitation, and there was a lagged effect of precipitation, temperature, and evaporation on NDVI change. However, lagged effects were only significant in specific months. The results could be helpful to agricultural practices; e.g., based on lagged effect of precipitation, irrigation in July is very important for crop growth.

  11. A Non-Stationary 1981-2015 AVHRR NDVI3g Time Series

    Science.gov (United States)

    Pinzon, J. E.

    2015-12-01

    Long-term records of vegetation indices from Earth Observing instruments play a major role in monitoring terrestrial ecosystems and further our understanding on the varying effects of climate on vegetation. We describe 34+ years of an improved non-stationary 8-km normalized difference vegetation index (NDVI) produced from Advanced Very High Resolution Radiometer (AVHRR) instruments that extends from 1981 to the present. The AVHRR instruments have flown or are flying on fourteen polar-orbiting meteorological satellites operated by the National Oceanic and Atmospheric Administration (NOAA) and are currently flying on two European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) polar-orbiting meteorological satellites, MetOp-A and MetOp-B. This long AVHRR record is comprised of data from two different sensors: the AVHRR/2 instrument that spans July 1981 to November 2000 and the AVHRR/3 instrument that continues these measurements from November 2000 to the present. The main difficulty in processing AVHRR NDVI data is to properly deal with limitations of the AVHRR instruments. Complicating among-instrument AVHRR inter-calibration of channels one and two is the dual gain introduced in late 2000 on the AVHRR/3 instruments for both these channels. We have processed NDVI data derived from the Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) from 1997 to 2010 to overcome among-instrument AVHRR calibration difficulties. We use Bayesian methods with high quality well-calibrated SeaWiFS NDVI data for deriving AVHRR NDVI calibration parameters. Evaluation of the uncertainties of our resulting NDVI values gives an error of ± 0.005 NDVI units for our 1981 to present data set that is independent of time within our AVHRR NDVI continuum and has resulted in a non-stationary climate data set.

  12. Relationships between NDVI and Leaf Area Index for spring and winter camelina in Northeastern Montana

    Science.gov (United States)

    Jabro, Jay; Allen, Brett; long, Dan; Isbell, Terry; Gesch, Russ; Brown, Jack; Hatfield, Jerry; Archer, David; Oblath, Emily; Vigil, Merle; Kiniry, Jim

    2016-04-01

    To our knowledge no research has been reported on the relationship between the normalized difference vegetation index (NDVI) and leaf area index (LAI) in spring and winter camelina. Relationships between NDVI and LAI for winter camelina (Camelina sativa) "Joelle" and spring camelina "CO46" were determined and evaluated in a 3-yr field study conducted in Sidney Montana under dryland conditions. The NDVI and LAI were measured weekly throughout the growing season. The NDVI was continually measured at one sample per second across the whole plot using a Crop Circle ACS-470 active crop canopy sensor. The LAI was measured at two locations at 12 samples per plot using an AccuPar model LP-80 Ceptometer. Treatments were replicated four times in a randomized complete block design in plots of 3 m×9 m. Temporal dynamics of NDVI and LAI in various growth stages of both spring and winter camelina were evaluated throughout 2013, 2014 and 2015 growing seasons. Significant linear relationships between NDVI and LAI were obtained for both spring and winter camelina when all the measurements were pooled across three growing seasons. Coefficients of determination (R2) of linearity were 0.77 and 0.79 for spring and winter camelina, respectively.

  13. A tool for NDVI time series extraction from wide-swath remotely sensed images

    Science.gov (United States)

    Li, Zhishan; Shi, Runhe; Zhou, Cong

    2015-09-01

    Normalized Difference Vegetation Index (NDVI) is one of the most widely used indicators for monitoring the vegetation coverage in land surface. The time series features of NDVI are capable of reflecting dynamic changes of various ecosystems. Calculating NDVI via Moderate Resolution Imaging Spectrometer (MODIS) and other wide-swath remotely sensed images provides an important way to monitor the spatial and temporal characteristics of large-scale NDVI. However, difficulties are still existed for ecologists to extract such information correctly and efficiently because of the problems in several professional processes on the original remote sensing images including radiometric calibration, geometric correction, multiple data composition and curve smoothing. In this study, we developed an efficient and convenient online toolbox for non-remote sensing professionals who want to extract NDVI time series with a friendly graphic user interface. It is based on Java Web and Web GIS technically. Moreover, Struts, Spring and Hibernate frameworks (SSH) are integrated in the system for the purpose of easy maintenance and expansion. Latitude, longitude and time period are the key inputs that users need to provide, and the NDVI time series are calculated automatically.

  14. Variability of African Farming Systems from Phenological Analysis of NDVI Time Series

    Science.gov (United States)

    Vrieling, Anton; deBeurs, K. M.; Brown, Molly E.

    2011-01-01

    Food security exists when people have access to sufficient, safe and nutritious food at all times to meet their dietary needs. The natural resource base is one of the many factors affecting food security. Its variability and decline creates problems for local food production. In this study we characterize for sub-Saharan Africa vegetation phenology and assess variability and trends of phenological indicators based on NDVI time series from 1982 to 2006. We focus on cumulated NDVI over the season (cumNDVI) which is a proxy for net primary productivity. Results are aggregated at the level of major farming systems, while determining also spatial variability within farming systems. High temporal variability of cumNDVI occurs in semiarid and subhumid regions. The results show a large area of positive cumNDVI trends between Senegal and South Sudan. These correspond to positive CRU rainfall trends found and relate to recovery after the 1980's droughts. We find significant negative cumNDVI trends near the south-coast of West Africa (Guinea coast) and in Tanzania. For each farming system, causes of change and variability are discussed based on available literature (Appendix A). Although food security comprises more than the local natural resource base, our results can perform an input for food security analysis by identifying zones of high variability or downward trends. Farming systems are found to be a useful level of analysis. Diversity and trends found within farming system boundaries underline that farming systems are dynamic.

  15. Neural Networks as a Tool for Constructing Continuous NDVI Time Series from AVHRR and MODIS

    Science.gov (United States)

    Brown, Molly E.; Lary, David J.; Vrieling, Anton; Stathakis, Demetris; Mussa, Hamse

    2008-01-01

    The long term Advanced Very High Resolution Radiometer-Normalized Difference Vegetation Index (AVHRR-NDVI) record provides a critical historical perspective on vegetation dynamics necessary for global change research. Despite the proliferation of new sources of global, moderate resolution vegetation datasets, the remote sensing community is still struggling to create datasets derived from multiple sensors that allow the simultaneous use of spectral vegetation for time series analysis. To overcome the non-stationary aspect of NDVI, we use an artificial neural network (ANN) to map the NDVI indices from AVHRR to those from MODIS using atmospheric, surface type and sensor-specific inputs to account for the differences between the sensors. The NDVI dynamics and range of MODIS NDVI data at one degree is matched and extended through the AVHRR record. Four years of overlap between the two sensors is used to train a neural network to remove atmospheric and sensor specific effects on the AVHRR NDVI. In this paper, we present the resulting continuous dataset, its relationship to MODIS data, and a validation of the product.

  16. Can temporal and spatial NDVI predict regional bird-species richness?

    Directory of Open Access Journals (Sweden)

    Sebastián Nieto

    2015-01-01

    Full Text Available Understanding the distribution of the species and its controls over biogeographic scales is still a major challenge in ecology. National Park Networks provide an opportunity to assess the relationship between ecosystem functioning and biodiversity in areas with low human impacts. We tested the productivity–biodiversity hypothesis which states that the number of species increases with the available energy, and the ​variability–biodiversity hypothesis which states that the number of species increases with the diversity of habitats. The available energy and habitat heterogeneity estimated by the normalized difference vegetation index (NDVI was shown as a good predictor of bird-species richness for a diverse set of biomes in previously published studies. However, there is not a universal relationship between NDVI and bird-species richness. Here we tested if the NDVI can predict bird species richness in areas with low human impact in Argentina. Using a dataset from the National Park Network of Argentina we found that the best predictor of bird species richness was the minimum value of NDVI per year which explained 75% of total variability. The inclusion of the spatial heterogeneity of NDVI improved the explanation power to 80%. Minimum NDVI was highly correlated with precipitation and winter temperature. Our analysis provides a tool for assessing bird-species richness at scales on which land-use planning practitioners make their decisions for Southern South America.

  17. Tratamento dos sufixos modo-temporais na depreensão automática da morfologia dos verbos do português

    Directory of Open Access Journals (Sweden)

    Vera Vasilévski

    2012-01-01

    Full Text Available Este artigo apresenta um analisador morfológico automático de verbos do português, com destaque para seu desempenho no processamento das regras que regem esse sistema verbal e no tratamento das ambigüidades geradas. Nesta etapa, trabalha-se com as ambigüidades decorrentes da alomorfia dos sufixos modo-temporais e da possibilidade de esses morfemas serem zero (Ø em alguns modos e tempos, nas três conjugações do português. Para esclarecer o trabalho feito com o analisador, traz um resumo das regras morfológicas do sistema de verbos do português. Obteve-se êxito no tratamento de muitas das ambigüidades que o programa registrou, as quais eram esperadas, uma vez que coincidem com as ambigüidades do sistema de verbos da língua portuguesa. A resolução da maioria delas fez-se com base em regras computacionais (estruturas de seleção que consideram o contexto do enunciado. Conclui que a resolução de outras ambiguidades relacionadas a modo e tempo verbal somente será possível ao se levar em conta também os morfemas número-pessoais, que são objeto de outro trabalho.

  18. Séries temporais e redes neurais: uma análise comparativa de técnicas na previsão de vendas do varejo brasileiro

    Directory of Open Access Journals (Sweden)

    Claudio Felisoni de Angelo

    2011-01-01

    Full Text Available Uma importante atividade econômica em qualquer sociedade diz respeito à comercialização de bens. O varejo consiste exatamente no vínculo que se estabelece entre a indústria e o consumidor final. Prever as vendas é essencial para que se possa gerenciar de modo adequado os processos produtivos e de comercialização. No varejo esse aspecto reveste-se de importância ainda maior. Vender significa harmonizar os interesses dos que produzem com aqueles que compram. Portanto, o presente trabalho tem por propósito examinar comparativamente a aplicação de dois métodos de previsão de vendas de varejo no mercado brasileiro: as séries temporais e as redes neurais. A escolha dessas duas técnicas como objeto dessa comparação foi suscitada pela importância que essas duas concepções têm assumido na literatura. Embora a utilização de redes neurais tenha proporcionado a menor soma dos quadrados dos resíduos, pode-se dizer que os resultados empregando modelos do tipo ARIMA se mostraram praticamente equivalentes.

  19. Spatial-Temporal NDVI Variation of Different Alpine Grassland Classes and Groups in Northern Tibet from 2000 to 2013

    Directory of Open Access Journals (Sweden)

    Xiaoke Zhang

    2015-08-01

    Full Text Available The Normalized Difference Vegetation Index (NDVI can usually be used as a good proxy for evaluating potential variability in regional ecosystems and under climate change. We used 16-day MODIS-NDVI composite satellite data with 250-m resolution for the period 2000 to 2013 to assess the temporal and spatial variation of the NDVI among different alpine grassland classes and groups in northern Tibet. The annual average NDVI of the whole alpine grassland area in northern Tibet generally increased slightly from 2000 to 2003, and the annual average NDVI values ranged from 0.112 to 0.492 across all alpine grassland groups and years. The NDVI clearly decreased from the southeastern to the northwestern areas, with 22.50% of total grasslands significantly having increased or decreased, while 77.50% presented little change during 2000–2013. Both temperature and precipitation were key factors that controlled the NDVI variations of the entire alpine grassland. However, for different alpine grassland classes and groups, the NDVI displayed different correlation patterns with temperature and precipitation. Our results demonstrate that the NDVI variations of alpine grassland generally increased slightly but differed among different classes and groups. Although temperature and precipitation were the driving forces influencing the NDVI of the entire alpine grassland, it was more difficult to define the driving forces for the individual classes and groups, and more detailed analyses covering prolonged observation periods are still needed.

  20. Detecting leaf pulvinar movements on NDVI time series of desert trees: a new approach for water stress detection.

    Directory of Open Access Journals (Sweden)

    Roberto O Chávez

    Full Text Available Heliotropic leaf movement or leaf 'solar tracking' occurs for a wide variety of plants, including many desert species and some crops. This has an important effect on the canopy spectral reflectance as measured from satellites. For this reason, monitoring systems based on spectral vegetation indices, such as the normalized difference vegetation index (NDVI, should account for heliotropic movements when evaluating the health condition of such species. In the hyper-arid Atacama Desert, Northern Chile, we studied seasonal and diurnal variations of MODIS and Landsat NDVI time series of plantation stands of the endemic species Prosopis tamarugo Phil., subject to different levels of groundwater depletion. As solar irradiation increased during the day and also during the summer, the paraheliotropic leaves of Tamarugo moved to an erectophile position (parallel to the sun rays making the NDVI signal to drop. This way, Tamarugo stands with no water stress showed a positive NDVI difference between morning and midday (ΔNDVI mo-mi and between winter and summer (ΔNDVI W-S. In this paper, we showed that the ΔNDVI mo-mi of Tamarugo stands can be detected using MODIS Terra and Aqua images, and the ΔNDVI W-S using Landsat or MODIS Terra images. Because pulvinar movement is triggered by changes in cell turgor, the effects of water stress caused by groundwater depletion can be assessed and monitored using ΔNDVI mo-mi and ΔNDVI W-S. For an 11-year time series without rainfall events, Landsat ΔNDVI W-S of Tamarugo stands showed a positive linear relationship with cumulative groundwater depletion. We conclude that both ΔNDVI mo-mi and ΔNDVI W-S have potential to detect early water stress of paraheliotropic vegetation.

  1. High resolution mapping of Normalized Difference Vegetation Indices (NDVI) of biological soil crusts

    Science.gov (United States)

    Fischer, T.; Veste, M.; Eisele, A.; Bens, O.; Spyra, W.; Hüttl, R. F.

    2012-04-01

    Normalized Difference Vegetation Indices (NDVI) are typically determined using satellite or airborne remote sensing, or field portable spectrometers, which give an averaged signal on centimetre to meter scale plots. Biological soil crust (BSC) patches may have smaller sizes, and ecophysiological, hydrological as well as pedological processes may be heterogeneously distributed within this level of resolution. A ground-based NDVI imaging procedure using low-cost equipment (Olympus Camedia 5000z digital camera equipped with a Hoya R72 infrared filter) was developed in this study to fill this gap at the level of field research, where carrying costly and bulky equipment to remote locations is often the limiting factor for data collection. A commercially available colour rendition chart (GretagMacbeth ColorChecker®) with known red (600-700 nm) and NIR (800-900 nm) reflectances was placed into each scene and used for calibration purposes on a per-image basis. Generation of NDVI images involved (i) determination of red and NIR reflectances from the pixel values of the red and NIR channels, respectively, and (ii) calculation and imaging of the NDVI, where NDVI values of -1 to +1 were mapped to grey values of 0 to 255. The correlation between NDVI values retrieved from these images and NDVI values determined using conventional field spectrometry (ASD FieldSpec 3 portable spectroradiometer) was close (r2 =0.91), the 95% confidence interval amounted to 0.10 NDVI units. The pixel resolution was 0.8 mm in the field and 0.2 mm in the laboratory, but can still be improved significantly with closer distance to the crust or with higher camera resolution. Geostatistical analysis revealed that both spatial variability as well as size of individual objects characterized by the NDVI increased with crust development. The latter never exceeded 4 mm in the investigated crusts, which points to the necessity of high resolution imaging for linking remote sensing with ecophysiology

  2. Comparison of Bioclimatic, NDVI and Elevation variables in assessing extent of Commiphora wightii (Arnt.) Bhand.

    Science.gov (United States)

    Kulloli, R. N.; Kumar, S.

    2014-11-01

    Commiphora wightii (Arnt.) Bhand., is an important medicinal plant of Indian Medicine System (IMS) since ancient time. It is used in different ailments of obesity, arthritis, rheumatism and high cholesterol. Due to overexploitation its natural populations declined to large extent. IUCN has put it under Data Deficient (DD) category due to lack of data on its extent of occurrence in nature. Hence, the study was carried out using MaxEnt distribution modelling algorithm to estimate its geographic distribution and to identify potential habitats for its reintroduction. For modelling employed 68 presence locality data, 19 bioclimatic variables, Normalize Difference Vegetation Index (NDVI) and elevation data. These were tested for multicollinearity and those variables having r-value less than 0.8 were selected for further analysis, which was carried out in two ways i) Bioclimatic variables and elevation; ii) NDVI and elevation. Area Under the Curve (AUC) in both analysis was above 0.9 for all variables, indicating very high accuracy of prediction. Variables governing distribution of C. wightii in the analysis using bioclimatic and elevation data set are precipitation seasonality (56.6 %), annual precipitation (16.4 %) and elevation (14.7 %). Extent of occurrence of C.wightii predicted by model closely matched in the districts of Jaisalmer and Barmer. In the second analysis elevation (48.3 %), NDVI of June (11.1 %) and August (11.2 %) contributed for NDVI and Elevation data set. NDVI of June corresponds to its leafing phase while NDVI of August to flowering phase. Area of its occurrence predicted for NDVI and elevation data set are Bikaner, Churu, Jhunjhunun some part of Jodhpur which are completely sandy, where C. wightii is totally absent. Extent of occurrence was also validated in ground survey. Potential areas for its reintroduction were identified as Jaisalmer and Barmer districts in Indian arid zone.

  3. Combined analysis of land cover change and NDVI trends in the Northern Eurasian grain belt

    Institute of Scientific and Technical Information of China (English)

    Christopher K.WRIGHT; Kirsten M.de BEURS; Geoffrey M.HENEBRY

    2012-01-01

    We present an approach to regional environmental monitoring in the Northern Eurasian grain belt combining time series analysis of MODIS normalized difference vegetation index (NDVI) data over the period 2001-2008 and land cover change (LCC) analysis of the 2001and 2008 MODIS Global Land Cover product (MCD12Q1).NDVI trends were overwhelmingly negative across the grain belt with statistically significant (p ≤ 0.05)positive trends covering only 1% of the land surface.LCC was dominated by transitions between three classes;cropland,grassland,and a mixed cropland/natural vegetation mosaic.Combining our analyses of NDVI trends and LCC,we found a pattern of agricultural abandonment (cropland to grassland) in the southern range of the grain belt coinciding with statistically significant (p≤0.05)negative NDVI trends and likely driven by regional drought.In the northern range of the grain belt we found an opposite tendency toward agricultural intensification; in this case,represented by LCC from cropland mosaic to pure cropland,and also associated with statistically significant (p≤0.05) negative NDVI trends.Relatively small clusters of statistically significant (p ≤ 0.05) positive NDVI trends corresponding with both localized land abandonment and localized agricultural intensification show that land use decision making is not uniform across the region.Land surface change in the Northern Eurasian grain belt is part of a larger pattern of land cover land use change (LCLUC) in Eastern Europe,Russia,and former territories of the Soviet Union following realignment of socialist land tenure and agricultural markets.Here,we show that a combined analysis of LCC and NDVI trends provides a more complete picture of the complexities of LCLUC in the Northern Eurasian grain belt,involving both broader climatic forcing,and narrower anthropogenic impacts,than might be obtained from either analysis alone.

  4. Combined analysis of land cover change and NDVI trends in the Northern Eurasian grain belt

    Science.gov (United States)

    Wright, Christopher K.; de Beurs, Kirsten M.; Henebry, Geoffrey M.

    2012-06-01

    We present an approach to regional environmental monitoring in the Northern Eurasian grain belt combining time series analysis of MODIS normalized difference vegetation index (NDVI) data over the period 2001-2008 and land cover change (LCC) analysis of the 2001 and 2008 MODIS Global Land Cover product (MCD12Q1). NDVI trends were overwhelmingly negative across the grain belt with statistically significant ( p⩽0.05) positive trends covering only 1% of the land surface. LCC was dominated by transitions between three classes; cropland, grassland, and a mixed cropland/natural vegetation mosaic. Combining our analyses of NDVI trends and LCC, we found a pattern of agricultural abandonment (cropland to grassland) in the southern range of the grain belt coinciding with statistically significant ( p⩽0.05) negative NDVI trends and likely driven by regional drought. In the northern range of the grain belt we found an opposite tendency toward agricultural intensification; in this case, represented by LCC from cropland mosaic to pure cropland, and also associated with statistically significant ( p⩽0.05) negative NDVI trends. Relatively small clusters of statistically significant ( p⩽0.05) positive NDVI trends corresponding with both localized land abandonment and localized agricultural intensification show that land use decision making is not uniform across the region. Land surface change in the Northern Eurasian grain belt is part of a larger pattern of land cover land use change (LCLUC) in Eastern Europe, Russia, and former territories of the Soviet Union following realignment of socialist land tenure and agricultural markets. Here, we show that a combined analysis of LCC and NDVI trends provides a more complete picture of the complexities of LCLUC in the Northern Eurasian grain belt, involving both broader climatic forcing, and narrower anthropogenic impacts, than might be obtained from either analysis alone.

  5. Pasture Drought Insurance Based on NDVI and SAVI

    Science.gov (United States)

    Escribano Rodríguez, J. A.; Tarquis, A. M.; Hernandez Díaz-Ambrona, C. G.

    2012-04-01

    Drought is a complex phenomenon, which is difficult to define. The term is used to refer to deficiency in rainfall, soil moisture, vegetation greenness, ecological conditions or socio economic conditions, and different drought types can be inferred. In this study, drought is considered as a period when the pasture growth is low in regard to long-term average conditions. The extensive livestock production is based on the natural resources available. The good management practices concurs the maximum livestock nutrition needs with the maximum pasture availability. Therefore, early drought detection and impact assessment on the amount of pasture biomass are important in several areas in Spain, whose economy strongly depends on livestock production. The use of remote sensing data presents a number of advantages when determining drought impact on vegetation. The information covers the whole of a territory and the repetition of images provides multi-temporal measurements. In addition, vegetation indexes, being NDVI (normalized difference vegetation index) and SAVI (soil-adjusted vegetation index) the most common ones, obtainedfrom satellite data allow areas affected by droughts to be identified. These indices are being used for estimation of vegetation photosynthesis activity and monitoring drought. The present study shows the application of these vegetation indices for pasture drought monitoring in three places in Spain and their correlation with several field measurements. During 2010 and 2011 three locations, El Cubo de Don Sancho (Salamanca), Trujillo (Cáceres) and Pozoblanco (Córdoba), were selected and a periodic pasture monitoring and botanic composition were achieved. Daily precipitation, temperature and monthly soil water content were measurement as well as fresh and dry pasture weight. At the same time, remote sensing images were capture by DEIMOS-1 of the chosen places.This satellite is based on the concept Microsat-100 from Surrey. It is conceived for

  6. Multi-scale evaluation of ISIMIP biome models against NDVI and MODIS NPP data

    Science.gov (United States)

    Rafique, Rashad; Zhao, Fang; Zeng, Ning; Asrar, Ghassem; Reyer, Christopher; Ostberg, Sebastian; Francois, Louis; Tian, Hanqin; Chnag, Jinfeng; Nishina, Kazuya

    2016-04-01

    The net primary productivity (NPP) is commonly used for understanding the dynamics of terrestrial ecosystems and their role in carbon cycle. The global NPP, highly variable over space and time, cannot be directly observed, therefore, satellite based observations of Normalized Difference Vegetation Index (NDVI) are used as a proxy to understand and monitor the NPP dynamics. In this study, we used a combination of most recent NDVI and modeled NPP data for the period 1982-2012, to study the role of terrestrial ecosystems in carbon cycle under the prevailing climate conditions. We found that in general there is good agreement between the spatial patterns and global seasonal cycles between observed NDVI and modeled NPP values. Simulated NPP values also generally agree with MODIS NPP spatially, and temporally, MODIS NPP falls within the model spread of NPP values. Despite of the general agreement in the trends of global total NDVI, MODIS NPP and modeled NPP, considerable spatial differences are found, and the ensemble mean of the models often agrees better with the spatial patterns of observed NDVI and MODIS NPP than individual models.

  7. Global Trends in Seasonality of Normalized Difference Vegetation Index (NDVI, 1982–2011

    Directory of Open Access Journals (Sweden)

    Assaf Anyamba

    2013-09-01

    Full Text Available A 30-year series of global monthly Normalized Difference Vegetation Index (NDVI imagery derived from the Global Inventory Modeling and Mapping Studies (GIMMS NDVI3g archive was analyzed for the presence of trends in changing seasonality. Using the Seasonal Trend Analysis (STA procedure, over half (56.30% of land surfaces were found to exhibit significant trends. Almost half (46.10% of the significant trends belonged to three classes of seasonal trends (or changes. Class 1 consisted of areas that experienced a uniform increase in NDVI throughout the year, and was primarily associated with forested areas, particularly broadleaf forests. Class 2 consisted of areas experiencing an increase in the amplitude of the annual seasonal signal whereby increases in NDVI in the green season were balanced by decreases in the brown season. These areas were found primarily in grassland and shrubland regions. Class 3 was found primarily in the Taiga and Tundra biomes and exhibited increases in the annual summer peak in NDVI. While no single attribution of cause could be determined for each of these classes, it was evident that they are primarily found in natural areas (as opposed to anthropogenic land cover conversions and that they are consistent with climate-related ameliorations of growing conditions during the study period.

  8. NDVI from Landsat 8 Vegetation Indices to Study Movement Dynamics of Capra Ibex in Mountain Areas

    Science.gov (United States)

    Pirotti, F.; Parraga, M. A.; Stuaro, E.; Dubbini, M.; Masiero, A.; Ramanzin, M.

    2014-09-01

    In this study we analyse the correlation between the spatial positions of Capra ibex (mountain goat) on an hourly basis and the information obtained from vegetation indices extracted from Landsat 8 datasets. Eight individuals were tagged with a collar with a GNSS receiver and their position was recorded every hour since the beginning of 2013 till 2014 (still ongoing); a total of 16 Landsat 8 cloud-free datasets overlapped that area during that time period. All images were brought to a reference radiometric level and NDVI was calculated. To assess behaviour of animal movement, NDVI values were extracted at each position (i.e. every hour). A daily "area of influence" was calculated by spatially creating a convex hull perimeter around the 24 points relative to each day, and then applying a 120 m buffer (figure 4). In each buffer a set of 24 points was randomly chosen and NDVI values again extracted. Statistical analysis and significance testing supported the hypothesis of the pseudo-random NDVI values to be have, in average, lower values than the real NDVI values, with a p value of 0.129 for not paired t test and p value of accounted for, such as the behaviour of animals when not feeding (e.g. resting) and the statistical significance of daily distributions, which might be improved by analysing broader gaps of time.

  9. The Influence of Drought and Flood Disasters on Rice NDVI in Summer

    International Nuclear Information System (INIS)

    During the period from 1995 to 2010, flooding and drought occurred frequently in North Korea. This greatly affected agriculture. The precipitation data was the main factor evaluated in flood and drought monitoring. In this study, the Z index method was used to estimate the change in precipitation, calculated from TRMM (Tropical Rainfall Measuring Mission) data. The Z index and the NDVI were combined with the map of distribution of rice to analyze the relationship between the Z index and NDVI during the growing months of rice in recent 12 years. The results revealed that the Z index is a good indicator to study the relative changes of precipitation in North Korea, and that the relationship between the Z index and NDVI in a quadratic function

  10. Corn Response to Climate Stress Detected with Satellite-Based NDVI Time Series

    Directory of Open Access Journals (Sweden)

    Ruoyu Wang

    2016-03-01

    Full Text Available Corn growth conditions and yield are closely dependent on climate variability. Leaf growth, measured as the leaf area index, can be used to identify changes in crop growth in response to climate stress. This research was conducted to capture patterns of spatial and temporal corn leaf growth under climate stress for the St. Joseph River watershed, in northeastern Indiana. Leaf growth is represented by the Normalized Difference Vegetative Index (NDVI retrieved from multiple years (2000–2010 of Landsat 5 TM images. By comparing NDVI values for individual image dates with the derived normal curve, the response of crop growth to environmental factors is quantified as NDVI residuals. Regression analysis revealed a significant relationship between yield and NDVI residual during the pre-silking period, indicating that NDVI residuals reflect crop stress in the early growing period that impacts yield. Both the mean NDVI residuals and the percentage of image pixels where corn was under stress (risky pixel rate are significantly correlated with water stress. Dry weather is prone to hamper potential crop growth, with stress affecting most of the observed corn pixels in the area. Oversupply of rainfall at the end of the growing season was not found to have a measurable effect on crop growth, while above normal precipitation earlier in the growing season reduces the risk of yield loss at the watershed scale. The spatial extent of stress is much lower when precipitation is above normal than under dry conditions, masking the impact of small areas of yield loss at the watershed scale.

  11. Trends in normalized difference vegetation index (NDVI) associated with urban development in northern West Siberia

    Science.gov (United States)

    Esau, Igor; Miles, Victoria V.; Davy, Richard; Miles, Martin W.; Kurchatova, Anna

    2016-08-01

    Exploration and exploitation of oil and gas reserves of northern West Siberia has promoted rapid industrialization and urban development in the region. This development leaves significant footprints on the sensitive northern environment, which is already stressed by the global warming. This study reports the region-wide changes in the vegetation cover as well as the corresponding changes in and around 28 selected urbanized areas. The study utilizes the normalized difference vegetation index (NDVI) from high-resolution (250 m) MODIS data acquired for summer months (June through August) over 15 years (2000-2014). The results reveal the increase of NDVI (or "greening") over the northern (tundra and tundra-forest) part of the region. Simultaneously, the southern, forested part shows the widespread decrease of NDVI (or "browning"). These region-wide patterns are, however, highly fragmented. The statistically significant NDVI trends occupy only a small fraction of the region. Urbanization destroys the vegetation cover within the developed areas and at about 5-10 km distance around them. The studied urbanized areas have the NDVI values by 15 to 45 % lower than the corresponding areas at 20-40 km distance. The largest NDVI reduction is typical for the newly developed areas, whereas the older areas show recovery of the vegetation cover. The study reveals a robust indication of the accelerated greening near the older urban areas. Many Siberian cities become greener even against the wider browning trends at their background. Literature discussion suggests that the observed urban greening could be associated not only with special tending of the within-city green areas but also with the urban heat islands and succession of more productive shrub and tree species growing on warmer sandy soils.

  12. Deriving phenological metrics from NDVI through an open source tool developed in QGIS

    Science.gov (United States)

    Duarte, Lia; Teodoro, A. C.; Gonçalves, Hernãni

    2014-10-01

    Vegetation indices have been commonly used over the past 30 years for studying vegetation characteristics using images collected by remote sensing satellites. One of the most commonly used is the Normalized Difference Vegetation Index (NDVI). The various stages that green vegetation undergoes during a complete growing season can be summarized through time-series analysis of NDVI data. The analysis of such time-series allow for extracting key phenological variables or metrics of a particular season. These characteristics may not necessarily correspond directly to conventional, ground-based phenological events, but do provide indications of ecosystem dynamics. A complete list of the phenological metrics that can be extracted from smoothed, time-series NDVI data is available in the USGS online resources (http://phenology.cr.usgs.gov/methods_deriving.php).This work aims to develop an open source application to automatically extract these phenological metrics from a set of satellite input data. The main advantage of QGIS for this specific application relies on the easiness and quickness in developing new plug-ins, using Python language, based on the experience of the research group in other related works. QGIS has its own application programming interface (API) with functionalities and programs to develop new features. The toolbar developed for this application was implemented using the plug-in NDVIToolbar.py. The user introduces the raster files as input and obtains a plot and a report with the metrics. The report includes the following eight metrics: SOST (Start Of Season - Time) corresponding to the day of the year identified as having a consistent upward trend in the NDVI time series; SOSN (Start Of Season - NDVI) corresponding to the NDVI value associated with SOST; EOST (End of Season - Time) which corresponds to the day of year identified at the end of a consistent downward trend in the NDVI time series; EOSN (End of Season - NDVI) corresponding to the NDVI value

  13. A ground-validated NDVI dataset for monitoring vegetation dynamics and mapping phenology in Fennoscandia and the Kola peninsula

    NARCIS (Netherlands)

    Beck, P.S.A.; Jonsson, P.; Hogda, K.A.; Karlsen, S.R.; Skidmore, A.K.; Eklundh, L.

    2007-01-01

    An NDVI dataset covering Fennoscandia and the Kola peninsula was created for vegetation and climate studies, using Moderate Resolution Imaging Spectroradiometer 16-day maximum value composite data from 2000 to 2005. To create the dataset, (1) the influence of the polar night and snow on the NDVI val

  14. Assessment of MODIS sun-sensor geometry variations effect on observed NDVI using MSG SEVIRI geostationary data

    DEFF Research Database (Denmark)

    Fensholt, R.; Sandholt, I.; Proud, Simon Richard;

    2010-01-01

    viewing geometry on red, near-infrared (NIR) and NDVI needs to be quantified. Data from the geostationary MSG (Meteosat Second Generation) SEVIRI (Spinning Enhanced Visible and Infrared Imager) sensor is well suited for this purpose due to the fixed position of the sensor, the spectral resolution...... cloud cover for three consecutive years (2004-2006). An analysis covering the entire range of NDVI revealed day-to-day variations in observed MODIS NDVI of 50-60% for medium dense vegetation (NDVI approximate to 0.5) caused by variations in MODIS view zenith angles (VZAs) between nadir and the high...... forward-scatter view direction. Statistical analysis on red, NIR and NDVI from MODIS and MSG SEVIRI for three transects (characterized by different vegetation densities) showed that both MODIS red and NIR reflectances are highly dependant on MODIS VZA and relative azimuth angle (RAA), due...

  15. Tendências temporais de atividade física no Brasil (2006-2009 Time trends of physical activity in Brazil (2006-2009

    Directory of Open Access Journals (Sweden)

    Pedro C Hallal

    2011-09-01

    Full Text Available OBJETIVO: Analisar as tendências temporais de atividade física (AF nas capitais brasileiras entre 2006 e 2009. MÉTODOS: A análise apresentada neste artigo é baseada nos dados do VIGITEL, totalizando uma amostra anual aproximada de 54.000 indivíduos. Foram analisados indicadores de AF no tempo livre, trabalho, em casa e no deslocamento, além do tempo assistindo à televisão e de inatividade considerando todos os domínios de AF. A variação dos indicadores no período foi aferida por meio de modelos de regressão de Poisson, tendo como variável explanatória o ano do inquérito. Foi considerada significativa a evolução correspondente a um coeficiente de regressão diferente de zero (pOBJECTIVE: To examine time trends in physical activity (PA in Brazilian state capitals from 2006 to 2009. METHODS: This analysis is based on data from the Telephone-based Surveillance of Risk and Protective Factors for Chronic Diseases (VIGITEL accounting for an annual sample of approximately 54,000 individuals. PA indicators were analyzed in free time (leisure, work, home and transportation, time spent in front of the television and inactivity considering all PA domains. Poisson regression models were used to measure the variation of indicators over time. We considered the changes corresponding to a regression coefficient different from zero as being statistically significant (p<0.05. RESULTS: The percentage of active commuters increased from 11.7 to 14.4% (p<0.001 whereas the proportion of physically inactive individuals in the four domains decreased from 11.7 to 8.7% (p<0.001. There were no significant changes in the other indicators. Women were less active than men in all indicators, except for household chores. However, in this indicator the percentage of active women decreased from 71.4 to 67.1% (p<0.001. Between 2006 and 2009, PA levels in the Brazilian population were stable during free time and household chores, but increased in transportation

  16. Quantification of spatial distribution of vegetation in the Qilian Mountain area with MODIS NDVI

    NARCIS (Netherlands)

    Jin, X.; Wan, L.; Zhang, Y.K.; Hu, G.; Schaepman, M.E.; Clevers, J.G.P.W.; Su, Z.

    2009-01-01

    The spatial distribution of vegetation in the Qilian Mountain area was quantified with remote sensing data. The MODIS NDVI values for June, July, August and September are the best indicators for the vegetation growth during a year in this area and thus were used in this study. The results obtained b

  17. NDVI dynamics of the taiga zone in connection with modern climate changes

    Science.gov (United States)

    Bobkov, A.; Panidi, E.; Torlopova, N.; Tsepelev, V.

    2015-04-01

    This research is dedicated to the investigation of the relations between the XXI century climate changes and Normalized Difference Vegetation Index (NDVI) variability of the taiga zone. For this purposes was used the observations of vegetation variability on the test area located nearby Syktyvkar city (Komi Republic, Russia), 16-day averages of NDVI data derived from TERRA/MODIS space imagery (spatial resolution is about 250 meters), and the air temperature and precipitation observations from Syktyvkar meteorological station. The research results confirmed the statistically significant positive correlation between NDVI and air temperature for all vegetation types of the test area, for both spring and autumn seasons. The weakest correlation was found for coniferous forest, namely, pine forest on poor soils, and the strongest correlation was found for meadows and bogs. Additionally the map of NDVI trends of the test area shows that the sectors of greatest positive trend located on the territories with non-forest cover, and as a result, the positive trend of air temperature is indicated most brightly on vegetation of non-forest lands. Thereby these lands can serve as climate changes indicator in the investigated region. The study was partially supported by Russian Foundation for Basic Research (RFBR), research project No. 14-05-00858 a.

  18. Spatio-Temporal Relationship Between Surface Temperature and NDVI Using Remotely Sensed data

    Science.gov (United States)

    Ghobadi, Yasser; Pradhan, Biswajeet; Kabiri, Keivan

    2016-07-01

    Land surface temperature (LST) is a significant factor to analyze the global climate changes, and LULC (Land use/Land cover) changes, as well as urban thermal behavior. Land surface temperature exhibit the surface atmosphere in relation with energy flux between earth and atmosphere. This paper intended to examine the evaluation of LST and assessment of relationship between LST and normalized difference vegetation index (NDVI) with associated different LULC. Al- Hawizeh wetland located in the Iraq-Iran border was selected as a study area. Two Landsat satellite thermal infrared (TIR) images of October 26, 1998, thematic mapper (TM), and October 26, 2002 enhanced thematic mapper (ETM+) were used. Both images were corrected geometrically and atmospherically before carried out any analysis. NDVI was estimated from reflectance values of the visible band (band 3, Red) and the near infrared band (band 4, VNIR). Maximum likelihood classifier (MLC) was applied to determine the different LULC. Plank equation was utilized to extract land surface temperature over the study region. The results provide information about the spatial distribution of LST over different LULC during mentioned date. The highest mean temperature was observed over the rangeland and the lowest mean temperature was found in water bodies. The results of regression analysis exhibited that the LST and NDVI has an inverse correlation except for water bodies. The negative correlation coefficient was observed over vegetation (-0.733, R2=0.66). Keywords-component; Land Surface Temperature, Remote Sensing, Al-Havizeh wetland, Regression Analysis, NDVI, GIS

  19. Forest fire risk estimation from time series analisys of NOAA NDVI data

    Science.gov (United States)

    Gabban, Andrea; Liberta, Giorgio; San-Miguel-Ayanz, Jesus; Barbosa, Paulo

    2004-02-01

    The values of the Normalized Difference Vegetation Index obtained from NOAA Advanced Very High Resolution Radiometer (AVHRR) have often been used for forestry application, including the assessment of fire risk. Forest fire risk estimates were based mainly on the decrease of NDVI values during the summer in areas subject to summer drought. However, the inter-annual variability of the vegetation response has never been extensively taken into account. The present work was based on the assumption that Mediterranean vegetation is adapted to summer drought and one possible estimator of the vegetation stress was the inter-annual variability of the vegetation status, as reflected by NDVI values. This article presents a novel methodology for the assessment of fire risk based on the comparison of the current NDVI values, on a given area, with the historical values along a time series of 13 years. The first part of the study is focused on the characterization of the Minimum and Maximum long term daily images. The second part is centered on the best method to compare the long term Maximum and Minimum with the current NDVI. A statistical index, Dynamic Relative Greenness, DRG, was tested on as a novel potential fire risk indicator.

  20. Monitoring leaf area index at watershed level through NDVI from Landsat-7/ETM+ data

    Directory of Open Access Journals (Sweden)

    Xavier Alexandre Cândido

    2004-01-01

    Full Text Available Leaf area index (LAI is an important parameter of the vegetation canopy, and is used, for instance, to estimate evapotranspiration, an important component of the hydrological cycle. This work analyzed the relationship between LAI, measured in field, and NDVI from four dates (derived from Landsat-7/ETM+ data, and with such vegetation index, to generate and analyze LAI maps of the study area for the diverse dates. LAI data were collected monthly in the field with LAI-2000 equipment in stands of sugar cane, pasture, corn, eucalypt, and riparian forest. The relationships between LAI and NDVI were adjusted by a potential model; 57% to 72% of the NDVI variance were explained by the LAI. LAI maps generated by empirical relationships between LAI and NDVI showed reasonable precision (standard error of LAI estimate ranged from 0.42 to 0.87 m² m-2. The mean LAI value of each monthly LAI map was shown to be related to the total precipitation in the three previous months.

  1. Fourier analysis of time series of NOAA-AVHRR NDVI composites to map isogrowth zones

    NARCIS (Netherlands)

    Menenti, M.; Azzali, S.; Verhoef, W.

    1995-01-01

    A measurement of the quality of vegetation zones in dynamic terms is provided by the Fourier analysis of time series of AVHRR/NDVI monthly observations over ten years. The present approach is shown to be a powerful way to classify and extract various dynamic parameters of the vegetation in Southern

  2. Detecting clear-cuts and decreases in forest vitality using MODIS NDVI time series

    NARCIS (Netherlands)

    Lambert, J.; Denux, J.P.; Verbesselt, J.; Balent, G.; Cheret, V.

    2015-01-01

    This paper examines the potential of MODIS-NDVI time series for detecting clear-cuts in a coniferous forest stand in the south of France. The proposed approach forms part of a survey monitoring the status of forest health and evaluating the forest decline phenomena observed over the last few decades

  3. Using MODIS NDVI products for vegetation state monitoring on the oil production territory in Western Siberia

    Directory of Open Access Journals (Sweden)

    Kovalev Anton

    2016-01-01

    Full Text Available Article describes the results of using remote sensing data for vegetation state monitoring on the oil field territories in Western Siberia. We used MODIS data product providing the normalized difference vegetation index (NDVI values. Average NDVI values of each studied area were calculated for the period from 2010 to 2015 with one year interval for June, July and August. Analysis was carried out via an open tool of geographic information system QGIS used for spatial analysis and calculation of statistical parameters within chosen polygons. Results are presented in graphs showing the variation of NDVI for each study area and explaining the changes in trend lines for each field. It is shown that the majority of graphs are similar in shape which is caused by similar weather conditions. To confirm these results, we have conducted data analysis including temperature conditions and information about the accidents for each area. Abnormal changes in NDVI values revealed an emergency situation on the Priobskoe oil field caused by the flood in 2015. To sum up, the research results show that vegetation of studied areas is in a sufficiently stable state.

  4. Characterising and quantifying vegetative drought in East Africa using fuzzy modelling and NDVI data

    NARCIS (Netherlands)

    Rulinda, Coco M.; Dilo, Arta; Bijker, Wietske; Stein, Alfred

    2012-01-01

    This study aims at improving the characterisation and quantification of vegetative drought as a vague spatial phenomenon. 10-day NOAA-AVHRR NDVI images of East Africa from September 2005 to April 2006 are used. Vegetative drought is characterised using a membership function to model the gradual tran

  5. Trends in the normalized difference vegetation index (NDVI) associated with urban development in arctic and subarctic Western Siberia

    Science.gov (United States)

    Outten, S.; Miles, V.; Ezau, I.

    2015-12-01

    Changes in normalized difference vegetation index (NDVI) in the high Arctic have been reliably documented, with widespread "greening" (increase in NDVI), specifically along the northern rim of Eurasia and Alaska. Whereas in West Siberia south of 65N, widespread "browning" (decrease in NDVI) has been noted, although the causes remain largely unclear. In this study we report results of statistical analysis of the spatial and temporal changes in NDVI around 28 major urban areas in the arctic and subarctic Western Siberia. Exploration and exploitation of oil and gas reserves has led to rapid industrialization and urban development in the region. This development has significant impact on the environment and particularly in the vegetation cover in and around the urbanized areas. The analysis is based on 15 years (2000-2014) of high-resolution (250 m) Moderate Resolution Imaging Spectroradiometer (MODIS) data acquired for summer months (June through August) over the entire arctic and subarctic Western Siberian region. The analysis shows that the NDVI background trends are generally in agreement with the trends reported in previous coarse-resolution NDVI studies. Our study reveals greening over the arctic (tundra and tundra-forest) part of the region. Simultaneously, the southern (boreal taiga forest) part is browning, with the more densely vegetation areas or areas with highest NDVI, particularly along Ob River showing strong negative trend. The unexpected and interesting finding of the study is statistically robust indication of the accelerated increase of NDVI ("greening") in the older urban areas. Many Siberian cities become greener even against the decrease in the NDVI background. Moreover, interannual variations of urban NDVI are not coherent with the NDVI background variability. We also find that in tundra zones, NDVI values are higher in a 5-10 km buffer zone around the city edge than in rural areas (40 km distance from the city edge), and in taiga in a 5-10 km

  6. An application of plot-scale NDVI in predicting carbon dioxide exchange and leaf area index in heterogeneous subarctic tundra

    International Nuclear Information System (INIS)

    This paper reported on a study that examined the flow of carbon into and out of tundra ecosystems. It is necessary to accurately predict carbon dioxide (CO2) exchange in the Tundra because of the impacts of climate change on carbon stored in permafrost. Understanding the relationships between the normalized difference vegetation index (NDVI) and vegetation and CO2 exchange may explain how small-scale variation in vegetation community extends to remotely sensed estimates of landscape characteristics. In this study, CO2 fluxes were measured with a portable chamber in a range of Tundra vegetation communities. Biomass and leaf area were measured with destructive harvest, and NDVI was obtained using a hand-held infrared camera. There was a weak correlation between NDVI and leaf area index in some vegetation communities, but a significant correlation between NDVI and biomass, including mosses. NDVI was found to be strongly related to photosynthetic activity and net CO2 uptake in all vegetation groups. However, NDVI related to ecosystem respiration only in wet sedge. It was concluded that at plot scale, the ability of NDVI to predict ecosystem properties and CO2 exchange in heterogeneous Tundra vegetation is variable.

  7. Assessing Fractional Tree, Grass, and Bare Soil Cover from NDVI and Rainfall Time Series along the Kalahari Transect, Africa

    Science.gov (United States)

    Scanlon, T. M.; Albertson, J. D.; Caylor, K. K.; Williams, C. A.

    2001-12-01

    Savanna ecosystems are water-limited, a characteristic that can be exploited to estimate fractional cover of trees, grass, and bare soil over large-scale areas from synthesis of remote sensing and rainfall measurements. A method is presented to estimate fractional cover components along the Kalahari Transect (KT), an aridity gradient in southern Africa, based upon the differing ways in which grasses and trees respond to rainfall. Mean wet season normalized difference vegetation index (NDVI) and the sensitivity of the NDVI to variation in wet season rainfall are used as input into a linear unmixing model, and end-members for this analysis are extracted on the basis of best fit to the observed data. The end-members for the mixing analysis are consistent with the qualitative characteristics of trees (high NDVI, low sensitivity of NDVI to interannual variations in rainfall), bare soil (low NDVI, low sensitivity), and the transient grass/ bare soil area (moderate NDVI, high sensitivity). Sensitivity of NDVI to rainfall was based upon the relationship between NDVI and the standardized anomalies, or z-score, of the wet season precipitation, resulting in a 22% improvement in the number of significant relationships (parea is limited by the tree fractional cover on the wetter end of the transect, peaks at approximately 450 mm of mean wet season rainfall, and is limited by rainfall on the more arid portion of the transect. With NDVI for grass inferred from the data, predictions of yearly tree, grass, and bare soil fractional cover can be derived. No calibration or training sets were required for this unmixing procedure, and an additional advantage of this method over traditional unmixing approaches is that cover components can be predicted for future rainfall scenarios. This remote sensing-based model framework, together with a tree/grass interaction submodel, could be used to predict long-term migration of the cover components along this gradient in response to climate

  8. Alpine Grassland Phenology as Seen in AVHRR, VEGETATION, and MODIS NDVI Time Series - a Comparison with In Situ Measurements

    Directory of Open Access Journals (Sweden)

    Stefan Wunderle

    2008-04-01

    Full Text Available This study evaluates the ability to track grassland growth phenology in the Swiss Alps with NOAA-16 Advanced Very High Resolution Radiometer (AVHRR Normalized Difference Vegetation Index (NDVI time series. Three growth parameters from 15 alpine and subalpine grassland sites were investigated between 2001 and 2005: Melt-Out (MO, Start Of Growth (SOG, and End Of Growth (EOG.We tried to estimate these phenological dates from yearly NDVI time series by identifying dates, where certain fractions (thresholds of the maximum annual NDVI amplitude were crossed for the first time. For this purpose, the NDVI time series were smoothed using two commonly used approaches (Fourier adjustment or alternatively Savitzky-Golay filtering. Moreover, AVHRR NDVI time series were compared against data from the newer generation sensors SPOT VEGETATION and TERRA MODIS. All remote sensing NDVI time series were highly correlated with single point ground measurements and therefore accurately represented growth dynamics of alpine grassland. The newer generation sensors VGT and MODIS performed better than AVHRR, however, differences were minor. Thresholds for the determination of MO, SOG, and EOG were similar across sensors and smoothing methods, which demonstrated the robustness of the results. For our purpose, the Fourier adjustment algorithm created better NDVI time series than the Savitzky-Golay filter, since latter appeared to be more sensitive to noisy NDVI time series. Findings show that the application of various thresholds to NDVI time series allows the observation of the temporal progression of vegetation growth at the selected sites with high consistency. Hence, we believe that our study helps to better understand largescale vegetation growth dynamics above the tree line in the European Alps.

  9. NDVI saturation adjustment: a new approach for improving cropland performance estimates in the Greater Platte River Basin, USA

    Science.gov (United States)

    Gu, Yingxin; Wylie, Bruce K.; Howard, Daniel M.; Phuyal, Khem P.; Ji, Lei

    2013-01-01

    In this study, we developed a new approach that adjusted normalized difference vegetation index (NDVI) pixel values that were near saturation to better characterize the cropland performance (CP) in the Greater Platte River Basin (GPRB), USA. The relationship between NDVI and the ratio vegetation index (RVI) at high NDVI values was investigated, and an empirical equation for estimating saturation-adjusted NDVI (NDVIsat_adjust) based on RVI was developed. A 10-year (2000–2009) NDVIsat_adjust data set was developed using 250-m 7-day composite historical eMODIS (expedited Moderate Resolution Imaging Spectroradiometer) NDVI data. The growing season averaged NDVI (GSN), which is a proxy for ecosystem performance, was estimated and long-term NDVI non-saturation- and saturation-adjusted cropland performance (CPnon_sat_adjust, CPsat_adjust) maps were produced over the GPRB. The final CP maps were validated using National Agricultural Statistics Service (NASS) crop yield data. The relationship between CPsat_adjust and the NASS average corn yield data (r = 0.78, 113 samples) is stronger than the relationship between CPnon_sat_adjust and the NASS average corn yield data (r = 0.67, 113 samples), indicating that the new CPsat_adjust map reduces the NDVI saturation effects and is in good agreement with the corn yield ground observations. Results demonstrate that the NDVI saturation adjustment approach improves the quality of the original GSN map and better depicts the actual vegetation conditions of the GPRB cropland systems.

  10. NDVI-Based Long-Term Vegetation Dynamics and Its Response to Climatic Change in the Mongolian Plateau

    Directory of Open Access Journals (Sweden)

    Gang Bao

    2014-09-01

    Full Text Available The response of vegetation to regional climate change was quantified between 1982 and 2010 in the Mongolian plateau by integrating the Advanced Very High Resolution Radiometer (AVHRR Global Inventory Modeling and Mapping Studies (GIMMS normalized difference vegetation index (NDVI (1982–2006 and the Moderate Resolution Imaging Spectroradiometer (MODIS NDVI (2000–2010. Average NDVI values for the growing season (April–October were extracted from the AVHRR and MODIS NDVI datasets after cross-calibrating and consistency checking the dataset, based on the overlapping period of 2000–2006. Correlations between NDVI and climatic variables (temperature and precipitation were analyzed to understand the impact of climate change on vegetation dynamics in the plateau. The results indicate that the growing-season NDVI generally exhibited an upward trend with both temperature and precipitation before the mid- or late 1990s. However, a downward trend in the NDVI with significantly decreased precipitation has been observed since the mid- or late 1990s. This is an apparent reversal in the NDVI trend from 1982 to 2010. Pixel-based analysis further indicated that the timing of the NDVI trend reversal varied across different regions and for different vegetation types. We found that approximately 66% of the plateau showed an increasing trend before the reversal year, whereas 60% showed a decreasing trend afterwards. The vegetation decline in the last decade is mostly attributable to the recent tendency towards a hotter and drier climate and the associated widespread drought stress. Monitoring precipitation stress and associated vegetation dynamics will be important for raising the alarm and performing risk assessments for drought disasters and other related natural disasters like sandstorms.

  11. NDVI as a tool for measuring impact of climate variability upon vegetation

    Science.gov (United States)

    Delitala, Alessandro M. S.; Vizzari, Marco; Capece, Paolo; Fiori, Michele; Mannu, Giovanna Maria; Pacicco, Ciro Luca; Pinna Nossai, Roberto

    2010-05-01

    Land-atmosphere interactive processes are useful to understand impacts of year by year climate variability and to highlight possible trends, since the status of the natural vegetation cover is strongly controlled by climate factors. The so-called NDVI (Normalized Difference Vegetation Index), derived from the red and the near infrared channels of NOAA satellite, is a reliable indicator applicable to the analysis of photosynthetic biomass variations in vegetated areas. NDVI images, derived on a monthly basis by maximum composite value technique, can become a useful tool to monitor the dynamics of vegetation and to determine the maximum level of vegetation greenness observed over every year. Interannual variability of precipitation is likely to have a significant impact on the greenness of vegetation cover, since rainy seasons are expected to stimulate a much richer plants development than drier ones. The present poster intends to outline a research, jointly carried by ARPAS (the Regional Environmental Protection Agency of Sardinia) and the 'Department of Man and Territory' of the University of Perugia, that aimed to correlate the year by year variability of hydrological variables (precipitation and soil water content) and the maximum annual NDVI over the island of Sardinia. In order to do that, the authors defined four test areas, extending from 235 km2 to 1015 km2. Test areas were chosen in order to be mostly covered by natural vegetations, according to CORINE land-cover. Over such areas surface measures by ARPAS stations were compared against annual maximum NDVI index from 1998 to 2008, focusing on the so-called 'rainy season' that in Sardinia ranges from October to April. Precipitation for the selected areas was measured with the network of ground stations of ARPAS. Evapotranspiration was estimated by means of Hargreaves-Samani method applied to data from the above stations. Finally, estimation of the soil moisture content was carried out by means of a daily time

  12. Tabagismo em estudantes de Medicina: tendências temporais e fatores associados Smoking among medical students: temporal trends and related variables

    Directory of Open Access Journals (Sweden)

    Ana Maria Baptista Menezes

    2004-06-01

    Full Text Available INTRODUÇÃO: Após o declínio observado na prevalência de tabagismo entre estudantes de Medicina entre as décadas de 1960 e 1980, parece estar ocorrendo, atualmente, uma estabilização nessa prevalência. OBJETIVO: Avaliar as tendências temporais de tabagismo entre estudantes de Medicina da Universidade Federal de Pelotas (RS nos últimos dezessete anos, e alguns dos fatores associados ao hábito de fumar desses estudantes. MÉTODO: Estudos transversais com metodologias comparáveis foram conduzidos em 1986, 1991, 1996 e 2002. Questionários auto-aplicáveis foram utilizados. Definiu-se como fumante o indivíduo que fumava mais de um cigarro por dia há mais de um mês. Foram realizadas análises descritivas iniciais, análises brutas com utilização dos testes de qui-quadrado para heterogeneidade e tendência linear, e regressão de Poisson para avaliar o efeito do ano cursado sobre a freqüência de tabagismo, com controle para a idade do estudante. RESULTADOS: A prevalência atual de tabagismo entre os estudantes foi de 10,1%, valor estatisticamente similar ao dos levantamentos de 1991 e 1996. Não foram encontradas diferenças na prevalência de tabagismo por sexo, idade, tabagismo materno ou paterno. A freqüência de tabagismo aumentou durante a faculdade. CONCLUSÕES: A tendência de declínio na prevalência de tabagismo em estudantes de Medicina da Universidade Federal de Pelotas parece estar sendo substituída por uma estabilização em torno de 10% a 15%. O combate ao fumo ainda parece indispensável em ambientes universitários, especialmente nas escolas de Medicina.BACKGROUND: Although the prevalence of smoking among medical students declined steadily between the 1960s and 1980s, it seems to have stabilized in recent years. OBJECTIVES: To evaluate temporal trends, over the last 17 years, in the smoking habits of medical students at the Universidade Federal de Pelotas, in the state of Rio Grande do Sul, Brazil, and to identify

  13. Aspectos prosódicos temporais da leitura de escolares com dislexia do desenvolvimento Temporal prosodic aspects of reading in students with developmental dyslexia

    Directory of Open Access Journals (Sweden)

    Luciana Mendonça Alves

    2009-01-01

    Full Text Available OBJETIVO: Analisar, do ponto de vista fonético, por meio de medidas acústicas e perceptivas, os aspectos prosódicos temporais presentes na leitura em voz alta de escolares com e sem dislexia, a fim de identificar diferenças de desempenho entre os dois tipos de leitores que possam apontar para características peculiares da dislexia. MÉTODOS: Gravação da leitura de um texto por 40 escolares (entre nove e 14 anos, cursando da 3ª à 5ª série, sendo 10 disléxicos (grupo clínico e 30 escolares sem queixas de alterações de aprendizagem (grupo não-clínico. Os dados foram analisados perceptivamente e acusticamente, utilizando-se o programa WinPitch. As seguintes medidas foram realizadas: duração e localização das pausas, tempo total de elocução, taxa de elocução, tempo de articulação e taxa de articulação. RESULTADOS: Em comparação com o grupo não-clínico, o grupo clínico apresentou maior número de pausas e pausas mais longas; os valores obtidos para as taxas de elocução e de articulação indicaram respectivamente menor velocidade de leitura e uma lentidão na produção de cada gesto articulatório. CONCLUSÃO: As dificuldades identificadas no processamento da leitura pelas crianças com dislexia dificultam a organização prosódica na leitura de um texto.PURPOSE: To analyze the temporal prosodic aspect in loud reading of students with and without dyslexia from the phonetic point of view through acoustic and perceptual evaluation, in order to identify differences in performance between the two types of readers that may point to particular characteristics of dyslexia. METHODS: Forty students from 3rd to 5th grades with ages ranging from nine to 14 years, ten dyslexic (clinical group and 30 without any complaints of learning deficits (non-clinical group were recorded during loud reading of a text. Data were perceptually and acoustically analyzed using the software WinPitch. The following measures were taken: pause

  14. A five-year analysis of MODIS NDVI and NDWI for grassland drought assessment over the central Great Plains of the United States

    Science.gov (United States)

    Gu, Y.; Brown, J.F.; Verdin, J.P.; Wardlow, B.

    2007-01-01

    A five-year (2001-2005) history of moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) data was analyzed for grassland drought assessment within the central United States, specifically for the Flint Hills of Kansas and Oklahoma. Initial results show strong relationships among NDVI, NDWI, and drought conditions. During the summer over the Tallgrass Prairie National Preserve, the average NDVI and NDWI were consistently lower (NDVI 0.6 and NDWI>0.4). NDWI values exhibited a quicker response to drought conditions than NDVI. Analysis revealed that combining information from visible, near infrared, and short wave infrared channels improved sensitivity to drought severity. The proposed normalized difference drought index (NDDI) had a stronger response to summer drought conditions than a simple difference between NDVI and NDWI, and is therefore a more sensitive indicator of drought in grasslands than NDVI alone. Copyright 2007 by the American Geophysical Union.

  15. Evaluation of vegetation cover using the normalized difference vegetation index (NDVI

    Directory of Open Access Journals (Sweden)

    Gabriela Camargos Lima

    2013-08-01

    Full Text Available Soil loss by water erosion is the main cause of soil degradation in Brazil. However, erosion can be reduced by the presence of vegetation. The Normalized Difference Vegetation Index (NDVI makes it possible to identify the vegetative vigor of crops or natural vegetation which facilities the identification of areas with vegetation covers. This information is very important in identifying the phenomena which might be occurring in a particular area, especially those related to soil degradation by water erosion. Thus, the aim of this work was to assess the canopy cover by using NDVI, checking the image accuracy using the Coverage Index (CI based on the Stocking method, in the Sub-basin of Posses, which belongs to the Cantareira System, located in the Extrema municipality, Minas Gerais, Brazil. Landsat-5 TM images were used. The sub-basin of Posses was very altered in comparison to the surrounding areas. The NDVI technique proved to be a suitable tool to assess the uses that occur in the sub-basin of Posses, as validated by the Stocking methodology. The map derived from NDVI allowed the geographic distribution of different land uses to be observed and allowed for the identification of critical areas in relation to vegetation cover as well. This finding can be used to optimize efforts to recover and protect soil in areas with bare soil and degraded pasture, in order to reduce environmental degradation. The CI has not exceeded 40% for land use classes that occur in the majority of the sub-basin (91%, except in areas of woody vegetation.

  16. Mapping deciduous forests by using time series of filtered MODIS NDVI and neural networks

    OpenAIRE

    Thomaz Chaves de Andrade Oliveira; Luis Marcelo Tavares de Carvalho; Luciano Teixeira de Oliveira; Adriana Zanella Martinhago; Fausto Weimar Acerbi Júnior; Mariana Peres de Lima

    2010-01-01

    Multi-temporal images are now of standard use in remote sensing of vegetation during monitoring and classification.Temporal vegetation signatures (i. e., vegetation indices as functions of time) generated, poses many challenges, primarily due tosignal to noise-related issues. This study investigates which methods generate the most appropriate smoothed curves of vegetationsignatures on MODIS NDVI time series. The filtering techniques compared were the HANTS algorithm which is based on Fouriera...

  17. Corn Response to Climate Stress Detected with Satellite-Based NDVI Time Series

    OpenAIRE

    Ruoyu Wang; Keith Cherkauer; Laura Bowling

    2016-01-01

    Corn growth conditions and yield are closely dependent on climate variability. Leaf growth, measured as the leaf area index, can be used to identify changes in crop growth in response to climate stress. This research was conducted to capture patterns of spatial and temporal corn leaf growth under climate stress for the St. Joseph River watershed, in northeastern Indiana. Leaf growth is represented by the Normalized Difference Vegetative Index (NDVI) retrieved from multiple years (2000–2010) o...

  18. Comparison of eMODIS and MOD/MYD13A2 NDVI products during 2012-2014 spring green-up periods in Alaska and northwest Canada

    Science.gov (United States)

    Verbyla, David

    2015-04-01

    Accurate monitoring of vegetation dynamics is required to understand the inter-annual variability and long term trends in terrestrial carbon exchange in tundra and boreal ecoregions. In western North America, two Normalized Vegetation Index (NDVI) products based on spectral reflectance data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are available. The MOD/MYD13A2 NDVI product is available as a 16-day composite product in a sinusoidal projection as global hdf tiles. The eMODIS Alaska NDVI product is available as a 7-day composite geotif product in a regional equal area conic projection covering Alaska and the entire Yukon River Basin. These two NDVI products were compared for the 2012-2014 late May-late June spring green-up periods in Alaska and the Yukon Territory. Relative to the MOD/MYD13A2 NDVI product, it is likely that the eMODIS NDVI product contained more cloud-contaminated NDVI values. For example, the MOD/MYD13A2 product flagged substantially fewer pixels as "good quality" in each 16-day composite period compared to the corresponding MODIS Alaska NDVI product from a 7-day composite period. During the spring green-up period, when field-based NDVI increases, the eMODIS NDVI product averaged 43 percent of pixels that declined by at least 0.05 NDVI between 2 composite periods, consistent with cloud-contamination problems, while the MOD/MYD13A2 NDVI averaged only 6 percent of pixels. Based on a cloudy Landsat-8 scene, the eMODIS compositing process selected 23 percent pixels, while the MOD/MYD13A2 compositing process selected less than 0.003 percent pixels. Based on the results, it appears that the MOD/MYD13A2 NDVI product is superior for scientific applications based on NDVI phenology in the tundra and boreal regions of northwestern North America.

  19. MODIS NDVI Change Detection Techniques and Products Used in the Near Real Time ForWarn System for Detecting, Monitoring, and Analyzing Regional Forest Disturbances

    Science.gov (United States)

    Spruce, Joseph P.; Hargrove, William; Gasser, Jerry; Smoot, James; Kuper, Philip D.

    2014-01-01

    This presentation discusses MODIS NDVI change detection methods and products used in the ForWarn Early Warning System (EWS) for near real time (NRT) recognition and tracking of regionally evident forest disturbances throughout the conterminous US (CONUS). The latter has provided NRT forest change products to the forest health protection community since 2010, using temporally processed MODIS Aqua and Terra NDVI time series data to currently compute and post 6 different forest change products for CONUS every 8 days. Multiple change products are required to improve detectability and to more fully assess the nature of apparent disturbances. Each type of forest change product reports per pixel percent change in NDVI for a given 24 day interval, comparing current versus a given historical baseline NDVI. EMODIS 7 day expedited MODIS MOD13 data are used to obtain current and historical NDVIs, respectively. Historical NDVI data is processed with Time Series Product Tool (TSPT); and 2) the Phenological Parameters Estimation Tool (PPET) software. While each change products employ maximum value compositing (MVC) of NDVI, the design of specific products primarily differs in terms of the historical baseline. The three main change products use either 1, 3, or all previous years of MVC NDVI as a baseline. Another product uses an Adaptive Length Compositing (ALC) version of MVC to derive an alternative current NDVI that is the freshest quality NDVI as opposed to merely the MVC NDVI across a 24 day time frame. The ALC approach can improve detection speed by 8 to 16 days. ForWarn also includes 2 change products that improve detectability of forest disturbances in lieu of climatic fluctuations, especially in the spring and fall. One compares current MVC NDVI to the zonal maximum under the curve NDVI per pheno-region cluster class, considering all previous years in the MODIS record. The other compares current maximum NDVI to the mean of maximum NDVI for all previous MODIS years.

  20. Spatiotemporal NDVI, LAI, albedo, and surface temperature dynamics in the southwest of the Brazilian Amazon forest

    Science.gov (United States)

    Querino, Carlos Alexandre Santos; Beneditti, Cristina Aparecida; Machado, Nadja Gomes; da Silva, Marcelo José Gama; da Silva Querino, Juliane Kayse Albuquerque; dos Santos Neto, Luiz Alves; Biudes, Marcelo Sacardi

    2016-04-01

    During the last decades, the Amazon rainforest underwent uncontrolled exploitation that modified its environmental variables. The current paper analyzes the spatiotemporal dynamics of the normalized difference vegetation index (NDVI), leaf area index (LAI), and surface albedo, and temperature in two different vegetation covers, preserved and deforested areas. We calculated the remote-sensing products using Landsat 5 TM images obtained during the dry season 1984, 1991, 2000, and 2011 of the central region of the State of Rondônia, Brazil. The results showed a reduction of vegetation indexes NDVI (˜0.70 in 1984 to ˜0.27 in 2011) and LAI (˜1.8 in 1984 to ˜0.3 in 2011), with an increase of surface albedo (0.12 in 1984 to 0.20 in 2011) and temperature (˜24°C in 1984 to 30°C in 2011) as the effect of the rainforest converted in grassland during the study period. No changes in any variables were observed in the protected area. Forest conversion into grassland resulted in a decrease of 69% in NDVI and 110% in LAI and a rise of 59% and 24% in albedo and surface temperature, respectively.

  1. Towards Detection of Cutting in Hay Meadows by Using of NDVI and EVI Time Series

    Directory of Open Access Journals (Sweden)

    Andrej Halabuk

    2015-05-01

    Full Text Available The main requirement for preserving European hay meadows in good condition is through prerequisite cut management. However, monitoring these practices on a larger scale is very difficult. Our study analyses the use of MODIS vegetation indices products, namely EVI and NDVI, to discriminate cut and uncut meadows in Slovakia. We tested the added value of simple transformations of raw data series (seasonal statistics, first difference series, compared EVI and NDVI, and analyzed optimal periods, the number of scenes and the effect of smoothing on classification performance. The first difference series transformation saw substantial improvement in classification results. The best case NDVI series classification yielded overall accuracy of 85% with balanced rates of producer’s and user’s accuracies for both classes. EVI yielded slightly lower values, though not significantly different, although user accuracy of cut meadows achieved only 67%. Optimal periods for discriminating cut and uncut meadows lay between 16 May and 4 August, meaning only seven consecutive images are enough to accurately detect cutting in hay meadows. More importantly, the 16-day compositing period seemed to be enough for detection of cutting, which would be the time span that might be hopefully achieved by upcoming on-board HR sensors (e.g., Sentinel-2.

  2. Multisensor NDVI-Based Monitoring of the Tundra-Taiga Interface (Mealy Mountains, Labrador, Canada

    Directory of Open Access Journals (Sweden)

    Heather Ward

    2013-03-01

    Full Text Available The analysis of a series of five normalized difference vegetation index (NDVI images produced information about a Labrador (Canada portion of the tundra-taiga interface. The twenty-five year observation period ranges from 1983 to 2008. The series composed of Landsat, SPOT and ASTER images, provided insight into regional scale characteristics of the tundra-taiga interface that is usually monitored from coarse resolution images. The image set was analyzed by considering an ordinal classification of the NDVI to account for the cumulative effect of differences of near-infrared spectral resolutions, the temperature anomalies, and atmospheric conditions. An increasing trend of the median values in the low, intermediate and high NDVI classes is clearly marked while accounting for variations attributed to cross-sensor radiometry, phenology and atmospheric disturbances. An encroachment of the forest on the tundra for the whole study area was estimated at 0 to 60 m, depending on the period of observation, as calculated by the difference between the median retreat and advance of an estimated location of the tree line. In small sections, advances and retreats of up to 320 m are reported for the most recent four- and seven-year periods of observations.

  3. Interannual Variations in Growing-Season NDVI and Its Correlation with Climate Variables in the Southwestern Karst Region of China

    Directory of Open Access Journals (Sweden)

    Wenjuan Hou

    2015-08-01

    Full Text Available In this study, the updated Global Inventory Modeling and Mapping Studies (GIMMS Normalized Difference Vegetation Index (NDVI dataset for growing season (April to October, which can better reflect the vegetation vigor, was used to investigate the interannual variations in NDVI and its relationship with climatic factors, in order to preliminarily understand the climate impact on vegetation and provide theoretical basis for the response of ecosystem to climate change. Multivariate linear regression models, including the Ordinary Least Squares (OLS and Geographically Weighted Regression (GWR, were adopted to analyze the correlation between NDVI and climatic factors (temperature and precipitation together. Average growing-season NDVI significantly increased at a rate of 0.0015/year from 1982 to 2013, larger than several regions in China. On the whole, its relationship with temperature is positive and also stronger than precipitation, which indicated that temperature may be a limiting factor for the vegetation growth in the Karst region. Moreover, the correlation coefficients between grassland NDVI and climatic factors are the largest. Under the background of NDVI increasing trend from 1982 to 2013, the period of 2009–2012 was chosen to investigate the influencing factors of a sharp decline in NDVI. It can be found that the reduced temperature and solar radiation, caused by the increase in cloud cover and precipitation, may play important roles in the vegetation cover change. All in all, the systematic research on the interannual variations of growing-season NDVI and its relationship with climate revealed the heterogeneity and variability in the complicated climate change in the Karst ecosystem for the study area. It is the Karst characteristics that hinder obtaining more representative conclusions and tendencies in this region. Hence, more attention should be paid to promoting Karst research in the future.

  4. Uso de séries temporais na análise de vazão de água na represa de furnas Use of time series analysis for the water outflow at furnas dam

    Directory of Open Access Journals (Sweden)

    Thelma Sáfadi

    2004-02-01

    Full Text Available Com este trabalho teve-se como principal objetivo analisar o comportamento da série de vazão de água na barragem de Furnas, empregando análise de séries temporais e estudando o efeito de sazonalidade, tendência e intervenção. Para a análise, foram considerados modelos de séries temporais com e sem a presença de intervenção. Os dados referem-se à vazão (m³/s da Barragem de Furnas - MG, coletada diariamente no período de janeiro de 1963 a dezembro de 1994. Foi realizada uma média mensal dos dados, em que cada média representa uma observação, num total de 372. Observou-se que a série de vazão fica bem ajustada utilizando modelos sazonais e a incorporação do parâmetro de intervenção forneceu informações complementares na análise.This work aimed to fit time series models to the series of water outflow at Furnas Dam. We studied the effect of trend, seasonality and intervention factor in the analysis. Data were colleted daily from January of 1963 to December of 1994 at Furnas Dam. We considered Box & Jenkins models models with and without the intervention factor. We noted that the series of water outflow are fitted by SARIMA models and the intervention factor gave us more information.

