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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. 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.

  5. 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...

  6. Modelling critical NDVI curves in perennial ryegrass

    DEFF Research Database (Denmark)

    Gislum, R; Boelt, B

    2010-01-01

    NDVI curve where the critical NDVI, defined as the minimum NDVI obtained to achieve a high seed yield, will be modelled during the growing season. NDVI measurements were made at different growing degree days (GDD) in a three year field experiment where different N application rates were applied. There...... additional N application at a time where the crop is able to take up and utilise the applied N....

  7. Explaining NDVI trends in northern Burkina Faso

    DEFF Research Database (Denmark)

    Rasmussen, Kjeld; Fensholt, Rasmus; Fog, Bjarne; Rasmussen, Laura Vang; Yanogo, Isidore

    2014-01-01

    -climatic factors are involved. By relating NDVI trends to landscape elements and land use change we demonstrate that NDVI trends in the north-western parts of the study area are mostly related to landscape elements, while this is not the case in the south-eastern parts, where rapidly changing land use, including......Many studies have shown a ‘greening of the Sahel’ on the basis of analysis of time series of satellite images and this has shown to be, at least partly, explained by changes in rainfall. In northern Burkina Faso, an area stands out as anomalous in such analysis, since it is characterized by a...... distinct spatial pattern and strongly dominated by negative trends in Normalized Difference Vegetation Index (NDVI). The aim of the paper is to explain this distinct pattern. When studied over the period 2000–2012, using NDVI data from the MODIS sensor the spatial pattern of NDVI trends indicates that non...

  8. Variabilidade climática nas diferentes escalas espaciais-temporais

    OpenAIRE

    Chorro, Maria José Neves

    2009-01-01

    A realização deste trabalho constitui um estudo sobre a variabilidade climática a diferentes escalas espaço-temporais. Assim, na primeira parte deste trabalho, analisa-se, a grande escala espacial, o comportamento das variáveis temperatura e pressão atmosférica em termos comparativos nos planetas Terra e Marte. Conclui-se que o comportamento da temperatura media anual é semelhante nos dois planetas relativamente a variabilidade espacial (máxima no equador e minima nos ...

  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. Predição de Séries Temporais de parâmetros de Rede WCDMA – HSPA

    Directory of Open Access Journals (Sweden)

    Tiago dos Santos Bezerra

    2014-02-01

    Full Text Available Em telecomunicações, com o crescimento da demanda de tráfego de dados nas redes de terceira geração (3G, as operadoras de telefonia móvel têm atentado para o direcionamento dos recursos em infraestrutura nos locais onde se identifica maior necessidade. O direcionamento desses investimentos tem o objetivo de manter a qualidade do serviço prestado, principalmente, em regiões urbanas densas. Neste trabalho, é realizada a predição de séries temporais em redes HSPA – WCDMA dos parâmetros: potência recebida (Rx Power, potência de código do sinal recebido (Received Signal Code Power – RSCP, relação energia por chip em função da interferência (Energy per chip/Interference – Ec/Io e taxa de transmissão (throughput na camada física. A coleta dos valores dos parâmetros foi realizada numa rede em pleno funcionamento através de um drive test na cidade de Natal – RN. O modelo utilizado para predição das séries temporais foi o Modelo de Alisamento Exponencial de Holt. O objetivo das predições das séries temporais é verificar para quais parâmetros da rede HSPA – WCDMA o modelo de Holt melhor se adequou.

  11. 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.

  12. 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...

  13. NDVI to Detect Sugarcane Aphid Injury to Grain Sorghum.

    Science.gov (United States)

    Elliott, N C; Backoulou, G F; Brewer, M J; Giles, K L

    2015-06-01

    Multispectral remote sensing has potential to provide quick and inexpensive information on sugarcane aphid, Melanaphis sacchari (Zehntner), pest status in sorghum fields. We describe a study conducted to determine if injury caused by sugarcane aphid to sorghum plants in fields of grain sorghum could be detected using multispectral remote sensing from a fixed wing aircraft. A study was conducted in commercial grain sorghum fields in the Texas Gulf Coast region in June 2014. Twenty-six commercial grain sorghum fields were selected and rated for the level of injury to sorghum plants in the field caused by sugarcane aphid. Plant growth stage ranged from 5.0 (watery ripe) to 7.0 (hard dough) among fields; and plant injury rating from sugarcane aphid ranged from 1.0 (little or no injury) to 4.0 (>40% of plants displaying injury) among fields. The normalized differenced vegetation index (NDVI) is calculated from light reflectance in the red and near-infrared wavelength bands in multispectral imagery and is a common index of plant stress. High NDVI indicates low levels of stress and low NDVI indicates high stress. NDVI ranged from -0.07 to 0.26 among fields. The correlation between NDVI and plant injury rating was negative and significant, as was the correlation between NDVI and plant growth stage. The negative correlation of NDVI with injury rating indicated that plant stress increased with increasing plant injury. Reduced NDVI with increasing plant growth probably resulted from reduced photosynthetic activity in more mature plants. The correlation between plant injury rating and plant growth stage was positive and significant indicating that plant injury from sugarcane aphid increased as plants matured. The partial correlation of NDVI with plant injury rating was negative and significant indicating that NDVI decreased with increasing plant injury after adjusting for its association with plant growth stage. We demonstrated that remotely sensed imagery acquired from grain

  14. O desenvolvimento de noções temporais através da linguagem The development of temporal concepts through language

    Directory of Open Access Journals (Sweden)

    Zena Winona Eisenberg

    2011-01-01

    Full Text Available A vida nas cidades modernas expõe a criança a inúmeros conceitos temporais abstratos: após o seu nascimento, a criança toma conhecimento da programação de atividades com horários específicos, a ordem em que ocorrem e sua duração. Neste estudo investigamos o desenvolvimento de conceitos temporais através da linguagem. Participaram do estudo 20 famílias e suas crianças de 36 a 65 meses de idade que foram recrutadas em creches e pré-escolas numa grande área metropolitana dos Estados Unidos. Pedimos às famílias que gravassem quatro conversas com suas crianças durante o jantar. Os resultados demonstram os diferentes papéis que pais e mães desempenham na negociação de conceitos temporais, assim como a importância do desenvolvimento verbal da criança para sua utilização de conceitos temporais.Life in modern cities exposes a young child to numerous abstract concepts of time. Since birth, a child is introduced to activities with set schedule, set order, and duration. In this study it was investigated the development of time concepts through language. Twenty families and their 36 to 65 months old children who were recruited from day care centers and preschools in a large metropolitan area in the USA participated in this study. Parents were asked to audiotape four dinner conversations at home with their child. Results point to the different roles parents play in the negotiation of time concepts, as well as the importance of children's verbal development in the use of time concepts.

  15. 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

  16. The precision of the NDVI derived from AVHRR observations

    International Nuclear Information System (INIS)

    Vegetation studies using NOAA-AVHRR data have tended to focus on the use of the normalized difference vegetation index (NDVI). This unitless index is computed using near-infrared and red reflectances, and thus has both an accuracy and precision. This article reports on a formal statistical framework for assessing the precision of the NDVI derived from NOAA-AVHRR observations. The framework is based on the “best possible” precision concept, which assumes that signal quantization is the only source of observational error. While the radiance resolution of a spectral observation is essentially fixed by the instrument characteristics, the reflectance resolution is the radiance resolution divided by the cosine of the solar zenith angle. Using typical solar zenith angles for AVHRR image acquisitions over Australia, ± 0.01 NDVI units is typically with “best possible” precision attainable in the NDVI, although this degrades significantly over dark targets, and at large solar zenith angles. Transforming the computed NDVI into a single byte for disk storage results in little or no loss of precision. The framework developed in this article can be adapted to estimate the “best possible” precision of other vegetation indices derived using data from other remote sensing satellites. (author)

  17. 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.

  18. 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...

  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. Impact of Sensor Degradation on the MODIS NDVI Time Series

    Science.gov (United States)

    Wang, Dongdong; Morton, Douglas Christopher; Masek, Jeffrey; Wu, Aisheng; Nagol, Jyoteshwar; Xiong, Xiaoxiong; Levy, Robert; Vermote, Eric; Wolfe, Robert

    2012-01-01

    Time series of satellite data provide unparalleled information on the response of vegetation to climate variability. Detecting subtle changes in vegetation over time requires consistent satellite-based measurements. Here, the impact of sensor degradation on trend detection was evaluated using Collection 5 data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra and Aqua platforms. For Terra MODIS, the impact of blue band (Band 3, 470 nm) degradation on simulated surface reflectance was most pronounced at near-nadir view angles, leading to a 0.001-0.004 yr-1 decline in Normalized Difference Vegetation Index (NDVI) under a range of simulated aerosol conditions and surface types. Observed trends in MODIS NDVI over North America were consistentwith simulated results,with nearly a threefold difference in negative NDVI trends derived from Terra (17.4%) and Aqua (6.7%) MODIS sensors during 2002-2010. Planned adjustments to Terra MODIS calibration for Collection 6 data reprocessing will largely eliminate this negative bias in detection of NDVI trends.

  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. 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

  4. Relative time NDVI mosaics as an indicator of crop growth

    Science.gov (United States)

    Savin, Igor Y.; Negre, Thierry

    2003-03-01

    Relative time NDVI mosaics are proposed as a tool for crop growth monitoring and yield forecasting. The mosaics are constructed for the region of interest for a given phenological phase of crop development (for example, flowering). Mosaics for different years, created for the same characteristic time of crop development, are used for crop growth monitoring and yield forecasting. The approach is illustrated through two case studies: - forecasting of wheat yield in the countries of Northern Africa (relative time NDVI mosaics are constructed for the flowering stage of crop development); - assessing winter crop status in southern areas of Russia after the winter season (mosaics are constructed two dekads before the establishment of snow cover and two dekads after its disappearance). NDVI values, calculated from SPOT4-Vegetation data, were used in both cases. Dates of crop phenological phases were determined applying the WOFOST crop growth model and ECMWF-derived meteorological grid data. Results demonstrate the validity of the approach and the improvements obtained as compared with traditional methods.

  5. 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

  6. 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.

  7. 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.

  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. Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors

    OpenAIRE

    Gamon, J. A.; Kovalchuk, O.; C. Y. S. Wong; Harris, A; S. R. Garrity

    2015-01-01

    The vegetation indices normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI) provide indicators of pigmentation and photosynthetic activity that can be used to model photosynthesis from remote sensing with the light-use efficiency model. To help develop and validate this approach, reliable proximal NDVI and PRI sensors have been needed. We tested new NDVI and PRI sensors, "SRS" sensors recently developed by Decagon Devices, during spring act...

  10. Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors

    OpenAIRE

    Gamon, J. A.; O. Kovalchuck; C. Y. S. Wong; Harris, A; S. R. Garrity

    2015-01-01

    The vegetation indices normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI) provide indicators of pigmentation and photosynthetic activity that can be used to model photosynthesis from remote sensing with the light-use-efficiency model. To help develop and validate this approach, reliable proximal NDVI and PRI sensors have been needed. We tested new NDVI and PRI sensors, "spectral reflectance sensors" (SRS sensors; recently developed by Dec...

  11. Land Cover Classification of Landsat Data with Phenological Features Extracted from Time Series MODIS NDVI Data

    OpenAIRE

    Kun Jia; Shunlin Liang; Xiangqin Wei; Yunjun Yao; Yingru Su; Bo Jiang; Xiaoxia Wang

    2014-01-01

    Temporal-related features are important for improving land cover classification accuracy using remote sensing data. This study investigated the efficacy of phenological features extracted from time series MODIS Normalized Difference Vegetation Index (NDVI) data in improving the land cover classification accuracy of Landsat data. The MODIS NDVI data were first fused with Landsat data via the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) algorithm to obtain NDVI data at the La...

  12. 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

  13. 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.

  14. Aggregation and Association of NDVI, Boll Injury, and Stink Bugs in North Carolina Cotton.

    Science.gov (United States)

    Reisig, Dominic D; Reay-Jones, F P F; Meijer, A D

    2015-01-01

    Sampling of herbivorous stink bugs in southeastern U.S. cotton remains problematic. Remote sensing was explored to improve sampling of these pests and associated boll injury. Two adjacent 14.5-ha cotton fields were grid sampled in 2011 and 2012 by collecting stink bug adults and bolls every week during the third, fourth, and fifth weeks of bloom. Satellite remote sensing data were collected during the third week of bloom during both years, and normalized difference vegetation index (NDVI) values were calculated. Stink bugs were spatially aggregated on the third week of bloom in 2011. Boll injury from stink bugs was spatially aggregated during the fourth week of bloom in 2012. The NDVI values were aggregated during both years. There was a positive association and correlation between stink bug numbers and NDVI values, as well as injured bolls and NDVI values, during the third week of bloom in 2011. During the third week of bloom in 2012, NDVI values were negatively correlated with stink bug numbers. During the fourth week of bloom in 2011, stink bug numbers and boll injury were both positively associated and correlated with NDVI values. During the fourth week of bloom in 2012, stink bugs were negatively correlated with NDVI values, and boll injury was negatively associated and correlated with NDVI values. This study suggests the potential of remote sensing as a tool to assist with sampling stink bugs in cotton, although more research is needed using NDVI and other plant measurements to predict stink bug injury. PMID:26411787

  15. 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

  16. 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

  17. 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.

  18. Agreement evaluation of AVHRR and MODIS 16-day composite NDVI data sets

    Science.gov (United States)

    Ji, L.; Gallo, K.; Eidenshink, J.C.; Dwyer, J.

    2008-01-01

    Satellite-derived normalized difference vegetation index (NDVI) data have been used extensively to detect and monitor vegetation conditions at regional and global levels. A combination of NDVI data sets derived from AVHRR and MODIS can be used to construct a long NDVI time series that may also be extended to VIIRS. Comparative analysis of NDVI data derived from AVHRR and MODIS is critical to understanding the data continuity through the time series. In this study, the AVHRR and MODIS 16-day composite NDVI products were compared using regression and agreement analysis methods. The analysis shows a high agreement between the AVHRR-NDVI and MODIS-NDVI observed from 2002 and 2003 for the conterminous United States, but the difference between the two data sets is appreciable. Twenty per cent of the total difference between the two data sets is due to systematic difference, with the remainder due to unsystematic difference. The systematic difference can be eliminated with a linear regression-based transformation between two data sets, and the unsystematic difference can be reduced partially by applying spatial filters to the data. We conclude that the continuity of NDVI time series from AVHRR to MODIS is satisfactory, but a linear transformation between the two sets is recommended.

  19. 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...... sensor shifts potentially introduce substantial uncertainties and artifacts in the analysis of trends. The temporal consistency of NDVI datasets should therefore be evaluated before performing trend analysis to obtain reliable results. In this study we analyze the temporal consistency of multi......-sensor NDVI time series by analyzing the co-occurrence between breaks in the NDVI time series and sensor shifts from GIMMS3g (Global Inventory Modeling and Mapping Studies 3rd generation), VIP3 (Vegetation Index and Phenology version 3), LTDR4 (Long Term Data Record version 4) and SPOT-VGT (Système Pour l...

  20. 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

    -sensor geometry variations will have a more visible impact on the Normalized Difference Vegetation Index (NDVI) from MODIS compared to earlier data sources, since noise related to atmosphere and sensor calibration is substantially reduced in the MODIS data stream. For this reason, the effect of varying MODIS...... 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...... reflectances depends on the amount of vegetation present. MODIS VZA and RAA effects on NDVI were highest for medium dense vegetation (NDVI approximate to 0.5-0.6). The VZA and RAA effects were less for sparsely vegetated areas (NDVI approximate to 0.3-0.35) and the smallest effect on NDVI was found for dense...

  1. 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...

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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...

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

    OpenAIRE

    Fabrício Pinheiro Povh; José Paulo Molin; Leandro Maria Gimenez; Volnei Pauletti; Rudimar Molin; José Vitor Salvi

    2008-01-01

    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...

  10. 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.

  11. 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.

  12. A New Neighboring Pixels Method for Reducing Aerosol Effects on the NDVI Images

    OpenAIRE

    Dandan Wang; Yunhao Chen; Mengjie Wang; Jingling Quan; Tao Jiang

    2016-01-01

    A new algorithm was developed in this research to minimize aerosol effects on the normalized difference vegetation index (NDVI). Simulation results show that in red-NIR reflectance space, variations in red and NIR channels to aerosol optical depth (AOD) follow a specific pattern. Based on this rational, the apparent reflectance in these two bands of neighboring pixels were used to reduce aerosol effects on NDVI values of the central pixel. We call this method the neighboring pixels (NP) algor...

  13. 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 ...

  14. 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.

  15. 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.

  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. 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.

  18. 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.

  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. 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.

  2. Relationships between NDVI, canopy structure, and photosynthesis in three California vegetation types

    International Nuclear Information System (INIS)

    In a range of plant species from three Californian vegetation types, we examined the widely used ''normalized difference vegetation index'' (NDVI) and ''simple ratio'' (SR) as indicators of canopy structure, light absorption, and photosynthetic activity. These indices, which are derived from canopy reflectance in the red and near-infrared wavebands, highlighted phenological differences between evergreen and deciduous canopies. They were poor indicators of total canopy biomass due to the varying abundance of non-green standing biomass in these vegetation types. However, in sparse canopies (leaf area index (LAI) apprxeq 0-2), NDVI was a sensitive indicator of canopy structure and chemical content (green biomass, green leaf area index, chlorophyll content, and foliar nitrogen content). At higher canopy green LAI values ( gt 2; typical of dense shrubs and trees), NDVI was relatively insensitive to changes in canopy structure. Compared to SR, NDVI was better correlated with indicators of canopy structure and chemical content, but was equivalent to the logarithm of SR. In agreement with theoretical expectations, both NDVI and SR exhibited near-linear correlations with fractional PAR intercepted by green leaves over a wide range of canopy densities. Maximum daily photosynthetic rates were positively correlated with NDVI and SR in annual grassland and semideciduous shrubs where canopy development and photosynthetic activity were in synchrony. The indices were also correlated with peak springtime canopy photosynthetic rates in evergreens. However, over most of the year, these indices were poor predictors of photosynthetic performance in evergreen species due to seasonal reductions in photosynthetic radiation-use efficiency that occurred without substantial declines in canopy greenness. Our results support the use of these vegetation indices as remote indicators of PAR absorption, and thus potential photosynthetic activity, even in

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Land Cover Classification of Landsat Data with Phenological Features Extracted from Time Series MODIS NDVI Data

    Directory of Open Access Journals (Sweden)

    Kun Jia

    2014-11-01

    Full Text Available Temporal-related features are important for improving land cover classification accuracy using remote sensing data. This study investigated the efficacy of phenological features extracted from time series MODIS Normalized Difference Vegetation Index (NDVI data in improving the land cover classification accuracy of Landsat data. The MODIS NDVI data were first fused with Landsat data via the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM algorithm to obtain NDVI data at the Landsat spatial resolution. Next, phenological features, including the beginning and ending dates of the growing season, the length of the growing season, seasonal amplitude, and the maximum fitted NDVI value, were extracted from the fused time series NDVI data using the TIMESAT tool. The extracted data were integrated with the spectral data of the Landsat data to improve classification accuracy using a maximum likelihood classifier (MLC and support vector machine (SVM classifier. The results indicated that phenological features had a statistically significant effect on improving the land cover classification accuracy of single Landsat data (an approximately 3% increase in overall classification accuracy, especially for vegetation type discrimination. However, the phenological features did not improve on statistical measures including the maximum, the minimum, the mean, and the standard deviation values of the time series NDVI dataset, especially for human-managed vegetation types. Regarding different classifiers, SVM could achieve better classification accuracy than the traditional MLC classifier, but the improvement in accuracy obtained using advanced classifiers was inferior to that achieved by involving the temporally derived features for land cover classification.

  8. 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.

  9. Improving agricultural drought monitoring in West Africa using root zone soil moisture estimates derived from NDVI

    Science.gov (United States)

    McNally, A.; Funk, C. C.; Yatheendradas, S.; Michaelsen, J.; Cappelarere, B.; Peters-Lidard, C. D.; Verdin, J. P.

    2012-12-01

    The Famine Early Warning Systems Network (FEWS NET) relies heavily on remotely sensed rainfall and vegetation data to monitor agricultural drought in Sub-Saharan Africa and other places around the world. Analysts use satellite rainfall to calculate rainy season statistics and force crop water accounting models that show how the magnitude and timing of rainfall might lead to above or below average harvest. The Normalized Difference Vegetation Index (NDVI) is also an important indicator of growing season progress and is given more weight over regions where, for example, lack of rain gauges increases error in satellite rainfall estimates. Currently, however, near-real time NDVI is not integrated into a modeling framework that informs growing season predictions. To meet this need for our drought monitoring system a land surface model (LSM) is a critical component. We are currently enhancing the FEWS NET monitoring activities by configuring a custom instance of NASA's Land Information System (LIS) called the FEWS NET Land Data Assimilation System. Using the LIS Noah LSM, in-situ measurements, and remotely sensed data, we focus on the following questions: What is the relationship between NDVI and in-situ soil moisture measurements over the West Africa Sahel? How can we use this relationship to improve modeled water and energy fluxes over the West Africa Sahel? We investigate soil moisture and NDVI cross-correlation in the time and frequency domain to develop a transfer function model to predict soil moisture from NDVI. This work compares sites in southwest Niger, Benin, Burkina Faso, and Mali to test the generality of the transfer function. For several sites with fallow and millet vegetation in the Wankama catchment in southwest Niger we developed a non-parametric frequency response model, using NDVI inputs and soil moisture outputs, that accurately estimates root zone soil moisture (40-70cm). We extend this analysis by developing a low order parametric transfer function

  10. Monitoring Grassland Seasonal Carbon Dynamics, by Integrating MODIS NDVI, Proximal Optical Sampling, and Eddy Covariance Measurements

    Directory of Open Access Journals (Sweden)

    Enrica Nestola

    2016-03-01

    Full Text Available This study evaluated the seasonal productivity of a prairie grassland (Mattheis Ranch, in Alberta, Canada using a combination of remote sensing, eddy covariance, and field sampling collected in 2012–2013. A primary objective was to evaluate different ways of parameterizing the light-use efficiency (LUE model for assessing net ecosystem fluxes at two sites with contrasting productivity. Three variations on the NDVI (Normalized Difference Vegetation Index, differing by formula and footprint, were derived: (1 a narrow-band NDVI (NDVI680,800, derived from mobile field spectrometer readings; (2 a broad-band proxy NDVI (derived from an automated optical phenology station consisting of broad-band radiometers; and (3 a satellite NDVI (derived from MODIS AQUA and TERRA sensors. Harvested biomass, net CO2 flux, and NDVI values were compared to provide a basis for assessing seasonal ecosystem productivity and gap filling of tower flux data. All three NDVIs provided good estimates of dry green biomass and were able to clearly show seasonal changes in vegetation growth and senescence, confirming their utility as metrics of productivity. When relating fluxes and optical measurements, temporal aggregation periods were considered to determine the impact of aggregation on model accuracy. NDVI values from the different methods were also calibrated against fAPARgreen (the fraction of photosynthetically active radiation absorbed by green vegetation values to parameterize the APARgreen (absorbed PAR term of the LUE (light use efficiency model for comparison with measured fluxes. While efficiency was assumed to be constant in the model, this analysis revealed hysteresis in the seasonal relationships between fluxes and optical measurements, suggesting a slight change in efficiency between the first and second half of the growing season. Consequently, the best results were obtained by splitting the data into two stages, a greening phase and a senescence phase, and

  11. Active-Optical Sensors Using Red NDVI Compared to Red Edge NDVI for Prediction of Corn Grain Yield in North Dakota, U.S.A.

    OpenAIRE

    Sharma, Lakesh K.; Honggang Bu; Anne Denton; Franzen, David W.

    2015-01-01

    Active-optical sensor readings from an N non-limiting area standard established within a farm field are used to predict yield in the standard. Lower yield predictions from sensor readings obtained from other parts of the field outside of the N non-limiting standard area indicate a need for supplemental N. Active-optical sensor algorithms for predicting corn (Zea mays, L.) yield to direct in-season nitrogen (N) fertilization in corn utilize red NDVI (normalized differential vegetative index). ...

  12. Assessment of spatio-temporal patterns of NDVI in response to precipitation using NOAA-AVHRR rainfall estimate and NDVI data from 1996-2008, Ethiopia

    OpenAIRE

    Kabthimer, Getahun Tadesse

    2012-01-01

    The role of remote sensing data for monitoring different parameters in the study of ecosystems has been increasing. Particularly the development of different indices has played a great role to study the properties of vegetation and vegetation dynamics in large countries. In addition to this, satellite rainfall estimate data has been used to study the pattern of precipitation in areas where station rain-gauge data is not available. The Normalized Difference Vegetation Index (NDVI) and rainfall...

  13. 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

  14. 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

  15. 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

  16. Check and modification of GlobeLand30 with MODIS NDVI

    Science.gov (United States)

    Zhang, Weiwei; Liao, Anping; Peng, Shu; Zheng, Xinyan; Li, Ming

    2015-10-01

    MODIS NDVI time-series data could indicate vegetation status in each season and have been widely used for land cover classification and studies in the fields of vegetation and land degradation monitoring. During global land cover mapping project at 30m resolution aiming at developing high quality product, there were mistakes of classification between bareland and vegetation in GlobeLand30 data in regions surrounding deserts because that the dates of some images are not in growing season. In this paper, we proposed a method to check GlobeLand30 data of 2010 in these areas. Max NDVI value of MODIS NDVI time-series data is chosen to represent growing conditions of vegetation. And then vegetation fraction (VF) calculated from the max NDVI value is divided into bareland and vegetation based on the definition of bareland that VF of bareland is lower than 10%. The dimidiated VF maps are employed to check GlobeLand30 with the help of high resolution images and other references. Finally, errors found out by steps above are modified with VF maps and segmentation objects of images at 30m resolution. 149 map sheets of GlobeLand30 were checked and 105 of them were modified. 13409 samples in 10 map sheets totally were selected to assess the effect of the approach. The result showed that the accuracy after modification of GlobeLand30 was higher than that before modification.

