WorldWideScience

Sample records for monsoon nam region

  1. Quaternary ecological responses and impacts of the Indian Ocean Summer Monsoon at Nam Co, Southern Tibetan Plateau

    NARCIS (Netherlands)

    Günther, F.; Witt, R.; Schouten, Stefan|info:eu-repo/dai/nl/137124929; Mausbacher, R.; Daut, G.; Zhu, Liping; Xu, B.; Yao, T.; Gleixner, G.

    2015-01-01

    The transition from the Last Glacial to the current Interglacial, the Holocene, represents an important period with climatic and environmental changes impacting ecosystems. In this study, we examined the interplay between the Indian Ocean Summer Monsoon (IOSM) and the Westerlies at lake Nam Co, sout

  2. Quaternary ecological responses and impacts of the Indian Ocean Summer Monsoon at Nam Co, Southern Tibetan Plateau

    NARCIS (Netherlands)

    Günther, F.; Witt, R.; Schouten, S.; Mausbacher, R.; Daut, G.; Zhu, L.; Xu, B.Q.; Yao, T.; Gleixner, G.

    2015-01-01

    The transition from the Last Glacial to the current Interglacial, the Holocene, represents an important period with climatic and environmental changes impacting ecosystems. In this study, we examined the interplay between the Indian Ocean Summer Monsoon (IOSM) and the Westerlies at lake Nam Co,

  3. Quaternary ecological responses and impacts of the Indian Ocean Summer Monsoon at Nam Co, Southern Tibetan Plateau

    NARCIS (Netherlands)

    Günther, F.; Witt, R.; Schouten, Stefan|info:eu-repo/dai/nl/137124929; Mausbacher, R.; Daut, G.; Zhu, Liping; Xu, B.; Yao, T.; Gleixner, G.

    The transition from the Last Glacial to the current Interglacial, the Holocene, represents an important period with climatic and environmental changes impacting ecosystems. In this study, we examined the interplay between the Indian Ocean Summer Monsoon (IOSM) and the Westerlies at lake Nam Co,

  4. Process-based characterization of evapotranspiration sources over the North American monsoon region

    Science.gov (United States)

    Bohn, Theodore J.; Vivoni, Enrique R.

    2016-01-01

    Evapotranspiration (ET) is a poorly constrained flux in the North American monsoon (NAM) region, leading to potential errors in land-atmosphere feedbacks. We quantified the spatiotemporal variations of ET using the Variable Infiltration Capacity (VIC) model, modified to account for soil evaporation (Esoil), irrigated agriculture, and the variability of land surface properties derived from the Moderate Resolution Imaging Spectroradiometer during 2000-2012. Simulated ET patterns were compared to field observations at 59 eddy covariance towers, water balance estimates in nine basins, and six available gridded ET products. The modified VIC model performed well at eddy covariance towers representing the natural and agricultural land covers in the region. Simulations revealed that major sources of ET were forested mountain areas during the summer season and irrigated croplands at peak times of growth in the winter and summer, accounting for 22% and 9% of the annual ET, respectively. Over the NAM region, Esoil was the largest component (60%) of annual ET, followed by plant transpiration (T, 32%) and evaporation of canopy interception (8%). Esoil and T displayed different relationships with P in natural land covers, with Esoil tending to peak earlier than T by up to 1 month, while only a weak correlation between ET and P was found in irrigated croplands. Based on the model performance, the VIC-based estimates are the most realistic to date for this region. Furthermore, spatiotemporal patterns reveal new information on the magnitudes, locations, and timing of ET in the North American monsoon region with implications on land-atmosphere feedbacks.

  5. Monsoon variability for the past 4 ka derived from high-resolution analyses of sediments from lake Nam Co, central Tibetan Plateau

    Science.gov (United States)

    Kasper, T.; Haberzettl, T.; Doberschütz, S.; Daut, G.; Mäusbacher, R.; Wang, J.; Zhu, L.; Wennrich, V.

    2010-12-01

    The presented project aims to reconstruct processes within lake Nam Co (central Tibetan Plateau; 4718 m a.s.l.), its environment and climatic conditions. By using a multi-proxy approach for this study we present high resolution data covering the past 4 ka. During a field campaign in September 2008 five gravity cores (68 cm to 115 cm length) were recovered in addition to one piston core with a total length of 11 m (water depth: 93 m). This study focuses on data from sediments of two gravity cores (NC08/01 Pilot 3 & Pilot 4). A wide spectrum of sedimentological, geochemical and mineralogical investigations was carried out. Results are presented for XRD measurements, XRF-core scans, grain size analysis and SEM-image analyses. Data are completed by an age-depth model using 210Pb and 137Cs analyses as well as eleven AMS 14C-ages. In addition this model is supported by excellent agreement between secular variations detected in one of the cores to geomagnetic field models. This is a significant improvement of the chronology as the catchments of most lacustrine systems on the plateau contain carbonates resulting in a carbon reservoir effect for radiocarbon dates. By the comparison of our record with the geomagnetic field models we assure that there is no change in this effect through time. Sediments exhibit homogeneous color and only minor variations regarding grain size distribution. According to the XRD measurements the main minerogenic components of the sediment, such as quartz, calcite, feldspars (albite & orthoclase) and muscovite show only minor fluctuations. In addition the presence of monohydrocalcite (CaCO3×H2O) (MHC), was proven by both XRD-measurements and SEM imaging. The presence of this metastable phase of CaCO3 is meant to be an indicator for intervals of cold climate or for evaporative settings (Li et al. 2008). Results of the high-resolution XRF-core scan (0.2 cm interval) show clear variability. After removing elements with too low counts 8 element scans

  6. Forecast Verification for North American Mesoscale (NAM) Operational Model over Karst/Non-Karst regions

    Science.gov (United States)

    Sullivan, Z.; Fan, X.

    2014-12-01

    Karst is defined as a landscape that contains especially soluble rocks such as limestone, gypsum, and marble in which caves, underground water systems, over-time sinkholes, vertical shafts, and subterranean river systems form. The cavities and voids within a karst system affect the hydrology of the region and, consequently, can affect the moisture and energy budget at surface, the planetary boundary layer development, convection, and precipitation. Carbonate karst landscapes comprise about 40% of land areas over the continental U.S east of Tulsa, Oklahoma. Currently, due to the lack of knowledge of the effects karst has on the atmosphere, no existing weather model has the capability to represent karst landscapes and to simulate its impact. One way to check the impact of a karst region on the atmosphere is to check the performance of existing weather models over karst and non-karst regions. The North American Mesoscale (NAM) operational forecast is the best example, of which historical forecasts were archived. Variables such as precipitation, maximum/minimum temperature, dew point, evapotranspiration, and surface winds were taken into account when checking the model performance over karst versus non-karst regions. The forecast verification focused on a five-year period from 2007-2011. Surface station observations, gridded observational dataset, and North American Regional Reanalysis (for certain variables with insufficient observations) were used. Thirteen regions of differing climate, size, and landscape compositions were chosen across the Contiguous United States (CONUS) for the investigation. Equitable threat score (ETS), frequency bias (fBias), and root-mean-square error (RMSE) scores were calculated and analyzed for precipitation. RMSE and mean bias (Bias) were analyzed for other variables. ETS, fBias, and RMSE scores show generally a pattern of lower forecast skills, a greater magnitude of error, and a greater under prediction of precipitation over karst than

  7. Aerosols and contrasting monsoon conditions over the Himalayan region

    Science.gov (United States)

    Singh, Charu; Ganguly, Dilip; Dash, S. K.

    2016-05-01

    Impact of aerosols on the Indian summer monsoon (ISM) variability is well documented; however there are limited studies which have quantified the role of aerosols in modifying the amount of rainfall. To address this research problem, we make use of the remotely sensed data set of precipitation and aerosols from different observations. In the present study remotely sensed precipitation data set has been utilised to define contrasting monsoon conditions over the Himalayan region. As per the classical definition, active and break spells are defined over the central part of the Indian land region, and during the break spells over the central Indian region, the Himalayan region receives substantial amount of rainfall. It is found that accumulation of more dust over the Uttarakhand region significantly (negative correlation with rainfall; significant at 5% significance level) suppresses the rainfall during break spells. We propose that the substantial aerosol loading and its associated dynamical feedback over the Himalayan foothills may have considerable impact on the amount of rainfall over the mountainous regions of the Indian subcontinent. Results presented in this paper are supported by the statistically robust significance test and would be useful to develop the understanding of the role of aerosols in modulating the rainfall intensity during the summer monsoon season.

  8. North American Monsoon Variability from Instrumental and Tree-Ring Data: A Progress Report (Invited)

    Science.gov (United States)

    Woodhouse, C. A.; Meko, D. M.; Touchan, R.; Leavitt, S. W.; Griffin, D.; Castro, C. L.; Ciancarelli, B.

    2009-12-01

    The main goal of this research project is to investigate the long-term variability of the North American Monsoon (NAM), both spatially and temporally, using instrumental data and paleoclimatic data from tree-ring widths and stable-carbon isotopes. The NAM has been the topic of much research in recent years and a great deal of progress has been made in improving our understanding of the NAM. However, questions remain about the long-term behavior of the monsoon, as well as its relationship to cool season climate and to large-scale circulation. In addition, it is unclear how the monsoon will respond to global warming as GCMs do not yet appear to adequately capture the monsoon system dynamics. This research project involves analyses of instrumental and paleoclimatic data to determine NAM spatial patterns in the U.S., relationships to large-scale atmospheric circulation drivers, and the nature of the NAM variability over past centuries. Paleoclimatic data will also be used to assess the skill of downscaled GCMs in replicating the range of NAM variability. The first step in this work has been to design and implement a sampling and analysis strategy for a network of tree-ring data that reflects summer moisture in the NAM region, informed by previous collections and analysis of instrumental data. Here we report on the results from our first year, focusing on three specific areas: 1) definition of dominant patterns of NAM variability using the standard precipitation index (SPI), and relationships to large-scale atmospheric circulation, 2) the tree-ring collection network and preliminary results, and 3) strategies for enhancing and extracting summer precipitation information from tree rings using partial ring widths and isotope analysis. Although our collections have included both the monsoon core region of southeastern Arizona and southwestern New Mexico, and areas at the fringe of the monsoon influence in the U.S, our initial focus is on the analysis of the collections for

  9. Stable isotopic signature of Australian monsoon controlled by regional convection

    Science.gov (United States)

    Zwart, C.; Munksgaard, N. C.; Kurita, N.; Bird, M. I.

    2016-11-01

    The aim of this study was to identify the main meteorological drivers of rainfall isotopic variation in north Australia in order to improve the interpretation of isotopic proxy records in this region. An intense monitoring program was conducted during two monsoonal events that showed significant and systematic isotopic change over time. The results showed a close link between isotopic variation in precipitation and variability in monsoon conditions, associated with the presence of large convective envelopes propagating through the study site. The largest negative amplitudes in the isotopic signal were observed when eastward and westward moving precipitation systems within the convective envelope merged over the measurement site. This suggests that the amplitude of the isotopic signal is related to the size and activity of the convective envelope. The strong correlation between rainfall isotopic variation, regional outgoing longwave radiation and regional rainfall amount supports this conclusion. This is further strengthened by the strong relationship between isotopic variation and the integrated rainfall history of air masses prior to arriving at the measurement locations. A local amount effect was not significant and these findings support the interpretation of δ18O as proxy for regional climatic conditions rather than local rainfall amount. Meteorological parameters that characterize intra-seasonal variability of monsoon conditions were also found to be strongly linked to inter-seasonal variability of the monthly based δ18O values in the Global Network of Isotopes in Precipitation (GNIP) database. This leads to the conclusion that information about the Australian monsoon variability can likely be inferred from the isotopic proxy record in North Australia on short (intra seasonal) and long (inter seasonal or longer) timescales.

  10. Enhancing the Variable Infiltration Capacity Model to Account for Natural and Anthropogenic Impacts on Evapotranspiration in the North American Monsoon Region

    Science.gov (United States)

    Bohn, T. J.; Vivoni, E. R.

    2015-12-01

    Evapotranspiration (ET) is a poorly constrained flux in the North American monsoon (NAM) region, leading to potential errors in land-atmosphere feedbacks. Due to the region's arid to semi-arid climate, two factors play major roles in ET: sparse vegetation that exhibits dramatic seasonal greening, and irrigated agriculture. To more accurately characterize the spatio-temporal variations of ET in the NAM region, we used the Variable Infiltration Capacity (VIC) model, modified to account for soil evaporation (Esoil), irrigated agriculture, and the variability of land surface properties derived from the Moderate Resolution Imaging Spectroradiometer during 2000-2012. Simulated ET patterns were compared to field observations at fifty-nine eddy covariance towers, water balance estimates in nine basins, and six available gridded ET products. The modified VIC model performed well at eddy covariance towers representing the natural and agricultural land covers in the region. Simulations revealed that major source areas for ET were forested mountain areas during the summer season and irrigated croplands at peak times of growth in the winter and summer, accounting for 22% and 9% of the annual ET, respectively. Over the NAM region, Esoil was the largest component (60%) of annual ET, followed by plant transpiration (T, 32%) and evaporation of canopy interception (8%). Esoil and T displayed different relations with P in natural land covers, with Esoil tending to peak earlier than T by up to one month, while only a weak correlation between ET and P was found in irrigated croplands. These VIC-based estimates are the most realistic to date for this region, outperforming several other process-based and remote-sensing-based gridded ET products. Furthermore, spatio-temporal patterns reveal new information on the magnitudes, locations and timing of ET in the North American monsoon region, with implications for land-atmosphere feedbacks.

  11. Severe weather during the North American monsoon and its response to rapid urbanization and a changing global climate within the context of high resolution regional atmospheric modeling

    Science.gov (United States)

    Luong, Thang Manh

    The North American monsoon (NAM) is the principal driver of summer severe weather in the Southwest U.S. With sufficient atmospheric instability and moisture, monsoon convection initiates during daytime in the mountains and later may organize, principally into mesoscale convective systems (MCSs). Most monsoon-related severe weather occurs in association with organized convection, including microbursts, dust storms, flash flooding and lightning. The overarching theme of this dissertation research is to investigate simulation of monsoon severe weather due to organized convection within the use of regional atmospheric modeling. A commonly used cumulus parameterization scheme has been modified to better account for dynamic pressure effects, resulting in an improved representation of a simulated MCS during the North American monsoon experiment and the climatology of warm season precipitation in a long-term regional climate model simulation. The effect of urbanization on organized convection occurring in Phoenix is evaluated in model sensitivity experiments using an urban canopy model (UCM) and urban land cover compared to pre-settlement natural desert land cover. The presence of vegetation and irrigation makes Phoenix a "heat sink" in comparison to its surrounding desert, and as a result the modeled precipitation in response to urbanization decreases within the Phoenix urban area and increase on its periphery. Finally, analysis of how monsoon severe weather is changing in association with observed global climate change is considered within the context of a series of retrospectively simulated severe weather events during the period 1948-2010 in a numerical weather prediction paradigm. The individual severe weather events are identified by favorable thermodynamic conditions of instability and atmospheric moisture (precipitable water). Changes in precipitation extremes are evaluated with extreme value statistics. During the last several decades, there has been

  12. Trends and variability of droughts over the Indian monsoon region

    Directory of Open Access Journals (Sweden)

    Ganeshchandra Mallya

    2016-06-01

    Full Text Available Drought characteristics for the Indian monsoon region are analyzed using two different datasets and standard precipitation index (SPI, standardized precipitation-evapotranspiration index (SPEI, Gaussian mixture model-based drought index (GMM-DI, and hidden Markov model-based drought index (HMM-DI for the period 1901–2004. Drought trends and variability were analyzed for three epochs: 1901–1935, 1936–1971 and 1972–2004. Irrespective of the dataset and methodology used, the results indicate an increasing trend in drought severity and frequency during the recent decades (1972–2004. Droughts are becoming more regional and are showing a general shift to the agriculturally important coastal south-India, central Maharashtra, and Indo-Gangetic plains indicating higher food security and socioeconomic vulnerability in the region.

  13. Effects of large-scale deforestation on precipitation in the monsoon regions: remote versus local effects.

    Science.gov (United States)

    Devaraju, N; Bala, Govindasamy; Modak, Angshuman

    2015-03-17

    In this paper, using idealized climate model simulations, we investigate the biogeophysical effects of large-scale deforestation on monsoon regions. We find that the remote forcing from large-scale deforestation in the northern middle and high latitudes shifts the Intertropical Convergence Zone southward. This results in a significant decrease in precipitation in the Northern Hemisphere monsoon regions (East Asia, North America, North Africa, and South Asia) and moderate precipitation increases in the Southern Hemisphere monsoon regions (South Africa, South America, and Australia). The magnitude of the monsoonal precipitation changes depends on the location of deforestation, with remote effects showing a larger influence than local effects. The South Asian Monsoon region is affected the most, with 18% decline in precipitation over India. Our results indicate that any comprehensive assessment of afforestation/reforestation as climate change mitigation strategies should carefully evaluate the remote effects on monsoonal precipitation alongside the large local impacts on temperatures.

  14. Rainfall analysis for Indian monsoon region using the merged rain gauge observations and satellite estimates: Evaluation of monsoon rainfall features

    Indian Academy of Sciences (India)

    S K Roy Bhowmik; Ananda K Das

    2007-06-01

    Objective analysis of daily rainfall at the resolution of 1° grid for the Indian monsoon region has been carried out merging dense land rainfall observations and INSAT derived precipitation estimates. This daily analysis, being based on high dense rain gauge observations was found to be very realistic and able to reproduce detailed features of Indian summer monsoon. The inter-comparison with the observations suggests that the new analysis could distinctly capture characteristic features of the summer monsoon such as north–south oriented belt of heavy rainfall along the Western Ghats with sharp gradient of rainfall between the west coast heavy rain region and the rain shadow region to the east, pockets of heavy rainfall along the location of monsoon trough/low, over the east central parts of the country, over north–east India, along the foothills of Himalayas and over the north Bay of Bengal. When this product was used to assess the quality of other available standard climate products (CMAP and ECMWF reanalysis) at the grid resolution of 2.5°, it was found that the orographic heavy rainfall along Western Ghats of India was poorly identified by them. However, the GPCC analysis (gauge only) at the resolution of 1° grid closely discerns the new analysis. This suggests that there is a need for a higher resolution analysis with adequate rain gauge observations to retain important aspects of the summer monsoon over India. The case studies illustrated show that the daily analysis is able to capture large-scale as well as mesoscale features of monsoon precipitation systems. This study with data of two seasons (2001 and 2003) has shown sufficiently promising results for operational application, particularly for the validation of NWP models.

  15. INTRODUCING A NEW INTERNATIONAL PROGRAM: MONSOON ASIA INTEGRATED REGIONAL STUDY (MAIRS)

    Institute of Scientific and Technical Information of China (English)

    Congbin Fu; Ailikun; Renjian Zhang; Xiaodong Yan

    2006-01-01

    The Monsoon Asia Integrated Regional Study (MAIRS) is a new Earth System Science Partnership (ESSP)program aimed at the integrated study of environmental changes over monsoon Asian region. This paper briefly introduces MAIRS, its background and concept, scientific themes and objectives, data requirements and its information system, intensive observation experiment, and its linkage with ongoing international projects.

  16. Indian monsoon variability in relation to Regional Pressure Index

    Indian Academy of Sciences (India)

    S S Dugam; S B Kakade

    2003-12-01

    In this paper Regional Pressure Index (RPI) over the Indian region (20°N-40°N and 70°E-85°E) has been constructed for 101 years (1899-1999) on a monthly scale. The relationship of these indices was carried out with the Indian Summer Monsoon Rainfall (June-September) (ISMR) over the various homogeneous regions, for all the time scales. From the analysis it has been seen that RPI in the month of May is significantly associated with ISMR over various regions on all the scales. The relationship is statistically significant at 1% level. The study reveals that RPI in the month of May and January will be a new precursor for the long range forecasting of ISMR on the smaller spatial scale. On the decadal and climatological scale, winter and spring time RPI show a significant inverse relationship with the rainfall over the regions Peninsular India (PI) and North West India (NWI), while the association is direct with Central North East India (CNEI) and North East India (NEI). The relationship is significant at 0.1 and 1% level respectively.

  17. Examining Impact of Global warming on the summer monsoon system using regional Climate Model (PRECIS)

    Science.gov (United States)

    Patwardhan, S. K.; Kundeti, K.; Krishna Kumar, K.

    2011-12-01

    Every year, southwest monsoon arrives over Indian region with remarkable regularity. It hits the southern state of Kerala first by the end of May or the early June. More than 70% of the annual precipitation is received during the four monsoon months viz. June to September. This monsoon rainfall is vital for the agriculture as well as for the yearly needs of Indian population. The performance of the monsoon depends on the timely onset over southern tip of India and its progress along the entire country. This northward progression of monsoon to cover the entire Indian landmass, many times, is associated with the formation of synoptic scale system in the Bay of Bengal region and their movement along the monsoon trough region. The analysis of the observed cyclonic disturbances show that their frequency has reduced in recent decades. It is, therefore, necessary to assess the effect of global warming on the monsoon climate of India. A state-of-art regional climate modelling system, known as PRECIS (Providing REgional Climates for Impacts Studies) developed by the Hadley Centre for Climate Prediction and Research, U.K. is applied over the South Asian domain to investigate the impact of global warming on the cyclonic disturbances. The PRECIS simulations at 50 km x 50 km horizontal resolution are made for two time slices, present (1961-1990) and the future (2071-2100), for two socio-economic scenarios A2 and B2. The model skills are evaluated using observed precipitation and surface air temperature. The model has shown reasonably good skill in simulating seasonal monsoon rainfall, whereas cold bias is seen in surface air temperature especially in post-monsoon months. The typical monsoon features like monsoon trough, precipitation maxima over west coast and northeast India are well simulated by the model. The model simulations under the scenarios of increasing greenhouse gas concentrations and sulphate aerosols are analysed to study the likely changes in the quasi

  18. Aerosol and rainfall variability over the Indian monsoon region. Distributions, trends and coupling

    Energy Technology Data Exchange (ETDEWEB)

    Gautam, R. [Maryland Univ., Baltimore County, MD (United States). Goddard Earth Science and Technology Center; NASA Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Hsu, N.C.; Lau, K.M. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Kafatos, M. [Chapman Univ., Orange, CA (United States). Center of Excellence in Earth Observing

    2009-07-01

    Aerosol solar absorption over the Indian monsoon region has a potential role of modulating the monsoon circulation and rainfall distribution as suggested by recent studies based on model simulations. Prior to the onset of the monsoon, northern India is influenced by significant dust transport that constitutes the bulk of the regional aerosol loading over the Gangetic-Himalayan region. In this paper, a multi-sensor characterization of the increasing pre-monsoon aerosol loading over northern India, in terms of their spatial, temporal and vertical distribution is presented. Aerosol transport from the northwestern arid regions into the Indo-Gangetic Plains and over the foothills of the Himalayas is found to be vertically extended to elevated altitudes (up to 5 km) as observed from the space-borne lidar measurements (CALIPSO). In relation with the enhanced pre-monsoon aerosol loading and the associated solar absorption effects on tropospheric temperature anomalies, this paper investigates the monsoon rainfall variability over India in recent past decades from an observational viewpoint. It is found that the early summer monsoon rainfall over India is on the rise since 1950s, as indicated by historical rainfall data, with over 20% increase for the period 1950-2004. This large sustained increase in the early summer rainfall is led by the observed strengthening of the pre-monsoon tropospheric land-sea thermal gradient over the Indian monsoon region as indicated by microwave satellite measurements (MSU) of tropospheric temperatures from 1979-2007. Combined analysis of changes in tropospheric temperatures and summer monsoon rainfall in the past three decades, suggest a future possibility of an emerging rainfall pattern of a wetter monsoon over South Asia in early summer followed by a drier period. (orig.)

  19. Relationships between Indian summer monsoon rainfall and ice cover over selected oceanic regions

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.

    The variations in oceanic ice cover at selected polar regions during 1973 to 1987 have been analysed in relation to the seasonal Indian summer monsoon rainfall. The ice cover over the Arctic regions in June has negative relationship (correlation...

  20. The online measured black carbon aerosol and source orientations in the Nam Co region, Tibet.

    Science.gov (United States)

    Zhang, Xin; Ming, Jing; Li, Zhongqin; Wang, Feiteng; Zhang, Guoshuai

    2017-09-17

    Equivalent black carbon (eBC) mass concentrations were measured by an aethalometer (AE-31) in the Nam Co, central Tibet from 2010 to 2014. Different from previous filter-sampling studies (Ming et al., J Environ Sci 22(11):1748-1756, 2010; Zhao et al., Environ Sci Pollut Res 20:5827-5838, 2013), the first high-resolution online eBC measurement conducted in central Tibet is reported here, allowing to discuss the diurnal variations as well as seasonal variabilities of eBC. Average daily eBC concentration was 74 ± 50 ng/m(3), reflecting a global background level. Meteorological conditions influenced eBC concentrations largely at seasonal scale, which are higher in February-May but lower in June-January. The highest eBC concentrations (greater than 210 ng/m(3)) were more associated with the W and WSW winds smaller than 6 m/s. The diurnal variations of eBC showed plateaus from 10:00 to 15:00 with seasonal variations, associated with local anthropogenic activities, such as indigenous Tibetan burning animal waste and tourism traffic. The PBLHs showed a co-variance with eBC concentrations, implicating close sources. The aerosol optical depths derived from the MODIS data over the Nam Co Observatory Station (NCOS)-included sub-area (30° N-40° N, 90° E-100° E) showed significant relationship with eBC concentrations. This suggests that nearby or short-distance sources other than long-distance transported pollutants could be important contributors to eBC concentrations at the NCOS, different from the conclusions suggested by previous studies.

  1. On the diurnal cycle of surface energy fluxes in the North American monsoon region using the WRF-Hydro modeling system

    Science.gov (United States)

    Xiang, Tiantian; Vivoni, Enrique R.; Gochis, David J.; Mascaro, Giuseppe

    2017-09-01

    The diurnal cycles of surface energy fluxes are important drivers of atmospheric boundary layer development and convective precipitation, particularly in regions with heterogeneous land surface conditions such as those under the influence of the North American monsoon (NAM). Characterization of diurnal surface fluxes and their controls has not been well constrained due to the paucity of observations in the NAM region. In this study, we evaluate the performance of the uncoupled WRF-Hydro modeling system in its ability to represent soil moisture, turbulent heat fluxes, and surface temperature observations and compare these to operational analyses from other commonly used land surface models (LSMs). After a rigorous model evaluation, we quantify how the diurnal cycles of surface energy fluxes vary during the warm season for the major ecosystems in a regional basin. We find that the diurnal cycle of latent heat flux is more sensitive to ecosystem type than sensible heat flux due to the response of plant transpiration to variations in soil water content. Furthermore, the peak timing of precipitation affects the shape and magnitude of the diurnal cycle of plant transpiration in water-stressed ecosystems, inducing mesoscale heterogeneity in land surface conditions between the major ecosystems within the basin. Comparisons to other LSMs indicate that ecosystem differences in the diurnal cycle of turbulent fluxes are underestimated in these products. While this study shows how land surface heterogeneity affects the simulated diurnal cycle of turbulent fluxes, additional coupled modeling efforts are needed to identify the potential impacts of these spatial differences on convective precipitation.

  2. Impact of East Asian summer monsoon circulation on the regional aerosol distribution in observations and models

    Science.gov (United States)

    Wang, Hongli; Xie, Xiaoning; Yan, Libin; Liu, Xiaodong

    2017-06-01

    The East Asian summer monsoon (EASM) can change the spatio-temporal distribution of aerosols by influencing the aerosol horizontal and vertical transports and the wet deposition of aerosols over East Asia. In this paper, we examined the aerosol optical depth (AOD) during summer together with the intensity of the EASM based on moderate-resolution imaging spectroradiometer products on board the Terra satellite and the modeling results from the NCAR Community Atmospheric Model 5.1 in the mid-latitude monsoonal East Asia (20-45° N, 105-130° E). Our results from both observations and simulations show positive correlations of AOD with the monsoon intensity over the Northeast Asia sub-region (32.5-45° N, 105-130° E), and negative correlations with that over the southeast Asia sub-region (20-32.5° N, 105-130° E). The observed and simulated AODs were much larger over the northern sub-region and much smaller over the southern sub-region in the strongest monsoon years compared with those in the weakest monsoon years. The model results suggest that the mechanism responsible for the north-south difference in the aerosol distribution was mainly caused by lower-tropospheric meridional wind anomalies related to EASM. Compared with the weakest monsoon years, the strongest monsoon years experienced southerly wind anomalies, which enabled more aerosols to be transported northward and resulted in a convergence of aerosols over the northern sub-region. In addition, the wet deposition of aerosols reduced (enhanced) the aerosol concentrations in the northern (southern) sub-region during the strongest monsoon years compared with the weakest monsoon years, which partly offset the impact of the lower southerly winds on the aerosol distribution over East Asia.

  3. Catastrophic drought in East Asian monsoon region during Heinrich event 1

    Science.gov (United States)

    Zhou, Xin; Sun, Liguang; Chu, Yangxi; Xia, Zehui; Zhou, Xinying; Li, Xiangzhong; Chu, Zhuding; Liu, Xiangjun; Shao, Da; Wang, Yuhong

    2016-06-01

    Heinrich event 1 (H1) is an important millennial climate event during the last deglaciation. The substantial decreasing of monsoon strength in the East Asian monsoon region during the H1, as shown by stalagmite δ18O records, has been attributed to the southward shift of the intertropical convergence zone (ITCZ), which is caused by the slowdown/collapse of the Atlantic meridional overturning circulation (AMOC). However, records from different Asian monsoon regions show various trends in precipitation changes during the H1, and these trends cannot be solely interpreted by the southward shift of the ITCZ. In the present study, we reconstructed time-series of East Asian monsoon precipitation between 25,000 and 10,000 a BP from floodplain sediments in the Huai River Basin. A white sediment layer, distinct from other layers in the profile, contains significantly low TOC, tree pollen and fern spore contents, and more positive δ13Corg, and it is deposited during the H1 event. The determined TOC, pollen and δ13Corg time-series, together with previously reported stalagmite δ18O, indicate a catastrophic (severe) drought in Jianghuai Region, one of the East Asian monsoon regions, during the H1. The La Niña condition in tropical Pacific likely also contributes to the catastrophic drought in Jianghuai Region and the precipitation variations in the Asian monsoon region during the H1.

  4. Contribution of Monthly and Regional Rainfall to the Strength of Indian Summer Monsoon

    Science.gov (United States)

    Zheng, Y.; Ali, M.; Bourassa, M. A.

    2015-12-01

    Indian Summer Monsoon Rainfall (ISMR: June-September) has both temporal and spatial variability causing floods/droughts in different seasons/locations leading to a strong or weak monsoon. Here, we present the contribution of all-India monthly, seasonal and regional rainfall to the ISMR, with special reference to the strong and weak monsoons. For this purpose, rainfall data provided by the India Meteorological Department (IMD: http://www.imd.gov.in/section/nhac/dynamic/Monsoon_frame.htm) for 1901-2013 have been used. The IMD divided the Indian sub-continent into four homogeneous regions of northwest India (NWI), northeast India (NEI), central India (CI), and south peninsula India (SPIN). Rainfall during July-August contributes the most to the total seasonal rainfall, whether it is a strong or weak monsoon. Although the NEI has the maximum area-weighted rainfall, its contribution is the least toward a strong or weak monsoon. The rainfall in the remaining three regions (NWI, CI, and SPIN) controls whether an ISMR is strong or weak. Compared to the monthly rainfall, the regional rainfall dominates the strong or weak rainfall periods.

  5. A Study of the Teleconnections in the Asian-Pacific Monsoon Region

    Institute of Scientific and Technical Information of China (English)

    DING Yihui; LIU Yunyun

    2008-01-01

    The interactions among the Asian-Pacific monsoon subsystems have significant impacts on the climatic regimes in the monsoon region and even the whole world. Based on the domestic and foreign related research, an analysis is made of four different teleconnection modes found in the Asian-Pacific monsoon region, which reveal clearly the interactions among the Indian summer monsoon (ISM), the East Asian summer monsoon (EASM), and the western North Pacific summer monsoon (WNPSM). The results show that: (1) In the period of the Asian monsoon onset, the date of ISM onset is two weeks earlier than the beginning of the Meiyu over the Yangtze River Basin, and a teleconnection mode is set up from the southwestern India via the Bay of Bengal (BOB) to the Yangtze River Basin and southern Japan, I.e., the "southern" teleconnection of the Asian summer monsoon. (2) In the Asian monsoon culmination period, the precipitation of the Yangtze River Basin is influenced significantly by the WNPSM through their teleconnection relationship, and is negatively related to the WNPSM rainfall, that is, when the WNPSM is weaker than normal, the precipitation of the Yangtze River Basin is too.re than normal. (3) In contrast to the rainfall over the Yangtze River Basin, the precipitation of northern China (from the 4th pentad of July to the 3rd pentad of August) is positively related to the WNPSM. When the WNPSM is stronger than normal, the position of the western Pacific subtropical high (WPSH) becomes farther northeast than normal, the anomalous northeastward water vapor transport along the southwestern flank of WPSH is converged over northern China, providing adequate moisture for more rainfalls than normal there. (4) The summer rainfall in northern China has also a positive correlation with the ISM. During the peak period of ISM, a teleconnection pattern is formed from Northwest India via the Tibetan Plateau to northern China, I.e., the "northern" teleconnection of the Asian summer monsoon

  6. Regional climate model experiments to investigate the Asian monsoon in the Late Miocene

    Directory of Open Access Journals (Sweden)

    H. Tang

    2011-08-01

    Full Text Available The Late Miocene (11.6–5.3 Ma is a crucial period in the history of the Asian monsoon. Significant changes in the Asian climate regime have been documented for this period, which saw the formation of the modern Asian monsoon system. However, the spatiotemporal structure of these changes is still ambiguous, and the associated mechanisms are debated. Here, we present a simulation of the average state of the Asian monsoon climate for the Tortonian (11–7 Ma using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1° × 1° and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our regional Tortonian run shows a stronger-than-present East Asian winter monsoon wind as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered present-day northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. Precipitation decreases in northern China and northern India, but increases in southern China, the western coast and the southern tip of India. This can be attributed to the changes in both the regional topography (e.g. the lower northern Tibetan Plateau and the global climate conditions (e.g. the higher sea surface temperature. The spread of dry summer conditions over northern China and northern Pakistan in our Tortonian run further implies that the monsoonal climate may not have been fully established in these regions in the Tortonian. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better

  7. Investigation of dominant modes of monsoon ISO in the northwest and eastern Himalayan region

    Science.gov (United States)

    Mukherjee, Sandipan; Ballav, Srabanti; Soni, Sandeep; Kumar, Kireet; Kumar De, Utpal

    2016-08-01

    This study investigates the altitudinal variation of dominant modes of summer monsoon intra-seasonal oscillation (ISO) over the Northwest (NWH) and Eastern Himalayan (EH) region using (i) spatially scattered 133 number of station rainfall observations and (ii) latitudinal transect-wise (LT) rainfall variation, obtained from an observed interpolated gridded rainfall data for the period 1995-2004. The altitudinal variation of dominant modes of monsoon ISO were investigated by exploring the strong and weak phases of the principal components of 10-90 days bandpass rainfall data of June to September with respect to location specific station height. Investigation of frequency of days for light and moderate rainfall along with the occurrence of total seasonal rainy days has revealed existence of a rainfall maximum around 2100 m height for the NWH region. Similarly, the total seasonal rainy days of EH region was found to have maxima between 1100 and 1400 m height. Analyses of the spatially scattered station rainfall observation for the NWH region showed that the strong periods of ISO modes exist around 747.9 (±131.7) m and 2227.2 (±100.2) m heights. Over the EH region, the dominant modes of the monsoon ISO were found to be centred around 1200 m. Significant alterations of strong and weak phases of monsoon ISO as a response to altitudinal variation in the mountain surface were observed when latitudinal transect-wise variation of monsoon ISO modes were investigated.

  8. Deep learning for predicting the monsoon over the homogeneous regions of India

    Science.gov (United States)

    Saha, Moumita; Mitra, Pabitra; Nanjundiah, Ravi S.

    2017-06-01

    Indian monsoon varies in its nature over the geographical regions. Predicting the rainfall not just at the national level, but at the regional level is an important task. In this article, we used a deep neural network, namely, the stacked autoencoder to automatically identify climatic factors that are capable of predicting the rainfall over the homogeneous regions of India. An ensemble regression tree model is used for monsoon prediction using the identified climatic predictors. The proposed model provides forecast of the monsoon at a long lead time which supports the government to implement appropriate policies for the economic growth of the country. The monsoon of the central, north-east, north-west, and south-peninsular India regions are predicted with errors of 4.1%, 5.1%, 5.5%, and 6.4%, respectively. The identified predictors show high skill in predicting the regional monsoon having high variability. The proposed model is observed to be competitive with the state-of-the-art prediction models.

  9. Regional climate model experiments to investigate the Asian monsoon in the Late Miocene

    Directory of Open Access Journals (Sweden)

    H. Tang

    2011-03-01

    Full Text Available The Late Miocene (11.6–5.3 Ma is a crucial period for the Asian monsoon evolution. However, the spatiotemporal changes of the Asian monsoon system in the Late Miocene are still ambiguous, and the mechanisms responsible for these changes are debated. Here, we present a simulation of the Asian monsoon climate (0 to 60° N and 50 to 140° E in the Tortonian (11–7 Ma using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1° × 1° and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our results show a stronger-than-present E-Asian winter monsoon wind in the Tortonian, as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. The precipitation decreases in N-China and N-India, but increases in S-China, the western coast and the southern tip of India. This can be attributed to the combined effect of both the regional topographical changes and the other forcings related to our global model. The spread of the dry summer conditions over N-China and NW-India further implies that the monsoonal climate may not be fully established over these regions in the Tortonain. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better characterizes the convective activity and its response to topographical changes. It therefore provides a useful and compared to global models complementary tool to improve our understanding of the Asian

  10. Applications of monsoon research: Opportunities to inform decisionmaking and reduce regional vulnerability

    Science.gov (United States)

    Ray, A. J.; Garfin, G. M.; Wilder, M.; Lenart, M.; Vásquez-León, M.; Comrie, A. C.

    2007-05-01

    This presentation will describe ongoing efforts to understand interactions between the North American Monsoon and society, in order to develop applications for monsoon research in a highly complex, multicultural and binational region. The North American Monsoon is an annual precipitation regime that begins in early June in Mexico and progresses northward to the southwestern United States. The region includes stakeholders in large urban complexes, productive agricultural areas, and sparsely populated arid and semi-arid ecosystems. The political, cultural, and socioeconomic divisions between the U.S. and Mexico create a broad range of sensitivities to climate variability as well as capacities to use forecasts and other information to cope with climate. We will highlight methodologies to link climate science with society and analyze opportunities for monsoon science to benefit society in four sectors: natural hazards management, agriculture, public health, and water management. We present a synthesized list of stakeholder needs and a calendar of decisions to help scientists link user needs to potential forecasts and products. To ensure usability of forecasts and other research products, we recommend iterative scientist-stakeholder interactions, through integrated assessments. These knowledge- exchange interactions can improve the capacity for stakeholders to use forecasts thoughtfully and inform the development of research, and for the research community to obtain feedback on climate-related products and receive insights to guide research direction. We expect that integrated assessments can capitalize on the opportunities for monsoon science to inform decisionmaking, in the best instances, reduce regional climate vulnerabilities and enhance regional sustainability

  11. Transport pathways of peroxyacetyl nitrate in the upper troposphere and lower stratosphere from different monsoon systems during the summer monsoon season

    Directory of Open Access Journals (Sweden)

    S. Fadnavis

    2014-08-01

    Full Text Available The Asian summer monsoon involves complex transport patterns with large scale redistribution of trace gases in the upper troposphere and lower stratosphere (UTLS. We employ the global chemistry–climate model ECHAM5-HAMMOZ in order to evaluate the transport pathways and the contributions of nitrogen oxide reservoir species PAN, NOx, and HNO3 from various monsoon regions, to the UTLS over Southern Asia and vice versa. The model is evaluated with trace gas retrievals from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-E and aircraft campaigns during the monsoon season (June–September. There are three regions which contribute substantial pollution to the UTLS during the monsoon: the Asian summer monsoon (ASM, the North American Monsoon (NAM and the West African monsoon (WAM. However, penetration due to ASM convection is deeper into the UTLS as compared to NAM and WAM outflow. The circulation in these monsoon regions distributes PAN into the tropical latitude belt in the upper troposphere. Remote transport also occurs in the extratropical upper troposphere where westerly winds drive North American and European pollutants eastward to partly merge with the ASM plume. Strong ASM convection transports these remote and regional pollutants into the lower stratosphere. In the lower stratosphere the injected pollutants are transported westward by easterly winds. The intense convective activity in the monsoon regions is associated with lightning generation and thereby the emission of NOy species. This will affect the distribution of PAN in the UTLS. The estimates of lightning produced PAN, HNO3, NOx and ozone obtained from control and lightning-off simulations shows high percentage changes over the regions of convective transport especially equatorial Africa and America and comparatively less over the ASM. This indicates higher anthropogenic pollution transport from the ASM region into the UTLS.

  12. On the atmospheric dynamical responses to land-use change in East Asian monsoon region

    Science.gov (United States)

    Zhang, Huqiang; Gao, Xuejie

    2009-08-01

    This study aims at (1) exploring dominant atmospheric dynamical processes which are responsible for climate model-simulated land-use impacts on Asian monsoon; and (2) assessing uncertainty in such model simulations due to their skills in simulating detailed monsoon circulations in the region. Firstly, results from a series of the Australian Bureau of Meteorology Research Centre (BMRC) global model simulations of land-use vegetation changes (LUC) in China are analysed. The model showed consistent signals of changes in atmospheric low-level vertical profile and regional circulations responding to LUC. In northern winter, the model-simulated rainfall reduction and surface cooling are associated with an enhanced southward penetration of dry and cold air mass, which impedes warm and humid air reaching the region for generating cold-front rainfall. In its summer, an enhanced cyclonic circulation responding to LUC further blocks the northeast penetration of southwestly summer monsoon flow into the region and results in rainfall decreases and a surface warming. Secondly, we have explored uncertainties in the proposed mechanism operating in the global model. By comparing its results with a set of high-resolution regional model simulations using the same vegetation datasets, it reveals similar changes in winter rainfall but opposite features in summer rainfall responses. In the global model, there is a cyclonic low-level circulation pattern over the South China Sea and adjacent region, an unsatisfactory feature commonly seen in other global climate models. With the reduction in surface roughness following LUC, such a deficiency becomes more prominent which further results in a weakened south/southwestly summer monsoon flow and rainfall reduction. In contrast, in the regional model, its southwestly summer monsoon flow is further enhanced due to the same process as reduced surface roughness. The enhanced monsoon flow further pushes the East Asian monsoon rainfall belt more

  13. Seasonal and Intraseasonal Variability of Mesoscale Convective Systems over the South Asian Monsoon Region

    Energy Technology Data Exchange (ETDEWEB)

    Virts, Katrina S.; Houze, Robert A.

    2016-12-01

    Seasonal and intraseasonal differences in mesoscale convective systems (MCSs) over South Asia are examined using A-Train satellites, a ground-based lightning network, and reanalysis fields. Pre-monsoon (April-May) MCSs occur primarily over Bangladesh and the eastern Bay of Bengal. During the monsoon (June-September), small MCSs occur over the Meghalaya Plateau and northeast Himalayan notch, while large and connected MCSs are most widespread over the Bay of Bengal. Monsoon MCSs produce less lightning and exhibit more extensive stratiform and anvil reflectivity structures in CloudSat observations than do pre-monsoon MCSs. During the monsoon season, Bay of Bengal and Meghalaya Plateau MCSs vary with the 30-60 day northward-propagating intraseasonal oscillation, while northeast Himalayan notch MCSs are associated with weak large-scale anomalies but locally enhanced CAPE. During intraseasonal active periods, a zone of enhanced large and connected MCSs, precipitation, and lightning extends from the northeastern Arabian Sea southeast over India and the Bay of Bengal, flanked by suppressed anomalies. Spatial variability is observed within this enhancement zone: lightning is most enhanced where MCSs are less enhanced, and vice versa. Reanalysis composites indicate that Bay of Bengal MCSs are associated with monsoon depressions, which are frequent during active monsoon periods, while Meghalaya Plateau MCSs are most frequent at the end of break periods, as anomalous southwesterly winds strengthen moist advection toward the terrain. Over both regions, MCSs exhibit more extensive stratiform and anvil regions and less lightning when the large-scale environment is moister, and vice versa.

  14. Precipitation top heights of orographic heavy rainfall in the Asian monsoon regions

    Science.gov (United States)

    Shige, Shoichi; Kummerow, Christian

    2016-04-01

    In contrast to the dominant view that heavy rainfall results from deep clouds, the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) frequently observed heavy, but shallow orographic rainfall over coastal mountain ranges of the Asian monsoon regions. The low-level horizontal winds, leading to topographic forced upward motion on the windward slopes, are dynamically important for its occurrence. This paper focuses on the thermodynamic character of the atmospheric environment associated with shallow orographic heavy rainfall. The precipitation-top heights of orographic heavy rainfall generally decrease with low- and mid-level relative humidity especially for coastal mesoscale mountain ranges during summer monsoon. This differs from what has been observed for convection over the tropical ocean in previous studies, but is consistent with abundant shallow convection during the moist summer monsoon season. In contrast, the precipitation-top heights over Annam Cordillera during the transition phase from boreal summer to winter monsoon seasons, facing the prevailing northeasterly, increase with low-level and mid-level relative humidity, demonstrating that convection depth is not a simple function of humidity. The precipitation-top heights of orographic heavy rainfall decrease with the low-level stability for all regions considered in this study as well as Annam Cordillera during the transition phase from boreal summer to winter monsoon seasons. Therefore, low-level static stability, which inhibits cloud growth and promotes cloud detrainment, is inferred to be an equally important parameter in determining the precipitation-top heights.

  15. Seasonal Transition Features of Large-Scale Moisture Transport in the Asian-Australian Monsoon Region

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Using NCEP/NCAR reanalysis data for the period of 1957-2001, the climatological seasonal transition features of large-scale vertically integrated moisture transport (VIMT) in the Asian-Australian monsoon region are investigated in this paper. The basic features of the seasonal transition of VIMT from winter to summer are the establishment of the summertime "great moisture river" pattern (named the GMR pattern)and its eastward expansion, associated with a series of climatological events which occurred in some "key periods", which include the occurrence of the notable southerly VIMT over the Indochina Peninsula in mid March, the activity of the low VIMT vortex around Sri Lanka in late April, and the onset of the South China Sea summer monsoon in mid May, among others. However, during the transition from summer to winter, the characteristics are mainly exhibited by the establishment of the easterly VIMT belt located in the tropical area, accompanied by some events occurring in "key periods". Further analyses disclose a great difference between the Indian and East Asian monsoon regions when viewed from the meridional migration of the westerly VIMT during the seasonal change process, according to which the Asian monsoon region can be easily divided into two parts along the western side of the Indochina Peninsula and it may also denote different formation mechanisms between the two regions.