  5. Quantifying Fertilizer Application Response Variability with VHR Satellite NDVI Time Series in a Rainfed Smallholder Cropping System of Mali

    Directory of Open Access Journals (Sweden)

    Xavier Blaes

    2016-06-01

    Full Text Available Soil fertility in smallholder farming areas is known to vary strongly on multiple scales. This study measures the sensitivity of the recorded satellite signal to on-farm soil fertility treatments applied to five crop types, and quantifies this fertilization effect with respect to within-field variation, between-field variation and field position in the catena. Plant growth was assessed in 5–6 plots per field in 48 fields located in the Sudano-Sahelian agro-ecological zone of southeastern Mali. A unique series of Very High Resolution (VHR satellite and Unmanned Aerial Vehicle (UAV images were used to calculate the Normalized Difference Vegetation Index (NDVI. In this experiment, for half of the fields at least 50% of the NDVI variance within a field was due to fertilization. Moreover, the sensitivity of NDVI to fertilizer application was crop-dependent and varied through the season, with optima at the end of August for peanut and cotton and early October for sorghum and maize. The influence of fertilizer on NDVI was comparatively small at the landscape scale (up to 35% of total variation, relative to the influence of other components of variation such as field management and catena position. The NDVI response could only partially be benchmarked against a fertilization reference within the field. We conclude that comparisons of the spatial and temporal responses of NDVI, with respect to fertilization and crop management, requires a stratification of soil catena-related crop growth conditions at the landscape scale.

  6. A Kalman Filter-Based Method to Generate Continuous Time Series of Medium-Resolution NDVI Images

    Directory of Open Access Journals (Sweden)

    Fernando Sedano

    2014-12-01

    Full Text Available A data assimilation method to produce complete temporal sequences of synthetic medium-resolution images is presented. The method implements a Kalman filter recursive algorithm that integrates medium and moderate resolution imagery. To demonstrate the approach, time series of 30-m spatial resolution NDVI images at 16-day time steps were generated using Landsat NDVI images and MODIS NDVI products at four sites with different ecosystems and land cover-land use dynamics. The results show that the time series of synthetic NDVI images captured seasonal land surface dynamics and maintained the spatial structure of the landscape at higher spatial resolution. The time series of synthetic medium-resolution NDVI images were validated within a Monte Carlo simulation framework. Normalized residuals decreased as the number of available observations increased, ranging from 0.2 to below 0.1. Residuals were also significantly lower for time series of synthetic NDVI images generated at combined recursion (smoothing than individually at forward and backward recursions (filtering. Conversely, the uncertainties of the synthetic images also decreased when the number of available observations increased and combined recursions were implemented.

  7. NDVI statistical distribution of pasture areas at different times in the Community of Madrid (Spain)

    Science.gov (United States)

    Martín-Sotoca, Juan J.; Saa-Requejo, Antonio; Díaz-Ambrona, Carlos G. H.; Tarquis, Ana M.

    2015-04-01

    The severity of drought has many implications for society, including its impacts on the water supply, water pollution, reservoir management and ecosystem. However, its impacts on rain-fed agriculture are especially direct. Because of the importance of drought, there have been many attempts to characterize its severity, resulting in the numerous drought indices that have been developed (Niemeyer 2008). 'Biomass index' based on satellite image derived Normalized Difference Vegetation Index (NDVI) has been used in countries like United States of America, Canada and Spain for pasture and forage crops for some years (Rao, 2010). This type of agricultural insurance is named as 'index-based insurance' (IBI). IBI is perceived to be substantially less costly to operate and manage than multiple peril insurance. IBI contracts pay indemnities based not on the actual yield (or revenue) losses experienced by the insurance purchaser but rather based on realized NDVI values (historical data) that is correlated with farm-level losses (Xiaohui Deng et al., 2008). Definition of when drought event occurs is defined on NDVI threshold values mainly based in statistical parameters, average and standard deviation that characterize a normal distribution. In this work a pasture area at the north of Community of Madrid (Spain) has been delimited. Then, NDVI historical data was reconstructed based on remote sensing imaging MODIS, with 500x500m2 resolution. A statistical analysis of the NDVI histograms at consecutives 46 intervals of that area was applied to search for the best statistical distribution based on the maximum likelihood criteria. The results show that the normal distribution is not the optimal representation when IBI is available; the implications in the context of crop insurance are discussed (Martín-Sotoca, 2014). References Kolli N Rao. 2010. Index based Crop Insurance. Agriculture and Agricultural Science Procedia 1, 193-203. Martín-Sotoca, J.J. (2014) Estructura Espacial

  8. Global and Regional Variability and Change in Terrestrial Ecosystems Net Primary Production and NDVI: A Model-Data Comparison

    Energy Technology Data Exchange (ETDEWEB)

    Rafique, Rashid; Zhao, Fang; de Jong, Rogier; Zeng, Ning; Asrar, Ghassem R.

    2016-02-25

    The net primary productivity (NPP) is commonly used for understanding the dynamics of terrestrial ecosystems and their role in carbon cycle. We used a combination of the most recent NDVI and model–based NPP estimates (from five models of the TRENDY project) for the period 1982-2012, to study the role of terrestrial ecosystems in carbon cycle under the prevailing climate conditions. We found that 80% and 67% of the global land area showed positive NPP and NDVI values, respectively, for this period. The global NPP was estimated to be about 63 Pg C y-1, with an increase of 0.214 Pg C y-1 y-1. Similarly, the global mean NDVI was estimated to be 0.33, with an increasing trend of 0.00041 y-1. The spatial patterns of NPP and NDVI demonstrated substantial variability, especially at the regional level, for most part of the globe. However, on temporal scale, both global NPP and NDVI showed a corresponding pattern of increase (decrease) for the duration of this study except for few years (e.g. 1990 and 1995-98). Generally, the Northern Hemisphere showed stronger NDVI and NPP increasing trends over time compared to the Southern Hemisphere; however, NDVI showed larger trends in Temperate regions while NPP showed larger trends in Boreal regions. Among the five models, the maximum and minimum NPP were produced by JULES (72.4 Pg C y-1) and LPJ (53.72 Pg C y-1) models, respectively. At latitudinal level, the NDVI and NPP ranges were ~0.035 y-1 to ~-0.016 y-1 and ~0.10 Pg C y-1 y-1 to ~-0.047 Pg C y-1 y-1, respectively. Overall, the results of this study suggest that the modeled NPP generally correspond to the NDVI trends in the temporal dimension. The significant variability in spatial patterns of NPP and NDVI trends points to a need for research to understand the causes of these discrepancies between molded and observed ecosystem dynamics, and the carbon cycle.

  9. Correlation analysis of Normalized Different Vegetation Index (NDVI)difference series and climate variables in the Xilingole steppe,China from 1983 to 1999

    Institute of Scientific and Technical Information of China (English)

    GU Zhihui; CHEN Jin; SHI Peijun; XU Ming

    2007-01-01

    There is a crucial need in the study of global change to understand how terrestrial ecosystems respond to the climate system.It has been demonstrated by many researches that Normalized Different Vegetation Index (NDVI)time series from remotely sensed data,which provide effective information of vegetation conditions on a large scale with highly temporal resolution,have a good relation with meteorological factors.However,few of these studies have taken the cumulative property of NDVI time series into account.In this study,NDVI difference series were proposed to replace the original NDVI time series with NDVI difference series to reappraise the relationship between NDVI and meteorological factors.As a proxy of the vegetation growing process,NDVI difference represents net primary productivity of vegetation at a certain time interval under an environment controlled by certain climatic conditions and other factors.This data replacement is helpful to eliminate the cumulative effect that exist in original NDVI time series,and thus is more appropriate to understand how climate system affects vegetation growth in a short time scale.By using the correlation analysis method,we studied the relationship between NOAA/AVHRR ten-day NDVI difference series and corresponding meteorological data from 1983 to 1999 from 11 meteorological stations located in the Xilingole steppe in Inner Mongolia.The results show that:(1)meteorological factors are found to be more significantly correlation with NDVI difference at the biomass-rising phase than that at the falling phase;(2)the relationship between NDVI difference and climate variables varies with vegetation types and vegetation communities.In a typical steppe dominated by Leymus chinensis,temperature has higher correlation with NDVI difference than precipitation does,and in a typical steppe dominated by Stipa krylovii,the correlation between temperature and NDVI difference is lower than that between precipitation and NDVI difference.In a

  10. Analysis of NDVI variance across landscapes and seasons allows assessment of degradation and resilience to shocks in Mediterranean dry ecosystems

    Science.gov (United States)

    liniger, hanspeter; jucker riva, matteo; schwilch, gudrun

    2016-04-01

    Mapping and assessment of desertification is a primary basis for effective management of dryland ecosystems. Vegetation cover and biomass density are key elements for the ecological functioning of dry ecosystem, and at the same time an effective indicator of desertification, land degradation and sustainable land management. The Normalized Difference Vegetation Index (NDVI) is widely used to estimate the vegetation density and cover. However, the reflectance of vegetation and thus the NDVI values are influenced by several factors such as type of canopy, type of land use and seasonality. For example low NDVI values could be associated to a degraded forest, to a healthy forest under dry climatic condition, to an area used as pasture, or to an area managed to reduce the fuel load. We propose a simple method to analyse the variance of NDVI signal considering the main factors that shape the vegetation. This variance analysis enables us to detect and categorize degradation in a much more precise way than simple NDVI analysis. The methodology comprises identifying homogeneous landscape areas in terms of aspect, slope, land use and disturbance regime (if relevant). Secondly, the NDVI is calculated from Landsat multispectral images and the vegetation potential for each landscape is determined based on the percentile (highest 10% value). Thirdly, the difference between the NDVI value of each pixel and the potential is used to establish degradation categories . Through this methodology, we are able to identify realistic objectives for restoration, allowing a targeted choice of management options for degraded areas. For example, afforestation would only be done in areas that show potential for forest growth. Moreover, we can measure the effectiveness of management practices in terms of vegetation growth across different landscapes and conditions. Additionally, the same methodology can be applied to a time series of multispectral images, allowing detection and quantification of

  11. Mapping return levels of absolute NDVI variations for the assessment of drought risk in Ethiopia

    Science.gov (United States)

    Tonini, F.; Hochmair, H. H.; Jona Lasinio, G.

    2012-12-01

    The analysis and forecasting of extreme climatic events has become increasingly relevant to planning effective financial and food-related interventions in third-world countries. Natural disasters and climate change, both large and small scale, have a great impact on non-industrialized populations who rely exclusively on activities such as crop production, fishing, and similar livelihood activities. It is important to identify the extent of the areas prone to severe drought conditions in order to study the possible consequences of the drought on annual crop production. In this paper, we aim to identify such areas within the South Tigray zone, Ethiopia, using a transformation of the Normalized Difference Vegetation Index (NDVI) called Absolute Difference NDVI (ADVI). Negative NDVI shifts from the historical average can generally be linked to a reduction in the vigor of local vegetation. Drought is more likely to increase in areas where negative shifts occur more frequently and with high magnitude, making it possible to spot critical situations. We propose a new methodology for the assessment of drought risk in areas where crop production represents a primary source of livelihood for its inhabitants. We estimate ADVI return levels pixel per pixel by fitting extreme value models to independent monthly minima. The study is conducted using SPOT-Vegetation (VGT) ten-day composite (S10) images from April 1998 to March 2009. In all short-term and long-term predictions, we found that central and southern areas of the South Tigray zone are prone to a higher drought risk compared to other areas.; Temporal autocorrelation among monthly minima within the Alamata woreda. (a) ACF-Boxplot and (b) PACF-Boxplot. ; ADVI return level estimates. (a) 10-Month return levels. (b) 100-Month return levels. (c) 1000-Month return levels.

  12. Recent variations in NDVI-based plant growth and their relationship with climate in boreal intact forest landscapes

    Science.gov (United States)

    Jin, J.; Jiang, H.; Lu, X.; Zhang, X.

    2015-12-01

    Intact Forest Landscapes (IFLs), defined as large unbroken expanses of forest landscape without signs of significant human activity, have significant ecological values. Previous studies suggest a reversal in the greening of boreal plants was exhibited in the late 1990s. In this study, we focus on variations in plant growth of boreal IFLs from 2000 to 2014 and their correlation with local climatic factors between 45°N and 70°N. The average Normalized Difference Vegetation Index (NDVI) during the growing season (GS, which is from April to October) derived from MOD13C2, is used as a proxy of plant growth. Compared to a significant increase in GS NDVI of boreal plants during the 1980s and early 1990s, GS NDVI of ca. 85.7% of total IFLs in the study area exhibited insignificant change after 2000. About 10.2% of total boreal IFLs exhibited significant greening (an increase in GS NDVI), and only 4.1% of the total showed significant browning (a decrease in GS NDVI) during the study period. For greening boreal IFLs, ca. 46.0% of these showed a significant correlation between GS temperature and NDVI. For browning IFLs, an increase in precipitation during the non-growing season (NGS, which is from previous November to current March) and cooling in GS and NGS were the main climatic causes for decreases of GS NDVI. However, over 65% of browning boreal IFLs did not correlate with any climatic factor, and the browning may be associated with artificial activities. About 49.4% of no-change boreal IFLs showed significant correlation between GS NDVI and climatic factors, and 72.5% of these sensitive plants exhibited a significant positive correlation between GS temperature and NDVI. On the whole, an increase in GS and NGS temperature could promote plant growth of boreal IFLs, while an increase of NGS precipitation mainly inhibited plant growth. However, nearly half of total boreal IFLs displayed no sensitivity to any climatic factors chosen in our present work.

  13. Comparison of Alternative Crop Phenology Detection Algorithms using MODIS NDVI Time Series Data in US Corn Belt Region

    Science.gov (United States)

    Lee, J.; Hong, S. Y.; Kang, S.

    2015-12-01

    Predicting crop phenology is important for understanding of crop development and growth processes and improving the accuracy of crop model. Remote sensing offers a feasible tool for monitoring spatio-temporal patterns of crop phenology in region and continental scales. Various methods have developed to determine the timing of crop phenological stages using spectral vegetation indices (i.e. NDVI and EVI) derived from satellite data. In our study, it was compared four alternative detection methods to identify crop phenological stages (i.e. the emergence and harvesting date) using high quality NDVI time series data derived from MODIS. In threshold method assumes the emergence and harvesting date when NDVI values exceed and decreases down to a given threshold, respectively. Two kind of threshold values were applied for NDVI and it increment for eight days. The other two methods use a logistic fitting model and inflection points on fitted curve, respectively. It was compared the four methods for corn and soybean, respectively. For validation, three kinds of datasets were utilized: AmeriFlux biological data of planting and harvest dates, and emergence date estimated from growing degree days (AGDDs) at flux tower sites, and state-level USDA Crop Progress Report (CPR). All methods showed substantial uncertainty but the threshold method showed relatively better agreement against with both site- and state-level data for soybean phenology. For better NDVI-based regional estimation of crop phenology, factors of uncertainty were examined and discussed in this study.

  14. Monitoring of wildfires in boreal forests using large area AVHRR NDVI composite image data

    Energy Technology Data Exchange (ETDEWEB)

    Kasischke, E.S.; French, N.H.F. (Environmental Research Inst. of Michigan, Ann Arbor (United States)); Harrell, P.; Christensen, N.L. Jr. (Duke Univ., Durham, NC (United States)); Ustin, S.L. (Univ. of California, Davis (United States)); Barry, D. (U.S. Bureau of Land Management, Fairbanks, AK (United States))

    1993-06-01

    Normalized difference vegetation index (NDVI) composite image data, produced from AVHRR data collected in 1990, were evaluated for locating and mapping the areal extent of wildfires in the boreal forests of Alaska during that year. A technique was developed to map forest fire boundaries by subtracting a late-summer AVHRR NDVI image from an early summer scene. The locations and boundaries of wildfires within the interior region of Alaska were obtained from the Alaska Fire Service, and compared to the AVHRR-derived fire-boundary map. It was found that AVHRR detected 89.5% of all fires with sizes greater than 2,000ha with no false alarms and that, for most cases, the general shape of the fire boundary detected by AVHRR matched those mapped by field observers. However, the total area contained within the fire boundaries mapped by AVHRR were only 61% of those mapped by the field observers. However, the AVHRR data used in this study did not span the entire time period during which fires occurred, and it is believed the areal estimates could be improved significantly if an expanded AVHRR data set were used.

  15. Inter-annual variation of NDVI over Korea Peninsula using harmonic analysis

    Science.gov (United States)

    Kim, In-hwan; Han, Kyung-Soo; Pi, Kyoung-Jin; Park, Soo-Jae; Kim, Sang-Il

    2010-10-01

    Global warming and climatic changes due to human activities impact on marine and terrestrial ecosystems, which feedbacks to climate system. These negative feedbacks amplify or accelerate again global climate change. In particular, life cycle of vegetation sensitively vary according to global climate change. This study attempts to analyze quantitatively vegetation change in Korea peninsula using harmonic analysis. Satellite data was extracted from SPOT/VEGETATION S10 MVC (Maximum Value Composite) NDVI (Normalized Difference Vegetation Index) products during 10 years (1999 to 2008) around Korea peninsula. This NDVI data set was pre-processed to correct noise pixels cause by cloud and ground wetness. Variation of vegetation life cycle was analyzed through amplitudes and phases of annual harmonic components (first harmonic components) per year for two land cover types (cropland and forest). The results clearly show that the peak of vegetation life cycle in Korea peninsula is brought forward to early. Especially, it represents that the phases over low latitudes area between 32.8°N and 38°N steadily decrease every year both forest and cropland. The study estimated that phase values moved up approximately 0.5 day per year in cropland and 0.8 day per year in forest.

  16. Satellite NDVI Assisted Monitoring of Vegetable Crop Evapotranspiration in California’s San Joaquin Valley

    Directory of Open Access Journals (Sweden)

    Thomas J. Trout

    2012-02-01

    Full Text Available Reflective bands of Landsat-5 Thematic Mapper satellite imagery were used to facilitate the estimation of basal crop evapotranspiration (ETcb, or potential crop water use, in San Joaquin Valley fields during 2008. A ground-based digital camera measured green fractional cover (Fc of 49 commercial fields planted to 18 different crop types (row crops, grains, orchard, vineyard of varying maturity over 11 Landsat overpass dates. Landsat L1T terrain-corrected images were transformed to surface reflectance and converted to normalized difference vegetation index (NDVI. A strong linear relationship between NDVI and Fc was observed (r2 = 0.96, RMSE = 0.062. The resulting regression equation was used to estimate Fc for crop cycles of broccoli, bellpepper, head lettuce, and garlic on nominal 7–9 day intervals for several study fields. Prior relationships developed by weighing lysimeter were used to transform Fc to fraction of reference evapotranspiration, also known as basal crop coefficient (Kcb. Measurements of grass reference evapotranspiration from the California Irrigation Management Information System were then used to calculate ETcb for each overpass date. Temporal profiles of Fc, Kcb, and ETcb were thus developed for the study fields, along with estimates of seasonal water use. Daily ETcb retrieval uncertainty resulting from error in satellite-based Fc estimation was < 0.5 mm/d, with seasonal uncertainty of 6–10%. Results were compared with FAO-56 irrigation guidelines and prior lysimeter observations for reference.

  17. Using Time Series Segmentation for Deriving Vegetation Phenology Indices from MODIS NDVI Data

    Energy Technology Data Exchange (ETDEWEB)

    Chandola, Varun [ORNL; Vatsavai, Raju [ORNL; Hui, Dafeng [ORNL; Gu, Lianhong [ORNL; Bhaduri, Budhendra L [ORNL

    2010-01-01

    Characterizing vegetation phenology is a highly significant problem, due to its importance in regulating ecosystem carbon cycling, interacting with climate changes, and decision-making of croplands managements. While ground based sensors, such as the AmeriFlux sensors, can provide measurements at high temporal resolution (every hour) and can be used to accurately calculate vegetation phenology indices, they are limited to only a few sites. Remote sensing data, such as the Normalized Difference Vegetation Index (NDVI), collected using the MODerate Resolution Imaging Spectroradiometer (MODIS), can provide global coverage, though at a much coarser temporal resolution (16 days). In this study we use data mining based time series segmentation methods to derive phenology indices from NDVI data, and compare it with the phenology indices derived from the AmeriFlux data using a widely used model fitting approach. Results show a significant correlation (as high as 0.60) between the indices derived from these two different data sources. This study demonstrates that data driven methods can be effectively employed to provide realistic estimates of vegetation phenology indices using periodic time series data and has the potential to be used at large spatial scales and for long-term remote sensing data.

  18. MODIS NDVI and vegetation phenology dynamics in the Inner Mongolia grassland

    Directory of Open Access Journals (Sweden)

    Z. Gong

    2015-08-01

    Full Text Available The Inner Mongolia grassland, one of the most important grazing regions in China, has long been threatened by land degradation and desertification, mainly due to overgrazing. To understand vegetation responses over the last decade, this study evaluated trends in vegetation cover and phenology dynamics in the Inner Mongolia grassland by applying a normalized difference vegetation index (NDVI time series obtained by the Terra Moderate Resolution Imaging Spectroradiometer (MODIS during 2002–2014. The results showed that the cumulative annual NDVI increased to over 77.10 % in the permanent grassland region (2002–2014. The mean value of the total change showed that the start of season (SOS date and the peak vegetation productivity date of the season (POS had advanced by 5.79 and 2.43 days respectively. The end of season (EOS was delayed by 5.07 days. These changes lengthened the season by 10.86 days. Our results also confirmed that grassland changes are closely related to spring precipitation (February–May and increasing temperature during the growing period because of the global warming. Overall, productivity in the Inner Mongolia Autonomous Region tends to increase, but in some grassland areas with grazing, land degradation is ongoing.

  19. Detecting Clear-Cuts and Decreases in Forest Vitality Using MODIS NDVI Time Series

    Directory of Open Access Journals (Sweden)

    Jonas Lambert

    2015-03-01

    Full Text Available This paper examines the potential of MODIS-NDVI time series for detecting clear-cuts in a coniferous forest stand in the south of France. The proposed approach forms part of a survey monitoring the status of forest health and evaluating the forest decline phenomena observed over the last few decades. One of the prerequisites for this survey was that a rapid and easily reproducible method had to be developed that differentiates between forest clear-cuts and changes in forest health induced by environmental factors such as summer droughts. The proposed approach is based on analysis of the breakpoints detected within NDVI time series, using the “Break for Additive Seasonal and Trend” (BFAST algorithm. To overcome difficulties detecting small areas on the study site, we chose a probabilistic approach based on the use of a conditional inference tree. For model calibration, clear-cut reference data were produced at MODIS resolution (250 m. According to the magnitude of the detected breakpoints, probability classes for the presence of clear-cuts were defined, from greater than 90% to less than 3% probability of a clear-cut. One of the advantages of the probabilistic model is that it allows end users to choose an acceptable level of uncertainty depending on the application. In addition, the use of BFAST allows events to be dated, thus making it possible to perform a retrospective analysis of decreases in forest vitality in the study area.

  20. Evaluation of methods to derive green-up dates based on daily NDVI satellite observations

    Science.gov (United States)

    Doktor, Daniel

    2010-05-01

    Bridging the gap between satellite derived green-up dates and in situ phenological observations has been the purpose of many studies over the last decades. Despite substantial advancements in satellite technology and data quality checks there is as yet no universally accepted method for extracting phenological metrics based on satellite derived vegetation indices. Dependent on the respective method derived green-up dates can vary up to serveral weeks using identical data sets. Consequently, it is difficult to compare various studies and to accurately determine an increased vegetation length due to changing temperature patterns as observed by ground phenological networks. Here, I compared how the characteristic NDVI increase over temperate deciduous forests in Germany in spring relates to respective budburst events observed on the ground. MODIS Terra daily surface reflectances with a 250 m resolution (2000-2008) were gathered to compute daily NDVI values. As ground truth, observations of the extensive phenological network of the German Weather Service were used. About 1500 observations per year and species (Beech, Oak and Birch) were available evenly distributed all over Germany. Two filtering methods were tested to reduce the noisy raw data. The first method only keeps NDVI values which are classified as ‚ideal global quality' and applies on those a temporal moving window where values are removed which differ more than 20% of the mean. The second method uses an adaptation of the BISE (Best Index Slope Extraction) algorithm. Subsequently, three functions were fitted to the selected observations: a simple linear interpolation, a sigmoidal function and a double logistic sigmoidal function allowing to approximate two temporally separated green-up signals. The green-up date was then determined at halfway between minimum and maximum (linear interpolation) or at the inflexion point of the sigmoidal curve. A number of global threshold values (NDVI 0.4,0.5,0.6) and

  1. The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature

    International Nuclear Information System (INIS)

    Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.

  2. [Dynamic changes in vegetation NDVI from 1982 to 2012 and its responses to climate change and human activities in Xinjiang, China].

    Science.gov (United States)

    Du, Jia-qiang; Jiaerheng, Ahati; Zhao, Chenxi; Fang, Guang-ling; Yin, Jun-qi; Xiang, Bao; Yuan, Xin-jie; Fang, Shi-feng

    2015-12-01

    Vegetation plays an important role in regulating the terrestrial carbon balance and the climate system, and also overwhelmingly dominates the provisioning of ecosystem services. Therefore, it has significance to monitor the growth of vegetation. Based on AVHRR GIMMS NDVI and MODIS NDVI datasets, we analyzed the spatiotemporal patterns of change in NDVI and their linkage with climate change and human activity from 1982 to 2012 in the typical arid region, Xinjiang of northwestern China, at pixel and regional scales. At regional scale, although a statistically significant positive trend of growing season NDVI with a rate of 4.09 x 10⁻⁴· a⁻¹ was found during 1982-2012, there were two distinct periods with opposite trends in growing season NDVI before and after 1998, respectively. NDVI in growing season first significantly increased with a rate of 10 x 10⁻⁴· a⁻¹ from 1982 to 1998, and then decreased with a rate of -3 x 10⁻⁴· a⁻¹ from 1998 to 2012. The change in trend of NDVI from increase to decrease mainly occurred in summer, followed by autumn, and the reversal wasn't observed in spring. At pixel scale, the NDVI in farmland significantly increased; the NDVI changes in the growing season and all seasons showed polarization: Areas with significant change mostly increased in size as the NDVI record grown in length. The rate of increase in size of areas with significantly decreasing NDVI was larger than that with significantly increasing NDVI, which led to the NDVI increase obviously slowing down or stopping at regional scale. The vegetation growth in the study area was regulated by both climate change and human activity. Temperature was the most important driving factor in spring and autumn, whereas precipitation in summer. Extensive use of fertilizers and increased farmland irrigated area promoted the vegetation growth. However, the rapid increase in the proportion of cotton cultivation and use of drip irrigation might reduce spring NDVI in the

  3. [Dynamic changes in vegetation NDVI from 1982 to 2012 and its responses to climate change and human activities in Xinjiang, China].

    Science.gov (United States)

    Du, Jia-qiang; Jiaerheng, Ahati; Zhao, Chenxi; Fang, Guang-ling; Yin, Jun-qi; Xiang, Bao; Yuan, Xin-jie; Fang, Shi-feng

    2015-12-01

    Vegetation plays an important role in regulating the terrestrial carbon balance and the climate system, and also overwhelmingly dominates the provisioning of ecosystem services. Therefore, it has significance to monitor the growth of vegetation. Based on AVHRR GIMMS NDVI and MODIS NDVI datasets, we analyzed the spatiotemporal patterns of change in NDVI and their linkage with climate change and human activity from 1982 to 2012 in the typical arid region, Xinjiang of northwestern China, at pixel and regional scales. At regional scale, although a statistically significant positive trend of growing season NDVI with a rate of 4.09 x 10⁻⁴· a⁻¹ was found during 1982-2012, there were two distinct periods with opposite trends in growing season NDVI before and after 1998, respectively. NDVI in growing season first significantly increased with a rate of 10 x 10⁻⁴· a⁻¹ from 1982 to 1998, and then decreased with a rate of -3 x 10⁻⁴· a⁻¹ from 1998 to 2012. The change in trend of NDVI from increase to decrease mainly occurred in summer, followed by autumn, and the reversal wasn't observed in spring. At pixel scale, the NDVI in farmland significantly increased; the NDVI changes in the growing season and all seasons showed polarization: Areas with significant change mostly increased in size as the NDVI record grown in length. The rate of increase in size of areas with significantly decreasing NDVI was larger than that with significantly increasing NDVI, which led to the NDVI increase obviously slowing down or stopping at regional scale. The vegetation growth in the study area was regulated by both climate change and human activity. Temperature was the most important driving factor in spring and autumn, whereas precipitation in summer. Extensive use of fertilizers and increased farmland irrigated area promoted the vegetation growth. However, the rapid increase in the proportion of cotton cultivation and use of drip irrigation might reduce spring NDVI in the

  4. Multifractal characteristics of NDVI maps in space and time in the Community of Madrid (Spain)

    Science.gov (United States)

    Sotoca, Juan J. Martin; Saa-Requejo, Antonio; Grau, Juan B.; Tarquis, Ana M.

    2015-04-01

    Satellite information has contributed to improve our understanding of the spatial variability of hydro-climatic and ecological processes. Vegetation activity is tightly coupled with climate, hydro-ecological fluxes, and terrain dynamics in river basins at a wide range of space-time scales (Scheuring and Riedi, 1994). Indices of vegetation activity are constructed using satellite information of reflectance of the relevant spectral bands which enhance the contribution of vegetation being Normalized Difference Vegetation Index (NDVI) widely used. How can we study such a complex system? Multifractals and fractals are related techniques mainly used in physics to characterize the scaling behaviour of a system; they differ in that fractals look at the geometry of presence/absence patterns, while multifractals look at the arrangement of quantities such as population or biomass densities (Saravia et al., 2012). Scaling laws are an emergent general feature of ecological systems; they reflect constraints in their organization that can provide tracks about the underlying mechanisms (Solé and Bascompte, 2006). In this work, we have applied these techniques to study the spatial pattern through one year of NDVI maps. A rectangular area that includes the Community of Madrid and part of the surroundings, consisting of 300 x 280 pixels with a resolution of 500 x 500 m2 has been selected and monthly NDVI maps analyzed using the multifractal spectrum and the map of singularities (Cheng and Agterberg, 1996). The results show a cyclical pattern in the multifractal behaviour and singularity points related to river basin networks (Martín-Sotoca, 2014). References Cheng, Q. and Agterberg, F.P. (1996). Multifractal modeling and spatial statistics. Math. Geol. Vol 28, 1-16. Martín-Sotoca, J.J. (2014) Estructura Espacial de la Sequía en Pastos y sus Aplicaciones en el Seguro Agrario. Master Thesis, UPM (In Spanish). Saravia LA, Giorgi A, Momo F.: Multifractal growth in periphyton

  5. Mapping irrigated areas in Afghanistan over the past decade using MODIS NDVI

    Science.gov (United States)

    Pervez, Md Shahriar; Budde, Michael; Rowland, James

    2014-01-01

    Agricultural production capacity contributes to food security in Afghanistan and is largely dependent on irrigated farming, mostly utilizing surface water fed by snowmelt. Because of the high contribution of irrigated crops (> 80%) to total agricultural production, knowing the spatial distribution and year-to-year variability in irrigated areas is imperative to monitoring food security for the country. We used 16-day composites of the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor to create 23-point time series for each year from 2000 through 2013. Seasonal peak values and time series were used in a threshold-dependent decision tree algorithm to map irrigated areas in Afghanistan for the last 14 years. In the absence of ground reference irrigated area information, we evaluated these maps with the irrigated areas classified from multiple snapshots of the landscape during the growing season from Landsat 5 optical and thermal sensor images. We were able to identify irrigated areas using Landsat imagery by selecting as irrigated those areas with Landsat-derived NDVI greater than 0.30–0.45, depending on the date of the Landsat image and surface temperature less than or equal to 310 Kelvin (36.9 ° C). Due to the availability of Landsat images, we were able to compare with the MODIS-derived maps for four years: 2000, 2009, 2010, and 2011. The irrigated areas derived from Landsat agreed well r2 = 0.91 with the irrigated areas derived from MODIS, providing confidence in the MODIS NDVI threshold approach. The maps portrayed a highly dynamic irrigated agriculture practice in Afghanistan, where the amount of irrigated area was largely determined by the availability of surface water, especially snowmelt, and varied by as much as 30% between water surplus and water deficit years. During the past 14 years, 2001, 2004, and 2008 showed the lowest levels of irrigated area (~ 1.5 million hectares), attesting to

  6. Mapping deciduous forests by using time series of filtered MODIS NDVI and neural networks

    Directory of Open Access Journals (Sweden)

    Thomaz Chaves de Andrade Oliveira

    2010-06-01

    Full Text Available Multi-temporal images are now of standard use in remote sensing of vegetation during monitoring and classification.Temporal vegetation signatures (i. e., vegetation indices as functions of time generated, poses many challenges, primarily due tosignal to noise-related issues. This study investigates which methods generate the most appropriate smoothed curves of vegetationsignatures on MODIS NDVI time series. The filtering techniques compared were the HANTS algorithm which is based on Fourieranalyses and Wavelet temporal algorithm which uses the wavelet analysis to generate the smoothed curves. The study was conductedin four different regions of the Minas Gerais State. The smoothed data were used as input data vectors for vegetation classificationby means of artificial neural networks for comparison purpose. A comparison of the results was ultimately discussed in this workshowing encouraging results and similarity between the two filtering techniques used.

  7. Assessment of the environmental effects of mining using SPOT-Vegetation NDVI

    Science.gov (United States)

    Tote, C.; Swinnen, E.; Goossens, M.; Reusen, I.; Delalieux, S.

    2012-04-01

    Within the ImpactMin project, funded by the Framework Programme 7 of the European Commission, new methods for the environmental impact monitoring of mining operations are being developed. The objective of this study is to analyze the impact of mining on soil properties through assessment of the vegetation status using time series analysis of low resolution Normalized Difference Vegetation Index (NDVI) images derived from SPOT-Vegetation. The study focuses on the surroundings of mining areas in the Orenburg region in the Russian Urals. Karabash has been a centre for mining and metal production for well over 3000 years, and environmental impact of (historical) mining in the area is extremely severe. The area was characterized as an 'ecological disaster zone', based on chemical analysis of soil samples in the area [1]. The mining activities were intensified in the early to mid-20th century, but the old smelter was modernized in the 1990s. A time series of 10-daily NDVI images from SPOT-Vegetation (S10 April/1998-December/2010 at 1km2 resolution, http://www.vgt.vito.be/) is analyzed. Different land cover types clearly show different phenology. To remove seasonal vegetation changes and thus to facilitate the interpretation through the historical record, a Standardized Difference Vegetation Index (SDVI) was calculated for each pixel and for each record of the time series. The first results of trend analyses indicate a strong recovery of open forests in the Karabash region in the last decade. To what extent this can be related to reduced mining impact or climate factors, still needs to be assessed. Further research will also focus on the spatial heterogeneity of phenological parameters, in relation to distance to and wind direction of the smelters and soil properties. [1] V. Nestersnko, "Urban associations of elements- environmental pollutants in Karabash city (Chelyabinsk oblast) as a reflection of ore-chemical descriptions of mineral raw material", Proceedings of the

  8. Changes in greening in the high Arctic: insights from a 30 year AVHRR max NDVI dataset for Svalbard

    Science.gov (United States)

    Vickers, Hannah; Arild Høgda, Kjell; Solbø, Stian; Rune Karlsen, Stein; Tømmervik, Hans; Aanes, Ronny; Hansen, Brage B.

    2016-10-01

    Satellite-aided studies of vegetation cover, biomass and productivity are becoming increasingly important for monitoring the effects of a changing climate on the biosphere. With their large spatial coverage and good temporal resolution, space-borne instruments are ideal to observe remote areas over extended time periods. However, long time series datasets with global coverage have in many cases too low spatial resolution for sparsely vegetated high latitude areas. This study has made use of a newly developed 30 year 1 km spatial resolution dataset from 1986 to 2015, provided by the NOAA AVHRR series of satellites, in order to calculate the annual maximum NDVI over parts of Svalbard (78°N). This parameter is indicative of vegetation productivity and has therefore enabled us to study long-term changes in greening within the Inner Fjord Zone on Svalbard. In addition, local meteorological data are available to link maximum NDVI values to the temporal behavior of the mean growing season (summer) temperature for the study area. Over the 30 year period, we find positive trends in both maximum NDVI (average increase of 29%) and mean summer temperature (59%), which were significantly positively correlated with each other. This suggests a temporal greening trend mediated by summer warming. However, as also recently reported for lower latitudes, the strength of the year-to-year correlation between maximum NDVI and mean summer temperature decreased, suggesting that the response of vegetation to summer warming has not remained the same over the entire study period.

  9. Increased wetness confounds Landsat-derived NDVI trends in the central Alaska North Slope region, 1985–2011

    Science.gov (United States)

    Raynolds, Martha K.; Walker, Donald A.

    2016-08-01

    Satellite data from the circumpolar Arctic have shown increases in vegetation indices correlated to warming air temperatures (e.g. Bhatt et al 2013 Remote Sensing 5 4229–54). However, more information is needed at finer scales to relate the satellite trends to vegetation changes on the ground. We examined changes using Landsat TM and ETM+ data between 1985 and 2011 in the central Alaska North Slope region, where the vegetation and landscapes are relatively well-known and mapped. We calculated trends in the normalized difference vegetation index (NDVI) and tasseled-cap transformation indices, and related them to high-resolution aerial photographs, ground studies, and vegetation maps. Significant, mostly negative, changes in NDVI occurred in 7.3% of the area, with greater change in aquatic and barren types. Large reflectance changes due to erosion, deposition and lake drainage were evident. Oil industry-related changes such as construction of artificial islands, roads, and gravel pads were also easily identified. Regional trends showed decreases in NDVI for most vegetation types, but increases in tasseled-cap greenness (56% of study area, greatest for vegetation types with high shrub cover) and tasseled-cap wetness (11% of area), consistent with documented degradation of polygon ice wedges, indicating that increasing cover of water may be masking increases in vegetation when summarized using the water-sensitive NDVI.

  10. NDVI changes in China between 1989 and 1999 using change vector analysis based on time series data

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Change vector analysis (CVA) and principal component analysis in NDVI time-trajectories space are powerful tools to analyze land-cover change. The magnitude of the change vector indicates amplitude of the change, while its direction indicates the nature of the change. CVA is applied to two remotely sensed indicators of land surface conditions, NDVI and spatial structure, in order to improve the capability to detect and categorize land-cover change. The magnitude and type of changes are calculated in China from 1989 to 1999. Through the research, the main conclusions are drawn as follows: 1) The changes of NDVI are quite different between eastern China and western China, and the change range in the east is bigger than that in the west. The trend in NDVI time series is smoothly increasing, the increases happen mostly in Taiwan, Ftjian, Sichuan and Henan provinces and the decreases occur in Yunnan and Xinjiang. 2) The spatial structure index can indicate changes in theseasonal ecosystem dynamics for spatially heterogeneous landscapes. Most of spatial structurechanges, which occurred in southern China, correlated with vegetation growth processes and strike of mountains.

  11. PENGGUNAAN ALGORITMA NDVI DAN EVI PADA CITRA MULTISPEKTRAL UNTUK ANALISA PERTUMBUHAN PADI (STUDI KASUS : KABUPATEN INDRAMAYU, JAWA BARAT

    Directory of Open Access Journals (Sweden)

    Aulia Hafizh S

    2015-02-01

    Full Text Available Kabupaten Indramayu merupakan salah satu kabupaten yang merupakan daerah sentra pertanian dimana sektor ini menyumbang 43% dari total PDRB (Produk Domestik Regional Bruto. Strategi yang tepat dan cepat harus dicanangkan untuk selalu memenuhi kebutuhan akan bahan pokok tersebut. Teknologi penginderaan jauh dapat mengakomodir informasi suatu objek secara cepat dan akurat tanpa harus berinteraksi langsung dengan objek dan dapat dimanfaatkan dalam berbagai aplikasi yang diinginkan. Pembangunan model - model estimasi produktivitas pada beberapa komoditas vegetasi pertanian seperti padi telah digunakan sejak dua dekade lalu. Dari berbagai macam permodelan vegetasi, indeks vegetasi yang paling umum digunakan adalah NDVI (Normalized Difference Vegetation Index dan EVI (Enhanced Vegetation Index. Hasil dari penelitian ini adalah penentuan fase pertumbuhan , masa tanam, dan masa panen tumbuhan padi pada citra MODIS L1B. Masa tanam padi di kabupaten Indramayu berada pada bulan Juni dan Desember 2011, masa panen berada pada bulan  Mei dan September 2011. Citra Aster digunakan sebagai data pendukung untuk menentukan korelasi linear  terhadap data lapangan (fieldspectometer. Korelasi yang dihasilkan Antara Modis - Aster sebesar 0.9576 pada EVI dan 0.9654 pada NDVI; Modis - Fieldspectometer sebesar 0.8798 pada EVI dan 0.9077 pada NDVI; dan pada Aster - Fieldspectometer sebesar 0.9220 pada EVI dan 0.9460 pada NDVI. Korelasi dari ketiga data tersebut memiliki hubungan yang cukup kuat dikarenakan nilai yang dihasilkan mendekati nilai 1.

  12. Exploring Long Term Spatial Vegetation Trends in Taiwan from AVHRR NDVI3g Dataset Using RDA and HCA Analyses

    Directory of Open Access Journals (Sweden)

    Hui Ping Tsai

    2016-03-01

    Full Text Available Due to 4000 m elevation variation with temperature differences equivalent to 50 degrees of latitudinal gradient, exploring Taiwan’s spatial vegetation trends is valuable in terms of diverse ecosystems and climatic types covering a relatively small island with an area of 36,000 km2. This study analyzed Taiwan’s spatial vegetation trends with controlling environmental variables through redundancy (RDA and hierarchical cluster (HCA analyses over three decades (1982–2012 of monthly normalized difference vegetation index (NDVI derived from the Advanced Very High Resolution Radiometer (AVHRR NDVI3g data for 19 selected weather stations over the island. Results showed two spatially distinct vegetation response groups. Group 1 comprises weather stations which remained relatively natural showing a slight increasing NDVI tendency accompanied with rising temperature, whereas Group 2 comprises stations with high level of human development showing a slight decreasing NDVI tendency associated with increasing temperature-induced moisture stress. Statistically significant controlling variables include climatic factors (temperature and precipitation, orographic factors (mean slope and aspects, and anthropogenic factor (population density. Given the potential trajectories for future warming, variable precipitation, and population pressure, challenges, such as land-cover and water-induced vegetation stress, need to be considered simultaneously for establishing adequate adaptation strategies to combat climate change challenges in Taiwan.

  13. Different responses of MODIS-derived NDVI to root-zone soil moisture in semi-arid and humid regions

    Science.gov (United States)

    Wang, Xianwei; Xie, Hongjie; Guan, Huade; Zhou, Xiaobing

    2007-06-01

    SummarySurface representation of the root-zone soil moisture is investigated so that feasibility of using optical remote sensing techniques to indirectly map root-zone soil moisture is assessed. Specifically, covariation of root-zone soil moisture with the normalized difference of vegetation index (NDVI) from Moderate Resolution Imaging Spectroradiometer (MODIS) is studied at three sites (New Mexico, Arizona, and Texas) selected from the Soil Climate Analysis Network (SCAN). The three sites represent two types of vegetation (shrub and grass) and two types of climate conditions: semi-arid (New Mexico and Arizona) and humid (Texas). Collocated deseasonalized time series of soil moistures at five depths (5 cm, 10 cm, 20 cm, 50 cm, and 100 cm) and NDVI (8-day composite in 250 m resolution) during the period of February 2000 through April 2004 were used for correlation analysis. Similar analysis was also conducted for the raw time series for comparison purposes. The linear regression of both the deseasonalized time series and the raw time series was used to estimate root-zone soil moisture. Results show that (1) the deseasonalized time series results in consistent and significant correlation (0.46-0.55) between NDVI and root-zone soil moisture at the three sites; (2) vegetation (NDVI) at the humid site needs longer time (10 days) to respond to soil moisture change than that at the semi-arid sites (5 days or less); (3) the time-series of root-zone soil moisture estimated by a linear regression model based on deseasonalized time series accounts for 42-71% of the observed soil moisture variations for the three sites; and (4) in the semi-arid region, root-zone soil moisture of shrub-vegetated area can be better estimated using NDVI than that of grass-vegetated area.

  14. High-Resolution NDVI from Planet's Constellation of Earth Observing Nano-Satellites: A New Data Source for Precision Agriculture

    KAUST Repository

    Houborg, Rasmus

    2016-09-19

    Planet Labs ("Planet") operate the largest fleet of active nano-satellites in orbit, offering an unprecedented monitoring capacity of daily and global RGB image capture at 3-5 m resolution. However, limitations in spectral resolution and lack of accurate radiometric sensor calibration impact the utility of this rich information source. In this study, Planet\\'s RGB imagery was translated into a Normalized Difference Vegetation Index (NDVI): a common metric for vegetation growth and condition. Our framework employs a data mining approach to build a set of rule-based regression models that relate RGB data to atmospherically corrected Landsat-8 NDVI. The approach was evaluated over a desert agricultural landscape in Saudi Arabia where the use of near-coincident (within five days) Planet and Landsat-8 acquisitions in the training of the regression models resulted in NDVI predictabilities with an r2 of approximately 0.97 and a Mean Absolute Deviation (MAD) on the order of 0.014 (~9%). The MAD increased to 0.021 (~14%) when the Landsat NDVI training image was further away (i.e., 11-16 days) from the corrected Planet image. In these cases, the use of MODIS observations to inform on the change in NDVI occurring between overpasses was shown to significantly improve prediction accuracies. MAD levels ranged from 0.002 to 0.011 (3.9% to 9.1%) for the best performing 80% of the data. The technique is generic and extendable to any region of interest, increasing the utility of Planet\\'s dense time-series of RGB imagery.

  15. Comparison of Gross Primary Productivity Derived from GIMMS NDVI3g, GIMMS, and MODIS in Southeast Asia

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    Junbang Wang

    2014-03-01

    Full Text Available Gross primary production (GPP plays an important role in the net ecosystem exchange of CO2 between the atmosphere and terrestrial ecosystems. It is particularly important to monitor GPP in Southeast Asia because of increasing rates of tropical forest degradation and deforestation in the region in recent decades. The newly available, improved, third generation Normalized Difference Vegetation Index (NDVI3g from the Global Inventory Modelling and Mapping Studies (GIMMS group provides a long temporal dataset, from July 1981 to December 2011, for terrestrial carbon cycle and climate response research. However, GIMMS NDVI3g-based GPP estimates are not yet available. We applied the GLOPEM-CEVSA model, which integrates an ecosystem process model and a production efficiency model, to estimate GPP in Southeast Asia based on three independent results of the fraction of photosynthetically active radiation absorbed by vegetation (FPAR from GIMMS NDVI3g (GPPNDVI3g, GIMMS NDVI1g (GPPNDVI1g, and the Moderate Resolution Imaging Spectroradiometer (MODIS MOD15A2 FPAR product (GPPMOD15. The GPP results were validated using ground data from eddy flux towers located in different forest biomes, and comparisons were made among the three GPPs as well as the MOD17A2 GPP products (GPPMOD17. Based on validation with flux tower derived GPP estimates the results show that GPPNDVI3g is more accurate than GPPNDVI1g and is comparable in accuracy with GPPMOD15. In addition, GPPNDVI3g and GPPMOD15 have good spatial-temporal consistency. Our results indicate that GIMMS NDVI3g is an effective dataset for regional GPP simulation in Southeast Asia, capable of accurately tracking the variation and trends in long-term terrestrial ecosystem GPP dynamics.

  16. Clinical and eeg analysis of mesial and lateral temporal lobe seizures Análise clínica e eletrencefalográfica de crises epilépticas temporais de origem mesial e lateral

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    FÁBIO GALVÃO DANTAS

    1998-09-01

    contralateral à área epileptogênica. Verbalização crítica, automatismo de cuspir, piscamento palpebral bilateral, desorientação espacial prolongada e maior percentual de preservação da linguagem no período pós-crítico foram relacionados a crises temporais direitas. Afasia pós-crítica e desorientação global, a crises temporais esquerdas. O EEG teve importante acurácia lateralizatória em ambos os grupos, especialmente quanto à atividade crítica rítmica e achados pós-críticos.

  17. Evaluating and Quantifying the Climate-Driven Interannual Variability in Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI3g) at Global Scales

    Science.gov (United States)

    Zeng, Fanwei; Collatz, George James; Pinzon, Jorge E.; Ivanoff, Alvaro

    2013-01-01

    Satellite observations of surface reflected solar radiation contain informationabout variability in the absorption of solar radiation by vegetation. Understanding thecauses of variability is important for models that use these data to drive land surface fluxesor for benchmarking prognostic vegetation models. Here we evaluated the interannualvariability in the new 30.5-year long global satellite-derived surface reflectance index data,Global Inventory Modeling and Mapping Studies normalized difference vegetation index(GIMMS NDVI3g). Pearsons correlation and multiple linear stepwise regression analyseswere applied to quantify the NDVI interannual variability driven by climate anomalies, andto evaluate the effects of potential interference (snow, aerosols and clouds) on the NDVIsignal. We found ecologically plausible strong controls on NDVI variability by antecedent precipitation and current monthly temperature with distinct spatial patterns. Precipitation correlations were strongest for temperate to tropical water limited herbaceous systemswhere in some regions and seasons 40 of the NDVI variance could be explained byprecipitation anomalies. Temperature correlations were strongest in northern mid- to-high-latitudes in the spring and early summer where up to 70 of the NDVI variance was explained by temperature anomalies. We find that, in western and central North America,winter-spring precipitation determines early summer growth while more recent precipitation controls NDVI variability in late summer. In contrast, current or prior wetseason precipitation anomalies were correlated with all months of NDVI in sub-tropical herbaceous vegetation. Snow, aerosols and clouds as well as unexplained phenomena still account for part of the NDVI variance despite corrections. Nevertheless, this study demonstrates that GIMMS NDVI3g represents real responses of vegetation to climate variability that are useful for global models.

  18. Mapping and Evaluation of NDVI Trends from Synthetic Time Series Obtained by Blending Landsat and MODIS Data around a Coalfield on the Loess Plateau

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    Kun Wang

    2013-09-01

    Full Text Available The increasingly intensive and extensive coal mining activities on the Loess Plateau pose a threat to the fragile local ecosystems. Quantifying the effects of coal mining activities on environmental conditions is of great interest for restoring and managing the local ecosystems and resources. This paper generates dense NDVI (Normalized Difference Vegetation Index time series between 2000 and 2011 at a spatial resolution of 30 m by blending Landsat and MODIS (Moderate Resolution Imaging Spectroradiometer data using the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM and further evaluates its capability for mapping vegetation trends around a typical coalfield on the Loss Plateau. Synthetic NDVI images were generated using (1 STARFM-generated NIR (near infrared and red band reflectance data (scheme 1 and (2 Landsat and MODIS NDVI images directly as inputs for STARFM (scheme 2. By comparing the synthetic NDVI images with the corresponding Landsat NDVI, we found that scheme 2 consistently generated better results (0.70 < R2 < 0.76 than scheme 1 (0.56 < R2 < 0.70 in this study area. Trend analysis was then performed with the synthetic dense NDVI time series and the annual maximum NDVI (NDVImax time series. The accuracy of these trends was evaluated by comparing to those from the corresponding MODIS time series, and it was concluded that both the trends from synthetic/MODIS NDVI dense time series and synthetic/MODIS NDVImax time series (2000–2011 were highly consistent. Compared to trends from MODIS time series, trends from synthetic time series are better able to capture fine scale vegetation changes. STARFM-generated synthetic NDVI time series could be used to quantify the effects of mining activities on vegetation, but the test areas should be selected with caution, as the trends derived from synthetic and MODIS time series may be significantly different in some areas.

  19. Satellite and ground-based observations of patterns and seasonality of sea-ice, summer warmth, snow, and NDVI along the North America and Eurasia Arctic transects

    Science.gov (United States)

    Walker, D. A.; Epstein, H. E.; Raynolds, M. K.; Bhatt, U. S.; Bieniek, P. A.

    2011-12-01

    We analyzed vegetation, climate, and spectral data from zonal sites along two >1500 km long transects that span all five Arctic bioclimate subzones in North America and Eurasia to help interpret the long-term changes in satellite-derived trends of pattern and seasonality of vegetation greenness. Despite large differences in environment and vegetation along the two transects, there is nearly an identical logarithmic relationship between biomass and the summer maximum normalized difference vegetation index derived from AVHRR sensors (MaxNDVI) along the two transects. Summer open water in the Northern Alaska/Beaufort Sea region has increased by 39%, the summer warmth index (SWI) of the tundra increased by 14%, MaxNDVI by 28% and time-integrated NDVI (TI-NDVI) by 21%. The increased open water in the Beaufort is associated with a warming of the land and a large positive increase in the NDVI. In the eastern Kara Sea/Yamal Peninsula region, summer-fall open water has increased by 115%, the SWI decreased by -3%, MaxNDVI increased by only 6%, and TI-NDVI by 2%. The greatly reduced sea ice has affected the summer total warmth and NDVI of the Eurasia transect minimally possibly due to increased winter snow and delayed snowmelt in much of northwest Russian Arctic. In northern Alaska, there is distinctive trend of earlier snow melt at most stations; whereas the northern Yamal has seen an increase in the snow water equivalent and delayed melt on much of the Yagorsky, Yamal, Gydan, and Taimyr peninsulas. This appears to be associated with the reduction in the total summer warmth and relatively small increase in NDVI.

  20. Situação de saúde da criança em área da região sul do Brasil, 1980-1992: tendências temporais e distribuição espacial

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    Cesar G. Victora

    1994-12-01

    Full Text Available Embora as estatísticas vitais sejam de fundamental importância para o planejamento e avaliação das ações de saúde, são poucos os Estados brasileiros que dispõem de sistema de registro com cobertura e agilidade suficiente para atingir estas metas. Objetivou, portanto, analisar os dados gerados no Rio Grande do Sul, Brasil, para descrever tendências temporais e distribuição espacial de indicadores de saúde infantil, incluindo os coeficientes de mortalidade infantil e de mortalidade proporcional de menores de um ano, prevalência de baixo peso ao nascer, e cobertura vacinal. Entre 1980 e 1992, observaram-se reduções marcantes na mortalidade infantil (de 39,0 para 19,3 por mil e na mortalidade proporcional de menores de um ano (de 13,9% para 5,9%. A prevalência de baixo peso ao nascer mostrou-se estável entre 8 e 10%, tendo mesmo sido observado discreto aumento até 1991. A cobertura de vacina tríplice oscilou marcadamente de ano a ano, entre 79% e 99%. Houve forte correlação, ao nível de Delegacias Regionais de Saúde, entre mortalidade infantil e baixo peso ao nascer. Os 4 indicadores estudados foram combinados de forma a construir um escore para identificar as Delegacias de Saúde com maiores necessidades de intervenções sanitárias. A região sul do Estado, caracterizada pela presença de grandes latifúndios, mostrou os piores índices de saúde infantil.

  1. High spatial resolution WorldView-2 imagery for mapping NDVI and its relationship to temporal urban landscape evapotranspiration factors

    Science.gov (United States)

    Nouri, Hamideh; Beecham, Simon; Anderson, Sharolyn; Nagler, Pamela

    2014-01-01

    Evapotranspiration estimation has benefitted from recent advances in remote sensing and GIS techniques particularly in agricultural applications rather than urban environments. This paper explores the relationship between urban vegetation evapotranspiration (ET) and vegetation indices derived from newly-developed high spatial resolution WorldView-2 imagery. The study site was Veale Gardens in Adelaide, Australia. Image processing was applied on five images captured from February 2012 to February 2013 using ERDAS Imagine. From 64 possible two band combinations of WorldView-2, the most reliable one (with the maximum median differences) was selected. Normalized Difference Vegetation Index (NDVI) values were derived for each category of landscape cover, namely trees, shrubs, turf grasses, impervious pavements, and water bodies. Urban landscape evapotranspiration rates for Veale Gardens were estimated through field monitoring using observational-based landscape coefficients. The relationships between remotely sensed NDVIs for the entire Veale Gardens and for individual NDVIs of different vegetation covers were compared with field measured urban landscape evapotranspiration rates. The water stress conditions experienced in January 2013 decreased the correlation between ET and NDVI with the highest relationship of ET-Landscape NDVI (Landscape Normalized Difference Vegetation Index) for shrubs (r2 = 0.66) and trees (r2 = 0.63). However, when the January data was excluded, there was a significant correlation between ET and NDVI. The highest correlation for ET-Landscape NDVI was found for the entire Veale Gardens regardless of vegetation type (r2 = 0.95, p > 0.05) and the lowest one was for turf (r2 = 0.88, p > 0.05). In support of the feasibility of ET estimation by WV2 over a longer period, an algorithm recently developed that estimates evapotranspiration rates based on the Enhanced Vegetation Index (EVI) from MODIS was employed. The results revealed a significant positive

  2. Dynamic change of net primary productivity and fractional vegetation cover in the Yellow River Basin using multi-temporal AVHRR NDVI Data

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An exponential relationship between net primary productivity (NPP) and integrated NDVI has been found in this paper. Based on the relationship and using multi-temporal 8 km resolution NOAA AVHRR-NDVI data, the spatial distribution and dynamic change of NPP and fractional vegetation cover in the Yellow River Basin from 1982 to 1999 are analyzed. Finally, the effect of rainfall on NDVI is examined. Results show that mean NPP and fractional vegetation cover have an inclining trend for the whole basin, and rainfall in flood season influences vegetation cover most.

  3. NDVI anomalies associated with the European drought and heat wave of 2003

    Science.gov (United States)

    Bevan, Suzanne; Los, Sietse; North, Peter

    2013-04-01

    The European drought and heat wave of 2003 is commonly used as an example of extreme summer climate conditions that are likely to become more common towards the end of the 21st century, under predicted climate change scenarios. The extreme conditions are known to have had an impact on biomass primary productivity as reflected in remotely sensed vegetation indices and fAPAR, flux-tower measurements, and the results from a variety of modelling approaches. Early remote sensing analyses were based on relatively short time series of data, 4 or 5 years only. We are now able to make use of 12 years of MODIS observations to highlight the statistical significance of the widespread and persistent anomalies in vegetation greenness in 2003 compared with other summers so far this century. Anomalies in excess of 2 standard deviations initially occur at the start of June in central and eastern France. By the end of July they are common also over Germany, by mid August have spread to the French border with Spain, and by the end of August are common over the north-western corner of France, England and eastern Scotland. Using the One-Degree Daily resolution Global Precipitation Climatology Project precipitation data and European Re-Analysis Interim 2 m air temperatures we are able to show where and whether either precipitation or temperature has the greatest impact on summer vegetation greenness. With the exception of mountainous regions such as the Alps and northern and western parts of the United Kingdom, summer NDVI anomalies are highly correlated with precipitation anomalies of the preceding month. The picture for temperature is more geographically variable with summer NDVI anomalies in southern France, Italy and central England and north-eastern Scotland being negatively correlated with temperature, and northern and western coasts of France and Germany being positively correlated with temperature. In addition, we analyse the anomalies in conjunction with vegetation height from

  4. STUDY ON THE VARIABILITY OF "NORMALIZED DIFFERENCE VEGETATION INDEX/NDVI" BY INDICATIVE KRIGING = ESTUDO DA VARIABILIDADE DO "ÍNDICE DE VEGETAÇÃO POR DIFERENÇA NORMALIZADA/NDVI" UTILIZANDO KRIGAGEM INDICATIVA

    Directory of Open Access Journals (Sweden)

    Roberto Wagner Lourenço

    2004-01-01

    Full Text Available The main purpose of this paper was to evaluate the “Normalized Difference Vegetation Index” (NDVI in an area at Baixada Santista, coastland of São Paulo State, Brazil, using the geostatistic technique of indicative kriging. The analyses were made using sensor TM images (Landsat satellite, dated from February/1989 and January/1997. The obtained NDVI maps showed vegetation loss during the analyzed period, and the probabilities map, resulting from the difference between the two periods of time, indicated a distinct contrast between loss and gains of vegetation index. Vegetation mapping and application of indicative kriging were shown as beingquite useful for monitoring and environmental management, being able to provide good results when jointly used. = Este trabalho teve por objetivo principal analisar o “índice de vegetação por diferença normalizada” (NDVI em uma área da Baixada Santista, litoral paulista,utilizando a técnica geoestatística da krigagem indicativa. As análises foram feitas em imagens do sensor TM do satélite Landsat datadas de fevereiro de 1989 e janeiro de 1997. Os mapas obtidos do NDVI mostraram perda de vegetação de um modo geral, durante o período analisado, e o mapa de probabilidades resultante da diferença entreos dois períodos indicou forte contraste entre perdas e ganhos do índice de vegetação. O mapeamento da vegetação e a aplicação da krigagem indicativa mostraram-se ferramentas de grande aplicabilidade para o monitoramento e gerenciamento ambiental e podem proporcionar bons resultados quando utilizadas de forma integrada.

  5. Historical Fire Detection of Tropical Forest from NDVI Time-series Data: Case Study on Jambi, Indonesia

    Directory of Open Access Journals (Sweden)

    Dyah R. Panuju

    2010-03-01

    Full Text Available In addition to forest encroachment, forest fire is a serious problem in Indonesia. Attempts at managing its widespread and frequent occurrence has led to intensive use of remote sensing data. Coarse resolution images have been employed to derive hot spots as an indicator of forest fire. However, most efforts to verify the hot spot data and to verify fire accidents have been restricted to the use of medium or high resolution data. At present, it is difficult to verify solely upon those data due to severe cloud cover and low revisit time. In this paper, we present a method to validate forest fire using NDVI time series data. With the freely available NDVI data from SPOT VEGETATION, we successfully detected changes in time series data which were associated with fire accidents.

  6. Salt marsh mapping based on a short-time interval NDVI time-series from HJ-1 CCD imagery

    Science.gov (United States)

    SUN, C.

    2015-12-01

    Salt marshes are regard as one of the most dynamic and valuable ecosystems in coastal zone. It is crucial to obtain accurate information on the species composition and spatial distribution of salt marshes in time since they are experiencing tremendous replacement and disappearance. However, discriminating various types of salt marshes is a rather difficult task because of the strong spectral similarities. In previous studies, salt marsh mappings were mainly focused on high-spatial and hyperspectral resolution imageries combined with auxiliary information but this method can hardly extend to a large region. With high temporal and moderate spatial resolutions, Chinese HJ-1 CCD imagery would not only allow monitoring phenological changes of salt marsh vegetation in short-time intervals, but also cover large areas of salt marshes. Taking the middle coast of Jiangsu (east China) as an example, our study first constructed a monthly NDVI time-series to classify various types of salt marshes. Then, we tested the idea of compressed time-series continuously to broaden the applicability and portability of this particular approach. The results showed that (1) the overall accuracy of salt marsh mapping based on the monthly NDVI time-series reached 90.3%, which increased approximately 16.0% in contrast with a single-phase classification strategy; (2) a compressed time-series, including NDVI from six key months (April, June to September, and November) demonstrated very little decline (2.3%) in overall accuracy but led to obvious improvements in unstable regions; (3) Spartina alterniflora identification could be achieved with only a scene NDVI image from November, which could provide an effective way to regularly monitor its distribution. Besides, by comparing the calibrated performance between HJ-1 CCD and other sensors (i.e., Landsat TM/ETM+, OLI), we certified the reliability of HJ-1 CCD imagery, which is expected to pave the way for laws expansibility from this imagery.

  7. Analisis Perubahan Tutupan Vegetasi Berdasarkan Nilai NDVI dan Faktor Biofisik Lahan di Cagar Alam Dolok Sibual-buali

    OpenAIRE

    PUTRA, ARDIANSYAH

    2015-01-01

    The absence of information about the level of change in vegetation index (NDVI) of forest land in the Nature Reserve Dolok Sibual-Buali so unclear that forest development and likely has damage. Forest damage will impact on the decrease of forest functions, especially its function as regulator of water management, flood prevention, erosion and carbon sequestration. This research was conducted in CADS in May-September 2009 using Geographic Information System (GIS), Remote Sensing (RS) and Globa...

  8. Thirty-two Years of Sahelian Zone Growing Season Non-Stationary NDVI3g Patterns and Trends

    Directory of Open Access Journals (Sweden)

    Assaf Anyamba

    2014-04-01

    Full Text Available We update the Global Inventory Modeling and Mapping Studies (GIMMS analysis of Sahelian vegetation dynamics and trends using the normalized difference vegetation index (NDVI; version 3g 1981 to 2012 data set. We compare the annual NDIV3g and July to October growing season averages with the three rainfall data sets: the Africa Rainfall Climatology from 1983 to 2012, the Variability Analyses of Surface Climate Observations Version-1.1 from 1951 to 2000, and the Nicholson ground-station precipitation rainfall data from 1981 to 1994. We use the Nicholson ground-station annual precipitation data to determine the reliability of the two continental precipitation data sets for specific locations and specific times, extrapolate these confirmed relationships over the Sahelian Zone from 1983 to 2012 with the Africa Rainfall Climatology, and then place these zonal findings within the 1951 to 2000 record of the Variability Analyses of Surface Climate Observations Version-1.1 precipitation data set. We confirm the extreme nature of the 1984–1985 Sahelian drought, a signature event that marked the minima during the 1980s desiccation period followed within ten years by near-maxima rainfall event in 1994 and positive departures is NDVI, marking beginning of predominantly wetter conditions that have persisted to 2012. We also show the NDVI3g data capture “effective” rainfall, the rainfall that is utilized by plants to grow, as compared to rainfall that evaporates or is runoff. Using our effective rainfall concept, we estimate average effective rainfall for the entire Sahelian Zone for the 1984 extreme drought was 223 mm/yr as compared to 406 mm/yr in during the 1994 wet period. We conclude that NDVI3g data can used as a proxy for analyzing and interpreting decadal-scale land surface variability and trends over semi arid-lands.

  9. Strategy for the Development of a Smart NDVI Camera System for Outdoor Plant Detection and Agricultural Embedded Systems

    Directory of Open Access Journals (Sweden)

    Ali Akbar Zarezadeh

    2013-01-01

    Full Text Available The application of (smart cameras for process control, mapping, and advanced imaging in agriculture has become an element of precision farming that facilitates the conservation of fertilizer, pesticides, and machine time. This technique additionally reduces the amount of energy required in terms of fuel. Although research activities have increased in this field, high camera prices reflect low adaptation to applications in all fields of agriculture. Smart, low-cost cameras adapted for agricultural applications can overcome this drawback. The normalized difference vegetation index (NDVI for each image pixel is an applicable algorithm to discriminate plant information from the soil background enabled by a large difference in the reflectance between the near infrared (NIR and the red channel optical frequency band. Two aligned charge coupled device (CCD chips for the red and NIR channel are typically used, but they are expensive because of the precise optical alignment required. Therefore, much attention has been given to the development of alternative camera designs. In this study, the advantage of a smart one-chip camera design with NDVI image performance is demonstrated in terms of low cost and simplified design. The required assembly and pixel modifications are described, and new algorithms for establishing an enhanced NDVI image quality for data processing are discussed.

  10. Mapping grassland productivity with 250-m eMODIS NDVI and SSURGO database over the Greater Platte River Basin, USA

    Science.gov (United States)

    Gu, Yingxin; Wylie, Bruce K.; Bliss, Norman B.

    2013-01-01

    This study assessed and described a relationship between satellite-derived growing season averaged Normalized Difference Vegetation Index (NDVI) and annual productivity for grasslands within the Greater Platte River Basin (GPRB) of the United States. We compared growing season averaged NDVI (GSN) with Soil Survey Geographic (SSURGO) database rangeland productivity and flux tower Gross Primary Productivity (GPP) for grassland areas. The GSN was calculated for each of nine years (2000–2008) using the 7-day composite 250-m eMODIS (expedited Moderate Resolution Imaging Spectroradiometer) NDVI data. Strong correlations exist between the nine-year mean GSN (MGSN) and SSURGO annual productivity for grasslands (R2 = 0.74 for approximately 8000 pixels randomly selected from eight homogeneous regions within the GPRB; R2 = 0.96 for the 14 cluster-averaged points). Results also reveal a strong correlation between GSN and flux tower growing season averaged GPP (R2 = 0.71). Finally, we developed an empirical equation to estimate grassland productivity based on the MGSN. Spatially explicit estimates of grassland productivity over the GPRB were generated, which improved the regional consistency of SSURGO grassland productivity data and can help scientists and land managers to better understand the actual biophysical and ecological characteristics of grassland systems in the GPRB. This final estimated grassland production map can also be used as an input for biogeochemical, ecological, and climate change models.

  11. Avaliação dos efeitos atmosféricos no albedo e NDVI obtidos com imagens de satélite Evaluation of the atmospheric effects on albedo and NDVI using satellite images

    Directory of Open Access Journals (Sweden)

    Marcus V. C. Bezerra

    2011-07-01

    Full Text Available O albedo é um elemento importante em estudos relacionados aos balanços de radiação e energia. Por conseguinte, alterações ocorridas em diversos biomas trazem grandes implicações ao conforto humano e animal. Neste sentido, o monitoramento do albedo através de imagens orbitais possibilita identificar a antropização de grandes áreas e seus impactos ambientais. O presente trabalho foi desenvolvido com o objetivo de avaliar o impacto da correção atmosférica na estimativa do albedo da superfície e do NDVI, utilizando-se a metodologia tradicional do SEBAL (Bastiaanssen, 2000 e a correção atmosférica no cômputo da refletância, banda a banda (Allen et al., 2007b, para quatro imagens Landsat 5 - TM da região do Cariri cearense. Os resultados mostraram diminuição no albedo da superfície e acréscimo no NDVI, corrigidos os efeitos atmosféricos para todas as áreas amostrais. De acordo com o teste de Student as diferenças entre os albedos e NDVIs, obtidas segundo os dois procedimentos considerados, são significativas a nível de significância de 0,01.The albedo is an important element in studies related to radiation and energy balances. Consequently, changes in different biomes bring major implications for human and animal comfort. Accordingly, the monitoring of the albedo by orbital images enables to identify the anthropic influence of large areas and their environmental impact. This work was developed with the objective of assessing the impact of atmospheric correction at surface albedo and the NDVI using the traditional method of SEBAL (Bastiaanssen, 2000 and atmospheric correction band to band (Allen et al., 2007b for four Landsat 5 TM images covering Cariri mesoregion of Ceará State. The results showed decrease in the surface albedo and increase in NDVI, corrected for atmospheric effects for all sample areas. According with Student test there was significant difference between the albedo and NDVI under the two methods

  12. Water scarcity-induced change in vegetation cover along Teesta River catchments in Bangladesh : NDVI, Tasseled Cap and System dynamics analysis

    OpenAIRE

    Rahman, Md. Azizur

    2013-01-01

    Water scarcity is both natural and man-made phenomenon. Water control and uneven distribution of upstream TeestaRiver water makes artificial scarcity in downstream areas which can be minimized at least to the water stress level by balancing distribution and sustainable water use. Tasseled Cap transformation and NDVI methods were used in this study in order to find the magnitude of water scarcity in the downstream areas. NDVI and Tasseled Cap Greenness methods were applied to get proxy for soi...

  13. Estimation of Protein Content in Rice Crop and Nitrogen Content in Rice Leaves Through Regression Analysis with NDVI Derived from Camera Mounted Radio-Control Helicopter

    OpenAIRE

    Kohei Arai; Masanori Sakashita; Osamu Shigetomi; Yuko Miura

    2014-01-01

    Estimation of protein content in rice crop and nitrogen content in rice leaves through regression analysis with Normalized Difference Vegetation Index: NDVI derived from camera mounted radio-control helicopter is proposed. Through experiments at rice paddy fields which is situated at Saga Prefectural Research Institute of Agriculture: SPRIA in Saga city, Japan, it is found that protein content in rice crops is highly correlated with NDVI which is acquired with visible and Near Infrared: NIR c...