  17. 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.

  18. 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.

  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. Comparison of Topographic Effects between the Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI)

    Science.gov (United States)

    Matsushita, B.; Yang, W.; Chen, J.; Onda, Y.

    2007-12-01

    Vegetation indices play an important role in monitoring variations in vegetation. The Enhanced Vegetation Index (EVI) proposed by the MODIS Land Discipline Group and the Normalized Difference Vegetation Index (NDVI) are both global-based vegetation indices aimed at providing consistent spatial and temporal information regarding global vegetation. However, many environmental factors such as atmospheric conditions and soil background may produce errors in these indices. The topographic effect is another very important factor, especially when the indices are used in areas of rough terrain. In this paper, we analyzed differences in the topographic effect between the EVI and the NDVI based on a non-Lambertian model and using two airborne-based images with a spatial resolution of 1.5m acquired from a mountainous area covered by a homogeneous Japanese cypress plantation. The results indicate that the soil adjustment factor "L" in the EVI makes it more sensitive to topographic conditions than is the NDVI. Based on these results, we strongly recommend that the topographic effect be removed from the EVI--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 conjunction with a high spatial resolution image of an area of rough terrain, where the topographic effect on the vegetarian indices having only a band ratio format (e.g., the NDVI) can usually be ignored.

  1. 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.

  2. Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors

    Science.gov (United States)

    Gamon, J. A.; Kovalchuck, O.; Wong, C. Y. S.; Harris, A.; Garrity, S. R.

    2015-07-01

    The vegetation indices normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI) provide indicators of pigmentation and photosynthetic activity that can be used to model photosynthesis from remote sensing with the light-use-efficiency model. To help develop and validate this approach, reliable proximal NDVI and PRI sensors have been needed. We tested new NDVI and PRI sensors, "spectral reflectance sensors" (SRS sensors; recently developed by Decagon Devices, during spring activation of photosynthetic activity in evergreen and deciduous stands. We also evaluated two methods of sensor cross-calibration - one that considered sky conditions (cloud cover) at midday only, and another that also considered diurnal sun angle effects. Cross-calibration clearly affected sensor agreement with independent measurements, with the best method dependent upon the study aim and time frame (seasonal vs. diurnal). The seasonal patterns of NDVI and PRI differed for evergreen and deciduous species, demonstrating the complementary nature of these two indices. Over the spring season, PRI was most strongly influenced by changing chlorophyll : carotenoid pool sizes, while over the diurnal timescale, PRI was most affected by the xanthophyll cycle epoxidation state. This finding demonstrates that the SRS PRI sensors can resolve different processes affecting PRI over different timescales. The advent of small, inexpensive, automated PRI and NDVI sensors offers new ways to explore environmental and physiological constraints on photosynthesis, and may be particularly well suited for use at flux tower sites. Wider application of automated sensors could lead to improved integration of flux and remote sensing approaches for studying photosynthetic carbon uptake, and could help define the concept of contrasting vegetation optical types.

  3. 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

  4. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Dagg, J.; Lafleur, P.

    2010-07-01

    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 (CO{sub 2}) 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 CO{sub 2} exchange may explain how small-scale variation in vegetation community extends to remotely sensed estimates of landscape characteristics. In this study, CO{sub 2} 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 CO{sub 2} 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 CO{sub 2} exchange in heterogeneous Tundra vegetation is variable.

  6. 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

  7. 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.

  8. 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.

  9. THE RELATIONSHIP BETWEEN NDVI AND FLORISTICS IN SEASONALLY DECIDUOUS FOREST IN THE PARANA VALLEY, GOIAS STATE, BRAZIL

    Directory of Open Access Journals (Sweden)

    Potira Meirelles Hermuche

    2011-03-01

    Full Text Available The objective of this paper was to evaluate the relationship between NDVI and the patterns of the dominant species in three fragments of seasonally deciduous forest (SDF in the Parana Valley in Goias State, Brazil. Landsat 7 ETM+ images from the year 2001 were used. The study showed a relation between NDVI and floristic patterns during the dry and rainy seasons for the three fragments studied. Exclusive species showed greater influence in the spectral response measured by NDVI than did the total species. The results confirmed the three fragments as SDF showing that even within the same physiognomy there were small phenological variations.

  10. Analysis of regional-scale vegetation dynamics of Mexico using stratified AVHRR NDVI data. [Normalized Difference Vegetaion Index

    Science.gov (United States)

    Turcotte, Kevin M.; Kramber, William J.; Venugopal, Gopalan; Lulla, Kamlesh

    1989-01-01

    Previous studies have shown that a good relationship exists between AVHRR Normalized Difference Vegetation Index (NDVI) measurements, and both regional-scale patterns of vegetation seasonality and productivity. Most of these studies used known samples of vegetation types. An alternative approach, and the objective was to examine the above relationships by analyzing one year of AVHRR NDVI data that was stratified using a small-scale vegetation map of Mexico. The results show that there is a good relationship between AVHRR NDVI measurements and regional-scale vegetation dynamics of Mexico.

  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. Conjoint Seasonal and Intraseasonal Dynamics of Precipitation and NDVI Over The Amazon And The Congo Rainforests

    Science.gov (United States)

    Yepes, L. J.; Poveda, G.

    2014-12-01

    We study the conjoint seasonal and intraseasonal variability of precipitation and NDVI over the Amazon and the Congo rainforests, using pentad precipitation from the Tropical Rainfall Measuring Mission (TRMM; 0.25°x0.25°; from 1998 to 2010), as well as from the CPC Merged Analysis of Precipitation (CMAP; 2.5°x2.5°; from 1979 to 2011). NDVI is obtained from NASA (DAAC-EOSDIS) (0.25°x0.25°, from 2000 to 2010). Results for Amazonia show a uni-modal out-phased seasonal cycle of precipitation and NDVI, whereas bi-modal and in-phase over the Congo (Figure 1). Dry months over Amazonia (August-September) correspond with lagged maximum NDVI values in June-July-August (Western-Central-Eastern) and with the second wet season over the Congo, whereas wet-season months over Amazonia (March-April) coincide with the lowest NDVI values, as well as with the first wet season and maximum NDVI over the Congo. A (tropical) transatlantic Empirical Orthogonal Functions (EOF) analysis of pentad precipitation (20-100 day filtered) indicates that EOF No. 1 (52% of variance; Fig. 2a) exhibits a meridional dipole with higher positive loadings over the tropical North Atlantic (5°N-10°N), and higher negative loadings from 5°N to the equator over the Atlantic, and to 15°S over the continents. The Principal Component No. 1 exhibits a predominant 37-day frequency. EOF No. 2 (18% of variance; Fig.2b) exhibits a tripole pattern with positive loadings over southern Amazonia, the tropical North Atlantic, and (south) equatorial Africa, and a transatlantic pattern of negative loadings from 0 to 5°N including both continents, with a 38-day periodicity. EOF No. 3 (8% of variance; Fig. 2c) exhibits a tripole between the Amazon, the Atlantic Ocean and the Congo, with a 19-day frequency. EOF No. 4 (5%; Fig. 2d) shows a dipole between the Amazon and Congo rainforests, with a predominant period of 20 days. The apparent west-to-east patterns identified in the principal EOFs could be associated with

  13. Utilização do software estatístico r na previsão de séries temporais: série prêmio de resseguro

    Directory of Open Access Journals (Sweden)

    Rafael Ferraz de Moraes

    2014-08-01

    Full Text Available O objetivo dos autores no presente artigo é a utilização de modelos estocásticos da família SARIMA multiplicativo, de Box & Jenkins, para análise e previsão de séries temporais. Para tanto, é utilizado o software R, um pacote estatístico desenvolvido em ambiente livre e muito utilizado nas universidades. Para o estudo de caso de aplicação e funcionalidade do software, nas fases de identificação e estimação de modelos, foi utilizada a série temporal Prêmio de Resseguro de jan/2001 a dez/2008. Dessa forma, são descritos os modelos utilizados, os passos básicos com a linguagem de programação R, os resultados obtidos e as considerações finais

  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. Applying Markov Chains for NDVI Time Series Forecasting of Latvian Regions

    Directory of Open Access Journals (Sweden)

    Stepchenko Arthur

    2015-12-01

    Full Text Available Time series of earth observation based estimates of vegetation inform about variations in vegetation at the scale of Latvia. A vegetation index is an indicator that describes the amount of chlorophyll (the green mass and shows the relative density and health of vegetation. NDVI index 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. In this paper, we make a one-step-ahead prediction of 7-daily time series of NDVI index using Markov chains. The choice of a Markov chain is due to the fact that a Markov chain is a sequence of random variables where each variable is located in some state. And a Markov chain contains probabilities of moving from one state to other.

  16. 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.

  17. 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.

  18. 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.

  19. 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...

  20. Does NDVI reflect variation in the structural attributes associated with increasing shrub dominance in arctic tundra?

    International Nuclear Information System (INIS)

    This study explores relationships between the normalized difference vegetation index (NDVI) and structural characteristics associated with deciduous shrub dominance in arctic tundra. Our structural measures of shrub dominance are stature, branch abundance, aerial per cent woody stem cover (deciduous and evergreen species), and per cent deciduous shrub canopy cover. All measurements were taken across a suite of transects that together represent a gradient of deciduous shrub height. The transects include tussock tundra shrub and riparian shrub tundra communities located in the northern foothills of the Brooks Range, in northern Alaska. Plot-level NDVI measurements were made in 2010 during the snow-free period prior to deciduous shrub leaf-out (early June, NDVIpre-leaf), at the point in the growing season when canopy NDVI has reached half of its maximum growing season value (mid-June, NDVIdemi-leaf) and during the period of maximum leaf-out (late July, NDVIpeak-leaf). We found that: (1) NDVIpre-leaf is best suited to capturing variation in the per cent woody stem cover, maximum shrub height, and branch abundance, particularly between 10 and 50 cm height in the canopy; (2) NDVIpeak-leaf is best suited to capturing variation in deciduous canopy cover; and (3) NDVIdemi-leaf does not capture variability in any of our measures of shrub dominance. These findings suggest that in situ NDVI measurements made prior to deciduous canopy leaf-out could be used to identify small differences in maximum shrub height, woody stem cover, and branch abundance (particularly between 10 and 50 cm height in the canopy). Because shrubs are increasing in size and regional extent in several regions of the Arctic, investigation into spectrally based tools for monitoring these changes are worthwhile as they provide a first step towards development of remotely sensed techniques for quantifying associated changes in regional carbon cycling, albedo, radiative energy balance, and wildlife habitat.

  1. Aggregation and Association of NDVI, Boll Injury, and Stink Bugs in North Carolina Cotton

    OpenAIRE

    Reisig, Dominic D.; Reay-Jones, F. P. F.; Meijer, A. D.

    2015-01-01

    Sampling of herbivorous stink bugs in southeastern U.S. cotton remains problematic. Remote sensing was explored to improve sampling of these pests and associated boll injury. Two adjacent 14.5-ha cotton fields were grid sampled in 2011 and 2012 by collecting stink bug adults and bolls every week during the third, fourth, and fifth weeks of bloom. Satellite remote sensing data were collected during the third week of bloom during both years, and normalized difference vegetation index (NDVI) val...

  2. NDVI FROM ACTIVE OPTICAL SENSORS AS A MEASURE OF CANOPY COVER AND BIOMASS

    OpenAIRE

    E. M. Perry; Fitzgerald, G J; Poole, N.; Craig, S; A. Whitlock

    2012-01-01

    Commercially available proximal sensors are being used in precision agriculture to provide non-destructive, real-time spatial information on 'green biomass' that may be of interest to the remote sensing community. The sensors are described as biomass sensors, but questions remain on which canopy characteristics can be best estimated by the sensor measurements. In this study Normalized Difference Vegetation Index (NDVI) measurements from active optical sensors were examined across mul...

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

    OpenAIRE

    Rossana Monica Ferrara; Costanza Fiorentino; Nicola Martinelli; Pasquale Garofalo; Gianfranco Rana

    2010-01-01

    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 c...

  4. Monitoring Grassland Seasonal Carbon Dynamics, by Integrating MODIS NDVI, Proximal Optical Sampling, and Eddy Covariance Measurements

    OpenAIRE

    Enrica Nestola; Carlo Calfapietra; Craig A. Emmerton; Wong, Christopher Y. S.; Donnette R. Thayer; Gamon, John A.

    2016-01-01

    This study evaluated the seasonal productivity of a prairie grassland (Mattheis Ranch, in Alberta, Canada) using a combination of remote sensing, eddy covariance, and field sampling collected in 2012–2013. A primary objective was to evaluate different ways of parameterizing the light-use efficiency (LUE) model for assessing net ecosystem fluxes at two sites with contrasting productivity. Three variations on the NDVI (Normalized Difference Vegetation Index), differing by formula and footprint,...

  5. 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...

  6. Landscape-scale characterization of vegetation phenology using AVHRR-NDVI and Landsat-TM data

    Science.gov (United States)

    Simoniello, Tiziana; Carone, M. T.; Lanfredi, Maria; Macchiato, Maria; Cuomo, Vincenzo

    2004-02-01

    The strict link between intra-annual vegetation dynamics (phenology) and Earth's climate makes phenological information fundamental to improve understanding and models of inter-annual variability in terrestrial carbon exchange and climate-biosphere interactions. In order to monitor phenology in a landscape characterized by heterogeneous features rapidly changing over the territory, we performed multitemporal classifications of NDVI-AVHRR data and interfaced them with Landsat-TM data and orography. The sample area is the Vulture basin (Southern Italy), where cultivated and densely vegetated areas coexist with urban and recently built industrial areas. These land cover patterns rapidly change over the territory at very small spatial scales; it is a complex zone very interesting for studying the use of remote sensing techniques in the integrated monitoring context. Clusters having homogeneous NDVI time behaviors were identified. In spite of its spatial resolution, AVHRR NDVI effectively picks up the characteristic phenology for different covers and altitudes. Moreover, some pixels having particular microclimate were clustered and their characterization was only possible by using orography and TM classification information. The comparison of two intra-annual classifications (1996 and 1998) showed that the proposed approach can be very useful for studying change in pattern of vegetation dynamics.

  7. 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.

  8. Scaling Effect of Area-Averaged NDVI: Monotonicity along the Spatial Resolution

    Directory of Open Access Journals (Sweden)

    Hiroki Yoshioka

    2012-01-01

    Full Text Available Changes in the spatial distributions of vegetation across the globe are routinely monitored by satellite remote sensing, in which the reflectance spectra over land surface areas are measured with spatial and temporal resolutions that depend on the satellite instrumentation. The use of multiple synchronized satellite sensors permits long-term monitoring with high spatial and temporal resolutions. However, differences in the spatial resolution of images collected by different sensors can introduce systematic biases, called scaling effects, into the biophysical retrievals. This study investigates the mechanism by which the scaling effects distort normalized difference vegetation index (NDVI. This study focused on the monotonicity of the area-averaged NDVI as a function of the spatial resolution. A monotonic relationship was proved analytically by using the resolution transform model proposed in this study in combination with a two-endmember linear mixture model. The monotonicity allowed the inherent uncertainties introduced by the scaling effects (error bounds to be explicitly determined by averaging the retrievals at the extrema of theresolutions. Error bounds could not be estimated, on the other hand, for non-monotonic relationships. Numerical simulations were conducted to demonstrate the monotonicity of the averaged NDVI along spatial resolution. This study provides a theoretical basis for the scaling effects and develops techniques for rectifying the scaling effects in biophysical retrievals to facilitate cross-sensor calibration for the long-term monitoring of vegetation dynamics.

  9. Mapping Rice Cropping Systems in Vietnam Using an NDVI-Based Time-Series Similarity Measurement Based on DTW Distance

    OpenAIRE

    Xudong Guan; Chong Huang; Gaohuan Liu; Xuelian Meng; Qingsheng Liu

    2016-01-01

    Normalized Difference Vegetation Index (NDVI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) time-series data has been widely used in the fields of crop and rice classification. The cloudy and rainy weather characteristics of the monsoon season greatly reduce the likelihood of obtaining high-quality optical remote sensing images. In addition, the diverse crop-planting system in Vietnam also hinders the comparison of NDVI among different crop stages. To address these proble...

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

    OpenAIRE

    Stefan Wunderle; Gabriel Aberegg; Tobias Jonas; Christian Rixen; Fabio Fontana

    2008-01-01

    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 fract...

  11. 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.

  12. 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.

  13. Recent NDVI-Based Variation in Growth of Boreal Intact Forest Landscapes and Its Correlation with Climatic Variables

    Directory of Open Access Journals (Sweden)

    Jiaxin Jin

    2016-04-01

    Full Text Available Intact Forest Landscape (IFL is of great value in protecting biodiversity and supporting core ecological processes. It is important to analyze the spatial variation in the growth dynamics of IFL. This study analyzed the change of the Normalized Difference Vegetation Index (NDVI during the growing season (April–October for boreal (45° N–70° N IFLs and the correlation with climatic variables over the period of 2000–2013. Our results show 85.5% of boreal IFLs did not show a significant change in the NDVI after 2000, and only 10.2% and 4.3% exhibited a statistically significant increase (greening or decrease (browning in NDVI, respectively. About 60.9% of the greening boreal IFLs showed that an increasing NDVI was significantly correlated to climatic variables, especially an increasing growing season temperature (over 47.0%. For browning boreal IFLs, a decrease in temperature or an increase in dormancy period precipitation could be the prime reason for a significant decrease in the NDVI. However, about 64.6% of the browning boreal IFLs were insensitive to any of the climatic variables, indicating other factors, such as fire, had caused the browning. Although it did not show a significant trend, the NDVI of 51.3% of no-change boreal IFLs significantly correlated to climatic variables, especially growing season temperatures (over 37.6%.

  14. 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

  15. 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.

  16. 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

  17. Study of the NDVI with multi-scale and time-series analysis using SPOT imagery during the period 1998-2012 in Uruguay

    OpenAIRE

    M. Ceroni; M. Achkar; I. Gazzano; J. Burgeño

    2015-01-01

    Vegetation indices are a relevant source of information for spatial monitoring of vegetation at multiple scales. Among them, the Normalized Difference Vegetation Index (NDVI) is one of the most commonly used. This study aims to describe and analyze the spatial patterns of the NDVI in terrestrial systems in Uruguay at the onset of the 21st Century. A multiscalar approach (country, basin and sites) was applied using time series analysis of NDVI values obtained from SPOT 4 and 5 images through t...

  18. 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.

  19. Historical extension of operational NDVI products for livestock insurance in Kenya

    Science.gov (United States)

    Vrieling, Anton; Meroni, Michele; Shee, Apurba; Mude, Andrew G.; Woodard, Joshua; de Bie, C. A. J. M. (Kees); Rembold, Felix

    2014-05-01

    Droughts induce livestock losses that severely affect Kenyan pastoralists. Recent index insurance schemes have the potential of being a viable tool for insuring pastoralists against drought-related risk. Such schemes require as input a forage scarcity (or drought) index that can be reliably updated in near real-time, and that strongly relates to livestock mortality. Generally, a long record (>25 years) of the index is needed to correctly estimate mortality risk and calculate the related insurance premium. Data from current operational satellites used for large-scale vegetation monitoring span over a maximum of 15 years, a time period that is considered insufficient for accurate premium computation. This study examines how operational NDVI datasets compare to, and could be combined with the non-operational recently constructed 30-year GIMMS AVHRR record (1981-2011) to provide a near-real time drought index with a long term archive for the arid lands of Kenya. We compared six freely available, near-real time NDVI products: five from MODIS and one from SPOT-VEGETATION. Prior to comparison, all datasets were averaged in time for the two vegetative seasons in Kenya, and aggregated spatially at the administrative division level at which the insurance is offered. The feasibility of extending the resulting aggregated drought indices back in time was assessed using jackknifed R2 statistics (leave-one-year-out) for the overlapping period 2002-2011. We found that division-specific models were more effective than a global model for linking the division-level temporal variability of the index between NDVI products. Based on our results, good scope exists for historically extending the aggregated drought index, thus providing a longer operational record for insurance purposes. We showed that this extension may have large effects on the calculated insurance premium. Finally, we discuss several possible improvements to the drought index.

  20. Identificação de estruturas não-lineares de séries temporais através de regressão linear local e modelos aditivos

    Directory of Open Access Journals (Sweden)

    Rosane M. Kirchner

    2008-04-01

    Full Text Available Este estudo trata da utilização de uma metodologia para identificação da estrutura de séries temporais não lineares (ou lineares baseada na estimação não e semi-paramétrica de curvas em modelos do tipo Yt = E(Yt|Xt + et , onde Xt = (Yt-1,Yt-2,...,Yt-d, d = 1,2,.... Aqui, a esperança condicional é estimada de modo totalmente não-paramétrico ou através de um modelo (semi-paramétrico aditivo. Especificamente, a função desconhecida será estimada através de regressões lineares locais, via estimadores núcleo. Com a metodologia proposta, verificamos que a "função de dependência da defasagem" (FDD e a "função de dependência parcial da defasagem" (FDPD conseguem captar estruturas não-lineares em séries temporais, generalizando as tradicionais funções de autocorrelação (FAC e autocorrelação parcial (FACP. Os estudos de simulação foram conduzidos de forma a avaliar e comparar a metodologia proposta com metodologias já existentes. Para dados reais a metodologia proposta foi exemplificada com uma série diária de preços da ação Petrobras PN.This paper suggests an approach for the identification of the structure of both linear and non-linear time series through semi-parametric estimation of the unknown curves in models of the type Yt=E(Yt| Xt +et , where Xt=(Yt-1,Yt-2,...,Yt-d, d=1,2,…. The conditional expectation is estimated either in a fully nonparametric fashion or via additive (semi-parametric models. Specifically, the unknown function will be estimated by local linear regression, with kernel estimators. Under the proposed methodology, it was verified that the Lag Dependence Function (LDF and the Partial Lag Dependence Function (PLDF are capable of identifying non-linear structures in time series, generalizing the traditional autocorrelation and partial autocorrelation functions. The simulation studies were conducted to evaluate and compare the proposed methodology to traditional ones. The approach was

  1. 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.

  2. 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.

  3. A Phenology-Based Method for Monitoring Woody and Herbaceous Vegetation in Mediterranean Forests from NDVI Time Series

    Directory of Open Access Journals (Sweden)

    David Helman

    2015-09-01

    Full Text Available We present an efficient method for monitoring woody (i.e., evergreen and herbaceous (i.e., ephemeral vegetation in Mediterranean forests at a sub pixel scale from Normalized Difference Vegetation Index (NDVI time series derived from the Moderate Resolution Imaging Spectroradiometer (MODIS. The method is based on the distinct development periods of those vegetation components. In the dry season, herbaceous vegetation is absent or completely dry in Mediterranean forests. Thus the mean NDVI in the dry season was attributed to the woody vegetation (NDVIW. A constant NDVI value was assumed for soil background during this period. In the wet season, changes in NDVI were attributed to the development of ephemeral herbaceous vegetation in the forest floor and its maximum value to the peak green cover (NDVIH. NDVIW and NDVIH agreed well with field estimates of leaf area index and fraction of vegetation cover in two differently structured Mediterranean forests. To further assess the method’s assumptions, understory NDVI was retrieved form MODIS Bidirectional Reflectance Distribution Function (BRDF data and compared with NDVIH. After calibration, leaf area index and woody and herbaceous vegetation covers were assessed for those forests. Applicability for pre- and post-fire monitoring is presented as a potential use of this method for forest management in Mediterranean-climate regions.

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

    Science.gov (United States)

    Gong, Z.; Kawamura, K.; Ishikawa, N.; Goto, M.; Wulan, T.; Alateng, D.; Yin, T.; Ito, Y.

    2015-08-01

    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.

  5. MODIS normalized difference vegetation index (NDVI) and vegetation phenology dynamics in the Inner Mongolia grassland

    Science.gov (United States)

    Gong, Z.; Kawamura, K.; Ishikawa, N.; Goto, M.; Wulan, T.; Alateng, D.; Yin, T.; Ito, Y.

    2015-11-01

    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 and increasing temperature at the early growing period because of global warming. Overall, productivity in the Inner Mongolia Autonomous Region tends to increase, but in some grassland areas with grazing, land degradation is ongoing.

  6. 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.

  7. Monitoring seasonal and diurnal changes in photosynthetic pigments with automated PRI and NDVI sensors

    Directory of Open Access Journals (Sweden)

    J. A. Gamon

    2015-02-01

    only, and the other that also considered diurnal sun angle effects. Cross-calibration clearly affected sensor agreement with independent measurements, with the best method dependent upon the study aim and time frame (seasonal vs. diurnal. The seasonal patterns of NDVI and PRI differed for evergreen and deciduous species, demonstrating the complementary nature of these two indices. Over the spring season, PRI was most strongly influenced by changing chlorophyll : carotenoid pool sizes, while over the diurnal time scale PRI was most affected by the xanthophyll cycle epoxidation state. This finding demonstrates that the SRS PRI sensors can resolve different processes affecting PRI over different time scales. The advent of small, inexpensive, automated PRI and NDVI sensors offers new ways to explore environmental and physiological constraints on photosynthesis, and may be particularly well-suited for use at flux tower sites. Wider application of automated sensors could lead to improved integration of flux and remote sensing approaches to studying photosynthetic carbon uptake, and could help define the concept of contrasting vegetation optical types.