  16. Transport pathways of peroxyacetyl nitrate in the upper troposphere and lower stratosphere from different monsoon systems during the summer monsoon season

    Directory of Open Access Journals (Sweden)

    S. Fadnavis

    2015-06-01

    Full Text Available The Asian summer monsoon involves complex transport patterns with large scale redistribution of trace gases in the upper troposphere and lower stratosphere (UTLS. We employ the global chemistry-climate model ECHAM5-HAMMOZ in order to evaluate the transport pathways and the contributions of nitrogen oxide species PAN, NOx, and HNO3 from various monsoon regions, to the UTLS over Southern Asia and vice versa. Simulated long term seasonal mean mixing ratios are compared with trace gas retrievals from the Michelson Interferometer for Passive Atmospheric Sounding aboard ENVISAT(MIPAS-E and aircraft campaigns during the monsoon season (June–September in order to evaluate the model's ability to reproduce these transport patterns. The model simulations show that there are three regions which contribute substantial pollution to the South Asian UTLS: the Asian summer monsoon (ASM, the North American Monsoon (NAM and the West African monsoon (WAM. However, penetration due to ASM convection reaches deeper into the UTLS as compared to NAM and WAM outflow. The circulation in all three monsoon regions distributes PAN into the tropical latitude belt in the upper troposphere. Remote transport also occurs in the extratropical upper troposphere where westerly winds drive North American and European pollutants eastward where they can become part of the ASM convection and be lifted into the lower stratosphere. In the lower stratosphere the injected pollutants are transported westward by easterly winds. The intense convective activity in the monsoon regions is associated with lightning and thereby the formation of additional NOx. This also affects the distribution of PAN in the UTLS. According to sensitivity simulations with and without lightning, increase in concentrations of PAN (~ 40%, HNO3 (75%, NOx (70% and ozone (30% over the regions of convective transport, especially over equatorial Africa and America and comparatively less over the ASM. This indicates that

  17. The ICTP Regional System Model (RESM) to simulate the monsoon in the South Asia CORDEX domain

    Science.gov (United States)

    Di Sante, Fabio; Coppola, Erika; Farneti, Riccardo; Giorgi, Filippo

    2016-04-01

    South Asian climate is characterized mainly by the wet and dry dipole that divides the annual cycle in two seasons: the monsoon season and the dry season. The life and the economy of those regions is very much influenced by the climate variability and the monsoon variability therefore is crucial to understand the physical mechanism associated with them. The spatial and temporal representation of the monsoons over the South Asian region is one of the main challenge of global and regional climate models principally because they fail to represent the SST (sea surface temperature) induced rainfall when forced with observed SST resulting in a poor representation of the monsoon cycle (Fu et al. 2002). The coupling with the ocean is essential to be able to simulate the correct air-sea interaction; the results are in general much improved and the monsoon patterns and the time representation (like the onset for example) are closer to the observations (Fu et al. 2002; Fu et al. 2007; Ratnam et Al. 2008; Seo et Al. 2009). Here we present a Regional Earth System Model (RESM) composed by a regional climate model RegCM4 (Giorgi et al, 2012) coupled with the regional oceanic model MITgcm (Marshall et al, 1997) and two hydrological model: ChyM (Cetemps Hydrological Model, Coppola et al, 2007) and HD model (Max-Planck's HD model; Hagemann and Dümenil, 1998). We simulate the Southern Asian Climate taking into account the whole hydrological cycle. Wind stress, water fluxes and heat fluxes are exchanged from the atmosphere to the ocean, SST are exchanged from ocean to the atmosphere and in order to conserve mass, the river discharge is calculated from the Hydrological model and sent to the ocean. The main goal of this work is to evaluate the impacts of local air-sea interaction in the simulation of the interannual variability, over the Indian CORDEX (Giorgi et al, 2009) domain through regionally ocean-atmosphere-river coupled and uncoupled simulations, with a focus on monsoon season

  18. Effects of Arctic geoengineering on precipitation in the tropical monsoon regions

    Science.gov (United States)

    Nalam, Aditya; Bala, Govindasamy; Modak, Angshuman

    2017-07-01

    Arctic geoengineering wherein sunlight absorption is reduced only in the Arctic has been suggested as a remedial measure to counteract the on-going rapid climate change in the Arctic. Several modeling studies have shown that Arctic geoengineering can minimize Arctic warming but will shift the Inter-tropical Convergence Zone (ITCZ) southward, unless offset by comparable geoengineering in the Southern Hemisphere. In this study, we investigate and quantify the implications of this ITCZ shift due to Arctic geoengineering for the global monsoon regions using the Community Atmosphere Model version 4 coupled to a slab ocean model. A doubling of CO2 from pre-industrial levels leads to a warming of 6 K in the Arctic region and precipitation in the monsoon regions increases by up to 15%. In our Arctic geoengineering simulation which illustrates a plausible latitudinal distribution of the reduction in sunlight, an addition of sulfate aerosols (11 Mt) in the Arctic stratosphere nearly offsets the Arctic warming due to CO2 doubling but this shifts the ITCZ southward by 1.5° relative to the pre-industrial climate. The combined effect from this shift and the residual CO2-induced climate change in the tropics is a decrease/increase in annual mean precipitation in the Northern Hemisphere/Southern Hemisphere monsoon regions by up to -12/+17%. Polar geoengineering where sulfate aerosols are prescribed in both the Arctic (10 Mt) and Antarctic (8 Mt) nearly offsets the ITCZ shift due to Arctic geoengineering, but there is still a residual precipitation increase (up to 7%) in most monsoon regions associated with the residual CO2 induced warming in the tropics. The ITCZ shift due to our Global geoengineering simulation, where aerosols (20 Mt) are prescribed uniformly around the globe, is much smaller and the precipitation changes in most monsoon regions are within ±2% as the residual CO2-induced warming in the tropics is also much less than in Arctic and Polar geoengineering. Further

  19. Fingerprinting the Impacts of Aerosols on Long-Term Trends of the Indian Summer Monsoon Regional Rainfall

    Science.gov (United States)

    Laul, K. M.; Kim, K. M.

    2010-01-01

    In this paper, we present corroborative observational evidences from satellites, in-situ observations, and re-analysis data showing possible impacts of absorbing aerosols (black carbon and dust) on subseasonal and regional summer monsoon rainfall over India. We find that increased absorbing aerosols in the Indo-Gangetic Plain in recent decades may have lead to long-term warming of the upper troposphere over northern India and the Tibetan Plateau, enhanced rainfall in northern India and the Himalayas foothill regions in the early part (may-June) of the monsoon season, followed by diminished rainfall over central and southern India in the latter part (July-August) of the monsoon season. These signals which are consistent with current theories of atmospheric heating and solar dimming by aerosol and induced cloudiness in modulating the Indian monsoon, would have been masked by conventional method of using al-India rainfall averaged over the entire monsoon season.

  20. Zonal propagation of kinetic energy and convection in the South China Sea and Indian monsoon regions in boreal summer

    Institute of Scientific and Technical Information of China (English)

    CHEN Longxun; GAO Hui; HE Jinhai; TAO Shiyan; JIN Zuhui

    2004-01-01

    Zonal propagation of kinetic energy (KE) and convection in the South China Sea (SCS) and Indian summer monsoon areas are examined in present study. Results suggest that the SCS and Indian summer monsoon prevailed regions (5-15°N) are dominated by the southwesterly wind, however, the disturbances of KE at 850 hPa and convection are observed mainly coming from the western Pacific Ocean (140-150°E), after passing through the SCS, and westward propagated into the Bay of Bengal (90-100°E). In the Indian summer monsoon domain, where the disturbances of KE are found mainly coming from the Arabian Sea (AS) and eastward propagated into the Bay of Bengal. Therefore, the SCS and the Indian summer monsoon are quite different in zonal propagation of KE and convection. The SCS summer monsoon is mainly affected by the KE and convection coming from the tropical western Pacific. The Indian summer monsoon, however, can be partly influenced by the AS and the SCS summer monsoon. The analysis also suggests that the interaction region between the SCS and the Indian summer monsoon is around 90-95°E, rather than 105°E as proposed by earlier studies.

  1. Impact of high resolution land surface initialization in Indian summer monsoon simulation using a regional climate model

    Science.gov (United States)

    Unnikrishnan, C. K.; Rajeevan, M.; Rao, S. Vijaya Bhaskara

    2016-06-01

    The direct impact of high resolution land surface initialization on the forecast bias in a regional climate model in recent years over Indian summer monsoon region is investigated. Two sets of regional climate model simulations are performed, one with a coarse resolution land surface initial conditions and second one used a high resolution land surface data for initial condition. The results show that all monsoon years respond differently to the high resolution land surface initialization. The drought monsoon year 2009 and extended break periods were more sensitive to the high resolution land surface initialization. These results suggest that the drought monsoon year predictions can be improved with high resolution land surface initialization. Result also shows that there are differences in the response to the land surface initialization within the monsoon season. Case studies of heat wave and a monsoon depression simulation show that, the model biases were also improved with high resolution land surface initialization. These results show the need for a better land surface initialization strategy in high resolution regional models for monsoon forecasting.

  2. NUMERICAL SIMULATION OF INFLUENCE OF INDIAN OCEAN SSTA ON WEATHER AND CLIMATE IN ASIAN MONSOON REGION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Sea surface temperature anomaly (SSTA) exerts great influence on the generation of global weather and climate. Much progress has been made with respect to SSTA in the Pacific Ocean region in contrast to the Indian Ocean. The IAP9L model, which is developed at the Institute of Atmospheric Physics of the Chinese Academy of Science, is used to simulate the influence of the Indian Ocean SSTA on the general circulation and weather/climate anomalies in the monsoon region of Asia. It is found that the warm (cool) SSTA in the equatorial low latitudes of the Indian Ocean triggers winter (summer) teleconnection patterns in middle and higher latitudes of the Northern Hemisphere that are similar to PNA or EAP. They play a very important role in the anomaly of circulation or weather and climate in the middle and lower latitudes of the Asian summer monsoon region. With the warm (cool) SSTA forcing in the Indian Ocean, the Asian summer monsoon sets up at a late (early) date and withdraws at a early (late) date, lasting for a short (long) duration at a weak (strong) intensity. The Indian Ocean SSTA is shown to be an indicator for precipitation variation in China.

  3. Prediction of seasonal summer monsoon rainfall over homogenous regions of India using dynamical prediction system

    Science.gov (United States)

    Ramu, Dandi A.; Rao, Suryachadra A.; Pillai, Prasanth A.; Pradhan, M.; George, G.; Rao, D. Nagarguna; Mahapatra, S.; Pai, D. S.; Rajeevan, M.

    2017-03-01

    Seasonal prediction of Indian summer monsoon rainfall is a challenging task for the modeling community and predicting seasonal mean rainfall at smaller regional scale is much more difficult than predicting all India averaged seasonal mean rainfall. The regional scale prediction of summer monsoon mean rainfall at longer lead time (e.g., predicting 3-4 months in advance) can play a vital role in planning of hydrological and agriculture aspects of the society. Previous attempts for predicting seasonal mean rainfall at regional level (over 5 Homogeneous regions) have resulted with limited success (anomaly correlation coefficient is low, ACC ≈ 0.1-0.4, even at a short lead time of one month). The high resolution Climate Forecast System, version 2 (CFSv2) model, with spectral resolution of T382 (∼38 km), can predict the Indian summer monsoon rainfall (ISMR) at lead time of 3-4 months, with a reasonably good prediction skill (ACC ≈ 0.55). In the present study, we have investigated whether the seasonal mean rainfall over different homogenous regions is predictable using the same model, at 3-4 months lead time? Out of five homogeneous regions of India three regions have shown moderate prediction skill, even at 3 months lead time. Compared to lower resolution model, high resolution model has good skill for all the regions except south peninsular India. High resolution model is able to capture the extreme events and also the teleconnections associated with large scale features at four months lead time and hence shows better skill (ACC ≈ 0.45) in predicting the seasonal mean rainfall over homogeneous regions.

  4. Impact of geographic variations of the convective and dehydration center on stratospheric water vapor over the Asian monsoon region

    Science.gov (United States)

    Zhang, Kai; Fu, Rong; Wang, Tao; Liu, Yimin

    2016-06-01

    The Asian monsoon region is the most prominent moisture center of water vapor in the lower stratosphere (LS) during boreal summer. Previous studies have suggested that the transport of water vapor to the Asian monsoon LS is controlled by dehydration temperatures and convection mainly over the Bay of Bengal and Southeast Asia. However, there is a clear geographic variation of convection associated with the seasonal and intra-seasonal variations of the Asian monsoon circulation, and the relative influence of such a geographic variation of convection vs. the variation of local dehydration temperatures on water vapor transport is still not clear. Using satellite observations from the Aura Microwave Limb Sounder (MLS) and a domain-filling forward trajectory model, we show that almost half of the seasonal water vapor increase in the Asian monsoon LS are attributable to geographic variations of convection and resultant variations of the dehydration center, of which the influence is comparable to the influence of the local dehydration temperature increase. In particular, dehydration temperatures are coldest over the southeast and warmest over the northwest Asian monsoon region. Although the convective center is located over Southeast Asia, an anomalous increase of convection over the northwest Asia monsoon region increases local diabatic heating in the tropopause layer and air masses entering the LS are dehydrated at relatively warmer temperatures. Due to warmer dehydration temperatures, anomalously moist air enters the LS and moves eastward along the northern flank of the monsoon anticyclonic flow, leading to wet anomalies in the LS over the Asian monsoon region. Likewise, when convection increases over the Southeast Asia monsoon region, dry anomalies appear in the LS. On a seasonal scale, this feature is associated with the monsoon circulation, convection and diabatic heating marching towards the northwest Asia monsoon region from June to August. The march of convection

  5. Do dynamic regional models add value to the global model projections of Indian monsoon?

    Science.gov (United States)

    Singh, Swati; Ghosh, Subimal; Sahana, A. S.; Vittal, H.; Karmakar, Subhankar

    2017-02-01

    Dynamic Regional Climate Models (RCMs) work at fine resolution for a limited region and hence they are presumed to simulate regional climate better than General Circulation Models (GCMs). Simulations by RCMs are used for impacts assessment, often without any evaluation. There is a growing debate on the added value made by the regional models to the projections of GCMs specifically for the regions like, United States and Europe. Evaluation of RCMs for Indian Summer Monsoon Rainfall (ISMR) has been overlooked in literature, though there are few disjoint studies on Indian monsoon extremes and biases. Here we present a comprehensive study on the evaluations of RCMs for the ISMR with all its important characteristics such as northward and eastward propagation, onset, seasonal rainfall patterns, intra-seasonal oscillations, spatial variability and patterns of extremes. We evaluate nine regional simulations from Coordinated Regional Climate Downscaling Experiment and compare them with their host Coupled Model Intercomparison Project-5 GCM projections. We do not find any consistent improvement in the RCM simulations with respect to their host GCMs for any of the characteristics of Indian monsoon except the spatial variation. We also find that the simulations of the ISMR characteristics by a good number of RCMs, are worse than those of their host GCMs. No consistent added value is observed in the RCM simulations of changes in ISMR characteristics over recent periods, compared to past; though there are few exceptions. These results highlight the need for proper evaluation before utilizing regional models for impacts assessment and subsequent policy making for sustainable climate change adaptation.

  6. Impact of land surface conditions on the predictability of hydrologic processes and mountain-valley circulations in the North American Monsoon region

    Science.gov (United States)

    Xiang, T.; Vivoni, E. R.; Gochis, D. J.; Mascaro, G.

    2015-12-01

    Heterogeneous land surface conditions are essential components of land-atmosphere interactions in regions of complex terrain and have the potential to affect convective precipitation formation. Yet, due to their high complexity, hydrologic processes over mountainous regions are not well understood, and are usually parameterized in simple ways within coupled land-atmosphere modeling frameworks. With the improving model physics and spatial resolution of numerical weather prediction models, there is an urgent need to understand how land surface processes affect local and regional meteorological processes. In the North American Monsoon (NAM) region, the summer rainy season is accompanied by a dramatic greening of mountain ecosystems that adds spatiotemporal variability in vegetation which is anticipated to impact the conditions leading to convection, mountain-valley circulations and mesoscale organization. In this study, we present results from a detailed analysis of a high-resolution (1 km) land surface model, Noah-MP, in a large, mountainous watershed of the NAM region - the Rio Sonora (21,264 km2) in Mexico. In addition to capturing the spatial variations in terrain and soil distributions, recently-developed features in Noah-MP allow the model to read time-varying vegetation parameters derived from remotely-sensed vegetation indices; however, this new implementation has not been fully evaluated. Therefore, we assess the simulated spatiotemporal fields of soil moisture, surface temperature and surface energy fluxes through comparisons to remote sensing products and results from coarser land surface models obtained from the North American Land Data Assimilation System. We focus attention on the impact of vegetation changes along different elevation bands on the diurnal cycle of surface energy fluxes to provide a baseline for future analyses of mountain-valley circulations using a coupled land-atmosphere modeling system. Our study also compares limited streamflow

  7. Spatio-temporal Distribution of Latent Heating in the Southeast Asian Monsoon Region

    Science.gov (United States)

    Zuluaga, M. D.; Hoyos, C. D.; Webster, P. J.

    2007-12-01

    The Latent Heat (LH), released as a result of deep convection, plays an important role in the vertical distribution of the diabatic energy budget from the surface to the atmosphere: the motor which drives the global atmospheric circulation, including the Southeast Asian Monsoon. In particular, knowing the spatio-temporal structure of the LH during the wet monsoon season could be a key factor to understand the interaction between seasonal features of the monsoon with the summer manifestation of the intra-seasonal oscillation in the Indian Ocean basin, and hence the distribution of the precipitation. Several studies have investigated how the structure of heating in the tropics has a direct influence in the dynamical response of the atmosphere to the large-scale dynamical forcing associated with tropical precipitating systems. However, these studies assume a uniform geographically distribution of the vertical diabatic heating profiles across the Tropics. The major objective of this study is to produce and to examine three-dimensional latent heating structures over the Indian Monsoon region for the three summer seasons of 1998-2000 period using TRMM-2A12 (GPROF algorithm) and TRMM-CSH (CSH algorithm) data. A specific goal in this work is to explore the differences in the distribution of the latent heating throughout the intraseasonal cycle. This intra- seasonal cycle not only generates wet and dry spells over the South-East Asian continent but also determines the spatial distribution of the climatological JJAS rainfall in the Indian Monsoon Region. Results show spatial distribution differences between the LH profiles during the suppressed and active phases of the oscillation as well as differences in the vertical. During an active phase of the oscillation over the Indian Ocean, the released latent heat is concentrated predominantly near the equator while during the suppressed phased the heating is concentrated in the Bay of Bengal and the continental South East Asia

  8. Drought variability at the northern fringe of the Asian summer monsoon region over the past millennia

    Science.gov (United States)

    Yang, Bao; Kang, Shuyuan; Ljungqvist, Fredrik Charpentier; He, Minhui; Zhao, Yan; Qin, Chun

    2014-08-01

    The northern fringe of the Asian summer monsoon region (NASM) in China refers to the most northwestern extent of the Asian summer monsoon. Understanding the characteristics and underlying mechanisms of drought variability at long and short time-scales in the NASM region is of great importance, because present and future water shortages are of great concern. Here, we used newly developed and existing tree-ring, historical documentary and instrumental data available for the region to identify spatial and temporal patterns, and possible mechanisms of drought variability, over the past two millennia. We found that drought variations were roughly consistent in the western (the Qilian Mountains and Hexi Corridor) and eastern (the Great Bend of the Yellow River, referred to as GBYR) parts of the NASM on decadal to centennial timescales. We also identified the spatial extent of typical multi-decadal GBYR drought events based on historical dryness/wetness data and the Monsoon Asia Drought Atlas. It was found that the two periods of drought, in AD 1625-1644 and 1975-1999, exhibited similar patterns: specifically, a wet west and a dry east in the NASM. Spatial characteristics of wetness and dryness were also broadly similar over these two periods, such that when drought occurred in the Karakoram Mountains, western Tianshan Mountains, the Pamirs, Mongolia, most of East Asia, the eastern Himalayas and Southeast Asia, a wet climate dominated in most parts of the Indian subcontinent. We suggest that the warm temperature anomalies in the tropical Pacific might have been mainly responsible for the recent 1975-1999 drought. Possible causes of the drought of 1625-1644 were the combined effects of the weakened Asian summer monsoon and an associated southward shift of the Pacific Intertropical Convergence Zone. These changes occurred due to a combination of Tibetan Plateau cooling together with more general Northern Hemisphere cooling, rather than being solely due to changes in the sea

  9. The influence of land cover change in the Asian monsoon region on present-day and mid-Holocene climate

    Directory of Open Access Journals (Sweden)

    A. Dallmeyer

    2011-02-01

    Full Text Available Using the general circulation model ECHAM5/JSBACH, we investigate the biogeophysical effect of large-scale afforestation and deforestation in the Asian monsoon domain on present-day and mid-Holocene climate. We demonstrate that the applied land cover change does not only modify the local climate but also change the climate in North Africa and the Middle East via teleconnections. Deforestation in the Asian monsoon domain enhances the rainfall in North Africa. In parts of the Sahara summer precipitation is more than doubled. In contrast, afforestation strongly decreases summer rainfall in the Middle East and even leads to the cessation of the rainfall-activity in some parts of this region.

    Regarding the local climate, deforestation results in a reduction of precipitation and a cooler climate as grass mostly has a higher albedo than forests. However, in the core region of the Asian monsoon the decrease of evaporative cooling in the monsoon season overcompensates this signal and results in a net warming. Afforestation has mainly the opposite effect, although the pattern of change is less clear. It leads to more precipitation in most parts of the Asian monsoon domain and a warmer climate except for the southern regions where a stronger evaporation decreases near-surface temperatures in the monsoon season.

    When prescribing mid-Holocene insolation, the pattern of local precipitation change differs. Afforestation particularly increases monsoon rainfall in the region along the Yellow River which was the settlement area of major prehistoric cultures. In this region, the effect of land cover change on precipitation is half as large as the orbitally-induced precipitation change. Thus, our model results reveal that mid- to late-Holocene land cover change could strongly have contributed to the decreasing Asian monsoon precipitation during the Holocene known from reconstructions.

  10. The influence of land cover change in the Asian monsoon region on present-day and mid-Holocene climate

    Science.gov (United States)

    Dallmeyer, A.; Claussen, M.

    2011-06-01

    Using the general circulation model ECHAM5/JSBACH, we investigate the biogeophysical effect of large-scale afforestation and deforestation in the Asian monsoon domain on present-day and mid-Holocene climate. We demonstrate that the applied land cover change does not only modify the local climate but also change the climate in North Africa and the Middle East via teleconnections. Deforestation in the Asian monsoon domain enhances the rainfall in North Africa. In parts of the Sahara summer precipitation is more than doubled. In contrast, afforestation strongly decreases summer rainfall in the Middle East and even leads to the cessation of the rainfall-activity in some parts of this region. Regarding the local climate, deforestation results in a reduction of precipitation and a cooler climate as grass mostly has a higher albedo than forests. However, in the core region of the Asian monsoon the decrease in evaporative cooling in the monsoon season overcompensates this signal and results in a net warming. Afforestation has mainly the opposite effect, although the pattern of change is less clear. It leads to more precipitation in most parts of the Asian monsoon domain and a warmer climate except for the southern regions where a stronger evaporation decreases near-surface temperatures in the monsoon season. When prescribing mid-Holocene insolation, the pattern of local precipitation change differs. Afforestation particularly increases monsoon rainfall in the region along the Yellow River which was the settlement area of major prehistoric cultures. In this region, the effect of land cover change on precipitation is half as large as the orbitally-induced precipitation change. Thus, our model results reveal that mid- to late-Holocene land cover change could strongly have contributed to the decreasing Asian monsoon precipitation during the Holocene known from reconstructions.

  11. Impact of high resolution land surface initialization in Indian summer monsoon simulation using a regional climate model

    Indian Academy of Sciences (India)

    C K Unnikrishnan; M Rajeevan; S Vijaya Bhaskara Rao

    2016-06-01

    The direct impact of high resolution land surface initialization on the forecast bias in a regional climatemodel in recent years over Indian summer monsoon region is investigated. Two sets of regional climatemodel simulations are performed, one with a coarse resolution land surface initial conditions and secondone used a high resolution land surface data for initial condition. The results show that all monsoonyears respond differently to the high resolution land surface initialization. The drought monsoon year2009 and extended break periods were more sensitive to the high resolution land surface initialization.These results suggest that the drought monsoon year predictions can be improved with high resolutionland surface initialization. Result also shows that there are differences in the response to the land surfaceinitialization within the monsoon season. Case studies of heat wave and a monsoon depression simulationshow that, the model biases were also improved with high resolution land surface initialization. Theseresults show the need for a better land surface initialization strategy in high resolution regional modelsfor monsoon forecasting.

  12. Cloud Radiative Forcing in Asian Monsoon Region Simulated by IPCC AR4 AMIP Models

    Institute of Scientific and Technical Information of China (English)

    LI Jiandong; LIU Yimin; WU Guoxiong

    2009-01-01

    This study examines cloud radiative forcing (CRF) in the Asian monsoon region (0°-50°N,60°-150°E)simulated by Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) AMIP models.During boreal winter,no model realistically reproduces the larger long-wave cloud radiative forcing (LWCF) over the Tibet Plateau (TP) and only a couple of models reasonably capture the larger short-wave CRF (SWCF) to the east of the TP.During boreal summer,there are larger biases for central location and intensity of simulated CRF in active convective regions.The CRF biases are closely related to the rainfall biases in the models.Quantitative analysis further indicates that the correlation between simulated CRF and observations are not high,and that the biases and diversity in SWCF are larger than that in LWCF.The annual cycle of simulated CRF over East Asia (0°-50°N,100°-145°E) is also examined.Though many models capture the basic annual cycle in tropics,strong LWCF and SWCF to the east of the TP beginning in early spring are underestimated by most models.As a whole,GFDL-CM2.1,MPI-ECHAM5,UKMO-HadGAM1,and MIROC3.2 (medres) perform well for CRF simulation in the Asian monsoon region,and the multi-model ensemble (MME) has improved results over the individual simulations. It is suggested that strengthening the physical parameterizations involved over the TP,and improving cumulus convection processes and model experiment design are crucial to CRF simulation in the Asian monsoon region.

  13. Comparative Hydrology Over Monsoonal Regions Using Seasonal Distributions of Stable Water Isotopes.

    Science.gov (United States)

    Brown, D. P.; Worden, J.; Noone, D. C.

    2007-12-01

    The hydrologic regimes of monsoonal regions contain complex balances of large-scale advective supply of water, surface exchange and atmospheric condensation, which are important for the regional energy balance and climate. Stable water isotopes are powerful tools for studying such processes, as isotopic fractionations occurring during evaporation and condensation give rise to measurable variations in the isotopic composition that reflects the history of moist processes for each observed air parcel. The HDO/H2O data set from the Tropospheric Emission Spectrometer (TES) on NASA's Aura spacecraft offers a unique global view of the isotopic composition of water vapor. The TES data set, and the analysis here, is complimentary to previous work using isotopic ratios in precipitation; however it need not be that the simple relationships found in the precipitation data hold for the atmospheric vapor case because of the variability induced by atmospheric mixing and convection. Over tropical continents, the intensity of water vapor recycling, precipitation rates and circulation patterns are thought to dominate the seasonal isotopic composition of water vapor and rainfall. By examining and contrasting the isotopic budgets of the Amazon, north Australia, and Asian monsoon regions, we gain insight into these hydrological processes, show which processes are regionally robust, and expose those processes that are regionally unique. To establish the importance of local processes on the regional isotopic composition, we first examine the relationship between the measured isotopic composition and meteorological parameters that capture the strength of the local processes. Secondly, we use the history of condensation, evaporation and air mass mixing during transport from five-day origin locations to the local TES observations, and the isotopic ratios of vapor at both locations, to examine isotopic changes that occur upstream. Using this information, as well as a simple isotopic exchange

  14. Type-segregated aerosol effects on regional monsoon activity: A study using ground-based experiments and model simulations

    Science.gov (United States)

    Vijayakumar, K.; Devara, P. C. S.; Sonbawne, S. M.

    2014-12-01

    Classification of observed aerosols into key types [e.g., clean-maritime (CM), desert-dust (DD), urban-industrial/biomass-burning (UI/BB), black carbon (BC), organic carbon (OC) and mixed-type aerosols (MA)] would facilitate to infer aerosol sources, effects, and feedback mechanisms, not only to improve the accuracy of satellite retrievals but also to quantify the assessment of aerosol radiative impacts on climate. In this paper, we report the results of a study conducted in this direction, employing a Cimel Sun-sky radiometer at the Indian Institute of Tropical Meteorology (IITM), Pune, India during 2008 and 2009, which represent two successive contrasting monsoon years. The study provided an observational evidence to show that the local sources are subject to heavy loading of absorbing aerosols (dust and black carbon), with strong seasonality closely linked to the monsoon annual rainfall cycle over Pune, a tropical urban station in India. The results revealed the absence of CM aerosols in the pre-monsoon as well as in the monsoon seasons of 2009 as opposed to 2008. Higher loading of dust aerosols is observed in the pre-monsoon and monsoon seasons of 2009; majority may be coated with fine BC aerosols from local emissions, leading to reduction in regional rainfall. Further, significant decrease in coarse-mode AOD and presence of carbonaceous aerosols, affecting the aerosol-cloud interaction and monsoon-rain processes via microphysics and dynamics, is considered responsible for the reduction in rainfall during 2009. Additionally, we discuss how optical depth, contributed by different types of aerosols, influences the distribution of monsoon rainfall over an urban region using the Monitoring Atmospheric Composition and Climate (MACC) aerosol reanalysis. Furthermore, predictions of the Dust REgional Atmospheric Model (DREAM) simulations combined with HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) cluster model are also discussed in support of the

  15. A regional ocean-atmosphere coupled model developed for CORDEX East Asia: assessment of Asian summer monsoon simulation

    Science.gov (United States)

    Zou, Liwei; Zhou, Tianjun

    2016-12-01

    In this study, a developed regional ocean-atmosphere coupled model FROALS was applied to the CORDEX East Asia domain. The performance of FROALS in the simulation of Asian summer monsoon during 1989-2010 was assessed using the metrics developed by the CLIVAR Asian-Australian Monsoon Panel Diagnostics Task Team. The results indicated that FROALS exhibited good performance in simulating Asian summer monsoon climatology. The simulated JJA mean SST biases were weaker than those of the CMIP5 multi-model ensemble mean (MMEM). The skill of FROALS approached that of CMIP5 MMEM in terms of the annual cycle of Asian summer monsoon. The simulated monsoon duration matched the observed counterpart well (with a spatial pattern correlation coefficient of 0.59). Some biases of CMIP5 MMEM were also found in FROALS, highlighting the importance of local forcing and model physics within the Asian monsoon domain. Corresponding to a strong East Asian summer monsoon, an anomalous anticyclone was found over western North Pacific in both observation and simulation. However, the simulated strength was weaker than the observed due to the responses to incorrect sea surface anomalies over the key regions. The model also accurately captured the spatial pattern of the intraseasonal variability variance and the extreme climate indices of Asian summer monsoons, although with larger amplitude. The results suggest that FROALS could be used as a dynamical downscaling tool nested within the global climate model with coarse resolution to develop high-resolution regional climate change projections over the CORDEX East Asia domain.

  16. Cloud-radiation-precipitation associations over the Asian monsoon region: an observational analysis

    Science.gov (United States)

    Li, Jiandong; Wang, Wei-Chyung; Dong, Xiquan; Mao, Jiangyu

    2017-01-01

    This study uses 2001-2014 satellite observations and reanalyses to investigate the seasonal characteristics of Cloud Radiative Effects (CREs) and their associations with cloud fraction (CF) and precipitation over the Asian monsoon region (AMR) covering Eastern China (EC) and South Asia (SA). The CREs exhibit strong seasonal variations but show distinctly different relationships with CFs and precipitation over the two regions. For EC, the CREs is dominated by shortwave (SW) cooling, with an annual mean value of - 40 W m- 2 for net CRE, and peak in summer while the presence of extensive and opaque low-level clouds contributes to large Top-Of-Atmosphere (TOA) albedo (>0.5) in winter. For SA, a weak net CRE exists throughout the year due to in-phase compensation of SWCRE by longwave (LW) CRE associated with the frequent occurrence of high clouds. For the entire AMR, SWCRE strongly correlates with the dominant types of CFs, although the cloud vertical structure plays important role particularly in summer. The relationships between CREs and precipitation are stronger in SA than in EC, indicating the dominant effect of monsoon circulation in the former region. SWCRE over EC is only partly related to precipitation and shows distinctive regional variations. Further studies need to pay more attention to vertical distributions of cloud micro- and macro-physical properties, and associated precipitation systems over the AMR.

  17. Evaluation of MODIS Vegetation Products in Regions of Complex Terrain and Monsoon Climates

    Science.gov (United States)

    Gebremichael, M.; Barros, A. P.

    2004-12-01

    An evaluation of the Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation products through comparison against independent surface observations is essential to establish quantitative measures of uncertainty and the confidence level of these satellite-based products for use in land-data assimilation models, for land-use change detection and attribution studies, and for process oriented research. Here, we focus specifically on Photosynthesis and Primary Productivity, Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation (FPAR), Land Surface Temperature and Emissivity, and Evapotranspiration data sets. Our objective is to perform extensive quantitative assessment of the accuracy and statistical properties of these products against independent estimates in tropical mountainous regions at two climatologically distinct sites. The first site, the Sonora river basin in northern Mexico, is a semi-arid region characterized by complex topography and highly heterogeneous vegetation cover, which exhibits dramatic and fast response to rainfall forcing at the onset of the North-American Monsoon. The second site, the Marsyandi river basin in central Nepal, is a humid region characterized by strong ecohydrological gradients on steep orography, which remain generally stable subsequent to the onset of the Indian Monsoon. Atmospheric soundings, flux tower measurements, and raingauge observations are available for both sites. We evaluate the MODIS products in two ways: 1) comparison with tower-based observations, and 2) evaluation of hydrological response and diurnal cycles of surface water and energy budgets prior, during and post monsoon onset as simulated by a 3D hydroecological model with assimilation of MODIS data. Statistical analysis of the scaling behavior of the variables, both in space and time, is also performed to address the scale discrepancy between flux tower observations and the resolution of MODIS data.

  18. Intraseasonal Variability of the Indian Summer Monsoon in the Regional Climate Model COSMO-CLM

    Science.gov (United States)

    Befort, Daniel J.; Leckebusch, Gregor C.; Cubasch, Ulrich

    2015-04-01

    The regional climate model COSMO-CLM driven by ERA-Interim reanalysis data with a spatial resolution of 55km is used to simulate observed features of the intraseasonal variability of the Indian summer monsoon (ISM) during the period 1979 until 2011. One of these features is the northward propagation of the monsoon intraseasonal oscillations. We find, that the temporal evolution of this oscillation between model and observation is in good agreement, but the strength is less well simulated. Additionally, the models capability to simulate observed dry and wet events on a weekly time scale is investigated using the standardized precipitation index. In general, the model is capable to simulate these events with a similar magnitude at the same time, but we find a higher ability for dry compared to wet events. We hypothesize this is related to differences in the atmospheric circulation during dry and wet events. Analyses show, that dry events are characterized by a cyclonic vortex over India as well as an anti-cyclonic vortex over Pakistan region in 500hPa, whereas wet events are characterized by an anti-cyclonic vortex over India, only. It is found that COSMO-CLM has a higher ability to simulate the observed anomalous circulation over Pakistan region compared to observed anomalous circulation patterns over India. Overall, this study shows that the current configuration of COSMO-CLM is able to simulate key features of the intraseasonal variability of the Indian summer monsoon. Thus, under consideration of its limitations, COSMO-CLM is suitable to investigate possible changes of the intraseasonal variability of ISM under changed climate conditions.

  19. Seasonal prediction of summer monsoon rainfall over cluster regions of India

    Indian Academy of Sciences (India)

    S B Kakade; Ashwini Kulkarni

    2017-04-01

    Shared nearest neighbour (SNN) cluster algorithm has been applied to seasonal (June–September) rainfall departures over 30 sub-divisions of India to identify the contiguous homogeneous cluster regions over India. Five cluster regions are identified. Rainfall departure series for these cluster regions are prepared by area weighted average rainfall departures over respective sub-divisions in each cluster. The interannual and decadal variability in rainfall departures over five cluster regions is discussed. In order to consider the combined effect of North Atlantic Oscillation (NAO) and Southern Oscillation (SO), an index called effective strength index (ESI) has been defined. It has been observed that the circulation is drastically different in positive and negative phases of ESI-tendency from January to April. Hence, for each phaseof ESI-tendency (positive and negative), separate prediction models have been developed for predicting summer monsoon rainfall over identified clusters. The performance of these models have been tested and found to be encouraging.

  20. Performance evaluation of regional climate model to simulate sub-seasonal variability of Indian Summer Monsoon

    Science.gov (United States)

    Umakanth, U.; Kesarkar, Amit P.

    2017-07-01

    The study aims to evaluate the regional climate model (RegCM) over South Asian (SA) CORDEX domain to represent seasonal and sub-seasonal variability of Indian Summer Monsoon (ISM). The model's ability is evaluated by conducting two sets of experiments using one-tier approach of coupling the RegCM with a simple mixed-layer slab ocean model (SOM) and the two-tier approach of prescribing sea surface temperature (SST) to RegCM. Two model experiments are initialized at 1st January 2000 for a period of 13 year continuous simulation at a spatial resolution of 50 km. It is found that, one-tier approach realistically represents the spatial distribution of precipitation with significant improvement noticed over central India (CI) and head Bay of Bengal (BoB) regions. In addition, it also fairly reproduced the observed mean meridional circulation response to the diabatic heating produced during ISM. Most importantly, in one-tier approach the model could able to represent the observed SST and precipitation (P) relationship with significant improvement in correlation and model response time. An important result is the representation of northwest-southeast tilt of precipitation anomalies during active/break phase of monsoon. Additionally, the lagged response of vertical profiles of specific humidity, omega, vorticity and divergence over CI with respect to peak rainfall anomaly (active phase) are relatively better represented in one-tier approach. In brief, coupling improves the performance of RegCM in simulating the space-time characteristics of monsoon ISO mode.

  1. Winter climate changes over East Asian region under RCP scenarios using East Asian winter monsoon indices

    Science.gov (United States)

    Hong, Ja-Young; Ahn, Joong-Bae; Jhun, Jong-Ghap

    2017-01-01

    The changes in the winter climatology and variability of the East Asian winter monsoon (EAWM) for the late 21st century (2070-2099) under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios are projected in terms of EAWM indices (EAWMIs). Firstly, the capability of the climate models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) in simulating the boreal winter climatology and the interannual variability of the EAWM for the late 20th century (1971-2000) is examined. Nine of twenty-three climate models are selected based on the pattern correlations with observation and a multi-model ensemble is applied to the nine model data. Three of twelve EAWMIs that show the most significant temporal correlations between the observation and CMIP5 surface air temperatures are utilized. The ensemble CMIP5 is capable of reproducing the overall features of the EAWM in spite of some biases in the region. The negative correlations between the EAWMIs and boreal winter temperature are well reproduced and 3-5 years of the major interannual variation observed in this region are also well simulated according to power spectral analyses of the simulated indices. The fields regressed onto the indices that resemble the composite strong winter monsoon pattern are simulated more or less weakly in CMIP5 compared to the observation. However, the regressed fields of sea level pressure, surface air temperature, 500-hPa geopotential height, and 300-hPa zonal wind are well established with pattern correlations above 0.83 between CMIP5 and observation data. The differences between RCPs and Historical indicate strong warming, which increases with latitude, ranging from 1 to 5 °C under RCP4.5 and from 3 to 7 °C under RCP8.5 in the East Asian region. The anomalous southerly winds generally become stronger, implying weaker EAWMs in both scenarios. These features are also identified with fields regressed onto the indices in RCPs. The future projections reveal

  2. Winter climate changes over East Asian region under RCP scenarios using East Asian winter monsoon indices

    Science.gov (United States)

    Hong, Ja-Young; Ahn, Joong-Bae; Jhun, Jong-Ghap

    2016-03-01

    The changes in the winter climatology and variability of the East Asian winter monsoon (EAWM) for the late 21st century (2070-2099) under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios are projected in terms of EAWM indices (EAWMIs). Firstly, the capability of the climate models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) in simulating the boreal winter climatology and the interannual variability of the EAWM for the late 20th century (1971-2000) is examined. Nine of twenty-three climate models are selected based on the pattern correlations with observation and a multi-model ensemble is applied to the nine model data. Three of twelve EAWMIs that show the most significant temporal correlations between the observation and CMIP5 surface air temperatures are utilized. The ensemble CMIP5 is capable of reproducing the overall features of the EAWM in spite of some biases in the region. The negative correlations between the EAWMIs and boreal winter temperature are well reproduced and 3-5 years of the major interannual variation observed in this region are also well simulated according to power spectral analyses of the simulated indices. The fields regressed onto the indices that resemble the composite strong winter monsoon pattern are simulated more or less weakly in CMIP5 compared to the observation. However, the regressed fields of sea level pressure, surface air temperature, 500-hPa geopotential height, and 300-hPa zonal wind are well established with pattern correlations above 0.83 between CMIP5 and observation data. The differences between RCPs and Historical indicate strong warming, which increases with latitude, ranging from 1 to 5 °C under RCP4.5 and from 3 to 7 °C under RCP8.5 in the East Asian region. The anomalous southerly winds generally become stronger, implying weaker EAWMs in both scenarios. These features are also identified with fields regressed onto the indices in RCPs. The future projections reveal

  3. Regional integrated environmental model system and its simulation of East Asia summer monsoon

    Institute of Scientific and Technical Information of China (English)

    XIONG Zhe; FU CongBin; YAN XiaoDong

    2009-01-01

    A continuous 22-year simulation in Asia for the period of 1 January 1979 to 31 December 2000 was conducted using the Regional Integrated Environmental Model System (RIEMS 2.0) with NCEP Reanalysis Ⅱ data as the driving fields.The model processes include surface physics state package (BATS le),a Grell cumulus parameterization,and a modified radiation package (CCM3) with the focus on the ability of the model to simulate the summer monsoon over East Asia.The analysis results show that (1)RIEMS reproduces well the spatial pattern and the seasonal cycle of surface temperature.When regionally averaged,the summer mean temperature biases are within 1-2℃.(2) For precipitation,the model reproduces well the spatial pattern,and temporal evolution of the East Asia summer monsoon rain belt,with steady phases separated by more rapid transitions,is reproduced.The rain belt simulated by RIEMS 2.0 is closer to observation than by RIEMS 1.0.(3) RIEMS 2.0 can reasonably reproduce the large-scale circulation.

  4. The surface geochemical exploration of oil and gas in the Gangbatong-Ya’anxiang and the Dongqiao-Nam Co of the Qinghai-Tibet region

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Due to the complexity of geological background and the adverseness of natural geographical environment in the Qinghai-Tibet Plateau,it is very difficult to carry out petroleum geological study in this region. The Qinghai-Tibet Plateau is the only blank space of petroleum exploration on a large scale. The authors carried out the surface geochemical exploration of oil and gas in the Gangbatong-Ya’anxiang and Dongqiao-Nam Co of the Qinghai-Tibet region. Based on the data of actual detection and experiments in the studied area,the characteristics of concentration and profile distribution of the main geochemical exploration indicators(total adsorbed hydrocarbon,altered carbonate,thermal released mercury,etc.) were discussed. The origin of hydrocarbon was also discussed. Moreover,the oil and gas potential of different sections in the Qiangtang Basin and the Biru Basin were evaluated,which could provide references for the exploration and prediction of oil and gas in this region. The concentrations of total adsorbed hydrocarbons in the Ya’anxiang of Suoxian County-Zadong of Baqing County and the Jiecha-Dangxiong of Anduo County in the Qinghai-Tibet region are high,averaging 312.64 μL·kg-1 and 164.36 μL·kg-1. Their altered carbonate concentrations are relatively low,averaging 0.11% and 0.56%. Their concentrations of thermal released mercury are relatively high,averaging 13.09×10-9 and 1.94×10-9. Geochemical exploration results in fact reflect hydrocarbon information in the underground,which are mainly petroleum associated gas and over-matured cracking gas. The Jiecha-Charenluma and the Xiamaya’ertong-Suoba sections in the Qiangtang Basin are the most favorable ones for oil and gas and the Ekou-Zadong section is relatively favorable one,while the Nam Co and the Zigetangcuo-Dongqiao sections in the Biru Basin are the favorable ones for oil and gas,and the Jiang Co-Nading Co and the Ya’anxiang-Ya’ertong sections are relatively favorable ones.

  5. Impact of the Desert dust on the summer monsoon system over Southwestern North America

    Directory of Open Access Journals (Sweden)

    C. Zhao

    2012-04-01

    Full Text Available The radiative forcing of dust emitted from the Southwest United States (US deserts and its impact on monsoon circulation and precipitation over the North America monsoon (NAM region are simulated using a coupled meteorology and aerosol/chemistry model (WRF-Chem for 15 years (1995–2009. During the monsoon season, dust has a cooling effect (−0.90 W m−2 at the surface, a warming effect (0.40 W m−2 in the atmosphere, and a negative top-of-the-atmosphere (TOA forcing (−0.50 W m−2 over the deserts on 24-h average. Most of the dust emitted from the deserts concentrates below 800 hPa and accumulates over the western slope of the Rocky Mountains and Mexican Plateau. The absorption of shortwave radiation by dust heats the lower atmosphere by up to 0.5 K day−1 over the western slope of the Mountains. Model sensitivity simulations with and without dust for 15 summers (June-July-August show that dust heating of the lower atmosphere over the deserts strengthens the low-level southerly moisture fluxes on both sides of the Sierra Madre Occidental. It also results in an eastward migration of NAM-driven moisture convergence over the western slope of the Mountains. These monsoonal circulation changes lead to a statistically significant increase of precipitation by up to ~40 % over the eastern slope of the Mountains (Arizona-New~Mexico-Texas regions. This study highlights the interaction between dust and the NAM system and motivates further investigation of possible dust feedback on monsoon precipitation under climate change and the mega-drought conditions projected for the future.