  14. Using NDVI and EVI to Map Spatiotemporal Variation in the Biomass and Quality of Forage for Migratory Elk in the Greater Yellowstone Ecosystem

    Directory of Open Access Journals (Sweden)

    Erica L. Garroutte

    2016-05-01

    Full Text Available The Normalized Difference Vegetation Index (NDVI and the Enhanced Vegetation Index (EVI have gained considerable attention in ecological research and management as proxies for landscape-scale vegetation quantity and quality. In the Greater Yellowstone Ecosystem (GYE, these indices are especially important for mapping spatiotemporal variation in the forage available to migratory elk (Cervus elaphus. Here, we examined how the accuracy of using MODIS-derived NDVI and EVI as proxies for forage biomass and quality differed across elevation-related phenology and land use gradients, determined if polynomial NDVI/EVI, site, and season effects improved these models, and then mapped spatiotemporal variation in the abundance of high quality forage available to elk across the Upper Yellowstone River Basin (UYRB of the GYE. Models with a polynomial NDVI effect explained 19%–55% more variation in biomass than the linear NDVI and EVI models. Models with linear season effect explained 14%–20% more variation in chlorophyll, 37%–69% more variation in crude protein, and 26%–50% more variation in in vitro dry matter digestibility (IVDMD than the linear NDVI and EVI models. Linear NDVI models explained more variation in biomass and quality across the UYRB than the linear EVI models. The accuracy of these models was lowest in grasslands with late onset of growth, in irrigated agriculture, and after the peak in biomass. Forage biomass and quality varied across the elevation-related phenology and land use gradients in the UYRB throughout the season. At their seasonal peak, the abundance of high quality forage for elk was 50% greater in grasslands with late onset of growth and 200% greater in irrigated agriculture than in all other grasslands, suggesting that these grasslands play an especially important role in the movement and fitness of migratory elk. These results provide novel information on the utility of NDVI and EVI for mapping spatiotemporal patterns of

  15. Combined Spatial and Temporal Effects of Environmental Controls on Long-Term Monthly NDVI in the Southern Africa Savanna

    Directory of Open Access Journals (Sweden)

    Miguel A. Campo-Bescós

    2013-12-01

    Full Text Available Deconstructing the drivers of large-scale vegetation change is critical to predicting and managing projected climate and land use changes that will affect regional vegetation cover in degraded or threated ecosystems. We investigate the shared dynamics of spatially variable vegetation across three large watersheds in the southern Africa savanna. Dynamic Factor Analysis (DFA, a multivariate time-series dimension reduction technique, was used to identify the most important physical drivers of regional vegetation change. We first evaluated the Advanced Very High Resolution Radiometer (AVHRR- vs. the Moderate Resolution Imaging Spectroradiometer (MODIS-based Normalized Difference Vegetation Index (NDVI datasets across their overlapping period (2001–2010. NDVI follows a general pattern of cyclic seasonal variation, with distinct spatio-temporal patterns across physio-geographic regions. Both NDVI products produced similar DFA models, although MODIS was simulated better. Soil moisture and precipitation controlled NDVI for mean annual precipitation (MAP < 750 mm, and above this, evaporation and mean temperature dominated. A second DFA with the full AVHRR (1982–2010 data found that for MAP < 750 mm, soil moisture and actual evapotranspiration control NDVI dynamics, followed by mean and maximum temperatures. Above 950 mm, actual evapotranspiration and precipitation dominate. The quantification of the combined spatio-temporal environmental drivers of NDVI expands our ability to understand landscape level changes in vegetation evaluated through remote sensing and improves the basis for the management of vulnerable regions, like the southern Africa savannas.

  16. Non-Parametric Responses of Aboveground Biomass and NDVI to Land Surface Parameters in Arctic-Alpine Environments

    Science.gov (United States)

    Riihimäki, H. K.; Heiskanen, J.; Luoto, M.

    2015-12-01

    Aboveground biomass (AGB) is an important carbon pool and it affects various phenomena in Arctic and alpine areas, e.g. biodiversity, surface albedo and soil conditions. The growing availability of high-resolution digital elevation models (DEM) makes it possible to utilize topographical information for modeling local ground surface conditions globally. We investigated the effect of topography on field measured AGB (n = 359) and its commonly used proxy, the Normalized Difference Vegetation Index (NDVI) calculated from SPOT 5 imagery. The study area located in an Arctic-alpine treeline environment (69 °N, 21 °E). We performed the analyses with boosted regression trees method by using elevation and four land surface parameters (LSPs), derived from 10 m DEM, as predictors. The LSPs were namely Potential Incoming Solar Radiation (PISR, MJ m-2 a-1), Topographic Position Index (TPI, r = 300 m), Slope (angle in degrees) and Topographic Wetness Index (TWI). AGB varied from 0 to 5647 g m-2, while median AGB of the data was 449 g m-2. The explained deviance of the AGB and NDVI models were 53 % and 65 %, respectively. Elevation and PISR were the most important predictors. Their interaction was also significant in both cases as the highest AGB were at low-elevation, high-radiation sites, which implicates that PISR significantly improves the modelling of temperature related growing conditions. TWI had no clear effect to AGB nor to NDVI. TPI and Slope had a minor effect on AGB, but no effect to NDVI. Areas lower than their surroundings (negative TPI) had relatively high AGB. Furthermore, steeper slopes had higher AGB compared to flat sites. This is probably caused by the presence of mountain birch (Betula pubescens ssp. czerepanovii), which favors protected and steeper topography. Local topography is an important driver of the fine scale AGB patterns. Thus, DEM derived LSPs should be taken into account when modelling current and future biomass distributions in Arctic and alpine

  17. Spatio-temporal variability of NDVI-precipitation over southernmost South America: possible linkages between climate signals and epidemics

    Science.gov (United States)

    Tourre, Y. M.; Jarlan, L.; Lacaux, J.-P.; Rotela, C. H.; Lafaye, M.

    2008-10-01

    Climate-environment variability affects the rates of incidence of vector-borne and zoonotic diseases and is possibly associated with epidemics outbreaks. Over southernmost South America the joint spatio-temporal evolution of climate-environment is analyzed for the 1982-2004 period. Detailed mapping of normalized difference vegetation index (NDVI) and rainfall variability are then compared to zones with preliminary epidemiological reports. A significant quasi-biennial signal (2.2- to 2.4-year periods, or QB) for joint NDVI-rainfall variability is revealed. From rotated EOFs, dominant NDVI patterns are partitioned according to their lead frequencies: (1) the 'QB group' (2.1-to 3-year periods) includes six modes over southern Brazil, Uruguay, northern-central Argentina (two modes), the southern Paraguay-northern Argentina border, and the Santa Cruz Province; (2) the QB1 (2.4- to 3-year periods) + quasi-quadrennial (QQ) mode over the Misiones Province; and (3) the QB2 (2.1- to 2.5-year periods) + QQ + inter-annual (IA) (3- to 7-year periods) two modes over south-eastern Argentina. Modes within the 'QB group' are positively correlated with global climate signals and SST. The Uruguayan mode is correlated with global ENSO (8-month lag) whilst the southern Entre-Rios/northern Buenos Aires provinces are correlated with central equatorial Pacific SSTs (3-month lag). The Santa Cruz (Patagonia) Province is most correlated with the Pacific South America (PSA) index and SST patterns (3-month lag) along the Antarctica circumpolar current. The spatial distribution of lead NDVI modes includes the Formosa, Misiones, Chaco and Buenos Aires provinces among others, known for being prone to vector-borne epidemics such as dengue fever, malaria, leishmaniasis (American cutaneous leishmaniasis or ACL), hantivirus, chagas and Argentine hemorrhagic fever (AHF). Some provinces also correspond to regions where lead NDVI PCs' modes are associated with high-frequency climate signals such as the

  18. Spatio-temporal variability of NDVI-precipitation over southernmost South America: possible linkages between climate signals and epidemics

    International Nuclear Information System (INIS)

    Climate-environment variability affects the rates of incidence of vector-borne and zoonotic diseases and is possibly associated with epidemics outbreaks. Over southernmost South America the joint spatio-temporal evolution of climate-environment is analyzed for the 1982-2004 period. Detailed mapping of normalized difference vegetation index (NDVI) and rainfall variability are then compared to zones with preliminary epidemiological reports. A significant quasi-biennial signal (2.2- to 2.4-year periods, or QB) for joint NDVI-rainfall variability is revealed. From rotated EOFs, dominant NDVI patterns are partitioned according to their lead frequencies: (1) the 'QB group' (2.1-to 3-year periods) includes six modes over southern Brazil, Uruguay, northern-central Argentina (two modes), the southern Paraguay-northern Argentina border, and the Santa Cruz Province; (2) the QB1 (2.4- to 3-year periods) + quasi-quadrennial (QQ) mode over the Misiones Province; and (3) the QB2 (2.1- to 2.5-year periods) + QQ + inter-annual (IA) (3- to 7-year periods) two modes over south-eastern Argentina. Modes within the 'QB group' are positively correlated with global climate signals and SST. The Uruguayan mode is correlated with global ENSO (8-month lag) whilst the southern Entre-Rios/northern Buenos Aires provinces are correlated with central equatorial Pacific SSTs (3-month lag). The Santa Cruz (Patagonia) Province is most correlated with the Pacific South America (PSA) index and SST patterns (3-month lag) along the Antarctica circumpolar current. The spatial distribution of lead NDVI modes includes the Formosa, Misiones, Chaco and Buenos Aires provinces among others, known for being prone to vector-borne epidemics such as dengue fever, malaria, leishmaniasis (American cutaneous leishmaniasis or ACL), hantivirus, chagas and Argentine hemorrhagic fever (AHF). Some provinces also correspond to regions where lead NDVI PCs' modes are associated with high-frequency climate signals such as the

  19. Spatio-temporal variability of NDVI-precipitation over southernmost South America: possible linkages between climate signals and epidemics

    Energy Technology Data Exchange (ETDEWEB)

    Tourre, Y M [METEO-France, Meteopole, 42 Avenue Coriolis, 31057 Toulouse Cedex 1 (France); Jarlan, L [Centre d' Etudes Spatiales de la Biosphere (CESBIO), 18 avenue Edouard Belin, F-31401 Toulouse Cedex 4 (France); Lacaux, J-P [Universite Paul Sabatier (UPS), Observatoire Midi Pyrenees (OMP), 12 Avenue Edouard Belin, 31400 Toulouse (France); Rotela, C H [Instituto de Altos Estudios Espaciales ' Mario Gulich' , Comision Nacional de Actividades Espaciales (CONAE), Universidad Nacional de Cordoba (Argentina); Lafaye, M [CNES, DSP/ARP/AV, 18 Avenue Edouard Belin, F-31401 Toulouse Cedex 4 (France)

    2008-10-15

    Climate-environment variability affects the rates of incidence of vector-borne and zoonotic diseases and is possibly associated with epidemics outbreaks. Over southernmost South America the joint spatio-temporal evolution of climate-environment is analyzed for the 1982-2004 period. Detailed mapping of normalized difference vegetation index (NDVI) and rainfall variability are then compared to zones with preliminary epidemiological reports. A significant quasi-biennial signal (2.2- to 2.4-year periods, or QB) for joint NDVI-rainfall variability is revealed. From rotated EOFs, dominant NDVI patterns are partitioned according to their lead frequencies: (1) the 'QB group' (2.1-to 3-year periods) includes six modes over southern Brazil, Uruguay, northern-central Argentina (two modes), the southern Paraguay-northern Argentina border, and the Santa Cruz Province; (2) the QB1 (2.4- to 3-year periods) + quasi-quadrennial (QQ) mode over the Misiones Province; and (3) the QB2 (2.1- to 2.5-year periods) + QQ + inter-annual (IA) (3- to 7-year periods) two modes over south-eastern Argentina. Modes within the 'QB group' are positively correlated with global climate signals and SST. The Uruguayan mode is correlated with global ENSO (8-month lag) whilst the southern Entre-Rios/northern Buenos Aires provinces are correlated with central equatorial Pacific SSTs (3-month lag). The Santa Cruz (Patagonia) Province is most correlated with the Pacific South America (PSA) index and SST patterns (3-month lag) along the Antarctica circumpolar current. The spatial distribution of lead NDVI modes includes the Formosa, Misiones, Chaco and Buenos Aires provinces among others, known for being prone to vector-borne epidemics such as dengue fever, malaria, leishmaniasis (American cutaneous leishmaniasis or ACL), hantivirus, chagas and Argentine hemorrhagic fever (AHF). Some provinces also correspond to regions where lead NDVI PCs' modes are associated with high

  20. Mapping cropland-use intensity across Europe using MODIS NDVI time series

    Science.gov (United States)

    Estel, Stephan; Kuemmerle, Tobias; Levers, Christian; Baumann, Matthias; Hostert, Patrick

    2016-02-01

    Global agricultural production will likely need to increase in the future due to population growth, changing diets, and the rising importance of bioenergy. Intensifying already existing cropland is often considered more sustainable than converting more natural areas. Unfortunately, our understanding of cropping patterns and intensity is weak, especially at broad geographic scales. We characterized and mapped cropping systems in Europe, a region containing diverse cropping systems, using four indicators: (a) cropping frequency (number of cropped years), (b) multi-cropping (number of harvests per year), (c) fallow cycles, and (d) crop duration ratio (actual time under crops) based on the MODIS Normalized Difference Vegetation Index (NDVI) time series from 2000 to 2012. Second, we used these cropping indicators and self-organizing maps to identify typical cropping systems. The resulting six clusters correspond well with other indicators of agricultural intensity (e.g., nitrogen input, yields) and reveal substantial differences in cropping intensity across Europe. Cropping intensity was highest in Germany, Poland, and the eastern European Black Earth regions, characterized by high cropping frequency, multi-cropping and a high crop duration ratio. Contrarily, we found lowest cropping intensity in eastern Europe outside the Black Earth region, characterized by longer fallow cycles. Our approach highlights how satellite image time series can help to characterize spatial patterns in cropping intensity—information that is rarely surveyed on the ground and commonly not included in agricultural statistics: our clustering approach also shows a way forward to reduce complexity when measuring multiple indicators. The four cropping indicators we used could become part of continental-scale agricultural monitoring in order to identify target regions for sustainable intensification, where trade-offs between intensification and the environmental should be explored.

  1. Maize yield and rainfall on different spatial and temporal scales in Southern Brazil Rendimento de milho e chuva em diferentes escalas espaço-temporais no Sul do Brasil

    Directory of Open Access Journals (Sweden)

    Homero Bergamaschi

    2007-05-01

    Full Text Available This study aimed to establish relationships between maize yield and rainfall on different temporal and spatial scales, in order to provide a basis for crop monitoring and modelling. A 16-year series of maize yield and daily rainfall from 11 municipalities and micro-regions of Rio Grande do Sul State was used. Correlation and regression analyses were used to determine associations between crop yield and rainfall for the entire crop cycle, from tasseling to 30 days after, and from 5 days before tasseling to 40 days after. Close relationships between maize yield and rainfall were found, particularly during the reproductive period (45-day period comprising the flowering and grain filling. Relationships were closer on a regional scale than at smaller scales. Implications of the crop-rainfall relationships for crop modelling are discussed.Este trabalho teve como objetivo estabelecer relações entre rendimentos de milho e totais de chuva em diferentes escalas temporais e espaciais, com a finalidade de fornecer bases para modelagem e monitoramento de safras. Utilizou-se uma série de 16 anos de rendimento de milho e dados diários de chuva de 11 municípios e microrregiões do Estado do Rio Grande do Sul. Análises de correlação e regressão foram utilizadas para determinar associações entre rendimento e total de chuva no ciclo do milho, do pendoamento até 30 dias depois, e de 5 dias antes a 40 dias após o pendoamento. Altas relações foram encontradas entre rendimento de milho e chuvas do período reprodutivo, em particular dos 45 dias que englobam florescimento e enchimento de grãos. Essas relações foram mais elevadas em escala regional do que em nível de município. São discutidas implicações das relações clima-chuva para modelagem de cultivos.

  2. Poluição do ar e doenças respiratórias e cardiovasculares: estudo de séries temporais em Cubatão, São Paulo, Brasil

    Directory of Open Access Journals (Sweden)

    Adelaide Cassia Nardocci

    2013-09-01

    Full Text Available Foi avaliado o impacto da poluição do ar nas internações por doenças respiratórias e cardiovasculares em residentes do Município de Cuba-tão, São Paulo, Brasil. Utilizaram-se modelos de séries temporais, com modelos aditivos generalizados, em regressão de Poisson, testando como variáveis independentes as concentrações diárias de material particulado (PM10; dióxido de enxofre (SO2 e o ozônio (O3. Como variáveis de controle a temperatura, umidade, dias da semana e feriados. Para cada incremento de 10µg/m³ de PM10, encontrou-se um excesso de internações de 4,25% (IC95%: 2,82; 5,71; 5,74% (IC95%: 3,80; 7,71 e 2,29% (IC95%: 0,86; 3,73 para doenças respiratórias totais, doenças respiratórias em menores de 5 anos e doenças cardiovasculares em maiores de 39 anos, respectivamente. O SO2 apresentou relação com as doenças cardiovasculares em maiores de 39 anos de 3,51% (IC95%: 1,24; 5,83 e o O3 com as doenças cardiovasculares em maiores de 39 anos: 2,85% (IC95%: 0,77; 4,98 e doenças respiratórias em menores de 5 anos: 3,91% (IC95%: 1,37; 6,51. Os efeitos da poluição atmosférica na saúde em Cubatão são pronunciados, indicando a necessidade de melhoria das políticas de controle.

  3. Sugarcane yield estimates using time series analysis of spot vegetation images Estimativa de produtividade da cana-de-açúcar por meio de séries temporais de imagens spot vegetation

    Directory of Open Access Journals (Sweden)

    Jeferson Lobato Fernandes

    2011-04-01

    Full Text Available The current system used in Brazil for sugarcane (Saccharum officinarum L. crop forecasting relies mainly on subjective information provided by sugar mill technicians and on information about demands of raw agricultural products from industry. This study evaluated the feasibility to estimate the yield at municipality level in São Paulo State, Brazil, using 10-day periods of SPOT Vegetation NDVI images and ECMWF meteorological data. Twenty municipalities and seven cropping seasons were selected between 1999 and 2006. The plant development cycle was divided into four phases, according to the sugarcane physiology, obtaining spectral and meteorological attributes for each phase. The most important attributes were selected and the average yield was classified according to a decision tree. Values obtained from the NDVI time profile from December to January next year enabled to classify yields into three classes: below average, average and above average. The results were more effective for 'average' and 'above average' classes, with 86.5 and 66.7% accuracy respectively. Monitoring sugarcane planted areas using SPOT Vegetation images allowed previous analysis and predictions on the average municipal yield trend.O atual sistema de previsão de safras para a cultura da cana-de-açúcar (Saccharum officinarum L. usado no Brasil depende, em boa parte, de informações subjetivas, baseadas no conhecimento de técnicos do setor sucroalcooleiro e em informações sobre demanda de insumos na cadeia produtiva. Avaliou-se o uso de imagens decendiais de NDVI do sensor SPOT Vegetation e variáveis meteorológicas do modelo do ECMWF para inferir sobre os dados de produtividade oficiais registrados em municípios e safras previamente selecionados. Foram selecionados 20 municípios e sete safras compreendidas entre o período de 1999 e 2006. O ciclo de desenvolvimento da cultura foi dividido em quatro fases, de acordo com a fisiologia, gerando para cada fase atributos

  4. Análise de séries temporais em epidemiologia: uma introdução sobre os aspectos metodológicos Time series analysis in epidemiology: an introduction to methodological aspects

    Directory of Open Access Journals (Sweden)

    Maria do Rosário Dias de Oliveira Latorre

    2001-11-01

    Full Text Available Este é um artigo introdutório sobre análise de séries temporais, onde se pretende apresentar, de maneira sumária, alguns modelos estatísticos mais utilizados em análise de séries temporais . Uma série temporal, também denominada série histórica, é uma seqüência de dados obtidos em intervalos regulares de tempo durante um período específico. Na análise de uma série temporal, primeiramente deseja-se modelar o fenômeno estudado para, a partir daí, descrever o comportamento da série, fazer estimativas e, por último, avaliar quais os fatores que influenciaram o comportamento da série, buscando definir relações de causa e efeito entre duas ou mais séries. Para tanto, há um conjunto de técnicas estatísticas disponíveis que dependem do modelo definido (ou estimado para a série, bem como do tipo de série analisada e do objetivo do trabalho. Para analise de tendências, podem se ajustar modelos de regressão polinomial baseados na série inteira ou em vizinhança de um determinado ponto. Isso também pode ser realizado com funções matemáticas. Define-se como um fenômeno sazonal aquele que ocorre regularmente em períodos fixos de tempo e, se existir sazonalidade dita determinística na série, podem-se utilizar modelos de regressão que incorporem funções do tipo seno ou cosseno à variável tempo. Os modelos auto-regressivos formam outra classe de modelos. Na análise do comportamento de uma série histórica livre de tendência e de sazonalidade podem ser utilizados modelos auto-regressivos (AR ou que incorporem médias móveis (ARMA. Quando há tendência, utilizam-se os modelos auto-regressivos integrados de médias móveis (ARIMA e, para incorporar o componente de sazonalidade, utilizam-se os modelos SARIMA. Por último há os modelos lineares generalizados. Neste grupo de modelos estatísticos, a variável resposta é um processo de contagem e as variáveis independentes são variáveis candidatas a explicar o

  5. Land Degradation Assessment Using Residual Trend Analysis of GIMMS NDVI3g, Soil Moisture and Rainfall in Sub-Saharan West Africa from 1982 to 2012

    Directory of Open Access Journals (Sweden)

    Yahaya Z. Ibrahim

    2015-04-01

    Full Text Available Areas affected by land degradation in Sub-Saharan West Africa between 1982 and 2012 are identified using time-series analysis of vegetation index data derived from satellites. The residual trend (RESTREND of a Normalized Difference Vegetation Index (NDVI time-series is defined as the fraction of the difference between the observed NDVI and the NDVI predicted from climate data. It has been widely used to study desertification and other forms of land degradation in drylands. The method works on the assumption that a negative trend of vegetation photosynthetic capacity is an indication of land degradation if it is independent from climate variability. In the past, many scientists depended on rainfall data as the major climatic factor controlling vegetation productivity in drylands when applying the RESTREND method. However, the water that is directly available to vegetation is stored as soil moisture, which is a function of cumulative rainfall, surface runoff, infiltration and evapotranspiration. In this study, the new NDVI third generation (NDVI3g, which was generated by the National Aeronautics and Space Administration-Goddard Space Flight Center Global Inventory Modeling and Mapping Studies (NASA-GSFC GIMMS group, was used as a satellite-derived proxy of vegetation productivity, together with the soil moisture index product from the Climate Prediction Center (CPC and rainfall data from the Climate Research Unit (CRU. The results show that the soil moisture/NDVI pixel-wise residual trend indicates land degraded areas more clearly than rainfall/NDVI. The spatial and temporal trends of the RESTREND in the region follow the patterns of drought episodes, reaffirming the difficulties in separating the impacts of drought and land degradation on vegetation photosynthetic capacity. Therefore, future studies of land degradation and desertification in drylands should go beyond using rainfall as a sole predictor of vegetation condition, and include soil

  6. Modelling the Phenological Relationships of Questing Immature Ixodes Ricinus (Ixodidae) Using Temperature and NDVI Data.

    Science.gov (United States)

    Alonso-Carné, J; García-Martín, A; Estrada-Peña, A

    2016-02-01

    All active stages of the tick Ixodes ricinus were collected monthly at two sites in northern Spain between the years 2000 and 2007. We used percentile accumulation of the active stage in the environment to evaluate simple and coherent correlations between accumulation of the active stages of larvae and nymphs and medium-resolution MODIS satellite-derived information on the climate, including monthly and accumulated temperature and the Normalized Difference Vegetation Index (NDVI). This framework is not intended to predict the actual abundance of ticks in the field as a measure of the hazard to humans, but to provide a basic structure for addressing the phenology of the tick in its geographic range. We demonstrated that the accumulation of larval ticks in the active stage is a sigmoid function of the accumulated temperature from the beginning of the calendar year. We also demonstrated that the accumulated temperature necessary to recruit nymphs from the questing larval stage is a function of the changes in accumulated larvae and nymphs and the accumulated temperature and NDVI recorded by the Aqua sensor. The low p-values obtained in the regressions confirmed that such recruitment can be calculated using time intervals to estimate, for example, the beginning of the questing period or the time of the year when a population peak can be expected. The comparison among predicted and actual accumulated temperatures between larvae and nymph recruitment had an averaged error of ±20 days in one complete year. The use of accumulated temperature and NDVI proposed in this study opens up the re-evaluation of reports on the phenology of the tick in Europe. This framework is intended to evaluate the same correlations along the tick's range and predict its phenological patterns in areas of pathogen transmission risk for humans. PMID:25965508

  7. Spatial and Temporal Variation in Primary Productivity (NDVI) of Coastal Alaskan Tundra: Decreased Vegetation Growth Following Earlier Snowmelt

    Science.gov (United States)

    Gamon, John A.; Huemmrich, K. Fred; Stone, Robert S.; Tweedie, Craig E.

    2015-01-01

    In the Arctic, earlier snowmelt and longer growing seasons due to warming have been hypothesized to increase vegetation productivity. Using the Normalized Difference Vegetation Index (NDVI) from both field and satellite measurements as an indicator of vegetation phenology and productivity, we monitored spatial and temporal patterns of vegetation growth for a coastal wet sedge tundra site near Barrow, Alaska over three growing seasons (2000-2002). Contrary to expectation, earlier snowmelt did not lead to increased productivity. Instead, productivity was associated primarily with precipitation and soil moisture, and secondarily with growing degree days, which, during this period, led to reduced growth in years with earlier snowmelt. Additional moisture effects on productivity and species distribution, operating over a longer time scale, were evident in spatial NDVI patterns associated with microtopography. Lower, wetter regions dominated by graminoids were more productive than higher, drier locations having a higher percentage of lichens and mosses, despite the earlier snowmelt at the more elevated sites. These results call into question the oft-stated hypothesis that earlier arctic growing seasons will lead to greater vegetation productivity. Rather, they agree with an emerging body of evidence from recent field studies indicating that early-season, local environmental conditions, notably moisture and temperature, are primary factors determining arctic vegetation productivity. For this coastal arctic site, early growing season conditions are strongly influenced by microtopography, hydrology, and regional sea ice dynamics, and may not be easily predicted from snowmelt date or seasonal average air temperatures alone. Our comparison of field to satellite NDVI also highlights the value of in-situ monitoring of actual vegetation responses using field optical sampling to obtain detailed information on surface conditions not possible from satellite observations alone.

  8. Preliminary analysis on the relationships between Tibetan Plateau NDVI change and its surface heat source and precipitation of China

    Institute of Scientific and Technical Information of China (English)

    HUA Wei; FAN GuangZhou; ZHOU DingWen; NI ChangJian; LI XueMin; WANG YongLi; LIU YaQin; HUANG XianLun

    2008-01-01

    Using the automatic weather station data obtained from the Tibetan Plateau (TP), the normalized dif-ference vegetation index and the monthly precipitation data of China and by the methods of correlation and composite analysis, preliminary analytical results are achieved concerning the relationships be-tween TP NDVI change and its surface heat source and precipitation of China. The results of our re-search may lead to the following conclusions: (1) A positive correlation relationship exists between TP NDVI change and its surface heat source, including the sensible heat and the latent heat. As to the correlation of the former, it is more remarkable in western TP than in eastern TP, and as to the correla-tion of the latter, however it turns out contrary. (2) With the improvement of TP vegetation, its surface heat source of every season is also mainly reinforced, especially in summer. As to the contribution of the sensible heat and the latent heat to the increment of the TP surface heat source intensity, the for-mer is comparatively more significant than the latter in winter and spring, while in summer and autumn, the two have almost the same importance. (3) The correlation coefficient between summer NDVI over TP and the corresponding period precipitation of China displays a belt distribution of "+-+" from south to north China. (4) Anomalous surface heating field over TP derived from vegetation change is probably an important factor to affect summer precipitation of China.keywords Tibetan Plateau, vegetation change, surface heat source, precipitation of China.

  9. Relation of NDVI obtained from different remote sensing at different space and resolutions sensors in Spanish Dehesas

    Science.gov (United States)

    Escribano Rodríguez, Juan; Tarquis, Ana M.; Saa-Requejo, Antonio; Díaz-Ambrona, Carlos G. H.

    2015-04-01

    Satellite data are an important source of information and serve as monitoring crops on large scales. There are several indexes, but the most used for monitoring vegetation is NDVI (Normalized Difference Vegetation Index), calculated from the spectral bands of red (RED) and near infrared (NIR), obtaining the value according to relationship: [(NIR - RED) / (NIR + RED)]. During the years 2010-2013 monthly monitoring was conducted in three areas of Spain (Salamanca, Caceres and Cordoba). Pasture plots were selected and satellite images of two different sensors, DEIMOS-1 and MODIS were obtained. DEIMOS-1 is based on the concept Microsat-100 from Surrey. It is designed for imaging the Earth with a resolution good enough to study terrestrial vegetation cover (20x20 m), although with a wide range of visual field (600 km) to get those images with high temporal resolution. By contrast, MODIS images present a much lower spatial resolution (500x500 m). Indices obtained from both sensors to the same area and date are compared and the results show r2 = 0.56; r2 = 0.65 and r2 = 0.90 for the areas of Salamanca, Cáceres and Cordoba respectively. According to the results obtained show that the NDVI obtained by MODIS is slightly larger than that obtained by the sensor for DEIMOS for same time and area. References J.A. Escribano, C.G.H. Diaz-Ambrona, L. Recuero, M. Huesca, V. Cicuendez, A. Palacios-Orueta y A.M. Tarquis. Aplicacion de Indices de Vegetacion para evaluar la falta de produccion de pastos y montaneras en dehesas. I Congreso Iberico de la Dehesa y el Montado. 6-7 Noviembre, 2013, Badajoz. J.A. Escribano Rodriguez, A.M. Tarquis, C.G. Hernandez Diaz-Ambrona. Pasture Drought Insurance Based on NDVI and SAVI. Geophysical Research Abstracts, 14, EGU2012-13945, 2012. EGU General Assembly 2012. Juan Escribano Rodriguez, Carmelo Alonso, Ana Maria Tarquis, Rosa Maria Benito, Carlos Hernandez Diaz-Ambrona. Comparison of NDVI fields obtained from different remote sensors

  10. Vegetation biomass, leaf area index, and NDVI patterns and relationships along two latitudinal transects in arctic tundra

    Science.gov (United States)

    Epstein, H. E.; Walker, D. A.; Raynolds, M. K.; Kelley, A. M.; Jia, G.; Ping, C.; Michaelson, G.; Leibman, M. O.; Kaarlejärvi, E.; Khomutov, A.; Kuss, P.; Moskalenko, N.; Orekhov, P.; Matyshak, G.; Forbes, B. C.; Yu, Q.

    2009-12-01

    Analyses of vegetation properties along climatic gradients provide first order approximations as to how vegetation might respond to a temporally dynamic climate. Until recently, no systematic study of tundra vegetation had been conducted along bioclimatic transects that represent the full latitudinal extent of the arctic tundra biome. Since 1999, we have been collecting data on arctic tundra vegetation and soil properties along two such transects, the North American Arctic Transect (NAAT) and the Yamal Arctic Transect (YAT). The NAAT spans the arctic tundra from the Low Arctic of the North Slope of Alaska to the polar desert of Cape Isachsen on Ellef Ringnes Island in the Canadian Archipelago. The Yamal Arctic Transect located in northwest Siberia, Russia, presently ranges from the forest-tundra transition at Nadym to the High Arctic tundra on Belyy Ostrov off the north coast of the Yamal Peninsula. The summer warmth indices (SWI - sum of mean monthly temperatures greater than 0°C) range from approximately 40 °C months to 3 °C months from south to north. For largely zonal sites along these transects, we systematically collected leaf area index (LAI-2000 Plant Canopy Analyzer), normalized difference vegetation index (NDVI - PSII hand-held spectro-radiometer), and vegetation biomass (clip harvests). Site-averaged LAI ranges from 1.08 to 0 along the transects, yet can be highly variable at the landscape scale. Site-averaged NDVI ranges from 0.67 to 0.26 along the transects, and is less variable than LAI at the landscape scale. Total aboveground live biomass ranges from approximately 700 g m-2 to < 50 g m-2 along the NAAT, and from approximately 1100 g m-2 to < 400 g m-2 along the YAT (not including tree biomass at Nadym). LAI and NDVI are highly correlated logarithmically (r = 0.80) for the entire dataset. LAI is significantly related to total aboveground (live plus dead) vascular plant biomass, although there is some variability in the data (r = 0.63). NDVI is

  11. NDVI Variation of Tree Rings between March and May since 1915 in the Eastern Part of the Qilian Mountains of China

    Institute of Scientific and Technical Information of China (English)

    Yajun WANG; Ruijie LU; Hongwei MENG; Yanli SANG

    2013-01-01

    [Objective] The aim was to analyze the correlation between tree-ring width of Picea crassifolia in the east of Qilian Mountains and the precipitation,temperature and the normalized difference vegetation index (NDVI).[Method] The correlation analysis and the regression analysis were used in this study.[Result] The tree-ring width was significantly correlated with the autumn precipitation and the spring average NDVI.The conversion equation between tree-ring width and spring NDVI (R2=48.5%,R2ad=46.2%,F=21.627,P<0.001) was developed and NDVI sequence was reconstructed during the period 1915-2007.The drought in the 1920s was pronounced.Vegetation cover in the Qilian Mountains increased during the period 1922-1934,1940-1957,1965-1969,1984-1988 and 1995-1997,but decreased during 1935-1939,1958-1964,1970-1983,1989-1994 and 1998-2005.[Conclusion]The reconstructed NDVI showed the drought evolution in the study area.

  12. Pattern of NDVI-based vegetation greening along an altitudinal gradient in the eastern Himalayas and its response to global warming.

    Science.gov (United States)

    Li, Haidong; Jiang, Jiang; Chen, Bin; Li, Yingkui; Xu, Yuyue; Shen, Weishou

    2016-03-01

    The eastern Himalayas, especially the Yarlung Zangbo Grand Canyon Nature Reserve (YNR), is a global hotspot of biodiversity because of a wide variety of climatic conditions and elevations ranging from 500 to > 7000 m above sea level (a.s.l.). The mountain ecosystems at different elevations are vulnerable to climate change; however, there has been little research into the patterns of vegetation greening and their response to global warming. The objective of this paper is to examine the pattern of vegetation greening in different altitudinal zones in the YNR and its relationship with vegetation types and climatic factors. Specifically, the inter-annual change of the normalized difference vegetation index (NDVI) and its variation along altitudinal gradient between 1999 and 2013 was investigated using SPOT-VGT NDVI data and ASTER global digital elevation model (GDEM) data. We found that annual NDVI increased by 17.58% in the YNR from 1999 to 2013, especially in regions dominated by broad-leaved and coniferous forests at lower elevations. The vegetation greening rate decreased significantly as elevation increased, with a threshold elevation of approximately 3000 m. Rising temperature played a dominant role in driving the increase in NDVI, while precipitation has no statistical relationship with changes in NDVI in this region. This study provides useful information to develop an integrated management and conservation plan for climate change adaptation and promote biodiversity conservation in the YNR.

  13. Response to climate change of different tree species and NDVI variation since 1923 in the middle arid region of Ningxia, China

    Institute of Scientific and Technical Information of China (English)

    YaJun Wang; RuiJie Lu; YuZhen Ma; HongWei Meng; ShangYu Gao

    2014-01-01

    The normalized difference vegetation index (NDVI) is used extensively to describe vegetation cover and ecological environ-ment change. The purpose of this study was to contrast the response of different tree species growing in the same habitat to climate change and retrieve past NDVI using tree-ring width data from tree cores collected from the transitional zone of Pinus tabulaeformis and Picea crassifolia in the Luoshan Mountains in the middle arid region of Ningxia. Correlation analysis indi-cated that radial growth of P. tabulaeformis is more sensitive to precipitation and temperature change than that of P. crassifolia. Natural factors such as water availability and heat at this elevation are more suited to the growth of P. crassifolia, and are more advantageous to its renewal and succession. P. crassifolia is probably the better of the two species for protecting the forest ecosystem and conserving water in the Luoshan desertification area. Ring width of P. crassifolia correlates significantly with average NDVI for April-May (r=0.641, p<0.01), and both of them are influenced positively by precipitation in April-May. The reconstructed NDVI for 1923-2007 shows the relatively low vegetation cover occurred in the 1920s-1930s, the 1960s-1970s, and the early 21st century. The reconstructed NDVI better reflected the drought climate in the study area.

  14. Padrões espaço-temporais da mortalidade por câncer de pulmão no Sul do Brasil Space-time analysis of lung cancer mortality in Southern Brazil

    Directory of Open Access Journals (Sweden)

    Mônica Silva Monteiro de Castro

    2004-06-01

    Full Text Available As neoplasias representam a segunda causa mais comum de mortalidade no Brasil, juntamente com as chamadas causas externas. Dentre as neoplasias, o câncer de pulmão é um dos mais freqüentes, tanto em homens quanto em mulheres, e é também um dos que apresentam maior letalidade. Além disso, o risco atribuível do tabagismo como agente etiológico deste câncer é bastante alto, o que o torna potencialmente susceptível a medidas preventivas de saúde pública. O objetivo deste trabalho foi analisar os padrões espaço-temporais de câncer de pulmão em quatro Estados brasileiros (Rio Grande do Sul, Santa Catarina, Paraná e São Paulo, no período de 1996 a 2000. Os valores observados foram obtidos do Sistema de Informações de Mortalidade do Ministério da Saúde. Os valores esperados foram calculados utilizando-se a técnica de padronização indireta segundo sexo e faixa etária. As unidades geográficas utilizadas foram microrregiões definidas pelo IBGE. Foi utilizado um modelo bayesiano que permite interação espaço-temporal, ajustado através do software WinBUGS. Os resultados encontrados mostraram que no sul do Brasil existe um padrão em "U" nas razões de mortalidade por câncer de pulmão para homens, além de indicar áreas específicas que apresentaram riscos mais elevados e/ou maior ritmo de crescimento. A principal hipótese para este resultado seria diferentes incidências de tabagismo, mas a inexistência desta informação de abrangência regional impediu que esta variável fosse incluída na análise. Os resultados deste artigo podem ser utilizados para instruir políticas públicas voltadas para a redução do tabagismo e da mortalidade por câncer de pulmão.Neoplasms are the second most common mortality cause in Brazil, together with injuries and accidents. Amongst the neoplasms, lung cancer is one of most frequent in men and in women, and it is also one of the most lethal. Moreover, the attributed risk of tobacco as

  15. Variações espaço-temporais no estoque de sementes do solo na floresta amazônica Space-time variations in soil seed stock in an amazon rainforest

    Directory of Open Access Journals (Sweden)

    Niwton Leal Filho

    2013-09-01

    Full Text Available A dispersão eficiente, a longevidade e a capacidade das sementes de permanecer em estado latente a espera de condições adequadas de germinação no banco de sementes do solo da floresta garantem a presença de espécies arbóreas pioneiras nas áreas perturbadas. As variações estacionais e espaciais na densidade e na composição florística do banco de sementes em Florestas Tropicais Úmidas são assuntos ainda pouco compreendidos. Este trabalho verificou a existência de modificações espaço-temporais do banco de sementes presente em áreas de Floresta Tropical úmida localizadas próximas a Manaus, AM. Em cada uma das seis áreas estudadas, foram coletadas 40 amostras circulares de solo superficial (10 cm de diâmetro e 2 cm de profundidade ao acaso. Essas amostras foram coletadas a cada dois meses, entre agosto/2004 e junho/2005,. As amostras de solo foram distribuídas em bandejas em casa de vegetação e a emergência das sementes presentes no solo foi acompanhada por 4 meses. Houve uma redução significativa (H: 14,09, p The dispersion efficiency, longevity and the ability of seeds to remain latent waiting for suitable conditions for germination in the forest soil seed bank ensures the presence of pioneer tree species in disturbed areas. The seasonal and spatial variations in the density and floristic composition of the seed bank in tropical rainforests is a subject still little understood. This work verified the existence of spatio-temporal changes of the seed bank present in areas of humid tropical rain forest located near Manaus, Amazonas. In each of the six study areas, 40 circular samples of topsoil (10 cm in diameter and 2 cm deep were randomly collected every two months, from August 2004 to June/2005. Inside a greenhouse, the collected soil samples were distributed in trays and the emergence of seeds present in the soil was accompanied during four months. There was a significant reduction (H: 14.09112, p <0.05 in the mean

  16. Preditores espaço-temporais do andar para testes de capacidade funcional em pacientes com doença de Parkinson Gait spatial and temporal predictors for functional capacity tests in Parkinson's disease patients

    Directory of Open Access Journals (Sweden)

    MDR Sánchez-Arias

    2008-10-01

    Full Text Available OBJETIVOS: Determinar quais parâmetros espaço-temporais são preditores do andar de indivíduos com doença de Parkinson idiopática para os testes de resistência aeróbia e agilidade, propostos pela bateria de testes da American Alliance for Health, Physical Education, Recreation and Dance (AAHPERD. MATERIAIS E MÉTODOS: Foram selecionados seis homens e seis mulheres com comprometimento e estágio da doença em níveis leve e moderado, que realizaram os testes de agilidade e resistência aeróbia, conforme o protocolo da AAHPERD, e andaram 8m sobre uma passarela. Uma câmera digital registrou uma passada central. Marcadores foram fixados no quinto metatarso e na face lateral do calcâneo do membro inferior direito e no primeiro metatarso e na face medial do calcâneo do membro inferior esquerdo. As variáveis dependentes selecionadas foram: tempo nos testes de agilidade e resistência e as variáveis cinemáticas (comprimento da passada - CP, cadência - CAD, duração da passada - DP, duração da fase de duplo suporte - DDS, duração do suporte simples - SS, duração da fase de balanço - DB e velocidade da passada - VP. RESULTADOS: Para agilidade, o teste de Pearson apontou correlação estatisticamente significativa entre as variáveis CP (r=-0,70; pOBJECTIVE: To determine which spatial and temporal parameters are predictors of the gait pattern of individuals with idiopathic Parkinson's disease, for the aerobic endurance and agility tests included in the battery of tests of the AAHPERD protocol. METHODS: Six men and six women with mild and moderate impairment and disease stage were selected. They performed agility and aerobic endurance test in accordance with the AAHPERD protocol, and walked 8 m on a walkway. A digital video camera recorded one central stride. Markers were attached to the fifth metatarsal and lateral face of the calcaneus of the right leg and to the first metatarsal and medial face of the calcaneus of the left leg. The

  17. Particle Filter Approach for Real-Time Estimation of Crop Phenological States Using Time Series of NDVI Images

    Directory of Open Access Journals (Sweden)

    Caleb De Bernardis

    2016-07-01

    Full Text Available Knowing the current phenological state of an agricultural crop is a powerful tool for precision farming applications. In the past, it has been estimated with remote sensing data by exploiting time series of Normalised Difference Vegetation Index (NDVI, but always at the end of the campaign and only providing results for some key states. In this work, a new dynamical framework is proposed to provide real-time estimates in a continuous range of states, for which NDVI images are combined with a prediction model in an optimal way using a particle filter. The methodology is tested over a set of 8 to 13 rice parcels during 2008–2013, achieving a high determination factor R 2 = 0.93 ( n = 379 for the complete phenological range. This method is also used to predict the end of season date, obtaining a high accuracy with an anticipation of around 40–60 days. Among the key advantages of this approach, phenology is estimated each time a new observation is available, hence enabling the potential detection of anomalies in real-time during the cultivation. In addition, the estimation procedure is robust in the case of noisy observations, and it is not limited to a few phenological stages.

  18. Monitoring the Sequential Cropping Index of Arable Land in Zhejiang Province of China Using MODIS-NDVI

    Institute of Scientific and Technical Information of China (English)

    PENG Dai-liang; HUANG Jing-feng; JIN Hui-min

    2007-01-01

    The sequential cropping index of arable land is important agricultural information. The aim of this article is to monitor and analyze the parameter, and offer reference for agricultural production. The cropping index of arable land in Zhejiang Province, China from 2001 to 2004 was calculated using the second order difference based MODIS (moderate resolution imagine spectroradimeter) vegetation data from NASA (National Aeronautic and Space Administration) in America and the land use map with a scale of 1:25 000. It was found that the peak of the time series of the NDVI curve indicated that the ground biomass of crops reached the maximum, and fluctuated with the crops growing processes such as sowing,seeding, heading, ripeness, and harvesting within one year. Thus, the sequential cropping index was defined as the number of peaks of the time series of the NDVI curve. The sequential cropping index of all cities in Zhejiang Province,China was worked out. It is seen from the spatial distribution that the cropping index in the southwest Zhejiang Province is larger than that in the northeast. As for the temporal distribution, the sequential cropping index decreased from 2001 to 2003, whereas it increased slightly from 2003 to 2004. However, the index of arable land was relatively low, as far as the geographic position and climatic resource were concerned, and the potential of the sequential cropping index was great.

  19. Trends and ENSO/AAO Driven Variability in NDVI Derived Productivity and Phenology alongside the Andes Mountains

    Directory of Open Access Journals (Sweden)

    Francisco J. Meza

    2013-03-01

    Full Text Available Increasing water use and droughts, along with climate variability and land use change, have seriously altered vegetation growth patterns and ecosystem response in several regions alongside the Andes Mountains. Thirty years of the new generation biweekly normalized difference vegetation index (NDVI3g time series data show significant land cover specific trends and variability in annual productivity and land surface phenological response. Productivity is represented by the growing season mean NDVI values (July to June. Arid and semi-arid and sub humid vegetation types (Atacama desert, Chaco and Patagonia across Argentina, northern Chile, northwest Uruguay and southeast Bolivia show negative trends in productivity, while some temperate forest and agricultural areas in Chile and sub humid and humid areas in Brazil, Bolivia and Peru show positive trends in productivity. The start (SOS and length (LOS of the growing season results show large variability and regional hot spots where later SOS often coincides with reduced productivity. A longer growing season is generally found for some locations in the south of Chile (sub-antarctic forest and Argentina (Patagonia steppe, while central Argentina (Pampa-mixed grasslands and agriculture has a shorter LOS. Some of the areas have significant shifts in SOS and LOS of one to several months. The seasonal Multivariate ENSO Indicator (MEI and the Antarctic Oscillation (AAO index have a significant impact on vegetation productivity and phenology in southeastern and northeastern Argentina (Patagonia and Pampa, central and southern Chile (mixed shrubland, temperate and sub-antarctic forest, and Paraguay (Chaco.

  20. Assessing the consistency between AVHRR and MODIS NDVI datasets for estimating terrestrial net primary productivity over India

    Indian Academy of Sciences (India)

    R K Nayak; N Mishra; V K Dadhwal; N R Patel; M Salim; K H Rao; C B S Dutt

    2016-08-01

    This study examines the consistency between the AVHRR and MODIS normalized difference vegetation index (NDVI) datasets in estimating net primary productivity (NPP) and net ecosystem productivity (NEP) over India during 2001–2006 in a terrestrial ecosystem model. Harmonic analysis is employed to estimate seasonal components of the time series. The stationary components (representing long-termmean) of the respective NDVI time series are highly coherent and exhibit inherent natural vegetation characteristics with high values over the forest, moderate over the cropland, and small over the grassland. Both data exhibit strong semi-annual oscillations over the cropland dominated Indo-Gangetic plains while annual oscillations are strong over most parts of the country. MODIS has larger annual amplitude than that of the AVHRR. The similar variability exists on the estimates of NPP and NEP across India. In an annual scale, MODIS-based NPP budget is 1.78 PgC, which is 27% higher than the AVHRR-based estimate. It revealed that the Indian terrestrial ecosystem remained the sink of atmospheric CO$_2$during the study period with 42 TgC y$^{−1}$ NEP budget associated with MODIS-based estimate against 18 TgC y$^{−1}$ for the AVHRR-based estimate.

  1. Future Climate Impact on the Desertification in the Dry Land Asia Using AVHRR GIMMS NDVI3g Data

    Directory of Open Access Journals (Sweden)

    Lijuan Miao

    2015-04-01

    Full Text Available Dry Land Asia is the largest arid and semi-arid region in the northern hemisphere that suffers from land desertification. Over the period 1982–2011, there were both overall improvement and regional degeneration in the vegetation NDVI. We analyze future climate changes in these area using two ensemble-average methods from CMIP5 data. Bayesian Model Averaging shows a better capability to represent the future climate and less uncertainty represented by the 22-model ensemble than does the Simple Model Average. From 2006 to 2100, the average growing season temperature value will increase by 2.9 °C, from 14.4 °C to 17.3 °C under three climate scenarios (RCP 26, RCP 45 and RCP 85. We then conduct multiple regression analysis between climate changes compiled from the Climate Research Unit database and vegetation greenness from the GIMMS NDVI3g dataset. There is a general acceleration in the desertification trend under the RCP 85 scenario in middle and northern part of Middle Asia, northwestern China except Xinjiang and the Mongolian Plateau (except the middle part. The RCP 85 scenario shows a more severe desertification trend than does RCP 26. Desertification in dry land Asia, particularly in the regions highlighted in this study, calls for further investigation into climate change impacts and adaptations.

  2. Assessing the consistency between AVHRR and MODIS NDVI datasets for estimating terrestrial net primary productivity over India

    Science.gov (United States)

    Nayak, R. K.; Mishra, N.; Dadhwal, V. K.; Patel, N. R.; Salim, M.; Rao, K. H.; S Dutt, C. B.

    2016-08-01

    This study examines the consistency between the AVHRR and MODIS normalized difference vegetation index (NDVI) datasets in estimating net primary productivity (NPP) and net ecosystem productivity (NEP) over India during 2001-2006 in a terrestrial ecosystem model. Harmonic analysis is employed to estimate seasonal components of the time series. The stationary components (representing long-term mean) of the respective NDVI time series are highly coherent and exhibit inherent natural vegetation characteristics with high values over the forest, moderate over the cropland, and small over the grassland. Both data exhibit strong semi-annual oscillations over the cropland dominated Indo-Gangetic plains while annual oscillations are strong over most parts of the country. MODIS has larger annual amplitude than that of the AVHRR. The similar variability exists on the estimates of NPP and NEP across India. In an annual scale, MODIS-based NPP budget is 1.78 PgC, which is 27% higher than the AVHRR- based estimate. It revealed that the Indian terrestrial ecosystem remained the sink of atmospheric CO 2 during the study period with 42 TgC y -1 NEP budget associated with MODIS-based estimate against 18 TgC y -1 for the AVHRR-based estimate.

  3. Assessing Habitat Quality of Forest-Corridors through NDVI Analysis in Dry Tropical Forests of South India: Implications for Conservation

    Directory of Open Access Journals (Sweden)

    Paramesha Mallegowda

    2015-02-01

    Full Text Available Most wildlife habitats and migratory routes are extremely threatened due to increasing demands on forestland and forest resources by burgeoning human population. Corridor landscape in Biligiri Rangaswamy Temple Tiger Reserve (BRT is one among them, subjected to various anthropogenic pressures. Human habitation, intensive farming, coffee plantations, ill-planned infrastructure developments and rapid spreading of invasive plant species Lantana camara, pose a serious threat to wildlife habitat and their migration. Aim of this work is to create detailed NDVI based land change maps and to use them to identify time-series trends in greening and browning in forest corridors in the study area and to identify the drivers that are influencing the observed changes. Over the four decades in BRT, NDVI increased in the core area of the forest and reduced in the fringe areas. The change analysis between 1973 and 2014 shows significant changes; browning due to anthropogenic activities as well as natural processes and greening due to Lantana spread. This indicates that the change processes are complex, involving multiple driving factors, such as socio-economic changes, high population growth, historical forest management practices and policies. Our study suggests that the use of updated and accurate change detection maps will be useful in taking appropriate site specific action-oriented conservation decisions to restore and manage the degraded critical wildlife corridors in human-dominated landscape.

  4. Does EO NDVI seasonal metrics capture variations in species composition and biomass due to grazing in semi-arid grassland savannas?

    DEFF Research Database (Denmark)

    Olsen, J. L.; Miehe, S.; Ceccato, Pietro;

    2015-01-01

    Most regional scale studies of vegetation in the Sahel have been based on Earth observation (EO) imagery due to the limited number of sites providing continuous and long term in situ meteorological and vegetation measurements. From a long time series of coarse resolution normalized difference...... series of Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI metrics by comparing it with data from the Widou Thiengoly test site in northern Senegal. Field data include grazing intensity, end of season standing biomass (ESSB) and species composition from sizeable areas suitable for comparison...... to estimate start and end of growing seasons, is identified as the metric most strongly related to ESSB for all grazing regimes. However plot-pixel comparisons demonstrate how the NDVI/ESSB relationship changes due to grazing-induced variation in annual plant species composition and the NDVI values for grazed...

  5. Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic

    Science.gov (United States)

    Walker, D. A.; Epstein, H. E.; Jia, G. J.; Balser, A.; Copass, C.; Edwards, E. J.; Gould, W. A.; Hollingsworth, J.; Knudson, J.; Maier, H. A.; Moody, A.; Raynolds, M. K.

    2003-01-01

    We examined the effects of summer warmth on leaf area index (LAI), total aboveground phytomass (TAP), and normalized difference vegetation index (NDVI) across the Arctic bioclimate zone in Alaska and extrapolated our results to the circumpolar Arctic. Phytomass, LAI, and within homogeneous areas of vegetation on acidic and nonacidic soils were regressed against the total summer warmth index (SWI) at 12 climate stations in northern Alaska (SWI = sum of mean monthly temperatures greater than 0°C). SWI varies from 9°C at Barrow to 37°C at Happy Valley. A 5°C increase in the SWI is correlated with about a 120 g m-2 increase in the aboveground phytomass for zonal vegetation on acidic sites and about 60 g m-2 on nonacidic sites. Shrubs account for most of the increase on acidic substrates, whereas mosses account for most of the increase on nonacidic soils. LAI is positively correlated with SWI on acidic sites but not on nonacidic sites. The NDVI is positively correlated with SWI on both acidic and nonacidic soils, but the NDVI on nonacidic parent material is consistently lower than the NDVI on acidic substrates. Extrapolation to the whole Arctic using a five-subzone zonation approach to stratify the circumpolar NDVI and phytomass data showed that 60% of the aboveground phytomass is concentrated in the low-shrub tundra (subzone 5), whereas the high Arctic (subzones 1-3) has only 9% of the total. Estimated phytomass densities in subzones 1-5 are 47, 256, 102, 454, and 791 g m-2, respectively. Climate warming will likely result in increased phytomass, LAI, and NDVI on zonal sites. These changes will be most noticeable in acidic areas with abundant shrub phytomass.

  6. Monitoring Vegetation Phenological Cycles in Two Different Semi-Arid Environmental Settings Using a Ground-Based NDVI System: A Potential Approach to Improve Satellite Data Interpretation

    Directory of Open Access Journals (Sweden)

    Malika Baghzouz

    2010-04-01

    Full Text Available In semi-arid environmental settings with sparse canopy covers, obtaining remotely sensed information on soil and vegetative growth characteristics at finer spatial and temporal scales than most satellite platforms is crucial for validating and interpreting satellite data sets. In this study, we used a ground-based NDVI system to provide continuous time series analysis of individual shrub species and soil surface characteristics in two different semi-arid environmental settings located in the Great Basin (NV, USA. The NDVI system was a dual channel SKR-1800 radiometer that simultaneously measured incident solar radiation and upward reflectance in two broadband red and near-infrared channels comparable to Landsat-5 TM band 3 and band 4, respectively. The two study sites identified as Spring Valley 1 site (SV1 and Snake Valley 1 site (SNK1 were chosen for having different species composition, soil texture and percent canopy cover. NDVI time-series of greasewood (Sarcobatus vermiculatus from the SV1 site allowed for clear distinction between the main phenological stages of the entire growing season during the period from January to November, 2007. NDVI time series values were significantly different between sagebrush (Artemisia tridentata and rabbitbrush (Chrysothamnus viscidiflorus at SV1 as well as between the two bare soil types at the two sites. Greasewood NDVI from the SNK1 site produced significant correlations with chlorophyll index (r = 0.97, leaf area index (r = 0.98 and leaf xylem water potential (r = 0.93. Whereas greasewood NDVI from the SV1 site produced lower correlations (r = 0.89, r = 0.73, or non significant correlations (r = 0.32 with the same parameters, respectively. Total percent cover was estimated at 17.5% for SV1 and at 63% for SNK1. Results from this study indicated the potential capabilities of using this ground-based NDVI system to extract spatial and temporal details of soil and vegetation optical properties not possible

  7. Análise de séries temporais na operação de sistema de tratamento de águas residuárias de abatedouro de frango Time series analysis on the operation of a poultry slaughterhouse wastewater treatment plant

    Directory of Open Access Journals (Sweden)

    Ivana Ribeiro de Nardi

    2005-12-01

    Full Text Available Esse trabalho apresenta a avaliação de dados de operação de sistema de tratamento de águas residuárias de abatedouro de frango, através da análise de séries temporais. O objetivo principal foi a obtenção de modelo de previsão capaz de antecipar o controle da operação do sistema de tratamento de águas residuárias do abatedouro, constituindo subsídio para obtenção de estratégias de gestão do sistema de tratamento existente. Registros de 42 meses de parâmetros de monitoramento foram utilizados na modelagem de séries temporais. O modelo de ajuste exponencial para previsão dos valores de demanda química de oxigênio do efluente industrial e do afluente dos reatores biológicos apresentou bom ajuste (erro percentual absoluto da média aritmética menor que 20% com diferenças na capacidade de previsão menores que 15%.This paper presents the evaluation of the operating data of the poultry slaughterhouse wastewater treatment plant, by means of time series analysis. It aimed at obtaining a forecasting model able to have the operation of the slaughterhouse wastewater treatment system under control, what leads to subsidy for acquiring the management strategies of the wastewater treatment system. Records of 42 months of the monitoring parameters were used in the time series modeling. The exponentially weighted moving average model for obtaining chemical oxygen demand values of the industrial effluent and the reactors influent stream showed proper adjustment (mean absolute percentage error values smaller than 20%, where the differences on the prediction feasibility were smaller than 15%.

  8. Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships

    Science.gov (United States)

    Moreno-de las Heras, M.; Diaz-Sierra, R.; Turnbull, L.; Wainwright, J.

    2015-01-01

    Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. A classic case of vegetation change is the shrub-encroachment process that has been taking place over the last 150 years in the Chihuahuan Desert, where large areas of grasslands dominated by perennial grass species (black grama, Bouteloua eriopoda, and blue grama, B. gracilis) have transitioned to shrublands dominated by woody species (creosotebush, Larrea tridentata, and mesquite, Prosopis glandulosa), accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including exogenous triggering factors such as precipitation variations and land-use change, and endogenous amplifying mechanisms brought about by soil erosion-vegetation feedbacks. In this study, simulations of plant biomass dynamics with a simple modelling framework indicate that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant growth and water-use patterns, and therefore shrub encroachment may be reflected in the analysis of landscape-scale vegetation-rainfall relationships. We analyze the structure and dynamics of vegetation at an 18 km2 grassland-shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000-2013) records of medium-resolution remote sensing of vegetation greenness (MODIS NDVI) and precipitation. Spatial evaluation of NDVI-rainfall relationship at the studied ecotone indicates that herbaceous vegetation shows quick growth pulses associated with short-term (previous 2 months) precipitation, while shrubs show a slow response to medium-term (previous 5 months) precipitation. We use these relationships to (a) classify landscape types as a function of the spatial distribution of dominant vegetation

  9. NDVI e fluxo de CO2 em lavoura de soja no Rio Grande do Sul NDVI and CO2 flow in a soybean crop in Rio Grande do Sul, Brasil

    Directory of Open Access Journals (Sweden)

    Celso Pinheiro Rodrigues

    2013-03-01

    Full Text Available O aumento das emissões dos gases de efeito estufa (GEE se configura, atualmente, como um dos principais problemas ambientais, o que pode afetar significativamente as atividades humanas e os ecossistemas terrestres. Um dos principais GEE é o CO2, o qual tem sido emitido indiscriminadamente em função do estilo de vida atual, assim como pela intensificação das atividades agrícolas. Neste contexto, o objetivo da pesquisa foi estudar a relação entre o comportamento espectral da cultura de soja ao longo de seu ciclo de desenvolvimento, utilizando imagens NDVI (Normalized Difference Vegetation Index e o fluxo de CO2, calculado pelo método de covariância de vórtices (eddy covariance, gerando informações e metodologia para investigar as trocas de carbono em uma área de cultivo de soja no estado do Rio Grande do Sul, durante a safra de 2008/2009. Utilizou-se imagens TM do satélite Landsat 5, dados fenológicos e dados coletados em estação micrometeorológica ao longo do ciclo de desenvolvimento da soja. Os resultados mostraram que o padrão temporal do fluxo de CO2 ao longo do dia é cíclico, sendo que no período diurno apresenta valores negativos (captura e no período noturno, positivos (liberação. A radiação solar global determina a magnitude do aprisionamento de CO2 pela cultura da soja, mas o fluxo é modulado pelo estádio fenológico da cultura. A atividade fotossintética das plantas de soja é maior durante o estádio vegetativo, quando coincide a maior incidência de radiação solar e o maior aparato fotossintético. O NDVI, obtido de imagens Landsat, é um indicador da evolução da biomassa da soja ao longo do ciclo. Existe correlação entre o NDVI e o fluxo negativo de CO2 (captura, ocorridos no período diurno. Portanto, técnicas de sensoriamento remoto demonstram potencialidade na geração de informações úteis sobre as trocas de CO2 entre a superfície e a atmosfera.The increasing on the greenhouse gases (GHG

  10. The effect of preceding wintertime Arctic polar vortex on springtime NDVI patterns in boreal Eurasia, 1982-2015

    Science.gov (United States)

    Li, Jing; Fan, Ke; Xu, Jianjun; Powell, Alfred M.; Kogan, Felix

    2016-08-01

    The polar vortex is implicated in certain cold events in boreal Eurasia and has a further influence on land surface properties (e.g., vegetation and snow) during spring. The Normalized Difference Vegetation Index (NDVI) can be used as a proxy of land surface responses to climate changes to a certain degree. In this study, we demonstrate the significant correlation between preceding wintertime Arctic polar vortex intensity (WAPVI) and springtime NDVI (SNDVI) over a 34-year period (1982-2015) in boreal Eurasia (50°-75°N, 0°-150°E). Results show that a positive phase of WAPVI tends to increase the SNDVI in Europe and Lake Baikal, but causes a significant decrease in Siberia; the physical mechanisms involved in this relationship are then investigated. A positive phase of WAPVI leads to anomalies in surface air temperature and rainfall over Eurasia, which then induces a significant decrease in snow cover and snow depth in Europe and Lake Baikal and an increase of snow depth in Siberia. The colder ground temperature in Siberia during spring is considered responsible for the stronger snow depth and weaker vegetation growth in this region. The weaker and thinner snow cover in Europe and Baikal produces a decrease in albedo and an increase in heat. Thin snow melts fast in the following spring and land releases more heat to the atmosphere; consequently, warm and moist land surface facilitates vegetation growth in Europe and the Baikal regions during positive WAPVI years. In addition, WAPVI can induce sea surface temperature (SST) anomalies in the North Atlantic, which displays a tripole pattern similar to that of the empirical mode pattern in winter. Furthermore, the SST anomalous pattern persisting from winter to spring can trigger a stationary wave-train propagating from west to east in boreal Eurasia, with "negative-positive-negative-positive" geopotential height anomalies, which further exerts an impact on vegetation growth through modulation of the heat balance.

  11. Automatic calibration of a parsimonious ecohydrological model in a sparse basin using the spatio-temporal variation of the NDVI

    Science.gov (United States)

    Ruiz-Pérez, Guiomar; Manfreda, Salvatore; Caylor, Kelly; Francés, Félix

    2016-04-01

    Drylands are extensive, covering 30% of the Earth's land surface and 50% of Africa. In these water-controlled areas, vegetation plays a key role in the water cycle. Ecohydrological models provide a tool to investigate the relationships between vegetation and water resources. However, studies in Africa often face the problem that many ecohydrological models have quite extensive parametrical requirements, while available data are scarce. Therefore, there is a need for searching new sources of information such as satellite data. The advantages of the use of satellite data in dry regions has been deeply demonstrated and studied. But, the use of this kind of data forces to introduce the concept of spatio-temporal information. In this context, we have to deal with the fact that there is a lack in terms of statistics and methodologies to incorporate the spatio-temporal data during the calibration and validation processes. This research wants to be a contribution in that sense. The used ecohydrological model was calibrated in the Upper Ewaso river basin in Kenya only using NDVI (Normalized Difference Vegetation Index) data from MODIS. An automatic calibration methodology based on Singular Value Decomposition techniques was proposed in order to calibrate the model taking into account the temporal variation and, also, the spatial pattern of the observed NDVI and the simulated LAI. The obtained results have demonstrated: (1) the satellite data is an extraordinary useful tool of information and it can be used to implement ecohydrological models in dry regions; (2) the proposed model calibrated only using satellite data is able to reproduce the vegetation dynamics (in time and in space) and, also, the observed discharge at the outlet point; and (3) the proposed automatic calibration methodology works satisfactorily and it includes spatio-temporal data, in other words, it takes into account the temporal variation and the spatial pattern of the analyzed data.

  12. A Web Architecture to Geographically Interrogate CHIRPS Rainfall and eMODIS NDVI for Land Use Change

    Science.gov (United States)

    Burks, Jason E.; Limaye, Ashutosh

    2014-01-01

    Monitoring of rainfall and vegetation over the continent of Africa is important for assessing the status of crop health and agriculture, along with long-term changes in land use change. These issues can be addressed through examination of long-term precipitation (rainfall) data sets and remote sensing of land surface vegetation and land use types. Two products have been used previously to address these goals: the Climate Hazard Group Infrared Precipitation with Stations (CHIRPS) rainfall data, and multi-day composites of Normalized Difference Vegetation Index (NDVI) from the USGS eMODIS product. Combined, these are very large data sets that require unique tools and architecture to facilitate a variety of data analysis methods or data exploration by the end user community. To address these needs, a web-enabled system has been developed to allow end-users to interrogate CHIRPS rainfall and eMODIS NDVI data over the continent of Africa. The architecture allows end-users to use custom defined geometries, or the use of predefined political boundaries in their interrogation of the data. The massive amount of data interrogated by the system allows the end-users with only a web browser to extract vital information in order to investigate land use change and its causes. The system can be used to generate daily, monthly and yearly averages over a geographical area and range of dates of interest to the user. It also provides analysis of trends in precipitation or vegetation change for times of interest. The data provided back to the end-user is displayed in graphical form and can be exported for use in other, external tools. The development of this tool has significantly decreased the investment and requirements for end-users to use these two important datasets, while also allowing the flexibility to the end-user to limit the search to the area of interest.

  13. Large-scale heterogeneity of Amazonian phenology revealed from 26-year long AVHRR/NDVI time-series

    International Nuclear Information System (INIS)

    Depiction of phenological cycles in tropical forests is critical for an understanding of seasonal patterns in carbon and water fluxes as well as the responses of vegetation to climate variations. However, the detection of clear spatially explicit phenological patterns across Amazonia has proven difficult using data from the Moderate Resolution Imaging Spectroradiometer (MODIS). In this work, we propose an alternative approach based on a 26-year time-series of the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR) to identify regions with homogeneous phenological cycles in Amazonia. Specifically, we aim to use a pattern recognition technique, based on temporal signal processing concepts, to map Amazonian phenoregions and to compare the identified patterns with field-derived information. Our automated method recognized 26 phenoregions with unique intra-annual seasonality. This result highlights the fact that known vegetation types in Amazonia are not only structurally different but also phenologically distinct. Flushing of new leaves observed in the field is, in most cases, associated to a continuous increase in NDVI. The peak in leaf production is normally observed from the beginning to the middle of the wet season in 66% of the field sites analyzed. The phenoregion map presented in this work gives a new perspective on the dynamics of Amazonian canopies. It is clear that the phenology across Amazonia is more variable than previously detected using remote sensing data. An understanding of the implications of this spatial heterogeneity on the seasonality of Amazonian forest processes is a crucial step towards accurately quantifying the role of tropical forests within global biogeochemical cycles. (letter)

  14. Fisher-Shannon information plane analysis of SPOT/VEGETATION Normalized Difference Vegetation Index (NDVI) time series to characterize vegetation recovery after fire disturbance

    Science.gov (United States)

    Lanorte, Antonio; Lasaponara, Rosa; Lovallo, Michele; Telesca, Luciano

    2014-02-01

    The time dynamics of SPOT-VEGETATION Normalized Difference Vegetation Index (NDVI) time series are analyzed by using the statistical approach of the Fisher-Shannon (FS) information plane to assess and monitor vegetation recovery after fire disturbance. Fisher-Shannon information plane analysis allows us to gain insight into the complex structure of a time series to quantify its degree of organization and order. The analysis was carried out using 10-day Maximum Value Composites of NDVI (MVC-NDVI) with a 1 km × 1 km spatial resolution. The investigation was performed on two test sites located in Galizia (North Spain) and Peloponnese (South Greece), selected for the vast fires which occurred during the summer of 2006 and 2007 and for their different vegetation covers made up mainly of low shrubland in Galizia test site and evergreen forest in Peloponnese. Time series of MVC-NDVI have been analyzed before and after the occurrence of the fire events. Results obtained for both the investigated areas clearly pointed out that the dynamics of the pixel time series before the occurrence of the fire is characterized by a larger degree of disorder and uncertainty; while the pixel time series after the occurrence of the fire are featured by a higher degree of organization and order. In particular, regarding the Peloponneso fire, such discrimination is more evident than in the Galizia fire. This suggests a clear possibility to discriminate the different post-fire behaviors and dynamics exhibited by the different vegetation covers.

  15. Sensitivity of the Enhanced Vegetation Index (EVI and Normalized Difference Vegetation Index (NDVI to Topographic Effects: A Case Study in High-density Cypress Forest

    Directory of Open Access Journals (Sweden)

    Guoyu Qiu

    2007-11-01

    Full Text Available Vegetation indices play an important role in monitoring variations in vegetation.The Enhanced Vegetation Index (EVI proposed by the MODIS Land Discipline Groupand the Normalized Difference Vegetation Index (NDVI are both global-based vegetationindices aimed at providing consistent spatial and temporal information regarding globalvegetation. However, many environmental factors such as atmospheric conditions and soilbackground may produce errors in these indices. The topographic effect is another veryimportant factor, especially when the indices are used in areas of rough terrain. In thispaper, we theoretically analyzed differences in the topographic effect on the EVI and theNDVI based on a non-Lambertian model and two airborne-based images acquired from amountainous area covered by high-density Japanese cypress plantation were used as a casestudy. The results indicate that the soil adjustment factor “L” in the EVI makes it moresensitive to topographic conditions than is the NDVI. Based on these results, we stronglyrecommend that the topographic effect should be removed in the reflectance data beforethe EVI was calculated—as well as from other vegetation indices that similarly include a term without a band ratio format (e.g., the PVI and SAVI—when these indices are used in the area of rough terrain, where the topographic effect on the vegetation indices having only a band ratio format (e.g., the NDVI can usually be ignored.

  16. Evaluating EO-based canopy water stress from seasonally detrended NDVI and SIWSI with modeled evapotranspiration in the Senegal River Basin

    DEFF Research Database (Denmark)

    Olsen, Jørgen L.; Stisen, Simon; Proud, Simon Richard;

    2015-01-01

    detrended anomalies are evaluated using a gridded rainfall product (RFE2) and modeled actual evapotranspiration (ETa) for the Senegal River basin in 2008. Daily NDVI and SIWSI were found spatially highly correlated to ETa with r=0.73 for both indices, showing the importance of the north/south vegetation...

  17. Characterizing Post-Drainage Succession in Thermokarst Lake Basins on the Seward Peninsula, Alaska with TerraSAR-X Backscatter and Landsat-based NDVI Data

    Directory of Open Access Journals (Sweden)

    Prajna Regmi

    2012-11-01

    Full Text Available Drained thermokarst lake basins accumulate significant amounts of soil organic carbon in the form of peat, which is of interest to understanding carbon cycling and climate change feedbacks associated with thermokarst in the Arctic. Remote sensing is a tool useful for understanding temporal and spatial dynamics of drained basins. In this study, we tested the application of high-resolution X-band Synthetic Aperture Radar (SAR data of the German TerraSAR-X satellite from the 2009 growing season (July–September for characterizing drained thermokarst lake basins of various age in the ice-rich permafrost region of the northern Seward Peninsula, Alaska. To enhance interpretation of patterns identified in X-band SAR for these basins, we also analyzed the Normalized Difference Vegetation Index (NDVI calculated from a Landsat-5 Thematic Mapper image acquired on July 2009 and compared both X-band SAR and NDVI data with observations of basin age. We found significant logarithmic relationships between (a TerraSAR-X backscatter and basin age from 0 to 10,000 years, (b Landat-5 TM NDVI and basin age from 0 to 10,000 years, and (c TerraSAR-X backscatter and basin age from 50 to 10,000 years. NDVI was a better indicator of basin age over a period of 0–10,000 years. However, TerraSAR-X data performed much better for discriminating radiocarbon-dated basins (50–10,000 years old. No clear relationships were found for either backscatter or NDVI and basin age from 0 to 50 years. We attribute the decreasing trend of backscatter and NDVI with increasing basin age to post-drainage changes in the basin surface. Such changes include succession in vegetation, soils, hydrology, and renewed permafrost aggradation, ground ice accumulation and localized frost heave. Results of this study show the potential application of X-band SAR data in combination with NDVI data to map long-term succession dynamics of drained thermokarst lake basins.

  18. High-Resolution NDVI from Planet’s Constellation of Earth Observing Nano-Satellites: A New Data Source for Precision Agriculture

    Directory of Open Access Journals (Sweden)

    Rasmus Houborg

    2016-09-01

    Full Text Available Planet Labs (“Planet” operate the largest fleet of active nano-satellites in orbit, offering an unprecedented monitoring capacity of daily and global RGB image capture at 3–5 m resolution. However, limitations in spectral resolution and lack of accurate radiometric sensor calibration impact the utility of this rich information source. In this study, Planet’s RGB imagery was translated into a Normalized Difference Vegetation Index (NDVI: a common metric for vegetation growth and condition. Our framework employs a data mining approach to build a set of rule-based regression models that relate RGB data to atmospherically corrected Landsat-8 NDVI. The approach was evaluated over a desert agricultural landscape in Saudi Arabia where the use of near-coincident (within five days Planet and Landsat-8 acquisitions in the training of the regression models resulted in NDVI predictabilities with an r2 of approximately 0.97 and a Mean Absolute Deviation (MAD on the order of 0.014 (~9%. The MAD increased to 0.021 (~14% when the Landsat NDVI training image was further away (i.e., 11–16 days from the corrected Planet image. In these cases, the use of MODIS observations to inform on the change in NDVI occurring between overpasses was shown to significantly improve prediction accuracies. MAD levels ranged from 0.002 to 0.011 (3.9% to 9.1% for the best performing 80% of the data. The technique is generic and extendable to any region of interest, increasing the utility of Planet’s dense time-series of RGB imagery.