  8. Mapping Impervious Surface Distribution with Integration of SNNP VIIRS-DNB and MODIS NDVI Data

    Directory of Open Access Journals (Sweden)

    Wei Guo

    2015-09-01

    Full Text Available Data from the U.S. Defense Meteorological Satellite Program’s Operational Line-scan System are often used to map impervious surface area (ISA distribution at regional and global scales, but its coarse spatial resolution and data saturation produce high inaccuracy in ISA estimation. Suomi National Polar-orbiting Partnership (SNPP Visible Infrared Imaging Radiometer Suite’s Day/Night Band (VIIRS-DNB with its high spatial resolution and dynamic data range may provide new insights but has not been fully examined in mapping ISA distribution. In this paper, a new variable—Large-scale Impervious Surface Index (LISI—is proposed to integrate VIIRS-DNB and Moderate Resolution Imaging Spectroradiometer (MODIS normalized difference vegetation index (NDVI data for mapping ISA distribution. A regression model was established, in which LISI was used as an independent variable and the reference ISA from Landsat images was a dependent variable. The results indicated a better estimation performance using LISI than using a single VIIRS-DNB or MODIS NDVI variable. The LISI-based approach provides accurate spatial patterns from high values in core urban areas to low values in rural areas, with an overall root mean squared error of 0.11. The LISI-based approach is recommended for fractional ISA estimation in a large area.

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

    International Nuclear Information System (INIS)

    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

  10. Environment, vegetation and greenness (NDVI) along the North America and Eurasia Arctic transects

    International Nuclear Information System (INIS)

    Satellite-based measurements of the normalized difference vegetation index (NDVI; an index of vegetation greenness and photosynthetic capacity) indicate that tundra environments are generally greening and becoming more productive as climates warm in the Arctic. The greening, however, varies and is even negative in some parts of the Arctic. To help interpret the space-based observations, the International Polar Year (IPY) Greening of the Arctic project conducted ground-based surveys along two >1500 km transects that span all five Arctic bioclimate subzones. Here we summarize the climate, soil, vegetation, biomass, and spectral information collected from the North America Arctic transect (NAAT), which has a more continental climate, and the Eurasia Arctic transect (EAT), which has a more oceanic climate. The transects have broadly similar summer temperature regimes and overall vegetation physiognomy, but strong differences in precipitation, especially winter precipitation, soil texture and pH, disturbance regimes, and plant species composition and structure. The results indicate that summer warmth and NDVI increased more strongly along the more continental transect. (letter)

  11. Environment, vegetation and greenness (NDVI) along the North America and Eurasia Arctic transects

    Science.gov (United States)

    Walker, D. A.; Epstein, H. E.; Raynolds, M. K.; Kuss, P.; Kopecky, M. A.; Frost, G. V.; Daniëls, F. J. A.; Leibman, M. O.; Moskalenko, N. G.; Matyshak, G. V.; Khitun, O. V.; Khomutov, A. V.; Forbes, B. C.; Bhatt, U. S.; Kade, A. N.; Vonlanthen, C. M.; Tichý, L.

    2012-03-01

    Satellite-based measurements of the normalized difference vegetation index (NDVI; an index of vegetation greenness and photosynthetic capacity) indicate that tundra environments are generally greening and becoming more productive as climates warm in the Arctic. The greening, however, varies and is even negative in some parts of the Arctic. To help interpret the space-based observations, the International Polar Year (IPY) Greening of the Arctic project conducted ground-based surveys along two >1500 km transects that span all five Arctic bioclimate subzones. Here we summarize the climate, soil, vegetation, biomass, and spectral information collected from the North America Arctic transect (NAAT), which has a more continental climate, and the Eurasia Arctic transect (EAT), which has a more oceanic climate. The transects have broadly similar summer temperature regimes and overall vegetation physiognomy, but strong differences in precipitation, especially winter precipitation, soil texture and pH, disturbance regimes, and plant species composition and structure. The results indicate that summer warmth and NDVI increased more strongly along the more continental transect.

  12. 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.

  13. [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

  14. 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.

  15. Relative sensitivity of Normalized Difference Vegetation Index (NDVI) and Microwave Polarization Difference Index (MPDI) for vegetation and desertification monitoring

    Science.gov (United States)

    Becker, Francois; Choudhury, Bhaskar J.

    1988-01-01

    A simple equation relating the Microwave Polarization Difference Index (MPDI) and the Normalized Difference Vegetation Index (NDVI) is proposed which represents well data obtained from Nimbus 7/SMMR at 37 GHz and NOAA/AVHRR Channels 1 and 2. It is found that there is a limit which is characteristic of a particular type of cover for which both indices are equally sensitive to the variation of vegetation, and below which MPDI is more efficient than NDVI. The results provide insight into the relationship between water content and chlorophyll absorption at pixel size scales.

  16. 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, J.; Hargrove, W. W.; Gasser, J.; Smoot, J.; Kuper, P.

    2014-12-01

    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). This EWS 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 and MODIS MOD13 data are used to obtain current and historical NDVIs, respectively. Historical NDVI data is processed with the Time Series Product Tool (TSPT) and the Phenological Parameters Estimation Tool (PPET) software. While each change product employs 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. The

  17. 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

  18. Spatial variability of NDVI at different seasons in the Community of Madrid (Spain)

    Science.gov (United States)

    Sotoca, Juan J. Martin; Saa-Requejo, Antonio; Borondo, Javier; Tarquis, Ana M.

    2015-04-01

    Agricultural drought quantification is one of the most important tasks in the characterization process of this natural hazard and its implications in crop insurance. Recently, several vegetation indexes based on remote-sensing data (VI) has been applied to quantify it (Dalezios et al, 2012). VIs are obtained combining several frequency bands that represent the relationship between photosynthesis and absorbed/reflected radiation. The most widely used VI is the Normalized Difference Vegetation Index (NDVI). It is based on the principle that healthy vegetation mainly absorbs visible light and reflects the near-infrared frequency band. Drought can be highly localized, and several authors have recognized the critical role of soil moisture and its spatial variability in agricultural losses (Anderson et al., 2011). Therefore, it is important to delimit locations within a homogeneous area that will share main NDVI statistics and in which the same threshold value can be applied to define drought event. In order to do so, we have applied for the first time in this context the method of singularity maps (Cheng and Agterberg, 1996) commonly used in localization of mineral deposits. The NDVI singularity maps calculated in each season through 2011/2012 are showed and discussed (Martín-Sotoca, 2014). References Anderson, M:C:, C. R. Hain, B. Wardlow, J. R. Mecikalski and W. P. Kustas (2011) Evaluation of drought indices based on thermal remote sensing of evapotranspiration over the continental United States. J. Climate, 24, 2025-2044. Dalezios, N.R., A. Blanta, N.V. Spyropoulos and A.M. Tarquis (2012) Risk identification of agricultural drought for sustainable Agroecosystems. Nat. Hazards Earth Syst. Sci., 14, 2435-2448. Cheng, Q. and F.P. Agterberg (1996) Multifractal modeling and spatial statistics. Math. Geol., 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

  19. 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; Fensholt, Rasmus

    2015-01-01

    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...... grazing exclosures as compared to grazed areas, substantially exceeding the amount of biomass expected to be ingested by livestock for this area. The seasonal integrated NDVI (NDVI small integral; capturing only the signal inherent to the growing season recurrent vegetation), derived using absolute...... thresholds 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...

  20. 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.

  1. Error simulations of uncorrected NDVI and DCVI during remote sensing measurements from UAS

    Directory of Open Access Journals (Sweden)

    Chiliński Michał T.

    2014-06-01

    Full Text Available Remote sensing from unmanned aerial systems (UAS has been gaining popularity in the last few years. In the field of vegetation mapping, digital cameras converted to calculate vegetation index (DCVI are one of the most popular sensors. This paper presents simulations using a radiative transfer model (libRadtran of DCVI and NDVI results in an environment of possible UAS flight scenarios. The analysis of the results is focused on the comparison of atmosphere influence on both indices. The results revealed uncertainties in uncorrected DCVI measurements up to 25% at the altitude of 5 km, 5% at 1 km and around 1% at 0.15 km, which suggests that DCVI can be widely used on small UAS operating below 0.2 km.

  2. Intra-annual NDVI validation of the Landsat 5 TM radiometric calibration

    Science.gov (United States)

    Chander, G.; Groeneveld, D.P.

    2009-01-01

    Multispectral data from the Landsat 5 (L5) Thematic Mapper (TM) sensor provide the backbone of the extensive archive of moderate-resolution Earth imagery. Even after more than 24 years of service, the L5 TM is still operational. Given the longevity of the satellite, the detectors have aged and the sensor's radiometric characteristics have changed since launch. The calibration procedures and parameters in the National Land Archive Production System (NLAPS) have also changed with time. Revised radiometric calibrations in 2003 and 2007 have improved the radiometric accuracy of recently processed data. This letter uses the Normalized Difference Vegetation Index (NDVI) as a metric to evaluate the radiometric calibration. The calibration change has improved absolute calibration accuracy, consistency over time, and consistency with Landsat 7 (L7) Enhanced Thematic radiometry and will provide the basis for continued long-term studies of the Earth's land surfaces.

  3. 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.

  4. 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.

  5. A categorical, improper probability method for combining NDVI and LiDAR elevation information for potential cotton precision agricultural applications

    Science.gov (United States)

    An algorithm is presented to fuse the Normalized Difference Vegetation Index (NDVI) with Light Detection and Ranging (LiDAR) elevation data to produce a map potentially useful for the site-specific scouting and pest management of several insect pests. In cotton, these pests include the Tarnished Pl...

  6. Exploring the Use of MODIS NDVI-Based Phenology Indicators for Classifying Forest General Habitat Categories

    Directory of Open Access Journals (Sweden)

    France Gerard

    2012-06-01

    Full Text Available The cost effective monitoring of habitats and their biodiversity remains a challenge to date. Earth Observation (EO has a key role to play in mapping habitat and biodiversity in general, providing tools for the systematic collection of environmental data. The recent GEO-BON European Biodiversity Observation Network project (EBONE established a framework for an integrated biodiversity monitoring system. Underlying this framework is the idea of integrating in situ with EO and a habitat classification scheme based on General Habitat Categories (GHC, designed with an Earth Observation-perspective. Here we report on EBONE work that explored the use of NDVI-derived phenology metrics for the identification and mapping of Forest GHCs. Thirty-one phenology metrics were extracted from MODIS NDVI time series for Europe. Classifications to discriminate forest types were performed based on a Random Forests™ classifier in selected regions. Results indicate that date phenology metrics are generally more significant for forest type discrimination. The achieved class accuracies are generally not satisfactory, except for coniferous forests in homogeneous stands (77–82%. The main causes of low classification accuracies were identified as (i the spatial resolution of the imagery (250 m which led to mixed phenology signals; (ii the GHC scheme classification design, which allows for parcels of heterogeneous covers, and (iii the low number of the training samples available from field surveys. A mapping strategy integrating EO-based phenology with vegetation height information is expected to be more effective than a purely phenology-based approach.

  7. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  11. Variações temporais e ontogenéticas na dieta de um peixe onívoro em ambiente impactado (reservatório) e em ambiente natural (baía) da bacia do rio Cuiabá = Temporal and ontogenetic diet changes of omnivorous fish in an impacted (reservoir) and in a natural environment (lagoon)

    OpenAIRE

    Edson Lourenço da Silva; Rosemara Fugi; Norma Segatti Hahn

    2007-01-01

    Neste trabalho, foram avaliadas as variações temporais e ontogenéticas na dieta de Pimelodus maculatus no reservatório de Manso e na baía Sinhá Mariana, Estado do Mato Grosso. Os peixes foram coletados, mensalmente, de março/2000 a fevereiro/2001 comredes de espera e de arrasto. Foram analisados 199 conteúdos estomacais por meio do método volumétrico. No reservatório, a dieta foi composta basicamente por insetos durante todo o período analisado e independente do tamanho dos exemplares. Na baí...

  12. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Global patterns of NDVI-indicated vegetation extremes and their sensitivity to climate extremes

    International Nuclear Information System (INIS)

    Extremes in climate have significant impacts on ecosystems and are expected to increase under future climate change. Extremes in vegetation could capture such impacts and indicate the vulnerability of ecosystems, but currently have not received a global long-term assessment. In this study, a robust method has been developed to detect significant extremes (low values) in biweekly time series of global normalized difference vegetation index (NDVI) from 1982 to 2006 and thus to acquire a global pattern of vegetation extreme frequency. This pattern coincides with vegetation vulnerability patterns suggested by earlier studies using different methods over different time spans, indicating a consistent mechanism of regulation. Vegetation extremes were found to aggregate in Amazonia and in the semi-arid and semi-humid regions in low and middle latitudes, while they seldom occurred in high latitudes. Among the environmental variables studied, extreme low precipitation has the highest slope against extreme vegetation. For the eight biomes analyzed, these slopes are highest in temperate broadleaf forest and temperate grassland, suggesting a higher sensitivity in these environments. The results presented here contradict the hypothesis that vegetation in water-limited semi-arid and semi-humid regions might be adapted to drought and suggest that vegetation in these regions (especially temperate broadleaf forest and temperate grassland) is highly prone to vegetation extreme events under more severe precipitation extremes. It is also suggested here that more attention be paid to precipitation-induced vegetation changes than to temperature-induced events. (letter)

  19. Deriving Vegetation Dynamics of Natural Terrestrial Ecosystems from MODIS NDVI/EVI Data over Turkey

    Directory of Open Access Journals (Sweden)

    Onder Gulbeyaz

    2008-09-01

    Full Text Available The 16-day composite MODIS vegetation indices (VIs at 500-m resolution for the period between 2000 to 2007 were seasonally averaged on the basis of the estimated distribution of 16 potential natural terrestrial ecosystems (NTEs across Turkey. Graphical and statistical analyses of the time-series VIs for the NTEs spatially disaggregated in terms of biogeoclimate zones and land cover types included descriptive statistics, correlations, discrete Fourier transform (DFT, time-series decomposition, and simple linear regression (SLR models. Our spatio-temporal analyses revealed that both MODIS VIs, on average, depicted similar seasonal variations for the NTEs, with the NDVI values having higher mean and SD values. The seasonal VIs were most correlated in decreasing order for: barren/sparsely vegetated land > grassland > shrubland/woodland > forest; (subnival > warm temperate > alpine > cool temperate > boreal = Mediterranean; and summer > spring > autumn > winter. Most pronounced differences between the MODIS VI responses over Turkey occurred in boreal and Mediterranean climate zones and forests, and in winter (the senescence phase of the growing season. Our results showed the potential of the time-series MODIS VI datasets in the estimation and monitoring of seasonal and interannual ecosystem dynamics over Turkey that needs to be further improved and refined through systematic and extensive field measurements and validations across various biomes.

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

    OpenAIRE

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

    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, 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...

  1. Detecting Leaf Pulvinar Movements on NDVI Time Series of Desert Trees: A New Approach for Water Stress Detection

    OpenAIRE

    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, 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...

  2. 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...

  3. 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.

  4. Ruimtelijke vergelijking van gemodelleerde biomassa met NDVI; onderzoek ter verbetering van de modellering in de Natuurplanner van het Natuurplanbureau

    OpenAIRE

    Hazeu, G.W.; Wamelink, G.W.W.

    2004-01-01

    In dit rapport wordt de ruimtelijke vergelijking van, door SUMO gesimuleerde bladbiomassa, met de via remote sensing verkregen NDVI beschreven. Vergelijking heeft plaats gevonden voor meer dan 90% met vegetatiestructuurtypen gevulde SUMO grids (250m*250m) binnen de EHS. De gevonden relaties voor verschillende tijdstippen, per vegetatiestructuurtype en per functioneel type zijn niet significant of als ze significant zijn wordt slechts een geringe deel van de variantie verklaard. Schaal verschi...

  5. THE MODEL OF WHEAT YIELD FORECAST BASED ON MODIS-NDVI – A CASE STUDY OF XINXIANG

    OpenAIRE

    Zhang, H.; Chen, H.; Zhou, G.

    2012-01-01

    The yield estimation models on a regional scale are generally constrained by the lack of spatially distributed information on major environmental. The utilization of remote sensing data with various spatial and temporal resolutions can settle this problem. The NDVI, which retrieved from satellite remote sensing, was adopted to forecast winter wheat yields in this paper. There are two key steps in the process of calculating. The first is the establishment of the relationship between N...

  6. Strategy for the development of a smart NDVI camera system for outdoor plant detection and agricultural embedded systems.

    Science.gov (United States)

    Dworak, Volker; Selbeck, Joern; Dammer, Karl-Heinz; Hoffmann, Matthias; Zarezadeh, Ali Akbar; Bobda, Christophe

    2013-01-01

    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. PMID:23348037

  7. 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.

  8. Estimation of leaf area index using ground-based remote sensed NDVI measurements: validation and comparison with two indirect techniques

    International Nuclear Information System (INIS)

    This study took place in an evergreen scrub oak ecosystem in Florida. Vegetation reflectance was measured in situ with a laboratory-made sensor in the red (640-665 nm) and near-infrared (750-950 nm) bands to calculate the normalized difference vegetation index (NDVI) and derive the leaf area index (LAI). LAI estimates from this technique were compared with two other nondestructive techniques, intercepted photosynthetically active radiation (PAR) and hemispherical photographs, in four contrasting 4 m2 plots in February 2000 and two 4m2 plots in June 2000. We used Beer's law to derive LAI from PAR interception and gap fraction distribution to derive LAI from photographs. The plots were harvested manually after the measurements to determine a 'true' LAI value and to calculate a light extinction coefficient (k). The technique based on Beer's law was affected by a large variation of the extinction coefficient, owing to the larger impact of branches in winter when LAI was low. Hemispherical photographs provided satisfactory estimates, slightly overestimated in winter because of the impact of branches or underestimated in summer because of foliage clumping. NDVI provided the best fit, showing only saturation in the densest plot (LAI = 3.5). We conclude that in situ measurement of NDVI is an accurate and simple technique to nondestructively assess LAI in experimental plots or in crops if saturation remains acceptable. (author)

  9. 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

  10. 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...

  11. 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...

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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.

  19. 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

  20. Distributed modelling of evapotranspiration using high-resolution NDVI maps over cropland in South-West France

    Science.gov (United States)

    Cherif, R.; Simonneaux, V.; Rivalland, V.; Gascoin, S.; Le Page, M.; Ceschia, E.

    2012-04-01

    Distributed hydrological modelling in cropland areas requires an accurate estimation of evapotranspiration (ET). Remotely sensed data can support ET computation by providing valuable information on the vegetation condition. Here, we assessed the potential of high-resolution satellite imagery to monitor crop evapotranspiration over a small rural catchment area of South-West France (3.35 km2). We used a series of 88 Normalized Difference Vegetation Index (NDVI) maps spanning 2006-2009 derived from Formosat-2 images (8-m spatial resolution) to drive a dual crop coefficient model (SAMIR model). This model is based on the FAO-56 method and includes a conceptual soil module to account for soil water storage and drainage. The model was first applied at the plot scale (i.e. in 1-D mode) over a research site located in the watershed, which is instrumented with an eddy covariance system and soil moisture probes. This comparison enabled to identify the most critical model parameters and to adjust them to match the observed daily ET rates. In particular this analysis allowed the calibration of the linear relationship between the basal crop coefficient (Kcb) and the NDVI for winter wheat, rapeseed and sunflower. The model performance was also found to depend on the initial soil water content. At this stage good model performances were achieved (annual R2 ranging from 0.7 to 0.8, bias 5% to 15%). Further validation of the simulated soil water content indicated acceptable results without calibration. Then, the model was run at the catchment-scale using the calibrated Kcb, the NDVI images and a high-resolution land cover map for every year to predict the annual catchment evapotranspiration. We will present the result of the catchment-scale model validation based on the river discharge measurements.

  1. 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.

  2. 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

  3. 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

  4. Prototype land-cover mapping of the Huascaran Biosphere Reserve (Peru) using DEM, NDSI and NDVI indices

    OpenAIRE

    Silverio Torres, Walter Claudio; Jaquet, Jean-Michel

    2009-01-01

    On the basis of Landsat 7 ETM+ imagery, a prototype land-cover map was prepared for the Huascarán Biosphere Reserve (Peru). This document should contribute to the sustainable management of the Huascarán Biosphere Reserve, while making it possible to establish a regional planning policy and to prepare a natural risks map, which is still lacking in the region. The influence of the topography on radiometry was attenuated by using NDSI and NDVI indices, which were segmented using their histogram....

  5. SACRA - a method for the estimation of global high-resolution crop calendars from a satellite-sensed NDVI

    Science.gov (United States)

    Kotsuki, S.; Tanaka, K.

    2015-11-01

    To date, many studies have performed numerical estimations of biomass production and agricultural water demand to understand the present and future supply-demand relationship. A crop calendar (CC), which defines the date or month when farmers sow and harvest crops, is an essential input for the numerical estimations. This study aims to present a new global data set, the SAtellite-derived CRop calendar for Agricultural simulations (SACRA), and to discuss advantages and disadvantages compared to existing census-based and model-derived products. We estimate global CC at a spatial resolution of 5 arcmin using satellite-sensed normalized difference vegetation index (NDVI) data, which corresponds to vegetation vitality and senescence on the land surface. Using the time series of the NDVI averaged from three consecutive years (2004-2006), sowing/harvesting dates are estimated for six crops (temperate-wheat, snow-wheat, maize, rice, soybean and cotton). We assume time series of the NDVI represent the phenology of one dominant crop and estimate CCs of the dominant crop in each grid. The dominant crops are determined using harvested areas based on census-based data. The cultivation period of SACRA is identified from the time series of the NDVI; therefore, SACRA considers current effects of human decisions and natural disasters. The difference between the estimated sowing dates and other existing products is less than 2 months (< 62 days) in most of the areas. A major disadvantage of our method is that the mixture of several crops in a grid is not considered in SACRA. The assumption of one dominant crop in each grid is a major source of discrepancy in crop calendars between SACRA and other products. The disadvantages of our approach may be reduced with future improvements based on finer satellite sensors and crop-type classification studies to consider several dominant crops in each grid. The comparison of the CC also demonstrates that identification of wheat type (sowing in

  6. 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

  7. 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

  8. Perimetria computadorizada e manual em pacientes com defeitos perimétricos temporais avançados causados por tumores supra-selares Computerized and manual perimetry in patientes with severe temporal visual field defects due to supraselar tumors

    Directory of Open Access Journals (Sweden)

    Andrea Pereira

    2005-10-01

    Full Text Available OBJETIVO: Estudar, ao perímetro de Goldmann, um grupo de pacientes com hemianopsia completa ao perímetro Humphrey (24-2 full threshold test, e verificar em quantos casos a perimetria computadorizada deixou de identificar a presença de campo visual periférico residual. MÉTODOS: Dezenove pacientes com defeitos campimétricos por compressão quiasmática foram estudados prospectivamente por meio das perimetrias manual e computadorizada. Vinte e cinco olhos com hemianopsia temporal completa pelo programa 24-2 do Humphrey Field Analyzer foram selecionados e estudados pela perimetria manual de Goldmann para avaliar a presença de campo visual periférico residual. De acordo com os resultados ao perímetro de Goldmann, os olhos foram divididos em 2 grupos: grupo 1, os portadores de hemianopsia temporal completa ao Goldmann e grupo 2, os portadores de campo visual temporal periférico residual. Foi calculada a média do "mean deviation" fornecido pelo aparelho nos dois grupos e o resultado foi comparado pelo teste t de Student. RESULTADOS: A perimetria computadorizada deixou de identificar a presença de campo visual periférico residual em 17 dos 25 olhos (68%. Os valores médios do "mean deviation" no grupo 1 e grupo 2 foram respectivamente -15,43 e -15,93. O estudo estatístico não mostrou diferença significativa entre os dois valores. CONCLUSÕES: A perimetria computadorizada Humphrey com o programa 24-2 threshold test deixa de identificar remanescentes temporais de campo visual em grande porcentagem de pacientes com compressão quiasmática grave. A análise do "mean deviation" fornecido pelo aparelho não permite identificar estes casos. Pacientes estudados ao perímetro automático e apresentando hemianopsia temporal completa, devem complementar sua avaliação perimétrica com a pesquisa por áreas remanescentes no campo visual temporal.PURPOSE: To study, on Goldmann perimetry, a group of patients with complete temporal hemianopia on

  9. 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. PMID:26908366

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

    Shortwave Infrared Water Stress Index (SIWSI) as compared to Normalized Difference Vegetation Index (NDVI). We perform a spatio-temporal evaluation of NDVI and SIWSI using geostationary remote sensing imagery from the Spinning Enhanced Visible and Infrared Imager (SEVIRI). The indices and their seasonally......Satellite remote sensing of vegetation parameters and stress is a key issue for semi-arid areas such as the Sahel, where vegetation is an important part of the natural resource base. In this study we examine if additional information can be obtained on intra-seasonal short term scale by using the...... gradient in the river catchment. The hypothesis that short term evolution of index anomalies are related to canopy water status was tested by comparing 10-day averages of ETa with short term changes in daily NDVI and SIWSI anomalies, and moderate to strong coefficients of determination where found when...