  6. Sensitivity of surface radiation budget to clouds over the Asian monsoon region

    Indian Academy of Sciences (India)

    S Balachandran; M Rajeevan

    2007-04-01

    Using the ISCCP–FD surface radiative flux data for the summer season (June to September) of the period 1992 to 1995, an analysis was done to understand the role of clouds on the surface radiation budget over the Asian monsoon region. At the top of atmosphere (TOA) of convective regions of the Asian monsoon region, the short wave radiative forcing (SWCRF) and long wave radiative forcing (LWCRF) do not cancel each other resulting in occurrence of the net cloud radiative forcing values exceeding −30W/m2. This type of imbalance between SWCRF and LWCRF at TOA is reflected down on the earth surface–atmosphere system also as an imbalance between surface netcloud radiative forcing (NETCRF) and atmospheric NETCRF. Based on the regression analysis of the cloud effects on the surface radiation budget quantities, it has been observed that generally, the variance explained by multiple type cloud data is 50% more than that of total cloud cover alone. In case of SWCRF, the total cloud cover can explain about 3% (7%) of the variance whereas the three cloud type descriptions of clouds can explain about 44% (42%) of the variance over oceanic (land) regions. This highlights the importance of cloud type information in explaining the variations of surface radiation budget. It has been observed that the clouds produce more cooling effect in short-wave band than the warming effect in long-wave band resulting in a net cooling at the surface. Over the oceanic region, variations in high cloud amount contribute more to variations in SWCRF while over land regions both middle and high cloud variations make substantial contributions to the variations in both SWCRF and NETCRF.

  7. Prediction and Monitoring of Monsoon Intraseasonal Oscillations over Indian Monsoon Region in an Ensemble Prediction System using CFSv2

    Science.gov (United States)

    Borah, Nabanita; Sukumarpillai, Abhilash; Sahai, Atul Kumar; Chattopadhyay, Rajib; Joseph, Susmitha; De, Soumyendu; Nath Goswami, Bhupendra; Kumar, Arun

    2014-05-01

    An ensemble prediction system (EPS) is devised for the extended range prediction (ERP) of monsoon intraseasonal oscillations (MISO) of Indian summer monsoon (ISM) using NCEP Climate Forecast System model version2 at T126 horizontal resolution. The EPS is formulated by producing 11 member ensembles through the perturbation of atmospheric initial conditions. The hindcast experiments were conducted at every 5-day interval for 45 days lead time starting from 16th May to 28th September during 2001-2012. The general simulation of ISM characteristics and the ERP skill of the proposed EPS at pentad mean scale are evaluated in the present study. Though the EPS underestimates both the mean and variability of ISM rainfall, it simulates the northward propagation of MISO reasonably well. It is found that the signal-to-noise ratio becomes unity by about18 days and the predictability error saturates by about 25 days. Though useful deterministic forecasts could be generated up to 2nd pentad lead, significant correlations are observed even up to 4th pentad lead. The skill in predicting large-scale MISO, which is assessed by comparing the predicted and observed MISO indices, is found to be ~17 days. It is noted that the prediction skill of actual rainfall is closely related to the prediction of amplitude of large scale MISO as well as the initial conditions related to the different phases of MISO. Categorical prediction skills reveals that break is more skillfully predicted, followed by active and then normal. The categorical probability skill scores suggest that useful probabilistic forecasts could be generated even up to 4th pentad lead.

  8. Assessing reliability of regional climate projections: the case of Indian monsoon.

    Science.gov (United States)

    Ramesh, K V; Goswami, Prashant

    2014-02-12

    Projections of climate change are emerging to play major roles in many applications. However, assessing reliability of climate change projections, especially at regional scales, remains a major challenge. An important question is the degree of progress made since the earlier IPCC simulations (CMIP3) to the latest, recently completed CMIP5. We consider the continental Indian monsoon as an example and apply a hierarchical approach for assessing reliability, using the accuracy in simulating the historical trend as the primary criterion. While the scope has increased in CMIP5, there is essentially no improvement in skill in projections since CMIP3 in terms of reliability (confidence). Thus, it may be necessary to consider acceptable models for specific assessment rather than simple ensemble. Analysis of climate indices shows that in both CMIP5 and CMIP3 certain common processes at large and regional scales as well as slow timescales are associated with successful simulation of trend and mean.

  9. Skills of different mesoscale models over Indian region during monsoon season: Forecast errors

    Indian Academy of Sciences (India)

    Someshwar Das; Raghavendra Ashrit; Gopal Raman Iyengar; Saji Mohandas; M Das Gupta; John P George; E N Rajagopal; Surya Kanti Dutta

    2008-10-01

    Performance of four mesoscale models namely,the MM5,ETA,RSM and WRF,run at NCMRWF for short range weather forecasting has been examined during monsoon-2006.Evaluation is carried out based upon comparisons between observations and day-1 and day-3 forecasts of wind,temperature,specific humidity,geopotential height,rainfall,systematic errors,root mean square errors and specific events like the monsoon depressions. It is very difficult to address the question of which model performs best over the Indian region? An honest answer is ‘none ’.Perhaps an ensemble approach would be the best.However, if we must make a final verdict,it can be stated that in general,(i)the WRF is able to produce best All India rainfall prediction compared to observations in the day-1 forecast and,the MM5 is able to produce best All India rainfall forecasts in day-3,but ETA and RSM are able to depict the best distribution of rainfall maxima along the west coast of India,(ii)the MM5 is able to produce least RMSE of wind and geopotential fields at most of the time,and (iii)the RSM is able to produce least errors in the day-1 forecasts of the tracks,while the ETA model produces least errors in the day-3 forecasts.

  10. Estimation of Pan Evaporation Using Mean Air Temperature and Radiation for Monsoon Season in Junagadh Region

    Directory of Open Access Journals (Sweden)

    Manoj J. Gundalia

    2013-11-01

    Full Text Available The abstract should summarize the content of the paper. Try to keep the abstract below 200 words. Do not make references nor display equations in the abstract. The journal will be printed from the same-sized copy prepared by you. Your manuscript should be printed on A4 paper (21.0 cm x 29.7 cm. It is imperative that the margins The significance of major meteorological factors, that influence the evaporation were evaluated at daily time-scale for monsoon season using the data from Junagadh station, Gujarat (India. The computed values were compared. The solar radiation and mean air temperature were found to be the significant factors influencing pan evaporation (Ep. The negative correlation was found between relative humidity and (Ep, while wind speed, vapour pressure deficit and bright sunshine hours were found least correlated and no longer remained controlling factors influencing (Ep. The objective of the present study is to compare and evaluate the performance of six different methods based on temperature and radiation to select the most appropriate equations for estimating (Ep. The three quantitative standard statistical performance evaluation measures, coefficient of determination (R2 root mean square of errors-observations standard deviation ratio (RSR and Nash-Sutcliffe efficiency coefficient (E are employed as performance criteria. The results show that the Jensen equation yielded the most reliable results in estimation of (Ep and it can be recommended for estimating (Ep for monsoon season in the study region.

  11. Online Time Series Analysis of Land Products over Asia Monsoon Region via Giovanni

    Science.gov (United States)

    Shen, Suhung; Leptoukh, Gregory G.; Gerasimov, Irina

    2011-01-01

    Time series analysis is critical to the study of land cover/land use changes and climate. Time series studies at local-to-regional scales require higher spatial resolution, such as 1km or less, data. MODIS land products of 250m to 1km resolution enable such studies. However, such MODIS land data files are distributed in 10ox10o tiles, due to large data volumes. Conducting a time series study requires downloading all tiles that include the study area for the time period of interest, and mosaicking the tiles spatially. This can be an extremely time-consuming process. In support of the Monsoon Asia Integrated Regional Study (MAIRS) program, NASA GES DISC (Goddard Earth Sciences Data and Information Services Center) has processed MODIS land products at 1 km resolution over the Asia monsoon region (0o-60oN, 60o-150oE) with a common data structure and format. The processed data have been integrated into the Giovanni system (Goddard Interactive Online Visualization ANd aNalysis Infrastructure) that enables users to explore, analyze, and download data over an area and time period of interest easily. Currently, the following regional MODIS land products are available in Giovanni: 8-day 1km land surface temperature and active fire, monthly 1km vegetation index, and yearly 0.05o, 500m land cover types. More data will be added in the near future. By combining atmospheric and oceanic data products in the Giovanni system, it is possible to do further analyses of environmental and climate changes associated with the land, ocean, and atmosphere. This presentation demonstrates exploring land products in the Giovanni system with sample case scenarios.

  12. Representation of monsoon intraseasonal oscillations in regional climate model: sensitivity to convective physics

    KAUST Repository

    Umakanth, U.

    2015-11-07

    The aim of the study is to evaluate the performance of regional climate model (RegCM) version 4.4 over south Asian CORDEX domain to simulate seasonal mean and monsoon intraseasonal oscillations (MISOs) during Indian summer monsoon. Three combinations of Grell (G) and Emanuel (E) cumulus schemes namely, RegCM-EG, RegCM-EE and RegCM-GE have been used. The model is initialized at 1st January, 2000 for a 13-year continuous simulation at a spatial resolution of 50 km. The models reasonably simulate the seasonal mean low level wind pattern though they differ in simulating mean precipitation pattern. All models produce dry bias in precipitation over Indian land region except in RegCM-EG where relatively low value of dry bias is observed. On seasonal scale, the performance of RegCM-EG is more close to observation though it fails at intraseasonal time scales. In wave number-frequency spectrum, the observed peak in zonal wind (850 hPa) at 40–50 day scale is captured by all models with a slight change in amplitude, however, the 40–50 day peak in precipitation is completely absent in RegCM-EG. The space–time characteristics of MISOs are well captured by RegCM-EE over RegCM-GE, however it fails to show the eastward propagation of the convection across the Maritime Continent. Except RegCM-EE all other models completely underestimates the moisture advection from Equatorial Indian Ocean onto Indian land region during life-cycle of MISOs. The characteristics of MISOs are studied for strong (SM) and weak (WM) monsoon years and the differences in model performances are analyzed. The wavelet spectrum of rainfall over central India denotes that, the SM years are dominated by high frequency oscillations (period <20 days) whereas little higher periods (>30 days) along with dominated low periods (<20 days) observed during WM years. During SM, RegCM-EE is dominated with high frequency oscillations (period <20 days) whereas in WM, RegCM-EE is dominated with periods >20

  13. Representation of monsoon intraseasonal oscillations in regional climate model: sensitivity to convective physics

    Science.gov (United States)

    Umakanth, U.; Kesarkar, Amit P.; Raju, Attada; Vijaya Bhaskar Rao, S.

    2016-08-01

    The aim of the study is to evaluate the performance of regional climate model (RegCM) version 4.4 over south Asian CORDEX domain to simulate seasonal mean and monsoon intraseasonal oscillations (MISOs) during Indian summer monsoon. Three combinations of Grell (G) and Emanuel (E) cumulus schemes namely, RegCM-EG, RegCM-EE and RegCM-GE have been used. The model is initialized at 1st January, 2000 for a 13-year continuous simulation at a spatial resolution of 50 km. The models reasonably simulate the seasonal mean low level wind pattern though they differ in simulating mean precipitation pattern. All models produce dry bias in precipitation over Indian land region except in RegCM-EG where relatively low value of dry bias is observed. On seasonal scale, the performance of RegCM-EG is more close to observation though it fails at intraseasonal time scales. In wave number-frequency spectrum, the observed peak in zonal wind (850 hPa) at 40-50 day scale is captured by all models with a slight change in amplitude, however, the 40-50 day peak in precipitation is completely absent in RegCM-EG. The space-time characteristics of MISOs are well captured by RegCM-EE over RegCM-GE, however it fails to show the eastward propagation of the convection across the Maritime Continent. Except RegCM-EE all other models completely underestimates the moisture advection from Equatorial Indian Ocean onto Indian land region during life-cycle of MISOs. The characteristics of MISOs are studied for strong (SM) and weak (WM) monsoon years and the differences in model performances are analyzed. The wavelet spectrum of rainfall over central India denotes that, the SM years are dominated by high frequency oscillations (period 30 days) along with dominated low periods (20 days. Except RegCM-EE, all other models fail to capture the observed spectral features for SM and WM years.

  14. Climate implications of major geochemical elements in the Holocene sediments of the North and East China monsoonal regions

    Institute of Scientific and Technical Information of China (English)

    Qianli SUN; Zhanghua WANG; Jing CHEN; Wu FENG

    2009-01-01

    Two Holocene sediment cores were retrieved respectively from the enclosed Lake Daihai in the monsoon/arid transition zone of North China and the Taihu Lake coast in the monsoonal area of the Yangtze delta, Eastern China. Distribution of major geochemical elements and their ratios were employed to reveal the characteristics of Holocene climate and associated envir-onmental implications in the two regions. It is suggested that the temporal distribution of major elements serve as a useful indicator to denote the variations of monsoon effective precipitation for the enclosed lake area. High values of resistant elements such as Al2O3, SiO2, TiO2, (FeO + Fe2O3), MnO in the lake sediments correspond to the depressed chemical weathering and weakened mon-soon effective precipitation, while the highs of mobile and easy soluble elements such as MgO, CaO, Na2O reflect the enhanced chemical weathering and increased monsoon effective precipitation in the lake basin. In comparison, the behaviors of the major elements in sediments of the Taihu Lake coast were largely controlled by the changes both in sea transgression in the different Holocene time periods and the monsoon precipitation. The relatively highs of Al2O3, TiO2, (FeO + Fe2O3), in marine-influenced sedi-ments suggest relatively strong coastal hydrodynamics and chemical weathering, and vice versa. Meanwhile, the lows of SiO2, Na2O and CaO in the non-marine-influenced sediments also denote relatively strong hydrodynamics and chemical weathering due to enhanced monsoon precipita-tion, and vice versa. Sedimentary environment should be taken into account when achieving a full understanding of their climate implications.

  15. Evaluating the influence of antecedent soil moisture on variability of the North American Monsoon precipitation in the coupled MM5/VIC modeling system

    Directory of Open Access Journals (Sweden)

    Dennis P. Lettenmaier

    2009-11-01

    Full Text Available The influence of antecedent soil moisture on North American monsoon system (NAMS precipitation variability was explored using the MM5 mesoscale model coupled with the Variable Infiltration Capacity (VIC land surface model. Sensitivity experiments were performed with extreme wet and dry initial soil moisture conditions for both the 1984 wet monsoon year and the 1989 dry year. The MM5-VIC model reproduced the key features of NAMS in 1984 and 1989 especially over northwestern Mexico. Our modeling results indicate that the land surface has memory of the initial soil wetness prescribed at the onset of the monsoon that persists over most of the region well into the monsoon season (e.g. until August. However, in contrast to the classical thermal contrast concept, where wetter soils lead to cooler surface temperatures, less land-sea thermal contrast, weaker monsoon circulations and less precipitation, the coupled model consistently demonstrated a positive soil moisture – precipitation feedback. Specifically, anomalously wet pre-monsoon soil moisture always lead to enhanced monsoon precipitation, and the reverse was also true. Both the large-scale circulation change and local land-atmospheric interactions in response to pre-monsoon soil moisture anomalies play important roles in the coupled model’s positive soil moisture – monsoon precipitation feedback. However, the former may be sensitive to the strength and location of the thermal anomalies, thus leaving open the possibility of both positive and negative soil moisture – precipitation feedbacks. Furthermore, our use of a regional model with prescribed large-scale circulation at the model boundaries leaves open the possibility that the model behavior may, to some extent, reflect its limited ability to adjust its large-scale circulation to the regional thermal changes.

  16. Recent decadal glacier mass balances over the Western Nyainqentanglha Mountains and the increase in their melting contribution to Nam Co Lake measured by differential bistatic SAR interferometry

    Science.gov (United States)

    Li, Gang; Lin, Hui

    2017-02-01

    The Western Nyainqentanglha Mountains locates in the southeastern center of the Inner Tibetan Plateau (ITP). Glaciers in this region are influenced by both the continental climate of Central Asia and the Indian Monsoon system. Their melting on the western slopes feeds the Nam Co Lake, which is the second largest endorheic lake in the ITP. The elevation of Nam Co Lake increased at a rate of 0.25 ± 0.12 m year- 1 from 2003 to 2009. In this study, aimed at quantifying the decadal glacier mass balance in the Western Nyainqentanglha Mountains and their increasing melting contribution to Nam Co Lake; we applied the differential Bistatic SAR interferometry method to five pairs of TanDEM CoSSC datasets observed between 2013 and 2014 and SRTM acquired in 2000. The mean annual mass loss rate was - 0.235 ± 0.127 m w.e. year- 1 for the entire range. The mass loss rate for the northwestern slope (inside the Nam Co Lake drainage basin) and the southeastern slope (outside the Nam Co Lake drainage basin) were - 0.268 ± 0.129 m w.e. year- 1 and ¬ 0.219 ± 0.126 m w.e. year- 1, respectively. Our results agree well with previous fieldwork at the Zhadang and Gurenhekou glaciers located on the northwestern and southeastern slopes. Debris-cover suppressed glacier downwasting to some extent. By presuming that all of the melted ice flows into the lake, the glaciers' melting contribution to Nam Co Lake's increasing water volume was approximately 10.50 ± 9.00% during the period between 2003 and 2009.

  17. The Influence of Regional SSTs on the Interdecadal Shift of the East Asian Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    FU Jianjian; LI Shuanglin

    2013-01-01

    East Asia has experienced a significant interdecadal climate shift since the late 1970s.This shift was accompanied by a decadal change of global SST.Previous studies have suggested that the decadal shift of global SST background status played a substantial role in such a climatic shift.However,the individual roles of different regional SSTs remain unclear.In this study,we investigated these roles using ensemble experiments of an atmospheric general circulation model,GFDL (Geophysical Fluid Dynamics Laboratory) AM2.Two kinds of ensembles were performed.The first was a control ensemble in which the model was driven with the observed climatological SSTs.The second was an experimental ensemble in which the model was driven with the observed climatological SSTs plus interdecadal SST background shifts in separate ocean regions.The results suggest that the SST shift in the tropics exerted more important influence than those in the extratropics,although the latter contribute to the shift modestly.The variations of summer monsoonal circulation systems,including the South Asian High,the West Pacific Subtropical High,and the lower-level air flow,were analyzed.The results show that,in comparison with those induced by extratropical SSTs,the shifts induced by tropical SSTs bear more similarity to the observations and to the simulations with global SSTs prescribed.In particular,the observed SST shift in the tropical Pacific Ocean,rather than the Indian Ocean,contributed significantly to the shift of East Asian summer monsoon since the 1970s.

  18. The West African Monsoon simulated by global and regional climate models

    Science.gov (United States)

    Nikulin, Grigory; Jones, Colin; Kjellström, Erik; Gbobaniyi, Emiola

    2013-04-01

    We present results from two ensembles of global and regional climate simulations with a focus on the West African Monsoon (WAM). The first ensemble includes eight coupled atmosphere ocean general circulation models (AOGCMs) from the CMIP5 project, namely: CanESM2, CNRM-CM5, HadGEM2-ES, NorESM1-M, EC-EARTH, MIROC5, GFDL-ESM2M and MPI-ESM-LR. The second ensemble consists of corresponding downscaling of all 8 AOGCMs by a regional climate model - RCA4 produced at the Rossby Centre (SMHI) in the Africa-CORDEX activities. Spatial resolution varies from about 1° to 3° in the AOGCM ensemble while all regional simulations are at the same 0.44° resolution. To see what added value higher resolution can provide ability of the eight AOGCMs and the downscaled RCA4(AOGCMs) to simulate the key characteristics of the WAM rainy season are evaluated and then inter-compared between the global and regional ensembles. The main focus in our analysis is on the WAM rainy season onset, cessation, length, total precipitation, its mean intensity and intraseasonal variability. Future climate projections under the RCP45 and RCP85 scenarios are analyzed and again inter-compared for both ensembles in order to assess uncertainties in the future projections of the WAM rainy season from the global and regional ensembles.

  19. Regional evaporation estimates in the eastern monsoon region of China: Assessment of a nonlinear formulation of the complementary principle

    Science.gov (United States)

    Liu, Xiaomang; Liu, Changming; Brutsaert, Wilfried

    2016-12-01

    The performance of a nonlinear formulation of the complementary principle for evaporation estimation was investigated in 241 catchments with different climate conditions in the eastern monsoon region of China. Evaporation (Ea) calculated by the water balance equation was used as the reference. Ea estimated by the calibrated nonlinear formulation was generally in good agreement with the water balance results, especially in relatively dry catchments. The single parameter in the nonlinear formulation, namely αe as a weak analog of the alpha parameter of Priestley and Taylor (), tended to exhibit larger values in warmer and humid near-coastal areas, but smaller values in colder, drier environments inland, with a significant dependency on the aridity index (AI). The nonlinear formulation combined with the equation relating the one parameter and AI provides a promising method to estimate regional Ea with standard and routinely measured meteorological data.

  20. Reanalysis of the Indian summer monsoon: four dimensional data assimilation of AIRS retrievals in a regional data assimilation and modeling framework

    Science.gov (United States)

    Attada, Raju; Parekh, Anant; Chowdary, J. S.; Gnanaseelan, C.

    2017-07-01

    This work is the first attempt to produce a multi-year downscaled regional reanalysis of the Indian summer monsoon (ISM) using the National Centers for Environmental Prediction (NCEP) operational analyses and Atmospheric Infrared Sounder (AIRS) version 5 temperature and moisture retrievals in a regional model. Reanalysis of nine monsoon seasons (2003-2011) are produced in two parallel setups. The first set of experiments simply downscale the original NCEP operational analyses, whilst the second one assimilates the AIRS temperature and moisture profiles. The results show better representation of the key monsoon features such as low level jet, tropical easterly jet, subtropical westerly jet, monsoon trough and the spatial pattern of precipitation when AIRS profiles are assimilated (compared to those without AIRS data assimilation). The distribution of temperature, moisture and meridional gradients of dynamical and thermodynamical fields over the monsoon region are better represented in the reanalysis that assimilates AIRS profiles. The change induced by AIRS data on the moist and thermodynamic conditions results in more realistic rendering of the vertical shear associated with the monsoon, which in turn leads to a proper moisture transport and the moist convective feedback. This feedback benefits the representation of the regional monsoon characteristics, the monsoon dynamics and the moist convective processes on the seasonal time scale. This study emphasizes the use of AIRS soundings for downscaling of ISM representation in a regional reanalysis.

  1. Reanalysis of the Indian summer monsoon: four dimensional data assimilation of AIRS retrievals in a regional data assimilation and modeling framework

    KAUST Repository

    Attada, Raju

    2017-07-04

    This work is the first attempt to produce a multi-year downscaled regional reanalysis of the Indian summer monsoon (ISM) using the National Centers for Environmental Prediction (NCEP) operational analyses and Atmospheric Infrared Sounder (AIRS) version 5 temperature and moisture retrievals in a regional model. Reanalysis of nine monsoon seasons (2003–2011) are produced in two parallel setups. The first set of experiments simply downscale the original NCEP operational analyses, whilst the second one assimilates the AIRS temperature and moisture profiles. The results show better representation of the key monsoon features such as low level jet, tropical easterly jet, subtropical westerly jet, monsoon trough and the spatial pattern of precipitation when AIRS profiles are assimilated (compared to those without AIRS data assimilation). The distribution of temperature, moisture and meridional gradients of dynamical and thermodynamical fields over the monsoon region are better represented in the reanalysis that assimilates AIRS profiles. The change induced by AIRS data on the moist and thermodynamic conditions results in more realistic rendering of the vertical shear associated with the monsoon, which in turn leads to a proper moisture transport and the moist convective feedback. This feedback benefits the representation of the regional monsoon characteristics, the monsoon dynamics and the moist convective processes on the seasonal time scale. This study emphasizes the use of AIRS soundings for downscaling of ISM representation in a regional reanalysis.

  2. Simulation of the Indian summer monsoon onset-phase rainfall using a regional model

    KAUST Repository

    Srinivas, C. V.

    2015-09-11

    This study examines the ability of the Advanced Research WRF (ARW) regional model to simulate Indian summer monsoon (ISM) rainfall climatology in different climate zones during the monsoon onset phase in the decade 2000–2009. The initial and boundary conditions for ARW are provided from the NCEP/NCAR Reanalysis Project (NNRP) global reanalysis. Seasonal onset-phase rainfall is compared with corresponding values from 0.25° IMD (India Meteorological Department) rainfall and NNRP precipitation data over seven climate zones (perhumid, humid, dry/moist, subhumid, dry/moist, semiarid and arid) of India to see whether dynamical downscaling using a regional model yields advantages over just using large-scale model predictions. Results show that the model could simulate the onset phase in terms of progression and distribution of rainfall in most zones (except over the northeast) with good correlations and low error metrics. The observed mean onset dates and their variability over different zones are well reproduced by the regional model over most climate zones. It has been found that the ARW performed similarly to the reanalysis in most zones and improves the onset time by 1 to 3 days in zones 4 and 7, in which the NNRP shows a delayed onset compared to the actual IMD onset times. The variations in the onset-phase rainfall during the below-normal onset (June negative) and above-normal onset (June positive) phases are well simulated. The slight underestimation of onset-phase rainfall in the northeast zone could be due to failure in resolving the wide extent of topographic variations and the associated multiscale interactions in that zone. Spatial comparisons showed improvement of pentad rainfall in both space and quantity in ARW simulations over NNRP data, as evident from a wider eastward distribution of pentad rainfall over the Western Ghats, central and eastern India, as in IMD observations. While NNRP under-represented the high pentad rainfall over northeast, east and

  3. Projected seasonal mean summer monsoon over India and adjoining regions for the twenty-first century

    Science.gov (United States)

    Dash, Sushil K.; Mishra, Saroj K.; Pattnayak, Kanhu C.; Mamgain, Ashu; Mariotti, Laura; Coppola, Erika; Giorgi, Filippo; Giuliani, Graziano

    2015-11-01

    In this study, we present the projected seasonal mean summer monsoon over India and adjoining regions for the twenty-first century under the representative concentration pathway (RCP) 4.5 and RCP 8.5 scenarios using the regional model RegCM4 driven by the global model GFDL-ESM2M. RegCM4 is integrated from 1970 to 2099 at 50 km horizontal resolution over the South Asia CORDEX domain. The simulated mean summer monsoon circulation and associated rainfall by RegCM4 are validated against observations in the reference period 1975 to 2004 based on the Global Precipitation Climatology Project (GPCP) and India Meteorological Department (IMD) data sets. Regional model results are also compared with those of the global model GFDL which forces the RegCM4, showing that the regional model in particular improves the simulation of precipitation trends during the reference period. Future projections are categorized as near future (2010-2039), mid future (2040-2069), and far future (2070-2099). Comparison of projected seasonal (June-September) mean rainfall from the different time slices indicate a gradual increase in the intensity of changes over some of the regions under both the RCP4.5 and RCP8.5 scenarios. RegCM4 projected rainfall decreases over most of the Indian land mass and the equatorial and northern Indian Ocean, while it increases over the Arabian Sea, northern Bay of Bengal, and the Himalayas. Results show that the monsoon circulation may become weaker in the future associated with a decrease in rainfall over Indian land points. The RegCM4 projected decrease in June, July, August, September (JJAS) rainfall under the RCP8.5 scenario over the central, eastern, and peninsular India by the end of the century is in the range of 25-40 % of their mean reference period values; it is significant at the 95 % confidence level and it is broadly in line with patterns of observed change in recent decades. Surface evaporation is projected to increase over the Indian Ocean, thereby

  4. North American Mesoscale Forecast System (NAM) [12 km

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The North American Mesoscale Forecast System (NAM) is one of the major regional weather forecast models run by the National Centers for Environmental Prediction...

  5. Impacts of Global Warming on Hydrological Cycles in the Asian Monsoon Region

    Institute of Scientific and Technical Information of China (English)

    Koji DAIRAKU; Seita EMORI; Toru NOZAWA

    2008-01-01

    The hydrologic changes and the impact of these changes constitute a fundamental global-warmingrelated concern. Faced with threats to human life and natural ecosystems, such as droughts, floods, and soil erosion, water resource planners must increasingly make future risk assessments. Though hydrological predictions associated with the global climate change are already being performed, mainly through the use of GCMs, coarse spatial resolutions and uncertain physical processes limit the representation of terrestrial water/energy interactions and the variability in such systems as the Asian monsoon. Despite numerous studies, the regional responses of hydrologic changes resulting from climate change remains inconclusive. In this paper, an attempt at dynamical downscaling of future hydrologic projection under global climate change in Asia is addressed. The authors conducted present and future Asian regional climate simulations which were nested in the results of Atmospheric General Circulation Model (AGCM) experiments. The regional climate model could capture the general simulated features of the AGCM. Also, some regional phenomena such as orographic precipitation, which did not appear in the outcome of the AGCM simulation, were successfully produced. Under global warming, the increase of water vapor associated with the warmed air temperature was projected. It was projected to bring more abundant water vapor to the southern portions of India and the Bay of Bengal, and to enhance precipitation especially over the mountainous regions, the western part of India and the southern edge of the Tibetan Plateau. As a result of the changes in the synoptic flow patterns and precipitation under global warming, the increases of annual mean precipitation and surface runoff were projected in many regions of Asia. However, both the positive and negative changes of seasonal surface runoff were projected in some regions which will increase the flood risk and cause a mismatch between water

  6. The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon

    Directory of Open Access Journals (Sweden)

    L. Guo

    2013-02-01

    Full Text Available The response of East Asian Summer Monsoon (EASM precipitation to long term changes in regional anthropogenic aerosols (sulphate and black carbon is explored in an atmospheric general circulation model, the atmospheric component of the UK High-Resolution Global Environment Model v1.2 (HiGAM. Separately, sulphur dioxide (SO2 and black carbon (BC emissions in 1950 and 2000 over East Asia are used to drive model simulations, while emissions are kept constant at year 2000 level outside this region. The response of the EASM is examined by comparing simulations driven by aerosol emissions representative of 1950 and 2000. The aerosol radiative effects are also determined using an off-line radiative transfer model. During June, July and August, the EASM was not significantly changed as either SO2 or BC emissions increased from 1950 to 2000 levels. However, in September, precipitation is significantly decreased by 26.4% for sulphate aerosol and 14.6% for black carbon when emissions are at the 2000 level. Over 80% of the decrease is attributed to changes in convective precipitation. The cooler land surface temperature over China in September (0.8 °C for sulphate and 0.5 °C for black carbon due to increased aerosols reduces the surface thermal contrast that supports the EASM circulation. However, mechanisms causing the surface temperature decrease in September are different between sulphate and BC experiments. In the sulphate experiment, the sulphate direct and the 1st indirect radiative effects contribute to the surface cooling. In the BC experiment, the BC direct effect is the main driver of the surface cooling, however, a decrease in low cloud cover due to the increased heating by BC absorption partially counteracts the direct effect. This results in a weaker land surface temperature response to BC changes than to sulphate changes. The resulting precipitation response is also weaker, and the responses of the monsoon circulation

  7. CloudSat observations of cloud-type distribution over the Indian summer monsoon region

    Directory of Open Access Journals (Sweden)

    K. V. Subrahmanyam

    2013-07-01

    Full Text Available The three-dimensional distribution of various cloud types over the Indian summer monsoon (ISM region using five years (2006–2010 of CloudSat observations during June-July-August-September months is discussed for the first time. As the radiative properties, latent heat released and microphysical properties of clouds differ largely depending on the cloud type, it becomes important to know what types of clouds occur over which region. In this regard, the present analysis establishes the three-dimensional distribution of frequency of occurrence of stratus (St, stratocumulus (Sc, nimbostratus (Ns, cumulus (Cu, altocumulus (Ac, altostratus (As, cirrus (Ci and deep convective (DC clouds over the ISM region. The results show that the various cloud types preferentially occur over some regions of the ISM, which are consistent during all the years of observations. It is found that the DC clouds frequently occur over northeast of Bay of Bengal (BoB, Ci clouds over a wide region of south BoB–Indian peninsula–equatorial Indian Ocean, and Sc clouds over the north Arabian Sea. Ac clouds preferentially occur over land, and a large amount of As clouds are found over BoB. The occurrence of both St and Ns clouds over the study region is much lower than all other cloud types.The interannual variability of all these clouds including their vertical distribution is discussed. It is envisaged that the present study opens up possibilities to quantify the feedback of individual cloud type in the maintenance of the ISM through radiative forcing and latent heat release.

  8. Observation and Model Comparison on Precipitation response to Volcanic Aerosols in the Asian Monsoon Region

    Science.gov (United States)

    Zhuo, Z.; Gao, C.

    2014-12-01

    Disagreement between observation and models were shown on the volcanic sulfate aerosols' effect on precipitation in Asia monsoon region. Here, we investigate it by classifying two groups of historical volcanism between AD 1300 and AD 1850 to 2, 1, and 0.5 times Pinatubo sulfate injection into the northern hemisphere (NH) stratosphere based on IVI2 and Crowley2013 volcanic reconstructions, then comparing precipitation response of BCC-CSM1 and CCSM4 model outputs under past1000 scenario to IVI2 volcanic group, and that of MIROC-ESM and MPI-ESM-P to Crowley2013 group with tree-ring reconstruction data MADA. In both groups, Superposed Epoch Analysis (SEA) of MADA and four model outputs show a drying trend over Asia monsoon regions after the NH injections and drier with larger sulfate magnitude, with a 1 or 2 year time lag in MADA comparing to the model outputs, this may result from the biological response of tree ring data that lag behind the meteorological forcing of model outputs. On the other hand, different responses to Southern Hemisphere (SH) only injections were found between the two groups as well as MADA and model outputs. Most of the results were found significant at 90% or even 95% significance level with a 10,000 Monte Carlo resampling procedure. Spatial variation of MADA show a significant drying effect in central Asia in year 1, and then move westward in year 2 and 3 after 2, 1×Pinatubo eruptions of IVI2, while a significant wetting effect in northwest Asia but drying effect in south Asia were shown in Crowley2013 group. However, model outputs did not show spatial variation, with a pattern drier in northwest than in southeast Asia along the years after the eruptions in both volcanic groups. Thus, observation and model outputs are well consistent on precipitation response to NH aerosol injections, but models may need large improvement on the response to SH aerosol injection as well as the spatial variation. Besides, opposite precipitation response to SH

  9. Assessment of two versions of regional climate model in simulating the Indian Summer Monsoon over South Asia CORDEX domain

    Science.gov (United States)

    Pattnayak, K. C.; Panda, S. K.; Saraswat, Vaishali; Dash, S. K.

    2017-07-01

    This study assess the performance of two versions of Regional Climate Model (RegCM) in simulating the Indian summer monsoon over South Asia for the period 1998 to 2003 with an aim of conducting future climate change simulations. Two sets of experiments were carried out with two different versions of RegCM (viz. RegCM4.2 and RegCM4.3) with the lateral boundary forcings provided from European Center for Medium Range Weather Forecast Reanalysis (ERA-interim) at 50 km horizontal resolution. The major updates in RegCM4.3 in comparison to the older version RegCM4.2 are the inclusion of measured solar irradiance in place of hardcoded solar constant and additional layers in the stratosphere. The analysis shows that the Indian summer monsoon rainfall, moisture flux and surface net downward shortwave flux are better represented in RegCM4.3 than that in the RegCM4.2 simulations. Excessive moisture flux in the RegCM4.2 simulation over the northern Arabian Sea and Peninsular India resulted in an overestimation of rainfall over the Western Ghats, Peninsular region as a result of which the all India rainfall has been overestimated. RegCM4.3 has performed well over India as a whole as well as its four rainfall homogenous zones in reproducing the mean monsoon rainfall and inter-annual variation of rainfall. Further, the monsoon onset, low-level Somali Jet and the upper level tropical easterly jet are better represented in the RegCM4.3 than RegCM4.2. Thus, RegCM4.3 has performed better in simulating the mean summer monsoon circulation over the South Asia. Hence, RegCM4.3 may be used to study the future climate change over the South Asia.

  10. Deglaciation in the tropical Indian Ocean driven by interplay between the regional monsoon and global teleconnections

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Lea, D.W.; Nigam, R.; Mackensen, A.; Naik, Dinesh K.

    by prominent weak monsoon intervals (WMI), lasting a few thousand years. Deglacial WMIs are interpreted as the result of cold temperature anomalies generated by sea ice feedbacks in the North Atlantic, most prominently during Heinrich Events. Recent modeling...

  11. Investigation of the aerosol-cloud-rainfall association over the Indian summer monsoon region

    Science.gov (United States)

    Sarangi, Chandan; Nand Tripathi, Sachchida; Kanawade, Vijay P.; Koren, Ilan; Sivanand Pai, D.

    2017-04-01

    Monsoonal rainfall is the primary source of surface water in India. Using 12 years of in situ and satellite observations, we examined the association of aerosol loading with cloud fraction, cloud top pressure, cloud top temperature, and daily surface rainfall over the Indian summer monsoon region (ISMR). Our results showed positive correlations between aerosol loading and cloud properties as well as rainfall. A decrease in outgoing longwave radiation and an increase in reflected shortwave radiation at the top of the atmosphere with an increase in aerosol loading further indicates a possible seminal role of aerosols in the deepening of cloud systems. Significant perturbation in liquid- and ice-phase microphysics was also evident over the ISMR. For the polluted cases, delay in the onset of collision-coalescence processes and an enhancement in the condensation efficiency allows for more condensate mass to be lifted up to the mixed colder phases. This results in the higher mass concentration of larger-sized ice-phase hydrometeors and, therefore, implies that the delayed rain processes eventually lead to more surface rainfall. A numerical simulation of a typical rainfall event case over the ISMR using a spectral bin microphysical scheme coupled with the Weather Research Forecasting (WRF-SBM) model was also performed. Simulated microphysics also illustrated that the initial suppression of warm rain coupled with an increase in updraft velocity under high aerosol loading leads to enhanced super-cooled liquid droplets above freezing level and ice-phase hydrometeors, resulting in increased accumulated surface rainfall. Thus, both observational and numerical analysis suggest that high aerosol loading may induce cloud invigoration, thereby increasing surface rainfall over the ISMR. While the meteorological variability influences the strength of the observed positive association, our results suggest that the persistent aerosol-associated deepening of cloud systems and an

  12. A dipole-like SST trend in the Somalia region during the monsoon season

    Science.gov (United States)

    Santos, F.; Gómez-Gesteira, M.; deCastro, M.; Días, J. M.

    2015-02-01

    SST trends measured in the Somalia region during the southwest monsoon season over the period 1982-2013 have shown the existence of a warming-cooling dipole. The positive spot, with a warming trend on the order of 0.37°C dec-1, is centered around 5.1°N-50.3°E and the negative one, with a trend on the order of -0.43°C dec-1, around 11.1°N-52.2°E. The migration of the Great Whirl (GW) over the last three decades at a speed of -0.3°C dec-1 in longitude and -0.6°C dec-1 in latitude was considered as the possible origin of the SST dipole. The displacement of the GW produces changes in the geostrophic currents which, in turn, generate changes in the amount of advected water from and to coast.

  13. Uncertainties in the regional climate models simulations of South-Asian summer monsoon and climate change

    Science.gov (United States)

    Syed, F. S.; Iqbal, Waheed; Syed, Ahsan Ali Bukhari; Rasul, G.

    2014-04-01

    The uncertainties in the regional climate models (RCMs) are evaluated by analyzing the driving global data of ERA40 reanalysis and ECHAM5 general circulation models, and the downscaled data of two RCMs (RegCM4 and PRECIS) over South-Asia for the present day simulation (1971-2000) of South-Asian summer monsoon. The differences between the observational datasets over South-Asia are also analyzed. The spatial and the quantitative analysis over the selected climatic regions of South-Asia for the mean climate and the inter-annual variability of temperature, precipitation and circulation show that the RCMs have systematic biases which are independent from different driving datasets and seems to come from the physics parameterization of the RCMs. The spatial gradients and topographically-induced structure of climate are generally captured and simulated values are within a few degrees of the observed values. The biases in the RCMs are not consistent with the biases in the driving fields and the models show similar spatial patterns after downscaling different global datasets. The annual cycle of temperature and rainfall is well simulated by the RCMs, however the RCMs are not able to capture the inter-annual variability. ECHAM5 is also downscaled for the future (2071-2100) climate under A1B emission scenario. The climate change signal is consistent between ECHAM5 and RCMs. There is warming over all the regions of South-Asia associated with increasing greenhouse gas concentrations and the increase in summer mean surface air temperature by the end of the century ranges from 2.5 to 5 °C, with maximum warming over north western parts of the domain and 30 % increase in rainfall over north eastern India, Bangladesh and Myanmar.

  14. A regional climate study of aerosol impacts on Indian monsoon and precipitations over the Himalayas

    Science.gov (United States)

    Solmon, F.; Von Hardenberg, J.; Nair, V.; Palazzi, E.

    2013-12-01

    In the context of the PAPRIKA program we are studying the potential effects of aerosol particle on Indian climate and Himalayan region. Using the RegCM4 regional climate model we performed some experiments including on-line representation of natural and anthropogenic aerosols for present day and future conditions over the CORDEX-India domain. Dynamical boundary forcing is taken for ERAI-Interim over the period 2000-2010, and chemical boundary-conditions are prescribed as a monthly climatology form an ECEARTH/CAM simulation for present day. Different set of anthropogenic emissions (SO2, carbonaceous aerosols) are considered (IPCC RCP4.5 and REAS) whereas natural aerosol (dust and sea-salt) are calculated on line. In order to account for aerosol radiative feedback on surface energy budget over the oceans, we also implemented a 'q-flux' slab ocean model as an alternative to pure SST forcing. After a step of validation of aerosol simulation against observations, we investigate through a series of experiments the dynamical feedback of direct radiative effect of aerosol over this domain, focusing specifically on Indian Monsoon and precipitation over the Himalayas. We discriminate the effect of anthropogenic vs. natural aerosol while outlining the main mechanism of the regional climate response, as well as the sensitivity to emissions inventory. Our results will be discussed notably against previous GCM based studies. Finally we will possibly discuss future projections based on RCP4.5 EC-EARTH forcing and including aerosol effects, as well as the potential radiative effects of absorbing aerosol deposition on the Himalayan snow covers.

  15. Multi-ensemble regional simulation of Indian monsoon during contrasting rainfall years: role of convective schemes and nested domain

    Science.gov (United States)

    Devanand, Anjana; Ghosh, Subimal; Paul, Supantha; Karmakar, Subhankar; Niyogi, Dev

    2017-08-01

    Regional simulations of the seasonal Indian summer monsoon rainfall (ISMR) require an understanding of the model sensitivities to physics and resolution, and its effect on the model uncertainties. It is also important to quantify the added value in the simulated sub-regional precipitation characteristics by a regional climate model (RCM), when compared to coarse resolution rainfall products. This study presents regional model simulations of ISMR at seasonal scale using the Weather Research and Forecasting (WRF) model with the synoptic scale forcing from ERA-interim reanalysis, for three contrasting monsoon seasons, 1994 (excess), 2002 (deficit) and 2010 (normal). Impact of four cumulus schemes, viz., Kain-Fritsch (KF), Betts-Janjić-Miller, Grell 3D and modified Kain-Fritsch (KFm), and two micro physical parameterization schemes, viz., WRF Single Moment Class 5 scheme and Lin et al. scheme (LIN), with eight different possible combinations are analyzed. The impact of spectral nudging on model sensitivity is also studied. In WRF simulations using spectral nudging, improvement in model rainfall appears to be consistent in regions with topographic variability such as Central Northeast and Konkan Western Ghat sub-regions. However the results are also dependent on choice of cumulus scheme used, with KF and KFm providing relatively good performance and the eight member ensemble mean showing better results for these sub-regions. There is no consistent improvement noted in Northeast and Peninsular Indian monsoon regions. Results indicate that the regional simulations using nested domains can provide some improvements on ISMR simulations. Spectral nudging is found to improve upon the model simulations in terms of reducing the intra ensemble spread and hence the uncertainty in the model simulated precipitation. The results provide important insights regarding the need for further improvements in the regional climate simulations of ISMR for various sub-regions and contribute

  16. Regional Frequency Analysis of Annual Maximum Rainfall in Monsoon Region of Pakistan using L-moments

    Directory of Open Access Journals (Sweden)

    Amina Shahzadi

    2013-02-01

    Full Text Available The estimation of magnitude and frequency of extreme rainfall has immense importance to make decisions about hydraulic structures like spillways, dikes and dams etc The main objective of this study is to get the best fit distributions for annual maximum rainfall data on regional basis in order to estimate the extreme rainfall events (quantiles for various return periods. This study is carried out using index flood method using L-moments by Hosking and wallis (1997. The study is based on 23 sites of rainfall which are divided into three homogeneous regions. The collective results of L-moment ratio diagram, Z-statistic and AWD values show the GLO, GEV and GNO to be best fit for all three regions and in addition PE3 for region 3. On the basis of relative RMSE, for region 1 and region 2, GLO, GEV and GNO are producing approximately the same relative RMSE for return periods upto 100. While GNO is producing less relative RMSE for large return periods of 500 and 1000. So for large return periods GNO could be best distribution. For region 3 GLO, GEV, GNO and PE3 are having approximately the same relative RMSE for return periods upto 100. While for large return periods of 500 and 1000 PE3 could be best on basis of less relative RMSE.

  17. SUNYA Regional Climate Model Simulations of East Asia Summer Monsoon: Effects of Cloud Vertical Structure on the Surface Energy Balance

    Directory of Open Access Journals (Sweden)

    Wei Gong Wei-Chyung Wang

    2007-01-01

    Full Text Available We used the State University of New York at Albany (SUNYA regional climate model to study the effect of cloud vertical distribution in affecting the surface energy balance of the East Asia summer monsoon (EASM. Simulations were conducted for the summers of 1988 and 1989, during which large contrast in the intra-seasonal cloud radiative forcing (CRF was observed at the top of the atmosphere.

  18. Behavior of predicted convective clouds and precipitation in the high-resolution Unified Model over the Indian summer monsoon region

    Science.gov (United States)

    Jayakumar, A.; Sethunadh, Jisesh; Rakhi, R.; Arulalan, T.; Mohandas, Saji; Iyengar, Gopal R.; Rajagopal, E. N.

    2017-05-01

    National Centre for Medium Range Weather Forecasting high-resolution regional convective-scale Unified Model with latest tropical science settings is used to evaluate vertical structure of cloud and precipitation over two prominent monsoon regions: Western Ghats (WG) and Monsoon Core Zone (MCZ). Model radar reflectivity generated using Cloud Feedback Model Intercomparison Project Observation Simulator Package along with CloudSat profiling radar reflectivity is sampled for an active synoptic situation based on a new method using Budyko's index of turbulence (BT). Regime classification based on BT-precipitation relationship is more predominant during the active monsoon period when convective-scale model's resolution increases from 4 km to 1.5 km. Model predicted precipitation and vertical distribution of hydrometeors are found to be generally in agreement with Global Precipitation Measurement products and BT-based CloudSat observation, respectively. Frequency of occurrence of radar reflectivity from model implies that the low-level clouds below freezing level is underestimated compared to the observations over both regions. In addition, high-level clouds in the model predictions are much lesser over WG than MCZ.