  19. High NDVI and Potential Canopy Photosynthesis of South American Subtropical Forests despite Seasonal Changes in Leaf Area Index and Air Temperature

    Directory of Open Access Journals (Sweden)

    Piedad M. Cristiano

    2014-02-01

    Full Text Available The canopy photosynthesis and carbon balance of the subtropical forests are not well studied compared to temperate and tropical forest ecosystems. The main objective of this study was to assess the seasonal dynamics of Normalized Difference Vegetation Index (NDVI and potential canopy photosynthesis in relation to seasonal changes in leaf area index (LAI, chlorophyll concentration, and air temperatures of NE Argentina subtropical forests throughout the year. We included in the analysis several tree plantations (Pinus, Eucalyptus and Araucaria species that are known to have high productivity. Field studies in native forests and tree plantations were conducted; stem growth rates, LAI and leaf chlorophyll concentration were measured. MODIS satellite-derived LAI (1 km SIN Grid and NDVI (250m SIN Grid from February 2000 to 2012 were used as a proxy of seasonal dynamics of potential photosynthetic activity at the stand level. The remote sensing LAI of the subtropical forests decreased every year from 6 to 5 during the cold season, similar to field LAI measurements, when temperatures were 10 °C lower than during the summer. The yearly maximum NDVI values were observed during a few months in autumn and spring (March through May and November, respectively because high and low air temperatures may have a small detrimental effect on photosynthetic activity during both the warm and the cold seasons. Leaf chlorophyll concentration was higher during the cold season than the warm season which may have a compensatory effect on the seasonal variation of the NDVI values. The NDVI of the subtropical forest stands remained high and fairly constant throughout the year (the intra-annual coefficient of variation was 1.9%, and were comparable to the values of high-yield tree plantations. These results suggest that the humid subtropical forests in NE Argentina potentially could maintain high canopy photosynthetic activity throughout the year and thus this ecosystem may

  20. Inter-annual Changes in Eurasian Continent NDVI and Its Sensitivity to the Large-scale Climate Variations in the Last 20 Years

    Institute of Scientific and Technical Information of China (English)

    GONGDao-Yi; SHIPei-Jun

    2004-01-01

    The influence of climate change on the terrestrial vegetation health (condition) is one of themost significant problems of global change study. The vegetation activity plays a key role in the globalcarbon cycle. The authors investigated the relationship of the advanced very high resolution radiometer-normalized difference vegetation index (AVHRR-NDVI) with the large-scale climate variations on the inter-annual time scale during the period 1982-2000 for the growing seasons (April to October). A singular valuedecomposition analysis was applied to the NDV! and surface air temperature data in the time-domain todetect the most predominant modes coupling them. The first paired-modes explain 60.9%, 39.5% and 24.6%of the squared covariance between NDV! and temperature in spring (April and May), summer (June andAugust), and autumn (September to October), respectively, which implies that there is the highest NDVIsensitivity to temperature in spring and the lowest in autumn. The spatial centers, as revealed by themaximum or minimum vector values corresponding to the leading singular values, indicate the highsensitive regions. Only considering the mode 1, the sensitive center for spring is located in westernSiberia and the neighbor eastern Europe with a sensitivity of about 0.308 0 NDVI/℃. For summer, thereare no predominantly sensitive centers, and on average for the relatively high center over 100o-120o E by 45o-60o N, the (110o-140o E,55o-65oN)sitivity is 0.248 0 NDVI/℃. For autumn, the center is located over the high latitudes ofeastern Asia (110o-140o E, 55o-65o N), and the sensitivity is 0.087 5 NDVI/℃. The coherent patters asrevealed by the singular decomposition analysis remain the same when coarser resolution NDVI data wereused, suggesting a robust and stable climate/vegetation relationship.

  1. Comparing the interannual variability of NDVI of croplands over China and India for the period 1982-2006: socioeconomic versus climatic drivers of change.

    Science.gov (United States)

    Milesi, C.; Hashimoto, H.; Ichii, K.; Wang, W.; Michaelis, A.; Melton, F.; Hiatt, S.; Nemani, R.

    2008-12-01

    China and India, holding the world's largest populations, have in the matter of a few decades moved from being among the poorest nations to becoming the fastest growing economies. The broadly similar economic goals of these two countries have been pursued under significantly different governing institutions and policies. Here we compare the effects of the different socio-economic trajectories of China and India on the patterns of vegetation greenness over cropland areas inferred from coarse resolution remote sensing data and their sensitivity to ongoing and future climate changes. For this purpose we analyze 1982-2006 NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) from the GIMMS data set along with climate data and socio-economic statistics. We find that the 1982-2006 NDVI patterns over India are characterized by a strong significant upward trend linked to a recent expansion of minor irrigation projects, which are heavily relying on groundwater exploitation and may now have reached a limit due to exhaustion of resources and increased sensitivity to climate changes. In China, large scale agricultural development preceding the 1980s has brought the NDVI over Chinese cropland to much higher values than over India, reflecting the much higher use of fertilizer and crop yields. After a period of increasing NDVI trends up to the late 1990s, previously documented as the result of a longer growing season due to increased spring temperatures, NDVI has declined, likely reflecting a more recent focus of China on industrial rather than agricultural growth. This study highlights the strong coupling of the socioeconomic and physical environment at scales relevant to ecosystem and climate models.

  2. Assessing vegetation response to precipitation in northwest Morocco during the last decade: an application of MODIS NDVI and high resolution reanalysis data

    Science.gov (United States)

    Otto, M.; Höpfner, C.; Curio, J.; Maussion, F.; Scherer, D.

    2016-01-01

    Understanding vegetation dynamics provides information on changes in land cover that can directly be related to regional changes in the climate system. In data-sparse regions, i.e. northwest Morocco studies are limited by the availability of comprehensive information on precipitation. We extracted precipitation data of high spatiotemporal resolution (2 km, 1 day) from the Northwest Africa Reanalysis (NwAR) and gridded Normalized Difference Negetation Index (NDVI) of the Moderate Resolution Imaging Spectroradiometer (MODIS) that cover northwest Morocco over ten hydrological years (September 2000 to August 2010). The results are based on a sequence of linear regression analyses. The mean precipitation of different input timeframes is systematically applied as the predicting variables to the mean NDVI of the growing seasons. Results show that 73 % of the variance in mean NDVI is explained by the variance in mean precipitation at the beginning of the growing season (November to the end of December). The results also show that 75 % of the variance in the mean NDVI of agriculturally used areas is explained by the variance in mean precipitation of beginning September to the end of December. Potentially irrigated land cover of low to medium explained variance but of a high seasonal range in NDVI cover about 14 % of the study region. We conclude that a considerable part of agricultural used areas are still potentially rain-fed. The applied methods and especially the re-analysed precipitation data of high spatiotemporal resolution open a new quality of analysis valuable for, e.g. monitoring aspects, policy decisions or regulatory actions.

  3. On the characterization of vegetation recovery after fire disturbance using Fisher-Shannon analysis and SPOT/VEGETATION Normalized Difference Vegetation Index (NDVI) time series

    Science.gov (United States)

    Lasaponara, Rosa; Lanorte, Antonio; Lovallo, Michele; Telesca, Luciano

    2015-04-01

    Time series can fruitfully support fire monitoring and management from statistical analysis of fire occurrence (Tuia et al. 2008) to danger estimation (lasaponara 2005), damage evaluation (Lanorte et al 2014) and post fire recovery (Lanorte et al. 2014). In this paper, the time dynamics of SPOT-VEGETATION Normalized Difference Vegetation Index (NDVI) time series are analyzed by using the statistical approach of the Fisher-Shannon (FS) information plane to assess and monitor vegetation recovery after fire disturbance. Fisher-Shannon information plane analysis allows us to gain insight into the complex structure of a time series to quantify its degree of organization and order. The analysis was carried out using 10-day Maximum Value Composites of NDVI (MVC-NDVI) with a 1 km × 1 km spatial resolution. The investigation was performed on two test sites located in Galizia (North Spain) and Peloponnese (South Greece), selected for the vast fires which occurred during the summer of 2006 and 2007 and for their different vegetation covers made up mainly of low shrubland in Galizia test site and evergreen forest in Peloponnese. Time series of MVC-NDVI have been analyzed before and after the occurrence of the fire events. Results obtained for both the investigated areas clearly pointed out that the dynamics of the pixel time series before the occurrence of the fire is characterized by a larger degree of disorder and uncertainty; while the pixel time series after the occurrence of the fire are featured by a higher degree of organization and order. In particular, regarding the Peloponneso fire, such discrimination is more evident than in the Galizia fire. This suggests a clear possibility to discriminate the different post-fire behaviors and dynamics exhibited by the different vegetation covers. Reference Lanorte A, R Lasaponara, M Lovallo, L Telesca 2014 Fisher-Shannon information plane analysis of SPOT/VEGETATION Normalized Difference Vegetation Index (NDVI) time series to

  4. Mapping the Spatial Distribution of Winter Crops at Sub-Pixel Level Using AVHRR NDVI Time Series and Neural Nets

    Directory of Open Access Journals (Sweden)

    Felix Rembold

    2013-03-01

    Full Text Available For large areas, it is difficult to assess the spatial distribution and inter-annual variation of crop acreages through field surveys. Such information, however, is of great value for governments, land managers, planning authorities, commodity traders and environmental scientists. Time series of coarse resolution imagery offer the advantage of global coverage at low costs, and are therefore suitable for large-scale crop type mapping. Due to their coarse spatial resolution, however, the problem of mixed pixels has to be addressed. Traditional hard classification approaches cannot be applied because of sub-pixel heterogeneity. We evaluate neural networks as a modeling tool for sub-pixel crop acreage estimation. The proposed methodology is based on the assumption that different cover type proportions within coarse pixels prompt changes in time profiles of remotely sensed vegetation indices like the Normalized Difference Vegetation Index (NDVI. Neural networks can learn the relation between temporal NDVI signatures and the sought crop acreage information. This learning step permits a non-linear unmixing of the temporal information provided by coarse resolution satellite sensors. For assessing the feasibility and accuracy of the approach, a study region in central Italy (Tuscany was selected. The task consisted of mapping the spatial distribution of winter crops abundances within 1 km AVHRR pixels between 1988 and 2001. Reference crop acreage information for network training and validation was derived from high resolution Thematic Mapper/Enhanced Thematic Mapper (TM/ETM+ images and official agricultural statistics. Encouraging results were obtained demonstrating the potential of the proposed approach. For example, the spatial distribution of winter crop acreage at sub-pixel level was mapped with a cross-validated coefficient of determination of 0.8 with respect to the reference information from high resolution imagery. For the eight years for which

  5. Incorporating NDVI in a gravity model setting to describe spatio-temporal patterns of Lyme borreliosis incidence

    Science.gov (United States)

    Barrios, J. M.; Verstraeten, W. W.; Farifteh, J.; Maes, P.; Aerts, J. M.; Coppin, P.

    2012-04-01

    Lyme borreliosis (LB) is the most common tick-borne disease in Europe and incidence growth has been reported in several European countries during the last decade. LB is caused by the bacterium Borrelia burgdorferi and the main vector of this pathogen in Europe is the tick Ixodes ricinus. LB incidence and spatial spread is greatly dependent on environmental conditions impacting habitat, demography and trophic interactions of ticks and the wide range of organisms ticks parasite. The landscape configuration is also a major determinant of tick habitat conditions and -very important- of the fashion and intensity of human interaction with vegetated areas, i.e. human exposure to the pathogen. Hence, spatial notions as distance and adjacency between urban and vegetated environments are related to human exposure to tick bites and, thus, to risk. This work tested the adequacy of a gravity model setting to model the observed spatio-temporal pattern of LB as a function of location and size of urban and vegetated areas and the seasonal and annual change in the vegetation dynamics as expressed by MODIS NDVI. Opting for this approach implies an analogy with Newton's law of universal gravitation in which the attraction forces between two bodies are directly proportional to the bodies mass and inversely proportional to distance. Similar implementations have proven useful in fields like trade modeling, health care service planning, disease mapping among other. In our implementation, the size of human settlements and vegetated systems and the distance separating these landscape elements are considered the 'bodies'; and the 'attraction' between them is an indicator of exposure to pathogen. A novel element of this implementation is the incorporation of NDVI to account for the seasonal and annual variation in risk. The importance of incorporating this indicator of vegetation activity resides in the fact that alterations of LB incidence pattern observed the last decade have been ascribed

  6. Responses of the reflectance indices PRI and NDVI to experimental warming and drought in European shrublands along a north–south climatic gradient

    DEFF Research Database (Denmark)

    Mänd, Pille; Hallik, Lea; Peñuelas, Josep;

    2010-01-01

    The aim of this study was to evaluate the use of ground-based canopy reflectance measurements to detect changes in physiology and structure of vegetation in response to experimental warming and drought treatment at six European shrublands located along a North–South climatic gradient. We measured...... NDVI680 [780 nm; 680 nm] using red spectral region, and NDVI570 [780 nm; 570 nm] using the same green spectral region as PRI. All three reflectance indices were significantly related to green LAIe and were able to detect changes in shrubland vegetation among treatments. In general warming treatment...... in vegetation areas with low green LAIe. As both soil reflectance and LAI varied between northern and southern sites it is problematic to draw universal conclusions of climate-derived changes in all vegetation types based merely on PRI measurements. We propose that canopy level PRI measurements can be more...

  7. The Effects of Increased Water Flow on Ecohydrology of Sawgrass Marshes in the Everglades as Observed in Multi-year Time Series of MODIS Terra NDVI imagery

    Science.gov (United States)

    Fuller, D. O.

    2015-12-01

    We utilized a 14-year time series (2001-2014) of 8-day composites of the normalized difference vegetation index (NDVI) from the MODIS Terra satellite to study how increased water flows have affected the photosynthetic activity in marshes and tree islands of the Shark River Slough in the northern portion of Everglades National Park, Florida, USA. Results showed that increased water flows associated with completion of 1.6 km bridge in 2013 increased photosynthetic activity of marsh and prairie plants in the dry seasons of 2013 and 2014. Time series analysis shows the potential of continuous NDVI monitoring as a way to follow the functional response of a large, subtropical wetland system to a large and sudden increase in freshwater inputs.

  8. Improving arable land heterogeneity information in available land cover products for land surface modelling using MERIS NDVI data

    Directory of Open Access Journals (Sweden)

    F. Zabel

    2010-07-01

    Full Text Available Regionalization of physical land surface models requires the supply of detailed land cover information. Numerous global and regional land cover maps already exist, but generally they do not resolve arable land into different crop types. However, the characteristic phenological behaviour of different crops affects the mass and energy fluxes on the land surface and thus its hydrology. The objective of this study is the generation of a land cover map for Central Europe based on CORINE Land Cover 2000, merged with CORINE Switzerland, but distinguishing different crop types. Accordingly, an approach was developed, subdividing the land cover class arable land into the regionally most relevant subclasses for Central Europe using statistical data from EUROSTAT. This database was analysed concerning the acreage of different crop types, taking a multiseasonal series of MERIS Normalized Difference Vegetation Index (NDVI into account. The satellite data were used for the separation of spring and summer crops. The hydrological impact of the improved land cover map was modelled exemplarily for the Upper Danube catchment.

  9. Cattle stocking rates estimated in temperate intensive grasslands with a spring growth model derived from MODIS NDVI time-series

    Science.gov (United States)

    Green, Stuart; Cawkwell, Fiona; Dwyer, Edward

    2016-10-01

    There is an identified need for high resolution animal stocking rate data in temperate grassland systems. Here is presented a 250 m scale characterization of early spring vegetation growth (DOY 32-DOY 120) from 2003 to 2012 based on MODIS NDVI products for this period for Ireland. The average rate of grass growth is determined locally as a simple linear model for each pixel, using only the highest quality data for the period. These decadal spring growth model coefficients, start of season cover and growth rate, are regressed against log of stocking rate (r2 = 0.75). This model stocking rate is used to map grassland use intensity in Ireland, which, when tested against an independent set of stocking rate data, is shown to be successful with an RMSE error of 0.13 for a range of stocking densities from 0.1 to 3.0 LSU/Ha. This model provides the first validated high resolution approach to mapping stocking rates in intensively managed European grassland systems.

  10. Analysis of trends in the Sahelian 'rain-use efficiency' using GIMMS NDVI, RFE and GPCP rainfall data

    DEFF Research Database (Denmark)

    Fensholt, Rasmus; Rasmussen, Kjeld

    2011-01-01

    Rain-use efficiency (RUE; the ratio of vegetation productivity to annual precipitation) has been suggested as a measure for assessing land degradation in arid/semi-arid areas. In the absence of anthropogenic influence, RUE has been reported to be constant over time, and any observed change may...... therefore be attributed to non-rainfall impacts. This study presents an analysis of the decadal time-scale changes in the relationship between a proxy for vegetation productivity (SNDVI) and annual rainfall in the Sahel-Sudanian zone of Africa. The aim is to test the quality of data input and the usefulness......–2007)) and SNDVI (AVHRR GIMMS NDVI dataset, 1982–2007). It is shown that the increase in SNDVI has been substantial in the Sahel-Sudanian zone over the 1982–2007 period,whereas for the period 1996–2007 the pattern of SNDVI trends is more complex. Also, trend analysis of annual rainfall from GPCP data (2...

  11. Assessing Impacts of Drought on Agriculture Production and Food Security in Karamoja of Northeastern Uganda with Meteorological and NDVI-Based Indices - Some findings and challenges

    Science.gov (United States)

    Nakalembe, C. L.; Zhang, J.; Justice, C. O.

    2015-12-01

    Drought monitoring and planning requires spatially and temporally continuous information and its impacts on production and on society can easily be quantified when long-term (both crop production and climate) information is available. Such historical information is scanty and at best qualitative for Karamoja in Northeastern Uganda, a region considered to be most vulnerable to drought. To demonstrate the capabilities of currently available satellite data in filling this data gap in smallholder agricultural regions; this study first characterized agricultural drought at multiple temporal and spatial scales using Normalized Difference Vegetation Index (NDVI) data (1999-2011) and monthly rainfall data (1960-2011). Correlation analyses of the NDVI based drought indicators, Standardized Precipitation Index (SPI) and a global product of Palmer Drought Severity Index (PDSI). Spatial information is derived for the 1999-2000 period using MODIS 250m resolution data. The 12 month SPI (SPI-12) had the highest correlation with the MODIS NDVI record from (1999-2011) derived indices reaffirming the cumulative effect of rainfall on vegetation during the growing season and the utility of NDVI as an indicator of drought. Time-series plots were generated, the droughts were ranked and spatial maps derived for the most severe droughts between 2000- 2011. Temporal drought information is correlated with proxy indicators such as food aid supplies, available historical production data, market prices from within and in neighbouring regions and with to primary data collected through interviews with farmers in Moroto district. This study demonstrates that operationalizing drought monitoring can be realized with remote sensing and further affirms the importance of drought and agriculture monitoring for food security.

  12. SACRA – global data sets of satellite-derived crop calendars for agricultural simulations: an estimation of a high-resolution crop calendar using satellite-sensed NDVI

    Directory of Open Access Journals (Sweden)

    S. Kotsuki

    2015-01-01

    Full Text Available To date, many studies have performed numerical estimations of food production and agricultural water demand to understand the present and future supply–demand relationship. A crop calendar (CC is an essential input datum to estimate food production and agricultural water demand accurately with the numerical estimations. CC defines the date or month when farmers plant and harvest in cropland. This study aims to develop a new global data set of a satellite-derived crop calendar for agricultural simulations (SACRA and reveal advantages and disadvantages of the satellite-derived CC compared to other global products. We estimate global CC at a spatial resolution of 5 min (≈10 km using the satellite-sensed NDVI data, which corresponds well to vegetation growth and death on the land surface. We first demonstrate that SACRA shows similar spatial pattern in planting date compared to a census-based product. Moreover, SACRA reflects a variety of CC in the same administrative unit, since it uses high-resolution satellite data. However, a disadvantage is that the mixture of several crops in a grid is not considered in SACRA. We also address that the cultivation period of SACRA clearly corresponds to the time series of NDVI. Therefore, accuracy of SACRA depends on the accuracy of NDVI used for the CC estimation. Although SACRA shows different CC from a census-based product in some regions, multiple usages of the two products are useful to take into consideration the uncertainty of the CC. An advantage of SACRA compared to the census-based products is that SACRA provides not only planting/harvesting dates but also a peak date from the time series of NDVI data.

  13. Assessing Seasonal and Inter-Annual Variations of Lake Surface Areas in Mongolia during 2000-2011 Using Minimum Composite MODIS NDVI.

    Science.gov (United States)

    Kang, Sinkyu; Hong, Suk Young

    2016-01-01

    A minimum composite method was applied to produce a 15-day interval normalized difference vegetation index (NDVI) dataset from Moderate Resolution Imaging Spectroradiometer (MODIS) daily 250 m reflectance in the red and near-infrared bands. This dataset was applied to determine lake surface areas in Mongolia. A total of 73 lakes greater than 6.25 km2in area were selected, and 28 of these lakes were used to evaluate detection errors. The minimum composite NDVI showed a better detection performance on lake water pixels than did the official MODIS 16-day 250 m NDVI based on a maximum composite method. The overall lake area detection performance based on the 15-day minimum composite NDVI showed -2.5% error relative to the Landsat-derived lake area for the 28 evaluated lakes. The errors increased with increases in the perimeter-to-area ratio but decreased with lake size over 10 km(2). The lake area decreased by -9.3% at an annual rate of -53.7 km(2) yr(-1) during 2000 to 2011 for the 73 lakes. However, considerable spatial variations, such as slight-to-moderate lake area reductions in semi-arid regions and rapid lake area reductions in arid regions, were also detected. This study demonstrated applicability of MODIS 250 m reflectance data for biweekly monitoring of lake area change and diagnosed considerable lake area reduction and its spatial variability in arid and semi-arid regions of Mongolia. Future studies are required for explaining reasons of lake area changes and their spatial variability. PMID:27007233

  14. A comparative study of cross-product NDVI dynamics in the Kilimanjaro region - a matter of sensor, degradation calibration, and significance

    Science.gov (United States)

    Detsch, Florian; Otte, Insa; Appelhans, Tim; Nauss, Thomas

    2016-04-01

    While satellite-based monitoring of vegetation activity at the earth's surface is of vital importance for many eco-climatological applications, the degree of agreement among certain sensors and products providing estimates of the Normalized Difference Vegetation Index (NDVI) has been found to vary considerably. In order to assess the extent of such differences in highly heterogeneous terrain, we analyze and compare seasonal fluctuations and long-term monotonic trends (2003-2012) in the Kilimanjaro region, Tanzania. The considered NDVI datasets include the Moderate Resolution Imaging Spectroradiometer (MODIS) products from Terra and Aqua, Collections 5 and 6, and the 3rd Generation Global Inventory Modeling and Mapping Studies (GIMMS) product. The degree of agreement in seasonal fluctuations is assessed by calculating a pairwise Index of Association (IOAs), whereas long-term trends are derived from the trend-free pre-whitened Mann-Kendall test. On the seasonal scale, the two Terra-MODIS products (and, accordingly, the two Aqua-MODIS products) are best associated with each other, indicating that the seasonal signal remained largely unaffected by the new Collection 6 calibration approach. As regards long-term trends, we find that the negative impacts of band ageing on Terra-MODIS NDVI have been accounted for in Collection 6, which now distinctly outweighs Aqua-MODIS in terms of greening trends. GIMMS NDVI, by contrast, fails to capture small-scale seasonal and trend patterns that are characteristic for the highly fragmented landscape which is likely owing to the coarse spatial resolution. As a short digression, we also demonstrate that the amount of false discoveries in the determined trend fraction is distinctly higher for p

  15. The 2010 Russian Drought Impact on Satellite Measurements of Solar-Induced Chlorophyll Fluorescence: Insights from Modeling and Comparisons with the Normalized Differential Vegetation Index (NDVI)

    Science.gov (United States)

    Yoshida, Y.; Joiner, J.; Tucker, C.; Berry, J.; Lee, J. -E.; Walker, G.; Reichle, R.; Koster, R.; Lyapustin, A.; Wang, Y.

    2015-01-01

    We examine satellite-based measurements of chlorophyll solar-induced fluorescence (SIF) over the region impacted by the Russian drought and heat wave of 2010. Like the popular Normalized Difference Vegetation Index (NDVI) that has been used for decades to measure photosynthetic capacity, SIF measurements are sensitive to the fraction of absorbed photosynthetically-active radiation (fPAR). However, in addition, SIF is sensitive to the fluorescence yield that is related to the photosynthetic yield. Both SIF and NDVI from satellite data show drought-related declines early in the growing season in 2010 as compared to other years between 2007 and 2013 for areas dominated by crops and grasslands. This suggests an early manifestation of the dry conditions on fPAR. We also simulated SIF using a global land surface model driven by observation-based meteorological fields. The model provides a reasonable simulation of the drought and heat impacts on SIF in terms of the timing and spatial extents of anomalies, but there are some differences between modeled and observed SIF. The model may potentially be improved through data assimilation or parameter estimation using satellite observations of SIF (as well as NDVI). The model simulations also offer the opportunity to examine separately the different components of the SIF signal and relationships with Gross Primary Productivity (GPP).

  16. NDVI-Based Analysis on the Influence of Climate Change and Human Activities on Vegetation Restoration in the Shaanxi-Gansu-Ningxia Region, Central China

    Directory of Open Access Journals (Sweden)

    Shuangshuang Li

    2015-08-01

    Full Text Available In recent decades, climate change has affected vegetation growth in terrestrial ecosystems. We investigated spatial and temporal patterns of vegetation cover on the Loess Plateau’s Shaanxi-Gansu-Ningxia region in central China using MODIS-NDVI data for 2000–2014. We examined the roles of regional climate change and human activities in vegetation restoration, particularly from 1999 when conversion of sloping farmland to forestland or grassland began under the national Grain-for-Green program. Our results indicated a general upward trend in average NDVI values in the study area. The region’s annual growth rate greatly exceeded those of the Three-North Shelter Forest, the upper reaches of the Yellow River, the Qinling–Daba Mountains, and the Three-River Headwater region. The green vegetation zone has been annually extending from the southeast toward the northwest, with about 97.4% of the region evidencing an upward trend in vegetation cover. The NDVI trend and fluctuation characteristics indicate the occurrence of vegetation restoration in the study region, with gradual vegetation stabilization associated with 15 years of ecological engineering projects. Under favorable climatic conditions, increasing local vegetation cover is primarily attributable to ecosystem reconstruction projects. However, our findings indicate a growing risk of vegetation degradation in the northern part of Shaanxi Province as a result of energy production facilities and chemical industry infrastructure, and increasing exploitation of mineral resources.

  17. Análise do NDVI/NOAA em cana-de-açúcar e Mata Atlântica no litoral norte de Pernambuco, Brasil Analysis of NDVI/NOAA in sugar cane and Atlantic Forest in the north of Pernambuco state, Brazil

    Directory of Open Access Journals (Sweden)

    Abdoral de A. Lucas

    2007-12-01

    Full Text Available Neste trabalho se realizou a análise espaço-temporal do NDVI (Índice de Vegetação da Diferença Normalizada na cultura da cana-de-açúcar, considerando-se a idade fenológica e a influência da precipitação pluvial dos meses atual e anterior relativos à safra 2003/2004. A metodologia foi aplicada em três áreas, ou seja, duas com cana-de-açúcar e uma de Mata Atlântica; cada área representa um pixel do satélite NOAA (National Oceanic and Atmospheric Administration. Os pontos amostrais P1 e P2 indicam áreas com plantio de cana e o ponto P3, um fragmento de Mata Atlântica, todos localizados na Usina São José, no Litoral Norte de Pernambuco. O estádio fenológico da cana-de-açúcar foi relacionado com o NDVI e com a precipitação referente a 6 épocas do ciclo da cultura. Aplicou-se, para a análise espaço-temporal, o índice de vegetação da diferença normalizada, utilizando-se imagens do sensor AVHRR (Advanced Very High Resolution Radiometric/NOAa-16. Os resultados mostraram maior influência da precipitação do mês anterior no comportamento do NDVI. Em relação ao ciclo da cultura, o estádio de desenvolvimento acompanha a evolução do NDVI, ou seja, na medida em que ocorre um ganho de biomassa, aumenta o valor do NDVI e ele começa, então, a decair quando se inicia o estádio de maturação, a partir do sétimo mês após o corte.This paper accomplished a space-temporal analysis of NDVI (Normalized Difference Vegetation Index in sugar cane crop, considering the phenological stage and the influence of pluvial precipitation of the current and previous month of 2003/2004 harvest. The methodology was applied in three areas, two with sugar cane and one of Atlantic Forest. Each area represents a pixel of the NOAA (National Oceanic and Atmospheric Administration satellite. Points P1 and P2 represent areas with sugar cane and point P3 a fragment of Atlantic Forest, all located at the Usina São José, in North of Pernambuco

  18. Patrones fenológicos de la Provincia de Mendoza, Argentina, mediante serie temporal de imágenes NOAA-AVHRR NDVI GAC Phenological patterns of the province of Mendoza, Argentina, through a temporal series of NOAA-AVHRR NDVI GAC images

    Directory of Open Access Journals (Sweden)

    M. M González Loyarte

    2010-12-01

    Full Text Available Se describe la dinámica temporal de la vegetación de Mendoza mediante análisis de la fenología foliar regional con una serie de 108 imágenes mensuales de índice de vegetación NOAA-AVHRR NDVI GAC. La serie se descompone aplicando la Transformada Rápida de Fourier en parámetros dinámicos: NDVI medio, amplitudes (máxima variabilidad del NDVI y fases (tiempo entre inicio del ciclo y máximo NDVI para diferentes períodos. Con los parámetros con mayor información (variablilidad inter e intraanual se hace una clasificación y se obtiene un mapa de 18 áreas de comportamiento fenológico. Éste se vincula con los ecosistemas y con las unidades de vegetación. Se modela el patrón fenológico (curva NDVI mensual para 17 unidades de vegetación. El mapa aporta elementos dinámicos al estudio regional de la vegetación generando una zonificación nueva explicada por variables que determinan la actividad vegetativa. El patrón fenológico describe el funcionamiento de la vegetación y permite comprender sus variaciones geográficas. El conjunto de la vegetación de Mendoza responde a un ciclo anual con matices localizados de ligera bimodalidad. Los patrones de bajo contraste invierno-verano corresponden a condiciones climáticas xéricas expresando su máximo vegetativo al final del verano; la disponibilidad hídrica incrementa este contraste acortando el tiempo de máxima expresión vegetativa.The temporal dynamics of vegetation in Mendoza is described through analysis of regional foliar phenology using a series of 108 monthly NOAA-AVHRR NDVI GAC images. A Fast Fourier Transform was used to decompose the series into dynamic parameters: mean NDVI, amplitudes (maximum NDVI variability and phases (time from start of cycle to maximum NDVI for different time periods. A classification is made based on those parameters with larger information content (inter- and intra-annual variability, achieving a map of 18 areas of phenological behaviour. This

  19. Evaluating the Consistency of the 1982–1999 NDVI Trends in the Iberian Peninsula across Four Time-series Derived from the AVHRR Sensor: LTDR, GIMMS, FASIR, and PAL-II

    Science.gov (United States)

    Alcaraz-Segura, Domingo; Liras, Elisa; Tabik, Siham; Paruelo, José; Cabello, Javier

    2010-01-01

    Successive efforts have processed the Advanced Very High Resolution Radiometer (AVHRR) sensor archive to produce Normalized Difference Vegetation Index (NDVI) datasets (i.e., PAL, FASIR, GIMMS, and LTDR) under different corrections and processing schemes. Since NDVI datasets are used to evaluate carbon gains, differences among them may affect nations’ carbon budgets in meeting international targets (such as the Kyoto Protocol). This study addresses the consistency across AVHRR NDVI datasets in the Iberian Peninsula (Spain and Portugal) by evaluating whether their 1982–1999 NDVI trends show similar spatial patterns. Significant trends were calculated with the seasonal Mann-Kendall trend test and their spatial consistency with partial Mantel tests. Over 23% of the Peninsula (N, E, and central mountain ranges) showed positive and significant NDVI trends across the four datasets and an additional 18% across three datasets. In 20% of Iberia (SW quadrant), the four datasets exhibited an absence of significant trends and an additional 22% across three datasets. Significant NDVI decreases were scarce (croplands in the Guadalquivir and Segura basins, La Mancha plains, and Valencia). Spatial consistency of significant trends across at least three datasets was observed in 83% of the Peninsula, but it decreased to 47% when comparing across the four datasets. FASIR, PAL, and LTDR were the most spatially similar datasets, while GIMMS was the most different. The different performance of each AVHRR dataset to detect significant NDVI trends (e.g., LTDR detected greater significant trends (both positive and negative) and in 32% more pixels than GIMMS) has great implications to evaluate carbon budgets. The lack of spatial consistency across NDVI datasets derived from the same AVHRR sensor archive, makes it advisable to evaluate carbon gains trends using several satellite datasets and, whether possible, independent/additional data sources to contrast. PMID:22205868

  20. Evaluating the Consistency of the 1982–1999 NDVI Trends in the Iberian Peninsula across Four Time-series Derived from the AVHRR Sensor: LTDR, GIMMS, FASIR, and PAL-II

    Directory of Open Access Journals (Sweden)

    José Paruelo

    2010-02-01

    Full Text Available Successive efforts have processed the Advanced Very High Resolution Radiometer (AVHRR sensor archive to produce Normalized Difference Vegetation Index (NDVI datasets (i.e., PAL, FASIR, GIMMS, and LTDR under different corrections and processing schemes. Since NDVI datasets are used to evaluate carbon gains, differences among them may affect nations’ carbon budgets in meeting international targets (such as the Kyoto Protocol. This study addresses the consistency across AVHRR NDVI datasets in the Iberian Peninsula (Spain and Portugal by evaluating whether their 1982–1999 NDVI trends show similar spatial patterns. Significant trends were calculated with the seasonal Mann-Kendall trend test and their spatial consistency with partial Mantel tests. Over 23% of the Peninsula (N, E, and central mountain ranges showed positive and significant NDVI trends across the four datasets and an additional 18% across three datasets. In 20% of Iberia (SW quadrant, the four datasets exhibited an absence of significant trends and an additional 22% across three datasets. Significant NDVI decreases were scarce (croplands in the Guadalquivir and Segura basins, La Mancha plains, and Valencia. Spatial consistency of significant trends across at least three datasets was observed in 83% of the Peninsula, but it decreased to 47% when comparing across the four datasets. FASIR, PAL, and LTDR were the most spatially similar datasets, while GIMMS was the most different. The different performance of each AVHRR dataset to detect significant NDVI trends (e.g., LTDR detected greater significant trends (both positive and negative and in 32% more pixels than GIMMS has great implications to evaluate carbon budgets. The lack of spatial consistency across NDVI datasets derived from the same AVHRR sensor archive, makes it advisable to evaluate carbon gains trends using several satellite datasets and, whether possible, independent/additional data sources to contrast.

  1. 基于 NDVI 时间序列数据的江西省水稻种植制度变化研究%Study on Rice Cropping System in Jiangxi Province with Time-series NDVI Dataset

    Institute of Scientific and Technical Information of China (English)

    欧立业; 罗烈琴; 易明华

    2016-01-01

    Multiple cropping system is an important way to improve the grain yield , and cropping index as a statistical indicator can re-flect the degree of utilization of the arable land in the time scale .Cropping index of remote sensing monitoring on arable land resource assessment, security of food production , agricultural condition prediction has important practical significance .Jiangxi has always been a big agricultural province , has never been interrupted the export of marketable grain since the founding of state , made an important contribution to national food security .In this case, Jiangxi Province ,as the object of study , using SPOT VGT multi-temporal NDVI data, combined with the SRTM DEM data , remote sensing interpretation of the 2000-2010 three years’ arable land data in a five-year interval , analyze the change of the cultivated land area , crop growth situation , and farming system in Jiangxi province in these three years and the influence factors .%利用Savitzky-Golay滤波对覆盖江西省范围的SPOT VGT NDVI时间序列数据进行平滑处理的基础上,结合坡度数据,通过非监督分类的方法提取了江西省2000、2005和2010年水稻种植范围,并根据NDVI的年内动态变化,从水稻种植范围、水稻生长季起始时间、水稻复种指数和NDVI最大振幅等分析了江西省水稻种植和生长情况,探讨2000~2010年江西省水稻生产的变化。

  2. Use of Empirical Mode Decomposition based Denoised NDVI in Extended Three-Temperature Model to estimate Evapotranspiration in Northeast Indian Ecosystems

    Science.gov (United States)

    Padhee, S. K.

    2015-12-01

    Evapotranspiration (ET) is an essential component involved in the energy balance and water budgeting methods, and its precise assessment are crucial for estimation of various hydrological parameters. Traditional point estimation methods for ET computation offer quantitative analysis, but lag in spatial distribution. The use of Remote Sensing (RS) data with good spatial, spectral and temporal resolution having broad spatial coverage, could lead the estimations with some advantages. However, approaches which requires data rich environment, demands time and resources. The estimation of spatially distributed soil evaporation (Es) and transpiration from canopy (Ec) by RS data, followed by their combination to provide the total ET, could be a simpler approach for accurate estimates of ET flux at macro-scale level. The 'Extended Three Temperature Model' (Extended 3T Model) is an established model based on same approach and is capable to compute ET and its partition of Es and Ec within the same algorithm. A case study was conducted using Extended 3T Model and MODIS products for the Brahmaputra river basin within the Northeast India for years 2000-2010. The extended 3T model was used by including its pre-requisite the land surface temperature (Ts), which was separated into the surface temperature of dry soil (Tsm) and the surface temperature of vegetation (Tcm), decided by a derivative of vegetation index (NDVI) called fractional vegetation cover (f). However, NDVI time series which is nonlinear and nonstationary can be decomposed by the Empirical Mode Decomposition (EMD) into components called intrinsic mode functions (IMFs), based on inherent temporal scales. The highest frequency component which was found to represent noise was subtracted from the original NDVI series to get the denoised product from which f was derived. The separated land surface temperatures (Tsm and Tcm) were used to calculate the Es and Ec followed by estimation of total ET. The spatiotemporal

  3. Improving arable land heterogeneity information in available land cover products for land surface modelling using MERIS NDVI data

    Directory of Open Access Journals (Sweden)

    F. Zabel

    2010-10-01

    Full Text Available Regionalization of physical land surface models requires the supply of detailed land cover information. Numerous global and regional land cover maps already exist but generally, they do not resolve arable land into different crop types. However, arable land comprises a huge variety of different crops with characteristic phenological behaviour, demonstrated in this paper with Leaf Area Index (LAI measurements exemplarily for maize and winter wheat. This affects the mass and energy fluxes on the land surface and thus its hydrology. The objective of this study is the generation of a land cover map for central Europe based on CORINE Land Cover (CLC 2000, merged with CORINE Switzerland, but distinguishing different crop types. Accordingly, an approach was developed, subdividing the land cover class arable land into the regionally most relevant subclasses for central Europe using multiseasonal MERIS Normalized Difference Vegetation Index (NDVI data. The satellite data were used for the separation of spring and summer crops due to their different phenological behaviour. Subsequently, the generated phenological classes were subdivided following statistical data from EUROSTAT. This database was analysed concerning the acreage of different crop types. The impact of the improved land use/cover map on evapotranspiration was modelled exemplarily for the Upper Danube catchment with the hydrological model PROMET. Simulations based on the newly developed land cover approach showed a more detailed evapotranspiration pattern compared to model results using the traditional CLC map, which is ignorant of most arable subdivisions. Due to the improved temporal behaviour and spatial allocation of evapotranspiration processes in the new land cover approach, the simulated water balance more closely matches the measured gauge.

  4. Improving arable land heterogeneity information in available land cover products for land surface modelling using MERIS NDVI data

    Science.gov (United States)

    Zabel, F.; Hank, T. B.; Mauser, W.

    2010-10-01

    Regionalization of physical land surface models requires the supply of detailed land cover information. Numerous global and regional land cover maps already exist but generally, they do not resolve arable land into different crop types. However, arable land comprises a huge variety of different crops with characteristic phenological behaviour, demonstrated in this paper with Leaf Area Index (LAI) measurements exemplarily for maize and winter wheat. This affects the mass and energy fluxes on the land surface and thus its hydrology. The objective of this study is the generation of a land cover map for central Europe based on CORINE Land Cover (CLC) 2000, merged with CORINE Switzerland, but distinguishing different crop types. Accordingly, an approach was developed, subdividing the land cover class arable land into the regionally most relevant subclasses for central Europe using multiseasonal MERIS Normalized Difference Vegetation Index (NDVI) data. The satellite data were used for the separation of spring and summer crops due to their different phenological behaviour. Subsequently, the generated phenological classes were subdivided following statistical data from EUROSTAT. This database was analysed concerning the acreage of different crop types. The impact of the improved land use/cover map on evapotranspiration was modelled exemplarily for the Upper Danube catchment with the hydrological model PROMET. Simulations based on the newly developed land cover approach showed a more detailed evapotranspiration pattern compared to model results using the traditional CLC map, which is ignorant of most arable subdivisions. Due to the improved temporal behaviour and spatial allocation of evapotranspiration processes in the new land cover approach, the simulated water balance more closely matches the measured gauge.

  5. Using Moderate-Resolution Temporal NDVI Profiles for High-Resolution Crop Mapping in Years of Absent Ground Reference Data: A Case Study of Bole and Manas Counties in Xinjiang, China

    Directory of Open Access Journals (Sweden)

    Pengyu Hao

    2016-05-01

    Full Text Available Most methods used for crop classification rely on the ground-reference data of the same year, which leads to considerable financial and labor cost. In this study, we presented a method that can avoid the requirements of a large number of ground-reference data in the classification year. Firstly, we extracted the Normalized Difference Vegetation Index (NDVI time series profiles of the dominant crops from MODIS data using the historical ground-reference data in multiple years (2006, 2007, 2009 and 2010. Artificial Antibody Network (ABNet was then employed to build reference NDVI time series for each crop based on the historical NDVI profiles. Afterwards, images of Landsat and HJ were combined to obtain 30 m image time series with 15-day acquisition frequency in 2011. Next, the reference NDVI time series were transformed to Landsat/HJ NDVI time series using their linear model. Finally, the transformed reference NDVI profiles were used to identify the crop types in 2011 at 30 m spatial resolution. The result showed that the dominant crops could be identified with overall accuracy of 87.13% and 83.48% in Bole and Manas, respectively. In addition, the reference NDVI profiles generated from multiple years could achieve better classification accuracy than that from single year (such as only 2007. This is mainly because the reference knowledge from multiple years contains more growing conditions of the same crop. Generally, this approach showed potential to identify crops without using large number of ground-reference data at 30 m resolution.

  6. Classification mapping and species identification of salt marshes based on a short-time interval NDVI time-series from HJ-1 optical imagery

    Science.gov (United States)

    Sun, Chao; Liu, Yongxue; Zhao, Saishuai; Zhou, Minxi; Yang, Yuhao; Li, Feixue

    2016-03-01

    Salt marshes are seen as the most dynamic and valuable ecosystems in coastal zones, and in these areas, it is crucial to obtain accurate remote sensing information on the spatial distributions of species over time. However, discriminating various types of salt marsh is rather difficult because of their strong spectral similarities. Previous salt marsh mapping studies have focused mainly on high spatial and spectral (i.e., hyperspectral) resolution images combined with auxiliary information; however, the results are often limited to small regions. With a high temporal and moderate spatial resolution, the Chinese HuanJing-1 (HJ-1) satellite optical imagery can be used not only to monitor phenological changes of salt marsh vegetation over short-time intervals, but also to obtain coverage of large areas. Here, we apply HJ-1 satellite imagery to the middle coast of Jiangsu in east China to monitor changes in saltmarsh vegetation cover. First, we constructed a monthly NDVI time-series to classify various types of salt marsh and then we tested the possibility of using compressed time-series continuously, to broaden the applicability of this particular approach. Our principal findings are as follows: (1) the overall accuracy of salt marsh mapping based on the monthly NDVI time-series was 90.3%, which was ∼16.0% higher than the single-phase classification strategy; (2) a compressed time-series, including NDVI from six key months (April, June-September, and November), demonstrated very little reduction (2.3%) in overall accuracy but led to obvious improvements in unstable regions; and (3) a simple rule for Spartina alterniflora identification was established using a scene solely from November, which may provide an effective way for regularly monitoring its distribution.

  7. Evaluation of Spatiotemporal Variations of Global Fractional Vegetation Cover Based on GIMMS NDVI Data from 1982 to 2011

    Directory of Open Access Journals (Sweden)

    Donghai Wu

    2014-05-01

    Full Text Available Fractional vegetation cover (FVC is an important biophysical parameter of terrestrial ecosystems. Variation of FVC is a major problem in research fields related to remote sensing applications. In this study, the global FVC from 1982 to 2011 was estimated by GIMMS NDVI data, USGS global land cover characteristics data and HWSD soil type data with a modified dimidiate pixel model, which considered vegetation and soil types and mixed pixels decomposition. The evaluation of the robustness and accuracy of the GIMMS FVC with MODIS FVC and Validation of Land European Remote sensing Instruments (VALERI FVC show high reliability. Trends of the annual FVCmax and FVCmean datasets in the last 30 years were reported by the Mann–Kendall method and Sen’s slope estimator. The results indicated that global FVC change was 0.20 and 0.60 in a year with obvious seasonal variability. All of the continents in the world experience a change in the annual FVCmax and FVCmean, which represents biomass production, except for Oceania, which exhibited a significant increase based on a significance level of p = 0.001 with the Student’s t-test. Global annual maximum and mean FVC growth rates are 0.14%/y and 0.12%/y, respectively. The trends of the annual FVCmax and FVCmean based on pixels also illustrated that the global vegetation had turned green in the last 30 years. A significant trend on the p = 0.05 level was found for 15.36% of the GIMMS FVCmax pixels on a global scale (excluding permanent snow and ice, in which 1.8% exhibited negative trends and 13.56% exhibited positive trends. The GIMMS FVCmean similarly produced a total of 16.64% significant pixels with 2.28% with a negative trend and 14.36% with a positive trend. The North Frigid Zone represented the highest annual FVCmax significant increase (p = 0.05 of 25.17%, which may be caused mainly by global warming, Arctic sea-ice loss and an advance in growing seasons. Better FVC predictions at large regional scales

  8. Spatiotemporal variability analysis of vegetation cover status for drought study purposes over North Africa using 8-km NDVI-GIMMS data

    Science.gov (United States)

    Chokmani, K.; El Alem, A.; Chebana, F.

    2013-12-01

    Africa is considered as the second driest continent in the world behind Australia, its arid lands cover approximately 60 percent. Droughts that hit the continent in recent decades and land degradations at the margins of deserts, particularly for countries neighboring the Sahara such as Algeria, Morocco, and Tunisia have renewed concerns about desertification progress. For a better understanding to the complete nature of drought and the degree in which human activities and climate changes contribute to its development, it is imperative to determine this phenomenon more accurately. Previous drought assessments had several weaknesses making them less reliable. Indeed, standard measurement methods, based on an unevenly distributed sampling point network, are unrepresentative neither for spatial distribution nor for temporal frequency of desertification. As an alternative to these conventional methods, remote sensing data could offer the needed spatial and temporal coverage. In fact, drought study is possible through monitoring vegetation and/or temperature conditions using vegetation and/or temperatures driven indices. Thus, several indices including the Normalized Difference Vegetation Index (NDVI), Transformed Difference Vegetation Index (TDVI), Soil Adjusted Vegetation Index (SAVI), and Temperature Condition Index (TCI), have been employed using various satellite sensors such as Advanced Very High Resolution Radiometer (AVHRR), Landsat Thematic Mapper (TM), and MODerate Resolution Imaging Spectroradiometer (MODIS) to monitor and analyze drought in various regions of the world. In this study, the AVHRR NDVI-GIMMS data at 8-km spatial resolution were used to study the evolution of the vegetation cover status in North Africa's countries over 25 years. The NDVI-GIMMS data were highly correlated with the rainfall in situ samples collected on different cities over the North Africa's countries as the determination coefficient (R2) was about 0.96. The vegetation cover study

  9. 应用归一化植被指数的玉米产量预测研究%Maize Yield Prediction Research Based on the NDVI

    Institute of Scientific and Technical Information of China (English)

    黄楠; 王强; 王鹏; 张国庆; 刘凌菲

    2014-01-01

    In order to use the Normalized Difference Vegetation Index (NDVI)effectively for maize production prediction ,taking Zhaodong city of Heilongjiang province as study area ,HJ1B remote sensing data and the field measured data in maize heading stage were used to predict maize yield .Combined with radiation calibration ,at-mospheric correction ,geometric correction and the spectral reflectance ,the NDVI was calculated to make curve-fitting with the field measured yield data .The results showed that the best correlation between maize NDVI in heading stage and yield was quadratic polynomial and the accuracy was 86% ,the maize yield in 2011 was pre-dict to generate the remote sensing thematic map compared with measured results .Therefore ,the determination of NDVI had a certain relevance with production .%为有效利用归一化植被指数(NDVI)对玉米产量进行预测,以黑龙江省肇东市为研究区域,利用玉米抽穗期H J1B遥感数据,结合野外实测数据,进行玉米单产遥感预测研究。通过辐射定标、大气校正、几何精校正等预处理,反演试验区域的实际光谱反射率,从而计算试验区域内玉米的归一化植被指数(NDVI)实际数值,进而与野外实测产量数据进行模型拟合。结果表明:肇东玉米抽穗期NDVI与产量之间二次多项式模型相关性最佳,对比实测数据准确率可达86%,并利用研究结果对肇东2011年玉米产量进行了预测,与实测结果比较后形成玉米单产遥感预测专题图,因此,确定归一化植被指数与玉米产量具有一定的相关性。

  10. Remote sensing of vegetation dynamics in drylands: Evaluating vegetation optical depth (VOD) using AVHRR NDVI and in situ green biomass data over West African Sahel

    DEFF Research Database (Denmark)

    Tian, Feng; Brandt, Martin; Liu, Yi Y.;

    2016-01-01

    , the seasonal metrics showing the highest degree of explained variance differ between the two data sources. While the observations in October (period of in situ data collection) perform best for VOD (r2 = 0.88), the small growing season integral (sensitive to recurrent vegetation) have the highest correlations......Monitoring long-term biomass dynamics in drylands is of great importance for many environmental applications including land degradation and global carbon cycle modeling. Biomass has extensively been estimated based on the normalized difference vegetation index (NDVI) as a measure of the vegetation...

  11. Previsão e séries temporais para tomada de decisão empresarial em uma indústria moveleira da região de Criciúma–SC = A study of forecasting and time series for business decision making in a furniture industry in Criciúma-SC

    Directory of Open Access Journals (Sweden)

    Fernanda Cristina Barbosa Pereira Queiroz

    2012-07-01

    Full Text Available Uma previsão adequada deve dar suporte a uma decisão minimizadora de risco por parte dos tomadores de decisão, sendo essencial para o planejamento individual e organizacional de agentes econômicos. Neste sentido, o objetivo deste artigo é realizar um estudo sobre previsão e séries temporais para tomada de decisão empresarial em uma indústria moveleira da região de Criciúma–SC. A metodologia utilizada fundamenta-se na construção de modelos univariados de previsão de preços, com base em dados de séries temporais. O estudo é classificado como exploratório, bibliográfico e um estudo de caso com dados quantitativos. Há uma grande variedade de modelos aplicáveis a estudos desta natureza. Para fins desta pesquisa, optou-se por selecionar o método linear Holt e Holt-Winters e o modelo ARIMA (Auto Regressive Integrate Moving Average. Procurou-se, neste sentido, apresentar os diferentes modelos disponíveis na literatura, objetivando estimar a demanda por móveis para banheiro e projetar vendas futuras. Os resultados mostraram que o modelo ARIMA (Auto Regressive Integrate Moving Average não se mostrou eficiente no caso analisado, devido ao número pequeno de dados, o que impossibilitou uma análise da sazonalidade, sugerindo-se que a empresa utilize o método de Holt, a fim de estimar o número de produtos a ser vendido e que, à medida que os novos produtos sejam vendidos, os demais modelos sejam testados novamente, uma vez que a incorporação de novos dados irá permitir confirmar a existência ou não da sazonalidade. An adequate forecast should give support to minimize risk decisions by the decision makers, being essential for individual and organizational planning of economic agents. In this sense, the purpose of this paper is to conduct a study about forecast and time series for business decision-making in a furniture industry in the region of Criciúma, SC. The methodology was based on the construction of univariate models

  12. Variáveis espaço-temporais da marcha de crianças com paralisia cerebral submetidas a eletroestimulação no músculo tibial anterior Spatio-temporal gait variables of children with cerebral palsy undergoing electrostimulation in the anterior tibial muscle

    Directory of Open Access Journals (Sweden)

    BP Jerônimo

    2007-08-01

    Full Text Available OBJETIVO: Este estudo teve como objetivo descrever variáveis espaço-temporais da marcha de crianças de 4 a 5 anos de idade com paralisia cerebral (PC do tipo hemiplegia espástica, antes e após sessões de eletroestimulação do músculo tibial anterior do dimídio plégico. METODOLOGIA: Cinco crianças foram submetidas à eletroestimulação durante 12 sessões (três vezes na semana. Para a coleta dos dados biomecânicos, foi realizada análise da marcha através do sistema Peak Motus versão 7.0 com duas câmeras de vídeo SVHS com taxa de aquisição de 60 Hz. Para reconstrução tridimensional dos movimentos, foi utilizado o método Direct Linear Trasformation (DLT. RESULTADOS: Após a intervenção, todas as crianças apresentaram diferenças menores entre o comprimento dos passos do dimídio plégico e não-plégico (p= 0,009. Observou-se o aumento no comprimento do ciclo em quatro crianças. Duas crianças tiveram aumento da cadência, velocidade e tempo de apoio simples do dimídio plégico. CONCLUSÕES: Foi verificada a melhoria da simetria da marcha relacionada ao comprimento do passo antes e após a intervenção, embora o aumento nas variáveis espaço-temporais não tenha ocorrido da mesma maneira para todas as crianças. Apesar das dificuldades em se obterem amostras maiores e mais homogêneas em estudos desse tipo, os dados sugerem a necessidade de identificação e maior controle das variáveis intervenientes no tratamento e na marcha de crianças portadoras de paralisia cerebral.OBJECTIVE: This study had the objective of describing spatiotemporal gait variables of four to five-year-old children with spastic hemiplegic cerebral palsy, before and after sessions of electrostimulation of the anterior tibial muscle on the paralyzed side. METHOD: Five children underwent 12 sessions of electrostimulation (three times a week. To collect biomechanical data, the gait was analyzed using the Peak Motus system, version 7.0, with two S

  13. Previsão da temperatura média mensal de Uberlândia, MG, com modelos de séries temporais Forecast of monthly mean temperatures in Uberlândia, Minas Gerais, Brazil using time series models

    Directory of Open Access Journals (Sweden)

    Maria I. S. Silva

    2008-10-01

    Full Text Available Modelos de séries temporais têm sido amplamente usados no estudo de variáveis climatológicas, como temperatura e precipitação. Diversos são os objetivos traçados neste trabalho a fim de se analisar a série de temperatura média mensal da cidade de Uberlândia, MG, descrevendo seus componentes, e fazer previsões para períodos subseqüentes através de modelos ajustados para a série. A análise permitiu identificar, na série, a presença dos componentes, tendência e sazonalidade. Modelos do tipo SARIMA foram ajustados e, por meio dos critérios AIC (Akaike Information Criterion, BIC (Bayesian Information Criterion e MSE (Mean Square Error foi selecionado o modelo SARIMA (3,1,0(0,1,1 para fins de previsão.Time series models have been used for climatological variables such as temperature and rainfall. In this paper, time series of monthly mean temperatures for the municipality of Uberlândia, Minas Gerais, were analyzed describing their components and making forecasts using the SARIMA models. The analysis showed trend and seasonality components. The SARIMA model was adjusted by AIC (Akaike Information Criterion, BIC (Bayesian Information Criterion and MSE (Mean Square Error criterion. The results showed that the SARIMA (3,1,0(0,1,1 was a good model for forecasting.

  14. Defining a quality index for electric power utilities using multiple criteria decision support and time series analysis Definição de um índice de qualidade para distribuidoras de energia elétrica utilizando o apoio à decisão multicritério e análise de séries temporais

    Directory of Open Access Journals (Sweden)

    Aderson Campos Passos

    2013-03-01

    Full Text Available This paper presents a hybrid multi-criteria method developed through the combination of the Analytical Hierarchy Process (AHP and exponential smoothing techniques applied in time series forecasting. To illustrate its use, a model was developed with the aim of creating a quality index for electric power distribution utilities. The conclusions highlight the need to take into account the results obtained in the latest months for those utilities, but giving less attention to those obtained in the earlier months. This characteristic of the problem led to the idea of incorporating the mathematical formulation of the exponential smoothing into the aggregation function of the AHP. At the end, the utility company is given a score between 0 (zero and 10 (ten.Este trabalho apresenta um método multicritério híbrido construído através da fusão entre o Método de Análise Hierárquica (AHP e técnicas de Amortecimento Exponencial, aplicadas na previsão de séries temporais. Para ilustrar a sua utilização foi construído um modelo com a finalidade de criar um índice de qualidade para distribuidoras de energia elétrica. As conclusões apresentadas revelam a necessidade de levar em consideração os resultados obtidos em meses anteriores por essas distribuidoras, mas dando menor importância a períodos mais distantes do tempo presente. Essa característica do problema sugeriu a idéia de incorporar a formulação matemática do amortecimento exponencial à função de agregação do AHP. Ao final é fornecida para a distribuidora avaliada uma nota entre 0 (zero e 10 (dez.

  15. 基于环境减灾卫星时序归一化植被指数的冬小麦产量估测%Yield forecasting for winter wheat using time series NDVI from HJ satellite

    Institute of Scientific and Technical Information of China (English)

    陈鹏飞; 杨飞; 杜佳

    2013-01-01

    A NDVI time series curve, proposed from high time resolution remote sensing images, contains rich information for crop yield forecasting. MODIS-NDVI and AVHRR-NDVI are normally used. However, the spatial resolution of MODIS and AVHRR are low. When they used for crop yield forecasting in China, the prediction accuracy will be reduced by a mixed pixel problem, as the farmland is small. China launched a HJ satellite constellation in 2009. The satellite constellation can provide an image with a time resolution of 2 days and a spatial resolution of 30 m. It would be helpful to make crop yield forecasting in field scale in China, based on the NDVI time series curve designed from higher spatial resolution HJ images. Taking Yucheng city as a research area, this study research the feasibility of proposing a NDVI time series curve using HJ satellite images and then making a winter wheat yield forecast using parameters extracted from the above curve. For this purpose, 11 images were acquired with a nearly 10 day interval from February 19th to June 5th, and the winter wheat yields of 12 sample sites were also measured during a field campaign in 2012. Firstly, quintic polynomial least square fitting was used to propose a NDVI time series curve using NDVI values extracted from the above images. The curve covered reviving, jointing, flowering, filling and mature stages of winter wheat. Secondly, parameters of a NDVI time series curve were calculated. They were maximum NDVI and accumulated NDVI during winter wheat growth stage, NDVI value at winter wheat reviving stage, NDVI change rate during winter wheat vegetation growth stage, and NDVI change rate during the winter wheat reproduction growth stage. Thirdly, using collected sample data, the yield prediction models were created, based on the above parameters respectively. Meanwhile, a single-phase image NDVI was also used to propose a yield prediction model, and it was compared to the above models, in order to show if a NDVI time

  16. A max-to-min technique for making projections of NDVI change in semi-arid Africa for food security early warning

    Science.gov (United States)

    Brown, M. E.; Funk, C. C.

    2005-12-01

    Climatic hazards such as droughts and floods often result in a decline in food production in economically vulnerable pre-industrial economies such as those in Africa. Early warning systems (EWS) have been developed to identify slow onset disasters such famine and epidemic disease that may result from hazardous environmental conditions. These conditions often precede food crises by many months, thus effective monitoring via satellite and in situ observations can allow for successful mitigation activities. Accurate forecasts of NDVI could increase monitoring lead times and allow for effective institutional planning of intervention, making early warning earlier. This paper presents a simple empirical max-to-min model for making 1 to 4 month NDVI projections. These statistical projections are based on parameterized satellite rainfall estimates (RFE) and relative humidity demand (RHD). A heuristic example in central Zimbabwe introduces the RFE growth and RHD loss terms. A quasi-global, one month ahead, 1 degree study then demonstrates reasonable accuracies in many semi-arid regions. In Africa, a 0.1 degree cross-validated skill assessment quantifies the technique's applicability at 1 to 4 month forecast intervals. These results suggest that useful projections can be made over many semi-arid, food insecure regions of Africa, with plausible extensions to drought prone areas of Asia, Australia and South America.

  17. Reconstructing rice phenology curves with frequency-based analysis and multi-temporal NDVI in double-cropping area in Jiangsu, China

    Science.gov (United States)

    Wang, Hongshuo; Lin, Hui; Munroe, Darla K.; Zhang, Xiaodong; Liu, Pengfei

    2016-06-01

    Crop phenology retrieval in the double-cropping area of China is of great significance in crop yield estimation and water management under the influences of global change. In this study, rice phenology in Jiangsu Province, China was extracted from multi-temporal MODIS NDVI using frequency-based analysis. Pure MODIS pixels of rice were selected with the help of TM images. Discrete Fourier Transformation (DFT), Discrete Wavelet Transformation (DWT), and Empirical Mode Decomposition (EMD) were performed to decompose time series into components of different frequencies. Rice phenology in the double-cropping area is mainly located on the last 2 IMFs of EMD and the first 2‒3 frequencies of DFT and DWT. Compared with DFT and DWT, EMD is limited to fewer frequencies. Multi-temporal MODIS NDVI data combined with frequency-based analysis can retrieve rice phenology dates with on average 79% valid estimates. The sorting result for effective estimations from different methods is DWT (85%)>EMD (80%)>DFT (74%). Planting date (88%) is easier to estimate than harvesting date (70%). Rice planting date is easily affected by the former cropping mode within the same year in a double-cropping region. This study sheds light on understanding crop phenology dynamics in the frequency domain of multi-temporal MODIS data.

  18. 大兴安岭不同植被火后NDVI恢复过程%NDVI Recovery Process for Post-Fire Vegetation in Daxing’anling

    Institute of Scientific and Technical Information of China (English)

    苗庆林; 田晓瑞; 赵凤君

    2015-01-01

    【目的】利用卫星遥感技术研究火后植被恢复过程及影响因子,分析不同火烧强度、不同植被类型的火后归一化植被指数( NDVI)变化特征,研究大兴安岭东南部火后不同植被恢复过程,为在长时间尺度上进行北方林火后植被恢复过程研究与监测提供参考。【方法】基于火烧前后一系列的 MODIS 数据,利用 NDVI 和地面调查数据,以2006年大兴安岭松岭特大森林火灾为例,研究不同植被类型在不同强度火烧后的植被恢复过程。根据火烧前后NDVI变化提取过火区;结合地面调查,利用监督分类方法划分火烧强度等级;根据火烧强度分级图和土地覆盖类型图,建立属性数据库,生成火烧强度等级-植被类型图。以2003—2005年同期 NDVI最大值为对照,在时间序列上分析植被类型和火烧强度对火后 NDVI 恢复的影响。根据邻近未过火区的 NDVI 变化,分析气象因子对NDVI的影响。【结果】轻度、中度和重度火烧区所占比例分别为29%,40%和31%。主要植被类型常绿针叶林、针阔混交林和灌丛的重度火烧部分分别占50%,52%和60%。重度火烧区域所占比例随着坡度增大而升高。在火后NDVI的变化过程中,各森林类型变化趋势相近,灌丛、草地和沼泽的变化趋势相近。【结论】火后 NDVI总体呈上升趋势,并呈现明显的年际波动。除草地外其余植被类型在重度火烧后的 NDVI值均明显低于中、轻度火烧,但中、轻度火烧的不同植被类型之间差异不明显。森林重度火烧区 NDVI在火后第2年达到最低,轻度火烧区火后6年NDVI基本恢复到火前水平。针阔混交林火后盖度的恢复速度较其他森林类型快。火烧强度对森林群落垂直结构的影响显著,森林火烧后灌木层盖度高于未火烧区,且火烧强度越高,这种现象越显著。双因素方差分析显示植被类

  19. Monitoring Regional Forest Disturbances across the US with near Real Time MODIS NDVI Products Resident to the ForWarn Forest Threat Early Warning System

    Science.gov (United States)

    Spruce, Joseph P.; Hargrove, William W.; Gasser, Gerald

    2013-01-01

    Forest threats across the US have become increasingly evident in recent years. Sometimes these have resulted in regionally evident disturbance progressions (e.g., from drought, bark beetle outbreaks, and wildfires) that can occur across multiyear durations and have resulted in extensive forest overstory mortality. In addition to stand replacement disturbances, other forests are subject to ephemeral, sometimes yearly defoliation from various insects and varying types and intensities of ephemeral damage from storms. Sometimes, after prolonged severe disturbance, signs of recovery in terms of Normalized Difference Vegetation Index (NDVI) can occur. The growing prominence and threat of forest disturbances in part have led to the formation and implementation of the 2003 Healthy Forest Restoration Act which mandated that national forest threat early warning system be developed and deployed. In response, the US Forest Service collaborated with NASA, DOE Oakridge National Laboratory, and the USGS Eros Data Center to build and roll-out the near real time ForWarn early warning system for monitoring regionally evident forest disturbances. Given the diversity of disturbance types, severities, and durations, ForWarn employs multiple historical baselines that are used with current NDVI to derive a suite of six forest change products that are refreshed every 8 days. ForWarn employs daily quarter kilometer MODIS NDVI data from the Aqua and Terra satellites, including MOD13 data for deriving historical baseline NDVIs and eMODIS 7 NDVI for compiling current NDVI. In doing so, the Time Series Product Tool and the Phenological Parameters Estimation Tool are used to temporally de-noise, fuse, and aggregate current and historical MODIS NDVIs into 24 day composites refreshed every 8 days with 46 dates of products per year. The 24 day compositing interval enables disturbances to be detected, while minimizing the frequency of residual atmospheric contamination. Forest change products are

  20. Monitoring Regional Forest Disturbances across the US with Near Real Time MODIS NDVI Products included in the ForWarn Forest Threat Early Warning System

    Science.gov (United States)

    Spruce, J.; Hargrove, W. W.; Gasser, J.; Norman, S. P.

    2013-12-01

    Forest threats across the US have become increasingly evident in recent years. These include regionally extensive disturbances (e.g., from drought, bark beetle outbreaks, and wildfires) that can occur across multiyear durations and result in extensive forest mortality. In addition, forests can be subject to ephemeral, sometimes yearly defoliation from various insects and types of storm damage. After prolonged severe disturbance, signs of forest recovery can vary in terms of satellite-based Normalized Difference Vegetation Index (NDVI) values. The increased extent and threat of forest disturbances in part led to the enactment of the 2003 Healthy Forest Restoration Act, which mandated that a national forest threat Early Warning System (EWS) be deployed. In response, the US Forest Service collaborated with NASA, DOE Oak Ridge National Laboratory, and the USGS Eros Data Center to build the near real time ForWarn forest threat EWS for monitoring regionally evident forest disturbances, starting on-line operations in 2010. Given the diversity of disturbance types, severities, and durations, ForWarn employs multiple historical baselines used with current NDVI to derive a suite of six nationwide 'weekly' forest change products. ForWarn uses daily 232 meter MODIS Aqua and Terra satellite NDVI data, including MOD13 products for deriving historical baseline NDVIs and eMODIS products for compiling current NDVI. Separately pre-processing the current and historical NDVIs, the Time Series Product Tool and the Phenological Parameters Estimation Tool are used to temporally reduce noise, fuse, and aggregate MODIS NDVIs into 24 day composites refreshed every 8 days with 46 dates of forest change products per year. The 24 day compositing interval typically enables new disturbances to be detected, while minimizing the frequency of residual atmospheric contamination. ForWarn's three standard forest change products compare current NDVI to that from the previous year, previous 3 years, and

  1. 青海湖布哈河流域树轮宽度指数与NDVI植被指数的关系%Relationship between Tree Ring Indices and Vegetation Index(NDVI) in Buha River Basin,Qinghai

    Institute of Scientific and Technical Information of China (English)

    汪青春; 时兴合; 刘义花; 秦宁生; 邵雪梅

    2012-01-01

    利用来自青海湖流域乌兰和天峻的树轮指数和1982—2003年逐月标准化植被指数(NDVI)数据及气候数据,在分析树轮指数及草地NDVI与气候因子关系的基础上,探讨了树轮宽度指数序列与青海湖布哈河流域草地NDVI之间的关系.结果表明:树轮宽度指数及草地NDVI主要受6-8月份的水热条件的影响,温度与同期树轮宽度指数及草地NDVI具有较高的正相关,而降水的影响存在滞后性.树木年轮指数序列与6-8月草地NDVI有显著的相关关系,与8月份的NDVI相关性最强.树轮指数与草地NDVI间的显著相关性为研究该地区草地过去的动态变化提供了基础,利用乌兰和天峻的两条树轮指数重建了8月份NDVI的千年变化.%In this paper,using tree ring indices and monthly normalized NDVI and meteorological data in Wulan and Tianjun Counties form 1982 to 2003,the relationships between tree ring indices and grass NDVI in Buha River basin are analyzed on the basis of the relationships between tree ring indices,grass NDVI and climatic factors.It is found that water-heat conditions distinctly affect the tree ring indices and grass NDVI from June to August.Between air temperature and tree ring indices,grass NDVI in the same period there is a significant correlation.However,the effect of precipitation lags behind air temperature.A remarkable correlation exists between the series of tree ring indices and grass NDVI from June to August,especially in August.The significant correlation between tree ring indices and grass NDVI will be in favour of studying the grass dynamic change in the past.A thousand year variations of grass NDVI in August are reconstructed in this paper based on two tree ring series in Wulan and Tianjun counties.