  18. 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.

  19. HUBUNGAN ANTARA INDEKS VEGETASI NDVI (NORMALIZED DIFFERENCE VEGETATION INDEX DAN KOEFISIEN RESESI BASEFLOW PADA BEBERAPA SUBDAS PROPINSI JAWA TENGAH DAN DAERAH ISTIMEWA YOGYAKARTA

    Directory of Open Access Journals (Sweden)

    Bokiraiya Latuamury

    2013-06-01

    Full Text Available The background of this research is the decrease of environment capacity in cacthment ecosystem, especially impact of vegetation forest on behavior streamflow. The indicators of cacthment destruction can be seen through hydrograph characteristics. Evaluation of cactment respons of flow hydrographic as an evaluation tools of river catchment responses becomes very important to analyze because it is a benchmark in determination several policy about flood, drough, sedimentation and landslide handling. The research purpose is to analyze the relationship between vegetation index NDVI (Normalized Difference Vegetation Index and the characteristic of baseflow recession coefficient at several subcatchment areas in province of Central Java and Specific District of Yogjakarta.The method of this research is surveillance on data recording of AWLR (Automatic Water Level Recorder and data of River Flow Measuring Stations in order to separate the baseflow by calibration curve, and image interpretation of Landsat ETM+ for the transformation of vegetation index (NDVI-Normalized Difference Vegetation Index.The analysis on recession coefficient data (Krb and NDVI were correlated to analyze the strength of relationship between these two parameters. The results of statistical analysis on index NDVI and recession coefficient showsthat NDVI and recession coefficient value at R2 is 0.1427, F = 2.17 which is not significant at 1% significance level of 0.1646. The result shows a very weak correlation of 0.077 which mean that vegetation density (NDVI indexhas a very weak control on low flows. Basically, river baseflow is a genetic component of river flow which comes from aquifer storage and/or other low flow sources. Thus, geology and soil have a significant effect on baseflow.

  20. 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

  1. Eclipse Impact on a Remote Sensing Data Set: PAL NDVI 10-Day Composite from February 11 to 20 in 1999 for Western Australia

    OpenAIRE

    Lim, Chai K.

    2010-01-01

    Pathfinder Normalized Difference Vegetation Index (NDVI) derived from Channel 1 (Red) and Channel 2 (near-infrared) of Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA 14 became abnormally high for the 10-day composite from February 11 to 20 in 1999 for Western Australia. There was a solar eclipse in the satellite path on February 16 about the same time when NOAA 14 was above the eclipse location, causing the Channel 1 value to be 0 in many cells. The NDVI composite updating rule...

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

    Science.gov (United States)

    Olsen, J. L.; Miehe, S.; Ceccato, P.; Fensholt, R.

    2015-07-01

    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 vegetation index (NDVI) data a greening of the Sahel since the 1980s has been identified. However, it is poorly understood how commonly applied remote sensing techniques reflect the influence of extensive grazing (and changes in grazing pressure) on natural rangeland vegetation. This paper analyses the time 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 with moderate - coarse resolution satellite imagery. It is shown that sampling plots excluded from grazing have a different species composition characterized by a longer growth cycle as compared to plots under controlled grazing or communal grazing. Also substantially higher ESSB is observed for grazing exclosures as compared to grazed areas, substantially exceeding the amount of biomass expected to be ingested by livestock for this area. The seasonal integrated NDVI (NDVI small integral; capturing only the signal inherent to the growing season recurrent vegetation), derived using absolute thresholds 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 plots are only slightly lower than the values observed for the ungrazed plots. Hence, average ESSB in ungrazed plots since 2000 was 0.93 t ha-1, compared to 0.51 t ha-1 for

  3. Variações temporais e ontogenéticas na dieta de um peixe onívoro em ambiente impactado (reservatório) e em ambiente natural (baía) da bacia do rio Cuiabá - DOI: 10.4025/actascibiolsci.v29i4.878 Temporal and ontogenetic diet changes of omnivorous fish in an impacted (reservoir) and in a natural environment (lagoon) - DOI: 10.4025/actascibiolsci.v29i4.878

    OpenAIRE

    Rosemara Fugi; Norma Segatti Hahn; Edson Lourenço da Silva

    2008-01-01

    Neste trabalho, foram avaliadas as variações temporais e ontogenéticas na dieta de Pimelodus maculatus no reservatório de Manso e na baía Sinhá Mariana, Estado do Mato Grosso. Os peixes foram coletados, mensalmente, de março/2000 a fevereiro/2001 com redes de espera e de arrasto. Foram analisados 199 conteúdos estomacais por meio do método volumétrico. No reservatório, a dieta foi composta basicamente por insetos durante todo o período analisado e independente do tamanho dos exemplares. Na ba...

  4. Calibration of remotely sensed, coarse resolution NDVI to CO2 fluxes in a sagebrush-steppe ecosystem

    Science.gov (United States)

    Wylie, B.K.; Johnson, D.A.; Laca, Emilio; Saliendra, Nicanor Z.; Gilmanov, T.G.; Reed, B.C.; Tieszen, L.L.; Worstell, B.B.

    2003-01-01

    The net ecosystem exchange (NEE) of carbon flux can be partitioned into gross primary productivity (GPP) and respiration (R). The contribution of remote sensing and modeling holds the potential to predict these components and map them spatially and temporally. This has obvious utility to quantify carbon sink and source relationships and to identify improved land management strategies for optimizing carbon sequestration. The objective of our study was to evaluate prediction of 14-day average daytime CO2 fluxes (Fday) and nighttime CO2 fluxes (Rn) using remote sensing and other data. Fday and Rn were measured with a Bowen ratio-energy balance (BREB) technique in a sagebrush (Artemisia spp.)-steppe ecosystem in northeast Idaho, USA, during 1996-1999. Micrometeorological variables aggregated across 14-day periods and time-integrated Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (iNDVI) were determined during four growing seasons (1996-1999) and used to predict Fday and Rn. We found that iNDVI was a strong predictor of Fday (R2 = 0.79, n = 66, P < 0.0001). Inclusion of evapotranspiration in the predictive equation led to improved predictions of Fday (R2= 0.82, n = 66, P < 0.0001). Crossvalidation indicated that regression tree predictions of Fday were prone to overfitting and that linear regression models were more robust. Multiple regression and regression tree models predicted Rn quite well (R2 = 0.75-0.77, n = 66) with the regression tree model being slightly more robust in crossvalidation. Temporal mapping of Fday and Rn is possible with these techniques and would allow the assessment of NEE in sagebrush-steppe ecosystems. Simulations of periodic Fday measurements, as might be provided by a mobile flux tower, indicated that such measurements could be used in combination with iNDVI to accurately predict Fday. These periodic measurements could maximize the utility of expensive flux towers for evaluating various carbon

  5. Calibration of remotely sensed, coarse resolution NDVI to CO2 fluxes in a sagebrush–steppe ecosystem

    Science.gov (United States)

    Wylie, Bruce K.; Johnson, Douglas A.; Laca, Emilio; Saliendra, Nicanor Z.; Gilmanov, Tagir G.; Reed, Bradley C.; Tieszen, Larry L.; Worstell, Bruce B.

    2003-01-01

    The net ecosystem exchange (NEE) of carbon flux can be partitioned into gross primary productivity (GPP) and respiration (R). The contribution of remote sensing and modeling holds the potential to predict these components and map them spatially and temporally. This has obvious utility to quantify carbon sink and source relationships and to identify improved land management strategies for optimizing carbon sequestration. The objective of our study was to evaluate prediction of 14-day average daytime CO2 fluxes (Fday) and nighttime CO2 fluxes (Rn) using remote sensing and other data. Fday and Rnwere measured with a Bowen ratio–energy balance (BREB) technique in a sagebrush (Artemisia spp.)–steppe ecosystem in northeast Idaho, USA, during 1996–1999. Micrometeorological variables aggregated across 14-day periods and time-integrated Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (iNDVI) were determined during four growing seasons (1996–1999) and used to predict Fday and Rn. We found that iNDVI was a strong predictor of Fday(R2=0.79, n=66, P<0.0001). Inclusion of evapotranspiration in the predictive equation led to improved predictions of Fday (R2=0.82, n=66, P<0.0001). Crossvalidation indicated that regression tree predictions of Fday were prone to overfitting and that linear regression models were more robust. Multiple regression and regression tree models predicted Rn quite well (R2=0.75–0.77, n=66) with the regression tree model being slightly more robust in crossvalidation. Temporal mapping of Fday and Rn is possible with these techniques and would allow the assessment of NEE in sagebrush–steppe ecosystems. Simulations of periodic Fday measurements, as might be provided by a mobile flux tower, indicated that such measurements could be used in combination with iNDVI to accurately predict Fday. These periodic measurements could maximize the utility of expensive flux towers for evaluating

  6. 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

  7. Assessing land cover performance in Senegal, West Africa using 1-km integrated NDVI and local variance analysis

    Science.gov (United States)

    Budde, M.E.; Tappan, G.; Rowland, J.; Lewis, J.; Tieszen, L.L.

    2004-01-01

    The researchers calculated seasonal integrated normalized difference vegetation index (NDVI) for each of 7 years using a time-series of 1-km data from the Advanced Very High Resolution Radiometer (AVHRR) (1992-93, 1995) and SPOT Vegetation (1998-2001) sensors. We used a local variance technique to identify each pixel as normal or either positively or negatively anomalous when compared to its surroundings. We then summarized the number of years that a given pixel was identified as an anomaly. The resulting anomaly maps were analysed using Landsat TM imagery and extensive ground knowledge to assess the results. This technique identified anomalies that can be linked to numerous anthropogenic impacts including agricultural and urban expansion, maintenance of protected areas and increased fallow. Local variance analysis is a reliable method for assessing vegetation degradation resulting from human pressures or increased land productivity from natural resource management practices. ?? 2004 Published by Elsevier Ltd.

  8. 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.

  9. A Combination of Plant NDVI and LiDAR Measurements Improve the Estimation of Pasture Biomass in Tall Fescue (Festuca arundinacea var. Fletcher

    Directory of Open Access Journals (Sweden)

    Michael T. Schaefer

    2016-02-01

    Full Text Available The total biomass of a tall fescue (Festuca arundinacea var. Fletcher pasture was assessed by using a vehicle mounted light detection and ranging (LiDAR unit to derive canopy height and an active optical reflectance sensor to determine the spectro-optical reflectance index, normalized difference vegetation index (NDVI. In a random plot design, measurements of NDVI and pasture height were combined to estimate biomass with a root mean square error of prediction (RMSEP equal to ±455.28 kg green dry matter (GDM/ha, over a range of 286 kg to 3933 kg GDM/ha. The combination of NDVI and height measurements were observed to be more accurate in assessing total biomass than just the NDVI (RMSEP ± 846.51 kg/ha and height (RMSEP ± 708.13 kg/ha. Based on the results of the study it was concluded the use of combined LiDAR and active optical reflectance sensors can help unlock the complex interrelationship between green fraction and biomass in swards containing both green and senescent material.

  10. 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.

  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. 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)

  13. 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.

  14. Does Vegetation Parameterization from EO NDVI Data Capture Grazing induced Variations in Species Composition and Biomass in Semi-Arid Grassland Savanna?

    Science.gov (United States)

    Olsen, J. L.; Miehe, S.; Ceccato, P.; Fensholt, R.

    2014-11-01

    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 measurement. From long time series of coarse resolution normalized difference vegetation index (NDVI) data a greening of the Sahel since the 1980s has been identified. The greening appears highly related to a general increase in rainfall following the severe droughts of the 1970s and 80s. In the same time period the region has experienced a drastic population boom and a resulting increase in numbers of livestock. However, it is poorly understood how commonly applied remote sensing techniques reflect the extensive influence of grazing on natural rangeland vegetation. This paper analyses time series of parameterized Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI data by comparison with data from the Widou Thiengoly test site in northern Senegal. Field data include grazing intensity, vegetation productivity, and species composition from sizeable areas suitable for comparison with moderate - coarse resolution satellite imagery. It is established that sampling plots excluded from grazing have higher Net Primary Production (NPP) and different species composition as compared to plots under controlled grazing or communal grazing. The seasonal small integrated NDVI, derived using absolute thresholds to estimate start and end of growing seasons, is identified as the parameter most strongly related to vegetation productivity for all grazing regimes. However plot-pixel comparisons demonstrates how the NDVI/biomass relationship changes due to grazing induced variation in annual plant species composition and the NDVI values for grazed plots are only slightly lower than the values observed for the ungrazed plots. Hence, average biomass in ungrazed plots since 2000 was 0.93 t ha-1, compared to 0.51 t ha-1 for plots subjected to controlled grazing and 0.49 t

  15. Does Vegetation Parameterization from EO NDVI Data Capture Grazing induced Variations in Species Composition and Biomass in Semi-Arid Grassland Savanna?

    Directory of Open Access Journals (Sweden)

    J. L. Olsen

    2014-11-01

    Full Text Available 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 measurement. From long time series of coarse resolution normalized difference vegetation index (NDVI data a greening of the Sahel since the 1980s has been identified. The greening appears highly related to a general increase in rainfall following the severe droughts of the 1970s and 80s. In the same time period the region has experienced a drastic population boom and a resulting increase in numbers of livestock. However, it is poorly understood how commonly applied remote sensing techniques reflect the extensive influence of grazing on natural rangeland vegetation. This paper analyses time series of parameterized Moderate Resolution Imaging Spectroradiometer (MODIS NDVI data by comparison with data from the Widou Thiengoly test site in northern Senegal. Field data include grazing intensity, vegetation productivity, and species composition from sizeable areas suitable for comparison with moderate – coarse resolution satellite imagery. It is established that sampling plots excluded from grazing have higher Net Primary Production (NPP and different species composition as compared to plots under controlled grazing or communal grazing. The seasonal small integrated NDVI, derived using absolute thresholds to estimate start and end of growing seasons, is identified as the parameter most strongly related to vegetation productivity for all grazing regimes. However plot-pixel comparisons demonstrates how the NDVI/biomass relationship changes due to grazing induced variation in annual plant species composition and the NDVI values for grazed plots are only slightly lower than the values observed for the ungrazed plots. Hence, average biomass in ungrazed plots since 2000 was 0.93 t ha−1, compared to 0.51 t ha−1 for plots subjected to

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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

  2. 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; Nilson, Tiit; Duce, Pierpaolo; Emmett, Bridget A.; Beier, Claus; Estiarte, Marc; Garadnai, János; Kalapos, Tibor; Schmidt, Inger Kappel; Kovács-Láng, Edit; Prieto, Patricia; Tietema, Albert; Westerveld, Joke W.; Kull, Olevi

    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...... canopy reflectance, effective green leaf area index (green LAIe) and chlorophyll fluorescence of dominant species. The treatment effects on green LAIe varied among sites. We calculated three reflectance indices: photochemical reflectance index PRI [531 nm; 570 nm], normalized difference vegetation index...... 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...

  3. Characterizing the Phenology of Semi-desert Grassland Dominated by Non-native Eragrostis lehmanniana or Native Grasses Using MODIS NDVI and Brightness Data

    Science.gov (United States)

    Huang, C.; Geiger, E.; van Leeuwen, W. J.; Marsh, S.

    2006-12-01

    In the past several decades, one of the most significant changes in semi-desert grasslands of southern Arizona is invasion of an exotic perennial grass from South Africa, Lehmann lovegrass (ERLE: Eragrostis lehmanniana). Understanding the seasonal variations of ERLE phenology is pivotal for managing these systems where dominance by ERLE is associated with decreases in native species richness and changes in fire regimes. Therefore, the objective of this study is to derive the phenology of vegetation dominated by ERLE or native grasses, using the Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) and brightness [red and near-infrared (NIR) reflectance] time-series data from 2000 to 2005. Field campaigns were conducted in spring (2000-2004) and fall (1999-2003) to collect the biomass of ERLE in the semi-desert grassland of southern Arizona. There were 18 sites each comprised of three 1-ha subplots. NDVI and brightness time-series data for each site were extracted and re-grouped into three categories based on average abundance of ERLE over 10 sampling periods: ERLE (153-229 g/m2 of ERLE), Mixed (82-134 g/m2) and Native (2-30 g/m2) sites. The results show that the season of distinct segregation of NDVI time-series data among these three groups is spring (mid-March to April) and/or early summer (May to July) depending on the amount and timing of precipitation. However, no significant separation was found in brightness time-series data. Annual temporal variation of NDVI time-series data at Native sites was lower than Mixed and ERLE sites, but within group variation of NDVI through time was higher. A similar trend was found in the red reflectance but no apparent trend was discerned in the NIR reflectance perhaps due to substantial amounts of variation in the data. The lower NDVI time-series data in ERLE infested sites (Mixed/ERLE), especially during spring/early summer may be caused by: (1) upper layers of bright- colored

  4. Data pre-processing: Stratospheric aerosol perturbing effect on the remote sensing of vegetation: Correction method for the composite NDVI after the Pinatubo eruption

    Science.gov (United States)

    Vermote, E.; Elsaleous, N.; Kaufman, Y. J.; Dutton, E.

    1994-01-01

    An operational stratospheric correction scheme used after the Mount Pinatubo (Phillipines) eruption (Jun. 1991) is presented. The stratospheric aerosol distribution is assumed to be only variable with latitude. Each 9 days the latitudinal distribution of the optical thickness is computed by inverting radiances observed in the NOAA AVHRR channel 1 (0.63 micrometers) and channel 2 (0.83 micrometers) over the Pacific Ocean. This radiance data set is used to check the validity of model used for inversion by checking consistency of the optical thickness deduced from each channel as well as optical thickness deduced from different scattering angles. Using the optical thickness profile previously computed and radiative transfer code assuming Lambertian boundary condition, each pixel of channel 1 and 2 are corrected prior to computation of NDVI (Normalized Difference Vegetation Index). Comparison between corrected, non corrected, and years prior to Pinatubo eruption (1989 to 1990) NDVI composite, shows the necessity and the accuracy of the operational correction scheme.

  5. 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.

  6. Early detection of eruptive dykes revealed by normalized difference vegetation index (NDVI) on Mt. Etna and Mt. Nyiragongo

    Science.gov (United States)

    Houlié, N.; Komorowski, J. C.; de Michele, M.; Kasereka, M.; Ciraba, H.

    2006-06-01

    Flank-fissure eruptions involve lateral injection and propagation of magma in a volcanic edifice along pre-existing fractures in the direction of the rift zones where magma intrusion and lava flow production are concentrated over time. Thus, the identification and mapping of active fractures and faults is a fundamental aspect of studies of active volcanic systems. However, gradual dyke wedge emplacement at depth in well-fractured zones on volcano flanks and in volcanic rift zones does not necessarily trigger large amplitude deformation signals susceptible to be recorded months or even years before the actual eruption. Here we show that active and potentially eruptive areas can be detected up to 2 yrs before the arrival to the surface of the final eruptive dyke and venting of lava flows by processing satellite images applying a normalized difference vegetation index (NDVI) algorithm. A posteriori analysis of satellite images indeed reveals that the surficial effects of dyke wedge injection and ascent on plant growth were apparent for Mt. Etna from 2000 to 2002 and for Mt. Nyiragongo in 2001, thus months to years before they erupted.

  7. 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 (images which are used to compute the RGBVI and (ii) NDVI is computed from a newly modified version of the Yara N-Sensor. The latter is a well-established tractor-based hyperspectral sensor for crop management and is available on the 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.

  8. Monitoring irrigation volumes using high-resolution NDVI image time series: calibration and validation in the Kairouan plain (Tunisia)

    Science.gov (United States)

    Saadi, S.; Simonneaux, V.; Boulet, G.; Mougenot, B.; Lili Chabaane, Z.

    2015-10-01

    The increasing availability of high resolution high repetitively VIS-NIR remote sensing, like the forthcoming Sentinel-2 mission to be launched in 2015, offers unprecedented opportunity to improve agricultural monitoring. In this study, regional evapotranspiration and crop water consumption were estimated over an irrigated area located in the Kairouan plain (central Tunisia) using the FAO-56 dual crop coefficient water balance model combined with NDVI image time series providing estimates of the actual basal crop coefficient (Kcb) and vegetation fraction cover. Three time series of high-resolution SPOT5 images have been acquired for the 2008-2009, 2011-2012 and 2012-2013 hydrological years. We also benefited from a SPOT4 time series acquired in the frame of the SPOT4-Take5 experiment. The SPOT5 images were radiometrically corrected, first, using the SMAC6s Algorithm, and then improved using invariant objects located on the scene. The method was first calibrated using ground measurements of evapotranspiration achieved using eddy-correlation devices installed on irrigated wheat and barley plots. For other crops for which no calibration data was available, parameters were taken from bibliography. Then, the model was run to spatialize irrigation over the whole area and a validation was done using cumulated seasonal water volumes obtained from ground survey for three irrigated perimeters. In a subsequent step, evapotranspiration estimates were obtained using a large aperture scintillometer and were used for an additional validation of the model outputs.

  9. 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.

  10. 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

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

    Science.gov (United States)

    Kotsuki, S.; Tanaka, K.

    2015-01-01

    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.

  12. 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

  13. 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.

  14. Performance and effects of land cover type on synthetic surface reflectance data and NDVI estimates for assessment and monitoring of semi-arid rangeland

    Science.gov (United States)

    Olexa, Edward M.; Lawrence, Rick L.

    2014-08-01

    Federal land management agencies provide stewardship over much of the rangelands in the arid and semi-arid western United States, but they often lack data of the proper spatiotemporal resolution and extent needed to assess range conditions and monitor trends. Recent advances in the blending of complementary, remotely sensed data could provide public lands managers with the needed information. We applied the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) to five Landsat TM and concurrent Terra MODIS scenes, and used pixel-based regression and difference image analyses to evaluate the quality of synthetic reflectance and NDVI products associated with semi-arid rangeland. Predicted red reflectance data consistently demonstrated higher accuracy, less bias, and stronger correlation with observed data than did analogous near-infrared (NIR) data. The accuracy of both bands tended to decline as the lag between base and prediction dates increased; however, mean absolute errors (MAE) were typically ≤10%. The quality of area-wide NDVI estimates was less consistent than either spectral band, although the MAE of estimates predicted using early season base pairs were ≤10% throughout the growing season. Correlation between known and predicted NDVI values and agreement with the 1:1 regression line tended to decline as the prediction lag increased. Further analyses of NDVI predictions, based on a 22 June base pair and stratified by land cover/land use (LCLU), revealed accurate estimates through the growing season; however, inter-class performance varied. This work demonstrates the successful application of the STARFM algorithm to semi-arid rangeland; however, we encourage evaluation of STARFM's performance on a per product basis, stratified by LCLU, with attention given to the influence of base pair selection and the impact of the time lag.

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

  18. 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.

  19. 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

  20. 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。

  1. Investigating agro-drought in the Lower Mekong Basin using MODIS NDVI and land surface temperature data

    Science.gov (United States)

    Son, N. T.; Chen, C. F.; Chen, C. R.

    2011-11-01

    Agro-drought usually refers to the shortage of water for crop irrigation in a short period, creating serve impacts on crop production due to insufficient soil moisture. This phenomenon has been considered as a challenge for rice farmers in the Lower Mekong Basin (LMB), especially in the dry season (from November to April). Thus, information on agro-drought is important for water scheduling to mitigate adverse impacts on rice production. The main objective of this study is to investigate the applicability of the monthly MODIS normalized difference vegetation index (NDVI) and land surface temperature (LST) data for drought monitoring from 2008 to 2010. The data was processed for the dry season because this period is usually suffered from droughts. A simple temperature vegetation difference index (TVDI) was used to estimate the surface soil moisture content. We investigated the sensitivity between the preliminary TVDI results and TRMM (Tropical Rainfall Measuring Mission) precipitation. The results revealed good agreement between the two datasets. TVDI was declined during or after rain events indicating greater soil moisture content, but increased again later indicating less soil moisture content. The results by analysis of TVDI showed that the moderate and serve droughts were spatially scattered over the region from November to March and returned to normal condition by the end of the dry season (April) with the onset of rainy season. The drought was found more serve and extensive in plains of Thailand and Cambodia. The larger area of serve drought was especially observed for the 2008-2009 dry seasons compared to 2010. The results achieved from this study could be useful for crop irrigation scheduling.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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, Joseph; Hargrove, William W.; Gasser, Gerald; Norman, Steve

    2013-01-01

    U.S. forests occupy approx.1/3 of total land area (approx. 304 million ha). Since 2000, a growing number of regionally evident forest disturbances have occurred due to abiotic and biotic agents. Regional forest disturbances can threaten human life and property, bio-diversity and water supplies. Timely regional forest disturbance monitoring products are needed to aid forest health management work. Near Real Time (NRT) twice daily MODIS NDVI data provide a means to monitor U.S. regional forest disturbances every 8 days. Since 2010, these NRT forest change products have been produced and posted on the US Forest Service ForWarn Early Warning System for Forest Threats.

  11. 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。

  12. 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.

  13. 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.

  14. Time-Series analysis of MODIS NDVI data along with ancillary data for Land use/Land cover mapping of Uttarakhand

    Science.gov (United States)

    Patakamuri, S. K.; Agrawal, S.; Krishnaveni, M.