  19. Impact of GCM boundary forcing on regional climate modeling of West African summer monsoon precipitation and circulation features

    Science.gov (United States)

    Kebe, Ibourahima; Sylla, Mouhamadou Bamba; Omotosho, Jerome Adebayo; Nikiema, Pinghouinde Michel; Gibba, Peter; Giorgi, Filippo

    2017-03-01

    In this study, the latest version of the International Centre for Theoretical Physics Regional Climate Model (RegCM4) driven by three CMIP5 Global Climate Models (GCMs) is used at 25 km grid spacing over West Africa to investigate the impact of lateral boundary forcings on the simulation of monsoon precipitation and its relationship with regional circulation features. We find that the RegCM4 experiments along with their multimodel ensemble generally reproduce the location of the main precipitation characteristics over the region and improve upon the corresponding driving GCMs. However, the provision of different forcing boundary conditions leads to substantially different precipitation magnitudes and spatial patterns. For instance, while RegCM4 nested within GFDL-ESM-2M and HadGEM2-ES exhibits some underestimations of precipitation and an excessively narrow Intertropical Convergence Zone, the MPI-ESM-MR driven run produces precipitation spatial distribution and magnitudes more similar to observations. Such a superior performance originates from a much better simulation of the interactions between baroclinicity, temperature gradient and African Easterly Jet along with an improved connection between the Isentropic Potential Vorticity, its gradient and the African Easterly Waves dynamics. We conclude that a good performing GCM in terms of monsoon dynamical features (in this case MPI-ESM-MR) is needed to drive RCMs in order to achieve a better representation of the West Africa summer monsoon precipitation.

  20. Regional Aerosol Forcing over India: Preliminary Results from the South West Asian Aerosol-Monsoon Interactions (SWAAMI) Aircraft Experiment

    Science.gov (United States)

    Morgan, W.; Brooks, J.; Fox, C.; Haslett, S.; Liu, D.; Kompalli, S. K.; Pathak, H.; Manoj, M. R.; Allan, J. D.; Haywood, J. M.; Highwood, E.; Langridge, J.; Nanjundaiah, R. S.; Krishnamoorthy, K.; Babu, S. S.; Satheesh, S. K.; Turner, A. G.; Coe, H.

    2016-12-01

    Aerosol particles from multiple sources across the Indian subcontinent build up to form a dense and extensive haze across the region in advance of the monsoon. These aerosols are thought to perturb the regional radiative balance and hydrological cycle, which may have a significant impact on the monsoon circulation, as well as influencing the associated cloud and rainfall of the system. However the nature and magnitude of such impacts are poorly understood or constrained. Major uncertainties relevant to the regional aerosol burden include its vertical distribution, the relative contribution of different pollution sources and natural emissions and the role of absorbing aerosol species (black carbon and mineral dust). The South West Asian Aerosol-Monsoon Interactions (SWAAMI) project sought to address these major uncertainties by conducting an airborne experiment during June/July 2016 on-board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft. Based out of Lucknow in the), The aircraft conducted multiple flights from Lucknow in the heart of the Indo-Gangetic Plain (IGP) in advance of the monsoon and during the onset phase. The spatial and vertical distribution of aerosol was evaluated across northern India, encompassing drier desert-like regions to the west, heavily populated urban and industrial centres over the IGP and air masses in outflow regions to the south-east towards the Bay of Bengal. Principal measurements included aerosol chemical composition using an Aerodyne Aerosol Mass Spectrometer and a DMT Single Particle Soot Photometer, alongside a Leosphere backscatter LIDAR. Sulphate was a major contributor to the aerosol burden across India, while the organic aerosol was elevated and more dominant over the most polluted regions of the IGP. Substantial aerosol concentrations were frequently observed up to altitudes of approximately 6km, with notable changes in aerosol chemical and physical properties when comparing different

  1. Interactions between trophic levels in upwelling and non-upwelling regions during summer monsoon

    Science.gov (United States)

    Malik, A.; Fernandes, C. E. G.; Gonsalves, M.-J. B. D.; Subina, N. S.; Mamatha, S. S.; Krishna, K.; Varik, S.; Kumari, R.; Gauns, M.; Cejoice, R. P.; Pandey, S. S.; Jineesh, V. K.; Kamaleson, A. S.; Vijayan, V.; Mukherjee, I.; Subramanyan, S.; Nair, S.; Ingole, B.; LokaBharathi, P. A.

    2015-01-01

    Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during summer monsoon (May-September). We hypothesize that there could be a shift in environmental parameters along with changes in the network of interactions between bacteria, phytoplankton, and zooplankton in upwelling and non-upwelling regions. During cruise # 267 on FORV Sagar Sampada, water samples were analysed for environmental and biological parameters from two transects, one upwelling region off Trivandrum (TVM) (8°26‧N, 76°20‧E-8°30‧N, 76°50‧E), and the other non-upwelling region off Calicut (CLT) (11°11‧N, 75°30‧E-11°14‧N,74°54‧E), about 230 nmi to the north. Meteorological, hydrological, and nutrient profiles confirmed upwelling off TVM. Bacteria, phytoplankton and zooplankton significantly responded. Primary and bacterial productivity enhanced together with increase in the percentage of viable bacteria (TVC). Pearson's correlation analysis pointed out the differences in bacterial interactions with other trophic levels at both transects. TVC played a prominent role in trophic interactions off TVM by depending on phytoplankton for substrate (r = 0.754). This contrasted with CLT where total counts (TC) played an important role. However, most interrelationships were less pronounced. Principal component analysis (PCA) confirmed the correlation analysis and further showed that the factor loadings of the biotic and abiotic parameters differed in strength and direction in the two regions. More importantly, the processes of mineralization by bacteria and uptake by phytoplankton are obviously more coupled off TVM as evidenced by the clustering of the related parameters in the PCA biplot. Canonical correspondence analysis also complements these findings and demonstrated that the abiotic factors influenced phytoplankton and bacteria similarly at TVM but differently at CLT. The impact on the trophic interrelationships is evident by the close association

  2. Past and future trends of hydroclimatic intensity over the Indian monsoon region

    Science.gov (United States)

    Mohan, T. S.; Rajeevan, M.

    2017-01-01

    The hydroclimatic intensity index (HY-INT) is a single index that quantitatively combines measures of precipitation intensity and dry spell length, thus providing an integrated response of the hydrological cycle to global warming. The HY-INT index is a product of the precipitation intensity (PINT, intensity during wet days) and dry spell length (DSL). Using the observed gridded rainfall data sets of 1951-2010 period, the changes in HY-INT, PINT, and DSL over the Indian monsoon region have been examined in addition to changes in maximum consecutive dry days (MCD). We have also considered 10 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models for examining the changes in these indices during the present-day and future climate change scenarios. For climate change projections, the Representative Concentration Pathway (RCP) 4.5 scenario was considered. The analysis of observational data during the period 1951-2010 suggested an increase in DSL and MCD over most of central India. Further, statistically significant (95% level) increase in HY-INT is also noted during the period of 1951-2010, which is mainly caused due to significant increase in precipitation intensity. The CMIP5 model projections of future climate also suggest a statistically significant increase in HY-INT over the Indian region. Out of the 10 models considered, seven models suggest a consistent increase in HY-INT during the period of 2010-2100 under the RCP4.5 scenario. However, the projected increase in HY-INT is mainly due to increase in the precipitation intensity, while dry spell length (DSL) showed little changes in the future climate.

  3. Impact of land surface conditions on 2004 North American monsoon in GCM experiments

    Science.gov (United States)

    Feng, X.; Bosilovich, M.; Houser, P.; Chern, J.-D.

    2013-01-01

    In this study, two sets of six-member ensemble simulations were performed for the boreal summer of 2004 using the Finite Volume General Circulation model to investigate the sensitivity of the North American monsoon (NAM) system to land surface conditions and further to identify the mechanisms by which land surface processes control the NAM precipitation. The control simulation uses a fully interactive land surface model, whereas the sensitivity experiment uses prescribed land surface fields from the Global Land Data Assimilation System.The response of the monsoon precipitation to land surface changes varies over different regions modulated by two different soil moisture-precipitation feedbacks. The vast northern NAM region, including most of Arizona and New Mexico, as well as the northwestern Mexico shows that soil moisture has a positive feedback with precipitation primarily due to local recycling mechanisms. The reduction of soil moisture decreases latent heat flux and increases sensible heat flux and consequently increases the Bowen ratio and surface temperature, leading to a deep (warm and dry) boundary layer, which suppresses convection and hence reduces precipitation. Over the west coast of Mexico near Sinaloa, a negative soil moisture-precipitation relationship is noted to be associated with a large-scale mechanism. The reduced soil moisture changes surface fluxes and hence boundary layer instability and ultimately low-level circulation. As a result, the changes in surface pressure and large scale wind field increase moisture flux convergence and consequently moisture content, leading to increased atmospheric instability and in turn enhancing convection and accordingly precipitation. These results further reinforce the important role of land surface conditions on surface process, boundary structure, atmospheric circulation, and rainfall during the NAM development.

  4. Multi-year simulation of the East Asian Monsoon and Precipitation in China using a Regional Climate Model and Evaluation

    Institute of Scientific and Technical Information of China (English)

    LI Qiaoping; DING Yihui

    2005-01-01

    By using the regional climate model (RegCM_NCC), East Asian monsoon and precipitation over China during 1998 to 2002 are simulated. Results show that the model can well reproduce the seasonal patterns of mean circulation as well as the intensity and seasonal march of the East Asian monsoon. The simulated onset or retreat time of the West Pacific subtropical high, and the intensity and location of the South Asian high are consistent with the fact. The spatial distribution and transport of moisture in lower layer are also well simulated. The seasonal variations of regional rainfall and temperature are reproduced in the model, with three northward shift time and intensity of the rain belts over the sub-regions (such as Mid-Lower Yangtze basins and South China) well corresponding to the observation. However, the simulated summer monsoon is stronger compared with NCEP reanalysis fields, with the location of subtropical high being further north by 2-3 degrees than normal. Error evaluation shows that there is a discernible systematic bias in the simulated mean circulation pattern, with air temperature bias being positive over the land and negative over the ocean in the lower troposphere in summer. The systematic bias exaggerates the summer temperature difference between the land and ocean, which may be a main responsible factor for the stronger simulated summer monsoon, thus resulting in the overestimated rainfall in North China and it can not reflect well the abnormal rainfall distribution in these 5 years. The deficiency may be mainly contributed to the complex topography and cloud-radiation parameterization scheme. The analyses also indicate that it is difficult to simulate the persistent abnormal precipitation pattern over China. It is necessary to improve the model's capability further.

  5. Regional Frequency Analysis of Annual Maximum Rainfall in Monsoon Region of Pakistan using L-moments

    OpenAIRE

    Amina Shahzadi; Ahmad Saeed Akhter; Betul Saf

    2013-01-01

    The estimation of magnitude and frequency of extreme rainfall has immense importance to make decisions about hydraulic structures like spillways, dikes and dams etc The main objective of this study is to get the best fit distributions for annual maximum rainfall data on regional basis in order to estimate the extreme rainfall events (quantiles) for various return periods. This study is carried out using index flood method using L-moments by Hosking and wallis (1997). The study is based on 23 ...

  6. Effects of crop growth and development on regional climate: a case study over East Asian monsoon area

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Feng [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); Zhejiang Institute of Meteorological Sciences, Hangzhou (China); Xie, Zhenghui [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China)

    2012-06-15

    In this study, the CERES phenological growth and development functions were implemented into the regional climate model, RegCM3 to give a model denoted as RegCM3{sub C}ERES. This model was used to represent interactions between regional climate and crop growth processes. The effects of crop growth and development processes on regional climate were then studied based on two 20-year simulations over the East Asian monsoon area conducted using the original regional climate model RegCM3, and the coupled RegCM3{sub C}ERES model. The numerical experiments revealed that incorporating the crop growth and development processes into the regional climate model reduced the root mean squared error of the simulated precipitation by 2.2-10.7% over north China, and the simulated temperature by 5.5-30.9% over the monsoon region in eastern China. Comparison of the simulated results obtained using RegCM3{sub C}ERES and RegCM3 showed that the most significant changes associated with crop modeling were the changes in leaf area index which in turn modify the aspects of surface energy and water partitions and lead to moderate changes in surface temperature and, to some extent, rainfall. Further analysis revealed that a robust representation of seasonal changes in plant growth and developmental processes in the regional climate model changed the surface heat and moisture fluxes by modifying the vegetation characteristics, and that these differences in simulated surface fluxes resulted in different structures of the boundary layer and ultimately affected the convection. The variations in leaf area index and fractional vegetation cover changed the distribution of evapotranspiration and heat fluxes, which could potentially lead to anomalies in geopotential height, and consequently influenced the overlying atmospheric circulation. These changes would result in redistribution of the water and energy through advection. Nevertheless, there are significant uncertainties in modeling how monsoon

  7. Mesoscale convection system and occurrence of extreme low tropopause temperatures. Observations over Asian summer monsoon region

    Energy Technology Data Exchange (ETDEWEB)

    Jain, A.R.; Mandal, T.K.; Gautam, R. [National Physical Laboratory, New Delhi (India). Radio and Atmospheric Div.; Panwar, V. [National Physical Laboratory, New Delhi (India). Radio and Atmospheric Div.; Delhi Univ. (India). Dept. of Physics and Astrophysics; Rao, V.R. [India Meteorology Dept., New Delhi (India). Satellite Meteorology Div.; Goel, A. [Delhi Univ. (India). Dept. of Physics and Astrophysics; Das, S.S. [Vikram Sarabhai Space Center, Trivandrum (India). Space Physics Lab.; Dhaka, S.K. [Delhi Univ., New Delhi (India). Dept. of Physics and Electronics

    2010-07-01

    The present study examines the process of how tropospheric air enters the stratosphere, particularly in association with tropical mesoscale convective systems (TMCS) which are considered to be one of the causative mechanisms for the observation of extremely low tropopause temperature over the tropics. The association between the phenomena of convection and the observation of extreme low tropopause temperature events is, therefore, examined over the Asian monsoon region using data from multiple platforms. Satellite observations show that the area of low outgoing long wave radiation (OLR), which is a proxy for the enhanced convection, is embedded with high altitude clouds top temperatures ({<=}193 K). A detailed analysis of OLR and 100 hPa temperature shows that both are modulated by westward propagating Rossby waves with a period of {proportional_to}15 days, indicating a close linkage between them. The process by which the tropospheric air enters the stratosphere may, in turn, be determined by how the areas of convection and low tropopause temperature (LTT) i.e. T {<=}191K are spatially located. In this context, the relative spatial distribution of low OLR and LTT areas is examined. Though, the locations of low OLR and LTT are noticed in the same broad area, the two do not always overlap, except for partial overlap in some cases. When there are multiple low OLR areas, the LTT area generally appears in between the low OLR areas. Implications of these observations are also discussed. The present analysis also shows that the horizontal mean winds have a role in the spatial distribution of low OLR and LTT. (orig.)

  8. On the dominant intra-seasonal modes over the East Asia-western North Pacific summer monsoon region

    Science.gov (United States)

    Ha, Kyung-Ja; Oh, Hyoeun

    2017-04-01

    Intra-seasonal monsoon prediction is the most imperative task due to high impact on 2/3 of world populations' daily life, but there remains an enduring challenge in climate science. The present study aims to provide a physical understanding of the sources for prediction of dominant intra-seasonal modes in the East Asian-western North Pacific summer monsoon (EA-WNPSM): preMeiyu&Baiu, Changma&Meiyu, WNPSM, and monsoon gyre modes classified by the self-organizing map analysis. The major modes tend to be dominated by the moisture convergence of the moisture budget equation along the rain-band. The preMeiyu-Baiu mode is strongly linked to both the anomalous low-level convergence and vertical wind shear through baroclinic instability, and the Changma&Meiyu mode has a strengthened tropic-subtropics connection along the western north Pacific subtropical high, which induces vertical destabilization and strong convective instability. The WNPSM and monsoon gyre modes are characterized by anomalous southeasterly flow of warm and moist air from western north Pacific monsoon, and low-level easterly flow, respectively. Prominent difference in response to the ENSO leads to different effects of the Indian Ocean and western Pacific thermal state, and consequently, the distinct moisture supply and instability variations for the EASM intra-seasonal modes. We discuss the major driving forces of sub-seasonal variability over EA-WNPSM regions. Lastly we attempted to determine the predictability sources for the four modes in the EA-WNPSM. The selected predictors are based on the persistent and tendency signals of the SST/2m air temperature and sea level pressure fields, which reflect the asymmetric response to the ENSO and the ocean and land surface anomalous conditions. For the preMeiyu&Baiu mode, the SST cooling tendency over the WNP, which persists into summer, is the distinguishing contributor that results in strong baroclinic instability. A major precursor for the Changma&Meiyu mode

  9. Impact of vegetation on the simulation of seasonal monsoon rainfall over the Indian subcontinent using a regional model

    Indian Academy of Sciences (India)

    Surya K Dutta; Someshwar Das; S C Kar; U C Mohanty; P C Joshi

    2009-10-01

    The change in the type of vegetation fraction can induce major changes in the local effects such as local evaporation,surface radiation,etc.,that in turn induces changes in the model simulated outputs.The present study deals with the effects of vegetation in climate modeling over the Indian region using the MM5 mesoscale model.The main objective of the present study is to investigate the impact of vegetation dataset derived from SPOT satellite by ISRO (Indian Space Research Organization)versus that of USGS (United States Geological Survey)vegetation dataset on the simulation of the Indian summer monsoon.The present study has been conducted for five monsoon seasons (1998 –2002),giving emphasis over the two contrasting southwest monsoon seasons of 1998 (normal)and 2002 (deficient). The study reveals mixed results on the impact of vegetation datasets generated by ISRO and USGS on the simulations of the monsoon.Results indicate that the ISRO data has a positive impact on the simulations of the monsoon over northeastern India and along the western coast.The MM5- USGS has greater tendency of overestimation of rainfall.It has higher standard deviation indicating that it induces a dispersive effect on the rainfall simulation.Among the five years of study,it is seen that the RMSE of July and JJAS (June –July –August –September)for All India Rainfall is mostly lower for MM5-ISRO.Also,the bias of July and JJAS rainfall is mostly closer to unity for MM5-ISRO.The wind fields at 850 hPa and 200 hPa are also better simulated by MM5 using ISRO vegetation.The synoptic features like Somali jet and Tibetan anticyclone are simulated closer to the veri fication analysis by ISRO vegetation.The 2 m air temperature is also better simulated by ISRO vegetation over the northeastern India,showing greater spatial variability over the region. However,the JJAS total rainfall over north India and Deccan coast is better simulated using the USGS vegetation.Sensible heat flux over

  10. Magnetostratigraphic age and monsoonal evolution recorded by the thickest Quaternary loess deposit of the Lanzhou region, western Chinese Loess Plateau

    Science.gov (United States)

    Zhang, Jun; Li, Jijun; Guo, Benhong; Ma, Zhenhua; Li, Xiaomiao; Ye, Xiyan; Yu, Hao; Liu, Jia; Yang, Cheng; Zhang, Shengda; Song, Chunhui; Hui, Zhengchuang; Peng, Tingjiang

    2016-05-01

    The loess-paleosol sequences of the Chinese Loess Plateau (CLP) are major paleoclimatic archives which document the evolution of the East Asian Monsoon (EAM) and changes in the Northern Hemisphere ice sheets during the Quaternary glacial-interglacial cycles. However, the mechanisms regulating the trend of EAM variations on a tectonic scale are unclear. The loess deposits of the western CLP, which have a close relationship with tectonics and climate, are much better-suited to exploring these mechanisms than those of the central CLP. However, studies of long-term EAM evolution from the western CLP have been hindered by the lack of long, accurately-dated sequences with high sediment accumulation rates. Here, we address this problem via high resolution magnetostratigraphic, magnetic susceptibility and grain-size analyses of a 416.2 m-long drill core located at Xijin Village, near Lanzhou. Paleomagnetic dating indicates that the basal age of the Xijin loess is ∼2.2 Ma. The χ and grain-size records reveal that the East Asian Summer Monsoon (EASM) and East Asian Winter Monsoon (EAWM) strengthened synchronously at ∼1.24 Ma. Subsequently, during interglacial periods, the EASM began to penetrate, and then dominate, in the Lanzhou region. This was followed by two stepwise uptrends, commencing at ∼0.87 and ∼0.62 Ma, which resulted in an increasingly moist interglacial climate in the region. We suggest that the uplift of the Tibetan Plateau was largely responsible for these three stepwise enhancements of the EASM. Overall, however, the long-term trend of strengthening in EAWM in the area may have been primarily caused by long-term global cooling from the Late Pliocene onwards.

  11. A study on the role of land-atmosphere coupling on the south Asian monsoon climate variability using a regional climate model

    Science.gov (United States)

    Unnikrishnan, C. K.; Rajeevan, M.; Vijaya Bhaskara Rao, S.

    2017-02-01

    Land-atmosphere coupling over the south Asian monsoon region is examined using a regional climate model. For this purpose, the Weather Research and Forecasting (WRF) model with a resolution of 45 km was used. In the control experiment (CTL), the model was integrated from the year 2000 to 2011 and allowed the soil moisture interaction with the atmosphere using a coupled land surface model. In the second experiment (CSM), the soil moisture evolution at each time step was replaced with the climatology of soil moisture taken from the control run. The results reveal that land-atmosphere coupling plays a critical role in influencing the south Asian monsoon climate variability. Soil moisture is found to have stronger impacts on daily maximum temperature compared to minimum temperature. Soil moisture also makes a significant contribution to monsoon rainfall variability over the monsoon region. The coupling strength for large-scale rainfall is found to be higher compared to that of cumulus rainfall. Soil moisture is found more strongly coupled to sensible heat flux over most of the monsoon region.

  12. Characteristics of precipitating monsoon clouds over rain-shadow and drought-hit regions of India using radar

    Science.gov (United States)

    Morwal, S. B.; Narkhedkar, S. G.; Padmakumari, B.; Maheskumar, R. S.; Kulkarni, J. R.

    2017-07-01

    C-band radars were installed at Baramati and Shegaon as a part of operational cloud seeding program of Maharashtra State in the monsoon season (June-September) 2004. These provided first time a unique opportunity to study (1) characteristics of precipitating monsoon clouds (2) convection and (3) number of seedable clouds over Indian meteorological subdivisions of Madhya Maharashtra (rain-shadow) and Vidarbha (drought-hit). The monsoon season is divided into active and break periods. The cloud characteristics studied are: diurnal variation, cloud top heights and durations. Diurnal variation of cloud frequency shows maximum in the afternoon hours (10-11 UTC) and minimum in the early morning hours (3-4 UTC) in both the periods. Cloud tops show trimodal distributions with modes at 2-3, 8-9 and above 9 km. Mean cloud duration is 55 min. Congestus has been found prominent cloud type (65%) with mean top height of 6.76 km. Frequency of cumulonimbus clouds is found higher in the break periods. Cloud scale is taken as a metric for characterization of convection. Maximum frequency of cloud scale is found at C scale (mesoscale: area 100-1000 km2). Mesoscale Convective System has been found dominating convection type. The convection over the area has been shown to be hybrid type, consisting of basic oceanic type modulated by land convection. Convective clouds having maximum reflectivities between 25 and 35 dBZ, suitable for hygroscopic and glaciogenic seeding, are found in a large number. Understanding of characteristics of clouds and convection is useful for the diagnostic and precipitation enhancement studies over the rain-shadow/drought-hit regions.

  13. The impact of soil moisture on the spin up of 1-D Noah land surface model at a site in monsoonal region

    Science.gov (United States)

    Bhattacharya, A.; Mandal, M.

    2014-12-01

    Model spin-up is the process through which the model is adequately equilibrated to ensure balance between the mass fields and velocity fields. In this study, an offline 1-D Noah land surface model (LSM) has been used to investigate the impact of soil moisture on the model spin up at Kharagpur, India which is a site in monsoonal region. The model is integrated recursively for 3-years to assess its spin-up behavior. Several numerical experiments are performed to investigate the impact of initial soil moisture and subsequent dry or wet condition on model spin-up. These include simulations with different initial soil moisture content (observed soil moisture; dry soil; moderately wet soil; saturated soil), simulations initialized before different rain conditions (no rain; infrequent rain; continuous rain) and simulations initialized in different seasons (Winter, Spring, Summer/Pre-Monsoon, Monsoon and Autumn). It is noted that the model has significantly longer spin-up when initialized with very low initial soil moisture content than with higher soil moisture content. It is also seen that in general, simulations initialized just before a continuous rainfall event have the least spin-up time. In a region affected by the monsoon, such as Kharagpur, this observation is reinforced by the results from the simulations initialized in different seasons. It is seen that for monsoonal region, the model spin-up time is least for simulations initialized during Summer/Pre-monsoon. Model initialized during the Monsoon has a longer spin-up than that initialized in any other season. It appears that the model has shorter spin-up if it reaches the equilibrium state predominantly via drying process. It is also observed that the spin-up of offline 1-D Noah LSM may be as low as two months under quasi-equilibrium condition if the initial soil moisture content and time of start of simulations are chosen carefully.

  14. River of kings [Mae Nam Chao Phraya

    Energy Technology Data Exchange (ETDEWEB)

    Mogg, R.

    1997-10-01

    Low rainfall and a growing demand for water have had profound effects on water supplies in Thailand`s Mae Nam Chao Phraya river basin. In particular, low water levels are causing problems at the Bhumibol and Sirikit dams, as rice farms are threatened. The work of a Government sponsored think-tank set up to coordinate water management in the region is describe. Strategies may include use of groundwater at peak demand, recycling waste water and improve technical efficiency to reduce distribution losses. Any such policy changes will inevitably have widespread political, economic and social consequences. (UK)

  15. Heterodynes dominate precipitation isotopes in the East Asian monsoon region, reflecting interaction of multiple climate factors

    Science.gov (United States)

    Thomas, Elizabeth K.; Clemens, Steven C.; Sun, Youbin; Prell, Warren L.; Huang, Yongsong; Gao, Li; Loomis, Shannon; Chen, Guangshan; Liu, Zhengyu

    2016-12-01

    For the past decade, East Asian monsoon history has been interpreted in the context of an exceptionally well-dated, high-resolution composite record of speleothem oxygen isotopes (δ18Ocave) from the Yangtze River Valley. This record is characterized by a unique spectral response, with variance concentrated predominantly within the precession band and an enigmatic lack of variance at the eccentricity and obliquity bands. Here we examine the spectral characteristics of all existing >250-kyr-long terrestrial water isotope records in Asia, including a new water isotope record using leaf wax hydrogen isotope ratios from the Chinese Loess Plateau. There exist profound differences in spectral characteristics among all orbital-scale Asian water isotope records. We demonstrate that these differences result from latitudinal gradients in the influence of the winter and summer monsoons, both of which impact climate and water isotopes throughout East Asia. Water isotope records therefore do not reflect precipitation during a single season or from a single circulation system. Rather, water isotope records in East Asia reflect the complex interplay of oceanic and continental moisture sources, operating at multiple Earth-orbital periods. These non-linear interactions are reflected in water isotope spectra by the presence of heterodynes. Although complex, we submit that water isotope records, when paired with rapidly developing isotope-enabled model simulations, will have the potential to elucidate mechanisms causing seasonal precipitation variability and moisture source variability in East Asia.

  16. Impact of satellite data assimilation on the predictability of monsoon intraseasonal oscillations in a regional model

    KAUST Repository

    Parekh, Anant

    2017-04-07

    This study reports the improvement in the predictability of circulation and precipitation associated with monsoon intraseasonal oscillations (MISO) when the initial state is produced by assimilating Atmospheric Infrared Sounder (AIRS) retrieved temperature and water vapour profiles in Weather Research Forecast (WRF) model. Two separate simulations are carried out for nine years (2003 to 2011) . In the first simulation, forcing is from National Centers for Environmental Prediction (NCEP, CTRL) and in the second, apart from NCEP forcing, AIRS temperature and moisture profiles are assimilated (ASSIM). Ten active and break cases are identified from each simulation. Three dimensional temperature states of identified active and break cases are perturbed using twin perturbation method and carried out predictability tests. Analysis reveals that the limit of predictability of low level zonal wind is improved by four (three) days during active (break) phase. Similarly the predictability of upper level zonal wind (precipitation) is enhanced by four (two) and two (four) days respectively during active and break phases. This suggests that the initial state using AIRS observations could enhance predictability limit of MISOs in WRF. More realistic baroclinic response and better representation of vertical state of atmosphere associated with monsoon enhance the predictability of circulation and rainfall.

  17. Latitudinal gradients in tree ring stable carbon and oxygen isotopes reveal differential climate influences of the North American Monsoon System

    Science.gov (United States)

    Szejner, Paul; Wright, William E.; Babst, Flurin; Belmecheri, Soumaya; Trouet, Valerie; Leavitt, Steven W.; Ehleringer, James R.; Monson, Russell K.

    2016-07-01

    The arrival of the North American Monsoon System (NAMS) terminates a presummer hyperarid period in the southwestern United States (U.S.), providing summer moisture that is favorable for forest growth. Montane forests in this region rely on winter snowpack to drive much of their growth; the extent to which they use NAMS moisture is uncertain. We addressed this by studying stable carbon and oxygen isotopes in earlywood and latewood from 11 sites along a latitudinal gradient extending from Arizona and New Mexico to Utah. This study provides the first regional perspective on the relative roles of winter versus summer precipitation as an ecophysiological resource. Here we present evidence that Ponderosa pine uses NAMS moisture differentially across this gradient. 13C/12C ratios suggest that photosynthetic water use efficiency during latewood formation is more sensitive to summer precipitation at the northern than at the southern sites. This is likely due to the fact that NAMS moisture provides sufficiently favorable conditions for tree photosynthesis and growth during most years in the southern sites, whereas the northern sites experience larger summer moisture variability, which in some years is limiting growth. Cellulose δ18O and δ13C values revealed that photoassimilates in the southern sites were produced under higher vapor pressure deficit conditions during spring compared to summer, demonstrating a previously underappreciated effect of seasonal differences in atmospheric humidity on tree ring isotope ratios. Our findings suggest that future changes in NAMS will potentially alter productivity and photosynthetic water use dynamics differentially along latitudinal gradients in southwestern U.S. montane forests.

  18. Arsenic contamination in agricultural soils of Bengal deltaic region of West Bengal and its higher assimilation in monsoon rice.

    Science.gov (United States)

    Shrivastava, Anamika; Barla, Anil; Singh, Surjit; Mandraha, Shivanand; Bose, Sutapa

    2017-02-15

    In the Bengal deltaic region, the shallow groundwater laced with arsenic is used for irrigation frequently and has elevated the soil arsenic in agricultural soil. However, the areas with seasonal flooding reduce arsenic in top layers of the soils. Study shows arsenic accumulation in the deeper soil layers with time in the contaminated agricultural soil (19.40±0.38mg/kg in 0-5cm, 27.17±0.44mg/kg in 5-10cm and 41.24±0.48mg/kg in 10-15cm) in 2013 whereas depletion in 2014 and its buildup in different parts of monsoon rice plant in Nadia, India. Principal Component Analysis and Cluster Analysis were performed, and Enrichment Factor was calculated to identify the sources of arsenic in the soil. Potential Ecological Risk was also calculated to estimate the extent of risk posed by arsenic in soil, along with the potential risk of dietary arsenic exposure. Remarkably, the concentration of arsenic detected in the rice grain showed average value of 1.4mg/kg in 2013 which has increased to 1.6 in 2014, both being above the permissible limit (1mg/kg). These results indicate that monsoon flooding enhances the infiltration of arsenic in the deeper soil layer, which lead to further contamination of shallow groundwater. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Significant impact of the East Asia monsoon on ozone seasonal behavior in the boundary layer of Eastern China and the west Pacific region

    Science.gov (United States)

    He, Y. J.; Uno, I.; Wang, Z. F.; Pochanart, P.; Li, J.; Akimoto, H.

    2008-12-01

    The impact of the East Asia monsoon on the seasonal behavior of O3 in the boundary layer of Eastern China and the west Pacific region was analyzed for 2004-2006 by means of full-year nested chemical transport model simulations and continuous observational data obtained from three inland mountain sites in central and eastern China and three oceanic sites in the west Pacific region. The basic common features of O3 seasonal behaviors over all the monitoring sites are the pre- and post-monsoon peaks with a summer trough. Such bimodal seasonal patterns of O3 are predominant over the region with strong summer monsoon penetration, and become weaker or even disappear outside the monsoon region. The seasonal/geographical distribution of the pre-defined monsoon index indicated that the East Asia summer monsoon is responsible for the bimodal seasonal O3 pattern, and also partly account for the differences in the O3 seasonal variations between the inland mountain and oceanic sites. Over the inland mountain sites, the O3 concentration increased gradually from the beginning of the year, reached a maximum in June, decreased rapidly to the summer valley in July or August, and then peaked in September or October, thereafter decreased gradually again. Over the oceanic sites, O3 abundance showed a similar increasing trend beginning in January, but then decreased gradually from the end of March, followed by a wide trough with the minimum in July and August and a small peak in October or November. A sensitivity analysis performed by setting China-emission to zero revealed that the chemically produced O3 from China-emission contributed substantially to the O3 abundance, particularly the pre- and post-monsoon O3 peaks, over China mainland. We found that China-emission contributed more than 40% to total boundary layer O3 during summertime (60-70% in July) and accounted for about 40 ppb of each peak value over the inland region if without considering the effect of the nonlinear chemical

  20. West African monsoon intraseasonal activity and its daily precipitation indices in regional climate models: diagnostics and challenges

    Science.gov (United States)

    Poan, E. D.; Gachon, P.; Dueymes, G.; Diaconescu, E.; Laprise, R.; Seidou Sanda, I.

    2016-11-01

    The West African monsoon intraseasonal variability has huge socio-economic impacts on local populations but understanding and predicting it still remains a challenge for the weather prediction and climate scientific community. This paper analyses an ensemble of simulations from six regional climate models (RCMs) taking part in the coordinated regional downscaling experiment, the ECMWF ERA-Interim reanalysis (ERAI) and three satellite-based and observationally-constrained daily precipitation datasets, to assess the performance of the RCMs with regard to the intraseasonal variability. A joint analysis of seasonal-mean precipitation and the total column water vapor (also called precipitable water— PW) suggests the existence of important links at different timescales between these two variables over the Sahel and highlights the relevance of using PW to follow the monsoon seasonal cycle. RCMs that fail to represent the seasonal-mean position and amplitude of the meridional gradient of PW show the largest discrepancies with respect to seasonal-mean observed precipitation. For both ERAI and RCMs, spectral decompositions of daily PW as well as rainfall show an overestimation of low-frequency activity (at timescales longer than 10 days) at the expense of the synoptic (timescales shorter than 10 days) activity. Consequently, the effects of the African Easterly Waves and the associated mesoscale convective systems are substantially underestimated, especially over continental regions. Finally, the study investigates the skill of the models with respect to hydro-climatic indices related to the occurrence, intensity and frequency of precipitation events at the intraseasonal scale. Although most of these indices are generally better reproduced with RCMs than reanalysis products, this study indicates that RCMs still need to be improved (especially with respect to their subgrid-scale parameterization schemes) to be able to reproduce the intraseasonal variance spectrum adequately.

  1. Multi-Site and Multi-Variables Statistical Downscaling Technique in the Monsoon Dominated Region of Pakistan

    Science.gov (United States)

    Khan, Firdos; Pilz, Jürgen

    2016-04-01

    South Asia is under the severe impacts of changing climate and global warming. The last two decades showed that climate change or global warming is happening and the first decade of 21st century is considered as the warmest decade over Pakistan ever in history where temperature reached 53 0C in 2010. Consequently, the spatio-temporal distribution and intensity of precipitation is badly effected and causes floods, cyclones and hurricanes in the region which further have impacts on agriculture, water, health etc. To cope with the situation, it is important to conduct impact assessment studies and take adaptation and mitigation remedies. For impact assessment studies, we need climate variables at higher resolution. Downscaling techniques are used to produce climate variables at higher resolution; these techniques are broadly divided into two types, statistical downscaling and dynamical downscaling. The target location of this study is the monsoon dominated region of Pakistan. One reason for choosing this area is because the contribution of monsoon rains in this area is more than 80 % of the total rainfall. This study evaluates a statistical downscaling technique which can be then used for downscaling climatic variables. Two statistical techniques i.e. quantile regression and copula modeling are combined in order to produce realistic results for climate variables in the area under-study. To reduce the dimension of input data and deal with multicollinearity problems, empirical orthogonal functions will be used. Advantages of this new method are: (1) it is more robust to outliers as compared to ordinary least squares estimates and other estimation methods based on central tendency and dispersion measures; (2) it preserves the dependence among variables and among sites and (3) it can be used to combine different types of distributions. This is important in our case because we are dealing with climatic variables having different distributions over different meteorological

  2. Using stable hydrogen and oxygen isotopes to reveal monsoonal and related hydrological effects on meteoric water in the Western Pacific monsoon region: A case study of the Ilan region, northeastern Taiwan

    Science.gov (United States)

    Peng, Tsung-Ren; Huang, Chun-Chun; Chen, Chi-Tsun; Chen, Jui-Er; Liang, Wen-Jui

    2016-10-01

    This study analyzes the isotopic compositions (δ2H and δ18O) of meteoric waters, including precipitation and stream water, to reveal what major hydrological processes affect the hydrological regime of the Ilan region, northeastern Taiwan. The isotopic results indicate monsoonal flows as the fundamental factors affecting studied precipitation and stream water. Summer precipitation sourced from southerly air mass exhibits lower δ and deuterium-excess (dE) values than winter precipitation sourced from northerly air masses. The δ18O and dE values are respectively -7.7‰ and 8‰ for summer precipitation and -3.3‰ and 24‰ for winter precipitation. Furthermore, semi-quantitative estimations using dE evidence indicate that summertime southerly air masses generally contribute more to stream water than wintertime northerly air-mass flows (approximately 54% vs. 46%). However, the contribution fractions are controlled by the orientation of catchments to the windward side of respective monsoonal flows. Northern catchments, located on the windward side of southerly air masses, receive about 60% of their water from precipitation condensed from the southerly air masses, and 40% from the northerly air masses. By comparison, southern catchments, located on the windward side of northerly air masses, receive about 59% of their water from northerly air masses and 41% from southerly air masses. Additionally, catchment effect, induced from δ value, is notable in stream basins with high elevations but this is not related to catchment sizes. Besides this, altitude effect, which is determined in terms of δ18O values, was derived using data from four precipitation stations of northern Taiwan. It ranges from -2.5 to -3.0‰ per 100 m depending on the season; moreover, based on the dE evidence, secondary evaporation effects are apparent with moisture recycling influencing inland summer precipitation and raindrop evaporation influencing inland winter precipitation.

  3. Sensitivity of a regional climate model to land surface parameterization schemes for East Asian summer monsoon simulation

    Science.gov (United States)

    Li, Wenkai; Guo, Weidong; Xue, Yongkang; Fu, Congbin; Qiu, Bo

    2016-10-01

    Land surface processes play an important role in the East Asian Summer Monsoon (EASM) system. Parameterization schemes of land surface processes may cause uncertainties in regional climate model (RCM) studies for the EASM. In this paper, we investigate the sensitivity of a RCM to land surface parameterization (LSP) schemes for long-term simulation of the EASM. The Weather Research and Forecasting (WRF) Model coupled with four different LSP schemes (Noah-MP, CLM4, Pleim-Xiu and SSiB), hereafter referred to as Sim-Noah, Sim-CLM, Sim-PX and Sim-SSiB respectively, have been applied for 22-summer EASM simulations. The 22-summer averaged spatial distributions and strengths of downscaled large-scale circulation, 2-m temperature and precipitation are comprehensively compared with ERA-Interim reanalysis and dense station observations in China. Results show that the downscaling ability of RCM for the EASM is sensitive to LSP schemes. Furthermore, this study confirms that RCM does add more information to the EASM compared to reanalysis that imposes the lateral boundary conditions (LBC) because it provides 2-m temperature and precipitation that are with higher resolution and more realistic compared to LBC. For 2-m temperature and monsoon precipitation, Sim-PX and Sim-SSiB simulations are more consistent with observation than simulations of Sim-Noah and Sim-CLM. To further explore the physical and dynamic mechanisms behind the RCM sensitivity to LSP schemes, differences in the surface energy budget between simulations of Ens-Noah-CLM (ensemble mean averaging Sim-Noah and Sim-CLM) and Ens-PX-SSiB (ensemble mean averaging Sim-PX and Sim-SSiB) are investigated and their subsequent impacts on the atmospheric circulation are analyzed. It is found that the intensity of simulated sensible heat flux over Asian continent in Ens-Noah-CLM is stronger than that in Ens-PX-SSiB, which induces a higher tropospheric temperature in Ens-Noah-CLM than in Ens-PX-SSiB over land. The adaptive

  4. The influence of soil type, vegetation cover and soil moisture on spin up behaviour of a land surface model in a monsoonal region

    Science.gov (United States)

    Bhattacharya, Anwesha; Mandal, Manabottam

    2015-04-01

    Model spin-up is the process through which the model is adequately equilibrated to ensure balance between the mass fields and velocity fields. In this study, an offline one dimensional Noah land surface model is integrated recursively for three years to assess its spin-up behavior at different sites over the Indian Monsoon domain. Several numerical experiments are performed to investigate the impact of soil category, vegetation cover, initial soil moisture and subsequent dry or wet condition on model spin-up. These include simulations with the dominant soil and vegetation covers of this region, different initial soil moisture content (observed soil moisture; dry soil; moderately wet soil; saturated soil), simulations initialized at different rain conditions (no rain; infrequent rain; continuous rain) and different seasons (Winter, Spring, Summer/Pre-Monsoon, Monsoon and Autumn). It is seen that the spin-up behavior of the model depends on the soil type and vegetation cover with soil characteristics having the larger influence. Over India, the model has the longest spin-up in the case of simulations with loamy soil covered with mixed-shrub. It is noted that the model has a significantly longer spin-up when initialized with very low initial soil moisture content than with higher soil moisture content. It is also seen that in general, simulations initialized just before a continuous rainfall event have the least spin-up time. This observation is reinforced by the results from the simulations initialized in different seasons. It is seen that for monsoonal region, the model spin-up time is least for simulations initialized just before the Monsoon. Model initialized during the Monsoon rain episodes has a longer spin-up than that initialized in any other season. Furthermore, it is seen that the model has a shorter spin-up if it reaches the equilibrium state predominantly via drying process and could be as low as two months under quasi-equilibrium condition depending on

  5. Assessing how seasonal hydrological balance has changed during the warming 20th century in the montane forests of Southeast Asian monsoon region using a stable isotope dendroclimatology approach

    Science.gov (United States)

    Zhu, M.; Stott, L. D.

    2010-12-01

    Tropical montane forests act as water catchment and host of biodiversity in the Southeast Asian monsoon region, and understanding how their hydrological conditions change with global warming is vitally important. Global climate model simulations project enhanced moisture cycle in the tropics, which would cause stronger summer monsoon precipitations, but on the other hand the adiabatic lapse rate would be shifted towards a moister condition (amplification of warming at high elevation), inhibiting dry season orographic lifting cloud/fog formation (lifting cloud base hypothesis), enhancing evapo-transpiration, and leading to a net moisture loss during winter dry season. In this study, we have attempted to investigate how the seasonal moisture balance in Southeast Asia has evolved in response to these influences through the 20th century using the oxygen isotopic composition (δ18O) of subannual tree cellulose samples extracted from the annual rings of pine trees that grow in Doi Chiang Dao, a limestone mountain in northern Thailand. At this location the δ18O of cellulose exhibits distinctive annual cycles of up to 12‰, which is primarily a reflection of both the so-called ‘isotope amount effect’ that is associated with the strong monsoon precipitation during summer wet season and the moisture availability from different sources during winter dry season. We have demonstrated that tree cellulose δ18O could be used as a proxy for regional monsoon strength by showing that the annual mean cellulose δ18O correlate significantly with All India Rainfall, Webster-Yang monsoon index, as well as with both local and regional monsoon precipitation. ENSO is the dominant influence on interannual rainfall variability and this is well expressed in the interannual cellulose δ18O record. Using a 21-year moving window correlation analysis we find a weakening of ENSO influence after 1980, coinciding with the most rapid atmospheric warming. We expect to analyze older trees to

  6. Trends in Peroxyacetyl Nitrate (PAN in the upper troposphere and lower stratosphere over Southern Asia during the summer monsoon season: regional impacts

    Directory of Open Access Journals (Sweden)

    S. Fadnavis

    2014-07-01

    Full Text Available We analyze temporal trends of Peroxyacetyl Nitrate (PAN retrievals from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS during 2002–2011 in the altitude range 8–23 km over the Asian summer monsoon (ASM region. The greatest enhancements of PAN mixing ratios in the upper troposphere and lower stratosphere (UTLS are seen during the summer monsoon season from June to September. During the monsoon season, the mole fractions of PAN show statistically significant (at 2 sigma level positive trends from 0.2 ± 0.05 to 4.6 ± 3.1 ppt year−1 (except between 12–14 km which is higher than the annual mean trends of 0.1 ± 0.05 to 2.7 ± 0.8 ppt year−1. These rising concentrations point to increasing NOx (=NO+NO2 and volatile organic compound (VOC emissions from developing nations in Asia, notably India and China. We analyze the influence of monsoon convection on the distribution of PAN in UTLS with simulations using the global chemistry-climate model ECHAM5-HAMMOZ. During the monsoon, transport into the UTLS over the Asian region primarily occurs from two convective zones, one extending from the Bay of Bengal to the South China Sea and the other over the southern flank of the Himalayas. India and China are NOx limited regions, and thus we use the model to evaluate the contributions from enhanced NOx emissions to the changes in PAN, HNO3 and O3 concentrations in the UTLS. From a set of sensitivity experiments with emission changes in particular regions it can be concluded that Chinese emissions have a greater impact on the concentrations of these species than Indian emissions. NOx emissions increases over India are about half of those over China.

  7. Sources of chemical species in rainwater during monsoon and non-monsoonal periods over two mega cities in India and dominant source region of secondary aerosols

    Science.gov (United States)

    Rao, P. S. P.; Tiwari, S.; Matwale, J. L.; Pervez, S.; Tunved, P.; Safai, P. D.; Srivastava, A. K.; Bisht, D. S.; Singh, S.; Hopke, P. K.

    2016-12-01

    Samples of rainwater (RW) were collected to characterize the chemistry and sources in two representative megacities at Pune (Southwest) and Delhi (Northern) India from 2011 to 2014 across two seasons: monsoon (MN) and non-monsoon (NMN). Collected RW samples were analyzed for major chemical constituents (F-, Cl-, SO42-, NO3-, NH4+, Na+, K+, Ca2+, and Mg2+), pH and conductivity. In addition, bicarbonate (HCO3-) was also estimated. The mean pH values of the RW were >6 at Pune and pollution effects in these Indian mega cities. Both the Ca2+ and SO42- were the dominant ions, accounting for 43% (Pune) and 54% (Delhi) of the total ions. The sum of measured ions during the NMN period was greater than the NM period by a factor of 1.5 for Pune (278.4: NM and 412.1: NMN μeq/l) and a factor of about 2.5 for Delhi (406 and 1037.7 μeq/l). The contributions of SO42- and NO3- to the RW acidity were ∼40% and 60%, respectively, at Pune and correspondingly, 36% and 64% at Delhi. The concentrations of secondary aerosols (SO42-and NO3-) were higher by a factor of two and three when the air masses were transported to Pune from the continental side. At Delhi, the concentrations of SO42-, NO3-, Ca2+, and Mg2+ were significantly higher when the air masses arrive from Punjab, Haryana, and Pakistan indicating the greater atmospheric pollution over the Indo-Gangetic Plain. Positive matrix factorization was applied to the source apportionment of the deposition fluxes of these ions. Three factors were obtained for Pune and four for Delhi. The sources at Pune were secondary aerosols from fossil fuel combustion, soil dust, and marine, whereas, at Delhi, the sources were soil, fossil fuel combustion, biomass burning, and industrial chlorine.