  2. 不同株型品种冬小麦NDVI变化特征及产量分析%Changes in NDVI and yield of winter wheat cultivars with different plant types

    Institute of Scientific and Technical Information of China (English)

    冯美臣; 杨武德

    2011-01-01

    Plant type and irrigation scheme are key influencing factors of real-time yield estimation and monitoring of winter wheat in precision farming. In this paper, MODIS remote sensing data were used in combination with GPS and ground-truth non-remote sensing data to determine the dynamics of normalized difference vegetation index (NDVI) of winter wheat cultivars with different plant types under irrigation and non-irrigation conditions. The relationship between NDVI and yield of different winter wheat cultivats in different growth stages was then analyzed. Results showed the trends in NDVI with developmental stages of different wheat cultivars were same, following a low-high-low curve. There were obvious differences in NDVI from jointing to booting stages for different cultivars, and NDVI for cultivars with horizontal plant types was higher than that for cultivars with erect plant types. It implied that the jointing-to-booting stage was the best period for identifying plant types of winter wheat cultivars. Even for the same cultivar, mean NDVI was obviously different at each growth stage for irrigated and non-irrigated lands. NDVI for irrigated winter wheat was higher than that for non-irrigated winter wheat, with a notable difference especially at the early heading stage. At early heading stage, NDVI was strongly correlated with yield in irrigated and non-irrigated lands. However, regression equation based on NDVI both in the early heading and filling stages gave better prediction for wheat yield than that based on NDVI only in the early heading stage. This was especially the case for non-irrigated wheat fields.%冬小麦不同株型品种和灌溉类型是影响产量遥感估测的重要因素,对二者的实时监测可以提高产量的估测精度.结合遥感数据(MODIS数据)与非遥感数据(GPS数据和外业调查资料),研究了不同株型品种冬小麦在水、旱地条件下归一化差值植被指数(NDVI)的动态变化特征,分析了不同生育

  3. Comparison of Eight Techniques for Reconstructing Multi-Satellite Sensor Time-Series NDVI Data Sets in the Heihe River Basin, China

    Directory of Open Access Journals (Sweden)

    Liying Geng

    2014-03-01

    Full Text Available More than 20 techniques have been developed to de-noise time-series vegetation index data from different satellite sensors to reconstruct long time-series data sets. Although many studies have compared Normalized Difference Vegetation Index (NDVI noise-reduction techniques, few studies have compared these techniques systematically and comprehensively. This study tested eight techniques for smoothing different vegetation types using different types of multi-temporal NDVI data (Advanced Very High Resolution Radiometer (AVHRR (Global Inventory Modeling and Map Studies (GIMMS and Pathfinder AVHRR Land (PAL, Satellite Pour l’ Observation de la Terre (SPOT VEGETATION (VGT, and Moderate Resolution Imaging Spectroradiometer (MODIS (Terra with the ultimate purpose of determining the best reconstruction technique for each type of vegetation captured with four satellite sensors. These techniques include the modified best index slope extraction (M-BISE technique, the Savitzky-Golay (S-G technique, the mean value iteration filter (MVI technique, the asymmetric Gaussian (A-G technique, the double logistic (D-L technique, the changing-weight filter (CW technique, the interpolation for data reconstruction (IDR technique, and the Whittaker smoother (WS technique. These techniques were evaluated by calculating the root mean square error (RMSE, the Akaike Information Criterion (AIC, and the Bayesian Information Criterion (BIC. The results indicate that the S-G, CW, and WS techniques perform better than the other tested techniques, while the IDR, M-BISE, and MVI techniques performed worse than the other techniques. The best de-noise technique varies with different vegetation types and NDVI data sources. The S-G performs best in most situations. In addition, the CW and WS are effective techniques that were exceeded only by the S-G technique. The assessment results are consistent in terms of the three evaluation indexes for GIMMS, PAL, and SPOT data in the study

  4. Tuberculosis in the twentieth century: time-series mortality in São Paulo, Brazil, 1900-97 A tuberculose através do século: séries temporais para a mortalidade em São Paulo, Brasil, 1900-97

    Directory of Open Access Journals (Sweden)

    José Leopoldo Ferreira Antunes

    1999-09-01

    Full Text Available The objective of this study was to characterize tuberculosis mortality trends in the Municipality of São Paulo, Brazil, from 1900 to 1997. Standardized tuberculosis mortality rates and proportional mortality ratios were calculated and stratified by gender and age group based on data provided by government agencies. These measures were submitted to time-series analysis. We verified distinct trends: high mortality and a stationary trend from 1900 to 1945, a heavy reduction in mortality (7.41% per year from 1945 to 1985, and a resumption of increased mortality (4.08% per year from 1985 to 1995. In 1996 and 1997 we observed a drop in tuberculosis mortality rates, which may be indicating a new downward trend for the disease. The period from 1945 to 1985 witnessed a real reduction in tuberculosis, brought about by social improvements, the introduction of therapeutic resources, and expansion of health services. Recrudescence of tuberculosis mortality from 1985 to 1995 may reflect the increasing prevalence of Mycobacterium and HIV co-infection, besides loss of quality in specific health programs.Com o objetivo de caracterizar tendências da mortalidade por tuberculose no Município de São Paulo, Brasil, 1900-1997, foram calculados e estratificados por gênero e grupo etário os coeficientes padronizados de mortalidade e as razões de mortalidade proporcional, por intermédio de dados providos por agências governamentais. Esxas medidas foram ainda submetidas à análise de séries temporais. Foram verificadas diferentes tendências: de 1900 a 1945, alta mortalidade e tendência estacionária; de 1945 a 1985, forte redução na mortalidade (7,41% por ano; e de 1985 a 1995, retomada do crescimento da mortalidade (4,08% por ano. Em 1996 e 1997, a redução observada nos coeficientes de mortalidade pode estar indicando um novo perfil descendente para a enfermidade. Os anos de 1945 a 1985 marcaram período de acentuada queda para a tuberculose, produzida

  5. Analysis of vegetation and land cover dynamics in north-western Morocco during the last decade using MODIS NDVI time series data

    Directory of Open Access Journals (Sweden)

    C. Höpfner

    2011-11-01

    Full Text Available Vegetation phenology as well as the current variability and dynamics of vegetation and land cover, including its climatic and human drivers, are examined in a region in north-western Morocco that is nearly 22 700 km2 big. A gapless time series of Normalized Differenced Vegetation Index (NDVI composite raster data from 29 September 2000 to 29 September 2009 is utilised. The data have a spatial resolution of 250 m and were acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS sensor.

    The presented approach allows to compose and to analyse yearly land cover maps in a widely unknown region with scarce validated ground truth data by deriving phenological parameters. Results show that the high temporal resolution of 16 d is sufficient for (a determining local land cover better than global land cover classifications of Plant Functional Types (PFT and Global Land Cover 2000 (GLC2000 and (b for drawing conclusions on vegetation dynamics and its drivers. Areas of stably classified land cover types (i.e. areas that did not change their land cover type show climatically driven inter- and intra-annual variability with indicated influence of droughts. The presented approach to determine human-driven influence on vegetation dynamics caused by agriculture results in a more than ten times larger area compared with stably classified areas. Change detection based on yearly land cover maps shows a gain of high-productive vegetation (cropland of about 259.3 km2. Statistically significant inter-annual trends in vegetation dynamics during the last decade could however not be discovered. A sequence of correlations was respectively carried out to extract the most important periods of rainfall responsible for the production of green biomass and for the extent of land cover types. Results show that mean daily precipitation from 1 October to 15 December has high correlation results (max. r2=0.85 on an intra

  6. MODIS 1B数据的预处理及归一化植被指数计算%Preprocessing and NDVI Calculation of MODIS 1B Data

    Institute of Scientific and Technical Information of China (English)

    杜灵通

    2008-01-01

    MODIS 1B数据的预处理是MODIS数据使用前的重要处理步骤之一.本文在分析MODIS数据畸变的基础上,利用ENVI软件对2006年7月覆盖宁夏全区的MODIS 1B数据进行了bow-tie校正和几何校正.在预处理的基础上,通过最大值合成法计算出了7月下旬宁夏全区的归一化植被指数(NDVI).结果表明,通过该方法得到的NDVI可以很好反映全区的植被状况.

  7. Analysis of vegetation and land cover dynamics in north-western Morocco during the last decade using MODIS NDVI time series data

    Directory of Open Access Journals (Sweden)

    C. Höpfner

    2011-04-01

    Full Text Available Vegetation phenology as well as current variability and dynamics of vegetation and land cover including its climatic and human drivers are examined in a region in north-western Morocco of nearly 22 700 km2. A gapless time series of Normalized Differenced Vegetation Index (NDVI composite raster data from 29 September 2000 to 29 September 2009 with a spatial resolution of 250 m and acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS sensor is utilised. The presented approach allows to compose and analyse yearly land cover maps in a widely unknown region with scarce validated ground truth data by deriving phenological parameters. Results show that high temporal resolution of 16 d is sufficient (a for determining land cover better than global land cover classifications of Plant Functional Types (PFT and Global Land Cover 2000 (GLC2000, and (b for drawing conclusions on vegetation dynamics and its drivers. Areas of stably classified land cover types show climatically driven inter- and intra-annual variability with indicated influence of droughts. The presented approach to determine human-driven influence on vegetation dynamics caused by agriculture results in a more than ten times larger area compared to the stably classified areas. Change detection based on yearly land cover maps shows a gain of high-productive vegetation (cropland of about 259.3 km2. However, statistically significant inter-annual trends in vegetation dynamics during the last decade could not be discovered. A sequence of correlations was done to extract the most important period of rainfall for production of green biomass and for the extent of land cover types, respectively. Results show that mean daily precipitation from 1 October to 15 December has high correlation results (max. r2=0.85 at intra-annual time scale to NDVI percentiles (50% of land cover types. Correlation results of mean daily precipitation from 16 September

  8. Spatial and Temporal Variability in the Onset of the Growing Season on Svalbard, Arctic Norway — Measured by MODIS-NDVI Satellite Data

    Directory of Open Access Journals (Sweden)

    Stein Rune Karlsen

    2014-08-01

    Full Text Available The Arctic is among the regions with the most rapid changes in climate and has the expected highest increase in temperature. Changes in the timing of phenological phases, such as onset of the growing season observed from remote sensing, are among the most sensitive bio-indicators of climate change. The study area here is the High Arctic archipelago of Svalbard, located between 76°30ʹ and 80°50ʹN. The goal of this study was to use MODIS Terra data (the MOD09Q1 and MOD09A1 surface reflectance products, both with 8-day temporal composites to map the onset of the growing season on Svalbard for the 2000–2013 period interpreted from field observations. Due to a short and intense period with greening-up and frequent cloud cover, all the cloud free data is needed, which requires reliable cloud masks. We used a combination of three cloud removing methods (State QA values, own algorithms, and manual removal. This worked well, but is time-consuming as it requires manual interpretation of cloud cover. The onset of the growing season was then mapped by a NDVI threshold method, which showed high correlation (r2 = 0.60, n = 25, p < 0.001 with field observations of flowering of Salix polaris (polar willow. However, large bias was found between NDVI-based mapped onset and field observations in bryophyte-dominated areas, which indicates that the results in these parts must be interpreted with care. On average for the 14-year period, the onset of the growing season occurs after July 1st in 68.4% of the vegetated areas of Svalbard. The mapping revealed large variability between years. The years 2000 and 2008 were extreme in terms of late onset of the growing season, and 2002 and 2013 had early onset. Overall, no clear trend in onset of the growing season for the 2000–2013 period was found.

  9. Assessing impacts of meteorological drought on vegetation at catchment scale in China based on SPEI and NDVI%基于 SPEI 和 NDVI 的中国流域尺度气象干旱及植被分布时空演变

    Institute of Scientific and Technical Information of China (English)

    王兆礼; 黄泽勤; 李军; 钟睿达; 黄文炜

    2016-01-01

    Drought is a natural disaster caused by long-time water shortage and uneven water distribution, which is one of the most common disasters around the world. Under the background of global warming, droughts have become more and more frequent and devastating, causing negative impacts on agricultural production, ecological environment and social economy. For the protection of vegetation and crops, it would be of practical significance to investigate how vegetation develops under the influence of drought which varies in time and space. This research applied the standard precipitation evaporation index (SPEI) derived from high spatial resolution dataset of precipitation and evaporation, as well as the newly published normalized difference vegetation index (NDVI) which represents the growth condition of vegetation on land. Mann-Kendall (MK) test and correlation analysis were taken to study the spatial and temporal evolution of SPEI and NDVI at catchment scale with the help of ArcGIS 10.1 software. The results of the research illustrated that: 1) The MK value of SPEI at catchment scale showed great coincidence with that of the 4189 grid points both in time and space, indicating the feasibility to investigate the response of vegetation growth under the influence of meteorological drought at catchment scale. SPEI was getting increasing slightly at different time scales during 1962-2012, indicating that China as a whole was being more humid. However, taking the time series of 1982-2012 as the research object, China was getting drier slightly at different time scales. In space, both at annual and at seasonal scale, drought trends were mainly detected in catchments in the Loess Plateau area, Northeast and Southwest China, while catchments in Northwest China presented significant humidifying tendency. 2) The NDVI value of the whole China was upgrading with time during 1982-2012, among which the NDVI in spring, growing season and whole year had a significant increasing trend. In

  10. A Comparison Between the Algorithms for Removing Cloud Pixel from MODIS NDVI Time Series Data%MODIS NDVI时间序列数据的去云算法比较

    Institute of Scientific and Technical Information of China (English)

    梁守真; 施平; 邢前国

    2011-01-01

    Although composite data present lower atmospheric contamination than raw time series, MODIS NDVI products are still contaminated by clouds, especially when cloud cover lasts longer than the composite period. e.g. , in the rainy season. The long - time cloud cover will weaken the application of MODIS NDVI time series data.To remove the effect of these clouds from NDVI data and reconstruct high -quality NDVI data, the authors propose three algorithms for cloud removal, namely SPLINE function, HANTS and Savizky - Golay. The capabilities of the three algorithms in cloud removal was compared with each other in this study, with the MODIS NDVI time series data in Shandong province serving as the test data. The results show that the three algorithms can remove the effect of cloud from NDVI time series data effectively, with each algorithm having its own advantages and disadvantages.For the algorithm of SPLINE function, the result of cloud removal mainly depends on the quality of cloud data and sometimes extreme values will occur; this algorithm fails to change the values of pixels which have not been contaminated atmospherically. When HANTS and Savizky - Golay algorithms are used, most of the pixels will lose their original values, and the parameters have to be determined after conducting many experiments because there is no objective rule to set them.%受多重因素的影响,MODIS NDVI数据产品中存在着大量的噪声,需要进行去噪重建.针对目前几种常用的NDVI时间序列数据去云方法,如HANTS法、SPLINE插值法以及Savizky-Golay法,以山东省MODIS NDVI时间序列数据(一年的)作为检验数据,从不同角度比较几种算法的去云能力和使用范围.结果表明:SPLINE插值法的去噪效果取决于云掩模数据的质量,但有时会产生异常值; HANTS算法和Savizky-Golay算法会改变几乎所有像元的值,得到一个比较平滑的时间序列曲线,但这两种算法的输入参数没有统一标准,需多次试验才能确定最优参数.

  11. Monitoring irrigation water consumption using high resolution NDVI image time series (Sentinel-2 like). Calibration and validation in the Kairouan plain (Tunisia)

    Science.gov (United States)

    Saadi, Sameh; Simonneaux, Vincent; Boulet, Gilles; Mougenot, Bernard; Zribi, Mehrez; Lili Chabaane, Zohra

    2015-04-01

    Water scarcity is one of the main factors limiting agricultural development in semi-arid areas. It is thus of major importance to design tools allowing a better management of this resource. Remote sensing has long been used for computing evapotranspiration estimates, which is an input for crop water balance monitoring. Up to now, only medium and low resolution data (e.g. MODIS) are available on regular basis to monitor cultivated areas. However, the increasing availability of high resolution high repetitivity VIS-NIR remote sensing, like the forthcoming Sentinel-2 mission to be lunched in 2015, offers unprecedented opportunity to improve this monitoring. In this study, regional crops water consumption was estimated with the SAMIR software (Satellite of Monitoring Irrigation) using the FAO-56 dual crop coefficient water balance model fed with high resolution NDVI image time series providing estimates of both the actual basal crop coefficient (Kcb) and the vegetation fraction cover. The model includes a soil water model, requiring the knowledge of soil water holding capacity, maximum rooting depth, and water inputs. As irrigations are usually not known on large areas, they are simulated based on rules reproducing the farmer practices. The main objective of this work is to assess the operationality and accuracy of SAMIR at plot and perimeter scales, when several land use types (winter cereals, summer vegetables…), irrigation and agricultural practices are intertwined in a given landscape, including complex canopies such as sparse orchards. Meteorological ground stations were used to compute the reference evapotranspiration and get the rainfall depths. Two time series of ten and fourteen high-resolution SPOT5 have been acquired for the 2008-2009 and 2012-2013 hydrological years over an irrigated area in central Tunisia. They span the various successive crop seasons. The images were radiometrically corrected, first, using the SMAC6s Algorithm, second, using invariant

  12. Time-variations of equivalent water heights'from Grace Mission and in-situ river stages in the Amazon basin Variações temporais do equivalente à altura d'água obtidas da Missão Grace e da altura d'água in-situ nos rios da bacia Amazônica

    Directory of Open Access Journals (Sweden)

    Flavio Guilherme Vaz de Almeida

    2012-03-01

    Full Text Available Gravity Recovery and Climate Experiment (GRACE mission is dedicated to measuring temporal variations of the Earth's gravity field. In this study, the Stokes coefficients made available by Groupe de Recherche en Géodésie Spatiale (GRGS at a 10-day interval were converted into equivalent water height (EWH for a ~4-year period in the Amazon basin (from July-2002 to May-2006. The seasonal amplitudes of EWH signal are the largest on the surface of Earth and reach ~ 1250mm at that basin's center. Error budget represents ~130 mm of EWH, including formal errors on Stokes coefficient, leakage errors (12 ~ 21 mm and spectrum truncation (10 ~ 15 mm. Comparison between in situ river level time series measured at 233 ground-based hydrometric stations (HS in the Amazon basin and vertically-integrated EWH derived from GRACE is carried out in this paper. Although EWH and HS measure different water bodies, in most of the cases a high correlation (up to ~80% is detected between the HS series and EWH series at the same site. This correlation allows adjusting linear relationships between in situ and GRACE-based series for the major tributaries of the Amazon river. The regression coefficients decrease from up to down stream along the rivers reaching the theoretical value 1 at the Amazon's mouth in the Atlantic Ocean. The variation of the regression coefficients versus the distance from estuary is analysed for the largest rivers in the basin. In a second step, a classification of the proportionality between in situ and GRACE time-series is proposed.A missão espacial Gravity Recovery and Climate Experiment (GRACE é dedicada às medidas das variações temporais no campo gravitacional da Terra. Neste estudo, os coeficientes de Stokes disponibilizados pelo Groupe de Recherche en Géodésie Spatiale (GRGS com intervalos de 10 dias foram convertidos no equivalente à altura d'água (EWH para um período de 4 anos na bacia Amazônica (de julho de 2002 a maio de 2006

  13. Assinatura de objectos em rádio frequência

    OpenAIRE

    Fernandes, Rui Miguel Félix

    2014-01-01

    The RF signature can be consider as a fingerprint of an object when submitted to electromagnetic radiation. Based on this concept, the initial goal of this work was to elaborate a comparative analysis of the Radio Frequency signature of different materials. Through the design of a prototype based on an adapted Wi-Fi network was developed an innovative system capable of distinguishing materials with the analysis of their interference in the propagated channel. In order to refine this dis...

  14. A User's Version View of a Robustified, Bayesian Weighted Least-Squares Recursive Algorithm for Interpolating AVHRR-NDVI Data: Applications to an Animated Visualization of the Phenology of a Semi-Arid Study Area

    Science.gov (United States)

    Hermance, J. F.; Jacob, R. W.; Bradley, B. A.; Mustard, J. F.

    2005-12-01

    In studying vegetation patterns remotely, the objective is to draw inferences on the development of specific or general land surface phenology (LSP) as a function of space and time by determining the behavior of a parameter (in our case NDVI), when the parameter estimate may be biased by noise, data dropouts and obfuscations from atmospheric and other effects. We describe the underpinning concepts of a procedure for a robust interpolation of NDVI data that does not have the limitations of other mathematical approaches which require orthonormal basis functions (e.g. Fourier analysis). In this approach, data need not be uniformly sampled in time, nor do we expect noise to be Gaussian-distributed. Our approach is intuitive and straightforward, and is applied here to the refined modeling of LSP using 7 years of weekly and biweekly AVHRR NDVI data for a 150 x 150 km study area in central Nevada. This site is a microcosm of a broad range of vegetation classes, from irrigated agriculture with annual NDVIvalues of up to 0.7 to playas and alkali salt flats with annual NDVI values of only 0.07. Our procedure involves a form of parameter estimation employing Bayesian statistics. In utilitarian terms, the latter procedure is a method of statistical analysis (in our case, robustified, weighted least-squares recursive curve-fitting) that incorporates a variety of prior knowledge when forming current estimates of a particular process or parameter. In addition to the standard Bayesian approach, we account for outliers due to data dropouts or obfuscations because of clouds and snow cover. An initial "starting model" for the average annual cycle and long term (7 year) trend is determined by jointly fitting a common set of complex annual harmonics and a low order polynomial to an entire multi-year time series in one step. This is not a formal Fourier series in the conventional sense, but rather a set of 4 cosine and 4 sine coefficients with fundamental periods of 12, 6, 3 and 1

  15. Using MODIS-NDVI for the Modeling of Post-Wildfire Vegetation Response as a Function of Environmental Conditions and Pre-Fire Restoration Treatments

    Directory of Open Access Journals (Sweden)

    Grant M. Casady

    2012-03-01

    Full Text Available Post-fire vegetation response is influenced by the interaction of natural and anthropogenic factors such as topography, climate, vegetation type and restoration practices. Previous research has analyzed the relationship of some of these factors to vegetation response, but few have taken into account the effects of pre-fire restoration practices. We selected three wildfires that occurred in Bandelier National Monument (New Mexico, USA between 1999 and 2007 and three adjacent unburned control areas. We used interannual trends in the Normalized Difference Vegetation Index (NDVI time series data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS to assess vegetation response, which we define as the average potential photosynthetic activity through the summer monsoon. Topography, fire severity and restoration treatment were obtained and used to explain post-fire vegetation response. We applied parametric (Multiple Linear Regressions-MLR and non-parametric tests (Classification and Regression Trees-CART to analyze effects of fire severity, terrain and pre-fire restoration treatments (variable used in CART on post-fire vegetation response. MLR results showed strong relationships between vegetation response and environmental factors (p < 0.1, however the explanatory factors changed among treatments. CART results showed that beside fire severity and topography, pre-fire treatments strongly impact post-fire vegetation response. Results for these three fires show that pre-fire restoration conditions along with local environmental factors constitute key processes that modify post-fire vegetation response.

  16. Evapotranspiração real obtida através da relação entre o coeficiente dual de cultura da FAO-56 e o NDVI Real actual evapotranspiration obtained through the relationship between the FAO-56 crop dual coefficient and NDVI

    Directory of Open Access Journals (Sweden)

    Bergson Guedes Bezerra

    2010-09-01

    Full Text Available Um requisito fundamental para adoção de manejo da irrigação é a determinação diária da evapotranspiração (ET das culturas. Em caráter operacional o método do coeficiente de cultura proposto pela Food Agriculture Organization (FAO, através do seu relatório 56 (Irrigation and Drainage Paper, é largamente utilizado na determinação da ET, e tem apresentado precisões que o tornam mundialmente aceito. A ET com base no coeficiente de cultura (Kc, obtido a partir de índices de vegetação, particularmente o NDVI, tem sido calculada em vários estudos e para diversas culturas alcançando muita precisão, quando comparado com observações de campo. Diante do exposto, este trabalho teve por objetivo calcular a ET diária e sazonal da cultura do algodoeiro utilizando o método do Kc dual obtido em função do Índice de Vegetação por Diferença Normalizada - NDVI, obtido a partir de imagens TM - Landsat 5 livre da presença de nuvens. Os resultados revelaram precisões bastante confiáveis, pois foram verificadas diferenças menores que 10%, quando comparados com valores da ET obtidos pela técnica da Bowen, corroborando com o desempenho alcançado pelo método em outras pesquisas realizadas em outras regiões do planeta. Dessa forma, pode-se concluir que o método apresenta bastante confiabilidade e simplicidade.A fundamental requirement for adoption of irrigation management is to determine the crop daily evapotranspiration (ET. On an operational basis the crop coefficient method proposed by the Food and Agriculture Organization (FAO through its report 56 (Irrigation and Drainage Paper is widely used in the determination of ET and due to its accurate estimative, it has been globally accepted. The ET-based crop coefficient (Kc obtained from vegetation indices, particularly the Vegetation Index Normalized Difference (NDVI has been measured in several studies and various crops showing great accuracy when compared to field observations

  17. 我国西北地区东部时间序列 NDVI数据集重建方法比较研究%Comparative studies of reconstruction methods for the long term NDVI dataset in the east of Northwest China

    Institute of Scientific and Technical Information of China (English)

    王玮; 郭铌; 沙莎; 胡蝶; 王小平; 李耀辉

    2016-01-01

    A high-level time-series NDVI dataset is not only the basis for continuous monitoring of the land sur-face,but also an important tool for studying change related to climate and land use factors in terrestrial eco-systems.We reconstructed the noise component of the LTDR NDVI data for the east of Northwestern China where the ecosystem is fragile,using various time-series reconstruction methods.This paper use agrometeoro-logical data and high-level NDVI data to evaluate the accuracy of different reconstruction methods.The results show that:1)The vegetation or crop land cover is an important factor affecting fitted results of the various re-construction methods.Each reconstruction method has a different noise reduction ability depending on differ-ences in vegetation or crop growth characters;2)The D-L reconstruction method has a better noise reduction ability and applicability in those areas of grassland,and woodland for which the annual average NDVI data is higher (NDVI≥0.3)and the NDVI curve has obvious seasonal changes;3)The S-G reconstruction method has better fidelity ability and applicability in some areas of crop land in winter wheat and in areas of sparse vegeta-tion for which annual average NDVI data are lower (NDVI<0.3)and where the NDVI curve have no obvious seasonal changes.%高质量、长时序归一化植被指数(NDVI)数据集不仅是连续监测陆地表面特征的基础,也是研究气候与陆地生态系统变化的重要参数。本研究以生态环境较为脆弱的西北地区东部为例,借助多种时间序列重建方法对 LT-DR NDVI 数据集中的噪声进行拟合重建,并结合农业气象资料和高质量 NDVI 数据,对不同重建方法的拟合结果开展适用性评价分析,结果表明,1)下垫面类型是影响重建方法拟合效果的重要因素。根据不同植被类型或作物生长特点,每种重建方法对其噪声消除能力有所不同;2)在年均 NDVI 较高(NDVI≥0.3

  18. Distribución espacial de anomalías del NDVI derivado del sensor VEGETATION SPOT 4/5 ysu relación con las coberturas vegetales, usos de la tierra y características geomorfológicas en la provincia de Santiago del Estero, Argentina / Spatial distribution of anomalies of NDVI derived from sensor VEGETATION SPOT 4/5 and its relation with vegetation cover, uses of ground and geomorphology in Santiago del Estero, Argentina

    Directory of Open Access Journals (Sweden)

    Jose Luis Tiedermann

    2010-12-01

    Full Text Available Se determinaron las anomalías negativas (AN y positivas (AP del NDVI derivado del sensor VEGETATION SPOT 4/5, en la provincia de Santiago del Estero, Argentina. El periodo analizado (1998-2008 tuvo fuertes variaciones en los patrones de precipitación, por efecto del ENSO, por cuanto las anomalías del NDVI fueron evaluadas, mediante tabulación cruzada, en función de dos periodos: húmedo (PH y seco (PS. Las AN, se relacionaron, durante todo el periodo, con vegetación halófila en áreas deprimidas salobres, con vegetación hidrófila en ambientes acuáticos y con suelo rocoso. Durante el PS, las AN se relacionaron con áreas deforestadas con fines agrícolas. Las AP, se relacionaron, durante todo el periodo, con el bosque Chaqueño denso y bosque Chaqueño Serrano denso. La mayor estabilidad y productividad de biomasa verde de los bosques, estaría relacionada, a su mayor biodiversidad, estratificación, al predominio de especies leñosas perennes de raíces profundas y a las estratégicas adaptaciones, morfológicas y fisiológicas, para el uso eficiente del agua. Las regiones geomorfológicas no se relacionan entre si entre periodos.AbstractThe negative (AN and positive (AP anomalies of the NDVI derived from sensor VEGETATION SPOT 4/5 were determined in the province of Santiago del Estero, Argentina. The analyzed period (1998-2008 presented strong variations in rainfall patterns, as a result of the ENSO, inasmuch as the anomalies of the NDVI were evaluated, by means of crossed tabulation, based on two periods: humid (PH and dry (PS. The AN, were related with halophytic species of depressed areas, with vegetation aquatic hydrophilic and rocky ground. During the dry period, the AN were related to deforested areas with agricultural aims. The AP, were related, throughout the period with the forest dense Chaco Semiarid and forest dense Chaco Serrano. The greater stability and productivity of green biomass of forest, would be related, greater

  19. 多种时序NDVI重建方法比较与应用分析%Comparison and Application Analysis of Several NDVI Time-Series Reconstruction Methods

    Institute of Scientific and Technical Information of China (English)

    张晗; 任志远

    2014-01-01

    NDVI时序数列能够模拟植物的生长过程,反映其生长状况。目前重建NDVI时序数列的方法有很多,由于模型和参数的不同导致结果存在不确定性以及偏差。本研究旨在对比3种模型(Whittaker平滑、HANTS和Savitzky-Golay滤波)在物候提取和复种指数提取中的应用,以探讨各模型的优缺点。采用16 d间隔的MODIS MOD13Q12000-2012年陕西地区影像,利用3种模型拟合重建NDVI时序数列。首先,将研究区划分为3个气候区,每区分别选择林地和耕地两个采样点,视觉比较各采样点3种模型拟合效果。其次,通过均方根误差、相关系数和信噪比对比各模型拟合精度,并探讨不同植被类型之间拟合精度的差异。然后,采用动态阈值法提取13年植被物候参数(生长开始日期SOS、生长结束日期EOS、生长周期LOS),对比模型提取不同植被类型物候参数均值和标准差的差异。最后,利用二次差分算法和提取规则获取陕西13年复种指数,对比3种模型提取和统计年鉴计算复种指数之间的差异。Savitzky-Golay 滤波拟合精度较高,复种指数提取精度较高,但是提取物候参数方面存在较大误差;HANTS提取物候参数效果较好,但参数设置复杂以及精度较差;Whittaker平滑参数设置简单,能有效降低原始影像的信噪比,在精度和物候参数提取均表现良好;均方根误差和相关系数作为精度检验的标准,二者存在负相关,相关系数比均方根误差更灵敏。Whittaker平滑能够很好地平衡NDVI时序数列的保真度和粗糙度,在提取物候参数方面表现良好,在提取复种指数方面还有待进一步研究。%[Objective]NDVI time-series can simulate plant growth and reflect its growing status. Several models have been fitted in the past to smooth time-series vegetation index data from different satellite sensors. However, differences

  20. Tendências temporais e fatores associados à duração do aleitamento materno em Pernambuco Tendencias temporales y factores asociados a la duración del amamantamiento materno en Pernambuco, Noreste de Brasil Time trends and factors associated with breastfeeding in the state of Pernambuco, Northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Maria de Fátima Costa Caminha

    2010-04-01

    Full Text Available OBJETIVO: Analisar as tendências temporais de duração do aleitamento materno exclusivo e os fatores de proteção. MÉTODOS: Foram analisadas as prevalências de amamentação total e o aleitamento materno exclusivo de lactentes aos quatro meses de idade. Os dados foram obtidos de inquéritos populacionais realizados em 1991, 1997 e 2006, com 935, 2.081 e 1.568 crianças, respectivamente. Os dados foram coletados por entrevista realizada com o responsável pela criança. As prevalências foram analisadas por regressão de Poisson em relação a: condições ambientais, comportamentais e socioeconômicas, variáveis maternas e fatores biológicos da criança. RESULTADOS: A duração mediana do aleitamento total elevou-se de 89 dias (1991 para 106 dias (1997 e, finalmente, 183 dias (2006. A mediana do aleitamento materno exclusivo manteve-se estacionária em torno de 30 dias entre 1997 e 2006. Na análise multivariada, das dez variáveis analisadas, apenas a escolaridade e idade maternas, situação do domicílio e a criança ser do sexo feminino se mantiveram no modelo explicativo final. CONCLUSÕES: Apesar do aleitamento total ter tido importante aumento de duração, o mesmo não ocorreu com a duração do aleitamento materno exclusivo.OBJETIVO: Analizar las tendencias temporales de duración del amamantamiento materno exclusivo y los factores de protección. MÉTODOS: Fueron analizadas las prevalencias de amamantamiento total y el amamantamiento materno exclusivo de lactantes a los cuatro meses de edad. Los datos fueron obtenidos de pesquisas poblacionales realizadas en 1991, 1997 y 2006, con 935, 2.081 y 1.568 niños, respectivamente. Los datos fueron colectados por entrevista realizada con el responsable del niño. Las prevalencias fueron analizadas por regresión de Poisson en relación a: condiciones ambientales, de comportamiento y socioeconómicas, variables maternas y factores biológicos del niño. RESULTADOS: La duración mediana

  1. ABSOLUTE RADIOMETRIC CALIBRATION OF THE GÖKTÜRK-2 SATELLITE SENSOR USING TUZ GÖLÜ (LANDNET SITE FROM NDVI PERSPECTIVE

    Directory of Open Access Journals (Sweden)

    U. Sakarya

    2016-06-01

    Full Text Available TÜBİTAK UZAY has conducted a research study on the use of space-based satellite resources for several aspects of agriculture. Especially, there are two precision agriculture related projects: HASSAS (Widespread application of sustainable precision agriculture practices in Southeastern Anatolia Project Region (GAP Project and AKTAR (Smart Agriculture Feasibility Project. The HASSAS project aims to study development of precision agriculture practice in GAP region. Multi-spectral satellite imagery and aerial hyperspectral data along with ground measurements was collected to analyze data in an information system. AKTAR aims to develop models for irrigation, fertilization and spectral signatures of crops in Inner Anatolia. By the end of the project precision agriculture practices to control irrigation, fertilization, pesticide and estimation of crop yield will be developed. Analyzing the phenology of crops using NDVI is critical for the projects. For this reason, absolute radiometric calibration of the Red and NIR bands in space-based satellite sensors is an important issue. The Göktürk-2 satellite is an earth observation satellite which was designed and built in Turkey and was launched in 2012. The Göktürk-2 satellite sensor has a resolution 2.5 meters in panchromatic and 5 meters in R/G/B/NIR bands. The absolute radiometric calibration of the Göktürk-2 satellite sensor was performed via the ground-based measurements - spectra-radiometer, sun photometer, and meteorological station- in Tuz Gölü cal/val site in 2015. In this paper, the first ground-based absolute radiometric calibration results of the Göktürk-2 satellite sensor using Tuz Gölü is demonstrated. The absolute radiometric calibration results of this paper are compared with the published cross-calibration results of the Göktürk-2 satellite sensor utilizing Landsat 8 imagery. According to the experimental comparison results, the Göktürk-2 satellite sensor coefficients for

  2. Absolute Radiometric Calibration of the GÖKTÜRK-2 Satellite Sensor Using Tuz GÖLÜ (landnet Site) from Ndvi Perspective

    Science.gov (United States)

    Sakarya, Ufuk; Hakkı Demirhan, İsmail; Seda Deveci, Hüsne; Teke, Mustafa; Demirkesen, Can; Küpçü, Ramazan; Feray Öztoprak, A.; Efendioğlu, Mehmet; Fehmi Şimşek, F.; Berke, Erdinç; Zübeyde Gürbüz, Sevgi

    2016-06-01

    TÜBİTAK UZAY has conducted a research study on the use of space-based satellite resources for several aspects of agriculture. Especially, there are two precision agriculture related projects: HASSAS (Widespread application of sustainable precision agriculture practices in Southeastern Anatolia Project Region (GAP) Project) and AKTAR (Smart Agriculture Feasibility Project). The HASSAS project aims to study development of precision agriculture practice in GAP region. Multi-spectral satellite imagery and aerial hyperspectral data along with ground measurements was collected to analyze data in an information system. AKTAR aims to develop models for irrigation, fertilization and spectral signatures of crops in Inner Anatolia. By the end of the project precision agriculture practices to control irrigation, fertilization, pesticide and estimation of crop yield will be developed. Analyzing the phenology of crops using NDVI is critical for the projects. For this reason, absolute radiometric calibration of the Red and NIR bands in space-based satellite sensors is an important issue. The Göktürk-2 satellite is an earth observation satellite which was designed and built in Turkey and was launched in 2012. The Göktürk-2 satellite sensor has a resolution 2.5 meters in panchromatic and 5 meters in R/G/B/NIR bands. The absolute radiometric calibration of the Göktürk-2 satellite sensor was performed via the ground-based measurements - spectra-radiometer, sun photometer, and meteorological station- in Tuz Gölü cal/val site in 2015. In this paper, the first ground-based absolute radiometric calibration results of the Göktürk-2 satellite sensor using Tuz Gölü is demonstrated. The absolute radiometric calibration results of this paper are compared with the published cross-calibration results of the Göktürk-2 satellite sensor utilizing Landsat 8 imagery. According to the experimental comparison results, the Göktürk-2 satellite sensor coefficients for red and NIR bands

  3. 重庆2006年夏季特大干旱期间的NDVI与城市热岛%Analysis of NDVI and Urban Heat Island during the Unusual Drought in 2006 Summer in Chongqing

    Institute of Scientific and Technical Information of China (English)

    何泽能; 杨世琦; 易佳

    2011-01-01

    为了深入了解特大干旱期间的城市热岛现象和规律,以MODIS遥感资料和重庆市主城及其周边地区的自动气象站观测资料为基础,探讨了2006年夏季重庆市特大干旱期间的植被指数NDVI和城市热岛.结果表明:2006年夏季,重庆市NDVI的变化规律是:在时间上,基本呈逐渐减小的趋势,与2006年夏季重庆市特大干旱的发展过程较为一致.在干旱的整个时段内,NDVI与热岛强度总体上呈负相关关系,NDVI值越高,热岛效应越弱.城区和郊区干旱的非同步性导致了干旱在初中期主要起增强城市热岛效应的作用,而在后期则有减弱城市热岛效应的作用.总的来说,干旱的出现加重了城市热岛效应.%In order to learn about urban heat island phenomena and disciplinarian during the unusual drought period, the MODIS remote sensing data and temperature data measured in automatic weather stations, which distributed in the urban and suburb were used to investigate the relation of NDVI and urban heat island during the unusual drought in 2006 summer in Chongqing. The result showed that in 2006 summer, the NDVI decreased with time, which mainly was consistent with the change trend of drought in 2006 summer in Chongqing. In the whole period of drought, in the mass NDVI negatively correlate with the urban heat island,the higher the NDVI was, the feebler the urban heat island was. Because of non-synchronization of drought in urban and suburb areas, in the early period drought strengthened urban heat island and in the later period of drought, it weakened urban heat island. All in all, the appearance of drought aggravated the degree of urban heat island.

  4. Spatial and temporal variations of NDVI and its response to meterological factors over Heihe River basin of Qilian Mountains%祁连山黑河流域NDVI时空变化及其对气候因子的响应

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

      基于GIS和RS技术,利用SPOT-VGT( NDVI )数据和黑河流域15个常规气象站及自动气象观测站的气温、降水量、不同深度的土壤温度、体积含水量等资料,系统分析了黑河流域NDVI的变化特征及其对气候因子的响应特征。通过年平均累积和趋势线分析方法,得出1999−2011年黑河流域NDVI的时空分布特征:年累计NDVI和年均NDVI绝大部分处于增长趋势,只有下游的西部和上游的南部一些地区处于降低趋势;季节累积NDVI和季节平均NDVI绝大部分区域处于增长趋势;在植被退化的阶段,冬季植被退化较其他季节严重;在植被增长的阶段,秋季植被增长较快。通过数理统计方法分析了NDVI对气象因子的响应关系:土壤温度对NDVI的关系能够较好地拟合NDVI的发展趋势, NDVI对气温和降水量的滞后时间大约分别为2旬、1个月,春季NDVI受到前一年11月份和秋季降水量影响较大,总体上土壤水分对NDVI影响较复杂。%Based on GIS and RS technology, the SPOT-VGT NDVI, temperature, precipitation, ground tem-perature and volume of soil moisture content at different depths in 15 meteorological stations and automatic observing stations in Heihe River basin were used to analyse the character of NDVI variations and their response to the meteorological factors. By using the annual cumulative average method and trend line analysis method, the distribution character of spatial and temporal variations of NDVI in the Heihe River basin between 1999 and 2011 was determined. In general, there was a increasing tendency of annual cumulative average NDVI and mean yearly NDVI in most of the area, while the western down-stream and southern up-stream areas were decreasing. Seasonally cumulative NDVI and seasonally average NDVI were of an increasing tendency. In the decreasing stage, vegetation deterioration in winter was more serious than other seasons. In the increasing

  5. 地表温度-归一化植被指数特征空间干旱监测方法的改进及应用研究%An improvement of the land surface temperature-NDVI space drought monitoring method and its applications

    Institute of Scientific and Technical Information of China (English)

    于敏; 程明虎; 刘辉

    2011-01-01

    地表温度-归一化植被指数(Ts-NDVI)特征空间干旱监测方法易受到监测期地表湿度、植被覆盖状况和卫星观测质量的影响,导致特征空间干、湿边不稳定,在基于长时间、大范围卫星观测资料的基础上对Ts-NDVI特征空间方法进行改进,将其称为通用特征空间方法.首先基于某观测时段,单独构建每年基于该单一年份单一时段卫星观测数据的T-NDVI特征空间,然后在已构建的各单一时段特征空间的干、湿边地表温度中,分别用最大值、最小值合成法提取各植被指数对应的多年最大、最小地表温度,分别构成各年通用的Ts-NDVI特征空间的干、湿边地表温度,最后通过线性拟合,获得通用特征空间的干、湿边方程.选择中分辨率成像光谱仪的归一化植被指数(NDVI)和地表温度(Ts)数据在中国主要粮食产区黑龙江省进行干旱监测试验,对改进前、后特征空间的植被温度状态指数进行对比分析,并用10、20 cm土壤相对湿度和降水量进行检验.结果表明:通用特征空间方法合成的Ts-NDVI特征空间三角形结构特征显著,干、湿边明晰,比改进前更接近特征空间的理论边界,增强了特征空间干、湿边的稳定性,提高了干旱监测结果的精度,当单一时段特征空间稳定性较差时,改进效果最明显.通用特征空间对浅层土壤湿度更加敏感,与监测同期及前期总体降水都密切相关,且对降水的响应更敏感.%The land surface temperature (T,)- Normalized difference vegetation index (NDVI) space based drought monitoring is vulnerable to the soil moisture, vegetation cover and satellite observation state, which makes the dry edge and wet edge of Ts-NDVI space unstable, so it is likely to bring more errors in the drought monitoring. The paper develops a method named the general T.-NDVI space using the multi-year satellite data in the same period to resolve the instability of the T,-NDVI

  6. Evaluation of cropland productivity in the Hebei Plain via graded multi-year MODIS-NDVI data%基于多年MODIS NDVI分级的河北平原农田生产力评价

    Institute of Scientific and Technical Information of China (English)

    王芯; 李红军; 雷玉平

    2011-01-01

    根据中等分辨率航天成像光谱仪(MODIS)遥感数据计算的归一化植被指数(NDVI)被广泛用于作物长势监测和产量预报,但由于NDVI数值在不同年份的同一时期变化较大,直接用于评价农田生产力会有较大误差.本文以河北平原所在的北纬37°~39°之间连续种植的冬小麦农田为研究区域,通过对多年冬小麦MODISNDVI数据进行比较和分级,尝试用每季ND VI在区域内的高低级别评估区域农田生产力.Landsat卫星数据用于对不同时相MODIS图像进行精确配准,从而实现像素尺度上长时间序列数据的统计分析.首先,对区域内2000~2008年间每年作物返青期到成熟期的NDVI平均值及各生育阶段NDVI平均值分别进行高低分级,以了解河北平原农田生产力的空间变异,结果显示其中高水平农田分布在太行山山前平原,指数等级水平并没有完全按南北走向趋势分布,表明该研究方法受纬度差异的影响较小.不同年份分析结果显示,2008年东部地区也出现了较高等级的田块.其次,利用ND VI分级结果计算出9年间ND VI等级的变异系数,对采用不同生育期ND VI可能带来的误差进行了分析,结果显示不同小麦生育期NDVI等级的变异系数不同,返青期和成熟期变异系数较大,且具有一定的地理差异.最后,利用GIS空间分析方法以9年NDVI分级结果为基础制作了以县为单元的麦田生产力等级图,结果显示河北平原农田生产力高低分区,同时也表明中低水平区块有较大提升空间,为河北县级土地管理和耕地质量管理提供理论依据.%Moderate resolution imaging spectroradiometer sensor (MODIS) provides high-temporal, medium-spatial resolution science-quality global land cover data. Calculated normalized differential vegetation index {NDVI) from MODIS data is widely used for crop growth monitoring and yield forecasting. However, variations of NDVI values in the same season of

  7. Effects of short term and long term soil warming on ecosystem phenology of a sub-arctic grassland: an NDVI-based approach

    Science.gov (United States)

    Leblans, Niki; Sigurdsson, Bjarni D.; Janssens, Ivan A.

    2014-05-01

    Phenology has been defined as the study of the timing of recurring biological events and the causes of their timing with regard to abiotic and biotic factors. Ecosystem phenology, including the onset of the growing season and its senescence in autumn, plays an important role in the carbon, water and energy exchange between biosphere and atmosphere at higher latitudes. Factors that influence ecosystem phenology can therefore induce important climate-controlling feedback mechanisms. Global surface temperatures have been predicted to increase in the coming decades. Hence, a better understanding of the effect of temperature on ecosystem phenology is essential. Natural geothermal soil temperature gradients in Iceland offer a unique opportunity to study the soil temperature (Ts) dependence of ecosystem phenology and distinguish short-term (transient) warming effects (in recently established Ts gradients) from long-term (permanent) effects (in centuries-old Ts gradients). This research was performed in the framework of an international research project (ForHot; www.forhot.is). ForHot includes two natural grassland areas with gradients in Ts, dominated by Festuca sp., Agrostis sp.. The first warmed area was created in 2008, when an earthquake in S-Iceland caused geothermal systems to be shifted to previously cold soils. The second area is located about 3 km away from this newly warmed grassland. For this area, there are proofs that the natural soil warming has been continuous for at least 300 year. In the present study we focus on Ts elevation gradients of +0 to +10°C. The experiment consists of five transects with five temperature levels (+0,+1,+3,+5 and +10°C) in the two aforementioned grassland ecosystems (n=25 in each grassland). From April until November 2013, weekly measurements of the normalized difference vegetation index (NDVI) were taken. In the short-term warmed grassland, the greening of the vegetation was 36 days advanced at +10°C Ts and the date of 50

  8. 长白山区植被生长季NDVI时空变化及其对气候因子敏感性%Spatial-temporal Variation of NDVI in the Growing Season and Its Sensitivity to Climatic Factors in Changbai Mountains

    Institute of Scientific and Technical Information of China (English)

    侯光雷; 张洪岩; 郭聃; 郭笑怡

    2012-01-01

    本文利用长白山区SPOT/VGT NDVI数据和气象数据,分析该区不同植被类型NDVI时空变化特征以及与气候因子的相关关系,并探讨了植被对气候变化响应的滞后性。结果表明:①2000-2009年,长白山区植被NDVI逐年变化总体呈增长趋势,增长区域的面积占全区面积的83.91%,在空间上主要集中在北坡和西坡,NDVI减少区域集中在南坡;②NDVI变化率随季节和植被类型变化而不同,NDVI增长主要集中在5月和9月,而7月NDVI变化较小,甚至出现下降趋势;③植被NDVI与温度和降水存在着显著的正相关性(p〈0.01),且NDVI与温度的相关性高于与降水的相关性,且随海拔升高,NDVI与温度相关性增强;④NDVI对气温和降水变化的响应存在滞后期,不同植被类型,滞后期存在差异。苔原NDVI对温度和降水响应的滞后期大约10天,而针阔混交林和针叶林ND-VI对温度和降水响应的滞后期约为20天。%In order to reveal the response of mountain ecosystem to climate change, the spatial-temporal distri- bution of vegetation variation in the Changbai Mountains was investigated by using the 10-day SPOTNGT ND- VI data from 2000 to 2009. Combining the meteorological data, we discussed the relationship between NDVI and climatic factors and time lags of vegetation variation response to climate change. The results are shown as follows. 1) NDVI increased from 2000 to 2009 in Changbai Mountains. The NDVI increased and decreased area covered about 83.91% and 16.09% of the whole study area respectively. The increased area was mainly distribut- ed on the northern and western slopes, while the decreased area was distributed on the southern slope. The growth rate of NDVI centralized 0- 0.006/a. 2) The change rate of NDVI varied by seasons and vegetation types. The peak of NDVI slope appeared in May and September, but no increase, even a little decrease was ob- served in July; 3) There was a significantly positive

  9. 基于MODIS-NDVI时序数据的黄土丘陵区土地覆盖分类研究%Land Cover Classification in Loess Hilly and Gully Region Using Multi-temporal MODIS-NDVI Data

    Institute of Scientific and Technical Information of China (English)

    陆广勇; 杨勤科; 王海江

    2011-01-01

    为了获取年际土地覆盖基础数据以支持区域土壤侵蚀定量评价,探讨了采用基于时间序列谐波分析法(HA-NTS)对延河流域2006年MODIS-NDVI时间序列进行滤波;参考当地年植被变化特征,根据土地覆盖类型的NDVI时序曲线特征,选择定量化的分类特征,进行决策树分类,并以此为基础建立各个决策树类别掩膜;基于MODIS-NDVI和MOD09GA,在各个掩膜区内进行非监督分类,结合坡度图调整分类结果,形成延河流域土地覆盖类型图.结果表明:与2006年TM分类结果的总体一致性为75%,Kappa系数为0.620 9,影像分类结果可靠,分类方法现实可行.%The temporal features of various land objects were studied based on the MOD13Q1, and built the decision tree model for the land cover classification of Yanhe basin by filtering the MODIS-NDVI time-series data of 2006 in the area via the HNATS (Harmonic Analysis of Time Series) algorithm; analyzing the temporal curve features of NDVI, and selecting the rational quantitative classification features for the decision tree model, building masks for each land cover, and performing the unsupervised classifications in the masks based on the data of MODIS-NDVI or MOD09GA, modifying the results via slope data. The results showed the overall accuracy of the final land cover map was 75.00%, and the kappa coefficient was 0. 620 9. It is suggested that applying the temporal features in classification model and integrating decision tree with ISODATA for the land cover classification are feasible and promising.

  10. MODIS NDVI Time-series Data Reconstruction Integrating with the Quality Assessment Science Data Set(QA-SDS)%融合QA-SDS的MODIS NDVI时序数据重构

    Institute of Scientific and Technical Information of China (English)

    樊辉

    2013-01-01

    基于云南省MOD13Q1时序数据,对比分析了不同质量设置(UI5、UI5-CSS、UI3、UI3-CSS)和不同时序重构方法(简单线性插值、Savitzky-Golay滤波、非对称高斯函数拟合法和双逻辑函数拟合法)组合下NDVI时序重构效果.结果表明:NDVI时序中无效像元数和最大间隙长度在时间和地域上的分布差异受气候干、雨季影响显著.非对称高斯函数拟合法和双逻辑函数拟合法的稳健性和拟合效果较优.NDVI时序中无效像元最大间隙长度是衡量数据质量优劣和时序重构可行性的重要指标,雨季降水和多云天气过于集中是影响云南省境内部分地区时序重构质量提升的关键.基于重构NDVI时序,云南省全境NDVI时空分布呈现雨季大于干季、西部大于东部、南部高于北部、河谷大于山地的特征.%Satellite-derived NDVI time series are often contaminated by negative atmospheric conditions and sunsen-sor-surface viewing geometries. The reconstruction of high quality NDVI time-series is crucial to the detection of long-term vegetation cover changes and the remote sensing of vegetation phenology. In this paper,MOD13Q1 time-series data covered in Yunnan province were employed to address the performance effectiveness of time-series data reconstruction methods (e. g. linear interpolation,Savitzky-Golay filtering,asymmetric Gaussian and double logistic function-fitting) through integrating with different quality setting (e. g. UI5,UI5-CSS,UI3,UI3-CSS). The results show that seasonal and regional variations in the number and the maximum gap length of invalid pixels of time-series data were mainly controlled by local climate. A comparison of four selected methods revealed that the superiority of the robustness and fitting capability of asymmetric Gaussian and double logistic function-fitting methods over the other fitting techniques. The maximum gap length of invalid pixels in time-series data is an important data quality

  11. 用EOS/MODIS-NDVI监测枣树生长状况的分析%Study of Jujube Growth Situation to be Monitored with EOS/MODIS-NDVI Data

    Institute of Scientific and Technical Information of China (English)

    张学艺; 戴小笠; 张玉兰; 段晓凤; 官景得; 马力文

    2012-01-01

    This paper proved that remote sensing technology could be used to monitor the growth situation of jujube based on the data collected from two long-jujube planting bases, Ningxia Lingwu Racecourse Lake farm and Lingwu gardening field, as research objects. Based on the analysis of the cloudless sky EOS/MODIS data of the jujube child-bearing period from 2005 to 2009 through the Ningxia border, combined with GPS investigation and the indicators of jujube meteorological disaster occurred, the relationship between the NDVI changes and the meteorological disaster happened during the whole jujube growth period was revealed. It was finding that the NDVI curve during the whole growth stages of the jujube was a double peak type. The influence of the overwintering cold injury was more severe to the early growth stage of jujube, whereas the injury effect vanished over time. Further deep analysis of frost damage and variation coefficient indicated that the injury effect of the overwintering cold was severer to the Lingwu gardening field compared with the Lingwu Racecourse Lake farm. From the impact of florescence hot dry weather in late June, jujube NDVI values in early July to mid-August on the whole year lower than normal. However, the effects disappeared till late of August. In a summary, MODIS-NDVI could be used to monitor meteorological disasters rapidly, and provided the technical supports and guidance in the field of meteorological disaster prevention and selection of cultivation area.%为研究遥感技术监测宁夏枣树生长状况,以宁夏灵武马场湖农场和灵武园艺场两个长枣种植基地为研究对象,结合GPS调查、整理2005—2009年红枣生育期过宁夏境内EOS/MODIS晴空资料,并依据红枣气象灾害发生指标,分析红枣生育期归一化植被指数INDV变化及受灾前后的变化规律.结果表明,枣树全生育期INDv变化曲线为双峰型,越冬冻害对枣树前期生长影响大,并随时间推移

  12. Integration of Multisensor Remote Sensing Data for the Retrieval of Consistent Times Series of High-Resolution NDVI Images for Crop Monitoring in Landscapes Dominated By Small-Scale Farming Agricultural

    Science.gov (United States)

    Sedano, F.; Kempeneers, P.

    2014-12-01

    There is a need for timely and accurate information of food supply and early warnings of production shortfalls. Crop growth models commonly rely on information on vegetation dynamics from low and moderate spatial resolution remote sensing imagery. While the short revisit period of these sensors captures the temporal dynamics of crops, they are not able to monitor small-scale farming areas where environmental factors, crop type and management practices often vary at subpixel level. Although better suited to retrieve fine spatial structure, time series of higher resolution imagery (circa 30 m) are often incomplete due to larger revisit periods and persistent cloud coverage. However, as the Landsat archive expands and more fine resolution Earth observation sensors become available, the possibilities of multisensor integration to monitor crop dynamics with higher level of spatial detail are expanding. We have integrated remote sensing imagery from two moderate resolution sensors (MODIS and PROBA-V) and three medium resolution platforms (Landsat 7- 8; and DMC) to improve the characterization of vegetation dynamics in agricultural landscapes dominated by small-scale farms. We applied a data assimilation method to produce complete temporal sequences of synthetic medium-resolution NDVI images. The method implements a Kalman filter recursive algorithm that incorporates models, observations and their respective uncertainties to generate medium-resolution images at time steps for which only moderate-resolution imagery is available. The results for the study sites show that the time series of synthetic NDVI images captured seasonal vegetation dynamics and maintained the spatial structure of the landscape at higher spatial resolution. A more detailed characterization of spatiotemporal dynamics of vegetation in agricultural systems has the potential to improve the estimates of crop growth models and allow a more precise monitoring and forecasting of crop productivity.

  13. 基于MODIS黄河三角洲湿地NPP与NDVI相关性的时空变化特征%Spatial-temporal variation of NPP and NDVI correlation in wetland of Yellow River Delta based on MODIS data

    Institute of Scientific and Technical Information of China (English)

    蒋蕊竹; 李秀启; 朱永安; 张治国

    2011-01-01

    Study of vegetation productivity and carbon sequestration of wetland ecosystem is a main research topic of global carbon cycle and global change. The ecosystem productivity study of Yellow River Delta, a wetland delta with fastest reclamation speed in China and in the world, is therefore extremely important. Due to human activities have affected all of ecological systems, to find an expeditious way to assess the ecosystem health becomes the major topic of current study. Net primary productivity (NPP) is a key component of terrestrial carbon cycle, and it is defined as the accumulative organic matters by green plants per unit of time and space. NPP, the direct reflection of plant community productivity for a certain natural environment, is the basis of matter and energy cycles of terrestrial ecosystem. The Normalized Difference Vegetation Index has been used for many years to measure and monitor plant growth, vegetation cover, and biomass production from multispectral satellite data. It is an indicator of vegetation growth and its spatial distribution has a close relationship with climate conditions. We use MODIS NPP and NDVI data to analyze the characteristics of spatial-temporal variation of NPP and NDVI in Yellow River Delta between 2001 and 2006. Distribution of NDVI shows that soil water-salt distribution is the main controlling factor of plant growth in the delta. The distribution of primary productivity has been obviously affected by human activities. We further built a new coastal regression model. As the changeable different regions which have different distances from the coastline and which have different lengths, we discuss the correlation between annual NPP (aNPP) andaverage annual NDVI ( ANDVI). Results suggest that distribution of wetland ecosystems in the Yellow River Delta has obvious spatial heterogeneity from sea to land, along with the ecosystem succession. Mud flat along the coastline is a place for developing ecosystem with a large amount of

  14. 利用NDVI估算云覆盖地区的植被表面温度研究%Study on Estimation of Vegetation Surface Temperature in Cloudy Region by NDVI

    Institute of Scientific and Technical Information of China (English)

    刘梅; 覃志豪; 涂丽丽; 张军

    2011-01-01

    Drought monitoring and other practical applications all need to obtain comprehensive spatial distribution of LST,but cloud cover is a major barrier of this process.We attempt to study the method of estimating vegetation surface temperature of cloudy areas in the remote sensing images by the relationship between changes of LST and ground vegetation.Because of the vegetation transpiration,the density of vegetation has a great effect on changes of spatial distribution of LST.This effect not only exists in cloudless areas,but also can be applied to the cloudy areas.Therefore,we first analyzed the relationship between LST and NDVI in cloudless areas which were nearby cloudy areas and established the equation;Then we used the feature that NDVI was stable within a short time to acquire NDVI value of cloudy areas.At last,we estimated the LST of cloudy areas according to the relationship between the NDVI and LST.We applied this method to Landsat ETM+ images of Liaocheng city in Shandong province.The results show that,when the cloudy area is within or equal to 2 000 pixels(about 1.72 km2),the mean absolute error(MAE) of LST in cloudy area which estimated through NDVI is little than 0.7 ℃,the RMS is1.2 ℃.In order to verify its practicality,we also applied the method to TM images of Bengbu in Anhui province,when cloudy area is within 300 pixels,the MAE is less than 0.1 ℃.Hence,it can be argued that when the range of cloudy area is not very large,using NDVI to estimate the LST of cloudy area has certain feasibility.%干旱监测等实际应用都需要全面掌握地表温度(LST)的空间分布,而云覆盖是这种应用的重要阻碍。试图根据地表温度变化与地表植被之间的相互关系,研究遥感影像中云覆盖区域植被表面温度的估算方法。由于植被的蒸腾作用,植被茂密程度对其表面温度的空间分布有较大影响。这种影响不仅在晴朗无云区域存在,同样适用于云覆盖区域。因此,

  15. Evaluation of winter wheat productivity in Huang-Huai-Hai region by multi-year graded MODIS-NDVI%基于多年MODIS-NDVI的黄淮海农区冬小麦生产力评价

    Institute of Scientific and Technical Information of China (English)

    黄珂; 刘忠; 杨丽芳

    2014-01-01

    黄淮海农区是中国重要的粮食生产基地,研究该地区不同等级生产力耕地的空间分布,对提高该地区生产力有重要的意义。该文在提取研究区冬小麦种植空间分布的基础上,对10a时间序列冬小麦MODIS-NDVI进行特征参数提取,并将冬小麦主要生长季多年NDVI特征值均值和年际变异系数,作为多年平均产量水平和稳产水平的指示指标,进行黄淮海农区冬小麦种植区耕地生产力评价,得到黄淮海农区冬小麦生产力空间分布图。结果显示:1)多时相MODIS-NDVI数据可以用于研究区冬小麦种植空间分布提取。经县级尺度验证,有较高的提取精度;2)县级尺度的冬小麦单产水平与其辖区内冬小麦生长关键期多个NDVI特征值有显著的相关关系,可以用来评价冬小麦生产力水平;3)研究区冬小麦种植区耕地以中低生产力水平为主,高生产力水平的耕地只占不到20%。高生产力的麦田大多分布在水热条件较好的黄淮平原亚区,中等生产力麦田大多分布在燕山太行山山麓平原亚区和鲁西黄灌区,而低生产力的麦田多分布在冀、鲁、豫低洼平原亚区。低生产力麦田分布集中连片的区域多为春旱易发、土壤粘淤或低洼积盐的地区。呈现出整体气候条件主导,局部土壤条件影响的高中低生产力空间分布特征。研究结果可以为黄淮海农区的耕地质量管理和中低产田改良提供依据。%Productivity is one basic property of farm land and the spatial pattern can be used as the baseline information in making and implementing appropriate agricultural policies. As an important winter wheat production area of China, food production in the Huang-Huai-Hai region has been receiving considerable attention for a long time. The Normalized Difference Vegetation Index (NDVI) derived from remote sensing techniques is a widely utilized vegetation index in

  16. 基于NDVI加权指数的冬小麦种植面积遥感监测%Remote sensing monitoring winter wheat area based on weighted NDVI index

    Institute of Scientific and Technical Information of China (English)

    王利民; 刘佳; 杨玲波; 杨福刚; 滕飞; 王小龙

    2016-01-01

    该文针对农业信息服务中冬小麦种植面积调查业务的现状与需求,提出了一种基于NDVI(normal difference vegetation index)时间序列的冬小麦NDVI加权指数(WNDVI,weighted NDVI index)影像算法,可在训练样本、验证样本选择的基础上实现冬小麦面积的自动提取,并以河北省安平县及周边地区2013-2014年度冬小麦面积提取为例,采用GF-1/WFV(wide field view)数据进行了算法实现。算法的主要思路是在时序影像基础上,通过冬小麦NDVI加权指数影像的构建,扩大冬小麦地类与其他地类的差异,结合自适应的阈值获取方法,区分冬小麦地类,获取冬小麦作物面积。算法包括冬小麦时间序列影像的获取、基于网格的样本点设置、构建冬小麦 NDVI 加权指数影像、迭代确定冬小麦NDVI加权指数提取阈值、精度验证这5个部分。影像的获取根据冬小麦的生长时间确定,保证每月1景GF-1/WFV无云影像,并进行预处理及NDVI计算;同时将研究区划分为一定数量的网格,每个网格再等分为2×2个子网格,根据目视解译、专家知识、实地调查等方法,确定左上网格中心点及右下网格中心点的地物类型。统计该期所有左上网格点冬小麦及其他地物的NDVI均值,冬小麦NDVI大于其他地物的将该期影像的权值设置为1,否则设置为−1,将所有时相NDVI影像进行加权平均,即可获取冬小麦NDVI加权指数影像。获取冬小麦NDVI加权指数影像后,还需设置合适的阈值提取冬小麦。该文选用右下网格点目视解译分类结果作为阈值提取依据,具体方法是将冬小麦指数从小到大按照一定间隔划分,作为冬小麦 NDVI 加权指数提取阈值,将各阈值二值法运用,与右下网格点的冬小麦提取的目视解译结果对比,精度最高的就是最优冬小麦 NDVI 加权指数分割阈值。在所有

  17. Application and Analysis of MODIS Satellite NDVI Time Series Change in Winter Wheat Area Estimate%MODIS卫星NDVI时间序列变化在冬小麦面积估算中的应用分析

    Institute of Scientific and Technical Information of China (English)

    李红梅; 张树誉; 王钊

    2011-01-01

    The study area of this paper is Guanzhong in Shanxi province,which is a major wheat-growing region.Based on EOS/MODIS satellite data,the survey data of winter wheat and the classification of land cover based on Landsat/TM image,we can get a vegetation index time series curve of different land cover.According to the NDVI variety of winter wheat during its growth and development period,we eliminate the non-wheat area information.Different thresholds will be set though compared the wheat's NDVI which in different critical growth period.The distribution and area of winter wheat will be analyzed and estimated with the help of spatial analysis module of GIS.The result shows that the accuracy rate of area by using this method is high.This approach may be an important tool for estimating area of regional crop over large area,and application potential of MODIS data in agriculture is proved better.%以陕西小麦主产区关中地区为研究地点,EOS/MODIS卫星数据为主要数据源,借助冬小麦地面定位调查数据和土地覆盖类型图作为辅助信息,计算得到不同覆盖类型的植被指数时序曲线图,找出冬小麦发育期植被指数变化规律,剔除小麦生长季节的非麦区信息,用几个关键期的植被指数变化差值图设定不同阈值,利用GIS空间分析功能得到麦区分布图和麦区面积。结果表明,应用遥感估算麦区面积与实际调查统计结果较为一致。从实际应用来看,该方法为大区域作物面积估算提供了一种更为快捷、经济的途径,也进一步说明MODIS数据在农业领域中的应用潜力。

  18. Aplicação de índices das condições de vegetação no monitoramento em tempo quase real da seca em Moçambique usando NOAA_AVHRR- NDVI

    Directory of Open Access Journals (Sweden)

    Paulo Alberto Covele

    2011-12-01

    Full Text Available Normal 0 21 false false false PT-BR X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Este artigo tem por objetivo aplicar diferentes índices das condições de vegetação e avaliar suas diferenças e aptidão no monitoramento da distribuição espacial e temporal da seca em Moçambique com base em imagens NDVI da NOAA- AVHRR. Para tanto, avalia as differenças de aptidão dos índices das condições de vegetação especialmente o Índice das Condições de Vegetação (Vegetation Condition Index- VCI, Índice Padronizado de Vegetação (Standardized Vegetation Index- SVI e o Indicador de Productividade da Vegetação (Vegetation Productivity Indicator- VPI no monitoramento da seca em Moçambique. Estes índices são derivados a partir de imagens da Diferença Normalizada do Índice da Vegetação (Normalized Difference Vegetation Index- NDVI de 1981 a 2005, produzidas a partir dos canais 1 e 2 do sensor Advanced Very Higher Resolution Radiometer (AVHRR a bordo dos satélites da National Oceanic and Atmospheric Administration (NOAA.

  19. 地理信息系统支持下Spot/vegetation NDVI影像的大尺度神经网络分类%SPOT/VEGETATION NDVI IMAGE'S LARGE SCALE NEURAL NETWORKS CLASSIFICATION SUPPORTED BY GIS

    Institute of Scientific and Technical Information of China (English)

    巴雅尔; 敖登高娃; 沈彦俊; 朱林; Ryutaro Tateishi; 王一谋

    2005-01-01

    以内蒙古地区Spot/vegetation归一化植被指数(NDVI)影像为基本信息源,综合应用地理信息系统(GIS)技术进行了大尺度神经网络分类实验研究.建立多年份高分辨影像数据库,通过GIS软件集成与遥感影像目视解译方法,在全区范围选取了"纯净"样本数据,并辅助应用DTM数据和影像化多年气像观测数据,完成土地覆盖类型的BP人工神经网络分类.结果表明,GIS技术支持下,大面积区域尺度上spot/vegetation NDVI影像的BP神经网络分类可达到较高的分类精度.

  20. Spatial-Temporal Dynamics of NDVI and Its Response to Temperature and Precipitation in the Yellow River Delta during the Period 1998-2008%近十年黄河三角洲NDVI时空动态及其对气温和降水的响应特征

    Institute of Scientific and Technical Information of China (English)

    李明杰; 侯西勇; 应兰兰; 路晓; 朱明明

    2011-01-01

    本文基于SPOT-VGT S10产品(1998年4月-2008年12月)以及相应时段东营站点的气温、降水数据,利用一元线性回归方法、Hurst指数方法分析近10年黄河三角洲NDVI时空动态,并探讨NDVI与气温、降水因子的年际、季节、月际响应特征.研究表明:①NDVI变化以良性发展为主,但NDVI长期无变化区及弱持续性中度改善区值得关注,且NDVI弱、中、强持续性退化区面积较广,理应尤为关注,并探讨和寻找原因;②NDVI变化与气温、降水均有较高的相关性,相关系数分别为0.81、0.63,若考虑1个月的时间延迟,则相关系数分别为0.89、0.75;③延迟1个月的NDVI与气温、降水的相关性研究更具科学性和准确性.春季(2月-4月)、夏季(5月-7月)气温对植物生长起决定作用,秋季(8月-10月)气温无明显变化趋势,NDVI值变化受降水强度影响较大;不同月份气温、降水对NDVI的影响主导作用不同,延迟程度不同.%Satellite remote sensing represents a significant breakthrough in the scientific community, providing critical surface and atmospheric information at a variety of spatial and temporal scales. It has been widely used in the Earth sciences and can also be an effective way to monitor the vegetation dynamics and global changes. Vegetation cover and growth are influenced by climatic changes. Normalized Differential Vegetation Index (NDVI) can essentially reveal the status of vegetation and ecology; however, the relationship between NDVI and the major climatic factors remains still unclear, such as temperature and precipitation. There seems to be few published studies concerned with the use of time series NDVI data investigate the mechanisms of changes in vegetation in response to climatic factors. In this paper, we made use of time series NDVI data to examine the response of vegetation to major climatic factors based on geographic information system (GIS) and statistical methods. We described the

  1. Character analysis of mining disturbance and reclamation trajectory in surface coal-mine area by time-series NDVI%基于时序NDVI的露天煤矿区土地损毁与复垦过程特征分析

    Institute of Scientific and Technical Information of China (English)

    李晶; Zipper Carl E.; 李松; Donovan Patricia F.; Wynne Randolph H.; Oliphant Adam J.; 夏清

    2015-01-01

    露天煤矿区是人类活动强扰动地区之一。该文以阿巴拉契亚煤田区韦恩县为研究区域,应用遥感时序分析法分析了像元尺度的土地损毁和复垦过程特征。得出结论:1984-2010年间,韦兹县露天开采扰动区域占采矿权范围的45.80%,其中植被恢复区域占开采范围的66.45%,开采时间越早,植被恢复像元比例越高;开采造成的地表无植被覆盖期时长中位数为6 a,均值为7 a;已充分复垦的区域,NDVI值恢复至采前水平的加权平均时长为12 a。基于像元变化轨迹的研究,除揭示土地损毁-复垦过程特征外,能较好地反映空间异质性,可以为土地复垦管理和相关政策决策提供科学依据。%Open-pit coal mines are among the most drastic anthropogenic land disturbances. Using Wise County in the USA’s Appalachian coal field as the study area, this paper evaluates the mine land disturbance and reclamation process over a 27-year period by conducting time-series analysis of multispectral remote-sensing data at the pixel scale. Twenty TM/ETM images obtained by the Landsat satellites, with 30 m spatial resolution, are treated as a multiple-year chronosequence. Polygonal vector files defining mining permitted areas and 6 high-resolution aerial images are used as auxiliary data;and the normalized difference vegetation index (NDVI) is used as a vegetative cover indicator. The methodology and study process include 3 steps. First, training data are prepared and multispectral image data are preprocessed. Data preprocessing includes band stacking, extracting the study area as image subsets, masking of cloud, cloud shadow and water, and computing NDVI based on each study-area pixel in each image. After the training data are generated, they are used to identify the NDVI thresholds for separating bare-ground from vegetated pixels, and ever-mined pixels from those un-mined. These separations are performed by visually

  2. 基于植被指数阈值法的城市边界动态监测技术研究%Research on the Urban Boundary Dynamic Monitor Technology Based on NDVI

    Institute of Scientific and Technical Information of China (English)

    陈剑锋; 谌进波

    2011-01-01

    As accelerating economic growth,rapid urban sprawl and dramatic change of land use structure became an important issue.In order to control the urban rational scale,it is necessary to monitor the urban sprawl in time.With the development of remote sensing(RS) and geographic information system(GIS),RS and GIS techniques are applied more and more in urban land use change detection.Study area lies in Wuhan City,Hubei Province.On the basis of collecting and summarizing literatures,it is carried out monitoring of land use change by RS and GIS.The RS data we used is Landsat ETM+ acquired at 2002.7.The study focused on the methods of urban sprawl dynamic detection.And it is important to determine the threshold by the histogram of NDVI.It is needed to confirm the area that is not covered by vegetation using the threshold of NDVI,and then extract the urban area boundary.Comparing the areas of image,the boundary of city can be recognized.%社会经济的高速发展带动了城市的空间扩展,引起了城市土地利用结构的变化。为了对城市建设用地和城市发展规模进行合理的调控,应该对城市的扩展进行动态监测。在城区扩展动态监测方面,遥感和地理信息系统已经得到了一定的应用。本研究以湖北省武汉市为例,利用2002年7月9日陆地卫星ETM+数据,在遥感和地理信息系统技术支持下,开展武汉市城区扩展的卫星遥感动态监测技术研究。利用NDVI指数确定区分植被区与非植被区的阈值,得到相应的城区范围。该方法的关键在于根据不同土地利用类型的NDVI直方图确定植被区与非植被区的阈值。研究结果表明,在影像间相同地物光谱特征差异较小,且在植被长势好的情况下,利用NDVI植被指数阈值法可以较好地对城区扩展进行动态监测。

  3. 基于MODIS数据的重庆市植被覆盖度动态变化研究%An Analysis of Dynamic Changes in Vegetation Coverage in Chongqing Municipality Using MODIS/Terra NDVI Data

    Institute of Scientific and Technical Information of China (English)

    肖洋; 熊勤犁; 欧阳志云; 徐卫华; 肖燚; 肖强

    2013-01-01

    通过最佳指数斜率提取法(BISE)重建研究区MODIS-NDVI时间序列数据.以像元二分模型为基础,用IDL计算机语言构建植被覆盖度定量模型,估算了重庆市2006-2010年植被覆盖度,分析其空间分布与季节变化特征.结果表明:研究区植被覆盖度在缓慢增长,整体生态环境呈良性发展趋势.同时,较高的植被覆盖度反演精度(78%),证实通过BISE方法重构NDVI时间序列和运用像元二分模型来反演植被覆盖度的方法是可行的.%In this study,the modified best index slope extraction (BISE) method was successfully applied to reconstruct a high-quality NDVI time series dataset in recent years.A vegetation coverage quantitative estimation model was created by IDL programming language based on the dimidiate pixel model,and then it was used to make a quantitative estimation of the vegetation coverage in Chongqing municipality from 2006 to 2010 and analyze its spatial distribution and seasonal changes.The results indicated that the vegetation coverage in the study region increased slowly but steadily,and thus the overall ecological environment showed a positive development trend.In addition,the accuracy of vegetation fraction retrieval was assessed by the classification data from Landsat5/TM images,and it was shown that the detection of vegetation cover change by retrieving the fraction of the vegetation coverage based on BISE method and dimidiate pixel model is feasible.