    2014-12-01

    Land use and land cover plays an important role in biogeochemical cycles, global climate and seasonal changes. Mapping land use and land cover at various spatial and temporal scales is thus required. Reliable and up to date land use/land cover data is of prime importance for Uttarakhand, which houses twelve national parks and wildlife sanctuaries and also has a vast potential in tourism sector. The research is aimed at mapping the land use/land cover for Uttarakhand state of India using Moderate Resolution Imaging Spectroradiometer (MODIS) data for the year 2010. The study also incorporated smoothening of time-series plots using filtering techniques, which helped in identifying phenological characteristics of various land cover types. Multi temporal Normalized Difference Vegetation Index (NDVI) data for the year 2010 was used for mapping the Land use/land cover at 250m coarse resolution. A total of 23 images covering a single year were layer stacked and 150 clusters were generated using unsupervised classification (ISODATA) on the yearly composite. To identify different types of land cover classes, the temporal pattern (or) phenological information observed from the MODIS (MOD13Q1) NDVI, elevation data from Shuttle Radar Topography Mission (SRTM), MODIS water mask (MOD44W), Nighttime Lights Time Series data from Defense Meteorological Satellite Program (DMSP) and Indian Remote Sensing (IRS) Advanced Wide Field Sensor (AWiFS) data were used. Final map product is generated by adopting hybrid classification approach, which resulted in detailed and accurate land use and land cover map.

  15. Karst rock-desertification of extracting vegetation coverage inversion based on NDVI serial images and dimidiate pixel model: a case study of the Yachi demonstration area in Bijie city of Guizhou

    Science.gov (United States)

    Zhang, Hui; Zhou, Zhongfa; Xie, Jun

    2011-12-01

    With the technological development background of "3S", the research area is Yachi demonstrate area in Bijie city of Guizhou. For traditional methods, NDVI is always used to extract Vegetation information from remote sensing image. Based on theory of dimidiate pixel model,the study region defined NDVISsoil and NDVISveg,vegetation, the inversion dimidiate pixel model was established based on vegetation index(NDVI) to extract vegetation coverage, vegetation coverage can be calculated by using the model of quantifying vegetation fraction from normalized difference vegetation,then acquired relationships between NDVI Serial Images and landscape pattern karst rock-desertification, finally yachi demonstrate area gainer karst rocky desertification landscape pattern of distribution. Using this methods of karst rocky desertification landscape pattern research has significantly improved the accuracy of classification, providing a scientific basis to ecological restoration of karst rocky desertification and other integrated control.

  16. 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

  17. 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

  18. 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

  19. Variações temporais e ontogenéticas na dieta de um peixe onívoro em ambiente impactado (reservatório e em ambiente natural (baía da bacia do rio Cuiabá = Temporal and ontogenetic diet changes of omnivorous fish in an impacted (reservoir and in a natural environment (lagoon

    Directory of Open Access Journals (Sweden)

    Edson Lourenço da Silva

    2007-10-01

    Full Text Available Neste trabalho, foram avaliadas as variações temporais e ontogenéticas na dieta de Pimelodus maculatus no reservatório de Manso e na baía Sinhá Mariana, Estado do Mato Grosso. Os peixes foram coletados, mensalmente, de março/2000 a fevereiro/2001 comredes de espera e de arrasto. Foram analisados 199 conteúdos estomacais por meio do método volumétrico. No reservatório, a dieta foi composta basicamente por insetos durante todo o período analisado e independente do tamanho dos exemplares. Na baía Sinhá Mariana, a importância dos itens variou mensalmente, sendo que vegetais, peixes e escamas predominaram em alguns meses. Variações ontogenéticas foram observadas na baia, sendo que os menores indivíduos (3,6 a 8,0 cm consumiram predominantemente insetos, detritosedimento e escamas, enquanto os maiores (16,8 a 21,2 cm alimentaram-se essencialmentede peixes. Os alimentos de origem terrestre dominaram a dieta dos peixes do reservatório, enquanto os de origem aquática predominaram na baía. Os resultados obtidos mostraram a elevada plasticidade alimentar de P. maculatus e o comportamento oportunista da espécie noreservatório, demonstrando sua habilidade em consumir recursos temporariamente disponíveis, como os alimentos de origem terrestre, principalmente insetos, que são disponibilizados em reservatórios recém-formados.Temporal and ontogenetic changes in the diet of Pimelodus maculatus were assessed in the Manso Reservoir and Sinhá Mariana lagoon, Mato Grosso State. Fishes were collected monthly from March/2000 toFebruary/2001 by gillnets and seining. Stomach contents (N = 199 were analyzed by volumetric method. In the reservoir, P. maculatus consumed mainly insects, whereas in the Sinhá Mariana lagoon it was more generalist, feeding on similar proportions of higher plant,fish and scale. Terrestrial food was important in the reservoir, whereas aquatic food was more so in the bay. In the reservoir, the diet of P. maculatus was

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

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    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

  1. 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

  2. Analysis of Urban Heat Island (UHI in Relation to Normalized Difference Vegetation Index (NDVI: A Comparative Study of Delhi and Mumbai

    Directory of Open Access Journals (Sweden)

    Aakriti Grover

    2015-04-01

    Full Text Available The formation and occurrence of urban heat island (UHI is a result of rapid urbanization and associated concretization. Due to intensification of heat combined with high pollution levels, urban areas expose humans to unexpected health risks. In this context, the study aims at comparing the UHI in the two largest metropolitan cities of India, i.e., Delhi and Mumbai. The presence of surface UHI is analyzed using the Landsat 5 TM image of 5 May 2010 for Delhi and the 17 April 2010 image for Mumbai. The validation of the heat island is done in relation to the Normalized Difference Vegetation Index (NDVI patterns. The study reveals that built-up and fallow lands record high temperatures, whereas the vegetated areas and water bodies exhibit lower temperatures. Delhi, an inland city, possesses mixed land use and the presence of substantial tree cover along roads; the Delhi Ridge forests and River Yamuna cutting across the city have a high influence in moderating the surface temperatures. The temperature reaches a maximum of 35 °C in West Delhi and a minimum of 24 °C in the east at the River Yamuna. Maximum temperature in East Delhi goes to 30 °C, except the border areas. North, Central and south Delhi have low temperatures (28 °C–31 °C, but the peripheral areas have high temperatures (36 °C–37 °C. The UHI is not very prominent in the case of Delhi. This is proven by the correlations of surface temperature with NDVI. South Delhi, New Delhi and areas close to River Yamuna have high NDVI and, therefore, record low temperatures. Mumbai, on the other hand, is a coastal city with lower tree cover than Delhi. The Borivilli National Park (BNP is in the midst of dense horizontal and vertical growth of buildings. The UHI is much stronger where the heat is trapped that is, the built-up zones. There are four small rivers in Mumbai, which have low carrying capacity. In Mumbai suburban district, the areas adjoining the creeks, sea and the lakes act as

  3. Development and Application of an Annual Vegetation-Monitoring Tool in Gishwati Forest Reserve using MODIS NDVI product and Landsat-5 and 7

    Science.gov (United States)

    Makar, N. I.; Butler, K.; Fox, T.; Geddes, Q. A.; Janse van Vuuren, L.; Li, A.; Sharma, A.

    2012-12-01

    As the most densely populated country in Africa, Rwanda relies heavily on a limited supply of natural resources to sustain its agrarian economy. Population pressures, economic policy, and the aftermath of the genocide have placed particular stress on the Gishwati Forest in Rwanda's Western Province. Deforestation for agricultural purposes and fuel consumption has disrupted the local climate, soil structure, and topography, leading to increased erosion, landslides and flooding. Once 280 km2, by 1995 the Gishwati Forest was only 6 km2. The Rwandan government and international NGOs have started initiatives to reverse deforestation, which would benefit from monitoring and evaluation using remote sensing technology. This study filled the gaps in the tumultuous history of Gishwati Forest since 1982 using NASA's Earth Observing System, specifically Landsat 5 and AVHRR. In collaboration with partner organizations, we developed a robust, yet simple to use, forest monitoring tool employing MODIS NDVI product and Landsat that provide annual estimates of the forest's health.

  4. A procedure to derive intra-and inter-annual changes on vegetation from NDVI time series. A case study in Spain

    Energy Technology Data Exchange (ETDEWEB)

    Gilabert, M. A; Martinez, B.; Melia, J.

    2009-07-01

    The objective of this work is to study the spatial patterns of vegetation activity over spain and its temporal variability throughout the period 1989-2002. A multi-resolution analysis (MRA) bases on the wavelet transform has been implemented on NDVI time series from the MEDOKADS database. The MRA decomposes the original signal as a sum of series associated with temporal scales. Specifically, the intra-annual series is processed to define several key features in relation with the vegetation penology. In contras, the inter-annual components of the signal is used to detect trends by means of a Mann-Kendall test and map the magnitude of the land-cover change. Finally, a comprehensive identification of the areas presenting a negative value of the magnitude of change is carried out to select those linked to land degradation processes. Results show a major presence of these areas the Southeast of Spain. (Author) 5 refs.

  5. A procedure to derive intra-and inter-annual changes on vegetation from NDVI time series. A case study in Spain

    International Nuclear Information System (INIS)

    The objective of this work is to study the spatial patterns of vegetation activity over spain and its temporal variability throughout the period 1989-2002. A multi-resolution analysis (MRA) bases on the wavelet transform has been implemented on NDVI time series from the MEDOKADS database. The MRA decomposes the original signal as a sum of series associated with temporal scales. Specifically, the intra-annual series is processed to define several key features in relation with the vegetation penology. In contras, the inter-annual components of the signal is used to detect trends by means of a Mann-Kendall test and map the magnitude of the land-cover change. Finally, a comprehensive identification of the areas presenting a negative value of the magnitude of change is carried out to select those linked to land degradation processes. Results show a major presence of these areas the Southeast of Spain. (Author) 5 refs.

  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. Mapping crop based on phenological characteristics using time-series NDVI of operational land imager data in Tadla irrigated perimeter, Morocco

    Science.gov (United States)

    Ouzemou, Jamal-eddine; El Harti, Abderrazak; EL Moujahid, Ali; Bouch, Naima; El Ouazzani, Rabii; Lhissou, Rachid; Bachaoui, El Mostafa

    2015-10-01

    Morocco is a primarily arid to semi-arid country. These climatic conditions make irrigation an imperative and inevitable technique. Especially, agriculture has a paramount importance for the national economy. Retrieving of crops and their location as well as their spatial extent is useful information for agricultural planning and better management of irrigation water resource. Remote sensing technology was often used in management and agricultural research. Indeed, it's allows crops extraction and mapping based on phenological characteristics, as well as yield estimation. The study area of this work is the Tadla irrigated perimeter which is characterized by heterogeneous areas and extremely small size fields. Our principal objectives are: (1) the delimitation of the major crops for a good water management, (2) the insulation of sugar beet parcels for modeling its yields. To achieve the traced goals, we have used Landsat-8 OLI (Operational Land Imager) data pan-sharpened to 15 m. Spectral Angle Mapper (SAM) and Support Vector Machine (SVM) classifications were applied to the Normalized Difference Vegetation Index (NDVI) time-series of 10 periods. Classifications were calculated for a site of more than 124000 ha. This site was divided into two parts: the first part for selecting, training datasets and the second one for validating the classification results. The SVM and SAM methods classified the principal crops with overall accuracies of 85.27% and 57.17% respectively, and kappa coefficient of 80% and 43% respectively. The study showed the potential of using time-series OLI NDVI data for mapping different crops in irrigated, heterogeneous and undersized parcels in arid and semi-arid environment.

  9. Variações espaço-temporais na alimentação de Pimelodus ortmanni (Siluriformes, Pimelodidae no reservatório de Segredo e áreas adjacentes (PR Spatio temporal variations in Pimelodus ortmanni (Siluriformes, Pimelodidae feeding in Segredo reservoir and contigous areas (PR

    Directory of Open Access Journals (Sweden)

    Márcia Regina Russo

    1999-07-01

    Full Text Available Este trabalho teve como objetivo conhecer a dieta de Pimelodus ortmanni (Haseman, 1911 no reservatório de Segredo e nas áreas adjacentes, em três períodos consecutivos à formação desse reservatório (rio Iguaçu-PR. As coletas foram realizadas no período de março de 93 a fevereiro de 96 no reservatório, nos tributários e jusante. Foram analisados 808 estômagos pelos métodos de freqüência de ocorrência e volumétrico, combinados no índice alimentar. A espécie foi caracterizada como omnívora-carnívora, em função do amplo espectro alimentar (41 itens, embora peixes e insetos tenham se destacado, na dieta, durante o período de estudos. Recursos alimentares de origem alóctone foram mais expressivos no reservatório e na jusante no primeiro período, diminuindo no último, ao contrário dos tributários. Através da análise de correspondência destendenciada (DCA, foram discriminados dois grupos espaço-temporais em relação à dieta: - nos menores escores, agruparam-se exemplares provenientes da jusante (2º período e do reservatório (2º e 3º período e, nos maiores escores, exemplares da jusante (1º período e dos tributários (2º e 3º períodos. Essa segregação pode estar associada à disponibilidade dos recursos alimentares nas diferentes estações e períodos de coleta.The aim of this paper is to investigate the diet of Pimelodus ortmanni in Segredo reservoir and contigous areas in three different periods after the reservoir formation (Iguaçu river, state of Paraná, Brazil. The samples were collected from March/93 to February/96 in the reservoir, tributaries and downstream. A total of 808 stomachs were analyzed by occurrence and volumetric methods combined in the food index. The species was characterized as omnivorous-carnivorous due to the ample food spectrum (41 items, though fishes and insects prevailed in the diet over the whole investigated time. In the first and second periods allocthonous food

  10. Alterações químicas temporais nas faixas de adubação e entrelinhas do pomar, nutrição e produção de laranja após calagem superficial Yield and temporal chemical changes in fertilizer bands and inter-rows of an orange orchard after surface liming

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    Jonez Fidalski

    2008-04-01

    Full Text Available Apesar das diferenças químicas entre as faixas de adubação e entrelinhas de pomares de laranjeiras, o critério para a calagem superficial entre esses dois locais ainda é desconhecido. O objetivo deste estudo foi quantificar as alterações químicas temporais nas faixas de adubação e entrelinhas, nutrição e produção de laranja "Pêra" após calagens superficiais, em um Argissolo Vermelho distrófico latossólico, no noroeste do Paraná. Quatro calagens superficiais foram realizadas entre 1996 e 1999 para elevar a saturação por bases a 70 %, a partir da primeira colheita de frutos de laranja. Os calcários dolomítico e calcítico foram distribuídos sobre seis sistemas de manejo de plantas de cobertura permanente nas entrelinhas e nas faixas de adubação, as quais foram manejadas com roçadas mecânicas e herbicida pós-emergente, respectivamente. No período de 1996 a 2004 foram coletadas amostras de tecido foliar e do solo nas profundidades de 0-20 e 20-40 cm e avaliou-se a produção de laranja. As máximas alterações químicas na camada de 0-20 cm de profundidade e no tecido foliar das laranjeiras (Ca ocorreram quatro anos após sucessivas calagens superficiais anuais. A produção de laranja correlacionou-se negativamente com Al3+ e positivamente com pH-CaCl2, Ca2+ e Mg2+ das faixas de adubação e do centro das entrelinhas. As calagens superficiais elevaram a saturação por bases na camada de 0-20 cm de profundidade até 46 % nas faixas de adubação e 64 % nas entrelinhas.Despite the chemical differences in soils under the fertilizer bands and inter-rows in orange orchards, no criterion to determine the need of liming in the two areas is yet known. The objective of this study was to quantify the temporary chemical alterations in fertilizer bands and inter-rows of a "Pêra" orange orchard as well as nutrition and fruit yield after surface liming, in a Typic Paleudults, in northwestern Paraná, Brazil. The soil surface was

  11. 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

  12. 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.

  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. 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

  15. 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

  16. AVALIAÇÃO DOS ÍNDICES DE VEGETAÇÃO NDVI, SR E TVI NA DISCRIMINAÇÃO DE FITOFISIONOMIAS DOS AMBIENTES DO PANTANAL DE CÁCERES/MT

    Directory of Open Access Journals (Sweden)

    Edinéia Aparecida dos Santos Galvanin

    2014-09-01

    Full Text Available http://dx.doi.org/10.5902/1980509815729Este artigo faz uma comparação dos índices de vegetação Normalized Difference Vegetation Index (NDVI, Simple Ratio (SR e Transformed Vegetation Index (TVI, na discriminação das fitofisionomias de três ambientes do Pantanal de Cáceres, Mato Grosso, considerando a sazonalidade (períodos seco e úmido. As imagens utilizadas foram as do satélite Landsat TM 5, do ano de 2009 (período seco e de 2010 (período úmido. As análises mostraram que o NDVI apresentou melhor desempenho em relação ao SR e TVI para os diferentes ambientes.

  17. Satellite-derived NDVI, LST, and climatic factors driving the distribution and abundance of Anopheles mosquitoes in a former malarious area in northwest Argentina.

    Science.gov (United States)

    Dantur Juri, María Julia; Estallo, Elizabet; Almirón, Walter; Santana, Mirta; Sartor, Paolo; Lamfri, Mario; Zaidenberg, Mario

    2015-06-01

    Distribution and abundance of disease vectors are directly related to climatic conditions and environmental changes. Remote sensing data have been used for monitoring environmental conditions influencing spatial patterns of vector-borne diseases. The aim of this study was to analyze the effect of the Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), and climatic factors (temperature, humidity, wind velocity, and accumulated rainfall) on the distribution and abundance of Anopheles species in northwestern Argentina using Poisson regression analyses. Samples were collected from December, 2001 to December, 2005 at three localities, Aguas Blancas, El Oculto and San Ramón de la Nueva Orán. We collected 11,206 adult Anopheles species, with the major abundance observed at El Oculto (59.11%), followed by Aguas Blancas (22.10%) and San Ramón de la Nueva Orán (18.79%). Anopheles pseudopunctipennis was the most abundant species at El Oculto, Anopheles argyritarsis predominated in Aguas Blancas, and Anopheles strodei in San Ramón de la Nueva Orán. Samples were collected throughout the sampling period, with the highest peaks during the spring seasons. LST and mean temperature appear to be the most important variables determining the distribution patterns and major abundance of An. pseudopunctipennis and An. argyritarsis within malarious areas. PMID:26047182

  18. 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

  19. 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

  20. 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

  1. Variações temporais e ontogenéticas na dieta de um peixe onívoro em ambiente impactado (reservatório e em ambiente natural (baía da bacia do rio Cuiabá - DOI: 10.4025/actascibiolsci.v29i4.878 Temporal and ontogenetic diet changes of omnivorous fish in an impacted (reservoir and in a natural environment (lagoon - DOI: 10.4025/actascibiolsci.v29i4.878

    Directory of Open Access Journals (Sweden)

    Rosemara Fugi

    2008-02-01

    Full Text Available Neste trabalho, foram avaliadas as variações temporais e ontogenéticas na dieta de Pimelodus maculatus no reservatório de Manso e na baía Sinhá Mariana, Estado do Mato Grosso. Os peixes foram coletados, mensalmente, de março/2000 a fevereiro/2001 com redes de espera e de arrasto. Foram analisados 199 conteúdos estomacais por meio do método volumétrico. No reservatório, a dieta foi composta basicamente por insetos durante todo o período analisado e independente do tamanho dos exemplares. Na baía Sinhá Mariana, a importância dos itens variou mensalmente, sendo que vegetais, peixes e escamas predominaram em alguns meses. Variações ontogenéticas foram observadas na baia, sendo que os menores indivíduos (3,6 a 8,0 cm consumiram predominantemente insetos, detrito-sedimento e escamas, enquanto os maiores (16,8 a 21,2 cm alimentaram-se essencialmente de peixes. Os alimentos de origem terrestre dominaram a dieta dos peixes do reservatório, enquanto os de origem aquática predominaram na baía. Os resultados obtidos mostraram a elevada plasticidade alimentar de P. maculatus e o comportamento oportunista da espécie no reservatório, demonstrando sua habilidade em consumir recursos temporariamente disponíveis, como os alimentos de origem terrestre, principalmente insetos, que são disponibilizados em reservatórios recém-formados.Temporal and ontogenetic changes in the diet of Pimelodus maculatus were assessed in the Manso Reservoir and Sinhá Mariana lagoon, Mato Grosso State. Fishes were collected monthly from March/2000 to February/2001 by gillnets and seining. Stomach contents (N = 199 were analyzed by volumetric method. In the reservoir, P. maculatus consumed mainly insects, whereas in the Sinhá Mariana lagoon it was more generalist, feeding on similar proportions of higher plant, fish and scale. Terrestrial food was important in the reservoir, whereas aquatic food was more so in the bay. In the reservoir, the diet of P

  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. Ecosystem functional assessment based on the "optical type" concept and self-similarity patterns: An application using MODIS-NDVI time series autocorrelation

    Science.gov (United States)

    Huesca, Margarita; Merino-de-Miguel, Silvia; Eklundh, Lars; Litago, Javier; Cicuéndez, Victor; Rodríguez-Rastrero, Manuel; Ustin, Susan L.; Palacios-Orueta, Alicia

    2015-12-01

    Remote sensing (RS) time series are an excellent operative source for information about the land surface across several scales and different levels of landscape heterogeneity. Ustin and Gamon (2010) proposed the new concept of "optical types" (OT), meaning "optically distinguishable functional types", as a way to better understand remote sensing signals related to the actual functional behavior of species that share common physiognomic forms but differ in functionality. Whereas the OT approach seems to be promising and consistent with ecological theory as a way to monitor vegetation derived from RS, it received little implementation. This work presents a method for implementing the OT concept for efficient monitoring of ecosystems based on RS time series. We propose relying on an ecosystem's repetitive pattern in the temporal domain (self-similarity) to assess its dynamics. Based on this approach, our main hypothesis is that distinct dynamics are intrinsic to a specific OT. Self-similarity level in the temporal domain within a broadleaf forest class was quantitatively assessed using the auto-correlation function (ACF), from statistical time series analysis. A vector comparison classification method, spectral angle mapper, and principal component analysis were used to identify general patterns related to forest dynamics. Phenological metrics derived from MODIS NDVI time series using the TIMESAT software, together with information from the National Forest Map were used to explain the different dynamics found. Results showed significant and highly stable self-similarity patterns in OTs that corresponded to forests under non-moisture-limited environments with an adaptation strategy based on a strong phenological synchrony with climate seasonality. These forests are characterized by dense closed canopy deciduous forests associated with high productivity and low biodiversity in terms of dominant species. Forests in transitional areas were associated with patterns of less

  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. Multi-temporal land cover classification of the Konya Basin, south-central Turkey, based on a LANDSAT TM-derived NDVI/NDMI time series: satellite remote sensing in support of landscape-scale soil biogeochemistry research

    Science.gov (United States)

    Mayes, M. T.; Ozdogan, M.; Marin-Spiotta, E.

    2010-12-01

    Recently, terrestrial biogeochemists and soil scientists have called for new approaches to study human impacts on soil biogeochemical properties at landscape-wide, 100-1000 km2 spatial scales (Trumbore and Czimczik 2008). Here, we use satellite remote sensing to map land cover across a 16,000 km2 region in the Konya Basin, south-central Turkey, in support of research into agricultural and pastoral land use impacts on soil biogeochemistry. Our land cover classification is based on time series analysis of Normalized Difference Vegetation Index (NDVI) and Normalized Difference Moisture Index (NDMI) data, derived from eight LANDSAT TM images spanning the 2006-2007 growing seasons. Using a hierarchical, binary-split classification approach and a support vector machine (SVM) algorithm, we map five land cover classes that correspond with the following dominant land-use categories: 1) annual cultivated row-crops, 2) perennial orchards/cultivated woody vegetation, 3) fallow fields, 4) uncultivated woody vegetation, 5) steppe vegetation/rangeland. The final map has an overall classification accuracy of 87.4% (kappa = 0.842), determined via traditional confusion-matrix analysis and over 150 site visits during summer 2010. Classes 1 and 2, which have the highest per-pixel NDVI and NDMI sums across image dates, attain the highest producer and consumer accuracies (>95%). We also compare the relative contributions and efficacy of NDVI and NDMI in separating land cover classes, and the influence of radiometric correction and calibration across image dates on classification accuracies. Our results support previous research showing that NDVI time series can effectively classify agricultural landscapes in semi-arid to arid environments (Simonneaux et al. 2008; Pax-Lenny et al. 1996). By combining our land cover map with other geospatial information in a GIS, we demonstrate how satellite remote sensing can help expand spatial scales of terrestrial biogeochemistry research from

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Identification of chemical signatures of gunshot residues in different fabrics; Identificacao de assinaturas quimicas em residuos de disparos de arma de fogo em diferentes alvos

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Joao Carlos Dias de

    2010-07-01

    The modern forensic science goes hand in hand with scientific research. The forensic scientists are faced every day with many cases requiring the analysis of residues from firing gun (gunshot residues). This works describes the development of a methodology to determine chemical signatures of shots from a firearm, by measuring the concentrations of Pb, Ba e Sb in the residues from these shots deposited near the entrance hole of bullets, based on the technique with high resolution inductively coupled plasma mass spectrometry (HRICP-MS). Shots were performed on five types of target-fabrics and collected testimonies from regions close to the entrance hole of projectiles. The results showed that the method enabled us to identify and distinguish the residues of the .38 caliber revolver and pistols .40 and 9mm caliber. The use of ternary graphs as a tool for data analysis helped to identify specific patterns of distribution of blank samples and gunshot residues deposited after firing revolvers and pistols. The methodology enabled the assignment of the origin of the shot through the confirmation of the residues collected also from the hands of shooters. As a result the methodology in police procedures and aims to add a valuable contribution to forensic investigations. (author)

  17. 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...

  18. 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.

  19. 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...

  20. 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。

  1. 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

  2. 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 Este 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.

  3. 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...