  8. Dust load and rainfall characteristics and their relationship over the South Asian monsoon region under various warming scenarios

    Science.gov (United States)

    Singh, Charu; Ganguly, Dilip; Dash, S. K.

    2017-08-01

    Present study investigates the similarities and differences in the pattern of dust load and rainfall and their relationship over the South Asian monsoon region under various future warming scenarios with respect to the historical period using multiple coupled climate model runs that participated in Coupled Model Inter-comparison Project Phase 5 (CMIP5). Based on statistically robust significance tests, we unravel several likely changes in the pattern of the dust load and rainfall over the South Asia under different future warming scenarios by the end of 21st century compared to the historical period. Kolmogorov-Smirnov test results reveal a significant change (at 5% significance level) in the amount of dust and rainfall under different warming scenarios over the study region. Northern part of the Indian subcontinent is likely to witness increased dust loading in future, and regions with increase in dust load are also likely to be the regions of increased rainfall over North India. Positive correlation between rainfall over the Indian region and dust over the Arabian region is also likely to strengthen in future. Considerable changes in the spatial correlation pattern between dust and rainfall are noted under different representative concentration pathways; however, no noteworthy changes are recorded in their temporal relationship. Notable intermodel differences in the patterns of dust load and rainfall relationship over South Asia are possibly caused by variations in the dust emission schemes among the CMIP5 models as well as the parameterization of aerosol indirect effect in addition to the differences in the meteorology simulated by various models under identical forcing scenarios.

  9. Lake Nam Co (Tibet, China) - a suitable target for a deep drilling project as confirmed by a preliminary airgun seismic survey

    Science.gov (United States)

    Spiess, V.; Daut, G.; Wenau, S.; Gernhardt, F.; Wang, J.; Schwenk, T.; Haberzettl, T.; Zhu, L.; Maeusbacher, R.

    2014-12-01

    Lake Nam Co, located on the central Tibetan Plateau at the intersection of the Westerlies and the Indian Ocean Summer Monsoon, is well suited to study the monsoonal regime over different time scales. High-resolution and continuous sedimentary records from the Tibetan Plateau are still rare and only few reach back to the Last Glacial Maximum. For Nam Co, numerous multiproxy studies unravel the regional paleoclimate and paleoenvironmental history for the past 24,000 years. These promising results demonstrate the potential of Lake Nam Co as a geoarchive, but nature, thickness and geologic time of the sediment fill have not yet been determined. Therefore the Institute of Tibetan Plateau Research (Chinese Academy of Sciences) and the Universities of Bremen and Jena jointly carried out an airgun multichannel seismic survey at Nam Co in June/July 2014. As main equipment, a micro GI Gun(2 x 0.1 L) was used in conjunction with a 64 m long seismic streamer (32 channels/2 m spacing) to achieve deep signal penetration, to confirm a thick sediment infill and to prove the suitability for deep coring of several hundred meters. Although only few lines could be shot due to technical and weather issues, several lines particularly from the deepest part of the lake provide new insight. Preliminary data processing and interpretation reveal a well layered sediment cover of >700 m in the center of the lake. Seismic facies appears to vary in a cyclic manner, indicating a coupling to climatically-driven changes in lake level and sediment delivery. From a comparison with the Holocene/Late Glacial sedimentary and seismic record, several similar units could be imaged. Furthermore, rapid sedimentation is confirmed from the continuous cover of growth faults and doming, and continuous sedimentation throughout glacial/interglacial cycles appears likely due to the absence of erosional unconformities. By tentatively assigning these units to marine isotope stages, different seismostratigraphies can

  10. Aerosol meteorology of the Maritime Continent for the 2012 7SEAS southwest monsoon intensive study - Part 1: regional-scale phenomena

    Science.gov (United States)

    Reid, Jeffrey S.; Xian, Peng; Holben, Brent N.; Hyer, Edward J.; Reid, Elizabeth A.; Salinas, Santo V.; Zhang, Jianglong; Campbell, James R.; Chew, Boon Ning; Holz, Robert E.; Kuciauskas, Arunas P.; Lagrosas, Nofel; Posselt, Derek J.; Sampson, Charles R.; Walker, Annette L.; Welton, E. Judd; Zhang, Chidong

    2016-11-01

    The largest 7 Southeast Asian Studies (7SEAS) operation period within the Maritime Continent (MC) occurred in the August-September 2012 biomass burning season. Included was an enhanced deployment of Aerosol Robotic Network (AERONET) sun photometers, multiple lidars, and field measurements to observe transported smoke and pollution as it left the MC and entered the southwest monsoon trough. Here we describe the nature of the overall 2012 southwest monsoon (SWM) and biomass burning season to give context to the 2012 deployment. The MC in 2012 was in a slightly warm El Niño/Southern Oscillation (ENSO) phase and with spatially typical burning activity. However, overall fire counts for 2012 were 10 % lower than the Reid et al. (2012) baseline, with regions of significant departures from this norm, ranging from southern Sumatra (+30 %) to southern Kalimantan (-42 %). Fire activity and monsoonal flows for the dominant burning regions were modulated by a series of intraseasonal oscillation events (e.g., Madden-Julian Oscillation, or MJO, and boreal summer intraseasonal oscillation, or BSISO). As is typical, fire activity systematically progressed eastward over time, starting with central Sumatran fire activity in June related to a moderately strong MJO event which brought drier air from the Indian Ocean aloft and enhanced monsoonal flow. Further burning in Sumatra and Kalimantan Borneo occurred in a series of significant events from early August to a peak in the first week of October, ending when the monsoon started to migrate back to its wintertime northeastern flow conditions in mid-October. Significant monsoonal enhancements and flow reversals collinear with tropical cyclone (TC) activity and easterly waves were also observed. Islands of the eastern MC, including Sulawesi, Java, and Timor, showed less sensitivity to monsoonal variation, with slowly increasing fire activity that also peaked in early October but lingered into November. Interestingly, even though fire

  11. The Impact of the Atlantic Cold Tongue on West African Monsoon Onset in Regional Model Simulations for 1998-2002

    Science.gov (United States)

    Druyan, Leonard M.; Fulakeza, Matthew B.

    2014-01-01

    The Atlantic cold tongue (ACT) develops during spring and early summer near the Equator in the Eastern Atlantic Ocean and Gulf of Guinea. The hypothesis that the ACT accelerates the timing of West African monsoon (WAM) onset is tested by comparing two regional climate model (RM3) simulation ensembles. Observed sea surface temperatures (SST) that include the ACT are used to force a control ensemble. An idealized, warm SST perturbation is designed to represent lower boundary forcing without the ACT for the experiment ensemble. Summer simulations forced by observed SST and reanalysis boundary conditions for each of five consecutive years are compared to five parallel runs forced by SST with the warm perturbation. The article summarizes the sequence of events leading to the onset of the WAM in the Sahel region. The representation of WAM onset in RM3 simulations is examined and compared to Tropical Rainfall Measuring Mission (TRMM), Global Precipitation Climatology Project (GPCP) and reanalysis data. The study evaluates the sensitivity of WAM onset indicators to the presence of the ACT by analysing the differences between the two simulation ensembles. Results show that the timing of major rainfall events and therefore theWAM onset in the Sahel are not sensitive to the presence of the ACT. However, the warm SST perturbation does increase downstream rainfall rates over West Africa as a consequence of enhanced specific humidity and enhanced northward moisture flux in the lower troposphere.

  12. Application of regional climate models to the Indian winter monsoon over the western Himalayas.

    Science.gov (United States)

    Dimri, A P; Yasunari, T; Wiltshire, A; Kumar, P; Mathison, C; Ridley, J; Jacob, D

    2013-12-01

    The Himalayan region is characterized by pronounced topographic heterogeneity and land use variability from west to east, with a large variation in regional climate patterns. Over the western part of the region, almost one-third of the annual precipitation is received in winter during cyclonic storms embedded in westerlies, known locally as the western disturbance. In the present paper, the regional winter climate over the western Himalayas is analyzed from simulations produced by two regional climate models (RCMs) forced with large-scale fields from ERA-Interim. The analysis was conducted by the composition of contrasting (wet and dry) winter precipitation years. The findings showed that RCMs could simulate the regional climate of the western Himalayas and represent the atmospheric circulation during extreme precipitation years in accordance with observations. The results suggest the important role of topography in moisture fluxes, transport and vertical flows. Dynamical downscaling with RCMs represented regional climates at the mountain or even event scale. However, uncertainties of precipitation scale and liquid-solid precipitation ratios within RCMs are still large for the purposes of hydrological and glaciological studies. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Land-sea correlations in the Australian region: post-glacial onset of the monsoon in northwestern Western Australia

    Science.gov (United States)

    De Deckker, Patrick; Barrows, Timothy T.; Rogers, John

    2014-12-01

    Deep-sea core Fr10/95-GC17, collected offshore North West Cape at the western tip of Western Australia, is located beneath the path of the Leeuwin Current. This shallow, warm and low salinity current is an offshoot of the Indonesian Throughflow that transfers water and heat from the West Pacific Ocean into the Indian Ocean. The location is at the edge of the Indo Pacific Warm Pool, the source of large-scale transfer of moisture and heat from the ocean to the atmosphere. For this core, we combine previously published data with new research and use a revised chronology to re-examine the timing of climate change during the last 34,000 years in the tropics of northern Australia. The age model for the core is based on 15 radiocarbon dates complemented by luminescence ages and an oxygen isotope record. This study draws on an extensive range of analyses that have been performed on the core, including micropalaeontology of planktic and benthic foraminifera and coccoliths, stable isotopes analysis of foraminifera and their faunal composition, clay content, sediment composition and pollen analyses. Sea-surface and land temperatures are estimated from the foraminifer faunal analyses and from pollen spectra, respectively. The clay fraction and sediment composition and radiogenic isotopes of that fraction helped identify changes both on land and at sea: changes such as rainfall as shown by river discharge, and oceanic current tracing by neodymium, strontium and lead isotopes obtained from sediments. The most significant finding is that a major threshold was crossed at 13 ka BP. Prior to that time, rainfall over NW Western Australia was low as was sea-surface temperature (SST); river discharge to the ocean was also low as a result of the lack of monsoonal activity and finally, ocean alkalinity would have been lower than at present due to the uptake of atmospheric CO2. By 13 ka BP, the entire system moved away from glacial period conditions. The Indo-Australian monsoon commenced

  14. Climatic Changes and Evaluation of Their Effects on Agriculture in Asian Monsoon Region- A project of GRENE-ei programs in Japan

    Science.gov (United States)

    Mizoguchi, M.; Matsumoto, J.; Takahashi, H. G.; Tanaka, K.; Kuwagata, T.

    2015-12-01

    It is important to predict climate change correctly in regional scale and to build adaptation measures and mitigation measures in the Asian monsoon region where more than 60 % of the world's population are living. The reliability of climate change prediction model is evaluated by the reproducibility of past climate in general. However, because there are many developing countries in the Asian monsoon region, adequate documentations of past climate which are needed to evaluate the climate reproducibility have not been prepared. In addition, at present it is difficult to get information on wide-area agricultural meteorological data which affect the growth of agricultural crops when considering the impact on agriculture of climate. Therefore, we have started a research project entitled "Climatic changes and evaluation of their effects on agriculture in Asian monsoon region (CAAM)" under the research framework of the Green Network of Excellence (GRENE) for the Japanese fiscal years from 2011 to 2015 supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT). This project aims to improve the reliability of future climate prediction and to develop the information platform which will be useful to design adaptation and mitigation strategies in agriculture against the predicted climatic changes in Asian monsoon regions. What is GRENE?Based on the new growth strategy which was approved by the Cabinet of Japan in June 2010, Green Network of Excellence program (GRENE) has started under MEXT from FY 2011. The objectives of this program are that the domestic leading universities work together strategically and promote a comprehensive human resource development and research of the highest level in the world while sharing research resources and research goals. In the field of environmental information, it is required that universities and research institutions, which are working on issues such as adaptation to climate change, cooperate to

  15. Neutrophil activator of matrix metalloproteinase-2 (NAM).

    Science.gov (United States)

    Rollo, Ellen E; Hymowitz, Michelle; Schmidt, Cathleen E; Montana, Steve; Foda, Hussein; Zucker, Stanley

    2006-01-01

    We have isolated a novel soluble factor(s), neutrophil activator of matrix metalloproteinases (NAM), secreted by unstimulated normal human peripheral blood neutrophils that causes the activation of cell secreted promatrix metalloproteinase-2 (proMMP-2). Partially purified preparations of NAM have been isolated from the conditioned media of neutrophils employing gelatin-Sepharose chromatography and differential membrane filter centrifugation. NAM activity, as assessed by exposing primary human umbilical vein endothelial cells (HUVEC) or HT1080 cells to NAM followed by gelatin zymography, was seen within one hour. Tissue inhibitor of metalloproteinase-2 (TIMP-2) and hydroxamic acid derived inhibitors of MMPs (CT1746 and BB94) abrogated the activation of proMMP-2 by NAM, while inhibitors of serine and cysteine proteases showed no effect. NAM also produced an increase in TIMP-2 binding to HUVEC and HT1080 cell surfaces that was inhibited by TIMP-2, CT1746, and BB94. Time-dependent increases in MT1-MMP protein and mRNA were seen following the addition of NAM to cells. These data support a role for NAM in cancer dissemination.

  16. ANAM vs. NAM: Is the difference significant?

    NARCIS (Netherlands)

    Hammel, S.; Eijk, A.M.J. van; Tsintikidis, D.

    2004-01-01

    The Navy Aerosol Model (NAM, available in MODTRAN) is widely used as a tool to assess the aerosol extinction in the marine atmospheric surface layer. NAM was built as a regression model in the 1980s to represent the aerosol extinction at deck height as a function of the meteorological conditions. Th

  17. Vertical structure of cumulonimbus towers and intense convective clouds over the South Asian region during the summer monsoon season

    Science.gov (United States)

    Bhat, G. S.; Kumar, Shailendra

    2015-03-01

    The vertical structure of radar reflectivity factor in active convective clouds that form during the South Asian monsoon season is reported using the 2A25 version 6 data product derived from the precipitation radar measurements on board the Tropical Rainfall Measuring Mission satellite. We define two types of convective cells, namely, cumulonimbus towers (CbTs) and intense convective cells (ICCs). CbT is defined referring to a reflectivity threshold of 20 dBZ at 12 km altitude and is at least 9 km thick. ICCs are constructed referring to reflectivity thresholds at 8 km and 3 km altitudes. Cloud properties reported here are based on 10 year climatology. It is observed that the frequency of occurrence of CbTs is highest over the foothills of Himalayas, plains of northern India and Bangladesh, and minimum over the Arabian Sea and equatorial Indian Ocean west of 90°E. The regional differences depend on the reference height selected, namely, small in the case of CbTs and prominent in 6-13 km height range for ICCs. Land cells are more intense than the oceanic ones for convective cells defined using the reflectivity threshold at 3 km, whereas land versus ocean contrasts are not observed in the case of CbTs. Compared to cumulonimbus clouds elsewhere in the tropics, the South Asian counterparts have higher reflectivity values above 11 km altitude.

  18. The Arabian Sea as a high-nutrient, low-chlorophyll region during the late Southwest Monsoon

    Directory of Open Access Journals (Sweden)

    S. W. A. Naqvi

    2010-01-01

    Full Text Available Extensive observations during the late Southwest Monsoon of 2004 over the Indian and Omani shelves, and along an east-west transect reveal a mosaic of biogeochemical provinces including an unexpected high-nutrient, low-chlorophyll condition off the southern Omani coast. This feature, coupled with other characteristics of the system, suggest a close similarity between the Omani upwelling system and the Peruvian and California upwelling systems, where primary production (PP is limited by iron. An intensification of upwelling, reported to have been caused by the decline in the winter/spring Eurasian snow cover since 1997, is not supported by in situ hydrographic and chlorophyll measurements as well as a reanalysis of ocean colour data extending to 2009. Iron limitation of PP may complicate simple relationship between upwelling and PP assumed by previous workers, and contribute to the anomalous offshore occurrence of the most severe oxygen (O2 depletion in the region. Over the Indian shelf, affected by very shallow O2-deficient zone, high PP is restricted to a thin, oxygenated surface layer probably due to unsuitability of the O2-depleted environment for the growth of oxygenic photosynthesizers.

  19. Assessment of Seasonal Energy Efficiency Strategies of a Double Skin Façade in a Monsoon Climate Region

    Directory of Open Access Journals (Sweden)

    Choongwan Koo

    2013-08-01

    Full Text Available As climate change and global warming have become two of the most significant environmental issues today, the double-skin façade (DSF is getting considerable attention as an energy-efficient passive design. This study is aimed at assessing the seasonal energy efficiency strategies of a DSF targeting library facilities in the climate region with hot summers and cold winters. Toward this end, this study was conducted in four steps: (i establishment of seasonal energy-efficient strategies; (ii application of seasonal energy-efficient strategies; (iii analysis of energy saving effect by season; and (iv life cycle cost and life cycle CO2 analyses for selecting an optimal DSF. Results show that a shaft box DSF energy model (EMS #2, which applied winter strategies, was optimal with an energy saving rate of 4.13%, while a multi-story DSF energy model (EMM #5, which applied summer strategies, was optimal with an energy saving rate of 12.67%. In terms of savings to investment ratio (SIR40 and breakeven point (BEP40, the multi-story DSF (3.20; 9 years was superior. The results of this study can be used for (i seasonal energy efficiency strategies of a DSF in East Asian monsoon climates, and (ii as a guideline for the application of a DSF both in existing and new buildings.

  20. Distribution features of stable oxygen isotopes in the typical monsoon temperate-glacier region, Mountain Yulong in China

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    During the summers of 1999 and 2000, sampling was carried out in Mt.Yulong, for the investigation of the spatial distribution of oxygen stable isotope in the atmospheric-glacial-hydro system and similar results obtained in the two years have confirmed our conclusion. There is an evident negative correlation between stable isotopic composition and air temperature-precipitation amount, suggesting that there exits a strong “precipitation amount effect” in this typical monsoon temperate-glacier region. There are marked differences between the δ1'O values in winter-accumulated snow, glacial meltwater, summer precipitation and glacier-feeding stream. Under the control of varied climatic conditions, spatial and temporal variations of above glacialhydro mediums are apparent. Isotopic depletion or fractionation and ionic changes had occurred during the phase-change and transformation processes of snow-ice, icemeltwater, flowing of runoff and contact with bedrock. The variation of stable isotope in a runoff can reflect not only its own flowing process but also its different feeding sources.

  1. Attribution of aerosol radiative forcing over India during the winter monsoon to emissions from source categories and geographical regions

    Science.gov (United States)

    Verma, S.; Venkataraman, C.; Boucher, O.

    2011-08-01

    We examine the aerosol radiative effects due to aerosols emitted from different emission sectors (anthropogenic and natural) and originating from different geographical regions within and outside India during the northeast (NE) Indian winter monsoon (January-March). These studies are carried out through aerosol transport simulations in the general circulation (GCM) model of the Laboratoire de Météorologie Dynamique (LMD). The model estimates of aerosol single scattering albedo (SSA) show lower values (0.86-0.92) over the region north to 10°N comprising of the Indian subcontinent, Bay of Bengal, and parts of the Arabian Sea compared to the region south to 10°N where the estimated SSA values lie in the range 0.94-0.98. The model estimated SSA is consistent with the SSA values inferred through measurements on various platforms. Aerosols of anthropogenic origin reduce the incoming solar radiation at the surface by a factor of 10-20 times the reduction due to natural aerosols. At the top-of-atmosphere (TOA), aerosols from biofuel use cause positive forcing compared to the negative forcing from fossil fuel and natural sources in correspondence with the distribution of SSA which is estimated to be the lowest (0.7-0.78) from biofuel combustion emissions. Aerosols originating from India and Africa-west Asia lead to the reduction in surface radiation (-3 to -8 W m -2) by 40-60% of the total reduction in surface radiation due to all aerosols over the Indian subcontinent and adjoining ocean. Aerosols originating from India and Africa-west Asia also lead to positive radiative effects at TOA over the Arabian Sea, central India (CNI), with the highest positive radiative effects over the Bay of Bengal and cause either negative or positive effects over the Indo-Gangetic plain (IGP).

  2. Glacier Sensitivity in the Monsoonal Himalayas: Relative Contributions of Feedback Mechanisms to Regional Glacier Mass Balance

    Science.gov (United States)

    Johnson, E. S.; Rupper, S.

    2016-12-01

    Despite their societal relevance, glacier mass balances across High Mountain Asia (HMA) remain poorly constrained due, in part, to the limited number of direct measurements, regional climate heterogeneity, and uncertainty in glacier mass balance models. Many studies that model glaciers throughout HMA cite surface feedbacks as an important factor affecting glacier melt, however, little has been done to actually quantify their effects. This study develops a fully distributed surface energy- and mass-balance model to quantify the contributions of 3 surface feedbacks to glacier mass balance. The 3 target feedbacks are an accumulation/snow depth feedback, a sensible heat feedback, and an albedo feedback. The model follows well-known energy balance methods, but includes unique "switches" which allow individual feedbacks to be independently turned on and off. The model applies meteorological inputs from the High Asia Refined analysis to an idealized glacier for 4 different climate settings in HMA. The results show that surface feedbacks increase melt by up to 67% for a +1°C temperature forcing, but that feedback contributions vary significantly under different climate settings. For any given glacier, the feedback strength is highest near the equilibrium line altitude. Furthermore, feedbacks that directly reduce surface albedo consistently contribute the most to glacier mass loss. Feedback magnitude depends most strongly on the frequency of snowfall events occurring concurrently with the melt season, and on the magnitude of incoming shortwave radiation for that region. These results highlight the potential significance of feedbacks on glacier mass balance in HMA, what conditions maximize these feedback magnitudes, and what regions are likely most sensitive to them. They also highlight physical processes that need to be especially well constrained in future glacier mass balance models for glaciers in regions with high feedback sensitivity. Creating glacier mass balance

  3. Monsoon Country

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Heavy rains have battered areas of south China this year,causing death and destruction For most areas south of the Yangtze River,this year’s monsoon season has come early, with heavy rains triggering floods,damaging crops,threatening reservoirs and causing deaths.

  4. Summer monsoon rainfall variability over North East regions of India and its association with Eurasian snow, Atlantic Sea Surface temperature and Arctic Oscillation

    Science.gov (United States)

    Prabhu, Amita; Oh, Jaiho; Kim, In-won; Kripalani, R. H.; Mitra, A. K.; Pandithurai, G.

    2016-11-01

    This observational study during the 29-year period from 1979 to 2007 evaluates the potential role of Eurasian snow in modulating the North East-Indian Summer Monsoon Rainfall with a lead time of almost 6 months. This link is manifested by the changes in high-latitude atmospheric winter snow variability over Eurasia associated with Arctic Oscillation (AO). Excessive wintertime Eurasian snow leads to an anomalous cooling of the overlying atmosphere and is associated with the negative mode of AO, inducing a meridional wave-train descending over the tropical north Atlantic and is associated with cooling of this region. Once the cold anomalies are established over the tropical Atlantic, it persists up to the following summer leading to an anomalous zonal wave-train further inducing a descending branch over NE-India resulting in weak summer monsoon rainfall.

  5. Influence of southern oscillation and SSTs over Nino-3.4 region on the winter monsoon rainfall over coastal Andhra Pradesh

    Indian Academy of Sciences (India)

    O S R U Bhanu Kumar; C V Naidu; S R L Rao

    2004-09-01

    An analysis of the mean monthly data of 124 years reveals that the relationship between the Southern Oscillation Index in September and the winter monsoon rainfall (WMR) over Coastal Andhra Pradesh (CAP) is variable and non-stationary. In the recent four decades, however, SOI (Sept) is negatively and significantly correlated with CAP WMR. A similar analysis is performed using 50 years of mean monthly SSTs over Nino-3.4 region in August and September and CAP WMR to detect a possible relationship and there is a striking positive relation between them. In both of the above cases, the September signal is more significant in the recent four decades than for the other months and seasons for probable prediction of CAP WMR. Finally, to examine the influence of SO on the winter monsoon rainfall, a non-parametric test "Mann-Whitney Rank Statistics" test has been applied to the rainfall associated with extreme positive and negative SOI events.

  6. The Arabian Sea as a high-nutrient, low-chlorophyll region during the late Southwest Monsoon

    Science.gov (United States)

    Naqvi, S. W. A.; Moffett, J. W.; Gauns, M. U.; Narvekar, P. V.; Pratihary, A. K.; Naik, H.; Shenoy, D. M.; Jayakumar, D. A.; Goepfert, T. J.; Patra, P. K.; Al-Azri, A.; Ahmed, S. I.

    2010-07-01

    Extensive observations were made during the late Southwest Monsoon of 2004 over the Indian and Omani shelves, and along a transect that extended from the southern coast of Oman to the central west coast of India, tracking the southern leg of the US JGOFS expedition (1994-1995) in the west. The data are used, in conjunction with satellite-derived data, to investigate long-term trends in chlorophyll and sea surface temperature, indicators of upwelling intensity, and to understand factors that control primary production (PP) in the Arabian Sea, focussing on the role of iron. Our results do not support an intensification of upwelling in the western Arabian Sea, reported to have been caused by the decline in the winter/spring Eurasian snow cover since 1997. We also noticed, for the first time, an unexpected development of high-nutrient, low-chlorophyll condition off the southern Omani coast. This feature, coupled with other characteristics of the system, such as a narrow shelf and relatively low iron concentrations in surface waters, suggest a close similarity between the Omani upwelling system and the Peruvian and California upwelling systems, where PP is limited by iron. Iron limitation of PP may complicate simple relationship between upwelling and PP assumed by previous workers, and contribute to the anomalous offshore occurrence of the most severe oxygen (O2) depletion in the region. Over the much wider Indian shelf, which experiences large-scale bottom water O2-depletion in summer, adequate iron supply from reducing bottom-waters and sediments seems to support moderately high PP; however, such production is restricted to the thin, oxygenated surface layer, probably because of the unsuitability of the O2-depleted environment for the growth of oxygenic photosynthesizers.

  7. Contrasting sedimentation patterns in two semi-enclosed mesotidal bays along the west and south coasts of Korea controlled by their orientation to the regional monsoon climate

    Science.gov (United States)

    Hong, Seok Hwi; Chun, Seung Soo; Chang, Tae Soo; Jang, Dae Geon

    2017-08-01

    Sedimentation patterns of tidal flats along the Korean west coast have long been known to be largely controlled by the monsoon climate. On the other hand, much less is known about the effect of the monsoon on sedimentation in coastal embayments with mouths of different geographic orientations. Good examples are Hampyeong and Yeoja bays along the west and south coasts, respectively. Both have narrow entrances, but their mouths open toward the northwest and the south, respectively. With mean tidal ranges of 3.46 and 3.2 m, respectively, the two bays experience similar tidal regimes and are hence excellent candidates to compare the effect of different exposure to the same regional monsoon climate on their respective sediment distribution patterns. The winter monsoon, in particular, is characterized by strong northwesterly winds that directly impact the west coast, but blow offshore along the south coast. For the purpose of this study, surficial sediment samples were collected from intertidal and subtidal flats of the two bays, both in summer and winter. Grain-size analyses were carried out by sieving (sand fraction) and Sedigraph (mud fraction). In the case of Yeoja Bay, the sediments consist mostly of mud (mean grain sizes of 5.4 to 8.8 phi). Seasonal changes are very subtle, the sediments being slightly coarser in summer when silt-dominated sediments are supplied by two streams to the northern parts of the bay in response to heavy rainfall. With the exception of the deeper tidal channels, Yeoja Bay is characterized by a thick mud blanket the year round, which is modulated by processes associated with the summer monsoon that predominantly blows from the east. Textural parameters suggest severely restricted sediment mixing on the subtidal and intertidal flats, the overall low energy situation preventing sands from reaching the tidal flats. The sediments of Hampyeong Bay, by contrast, are characterized by a distinct shoreward fining trend. Mean grain sizes average

  8. Contrasting sedimentation patterns in two semi-enclosed mesotidal bays along the west and south coasts of Korea controlled by their orientation to the regional monsoon climate

    Science.gov (United States)

    Hong, Seok Hwi; Chun, Seung Soo; Chang, Tae Soo; Jang, Dae Geon

    2016-11-01

    Sedimentation patterns of tidal flats along the Korean west coast have long been known to be largely controlled by the monsoon climate. On the other hand, much less is known about the effect of the monsoon on sedimentation in coastal embayments with mouths of different geographic orientations. Good examples are Hampyeong and Yeoja bays along the west and south coasts, respectively. Both have narrow entrances, but their mouths open toward the northwest and the south, respectively. With mean tidal ranges of 3.46 and 3.2 m, respectively, the two bays experience similar tidal regimes and are hence excellent candidates to compare the effect of different exposure to the same regional monsoon climate on their respective sediment distribution patterns. The winter monsoon, in particular, is characterized by strong northwesterly winds that directly impact the west coast, but blow offshore along the south coast. For the purpose of this study, surficial sediment samples were collected from intertidal and subtidal flats of the two bays, both in summer and winter. Grain-size analyses were carried out by sieving (sand fraction) and Sedigraph (mud fraction). In the case of Yeoja Bay, the sediments consist mostly of mud (mean grain sizes of 5.4 to 8.8 phi). Seasonal changes are very subtle, the sediments being slightly coarser in summer when silt-dominated sediments are supplied by two streams to the northern parts of the bay in response to heavy rainfall. With the exception of the deeper tidal channels, Yeoja Bay is characterized by a thick mud blanket the year round, which is modulated by processes associated with the summer monsoon that predominantly blows from the east. Textural parameters suggest severely restricted sediment mixing on the subtidal and intertidal flats, the overall low energy situation preventing sands from reaching the tidal flats. The sediments of Hampyeong Bay, by contrast, are characterized by a distinct shoreward fining trend. Mean grain sizes average

  9. Nam June Paik / Nam June Paik ; interv. Tilman Baumgärtel

    Index Scriptorium Estoniae

    Paik, Nam June

    2006-01-01

    Korea-ameerika kunstnikust Nam June Paikist (sünd. 1932), telefoniintervjuu kunstnikuga tema talvekodus Floridas 20.01.2001. Nam June Paiki töödest "Participation TV" (1963), "Video Synthesizer" (1969/70),sateliidiperformance'itest "Good Morning, Mr. Orwell!" (1980), "Bye Bye, Kipling" (1987) ja "Wrap around the World" (1988), näitusest "Electronic Superhighway" (1994) jm. Nam June Paik ka Internetist, Interneti-kunstist, töötamisest laseriga

  10. Nam June Paik / Nam June Paik ; interv. Tilman Baumgärtel

    Index Scriptorium Estoniae

    Paik, Nam June

    2006-01-01

    Korea-ameerika kunstnikust Nam June Paikist (sünd. 1932), telefoniintervjuu kunstnikuga tema talvekodus Floridas 20.01.2001. Nam June Paiki töödest "Participation TV" (1963), "Video Synthesizer" (1969/70),sateliidiperformance'itest "Good Morning, Mr. Orwell!" (1980), "Bye Bye, Kipling" (1987) ja "Wrap around the World" (1988), näitusest "Electronic Superhighway" (1994) jm. Nam June Paik ka Internetist, Interneti-kunstist, töötamisest laseriga

  11. The response of future projections of the North American monsoon when combining dynamical downscaling and bias correction of CCSM4 output

    Science.gov (United States)

    Meyer, Jonathan D. D.; Jin, Jiming

    2016-09-01

    A 20-km regional climate model (RCM) dynamically downscaled the Community Climate System Model version 4 (CCSM4) to compare 32-year historical and future "end-of-the-century" climatologies of the North American Monsoon (NAM). CCSM4 and other phase 5 Coupled Model Intercomparison Project models have indicated a delayed NAM and overall general drying trend. Here, we test the suggested mechanism for this drier NAM where increasing atmospheric static stability and reduced early-season evapotranspiration under global warming will limit early-season convection and compress the mature-season of the NAM. Through our higher resolution RCM, we found the role of accelerated evaporation under a warmer climate is likely understated in coarse resolution models such as CCSM4. Improving the representation of mesoscale interactions associated with the Gulf of California and surrounding topography produced additional surface evaporation, which overwhelmed the convection-suppressing effects of a warmer troposphere. Furthermore, the improved land-sea temperature gradient helped drive stronger southerly winds and greater moisture transport. Finally, we addressed limitations from inherent CCSM4 biases through a form of mean bias correction, which resulted in a more accurate seasonality of the atmospheric thermodynamic profile. After bias correction, greater surface evaporation from average peak GoC SSTs of 32 °C compared to 29 °C from the original CCSM4 led to roughly 50 % larger changes to low-level moist static energy compared to that produced by the downscaled original CCSM4. The increasing destabilization of the NAM environment produced onset dates that were one to 2 weeks earlier in the core of the NAM and northern extent, respectively. Furthermore, a significantly more vigorous NAM signal was produced after bias correction, with >50 mm month-1 increases to the June-September precipitation found along east and west coasts of Mexico and into parts of Texas. A shift towards more

  12. Variability of the TRMM-PR total and convective and stratiform rain fractions over the Indian region during the summer monsoon

    Science.gov (United States)

    Pokhrel, Samir; Sikka, D. R.

    2013-07-01

    Level 3 (3A25) TRMM Precipitation Radar (PR) data are used for 13 years period (1998-2010) to prepare climatology of TRMM PR derived near surface rain (Total rain) and rain fractions for the 4-months duration of Indian Summer Monsoon season (June-September) as well as for individual months. It is found that the total rain is contributed mostly (99 %) by two rain fractions i.e. stratiform and convective rain fractions for the season as well as on the monthly basis. It is also found that total rain estimates by PR are about 65 % of the gauge measured rain over continental India as well as on sub-regional basis. Inter-annual variability of TRMM-PR rain estimates for India mainland and its sub-regions as well as over the neighboring oceanic regions, in terms of coefficient of variability (CV) is discussed. The heaviest rain region over north Bay of Bengal (BoB) is found to have the lowest CV. Another sub-region of low CV lies over the eastern equatorial Indian ocean (EEIO). The CVs of total rain as well as its two major constituents are found to be higher on monthly basis compared to seasonal basis. Existence of a well known dipole between the EEIO and the north BoB is well recognized in PR data also. Significant variation in PR rainfall is found over continental India between excess and deficit monsoon seasons as well as between excess and deficit rainfall months of July and August. Examination of rainfall fractions between the BoB and Central India on year to year basis shows that compensation in rainfall fractions exists on monthly scale on both the regions. Also on the seasonal and monthly scales, compensation is observed in extreme monsoon seasons between the two regions. However, much less compensation is observed between the north BoB and EEIO belts in extreme rain months. This leads to speculation that the deficit and excess seasons over India may result from slight shift of the rainfall from Central India to the neighboring oceanic regions of north Bo

  13. The impacts of summer monsoons on the ozone budget of the atmospheric boundary layer of the Asia-Pacific region.

    Science.gov (United States)

    Hou, Xuewei; Zhu, Bin; Fei, Dongdong; Wang, Dongdong

    2015-01-01

    The seasonal and inter-annual variations of ozone (O3) in the atmospheric boundary layer of the Asia-Pacific Ocean were investigated using model simulations (2001-2007) from the Model of Ozone and Related chemical Tracers, version 4 (MOZART-4). The simulated O3 and diagnostic precipitation are in good agreement with the observations. Model results suggest that the Asia-Pacific monsoon significantly influences the seasonal and inter-annual variations of ozone. The differences of anthropogenic emissions and zonal winds in meridional directions cause a pollutants' transition zone at approximately 20°-30°N. The onset of summer monsoons with a northward migration of the rain belt leads the transition zone to drift north, eventually causing a summer minimum of ozone to the north of 30°N. In years with an early onset of summer monsoons, strong inflows of clean oceanic air lead to low ozone at polluted oceanic sites near the continent, while strong outflows from the continent exist, resulting in high levels of O3 over remote portions of the Asia-Pacific Ocean. The reverse is true in years when the summer monsoon onset is late.

  14. Influence of Indian summer monsoon variability on the surface waves in the coastal regions of eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    SanilKumar, V.; Jesbin, G.

    >) of June was lowest (~1.5m) in 2009. The spectral peak shifted to lower frequencies in September due to the reduction of wind seas as a result of decrease in monsoon intensity. The study shows high positive correlation (r~0.84) between average low-level jet...

  15. Plankton food web and its seasonal dynamics in a large monsoonal estuary (Cochin backwaters, India)-significance of mesohaline region

    Digital Repository Service at National Institute of Oceanography (India)

    Sooria, P.M.; Jyothibabu, R.; Anjusha, A; Vineetha, G.; Vinita, J.; Lallu, K.R.; Paul, M.; Jagadeesan, L.

    The paper presents the ecology and dynamics of plankton food web in the Cochin backwaters (CBW), the largest monsoonal estuary along the west coast of India. The data source is a time series measurement carried out in the CBW during the Spring...

  16. The transfer of seasonal isotopic variability between precipitation and drip water at eight caves in the monsoon regions of China

    Science.gov (United States)

    Duan, Wuhui; Ruan, Jiaoyang; Luo, Weijun; Li, Tingyong; Tian, Lijun; Zeng, Guangneng; Zhang, Dezhong; Bai, Yijun; Li, Jilong; Tao, Tao; Zhang, Pingzhong; Baker, Andy; Tan, Ming

    2016-06-01

    This study presents new stable isotope data for precipitation (δ18Op) and drip water (δ18Od) from eight cave sites in the monsoon regions of China (MRC), with monthly to bi-monthly sampling intervals from May-2011 to April-2014, to investigate the regional-scale climate forcing on δ18Op and how the isotopic signals are transmitted to various drip sites. The monthly δ18Op values show negative correlation with surface air temperature at all the cave sites except Shihua Cave, which is opposite to that expected from the temperature effect. In addition, although the monthly δ18Op values are negatively correlated with precipitation at all the cave sites, only three sites are significant at the 95% level. These indicate that, due to the various vapor sources, a large portion of variability in δ18Op in the MRC cannot be explained simply by either temperature or precipitation alone. All the thirty-four drip sites are classified into three types based on the δ18Od variability. About 82% of them are static drips with little discernable variation in δ18Od through the whole study period, but the drip rates of these drips are not necessary constant. Their discharge modes are site-specific and the oxygen isotopic composition of the stalagmites growing from them may record the average of multi-year climatic signals, which are modulated by the seasonality of recharge and potential effects of evaporation, and in some cases infiltration from large rainfall events. About 12% of the thirty-four drip sites are seasonal drips, although the amplitude of δ18Od is narrower than that of δ18Op, the monthly response of δ18Od to coeval precipitation is not completely damped, and some of them follow the seasonal trend of δ18Op very well. These drips may be mainly recharged by present-day precipitation, mixing with some stored water. Thus, the stalagmites growing under them may record portions of the seasonal climatic signals embedded in δ18Op. About 6% of the thirty-four drip sites

  17. SUNYA Regional Climate Model Simulations of East Asia Summer Monsoon: Effects of Cloud Vertical Structure on the Surface Energy Balance

    Directory of Open Access Journals (Sweden)

    Wei Gong and Wei-Chyung Wang

    2007-01-01

    Full Text Available We used the State University of New York at Albany (SUNYA regional climate model to study the effect of cloud vertical distribution in affecting the surface energy balance of the East Asia summer monsoon (EASM. Simulations were conducted for the summers of 1988 and 1989, during which large contrast in the intra-seasonal cloud radiative forcing (CRF was observed at the top of the atmosphere. The model results indicate that both the high and low clouds are persistent throughout the summer months in both years. Because of large cloud water, low clouds significantly reduce the solar radiation flux reaching the surface, which nevertheless still dominate the surface energy balance, accounting for more than 50% of the surface heating. The low clouds also contribute significantly the downward longwave radiation to the surface with values strongly dependent on the cloud base temperature. The presence of low clouds effectively decreases the temperature and moisture gradients near surface, resulting in a substantial decrease in the sensible and latent heat fluxes from surface, which partially compensate the decrease of the net radiative cooling of the surface. For example, in the two days, May 8 and July 11 of 1988, the total cloud cover of 80% is simulated, but the respective low cloud cover (water was 63% (114 gm-2 and 22% (21 gm-2. As a result, the downward solar radiation is smaller by 161 Wm-2 in May 8. On the other hand, the cloud temperature was _ lower, yielding 56 Wm-2 smaller downward longwave radiation. The near surface temperature and gradient is more than _ smaller (and moisture gradient, leading to 21 and 81 Wm-2 smaller sensible heat and latent heat fluxes. It is also demonstrated that the model is capable to reproduce the intraseasonal variation of shortwave CRF, and catches the relationship between total cloud cover and SW CRF. The model results show the dominance of high cloud on the regional mean longwave CRF and low cloud on the intra

  18. Phylogeography of recently emerged DENV-2 in southern Viet Nam.

    Directory of Open Access Journals (Sweden)

    Maia A Rabaa

    Full Text Available Revealing the dispersal of dengue viruses (DENV in time and space is central to understanding their epidemiology. However, the processes that shape DENV transmission patterns at the scale of local populations are not well understood, particularly the impact of such factors as human population movement and urbanization. Herein, we investigated trends in the spatial dynamics of DENV-2 transmission in the highly endemic setting of southern Viet Nam. Through a phylogeographic analysis of 168 full-length DENV-2 genome sequences obtained from hospitalized dengue cases from 10 provinces in southern Viet Nam, we reveal substantial genetic diversity in both urban and rural areas, with multiple lineages identified in individual provinces within a single season, and indicative of frequent viral migration among communities. Focusing on the recently introduced Asian I genotype, we observed particularly high rates of viral exchange between adjacent geographic areas, and between Ho Chi Minh City, the primary urban center of this region, and populations across southern Viet Nam. Within Ho Chi Minh City, patterns of DENV movement appear consistent with a gravity model of virus dispersal, with viruses traveling across a gradient of population density. Overall, our analysis suggests that Ho Chi Minh City may act as a source population for the dispersal of DENV across southern Viet Nam, and provides further evidence that urban areas of Southeast Asia play a primary role in DENV transmission. However, these data also indicate that more rural areas are also capable of maintaining virus populations and hence fueling DENV evolution over multiple seasons.

  19. The Holocene history of the North American Monsoon: 'known knowns' and 'known unknowns' in understanding its spatial and temporal complexity

    Science.gov (United States)

    Metcalfe, Sarah E.; Barron, John A.; Davies, Sarah J.

    2015-01-01

    Evidence for climatic change across the North American Monsoon (NAM) and adjacent areas is reviewed, drawing on continental and marine records and the application of climate models. Patterns of change at 12,000, 9000, 6000 and 4000 cal yr BP are presented to capture the nature of change from the Younger Dryas (YD) and through the mid-Holocene. At the YD, conditions were cooler overall, wetter in the north and drier in the south, while moving into the Holocene wetter conditions became established in the south and then spread north as the NAM strengthened. Until c. 8000 cal yr BP, the Laurentide Ice Sheet influenced precipitation in the north by pushing the Bermuda High further south. The peak extent of the NAM seems to have occurred around 6000 cal yr BP. 4000 cal yr BP marks the start of important changes across the NAM region, with drying in the north and the establishment of the clear differences between the summer-rain dominated south and central areas and the north, where winter rain is more important. This differentiation between south and north is crucial to understanding many climate responses across the NAM. This increasing variability is coincident with the declining influence of orbital forcing. 4000 cal yr BP also marks the onset of significant anthropogenic activity in many areas. For the last 2000 years, the focus is on higher temporal resolution change, with strong variations across the region. The Medieval Climate Anomaly (MCA) is characterised by centennial scale ‘megadrought’ across the southwest USA, associated with cooler tropical Pacific SSTs and persistent La Niña type conditions. Proxy data from southern Mexico, Central America and the Caribbean reveal generally wetter conditions, whereas records from the highlands of central Mexico and much of the Yucatan are typified by long -term drought. The Little Ice Age (LIA), in the north, was characterised by cooler, wetter winter conditions that have been linked with increased

  20. A glacier inventory for the western Nyainqentanglha Range and the Nam Co Basin, Tibet, and glacier changes 1976–2009

    Directory of Open Access Journals (Sweden)

    T. Bolch

    2010-09-01

    Full Text Available The western Nyainqentanglha Range is located in the south-eastern centre of the Tibetan Plateau. Its north-western slopes drain into Lake Nam Co. The region is of special interest for glacio-climatological research as it is influenced by both the continental climate of Central Asia and the Indian Monsoon system, and situated at the transition zone between temperate and subcontinental glaciers. A glacier inventory for the whole mountain range was generated for the year around 2001 using automated remote sensing and GIS techniques based on Landsat ETM+ and SRTM3 DEM data. Glacier change analysis was based on data from Hexagon KH-9 and Landsat MSS (both 1976, Metric Camera (1984, and Landsat TM/ETM+ (1991, 2001, 2005, 2009. Manual adjustment was especially necessary for delineating the debris-covered glaciers and the glaciers on the panchromatic Hexagon data. In the years around 2001 the whole mountain range contained about 960 glaciers covering an area of 795.6 ± 22.3 km2 while the ice in the drainage basin of Nam Co covered 198.1 ± 5.6 km2. The median elevation of the glaciers was about 5800 m with the majority terminating around 5600 m. Five glaciers with debris-covered tongues terminated lower than 5200 m. The glacier area decreased by −6.1 ± 3% between 1976 and 2001. This is less than reported in previous studies based on the 1970s topographic maps and Landsat data from 2000. Glaciers continued to shrink during the period 2001–2009. No advancing glaciers were detected. Detailed length measurements for five glaciers indicated a retreat of around 10 m per year (1976–2009. Ice cover is higher south-east of the mountain ridge which reflects the windward direction to the monsoon. The temperature increase during the ablation period was probably the main driver of glacier wastage, but the complex glacier-climate interactions need further investigation.