  4. HJ-1/CCD地表反照率估算及其与NDVI关系分析%Surface Albedo Estimating Based on HJ-1/CCD and Relationship Analysis Between Albedo and NDVI

    Institute of Scientific and Technical Information of China (English)

    李慧芳; 袁占良; 余涛; 李家国; 米晓飞; 刘其悦; 魏占营

    2012-01-01

    Referring to TM surface albedo inversion algorithm, the surface albedo estimating algorithm for HJ-l/CCD sensor is established. With look-up table build based on 6S radiative transfer model .we completed the atmospheric correction of CCD images, covering Xilinhot in Inner Mongolia Autonomous Region. According to the definition of albedo .the surface albedo of visible band can be obtained by regression analysis. Through comparison and analysis with the ground measured data.it shows that this approach can estimate surface albedo with high-precision and the maximum relative error is 14. 32%. Furthermore.it demonstrated that there is a higher negative correlation between NDVI and albedo by fitting analysis.%参照TM地表反照率反演算法,建立了适用于HJ-1/CCD传感器估算地表反照率的算法.通过应用6S辐射传输模型建立查找表,对覆盖内蒙古自治区锡林浩特市的HJ-1/CCD数据进行大气校正,并根据反照率定义,回归分析得到可见光波段地表反照率;通过与地面实测数据进行对比分析,表明该算法估算得到的地表反照率精度较高,其最大相对误差为14.32%.同时,本文将估算结果与同时期NDVI进行拟合分析,得出地表反照率与NDVI存在较高的负相关关系.

  5. Winter Wheat Area Estimation with MODIS-NDVI Time Series Based on Parcel%地块支持下MODIS-NDVI时间序列冬小麦种植面积测量研究

    Institute of Scientific and Technical Information of China (English)

    李乐; 张锦水; 朱文泉; 胡潭高; 侯东

    2011-01-01

    在大尺度冬小麦种植面积测量中,MODIS(moderate resolution imaging spectrometer)数据对绝大部分地区可实现全覆盖数据保障,具有很好的时间序列特征,在探测植物季相节律进行作物估产与动态监测上得到很好的应用,但因受到空间分辨率的限制,其测量结果的可靠性受到较大质疑.地块数据具有明确的位置特征和明显的边界信息,在一定程度上降低了光谱差异和混合像元的复杂程度,在遥感影像上具有很强的相似光谱特征,较像元识别更有优势.以北京市通州为试验区,充分结合冬小麦生长季特征,首次尝试MODIS-NDVI空间地块化,建立其与中分辨率TM耕地地块识别结果的定量关系,进行地块支持下的MODIS-NDVI时间序列冬小麦种植面积测量.研究结果表明,当样本量达到15%以上时,MODIS和TM提取结果区域精度一致性稳定达到96%以上.该方法证明,地块数据可有效改善MODIS-NDVI时序数据遥感识别中,因空间分辨率低引起的误差.实现有碎云影响和无全覆盖中分辨影像时,利用部分中分辨影像样本结合低分辨率全覆盖影像实现大尺度的冬小麦种植面积测量,同时,为其他品种农作物种植面积测量进行先期的实验研究.%Several attributes of MODIS (moderate resolution imaging spectrometer) data, especially the short temporal intervals and the global coverage, provide an extremely efficient way to map cropland and monitor its seasonal change. However, the reliability of their measurement results is challenged because of the limited spatial resolution. The parcel data has clear geo-location and obvious boundary information of cropland. Also, the spectral differences and the complexity of mixed pixels are weak in parcels. All of these make that area estimation based on parcels presents more advantage than on pixels. In the present study, winter wheat area estimation based on MODIS-NDVI time series has been performed with

  6. Effects of Nitrogen Levels and the Methods on the Canopy NDVI, Nitrogen Content, Chlorophyll and Yield of Maize%施氮水平及方式对玉米冠层NDVI、氮含量、叶绿素和产量的影响

    Institute of Scientific and Technical Information of China (English)

    郭志顶; 李志洪; 李辛; 孙建华; 于磊; 矫丽娜; 徐静; 高凤臣

    2013-01-01

    在不同施氮水平和方式(不追肥和拔节期追肥)的田间试验条件下,采集并测定玉米不同生育期的冠层归一化植被指数(NDVI)、叶片SPAD值、叶绿素含量、叶片全氮含量和产量,研究不同氮素水平下各指标间的相互关系。结果表明,在不同生育期玉米叶片叶绿素含量和冠层NDVI值均随施氮量的增加而增大,追肥能显著提高叶片叶绿素含量和冠层NDVI值,灌浆期玉米叶片叶绿素含量增加幅度最大。冠层NDVI值与叶片氮含量、叶绿素含量的相关系数在各生育期均达到显著或极显著水平,叶片SPAD值与叶绿素含量的关系同冠层NDVI值一致,两者均可以对玉米进行氮素营养的诊断,但NDVI比SPAD更具有快速可靠的优点。追肥较不追肥处理有明显增产效果,平均增产幅度为29.23%,最大增幅为44.13%。%By the different nitrogen levels and fertilization methods(basic fertilizer and fertilizer) in the field of the test conditions, the collection and measurement of the vegetation index of canopy normalization, leaf SPAD value, chlorophyll content, leaf total nitrogen content and yield, and the relationship between them were studied. The results showed that leaf chlorophyll content and canopy NDVI value raise when the content of nitrogen increases at the differ-ent growth stages of maize. Top-dressing fertilizer can significantly improve the chlorophyll content and canopy NDVI value, leaf chlorophyll increase at the milking stage of the maize, the largest amount. Canopy NDVI value, leaf nitrogen content and chlorophyll content of the correlation coefficient in different growth stages were significantly or highly sig-nificantly, the relationships of leaf SPAD was consistent with chlorophyll content, the same of the NDVI, both of which could be to maize nitrogen nutrition diagnosis, but NDVI was more than the advantages of rapid and reliable. Com-pared with no topdressing fertilizer

  7. Application of MODIS/NDVI and MODIS EVI to extracting the information of cultivated land and comparison analysis%MODIS/NDVI和MODIS/EVI在耕地信息提取中的应用及对比分析

    Institute of Scientific and Technical Information of China (English)

    左丽君; 张增祥; 董婷婷; 汪潇

    2008-01-01

    MODIS植被指数数据是区域土地利用信息提取的重要数据源.为了对比MODIS两种主要植被指数(NDIV、EVI)在耕地信息提取中的应用,采用通过时间序列谐波分析法(Harmonic Analysis of Time Series,HANTS),对2006年全年MODIS 16天250m的NDVI和EVI时间谱数据进行了重构,从而进行了河西走廊绿洲中东部样区一系列耕地信息的提取实验,包括耕地、休耕地识别以及耕地复种指数、作物种类提取.在此基础上,对MODIS的NDVI与EVI数据的应用进行了对比分析.结果显示:(1)利用傅立叶谐波变换得到的EVI和NDVI时间谱曲线的谐波余项及谐波振幅对耕地进行识别,从识别精度来看,EVI要优于NDVI,识别精度分别为97.17%和95.99%,Kappa系数分别达到0.7938和0.6518;(2)通过计算时间序列曲线的波峰数能够提取耕地的复种指数,并且在EVI和NDVI曲线波峰阈值分别设为0.20和0.25时,休耕地能较为准确地被识别出来;(3)通过提取作物生长期内曲线的Ⅵ最大增长速率时间点以及峰值时间点等信息,作物种类能被初步识别,并且EVI较NDVI具有更强的识别能力.

  8. 基于MODIS NDVI多年时序数据的农作物种植识别%Crop information identification based on MODIS NDVI time-series data

    Institute of Scientific and Technical Information of China (English)

    许青云; 杨贵军; 龙慧灵; 王崇; 李鑫川; 黄登成

    2014-01-01

    Arable land is the foundation of the national economy. How to make the best of arable land resources has become a focus problem of modern science and technology information. The rapid development of agricultural condition remote sensing monitoring technology provides more scientific ways and information technology for monitoring the arable land in real-time. In order to obtain the information of Shaanxi Province agricultural condition monitoring for managing arable land more efficiently, this thesis aimed to study the crop planting patterns and types of arable land, and took the main crops (wheat, spring maize, summer maize, rice and rape) of arable land in Shaanxi Province as the research object. Firstly, the remote sensing datasets of 250 m MOD09Q1 time series during 2003-2012 were used, and the Savitzky-Golay filtering method of TIMESAT software was used to reconstruct the NDVI time series datasets. Secondly, combined with the agricultural meteorological station datasets, TM 30 m land cover classification data, and the main crops’ information and crop phenological information in Shaanxi Province, we extracted the change trends of typical terrain feature and determined the interannual dynamic thresholds. According to the threshold of a peak and crop growth period and other information, the crop planting patterns and crop types were identified. Thirdly, owing to the mixed pixel that the major factor affected the classification accuracy of the low spatial resolution remote sensing, therefore, the IDL optimization function (CONSTRAINED_MIN) was used to obtain each crop types’ abundance figure by the method of non-negative least squares. Two kinds of precision validation methods of spatial and quantitative were adopted in this paper. The total classification accuracy and Kappa coefficient were 88.18% and 59.64% respectively according to spatial comparative analysis. The classification results were revised by the crop types’ abundance figure, and the overall

  9. Evaluation of mechanical conditions of turbomachineries for spectral signature of vibration and neural networks; Avaliacao da condicao mecanica de turbomaquinas pela assinatura espectral da vibracao e redes neurais

    Energy Technology Data Exchange (ETDEWEB)

    Adejoro, Samuel T.; Lopes, Tiago A.P.; Rebello, Joao M.A. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia]. E-mail: samuel@peno.coppe.ufrj.br

    2003-07-01

    The condition monitoring of machinery generally considers the vibration signature as the main parameter to be measured and is one of the bases of predictive maintenance . The mechanical condition/integrity evaluation can be performed by comparing the measured spectrum to a reference spectrum and is based on the premise that usually exist spectral characteristics that identifies the fault. Nine typical faults are considered and the automation of the capability to interpret the vibration data is a field for the application of artificial neural networks. This article presents a comparative study for three types of neural networks: MLP, fuzzy-MLP and SOM for turbomachinery mechanical faults classification. The mean standards for the faults were obtained from available literature and random changes were introduced in order to establish the training data for the neural networks. (author)

  10. Assinatura metabólica do cancro do pulmão: estudo metabolómico de tecidos e biofluidos humanos

    OpenAIRE

    Rocha, Cláudia Manuela Mesquita da

    2015-01-01

    This thesis reports the application of metabolomics to human tissues and biofluids (blood plasma and urine) to unveil the metabolic signature of primary lung cancer. In Chapter 1, a brief introduction on lung cancer epidemiology and pathogenesis, together with a review of the main metabolic dysregulations known to be associated with cancer, is presented. The metabolomics approach is also described, addressing the analytical and statistical methods employed, as well as the current state of the...

  11. Assinatura da deposição atmosférica de testes nucleares em sedimentos da costa brasileira (240+239Pu e 137Cs

    Directory of Open Access Journals (Sweden)

    Christian J. Sanders

    2012-01-01

    Full Text Available The aim of this review is to take a look at Cold War era nuclear tests signatures found in Brazilian coastal sediments. Both137Cs and 240+239Pu signatures have been documented in mangrove, coastal mudflats and continental shelf sediments, associated with above ground nuclear tests beginning in the 1950's. The dates associated to the anthropogenic radionuclide signatures 137Cs and 240+239Pu along sediment columns are confirmed by 210Pb geochronology in many of the studies highlighted in this review. The results outlined in this review characterize the extent to which nuclear fallout products reach the Brazilian coast in quantities sufficient for detection, allowing the use of these radioisotopes as geochronometers.

  12. 基于NDVI的喀斯特水资源遥感定量监测及分析——以贵州省为例%Quantitative Remote Sensing Monitoring and Analysis of Karst Water Resources Based on NDVI --Taking Guizhou Province as a Case

    Institute of Scientific and Technical Information of China (English)

    贺中华; 陈晓翔; 梁虹; 黄法苏; 赵芳

    2012-01-01

    Karst is a vulnerable eco-environment. Water resources are important part of the fragile eco-envi- ronment. NDVI is the importance index of the Karst Basin water-holding condition and spatial distribution, therefore, to monitor the karst water resources is an important behavior of studying the vulnerable eco-envi- ronment. 20 watersheds were selected as the study areas in Guizhou Province in this paper. According to Landsat TM spectral characteristics of vegetation, LNDVI and pNDVI were extracted by using remote sens- ing techniques. The model of karst drainage basin water resources monitoring was established by using math- ematical analysis. It could be obtained by the analysis that the vegetation coverage was an important indicator of the karst basin water-holding, the karst basin water resources monitoring by using surface feature apparent reflectance of the normalized difference vegetation index was better results and higher accuracy, and the remote sensing monitoring model of karst water resources was established.%喀斯特是一类脆弱的生态环境,水资源是脆弱生态环境的重要组成部分,NDVI是流域赋水状况及空间分布的重要指标,因此,喀斯特水资源监测是研究脆弱生态环境的重要内容。在贵州省内选择20个流域作为研究样区,根据LandsatTM的植被光谱特征,利用遥感技术,提取LNDVI和ρNDVI;利用数学分析方法,建立喀斯特流域水资源监测模型。通过分析得出:①植被覆盖率是喀斯特流域赋水的重要指标;②利用地物表观反射率的归一化植被指数(ρNDVI)对喀斯特流域水资源进行监测,效果更好、精度更高;③建立了喀斯特水资源遥感监测模型。

  13. Características espectrais da soja ao longo do ciclo vegetativo com imagens landsat 5/TM em área agrícola no oeste do Paraná Spectral characteristics of soybean during the vegetative cycle with landsat 5/TM images in the western Paraná, Brazil

    OpenAIRE

    Erivelto Mercante; Lamparelli, Rubens A. C.; Miguel A. Uribe-Opazo; Jansle V. Rocha

    2009-01-01

    O objetivo deste trabalho foi estudar as mudanças no comportamento espectral da cultura da soja, por meio dos perfis espectrais temporais dos índices de vegetação NDVI e GVI, expressos em diferentes valores físicos: fator de reflectância bidirecional (FRB) aparente, de superfície e normalizado derivados de imagens Landsat 5/TM. Foi monitorada área de cultura de soja localizada próxima ao município de Cascavel - PR, utilizando cinco imagens da safra de 2004/2005, sendo realizados nessas imagen...

  14. Intra-Annual Response of NDVI to Changes in Temperature and Precipitation and Its Spatial Characteristics in Northwest China%西北地区NDVI对水热条件年内变化的响应及其空间特征

    Institute of Scientific and Technical Information of China (English)

    张翀; 任志远; 袁鑫

    2011-01-01

    利用西北地区1982年-2006年日均温与降水数据和GIMMS—NDVI数据,以时滞互相关法为基础,通过生态区划和植被类型两个层面分析了水热条件的季向变化同半月NDVI变化之间的相关关系,分析结果表明:①植被覆盖较好且海拔较低的山地区以及河流沿线的NDVI与气温、降水的相关程度相对较高,响应也较快,而盆地以及海拔较高的高原或山地区的相关程度相对较低且响应时间较长,初步判定是水热条件好的区域相关程度高且响应迅速,相反水热条件差的区域相关程度低且响应迟缓。进一步以西北地区生态地理区划分析西北地区水热状况对NDVI变化的影响,得出≥10℃积温和降水量大的地区NDVI与气温、降水的相关程度较大且响应快,相反则相关程度较小且响应慢,并且在半月均温和半月平均降水的共同作用下影响半月NDVI平均值的变化;②气温和降水变化对植被NDVI的影响程度从大到小依次为针叶林、灌丛和草原、草甸和草本沼泽、阔叶林与荒漠植被,即由东、西分别向荒漠植被,相关性逐渐减小。某一类型的植被的生长对气温的要求高,则这类植被与气温的相关程度高且响应快,相反植被的生长对气温的要求低,则这类植被与气温的相关程度则低且响应慢,对于降水也是如此。%Reducing human disturbance to natural systems is of importance in studying the relationships between vegetation and climate. Northwest China, as one of a few extensive regions with increasing human disturbance, provides an ideal region for examining response of natural vegetation cover to water/thermal conditions. Combined with daily mean temperature and precipitation data and 15-day NDVI of GIMMS VGT from 1982 through 2006, the lag cross-correlation method was used to analyze temporal and spatial characteristics of the relationships between water

  15. 利用 GIS地理统计模块预测海南岛植被指数季节性变化趋势%Prediction of the Seasonal Change Trend of NDVI in Hainan Island by GIS Geostatistical Analysis

    Institute of Scientific and Technical Information of China (English)

    刘少军; 黄彦彬; 张京红; 李天富; 陈汇林; 陈德明

    2006-01-01

    虽然采用遥感图像提取的植被指数在空间上能较好的反映作物的状况,但其不能预测植被指数在空间上的变化范围,如果能从整体上了解不同市县在不同季节的平均植被指数值,就可以对该区域整体植被状态进行量化分析,也就可以从大范围内进行植被指数的预测分析.利用地理信息系统(GIS)和地统计学相结合的地理统计分析模块(ArcGIS Geostatistical Analyst),根据MODIS遥感数据提取的每季度不同市县平均NDVI植被指数,采用Kriging插值的方法分析了海南岛归一化植被指数(NDVI)季节性变化趋势,并与实际采样值进行对比分析,结果表明,利用ArcGIS Geostatistical Analyst中的Kriging插值方法能较好地预测植被指数的空间分布范围.

  16. TweeProfiles: deteção de padrões espácio-temporais no Twitter

    OpenAIRE

    Tiago Daniel Sá Cunha

    2013-01-01

    Redes sociais na internet apresentam-se como fontes de informação valiosas, no que diz respeitoaos seus utilizadores e aos seus respectivos interesses. Tal informação tem sido sujeita a váriosestudos, conduzidos por investigadores de Data Mining de todo o Mundo, de forma a descobrircomportamentos e padrões dos utilizadores. Para além disso, tem existido também investimentoem criar plataformas para extracção contínua e visualização de informação.Esta dissertação espera identificar perfis de tw...

  17. ANÁLISES DE MÉTRICAS DE SIMILARIDADES EM SÉRIES TEMPORAIS PARA RECONHECIMENTO DE PADRÕES

    Directory of Open Access Journals (Sweden)

    João Francisco Monteiro Barragan

    2014-08-01

    Full Text Available 10.12957/cadest.2012.15775Este artigo apresenta uma metodologia para reconhecimento de padrões de operação de uma turbina a gás da unidade termelétrica (UTE Rômulo Almeida, integrante do parque da Petrobrás. A distinção de diferentes padrões de operação, mais especificamente, partidas sem falha e com falha devido a desarme (trip por dispersão de temperatura foi possível devido a um vasto banco de dados obtidos a partir de um Sistema de Gerenciamento de Informações de Plantas Industriais, ou Process Information Management System (PIMS, disponível na UTE. Os padrões identificados foram analisados utilizando métricas de similaridade univariáveis (distância euclidiana entre os coeficientes de autocorrelação, visando prever distinções entre as partidas sem e com trip por dispersão de temperatura. A possibilidade de gerar uma ferramenta que possa apontar para uma possível falha no equipamento com antecedência é um resultado potencial para a implementação de um sistema de controle inteligente.

  18. Decadal Variations in NDVI and Food Production in India

    Data.gov (United States)

    National Aeronautics and Space Administration — In this study we use long-term satellite, climate, and crop observations to document the spatial distribution of the recent stagnation in food grain production...

  19. Decadal Variations in NDVI and Food Production in India

    OpenAIRE

    Nemani, Ramakrishna R.; Srivastava, Ashok N.; Prasad S. Thenkabail; Sangram Ganguly; K. Krishna Kumar; Hirofumi Hashimoto; Arindam Samanta; Cristina Milesi; Ranga B. Myneni

    2010-01-01

    In this study we use long-term satellite, climate, and crop observations to document the spatial distribution of the recent stagnation in food grain production affecting the water-limited tropics (WLT), a region where 1.5 billion people live and depend on local agriculture that is constrained by chronic water shortages. Overall, our analysis shows that the recent stagnation in food production is corroborated by satellite data. The growth rate in annually integrated vegetation greenness, a mea...

  20. Decadal Variations in NDVI and Food Production in India

    Directory of Open Access Journals (Sweden)

    Ramakrishna R. Nemani

    2010-03-01

    Full Text Available In this study we use long-term satellite, climate, and crop observations to document the spatial distribution of the recent stagnation in food grain production affecting the water-limited tropics (WLT, a region where 1.5 billion people live and depend on local agriculture that is constrained by chronic water shortages. Overall, our analysis shows that the recent stagnation in food production is corroborated by satellite data. The growth rate in annually integrated vegetation greenness, a measure of crop growth, has declined significantly (p < 0.10 in 23% of the WLT cropland area during the last decade, while statistically significant increases in the growth rates account for less than 2%. In most countries, the decade-long declines appear to be primarily due to unsustainable crop management practices rather than climate alone. One quarter of the statistically significant declines are observed in India, which with the world’s largest population of food-insecure people and largest WLT croplands, is a leading example of the observed declines. Here we show geographically matching patterns of enhanced crop production and irrigation expansion with groundwater that have leveled off in the past decade. We estimate that, in the absence of irrigation, the enhancement in dry-season food grain production in India, during 1982–2002, would have required an increase in annual rainfall of at least 30% over almost half of the cropland area. This suggests that the past expansion of use of irrigation has not been sustainable. We expect that improved surface and groundwater management practices will be required to reverse the recent food grain production declines.

  1. Geochemical signature of columbite-tantalite and radiometric survey of radioactive pegmatites in the region of Parelhas, Rio Grande do Norte, Brazil; Assinatura geoquimica de columbita-tantalita e levantamento radiometrico de pegmatitos radioativos da regiao de Parelhas, RN, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Moura, Jorge Costa de

    2013-07-01

    This thesis is the result of geochemical, structural and radiometric investigations on radioactive pegmatites of the Borborema Pegmatitic Province in Northeast Brazil. The studied area, located in the surroundings of the city of Parelhas in the region of the Serra da Borborema, is well known for its thousands of pegmatitic bodies exploited in primitive mines called 'garimpos'. The main goal was to find an efficient, cheap and routine inspection procedure to identify the origin of commercialized radioactive columbite-tantalite (coltan) ore. The Brazilian Nuclear Energy Agency (CNEN) controls uranium commerce and nuclear activity in Brazil. Without an effective method to characterize coltan ores from different localities it is impossible to control the trade. The here presented new method was developed by correlating structural features of these pegmatites with the geochemical behavior of their coltan samples. It was found that the variation of the ratio U/Th versus Nb{sub 2}O{sub 5}/Ta{sub 2}O{sub 5} provides geochemical signatures (analytical fingerprints) for the source location of such ore. A test of the new method with coltan samples of commercial batches from the Brazilian states Amapa and Rondonia also generated distinct geochemical signatures. A radiometric survey (CPS) was carried out in several mines and pegmatites to study the environmental impact of gamma radiation. It included in situ measurements of pegmatite walls, host rocks, soil, and accumulated water and revealed that gamma emitters are hardly solubilized and environmental gamma radiation therefore generally is not enhanced to a dangerous level. (author)

  2. Chemical signature study of tupiguarani ceramic tradition from Central region of the Rio Grande do Sul state, Brazil; Estudo de assinaturas quimicas em ceramica da tradicao tupiguarani da regiao central do estado do Rio Grande do Sul, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Bona, Irene Akemy Tomiyoshi

    2006-07-01

    In this work a model based on experimental results using chemical composition data of the pottery sherds applied to Spearmann's no parametric test, principal component analysis and discriminant analysis, was applied. The samples are soils and Tupiguarani Tradition pottery sherd from the central area of the Rio Grande do Sul State. The chemical elements , Al, Ba, Ca, Cr, Fe, K Mn, Pb, Rb, S, Si, Sr, Ti, V and Zn were determined by energy dispersive X-ray fluorescence (EDXFR) while Ce, Cu, Gd, La, Nd, Pr, Sm, Th and Y by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) techniques. Relationships among the pottery characteristics, studied sites and sherd dispersion in the several sites were proposed. Indications of chemical signature of the small pottery with function to go or not to the fire were observed. The largest dispersion is of small pottery with surface treatment no corrugated. The potteries chemical fingerprints from Ijui River, Ibicui-Vacacai Mirim River and Jacui River were verified. (author)

  3. 杭州湾湾口水体含沙量的时空分布%Spaciai-temporai distribution of suspended sediment concentration in Hangzhou Bay

    Institute of Scientific and Technical Information of China (English)

    吴明阳; 许家帅; 冯玉林

    2011-01-01

    利用卫星遥感资料,结合现场实测数据,研究杭州湾湾口水体含沙量的时空分布,综合分析得出:杭州湾水体含沙量具有冬大夏小、高浓度悬沙广泛分布的特性,岛屿效应引起的局部高含沙是杭州湾岛屿群的共性.%Based on the information from the satelite remote sensing image and the measured SSC data from the field stations, this paper studies the spacial-temporal distribution of the sediment concentration in the Hangzhou Bay. The SSC of the Hangzhou Bay is high in winter and low in summer and the high SSC distributes extensively in the bay. It is common in the Hangzhou Bay that the locally high sediment concentration is caused by the archipelago effect.

  4. A transição nutricional no Brasil: tendências regionais e temporais Nutritional transition in Brazil: geographic and temporal trends

    Directory of Open Access Journals (Sweden)

    Malaquias Batista Filho

    2003-01-01

    Full Text Available Tendo como principal fonte de informações três estudos transversais realizados nas décadas de 70, 80 e 90, faz-se uma análise da transição nutricional do Brasil, referenciada no rápido declínio da prevalência de desnutrição em crianças e elevação, num ritmo mais acelerado, da prevalência de sobrepeso/obesidade em adultos. A correção dos déficits de estatura foi de 72% em crianças urbanas e de 54,4% no meio rural, enquanto a ocorrência de obesidade duplicou ou triplicou em homens e mulheres adultos nos extremos da série temporal analisada. Com exceção do Nordeste rural, a prevalência de desnutrição em mulheres adultas declinou para taxas aceitáveis (em torno de 5% a partir de 1989. Inversamente, as anemias continuam com prevalências elevadas e indicações de tendências epidêmicas. Descreve-se a evolução do estado nutricional da população brasileira segundo macrorregiões e distribuição social, analisando-se os prováveis fatores das mudanças ocorridas.Based on three cross-sectional studies conducted in the 1970s, 80s, and 90s, an analysis of the nutritional transition in Brazil was performed. This analysis found a rapid decrease in the prevalence of childhood malnutrition and an even more rapid increase in adult overweight/obesity. Correction of the height deficit was 72% in urban children and 54.4% in rural children. Obesity rates doubled or tripled in adult men and women at the extremes of the time series analyzed. Excluding the rural Northeast, malnutrition prevalence in adult women dropped to acceptable rates (about 5% starting in 1989. Inversely, anemia continued to display a high prevalence, and there is indication of an epidemic trend. The evolution of nutritional status in the Brazilian population according to macro-regions and social distribution is reported. The likely factors for the observed changes are analyzed.

  5. Convergência do PIB per capita agropecuário estadual: uma análise de séries temporais

    Directory of Open Access Journals (Sweden)

    Christiano Modesto Penna

    2012-12-01

    Full Text Available Esse artigo examina a existência de tendências comuns do PIB per capita agropecuário e a formação de clubes de convergência entre os estados do Brasil admitindo-se a possibilidade de heterogeneidade no processo de desenvolvimento tecnológico. A metodologia aqui empregada sugere a formação de dois grupos de convergência: o primeiro formado pelos estados do Acre, Espírito Santo, Goiás, Mato Grosso do Sul, Mato Grosso, Minas Gerais, Paraná, Rondônia, Roraima, Rio Grande do Sul, Santa Catarina, São Paulo e Tocantins; e o segundo formado por Alagoas, Amazonas, Amapá, Bahia, Ceará, Maranhão, Pará, Paraíba, Pernambuco, Piauí, Rio de Janeiro, Rio Grande do Norte e Sergipe.

  6. Convergência do PIB per capita agropecuário estadual: uma análise de séries temporais

    Directory of Open Access Journals (Sweden)

    Christiano Modesto Penna

    2012-12-01

    Full Text Available Esse artigo examina a existência de tendências comuns do PIB per capita agropecuário e a formação de clubes de convergência entre os estados do Brasil admitindo-se a possibilidade de heterogeneidade no processo de desenvolvimento tecnológico. A metodologia aqui empregada sugere a formação de dois grupos de convergência: o primeiro formado pelos estados do Acre, Espírito Santo, Goiás, Mato Grosso do Sul, Mato Grosso, Minas Gerais, Paraná, Rondônia, Roraima, Rio Grande do Sul, Santa Catarina, São Paulo e Tocantins; e o segundo formado por Alagoas, Amazonas, Amapá, Bahia, Ceará, Maranhão, Pará, Paraíba, Pernambuco, Piauí, Rio de Janeiro, Rio Grande do Norte e Sergipe.This article examines the existence of common trends of the participation of the agricultural sector in GDP per capita and the formation of convergence clubs among Brazilian states assuming the possibility of heterogeneity in their processes of development. The methodology employed here suggest the formation of two groups of convergence: the first formed by the states of Acre, Espírito Santo, Goiás, Mato Grosso do Sul, Mato Grosso, Minas Gerais, Paraná, Rondônia, Roraima, Rio Grande do Sul, Santa Catarina, São Paulo e Tocantins; and the second consisting of Alagoas, Amazonas, Amapá, Bahia, Ceará, Maranhão, Pará, Paraíba, Pernambuco, Piauí, Rio de Janeiro, Rio Grande do Norte e Sergipe.

  7. Failure time series prediction in industrial maintenance using neural networks; Previsao de series temporais de falhas em manutencao industrial usando redes neurais

    Energy Technology Data Exchange (ETDEWEB)

    Torres Junior, Rubiao G.; Machado, Maria Augusta S. [Instituto Brasileiro de Mercado de Capitais (IBMEC), Rio de Janeiro, RJ (Brazil); Souza, Reinaldo C. [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil)

    2005-07-01

    The objective of this work is the application of two failure prediction models in industrial maintenance with the use of Artificial Neural Networks (ANN). A characteristic of the modern industrial environment is a strong competition which leads companies to search for costs minimization methods. Thus, dada gathering and maintenance dada treatment becomes extremely important in this scenario for it aims the equipment and plant systems real repair necessity. Therefore, the objective becomes the widening of the system's full activity in a continuous manner, in the required period, without problems in their integrating parts. A daily time series is modeled based on maintenance interventions pauses dada from a five years period derived form many productive systems in the finalization areas of PETROFLEX Ind. and Com. S.A. Thus, the purpose is to introduce models based on neural networks and verify its system's pauses prediction capacity, so as to intervene with adequate timing before the system fails, extend the operational period and consequently increase its availability. The results obtained in this work demonstrate the employment of Neural Networks in the prediction of pauses in PETROFLEX industrial area maintenance. The ANN's prediction capacity in a group of dada with strong non-linear component where other statistical techniques have shown little efficient has also been confirmed. Discover neural models to predict failure systems time series has enable a breakthrough in the research field, especially due to the market demand. It's no doubt a technique that will evolve in the industrial maintenance area financing important managing decision. Prediction techniques, such as the ones illustrated in this study, work side by side maintenance planning and if carefully implemented and followed up can in the medium run supply a substantial increase in the available operational hours. (author)

  8. Research on TemporaI and Spatial Patterns and Dynamic Laws of Soil Water at Eco-tope between Oasis and Desert

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on long term and stationary research, the temporal and spatial patterns and dynamic laws of soil water content in Minqin desert area were studied. Some results are as follows:(1)The change of soil water content in different years is not obviously in shrub sand dune of Nitraria sibirica and Tamarix ramosissima, but it was great in shifting sand dune, the maximum is 2.538%; (2)The season dynamics can be divided into three stages: accumulating, consuming and stable; (3) The vertical change of soil wa...

  9. Identificação e análise de movimento humano com ultrassons

    OpenAIRE

    Verdasca, Nuno Miguel da Conceição Fernandes

    2013-01-01

    Faz-se nesta dissertação a análise do movimento humano utilizando sinais de ultrassons refletidos pelos diversos membros do corpo humano, designados por assinaturas de ultrassons. Estas assinaturas são confrontadas com os sinais gerados pelo contato dos membros inferiores do ser humano com o chão, recolhidos de forma passiva. O método seguido teve por base o estudo das assinaturas de Doppler e micro-Doppler. Estas assinaturas são obtidas através do processamento dos ecos de ultrassons reco...

  10. Parâmetros biofísicos na detecção de mudanças na cobertura e uso do solo em bacias hidrográficas Biophysical parameters in the detection of changes in soil cover and use in watersheds

    Directory of Open Access Journals (Sweden)

    Helio L. Lopes

    2010-11-01

    Full Text Available O estudo de parâmetros biofísicos como o Índice de Vegetação da Diferença Normalizada (NDVI, albedo e temperatura da superfície (LST, aplicado a ecossistemas, tem sido relevante para o entendimento de mudanças relacionadas à degradação do meio ambiente. Algumas alterações que provocam desequilíbrio de interações ecológicas em ecossistemas, como o desmatamento, a mineração, a agricultura inadequada e o superpastejo, entre outros, estão interrelacionadas. Para avaliação de mudanças temporais relacionadas à degradação do ecossistema caatinga obtiveram-se as imagens da diferença de três parâmetros: NDVI, albedo e temperatura da superfície, para os anos de 1985 e 2001 (estação seca, utilizando-se imagens TM. Este estudo foi aplicado à bacia do rio Brígida onde há uma exploração intensa dos recursos naturais, em que os resultados mostram aumento na temperatura da superfície, diminuição do NDVI e pouca variação no albedo da superfície evidenciando, assim, que entre os anos de 1985 e 2001 houve avanço na degradação dos recursos naturais, nesta bacia.The study of biophysical parameters such as NDVI, albedo and surface temperature has been reported as important for the understanding of land degradation changes of ecosystems. Degradation in ecosystems is related to the inadequate use of the environmental resources including deforestation, mining, inadequate agriculture, overgrazing, among others, that cause imbalance of ecological interactions. For multitemporal evaluation of changes related to the degradation of the 'caatinga' ecosystem three parameters were used with TM images: NDVI, albedo and surface temperature, in two different dates, 1985 and 2001 (dry season. This study was applied in the Brígida river basin where there is a great intensification in the exploration of the natural resources. The results show an increase in the surface temperature, decrease of NDVI and little variation in the surface

  11. Modeling of a photosynthetic crop production index for early warning using NDVI and meteorological data

    Science.gov (United States)

    Kaneko, Daijiro; Ohnishi, Masao; Ishiyama, Takashi; Tateishi, Ryutaro

    2004-10-01

    This paper aims to develop a remote sensing method of monitoring grain production in the early stages of crop growth. It is important to oversee the quantity of grain in production at an early stage in order to raise the alarm well in advance if a poor harvest is looming, especially in view of the rapid population increase in Asia and the long-term squeeze on water resources. Grain production monitoring would allow orderly crisis management to maintain food security in Japan, which is far from producing enough grain for its own population. We propose a photosynthesis-based crop production index CPI that takes into account all of: solar radiation, effective air temperature, vegetation biomass, the effect of temperature on photosynthesis by leaves of grain plants, low-temperature sterility, and high-temperature injury. These later factors, which extend the model of Rasmussen, are significant around the heading period of crops. The proposed photosynthesis-based crop production index CPI has accurately predicted the rice yield expressed by the Japanese Crop Situation Index in three years, including the worst yield in recent years, at a test site in Japan.

  12. Detecting Different Types of Directional Land Cover Changes Using MODIS NDVI Time Series Dataset

    OpenAIRE

    Lili Xu; Baolin Li; Yecheng Yuan; Xizhang Gao; Tao Zhang; Qingling Sun

    2016-01-01

    This study proposed a multi-target hierarchical detection (MTHD) method to simultaneously and automatically detect multiple directional land cover changes. MTHD used a hierarchical strategy to detect both abrupt and trend land cover changes successively. First, Grubbs’ test eliminated short-lived changes by considering them outliers. Then, the Brown-Forsythe test and the combination of Tomé’s method and the Chow test were applied to determine abrupt changes. Finally, Sen’s slope estimation co...

  13. Predicting soil erosion using Rusle and NDVI time series from TM Landsat 5

    Directory of Open Access Journals (Sweden)

    Daniel Fonseca de Carvalho

    2014-03-01

    Full Text Available The objective of this work was to evaluate the seasonal variation of soil cover and rainfall erosivity, and their influences on the revised universal soil loss equation (Rusle, in order to estimate watershed soil losses in a temporal scale. Twenty-two TM Landsat 5 images from 1986 to 2009 were used to estimate soil use and management factor (C factor. A corresponding rainfall erosivity factor (R factor was considered for each image, and the other factors were obtained using the standard Rusle method. Estimated soil losses were grouped into classes and ranged from 0.13 Mg ha-1 on May 24, 2009 (dry season to 62.0 Mg ha-1 on March 11, 2007 (rainy season. In these dates, maximum losses in the watershed were 2.2 and 781.5 Mg ha-1 , respectively. Mean annual soil loss in the watershed was 109.5 Mg ha-1 , but the central area, with a loss of nearly 300.0 Mg ha-1 , was characterized as a site of high water-erosion risk. The use of C factor obtained from remote sensing data, associated to corresponding R factor, was fundamental to evaluate the soil erosion estimated by the Rusle in different seasons, unlike of other studies which keep these factors constant throughout time.

  14. Mapping farmland abandonment and recultivation across Europe using MODIS NDVI time series

    DEFF Research Database (Denmark)

    Estel, Stephan; Kuemmerle, Tobias; Alcántara, Camilo;

    2015-01-01

    abandoned from 2001 to 2012, mainly in Eastern Europe, Southern Scandinavia, and Europe's mountain regions. Yet, recultivation is widespread too (up to 11.2. Mha) and occurred predominantly in Eastern Europe (e.g., European Russia, Poland, Belarus, Ukraine, and Lithuania) and in the Balkans. We also tested...

  15. Mapping land cover gradients through analysis of hyper-temporal NDVI imagery

    NARCIS (Netherlands)

    Ali, A.; Bie, de C.A.J.M.; Skidmore, A.K.; Scarrott, R.G.; Hamad, A.; Venus, V.; Lymberakis, P.

    2013-01-01

    The green cover of the earth exhibits various spatial gradients that represent gradual changes in space of vegetation density and/or in species composition. To date, land cover mapping methods differentiate at best, mapping units with different cover densities and/or species compositions, but typica

  16. Comparison of three NDVI time-series fitting methods in crop phenology detection in Northeast China

    Science.gov (United States)

    Wang, Meng; Tao, Fulu

    2014-03-01

    Phenological changes of cropland are the pivotal basis for farm management, agricultural production, and climate change research. Over the past decades, a range of methods have been used to extract phenological events based on satellite derived continuous vegetation index time series, however, large uncertainties still exist. In this study, three smoothing methods were compared to reduce the potential uncertainty and to quantify crop green-up dates over Northeast China. The results indicated that the crop spring onset dates estimated by three methods show variance in the dates, but with similar spatial pattern. In 60% of the study area, the standard deviation (SD) of the estimated starting date from different method is less than 10 days, while 39.5% of total pixels have SDs between 10days and 30 days. Through comparative analysis against the observation phenological data, we concluded that Asymmetric Gaussians produced the most approximative results of all, followed by Double Logistic algorithm, and Savizky-Glolay algorithm performed worst. The starting dates of crops occur mostly between May and June in this region. The Savitzky-Golay has the earliest estimates, while the Asymmetric Gaussians and Double logistic fitting method show similar and later estimates, which are more consistent with the observed data.

  17. Analysis of multi-temporal SPOT NDVI images for small-scale land-use mapping

    NARCIS (Netherlands)

    Bie, de C.A.J.M.; Khan, M.R.; Smakhtin, V.U.; Venus, V.; Weir, M.J.C.; Smaling, E.M.A.

    2011-01-01

    Land-use information is required for a number of purposes such as to address food security issues, to ensure the sustainable use of natural resources and to support decisions regarding food trade and crop insurance. Suitable land-use maps often either do not exist or are not readily available. This

  18. Evaluation of MODIS NDVI and NDWI for vegetation drought monitoring using Oklahoma Mesonet soil moisture data

    Science.gov (United States)

    Gu, Y.; Hunt, E.; Wardlow, B.; Basara, J.B.; Brown, J.F.; Verdin, J.P.

    2008-01-01

    The evaluation of the relationship between satellite-derived vegetation indices (normalized difference vegetation index and normalized difference water index) and soil moisture improves our understanding of how these indices respond to soil moisture fluctuations. Soil moisture deficits are ultimately tied to drought stress on plants. The diverse terrain and climate of Oklahoma, the extensive soil moisture network of the Oklahoma Mesonet, and satellite-derived indices from the Moderate Resolution Imaging Spectroradiometer (MODIS) provided an opportunity to study correlations between soil moisture and vegetation indices over the 2002-2006 growing seasons. Results showed that the correlation between both indices and the fractional water index (FWI) was highly dependent on land cover heterogeneity and soil type. Sites surrounded by relatively homogeneous vegetation cover with silt loam soils had the highest correlation between the FWI and both vegetation-related indices (r???0.73), while sites with heterogeneous vegetation cover and loam soils had the lowest correlation (r???0.22). Copyright 2008 by the American Geophysical Union.

  19. A colour composite of NOAA-AVHRR-NDVI based on time series analysis (1981-1992)

    NARCIS (Netherlands)

    Verhoef, W.; Menenti, M.; Azzali, S.

    1996-01-01

    This paper describes an image obtained by applying a Fast Fourier Transform algorithm to a long time-series of satellite images: ten years of monthly images of the Normalized Difference Vegetation Index, a measure of the amount of green vegetation cover, for the entire South and Central America. The

  20. Animal habitat quality and ecosystem functioning: Exploring seasonal patterns using NDVI

    OpenAIRE

    Wiegand, Thorsten; Naves, Javier; M.F. Garbulsky; Fernández, Néstor

    2008-01-01

    Many animal species have developed specific evolutionary adaptations to survive prolonged periods of low energy availability that characterize seasonal environments. The seasonal course of primary production, a major aspect of ecosystem functioning, should therefore be an important factor determining the habitat quality of such species. We tested this hypothesis by analyzing the relationship between habitat quality and ecosystem functioning for brown bears (Ursus arctos), a species showing hy...

  1. A evolução na mortalidade da população idosa portuguesa, por sexos e por causas de morte: identificação de aglomerados espácio-temporais por NUTSIII

    OpenAIRE

    Lagarto, Sandra; Nunes, Carla; Gomes, Dulce; Mendes, Maria Filomena

    2013-01-01

    Existem indícios de que a população portuguesa está a envelhecer de forma desigual. Considerando este facto, pretende-se identificar padrões de mortalidade e variações regionais entre a população idosa portuguesa (65 ou mais anos). Para tal, irá estudar-se a distribuição espácio-temporal das taxas de mortalidade, por causa de morte e por NUTIII, no território continental português. A caracterização dessa distribuição é essencial para perceber as dinâmicas e tendências evolutivas, no que se re...

  2. Redes Bayesianas: um método para avaliação de interdependência e contágio em séries temporais multivariadas

    Directory of Open Access Journals (Sweden)

    João Vinícius de França Carvalho

    2013-06-01

    Full Text Available O objetivo deste trabalho consiste em identificar a existência de contágio financeiro utilizando a inovadora metodologia de Redes Bayesianas, executando-se uma análise sequencial. A análise da interdependência de mercados internacionais é realizada em períodos de crises financeiras, ocorridas entre os anos 1996 e 2009, envolvendo países nos quais foi possível avaliar seus efeitos e objetos de estudos similares na literatura. Os resultados apontaram para diversas evidências de contágio em períodos de crise, com causadores bem definidos. Por fim, verificou-se que, após as diversas crises, os mercados estavam muito mais interligados do que no período inicialmente adotado.

  3. Concentrações de ozono superficial em Portugal: avaliação dos padrões temporais e dos contrastes espaciais em estações de fundo

    OpenAIRE

    Afonso, Paulo Alexandre Félix

    2014-01-01

    O ozono troposférico é um dos poluentes atmosféricos que mais preocupação tem causado ao homem quer pelos efeitos nocivos diretos na saúde das populações, quer pelos prejuízos económicos decorrentes da destruição de culturas agrícolas e florestais, de estruturas construídas e de diversos materiais. As variações das concentrações do ozono da camada superficial da atmosfera são complexas e relativamente rápidas devido a múltiplos fatores tais como as emissões de precursores, a fotoquímica, o tr...

  4. Sr and Nd isotopic signature of the high-K calc-alkaline magmatism of the central Ribeira belt: the Sao Pedro Granite in Lumiar, RJ; Assinatura isotopica de Sr e Nd do magmatismo calcio-alcalino de alto-K na Faixa Ribeira central: o exemplo do Granito Sao Pedro em Lumiar, RJ

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, Julio Cezar; Medeiros, Silvia Regina de; Chaves, Eduardo Amorim, E-mail: julio@geologia.ufrj.br, E-mail: silvia@geologia.ufrj.br, E-mail: edupc2@yahoo.com.br [Departamento de Geologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro (RJ) (Brazil)

    2011-09-15

    In the central-northern Ribeira belt there are many granitic to granodioritic bodies showing varied shape and size, characterizing a late- to post-collisional Ca-alkaline, cordilleran I-type province. The Sao Pedro Granite occurs in the mountain region of Rio de Janeiro State as small post-collisional bodies. It presents isotropic fabric, equigranular to seriate inequigranular texture, as well as local concentration of allanite, which gives discrete composition and texture variation to the rock. The granite has a high-K calcalkaline to alkali-calcic character and weakly peraluminous nature. Despite its short geochemical variation, high Ba, Zr and Th contents besides low concentrations of MgO and CaO are noticeable. High REE contents are associated with fractionated REE patterns showing strong negative Eu anomalies. A crustal origin for the granite can be assumed by its very negative and positive .Nd and .Sr values, respectively, as well as by 87Sr/86Sr initial ratios ranging from 0,718 to 0,740. TDM ages point to paleoproterozoic source, which agrees with geological time of intensive crust generation. (author)

  5. Influência geológica em assinaturas químicas das águas e solos do Parque Estadual do Itacolomi, Minas Gerais Influence of the geology in the chemical signature of water and soils from the Itacolomi State Park, Minas Gerais

    Directory of Open Access Journals (Sweden)

    Larice Nogueira de Andrade

    2009-06-01

    Full Text Available Esse trabalho apresenta uma avaliação geoquímica das águas superficiais do Parque Estadual do Itacolomi, relacionando-a com os cenários geológicos e com a geoquímica dos solos. Foram coletadas 36 amostras de solo de diferentes profundidades em pontos localizados em áreas representativas das diversas unidades litológicas. Também foram selecionados 18 pontos de amostragem de água em trechos com diferentes padrões de drenagem. os elementos maiores e traços foram determinados por ICP-OES. nas amostras de água, foram, também, determinados os parâmetros físico-químicos. Os resultados demonstram que a geologia exerce grande influência nas características químicas do solo e das águas superficiais da região. A comparação com valores-padrões definidos pelas normas CETESB 195/05 e CONAMA 357/05 indica concentrações anômalas de diversos elementos, possibilitando a comprovação da influência geológica e pedológica na qualidade das águas, já que a área de estudo é uma unidade de conservação livre de interferências antrópicas. Além disso, também foi possível observar a inadequação dessas normas em relação aos parâmetros de qualidade, que não consideram os fatores geológicos.This paper presents an analysis of the geochemistry of superficial waters in the Itacolomi State Park and their relationship to the geological scenario and soil geochemistry. Thirty six soil samples were collected at points located in representative areas from the different lithologies. In each region, the soil samples were collected at diverse depths. In addition, eighteen water sampling points were also selected in areas with different drainage patterns. In the ground and water samples, the concentrations of major and trace elements were determined by ICP-OES. Also, physical-chemical parameters were determined for the water samples. The results reveal that geology plays an essential role in the chemical signature of the soils and superficial waters. Comparison with standard values defined by the rules CETESB 195/05 and CONAMA 357/05 proved the influence of pedological and geological characteristics on the water quality. Anomalous concentrations of several elements were found in the water and ground samples. In addition, it was also possible to observe that the regulations for water quality of this area are inadequate since they do not take the geological factors into consideration.

  6. Spectral gamma-ray signature of fluvial deposits: a case study from the Late Permian Rio do Rasto Formation, Parana Basin, Brazil; Assinatura gamaespectrometrica de depositos fluviais: estudo de caso na Formacao do Rio do Rasto, Permiano Superior da Bacia do Parana

    Energy Technology Data Exchange (ETDEWEB)

    Sowek, Guilherme Arruda, E-mail: arruda@ufpr.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Programa de Pos-graduacao em Geologia; Ferreira, Francisco Jose Fonseca; Vesely, Fernando Farias, E-mail: francisco.ferreira@ufpr.br, E-mail: vesely@ufpr.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Geologia. Setor de Ciencias da Terra; Berton, Fabio, E-mail: fabioberton1@yahoo.com.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil)

    2013-09-15

    Fluvial channel-fill deposits form highly heterogeneous hydrocarbon reservoirs. The study of outcrop analogs can help in the characterization of these heterogeneities, which are usually not detected by subsurface geophysical methods. The aim of this research is to compare outcrop log signatures with grain size trends and depositional elements of the fluvial deposits of the Late Permian Rio do Rasto Formation. A series of vertical gamma-ray logs were assembled in two outcrops in order to: 1) characterize log-facies in a succession composed of alternated flood plain, channel fill and eolian strata; 2) define within-channel spectral gamma-ray variability of a mixed-load composite point bar deposit and its relationship with grain size trends and lithofacies; 3) correlate log signatures observed in the outcrop sections with deep exploratory wells drilled several tens of kilometers from the study area. The results of this study show that gamma-ray logs have good correlation with grain size trends and that different depositional elements have distinct signatures. On the other hand, point bar deposits exhibit strong lateral changes in log signature due variations in grain size and mud content within lateral accretion strata. Although frequent, the classic bell-shaped log motif was not always detected, which means that the amount of fluvial channel-fill deposits recognized in subsurface can be underestimated. Similar log signatures were detected in the boreholes, at least in the closest ones, helping in paleoenvironmental interpretation in the subsurface. (author)

  7. Geochemistry and Nd-Sr isotopic signatures of the Pensamiento Granitoid Complex, Rondonian-San Ignacio Province, eastern precambrian shield of Bolivia: petrogenetic constraints for a mesoproterozoic magmatic arc setting;Geoquimica e assinaturas Nd-Sr do Complexo Granitoide Pensamiento, provincia Rondoniana-San Ignacio, pre-cambriano de Bolivia Oriental: caracterizacao petrogenetica de um arco magmatico no mesoproterozoico

    Energy Technology Data Exchange (ETDEWEB)

    Matos, Ramiro, E-mail: rmatoss@igc.usp.b [Universidad Mayor de San Andre (UMSA), La Paz (Bolivia, Plurinational State of). Inst. de Investigaciones Geologicas y del Medio Ambiente; Teixeira, Wilson; Bettencourt, Jorge Silva, E-mail: wteixeir@usp.b, E-mail: jsbetten@usp.b [Universidade de Sao Paulo (IGC/USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica; Geraldes, Mauro Cesar, E-mail: geraldes@uerj.b [Universidade do Estado do Rio de Janeiro (FG/UERJ), RJ (Brazil). Faculdade de Geologia

    2009-07-01

    The Pensamiento Granitoid Complex (PGC), located in the northern part of the eastern Precambrian shield of Bolivia, is tectonically assigned to the Rondonian-San Ignacio Province (1.55 - 1.30 Ga) of the Amazonian Craton that is made up by Archean and Proterozoic provinces. The Proterozoic ones result from accretionary orogens that become successively younger south westwards, such as the Rondonian/San Ignacio (1.37 - 1.32 Ga) and the Sunsas orogenies (1.20 - 1.00 Ga). The PGC crops out mainly on the 'Paragua craton' bounded to the south by the Sunsas belt, and composed of granites and subvolcanic terms, and subordinately of syenites, granodiorites, tonalites, trondhjemites and diorites as orogenic representatives of the Rondonian/San Ignacio Orogeny, intrusive into the Lomas Maneches (ca. 1.68 Ga) and Chiquitania (ca. 1.7 Ga) complexes. Thirteen whole rock chemical analyses for major, trace and REE elements were performed for the La Junta, San Martin, Diamantina, Porvernir, San Cristobal, Piso Firme plutons of the PGC. The negative trends of MgO, Al{sub 2}O{sub 3} and CaO contents with increasing SiO{sub 2} suggest that fractional crystallization played an important role in the petrogenesis of the investigated rocks. The data also indicate a mainly peraluminous, sub-alkaline to high-K calc-alkaline composition, and fractionated LREE/HREE patterns are consistent with a magmatic arc character for these plutons. SHRIMP U-Pb zircon ages of the La Junta and San Martin syn- to late-kinematic plutons are 1347 {+-} 21 Ma and 1373 {+-} 20 Ma respectively, and the Sm-Nd T{sub DM} model ages are between 1.9 to 2.0 Ga, while {epsilon}{sub Nd(1330)} values range from +1.8 to -4.3, respectively. In addition, the late- to post-kinematic Diamantina pluton yields SHRIMP U-Pb zircon age of 1340 {+-} 20 Ma, and variable Sm-Nd T{sub DM} model ages (1.6 to 1.9 Ga) and {epsilon}{sub Nd(1330)} values (+0.4 to -1.2) that are comparable with previous results found for other coeval plutons. The Porvenir, San Cristobal and Piso Firme plutons show {epsilon}{sub Nd(1330)} signatures varying from +1.5 to +2.7, in agreement with a plutonic arc setting as is suggested for the Diamantina pluton. Integrated interpretation of the geochemical and isotopic data coupled with new geologic correlations of the PGC with contemporary units in the Brazilian counterpart establishes one Mesoproterozoic magmatic arc in the evolution of the Rondonian-San Ignacio province. (author)

  8. NDVI e fluxo de CO2 em lavoura de soja no Rio Grande do Sul NDVI and CO2 flow in a soybean crop in Rio Grande do Sul, Brasil

    OpenAIRE

    Celso Pinheiro Rodrigues; Denise Cybis Fontana; Osvaldo Luiz Leal de Moraes; Débora Regina Roberti

    2013-01-01

    O aumento das emissões dos gases de efeito estufa (GEE) se configura, atualmente, como um dos principais problemas ambientais, o que pode afetar significativamente as atividades humanas e os ecossistemas terrestres. Um dos principais GEE é o CO2, o qual tem sido emitido indiscriminadamente em função do estilo de vida atual, assim como pela intensificação das atividades agrícolas. Neste contexto, o objetivo da pesquisa foi estudar a relação entre o comportamento espectral da cultura de soja ao...

  9. Downscaling 250-m MODIS growing season NDVI based on multiple-date landsat images and data mining approaches

    Science.gov (United States)

    Gu, Yingxin; Wylie, Bruce K.

    2015-01-01

    The satellite-derived growing season time-integrated Normalized Difference Vegetation Index (GSN) has been used as a proxy for vegetation biomass productivity. The 250-m GSN data estimated from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors have been used for terrestrial ecosystem modeling and monitoring. High temporal resolution with a wide range of wavelengths make the MODIS land surface products robust and reliable. The long-term 30-m Landsat data provide spatial detailed information for characterizing human-scale processes and have been used for land cover and land change studies. The main goal of this study is to combine 250-m MODIS GSN and 30-m Landsat observations to generate a quality-improved high spatial resolution (30-m) GSN database. A rule-based piecewise regression GSN model based on MODIS and Landsat data was developed. Results show a strong correlation between predicted GSN and actual GSN (r = 0.97, average error = 0.026). The most important Landsat variables in the GSN model are Normalized Difference Vegetation Indices (NDVIs) in May and August. The derived MODIS-Landsat-based 30-m GSN map provides biophysical information for moderate-scale ecological features. This multiple sensor study retains the detailed seasonal dynamic information captured by MODIS and leverages the high-resolution information from Landsat, which will be useful for regional ecosystem studies.

  10. LINKING IN SITU TIME SERIES FOREST CANOPY LAI AND PHENOLOGY METRICS WITH MODIS AND LANDSAT NDVI AND LAI PRODUCTS

    Science.gov (United States)

    The subject of this presentation is forest vegetation dynamics as observed by the TERRA spacecraft's Moderate-Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper, and complimentary in situ time series measurements of forest canopy metrics related to Leaf Area...

  11. Comparison of Uncalibrated Rgbvi with Spectrometer-Based Ndvi Derived from Uav Sensing Systems on Field Scale

    Science.gov (United States)

    Bareth, G.; Bolten, A.; Gnyp, M. L.; Reusch, S.; Jasper, J.

    2016-06-01

    The development of UAV-based sensing systems for agronomic applications serves the improvement of crop management. The latter is in the focus of precision agriculture which intends to optimize yield, fertilizer input, and crop protection. Besides, in some cropping systems vehicle-based sensing devices are less suitable because fields cannot be entered from certain growing stages onwards. This is true for rice, maize, sorghum, and many more crops. Consequently, UAV-based sensing approaches fill a niche of very high resolution data acquisition on the field scale in space and time. While mounting RGB digital compact cameras to low-weight UAVs (UAV platform (UAV-based data acquisition. Consequently, we focus on three objectives in this contribution: (1) to evaluate the potential of the uncalibrated RGBVI for monitoring nitrogen status in winter wheat, (2) investigate the UAV-based performance of the modified Yara N-Sensor, and (3) compare the results of the two different UAV-based sensing approaches for winter wheat.

  12. Detecting leaf pulvinar movements on NDVI time series of desert trees: A new approach for water stress detection

    NARCIS (Netherlands)

    Chávez Oyanadel, R.O.; Clevers, J.G.P.W.; Verbesselt, J.; Naulin, P.; Herold, M.

    2014-01-01

    Heliotropic leaf movement or leaf ‘solar tracking’ occurs for a wide variety of plants, including many desert species and some crops. This has an important effect on the canopy spectral reflectance as measured from satellites. For this reason, monitoring systems based on spectral vegetation indices,

  13. Modeling Species Distribution Using Niche-Based Proxies Derived from Composite Bioclimatic Variables and MODIS NDVI

    OpenAIRE

    Hannes Feilhauer; He, Kate S.; Duccio Rocchini

    2012-01-01

    Vegetation mapping based on niche theory has proven useful in understanding the rules governing species assembly at various spatial scales. Remote-sensing derived distribution maps depicting occurrences of target species are frequently based on biophysical and biochemical properties of species. However, environmental conditions, such as climatic variables, also affect spectral signals simultaneously. Further, climatic variables are the major drivers of species distribution at macroscales. The...

  14. Investigating the Relationship between X-Band SAR Data from COSMO-SkyMed Satellite and NDVI for LAI Detection

    Directory of Open Access Journals (Sweden)

    Antonino Maltese

    2013-03-01

    Full Text Available Monitoring spatial and temporal variability of vegetation is important to manage land and water resources, with significant impact on the sustainability of modern agriculture. Cloud cover noticeably reduces the temporal resolution of retrievals based on optical data. COSMO-SkyMed (the new Italian Synthetic Aperture RADAR-SAR opened new opportunities to develop agro-hydrological applications. Indeed, it represents a valuable source of data for operational use, due to the high spatial and temporal resolutions. Although X-band is not the most suitable to model agricultural and hydrological processes, an assessment of vegetation development can be achieved combing optical vegetation indices (VIs and SAR backscattering data. In this paper, a correlation analysis has been performed between the crossed horizontal-vertical (HV backscattering (s°HV and optical VIs (VIopt on several plots. The correlation analysis was based on incidence angle, spatial resolution and polarization mode. Results have shown that temporal changes of s°HV (Δs°HV acquired with high angles (off nadir angle; θ > 40° best correlates with variations of VIopt (ΔVI. The correlation between ΔVI and Δs°HV has been shown to be temporally robust. Based on this experimental evidence, a model to infer a VI from s° (VISAR at the time, ti + 1, once known, the VIopt at a reference time, ti, and Δs°HV between times, ti + 1 and ti, was implemented and verified. This approach has led to the development and validation of an algorithm for coupling a VIopt derived from DEIMOS-1 images and s°HV. The study was carried out over the Sele plain (Campania, Italy, which is mainly characterized by herbaceous crops. In situ measurements included leaf area index (LAI, which were collected weekly between August and September 2011 in 25 sites, simultaneously to COSMO-SkyMed (CSK and DEIMOS-1 imaging. Results confirm that VISAR obtained using the combined model is able to increase the feasibility of operational satellite-based products for supporting agricultural practices. This study is carried out in the framework of the COSMOLAND project (Use of COSMO-SkyMed SAR data for LAND cover classification and surface parameters retrieval over agricultural sites funded by the Italian Space Agency (ASI.

  15. Mapping the irrigated rice cropping patterns of the Mekong delta, Vietnam, through hyper - temporal SPOT NDVI image analysis

    NARCIS (Netherlands)

    Nguyen, T.T.H.; Bie, de C.A.J.M.; Ali, A.; Smaling, E.M.A.

    2012-01-01

    Successful identification and mapping of different cropping patterns under cloudy conditions of a specific crop through remote sensing provides important baseline information for planning and monitoring. In Vietnam, this information is either missing or unavailable; several ongoing projects studying

  16. Mapping the irrigated rice cropping patterns of the Mekong delta, Vietnam through hyper-temporal SPOT NDVI image analysis

    NARCIS (Netherlands)

    Nguyen, Thi Thu Ha; Bie, de C.A.J.M.; Ali, A.; Smaling, E.M.A.; Hoanh, C.T.

    2012-01-01

    Successful identification and mapping of different cropping patterns under cloudy conditions of a specific crop through remote sensing provides important baseline information for planning and monitoring. In Vietnam, this information is either missing or unavailable; several ongoing projects studying

  17. Integration of MODIS-derived metrics to assess interannual variability in snowpack, lake ice, and NDVI in southwest Alaska

    Science.gov (United States)

    Reed, B.; Budde, M.; Spencer, P.; Miller, A.E.

    2009-01-01

    Impacts of global climate change are expected to result in greater variation in the seasonality of snowpack, lake ice, and vegetation dynamics in southwest Alaska. All have wide-reaching physical and biological ecosystem effects in the region. We used Moderate Resolution Imaging Spectroradiometer (MODIS) calibrated radiance, snow cover extent, and vegetation index products for interpreting interannual variation in the duration and extent of snowpack, lake ice, and vegetation dynamics for southwest Alaska. The approach integrates multiple seasonal metrics across large ecological regions. Throughout the observation period (2001-2007), snow cover duration was stable within ecoregions, with variable start and end dates. The start of the lake ice season lagged the snow season by 2 to 3??months. Within a given lake, freeze-up dates varied in timing and duration, while break-up dates were more consistent. Vegetation phenology varied less than snow and ice metrics, with start-of-season dates comparatively consistent across years. The start of growing season and snow melt were related to one another as they are both temperature dependent. Higher than average temperatures during the El Ni??o winter of 2002-2003 were expressed in anomalous ice and snow season patterns. We are developing a consistent, MODIS-based dataset that will be used to monitor temporal trends of each of these seasonal metrics and to map areas of change for the study area.

  18. Improving the SMAC atmospheric correction code by analysis of Meteosat Second Generation NDVI and surface reflectance data

    DEFF Research Database (Denmark)

    Proud, Simon Richard; Rasmussen, M.O.; Fensholt, R.;

    2010-01-01

    .5% for Channels 1, 2 and 3 respectively. Furthermore, the processing speed of the SMAC is found to remain largely unaffected, with only a small increase in the time taken to process a full SEVIRI scene. Whilst the method described within this paper is only applicable to SEVIRI data, a similar approach can...... be applied to other data sources than SEVIRI, and should result in a similar accuracy improvement no matter which instrument supplies the original data. © 2010 Elsevier Inc....

  19. Comparison and Analysis of MODIS NDVI and MODIS EVI%MODIS NDVI与MODIS EVI的比较分析

    Institute of Scientific and Technical Information of China (English)

    李文梅; 覃志豪; 李文娟; 杨强

    2010-01-01

    MODIS NDVI与MODIS EVI是目前应用比较广泛的植被指数,MODIS EVI是对NDVI的发展和延续,从植被指数计算公式和合成方法两方面做了改进.具体表现在:避免了MODIS NDVI在植被高覆盖区易饱和的问题,考虑了土壤背景对植被指数的影响,对气溶胶等残留做了进一步校正,采用BRDF/CV-MVC合成方法保证了合成采用最佳像元.EVI时间序列相较于NDVI时间序列季节性更明显,能够更好地反映高植被覆盖区的季节性变化特征,并且很少有突降现象,时间序列曲线较平滑.EVI的这些优势为高覆盖植被物候特征的季节性变化监测提供了新的思路.

  20. DEPENDENCE OF NDVI AND SAVI ON SUN/SENSOR GEOMETRY AND ITS EFFECT ON FAPAR RELATIONSHIPS IN ALFALFA. (R828676)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  1. Quasistationary areas of NDVI trend dynamics is a powerful research tool for studying spatial patterns of land vegetation

    Science.gov (United States)

    Shevyrnogov, Anatoly; Larko, Aleksandr

    The most important task for humankind is to study and understand global processes on Earth. Large factual material on the dynamics of the optical spectral characteristics of the land surface has been accumulated in recent decades. This has been only made possible due to the use of satellite information. The development of satellite measurement technologies and new methods for pre-processing and interpretation of satellite data allowed the research adequate to the scale of the Earth. This adequacy includes the compliance of scale terrestrial objects to the scale of satellite measurements. Research is not limited by any latitude or longitude of the objects studied. The second most important quality is the adequacy of the technologies used to velocities of processes on Earth. This is enabled by long-term continuous satellite measurements at almost all latitudes. Effectiveness of this approach to the study of natural systems has been shown by the authors in ASR publications (AP Shevyrnogov, GS Vysotskaya, JI Gitelson, Quasistationary areas of chlorophyll concentration in the world ocean as observed satellite data Advances in Space Research, Volume 18, Issue 7, Pages 129-132, 1996), which reported a method for determining the ocean surface quasistationary zones. This approach allowed us to identify different types of phytopigment dynamics and the hydrological structure of the ocean. We proposed a similar approach for the study of land vegetation. In some aspects, it is similar to the previously published approach, despite the different nature of terrestrial and aquatic ecosystems. The results are based on the processing of satellite data from 1981 to 2006. Dynamics is the most interesting and important parameter of ecosystems, especially their trends. Therefore, it has been chosen for the analysis of spatial patterns of plant biota. The first results showed great heterogeneity of variances in nonlinear trends of the study areas of the Earth's surface. They corresponded to different natural systems. Various scales of temporal and spatial windows highlight different features of land vegetation. Methods for normalization of the initial information are also effective for highlighting the features of the spatial structure of vegetation. Thus, we have a powerful tool to analyze the spatial distribution and dynamics of terrestrial vegetation based on satellite data. This approach provides a great opportunity to get fundamental knowledge on the functioning of the biosphere. This is global warming, shifts in permafrost boundaries, global gas exchange, etc. It can be used for practical applications in various fields of human activity: forestry, environmental protection, agriculture, etc. We show the illustration of this method: the global maps of land surface dynamics of trends with different parameters of data processing.

  2. Using earth observation-based dry season NDVI trends for assessment of changes in tree cover in the Sahel

    DEFF Research Database (Denmark)

    Horion, Stéphanie Marie Anne F; Fensholt, Rasmus; Tagesson, Håkan Torbern;

    2014-01-01

    as a proxy for tree cover in the Sahel, two factors that could potentially influence dry season NDVImin estimates were analysed: the total biomass accumulated during the preceding growing season and the percentage of burned area observed during the dry season. Time series of dry season NDVImin derived from...... low-resolution satellite time series were found to be uncorrelated to dry grass residues from the preceding growing season and to seasonal fire frequency and timing over most of the Sahel (88%), suggesting that NDVImin can serve as a proxy for assessing changes in tree cover. Good agreement (R2= 0.......79) between significant NDVImin trends (ptime series over the Western Sahel, whereas trends based on GIMMS data were negative for the greater part of the Sahel. EO...

  3. Comparison of Uncalibrated Rgbvi with Spectrometer-Based Ndvi Derived from Uav Sensing Systems on Field Scale

    Science.gov (United States)

    Bareth, G.; Bolten, A.; Gnyp, M. L.; Reusch, S.; Jasper, J.

    2016-06-01

    The development of UAV-based sensing systems for agronomic applications serves the improvement of crop management. The latter is in the focus of precision agriculture which intends to optimize yield, fertilizer input, and crop protection. Besides, in some cropping systems vehicle-based sensing devices are less suitable because fields cannot be entered from certain growing stages onwards. This is true for rice, maize, sorghum, and many more crops. Consequently, UAV-based sensing approaches fill a niche of very high resolution data acquisition on the field scale in space and time. While mounting RGB digital compact cameras to low-weight UAVs (market since a decade. It was modified for this study to fit the requirements of UAV-based data acquisition. Consequently, we focus on three objectives in this contribution: (1) to evaluate the potential of the uncalibrated RGBVI for monitoring nitrogen status in winter wheat, (2) investigate the UAV-based performance of the modified Yara N-Sensor, and (3) compare the results of the two different UAV-based sensing approaches for winter wheat.

  4. Assessing the Performance of MODIS NDVI and EVI for Seasonal Crop Yield Forecasting at the Ecodistrict Scale

    OpenAIRE

    Louis Kouadio; Nathaniel K. Newlands; Andrew Davidson; Yinsuo Zhang; Aston Chipanshi

    2014-01-01

    Crop yield forecasting plays a vital role in coping with the challenges of the impacts of climate change on agriculture. Improvements in the timeliness and accuracy of yield forecasting by incorporating near real-time remote sensing data and the use of sophisticated statistical methods can improve our capacity to respond effectively to these challenges. The objectives of this study were (i) to investigate the use of derived vegetation indices for the yield forecasting of spring wheat (Triticu...

  5. Downscaling 250-m MODIS Growing Season NDVI Based on Multiple-Date Landsat Images and Data Mining Approaches

    OpenAIRE

    Yingxin Gu; Bruce K. Wylie

    2015-01-01

    The satellite-derived growing season time-integrated Normalized Difference Vegetation Index (GSN) has been used as a proxy for vegetation biomass productivity. The 250-m GSN data estimated from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors have been used for terrestrial ecosystem modeling and monitoring. High temporal resolution with a wide range of wavelengths make the MODIS land surface products robust and reliable. The long-term 30-m Landsat data provide spatial detaile...

  6. Características espectrais da soja ao longo do ciclo vegetativo com imagens landsat 5/TM em área agrícola no oeste do Paraná Spectral characteristics of soybean during the vegetative cycle with landsat 5/TM images in the western Paraná, Brazil

    Directory of Open Access Journals (Sweden)

    Erivelto Mercante

    2009-06-01

    Full Text Available O objetivo deste trabalho foi estudar as mudanças no comportamento espectral da cultura da soja, por meio dos perfis espectrais temporais dos índices de vegetação NDVI e GVI, expressos em diferentes valores físicos: fator de reflectância bidirecional (FRB aparente, de superfície e normalizado derivados de imagens Landsat 5/TM. Foi monitorada área de cultura de soja localizada próxima ao município de Cascavel - PR, utilizando cinco imagens da safra de 2004/2005, sendo realizados nessas imagens os procedimentos de transformação radiométrica, correção atmosférica e normalização, determinando valores físicos dos fatores de reflectância bidirecional aparente, de superfície e normalizado, respectivamente. Com o intuito de caracterizar a resposta espectral da biomassa da soja, geraram-se imagens referentes aos índices de vegetação NDVI e GVI. Como resultado, a cultura mostrou-se diferente para os tratamentos dos fatores de reflectância bidirecional aparente, de superfície e de normalização. Por meio dos perfis médios espectrais do NDVI e GVI, foi possível acompanhar todo o ciclo da cultura da soja, caracterizando o seu desenvolvimento. Observou-se, ainda, que os dados provenientes do fator de reflectância bidirecional normalizado descaracterizaram a curva espectral da cultura da soja, principalmente em meio à fase de crescimento vegetativo, na data de 9-12-2004.The objective of this study was to analyze changes in the spectral behavior of the soybean crop through spectral profiles of the vegetation indexes NDVI and GVI, expressed by different physical values such as apparent bi-directional reflectance factor (BRF, surface BRF, and normalized BRF derived from images of the Landsat 5/TM. A soybean area located in Cascavel, Paraná, was monitored by using five images of Landsat 5/TM during the 2004/2005 harvesting season. The images were submitted to radiometric transformation, atmospheric correction and normalization

  7. Derivation from the Landsat 7 NDVI and ground truth validation of LAI and interception storage capacity for wetland ecosystems in Biebrza Valley, Poland

    Science.gov (United States)

    Suliga, Joanna; Chormański, Jarosław; Szporak-Wasilewska, Sylwia; Kleniewska, Małgorzata; Berezowski, Tomasz; van Griensven, Ann; Verbeiren, Boud

    2015-10-01

    Wetlands are very valuable areas because they provide a wide range of ecosystems services therefore modeling of wetland areas is very relevant, however, the most widely used hydrological models were developed in the 90s and usually are not adjusted to simulate wetland conditions. In case of wetlands including interception storage into the model's calculation is even more challenging, because literature data hardly exists. This study includes the computation of interception storage capacity based on Landsat 7 image and ground truthing measurements conducted in the Biebrza Valley, Poland. The method was based on collecting and weighing dry, wet and fully saturated samples of sedges. During the experiments measurements of fresh/dry biomass and leaf area index (LAI) were performed. The research was repeated three times during the same season (May, June and July 2013) to observe temporal variability of parameters. Ground truthing measurements were used for the validating estimation of parameters derived from images acquired in a similar period as the measurements campaigns. The use of remote sensing has as major advantage of being able to obtain an area covering spatially and temporally distributed estimate of the interception storage capacity. Results from this study proved that interception capacity of wetlands vegetation is changing considerably during the vegetation season (temporal variability) and reaches its maximum value when plants are fully developed. Different areas depending on existing plants species are characterized with different values of interception capacity (spatial variability). This research frames within the INTREV and HiWET projects, funded respectively by National Science Centre (NCN) in Poland and BELSPO STEREO III.