  4. Cálculo das variações em escalas temporais e aplicações à economia

    OpenAIRE

    Dryl, Monika

    2014-01-01

    We consider some problems of the calculus of variations on time scales. On the beginning our attention is paid on two inverse extremal problems on arbitrary time scales. Firstly, using the Euler-Lagrange equation and the strengthened Legendre condition, we derive a general form for a variation functional that attains a local minimum at a given point of the vector space. Furthermore, we prove a necessary condition for a dynamic integro-differential equation to be an Euler-Lag...

  5. PADRÕES DE DISTRIBUIÇÕES ESPACIAIS E TEMPORAIS DE TEMPERATURAS ASSOCIADOS AO BIOMA CERRADO

    Directory of Open Access Journals (Sweden)

    Nicali Bleyer Ferreira dos Santos

    2011-01-01

    Full Text Available La presencia de vegetación es un factor importante en el mantenimiento de los procesos biogeoquímicos de la naturaleza. En el Cerrado, la conversión de la vegetación natural en las áreas de la agricultura y de pastoreo induce cambios en las variables biofísicas tales como la temperatura de superficie, altamente sensible a los cambios en la cubierta terrestre. Así, con el fin de contribuir a la comprensión de la dinámica de causa y efecto del uso y ocupación de la región del Cerrado en variables biofísicas, este estudio pretende analizar, a partir de informaciones procedentes del sensor orbital (producto MOD11 - Land Surface Temperature, la correlación entre la ocupación de la tierra y la variabilidad térmica de la superfície. El estúdio fue hecho para el año 2003 en los meses de mayo y septiembre (principio y fin de la sequía. Con este fin, su investigación ha vinculado las diversas formas de ocupación (expresadas por las categorías de uso del suelo con la temperatura de superficie. El análisis de los datos mostro diferencias térmicas significtivas entre las classes naturales e antropizadas y revelo las dependências espaciales de la temperatura de la superfície, com uma fuerte influencia de la estacionalidad.

  6. 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...

  7. 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...

  8. 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.

  9. Deriving crop calendar using NDVI time-series

    OpenAIRE

    Patel, J. H.; Oza, M. P.

    2014-01-01

    Agricultural intensification is defined in terms as cropping intensity, which is the numbers of crops (single, double and triple) per year in a unit cropland area. Information about crop calendar (i.e. number of crops in a parcel of land and their planting & harvesting dates and date of peak vegetative stage) is essential for proper management of agriculture. Remote sensing sensors provide a regular, consistent and reliable measurement of vegetation response at various growth stages ...

  10. Global Data Sets of Vegetation Leaf Area Index (LAI3g and Fraction of Photosynthetically Active Radiation (FPAR3g Derived from Global Inventory Modeling and Mapping Studies (GIMMS Normalized Difference Vegetation Index (NDVI3g for the Period 1981 to 2011

    Directory of Open Access Journals (Sweden)

    Ranga B. Myneni

    2013-02-01

    Full Text Available Long-term global data sets of vegetation Leaf Area Index (LAI and Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR are critical to monitoring global vegetation dynamics and for modeling exchanges of energy, mass and momentum between the land surface and planetary boundary layer. LAI and FPAR are also state variables in hydrological, ecological, biogeochemical and crop-yield models. The generation, evaluation and an example case study documenting the utility of 30-year long data sets of LAI and FPAR are described in this article. A neural network algorithm was first developed between the new improved third generation Global Inventory Modeling and Mapping Studies (GIMMS Normalized Difference Vegetation Index (NDVI3g and best-quality Terra Moderate Resolution Imaging Spectroradiometer (MODIS LAI and FPAR products for the overlapping period 2000–2009. The trained neural network algorithm was then used to generate corresponding LAI3g and FPAR3g data sets with the following attributes: 15-day temporal frequency, 1/12 degree spatial resolution and temporal span of July 1981 to December 2011. The quality of these data sets for scientific research in other disciplines was assessed through (a comparisons with field measurements scaled to the spatial resolution of the data products, (b comparisons with broadly-used existing alternate satellite data-based products, (c comparisons to plant growth limiting climatic variables in the northern latitudes and tropical regions, and (d correlations of dominant modes of interannual variability with large-scale circulation anomalies such as the EI Niño-Southern Oscillation and Arctic Oscillation. These assessment efforts yielded results that attested to the suitability of these data sets for research use in other disciplines. The utility of these data sets is documented by comparing the seasonal profiles of LAI3g with profiles from 18 state-of-the-art Earth System Models: the models

  11. 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)

  12. 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)

  13. Data analysis of Allegro gravitational waves detector: verification of signatures of mini black hole systems; Analise de dados do detector de ondas gravitacionais Allegro: verificacao de assinaturas de sistemas de mini-buracos negros

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Katia Maria Florencio da

    2005-07-01

    In this work we constructed a two modes matched digital filter for a burst signal of gravitational radiation. The source is a binary black hole system, where this one is in coalescence time and has 0.5 solar mass. For determination of waveform, we have utilized the equations of the General Relativity Theory, and the Friedmann's theory for the expansion of the universe. We considered the formation of black holes in the very early universe when the temperature was about 1 GeV. The characteristics of the ALLEGRO detector were studied and we showed that this detector is sensitive to the studied signal. The events rate calculated are 5 x 10{sup -2} events per year and various per year for the local group. The power spectral density curve of the noises was determined. With the data of the signal and the noise we obtained the coefficients of the digital filter and elaborated the computer routines for the signals analysis. After filtering the data of the year 1997, we identified several candidates for gravitational wave. We showed that the constructed filter is more effective than the previous one because the temperature of the noise was reduced. We also demonstrated that the filters for impulsive sources have the characteristic of the detect signals of another types of impulsive sources. (author)

  14. 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.

  15. 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.

  16. 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)

  17. 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...

  18. 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

  19. 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...

  20. 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...

  1. Environment, vegetation and greenness (NDVI) along the North America and Eurasia Arctic transects

    Czech Academy of Sciences Publication Activity Database

    Walker, D. A.; Epstein, H. E.; Raynolds, M. K.; Kuss, P.; Kopecký, Martin; Frost, G. V.; Daniëls, F. J. A.; Leibman, M. O.; Moskalenko, N. G.; Matyshak, G. V.; Khitun, O. V.; Khomutov, A. V.; Forbes, B. C.; Bhatt, U. S.; Kade, A. N.; Vonlanthen, C. M.; Tichý, L.

    2012-01-01

    Roč. 7, č. 1 (2012), no.015504. ISSN 1748-9326 Institutional research plan: CEZ:AV0Z60050516 Institutional support: RVO:67985939 Keywords : biomass * leaf area index * tundra Subject RIV: EF - Botanics Impact factor: 3.582, year: 2012

  2. Land degradation monitoring in Sahelian Africa from both NDVI and rainfall data

    OpenAIRE

    San Emeterio, José Luis; Mering, Catherine; Lacaze, Bernard; Sultan, Benjamin

    2010-01-01

    The African Sahel has been a very controversial region in the climatic change debate during the last decades. From the studies that announced a dramatic advance of the desert in the 1970s [Lamprey 1975] and lead to the first conference about desertification [Nairobi, 1977] to the hopeful articles assuming a global recovery from the great droughts of the 70s and 80s [Prince et al., 1998; Hermann et al., 2005], many works have been carried out about this region. The studies of recent years are ...

  3. 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...

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

    OpenAIRE

    Trout, Thomas J.; Johnson, Lee F.

    2012-01-01

    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 ...

  5. 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.

  6. Getting NDVI spectral bands from a single standard RGB digital camera: a methodological approach

    OpenAIRE

    Rabatel, G.; Gorretta, N.; Labbé, S.

    2011-01-01

    Multispectral images including red and near-infrared bands have proved their efficiency for vegetation-soil discrimination and agricultural monitoring in remote sensing applications. But they remain rarely used in ground and UAV imagery, due to a limited availibility of adequate 2D imaging devices. In this paper, a generic methodology is proposed to obtain simultaneously the near-infrared and red bands from a standard RGB camera, after having removed the near-infrared blocking filter inside. ...

  7. Mapping Impervious Surface Distribution with Integration of SNNP VIIRS-DNB and MODIS NDVI Data

    OpenAIRE

    Wei Guo; Dengsheng Lu; Yanlan Wu; Jixian Zhang

    2015-01-01

    Data from the U.S. Defense Meteorological Satellite Program’s Operational Line-scan System are often used to map impervious surface area (ISA) distribution at regional and global scales, but its coarse spatial resolution and data saturation produce high inaccuracy in ISA estimation. Suomi National Polar-orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite’s Day/Night Band (VIIRS-DNB) with its high spatial resolution and dynamic data range may provide new insights but has not ...

  8. 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.

  9. Scaling Effect of Area-Averaged NDVI: Monotonicity along the Spatial Resolution

    OpenAIRE

    Hiroki Yoshioka; Takahiro Wada; Tomoaki Miura; Kenta Obata

    2012-01-01

    Changes in the spatial distributions of vegetation across the globe are routinely monitored by satellite remote sensing, in which the reflectance spectra over land surface areas are measured with spatial and temporal resolutions that depend on the satellite instrumentation. The use of multiple synchronized satellite sensors permits long-term monitoring with high spatial and temporal resolutions. However, differences in the spatial resolution of images collected by different sensors can introd...

  10. Assessment of NDVI, land surface temperature and precipitation anomalies for drought monitoring in Bayankhongor province, Mongolia

    OpenAIRE

    Guerreiro, Joana Ferreira

    2015-01-01

    During the last decade Mongolia’s region was characterized by a rapid increase of both severity and frequency of drought events, leading to pasture reduction. Drought monitoring and assessment plays an important role in the region’s early warning systems as a way to mitigate the negative impacts in social, economic and environmental sectors. Nowadays it is possible to access information related to the hydrologic cycle through remote sensing, which provides a continuous monitoring of variables...

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

    International Nuclear Information System (INIS)

    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

  12. Evaluation of a Reduced Cost Active NDVI Sensor for Crop Nutrient Management

    OpenAIRE

    Jared Crain; Ivan Ortiz-Monasterio; Bill Raun

    2012-01-01

    There are methods to increase fertilizer nitrogen use efficiency through optical sensor-based nitrogen application; however, the sensors are expensive and cost prohibitive to farmers in the developing world. This study evaluated a novel, reduced cost, prototype, and optical sensor to determine if it could be used with the same level of accuracy as a commercial sensor. The stability of the prototype sensor (pocket sensor) to maintain an accurate calibration over time, the effect of operator on...

  13. Estimating Crop Water use From Remotely Sensed NDVI, Crop Models and Reference ET

    Science.gov (United States)

    Crop water use can be estimated from reference evapotranspiration, ETo, calculated from weather station data, and estimated crop coefficients, Kc. However, because Kc varies with crop growth rate, planting density, and management practices, generic Kc curves often don’t match actual crop water use....

  14. 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.

  15. Remotely sensed NDVI as a support tool for agricultural drouhgt assessment

    Czech Academy of Sciences Publication Activity Database

    Hlavinka, Petr; Semerádová, Daniela; Trnka, Miroslav; Lukas, V.; Bohovic, R.; Balek, J.; Wardlow, B.; Hayes, M.; Tseagaye, T.; Žalud, Zdeněk

    Brno: Global change research centre, Academy of Sciences of the Czech Republic, v. v. i, 2013 - (Stojanov, R.; Žalud, Z.; Cudlín, P.; Farda, A.; Urban , O.; Trnka, M.), s. 152-156 ISBN 978-80-904351-8-6. [Global Change and Resilience. Brno (CZ), 22.05.2013-24.05.2013] R&D Projects: GA MŠk(CZ) EE2.4.31.0056; GA MŠk(CZ) EE2.3.20.0248 Institutional support: RVO:67179843 Keywords : remote sensing * yields * palmer drought severity index * data mining Subject RIV: EH - Ecology, Behaviour

  16. ИСПОЛЬЗОВАНИЕ ВЕГЕТАЦИОННЫХ ИНДЕКСОВ NDVI ДЛЯ ОЦЕНКИ ВЛИЯНИЯ ПОЖАРОВ НА ДИНАМИКУ РАСТИТЕЛЬНОСТИ ЦАСУЧЕЙСКОГО БОРА

    OpenAIRE

    КУРГАНОВИЧ КОНСТАНТИН АНАТОЛЬЕВИЧ; МАКАРОВ ВЛАДИМИР ПЕТРОВИЧ

    2015-01-01

    Описан опыт использования данных дистанционного зондирования для изучения влияния пожаров на динамику растительности Цасучейского бора в 2000-2013 гг. Проведен анализ временных рядов среднегодовых значений вегетационных индексов NDVI для пробных площадей в растительных сообществах с разной степенью нарушенности пожарами. В качестве исходных данных дистанционного зондирования поверхности Земли использовались космические снимки спектрорадиометра MODIS с космических аппаратов Terra и Aqua за пер...

  17. O reflexo revisitável. Inerências temporais e estéticas da criação e recepção cinemática

    OpenAIRE

    Castro, Mariana Braga

    2012-01-01

    Falar de um acto de criação no cinema começa por ser um falar da vontade de fazer cinema. A questão que aqui desenvolvemos é a de se um autor se instaura na obra artística que cria e de que forma isso sucede. Este trabalho desenvolve a ideia de um autor enquanto reflexo nas suas obras. Debruçamo-nos sobre a obra fílmica de um realizador para entrar no mundo da sua criação e do conhecimento da obra.

  18. 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...

  19. 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...

  20. 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.

  1. Expressão de certeza e dúvida na gagueira: estudo dos aspectos temporais da fala Expression of certainty and doubt on stuttering: study of speech's temporal features

    Directory of Open Access Journals (Sweden)

    Leticia Correa Celeste

    2012-01-01

    Full Text Available OBJETIVO: examinar o papel da organização temporal do discurso na expressão das atitudes de certeza e dúvida em grupo de adultos com gagueira, comparando-a em um grupo de adultos fluentes. MÉTODO: participaram desta pesquisa 24 indivíduos, sendo 12 com gagueira (GE1 e GE2 e 12 sem gagueira (GC. Foram coletadas amostras que teve como base um corpus de 10 frases chave que foram produzidas nas formas neutra, de dúvida e de certeza, totalizando 840 enunciados. A análise acústica foi realizada por meio do programa Praat e os seguintes parâmetros foram analisados: tempos e taxas de elocução e articulação, ocorrência e duração de pausas e disfluências, duração das vogais tônica e pré-tônica e ocorrência da vogal pós-tônica. A análise estatística foi realizada por meio dos testes Kruskall Wallis e qui-quadrado, com índice de significância de 95%. RESULTADOS: a expressão da dúvida apresenta taxa de articulação mais baixa no grupo controle, seguida da forma neutra e de certeza, com diferenças estatisticamente significantes. Ainda no grupo controle, foi observado presença de pausas e disfluências somente na expressão de dúvida. No grupo experimental, a maior diferença encontrada foi na duração da vogal da sílaba tônica. CONCLUSÃO: de uma forma geral, o GC variou mais sua organização temporal a fim de expressar as atitudes. No entanto, é possível observar também uma tendência semelhante no grupo de pessoas com gagueira. Quanto à velocidade de fala, ao retirar as pausas e as disfluências, vemos que tanto GE1 quanto GE2 diferenciam a certeza, articulando cada sílaba de forma mais rápida.PURPOSE: to examine the role of speech temporal organization on the expression as for the attitudes of certainty and doubt in the group of adults who stutter, comparing such analysis with a group of speech-fluent adults. METHOD: we analyzed 24 individuals, 12 with stuttering (SG1 and SG2 and 12 without stuttering (CG. Samples were collected with a corpus of 10 key phrases that were produced in the neutral form, expressing doubt and certainty, totaling 840 utterances. The acoustic analysis was performed using Praat and the following parameters were analyzed: time and speech rate and articulation, presence and duration of pauses and disfluencies, duration of vowels in pre-tonic and tonic syllables and occurrence of post-tonic vowel. Statistical analysis was performed by using Kruskall Wallis and chi-square tests, with a significance level of 95%. RESULTS: the expression of doubt has the lowest rate of articulation in the control group, followed by neutral and certainty expressions, with statistically significant differences. Also in the control group, there was presence of pauses and disfluencies only in the expression of doubt. In the experimental group, the largest difference was found in the vowel duration of the stressed syllable. CONCLUSION: generally speaking, CG varied more its temporal organization in order to express attitudes. However, it is also possible to note a trend in the group of people who stutter. As for the speech rate, by removing the pauses and disfluencies, we see that both GE1 and GE2 differentiate certainty, faster articulating each syllable.

  2. 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)

  3. 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.

  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. 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)

  6. 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...

  7. Mapping agroecological zones and time lag in vegetation growth by means of Fourier analysis of time series of NDVI images

    Science.gov (United States)

    Menenti, M.; Azzali, S.; Verhoef, W.; Van Swol, R.

    1993-01-01

    Examples are presented of applications of a fast Fourier transform algorithm to analyze time series of images of Normalized Difference Vegetation Index values. The results obtained for a case study on Zambia indicated that differences in vegetation development among map units of an existing agroclimatic map were not significant, while reliable differences were observed among the map units obtained using the Fourier analysis.

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

    OpenAIRE

    Paramesha Mallegowda; Ganesan Rengaian; Jayalakshmi Krishnan; Madhura Niphadkar

    2015-01-01

    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 ...

  9. 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.

  10. An Assessment of Mining Activities Impact on Vegetation in Bukuru Jos Plateau State Nigeria Using Normalized Differential Vegetation Index (NDVI)

    OpenAIRE

    Musa Haruna D.; Jiya Solomon N.

    2011-01-01

    The study area has a pathetic and deplorable condition of landuse/ landcover. The vegetal cover in the area has to be removed from the activities of tin mining which consequently resulted into adverse environmental effect such as erosion. Different forms of human induced stress such as tin mining and heavy rainfall have severely degraded soils on the Jos Plateau. Such degradation problems are also caused by deforestation, inappropriate farming system, bush burning and over-grazing which are h...

  11. 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.

  12. 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.

  13. SACRA – a method for the estimation of global high-resolution crop calendars from a satellite-sensed NDVI

    OpenAIRE

    Kotsuki, S.; K.Tanaka

    2015-01-01

    To date, many studies have performed numerical estimations of biomass production and agricultural water demand to understand the present and future supply–demand relationship. A crop calendar (CC), which defines the date or month when farmers sow and harvest crops, is an essential input for the numerical estimations. This study aims to present a new global data set, the SAtellite-derived CRop calendar for Agricultural simulations (SACRA), and to discuss advantages and disadv...

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

    OpenAIRE

    Hui Ping Tsai; Yu-Hao Lin; Ming-Der Yang

    2016-01-01

    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 ...

  15. 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

    In order to obtain high quality data, the correction of atmospheric perturbations acting upon land surface reflectance measurements recorded by a space-based sensor is an important topic within remote sensing. For many years the Second Simulation of the Satellite Signal in the Solar Spectrum (6S......) radiative transfer model and the Simplified Method for Atmospheric Correction (SMAC) codes have been used for this atmospheric correction, but previous studies have shown that in a number of situations the quality of correction provided by the SMAC is low. This paper describes a method designed to improve...... the quality of the SMAC atmospheric correction algorithm through a slight increase in its computational complexity. Data gathered from the SEVIRI aboard Meteosat Second Generation (MSG) is used to validate the additions to SMAC, both by comparison to simulated data corrected using the highly accurate...

  16. 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

  17. 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

  18. 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...

  19. 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.

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

    OpenAIRE

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

    2010-01-01

    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 ...

  2. 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.

  3. 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...

  4. 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

    the Sahel. EO-based trends were generally not confirmed at the local scale based on selected study cases, partly caused by a temporal mismatch between data sets (i.e. different periods of analysis). Analysis of desert area NDVImin trends indicates less stable values for VGT and GIMMS data as compared...

  5. COMPARATIVE PERFORMANCE ANALYSIS OF A HYPER-TEMPORAL NDVI ANALYSIS APPROACH AND A LANDSCAPE-ECOLOGICAL MAPPING APPROACH

    OpenAIRE

    Ali, A.; Bie, C. A. J. M; Scarrott, R. G.; N.T.T. Ha; A. K. Skidmore

    2012-01-01

    Both agricultural area expansion and intensification are necessary to cope with the growing demand for food, and the growing threat of food insecurity which is rapidly engulfing poor and under-privileged sections of the global population. Therefore, it is of paramount importance to have the ability to accurately estimate crop area and spatial distribution. Remote sensing has become a valuable tool for estimating and mapping cropland areas, useful in food security monitoring. This work contrib...

  6. High Spatial Resolution WorldView-2 Imagery for Mapping NDVI and Its Relationship to Temporal Urban Landscape Evapotranspiration Factors

    OpenAIRE

    Hamideh Nouri; Simon Beecham; Sharolyn Anderson; Pamela Nagler

    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 Febru...

  7. Estimation of actual evapotranspiration at large watershed scale in Africa using NOAA-AVHRR surface temperature and NDVI.

    OpenAIRE

    Touré, Souleymane; Tychon, Bernard

    1997-01-01

    To estimate actual evapotranspiration on regional scale, seven subcatchments were choosen on fleuve Niger catchment where we have selected stations for representative meteorological measurements. Precipitation values are spatially represented by using Thiessen polygons and Kriging methods and, based on water balance equation, we deduce the actual evapotranspiration term.The goal (objective) of this study is to deduce from the water balance equation the evapotranspiration term, to correlate re...

  8. A Simple Method for Retrieving Understory NDVI in Sparse Needleleaf Forests in Alaska Using MODIS BRDF Data

    OpenAIRE

    Wei Yang; Hideki Kobayashi; Rikie Suzuki; Kenlo Nishida Nasahara

    2014-01-01

    Global products of leaf area index (LAI) usually show large uncertainties in sparsely vegetated areas because the understory contribution is not negligible in reflectance modeling for the case of low to intermediate canopy cover. Therefore, many efforts have been made to include understory properties in LAI estimation algorithms. Compared with the conventional data bank method, estimation of forest understory properties from satellite data is superior in studies at a global or continental sca...

  9. LINCOLN – an algorithm for filtering daily NDVI MODIS data and deriving the start of the season

    Czech Academy of Sciences Publication Activity Database

    Bohovič, R.; Hlavinka, Petr; Semerádová, Daniela; Bálek, L.; Tadesse, T.; Hayes, M.; Wardlow, B.; Trnka, Miroslav

    Brno: Global Change Research Centre, The Czech Academy of Sciences, v. v. i., 2015 - (Urban, O.; Šprtová, M.; Klem, K.), s. 42-45 ISBN 978-80-87902-10-3. [Global Change: A Complex Challenge /4th/. Brno (CZ), 23.03.2015-24.03.2015] R&D Projects: GA MŠk(CZ) EE2.3.20.0248 Institutional support: RVO:67179843 Keywords : monitoring system * LINCOLN software * vegetation conditions Subject RIV: EH - Ecology, Behaviour

  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. 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...

  12. 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...

  13. 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.

  14. 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

  15. АНАЛИЗ КОСМИЧЕСКИХ ИЗОБРАЖЕНИЙ С РАСЧЕТОМ NDVI ДЛЯ ИЗУЧЕНИЯ ДИНАМИКИ ЛАНДШАФТНОГО ПОКРОВА ТЕРРИТОРИИ НЕФТЯНОГО МЕСТОРОЖДЕНИЯ В ОРЕНБУРГСКОЙ ОБЛАСТИ

    OpenAIRE

    Мячина, Ксения

    2013-01-01

    В статье предлагается пример использования данных дистанционного зондирования Земли для анализа динамики геоэкологического состояния ландшафтного покрова на территории Бобровского месторождения нефти, расположенного в степной зоне Оренбургской области. Выполнено визуальное и автоматическое дешифрование разновременных космоснимков Landsat-5ТМ с расчётом вегетационного индекса NDVI. Выявлено, что на территории месторождения за период более чем 20 лет значительно сократились площади древесного и...

  16. ОПЫТ ПРИМЕНЕНИЯ ИНДЕКСА ВЕГЕТАЦИИ (NDVI) ДЛЯ ОПРЕДЕЛЕНИЯ БИОЛОГИЧЕСКОЙ ПРОДУКТИВНОСТИ ФИТОЦЕНОЗОВ АРИДНОЙ ЗОНЫ НА ПРИМЕРЕ РЕГИОНА ЧЕРНЫЕ ЗЕМЛИ

    OpenAIRE

    Лиджиева, Лина; Уланова, Светлана; Федорова, Наталья

    2012-01-01

    В статье представлены результаты сопряженных наземных и дистанционных исследований по изучению растительных сообществ с различной степенью использования пастбищ (заповедный режим, охранный и выпасной) региона Черные Земли Республики Калмыкия. Проведенные исследования позволили выявить положительную корреляционную зависимость между показателем вегетационного индекса (NDVI) и продуктивностью для различных типов сообществ. Таким образом, выявленные при дистанционных и наземных исследованиях, кол...

  17. 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.

  18. 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.

  19. Variações espaço-temporais na alimentação de Pimelodus ortmanni (Siluriformes, Pimelodidae) no reservatório de Segredo e áreas adjacentes (PR) Spatio temporal variations in Pimelodus ortmanni (Siluriformes, Pimelodidae) feeding in Segredo reservoir and contigous areas (PR)

    OpenAIRE

    Márcia Regina Russo; Fabiane Abujanra; Norma Segatti Hahn

    1999-01-01

    Este trabalho teve como objetivo conhecer a dieta de Pimelodus ortmanni (Haseman, 1911) no reservatório de Segredo e nas áreas adjacentes, em três períodos consecutivos à formação desse reservatório (rio Iguaçu-PR). As coletas foram realizadas no período de março de 93 a fevereiro de 96 no reservatório, nos tributários e jusante. Foram analisados 808 estômagos pelos métodos de freqüência de ocorrência e volumétrico, combinados no índice alimentar. A espécie foi caracterizada como omnívora-car...