  1. Statistical Downscaling for Multi-Model Ensemble Prediction of Summer Monsoon Rainfall in the Asia-Pacific Region Using Geopotential Height Field

    Institute of Scientific and Technical Information of China (English)

    ZHU Congwen; Chung-Kyu PARK; Woo-Sung LEE; Won-Tae YUN

    2008-01-01

    The 21-yr ensemble predictions of model precipitation and circulation in the East Asian and western North Pacific(Asia-Pacific)summer monsoon region(0°-50°N,100°-150°E)were evaluated in nine different AGCM,used in the Asia-Pacific Economic Cooperation Climate Center(APCCl multi.model ensemble seasonal prediction system.The analysis indicates that the precipitation anomaly patterns of model ensemble predictions are substantially difierent from the observed counterparts in this region.but the summer monsoon circulations are reasonably predicted.For example,all models can well produce the interannual variability of the western North Pacific monsoon index(WNPMI)defined by 850 hPa winds,but they failed to predict the relationship between WNPMI and precipitation anomalies.The interannual variability of the 500 hPa geopotential height(GPH)can be well predicted by the models in contrast to precipitation anomalies.On the basis of such model performances and the relationship between the interannual variations of 500 hPa GPH and precipitation anomalies.we developed a statistical scheme used to downscale the summer monsoon precipitation anomaly Oll the basis of EOF and singular value decomposition(SVD).In this scheme,the three leading EOF modes of 500 hPa GPH anomaly fields predicted by the models are firstly corrected by the linear regression between the principal components in each model and observation.respectively.Then. the corrected model GPH is chosen as the predictor to downscale the precipitation anomaly field,which is assembled by the forecasted expansion toeffcients of model 500 hPa GPH and the three leading SVD modes of observed precipitation anomaly corresponding to the prediction of model 500 hPa GPH during a 19-year training period.The cross-validated forecasts suggest that this dowuscaling scheme may have a potential to improve the forecast skill of the precipitation anomaly in the South China Sea,western North Pacific and the East Asia Pacific regions

  2. Satellite-based 3D structure of cloud and aerosols over the Indian Monsoon region: implications for aerosol-cloud interaction

    Science.gov (United States)

    Dey, Sagnik; Sengupta, Kamalaika; Basil, George; Das, Sushant; Nidhi, Nidhi; Dash, S. K.; Sarkar, Arjya; Srivastava, Parul; Singh, Ajit; Agarwal, P.

    2012-11-01

    Accurate knowledge of vertical distributions of aerosol and cloud fields and their space-time variations are required to reduce the uncertainty in estimated climate forcing. Here, multi-sensor (both passive and active) data were used to construct the climatology of 3-D cloud and aerosol fields over the Indian monsoon region. Multilayer clouds are found to persist throughout the year, among which cumulus and stratocumulus dominate the low clouds and cirrus dominates the high clouds. A combination of passive stereo-technique (MISR) and radiometric technique (ISCPP) captures the multilayer cloud structure as revealed by active sensor CALIOP. Coexistence of low clouds throughout the year with high aerosol concentration beneath and above leads to a transition from increasing to decreasing cloud fraction with an increase in aerosol optical depth. Such transition is rapid in the monsoon season due to convergence of low clouds to form high clouds facilitated by high aerosol loading. Further, the regional climate model RegCM 4.1 has been used to examine aerosol-cloud interaction. The aerosol-induced changes of low cloud amount are under-estimated by the model. The observation-based seasonal climatology of aerosol and cloud fields presented here may help in improving the model simulations of cloud variability and associated rainfall.

  3. Orbitally-paced variations of water availability in the SE Asian Monsoon region following the Miocene Climate Transition

    Science.gov (United States)

    Heitmann, Emma O.; Ji, Shunchuan; Nie, Junsheng; Breecker, Daniel O.

    2017-09-01

    Middle Miocene Earth had several boundary conditions similar to those predicted for future Earth including similar atmospheric pCO2 and substantial Antarctic ice cover but no northern hemisphere ice sheets. We describe a 12 m outcrop of the terrestrial Yanwan Section in the Tianshui Basin, Gansu, China, following the Miocene Climate Transition (13.9-13.7 Ma). It consists of ∼25 cm thick CaCO3-cemented horizons that overprint siltstones every ∼1 m. We suggest that stacked soils developed in siltstones under a seasonal climate with a fluctuating water table, evidenced by roots, clay films, mottling, presence of CaCO3 nodules, and stacked carbonate nodule δ13 C and δ18 O profiles that mimic modern soils. We suggest that the CaCO3-cemented horizons are capillary-fringe carbonates that formed in an arid climate with a steady water table and high potential evapotranspiration rates (PET), evidenced by sharp upper and basal contacts, micrite, sparite, and root-pore cements. The CaCO3 of the cemented horizons and the carbonate nodules have similar mean δ18 O and δ13 C values but the cements have significantly smaller variance in δ13 C and δ18 O values and a different δ18 O versus δ13 C slope, supporting the conclusion that these carbonates are from different populations. The magneto-stratigraphic age model indicates obliquity pacing of the arid conditions required to form the CaCO3-cemented horizons suggesting an orbital control on water availability. We suggest two possible drivers for the obliquity pacing of arid conditions: 1) variability in the cross-equatorial pressure gradient that controls summer monsoon (ASM) strength and is influenced by obliquity-paced variations of Antarctic ice volume and 2) variability in Western Pacific Ocean-East Asian continent pressure gradient controlled by the 25-45°N meridional insolation gradient. We also suggest that variations in aridity were influenced by variations in PET and sensible heating of the regional land

  4. Non-stationary analysis of dry spells in monsoon season of Senegal River Basin using data from Regional Climate Models (RCMs)

    Science.gov (United States)

    Giraldo Osorio, J. D.; García Galiano, S. G.

    2012-07-01

    SummaryThe Senegal River Basin, located in West Africa, has been affected by several droughts since the end of the 1960s. In its valley, which is densely populated and highly vulnerable to climate variability and water availability, agricultural activities provide the livelihood for thousands of people. Increasing the knowledge about plausible trends of drought events will allow to improve the adaptation and mitigation measures in order to build "adaptive capacity" to climate change in West Africa. An innovative methodology for the non-stationary analysis of droughts events, which allows the prediction of regional trends associated to several return periods, is presented. The analyses were based on Regional Climate Models (RCMs) provided by the European ENSEMBLES project for West Africa, together with observed data. A non-stationary behaviour of the annual series of maximum length of dry spells (AMDSL) in the monsoon season is reflected in temporal changes in mean and variance. The non-stationary nature of hydrometeorological series, due to climate change and anthropogenic activities, is the main criticism to traditional frequency analysis. Therefore, in this paper, the modelling tool GAMLSS (Generalized Additive Models for Location, Scale and Shape), is applied to develop regional probability density functions (pdfs) fitted to AMDSL series for the monsoon season in the Senegal River Basin. The skills of RCMs in the representation of maximum length of dry spells observed for the period 1970-1990, are evaluated considering observed data. Based on the results obtained, a first selection of the RCMs with which to apply GAMLSS to the AMDSL series identified, for the time period 1970-2050, is made. The results of GAMLSS analysis exhibit divergent trends, with different value ranges for parameters of probability distributions being detected. Therefore, in the second stage of the paper, regional pdfs are constructed using bootstrapping distributions based on probabilistic

  5. Evaluation of soil moisture data products over Indian region and analysis of spatio-temporal characteristics with respect to monsoon rainfall

    Science.gov (United States)

    Sathyanadh, Anusha; Karipot, Anandakumar; Ranalkar, Manish; Prabhakaran, Thara

    2016-11-01

    Soil moisture (SM) is an essential climate variable of greater relevance in the monsoon scenario, hence validation and understanding of its spatio-temporal variability over the Indian region is of high significance. In the present study, five SM products are evaluated against in situ SM measurements conducted by India Meteorological Department and the selected data product is used for spatio-temporal characterization of SM in relation to monsoon rainfall. The data products evaluated are: European Space Agency's merged satellite SM, Modern-Era Retrospective analysis for Research and Applications (MERRA) Land SM, ECMWF's ERA interim SM, Climate Forecast System Reanalysis SM, and Global Land Data Assimilation System Noah Land Surface Model SM. Comparisons show that seasonal SM patterns in all products generally follow the characteristics of rainfall, even though there are certain differences in details. The statistical estimates indicate fairly good agreement between in situ and the five products, with some variations among them and over the homogeneous rainfall regions. On comparison, MERRA SM is found appropriate for further analyses on spatio-temporal characteristics, which are then carried out with the 20 year (1993-2012) SM data. Stability analyses revealed SM patterns indicative of relative SM variability as well as persistence. The spatial stability analysis depicts dry and wet patterns and their seasonal variations over different geographical locations in relation to all India spatial average. Large temporal variations are found over central, western and northern Indian regions caused by large intraseasonal variability in rainfall. In brief, intraseasonal and interannual soil moisture variations broadly follow the rainfall pattern, with long-term influences attributed to SM memory effects. The soil moisture persistence and dominant scales of variability are explored with autocorrelation and wavelet transform techniques. Seasonal persistence is large over

  6. Seasonal Variations in δ18O of Inflowing River Water, Lake Water, Sediment Trap Material and Ostracod Shells of Lake Nam Co and its Catchment (Tibet, China) — a Proxy Calibration Study

    Science.gov (United States)

    Daut, G.; Wang, J.; Ju, J.; Plessen, B.; Fürstenberg, S.; Baade, J.; Frenzel, P.; Haberzettl, T.; Maeusbacher, R.; Zhu, L.

    2014-12-01

    δ18O is a very common proxy used in palaeoclimate studies all over the world, but for most parts of the world and especially the Tibetan Plateau modern studies that trace the pathway of this isotope from sink to source are lacking. In this study, financed by the BMBF (German Ministry of Science and Education, Project CADY), we present data that fill this gap. The study was performed in the terminal lake Nam Co, the biggest lake on the central Tibetan Plateau and its catchment. Water of the main tributaries to the lake, lake water at three different stations and from different water depths, bulk carbonate collected from different water depths with sediment traps and shells of living ostracods were collected for one year at lake Nam Co in approx. monthly intervals and analyzed for their δ18O values. The inflowing river waters mainly reflect the precipitation and show regional as well as seasonal variations depending on their location and on Monsoon or Westerly season but are in general on the global meteoric waterline. The lake water shows only minor vertical and spatial variations and is clearly off the meteoric waterline due to strong evaporation effects in this terminal lake. δ18O values of the bulk carbonate of sediment collected in sediment traps show only minor vertical and spatial variations during the year and the δ18O offset compared to the lake water is with around 1 ‰ quite small. Most probably this is attributed to chemical fractionation during formation of monohydrocalcite in the water column. In contrast δ18O values of ostracod shells are significant heavier than the lake water indicating isotopic fractionation (vital effect) during shell formation. In addition a seasonal variability is visible. The data of this proxy calibration study give now for the first time the opportunity to validate δ18O proxy data measured on core material from Lake Nam Co for their palaeoclimatic significance.

  7. The West African monsoon: Contribution of the AMMA multidisciplinary programme to the study of a regional climate system.

    Science.gov (United States)

    Lebel, T.; Janicot, S.; Redelsperger, J. L.; Parker, D. J.; Thorncroft, C. D.

    2015-12-01

    The AMMA international project aims at improving our knowledge and understanding of the West African monsoon and its variability with an emphasis on daily-to-interannual timescales. AMMA is motivated by an interest in fundamental scientific issues and by the societal need for improved prediction of the WAM and its impacts on water resources, health and food security for West African nations. The West African monsoon (WAM) has a distinctive annual cycle in rainfall that remains a challenge to understand and predict. The location of peak rainfall, which resides in the Northern Hemisphere throughout the year, moves from the ocean to the land in boreal spring. Around the end of June there is a rapid shift in the location of peak rainfall between the coast and around 10°N where it remains until about the end of August. In September the peak rainfall returns equatorward at a relatively steady pace and is located over the ocean again by November. The fact that the peak rainfall migrates irregularly compared to the peak solar heating is due to the interactions that occur between the land, the atmosphere and the ocean. To gain a better understanding of this complex climate system, a large international research programme was launched in 2002, the biggest of its kind into environment and climate ever attempted in Africa. AMMA has involved a comprehensive field experiment bringing together ocean, land and atmospheric measurements, on timescales ranging from hourly and daily variability up to the changes in seasonal activity over a number of years. This presentation will focus on the description of the field programme and its accomplishments, and address some key questions that have been recently identified to form the core of AMMA-Phase 2.

  8. The impact of convection in the West African monsoon region on global weather forecasts - explicit vs. parameterised convection simulations using the ICON model

    Science.gov (United States)

    Pante, Gregor; Knippertz, Peter

    2017-04-01

    The West African monsoon is the driving element of weather and climate during summer in the Sahel region. It interacts with mesoscale convective systems (MCSs) and the African easterly jet and African easterly waves. Poor representation of convection in numerical models, particularly its organisation on the mesoscale, can result in unrealistic forecasts of the monsoon dynamics. Arguably, the parameterisation of convection is one of the main deficiencies in models over this region. Overall, this has negative impacts on forecasts over West Africa itself but may also affect remote regions, as waves originating from convective heating are badly represented. Here we investigate those remote forecast impacts based on daily initialised 10-day forecasts for July 2016 using the ICON model. One set of simulations employs the default setup of the global model with a horizontal grid spacing of 13 km. It is compared with simulations using the 2-way nesting capability of ICON. A second model domain over West Africa (the nest) with 6.5 km grid spacing is sufficient to explicitly resolve MCSs in this region. In the 2-way nested simulations, the prognostic variables of the global model are influenced by the results of the nest through relaxation. The nest with explicit convection is able to reproduce single MCSs much more realistically compared to the stand-alone global simulation with parameterised convection. Explicit convection leads to cooler temperatures in the lower troposphere (below 500 hPa) over the northern Sahel due to stronger evaporational cooling. Overall, the feedback of dynamic variables from the nest to the global model shows clear positive effects when evaluating the output of the global domain of the 2-way nesting simulation and the output of the stand-alone global model with ERA-Interim re-analyses. Averaged over the 2-way nested region, bias and root mean squared error (RMSE) of temperature, geopotential, wind and relative humidity are significantly reduced in

  9. Aerosol and monsoon climate interactions over Asia

    Science.gov (United States)

    Li, Zhanqing; Lau, W. K.-M.; Ramanathan, V.; Wu, G.; Ding, Y.; Manoj, M. G.; Liu, J.; Qian, Y.; Li, J.; Zhou, T.; Fan, J.; Rosenfeld, D.; Ming, Y.; Wang, Y.; Huang, J.; Wang, B.; Xu, X.; Lee, S.-S.; Cribb, M.; Zhang, F.; Yang, X.; Zhao, C.; Takemura, T.; Wang, K.; Xia, X.; Yin, Y.; Zhang, H.; Guo, J.; Zhai, P. M.; Sugimoto, N.; Babu, S. S.; Brasseur, G. P.

    2016-12-01

    The increasing severity of droughts/floods and worsening air quality from increasing aerosols in Asia monsoon regions are the two gravest threats facing over 60% of the world population living in Asian monsoon regions. These dual threats have fueled a large body of research in the last decade on the roles of aerosols in impacting Asian monsoon weather and climate. This paper provides a comprehensive review of studies on Asian aerosols, monsoons, and their interactions. The Asian monsoon region is a primary source of emissions of diverse species of aerosols from both anthropogenic and natural origins. The distributions of aerosol loading are strongly influenced by distinct weather and climatic regimes, which are, in turn, modulated by aerosol effects. On a continental scale, aerosols reduce surface insolation and weaken the land-ocean thermal contrast, thus inhibiting the development of monsoons. Locally, aerosol radiative effects alter the thermodynamic stability and convective potential of the lower atmosphere leading to reduced temperatures, increased atmospheric stability, and weakened wind and atmospheric circulations. The atmospheric thermodynamic state, which determines the formation of clouds, convection, and precipitation, may also be altered by aerosols serving as cloud condensation nuclei or ice nuclei. Absorbing aerosols such as black carbon and desert dust in Asian monsoon regions may also induce dynamical feedback processes, leading to a strengthening of the early monsoon and affecting the subsequent evolution of the monsoon. Many mechanisms have been put forth regarding how aerosols modulate the amplitude, frequency, intensity, and phase of different monsoon climate variables. A wide range of theoretical, observational, and modeling findings on the Asian monsoon, aerosols, and their interactions are synthesized. A new paradigm is proposed on investigating aerosol-monsoon interactions, in which natural aerosols such as desert dust, black carbon from

  10. A Late Glacial Environmental Reconstruction performed on Lacustrine Sediments from the Southern Tibetan Plateau identifies regional Monsoon Variations

    Science.gov (United States)

    Henkel, K.; Ahlborn, M.; Haberzettl, T.; Alivernini, M.; Kasper, T.; Thiele, A.; St-Onge, G.; Daut, G.; Frenzel, P.; Gleixner, G.; Wang, J.; Zhu, L.; Maeusbacher, R.

    2014-12-01

    The Tibetan Plateau (TP) is very sensitive to climate variations and is therefore an ideal study site to investigate past climate changes. Influenced by the Asian Monsoon system, the numerous lake systems on the TP serve as valuable archives for past hydrological changes, which are assumed to be caused by variations in strength and extent of the monsoonal impact. The lacustrine record from the terminal lake Tangra Yumco (4540 m a.s.l., 31°13'N, 86°43'E) consists of an interbedding of fine-grained silty sediments with laminations of different thicknesses (sub-mm to cm) and partly intercalated blackish sandy layers. Thin section analysis in the laminated areas reveals cyclic laminations composed of a carbonate and a detrital layer. Homogenous intervals represent turbidite deposits which are further detected based on lithology, radiography as well as changes in the water content, grain size, Ti-values (XRF) and in the paleomagnetic parameter median destructive field. The chronology is based on 27 AMS-radiocarbon ages on bulk organic matter and one piece of wood, which is of terrestrial origin. To determine a possible carbon reservoir effect, additional surface sediment samples and one modern aquatic plant were measured. The calculated reservoir effect of 2,120 +110/-90 years is assumed to be constant over the time and thus the base of the record reveals a corrected radiocarbon age of 17,270 +325/-310 cal BP. Additionally, investigations on paleomagnetic secular variations were carried out, showing that since 15,900 cal BP the record preserved a well-defined magnetization recording a genuine paleomagnetic signal. Regarding the geochemical (organic and inorganic), sedimentological, mineralogical and micropaleontological analyses, a low lake level with a high terrestrial input is observed for the Late Glacial. At 15.6 ka cal BP, a change in the sediment accumulation rate, increased allochthoneous input and changing ostracod fauna point to an increasing lake level. In

  11. Differences in atmospheric heat source between the Tibetan Plateau-South Asia region and the southern Indian Ocean and their impacts on the Indian summer monsoon outbreak

    Science.gov (United States)

    Zhang, Yiwei; Fan, Guangzhou; Hua, Wei; Zhang, Yongli; Wang, Bingyun; Lai, Xin

    2017-06-01

    In this paper, the NCEP-NCAR daily reanalysis data are used to investigate the characteristics of the atmospheric heat source/sink (AHSS) over South Asia (SA) and southern Indian Ocean (SIO). The thermal differences between these two regions and their influence on the outbreak of the Indian summer monsoon (ISM) are explored. Composite analysis and correlation analysis are applied. The results indicate that the intraseasonal variability of AHSS is significant in SA but insignificant in the SIO. Large inland areas in the Northern Hemisphere still behave as a heat sink in March, similar to the situation in winter. Significant differences are found in the distribution of AHSS between the ocean and land, with distinct land-ocean thermal contrast in April, and the pattern presents in the transitional period right before the ISM onset. In May, strong heat centers appear over the areas from the Indochina Peninsula to the Bay of Bengal and south of the Tibetan Plateau (TP), which is a typical pattern of AHSS distribution during the monsoon season. The timing of SA-SIO thermal difference turning positive is about 15 pentads in advance of the onset of the ISM. Then, after the thermal differences have turned positive, a pre-monsoon meridional circulation cell develops due to the near-surface heat center and the negative thermal contrast center, after which the meridional circulation of the ISM gradually establishes. In years of early (late) conversion of the SA-SIO thermal difference turning from negative to positive, the AHSS at all levels over the TP and SIO converts later (earlier) than normal and the establishment of the ascending and descending branches of the ISM's meridional circulation is later (earlier) too. Meanwhile, the establishment of the South Asian high over the TP is later (earlier) than normal and the conversion of the Mascarene high from winter to summer mode occurs anomalously late (early). As a result, the onset of the ISM is later (earlier) than normal

  12. How Sensitive is the Asian Monsoon System to Remote Forcing?: A Perspective from the late Quaternary Bay of Bengal and Arabian Sea Regions

    Science.gov (United States)

    Stoll, H. M.; Vance, D.; Arevalos, A.; Shimizu, N.; Burke, A.; Ziveri, P.

    2007-12-01

    Over the Quaternary has the Asian monsoon system responded predominantly to regional climate drivers such as orbital changes in summer insolation and the land-sea pressure gradient, or global climate boundary conditions such as the extent of northern hemisphere(NH) ice sheets and snow cover? Our paleorecords from the Bay of Bengal and Arabian Sea reveal contrasting influence of the NH ice sheets. Seawater Nd isotopic ratios in the northern Bay of Bengal, reconstructed from planktic foraminifera, are sensitive to the degree of northward penetration of the Asian summer monsoon precipitation into the nonradiogenic terranes of the Himalayas. Shifts in river sources from the more northerly Ganges-Brahmaputra watershed to the more southerly Arakan coastal river systems respond dominantly to ITCZ movement driven by Northern Hemisphere cooling during 100 ky glacial-interglacial cycles. A nonlinear correlation of epsilon Nd with ice volume suggests that ITCZ movement responds to aerial coverage of ice sheets and snow rather than to ice thickness and volume as expected from albedo forcing. These data add support to recent general circulation models of which in this region show strong ITCZ response to Northern Hemisphere ice coverage. A small component of Nd isotopic variation on precessional timescales corresponds to ITCZ movement within the southern Irrawaddy and Arakan coastal systems. There is a strong connection between ITCZ movement and productivity even in a non-upwelling system such as the Bay of Bengal. In the northernmost Bay of Bengal, productivity indicators from Sr-Ca ratios in coccoliths and from Ba-Ti ratios of sediments exhibit principally glacial-interglacial variability consistent with the epsilon Nd record. Higher productivity during interglacials may reflect either higher riverine nutrient sources or stronger wind- driven eddy pumping. In the more southerly Andaman Sea, Sr-Ca ratios in coccoliths reveal productivity variations dominantly on precessional

  13. Water Vapor Transport and Cross-Equatorial Flow over the Asian-Australia Monsoon Region Simulated by CMIP5 Climate Models

    Institute of Scientific and Technical Information of China (English)

    SONG Yajuan; QIAO Fangli; SONG Zhenya; JIANG Chunfei

    2013-01-01

    The summer mean water vapor transport (WVT) and cross-equatorial flow (CEF) over the AsianAustralian monsoon region simulated by 22 coupled atmospheric-oceanic general circulation models (AOGCMs)from the World Climate Research Programme's Coupled Model Intercomparison Project Phase 5 (CMIP5)were evaluated.Based on climatology of the twentieth-century simulations,most of models have a reasonably realistic representation of summer monsoon WVT characterized by southeast water vapor conveyor belt over the South Indian Ocean and southwest belt from the Arabian Sea to the East Asian.The correlation coefficients between NCEP reanalysis and simulations of BCC-CSM1-1,BNU-ESM,CanESM2,FGOALS-s2,MIROC4h and MPI-ESM-LR are up to 0.8.The simulated CEF depicted by the meridional wind along the equator includes the Somali jet and eastern CEF in low atmosphere and the reverse circulation in upper atmosphere,which were generally consistent with NCEP reanalysis.Multi-model ensemble means (MME) can reproduce more reasonable climatological features in spatial distribution both of WVT and CEF.Ten models with more reasonable WVT simulations were selected for future projection studies,including BCCCSM1-1,BNU-ESM,CanESM2,CCSM4,FGOALS-s2,FIO-ESM,GFDL-ESM2G,MRIOC5,MPI-ESM-LR and NorESM-1M.Analysis based on the future projection experiments in RCP (Representative Concentration Pathway) 2.6,RCP4.5,RCP6 and RCP8.5 show that the global warming forced by different RCP scenarios will results in enhanced WVT over the Indian area and the west Pacific and weaken WVT in the low latitudes of tropical Indian Ocean.

  14. Variation trends and influencing factors of total gaseous mercury in the Pearl River Delta-A highly industrialised region in South China influenced by seasonal monsoons

    Science.gov (United States)

    Chen, Laiguo; Liu, Ming; Xu, Zhencheng; Fan, Ruifang; Tao, Jun; Chen, Duohong; Zhang, Deqiang; Xie, Donghai; Sun, Jiaren

    2013-10-01

    Studies on atmospheric mercury in the Pearl River Delta (PRD) region are important because of the economic relevance of this region to China, because of its economic developmental pattern and because it is a highly industrialised area influenced by the strong seasonal monsoons. Total gaseous mercury (TGM), meteorological parameters and criteria pollutant concentrations were measured at Mt. Dinghu (DH, a regional monitoring site) and Guangzhou (GZ, an urban monitoring site) in the PRD region from October 2009 to April 2010 and from November 2010 to November 2011, respectively. The ranges of daily average TGM concentrations at the DH and GZ sites were 1.87-29.9 ng m-3 (5.07 ± 2.89 ng m-3) and 2.66-11.1 ng m-3 (4.60 ± 1.36 ng m-3), respectively, which were far more significant than the background values in the Northern Hemisphere (1.5-1.7 ng m-3), suggesting that the atmosphere in the PRD has suffered from mercury pollution. Similar TGM seasonal distributions at the two sites were observed, with a descending order of spring, winter, autumn and summer. The different seasonal monsoons were the dominant factor controlling the seasonal variability of the TGM, with variations in the boundary layer and oxidation also possibly partially contributing. Different diurnal patterns of the TGM at two sites were observed. TGM levels during the daytime were higher than those during the nighttime and were predominantly influenced by mountain and valley winds at the DH site, whereas the opposite trend was evident at the GZ site, which was primarily influenced by the boundary-layer height and O3 concentration. During the monitoring period, the correlations between the daily TGM levels and the SO2 and NO2 levels at the DH site were significant (r = 0.36, p mercury for this regional monitoring site. At the GZ site, the correlations between the daily TGM level and the NO, NO2, CO levels were significant (r = 0.501, p mercury sources for this urban monitoring site. The TGM distribution

  15. NAM: The 2004 RAS National Astronomy Meeting

    Science.gov (United States)

    Jones, Barrie; Norton, Andrew

    2004-06-01

    This year's RAS National Astronomy Meeting was held at the Open University's Milton Keynes campus from 29 March to 2 April. The event was organized by members of the OU Physics & Astronomy Department and Planetary & Space Science Research Institute. Around 450 people attended the meeting, at which more than 220 talks were presented, along with around 90 posters. Co-chairs of RAS NAM04, Barrie Jones and Andrew Norton, summarize.

  16. HOG-WILD IN VIET NAM

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Amid growing pains, a Chongqing company finds Viet Nam good for breeding its motorcycles Back in 1998, Yin Mingshan found his company was between a rock and a hard place with seemingly nowhere to scooter through. As Chairman of the Board of Chongqing Lifan Industry Co. Ltd., China's largest motorcycle manufacturer, Vm was seeing his domestic market dry up while export volume also was shrinking.

  17. Cloud characteristics over the rain-shadow region of North Central peninsular India during monsoon withdrawal and post-withdrawal periods

    Science.gov (United States)

    Morwal, S. B.; Narkhedkar, S. G.; Padmakumari, B.; Maheskumar, R. S.; Kothawale, D. R.; Dani, K. K.; Burger, R.; Bruintjes, R. T.; Kulkarni, J. R.

    2016-01-01

    Cloud characteristics over the rain-shadow region of the north central peninsular India has been studied using C-band radar data for the period 21 September-30 October 2011. The period covers withdrawal and post-withdrawal periods of monsoon 2011. Though the study has been carried out for one season, it has been shown that it is representative of climatic feature over the region. The cloud characteristics have been discussed in the context of large scale dynamical and thermodynamical conditions over the region using NCEP wind data and radiosonde data, respectively. The large scale dynamic and thermodynamical conditions were found favorable for occurrence of widespread and deep convection. The cloud top heights show tri-modal distribution with peaks at 2-3, 4-6 and 8-12 km which are associated with cumulus, congestus and cumulonimbus clouds, respectively. The tops of these three types of the clouds are found to be associated with the stable layers in the atmosphere. The frequency of congestus clouds was the highest. The cloud characteristics over the region differ from other tropical land and oceanic regions in respect of maximum height, mean duration and cumulative frequency distribution. Distribution of cloud top height and duration show deviation from lognormality in the lower ends. It indicates that the cloud growth mechanism is different than that observed over other tropical land and oceanic regions and also due to the large wind shear prevailed over the region. During the period, a large number of suitable clouds were found available for hygroscopic and glaciogenic cloud seeding.

  18. Global monsoon in a geological perspective

    Institute of Scientific and Technical Information of China (English)

    WANG PinXian

    2009-01-01

    Monsoon is now considered as a global system rather than regional phenomena only. For over 300 years, monsoon has been viewed as a gigantic land-sea breeze, but now satellite and conventional observations support an alternative hypothesis which considers monsoon as a manifestation of sea-sonal migration of the intertropical convergence zone (ITCZ) and, hence, a climate system of the global scale. As a low-latitude climate system, monsoon exists over all continents but Antarctica, and through all the geological history at least since the Phenorozoic. The time is ripe for systematical studies of monsoon variations in space and time.As evidenced by the geological records, the global monsoon is controlled by the Wilson cycle on the tectonic time scale (106-108a). A "Mega-continent" produces "Mega-monsoon", and its breakdown leads to weakening of the monsoon Intensity. On the time scales of 104-105 a, the global monsoon displays the precessional cycles of~20 ka and eccentricity cycles of 100- and 400-ka, i.e. the orbital cycles. On the time scales of 103 a and below, the global monsoon intensity is modulated by solar cy-cles and other factors. The cyclicity of global monsoon represents one of the fundamental factors re-sponsible for variations in the Earth surface system as well as for the environmental changes of the human society. The 400-ka long eccentricity cycles of the global monsoon is likened to "heartbeat" of the Earth system, and the precession cycle of the global monsoon was responsible for the collapse of several Asian and African ancient cultures at~4000 years ago, whereas the Solar cycles led to the de-mise of the Maya civilization about a thousand years ago. Therefore, paleoclimatology should be fo-cused not only on the high-latitude processes centered at ice cap variations, but also on the low-latitude processes such as monsoons, as the latter are much more common in the geological history compared to the glaciations.

  19. A new criterion for identifying breaks in monsoon conditions over the Indian subcontinent

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Dessai, U.R.P.

    of July. The quantum of monsoon rainfall also varies from year to year. The monsoon rainfall is not continuous within the life cycle of a monsoon; there are several spells of active, weak and break in monsoon conditions. The summer monsoon months...? to refer different features such as convection and circulation etc. over different regions. Further, the authors have used different durations to refer the break as well as looked them in different months. [4] By analyzing 80 years (1888...

  20. Natural and human-induced changes in summer climate over the East Asian monsoon region in the last half century: A review

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Ren-He

    2015-01-01

    In the last half century,a significant warming trend occurred in summer over eastern China in the East Asian monsoon region.However,there were no consistent trends with respect to the intensity of the East Asian summer monsoon(EASM) or the amount of summer rainfall averaged over eastern China.Both of the EASM and summer rainfall exhibited clear decadal variations.Obvious decadal shifts of EASM occurred around the mid- and late 1970 s,the late 1980 s and the early 1990 s,and the late 1990 s and early 2000 s,respectively.Summer rainfall over eastern China exhibited a change in spatial distribution in the decadal timescale,in response to the decadal shifts of EASM.From the mid- and late 1970 s to the late 1980 s and the early 1990 s,there was a meridional tri-polar rainfall distribution anomaly with more rainfall over the Yangtze River valley and less rainfall in North and South China; but in the period from the early 1990 s to the late 1990 s and the early 2000 s the tri-polar distribution changed to a dipolar one,with more rainfall appearing over southern China south to the Yangtze River valley and less rainfall in North China.However,from the early 2000 s to the late 2000 s,the Yangtze River valley received less rainfall.The decadal changes in EASM and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover,Arctic sea ice,sea surface temperatures in tropical Pacific and Indian Ocean,oceaneatmospheric coupled systems of the Pacific Decadal Oscillation(PDO) and AsianePacific Oscillation(APO),and uneven thermal forcing over the Asian continent.Up to now,the roles of anthropogenic factors,such as greenhouse gases,aerosols,and land usage/cover changes,on existing decadal variations of EASM and summer rainfall in this region remain uncertain.

  1. Investigating the impact of land-use land-cover change on Indian summer monsoon daily rainfall and temperature during 1951–2005 using a regional climate model

    Directory of Open Access Journals (Sweden)

    S. Halder

    2015-07-01

    Full Text Available Daily moderate rainfall events, that constitute a major portion of seasonal summer monsoon rainfall over central India, have decreased significantly during the period 1951 till 2005. Mean and extreme near surface daily temperature during the monsoon season have also increased by a maximum of 1–1.5 °C. Using simulations made with a high-resolution regional climate model (RegCM4 with prescribed vegetation cover of 1950 and 2005, it is demonstrated that part of the above observed changes in moderate rainfall events and temperature have been caused by land-use land-cover change (LULCC which is mostly anthropogenic. Model simulations show that the increase in seasonal mean and extreme temperature over central India coincides with the region of decreased (increased forest (crop cover. The results also show that land-use land-cover alone causes warming in the extremes of daily mean and maximum temperatures by maximum of 1–1.2 °C, that is comparable with the observed increasing trend in the extremes. Decrease (increase in forest (crop cover reduces the evapotranspiration over land and large-scale convective instability, apart from decreasing the moisture convergence. These factors act together not only in reducing the moderate rainfall events over central India but also the amount of rainfall in that category, significantly. This is the most interesting result of this study. Additionally, the model simulations are repeated by removing the warming trend in sea surface temperatures. As a result, there is enhanced warming at the surface and decrease in moderate rainfall events over central India. Results from the additional experiments corroborate our initial findings and confirm the contribution of land-use land-cover change on increase in daily mean and extreme temperature and decrease in moderate rainfall events. This study not only demonstrates the important implications of LULCC over India, but also shows the necessity for inclusion of projected

  2. A hemispheric climatology of monsoon depressions

    Science.gov (United States)

    Hurley, J. V.; Boos, W.

    2012-12-01

    Monsoon depressions are large (1000-2000 km diameter) cyclonic low pressure systems having organized deep convection, best known for forming in the Bay of Bengal and migrating northwest over northern India in the monsoon trough. About 3 to 5 of these systems occur during each monsoon season, contributing about half of the Indian summer rainfall. Despite their importance as a precipitation source, their dynamics are poorly constrained. Furthermore, although they do occur elsewhere, such as around Australia and in the southern Indian Ocean, there does not exist a collective inventory of these systems outside of the Bay of Bengal region. Here we present a climatology of monsoon depressions produced from the ERA-Interim Reanalysis. Feature tracks are identified using an automated tracking algorithm (K. Hodges' TRACK code) applied to the 850 hPa relative vorticity field for local summer, 1989 to 2003. Using criteria based on relative vorticity and sea level pressure, cyclonic low pressure systems are separated into different intensity categories, one of which corresponds to the definition for monsoon depressions used by the India Meteorological Department. The resultant distribution of storms obtained for the Bay of Bengal region compares well with a previously compiled climatology of monsoon depressions that was limited to the region surrounding India. Having validated our ability to identify monsoon depressions in their classic genesis region near India, we then extend the methods to include the western Pacific, Australia, and the southern Indian Ocean. Track distributions and composite structures of monsoon depressions for these different regions will be presented.

  3. Humidity Effect and Its Influence on the Seasonal Distribution of Precipitation δ18O in Monsoon Regions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xinping; LIU Jingmiao; HE Yuanqing; TIAN Lide; YAO Tandong

    2005-01-01

    rainfall, small △Td and weak evaporation enrichment function of stable isotopes in thefalling raindrops, under the influence of vapor from the oceans; but they are relatively higher because of the dry air, light rainfall, great △Td and strong evaporation enrichment function in falling raindrops, under the control of the continental air mass. Therefore, the δ18O in precipitation at Kunming can be used to indicate the humidity situation in the atmosphere to a certain degree, and thus indicate the intensity of the precipitation and the strength of the monsoon indirectly. The humidity effect changes not only the magnitude of the stable isotopic ratio in precipitation but also its seasonal distribution due to its influence on the strength of the evaporation enrichment of stable isotopes in falling raindrops and the direction of the net mass transfer of stable isotopes between the atmosphere and the raindrops. Consequently, it is inferred that the humidity effect is probably one of the foremost causes generating the amount effect.

  4. HONO and Inorganic Fine Particle Composition in Typical Monsoon Region with Intensive Anthropogenic Emission: In-situ Observations and Source Identification.

    Science.gov (United States)

    Xie, Y.; Nie, W.; Ding, A.; Huang, X.

    2015-12-01

    Yangtze River Delta (YRD) is one of the most typical monsoon area with probably the most largest population intensity in the world. With sharply economic development and the large anthropogenic emissions, fine particle pollution have been one of the major air quality problem and may further have impact on the climate system. Though a lot of control policy (sulfur emission have been decreasing from 2007) have been conducted in the region, studies showed the sulfate in fine particles still take major fraction as the nitrate from nitrogen oxides increased significantly. In this study, the role of inorganic chemical compositions in fine particles was investigated with two years in-situ observation. Sulfate and Nitrate contribute to fine particle mass equally in general, but sulfate contributes more during summer and nitrate played more important role in winter. Using lagrangian dispersion backward modeling and source contribution clustering method, the impact of airmass coming from different source region (industrial, dust, biogenic emissions, etc) on fine particle inorganic compositions were discussed. Furthermore, we found two unique cases showing in-situ implications for sulfate formation by nitrogen dioxide oxidation mechanisms. It was showed that the mixing of anthropogenic pollutants with long-range transported mineral dust and biomass burning plume would enhance the sulfate formation by different chemistry mechanisms. This study focus on the complex aspects of fine particle formation in airmasses from different source regions: . It highlights the effect of NOx in enhancing the atmospheric oxidization capacity and indicates a potentially very important impact of increasing NOx on air pollution formation and regional climate change in East Asia.

  5. The Joint Aerosol-Monsoon Experiment: A New Challenge to Monsoon Climate Research

    Science.gov (United States)

    Lau, William K. M.

    2008-01-01

    Aerosol and monsoon related droughts and floods are two of the most serious environmental hazards confronting more than 60% of the population of the world living in the Asian monsoon countries. In recent years, thanks to improved satellite and in-situ observations, and better models, great strides have been made in aerosol, and monsoon research respectively. There is now a growing body of evidence suggesting that interaction of aerosol forcing with water cycle dynamics in monsoon regions may substantially alter the redistribution of energy at the earth surface and in the atmosphere, and therefore significantly impact monsoon rainfall variability and long term trends. In this talk, I will describe issues related to societal needs, scientific background, and challenges in studies of aerosol-water cycle interaction in Asian monsoon regions. As a first step towards addressing these issues, the authors call for an integrated observation and modeling research approach aimed at the interactions between aerosol chemistry and radiative effects and monsoon dynamics of the coupled ocean-atmosphere-land system. A Joint Aerosol-Monsoon Experiment (JAMEX) is proposed for 2007-2011, with an enhanced observation period during 2008-09, encompassing diverse arrays of observations from surface, aircraft, unmanned aerial vehicles, and satellites of physical and chemical properties of aerosols, long range aerosol transport as well as meteorological and oceanographic parameters in the Indo-Pacific Asian monsoon region. JAMEX will leverage on coordination among many ongoing and planned national programs on aerosols and monsoon research in China, India, Japan, Nepal, Italy, US, as well as international research programs of the World Climate Research Program (WCRP) and the World Meteorological Organization (WMO).

  6. Climatological perspectives of air transport from atmospheric boundary layer to tropopause layer over Asian monsoon regions during boreal summer inferred from Lagrangian approach

    Directory of Open Access Journals (Sweden)

    B. Chen

    2012-02-01

    Full Text Available The Asian Summer Monsoon (ASM region has been recognized as a key region that plays a vital role in troposphere-to-stratosphere transport (TST, which can significantly impact the budget of global atmospheric constituents and climate change. However, the details of transport from the boundary layer (BL to tropopause layer (TL over this region, particularly from a climatological perspective, remains an issue of uncertainty. In this study, we present the climatological properties of BL-to-TL transport over the ASM region during boreal summer season (June-July-August from 2001 to 2009. A comprehensive tracking analysis is conducted based on a large ensemble of TST-trajectories departing from the atmospheric BL and arriving at TL. Driven by the winds fields from the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research Global Forecast System, all TST-trajectories are selected from the high resolution datasets generated by the Lagrangian particle transport model FLEXPART using a domain-filling technique. Three key atmospheric boundary layer sources for BL-to-TL transport are identified with their contributions: (i 38% from the region between tropical Western Pacific region and South China Seas (WP, (ii 21% from Bay of Bengal and South Asian subcontinent (BOB, and (iii 12% from the Tibetan Plateau, which includes the South Slope of the Himalayas (TIB. Controlled by the different patterns of atmospheric circulation, the air masses originating from these three source regions are transported along the different tracks into the TL. The spatial distributions of these three source regions remain similarly from year to year. The timescales of transport from BL to TL by the large-scale ascents range from 1 to 7 weeks, contributing up to 60–70% of the overall TST; whereas the transport governed by the deep convection overshooting becomes faster, with timescales of 1–2 days and contributions of 20–30%. These

  7. Climatological perspectives of air transport from atmospheric boundary layer to tropopause layer over Asian monsoon regions during boreal summer inferred from Lagrangian approach

    Directory of Open Access Journals (Sweden)

    B. Chen

    2012-07-01

    Full Text Available The Asian Summer Monsoon (ASM region has been recognized as a key region that plays a vital role in troposphere-to-stratosphere transport (TST, which can significant impact the budget of global atmospheric constituents and climate change. However, the details of transport from the boundary layer (BL to tropopause layer (TL over these regions, particularly from a climatological perspective, remain an issue of uncertainty. In this study, we present the climatological properties of BL-to-TL transport over the ASM region during boreal summer season (June-July-August from 2001 to 2009. A comprehensive tracking analysis is conducted based on a large ensemble of TST-trajectories departing from the atmospheric BL and arriving at TL. Driven by the winds fields from NCEP/NCAR Global Forecast System, all the TST-trajectories are selected from the high resolution datasets generated by the Lagrangian particle transport model FLEXPART using a domain-filling technique. Three key atmospheric boundary layer sources for BL-to-TL transport are identified with their contributions: (i 38% from the region between tropical Western Pacific region and South China Seas (WP (ii 21% from Bay of Bengal and South Asian subcontinent (BOB, and (iii 12% from the Tibetan Plateau, which includes the South Slope of the Himalayas (TIB. Controlled by the different patterns of atmospheric circulation, the air masses originated from these three source regions are transported along the different tracks into the TL. The spatial distributions of three source regions keep similarly from year to year. The timescales of transport from BL to TL by the large-scale ascents r-range from 1 to 7 weeks contributing up to 60–70% of the overall TST, whereas the transport governed by the deep convection overshooting become faster on a timescales of 1–2 days with the contributions of 20–30%. These results provide clear policy implications for the control of very short lived substances

  8. Statistical bias correction method applied on CMIP5 datasets over the Indian region during the summer monsoon season for climate change applications

    Science.gov (United States)

    Prasanna, V.

    2016-11-01

    This study makes use of temperature and precipitation from CMIP5 climate model output for climate change application studies over the Indian region during the summer monsoon season (JJAS). Bias correction of temperature and precipitation from CMIP5 GCM simulation results with respect to observation is discussed in detail. The non-linear statistical bias correction is a suitable bias correction method for climate change data because it is simple and does not add up artificial uncertainties to the impact assessment of climate change scenarios for climate change application studies (agricultural production changes) in the future. The simple statistical bias correction uses observational constraints on the GCM baseline, and the projected results are scaled with respect to the changing magnitude in future scenarios, varying from one model to the other. Two types of bias correction techniques are shown here: (1) a simple bias correction using a percentile-based quantile-mapping algorithm and (2) a simple but improved bias correction method, a cumulative distribution function (CDF; Weibull distribution function)-based quantile-mapping algorithm. This study shows that the percentile-based quantile mapping method gives results similar to the CDF (Weibull)-based quantile mapping method, and both the methods are comparable. The bias correction is applied on temperature and precipitation variables for present climate and future projected data to make use of it in a simple statistical model to understand the future changes in crop production over the Indian region during the summer monsoon season. In total, 12 CMIP5 models are used for Historical (1901-2005), RCP4.5 (2005-2100), and RCP8.5 (2005-2100) scenarios. The climate index from each CMIP5 model and the observed agricultural yield index over the Indian region are used in a regression model to project the changes in the agricultural yield over India from RCP4.5 and RCP8.5 scenarios. The results revealed a better

  9. Impact of assimilation of INSAT-3D retrieved atmospheric motion vectors on short-range forecast of summer monsoon 2014 over the South Asian region

    Science.gov (United States)

    Kumar, Prashant; Deb, Sanjib K.; Kishtawal, C. M.; Pal, P. K.

    2017-05-01

    The Weather Research and Forecasting (WRF) model and its three-dimensional variational data assimilation system are used in this study to assimilate the INSAT-3D, a recently launched Indian geostationary meteorological satellite derived from atmospheric motion vectors (AMVs) over the South Asian region during peak Indian summer monsoon month (i.e., July 2014). A total of four experiments were performed daily with and without assimilation of INSAT-3D-derived AMVs and the other AMVs available through Global Telecommunication System (GTS) for the entire month of July 2014. Before assimilating these newly derived INSAT-3D AMVs in the numerical model, a preliminary evaluation of these AMVs is performed with National Centers for Environmental Prediction (NCEP) final model analyses. The preliminary validation results show that root-mean-square vector difference (RMSVD) for INSAT-3D AMVs is ˜3.95, 6.66, and 5.65 ms-1 at low, mid, and high levels, respectively, and slightly more RMSVDs are noticed in GTS AMVs (˜4.0, 8.01, and 6.43 ms-1 at low, mid, and high levels, respectively). The assimilation of AMVs has improved the WRF model of produced wind speed, temperature, and moisture analyses as well as subsequent model forecasts over the Indian Ocean, Arabian Sea, Australia, and South Africa. Slightly more improvements are noticed in the experiment where only the INSAT-3D AMVs are assimilated compared to the experiment where only GTS AMVs are assimilated. The results also show improvement in rainfall predictions over the Indian region after AMV assimilation. Overall, the assimilation of INSAT-3D AMVs improved the WRF model short-range predictions over the South Asian region as compared to control experiments.