  8. Increasing summer net CO2 uptake in high northern ecosystems inferred from atmospheric inversions and comparisons to remote-sensing NDVI

    Science.gov (United States)

    Welp, Lisa R.; Patra, Prabir K.; Rödenbeck, Christian; Nemani, Rama; Bi, Jian; Piper, Stephen C.; Keeling, Ralph F.

    2016-07-01

    Warmer temperatures and elevated atmospheric CO2 concentrations over the last several decades have been credited with increasing vegetation activity and photosynthetic uptake of CO2 from the atmosphere in the high northern latitude ecosystems: the boreal forest and arctic tundra. At the same time, soils in the region have been warming, permafrost is melting, fire frequency and severity are increasing, and some regions of the boreal forest are showing signs of stress due to drought or insect disturbance. The recent trends in net carbon balance of these ecosystems, across heterogeneous disturbance patterns, and the future implications of these changes are unclear. Here, we examine CO2 fluxes from northern boreal and tundra regions from 1985 to 2012, estimated from two atmospheric inversions (RIGC and Jena). Both used measured atmospheric CO2 concentrations and wind fields from interannually variable climate reanalysis. In the arctic zone, the latitude region above 60° N excluding Europe (10° W-63° E), neither inversion finds a significant long-term trend in annual CO2 balance. The boreal zone, the latitude region from approximately 50-60° N, again excluding Europe, showed a trend of 8-11 Tg C yr-2 over the common period of validity from 1986 to 2006, resulting in an annual CO2 sink in 2006 that was 170-230 Tg C yr-1 larger than in 1986. This trend appears to continue through 2012 in the Jena inversion as well. In both latitudinal zones, the seasonal amplitude of monthly CO2 fluxes increased due to increased uptake in summer, and in the arctic zone also due to increased fall CO2 release. These findings suggest that the boreal zone has been maintaining and likely increasing CO2 sink strength over this period, despite browning trends in some regions and changes in fire frequency and land use. Meanwhile, the arctic zone shows that increased summer CO2 uptake, consistent with strong greening trends, is offset by increased fall CO2 release, resulting in a net neutral trend in annual fluxes. The inversion fluxes from the arctic and boreal zones covering the permafrost regions showed no indication of a large-scale positive climate-carbon feedback caused by warming temperatures on high northern latitude terrestrial CO2 fluxes from 1985 to 2012.

  9. Differences between MODIS NDVI and MODIS EVI in Response to Climatic Factors%MODIS NDVI与MODIS EVI对气候因子响应差异

    Institute of Scientific and Technical Information of China (English)

    陈燕丽; 罗永明; 莫伟华; 莫建飞; 黄永璘; 丁美花

    2014-01-01

    以喀斯特地区植被为研究载体,利用2001-2010年MODIS NDVI、MODIS EVI序列和气候资料,分析两种植被指数与同期及前1-9期水汽压、降水量、相对湿度、最高气温、最低气温、平均气温、露点温度、气压、风速、日照时数多个气候因子的相关性及响应差异,为合理选择植被指数序列对植被进行监测研究提供参考.结果表明:①喀斯特地区植被EVI和NDVI与多数气候因子显著相关,但二者对气候因子的响应有明显差异.除日照外,EVI与其他各气候因子相关性明显高于NDVI.与NDVI相关性较高的气候因子为日照、最高气温、平均气温,其对应的相关系数平均为0.616、0.535、0.474;而与EVI相关性较高的气候因子为水汽压、平均气温、露点温度,其对应的相关系数平均为0.857、0.844、0.839.②喀斯特地区植被EVI和NDVI对多数气候因子的响应存在明显的滞后性,较之于EVI,NDVI对气候因子的响应更为滞后.EVI与气候因子的相关系数最高时期多出现在前1期,NDVI与气候因子的相关系数最高时期多出现在前2期.两种植被指数对日照、风速的响应无滞后性.除相对湿度、日照、风速外,各站点两种植被指数与其他各气候因子在0-9期的响应趋势均较一致.

  10. Preliminary Comparison of MODIS-NDVI and MODIS-EVI in Eastern Asia%MODIS增强型植被指数EVI与NDVI初步比较

    Institute of Scientific and Technical Information of China (English)

    王正兴; 刘闯; 陈文波; 林昕

    2006-01-01

    利用东亚地区典型地带性植被和MODIS数据,对广泛使用的植被指数NDVI和新开发的增强型植被指数EVI进行了对比分析.由MODIS开发的NDVI和 EVI 对干旱-半湿润环境下低覆盖植被的描述能力相似,但对湿润环境下高密度植被的描述有明显差别:NDVI年时间过程的季节性不明显,表现为全年高平的曲线;而EVI仍然有季节性,表现为钟形曲线,与月平均温度关系更密切.EVI的这一特征为研究高覆盖植被的季节性变化提供了新的思路.

  11. Comparison Between MODIS/NDVI and MODIS/EVI in Northwest China%西北地区MODIS/NDVI与MODIS/EVI对比分析

    Institute of Scientific and Technical Information of China (English)

    杨嘉; 郭铌; 贾建华

    2007-01-01

    为了了解西北地区MODIS/NDVI和MODIS/EVI 2种植被指数的特点,利用2003年植被生长期TERRA/MODIS资料和西北地区植被类型数据,分析了西北地区MODIS/NDVI和MODIS/EVI空间分布特征和不同类型植被随时间变化特征,比较了大气订正对NDVI和EVI的影响.结果表明:NDVI和EVI空间分布格局一致,与降水空间分布形式比较一致.NDVI与EVI值的差异随着植被覆盖度的增加而增大.不同类型植被NDVI和EVI变化特征一致.大气对NDVI和EVI的影响较大,大气订正前许多地区NDVI值小于EVI值.大气订正使NDVI增大,EVI减小,大气订正后NDVI值普遍大于EVI值.通过对大气气溶胶粒子较多地区的NDVI和EVI值的对比分析,EVI具有较好的抗大气气溶胶的作用.

  12. Management current land use of perennial industrial crops by NDVI index: A case study in Chu Se District, Gia Lai Province, Vietnam

    OpenAIRE

    Nguyen, Hoang Khanh Linh; Nguyen, Bich Ngoc

    2015-01-01

    Remote sensing and Geographic Information System (GIS) - an effective tool for managing naturalresources, is quite common application in establishing thematic maps. However, the application of this modern technology in natural resource management has not yet been popular in Vietnam, particularly mapping the land use/cover. Currently, land use/cover map is constructed as traditional methods and gets limitations of management counting due to time-consuming for mapping andsynthesis the status of...

  13. 黄河三角洲NDVI与Albedo时空分布规律%Temporal and Spatial Distribution Law of NDVI and Albedo of the Yellow River Delta

    Institute of Scientific and Technical Information of China (English)

    李发鹏; 徐宗学

    2008-01-01

    采用MODIS科学组L3级产品,详细分析了黄河三角洲地区NDVI和Albedo的时空分布规律,结果表明:①该产品具备相当高的精度,基本反映了研究区的植被覆盖和地表反照率的变化规律,并与土地利用变化情况吻合较好;②MODIS地表反照率对黄河三角洲地区具有一定的适用性;③黄河三角洲地区人类活动特别是农业耕作的季节性更替对NDVI的年内变化影响显著;④黄河三角洲地区的Albedo也具有明显的季节性变化,但其变化规律要比NDVI复杂得多.

  14. Spatial and temporal change characterization of Ceratium furcoides (Dinophyta) in the equatorial reservoir Riogrande II, Colombia Caracterização das mudanças espaciais e temporais de Ceratium furcoides (Dinophyta) no reservatório equatorial Riogrande II (Entrerríos, Antioquia, Colombia)

    OpenAIRE

    Carolina Bustamante Gil; John Jairo Ramírez Restrepo; Andrés Boltovskoy; Amparo Vallejo

    2012-01-01

    AIM: To establish the dynamics of C. furcoides in horizontal and temporal scales; and to determine the main ecological factors related to its dynamics. METHODS: Samples were taken in five stations between July 2002 and July 2003. Physical and chemical variables were sampled monthly. Density was evaluated by sampling carried out within the photic zone. Growth rate (r), Turnover rate (T), Generation Time (gt), Niche Width (NW), Taylor's Power Law, and the rate of population change (σs), we...

  15. Spatial and temporal change characterization of Ceratium furcoides (Dinophyta in the equatorial reservoir Riogrande II, Colombia Caracterização das mudanças espaciais e temporais de Ceratium furcoides (Dinophyta no reservatório equatorial Riogrande II (Entrerríos, Antioquia, Colombia

    Directory of Open Access Journals (Sweden)

    Carolina Bustamante Gil

    2012-06-01

    Full Text Available AIM: To establish the dynamics of C. furcoides in horizontal and temporal scales; and to determine the main ecological factors related to its dynamics. METHODS: Samples were taken in five stations between July 2002 and July 2003. Physical and chemical variables were sampled monthly. Density was evaluated by sampling carried out within the photic zone. Growth rate (r, Turnover rate (T, Generation Time (gt, Niche Width (NW, Taylor's Power Law, and the rate of population change (σs, were used. Canonical Correspondence Analysis (CCA was used too. RESULTS: Total density was 264163.4 cel.L-1, the highest was found in Up Río Chico and the lowest in Dam. The species was more clustered in space than in time. r ranged between 0.29 and 0.3 cel.d-1, gt between 1.8 and 2.4 days, T between 0.55 and 0.42 divisions per day, NW between 0.58 and 0.72, and σs between 0.3 d-1 and 2.3 d-1. The first three components of CCA explained 92.2% of the variation. Density was positively associated with chlorophyll a, NH4+, RWCS and wind direction. Light attenuation, NO3-, SiO2 and O2 were negatively associated with C. furcoides. DISCUSSION: C. furcoides is a S strategist; it increases its density in the warmest periods under eutrophic conditions, low light penetration and high thermal stability; it is independent of the temperature but dependent of changes in rainfall and nutrients, - especially nitrogen - and not soluble phosphorus. Up Río Chico presented the best conditions for the increase of C. furcoides, since this station presented the highest levels of total nitrogen, and the highest relative stability. CONCLUSION: C. furcoides has a very similar ecology to that of C. hirundinella. It is an organism highly variable in temporal and spatial scales, with a wide niche and a clustered distribution. It belongs to the Morpho-funtional Group V and to Lo and L M Assotiations.OBJETIVO: determinar a dinâmica de C. furcoides em escalas horizontal e temporal, e determinar os principais fatores ecológicos relacionados com sua dinâmica. MÉTODOS: As amostras foram coletadas em cinco estações entre julho de 2002 e julho de 2003. As variáveis físicas e químicas foram amostrados mensalmente e a densidade foi estimada a través de coletas realizadas dentro da zona fótica, a taxa de crescimento (r, taxa de rotatividade (T, Tempo de Geração (GT, Largura do nicho (NW, Power Taylor's Law, e a taxa de mudança da população (σs foram utilizados. Análise de Correspondência Canônica (CCA foi usado também. RESULTADOS: A densidade total foi 264.163,4 cel.L-1, a maior foi encontrada em Up Río Chico e a mais baixa na barragem. As espécie foi achada mais agrupada no espaço que no tempo. O valor de r variou entre 0,29 e 0,3 cel.d-1, GT entre 1,8 e 2,4 dias, T entre 0,55 e 0,42 divisões por dia, NW entre 0,58 e 0,72, e σs entre 0,3 e 2,3 d-1. Os três primeiros componentes da CCA explicaram 92,2% da variação. A densidade foi positivamente associado com clorofila a, NH4+, RWCS e direção do vento. A atenuação da luz, NO3-, SiO2 e O2 estiveram associados negativamente com C. furcoides. DISCUSSÃO: C. furcoides é um estrategista tipo S, aumenta sua densidade nos periodos mais quentes perante condições eutróficas, penetração de luz baixa e alta estabilidade térmica. A espécie é independente da temperatura, mas dependente das mudanças na precipitação e nutrientes, - especialmente nitrogênio - não fósforo solúvel. Up Río Chico apresentou as melhores condições para o aumento de C. furcoides, porque esta estação apresentou os mais altos níveis de nitrogênio total e a maior estabilidade relativa. CONCLUSÃO: C. furcoides tem uma ecologia muito semelhante a aquela de C. hirundinella; é um organismo altamente variável nas escalas temporal e espacial, com uma vasta gama de nicho e uma distribuição agregada. Pertence ao Grupo morfo-funcional V e às associações Lo e LM.

  16. Tendências temporais no consumo de tabaco nas capitais brasileiras, segundo dados do VIGITEL, 2006 a 2011 Tendencias temporales en el consumo de tabaco en las capitales brasileñas, según datos de VIGITEL, 2006 a 2011 Trends in tobacco consumption from 2006 to 2011 in Brazilian capitals according to the VIGITEL survey

    Directory of Open Access Journals (Sweden)

    Micheline Gomes Campos da Luz

    2013-04-01

    Full Text Available O objetivo foi analisar a tendência de indicadores do tabagismo nas capitais brasileiras, segundo dados do Sistema de Vigilância de Fatores de Risco e Proteção para Doenças Crônicas por Inquérito Telefônico (VIGITEL em adultos, 2006 a 2011. Foi utilizado modelo de regressão linear simples (a = 5%. Houve redução da prevalência de fumantes e fumantes pesados entre homens e entre indivíduos com idade de 35 a 54 anos. Para fumantes, também houve redução no estrato de 9 a 11 anos de estudo e regiões Norte e Centro-oeste. Para fumantes pesados, a queda foi na Região Nordeste. A política regulatória adotada pelo Brasil tem sido responsável pelo declínio nas prevalências do tabaco.El objetivo fue analizar la tendencia de indicadores del tabaquismo en las capitales brasileñas, según datos del Sistema de Vigilancia de Factores de Riesgo y Protección para Enfermedades Crónicas por Encuesta Telefónica (VIGITEL en adultos, de 2006 a 2011. Fue utilizado el modelo de regresión lineal simple (a = 5%. Hubo una reducción de la prevalencia de fumadores y fumadores crónicos entre hombres y entre individuos con edad de 35 a 54 años. En los fumadores, también hubo reducción en el estrato de 9 a 11 años de estudio y regiones Norte y Centro-oeste. En los fumadores crónicos, la caída fue en la región Nordeste. La política regulatoria adoptada por Brasil ha sido responsable del declive en las prevalencias del tabaco.The aim of this study was to analyze trends in indicators of smoking in Brazilian State capitals, according to the Surveillance System for Risk and Protective Factors for Chronic Illnesses Using a Telephone Survey (VIGITEL in adults, from 2006 to 2011. A simple linear regression model was used (a = 5%. There was a decrease in the prevalence of smokers and heavy smokers among men and in individuals 35 to 54 years of age. Smoking also decreased among individuals with 9-11 years of schooling and in the Northeast, North, and Central West regions. For heavy smokers, the largest decline was in the Northeast. Brazil's regulatory policy has been responsible for the decline in tobacco prevalence.

  17. Padrões temporais na assembléia de peixes na gamboa do Sucuriú, Baía de Paranaguá, Brasil Temporal patterns of the fish assembly in the Sucuriú tidal creek, Paranaguá Bay, Brazil

    Directory of Open Access Journals (Sweden)

    Henry Louis Spach

    2003-12-01

    Full Text Available The ichthyofauna of a tidal creek in Rasa da Cotinga Island, Paranaguá Bay, Paraná was studied through monthly collections in the quadrature high and low tides, with seine net of 30 m x 1.5 m and 10 mm mesh and "fyke" net of 30 m x 1.5 m with 10 mm mesh in the wings and 8 mm mesh in the bag. Together with the nekton sampling, temperature, salinity and water transparency values were also obtained as well as current speed. A total of 9068 fish belonging to 54 species and 23 families were collected. The ichthyofauna was dominated by Harengula clupeola (Cuvier, 1829, Atherinella brasiliensis (Quoy & Gaimard, 1825, Sphoeroides greeley (Gilbert, 1900 and Sphoeroides testudineus (Linnaeus, 1758, that contributed to 66.1% of the capture in number and 79.7% in weight. Statistical differences between the collection months and months groups were observed for the number of species, number and weight of fish, species richness and species diversity (weight. The observed temporal biological structure seems to be better explained by the rainfall, rainfall and salinity and combined action of the rainfall, salinity and water transparency.

  18. Construção de cenários por análises temporais e métricas espaciais em área sob influência de reservatórios de hidrelétricas. Construction of scenarios by time series analysis and space metrics in region under the influence of hydroelectric dams reservoirs.

    Directory of Open Access Journals (Sweden)

    Rozely Ferreira dos SANTOS

    2008-12-01

    Full Text Available De forma geral, as mudanças ambientaissão diagnosticadas pela comparação de dados emdiferentes períodos tendo como base a composiçãodo uso e ocupação da terra. Somente sob essaperspectiva, a obtenção dos resultados não responde,de fato, a complexidade e a dinâmica da região.Nessa direção, o objetivo deste trabalho foidesenvolver, metodologicamente, um cenário históricoque relacionasse as decisões políticas adotadas parauma região com as mudanças no uso das terras,por meio do confronto dos mapas e os índicesespaciais de mudanças com as informaçõeshistóricas e entrevistas com as lideranças locais.A área de estudo é composta por cinco municípiosque margeiam os reservatórios de Jupiá, IlhaSolteira e Três Irmãos (SP. Esses reservatórios,reconhecidamente, mudaram a paisagem regional.Os índices e as métricas retrataram as informaçõeshistóricas, permitindo a discussão dos fatoresculturais, condições locais da terra, ações políticase estratégicas adotadas para a região. Constatou-se quea implantação das usinas teve forte influência sobrea dinâmica da ocupação local, principalmente pelacontratação de mão-de-obra das lavouras e reduçãodo arrendamento de terras. Porém, outros fatores,como a falência de empresas agrícolas e a implantaçãode frigoríficos nas proximidades, contribuíram paraa inversão das áreas agrícolas em pastagens.As lideranças têm consciência das mudançasocorridas na região e consideram que elas nãoforam boas, pois a região não se desenvolveu.Generally, the environmental changes arediagnosed by comparing data in different periodsbased on the land use occupation. Only under thatperspective, the achievement of results does notanswer, in fact, the complexity and dynamism ofthe region. In this way, the goal of this work was todevelop, methodologically, a historical scenariothat links the political decisions taken to a regionwith the land use changes, throught comparing themaps and the change spatial indexes with historicalinformation and interviews with the localleaderships. The study area have five cities thatborder the Jupiá, Ilha Solteira and Três Irmãosreservoirs (SP, BR. These reservoirs, admittedly,changed the regional landscape. The indexes andthe metrics were linked with the historicalinformation, allowing debates of cultural factors,land local conditions, political actions andstrategies adopted to the region. It was verified thatthe deployment of the dams had a great influenceon the region dynamics, mainly for the manpowerabsorption capacity, reducing the labor in the farmsand the renting land. However, other factors,as bankruptcy of agricultural companies andimplantation of cold storage rooms in theneighborhoods, had contributed for the exchangeof agricultural areas to pastures. The leadershipshave conscience of the changes in the region andthey consider that is not good, because there wasnot development in the region.

  19. Defining a quality index for electric power utilities using multiple criteria decision support and time series analysis Definição de um índice de qualidade para distribuidoras de energia elétrica utilizando o apoio à decisão multicritério e análise de séries temporais

    OpenAIRE

    Aderson Campos Passos; Reinaldo Castro Souza

    2013-01-01

    This paper presents a hybrid multi-criteria method developed through the combination of the Analytical Hierarchy Process (AHP) and exponential smoothing techniques applied in time series forecasting. To illustrate its use, a model was developed with the aim of creating a quality index for electric power distribution utilities. The conclusions highlight the need to take into account the results obtained in the latest months for those utilities, but giving less attention to those obtained in th...

  20. Mapping long-term changes in savannah crop productivity in Senegal through trend analysis of time-series of remote sensing data

    DEFF Research Database (Denmark)

    Tøttrup, Christian; Rasmussen, Michael Schultz

    2004-01-01

    Remote sensing, NDVI, trend analysis, environmental change, rainfall, land cover change, Senegal......Remote sensing, NDVI, trend analysis, environmental change, rainfall, land cover change, Senegal...

  1. Evaluación del interés del Índice Vegetativo Diferencial Normalizado (NDVI) para la definición de unidades de manejo diferenciado del viñedo en la Rioja Alavesa

    OpenAIRE

    Echevarría Fano, Nagore

    2010-01-01

    La variabilidad existente en una parcela condiciona en gran medida la implantación y el manejo de los cultivos. Esta variabilidad implica a su vez una variación espacial intraparcelar del rendimiento y de la calidad de la cosecha obtenida. El establecimiento de Unidades de Manejo Diferenciado en un viñedo permite, por un lado, diferenciar las labores de cultivo que se realizan en distintas zonas de una parcela, adaptándolas a las necesidades de cada una de ellas y, por otro, diferenciar nivel...

  2. Comparison between MODIS-NDVI and MODIS-EVI in Kasrt Rocky Desertification Area%不同等级石漠化区MODIS-NDVI与MODIS-EVI对比分析

    Institute of Scientific and Technical Information of China (English)

    陈燕丽; 莫伟华; 莫建飞; 黄永璘; 罗永明

    2014-01-01

    利用2001~2010年10a的MODIS资料,比较分析广西喀斯特不同等级石漠化区MODIS-NDVI和MODIS-EVI的时间变化特征差异,利用全时间序列及16 d 10 a均值序列分析NDVI和EVI之间的相关关系,比较线性及对数相关模型对两种植被指数相关关系的拟合效果,结果表明:石漠化等级由重度到潜在,两者之间的差值也随着植被覆盖度的增加而增大,植被覆盖度越低,NDVI和EVI所表征的植被变化特征越相似.NDVI的峰值出现时间多晚于EVI且其反映的植被变化趋势与实况更吻合,但其NDVI偏高;各等级石漠化的两种时间序列NDVI与EVI的对数相关关系优于线性相关,两种植被指数的相关性随着植被覆盖度的降低而增大,但全时间序列中轻度、中度石漠化相关性变化规律与16 d 10 a均值序列相反.

  3. Detection of Seasonal Trends in Vegetation Cover in Kogi State: Guinea Savannah Region of Nigeria Using Time Series MODIS NDVI Data. GI_Forum 2014 – Geospatial Innovation for Society|

    OpenAIRE

    Osunmadewa, Babatunde; Wessollek, Christine

    2014-01-01

    Natural vegetation is an important source of livelihood for rural communities living in the savannah region of Nigeria. Apart from the direct benefit derived from vegetation exploration, vegetation also is of vital importance in environmental processes such as protecting soil against erosion and maintaining the carbon cycle. Due to human perturbation and inherent climate variability, there has been an increasing decline in vegetation productivity over the last decades in the guinea savannah r...

  4. Albedo-NDVI Space and Remote Sensing Synthesis Index Models for Desertification Monitoring%Albedo-NDVI特征空间及沙漠化遥感监测指数研究

    Institute of Scientific and Technical Information of China (English)

    曾永年; 向南平; 冯兆东; 徐豁

    2006-01-01

    利用遥感数据和野外调查数据分析了沙漠化与地表定量参数之间的关系,提出了Albedo-NDVI特征空间的概念以及基于Albedo-NDVI特征空间的沙漠化遥感监测模型,即沙漠化遥感监测差值指数模型(DDI).这个模型充分利用了多维遥感信息,指标反映了沙漠化土地地表覆盖、水热组合及其变化,具有明确的生物物理意义.而且指标简单、易于获取,有利于沙漠化的定量分析与监测.

  5. 中国内陆河流域植被对气候变化的敏感性差异%Sensitivity analyses of different vegetations responding to climate change in inland river basin of China

    Institute of Scientific and Technical Information of China (English)

    HOU Peng; WANG Qiao; CAO Guangzhen; WANG Changzuo; ZHAN Zhiming; YANG Bingfeng

    2012-01-01

    @@%Terrestrial ecosystem and climate system are closely related to each other.Faced with the unavoidable global climate change,it is important to investigate terrestrial ecosystem responding to climate change.In inland river basin of arid and semi-arid regions in China,sensitivity difference of vegetation responding to climate change from 1998 to 2007 was analyzed in this paper.(1) Differences in the global spatio-temporal distribution of vegetation and climate are obvious.The vegetation change shows a slight degradation in this whole region.Degradation is more obvious in densely vegetated areas.Temperature shows a general downward trend with a linear trend coefficient of-1.1467.Conversely,precipitation shows an increasing trend with a linear trend coefficient of 0.3896.(2) About the central tendency response,there are similar features in spatial distribution of both NDVI responding to precipitation (NDVI-P) and NDVI responding to AI (NDVI-AI),which are contrary to that of NDVI responding to air temperature (NDVI-T).Typical sensitivity region of NDVI-P and NDVI-AI mainly covers the northern temperate arid steppe and the northern temperate desert steppe.NDVI-T typical sensitivity region mainly covers the northern temperate desert steppe.(3) Regarding the fluctuation amplitude response,NDVI-T is dominated by the lower sensitivity,typical regions of the warm temperate shrubby,selui-shrubby,bare extreme dry desert,and northern temperate meadow steppe in the east and temperate semi-shrubby,dwarf arboreous desert in the north are high response.(4) Fluctuation amplitude responses between NDVI-P and NDVI-AI present a similar spatial distribution.The typical sensitivity region mainly covers the northern temperate desert steppe.There are various linear change trend responses of NDVI-T,NDVI-P and NDVI-AI.As to the NDVI-T and NDVI-AI,which are influenced by the boundary effect of semi-arid and semi-humid climate zones,there is less correlation of their linear change tendency

  6. Agronegócio, responsabilidade social e erradicação do trabalho infantil

    OpenAIRE

    Marin, Joel Orlando Bevilaqua

    2008-01-01

    O artigo analisa estratégias adotadas por setores do agronegócio no campo das ações de responsabilidade social para erradicar a exploração do trabalho infantil no Brasil. No contexto da globalização da economia e da internacionalização dos direitos da infância, setores empresariais de cadeias produtivas do agronegócio passaram a desenvolver ações de responsabilidade social para combater o trabalho infantil, mediante a adesão aos selos sociais, assinatura de pactos e proposição de projetos soc...

  7. O pacto germano-soviético: a política externa soviética vista de uma perspectiva do realismo ofensivo

    OpenAIRE

    Porfírio, Manuel António Ferreira de Almeida

    2012-01-01

    Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Ciência Política e Relações Internacionais Análise da política externa soviética na década de 1930, da ascensão de Hitler ao poder até à assinatura do Pacto Molotov-Ribbentrop em 1939. Enquadramento desta na teoria das Relações Internacionais do realismo ofensivo e análise quanto à forma como se enquadra na teoria.

  8. Biogeoquímica em áreas minerais estano-volframíticas

    OpenAIRE

    Favas, Paulo Jorge de Campos

    2008-01-01

    Tese de Doutoramento em Geologia Os objectivos e os procedimentos metodológicos deste trabalho visaram, essencialmente: caracterizar a assinatura biogeoquímica do Sn, W e metais associados, nos solos e nas plantas, das áreas mineiras seleccionadas; identificar espécies vegetais, ou partes das mesmas, indicadoras de elementos químicos presentes em excesso nos solos, naturais e mineiros; e seleccionar espécies vegetais para utilização potencial em acções de bioindicação de contaminações e de...

  9. Metodologia para validar IPS’s de código-fonte aberto

    OpenAIRE

    Trentin, Marco Antônio S; Linden, Gustavo S; Zandoná, Tomás Damo

    2004-01-01

    O presente trabalho tem por objetivo descrever uma metodologia para realizar testes com ferramentas IPS (Intrusion Prevention Systems). Essas ferramentas são mecanismos que são implementados como gateways (in-line) em uma rede de computadores para receber, analisar e encaminhar o tráfego para o seu destino. A análise é feita através da procura por pacotes que contenham assinaturas de ataques aos computadores da rede. Como se trata de uma nova tecnologia é necessário determinar métricas para a...

  10. Desenvolvimento sustentável e garimpo: o caso do Garimpo do Engenho Podre em Mariana, Minas Gerais Sustainable development and garimpo: the case of the Engenho Podre Garimpo in Mariana, Minas Gerais

    OpenAIRE

    Pedro Amade; Hernani Mota de Lima

    2009-01-01

    Esse artigo avalia uma atividade garimpeira, garimpo de ouro do Engenho Podre, com base nos princípios de desenvolvimento sustentável. Esse estudo partiu da hipótese de que a implementação de um sistema de gestão ambiental, compromisso assumido pela Cooperativa dos Garimpeiros de Mariana (COOPERGAMA), na assinatura de um termo de ajuste de conduta, associado a uma melhora no desempenho técnico operacional, é possível, sendo que tal atividade pode ser levada adiante de forma sustentável com fo...

  11. Avaliação da motricidade orofacial em pacientes com mucopolissacaridose: um estudo transversal Evaluation of orofacial motricity in patients with mucopolysaccharidosis: a cross-sectional study

    OpenAIRE

    Giovana S. Turra; Schwartz, Ida Vanessa D.

    2009-01-01

    OBJETIVO: Caracterizar o sistema estomatognático e as funções estomatognáticas de pacientes com mucopolissacaridose. MÉTODOS: Estudo transversal e observacional de pacientes com mucopolissacaridose atendidos no ambulatório do Serviço de Genética Médica do Hospital de Clínicas de Porto Alegre. O critério de inclusão foi a existência de diagnóstico bioquímico ou molecular de qualquer tipo de mucopolissacaridose e a concordância em participar do estudo mediante assinatura do termo de consentimen...

  12. Plasticidade trófica em peixes de água doce Trophic plasticity in freshwater fishes

    OpenAIRE

    Angelo Antonio Agostinho; Milza Celi Fedatto Abelha; Erivelto Goulart

    2001-01-01

    Esta revisão apresenta uma síntese a respeito da plasticidade alimentar em teleósteos de água doce em relação às variações espaço-temporais, ontogenéticas, individuais e comportamentais. A ocorrência de dieta flexível é uma característica marcante da ictiofauna fluvial tropical, onde a maioria das espécies pode mudar de um alimento para outro tão logo ocorram oscilações na abundância relativa do recurso alimentar em uso, motivadas por alterações ambientais espaço-temporais. Quase todas as esp...

  13. A Convenção n.151 da OIT e seus impactos para os servidores públicos no Brasil

    Directory of Open Access Journals (Sweden)

    Cássio da Silva Calvete

    2014-08-01

    Full Text Available Em 2010, o Brasil tornou-se signatário da Convenção n.151 da Organização Internacional do Trabalho (OIT. Essa Convenção trata das relações trabalhistas no setor público, buscando melhores condições de trabalho para esses empregados. Contudo, a assinatura dessa norma não garante efetivamente que tais serão cumpridas internamente. Este artigo visa analisar as dificuldades que o Brasil enfrenta para regulamentá-la e traçar a evolução do processo de institucionalização da negociação coletiva no setor público brasileiro. Além disso, busca ressaltar as expectativas do movimento sindical com a assinatura da Convenção n.151 e quais os impactos que essa já provocou na regulamentação trabalhista do setor público.

  14. INVESTIGANDO OS FATORES QUE INFLUENCIAM A ADOÇÃO DE HDTV NO BRASIL

    Directory of Open Access Journals (Sweden)

    Daniel da Hora Alves Lima

    2012-12-01

    Full Text Available Três anos depois do lançamento da TV digital no Brasil, sua penetração ainda é pequena. O consumidor de conteúdo em alta definição tem sido principalmente assinantes de TV paga, em geral famílias com renda elevada, mas potenciais formadores de opinião. Para identificar estímulos e barreiras à adoção da TV por assinatura em alta definição (HD, quinze potenciais usuários foram entrevistados. Em seguida, um survey foi conduzido em amostra de 348 assinantes de TV paga que não contratavam pacotes HD. Os dados foram tratados por técnicas de data mining e árvore de decisão, identificando-se a relação entre atributos do serviço de HD percebidos e a intenção de contratá-lo. Os resultados sugerem que a disponibilidade de conteúdo em HD, recursos percebidos, renda familiar e a percepção de facilidade de uso da tecnologia têm impacto significativo na intenção de adoção de um serviço por assinatura de HDTV.

  15. Os Transgênicos na Imprensa: o caso da liberação da soja Roundup Ready

    Directory of Open Access Journals (Sweden)

    Mariana Pereira Barbosa

    2004-12-01

    Full Text Available Os organismos geneticamente modificados necessitam de regulamentação no Brasil. A sua chegada ao mercado de alimentos, ainda que de forma ilegal, tem exposto a variedade de argumentos e interesses que permeiam a sua liberação e comercialização. A assinatura da Medida Provisória 131/03, em setembro de 2003 (BRASIL. Medida..., 2003b, pelo presidente da República Luiz Inácio Lula da Silva, permitiu temporariamente o plantio legal de soja transgênica pelos agricultores. O fato motivou uma cobertura diária e massiva da imprensa gaúcha durante muitas edições. Partindo dos referenciais éticos jornalísticos e do conceito de jornalismo ambiental, o trabalho pretende analisar a cobertura de quatro jornais gaúchos no período que antecedeu a assinatura. O objetivo é levantar quais as fontes e os argumentos que foram evidenciados na cobertura com a intenção de analisar se houve eficiência na informação dos posicionamentos opostos sobre o tema.

  16. The Contribution of Moss to Plot-Based Spectral Signals in Moist Acidic Low Arctic Tundra

    Science.gov (United States)

    May, J. L.; Beamish, A. L.

    2015-12-01

    To determine the contribution of moss to peak season normalized difference index (NDVI) field measurement of intact vegetation communities were compared to communities with individual species and litter successively removed until only the moss layer remained. Spectral measurements (n=3) were collected using a field radiometer in five upland and five lowland plots in a moist acidic tundra ecosystem at the Imnaviat Creek Watershed, North Slope Alaska. After spectral measurements were taken individual species were removed in the same order in each plot by clipping them at the moss layer. As individual species were removed NDVI values decreased. Decreases were greatest when dwarf shrub species Salix richardsonii sb. pulchra and Betula nana were removed. Notable increases in NDVI were observed once standing litter was removed. The NDVI values of the moss layer were comparable to intact vegetation communities depending on the bryophyte species composition. This suggests that the NDVI signal of moss is largely masked by vascular species but represents a significant factor missing from overall, large-scale NDVI signals. The results of this study corroborate recent data that points to the mismatch between ground based NDVI and aerial and satellite derived NDVI. This preliminary case study provides a strong basis for better characterization of the contribution of moss to NDVI for improved correction of air and space borne imagery.

  17. Active sensing: An innovative tool for evaluating grain yield and nitrogen use efficiency of multiple wheat genotypes

    Science.gov (United States)

    Naser, Mohammed Abdulridha

    Precision agricultural practices have significantly contributed to the improvement of crop productivity and profitability. Remote sensing based indices, such as Normalized Difference Vegetative Index (NDVI) have been used to obtain crop information. It is used to monitor crop development and to provide rapid and nondestructive estimates of plant biomass, nitrogen (N) content and grain yield. Remote sensing tools are helping improve nitrogen use efficiency (NUE) through nitrogen management and could also be useful for high NUE genotype selection. The objectives of this study were: (i) to determine if active sensor based NDVI readings can differentiate wheat genotypes, (ii) to determine if NDVI readings can be used to classify wheat genotypes into grain yield productivity classes, (iii) to identify and quantify the main sources of variation in NUE across wheat genotypes, and (iv) to determine if normalized difference vegetation index (NDVI) could characterize variability in NUE across wheat genotypes. This study was conducted in north eastern Colorado for two years, 2010 and 2011. The NDVI readings were taken weekly during the winter wheat growing season from March to late June, in 2010 and 2011 and NUE were calculated as partial factor productivity and as partial nitrogen balance at the end of the season. For objectives i and ii, the correlation between NDVI and grain yield was determined using Pearson's product-moment correlation coefficient (r) and linear regression analysis was used to explain the relationship between NDVI and grain yield. The K-means clustering algorithm was used to classify mean NDVI and mean grain yield into three classes. For objectives iii and iv, the parameters related to NUE were also calculated to measure their relative importance in genotypic variation of NUE and power regression analysis between NDVI and NUE was used to characterize the relationship between NDVI and NUE. The results indicate more consistent association between grain

  18. Relationship of Remote Sensing Normalized Differential Vegetation Index to Anopheles Density and Malaria Incidence Rate

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    To study the relationship of remote sensing normalized differential vegetation index (NDVI) to Anopheles density and malaria incidence rate. Methods Data of monthly average climate, environment, Anopheles density and malaria incidence rate, and remote sensing NDVI were collected from 27 townships of 10 counties in southeastern Yunnan Province from 1984 to 1993. The relationship of remote sensing ecological proxy index, NDVI, to Anopheles density and malaria incidence rate was studied by principal component analysis, factor analysis and grey correlation analysis. Results The correlation matrix showed that NDVI highly correlated with Anopheles density in 4 townships of Mengla, Jinghong, and Yuanjiang counties, but in other 23 townships the relationship was not clear. Principal component and factor analyses showed that remote sensing NDVI was the representative index of the first principal component and the first common factor of Anopheles density evaluation. Grey correlation analysis showed that in rainy season NDVI had a high grey correlation with Anopheles density and malaria incidence rate. The grey correlation analysis showed that in rainy season the grey degree of NDVI correlated with Anopheles. Minimus density was 0.730, and 0.713 with Anopheles sinensis density, and 0.800 with malarial incidence rate. Conclusion Remote sensing NDVI can serve as a sensitive evaluation index of Anopheles density and malaria incidence rate.

  19. The utility of estimating net primary productivity over Alaska using baseline AVHRR data

    Science.gov (United States)

    Markon, C.J.; Peterson, K.M.

    2002-01-01

    Net primary productivity (NPP) is a fundamental ecological variable that provides information about the health and status of vegetation communities. The Normalized Difference Vegetation Index, or NDVI, derived from the Advanced Very High Resolution Radiometer (AVHRR) is increasingly being used to model or predict NPP, especially over large remote areas. In this article, seven seasonally based metrics calculated from a seven-year baseline NDVI dataset were used to model NPP over Alaska, USA. For each growing season, they included maximum, mean and summed NDVI, total days, product of total days and maximum NDVI, an integral estimate of NDVI and a summed product of NDVI and solar radiation. Field (plot) derived NPP estimates were assigned to 18 land cover classes from an Alaskan statewide land cover database. Linear relationships between NPP and each NDVI metric were analysed at four scales: plot, 1-km, 10-km and 20-km pixels. Results show moderate to poor relationship between any of the metrics and NPP estimates for all data sets and scales. Use of NDVI for estimating NPP may be possible, but caution is required due to data seasonality, the scaling process used and land surface heterogeneity.

  20. Assessing vegetation response to drought in the northern Great Plains using vegetation and drought indices

    Science.gov (United States)

    Ji, Lei; Peters, Albert J.

    2003-01-01

    The Normalized Difference Vegetation Index (NDVI) derived from the Advanced Very High Resolution Radiometer (AVHRR) has been widely used to monitor moisture-related vegetation condition. The relationship between vegetation vigor and moisture availability, however, is complex and has not been adequately studied with satellite sensor data. To better understand this relationship, an analysis was conducted on time series of monthly NDVI (1989–2000) during the growing season in the north and central U.S. Great Plains. The NDVI was correlated to the Standardized Precipitation Index (SPI), a multiple-time scale meteorological-drought index based on precipitation. The 3-month SPI was found to have the best correlation with the NDVI, indicating lag and cumulative effects of precipitation on vegetation, but the correlation between NDVI and SPI varies significantly between months. The highest correlations occurred during the middle of the growing season, and lower correlations were noted at the beginning and end of the growing season in most of the area. A regression model with seasonal dummy variables reveals that the relationship between the NDVI and SPI is significant in both grasslands and croplands, if this seasonal effect is taken into account. Spatially, the best NDVI–SPI relationship occurred in areas with low soil water-holding capacity. Our most important finding is that NDVI is an effective indicator of vegetation-moisture condition, but seasonal timing should be taken into consideration when monitoring drought with the NDVI.

  1. Vegetation Changes and the Relationship with Climate Variability in the Upper and Middle Reaches of the Nenjiang River Basin, China

    Science.gov (United States)

    Huang, F.; Wen, D. H.; Wang, P.

    2016-06-01

    To detect changes in vegetation is desirable for modeling and predicting interactions between land surface and atmosphere. Multitemporal series of SPOT VEGETATION NDVI dataset and meteorological data were integrated to interpret vegetation dynamics and the linkage with climate variations in the upper and middle reaches of the Nenjiang River Basin (NRB) from 1999 to 2010 using the correlation analysis and the rescaled range (R/S) analysis. The results demonstrate that annual NDVI increased slightly and 26.02% vegetation coverage of the study area significantly improved. The area of significantly decreased in vegetation cover took up 13.33% of the total land in spring. In autumn, 26.2% of the study area showed a significant vegetation increase. The improved activity of vegetation might reinforce in summer and autumn, while the decreasing tendency in spring might be persistent in the future. The yearly NDVI had significant positive linkages with precipitation and relative humidity. NDVI related significantly and negatively with temperature, sunshine hours and wind velocity, because they may have effects of increasing evapotranspiration and risk of drought and cold damage of vegetation. The variations of annual NDVI were much affected by summer temperature, relative humidity and sunshine duration in autumn and spring wind velocity. Seasonal NDVI decreased in parallel with elevated temperature, but there was no correlation between NDVI and precipitation. Spring temperature, relative humidity in summer and autumn contributed markedly to NDVI variations in the same season. The vegetation improving trend may induce by the warm-wetting climate in recent twelve years.

  2. Differentiating moss from higher plants is critical in studying the carbon cycle of the boreal biome

    DEFF Research Database (Denmark)

    Yuan, Wenping; Liu, Shuguang; Dong, Wenjie;

    2014-01-01

    The satellite-derived normalized difference vegetation index (NDVI), which is used for estimating gross primary production (GPP), often includes contributions from both mosses and vascular plants in boreal ecosystems. For the same NDVI, moss can generate only about one-third of the GPP that vascu...

  3. CERTIFICAÇÃO DIGITAL E ARQUIVOLOGIA: benefícios e aplicações

    Directory of Open Access Journals (Sweden)

    Tatiane Rodrigues do Nascimento

    2015-06-01

    Full Text Available A sociedade da informação abriu novos campos e oportunidades, e a informação nas redes digitais ganhou dimensões sem fronteiras, surgindo a necessidade de políticas de segurança para garantir a autenticação, privacidade, autorização e integridade dos dados. A solução encontrada para solucionar esses problemas foi a utilização de um sistema de criptografia. O governo brasileiro criou padrões técnicos para suportar um sistema criptográfico, chamado de Infraestrutura de Chaves Públicas Brasileira (ICP-Brasil, com o objetivo de regulamentar o uso de certificados digitais. Com o surgimento e crescimento intenso desse novo formato de documento, a Arquivologia sentiu necessidade de incorporar essa ferramenta. Se por um lado a assinatura digital confere autenticidade e integridade à informação, por outro os avanços não garantem a sua preservação no longo prazo. O valor legal da autenticidade desse documento está relacionado às assinaturas digitais. Sob a ótica da arquivística e da diplomática, a autenticidade dos documentos não depende apenas da assinatura, mas de um conjunto de elementos. O presente trabalho tem por objetivo analisar o mercado de certificado digital na cidade de Manaus, sob a ótica da Arquivologia, ou seja, da autenticidade e sigilo nos documentos digitais. Metodologicamente, refere-se a uma pesquisa de natureza qualitativa, com caráter exploratório-descritivo, realizada por meio de um estudo de caso e por possuir um objetivo definido. Buscou-se avaliar se as autoridades certificadoras possuem estruturas para garantir a segurança e transação dos documentos digitais na cidade de Manaus-AM. Como resultado, observou-se que o setor financeiro foi o primeiro a utilizar o certificado digital, seguido pelo setor fiscal, que ganhou destaque com a nota fiscal eletrônica, e mais tarde pelo judiciário, com o processo eletrônico, que ao mesmo tempo foi responsável por aumentar o número de advogados

  4. Carlos Chagas Filho: um articulador da história das ciências do Brasil Carlos Chagas Filho: an articulator of the history of sciences in Brazil

    OpenAIRE

    Heloisa Maria Bertol Domingues

    2012-01-01

    Uma carta enviada em 1982 por um grupo de cientistas ao presidente do Conselho Nacional de Desenvolvimento Científico e Tecnológico reivindicava uma política de preservação da cultura científica brasileira. O nome Carlos Chagas Filho encabeçava a lista de assinaturas, a mostrar seu engajamento naquela proposta, cuja estrutura ideológica fez parte da sua vivência na política científica, no Brasil e no exterior. Esse documento remete à prática da história das ciências no Brasil e à criação de l...

  5. Proteção e promoção do investimento estrangeiro no Mercosul uma ferramenta para a implementação de um bom clima de investimentos? Protection and promotion of foreign investment in Mercosur a tool to the implementation of a good investment climate?

    Directory of Open Access Journals (Sweden)

    José Augusto Fontoura Costa

    2006-12-01

    Full Text Available A assinatura de tratados bilaterais de investimento por países em desenvolvimento é vista como uma estratégia para competir por capitais estrangeiros escassos. Este artigo discute possíveis padrões cooperativos na América do Sul partindo do conceito de bom clima de investimentos e considerando os acordos argentinos com outros paises em desenvolvimento.The signature of bilateral investment treaties by developing countries is regarded as a strategy to compete for scarce foreign capital. This article discusses the existence of possible cooperative patterns in South America starting from the concept of good investment climate and considering the Argentinean agreements with other developing countries.

  6. Síndrome de Goldenhar: uma abordagem fonoaudiológica Goldenhar Syndrome: speech-language approach

    OpenAIRE

    Angela Ruviaro Busanello; Ana Maria Toniolo da Silva; Mara Keli Christmann; Marcele Machado Finamor; Marília Trevisan Sonego; Rafaeli Alves Barcellos; Tainara Milbradt Weich; Talita Marin Scherer

    2012-01-01

    TEMA: o objetivo deste trabalho foi relatar o caso de uma criança portadora de Síndrome de Goldenhar em tratamento fonoaudiológico em uma clínica escola. PROCEDIMENTOS: foram coletados dados do prontuário do paciente, mediante assinatura do Termo de Consentimento Livre e Esclarecido e aprovação no Comitê de Ética da instituição, durante aproximadamente 11 meses de fonoterapia. Trata-se de uma criança de 5 anos e 11 meses de idade, do gênero masculino, apresentando ao nascimento má formação na...

  7. Crítica cinematográfica: considerações do novo milênio

    Directory of Open Access Journals (Sweden)

    Roberto Moura

    2011-01-01

    Full Text Available A crítica cinematográfica no Brasil, um tema momentaneamente em baixa, uma vez que se perdeu momentaneamente a enorme popularidade que ela tinha e tiveram alguns críticos em nossos jornais em tempos não tão distantes. Distinta tanto das matérias informativas e dos anúncios publicados nos jornais como dos artigos teórico-analíticos nas revistas especializadas, a crítica é uma coisa muito específica logo localizada pelo leitor, muitas vezes destacada pela diagramação, carimbada pela assinatura do crítico.

  8. Introducing a rain-adjusted vegetation index (RAVI) for improvement of long-term trend analyses in vegetation dynamics

    Science.gov (United States)

    Wessollek, Christine; Karrasch, Pierre; Osunmadewa, Babatunde

    2015-10-01

    It seems to be obvious that precipitation has a major impact on greening during the rainy season in semi-arid regions. First results1 imply a strong dependence of NDVI on rainfall. Therefore it will be necessary to consider specific rainfall events besides the known ordinary annual cycle. Based on this fundamental idea, the paper will introduce the development of a rain adjusted vegetation index (RAVI). The index is based on the enhancement of the well-known normalized difference vegetation index (NDVI2) by means of TAMSAT rainfall data and includes a 3-step procedure of determining RAVI. Within the first step both time series were analysed over a period of 29 years to find best cross correlation values between TAMSAT rainfall and NDVI signal itself. The results indicate the strongest correlation for a weighted mean rainfall for a period of three months before the corresponding NDVI value. Based on these results different mathematical models (linear, logarithmic, square root, etc.) are tested to find a functional relation between the NDVI value and the 3-months rainfall period before (0.8). Finally, the resulting NDVI-Rain-Model can be used to determine a spatially individual correction factor to transform every NDVI value into an appropriate rain adjusted vegetation index (RAVI).

  9. Continuous 1985-2012 Landsat monitoring to assess fire effects on meadows in Yosemite National Park, California

    Science.gov (United States)

    Soulard, Christopher E.; Albano, Christine M.; Villarreal, Miguel; Walker, Jessica

    2016-01-01

    To assess how montane meadow vegetation recovered after a wildfire that occurred in Yosemite National Park, CA in 1996, Google Earth Engine image processing was applied to leverage the entire Landsat Thematic Mapper archive from 1985 to 2012. Vegetation greenness (normalized difference vegetation index [NDVI]) was summarized every 16 days across the 28-year Landsat time series for 26 meadows. Disturbance event detection was hindered by the subtle influence of low-severity fire on meadow vegetation. A hard break (August 1996) was identified corresponding to the Ackerson Fire, and monthly composites were used to compare NDVI values and NDVI trends within burned and unburned meadows before, immediately after, and continuously for more than a decade following the fire date. Results indicate that NDVI values were significantly lower at 95% confidence level for burned meadows following the fire date, yet not significantly lower at 95% confidence level in the unburned meadows. Burned meadows continued to exhibit lower monthly NDVI in the dormant season through 2012. Over the entire monitoring period, the negative-trending, dormant season NDVI slopes in the burned meadows were also significantly lower than unburned meadows at 90% confidence level. Lower than average NDVI values and slopes in the dormant season compared to unburned meadows, coupled with photographic evidence, strongly suggest that evergreen vegetation was removed from the periphery of some meadows after the fire. These analyses provide insight into how satellite imagery can be used to monitor low-severity fire effects on meadow vegetation.

  10. Spatial and temporal patterns of greenness on the Yamal Peninsula, Russia: interactions of ecological and social factors affecting the Arctic normalized difference vegetation index

    Science.gov (United States)

    Walker, D. A.; Leibman, M. O.; Epstein, H. E.; Forbes, B. C.; Bhatt, U. S.; Raynolds, M. K.; Comiso, J. C.; Gubarkov, A. A.; Khomutov, A. V.; Jia, G. J.; Kaarlejärvi, E.; Kaplan, J. O.; Kumpula, T.; Kuss, P.; Matyshak, G.; Moskalenko, N. G.; Orekhov, P.; Romanovsky, V. E.; Ukraientseva, N. G.; Yu, Q.

    2009-10-01

    The causes of a greening trend detected in the Arctic using the normalized difference vegetation index (NDVI) are still poorly understood. Changes in NDVI are a result of multiple ecological and social factors that affect tundra net primary productivity. Here we use a 25 year time series of AVHRR-derived NDVI data (AVHRR: advanced very high resolution radiometer), climate analysis, a global geographic information database and ground-based studies to examine the spatial and temporal patterns of vegetation greenness on the Yamal Peninsula, Russia. We assess the effects of climate change, gas-field development, reindeer grazing and permafrost degradation. In contrast to the case for Arctic North America, there has not been a significant trend in summer temperature or NDVI, and much of the pattern of NDVI in this region is due to disturbances. There has been a 37% change in early-summer coastal sea-ice concentration, a 4% increase in summer land temperatures and a 7% change in the average time-integrated NDVI over the length of the satellite observations. Gas-field infrastructure is not currently extensive enough to affect regional NDVI patterns. The effect of reindeer is difficult to quantitatively assess because of the lack of control areas where reindeer are excluded. Many of the greenest landscapes on the Yamal are associated with landslides and drainage networks that have resulted from ongoing rapid permafrost degradation. A warming climate and enhanced winter snow are likely to exacerbate positive feedbacks between climate and permafrost thawing. We present a diagram that summarizes the social and ecological factors that influence Arctic NDVI. The NDVI should be viewed as a powerful monitoring tool that integrates the cumulative effect of a multitude of factors affecting Arctic land-cover change.

  11. Interannual variability and correlation of vegetation cover and precipitation in Eastern China

    Science.gov (United States)

    Jiang, Dejuan; Zhang, Hua; Zhang, Yong; Wang, Kun

    2014-10-01

    Based on the SPOT/VEGETATION Normalized Difference Vegetation Index (NDVI) data and daily precipitation data of 357 meteorological stations, the spatial and temporal variability of vegetation cover, measured by NDVI, and precipitation as well as their relationships are investigated in Eastern China, which is portioned into three subregions (regions I, II, and III), for the period 1998-2010. The results show that high NDVI values appear mainly in Northeastern China and in August while high precipitation (PRETOT) occurs in Southeastern China and in July (June for Southern China). Extreme precipitation days (RD95p) and amount (EPRETOT) coincide well with PRETOT. Extreme precipitation intensity (RINTEN) has a similar spatial variability to PRETOT but with a smaller seasonal variation than PRETOT. Growing season NDVI is positively correlated with PRETOT in 11.7 % of the study area (mostly in arid to subhumid regions of Northern China), where precipitation is a limiting factor for vegetation growth. In contrast, a negative correlation between growing season NDVI and PRETOT is found in 4.8 % of the study area, mostly in areas around the Yangtze River and deep Northeastern China. No significant correlations between these two variables are found for the other regions because vegetation response to precipitation is affected by other factors such as temperature, radiation, and human disturbance. On a monthly scale, there is a positive correlation between NDVI and PRETOT in May (for region II) and September (all subregions except region I). NDVI variations lag 1 month behind PRETOT in June (for region I) and October. Correlations between NDVI and RD95p, EPRETOT are similar to that with PRETOT, but the relationships between NDVI and RINTEN are relatively weaker than with PRETOT. This study provides the technical basis for agriculture development and ecological construction in Eastern China.

  12. Spatial and temporal patterns of greenness on the Yamal Peninsula, Russia: interactions of ecological and social factors affecting the Arctic normalized difference vegetation index

    International Nuclear Information System (INIS)

    The causes of a greening trend detected in the Arctic using the normalized difference vegetation index (NDVI) are still poorly understood. Changes in NDVI are a result of multiple ecological and social factors that affect tundra net primary productivity. Here we use a 25 year time series of AVHRR-derived NDVI data (AVHRR: advanced very high resolution radiometer), climate analysis, a global geographic information database and ground-based studies to examine the spatial and temporal patterns of vegetation greenness on the Yamal Peninsula, Russia. We assess the effects of climate change, gas-field development, reindeer grazing and permafrost degradation. In contrast to the case for Arctic North America, there has not been a significant trend in summer temperature or NDVI, and much of the pattern of NDVI in this region is due to disturbances. There has been a 37% change in early-summer coastal sea-ice concentration, a 4% increase in summer land temperatures and a 7% change in the average time-integrated NDVI over the length of the satellite observations. Gas-field infrastructure is not currently extensive enough to affect regional NDVI patterns. The effect of reindeer is difficult to quantitatively assess because of the lack of control areas where reindeer are excluded. Many of the greenest landscapes on the Yamal are associated with landslides and drainage networks that have resulted from ongoing rapid permafrost degradation. A warming climate and enhanced winter snow are likely to exacerbate positive feedbacks between climate and permafrost thawing. We present a diagram that summarizes the social and ecological factors that influence Arctic NDVI. The NDVI should be viewed as a powerful monitoring tool that integrates the cumulative effect of a multitude of factors affecting Arctic land-cover change.

  13. Assessing Biodiversity from Space: an Example from the Western Ghats, India

    Directory of Open Access Journals (Sweden)

    K.N. Ganeshaiah

    2002-12-01

    Full Text Available We demonstrate for the first time the potential use of satellite imagery to characterize areas of high and low species richness of trees in tropical forests. Our studies, conducted in the Biligiri Rangaswamy hills in the Western Ghats, India, show a high positive correlation between species richness and the Normalized Difference Vegetation Index (NDVI, which is an index of green biomass. We discuss the application of NDVI values for biodiversity assessment and monitoring, as well as for conservation planning. The NDVI is a rough measure of green biomass.

  14. Understanding Pan-Arctic Tundra Vegetation Change Through Long-term Remotely Sensed Data

    Science.gov (United States)

    Bhatt, U.; Walker, D. A.; Bieniek, P.; Raynolds, M. K.; Epstein, H. E.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2012-12-01

    The goal of this paper is to present an analysis of the seasonality of tundra vegetation variability and change using long-term remotely sensed data as well as ground based measurements and reanalyses. An increase of Pan-Arctic tundra vegetation greenness has been documented using the remotely sensed Normalized Difference Vegetation Index (NDVI). Coherent variability between NDVI, springtime coastal sea ice (passive microwave) and land surface temperatures (AVHRR) has also been established. Satellite based snow and cloud cover data sets are being incorporated into this analysis. The Arctic tundra is divided into domains based on Treshnikov divisions that are modified based on floristic provinces. There is notable heterogeneity in Pan-Arctic vegetation and climate trends, which necessitates a regional analysis. This study uses remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2010. The GIMMS NDVI3g data has been corrected for biases during the spring and fall, with special focus on the Arctic. Trends of Maximum NDVI (MaxNDVI), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), and open water area are calculated for the Pan Arctic. Remotely sensed snow data trends suggest varying patterns throughout the Arctic and may in part explain the heterogeneous MaxNDVI trends. Standard climate data (station, reanalysis, and model data) and ground observations are used in the analysis to provide additional support for hypothesized mechanisms. Overall, we find that trends over the 30-year record are changing as evidenced by the following examples from recent years. The sea ice decline has increased in Eurasia and slowed in North America. The weekly AVHRR landsurface temperatures reveal that there has been summer cooling over Eurasia and that the warming over North America has slowed. The MaxNDVI rates of change have diverged between N. America and Eurasia

  15. Changing Seasonality of Tundra Vegetation and Associated Climatic Variables

    Science.gov (United States)

    Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Bieniek, P.; Epstein, H. E.; Comiso, J. C.; Pinzon, J.; Tucker, C. J.; Steele, M.; Ermold, W. S.; Zhang, J.

    2014-12-01

    This study documents changes in the seasonality of tundra vegetation productivity and its associated climate variables using long-term data sets. An overall increase of Pan-Arctic tundra greenness potential corresponds to increased land surface temperatures and declining sea ice concentrations. While sea ice has continued to decline, summer land surface temperature and vegetation productivity increases have stalled during the last decade in parts of the Arctic. To understand the processes behind these features we investigate additional climate parameters. This study employs remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2013. Maximum NDVI (MaxNDVI, Maximum Normalized Difference Vegetation Index), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), ocean heat content (PIOMAS, model incorporating ocean data assimilation), and snow water equivalent (GlobSnow, assimilated snow data set) are explored. We analyzed the data for the full period (1982-2013) and for two sub-periods (1982-1998 and 1999-2013), which were chosen based on the declining Pan-Arctic SWI since 1998. MaxNDVI has increased from 1982-2013 over most of the Arctic but has declined from 1999 to 2013 over western Eurasia, northern Canada, and southwest Alaska. TI-NDVI has trends that are similar to those for MaxNDVI for the full period but displays widespread declines over the 1999-2013 period. Therefore, as the MaxNDVI has continued to increase overall for the Arctic, TI-NDVI has been declining since 1999. SWI has large relative increases over the 1982-2013 period in eastern Canada and Greenland and strong declines in western Eurasia and southern Canadian tundra. Weekly Pan-Arctic tundra land surface temperatures warmed throughout the summer during the 1982-1998 period but display midsummer declines from 1999-2013. Weekly snow water equivalent over Arctic tundra has declined over

  16. USO, VIVÊNCIA E CONSERVAÇÃO DO MEIO AMBIENTE EM POPULAÇÕES TRADICIONAIS: O CASO DA COMUNIDADE QUILOMBOLA DE CAIANA DOS CRIOULOS, ALAGOA GRANDE (PB)

    OpenAIRE

    Diego de Oliveira Silvestre; Alecsandra P. da Costa Moreira

    2011-01-01

    O homem desde sua origem sempre desempenhou, ao longo da história do nosso planeta, atividades no entorno em que habita e trabalha. Em cada comunidade ou grupo social e em escalas temporais diferenciadas a natureza representa valores, ideologia e objetivos para cada agrupamento social. Este trabalho tem como principal objetivo compreender as diferentes formas e práticas de sociabilidade das populações tradicionais, em especial os quilombolas, e suas respectivas relações com o meio ambiente, t...

  17. Anelídeos poliquetas da plataforma continental norte do Estado de São Paulo: I - Padrões de densidade e diversidade específica Polychaetous annelids of the northern continental shelf of São Paulo State: I - Patterns of density and specific diversity

    OpenAIRE

    Paulo Cesar de Paiva

    1993-01-01

    Foram estudados os padrões de densidade e diversidade específica dos anelídeos poliquetas da plataforma continental norte do Estado de São Paulo. A densidade de poliquetas foi maior na plataforma interna, especialmente na radial Sul. Nas radiais Central e Norte foram observadas variações temporais nas isóbatas de 20 e 35 m, com valores maiores no verão. Os valores de diversidade específica foram preponderantemente mais baixos na plataforma externa, no verão, e altos, no inverno, enquanto a pl...

  18. A compreensão musical da criança

    OpenAIRE

    Caregnato, Caroline

    2012-01-01

    Resumo: A música é a arte dos sons organizados no tempo. Para que ela seja compreendida é preciso, dentre outras coisas, que se compreenda sua organização temporal. Neste trabalho foram abordados dois aspectos temporais da música: a simultaneidade e a igualdade de durações, no intuito de verificar como a criança desenvolve a compreensão de ambos. Esta pesquisa teve como objetivos identificar as etapas do desenvolvimento da compreensão da simultaneidade e da igualdade de durações em música; id...

  19. O sono como ativador do eletrencefalograma nos pacientes epilépticos The sleep as an activator on epileptic patient's electroencephalogram

    Directory of Open Access Journals (Sweden)

    Rosa Helena Longo

    1973-09-01

    Full Text Available Visando ao estudo da ação do sono como ativador do eletrencefalograma em pacientes epilépticos, foram estudados 1.868 pacientes com síndromes convulsivas (572 com crises generalizadas, 121 com crises temporais não psicomostras, 118 com crises psicomotoras, 410 com crises focais não temporais, 314 com crises noturnas, 165 com crises febris, 168 com crises convulsivas associadas a retardo psicomotor. Em todos os pacientes foram feitos eletrencefalogramas em vigília (repouso e hiperpnéia e durante o sono (fase lenta sendo os achados comparados. Em nosso material não encontramos diferença significativa de resposta entre o sono espontâneo e o medicamentoso. Na maioria de nossos pacientes o traçado realizado durante o sono confirmou os achados registrados em vigília. A ação ativadora do sono foi evidenciada em um número relativamente pequeno de casos, tendo atingido o seu máximo no grupo de pacientes com crises psicomotoras (26%. Nas crises generalizadas, temporais não psicomotoras, focais não temporais e noturnas o sono funcionou mais como desativador do que como ativador das anormalidades registradas em vigília.In order to study the influence of sleep on the electroencephalograms of epileptic patients the tracings obtained of 1.868 such patients were analised (572 generalized seizures; 121 non-psychomotor temporal; 118 psychomotor; 410 non-temporal focal; 314 noctural seizures; 165 febrile seizures; 168 convulsive seizures associated with psychomotor retard. The electroencephalograms were made with the patients awake (rest and hyperpnea and sleeping (slow phase, the findings being compared. There was not found any significant difference between the EEG tracings obtained during spontaneous sleep and medically induced sleep. In the majority of the cases the records obtained while the patients were asleep merely confirmed the ones made while the patients were awake. The activator action of sleep appeared only in small number of the

  20. Estrutura e organização trófica da ictiofauna de águas rasas em um estuário tropical

    OpenAIRE

    Andréa C. G. de Paiva; Paulo de Tarso da C Chaves; Maria E. Araújo

    2008-01-01

    O presente estudo avaliou: 1) se a diversidade da ictiofauna de águas rasas do Rio Formoso (Pernambuco) varia entre as zonas estuarinas superior e inferior, e entre os períodos seco e chuvoso e 2) se houve diferenças espaciais e temporais nas categorias tróficas dessa ictiofauna. Os peixes foram coletados bimestralmente com rede-de-arrasto tipo mangote. Foram coletados 5475 indivíduos pertencentes a 78 espécies, sendo 51,3% de origem recifal. Carangidae e Gerreidae tiveram a maior riqueza esp...

  1. PREVISÃO DOS PREÇOS DO AÇÚCAR E ANÁLISE DA SUA VOLATILIDADE NO MERCADO FUTURO BRASILEIRO (2003 A 2007): UMA APLICAÇÃO DE MODELOS DA FAMÍLIA ARCH

    OpenAIRE

    Nicola, Danieli Scalcon; Freitas, Clailton Ataides; PAZ, MARLON VIDAL

    2008-01-01

    Este trabalho objetiva mensurar a volatilidade dos preços futuros do açúcar negociados na BM&F, bem como verificar quais entre os modelos univariados propostos apresenta melhor desempenho preditivo para o preço da commodity em questão. Para tanto se utilizam modelos de análise de volatilidade do tipo ARCH e modelos univariados de previsão aplicados a séries temporais, entre os quais os modelos ARIMA e SARIMA. Os resultados empíricos sugerem não haver presença de assimetria entre choques posit...

  2. Investigation on the Patterns of Global Vegetation Change Using a Satellite-Sensed Vegetation Index

    Directory of Open Access Journals (Sweden)

    Ainong Li

    2010-06-01

    Full Text Available The pattern of vegetation change in response to global change still remains a controversial issue. A Normalized Difference Vegetation Index (NDVI dataset compiled by the Global Inventory Modeling and Mapping Studies (GIMMS was used for analysis. For the period 1982–2006, GIMMS-NDVI analysis indicated that monthly NDVI changes show homogenous trends in middle and high latitude areas in the northern hemisphere and within, or near, the Tropic of Cancer and Capricorn; with obvious spatio-temporal heterogeneity on a global scale over the past two decades. The former areas featured increasing vegetation activity during growth seasons, and the latter areas experienced an even greater amplitude in places where precipitation is adequate. The discussion suggests that one should be cautious of using the NDVI time-series to analyze local vegetation dynamics because of its coarse resolution and uncertainties.

  3. Plant species richness and shrub cover attenuate drought effects on ecosystem functioning across Patagonian rangelands.

    Science.gov (United States)

    Gaitán, Juan J; Bran, Donaldo; Oliva, Gabriel; Maestre, Fernando T; Aguiar, Martín R; Jobbágy, Esteban; Buono, Gustavo; Ferrante, Daniela; Nakamatsu, Viviana; Ciari, Georgina; Salomone, Jorge; Massara, Virginia

    2014-10-01

    Drought is an increasingly common phenomenon in drylands as a consequence of climate change. We used 311 sites across a broad range of environmental conditions in Patagonian rangelands to evaluate how drought severity and temperature (abiotic factors) and vegetation structure (biotic factors) modulate the impact of a drought event on the annual integral of normalized difference vegetation index (NDVI-I), our surrogate of ecosystem functioning. We found that NDVI-I decreases were larger with both increasing drought severity and temperature. Plant species richness (SR) and shrub cover (SC) attenuated the effects of drought on NDVI-I. Grass cover did not affect the impacts of drought on NDVI-I. Our results suggest that warming and species loss, two important imprints of global environmental change, could increase the vulnerability of Patagonian ecosystems to drought. Therefore, maintaining SR through appropriate grazing management can attenuate the adverse effects of climate change on ecosystem functioning. PMID:25339654

  4. Hurricane Effects on Mangrove Canopies Observed from MODIS and SPOT Imagery

    CERN Document Server

    Parenti, Michael

    2014-01-01

    The effects of four hurricanes on protected mangroves in southwest Florida (Katrina and Wilma) and the Yucatan Peninsula (Emily and Dean) were assessed using paired sets of 20m multispectral SPOT and 16-day 500m MODIS images. The normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) were used to assess possible damage to and recovery of mangrove canopies associated with each storm event. The results revealed decreases in the NDVI and EVI of mangrove canopies consistent with storm effects, although the effects in South Florida and Sian Ka'an were highly variable. Hurricane Wilma produced a large decrease in NDVI and EVI although values recovered within a year, suggesting resilience to this storm. Rainfall associated with Hurricane Emily apparently increased mangrove photosynthetic activity owing to the location of landfall outside the study area, the small size of the wind field and the apparent lack of storm surge. MODIS NDVI time series revealed pronounced seasonality in mangrove ...

  5. ANALYSIS OF SPECTRAL CHARACTERISTICS AMONG DIFFERENT SENSORS BY USE OF SIMULATED RS IMAGES

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This research, by use of RS image-simulating method, simulated apparent reflectance images at sensor level and ground-reflectance images of SPOT-HRV,CBERS-CCD,Landsat-TM and NOAA14-AVHRR' s corresponding bands. These images were used to analyze sensor's differences caused by spectral sensitivity and atmospheric impacts. The differences were analyzed on Normalized Difference Vegetation Index(NDVI). The results showed that the differences of sensors' spectral characteristics cause changes of their NDVI and reflectance. When multiple sensors' data are applied to digital analysis, the error should be taken into account. Atmospheric effect makes NDVI smaller, and atn~pheric correction has the tendency of increasing NDVI values. The reflectance and their NDVIs of different sensors can be used to analyze the differences among sensor' s features. The spectral analysis method based on RS simulated images can provide a new way to design the spectral characteristics of new sensors.

  6. Využití metod a dat DPZ při tvorbě KPÚ

    OpenAIRE

    PINKAVOVÁ, Šárka

    2008-01-01

    This diploma thesis covers questions of remote sensing in relation to land adjustment. On water area is showm usage of the vegetation index NDVI and the Tasseled Cap transformation. Satellite images were processed in computer software ERDAS IMAGINE.

  7. Role of MODIS Vegetation Phenology Products in the ForWarn System for Monitoring of Forest Disturbances in the Conterminous United States

    Science.gov (United States)

    Spruce, J.; Hargrove, W. W.; Norman, S.; Gasser, J.; Smoot, J.; Kuper, P.

    2012-12-01

    This presentation discusses MODIS vegetation phenology products used in the ForWarn Early Warning System (EWS) tool for near real time regional forest disturbance detection and surveillance at regional to national scales. The ForWarn EWS is being developed by the USDA Forest Service NASA, ORNL, and USGS to aid federal and state forest health management activities. ForWarn employs multiple historical land surface phenology products that are derived from MODIS MOD13 Normalized Difference Vegetation Index (NDVI) data. The latter is temporally processed into phenology products with the Time Series Product Tool (TSPT) and the Phenological Parameter Estimation Tool (PPET) software produced at NASA Stennis Space Center. TSPT is used to effectively noise reduce, fuse, and void interpolate MODIS NDVI data. PPET employs TSPT-processed NDVI time series data as an input, outputting multiple vegetation phenology products at a 232 meter resolution for 2000 to 2011, including NDVI magnitude and day of year products for seven key points along the growing season (peak of growing season and the minima, 20%, and 80% of the peak NDVI for both the left and right side of growing season), cumulative NDVI integral products for the most active part of the growing season and sequentially across the growing season at 8 day intervals, and maximum value NDVI products composited at 24 day intervals in which each product date has 8 days of overlap between the previous and following product dates. MODIS NDVI phenology products are also used to compute nationwide near real time forest change products every 8 days. These include percent change in forest NDVI products that compare the current NDVI from USGS eMODIS products to historical MODIS MOD13 NDVI. For each date, three forest change products are produced using three different maximum value NDVI baselines (from the previous year, three previous years, and all previous years). All change products are output with a rainbow color table in which

  8. Prediction of vegetation anomalies to improve food security and water management in India

    Science.gov (United States)

    Asoka, Akarsh; Mishra, Vimal

    2015-07-01

    Prediction of vegetation anomalies at regional scales is essential for management of food and water resources. Forecast of vegetation anomalies at 1-3 months lead time can help in decision making. Here we show that normalized difference vegetation index (NDVI) along with other hydroclimatic variables (soil moisture and sea surface temperature) can be effectively used to predict vegetation anomalies in India. The spatiotemporal analysis of NDVI showed significant greening over the region during the period of 1982-2013. The root-zone soil moisture showed a positive correlation with NDVI, whereas the El Niño-Southern Oscillation index (Nino 3.4) is negatively correlated in most of the regions. We extended this relationship to develop a model to predict NDVI in 1 to 3 months lead time. The predicted vegetation anomalies compare well with observations, which can be effectively utilized in early warning and better planning in water resources and agricultural sectors in India.