  20. 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...

  1. 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.

  2. A time series analysis of Prochilodus nigricans landings caught by small-scale fisheries in the lower stretch of the Amazon River Uma análise em séries temporais das capturas de Prochilodus nigricans pela frota artesanal no trecho inferior do Rio Amazonas

    OpenAIRE

    IF. Santana; CEC. Freitas

    2013-01-01

    We developed a time series analysis using data on curimatã (Prochilodus nigricans), which landed in Santarém, a small city located on the right banks of the Amazon River. A 10-year record of monthly average catches per day of P. nigricans was analyzed using forecasting procedures in the open-source software GRETL 1.7.8. We established two models from the identifications made with the correlograms of hyperparametrization and seasonal differences. The autoregressive terms of the model reach thr...

  3. 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...

  4. 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...

  5. HUBUNGAN ANTARA INDEKS VEGETASI NDVI (NORMALIZED DIFFERENCE VEGETATION INDEX) DAN KOEFISIEN RESESI BASEFLOW PADA BEBERAPA SUBDAS PROPINSI JAWA TENGAH DAN DAERAH ISTIMEWA YOGYAKARTA

    OpenAIRE

    Bokiraiya Latuamury

    2013-01-01

    The background of this research is the decrease of environment capacity in cacthment ecosystem, especially impact of vegetation forest on behavior streamflow. The indicators of cacthment destruction can be seen through hydrograph characteristics. Evaluation of cactment respons of flow hydrographic as an evaluation tools of river catchment responses becomes very important to analyze because it is a benchmark in determination several policy about flood, drough, sedimentation and landslide handl...

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

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

    OpenAIRE

    Campo-Bescós, Miguel A.; Rafael Muñoz-Carpena; Jane Southworth; Likai Zhu; Peter R. Waylen; Erin Bunting

    2013-01-01

    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 r...

  12. 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.

  13. 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

    OpenAIRE

    Bergson Guedes Bezerra; Bernardo Barbosa da Silva; José Renato Cortez Bezerra; Ziany Neiva Brandão

    2010-01-01

    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, particul...

  14. Correlação espacial do índice de vegetação (NDVI) de imagem Landsat/ETM+ com atributos do solo Spatial correlation of the vegetation index (NDVI) of a Landsat/ETM+ images with soil attributes

    OpenAIRE

    Fabricio V. Zanzarini; Teresa C. T. Pissarra; Flavia J. C. Brandão; Daniel D. B. Teixeira

    2013-01-01

    As tecnologias de agricultura de precisão, como o uso da variabilidade espacial dos atributos do solo, vêm sendo muito estudadas para a cultura de cana-de-açúcar. Dentre essas tecnologias se destaca o uso de índices de vegetação derivados de produtos de sensoriamento remoto, como poderosas ferramentas indicadoras do desenvolvimento da vegetação. Objetivou-se, neste estudo, analisar a variabilidade espacial dos teores de argila, fósforo e o pH de um Latossolo Vermelho-amarelo em área com produ...

  15. 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...

  16. Evolução dos homicídios e indicadores de segurança pública no Município de São Paulo entre 1996 a 2008: um estudo ecológico de séries temporais Homicide and public security indicator trends in the city of São Paulo between 1996 and 2008: a time-series ecological study

    Directory of Open Access Journals (Sweden)

    Maria Fernanda Tourinho Peres

    2012-12-01

    Full Text Available OBJETIVO: analisar a associação entre homicídios e indicadores de segurança pública no MSP entre 1996 e 2008, após controle para taxa de desemprego e proporção de jovens na população. METODOLOGIA: estudo ecológico de série temporal, tendo como unidade de análise o Município de São Paulo (MSP, entre 1996 e 2008. Variável dependente: óbitos por homicídio; variáveis independentes principais: taxa de aprisionamento-encarceramento (TAE, o acesso a armas de fogo (AAF, e a atividade policial (ATP. A análise dos dados foi realizada com o software Stata.IC 10.0. Modelos de regressão binomial negativa simples e multivariados foram construídos. RESULTADOS: A análise univariada demonstrou associação entre óbitos por homicídio e TAE e entre óbitos e ATP. O AAF não se mostrou associado à redução no número de óbitos por homicídios (p > 0,05. Após ajuste houve perda da significância na associação com ambos indicadores de Segurança Pública. CONCLUSÕES: No MSP o papel das ações de segurança pública perdem importância como fatores explicativos para a redução nos níveis de homicídios após controle para taxa de desemprego e redução na proporção de jovens. Os resultados reforçam a importância dos fatores socioeconômicos e demográficos para a mudança no cenário da segurança em São Paulo.The scope of this paper was to analyze the association between homicides and public security indicators in São Paulo between 1996 and 2008, after monitoring the unemployment rate and the proportion of youths in the population. A time-series ecological study for 1996 and 2008 was conducted with São Paulo as the unit of analysis. Dependent variable: number of deaths by homicide per year. Main independent variables: arrest-incarceration rate, access to firearms, police activity. Data analysis was conducted using Stata.IC 10.0 software. Simple and multivariate negative binomial regression models were created. Deaths by homicide and arrest-incarceration, as well as police activity were significantly associated in simple regression analysis. Access to firearms was not significantly associated to the reduction in the number of deaths by homicide (p>0,05. After adjustment, the associations with both the public security indicators were not significant. In São Paulo the role of public security indicators are less important as explanatory factors for a reduction in homicide rates, after adjustment for unemployment rate and a reduction in the proportion of youths. The results reinforce the importance of socioeconomic and demographic factors for a change in the public security scenario in São Paulo .

  17. 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...

  18. 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...

  19. 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.

  20. Analysis of the relationship between the volumetric soil moisture content and the NDVI from high resolution multi-spectral images for definition of vineyard management zones to improve irrigation

    Science.gov (United States)

    Martínez-Casasnovas, J. A.; Ramos, M. C.

    2009-04-01

    As suggested by previous research in the field of precision viticulture, intra-field yield variability is dependent on the variation of soil properties, and in particular the soil moisture content. Since the mapping in detail of this soil property for precision viticulture applications is highly costly, the objective of the present research is to analyse its relationship with the normalised difference vegetation index from high resolution satellite images to the use it in the definition of vineyard zonal management. The final aim is to improve irrigation in commercial vineyard blocks for better management of inputs and to deliver a more homogeneous fruit to the winery. The study was carried out in a vineyard block located in Raimat (NE Spain, Costers del Segre Designation of Origin). This is a semi-arid area with continental Mediterranean climate and a total annual precipitation between 300-400 mm. The vineyard block (4.5 ha) is planted with Syrah vines in a 3x2 m pattern. The vines are irrigated by means of drips under a partial root drying schedule. Initially, the irrigation sectors had a quadrangular distribution, with a size of about 1 ha each. Yield is highly variable within the block, presenting a coefficient of variation of 24.9%. For the measurement of the soil moisture content a regular sampling grid of 30 x 40 m was defined. This represents a sample density of 8 samples ha-1. At the nodes of the grid, TDR (Time Domain Reflectometer) probe tubes were permanently installed up to the 80 cm or up to reaching a contrasting layer. Multi-temporal measures were taken at different depths (each 20 cm) between November 2006 and December 2007. For each date, a map of the variability of the profile soil moisture content was interpolated by means of geostatistical analysis: from the measured values at the grid points the experimental variograms were computed and modelled and global block kriging (10 m squared blocks) undertaken with a grid spacing of 3 m x 3 m. On the other hand, three Quickbird-2 satellite images where acquired and processed to monitor plant vigour. The dates of images acquisition were: 29-07-2004, 13-07-2005 and 13-07-2006. They are within the range of

  1. 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.

  2. FAO Training in Crop Yield Forecasting - Remote Sensing - Method for Crop Yield Forecasting System (CYFS) from spatial Remote Sensing for Tajikistan. Integration of PROBA-V NDVI images. Belgium - Arlon Campus Environment - January 2015.

    OpenAIRE

    Denis, Antoine

    2015-01-01

    This manual has been written for the “Training for strengthening crop yield forecasting capacity of the State Administration for Hydrometeorology (Hydromet) of Tajikistan” that occurred between 12nd January and 7th February 2015 in Arlon – Belgium in the framework of the Food and Agriculture Organization (FAO) of the United Nations Project (GCP/TAJ/007/EC) “Support to Strengthening the National Food Security Information System in Tajikistan”. This manual is intended to cover the Remote S...

  3. How Normalized Difference Vegetation Index (NDVI) Trendsfrom Advanced Very High Resolution Radiometer (AVHRR) and Système Probatoire d’Observation de la Terre VEGETATION (SPOT VGT) Time Series Differ in Agricultural Areas: An Inner Mongolian Case Study

    OpenAIRE

    Patrick Hostert; Dirk Pflugmacher; Thomas Udelhoven; Rasmus Fensholt; He Yin

    2012-01-01

    Detailed information from global remote sensing has greatly advanced ourunderstanding of Earth as a system in general and of agricultural processes in particular.Vegetation monitoring with global remote sensing systems over long time periods iscritical to gain a better understanding of processes related to agricultural change over longtime periods. This specifically relates to sub-humid to semi-arid ecosystems, whereagricultural change in grazing lands can only be detected based on long time ...

  4. 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.

  5. Câncer gástrico: fatores de risco em clientes atendidos nos serviços de atenção terciária em um município do interior paulista

    OpenAIRE

    Teixeira Jesislei Bonolo do Amaral; Nogueira Maria Suely

    2003-01-01

    Realizamos o presente estudo com clientes com diagnóstico de câncer gástrico e submetidos a cirurgia, com o objetivo de identificar a exposição aos fatores de risco para a doença. Foram sujeitos do estudo 24 clientes que concordaram em participar através da assinatura do termo de consentimento livre, respondendo a um instrumento semi-estruturado, elaborado segundo a perspectiva do Campo de Saúde. A análise dos dados possibilitou identificar que 50,1% apontaram como fatores responsáveis dieta ...

  6. 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...

  7. Informe MERCOSUL número 13 : segundo semestre 2007-primeiro semestre 2008

    OpenAIRE

    Ricardo Carciofi; Uziel Nogueira; Romina Eliana Gayá; Rosario Campos; Alejandro Ramos; BID. INTAL

    2009-01-01

    O Mercado Comum do Sul (MERCOSUL) foi constituído a partir da assinatura do Tratado de Assunçao, em 1991, com o objetivo de avaliar os êxitos e os desafios que encerra o processo de integraçao vigente na América Latina e no Caribe. A intençao do INTAL, mediante a publicaçao do Informe MERCOSUL, é facilitar, para um universo de potenciais leitores interessados nesta regiao, o acesso à informaçao. Trata-se, também, de ultrapassar o interesse que o MERCOSUL desperta no nível sub-regional, facili...

  8. Informe MERCOSUL numero 12 : segundo semestre 2006-primeiro semestre 2007

    OpenAIRE

    Romina Eliana Gayá; Gustavo Svarzman; Ricardo Rozemberg; Alejo Espora; Aníbal Córdoba Sosa; Alejandro Ramos; Ricardo Carciofi; Uziel Nogueira

    2008-01-01

    O Mercado Comum do Sul (MERCOSUL) foi constituído a partir da assinatura do Tratado de Assunçao, em 1991, com o objetivo de avaliar os êxitos e os desafios que encerra o processo de integraçao vigente na América Latina e no Caribe. A intençao do INTAL, mediante a publicaçao do Informe MERCOSUL, é facilitar, para um universo de potenciais leitores interessados nesta regiao, o acesso à informaçao. Trata-se, também, de ultrapassar o interesse que o MERCOSUL desperta no nível sub-regional, facili...

  9. Fansites ou o "consumo da experiência" na mídia contemporânea

    OpenAIRE

    Laura Graziela Gomes

    2007-01-01

    O presente artigo apresenta resultados de uma pesquisa que pretendeu investigar uma faceta do consumo de mídia contemporâneo, especialmente associado ao uso da tecnologia digital. Para a realização da investigação, escolhi investigar e observar fansites de séries norte-americanas de TV, criados e administrados por fãs brasileiros para discutirem suas séries preferidas, divulgarem-nas, produzirem e trocarem entre si suas fanarts: fanfics, fanvideos, icons ou avatares, banners ou assinaturas e ...

  10. 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...

  11. 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...

  12. Efetividade de uma técnica educativa na aquisição de conhecimentos por pais sobre uso racional do flúor = Effectiveness of an educative techinique on knowledge acquisition on ratinal use of fluorine by parents

    OpenAIRE

    2006-01-01

    O objetivo do presente estudo foi testar o conhecimento sobre uso racional de flúor adquirido através de grupo de discussão (GD). Um grupo de 47 pais de crianças pré-escolares constituiu a amostra após a assinatura de um termo de consentimento livre e esclarecido. Este estudo foi aprovado por um Comitê de ética em Pesquisa. Para averiguação do nível de conhecimento inicial sobre o tema proposto, os participantes responderam a um questionário com 14 perguntas abertas e fechadas. Seis meses apó...

  13. 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...

  14. 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...

  15. Caracterização do perfil motor de escolares com transtorno autístico

    OpenAIRE

    Paola Matiko Okuda

    2010-01-01

    As alterações motoras podem fazer parte das chamadas comorbidades que podem coexistir com o transtorno autístico. Objetivo: caracterizar o perfil motor de escolares com espectro autístico. Método: participaram deste estudo 6 escolares com transtorno autístico do ensino fundamental, do gênero masculino, com idades variando entre 5 anos e 5 meses e 10 anos e 9 meses. Após a assinatura do termo de consentimento pelos pais ou responsáveis, os escolares foram submetidos à aplicação da Escala de De...

  16. Retrato de uma ideia

    Directory of Open Access Journals (Sweden)

    David Anfam

    2011-01-01

    Full Text Available Como chegar à "imagem abstrata" (cenário pictórico que consolidando um método ou idioma plastico tornou-se a "assinatura" do artista - e que propriamente reconhecemos como um "Rothko"? Examina-se aqui uma hipótese em que esta busca dirige-se antes a um meio de expressão direta de estados subjetivos, como uma ideia ou linguagem das emoções, mais que a questões representacionais herdadas da tradição.

  17. 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...

  18. Relationship between rainfall and vegetation indexes in Burkina Faso: a case study of the Nakambe basin

    OpenAIRE

    Diello, Pierre; Mahé, Gil; Paturel, Jean-Emmanuel; Dezetter, Alain (ed.); Delclaux, François; Servat, Eric; Ouattara, F.

    2005-01-01

    This work deals with the problem of the use of remote sensing data derived from NOAA/AVHRR observations for monitoring the West African Sahel climatic variability. NDVI is widely used in hydrological and climatological research, and in the study of global climatic changes. The relationships between NDVI and climatic parameters are not well established yet and are the focus of many studies. The relationships between NDVI and rainfall were studied at a 10-day time step in the Nakambe River basi...

  19. 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.

  20. 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.

  1. Responses of Natural Vegetation Dynamics to Climate Drivers in China from 1982 to 2011

    Directory of Open Access Journals (Sweden)

    Yanlan Liu

    2015-08-01

    Full Text Available This study investigated the spatiotemporal variation of vegetation growth and the influence of climatic drivers from 1982 to 2011 across China using datasets from the Normalized Difference Vegetation Index (NDVI and climatic drivers. Long term trends, significance and abrupt change points of interannual NDVI time series were analyzed. We applied both simple regression and multi-regression models to quantify the effects of climatic drivers on vegetation growth and compare their relative contributions. Results show that on average, the growing season NDVI significantly increased by 0.0007 year-1, with 76.5% of the research area showed increasing NDVI from 1982 to 2011. Seasonally, NDVI increased at high rates during the spring and autumn while changed slightly during the summer. At a national scale, the growing season NDVI was significantly and positively correlated to temperature and precipitation, with temperature being the dominant factor. At regional scales, the growing season NDVI was dominated by increasing temperature in most forest-covered areas in southern China and dominated by precipitation in most grassland in northern China. Within the past three decades, the increasing trend of national mean NDVI abruptly changed in 1994, slowing down from 0.0008 year-1 to 0.0003 year-1. To be regional specific, the growing season NDVI in forest covered southern China has accelerated together with temperature since mid 1990s, while parts of the grassland in northern China have undergone stalled NDVI trends corresponding to slowed temperature increment and dropped precipitation since around 2000. Typical region analysis suggested that apart from long term trends and abrupt change points of climatic drivers, the processes of NDVI variation were also affected by other external factors such as drought and afforestation. Further studies are needed to investigate the nonlinear responses of vegetation growth to climatic drivers and effects of non

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. High-latitude tree growth and satellite vegetation indices: Correlations and trends in Russia and Canada (1982-2008)

    Science.gov (United States)

    Berner, Logan T.; Beck, Pieter S. A.; Bunn, Andrew G.; Lloyd, Andrea H.; Goetz, Scott J.

    2011-03-01

    Vegetation in northern high latitudes affects regional and global climate through energy partitioning and carbon storage. Spaceborne observations of vegetation, largely based on the normalized difference vegetation index (NDVI), suggest decreased productivity during recent decades in many regions of the Eurasian and North American boreal forests. To improve interpretation of NDVI trends over forest regions, we examined the relationship between NDVI from the advanced very high resolution radiometers and tree ring width measurements, a proxy of tree productivity. We collected tree core samples from spruce, pine, and larch at 22 sites in northeast Russia and northwest Canada. Annual growth rings were measured and used to generate site-level ring width index (RWI) chronologies. Correlation analysis was used to assess the association between RWI and summer NDVI from 1982 to 2008, while linear regression was used to examine trends in both measurements. The correlation between NDVI and RWI was highly variable across sites, though consistently positive (r = 0.43, SD = 0.19, n = 27). We observed significant temporal autocorrelation in both NDVI and RWI measurements at sites with evergreen conifers (spruce and pine), though weak autocorrelation at sites with deciduous conifers (larch). No sites exhibited a positive trend in both NDVI and RWI, although five sites showed negative trends in both measurements. While there are technological and physiological limitations to this approach, these findings demonstrate a positive association between NDVI and tree ring measurements, as well as the importance of considering lagged effects when modeling vegetation productivity using satellite data.

  7. Comparison between two vegetation indices for measuring different types of forest damage in the north-eastern United States

    Science.gov (United States)

    Vogelmann, J. E.

    1990-01-01

    The relative effectiveness of the Landsat TM-derived normalized difference vegetative index (NDVI) and the short-wave IR to NIR ratio (SWIR/NIR) index was examined in measurements of different types of damage in several forest communities. The forests examined included a site with well-defined fir waves in New Hampshire, a site undergoing well-documented coniferous forest decline in Vermont, and predominantly deciduous regions in Vermont and northwestern Massachusetts seriously impacted by pear thrips. Both NDVI and SWIR/NIR images were produced for each area. Results demonstrated that the SWIR/NIR index was superior to NDVI in distinguishing between high and low conifer damage at both fir-wave and forest decline sites; high and low deciduous-forest damage sites were easily separable using either NDVI or SWIR/NIR, but the NDVI was superior in separation between medium and low deciduous damage.

  8. Agricultural impacts on ecosystem functioning in temperate areas of North and South America

    Science.gov (United States)

    Guerschman, Juan Pablo; Paruelo, José María

    2005-07-01

    Land use has a large impact on ecosystem functioning, though evidences of these impacts at the regional scale are scarce. The objective of this paper was to analyze the impacts of agricultural land use on ecosystem functioning (radiation interception and carbon uptake) in temperate areas of North and South America. From land cover maps generated using high-resolution satellite images we selected sites dominated by row crops (RC), small grain crops (SG), pastures (PA), and rangelands (RA) in the Central Plains of USA and the Pampas of Argentina. These two regions share climatic characteristics and the agricultural conditions (crop types) are also very similar. Both areas were originally dominated by temperate grasslands. In these sites we extracted the temporal series of the normalized difference vegetation index (NDVI) from the NOAA satellites for the period 1989-1998 and calculated the mean seasonal NDVI curve for each site. Additionally, we calculated the mean annual NDVI, the maximum NDVI, the date of the year when the max NDVI was recorded and the interannual variability of these three attributes. We compared the mean values of each NDVI-derived attribute between land cover types and between continents. The NDVI seasonal patterns for each land cover type were roughly similar between the Central Plains and the Pampas during the growing season. The largest differences were observed during the winter and spring, when the NDVI of all land cover types in the Central Plains remained at lower values than in the Pampas. This was probably caused by the high annual thermal amplitude in the Central Plains that results in a much more restricted growing season. As a result of these differences in the shape of the NDVI curve, the mean annual NDVI in the Central Plains was lower than in the Pampas for all land cover types but the maximum NDVI did not differ importantly. In both regions, row crops delayed the date of the NDVI peak, small grain crops advanced it and pastures

  9. Uma reflexão estratégica sobre a segurança e defesa em Angola e a intervenção no contexto regional subsaariano

    OpenAIRE

    Almeida, Eugénio Costa; Bernardino, Luís Manuel Brás

    2016-01-01

    No inovador e complexo paradigma secretário subsariano, Angola vem assumindo uma postura de afirmação nacional conducente com a sua estratégia de afirmação como produto de segurança regional, reflexo de uma intervenção crescente no plano geopolítico e geoestratégico Africano. Após o período de conflito interno e sua independência em 1975, e depois da assinatura do Acordo de Luena em 2002, Angola assumiu internamente uma política de reconstrução, especialmente ao nível da Segurança e Defesa, t...

  10. 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...

  11. 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

  12. Informe MERCOSUL No. 2 (1997)

    OpenAIRE

    Banco Interamericano de Desenvolvimento (BID)

    1997-01-01

    A série Informe MERCOSUL representa um esforço do INTAL destinado a fomentar o conhecimento e a difusão de informação relacionados com dinâmico processo de integração vigente na América Latina e no Caribe. Como parte dessa corrente integracionista, o Mercado Comum do Sul foi constituído a partir da assinatura do Tratado de Assunção em 1991, como um caso protótipo para avaliar os sucessos e o desafíos que encerra essa ambiciosa iniciativa. A intenção do INTAL, por meio da publicação dessa séri...

  13. Impacto de Entrada da Venezuela no Mercosul: Uma Simulação com Modelo de Equilíbrio Geral Computável

    OpenAIRE

    Goldbaum, Sergio; Coelho, Allexandro Mori; Lima, Maria Lúcia Labate Mantovanini Pádua; Cury, Samir

    2006-01-01

    O Objetivo deste Estudo é Avaliar os Impactos da Entrada da Venezuela no Mercosul Utilizando para Tanto o Modelo de Equilíbrio Geral Computável Multi-Setorial e Multi-Regional Denominado Global Trade Analysis Project (Gtap). Além da Introdução, o Estudo Está Dividido em Outras 5 Seções. na Seção 2, são Analisados os Documentos Mais Relevantes Assinados Pelos Estados-Parte, Ressaltando a Relativa Rapidez da Assinatura do Acordo de Adesão da Venezuela ao Bloco; na Seção 3, Descreve-Se o Estado ...

  14. O URUGUAI SOB O IMPACTO DAS PAPELERAS: ENTRE DOIS CAMINHOS OPOSTOS DE INSERÇÃO NO CENÁRIO INTERNACIONAL

    Directory of Open Access Journals (Sweden)

    Lucas Tasquetto

    2007-12-01

    Full Text Available O conflito decorrente da instalação de fábricas de celulose nas margens uruguaias do Rio Uruguai, fronteira com a Argentina, confrontou os dois países a uma pluralidade de marcos regulatórios e meios de solução de controvérsias. O desenvolvimento da controvérsia somado ao descumprimento das decisões tem acentuado o descontentamento do Uruguai com o Mercosul. Assim, logo começa uma aproximação com os EUA. A possibilidade da assinatura de um tratado de livre comércio coloca os uruguaios entre dois modelos bastante distintos de inserção no cenário internacional: a integração regional, com o aprofundamento do Mercosul; e a opção bilateral norte-americana

  15. 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.

  16. A gente se liga em voc: reconfiguraes da TV Globo em um cenrio de convergncia miditica

    Directory of Open Access Journals (Sweden)

    Diego Gouveia Moreira

    2012-06-01

    Full Text Available Os 46 anos da Rede Globo foram comemorados com o lanamento de uma nova assinatura. Em vez do a gente se v por aqui, a emissora passou a usar a gente se liga em voc. O novo slogan volta a ateno para o telespectador. Entender o processo de transio da TV em um cenrio de convergncia e as adaptaes que a TV Globo tem implementado para atender s novas demandas so os principais objetivos deste artigo. Para isso, so abordadas as mudanas que os meios tradicionais esto realizando diante dos novos meios e so mostradas as principais estratgias da Globo nesse ecossistema miditico. Por fim, o artigo constata a instaurao de um novo estatuto da televiso.

  17. 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...

  18. 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.

  19. Os "combatentes da paz": a participação dos comunistas brasileiros na Campanha Pela Proibição das Armas Atômicas (1950

    Directory of Open Access Journals (Sweden)

    Jayme Ribeiro

    2008-12-01

    Full Text Available O trabalho procura reconstituir a Campanha pela Proibição das Armas Atômicas, adotada pelo PCB no ano de 1950. Seguindo a linha pacifista da União Soviética, dirigida a todos os partidos comunistas, a campanha consistia no recolhimento, pelos militantes comunistas, de assinaturas a um apelo pela proibição da utilização das armas atômicas por qualquer país e pela eliminação dos arsenais atômicos existentes até aquele momento. Os comunistas brasileiros, mesmo na ilegalidade, articularam-se e obtiveram o apoio de diferentes grupos sociais à campanha.