  10. Aerosol and monsoon climate interactions over Asia: AEROSOL AND MONSOON CLIMATE INTERACTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhanqing [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Lau, W. K. -M. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Ramanathan, V. [Department of Atmospheric and Climate Sciences, University of California, San Diego California USA; Wu, G. [Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing China; Ding, Y. [National Climate Center, China Meteorological Administration, Beijing China; Manoj, M. G. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Liu, J. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Qian, Y. [Pacific Northwest National Laboratory, Richland Washington USA; Li, J. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Zhou, T. [Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing China; Fan, J. [Pacific Northwest National Laboratory, Richland Washington USA; Rosenfeld, D. [Institute of Earth Sciences, Hebrew University, Jerusalem Israel; Ming, Y. [Geophysical Fluid Dynamic Laboratory, NOAA, Princeton New Jersey USA; Wang, Y. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena California USA; Huang, J. [College of Atmospheric Sciences, Lanzhou University, Lanzhou China; Wang, B. [Department of Atmospheric Sciences, University of Hawaii, Honolulu Hawaii USA; School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing China; Xu, X. [Chinese Academy of Meteorological Sciences, Beijing China; Lee, S. -S. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Cribb, M. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Zhang, F. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Yang, X. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Zhao, C. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Takemura, T. [Research Institute for Applied Mechanics, Kyushu University, Fukuoka Japan; Wang, K. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Xia, X. [Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing China; Yin, Y. [School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing China; Zhang, H. [National Climate Center, China Meteorological Administration, Beijing China; Guo, J. [Chinese Academy of Meteorological Sciences, Beijing China; Zhai, P. M. [Chinese Academy of Meteorological Sciences, Beijing China; Sugimoto, N. [National Institute for Environmental Studies, Tsukuba Japan; Babu, S. S. [Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram India; Brasseur, G. P. [Max Planck Institute for Meteorology, Hamburg Germany

    2016-11-15

    Asian monsoons and aerosols have been studied extensively which are intertwined in influencing the climate of Asia. This paper provides a comprehensive review of ample studies on Asian aerosol, monsoon and their interactions. The region is the primary source of aerosol emissions of varies species, influenced by distinct weather and climatic regimes. On continental scale, aerosols reduce surface insolation and weaken the land-ocean thermal contrast, thus inhibiting the development of monsoons. Locally, aerosol radiative effects alter the thermodynamic stability and convective potential of the lower atmosphere leading to reduced temperatures, increased atmospheric stability, and weakened wind and atmospheric circulation. The atmospheric thermodynamic state may also be altered by the aerosol serving as cloud condensation nuclei or ice nuclei. Many mechanisms have been put forth regarding how aerosols modulate the amplitude, frequency, intensity, and phase of numerous monsoon climate variables. A wide range of theoretical, observational, and modeling findings on the Asian monsoon, aerosols, and their interactions are synthesized. A new paradigm is proposed on investigating aerosol-monsoon interactions, in which natural aerosols such as desert dust, black carbon from biomass burning, and biogenic aerosols from vegetation are considered integral components of an intrinsic aerosol-monsoon climate system, subject to external forcings of global warming, anthropogenic aerosols, and land use and change. Future research on aerosol-monsoon interactions calls for an integrated approach and international collaborations based on long-term sustained observations, process measurements, and improved models, as well as using observations to constrain model simulations and projections.

  11. The First Pan-WCRP Workshop on Monsoon Climate Systems: Toward Better Prediction of the Monsoons

    Energy Technology Data Exchange (ETDEWEB)

    Sperber, K R; Yasunari, T

    2005-07-27

    In 2004 the Joint Scientific Committee (JSC) that provides scientific guidance to the World Climate Research Programme (WCRP) requested an assessment of (1) WCRP monsoon related activities and (2) the range of available observations and analyses in monsoon regions. The purpose of the assessment was to (a) define the essential elements of a pan-WCRP monsoon modeling strategy, (b) identify the procedures for producing this strategy, and (c) promote improvements in monsoon observations and analyses with a view toward their adequacy, and addressing any undue redundancy or duplication. As such, the WCRP sponsored the ''1st Pan-WCRP Workshop on Monsoon Climate Systems: Toward Better Prediction of the Monsoons'' at the University of California, Irvine, CA, USA from 15-17 June 2005. Experts from the two WCRP programs directly relevant to monsoon studies, the Climate Variability and Predictability Programme (CLIVAR) and the Global Energy and Water Cycle Experiment (GEWEX), gathered to assess the current understanding of the fundamental physical processes governing monsoon variability and to highlight outstanding problems in simulating the monsoon that can be tackled through enhanced cooperation between CLIVAR and GEWEX. The agenda with links to the presentations can be found at: http://www.clivar.org/organization/aamon/WCRPmonsoonWS/agenda.htm. Scientific motivation for a joint CLIVAR-GEWEX approach to investigating monsoons includes the potential for improved medium-range to seasonal prediction through better simulation of intraseasonal (30-60 day) oscillations (ISO's). ISO's are important for the onset of monsoons, as well as the development of active and break periods of rainfall during the monsoon season. Foreknowledge of the active and break phases of the monsoon is important for crop selection, the determination of planting times and mitigation of potential flooding and short-term drought. With a few exceptions simulations of ISO are

  12. Waning of plankton food web in the upstream region of the Cochin backwaters during the southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Jyothibabu, R.; Madhu, N.V.; Martin, G.D.; Aneesh, C.; Sooria, P.M.; Vineetha, G.

    > and av 3 � 1 No L-1) as compared to the downstream region (av 6 � 3 x 106 No L-1 and av 3222 � 3619 No L-1) This clearly indicated a weak microbial food web in a major part of the Cochin backwaters during...

  13. Clay sediment accumulation rates on the monsoon-dominated western continental shelf and slope region of India

    Digital Repository Service at National Institute of Oceanography (India)

    Borole, D.V.

    Clay accumulation rates shown in sediment cores from the nearshore to outer continental shelf and slope regions in water depths of 10-1246 m on the western continental margins of India were determined by the 210Pb dating technique. The 210Pb excess...

  14. Monsoons, history of

    Digital Repository Service at National Institute of Oceanography (India)

    Niitsuma, N.; Naidu, P.D.

    The evolution of the Asian monsoon started at around 9.5 Ma, in response to the uplift of the Himalayas. The monsoonal intensity reached its maximum at around 5 Ma, and from that time the associated easterly trade winds caused intense upwelling...

  15. Evolution of the North American Monsoon from the middle Holocene to the present recorded in marine sediments from low Gulf of California

    Science.gov (United States)

    Nava, Cinthya; Herguera, Juan Carlos

    2016-04-01

    New results of a reconstruction of the summer precipitation in the North American Monsoon area, which is the largest atmospheric circulation feature over much of northwest Mexico, and the southwest the USA. This regime results from the interplay between sea surface temperatures (SSTs) in the northeast tropical Pacific, solar variability, continental topography, land snow cover and soil moisture over the western North America as well as patterns of atmospheric pressure. The links between these factors and the monsoonal variability appear to be of variable importance during the short instrumental record. This hampers any prediction on the future evolution of the climatic regime in a warming climate. We produce an X-Ray Fluorescence record of the relative abundances of Si and Al in high resolution laminated sediments obtained from the Pescadero basin (24N, 108W) as semi-quantitative index of terrigenous input. This record links the transport of terrigenous materials by summer precipitation in the North American Monsoon region, in mountain range Sierra Madre NW Mexico. The record was constructed from XRF scan measurements of a composite core (260cm long) based on several box and Kasten cores, the age model is based on 8 14C AMS ages, producing a record with a mean temporal resolution of 0.5 yr. The variability of the NAM shows a decreasing trend between the middle Holocene to the present. This general trend is parallel to many other records like speleothems, ice cores, pollen fossil, and elemental content in marine and lake sediments. Spectral and cross-spectral analysis were made in order to search for some similarities with other climatic features on global scale, and thus evaluate possible links between the low and high latitudes climate variability. In addition, we compare the last century precipitation with the past few thousand years and explore some possible effect of climate change in the North American Monsoon behaviour.

  16. Relationship Between East Asian Winter Monsoon and Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    YAN Hongming; YANG Hui; YUAN Yuan; LI Chongyin

    2011-01-01

    Using National Centers for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis data and monthly Hadley Center sea surface temperature (SST) data,and selecting a representative East Asian winter monsoon (EAWM) index,this study investigated the relationship between EAWM and East Asian summer monsoon (EASM) using statistical analyses and numerical simulations.Some possible mechanisms regarding this relationship were also explored.Results indicate a close relationship between EAWM and EASM:a strong EAWM led to a strong EASM in the following summer,and a weak EAWM led to a weak EASM in the following summer.Anomalous EAWM has persistent impacts on the variation of SST in the tropical Indian Ocean and the South China Sea,and on the equatorial atmospheric thermal anomalies at both lower and upper levels.Through these impacts,the EAWM influences the land-sea thermal contrast in summer and the low-level atmospheric divergence and convergence over the Indo-Pacific region.It further affects the meridional monsoon circulation and other features of the EASM.Numerical simulations support the results of diagnostic analysis.The study provides useful information for predicting the EASM by analyzing the variations of preceding EAWM and tropical SST.

  17. In-Situ Measurements of Cloud-Precipitation Microphysics in the East Asian Monsoon Region Since 1960

    Institute of Scientific and Technical Information of China (English)

    王东海; 尹金方; 翟国庆

    2015-01-01

    A large number of in-situ measurements of cloud-precipitation microphysical properties have been made since 1960, including measurements of particle size distribution, particle concentration, and liquid water content of clouds and rain. These measurements have contributed to considerable progress in understanding microphysical processes in clouds and precipitation and signifi cant improvements in parameterizations of cloud microphysics in numerical models. This work reviews key fi ndings regarding cloud-precipitation mi-crophysics over China. The total number concentrations of various particles vary signifi cantly, with certain characteristic spatial scales. The size distributions of cloud droplets in stratiform clouds can generally be fi t with gamma distributions, but the fi t parameters cover a wide range. Raindrop size distributions (RSDs) associated with stratiform clouds can be fi t with either exponential or gamma distributions, while RSDs associated with convective or mixed stratiform-cumuliform clouds are best fi t with gamma distributions. Concentrations of ice nuclei (IN) over China are higher than those observed over other regions, and increase exponentially as temperature decreases. The particle size distributions of ice crystals, snow crystals, and hailstones sampled at a variety of locations can be reliably approximated by using exponential distributions, while aerosol particle size distributions are best described as the sum of a modifi ed gamma distribution and a Junge power-law distribution. These results are helpful for evaluating and improving the fi delity of physical processes and hydrometeor fi elds simulated by microphysical parameterizations. The comprehensive summary and analysis of previous work presented here also provide useful guidelines for the design of future observational programs.

  18. East Asian monsoon climate simulated in the PlioMIP

    Directory of Open Access Journals (Sweden)

    R. Zhang

    2013-02-01

    Full Text Available Based on the simulations with fifteen climate models in the Pliocene Model Intercomparison Project (PlioMIP, the regional climate of East Asia (focusing on China during the mid-Pliocene is investigated in this study. Compared to the pre-industrial, the multi-model ensemble mean (MMM of all models shows the East Asian summer wind (EASW largely strengthens in monsoon China, and the East Asian winter wind (EAWW strengthens in south monsoon China but slightly weakens in north monsoon China in mid-Pliocene. The MMM of all models also illustrates a warmer and wetter mid-Pliocene climate in China. The simulated weakened mid-Pliocene EAWW in north monsoon China and intensified EASW in monsoon China agree well with geological reconstructions. However, the model-model discrepancy in simulating mid-Pliocene East Asian monsoon climate, in particular EAWW, should be further addressed in the future work of PlioMIP.

  19. Historical perspectives on typhoons and tropical storms in the natural and socio-economic system of Nam Dinh (Vietnam)

    NARCIS (Netherlands)

    Kleinen, J.

    2007-01-01

    This contribution starts with a brief introduction of the effects of typhoons and tropical storms on Vietnam, focusing in particular on the coastal region of Nam Dinh, a province in the northern part of the country and part of the Red River Delta. The magnitude of damage caused by a natural disaster

  20. Measuring the monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Nair, R.R.

    of the monsoons, there are also fluctuations arising from human activities. Most scientists believe that large-scale deforestation and burning of fossil fuels will alter global climatic patterns significantly. For the sake of those people whose lives...

  1. Evaporation over the Arabian Sea during two contrasting monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sadhuram, Y.

    monsoon rainfall. It is noticed that in general, the sea surface temperatures are higher in 1983 throughout the monsoon season than in 1979 in the Arabian Sea excepting western region. The mean rates of evaporation on a seasonal scale are found to be equal...

  2. "Bõvajut dni - nam hotshetsja pokoja..." : [luuletused] / Gennadi Vereshtshagin

    Index Scriptorium Estoniae

    Vereshtshagin, Gennadi

    2007-01-01

    Sisu: "Bõvajut dni - nam hotshetsja pokoja..." ; "- V ljubvi net strahha, - Pavel prav..." ; "K tshemu utshonõje slova..." ; "Ossoznannoje - tolko tshast..." ; "Proshtshaju Vass, no ne vernus..." ; "Uventshai tsar ljubvi nebesnoi..." ; "Ja znaju tvoi dushevnõi sterzhen..."

  3. Meteorological fields variability over the Indian seas in pre and summer monsoon months during extreme monsoon seasons

    Indian Academy of Sciences (India)

    U C Mohanty; R Bhatla; P V S Raju; O P Madan; A Sarkar

    2002-09-01

    In this study, the possible linkage between summer monsoon rainfall over India and surface meteorological fields (basic fields and heat budget components) over monsoon region (30° E-120°E, 30°S-30°N) during the pre-monsoon month of May and summer monsoon season (June to September) are examined. For this purpose, monthly surface meteorological fields anomaly are analyzed for 42 years (1958-1999) using reanalysis data of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research). The statistical significance of the anomaly (difference) between the surplus and deficient monsoon years in the surface meteorological fields are also examined by Student's t-test at 95% confidence level. Significant negative anomalies of mean sea level pressure are observed over India, Arabian Sea and Arabian Peninsular in the pre-monsoon month of May and monsoon season. Significant positive anomalies in the zonal and meridional wind (at 2m) in the month of May are observed in the west Arabian Sea off Somali coast and for monsoon season it is in the central Arabian Sea that extends up to Somalia. Significant positive anomalies of the surface temperature and air temperature (at 2m) in the month of May are observed over north India and adjoining Pakistan and Afghanistan region. During monsoon season this region is replaced by significant negative anomalies. In the month of May, significant positive anomalies of cloud amount are observed over Somali coast, north Bay of Bengal and adjoining West Bengal and Bangladesh. During monsoon season, cloud amount shows positive anomalies over NW India and north Arabian Sea. There is overall reduction in the incoming shortwave radiation flux during surplus monsoon years. A higher magnitude of latent heat flux is also found in surplus monsoon years for the month of May as well as the monsoon season. The significant positive anomaly of latent heat flux in May, observed over southwest Arabian Sea, may be considered

  4. 小麦中国春 NAM 转录因子 Gpc-1和 Gpc-2灌浆期时空表达模式分析%Spatiotemporal Expression Pattern Analysis of NAM Transcription Factors Gpc-1 and Gpc-2 in Bread Wheat Cultivar Chinese Spring During Grain Filling

    Institute of Scientific and Technical Information of China (English)

    吴丹; 董剑; 要燕杰; 赵万春; 高翔

    2015-01-01

    Objective]The objective of this experiment is to study the roles of no apical meristem (NAM) transcription factors Gpc-1 and Gpc-2 in early senescence and nutrient remobilization to the grain of bread wheat. [Method] Their spatiotemporal expression patterns were investigated during the grain-filling stage in wheat cultivar Chinese Spring. Their temporal expression dynamics were studied in penultimate leaf, flag leaf, peduncle, glume, rachis and the kernel using quantitative real time polymerase chain reaction (qRT-PCR). And the relative expression level was quantified using Pfaffl method with normalization against multiple verified reference genes. Applying mRNA in situ hybridization, the spatial expression pattern was explored in post-anthesis flag leaf, peduncle and the kernel only with digoxin-labeled oligonucleotide probes which were specifically targeting 5′ or 3′ untranslated regions (UTRs) of Gpc-1 and Gpc-2. [Result] Contrary to a previous report, the functional TaNAM-B1 rather than its dysfunctional paralog was found in Chinese Spring, and its nucleotide sequence was identical with the wild-type TtNAM-B1 in T. turgidum var.dicoccoides. All the results showed that Gpc-1 and Gpc-2 were all widely expressed in studied tissues with the exception of the root in which only the transcript of Gpc-1 was detected. The outcomes of mRNA in situ hybridization indicated that all five genes shared cell-type specificities. To be specific, no transcripts were distributed in leaf epidermal cells, pericarp and the seed coat;however, they mainly aggregated in leaf mesophyll cells, aleurone layer, embryo, and the tissues responsible for the mineral element transport (vascular bundle, pigment strand, nucellar projection and the transfer cell) in grain, in which the highest expression level was observed in embryo. In addition, lower expression level was detected in the peduncle and leaf vascular bundle as well. The results of qRT-PCR showed that the temporal expression

  5. High-resolution peat records for Holocene monsoon history in the eastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    YU; Xuefeng; ZHOU; Weijian; Lars; G.Franzen; XIAN; Feng; CHENG; Peng; A.J.; Tim; Jull

    2006-01-01

    The variations of summer and winter monsoons during the Holocene in the eastern Tibetan Plateau are shown to follow two basic models based on the reliable dating and high-resolution monsoon proxies determinations, one being a synchronous model in that both summer and winter monsoons are strengthening or decreasing, and the other to form a complementary pattern. These two different patterns evenly interact with each other on different time scales and together compose a complicated monsoon climatic model in this region. The climatic condition integrated by winter and summer monsoons is synchronous to the global pattern, which also shows the instability of the Holocene climate on centennial-millennial timescale. The abrupt monsoon event in about 6.2 ka cal.BP is much more severe than that in ca. 8.0 ka cal. BP, which indicates the regional character of the Asian monsoon and that the Asian monsoon climate is indeed a window on the global climate system.

  6. Onset, active and break periods of the Australian monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Shaik, Hakeem A [Northern Territory Regional Office, Australian Bureau of Meteorology, PO Box 40050, NT Regional Office, Bureau of Meteorology, Casuarina NT 0811, Darwin (Australia); Cleland, Samuel J, E-mail: h.shaik@bom.gov.a [Bureau of Meteorology, Cape Grim BAPS, Smithton Tasmania TAS 7300 (Australia)

    2010-08-15

    Four operational techniques of monsoon monitoring the Australian monsoon at Darwin have been developed in the Darwin Regional Specialised Meteorological Centre. Two techniques used the rainfall only criteria and look into the onset of wet season rainfall/monsoon rainfall. The other two techniques are based purely on Darwin wind data. The data used for the study ranges from 14 to 21 years. The main purpose of the study is to develop near-real time monitoring tools for the Australian monsoon at Darwin. The average date of onset of the monsoon ranges from 19 December to 30 December. The average date of monsoon onset is 28 December. In eleven out of twenty-one years the onset date remained within three days range between the two rainfall techniques, whereas it is eleven out of fourteen years between the wind techniques. The median number of active monsoon spells in a wet season is 3 for the rainfall techniques and 6 for the wind techniques. The average length of each active monsoon spell is around 4 days for all of the techniques. The date of onset of the monsoon has shown negative correlation with the Southern Oscillation Index (SOI) that is late onset is found to occur in El Nino years while early onset is more likely in La Nina years.

  7. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    NARCIS (Netherlands)

    Ao, H.; Roberts, A.P.; Dekkers, M.J.|info:eu-repo/dai/nl/073463744; Liu, X.; Rohling, E.J.; Shi, Z.; An, Z.; Zhao, X.

    2016-01-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential rel

  8. Potential controls on millennial and multicentennial time scales of the North American Monsoon: a 6 Ky record from the lower Gulf of California

    Science.gov (United States)

    Nava-Fernandez, C. E.; Herguera Garcia, J. C., Sr.

    2015-12-01

    The Western North American climate is influenced by the sea surface temperatures in the NE tropical Pacific, the summer expansion of the subtropical high, the mid-latitude Westerlies and land snow covering. The interplay of these features of the climate exert further control to the largest phenomenon of convective summer precipitation in NW Mexico and SW US: the North American Monsoon (NAM) which is the most important source of fresh water for the region. There is a pressing need to better understand especially in times of rapid warming how this monsoonal system is going to respond. Here we explore on the different modes of variability of the monsoonal regime in high-resolution reconstructions of the marine sediment record and their possible controls during the Holocene. The role of the teleconnections between the high and low latitudes climate, the interaction with the ITCZ, ENSO, PDO and AMDO are critical for the understanding of global climate. We produced an XRF record of the relative abundance of Si and Al in high resolution laminated sediments obtained from the western margin of Pescadero basin (24N,108W) in the southern domain of the Gulf of California as proxies of terrigenous input. The laminated nature of this deposits at intermediate depths on its slopes sets the foundation for a potentially good record of changes in the transfer of lithogenic materials between the continent and the ocean in this region. Here we present recently acquired data from the terrigenous fraction on the marine sediment composite record from Pescadero basin (522 m water depth / 220 cm long). We determined the relative abundance of Si and Al from X-ray fluorescence from records that were absolutely dated with the aid and eight radiocarbon ages, which allowed us to produce a continuous record with a decadal temporal resolution. The time series analysis of the entire record of Si and Al show significant periodicities which were further cross-correlated with other paleoclimate proxy

  9. An Assessment of the South Asian Summer Monsoon Variability for Present and Future Climatologies Using a High Resolution Regional Climate Model (RegCM4.3 under the AR5 Scenarios

    Directory of Open Access Journals (Sweden)

    Mujtaba Hassan

    2015-11-01

    Full Text Available We assessed the present and future climatologies of mean summer monsoon over South Asia using a high resolution regional climate model (RegCM4 with a 25 km horizontal resolution. In order to evaluate the performance of the RegCM4 for the reference period (1976–2005 and for the far future (2070–2099, climate change projections under two greenhouse gas representative concentration pathways (RCP4.5 and RCP8.5 were made, the lateral boundary conditions being provided by the geophysical fluid dynamic laboratory global model (GFDL-ESM2M. The regional climate model (RCM improves the simulation of seasonal mean temperature and precipitation patterns compared to driving global climate model (GCM during present-day climate conditions. The regional characteristic features of South Asian summer monsoon (SASM, like the low level jet stream and westerly flow over the northern the Arabian Sea, are well captured by the RegCM4. In spite of some discrepancies, the RegCM4 could simulate the Tibetan anticyclone and the direction of the tropical easterly jet reasonably well at 200 hPa. The projected temperature changes in 2070–2099 relative to 1976–2005 for GFDL-ESM2M show increased warming compared to RegCM4. The projected patterns at the end of 21st century shows an increase in precipitation over the Indian Peninsula and the Western Ghats. The possibilities of excessive precipitation include increased southwesterly flow in the wet period and the effect of model bias on climate change. However, the spatial patterns of precipitation are decreased in intensity and magnitude as the monsoon approaches the foothills of the Himalayas. The RegCM4-projected dry conditions over northeastern India are possibly related to the anomalous anticyclonic circulations in both scenarios.

  10. [Identification of Nam Dinh virus in China].

    Science.gov (United States)

    Liu, Qu; Lin, Lin; Zhou, Jian-Ming; Chen, Ying-Jian; Zhang, Qi-Wen; Wang, De-Quan; Li, Jing-Mei; Jin, Yu-Juan

    2013-01-01

    During 2009-2012, the Nam Dinh virus (NDiv) was detected from the samples of Culex pipiens quinquefasciatus in Shenzhen China. In this study, cell culture,SYBR Green I based real time RT-PCR and RT-PCR were performed to analyze the cell susceptibility and other biological characteristics of the NDiV isolates. The results showed that C6/36 cell line was susceptible to four isolates of Culex pipiens quinquefasciatus. The "S" type amplification curve and specific melting curve were obtained in the realtime fluorescence quantitative RT-PCR based on SYBR Green I for the detection of the NDiV from the mosquito. The target bands from the RdRp gene and partial fragment of ZmHel1 gene were observed using agarose gel electrophoresis. Both the nucleotide and amino acid sequences of four Shenzhen isolates showed more than 99.00% homology with the Vietnam representative NDiV strain (02VN178). Phylogenetic analysis showed that four Shenzhen isolates shared the same evolution branch as the Vietnam representative NDiV strain. This is the first report of NDiV in China.

  11. The contrasting features of Asian summer monsoon during surplus and deficient rainfall over India

    Science.gov (United States)

    Raju, P. V. S.; Mohanty, U. C.; Rao, P. L. S.; Bhatla, R.

    2002-12-01

    An endeavour is made to distinguish the mean summer monsoon features during surplus and deficient monsoon seasons. Based on all-India summer monsoon rainfall, over 42 years (1958-99), seven surplus and ten deficient monsoon seasons are identified. Making use of daily averaged (00 Z and 12 Z) reanalysis data sets from the National Center for Environmental Prediction-National Center for Atmospheric Research for the corresponding surplus and deficient monsoon seasons, the mean circulation characteristics and large-scale energetics are examined.The circulation features denote that the cross equatorial flow, low-level jet and tropical easterly jet are stronger during a surplus monsoon. Further, strong Tibetan anticyclonic flow characterizes a surplus monsoon. The large-scale balances of kinetic energy, heat and moisture show a significantly large quantity of diabatic heating, adiabatic generation of kinetic energy, and horizontal convergence of heat and moisture during the surplus monsoon season compared with the deficient state. The regions with statistically significant difference between surplus and deficient monsoon seasons are delineated by a Student's t-test at the 95% confidence level. The remarkable aspect noticed in this study is that the Arabian Sea branch of the monsoon circulation is more vigorous during a surplus monsoon season, whereas the eastern Bay of Bengal branch is stronger during a deficient monsoon. The various large-scale budget terms of kinetic energy, heat and moisture are found to be consistent and in agreement with the seasonal monsoon activity over India.

  12. Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

    Science.gov (United States)

    Beaufort, L.; van der Kaars, S.; Bassinot, F. C.; Moron, V.

    2010-10-01

    Past variations in the dynamics of the Australian monsoon have been estimated from multi-proxy analysis of a core retrieved in the Eastern Banda Sea. Records of coccolith and pollen assemblages, spanning the last 150 000 years, allow reconstruction of past primary production in the Banda Sea, summer moisture availability, and the length of the dry season in northern Australia and southeastern Indonesia. The amount of moisture available during the summer monsoon follows typical glacial/interglacial dynamics with a broad asymmetrical 100-kyr cycle. Primary production and length of the dry season appear to be closely related, given that they follow the precessional cycle with the same phase. This indicates their independence from ice-volume variations. The present inter-annual variability of both parameters is related to El Niño Southern Oscillation (ENSO), which modulates the Australian Winter Monsoon (AWM). The precessional pattern observed in the past dynamics of the AWM is found in ENSO and monsoon records of other regions. A marked shift in the monsoon intensity occurring during the mid Holocene during a period of constant ice volume, suggests that low latitude climatic variation precedes increases in global ice volume. This precessional pattern suggests that a common forcing mechanism underlies low latitude climate dynamics, acting specifically and synchronously on the different monsoon systems.

  13. Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon

    Science.gov (United States)

    Beaufort, L.; van der Kaars, S.; Bassinot, F. C.; Moron, V.

    2010-06-01

    Past variations in the dynamics of the Australian monsoon have been estimated from multi-proxy analysis of a core retrieved in the Eastern Banda Sea. Records of coccolith and pollen assemblages, spanning the last 150,000 years, allow reconstruction of past primary production in the Banda Sea, summer moisture availability, and the length of the dry season in Northern Australia and Southeastern Indonesia. The amount of moisture available during the summer monsoon follows typical glacial/interglacial dynamics with a broad asymmetrical 100-kyr cycle. Primary production and length of the dry season appear to be closely related, given that they follow the precessional cycle with the same phase (August insolation). This indicates their independence from ice-volume variations. The present inter-annual variability of both parameters is related to El Niño Southern Oscillation (ENSO), which modulates the Australian Winter Monsoon (AWM). The precessional pattern observed in the past dynamics of the AWM is found in ENSO and monsoon records of other regions. A marked shift in the monsoon intensity occurring during the mid Holocene during a period of constant ice volume, suggest that low latitude climatic variation precedes global ice volume. This precessional pattern suggests that a common forcing mechanism underlies low latitude climate dynamics, acting specifically and synchronically on the different monsoon systems.

  14. On breaks of the Indian monsoon

    Indian Academy of Sciences (India)

    Sulochana Gadgil; P V Joseph

    2003-12-01

    For over a century, the term break has been used for spells in which the rainfall over the Indian monsoon zone is interrupted. The phenomenon of `break monsoon' is of great interest because long intense breaks are often associated with poor monsoon seasons. Such breaks have distinct circulation characteristics (heat trough type circulation) and have a large impact on rainfed agriculture.Although interruption of the monsoon rainfall is considered to be the most important feature of the break monsoon, traditionally breaks have been identified on the basis of the surface pressure and wind patterns over the Indian region. We have defined breaks (and active spells) on the basis of rainfall over the monsoon zone. The rainfall criteria are chosen so as to ensure a large overlap with the traditional breaks documented by Ramamurthy (1969) and De et al (1998). We have identified these rainbreaks for 1901-89. We have also identified active spells on the basis of rainfall over the Indian monsoon zone. We have shown that the all-India summer monsoon rainfall is significantly negatively correlated with the number of rainbreak days (correlation coefficient −0.56) and significantly positively correlated with the number of active days (correlation coefficient 0.47).Thus the interannual variation of the all-India summer monsoon rainfall is shown to be related to the number of days of rainbreaks and active spells identified here. There have been several studies of breaks (and also active spells in several cases) identified on the basis of different criteria over regions differing in spatial scales (e.g., Webster et al 1998; Krishnan et al 2000; Goswami and Mohan 2000; and Annamalai and Slingo 2001). We find that there is considerable overlap between the rainbreaks we have identified and breaks based on the traditional definition. There is some overlap with the breaks identified by Krishnan et al (2000) but little overlap with breaks identified by Webster et al (1998). Further

  15. Impacts of East Asian aerosols on the Asian monsoon

    Science.gov (United States)

    Bartlett, Rachel; Bollasina, Massimo; Booth, Ben; Dunstone, Nick; Marenco, Franco

    2016-04-01

    Over recent decades, aerosol emissions from Asia have increased rapidly. Aerosols are able to alter radiative forcing and regional hydroclimate through direct and indirect effects. Large emissions within the geographical region of the Asian monsoon have been found to impact upon this vital system and have been linked to observed drying trends. The interconnected nature of smaller regional monsoon components (e.g. the Indian monsoon and East Asian monsoon) presents the possibility that aerosol sources could have far-reaching impacts. Future aerosol emissions are uncertain and may continue to dominate regional impacts on the Asian monsoon. Standard IPCC future emissions scenarios do not take a broad sample of possible aerosol pathways. We investigate the sensitivity of the Asian monsoon to East Asian aerosol emissions. Experiments carried out with HadGEM2-ES use three time-evolving future anthropogenic aerosol emissions scenarios with similar time-evolving greenhouse gases. We find a wetter summer over southern China and the Indochina Peninsula associated with increased sulfate aerosol over China. The southern-flood-northern-drought pattern seen in observations is reflected in these results. India is found to be drier in the summer overall, although wetter in June. These precipitation changes are linked to the increase in sulfate through the alteration of large scale dynamics. Sub-seasonal changes are also seen, with an earlier withdrawal of the monsoon over East Asia.

  16. Summer monsoon rainfall prediction for India - Some new ideas

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    Present methods of forecasting of mean Indian rainfall for summer monsoon season are critically examined. Considering the wide variations in mean seasonal rainfalls (more than 5 to less than 400 cm) and crops in various regions of India...

  17. Transient coupling relationships of the Holocene Australian monsoon

    CERN Document Server

    McRobie, Fiona H; Wyrwoll, Karl-Heinz

    2015-01-01

    The modern-day northwest Australian summer monsoon is dynamically coupled to other regional monsoon systems and inflows from the Indian Ocean, however, the nature of these relationships over longer time scales is uncertain. Previous attempts to evaluate how proxy records from the Indonesian-Australian monsoon region correspond to other records from the Indian and East Asian monsoon regions, as well as to El Ni\\~no-related proxy records, has been qualitative, relying on `curve-fitting' methods. Here, we seek a quantitative approach for identifying coupling relationships between paleoclimate proxy records, employing statistical techniques to compute the interdependence of two paleoclimate time series. We verify the use of complex networks to identify coupling relationships between modern climate indices which correspond to physically-based mechanisms. This method is then extended to a set of paleoclimate proxy records from the Asian, Australasian and South American regions spanning the past 9,000 years. The res...

  18. Disability from Japanese encephalitis in Cambodia and Viet Nam.

    Science.gov (United States)

    Hills, Susan L; Van Cuong, Nguyen; Touch, Sok; Mai, Hoang Hong; Soeung, Sann Chan; Lien, Tran Thi Huong; Samnang, Chham; Sovann, Ly; Van Diu, Pham; Lac, Luc Duy; Heng, Seng; Huong, Vu Minh; Grundy, John J; Huch, Chea; Lewthwaite, Penny; Solomon, Tom; Jacobson, Julie A

    2011-08-01

    A cohort of Japanese encephalitis (JE) survivors in Cambodia and Viet Nam were assessed at least 4 months after hospital discharge in order to understand the extent of disability after JE. We used a simple assessment tool which focuses on the impact on daily life. In total, 64 disability assessments were conducted: 38 in Cambodia and 26 in Viet Nam. In Cambodia, 4 (11%) children had severe sequelae, suggesting the children would likely be dependent, 15 (39%) had moderate sequelae and 17 (45%) had mild sequelae. In Viet Nam, two (8%) persons had severe sequelae, five (19%) had moderate sequelae and eight (31%) had mild sequelae. In many JE-endemic areas there are no multi-disciplinary teams with sophisticated equipment to assess patients after JE disease. This assessment tool can assist with patient management and generate data to support the need for programmes to prevent disease and improve outcomes for survivors.

  19. Transport of aerosols into the UTLS and their impact on the Asian monsoon region as seen in a global model simulation

    Directory of Open Access Journals (Sweden)

    S. Fadnavis

    2013-09-01

    Full Text Available An eight-member ensemble of ECHAM5-HAMMOZ simulations for a boreal summer season is analysed to study the transport of aerosols in the upper troposphere and lower stratosphere (UTLS during the Asian summer monsoon (ASM. The simulations show persistent maxima in black carbon, organic carbon, sulfate, and mineral dust aerosols within the anticyclone in the UTLS throughout the ASM (period from July to September, when convective activity over the Indian subcontinent is highest, indicating that boundary layer aerosol pollution is the source of this UTLS aerosol layer. The simulations identify deep convection and the associated heat-driven circulation over the southern flanks of the Himalayas as the dominant transport pathway of aerosols and water vapour into the tropical tropopause layer (TTL. Comparison of model simulations with and without aerosols indicates that anthropogenic aerosols are central to the formation of this transport pathway. Aerosols act to increase cloud ice, water vapour, and temperature in the model UTLS. Evidence of ASM transport of aerosols into the stratosphere is also found, in agreement with aerosol extinction measurements from the Halogen Occultation Experiment (HALOE and Stratospheric Aerosol and Gas Experiment (SAGE II. As suggested by the observations, aerosols are transported into the Southern Hemisphere around the tropical tropopause by large-scale mixing processes. Aerosol-induced circulation changes also include a weakening of the main branch of the Hadley circulation and a reduction of monsoon precipitation over India.

  20. NAM-1gene polymorphism and grain protein content in Hordeum.

    Science.gov (United States)

    Jamar, Catherine; Loffet, Francois; Frettinger, Patrick; Ramsay, Luke; Fauconnier, Marie-Laure; du Jardin, Patrick

    2010-04-15

    Grain protein content (GPC) is a key quality factor for malting and brewing process. In wheat, a QTL explaining a large part of GPC variation was identified, which co-localizes with a gene encoding a NAC transcription factor (TtNAM-B1). NAC transcription factors influence GPC by their role in the regulation of senescence and in protein remobilization. An orthologous gene was discovered on barley chromosome 6H where a GPC QTL was mapped. In this study, we identify allelic variation of the NAM-1 gene for three species of Hordeum representing wild and cultivated barley and we investigate the possible link with GPC. Three haplotypes were identified, one corresponds to the sequences of 11 European varieties representing H. vulgare, one corresponds to the sequence found in H. spontaneum and one represents the sequence of H. bulbosum. Three SNPs were identified between H. spontaneum sequence and H. vulgare sequence. One of the H. bulbosum polymorphisms leads to the introduction of a stop codon and a non-functional protein. Differences in GPC between the 11 varieties were found but no polymorphism in the NAM-1 gene was observed, suggesting that differences in expression of the HvNAM-1 gene or other genes should play a role in GPC regulation. Nevertheless based on published values for GPC of H. bulbosum and H. spontaneum compared to GPC measured here in H. vulgare, the non-functional protein is associated with the lower GPC, suggesting that loss of functionality of the NAM-1 gene in Hordeum is related to lower GPC. Moreover H. spontaneum GPC seems to be higher than H. vulgare GPC, suggesting also that allelic variation of the functional NAM-1 gene could be associated with GPC variation within the genus Hordeum. Copyright 2009 Elsevier GmbH. All rights reserved.

  1. Early forecasting of Indian Summer Monsoon: case study 2016

    Science.gov (United States)

    Surovyatkina, Elena; Stolbova, Veronika; Kurths, Jurgen

    2017-04-01

    The prior knowledge of dates of onset and withdrawal of monsoon is of vital importance for the population of the Indian subcontinent. In May 2016 before monsoon season, India recorded its highest-ever temperature of 51C. Hot waves have decimated crops, killed livestock and left 330 million people without enough water. At the end of monsoon season the floods in Indian this year have also broken previous records. Severe and devastating rainfall poured down, triggering dams spilling and floods. Such extreme conditions pose the vital questions such as: When will the monsoon come? When will the monsoon withdraw? More lead time in monsoon forecast warning is crucial for taking appropriate decisions at various levels - from the farmer's field (e.g. plowing day, seeding) to the central government (e.g. managing water and energy resources, food procurement policies). The Indian Meteorological Department issues forecasts of onset of monsoon for Kerala state in South India on May 15-th. It does not give such predictions for the other 28 states of the country. Our study concerns the central part of India. We made the monsoon forecast using our recently developed method which focuses on Tipping elements of the Indian monsoon [1]. Our prediction relies on observations of near-surface air temperature and relative humidity from both the ERA-40 and NCEP/NCAR reanalyses. We performed both of our forecasts for the onset and withdrawal of monsoon for the central part of India, the Eastern Ghats (20N,80E). We predicted the monsoon arrival to the Eastern Ghats (20N,80E) on the 13th of June with a deviation of +/-4 days. The prediction was made on May 6-th, 2016 [2], that is 40 days in advance of the date of the forecast. The actual monsoon arrival was June 17-th. In this day near-surface air temperature and relative humidity overcame the critical values and the monsoon season started, that was confirmed by observations of meteorological stations located around the EG-region. We

  2. Impact of climate change on sediment yield in the Mekong River basin: a case study of the Nam Ou basin, Lao PDR

    NARCIS (Netherlands)

    Shrestha, B.; Babel, M.S.; Maskey, S.; Van Griensven, A.; Uhlenbrook, S.; Green, A.; Akkharath, I.

    2013-01-01

    This paper evaluates the impact of climate change on sediment yield in the Nam Ou basin located in northern Laos. Future climate (temperature and precipitation) from four general circulation models (GCMs) that are found to perform well in the Mekong region and a regional circulation model (PRECIS) a

  3. Origin of worldwide cultivated barley revealed by NAM-1 gene and grain protein content

    Directory of Open Access Journals (Sweden)

    Yonggang eWang

    2015-09-01

    Full Text Available The origin, evolution and distribution of cultivated barley provides powerful insights into the historic origin and early spread of agrarian culture. Here, population-based genetic diversity and phylogenetic analyses were performed to determine the evolution and origin of barley and how domestication and subsequent introgression have affected the genetic diversity and changes in cultivated barley on a worldwide scale. A set of worldwide cultivated and wild barleys from Asia and Tibet of China were analyzed using the sequences for NAM-1 gene and gene-associated traits-GPC (grain protein content. Our results showed Tibetan wild barley distinctly diverged from Near Eastern barley, and confirmed that Tibet is one of the origin and domestication centers for cultivated barley, and in turn supported a polyphyletic origin of domesticated barley. Comparison of haplotype composition among geographic regions revealed gene flow between Eastern and Western barley populations, suggesting that the Silk Road might have played a crucial role in the spread of genes. The GPC in the 118 cultivated and 93 wild barley accessions ranged from 6.73% to 12.35% with a mean of 9.43%. Overall, wild barley had higher averaged GPC (10.44% than cultivated barley. Two unique haplotypes (Hap2 and Hap7 caused by a base mutations (at position 544 in the coding region of the NAM-1 gene might have a significant impact on the GPC. SNPs and haplotypes of NAM-1 associated with GPC in barley could provide a useful method for screening GPC in barley germplasm. The Tibetan wild accessions with lower GPC could be useful for malt barley breeding

  4. Paragonimiasis in Sin Ho District, Lai Chau Province, Viet Nam.

    Science.gov (United States)

    Vien, C V; Phue, N C; Ha, L D; Tuan, L M; Van, N T; Pao, T C; Hoa, L T; Phoung, C T

    1997-01-01

    Forty-four cases of pulmonary paragonimiasis, two also with evidence of cerebral infection, were found in Sin Ho District in Northern Viet Nam. There were 30 males and 14 females, 2-30 years of age. The diagnosis was made by sputum examination. Pet dogs and wild dogs in the area were also found infected and the people often eat roasted crabs.

  5. Globalization and the Governance of Education in Viet Nam

    Science.gov (United States)

    London, Jonathan D.

    2010-01-01

    In a globalizing world, local and global governance arrangements are increasingly interdependent, which produces harmonization in some instances and new tensions and contradictions in others. Analysis shows that successive waves of globalization have affected the governance of education in Viet Nam differently. It shows that the globalization of…

  6. National survey of tuberculosis prevalence in Viet Nam

    NARCIS (Netherlands)

    Hoa, N.B.; Sy, D.N.; Nhung, N.V.; Tiemersma, E.W.; Borgdorff, M.W.; Cobelens, F.G.J.

    2010-01-01

    OBJECTIVE: To estimate the prevalence of tuberculosis in Viet Nam with data from a population-based survey, compare it with the prevalence estimated by the World Health Organization, and identify major demographic determinants of tuberculosis prevalence. METHODS: A cross-sectional survey with multis

  7. Wave overtopping resistance of grassed slopes in Viet Nam

    NARCIS (Netherlands)

    Trung, L.H.; Verhagen, H.J.; Van der Meer, J.W.

    2011-01-01

    The Simulator was applied to test the resistance against wave overtopping of grass covered dike slopes in Viet Nam. Observation and measurement during destructive tests were performed to investigate the development process of damage induced by overtopping flow. Damages were likely to be initiated at

  8. Globalization and the Governance of Education in Viet Nam

    Science.gov (United States)

    London, Jonathan D.

    2010-01-01

    In a globalizing world, local and global governance arrangements are increasingly interdependent, which produces harmonization in some instances and new tensions and contradictions in others. Analysis shows that successive waves of globalization have affected the governance of education in Viet Nam differently. It shows that the globalization of…

  9. Adequacy of anti-tuberculosis drug prescriptions in Viet Nam

    DEFF Research Database (Denmark)

    Hoa, N B; Lauritsen, J M; Rieder, H L

    2012-01-01

    SETTING: National Tuberculosis Program, Viet Nam, 2008. OBJECTIVES: To determine drug prescription adherence to national guidelines, to examine factors associated with an erroneous dosage of rifampin (RMP) and to evaluate the impact of an insufficient RMP dosage on treatment outcome. METHODS: A r...

  10. Wave overtopping resistance of grassed slopes in Viet Nam

    NARCIS (Netherlands)

    Trung, L.H.; Verhagen, H.J.; Van der Meer, J.W.

    2011-01-01

    The Simulator was applied to test the resistance against wave overtopping of grass covered dike slopes in Viet Nam. Observation and measurement during destructive tests were performed to investigate the development process of damage induced by overtopping flow. Damages were likely to be initiated at

  11. Impacts of intraseasonal oscillation on the onset and interannual variation of the Indian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    QI YanJun; ZHANG RenHe; LI Tim; WEN Min

    2009-01-01

    The role of the intraseasonal oscillation (ISO) on the seasonal and interannual variations of the Indian summer monsoon is investigated based on the analysis of observational data. It is shown that the ISO significantly contributes to the establishment of low-level westerlies during the monsoon onset and developing periods. The effect of the ISO on the annual cycle of the monsoon is through nonlinear eddy momentum transport. On the interannual timescale, the Indian summer monsoon rainfall exhibits a significant out-of-phase relationship with the ISO intensity over the Indian monsoon region. In strong ISO years it appears the weak monsoon when there is an abnormal high over the India subcontinent in the lower troposphere. In weak ISO years there exists an abnormal low and the strong monsoon ap-pears.

  12. Recent increase in sex ratio at birth in Viet Nam.

    Directory of Open Access Journals (Sweden)

    Christophe Z Guilmoto

    Full Text Available INTRODUCTION: Since the 1980s, sex ratio at birth (male births per 100 female births has increased in many Asian countries as a result of selective abortions, but to date there has been no such evidence for Viet Nam. Our aim in this paper is to ascertain the situation with respect to sex ratio at birth in Viet Nam over the past five years. MATERIALS AND METHODS: Original data were obtained from sample population surveys in Viet Nam recording annual birth rates since 2000 of about 450,000 women, as well as from two successive birth surveys conducted for the first time in 2007 (1.1 million births. The annual population surveys include specific information on birth history and mothers' characteristics to be used for the analysis of trends and differentials in sex ratio at birth. RESULTS AND DISCUSSION: Birth history statistics indicate that the SRB in Viet Nam has recorded a steady growth since 2001. Starting from a level probably close to the biological standard of 105, the SRB reached 108 in 2005 and 112 in 2006, a value significantly above the normal level. An independent confirmation of these results comes from the surveys of births in health facilities which yielded a SRB of 110 in 2006-07. High SRB is linked to various factors such as access to modern health care, number of prenatal visits, level of higher education and employment status, young age, province of residence and prenatal sex determination. These results suggest that prenatal sex determination followed by selective abortion has recently become more common in Viet Nam. This recent trend is a consequence of various factors such as preference for sons, declining fertility, easy access to abortion, economic development as well as the increased availability of ultrasonography facilities.

  13. Anomalous behaviour of the Indian summer monsoon 2009

    Indian Academy of Sciences (India)

    B Preethi; J V Revadekar; R H Kripalani

    2011-10-01

    The Indian subcontinent witnessed a severe monsoon drought in the year 2009. India as a whole received 77% of its long period average during summer monsoon season (1 June to 30 September) of 2009, which is the third highest deficient all India monsoon season rainfall year during the period 1901–2009. Therefore, an attempt is made in this paper to study the characteristic features of summer monsoon rainfall of 2009 over the country and to investigate some of the possible causes behind the anomalous behaviour of the monsoon. Presence of El Niño like conditions in the Pacific and warming over the equatorial Indian Ocean altered the circulation patterns and produced an anomalous low level convergence and ascending motion over the Indian Ocean region and large scale subsidence over the Indian landmass. Furthermore, the crossequatorial flow was weak, the monsoon was dominated by the slower 30–60 day mode, and the synoptic systems, which formed over the Bay of Bengal and the Arabian Sea, did not move inland. All the above features resulted in less moisture supply over the Indian landmass, resulting in subdued rainfall activity leading to a severe monsoon drought during 2009.