  9. AVHRR Composites = Advanced Very High Resolution Radiometer U.S. Alaska: 1989 - Present

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Normalized Difference Vegetation Index (NDVI) Composites are produced from multiple Advanced Very High Resolution Radiometer (AVHRR) daily observations that have...

  10. Development of an unmanned agricultural robotics system for measuring crop conditions for precision aerial application

    Science.gov (United States)

    An Unmanned Agricultural Robotics System (UARS) is acquired, rebuilt with desired hardware, and operated in both classrooms and field. The UARS includes crop height sensor, crop canopy analyzer, normalized difference vegetative index (NDVI) sensor, multispectral camera, and hyperspectral radiometer...

  11. Assessing Land Degradation/Recovery in the African Sahel from Long-Term Earth Observation Based Primary Productivity and Precipitation Relationships

    DEFF Research Database (Denmark)

    Fensholt, Rasmus; Rasmussen, Kjeld; Kaspersen, Per Skougaard;

    2013-01-01

    be achieved by use of Earth Observation (EO) data. This paper demonstrates that the use of the standard EO-based proxy for ANPP, summed normalized difference vegetation index (NDVI) (National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) Global Inventory...... useless as a means of normalizing for the impact of annual precipitation on ANPP. By replacing ΣNDVI by a ‘small NDVI integral’, covering only the rainy season and counting only the increase of NDVI relative to some reference level, this problem is solved. Using this approach, RUE is calculated...... for the period 1982–2010. The result is that positive RUE-trends dominate in most of the Sahel, indicating that non-precipitation related land degradation is not a widespread phenomenon. Furthermore, it is argued that two preconditions need to be fulfilled in order to obtain meaningful results from the RUE...

  12. Improving Post-Hurricane Katrina Forest Management with MODIS Time Series Products

    Science.gov (United States)

    Lewis, Mark David; Spruce, Joseph; Evans, David; Anderson, Daniel

    2012-01-01

    Hurricane damage to forests can be severe, causing millions of dollars of timber damage and loss. To help mitigate loss, state agencies require information on location, intensity, and extent of damaged forests. NASA's MODerate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) time series data products offers a potential means for state agencies to monitor hurricane-induced forest damage and recovery across a broad region. In response, a project was conducted to produce and assess 250 meter forest disturbance and recovery maps for areas in southern Mississippi impacted by Hurricane Katrina. The products and capabilities from the project were compiled to aid work of the Mississippi Institute for Forest Inventory (MIFI). A series of NDVI change detection products were computed to assess hurricane induced damage and recovery. Hurricane-induced forest damage maps were derived by computing percent change between MODIS MOD13 16-day composited NDVI pre-hurricane "baseline" products (2003 and 2004) and post-hurricane NDVI products (2005). Recovery products were then computed in which post storm 2006, 2007, 2008 and 2009 NDVI data was each singularly compared to the historical baseline NDVI. All percent NDVI change considered the 16-day composite period of August 29 to September 13 for each year in the study. This provided percent change in the maximum NDVI for the 2 week period just after the hurricane event and for each subsequent anniversary through 2009, resulting in forest disturbance products for 2005 and recovery products for the following 4 years. These disturbance and recovery products were produced for the Mississippi Institute for Forest Inventory's (MIFI) Southeast Inventory District and also for the entire hurricane impact zone. MIFI forest inventory products were used as ground truth information for the project. Each NDVI percent change product was classified into 6 categories of forest disturbance intensity. Stand age

  13. Circumpolar Dynamics of Arctic Tundra Vegetation in Relation to Temperature Trends

    Science.gov (United States)

    Epstein, H. E.; Bhatt, U. S.; Raynolds, M. K.; Walker, D. A.; Reichle, L.

    2015-12-01

    Arctic tundra vegetation has generally exhibited a "greening" trend for at least the past three decades. However, these temporal trends in tundra vegetation are highly heterogeneous in space across different arctic regions, as well as showing variability over time. The factors controlling this variability are likely numerous with complex interactions, however, a first approach is to examine how vegetation dynamics relate to trends in temperature. We used a 32-year record (1982-2013) of the Normalized Difference Vegetation Index (NDVI) and Land Surface Temperatures from Advanced Very High Resolution Radiometer (AVHRR) sensors onboard NOAA satellites (GIMMS 3g dataset) to analyze observed changes in both aboveground tundra vegetation and surface temperatures. We divided the circumpolar dataset into two continental regions (North America and Eurasia), as well as by tundra subzone (A-E) sensu the Circumpolar Arctic Vegetation Map (CAVM). We 1) compared temporal trends in both MaxNDVI (peak values) and TI-NDVI (seasonally integrated values) with those of the Summer Warmth Index (SWI - sum of mean monthly temperatures > 0 °C); 2) assessed how the detrended interannual variabilities in NDVI compared to those of SWI; and 3) analyzed current and prior year SWI, as well as prior year NDVI, as controls on current year NDVI. Interannual coefficients of variation for SWI were 2.0 - 2.5 times greater than those for NDVI, and the temporal trendlines for NDVI were much "tighter" with greater r² values than those for SWI. Interannual variability in NDVI was greatest in the "Mid-Low" Arctic, whereas interannual variability in SWI was greatest in the most southern Arctic. Surprisingly, the observed relative rates of change in NDVI were greater than those of SWI for the warmer subzones for both North America and Eurasia. Finally, the change in NDVI from one year to the next was only weakly correlated with current year SWI. These results suggest that 1) there are clearly factors

  14. Interannual Variability in Dry Mixed-Grass Prairie Yield: A Comparison of MODIS, SPOT, and Field Measurements

    Directory of Open Access Journals (Sweden)

    Donald C. Wehlage

    2016-10-01

    Full Text Available Remote sensing is often used to assess rangeland condition and biophysical parameters across large areas. In particular, the relationship between the Normalized Difference Vegetation Index (NDVI and above-ground biomass can be used to assess rangeland primary productivity (seasonal carbon gain or above-ground biomass “yield”. We evaluated the NDVI–yield relationship for a southern Alberta prairie rangeland, using seasonal trends in NDVI and biomass during the 2009 and 2010 growing seasons, two years with contrasting rainfall regimes. The study compared harvested biomass and NDVI from field spectrometry to NDVI from three satellite platforms: the Aqua and Terra Moderate Resolution Imaging Spectroradiometer (MODIS and Système Pour l’Observation de la Terre (SPOT 4 and 5. Correlations between ground spectrometry and harvested biomass were also examined for each growing season. The contrasting precipitation patterns were easily captured with satellite NDVI, field NDVI and green biomass measurements. NDVI provided a proxy measure for green plant biomass, and was linearly related to the log of standing green biomass. NDVI phenology clearly detected the green biomass increase at the beginning of each growing season and the subsequent decrease in green biomass at the end of each growing season due to senescence. NDVI–biomass regressions evolved over each growing season due to end-of-season senescence and carryover of dead biomass to the following year. Consequently, mid-summer measurements yielded the strongest correlation (R2 = 0.97 between NDVI and green biomass, particularly when the data were spatially aggregated to better match the satellite sampling scale. Of the three satellite platforms (MODIS Aqua, MODIS Terra, and SPOT, Terra yielded the best agreement with ground-measured NDVI, and SPOT yielded the weakest relationship. When used properly, NDVI from satellite remote sensing can accurately estimate peak-season productivity and

  15. Climatic change controls productivity variation in global grasslands

    OpenAIRE

    Qingzhu Gao; Wenquan Zhu; Schwartz, Mark W.; Hasbagan Ganjurjav; Yunfan Wan; Xiaobo Qin; Xin Ma; Williamson, Matthew A.; Yue Li

    2016-01-01

    Detection and identification of the impacts of climate change on ecosystems have been core issues in climate change research in recent years. In this study, we compared average annual values of the normalized difference vegetation index (NDVI) with theoretical net primary productivity (NPP) values based on temperature and precipitation to determine the effect of historic climate change on global grassland productivity from 1982 to 2011. Comparison of trends in actual productivity (NDVI) with ...

  16. A Spatio-temporal disaggregation method to derive time series of Normalized Difference Vegetation Index and Land Surface Temperature at fine spatial resolution

    Science.gov (United States)

    Bindhu, V. M.; Narasimhan, B.

    2014-12-01

    Estimation of evapotranspiration (ET) from remote sensing based energy balance models have evolved as a promising tool in the field of water resources management. Performance of energy balance models and reliability of ET estimates is decided by the availability of remote sensing data at high spatial and temporal resolutions. However huge tradeoff in the spatial and temporal resolution of satellite images act as major constraints in deriving ET at fine spatial and temporal resolution using remote sensing based energy balance models. Hence a need exists to derive finer resolution data from the available coarse resolution imagery, which could be applied to deliver ET estimates at scales to the range of individual fields. The current study employed a spatio-temporal disaggregation method to derive fine spatial resolution (60 m) images of NDVI by integrating the information in terms of crop phenology derived from time series of MODIS NDVI composites with fine resolution NDVI derived from a single AWiFS data acquired during the season. The disaggregated images of NDVI at fine resolution were used to disaggregate MODIS LST data at 960 m resolution to the scale of Landsat LST data at 60 m resolution. The robustness of the algorithm was verified by comparison of the disaggregated NDVI and LST with concurrent NDVI and LST images derived from Landsat ETM+. The results showed that disaggregated NDVI and LST images compared well with the concurrent NDVI and LST derived from ETM+ at fine resolution with a high Nash Sutcliffe Efficiency and low Root Mean Square Error. The proposed disaggregation method proves promising in generating time series of ET at fine resolution for effective water management.

  17. Growing Degree Vegetation Production Index (GDVPI): A Novel and Data-Driven Approach to Delimit Season Cycles

    Science.gov (United States)

    Graham, W. D.; Spruce, J.; Ross, K. W.; Gasser, J.; Grulke, N.

    2014-12-01

    Growing Degree Vegetation Production Index (GDVPI) is a parametric approach to delimiting vegetation seasonal growth and decline cycles using incremental growing degree days (GDD), and NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) 8-day composite cumulative integral data. We obtain a specific location's daily minimum and maximum temperatures from the nearest National Oceanic and Atmospheric Administration (NOAA) weather stations posted on the National Climate Data Center (NCDC) Climate Data Online (CDO) archive and compute GDD. The date range for this study is January 1, 2000 through December 31, 2012. We employ a novel process, a repeating logistic product (RLP), to compensate for short-term weather variability and data drops from the recording stations and fit a curve to the median daily GDD values, adjusting for asymmetry, amplitude, and phase shift that minimize the sum of squared errors when comparing the observed and predicted GDD. The resulting curve, here referred to as the surrogate GDD, is the time-temperature phasing parameter used to convert Cartesian NDVI values into polar coordinate pairs, multiplying the NDVI values as the radial by the cosine and sine of the surrogate GDD as the angular. Depending on the vegetation type and the original NDVI curve, the polar NDVI curve may be nearly circular, kidney-shaped, or pear-shaped in the case of conifers, deciduous, or agriculture, respectively. We examine the points of tangency about the polar coordinate NDVI curve, identifying values of 1, 0, -1, or infinity, as each of these represent natural inflection points. Lines connecting the origin to each tangent point illustrate and quantify the parametrically segmentation of the growing season based on the GDD and NDVI ostensible dependency. Furthermore, the area contained by each segment represents the apparent vegetation production. A particular benefit is that the inflection points are determined

  18. Trends in Global Vegetation Activity and Climatic Drivers Indicate a Decoupled Response to Climate Change.

    Directory of Open Access Journals (Sweden)

    Antonius G T Schut

    Full Text Available Detailed understanding of a possible decoupling between climatic drivers of plant productivity and the response of ecosystems vegetation is required. We compared trends in six NDVI metrics (1982-2010 derived from the GIMMS3g dataset with modelled biomass productivity and assessed uncertainty in trend estimates. Annual total biomass weight (TBW was calculated with the LINPAC model. Trends were determined using a simple linear regression, a Thiel-Sen medium slope and a piecewise regression (PWR with two segments. Values of NDVI metrics were related to Net Primary Production (MODIS-NPP and TBW per biome and land-use type. The simple linear and Thiel-Sen trends did not differ much whereas PWR increased the fraction of explained variation, depending on the NDVI metric considered. A positive trend in TBW indicating more favorable climatic conditions was found for 24% of pixels on land, and for 5% a negative trend. A decoupled trend, indicating positive TBW trends and monotonic negative or segmented and negative NDVI trends, was observed for 17-36% of all productive areas depending on the NDVI metric used. For only 1-2% of all pixels in productive areas, a diverging and greening trend was found despite a strong negative trend in TBW. The choice of NDVI metric used strongly affected outcomes on regional scales and differences in the fraction of explained variation in MODIS-NPP between biomes were large, and a combination of NDVI metrics is recommended for global studies. We have found an increasing difference between trends in climatic drivers and observed NDVI for large parts of the globe. Our findings suggest that future scenarios must consider impacts of constraints on plant growth such as extremes in weather and nutrient availability to predict changes in NPP and CO2 sequestration capacity.

  19. Monitoring the Natural Factors Influence on Vegetation Development by Using Moderate-Resolution Imaging Spectroradiometer (Modis) Images with OBIA Method in Uzbekistan

    OpenAIRE

    Sh.B., Akmalov; J. V., Gerts; D. B., Omonov

    2016-01-01

    In the study, natural and anthropogenic effects on vegetation are discussed and degree of their influence are shown in Syrdarya province (Uzbekistan). A statistical model of integrated meteo-and hydro-remote sensing data was developed. By the use of this model the correlation of various natural factors in vegetation period was analyzed and scale-dependency of spatial relationships between NDVI and three climatic factors were investigated. MODIS NDVI images have been used for the study area an...

  20. Responses of Grassland and Forest to Temperature and Precipitation Changes in Northeast China

    Institute of Scientific and Technical Information of China (English)

    PENG Jing; DONG Wenjie; YUAN Wenping; ZHANG Yong

    2012-01-01

    Using the Normalized Difference Vegetation Index (NDVI) as an indicator of vegetation growth,we explored the characteristics and differences in the response to drought of five vegetation biomes in Northeast China,including typical steppe,desert steppe,meadow steppe,deciduous coniferous forest and deciduous broad-leaved forest during the period 1982 2009.The results indicate that growing season precipitation may be the primary vegetation growth-limiting factor in grasslands.More than 70% of the temporal variations in NDVI can be explained by the amount of precipitation during the growing season in typical and desert steppes.During the same period,the mean temperature in the growing season could explain nearly 43% of the variations in the mean growing season NDVI and is therefore a dominant growth-limiting factor for forest ecosystems.Therefore,the NDVI trends differ largely due to differences in the vegetation growth-limiting factors of the different vegetation biomes.The NDVI responses to droughts vary in magnitude and direction and depend on the drought-affected areas of the five vegetation types.Specifically,the changes in NDVI are consistent with the variations in precipitation for grassland ecosystems.A lack of precipitation resulted in decreases in NDVI,thereby reducing vegetation growth in these regions.Conversely,increasing precipitation decreased the NDVI of forest ecosystems.The results also suggest that grasslands under arid and semi-arid environments may be more sensitive to drought than forests under humid environments.Among grassland ecosystems,desert steppe was most sensitive to drought,followed by typical steppe; meadow steppe was the least sensitive.

  1. [Change trend of vegetation cover in Beijing metropolitan region before and after the 2008 Olympics].

    Science.gov (United States)

    Sun, Xiao-Peng; Wang, Tian-Ming; Wu, Jian-Guo; Ge, Jian-Ping

    2012-11-01

    The MODIS-NDVI data from 2000 to 2009 were used to analyze the temporal dynamics and spatial distribution of the vegetation cover in the Beijing metropolitan region before and after the 2008 Olympics. During the study period, the proportion of the significantly increased pixels of NDVI occupied 20.7% while that of the significantly decreased pixels only occupied 4.1% of the total, and the decreasing rate of the NDVI was slightly faster than the increasing rate. The significant changes of the NDVI were mainly concentrated in the low altitude and small slope areas with intensive human activities, and two bands were formed in the plain area, i. e., the vegetation increasing band within the 5th Ring Road and the vegetation decreasing band from the 5th Ring Road to the outside areas of the 6th Ring Road. In the areas with significant vegetation change, there was an obvious transition between the high and low NDVI sections but less change in the medium NDVI section, mainly due to the conversion of land cover type. In the Capital function core area and ecological conservation zones, vegetation change represented a positive trend; while in the urban function expansion area and urban development area, vegetation change had the dual characteristics of both positive and negative trends. A series of ecological engineering projects during the preparatory period of the 2008 Olympics was the main cause of the vegetation increase in the study area.

  2. Elevation-Dependent Vegetation Greening of the Yarlung Zangbo River Basin in the Southern Tibetan Plateau, 1999–2013

    Directory of Open Access Journals (Sweden)

    Haidong Li

    2015-12-01

    Full Text Available The Yarlung Zangbo River basin is an important alley to transport moisture from the Indian Ocean to the inner Tibetan Plateau. With a wide range of elevations from 147 m to over 7000 m above sea level (a.s.l., ecosystems respond differently to climate change at various elevations. However, the pattern of elevation-dependent vegetation change and how it responds to recent warming have been rarely reported. Here, we investigated the pattern of vegetation greening at different elevations in this river basin using SPOT normalized difference vegetation index (NDVI data during 1999–2013, and examined its relationship with elevation-dependent changes in temperature and precipitation. The annual NDVI has increased by 8.83% from 1999 to 2013. In particular, the NDVI increased more apparently at lower elevations, but remained relatively stable or even decreased at high elevations. It seems that rising temperature has driven the basin-wide vegetation greening, but the greening rate is in contrast to the pattern of elevation-dependent warming (EDW with more significant temperature increase at higher elevations. It appears that decreasing precipitation does not reverse the overall increasing trend in NDVI, but relatively limited precipitation (<500 mm may constrain the NDVI increases, causing apparently stable or even decreased NDVI at higher elevations (>4000 m.

  3. 植被和气候对阿拉斯加和加拿大北部北极苔原地区多年冻土活动层厚度的影响%Role of Vegetation and Climate in Permafrost Active Layer Depth in Arctic Tundra of Northern Alaska and Canada

    Institute of Scientific and Technical Information of China (English)

    Alexia M. Kelley; Howard E. Epstein; Donald A. Walker

    2004-01-01

    The active layer is the top layer of permafrost soils that thaws during the summer season due to increased ambient temperatures and solar radiation inputs. This layer is important because almost all biological activity takes place there luring the summer. The depth of active layer thaw is influenced by climatic conditions. Vegetation has also been found to have a strong impact on active layer thaw, because it can intercept incoming radiation, thereby insulating the soil from ambient conditions. In order to look at the role of vegetation and climate on active layer thaw, we measured thaw depth and the Normalized Difference Vegetation Index (NDVI; a proxy for aboveground plant biomass) along a latitudinal temperature gradient in arctic Alaska and Canada. At each site several measurements of thaw and NDVI were taken in areas with high amounts of vegetation and areas with little to no vegetation. Results show that the warmest regions, which had the greatest levels of NDVI, had relatively shallow thaw depths, and the coldest regions, which had the lowest levels of NDVI, also had relatively shallow thaw depths. The intermediate regions, which had moderate levels of NDVI and air temperature, had the greatest depth of thaw. These results indicate that temperature and vegetation interact to control the depth of the active layer across a range of arctic ecosystems. By developing a relationship to explain thaw depth through NDVI and temperature or latitude, the possibility exists to extrapolate thaw depth over large scales via remote sensing applications.

  4. Seasonal relationship between normalized difference vegetation index and abundance of the Phlebotomus kala-azar vector in an endemic focus in Bihar, India

    Directory of Open Access Journals (Sweden)

    Gouri S. Bhunia

    2012-11-01

    Full Text Available Remote sensing was applied for the collection of spatio-temporal data to increase our understanding of the potential distribution of the kala-azar vector Phlebotomus argentipes in endemic areas of the Vaishali district of Bihar, India. We produced monthly distribution maps of the normalized difference vegetation index (NDVI based on data from the thematic mapper (TM sensor onboard the Landsat-5 satellite. Minimum, maximum and mean NDVI values were computed for each month and compared with the concurrent incidence of kala-azar and the vector density. Maximum and mean NDVI values (R2 = 0.55 and R2 = 0.60, respectively, as well as the season likelihood ratio (X2 = 17.51; P <0.001, were found to be strongly associated with kala-azar, while the correlation with between minimum NDVI values and kala-azar was weak (R2 = 0.25. Additionally, a strong association was found between the mean and maximum NDVI values with seasonal vector abundance (R2 = 0.60 and R2 = 0.55, respectively but there was only a marginal association between minimum NDVI value and the spatial distribution of kala-azar vis-à-vis P. argentipes density.

  5. Impacts of Sloping Land Conversion Program on the vegetation in loess hilly and gully area of northern Shaanxi

    Institute of Scientific and Technical Information of China (English)

    Ma Junfei; Lu Changhe; Yu Bohua

    2009-01-01

    Aiming at alleviating the serious soil erosion,the Chinese government initiated the Sloping Land Con.version Program (SLCP) in 1999.Now,after 8 years of project implementation,the ecological recovery effects of the SLCP have become the hot issue of academic circle.This paper,taking the loess hdl and gully area of northern Shaanxi as an example,presents a methodology for assessing the vegetation restoration effect of SLCP with normalized difference vegetation index (NDVI).The key components include calculation of the Growing Season NDVI (GSNDVI),and estimation of the NVDI change induced by climate and SLCP,re,wectively.Based on the method,the NDVI change between 2000 and 2006 was obtained using the GSNDVI that excluded the noise from snow and ice.Afier the part of total NDVI change caused by climate variation was estimated using empiric formulae,we obtained the part induced by human factors,i.e.the SLCP.The human induced part of NDVI change was considered as an approximation indicating the effect of the SLCP on the vegetation.Finally,we analyzed the NDVI change characters of the whole study area,different slope lands and different land use types by spatial statistics method Results show that the vegetation condition is significantly improved by the SLCP,particularly land types that directly involved in the SLCP,such as steeply slope farmlands,degraded grasslands,etc.

  6. Poverty, health and satellite-derived vegetation indices: their inter-spatial relationship in West Africa

    Science.gov (United States)

    Sedda, Luigi; Tatem, Andrew J.; Morley, David W.; Atkinson, Peter M.; Wardrop, Nicola A.; Pezzulo, Carla; Sorichetta, Alessandro; Kuleszo, Joanna; Rogers, David J.

    2015-01-01

    Background Previous analyses have shown the individual correlations between poverty, health and satellite-derived vegetation indices such as the normalized difference vegetation index (NDVI). However, generally these analyses did not explore the statistical interconnections between poverty, health outcomes and NDVI. Methods In this research aspatial methods (principal component analysis) and spatial models (variography, factorial kriging and cokriging) were applied to investigate the correlations and spatial relationships between intensity of poverty, health (expressed as child mortality and undernutrition), and NDVI for a large area of West Africa. Results This research showed that the intensity of poverty (and hence child mortality and nutrition) varies inversely with NDVI. From the spatial point-of-view, similarities in the spatial variation of intensity of poverty and NDVI were found. Conclusions These results highlight the utility of satellite-based metrics for poverty models including health and ecological components and, in general for large scale analysis, estimation and optimisation of multidimensional poverty metrics. However, it also stresses the need for further studies on the causes of the association between NDVI, health and poverty. Once these relationships are confirmed and better understood, the presence of this ecological component in poverty metrics has the potential to facilitate the analysis of the impacts of climate change on the rural populations afflicted by poverty and child mortality. PMID:25733559

  7. Analyzing millet price regimes and market performance in Niger with remote sensing data

    Science.gov (United States)

    Essam, Timothy Michael

    This dissertation concerns the analysis of staple food prices and market performance in Niger using remotely sensed vegetation indices in the form of normalized differenced vegetation index (NDVI). By exploiting the link between weather-related vegetation production conditions, which serve as a proxy for spatially explicit millet yields and thus millet availability, this study analyzes the potential causal links between NDVI outcomes and millet market performance and presents an empirical approach for predicting changes in market performance based on NDVI outcomes. Overall, the thesis finds that inter-market price spreads and levels of market integration can be reasonably explained by deviations in vegetation index outcomes from the growing season. Negative (positive) NDVI shocks are associated with better (worse) than expected market performance as measured by converging inter-market price spreads. As the number of markets affected by negatively abnormal vegetation production conditions in the same month of the growing season increases, inter-market price dispersion declines. Positive NDVI shocks, however, do not mirror this pattern in terms of the magnitude of inter-market price divergence. Market integration is also found to be linked to vegetation index outcomes as below (above) average NDVI outcomes result in more integrated (segmented) markets. Climate change and food security policies and interventions should be guided by these findings and account for dynamic relationships among market structures and vegetation production outcomes.

  8. Global GPP based on Plant Functional Types

    Science.gov (United States)

    Veroustraete, Frank; Balzarolo, Manuela

    2016-04-01

    Vegetation variables like Gross Primary productivity (GPP) and the Normalized Difference Vegetation Index (NDVI) are key variables in vegetation carbon exchange studies. Field measurements of the NDVI are time consuming due to landscape heterogeneity across time. Typically a sampling protocol adopted during field campaigns is based on the VALERI protocol in that case toe estimate LAI. Field campaign GPP or NDVI measurements can be scaled up to using in-situ FLUXNET radiation raster maps. Regression analysis can then be applied to construct transfer functions for the determination of GPP raster maps raster imagery from Normalized Difference Vegetation Index (NDVI) raster maps derived from in-situ FLUXNET radiation raster maps. Subsequently, in the VALERI approach the scaling up of raster maps is performed by aggregation of high resolution in-situ FLUXNET radiation raster maps data into high resolution raster maps and subsequently aggregating these to 1x1 km MODIS NDVI raster maps by calculating average NDVI values for the low resolution data. The up-scaled 1x1 km pixels are then used to validate the MODIS GPP and NVI products. Hence up scaling based on in-situ FLUXNET radiation measurements are not a luxury for large and heterogeneous sites. Therefore this paper tackles the problem of up scaling using in-situ FLUXNET radiation measurements. Key Words: FLUXNET, GPP, Plant Functional Types, Up-scaling

  9. Estabilidade e instabilidade sistêmica: as orações de tempo sob uma perspectiva diacrônica

    Directory of Open Access Journals (Sweden)

    Maria Luíza Braga

    2014-03-01

    Full Text Available Neste artigo, focalizamos as orações complexas de tempo sob uma perspectiva em que se conjugam as dimensões diacrônica e sincrônica. Analisamos o uso dos diferentes conectores que expressam a relação de tempo, ao longo do período compreendido entre os séculos 18 a 21, buscando identificar a estabilidade / instabilidade nas propriedades a eles associadas. O estudo permite mostrar a estabilidade no conjunto de conectores utilizado nesse período da história, destacando-se, sobretudo, a maior frequência de quando e enquanto. Além disso, trazemos evidências quanto à necessidade de considerar as subespecificações semânticas codificadas pelas orações temporais. As orações temporais que codificam superposição e coextensividade temporal apresentam comportamento distinto daquelas que expressam sequencialidade.

  10. As categorias aspectuais e a formação de construções com o Verbo leve dar

    Directory of Open Access Journals (Sweden)

    Ana Paula Scher

    2013-11-01

    Full Text Available Este trabalho revela que, embora bastante produtiva, a ocorrência de sentenças com a forma "dar uma Xada em Y", no português do Brasil, depende de algumas restrições semânticas bastante sistemáticas. Através da observação de um conjunto de dados baseados na intuição de vários falantes do português brasileiro, descreve-se, em termos dos traços temporais que compõem as categorias aspectuais, a interpretação semântica que se pode atribuir a sentenças como essas, em que uma nominalização em -ada ocorre associada ao verbo leve dar. Ao final, sugere-se que a formação de tais sentenças depende da presença ou não de alguns dos traços temporais intrínsecos às eventualidades denotadas pelos predicados dos quais derivam.

  11. Hipotaxe e Gramaticalização: uma Análise das Construções de Tempo e de Condição

    Directory of Open Access Journals (Sweden)

    NEVES Maria Helena de Moura

    1998-01-01

    Full Text Available O trabalho estuda construções de orações hipotáticas temporais e construções de orações hipotáticas condicionais, com a finalidade de investigar o grau de gramaticalização que se verifica nesses dois tipos de enunciados. A hipótese é que quanto maior a integração da oração hipotática à nuclear, maior o grau de gramaticalização. Essa maior integração foi medida segundo três grupos de fatores, e os resultados mostraram que, em duas das variáveis avaliadas, as orações condicionais são as mais integradas a seu núcleo, mas, em outra ordem de avaliação, as orações temporais são as mais integradas. Dentro da base funcionalista em que o trabalho se move, esses resultados podem ser interpretados segundo o princípio da existência de competição de motivações no jogo da linguagem, entendendo-se que cada enunciado que se produz é o resultado do equilíbrio dessas pressões.

  12. Ressonância magnética na esquizofrenia: um estudo morfométrico

    Directory of Open Access Journals (Sweden)

    Castro Cláudio Campi de

    2001-01-01

    Full Text Available Trinta e três pacientes esquizofrênicos crônicos e 21 indivíduos normais foram submetidos a exames de ressonância magnética em aparelho de 1,5 T, sendo realizadas imagens ponderadas em T2 nos planos axial e coronal. Foram analisados, por métodos morfométricos semi-automáticos, os volumes intracraniano, supratentorial, infratentorial, do líquido cefalorraquiano total, ventricular e subaracnóide e do encéfalo. Foram ainda medidos os volumes do complexo amígdala-hipocampo, córtex do giro para-hipocampal, putâmen, globo pálido, lobo temporal e substâncias branca e cinzenta do lobo temporal. Foram calculados os volumes relativos dessas estruturas, corrigidos pelo volume intracraniano. As alterações mais relevantes observadas nos esquizofrênicos, em comparação com os controles, foram de redução do volume relativo do encéfalo, aumento do volume relativo do líquido cefalorraquiano ventricular, subaracnóide e total. Foi ainda observada redução do volume dos complexos amígdala-hipocampo, dos lobos temporais e da substância branca dos lobos temporais, e aumento de volume dos putâmens.

  13. Seasonality of Air-sea-ice-land Variables for Arctic Tundra in Northern Eurasia and North America

    Science.gov (United States)

    Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Steele, M.; Epstein, H.; Jia, G.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2009-12-01

    The strength of tundra productivity trends as measured by the annual maximum Normalized Difference Vegetation Index (MaxNDVI) and time integrated NDVI (TI-NDVI) vary around the Arctic over the 1982-2008 period. Our analysis suggests that the timing of terrestrial vegetation growth is connected to seasonal patterns of sea-ice concentrations, ocean temperatures and land surface temperatures. This study used SSMI estimates of sea ice concentration, based on a bootstrap algorithm and AVHRR radiometric surface temperature. Summer Warmth Index (SWI) was calculated as the sum from May to August of the degree months above freezing of surface temperature at each pixel and is an accepted measure of plant growth potential. The Normalized Difference Vegetation Index (NDVI) represents vegetation greenness and has been used extensively to monitor changes in the Arctic. The albedo of green plants varies with solar radiation wavelength, which is the basis for the NDVI index. The analysis was conducted within 50 km of the Arctic coastline to focus on the region of maximum maritime influence. Time series of regional sea-ice concentration, SWI and NDVI were constructed for the 50-km width domains for the Pan-Arctic, North America, Eurasia and Arctic subregions. Standard climate analysis techniques were applied to the regional time series to investigate the seasonality of sea ice, NDVI and SWI. MaxNDVI has increased in the 50-km land domain contiguous to the Beaufort Sea by 17% since 1982, whereas it has only increased by 3% in the coastal Kara Sea region. Analysis of semimonthly MaxNDVI indicates that the vegetation greens up more rapidly in the spring in the Beaufort than the W. Kara and the Kara has slightly higher NDVI in the fall. The climatological weekly sea ice concentrations in 50-km coastal domain displays an earlier breakup in the Beaufort and a later freeze-up in the Kara Sea area. Regional differences in the seasonal cycle can in part explain the spatially varied trends

  14. [Spatial and Temporal Variations in Spectrum-Derived Vegetation Growth Trend in Qinghai-Tibetan Plateau from 1982 to 2014].

    Science.gov (United States)

    Wang, Zhi-wei; Wu, Xiao-dong; Yue, Guang-yang; Zhao, Lin; Wang, Qian; Nan, Zhuo-tong; Qin, Yu; Wu, Tong-hua; Shi, Jian-zong; Zou, De-fu

    2016-02-01

    Recently considerable researches have focused on monitoring vegetation changes because of its important role in regula- ting the terrestrial carbon cycle and the climate system. There were the largest areas with high-altitudes in the Qinghai-Tibet Plateau (QTP), which is often referred to as the third pole of the world. And vegetation in this region is significantly sensitive to the global warming. Meanwhile NDVI dataset was one of the most useful tools to monitor the vegetation activity with high spatial and temporal resolution, which is a normalized transform of the near-infrared radiation (NIR) to red reflectance ratio. Therefore, an extended GIMMS NDVI dataset from 1982-2006 to 1982-2014 was presented using a unary linear regression by MODIS dataset from 2000 to 2014 in QTP. Compared with previous researches, the accuracy of the extended NDVI dataset was improved again with consideration the residuals derived from scale transformation. So the model of extend NDVI dataset could be a new method to integrate different NDVI products. With the extended NDVI dataset, we found that in growing season there was a statistically significant increase (0.000 4 yr⁻¹, r² = 0.585 9, p temperature and precipitation was used to explore the reason of vegetation changed. Although the trends of them are both increased, the correlation between NDVI and temperature is higher than precipitation in vegetation grow- ing season, spring, summer and autumn. Furthermore, there is significant spatial heterogeneity of the changing trends for ND- VI, temperature and precipitation at Qinghai-Tibet Plateau scale. PMID:27209752

  15. Development of regional wheat VI-LAI models using Resourcesat-1 AWiFS data

    Indian Academy of Sciences (India)

    Sasmita Chaurasia; R Nigam; B K Bhattacharya; V N Sridhar; K Mallick; S P Vyas; N K Patel; J Mukherjee; Chander Shekhar; Dhiraj Kumar; K R P Singh; G D Bairagi; N L Purohit; J S Parihar

    2011-12-01

    The time of forcing of spatial LAI to crop models at single or multiple stages is important to simulate crop biomass and yield in varying agro-climatic conditions and scales. The high temporal resolution (5-day) by Advanced Wide Field Sensor (AWiFS) on-board Resourcesat-1 Satellite IRS-P6 with 56 m spatial resolution and large swath (740 km) has substantially increased the availability of regional clear sky optical remote sensing data. The present study aimed at developing empirical vegetation index VI-LAI models for wheat using AWiFS optical data in four bands and in-situ measurements sampled over five different agro-climatic regions (ACRs) during 2005–2006 followed by validation during 2006–2007. While nonlinear relations exist for all the three normalized indices such as normalized difference vegetation index (NDVI), normalized difference water index (NDWI) and Green NDVI, linear relation was the best fit for ratio vegetation index (RVI). Both NDVI and RVI models generally showed better correlation ranges (0.65–0.84 for NDVI and 0.37–0.76 for RVI) than other indices. The common NDVI-LAI model was found to produce lower root mean square errors (RMSE) between 0.5 and 1.1 from pooled model than those between 0.5 and 1.32 from regional models. The rate of substantial increase in errors from NDVILAI model (RMSE of modelled LAI: 0.85 to 1.28) as compared to RVI-LAI model (RMSE of modeled LAI: 1.12 to 1.17) at LAI greater than 3, than below 3 revealed the early saturation of NDVI than RVI. It is therefore recommended that LAI estimates can be used to force crop simulation model up to early vegetative stage based on NDVI and maximum vegetative to reproductive stages based on RVI.

  16. Changes in Growing Season Vegetation and Their Associated Driving Forces in China during 2001–2012

    Directory of Open Access Journals (Sweden)

    Xianfeng Liu

    2015-11-01

    Full Text Available In recent decades, the monitoring of vegetation dynamics has become crucial because of its important role in terrestrial ecosystems. In this study, a satellite-derived normalized difference vegetation index (NDVI was combined with climate factors to explore the spatiotemporal patterns of vegetation change during the growing season, as well as their driving forces in China from 2001 to 2012. Our results showed that the growing season NDVI increased continuously during 2001–2012, with a linear trend of 1.4%/10 years (p < 0.01. The NDVI in north China mainly exhibited an increasing spatial trend, but this trend was generally decreasing in south China. The vegetation dynamics were mainly at a moderate intensity level in both the increasing and decreasing areas. The significantly increasing trend in the NDVI for arid and semi-arid areas of northwest China was attributed mainly to an increasing trend in the NDVI during the spring, whereas that for the north and northeast of China was due to an increasing trend in the NDVI during the summer and autumn. Different vegetation types exhibited great variation in their trends, where the grass-forb community had the highest linear trend of 2%/10 years (p < 0.05, followed by meadow, and needle-leaf forest with the lowest increasing trend, i.e., a linear trend of 0.3%/10 years. Our results also suggested that the cumulative precipitation during the growing season had a dominant effect on the vegetation dynamics compared with temperature for all six vegetation types. In addition, the response of different vegetation types to climate variability exhibited considerable differences. In terms of anthropological activity, our statistical analyses showed that there was a strong correlation between the cumulative afforestation area and NDVI during the study period, especially in a pilot region for ecological restoration, thereby suggesting the important role of ecological restoration programs in ecological recovery

  17. The role of seasonality and large-scale climate drivers in recent Pan-Arctic tundra vegetation variability and change

    Science.gov (United States)

    Bhatt, U. S.; Walker, D. A.; Bieniek, P. A.; Raynolds, M. K.; Comiso, J. C.; Pinzon, J.; Tucker, C. J.

    2011-12-01

    An increase of Pan-Arctic tundra vegetation greenness has been documented using the remotely sensed Normalized Difference Vegetation Index (NDVI) and a coherent variability between NDVI, springtime coastal sea ice and land surface temperatures has been shown. The goal of this paper is to understand the forcing factors of this change and variability better through an analysis of the seasonality of these remotely sensed variables as well as long-term climate data sets. This study uses remotely sensed submonthly 25-km sea ice concentration, surface temperature, and NDVI from 1982 to 2010. The NDVI3g data has been corrected for biases in the spring and fall. Standard climate data (station, reanalysis, and model data) and ground observations are also examined. For overall trends, we find that summer time open water area has increased most in the Beaufort, and Siberian Seas. The seasonality of SWI trends display distinct heterogeneity across the Arctic, with maximum warming in August for most regions (Figure 1). The monthly time integrated NDVI trends display the largest positive values for most of the Arctic in July, with the exception of the E. Bering and Kara regions, which show declines during most months (Figure 2). The largest magnitude increases in Max-NDVI tend to be in subzones that are inland, particularly in the Beaufort and Chukchi regions. NDVI has increased more during spring in Eurasia and more during peak vegetation activity (July) over North America. The analysis suggests that local atmospheric circulation as well as other local factors likely plays an important role in vegetation productivity.

  18. Evidences of delayed size recovery in Araucaria angustifolia populations after post-glacial colonization of highlands in Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Valdir M. Stefenon

    2008-09-01

    Full Text Available Up to date, little is known about the relationship between historical demography and the current genetic structure of A. Angus As a first effort towards overcoming this lack, microsatellite data scored in six populations and isozyme allele frequencies published for 11 natural stands of this species were analysed in order to assess molecular signatures of populations' demographic history. Signatures of genetic bottlenecks were captured in all analysed populations of southeastern Brazil. Among southern populations, signatures of small effective population size were observed in only three out of 13 populations. Southern populations likely experienced faster recovery of population size after migration onto highlands. Accordingly, current genetic diversity of the southern populations gives evidence of fast population size recovery. In general, demographic history of A. Angusmatches climatic dynamics of southern and southeastern Brazil during the Pleistocene and Holocene. Palynological records and reconstruction of the past climatic dynamics of southeastern and southern Brazil support the hypothesis of different population size recovery dynamics for populations from these regions.Até o momento, pouco se conhece sobre a relação entre história demográfica e a presente estrutura genética da A. Angus Como uma primeira tentativa em transpor esta deficiência, dados de microssatélites coletados em seis populações e freqüências alélicas de isoenzimas publicadas para 11 populações naturais desta espécie foram analisadas com o objetivo de acessar assinaturas moleculares da história demográfica populacional. Assinaturas de gargalos genéticos foram capturadas em todas as populações analisadas provenientes do Sudeste do Brasil. Entre as populações do Sul, assinaturas de pequeno tamanho populacional efetivo foram observadas em somente três entre 13 populações. Populações do Sul provavelmente apresentaram uma rápida recuperação do

  19. Directory of Open Access Journals (Sweden)

    Ana Paula Madeira Di Beneditto

    2013-03-01

    Full Text Available This study applies total mercury (THg concentration and stable isotope signature (δ15N and δ13C to evaluate the trophic status and feeding ground of Trichiurus lepturus during its ontogeny in northern Rio de Janeiro, south-eastern Brazil. The trophic position of T. lepturus is detected well by THg and δ15N as the sub-adult planktivorous specimens are distinct from the adult carnivorous specimens. The δ13C signatures suggest a feeding ground associated with marine coastal waters that are shared by fish in different ontogenetic phases. The diet tracers indicated that the fish feeding habits do not vary along seasons of the year, probably reflecting the prey availability in the study area. This fish has economic importance and the concentration of THg was compared to World Health Organization limit, showing that the adult specimens of T. lepturus are very close to the tolerable limit for safe regular ingestion.Este estudo utilizou a concentração de mercúrio total (THg e a assinatura isotópica (δ15N e δ13C para avaliar a posição trófica e a área de alimentação de Trichiurus lepturus durante sua ontogenia no norte do Rio de Janeiro, sudeste do Brasil. A posição trófica de T. lepturus foi bem detectada pelo THg e δ15N com os espécimes sub-adultos planctívoros distintos dos espécimes adultos carnívoros. As assinaturas de δ13C sugerem uma área de alimentação associada a águas marinhas costeiras que são compartilhadas por peixes em diferentes fases ontogenéticas. Os traçadores de dieta indicaram que os hábitos alimentares desse peixe não variam ao longo das estações do ano, refletindo provavelmente a disponibilidade de presas na área de estudo. Esse peixe tem importância econômica e a concentração de THg foi comparada com o limite estabelecido pela Organização Mundial de Saúde, demonstrando que os espécimes adultos de T. lepturus estão bem próximos do limite tolerável para uma ingestão regular segura.

  20. Estimativa do potencial produtivo em trigo utilizando sensor óptico ativo para adubação nitrogenada em taxa variável Wheat yield potential estimation using active optical sensor for site-specific nitrogen fertilization

    Directory of Open Access Journals (Sweden)

    Christian Bredemeier

    2013-01-01

    Full Text Available A adubação nitrogenada em trigo é baseada no potencial produtivo da cultura, teor de matéria orgânica do solo e cultura antecessora. A definição do potencial produtivo é complexa, pois este varia com as condições meteorológicas de cada ano específico. O objetivo deste trabalho foi avaliar a relação entre o índice de vegetação por diferença normalizada (NDVI, medido por sensor óptico ativo e o rendimento de grãos em quatro cultivares de trigo, visando a desenvolver procedimentos para a adubação nitrogenada em cobertura em taxa variável. O experimento foi realizado em campo em 2009. Foram avaliados o NDVI em diferentes estádios de desenvolvimento e o rendimento de grãos. As leituras do NDVI ao longo do ciclo ativo foram eficientes em identificar variações de produtividade do trigo. Assim, o potencial de produtividade pode ser estimado através de medições desse índice durante a ontogenia da planta. Pode-se adotar um modelo único para descrever a relação entre NDVI e potencial produtivo para as cultivares testadas neste trabalho.Nitrogen fertilization in spring wheat is based on yield potential, soil organic matter content and previous crop. Yield potential definition is difficult, since it is affected by weather conditions. The objective of this research was to evaluate the relationship between Normalized Difference Vegetation Index (NDVI measured by an active sensor and grain yield of four wheat cultivars. The experiment was carried out at field conditions in 2009. NDVI in different growth stages and grain yield were evaluated. NDVI measured was efficient to detect growth variability generated by N availability and correlated well with grain yield for all cultivars tested, indicating that yield potential can be estimated by NDVI evaluations during crop ontogeny. One single model for the relationship between NDVI and yield potential can be used considering cultivars used in this research.

  1. Greening Trends in North American Boreal Forest and Tundra during 2000-2009 from MODIS and in situ Measurements

    Science.gov (United States)

    Wang, D.; Morton, D. C.; Masek, J. G.; McManus, K. M.; Sexton, J. O.

    2010-12-01

    High northern latitudes have experienced the strongest warming trends during the satellite era (1970-present). The response of boreal forest and tundra vegetation to recent and projected warming plays a pivotal role for carbon cycling in these ecosystems and related feedbacks within the Earth system. Long time series of normalized differenced vegetation index (NDVI), calculated from historical Advanced Very High Resolution Radiometer (AVHRR) data, provided the first opportunity to evaluate vegetation dynamics over decadal temporal scales and continental to global spatial scales. However, due to coarse spatial resolution (1-8 km), previous studies of greening in North America with aggregated AVHRR NDVI data were unable to separate the contributions from changes in growing season length and vegetation cover to the greening signal in forest and tundra ecosystems. In this study, we isolated trends in peak growing season vegetation cover using NDVI data from the MODerate resolution Imaging Spectroradiometer (MODIS) during 2000-2009. Our time series analysis compared 500 m NDVI data from the same 16-day composite period during peak growing season months to characterize changes in vegetation abundance during 2000-2009. This approach minimized impacts of phenology, changes in growing season length, and clouds or other data artifacts. For comparison with satellite-based observations, we used measurements of upwelling and downwelling spectral radiances over FLUXNET tower sites to derive broadband NDVI values. Trends in vegetation cover from MODIS NDVI during 2000-2009 differ from previous studies with AVHRR data. Approximately 26% of all vegetated area exhibited significant linear trends in NDVI during 2000-2009 (ptrendfire, insect damage, or harvest, and these trends were captured in both MODIS and broadband NDVI from FLUXNET tower sites. However, greening trends were not observed over mature forests due to saturation of NDVI at MODIS resolution. Therefore, satellite

  2. Vegetation pattern of Istanbul from the Landsat data and the relationship with meteorological parameters

    Directory of Open Access Journals (Sweden)

    Zafer Aslan

    Full Text Available This paper discusses the preliminary results of a study on the vegetation pattern and its relationship with meteorological parameters in and around Istanbul. The study covers an area of over 6800 km2 consisting of urban and suburban centers, and uses the visible and near-infrared bands of Landsat. The spatial variation of the Normalized Difference Vegetation Index (NDVI and meteorological parameters such as sensible heat flux, momentum flux, relative humidity, moist static energy, rainfall rate and temperature have been investigated based on observations in ten stations in the European (Thracian and Anatolian parts of Istanbul. NDVI values have been evaluated from the Landsat data for a single day, viz. 24 October 1986, using ERDAS in ten different classes. The simultaneous spatial variations of sensible heat and momentum fluxes have been computed from the wind and temperature profiles using the Monin-Obukhov similarity theory. The static energy variations are based on the surface meteorological observations. There is very good correlation between NDVI and rainfall rate. Good correlation also exists between: NDVI and relative humidity; NDVI, sensible heat flux and relative humidity; NDVI, momentum flux and emissivity; and NDVI, sensible heat flux and emissivity. The study suggests that the momentum flux has only marginal impact on NDVI. Due to rapid urbanization,the coastal belt is characterized by reduced NDVI compared to the interior areas, suggesting that thermodynamic discontinuities considerably influence the vegetation pattern. This study is useful for the investigation of small-scale circulation models, especially in urban and suburban areas where differential heating leads to the formation of heat islands. In the long run, such studies on a global scale are vital to gain accurate, timely information on the distribution of vegetation on the earth's surface. This may lead to an understanding of how changes in land cover

  3. Modelling malaria incidence with environmental dependency in a locality of Sudanese savannah area, Mali

    Directory of Open Access Journals (Sweden)

    Demongeot Jacques

    2009-04-01

    Full Text Available Abstract Background The risk of Plasmodium falciparum infection is variable over space and time and this variability is related to environmental variability. Environmental factors affect the biological cycle of both vector and parasite. Despite this strong relationship, environmental effects have rarely been included in malaria transmission models. Remote sensing data on environment were incorporated into a temporal model of the transmission, to forecast the evolution of malaria epidemiology, in a locality of Sudanese savannah area. Methods A dynamic cohort was constituted in June 1996 and followed up until June 2001 in the locality of Bancoumana, Mali. The 15-day composite vegetation index (NDVI, issued from satellite imagery series (NOAA from July 1981 to December 2006, was used as remote sensing data. The statistical relationship between NDVI and incidence of P. falciparum infection was assessed by ARIMA analysis. ROC analysis provided an NDVI value for the prediction of an increase in incidence of parasitaemia. Malaria transmission was modelled using an SIRS-type model, adapted to Bancoumana's data. Environmental factors influenced vector mortality and aggressiveness, as well as length of the gonotrophic cycle. NDVI observations from 1981 to 2001 were used for the simulation of the extrinsic variable of a hidden Markov chain model. Observations from 2002 to 2006 served as external validation. Results The seasonal pattern of P. falciparum incidence was significantly explained by NDVI, with a delay of 15 days (p = 0.001. An NDVI threshold of 0.361 (p = 0.007 provided a Diagnostic Odd Ratio (DOR of 2.64 (CI95% [1.26;5.52]. The deterministic transmission model, with stochastic environmental factor, predicted an endemo-epidemic pattern of malaria infection. The incidences of parasitaemia were adequately modelled, using the observed NDVI as well as the NDVI simulations. Transmission pattern have been modelled and observed values were adequately

  4. Using Landsat TM Imagery to Monitor Vegetation Change Following Flow Restoration to the Lower Owens River, California

    Science.gov (United States)

    Bross, Lesley Crandell

    Rehabilitating river corridors to restore valuable riparian habitat consumes significant resources from both governments and private companies. Given these considerable expenditures, it is important to monitor the progress of such projects. This study evaluated the utility of using Landsat Thematic Mapper remotely-sensed data from 2002 and 2009 to monitor vegetation change induced by instream flow restoration to the Lower Owens River in central California. This study compared the results of an unsupervised classification with an NDVI threshold classification to appraise the resources required and effectiveness of each analysis method. The results were inspected by creating standard remote sensing accuracy error matrices and by correlating landscape pattern metrics with bird indicator species. Both sets of classified maps show a noticeable increase in riparian vegetation in the study area following flow restoration in 2006, indicating an improvement of the quality of bird habitat. The study concluded that analyzing vegetation change using the unsupervised classification technique required more effort, expert knowledge, and supplementary data than using the NDVI threshold method. If these prerequisites are met, the output from the unsupervised classification process produces a more precise map of land cover change than the NDVI threshold method. However, if an analyst is lacking either resources or ground verification data, the NDVI threshold technique is capable of providing a generalized, but still valid evaluation of vegetation change. This conclusion is supported by higher correlations between indicator bird species under the unsupervised classification method than were found with the NDVI threshold method.

  5. Assessment of Watershed Drought Using Remote Sensing

    Science.gov (United States)

    Chataut, S.; Piechota, T.

    2005-12-01

    This paper focuses on drought assessment of the Upper Colorado River Basin (UCRB) using remote sensing. Lee's Ferry discharge data for Colorado river in the UCRB and the various Palmer Drought Indices (PDI) such as Palmer Hydrological Drought Indices (PHDI), Palmer Drought Severity Index (PDSI), and Palmer Z Index (ZINDX) for the five climatic divisions of the UCRB for last 100 years will be analyzed to find out the best climatic division in the UCRB for carrying out the further analysis between the Normalized Difference Vegetation Index (NDVI) obtained from 5 km resolution Advanced Very High Radiometric Radar (AVHRR) data and the various PDI. The multivariate statistical technique called rotated principal component analysis will be carried out in the time series of the NDVI data in order to avoid multicollinearity and to extract the component that significantly explains the variance in the dataset. The corresponding significant principal scores will be correlated with the PDI to derive relationship between the NDVI and PDI. Preliminary analysis has shown that there is significant correlation between the NDVI and the various PDI, which implies that NDVI could be used as an important data source to detect and monitor the drought condition in the UCRB.

  6. The relationship between satellite-derived indices and species diversity across African savanna ecosystems

    Science.gov (United States)

    Mapfumo, Ratidzo B.; Murwira, Amon; Masocha, Mhosisi; Andriani, R.

    2016-10-01

    The ability to use remotely sensed diversity is important for the management of ecosystems at large spatial extents. However, to achieve this, there is still need to develop robust methods and approaches that enable large-scale mapping of species diversity. In this study, we tested the relationship between species diversity measured in situ with the Normalized Difference Vegetation Index (NDVI) and the Coefficient of Variation in the NDVI (CVNDVI) derived from high and medium spatial resolution satellite data at dry, wet and coastal savanna woodlands. We further tested the effect of logging on NDVI along the transects and between transects as disturbance may be a mechanism driving the patterns observed. Overall, the results of this study suggest that high tree species diversity is associated with low and high NDVI and at intermediate levels is associated with low tree species diversity and NDVI. High tree species diversity is associated with high CVNDVI and vice versa and at intermediate levels is associated with high tree species diversity and CVNDVI.

  7. Modelling spatial and temporal vegetation variability with the Climate Constrained Vegetation Index: evidence of CO2 fertilisation and of water stress in continental interiors

    Directory of Open Access Journals (Sweden)

    S. O. Los

    2015-06-01

    Full Text Available A model was developed to simulate spatial, seasonal and interannual variations in vegetation in response to temperature, precipitation and atmospheric CO2 concentrations; the model addresses shortcomings in current implementations. The model uses the minimum of 12 temperature and precipitation constraint functions to simulate NDVI. Functions vary based on the Köppen–Trewartha climate classification to take adaptations of vegetation to climate into account. The simulated NDVI, referred to as the climate constrained vegetation index (CCVI, captured the spatial variability (0.82 r r = 0.83 and interannual variability (median global r = 0.24 in NDVI. The CCVI simulated the effects of adverse climate on vegetation during the 1984 drought in the Sahel and during dust bowls of the 1930s and 1950s in the Great Plains in North America. A global CO2 fertilisation effect was found in NDVI data, similar in magnitude to that of earlier estimates (8 % for the 20th century. This effect increased linearly with simple ratio, a transformation of the NDVI. Three CCVI scenarios, based on climate simulations using the representative concentration pathway RCP4.5, showed a greater sensitivity of vegetation towards precipitation in Northern Hemisphere mid latitudes than is currently implemented in climate models. This higher sensitivity is of importance to assess the impact of climate variability on vegetation, in particular on agricultural productivity.

  8. Correlation between the habitats productivity and species richness (amphibians and reptiles) in Portugal through remote sensed data

    Science.gov (United States)

    Teodoro, A. C.; Sillero, N.; Alves, S.; Duarte, L.

    2013-10-01

    Several biogeographic theories propose that the species richness depends on the structure and ecosystems diversity. The habitat productivity, a surrogate for these variables, can be evaluated through satellite imagery, namely using vegetation indexes (e.g. NDVI). We analyzed the correlation between species richness (from the Portuguese Atlas of Amphibians and Reptiles) and NDVI (from Landsat, MODIS, and Vegetation images). The species richness database contains more than 80000 records, collected from bibliographic sources (at 1 or 10 km of spatial resolution) and fieldwork sampling stations (recorded with GPS devices). Several study areas were chosen for Landsat images (three subsets), and all Portugal for MODIS and Vegetation images. The Landsat subareas had different climatic and habitat characteristics, located in the north, center and south of Portugal. Different species richness datasets were used depending on the image spatial resolution: data with metric resolution were used for Landsat, and with 1 km resolution, for MODIS and Vegetation images. The NDVI indexes and all the images were calculated/processed in an open source software (Quantum GIS). Several plug-ins were applied in order to automatize several procedures. We did not find any correlation between the species richness of amphibians and reptiles (not even after separating both groups by species of Atlantic and Mediterranean affinity) and the NDVI calculated with Landsat, MODIS and Vegetation images. Our results may fail to find a relationship because as the species richness is not correlated with only one variable (NDVI), and thus other environmental variables must be considered.

  9. Corn yield estimation in Serbia using MODIS 13Q1 product

    Science.gov (United States)

    Govedarica, Miro; Jovanović, Dušan; Sabo, Filip

    2015-06-01

    The aim of our study was to verify the accuracy and the usability of Moderate resolution imaging spectroradiometer (MODIS) 13Q1 product for corn yield estimation on a local level for 2014 year. Product 13Q1 consists of Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) 16-day composites with 250 m spatial resolution. The estimation is based on ground truth data (sowing structures for 8 years) which was provided by local agricultural organization in Vojvodina, Serbia. The indices were used in linear regression, where the average yield for corn was the dependent variable, NDVI and EVI were independent variables. Average corn yield was estimated approximately 15 days before the beginning of the harvest and compared with official results. Depending on the used linear method, relative errors ranged from 0.6 % to 7.4 %. Overall, coefficients of determination (R2) ranged from 0.66 to 0.75 and were significant at 0.05. The smallest difference between official results for corn yield and our estimate when using NDVI was 0.59 t/ha, when using EVI the smallest difference was 0.07 t/ha. Paper showed that NDVI and EVI from MODIS follow linear relationship with average corn yield and can be used in estimation of crop yields in Serbia and also that EVI produces better prediction results than NDVI. The crop yield estimation can be used for similar cultivated plants in Serbia and for longer period dataset.

  10. MODIS-informed greenness responsesto daytime land surface temperaturefluctuations and wildfire disturbancesin the Alaskan Yukon River Basin

    Science.gov (United States)

    Tan, Zhengxi; Liu, Shu-Guang; Jenkerson, Calli; Oeding, Jennifer; Wylie, Bruce K.; Rover, Jennifer R.; Young, Claudia J.

    2012-01-01

    Pronounced climate warming and increased wildfire disturbances are known to modify forest composition and control the evolution of the boreal ecosystem over the Yukon River Basin (YRB) in interior Alaska. In this study, we evaluate the post-fire green-up rate using the normalized difference vegetation index (NDVI) derived from 250 m 7 day eMODIS (an alternative and application-ready type of Moderate Resolution Imaging Spectroradiometer (MODIS) data) acquired between 2000 and 2009. Our analyses indicate measureable effects on NDVI values from vegetation type, burn severity, post-fire time, and climatic variables. The NDVI observations from both fire scars and unburned areas across the Alaskan YRB showed a tendency of an earlier start to the growing season (GS); the annual variations in NDVI were significantly correlated to daytime land surface temperature (LST) fluctuations; and the rate of post-fire green-up depended mainly on burn severity and the time of post-fire succession. The higher average NDVI values for the study period in the fire scars than in the unburned areas between 1950 and 2000 suggest that wildfires enhance post-fire greenness due to an increase in post-fire evergreen and deciduous species components

  11. Detecting the Land-Cover Changes Induced by Large-Physical Disturbances Using Landscape Metrics, Spatial Sampling, Simulation and Spatial Analysis

    Directory of Open Access Journals (Sweden)

    Hone-Jay Chu

    2009-08-01

    Full Text Available The objectives of the study are to integrate the conditional Latin Hypercube Sampling (cLHS, sequential Gaussian simulation (SGS and spatial analysis in remotely sensed images, to monitor the effects of large chronological disturbances on spatial characteristics of landscape changes including spatial heterogeneity and variability. The multiple NDVI images demonstrate that spatial patterns of disturbed landscapes were successfully delineated by spatial analysis such as variogram, Moran’I and landscape metrics in the study area. The hybrid method delineates the spatial patterns and spatial variability of landscapes caused by these large disturbances. The cLHS approach is applied to select samples from Normalized Difference Vegetation Index (NDVI images from SPOT HRV images in the Chenyulan watershed of Taiwan, and then SGS with sufficient samples is used to generate maps of NDVI images. In final, the NDVI simulated maps are verified using indexes such as the correlation coefficient and mean absolute error (MAE. Therefore, the statistics and spatial structures of multiple NDVI images present a very robust behavior, which advocates the use of the index for the quantification of the landscape spatial patterns and land cover change. In addition, the results transferred by Open Geospatial techniques can be accessed from web-based and end-user applications of the watershed management.

  12. Estimating carbon dioxide fluxes from temperate mountain grasslands using broad-band vegetation indices

    Directory of Open Access Journals (Sweden)

    G. Wohlfahrt

    2010-02-01

    Full Text Available The broad-band normalised difference vegetation index (NDVI and the simple ratio (SR were calculated from measurements of reflectance of photosynthetically active and short-wave radiation at two temperate mountain grasslands in Austria and related to the net ecosystem CO2 exchange (NEE measured concurrently by means of the eddy covariance method. There was no significant statistical difference between the relationships of midday mean NEE with narrow- and broad-band NDVI and SR, measured during and calculated for that same time window, respectively. The skill of broad-band NDVI and SR in predicting CO2 fluxes was higher for metrics dominated by gross photosynthesis and lowest for ecosystem respiration, with NEE in between. A method based on a simple light response model whose parameters were parameterised based on broad-band NDVI allowed to improve predictions of daily NEE and is suggested to hold promise for filling gaps in the NEE time series. Relationships of CO2 flux metrics with broad-band NDVI and SR however generally differed between the two studied grassland sites indicting an influence of additional factors not yet accounted for.

  13. Impact of Climate and Environmental Factors on West Nile Virus Circulation in Iran

    Directory of Open Access Journals (Sweden)

    Farzaneh Ahmadnejad

    2016-01-01

    Full Text Available Background: Geographic distribution of West Nile virus (WNV is heterogeneous in Iran by a high circulation in the southern-western areas. The objective of our study was to determine environmental and climatic factors associ­ated with the risk of WNV equine seropositivity in Iran.Methods: Serological data were obtained from a serosurvey conducted in equine population in 260 districts in Iran. The climate and environmental parameters included in the models were distance to the nearest wetland area, type of stable, Normalized Difference Vegetation Index (NDVI, annual mean temperature, humidity and precipitation.Results: The important risk factors included annual mean temperature, distance to wetlands, local and seasonal NDVI differences. The effect of local NDVI differences in spring was particularly notable. This was a normalized difference of average NDVI between two areas: a 5 km radius area centered on the stable and the 5–10 km sur­rounding area.Conclusion: The model indicated that local NDVI’s contrast during spring is a major risk factor of the transmission of West-Nile virus in Iran. This so-called oasis effect consistent with the seasonal production of vegetation in spring, and is associated to the attractiveness of the local NDVI environment for WNV vectors and hosts.  

  14. Características miofuncionais e eletromiográficas de crianças e adolescentes obesos

    Directory of Open Access Journals (Sweden)

    Denise Bolzan Berlese

    2013-08-01

    Full Text Available OBJETIVO: investigar as características miofuncionais e eletromiográficas de obesos em relação ao sexo e faixa de idade. MÉTODO: amostra de conveniência de 28 crianças e adolescentes obesos, de ambos os sexos, participantes do grupo de Obesidade do Ambulatório de Pediatria do Hospital Universitário do Hospital Universitário de Santa Maria, no período de janeiro a julho de 2011. As características Miofuncionais foram realizadas por fonoaudióloga experiente por meio do Protocolo de Avaliação Miofuncional com Escores (AMIOFE. A avaliação eletromiografica dos músculos masseter e temporal foi obtida utilizando o Eletromiógrafo Lynx e realizada três coletas para cada uma das situações (repouso, mastigação, deglutição e máxima intercuspidação. Os dados eletromiográficos foram normalizados, expressos em percentual, utilizando-se a média da máxima intercuspidação de cada músculo estudado nas avaliações realizadas. RESULTADOS: a maioria dos obesos desta pesquisa apresentaram características miofuncionais dentro da normalidade, não sendo observada diferença estatística significante quando comparados por sexo e idade. Embora a média normalizada da atividade elétrica dos músculos masseter e temporais durante o repouso, mastigação e deglutição dos obesos de acordo com sexo e idade não apresentaram diferença estatística significante, observa-se uma maior ativação dos músculos masseter do que os músculos temporais. CONCLUSÕES: pode-se concluir que crianças e adolescentes obesos, de ambos os sexo têm características miofuncionais dentro da normalidade e que há uma maior ativação dos músculos masseteres para a função da mastigação e deglutição do que os músculos temporais.

  15. Avaliação da função muscular em usuários de prótese total dupla = Evaluation of muscular function in wearers of double complete denture

    Directory of Open Access Journals (Sweden)

    Ferreira, Daniel Filgueiras

    2006-01-01

    Full Text Available O objetivo deste estudo foi avaliar, através da eletromiografia, o comportamento da atividade muscular resultante do uso da técnica Convencional para obtenção de equilíbrio em prótese total dupla. Doze pacientes totalmente edêntulos, livres de sinais e sintomas de disfunção temporomandibular com no mínimo cinco anos de uso de próteses totais, foram selecionados. Os pacientes tiveram suas próteses substituídas por novas próteses e o equilíbrio articular obtido através do estabelecimento de contatos interferentes entre dentes artificiais. O padrão da atividade eletromiográfica (EMG foi mensurado com o eletromiógrafo Myosystem Iâ (Prosecon Ltda nos músculos temporais (porção anterior e masseteres nas posições de repouso (R e na contração isométrica em máxima intercuspidação (CIMI, em quatro tempos: T0 – instalação; T1 – 1° mês; T2 – 2° mês; T3 – 3° mês de uso das próteses. O sinal eletromiográfico foi condicionado por um filtro digital passa faixa e analisado em relação a sua amplitude através do RMS (Root Mean Square. Observou-se pequenas alterações nos valores da atividade EMG dos músculos temporais e masseteres na posição de R. Na posição de CIMI os músculos temporais apresentaram valores finais menores que os iniciais, e situação inversa foi observada para os masseteres, com valores finais maiores que os iniciais. A análise dos dados através do teste de Friedman não mostrou diferenças estatísticamente significantes (p < 0. 05 entre os tempos avaliados. Conclui-se que a técnica Convencional, no período avaliado, não proporcionou equilíbrio dos músculos mastigatórios estudados

  16. LAND SURFACE COEFFICIENT EXTRACTION OF DIFFERENT LAND USE TYPE DERIVED FROM REMOTE SENSING INVERTION MODELING IN THE MAOTIAO RIVER WATERSHED%不同土地利用类型的地表特征参量的遥感反演研究——以猫跳河流域为例

    Institute of Scientific and Technical Information of China (English)

    原菲菲; 徐增让; 詹卫华; 鲁春霞; 曹文德; 茹伟娜

    2013-01-01

    利用2007年5月Lansat5 TM数据,运用单通道算法,基于全国遥感监测土地利用/覆盖分类体系,对贵州省猫跳河流域的地表特征参量进行了反演,得到不同土地利用类型下的典型地表特征参数值.在3种主要的土地利用类型中,林地的植被指数最高、地表温度最低,农田的植被指数最低而地表温度最高,草地介乎林地和农田之间.城镇建设用地主要表现为热岛效应,而水域则主要表现为地表温度(LST)和归一化植被指数(NDVI)的双低特征.进一步对二级土地利用类型的分析表明,由于结构、功能的不同,土地利用二级类在地表特征参量方面也表现出了有规律地变化.有助于深入认识不同土地利用类型的物理特征,可以丰富主要土地利用类型的影像分类的先验知识,有望将不同土地利用方式的生态环境效应研究推进一步.%Landsat thematic mapper(TM) has a thermal band(TM6),and this band can be used for retrieving land surface temperature(LST).In this paper,typical surface features parameter values were retrieved base on Landsat 5 TM remote sensing data of May,2007 in the Maotiao River watershed.The NDVI(normalized difference vegetation index) can be calculated using TM3 and TM4 band data,the land surface emissivity(LSE) of TM6 can be obtained by using NDVITEM (NDVI Thresholds Method),and the LST(land surface temperature) can be retrieved by single channel algorithm.The classification of land use types uses the China land use/cover of remote sensing monitoring classification system(geographical resources of Chinese academy of sciences,1999).According to this system,the researched area can be divided into 5 class including the forest land,grassland,cultivated land,water area and urban and rural construction land,and 13 subclass by which NDVI and LST can be respectively statisticed.The results indicated that in the three main types of the land use,the forest land had the highest NDVI and

  17. Remote sensing based evapotranspiration and runoff modeling of agricultural, forest and urban flux sites in Denmark: From field to macro-scale

    DEFF Research Database (Denmark)

    Bøgh, E.; Poulsen, R.N.; Butts, M.;

    2009-01-01

    conditions, and the EOS/MODIS Normalized Difference Vegetation Index (NDVI) was used to map (a) the temporal development in leaf area index for agricultural fields, (b) a dynamic “canopy” coefficient (Kc) of forests being scaled between its minimum and maximum values for use in the FAO Penman...... surface heterogeneity is based on the assumption that sub-class soil heterogeneity can be indirectly represented by the observed spatial variations in NDVI due to its close affiliation with vegetation growth, soil water uptake and evapotranspiration. Multiple spatial resolution water balance simulations...... is negligible (Days 125–300). The presence/absence of pipe drains, urban surface runoff and forest parameterization cause very large differences in the water balance of agricultural, forest and urban regions. The results show that the use of local-scale standard model parameters and NDVI time series...

  18. Trends in global vegetation activity and climatic drivers indicate a decoupled response to climate change

    DEFF Research Database (Denmark)

    Schut, Antonius G T; Ivits, Eva; Conijn, Jacob G.;

    2015-01-01

    Detailed understanding of a possible decoupling between climatic drivers of plant productivity and the response of ecosystems vegetation is required. We compared trends in six NDVI metrics (1982-2010) derived from the GIMMS3g dataset with modelled biomass productivity and assessed uncertainty...... an increasing difference between trends in climatic drivers and observed NDVI for large parts of the globe. Our findings suggest that future scenarios must consider impacts of constraints on plant growth such as extremes in weather and nutrient availability to predict changes in NPP and CO2 sequestration...... in trend estimates. Annual total biomass weight (TBW) was calculated with the LINPAC model. Trends were determined using a simple linear regression, a Thiel-Sen medium slope and a piecewise regression (PWR) with two segments. Values of NDVI metrics were related to Net Primary Production (MODIS...

  19. Retrieval of seasonal dynamics of forest understory reflectance from semiarid to boreal forests using MODIS BRDF data

    Science.gov (United States)

    Pisek, Jan; Chen, Jing M.; Kobayashi, Hideki; Rautiainen, Miina; Schaepman, Michael E.; Karnieli, Arnon; Sprinstin, Michael; Ryu, Youngryel; Nikopensius, Maris; Raabe, Kairi

    2016-03-01

    Spatial and temporal patterns of forest background (understory) reflectance are crucial for retrieving biophysical parameters of forest canopies (overstory) and subsequently for ecosystem modeling. In this communication, we retrieved seasonal courses of understory normalized difference vegetation index (NDVI) from multiangular Moderate Resolution Imaging Spectroradiometer bidirectional reflectance distribution function (MODIS BRDF)/albedo data. We compared satellite-based seasonal courses of understory NDVI to understory NDVI values measured in different types of forests distributed along a wide latitudinal gradient (65.12°N-31.35°N). Our results indicated that the retrieval method performs well particularly over open forests of different types. We also demonstrated the limitations of the method for closed canopies, where the understory signal retrieval is much attenuated.

  20. Normalized Difference Vegetation Index as a Tool for Wheat Yield Estimation: A Case Study from Faisalabad, Pakistan

    Directory of Open Access Journals (Sweden)

    Syeda Refat Sultana

    2014-01-01

    Full Text Available For estimation of grain yield in wheat, Normalized Difference Vegetation Index (NDVI is considered as a potential screening tool. Field experiments were conducted to scrutinize the response of NDVI to yield behavior of different wheat cultivars and nitrogen fertilization at agronomic research area, University of Agriculture Faisalabad (UAF during the two years 2008-09 and 2009-10. For recording the value of NDVI, Green seeker (Handheld-505 was used. Split plot design was used as experimental model in, keeping four nitrogen rates (N1= 0 kg ha−1, N2= 55 kg ha−1, N3=110 kg ha−1, and N4= 220 kg ha−1 in main plots and ten wheat cultivars (Bakkhar-2001, Chakwal-50, Chakwal-97, Faisalabad-2008, GA-2002, Inqlab-91, Lasani-2008, Miraj-2008, Sahar-2006, and Shafaq-2006 in subplots with four replications. Impact of nitrogen and difference between cultivars were forecasted through NDVI. The results suggested that nitrogen treatment N4 (220 kg ha−1 and cultivar Faisalabad-2008 gave maximum NDVI value (0.85 at grain filling stage among all treatments. The correlation among NDVI at booting, grain filling, and maturity stages with grain yield was positive (R2 = 0.90; R2 = 0.90; R2 = 0.95, respectively. So, booting, grain filling, and maturity can be good depictive stages during mid and later growth stages of wheat crop under agroclimatic conditions of Faisalabad and under similar other wheat growing environments in the country.