  20. Certificação de software de facturação

    OpenAIRE

    Correia, Joel Carlos Campos

    2011-01-01

    A portaria de nº 363/2010 (1), de vinte e três de Junho do ano de dois mil e dez, que regulamentou a certificação prévia dos programas informáticos de facturação, requereu que as Software Houses que comercializam aplicações de facturação, preparassem um conjunto de funcionalidades que permitam que um software garanta o cumprimento da lei e minimize a possibilidade de fugas fiscais. De entre estas funcionalidades, destaca-se a criação de assinaturas de modo a utilizar o método de encriptação R...

  1. Relationships between high resolution RapidEye based fPAR and MODIS vegetation indices in a heterogeneous agricultural region

    Science.gov (United States)

    Fritsch, Sebastian; Machwitz, Miriam; Conrad, Christopher; Dech, Stefan

    2011-11-01

    The Moderate Imaging Spectroradiometer (MODIS) provides operational products of the Normalized Difference Vegetation Index (NDVI), the Enhanced Vegetation Index (EVI), and the fraction of photosynthetic active radiation (fPAR). FPAR can be used in productivity models, but agricultural applications depend on sub-pixel heterogeneity. Examples for heterogeneous areas are the irrigation systems of the inner Aral Sea Basin, where the 1 km fPAR product proved less suited. An alternative can be to upscale fPAR to the 250 m scale, but there are few studies evaluating this approach. In this study, the use of MODIS 250 m NDVI and EVI for this approach was investigated in an irrigation system in western Uzbekistan. The analysis was based on high resolution fPAR maps and a crop map for the growing season 2009, derived from ground measurements and multitemporal RapidEye data. The data was used to explore statistical relationships between RapidEye fPAR and MODIS NDVI/EVI with respect to spatial heterogeneity. The correlations varied between products (daily NDVI, 8-day NDVI, 16-day NDVI/EVI), with results suggesting that 8-day NDVI performed best. The analyses and the compiled fPAR maps show that, compared to 1 km MODIS fPAR, the 250 m scale is more homogeneous, allows for crop-specific analyses, and better captures the spatial patterns in the study region.

  2. Remote Sensing Data with the Conditional Latin Hypercube Sampling and Geostatistical Approach to Delineate Landscape Changes Induced by Large Chronological Physical Disturbances

    Directory of Open Access Journals (Sweden)

    Yu-Pin Lin

    2009-01-01

    Full Text Available This study applies variogram analyses of normalized difference vegetation index (NDVI images derived from SPOT HRV images obtained before and after the ChiChi earthquake in the Chenyulan watershed, Taiwan, as well as images after four large typhoons, to delineate the spatial patterns, spatial structures and spatial variability of landscapes caused by these large disturbances. The conditional Latin hypercube sampling approach was applied to select samples from multiple NDVI images. Kriging and sequential Gaussian simulation with sufficient samples were then used to generate maps of NDVI images. The variography of NDVI image results demonstrate that spatial patterns of disturbed landscapes were successfully delineated by variogram analysis in study areas. The high-magnitude Chi-Chi earthquake created spatial landscape variations in the study area. After the earthquake, the cumulative impacts of typhoons on landscape patterns depended on the magnitudes and paths of typhoons, but were not always evident in the spatiotemporal variability of landscapes in the study area. The statistics and spatial structures of multiple NDVI images were captured by 3,000 samples from 62,500 grids in the NDVI images. Kriging and sequential Gaussian simulation with the 3,000 samples effectively reproduced spatial patterns of NDVI images. However, the proposed approach, which integrates the conditional Latin hypercube sampling approach, variogram, kriging and sequential Gaussian simulation in remotely sensed images, efficiently monitors, samples and maps the effects of large chronological disturbances on spatial characteristics of landscape changes including spatial variability and heterogeneity.

  3. Investigation of Vegetation Dynamics using Long-Term Normalized Difference Vegetation Index Time-Series

    Directory of Open Access Journals (Sweden)

    Tamara Bellone

    2009-01-01

    Full Text Available Problem statement: The Normalized Difference Vegetation Index (NDVI is the most extensively used satellite-derived index of vegetation health and density. Since climate is one of the most important factors affecting vegetation condition, satellite-derived vegetation indexes have been often used to evaluate climatic and environmental changes at regional and global scale. The proposed study attempted to investigate the temporal vegetation dynamics in the whole Africa using historical NDVI time-series. Approach: For this aim, 15 day maximum value NDVI composites at 8 km spatial resolution produced from the NASA Global Inventory Mapping and Monitoring System (GIMMS had been used. They were derived from data collected daily by NOAA AVHRR satellites. The AVHRR NDVI GIMMS dataset was freely available and gives global coverage over an extensive time period. First of all, the selected NDVI base data had been geometrically pre-processed and organized into a historical database implemented in order to grant their spatial integration. Starting from this archive, monthly and yearly NDVI historical time-series, extended from 1982-2006, had been then developed and analysed on a pixel basis. Several routines hade been developed in IDL (Interactive Data Language programming tool with the purpose of applying suitable statistical analysis techniques to the historical information in the database in order to identify the long-term trend components of generated NDVI time-series and extract vegetation dynamics. Specific tests had been then considered in order to define the validity of results. Results: The existence of clear regional trends of NDVI, both decreasing and increasing had been showed, which helped to highlight areas subject, respectively to reduction or increase in vegetation greenness. Conclusion: As the relationship between the NDVI and vegetation productivity was well established, these estimated long-term trend components may be also, with much more

  4. 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.

  5. Recent Change of Vegetation Growth Trend in China

    Science.gov (United States)

    Peng, Shushi; Chen, Anping; Xu, Liang; Cao, Chunxiang; Fang, Jingyun; Myneni, Ranga B.; Pinzon, Jorge E.; Tucker, COmpton J.; Piao, Shilong

    2011-01-01

    Using satellite-derived normalized difference vegetation index (NDVI) data, several previous studies have indicated that vegetation growth significantly increased in most areas of China during the period 1982-99. In this letter, we extended the study period to 2010. We found that at the national scale the growing season (April-October) NDVI significantly increased by 0.0007/yr from 1982 to 2010, but the increasing trend in NDVI over the last decade decreased in comparison to that of the 1982-99 period. The trends in NDVI show significant seasonal and spatial variances. The increasing trend in April and May (AM) NDVI (0.0013/yr is larger than those in June, July and August (JJA) (0.0003/yr) and September and October (SO) (0.0008/yr). This relatively small increasing trend of JJA NDVI during 1982-2010 compared with that during 1982-99 (0.0012/yr) (Piao et al 2003 J. Geophys. Res.-Atmos. 108 4401) implies a change in the JJA vegetation growth trend, which significantly turned from increasing (0.0039/yr) to slightly decreasing (0:0002/yr) in 1988. Regarding the spatial pattern of changes in NDVI, the growing season NDVI increased (over 0.0020/yr) from 1982 to 2010 in southern China, while its change was close to zero in northern China, as a result of a significant changing trend reversal that occurred in the 1990s and early 2000s. In northern China, the growing season NDVI significantly increased before the 1990s as a result of warming and enhanced precipitation, but decreased after the 1990s due to drought stress strengthened by warming and reduced precipitation. Our results also show that the responses of vegetation growth to climate change vary across different seasons and ecosystems.

  6. Recent change of vegetation growth trend in China

    International Nuclear Information System (INIS)

    Using satellite-derived normalized difference vegetation index (NDVI) data, several previous studies have indicated that vegetation growth significantly increased in most areas of China during the period 1982–99. In this letter, we extended the study period to 2010. We found that at the national scale the growing season (April–October) NDVI significantly increased by 0.0007 yr−1 from 1982 to 2010, but the increasing trend in NDVI over the last decade decreased in comparison to that of the 1982–99 period. The trends in NDVI show significant seasonal and spatial variances. The increasing trend in April and May (AM) NDVI (0.0013 yr−1) is larger than those in June, July and August (JJA) (0.0003 yr−1) and September and October (SO) (0.0008 yr−1). This relatively small increasing trend of JJA NDVI during 1982–2010 compared with that during 1982–99 (0.0012 yr−1) (Piao et al 2003 J. Geophys. Res.—Atmos. 108 4401) implies a change in the JJA vegetation growth trend, which significantly turned from increasing (0.0039 yr−1) to slightly decreasing ( − 0.0002 yr−1) in 1988. Regarding the spatial pattern of changes in NDVI, the growing season NDVI increased (over 0.0020 yr−1) from 1982 to 2010 in southern China, while its change was close to zero in northern China, as a result of a significant changing trend reversal that occurred in the 1990s and early 2000s. In northern China, the growing season NDVI significantly increased before the 1990s as a result of warming and enhanced precipitation, but decreased after the 1990s due to drought stress strengthened by warming and reduced precipitation. Our results also show that the responses of vegetation growth to climate change vary across different seasons and ecosystems.

  7. 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.

  8. Grupoterapia cognitivo-comportamental para crianças e adolescentes vítimas de abuso sexual Terapia de grupo congnitivo-comportamental para niñas y adolescentes víctimas de abuso sexual Cognitive behavioral group therapy for sexually abused girls

    OpenAIRE

    Luísa Fernanda Habigzang; Fernanda Helena Stroeher; Roberta Hatzenberger; Rafaela Cassol Cunha; Michele da Silva Ramos; Sílvia Helena Koller

    2009-01-01

    OBJETIVO: Avaliar os efeitos do modelo de grupoterapia cognitivo-comportamental para crianças e adolescentes do sexo feminino vítimas de abuso sexual. MÉTODOS: Foi utilizado delineamento não-randomizado intragrupos de séries temporais. Crianças e adolescentes do sexo feminino com idade entre nove e 16 anos (N=40) da região metropolitana de Porto Alegre (RS), foram clinicamente avaliadas em três encontros individuais, de 2006 a 2008. A grupoterapia consistiu de 16 sessões semi-estruturadas. In...

  9. A Periodização nos Estudos de Televisão

    Directory of Open Access Journals (Sweden)

    Sérgio Capparelli

    2008-12-01

    Full Text Available Capparelli dá continuidade as suas análises sobre sistemas de televisão, com um exame dos critérios historiográficos utilizados para a periodização dos estudos sobre a televisão brasileira. Em seu artigo, o autor enfoca questões conceituais de historiografia e propõe a problematização dos cortes temporais produzidos ad hoc. Capparelli objetiva alertar para a necessidade de uma compreensão menos linear e mais crítica da periodização dos estudos da TV no Brasil.

  10. 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

  11. 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...

  12. Estruturação de assembleias de peixes recifais em múltiplas escalas

    OpenAIRE

    Gomes, Mariana Bender

    2014-01-01

    Resumo: Os mecanismos por trás da estruturação de comunidades constituem uma questão central em ecologia e biogeografia. Identificar estes mecanismos é fundamental para prever as implicações da perda da biodiversidade no futuro. Uma gama de processos atuam em diferentes escalas temporais e espaciais interagem para produzir comunidades ecológicas. Além disso, tais processos podem influenciar de maneira distinta os componentes taxonômico, funcional e filogenético das comunidades. Neste estudo i...

  13. Transtorno somatoforme de causa orgânica: relato de caso Organic somatoform disorder: case report

    Directory of Open Access Journals (Sweden)

    MARCELO CAIXETA

    1999-03-01

    Full Text Available Realizamos estudo a respeito do diagnóstico diferencial de um doente somatoforme apresentando sinais neuropsicológicos de natureza frontal, visando distingui-lo dos hipocondríacos e dismorfofóbicos obsessivos, bem como dos esquizofrênicos, melancólicos e lesionados cerebrais parietais e temporais.Based on the neuropsychological and imagenological evaluation of a frontal damaged patient with a somatoform disorder, we study the differential diagnosis of this condition compared to that of other patients: temporal or parietal damaged ones, schizophrenics, melancholics, obsessives, hypochondriacs and dismorphophobics.

  14. 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...

  15. Searching without information:a quantitative analysis of Caenorhabditis elegans locomotion

    OpenAIRE

    Salvador, Liliana M.

    2012-01-01

    Movimento animal é um processo muito importante e altamente complexo que afecta vários sistemas ecológicos a diferentes escalas temporais e espaciais . Quando a fonte de alimento não está acessível, os animais exploram o ambiente tentando aumentar as suas chances de a localizar, e tendo que balancear, da melhor forma, a execução entre uma busca local e uma busca não-local do ambiente. Apesar do processo de busca ser um processo ecológico muito importante, ainda muito pouco se sabe sobre os se...

  16. O tempo subjectivo como instrumento (des)adaptativo no processo desenvolvimental

    OpenAIRE

    Ortuño, Vícitor E. C.; Paixão, Maria Paula; Janeiro, Isabel Nunes

    2013-01-01

    A Perspectiva Temporal – PT (Zimbardo & Boyd, 1999) é o processo através do qual as experiências pessoais e sociais dos sujeitos são categorizadas, arquivadas e recuperadas mediante categorias temporais que têm por base as noções subjectivas do passado, o presente e o futuro. Assim, através de uma análise da PT é possível compreender mudanças em diversas variáveis, tenham estas um carácter funcional (auto-estima, investimento escolar, comportamentos pró-activos e de empreendedorismo) ou disfu...

  17. O Cinema na Requisição das Mitologias da Pós-Modernidade

    OpenAIRE

    Santos, Jorge Manuel Torres Ferreira dos

    2012-01-01

    Podemos procurar as razões pelas quais o fenómeno cinemático também reflete inusitado sucesso na pós-modernidade. Diversos fatores permitiram o libertar do homem das grilhetas espácio-temporais, ajudando partilhas em permanência. Hipoteticamente facilitada uma necessidade antropológica, paradigma do pós-moderno. O cinema requisita uma superior capacidade de expressão para o próprio. Damos assim início a uma procura de entendimento do pensamento humano até ao contemporâneo, pela história, pela...

  18. 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...

  19. 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...

  20. 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...

  1. Poder de mercado no varejo alimentar: uma análise usando os preços do estado de São Paulo

    OpenAIRE

    Danilo R. D. Aguiar; Adelson Martins Figueiredo

    2011-01-01

    O setor varejista brasileiro tem apresentado expressivas transformações em sua organização estrutural desde a década de 1990. Se, por um lado, o mercado se mostra bastante concentrado, por outro, há evidências de uma crescente rivalidade entre as empresas. Esta pesquisa objetivou examinar o impacto da concentração de mercado sobre o uso de poder de mercado para produtos agrícolas específicos, por meio de análise de séries temporais dos preços do estado de São Paulo. Os resultados indicaram qu...

  2. Uso de textos literários no ensino de língua italiana

    OpenAIRE

    2011-01-01

    Resumo: O emprego de textos literários no ensino de língua e cultura italiana a estrangeiros comprova sua eficiência na medida em que favorece a aproximação entre alunos e contextos sociolingüísticos narrados. A aplicabilidade deste corpus tão variado é ainda definida pela necessidade de romper, durante o ensino do idioma, as barreiras que dificultam a compreensão do repertório lingüístico italiano, principalmente no tocante às peculiaridades espaço-temporais tais como dialetos e regionalismo...

  3. O comércio electrónico : fundamentos, modelos, sistemas de segurança e pagamentos : experiência de comércio electrónico dos alunos do ensino superior do Instituto Politécnico de Tomar : estudo de caso

    OpenAIRE

    Silva, Vasco Renato Marques Gestosa da

    2010-01-01

    A evolução das tecnologias de informação e comunicação, nomeadamente da Internet, vieram introduzir novas formas de comprar e vender produtos e serviços, proporcionaram o aumento da dimensão dos mercados, maior transparência na negociação, maior facilidade de acesso das empresas ao seu mercado alvo, a presença permanente (24 horas por dia, 7 dias por semana), impuseram a redução de custos, entre outras oportunidades (Cunha, 2007). A inexistência de barreiras regionais ou temporais na Internet...

  4. 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

  5. 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

  6. Identification and application of the valid wavelength bands for burnt area detection and fire severity classification using Landsat/TM data

    International Nuclear Information System (INIS)

    Firstly, by using Landsat Thematic Mapper (TM) imagery before and after forest fire, the valid wavelength bands for detecting burnt areas were examined and compared to NDVI. Secondly, by using the valid wavelength bands, mapping of burnt area and classification of fire severity were examined. The results show that (a) channel 4 and 7 were more sensitive than other channels for detecting burnt area, (b) BAI (Burnt Area Index) [(ch. 4-ch. 7)/(ch. 4+ch. 7)] was more useful than NDVI for detecting burnt areas, and (c) BAI imagery was more useful for classification of burn severity than NDVI imagery

  7. 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.

  8. 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, Joseph P.; Hargrove, William; Norman, Steve; Gasser, Jerry; Smoot, James; Kuper, Philip D,

    2012-01-01

    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 NRT forest change products refreshed 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

  9. Development of a Mobile Multispectral Imaging Platform for Precise Field Phenotyping

    Czech Academy of Sciences Publication Activity Database

    Svensgaard, J.; Roitsch, Thomas; Christensen, C.

    2014-01-01

    Roč. 4, č. 3 (2014), s. 322-336. ISSN 2073-4395 Institutional support: RVO:67179843 Keywords : field phenotyping * multispectral imaging * supervised classification * canonical discriminant analysis * vegetation coverage * NDVI Subject RIV: EH - Ecology, Behaviour

  10. 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

  11. 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.

  12. 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...

  13. 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 ...

  14. 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.

  15. TERRESTRIAL VEGETATION GREENNESS OF THE LOWER GALVESTON BAY WATERSHED FROM SATELLITE REMOTE SENSING AND ITS RELATION TO WATER AND THE SALINITY REGIME OF THE GALVESTON BAY ESTUARY

    Science.gov (United States)

    Spatial and temporal variability of vegetation greenness have been determined for coastal Texas using biweekly Normalized Difference Vegetation Index (NDVI) data derived from the Advanced Very High Resolution Radiometer (AVHRR). Results are presented on relationships between grou...

  16. 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...

  17. 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.

  18. 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

  19. 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

  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. 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.

  2. 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 ...

  3. 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

  4. 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...

  5. Technical Note: Comparing and ranking soil drought indices performance over Europe, through remote-sensing of vegetation

    OpenAIRE

    Peled, E.; Dutra, E; Viterbo, P; Angert, A.

    2010-01-01

    In the past years there have been many attempts to produce and improve global soil-moisture datasets and drought indices. However, comparing and validating these various datasets is not straightforward. Here, interannual variations in drought indices are compared to interannual changes in vegetation, as captured by NDVI. By comparing the correlations of the different indices with NDVI we evaluated which drought index describes most realistically the actual changes in vegetation. Strong correl...

  6. Impact of elevation and aspect on the spatial distribution of vegetation in the Qilian mountain area with remote sensing data

    OpenAIRE

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

    2008-01-01

    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 by analyzing the NDVI data for seven years from 2000 to 2006 clearly indicated that elevation is the dominating factor determining the vertical distribution of vegetation in the area: the vegetation...

  7. Seasonal relationship between normalized difference vegetation index and abundance of the Phlebotomus kala-azar vector in an endemic focus in Bihar, India

    OpenAIRE

    Gouri S. Bhunia; Shreekant Kesari; Nandini Chatterjee; Rakesh Mandal; Vijay Kumar; Pradeep Das

    2012-01-01

    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 t...

  8. Global changes in dryland vegetation dynamics (1988–2008) assessed by satellite remote sensing: comparing a new passive microwave vegetation density record with reflective greenness data

    OpenAIRE

    N. Andela; Liu, Y.Y.; A. I. J. M. van Dijk; R. A. M. de Jeu; Mcvicar, T. R.

    2013-01-01

    Drylands, covering nearly 30% of the global land surface, are characterized by high climate variability and sensitivity to land management. Here, two satellite-observed vegetation products were used to study the long-term (1988–2008) vegetation changes of global drylands: the widely used reflective-based Normalized Difference Vegetation Index (NDVI) and the recently developed passive-microwave-based Vegetation Optical Depth (VOD). The NDVI is sensitive to the chlorophyll con...

  9. Remote Sensing Data with the Conditional Latin Hypercube Sampling and Geostatistical Approach to Delineate Landscape Changes Induced by Large Chronological Physical Disturbances

    OpenAIRE

    Yu-Pin Lin; Hone-Jay Chu; Cheng-Long Wang; Yung-Chieh Wang; Hsiao-Hsuan Yu

    2009-01-01

    This study applies variogram analyses of normalized difference vegetation index (NDVI) images derived from SPOT HRV images obtained before and after the ChiChi earthquake in the Chenyulan watershed, Taiwan, as well as images after four large typhoons, to delineate the spatial patterns, spatial structures and spatial variability of landscapes caused by these large disturbances. The conditional Latin hypercube sampling approach was applied to select samples from multiple NDVI images. Kriging an...

  10. Post-fire vegetation recovery in Portugal based on spot/vegetation data

    OpenAIRE

    Gouveia, C.; DaCamara, C. C.; Trigo, R. M.

    2010-01-01

    A procedure is presented that allows identifying large burned scars and the monitoring of vegetation recovery in the years following major fire episodes. The procedure relies on 10-day fields of Maximum Value Composites of Normalized Difference Vegetation Index (MVC-NDVI), with a 1 km×1 km spatial resolution obtained from the VEGETATION instrument. The identification of fire scars during the extremely severe 2003 fire season is performed based on cluster analysis of NDVI anomalies t...

  11. AS INFLUÊNCIAS DA FILOSOFIA NATURAL E DA NATURPHILOSOPHIE NA CONSTITUIÇÃO DO DARWINISMO: ELEMENTOS PARA UMA FILOSOFIA DA GEOGRAFIA FÍSICA MODERNA

    Directory of Open Access Journals (Sweden)

    Antonio Carlos Vitte

    2009-06-01

    Full Text Available Esse trabalho argumenta que a teoria da evolução de Charles Darwin sofreu forte influência da naturphilosophie de Schelling e Hegel, representando um avanço positivo nas concepções de teleologia da natureza. Fortemente influenciado pelas obras de Alexander von Humboldt, de Werner e pelas pesquisas no campo da paleontologia, a Teoria da Evolução, concebeu a transformação dos organismos e a sua especiação a partir determinantes geográficos e temporais. Ideologicamente influenciado por Lyell, que acreditava na hipótese da vera causa, Darwin relegou a matriz espacial e concentrou suas argumentações nas mudanças temporais, basicamente climáticas, como determinante da evolução. Os impactos da teoria da evolução atingem tanto o campo da geografia física, quanto da geografia humana, influenciando fortemente na postura metodológica das pesquisas geográficas, mas chamando a atenção para a complexidade das relações entre o espaço e tempo que estão em constante mudança.

  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. 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.

  14. 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

  15. 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.

  16. Drought risk mapping of south-western state in the Indian peninsula - A web based application.

    Science.gov (United States)

    Gopinath, Girish; Ambili, G K; Gregory, Shery Joseph; Anusha, C K

    2015-09-15

    Application of geospatial technology is very shimmering in drought monitoring. Drought severity in crops for six northern districts of Kerala has been attempted using Geospatial Techniques. Normalized Difference Vegetation Index (NDVI) is the major parameter used to measure vegetation health obtained from MODIS, Terra satellite products MOD13Q1, MOD02QKM. The mean Normalized Difference Vegetation Index (NDVI) of Kerala state over 13 years was calculated. The daily anomalies of NDVI from its long term mean NDVI over the same period was determined based on which drought risk classification was done. High negative NDVI anomaly areas are susceptible to drought and the severity of drought risk on each crop can be identified using Land Use/Land Cover data. Overlaying daily NDVI Anomaly based drought risk map on land use/land cover map gives the drought risk for different crops. Based on this, a web application has been developed for Northern districts of Kerala state in India. This web application can be used to plan for drought management measures and can also serve as a database for drought analysis. PMID:25560658

  17. 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.

  18. 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.

  19. 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.

  20. Vegetation Greenness in Northeastern Brazil and Its Relation to ENSO Warm Events

    Directory of Open Access Journals (Sweden)

    Stefan Erasmi

    2014-04-01

    Full Text Available The spatio-temporal variability of trends in vegetation greenness in dryland areas is a well-documented phenomenon in remote sensing studies at global to regional scales. The underlying causes differ, however, and are often not well understood. Here, we analyzed the trends in vegetation greenness for a semi-arid area in northeastern Brazil (NEB and examined the relationships between those dynamics and climate anomalies, namely the El Nino Southern Oscillation (ENSO for the period 1982 to 2010, based on annual Normalized Difference Vegetation Index (NDVI values from the latest version of the Global Inventory Modeling and Mapping Studies (GIMMS NDVI dataset (NDVI3g dataset. Against the ample assumption of ecological and socio-economic research, the results of our inter-annual trend analysis of NDVI and precipitation indicate large areas of significant greening in the observation period. The spatial extent and strength of greening is a function of the prevalent land-cover type or biome in the study area. The regression analysis of ENSO indicators and NDVI anomalies reveals a close relation of ENSO warm events and periods of reduced vegetation greenness, with a temporal lag of 12 months. The spatial patterns of this relation vary in space and time. Thus, not every ENSO warm event is reflected in negative NDVI anomalies. Xeric shrublands (Caatinga are more sensitive to ENSO teleconnections than other biomes in the study area.