  14. Predictor-Year Subspace Clustering Based Ensemble Prediction of Indian Summer Monsoon

    Directory of Open Access Journals (Sweden)

    Moumita Saha

    2016-01-01

    Full Text Available Forecasting the Indian summer monsoon is a challenging task due to its complex and nonlinear behavior. A large number of global climatic variables with varying interaction patterns over years influence monsoon. Various statistical and neural prediction models have been proposed for forecasting monsoon, but many of them fail to capture variability over years. The skill of predictor variables of monsoon also evolves over time. In this article, we propose a joint-clustering of monsoon years and predictors for understanding and predicting the monsoon. This is achieved by subspace clustering algorithm. It groups the years based on prevailing global climatic condition using statistical clustering technique and subsequently for each such group it identifies significant climatic predictor variables which assist in better prediction. Prediction model is designed to frame individual cluster using random forest of regression tree. Prediction of aggregate and regional monsoon is attempted. Mean absolute error of 5.2% is obtained for forecasting aggregate Indian summer monsoon. Errors in predicting the regional monsoons are also comparable in comparison to the high variation of regional precipitation. Proposed joint-clustering based ensemble model is observed to be superior to existing monsoon prediction models and it also surpasses general nonclustering based prediction models.

  15. Soil moisture initialization effects in the Indian monsoon system

    OpenAIRE

    Asharaf, S.; A. Dobler; Ahrens, B.

    2011-01-01

    Towards the goal to understand the role of land-surface processes over the Indian sub-continent, a series of soil-moisture sensitivity simulations have been performed using a non-hydrostatic regional climate model COSMO-CLM. The experiments were driven by the lateral boundary conditions provided by the ERA-Interim (ECMWF) reanalysis. The simulation results show that the pre-monsoonal soil moisture has a significant influence on the monsoonal precipitation. Both, positive and negative soil-moi...

  16. The Aerosol-Monsoon Climate System of Asia

    Science.gov (United States)

    Lau, William K. M.; Kyu-Myong, Kim

    2012-01-01

    In Asian monsoon countries such as China and India, human health and safety problems caused by air-pollution are worsening due to the increased loading of atmospheric pollutants stemming from rising energy demand associated with the rapid pace of industrialization and modernization. Meanwhile, uneven distribution of monsoon rain associated with flash flood or prolonged drought, has caused major loss of human lives, and damages in crop and properties with devastating societal impacts on Asian countries. Historically, air-pollution and monsoon research are treated as separate problems. However a growing number of recent studies have suggested that the two problems may be intrinsically intertwined and need to be studied jointly. Because of complexity of the dynamics of the monsoon systems, aerosol impacts on monsoons and vice versa must be studied and understood in the context of aerosol forcing in relationship to changes in fundamental driving forces of the monsoon climate system (e.g. sea surface temperature, land-sea contrast etc.) on time scales from intraseasonal variability (weeks) to climate change ( multi-decades). Indeed, because of the large contributions of aerosols to the global and regional energy balance of the atmosphere and earth surface, and possible effects of the microphysics of clouds and precipitation, a better understanding of the response to climate change in Asian monsoon regions requires that aerosols be considered as an integral component of a fully coupled aerosol-monsoon system on all time scales. In this paper, using observations and results from climate modeling, we will discuss the coherent variability of the coupled aerosol-monsoon climate system in South Asia and East Asia, including aerosol distribution and types, with respect to rainfall, moisture, winds, land-sea thermal contrast, heat sources and sink distributions in the atmosphere in seasonal, interannual to climate change time scales. We will show examples of how elevated

  17. [Chemical composition and daily variation of melt water during ablation season in monsoonal temperate Glacier region: a case study of Baishui Glacier No. 1].

    Science.gov (United States)

    Zhu, Guo-Feng; Pu, Tao; He, Yuan-Qing; Wang, Pei-Zhen; Kong, Jian-Long; Zhang, Ning-Ning; Xin, Hui-Juan

    2012-12-01

    Melt water samples collected continuously from 29 August to 3 September 2009 in the Baishui Glacier No. 1 at elevation of 4750 m were analyzed for pH, conductivity, delta18O and inorganic ions. The results showed that the pH had obvious diurnal variations and was increased slightly by the influence of precipitation. The dissolution of alkaline soluble salts in the dust was the main reason for the increase of melt water conductivity; the value of delta18O was relatively low in strong ablation period and high in slight ablation period. Different from other research areas, the concentrations of Na+, K+, which were influenced by lithological and marine water vapor, were higher than that of Mg2+ in the study area; HCO3- and Ca2+ accounted for more than 80% of total ions in snow and ice melt water, indicating that the ions mainly came from limestone and the melt water was a typical carbonate solution; The content of melt water had an obvious daily change with temperature change, but the response amplitudes were different; Monsoon transport, local rock lithology, human industrial and agricultural activities were the main sources of inorganic ions and the deciding factors of the ion composition in the Baishui Glacier No. 1.

  18. Emerging Technologies for Ecohydrological Studies during the North American Monsoon in a Chihuahuan Desert Watershed

    Science.gov (United States)

    Templeton, R. C.; Vivoni, E. R.; Mendez-Barroso, L. A.; Rango, A.; Laliberte, A.; Saripalli, S.

    2010-12-01

    Monsoonal systems are due to seasonal shifts in atmospheric circulation that may result in a large fraction of the annual precipitation falling within a few months. The North American Monsoon System (NAMS) contributes approximately 55% of the annual rainfall in the New Mexico Chihuahuan Desert during the summer period. Relatively frequent storm events during the NAMS result in increased soil moisture that drive greater soil microbial activity and increased ecosystem primary productivity. During severe storms, runoff production can lead to flood events that recharge the subsurface through channel losses. In this study, we present preliminary results from a network of soil, channel, and atmospheric monitoring equipment in a small watershed (~0.05 km2) located in the Jornada Experimental Range (JER) near Las Cruces, New Mexico. Using the instrument network, we characterize the temporal and spatial variability of rainfall (5 rain gauges), soil moisture and temperature (16 profile locations), and channel runoff (4 flumes) within the watershed during the summer of 2010. In addition, we utilize CO2, H2O, and energy flux measurements by an eddy covariance tower to quantify the seasonal changes in land-atmosphere exchanges. These coordinated, spatially-distributed observations are complemented by the novel use of two Unmanned Aerial Vehicle (UAV) platforms for watershed characterization. Using a small airplane (the MLB BAT 3), we obtained a set of very high-resolution images (~7 cm) and created an orthomosaic to characterize vegetation cover and species prior to the NAMS and after full canopy development. Several instrument packages (optical, stereo and LIDAR) on board a SR30 UAV Electric helicopter also provide detailed information on the watershed, including a high-resolution digital elevation model (DEM). The conjunctive use of these datasets will allow for unprecedented analysis of how the onset and progression of the NAMS affects water, energy and carbon fluxes in a

  19. External evaluation of the Ban Nam Paeng & Ban Nam Ki ComMod case study in Nan Province, Northern Thailand : Final Report

    NARCIS (Netherlands)

    Paassen, van A.; Patamadit, I.

    2007-01-01

    Verslag van de evaluatie rondom het gebruik van Companion Modelling (ComMod) bij projecten in Ban Nam Paeng & Ban Nam Ki, in de provincie Nan, in het noorden van Thailand. Een van de doelen is om de lokale bevolking (meer) inspraak te geven bij besluitvorming rond bijvoorbeeld het oprichten van

  20. Recent change of the global monsoon precipitation (1979-2008)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bin [University of Hawaii at Manoa, Department of Meteorology, Honolulu, HI (United States); University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); Liu, Jian [Chinese Academy of Sciences, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Nanjing (China); Kim, Hyung-Jin [Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Yokohama, Kanagawa (Japan); Webster, Peter J. [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); Yim, So-Young [University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States)

    2012-09-15

    The global monsoon (GM) is a defining feature of the annual variation of Earth's climate system. Quantifying and understanding the present-day monsoon precipitation change are crucial for prediction of its future and reflection of its past. Here we show that regional monsoons are coordinated not only by external solar forcing but also by internal feedback processes such as El Nino-Southern Oscillation (ENSO). From one monsoon year (May to the next April) to the next, most continental monsoon regions, separated by vast areas of arid trade winds and deserts, vary in a cohesive manner driven by ENSO. The ENSO has tighter regulation on the northern hemisphere summer monsoon (NHSM) than on the southern hemisphere summer monsoon (SHSM). More notably, the GM precipitation (GMP) has intensified over the past three decades mainly due to the significant upward trend in NHSM. The intensification of the GMP originates primarily from an enhanced east-west thermal contrast in the Pacific Ocean, which is coupled with a rising pressure in the subtropical eastern Pacific and decreasing pressure over the Indo-Pacific warm pool. While this mechanism tends to amplify both the NHSM and SHSM, the stronger (weaker) warming trend in the NH (SH) creates a hemispheric thermal contrast, which favors intensification of the NHSM but weakens the SHSM. The enhanced Pacific zonal thermal contrast is largely a result of natural variability, whilst the enhanced hemispherical thermal contrast is likely due to anthropogenic forcing. We found that the enhanced global summer monsoon not only amplifies the annual cycle of tropical climate but also promotes directly a ''wet-gets-wetter'' trend pattern and indirectly a ''dry-gets-drier'' trend pattern through coupling with deserts and trade winds. The mechanisms recognized in this study suggest a way forward for understanding past and future changes of the GM in terms of its driven mechanisms. (orig.)

  1. Two Integrator Loop Filters: Generation Using NAM Expansion and Review

    Directory of Open Access Journals (Sweden)

    Ahmed M. Soliman

    2010-01-01

    Full Text Available Systematic synthesis method to generate a family of two integrator loop filters based on nodal admittance matrix (NAM expansion is given. Eight equivalent circuits are obtained; six of them are new. Each of the generated circuits uses two grounded capacitors and employs two current conveyors (CCII or two inverting current conveyors (ICCII or a combination of both. The NAM expansion is also used to generate eight equivalent grounded passive elements two integrator loop filters using differential voltage current conveyor (DVCC; six of them are new. Changing the input port of excitation, two new families of eight unity gain lowpass filter circuits each using two CCII or ICCII or combination of both or two DVCC are obtained.

  2. Predicting onset and withdrawal of Indian Summer Monsoon in 2016: results of Tipping elements approach

    Science.gov (United States)

    Surovyatkina, Elena; Stolbova, Veronika; Kurths, Jurgen

    2017-04-01

    The monsoon is the season of rain caused by a global seasonal reverse in winds direction and a change in pressure distribution. The Southwest winds bring summer monsoon to India. The economy of India is able to maintain its GDP in the wake of a good monsoon. However, if monsoon gets delayed by even two weeks, it can spell disaster because the high population depending on agriculture - 70% of its people directly related to farming. Agriculture, in turn, is dependent on the monsoon. Although the rainy season happens annually between June and September, the time of monsoon season's onset and withdrawal varies within a month from year to year. The important feature of the monsoon is that it starts and ends suddenly. Hence, despite enormous progress having been made in predicting monsoon since 1886, it remains a significant scientific challenge. To make predictions of monsoon timing in 2016, we applied our recently developed method [1]. Our approach is based on a teleconnection between the Eastern Ghats (EG) and North Pakistan (NP) - Tipping Elements of Indian Summer Monsoon. Both our predictions - for monsoon onset and withdrawal - were made for the Eastern Ghats region (EG-20N,80E) in the central part of India, while the Indian Meteorological Department forecasts monsoon over Kerala - a state at the southern tip of the Indian subcontinent. Our prediction for monsoon onset was published on May 6-th, 2016 [2]. We predicted the monsoon arrival to the EG on the 13th of June with a deviation of +/-4 days. In fact, monsoon onset was on June 17-th, that was confirmed by information from meteorological stations located around the EG-region. Hence, our prediction of monsoon onset (made 40 days in advance) was correct. We delivered the prediction of monsoon withdrawal on July 27, 2016 [3], announcing the monsoon withdrawal from the EG on October 5-th with a deviation of +/-5 days. The actual monsoon withdrawal started on October 10-th when the relative humidity in the region

  3. Shifting covariability of North American summer monsoon precipitation with antecedent winter precipitation

    Science.gov (United States)

    McCabe, G.J.; Clark, M.P.

    2006-01-01

    Previous research has suggested that a general inverse relation exists between winter precipitation in the southwestern United states (US) and summer monsoon precipitation. In addition, it has been suggested that this inverse relation between winter precipitation and the magnitude of the southwestern US monsoon breaks down under certain climatic conditions that override the regional winter/monsoon precipitation relations. Results from this new study indicate that the winter/monsoon precipitation relations do not break down, but rather shift location through time. The strength of winter/monsoon precipitation relations, as indexed by 20-year moving correlations between winter precipitation and monsoon precipitation, decreased in Arizona after about 1970, but increased in New Mexico. The changes in these correlations appear to be related to an eastward shift in the location of monsoon precipitation in the southwestern US. This eastward shift in monsoon precipitation and the changes in correlations with winter precipitation also appear to be related to an eastward shift in July/August atmospheric circulation over the southwestern US that resulted in increased monsoon precipitation in New Mexico. Results also indicate that decreases in sea-surface temperatures (SSTs) in the central North Pacific Ocean also may be associated with th changes in correlations between winter and monsoon precipitation. Copyright ?? 2006 Royal Meteorological Society.

  4. ON THE PROCESS OF SUMMER MONSOON ONSET OVER EAST ASIA

    Institute of Scientific and Technical Information of China (English)

    陈隆勋; 李薇; 赵平; 陶诗言

    2001-01-01

    Using daily observational rainfall data covered 194 stations of China from 1961 to 1995 and NCEP model analyzed pentad precipitation data of global grid point from 1979 to 1997, the distribution of onset date of rainy season over Asian area from spring to summer is studied in this paper. The analyzed results show that there exist two stages of rainy season onset over East Asian region from spring to summer rainy season onset accompanying subtropical monsoon and tropical monsoon respectively. The former rain belt is mainly formed by the convergence of cold air and the recurved southwesterly flow from western part of subtropical high and westerly flow from the so-called western trough of subtropical region occurring during winter to spring over South Asia. The latter is formed in the process of subtropical monsoon rain belt over inshore regions of South China Sea originally coming from south of Changjiang (Yangtze) River Basin advancing with northward shift of subtropical high after the onset of tropical monsoon over South China Sea. The pre-flood rainy season over South China region then came into mature period and the second peak of rainfall appeared. Meiyu, the rainy season over Changjiang-Huaihe River Basin and North China then formed consequently. The process of summer tropical monsoon onset over South China Sea in 1998 is also discussed in this paper. It indicated that the monsoon during summer tropical monsoon onset over South China Sea is the result of the westerly flow over middle part of South China Sea,which is from the new generated cyclone formed in north subtropical high entering into South China Sea, converged with the tropical southwesterly flow recurved by the intensified cross-equatorial flow.

  5. Comparative Study of Monsoon Rainfall Variability over India and the Odisha State

    Directory of Open Access Journals (Sweden)

    K C Gouda

    2017-10-01

    Full Text Available Indian summer monsoon (ISM plays an important role in the weather and climate system over India. The rainfall during monsoon season controls many sectors from agriculture, food, energy, and water, to the management of disasters. Being a coastal province on the eastern side of India, Odisha is one of the most important states affected by the monsoon rainfall and associated hydro-meteorological systems. The variability of monsoon rainfall is highly unpredictable at multiple scales both in space and time. In this study, the monsoon variability over the state of Odisha is studied using the daily gridded rainfall data from India Meteorological Department (IMD. A comparative analysis of the behaviour of monsoon rainfall at a larger scale (India, regional scale (Odisha, and sub-regional scale (zones of Odisha is carried out in terms of the seasonal cycle of monsoon rainfall and its interannual variability. It is seen that there is no synchronization in the seasonal monsoon category (normal/excess/deficit when analysed over large (India and regional (Odisha scales. The impact of El Niño, La Niña, and the Indian Ocean Dipole (IOD on the monsoon rainfall at both scales (large scale and regional scale is analysed and compared. The results show that the impact is much more for rainfall over India, but it has no such relation with the rainfall over Odisha. It is also observed that there is a positive (negative relation of the IOD with the seasonal monsoon rainfall variability over Odisha (India. The correlation between the IAV of monsoon rainfall between the large scale and regional scale was found to be 0.46 with a phase synchronization of 63%. IAV on a sub-regional scale is also presented.

  6. A statistically predictive model for future monsoon failure in India

    Science.gov (United States)

    Schewe, Jacob; Levermann, Anders

    2012-12-01

    Indian monsoon rainfall is vital for a large share of the world’s population. Both reliably projecting India’s future precipitation and unraveling abrupt cessations of monsoon rainfall found in paleorecords require improved understanding of its stability properties. While details of monsoon circulations and the associated rainfall are complex, full-season failure is dominated by large-scale positive feedbacks within the region. Here we find that in a comprehensive climate model, monsoon failure is possible but very rare under pre-industrial conditions, while under future warming it becomes much more frequent. We identify the fundamental intraseasonal feedbacks that are responsible for monsoon failure in the climate model, relate these to observational data, and build a statistically predictive model for such failure. This model provides a simple dynamical explanation for future changes in the frequency distribution of seasonal mean all-Indian rainfall. Forced only by global mean temperature and the strength of the Pacific Walker circulation in spring, it reproduces the trend as well as the multidecadal variability in the mean and skewness of the distribution, as found in the climate model. The approach offers an alternative perspective on large-scale monsoon variability as the result of internal instabilities modulated by pre-seasonal ambient climate conditions.

  7. Possible role of pre-monsoon sea surface warming in driving the summer monsoon onset over the Bay of Bengal

    Science.gov (United States)

    Li, Kuiping; Liu, Yanliang; Yang, Yang; Li, Zhi; Liu, Baochao; Xue, Liang; Yu, Weidong

    2016-08-01

    Sea surface temperature (SST) reaches its annual maximum just before the summer monsoon onset and collapses soon after in the central areas of the Bay of Bengal (BoB). Here, the impact of the peak in the pre-monsoon SST on triggering the earliest monsoon onset in the BoB is investigated, with a focus on the role they play in driving the first-branch northward-propagating intra-seasonal oscillations (FNISOs) over the equatorial Eastern Indian Ocean (EIO). During the calm pre-monsoon period, sea surface warming in the BoB could increase the surface equivalent potential temperature (θe) in several ways. Firstly, warming of the sea surface heats the surface air through sensible heating, which forces the air temperature to follow the SST. The elevated air surface temperature accounts for 30 % of the surface θe growth. Furthermore, the elevated air temperature raises the water vapor capacity of the surface air to accommodate more water vapor. Constrained by the observation that the surface relative humidity is maintained nearly constant during the monsoon transition period, the surface specific humidity exhibits a significant increase, according to the Clausius-Clapeyron relationship. Budget analysis indicates that the additional moisture is primarily obtained from sea surface evaporation, which also exhibits a weak increasing trend due to the sea surface warming. In this way, it contributes about 70 % to the surface θe growth. The rapid SST increase during the pre-monsoon period preconditions the summer monsoon onset over the BoB through its contributions to significantly increase the surface θe, which eventually establishes the meridional asymmetry of the atmospheric convective instability in the EIO. The pre-established greater convective instability leads to the FNISO convections, and the summer monsoon is triggered in the BoB region.

  8. Active and break events of Indian summer monsoon during 1901-2014

    Digital Repository Service at National Institute of Oceanography (India)

    Pai, D.S.; Sridhar, L.; RameshKumar, M.R.

    The study lists active and break monsoon events over India over a very long period (1901-2014) identified using criteria based on a rainfall index derived over a critical high rainfall region called core monsoon zone. The break and active spells...

  9. Role of dynamics in the advection of aerosols over the Arabian Sea along the west coast of peninsular India during pre-monsoon season: A case study based on satellite data and regional climate model

    Indian Academy of Sciences (India)

    Marina Aloysius; S Sijikumar; S S Prijith; Mannil Mohan; K Parameswaran

    2011-04-01

    The circulation dynamics of an event marked by the formation of an aerosol cluster off the coast of Maharashtra on April 22, 2006, its southward migration along the Indian west coast with a mean speed of ∼200 km/day and its final dissipation after reaching the end of the peninsula by April 28, 2006 as revealed by MODIS (Moderate Resolution Imaging Spectroradiometer) against the pre-monsoon conditions of April 2006 are examined in this study. The maximum aerosol concentration in the cluster was found getting confined to lower and lower altitudes during its southward movement. The NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis wind field indicates that the atmospheric circulation, especially the horizontal wind convergence is the major factor that guides the formation and the dynamics of the cluster. Fine mode fraction from MODIS suggests that the cluster mainly consists of coarse dust particles. The regional climate model, RegCM3 with an efficient dust generation module simulates the formation and movement of the cluster appreciably well. The simulations which also exhibit the altitudinally descending nature of the cluster during its southward movement confirm the mechanism which governs the cluster dynamics suggested based on MODIS and NCEP/NCAR reanalysis data.

  10. Asian Monsoon Variability from the Monsoon Asia Drought Atlas (MADA) and Links to Indo-Pacific Climate

    Science.gov (United States)

    Ummenhofer, Caroline; D'Arrigo, Rosanne; Anchukaitis, Kevin; Hernandez, Manuel; Buckley, Brendan; Cook, Edward

    2014-05-01

    Drought patterns across monsoon and temperate Asia over the period 1877-2005 are linked to Indo-Pacific climate variability associated with the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). Using the Monsoon Asia Drought Atlas (MADA) composed of a high-resolution network of hydroclimatically sensitive tree-ring records with a focus on the June-August months, spatial drought patterns during El Niño and IOD events are assessed as to their agreement with an instrumental drought index and consistency in the drought response amongst ENSO/IOD events. Spatial characteristics in drought patterns are related to regional climate anomalies over the Indo-Pacific basin, using reanalysis products, including changes in the Asian monsoon systems, zonal Walker circulation, moisture fluxes, and precipitation. A weakening of the monsoon circulation over the Indian subcontinent and Southeast Asia during El Niño events, along with anomalous subsidence over monsoon Asia and reduced moisture flux, is reflected in anomalous drought conditions over India, Southeast Asia and Indonesia. When an IOD event co-occurs with an El Niño, severe drought conditions identified in the MADA for Southeast Asia, Indonesia, eastern China and central Asia are associated with a weakened South Asian monsoon, reduced moisture flux over China, and anomalous divergent flow and subsidence over Indonesia. Variations in the strength of the South Asian monsoon can also be linked to the Strange Parallels Drought (1756-1768) affecting much of Southeast Asia and the Indian subcontinent in the mid-18th Century. Large-scale climate anomalies across the wider region during years with an anomalously strengthened/weakened South Asian monsoon are discussed with implications for severe droughts prior to the instrumental period. Insights into the relative influences of Pacific and Indian Ocean variability for Asian monsoon climate on interannual to decadal and longer timescales, as recorded in the

  11. Book Review: Late Cenozoic Climate Change in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution

    Science.gov (United States)

    Clemens, Steven C.

    2015-01-01

    Loess-Paleosol deposits drape >500,000 km2 of eastern China, spanning environments from the humid, monsoon-influenced regions near the coast to the arid, westerlies-dominated regions inland. Sections, up to hundreds of meters thick, are exposed in deeply incised river valleys and can be accessed as well by drilling. Combined, the high sedimentation rates and extensive geographic coverage make these sections unique among global terrestrial sediment archives. The Chinese loess-paleosol sequences, and the arid interior regions to the northwest, record diverse aspects of geologic and environmental change ranging from the tectonic evolution of the Tibetan Plateau (106 year time scale) through glacial-interglacial scale changes in global ice volume and greenhouse gasses (105 year time scale) on down through the orbital (104 years) to millennial and centennial scale events (103-102 year) relevant to the underpinnings of human interactions with changing environmental pressures. 'Late Cenozoic Climate Chang in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution' is a timely contribution that synthesizes findings derived from the extensive work in these areas, places the findings in the broader context of global climate change and helps to define avenues for future research.

  12. Plague foci in Viet Nam: zoological and parasitological aspects.

    OpenAIRE

    Suntsov, V. V.; Huong, L. T.; Suntsova, N. I.; Gratz, N. G.

    1997-01-01

    Reported are the results of studies over the period 1989-94 on host-flea complexes in small mammals and their flea ectoparasites in and around a number of human settlements in Viet Nam in which human cases of plague had been found. Collections were also made in savanna and tropical forest areas within a 10-km radius of the settlements. The greatest numbers of small mammals, for the most part Rattus spp., and of the flea ectoparasite Xenopsylla cheopis were found in inhabited areas. X. cheopis...

  13. Investigation of summer monsoon rainfall variability in Pakistan

    Science.gov (United States)

    Hussain, Mian Sabir; Lee, Seungho

    2016-08-01

    This study analyzes the inter-annual and intra-seasonal rainfall variability in Pakistan using daily rainfall data during the summer monsoon season (June to September) recorded from 1980 to 2014. The variability in inter-annual monsoon rainfall ranges from 20 % in northeastern regions to 65 % in southwestern regions of Pakistan. The analysis reveals that the transition of the negative and positive anomalies was not uniform in the investigated dataset. In order to acquire broad observations of the intra-seasonal variability, an objective criterion, the pre-active period, active period and post-active periods of the summer monsoon rainfall have demarcated. The analysis also reveals that the rainfall in June has no significant contribution to the increase in intra-seasonal rainfall in Pakistan. The rainfall has, however, been enhanced in the summer monsoon in August. The rainfall of September demonstrates a sharp decrease, resulting in a high variability in the summer monsoon season. A detailed examination of the intra-seasonal rainfall also reveals frequent amplitude from late July to early August. The daily normal rainfall fluctuates significantly with its maximum in the Murree hills and its minimum in the northwestern Baluchistan.

  14. Monsoon dynamics over the past millennium on the southern-central Tibetan Plateau

    Science.gov (United States)

    Ahlborn, Marieke; Haberzettl, Torsten; Kasper, Thomas; Henkel, Karoline; Doberschütz, Stefan; Daut, Gerhard; Reinwarth, Bastian; Ju, Jianting; Wang, Junbo; Zhu, Liping; Mäusbacher, Roland

    2013-04-01

    The Tibetan Plateau has experienced abrupt climate change superimposed by a gradual weakening of the summer monsoon systems during the Holocene. Although lake sediment records from the Tibetan Plateau are considered to be particularly sensitive to climate variations a holistic picture of the spatial and temporal monsoon evolution is still lacking due to the interplay of different moisture-transporting wind systems (Indian summer monsoon, East Asian summer monsoon, Westerlies). Closing this data gap is important since the Tibetan Plateau is a key area for understanding the climate evolution and its impact on the availability of current and future water resources in Central Asia. Hence, well-dated and high-resolution records are essential to improve the understanding of the spatial and temporal monsoonal evolution. To investigate the hydrological cycle indicating past monsoon variability on the southern-central Tibetan Plateau, records of several lakes were studied along an E-W-transect including Nam Co, Tangra Yumco, Taro Co and a small lake named TT Lake. In this study, a high-resolution sediment record from TT Lake (31.10° N, 86.57° E; 4,745 m asl) was investigated to reveal monsoonal dynamics and northern hemispheric climate oscillations over the past millennium. The 9 m deep TT Lake has a surface area of ~14,500 sqm and is located ~1,500 m west and 205 m above the recent western shoreline of Tangra Yumco. Terraces of former lake level highstands indicate that the TT Lake was part of the Tangra Yumco, but the timing remains unknown. Three sediment gravity cores, obtained in 2011 and 2012, were investigated with geochemical and sedimentological methods. By now a sedimentological core description, magnetic susceptibility data, radiocarbon age determinations, XRF scanning data, and grain size data are available. Further bio-geochemical as well as magnetostratigraphic analyses are in progress. The sedimentological description of the 50 to 89 cm long cores revealed

  15. A multicentre molecular analysis of hepatitis B and blood-borne virus coinfections in Viet Nam.

    Directory of Open Access Journals (Sweden)

    Linda Dunford

    Full Text Available Hepatitis B (HBV infection is endemic in Viet Nam, with up to 8.4 million individuals estimated to be chronically infected. We describe results of a large, multicentre seroepidemiological and molecular study of the prevalence of HBV infection and blood-borne viral coinfections in Viet Nam. Individuals with varying risk factors for infection (n = 8654 were recruited from five centres; Ha Noi, Hai Phong, Da Nang, Khanh Hoa and Can Tho. A mean prevalence rate of 10.7% was observed and levels of HBsAg were significantly higher in injecting drug users (IDUs (17.4%, n = 174/1000 and dialysis patients (14.3%, n = 82/575 than in lower-risk groups (9.4%; p<0.001. Coinfection with HIV was seen in 28% of HBV-infected IDUs (n = 49/174 and 15.2% of commercial sex workers (CSWs; n = 15/99. HCV infection was present in 89.8% of the HBV-HIV coinfected IDUs (n = 44/49 and 40% of HBV-HIV coinfected CSWs (n = 16/40. Anti-HDV was detected in 10.7% (n = 34/318 of HBsAg positive individuals. Phylogenetic analysis of HBV S gene (n = 187 showed a predominance of genotype B4 (82.6%; genotypes C1 (14.6%, B2 (2.7% and C5 (0.5% were also identified. The precore mutation G1896A was identified in 35% of all specimens, and was more frequently observed in genotype B (41% than genotype C (3%; p<0.0001. In the immunodominant 'a' region of the surface gene, point mutations were identified in 31% (n = 58/187 of sequences, and 2.2% (n = 4/187 and 5.3% (n = 10/187 specimens contained the major vaccine escape mutations G145A/R and P120L/Q/S/T, respectively. 368 HBsAg positive individuals were genotyped for the IL28B SNP rs12979860 and no significant association between the IL28B SNP and clearance of HBsAg, HBV viral load or HBeAg was observed. This study confirms the high prevalence of HBV infection in Viet Nam and also highlights the significant levels of blood-borne virus coinfections, which have important implications for hepatitis-related morbidity and development of effective

  16. Variations of Indian monsoon precipitation during the last 32 kyr reflected in the surface hydrography of the Western Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Govil, P.; Naidu, P.D.

    (Pierrehumbert, 2000). Furthermore, a decrease in Asian monsoon activity during stadials was related to less convective activity in the monsoon regions (Wang et al., 2001), which supports the concept that tropical convection and monsoon strength are related.... Climate Dynamics 12, 213–225. Pierrehumbert, R.T., 2000. Climate change and the tropical Pacific: The sleeping dragon wakes. Proceedings of National Academy of sciences 97, 1355-1358. Prell, W.L., 1984. Variation of monsoonal upwelling: a response...

  17. Study on the association of green house gas (CO2) with monsoon rainfall using AIRS and TRMM satellite observations

    Science.gov (United States)

    Singh, R. B.; Janmaijaya, M.; Dhaka, S. K.; Kumar, V.

    Monsoon water cycle is the lifeline to over 60 per cent of the world's population. Throughout history, the monsoon-related calamities of droughts and floods have determined the life pattern of people. The association of Green House Gases (GHGs) particularly Carbon dioxide (CO2) with monsoon has been greatly debated amongst the scientific community in the past. The effect of CO2 on the monsoon rainfall over the Indian-Indonesian region (8-30°N, 65°-100°E) is being investigated using satellite data. The correlation coefficient (Rxy) between CO2 and monsoon is analysed. The Rxy is not significantly positive over a greater part of the study region, except a few regions. The inter-annual anomalies of CO2 is identified for playing a secondary role to influencing monsoon while other phenomenon like ENSO might be exerting a much greater influence.

  18. Cooperation of nuclear manpower development between Viet Nam and Korea in order to enhance establishment of infrastructure in exporting nuclear technology to Viet Nam

    Energy Technology Data Exchange (ETDEWEB)

    Lee, E. J.; Han, K. W.; Park, J. K.; Kim, Y. T.; Nam, Y. M.; Jang, Y. H.; Yang, M. H

    2003-08-15

    Through this project, KAERI provided OJT Programme to 3 nuclear experts of Viet Nam at the KAERI for 3 months as a cooperation of human resource development in the field of nuclear policy, nuclear safety analysis and thermo hydraulic. We could have publicity activities of S/W and H/W then achieve an advantage position of economical and technical in exporting nuclear technology to Viet Nam. Also we have provided a training course and seminar for a high-level delegation of nuclear policy decision makers, which is consisted of 5 deputy ministers and general directors of Viet Nam in Korea. Thus we could have Vietnamese who are favoring Korea. The KAERI will also prepare a data base of trained Vietnamese in Korea for the maximum utilization of them in cooperating with Viet Nam. We accomplished the cooperation of human resource development and providing program and curriculum of the nuclear education and training in Viet Nam. Furthermore, it is expected that the enhancement of nuclear technical cooperation between Viet Nam and Korea and the nuclear human resource development.

  19. Synthesis of Oscillators Using Limit Variables and NAM Expansion

    Directory of Open Access Journals (Sweden)

    Ahmed M. Soliman

    2011-01-01

    Full Text Available A systematic synthesis procedure for generating second-order grounded passive element canonic oscillators is given. The synthesis procedure is based on using nodal admittance matrix (NAM expansion with the bracket method as well as using the infinity parameters. The resulting derived oscillators include circuits using various types of current conveyors. Two classes of oscillators are considered in this paper, and they have the advantages of having independent control on the condition of oscillation and on the frequency of oscillation by varying two different grounded resistors. The two classes of oscillators considered can be easily compensated for the parasitic element effects introduced by the current conveyors. This paper is considered to be continuation to the recently published paper on oscillators using NAM expansion D. G. Haigh et al. (2006. This is the first paper in the literature which uses limit-variables called infinity-variables D. G. Haigh et al. (2005 in the synthesis of oscillator circuits. Simulation results demonstrating the practicality of some of the generated circuits are included.

  20. Mandatory helmet legislation and the print media in Viet Nam.

    Science.gov (United States)

    Hill, Peter S; Ngo, Anh D; Khuong, Tuan A; Dao, Huong L; Hoang, Hanh T M; Trinh, Hang T; Nguyen, Lien T N; Nguyen, Phong H

    2009-07-01

    With motorcycle ownership high and rising in Viet Nam, and motorcycle riders vulnerable to both fatal and non-fatal injury, the re-introduction of mandatory helmet legislation in 2007 has been a priority for the Vietnamese government. The paper uses a qualitative analysis of web-based versions of the eight most popular newspapers in Viet Nam to track reporting over four phases of the implementation of the legislation, identifying codes and constructing the dominant themes of the media coverage. The study documents the justification and promotion of the legislation, and the mechanisms for preparing for its implementation at a national and local level, developing solutions and encouraging the replication of successful strategies. It records opposition and obstacles to helmet use, and concerns raised around the quality of helmets purchased. In return, the press notes the response of the market in innovative solutions to these problems. With the successful implementation of the legislation, the functions of the print media in promulgating and promoting the legislation, together with the reporting of ongoing resistance to the process, serve to enable a dialogue between the State and population around expressed concerns. In highlighting quality control of helmets as a key issue, the media have identified a potential ongoing role in monitoring the state's initiative in reducing the road toll from traumatic brain injury in motorcyclists.

  1. Plague foci in Viet Nam: zoological and parasitological aspects.

    Science.gov (United States)

    Suntsov, V V; Huong, L T; Suntsova, N I; Gratz, N G

    1997-01-01

    Reported are the results of studies over the period 1989-94 on host-flea complexes in small mammals and their flea ectoparasites in and around a number of human settlements in Viet Nam in which human cases of plague had been found. Collections were also made in savanna and tropical forest areas within a 10-km radius of the settlements. The greatest numbers of small mammals, for the most part Rattus spp., and of the flea ectoparasite Xenopsylla cheopis were found in inhabited areas. X. cheopis was not found on any feral or sylvan mammal further than 0.6 km from settlements. A possible link between wild and commensal mammals may be provided by the flea Lentistivalius klossi, a specific parasite of squirrels and tree-shrews but also found in very small numbers on commensal rats. No zoonotic foci of plague were found in the immediate vicinity of the villages studied and it is most likely that plague persists in a commensal rat-X. cheopis cycle in and around human settlements in Viet Nam.

  2. A new index to describe the tropical Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    XU ZhongFeng; FU CongBin; QIAN YongFu

    2009-01-01

    We define a new monsoon index (MV) as the product of relative vorticity and equivalent potential tem-perature using the long-term NCEP/NCAR reanalysis data.The MV index provides new insights into the intraseasonal and interannual variabilities of the broad-scale tropical Asian summer monsoon (TASM),including the South Asian summer monsoon (SASM) and the South China Sea summer monsoon (SCSSM).On the intraseasonal timescale,the pentad-to-pentad MV index bears a close relationship to the broad-scale rainfall in the TASM regions.Among 29 summers from 1979 to 2007,in 23/27 summers the correlation coefficients are higher than 0.7 in the SASM/SCSSM region.However,in fewer than 9 summers,the correlations between the broad-scale rainfall and the existing circulation indices are higher than 0.7.On the interannual timescale,various existing SASM circulation indices are moderately or well correlated with all-India summer monsoon rainfall,whereas their correlations with broad-scale SASM rainfall are weak.In contrast,the summer mean MV index correlates well with the broad-scale SASM rainfall and all-India summer monsoon rainfall (correlation of 0.73 and 0.65,respectively).In the SCSSM region,the summer mean MV index also bears a close relationship to the SCSSM rainfall,al-though some discrepancies exist during certain years.The composite strong TASM shows a stronger low-tropospheric low pressure in association with the enhanced westerly winds and moisture transfer,stronger convection,and upper-tropospheric easterly winds,which indicate that the MV index can well capture the features of TASM.

  3. A new index to describe the tropical Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    We define a new monsoon index (MV) as the product of relative vorticity and equivalent potential temperature using the long-term NCEP/NCAR reanalysis data. The MV index provides new insights into the intraseasonal and interannual variabilities of the broad-scale tropical Asian summer monsoon (TASM), including the South Asian summer monsoon (SASM) and the South China Sea summer monsoon (SCSSM). On the intraseasonal timescale, the pentad-to-pentad MV index bears a close relationship to the broad-scale rainfall in the TASM regions. Among 29 summers from 1979 to 2007, in 23/27 summers the correlation coefficients are higher than 0.7 in the SASM/SCSSM region. However, in fewer than 9 summers, the correlations between the broad-scale rainfall and the existing circulation indices are higher than 0.7. On the interannual timescale, various existing SASM circulation indices are moderately or well correlated with all-India summer monsoon rainfall, whereas their correlations with broad-scale SASM rainfall are weak. In contrast, the summer mean MV index correlates well with the broad-scale SASM rainfall and all-India summer monsoon rainfall (correlation of 0.73 and 0.65, respectively). In the SCSSM region, the summer mean MV index also bears a close relationship to the SCSSM rainfall, although some discrepancies exist during certain years. The composite strong TASM shows a stronger low-tropospheric low pressure in association with the enhanced westerly winds and moisture transfer, stronger convection, and upper-tropospheric easterly winds, which indicate that the MV index can well capture the features of TASM.

  4. Role of low level flow on the summer monsoon rainfall over the Indian subcontinent during two contrasting monsoon years

    Digital Repository Service at National Institute of Oceanography (India)

    Swapna, P.; RameshKumar, M.R.

    The summer monsoon rainfall over the Indian subcontinent shows 1 large inter-annual variability in three important aspects, namely, the onset date, quantum of monsoon rainfall and the monsoon activity within the monsoon (June - September) period...

  5. Natural and human-induced changes in summer climate over the East Asian monsoon region in the last half century: A review

    Directory of Open Access Journals (Sweden)

    Ren-He Zhang

    2015-06-01

    The decadal changes in EASM and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover, Arctic sea ice, sea surface temperatures in tropical Pacific and Indian Ocean, ocean–atmospheric coupled systems of the Pacific Decadal Oscillation (PDO and Asian–Pacific Oscillation (APO, and uneven thermal forcing over the Asian continent. Up to now, the roles of anthropogenic factors, such as greenhouse gases, aerosols, and land usage/cover changes, on existing decadal variations of EASM and summer rainfall in this region remain uncertain.

  6. EVOLUTION OF TROPOSPHERIC TEMPERATURE FIELDS AND CORRESPONDING THERMAL MECHANISMS BEFORE/AFTER ONSET PERIODS OF ASIAN SUMMER MONSOON

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The evolution of the tropospheric temperature fields over Indian and South China Sea monsoon areas and their thermal mechanisms are compared and analyzed during the period from March to June, 1996. The results show that the onsets of the Indian and South China Sea summer monsoons are closely associated with the seasonal warming in the troposphere over the zonal belt of 10° N ~ 30° N in these areas, which leads to the inversion of meridional temperature gradient. During the pre-onset period, the warming over the South China Sea monsoon region is mainly due to the warm horizontal advection and diabatic (latent) heating processes. Meanwhile, the warming is suppressed by the vertical adiabatic process (cooling). In spring over the Indian monsoon region, the significant adiabatic heating due to the subsidence motion, which compensates the cooling due to the strong cold advection and diabatic cooling processes, results in a larger warming rate than over the South China Sea monsoon region. However, the meridional temperature gradient over the Indian monsoon region is so large during the late winter and early spring that it takes longer time to warm the troposphere to have the reversion of meridional temperature gradient than it does over the South China Sea monsoon region. It results in the phenomenon that the South China Sea summer monsoon generally breaks out earlier than the Indian summer monsoon.

  7. Indian monsoon variability on millennial-orbital timescales.

    Science.gov (United States)

    Kathayat, Gayatri; Cheng, Hai; Sinha, Ashish; Spötl, Christoph; Edwards, R Lawrence; Zhang, Haiwei; Li, Xianglei; Yi, Liang; Ning, Youfeng; Cai, Yanjun; Lui, Weiguo Lui; Breitenbach, Sebastian F M

    2016-04-13

    The Indian summer monsoon (ISM) monsoon is critical to billions of people living in the region. Yet, significant debates remain on primary ISM drivers on millennial-orbital timescales. Here, we use speleothem oxygen isotope (δ(18)O) data from Bittoo cave, Northern India to reconstruct ISM variability over the past 280,000 years. We find strong coherence between North Indian and Chinese speleothem δ(18)O records from the East Asian monsoon domain, suggesting that both Asian monsoon subsystems exhibit a coupled response to changes in Northern Hemisphere summer insolation (NHSI) without significant temporal lags, supporting the view that the tropical-subtropical monsoon variability is driven directly by precession-induced changes in NHSI. Comparisons of the North Indian record with both Antarctic ice core and sea-surface temperature records from the southern Indian Ocean over the last glacial period do not suggest a dominant role of Southern Hemisphere climate processes in regulating the ISM variability on millennial-orbital timescales.

  8. Modelling Monsoons: Understanding and Predicting Current and Future Behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Turner, A; Sperber, K R; Slingo, J M; Meehl, G A; Mechoso, C R; Kimoto, M; Giannini, A

    2008-09-16

    The global monsoon system is so varied and complex that understanding and predicting its diverse behaviour remains a challenge that will occupy modellers for many years to come. Despite the difficult task ahead, an improved monsoon modelling capability has been realized through the inclusion of more detailed physics of the climate system and higher resolution in our numerical models. Perhaps the most crucial improvement to date has been the development of coupled ocean-atmosphere models. From subseasonal to interdecadal timescales, only through the inclusion of air-sea interaction can the proper phasing and teleconnections of convection be attained with respect to sea surface temperature variations. Even then, the response to slow variations in remote forcings (e.g., El Nino-Southern Oscillation) does not result in a robust solution, as there are a host of competing modes of variability that must be represented, including those that appear to be chaotic. Understanding the links between monsoons and land surface processes is not as mature as that explored regarding air-sea interactions. A land surface forcing signal appears to dominate the onset of wet season rainfall over the North American monsoon region, though the relative role of ocean versus land forcing remains a topic of investigation in all the monsoon systems. Also, improved forecasts have been made during periods in which additional sounding observations are available for data assimilation. Thus, there is untapped predictability that can only be attained through the development of a more comprehensive observing system for all monsoon regions. Additionally, improved parameterizations - for example, of convection, cloud, radiation, and boundary layer schemes as well as land surface processes - are essential to realize the full potential of monsoon predictability. Dynamical considerations require ever increased horizontal resolution (probably to 0.5 degree or higher) in order to resolve many monsoon features

  9. Export of non-point source suspended sediment, nitrogen, and phosphorus from sloping highland agricultural fields in the East Asian monsoon region.

    Science.gov (United States)

    Reza, Arif; Eum, Jaesung; Jung, Sungmin; Choi, Youngsoon; Owen, Jeffrey S; Kim, Bomchul

    2016-12-01

    Excess sediment and nutrient export from agricultural fields with steep slopes is a major concern linked to surface water quality in Korea. In this study, the export of suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) and their event mean concentrations (EMCs) in surface runoff from a highland mixed land use (61% forested, 30% cropped, 9% other) watershed were quantified. In 2007, the Korean Ministry of Environment (MoE) declared the study area as a priority region for non-point source (NPS) pollution management and initiated various best management practices (BMPs) in the study watershed. SS, TN, and TP concentrations in Mandae Stream were monitored for 5 years (2009-2013) to evaluate the effectiveness of BMPs. Average EMCs for SS, TN, and TP were as high as 986, 3.4 and 0.8 mg/L, respectively. The agricultural export coefficients of agricultural land in the study watershed for SS, TN, and TP were 5611, 171, and 6.83 kg/ha/year, respectively. A comparison with results from other studies shows that both EMCs and agricultural export coefficients in the study watershed were much higher than most of the results reported for watersheds in other regions. The results show that sediment and nutrient export from intensive agriculture areas with steep slopes continue to be a major concern for the downstream reservoir, Lake Soyang. Remedial strategies should be directed towards controlling sources of SS, TN, and TP to improve downstream water quality in sloping highland agricultural areas in Korea.

  10. Effect of climate change on seasonal monsoon in Asia and its impact on the variability of monsoon rainfall in Southeast Asia

    Directory of Open Access Journals (Sweden)

    Yen Yi Loo

    2015-11-01

    Full Text Available Global warming and climate change is one of the most extensively researched and discussed topical issues affecting the environment. Although there are enough historical evidence to support the theory that climate change is a natural phenomenon, many research scientists are widely in agreement that the increase in temperature in the 20th century is anthropologically related. The associated effects are the variability of rainfall and cyclonic patterns that are being observed globally. In Southeast Asia the link between global warming and the seasonal atmospheric flow during the monsoon seasons shows varying degree of fuzziness. This study investigates the impact of climate change on the seasonality of monsoon Asia and its effect on the variability of monsoon rainfall in Southeast Asia. The comparison of decadal variation of precipitation and temperature anomalies before the 1970s found general increases which were mostly varying. But beyond the 1970s, global precipitation anomalous showed increases that almost corresponded with increases in global temperature anomalies for the same period. There are frequent changes and a shift westward of the Indian summer monsoon. Although precipitation is observed to be 70% below normal levels, in some areas the topography affects the intensity of rainfall. These shifting phenomenon of other monsoon season in the region are impacting on the variability of rainfall and the onset of monsoons in Southeast Asia and is predicted to delay for 15 days the onset of the monsoon in the future. The variability of monsoon rainfall in the SEA region is observed to be decadal and the frequency and intensity of intermittent flooding of some areas during the monsoon season have serious consequences on the human, financial, infrastructure and food security of the region.

  11. Effect of climate change on seasonal monsoon in Asia and its impact on the variability of monsoon rainfall in Southeast Asia

    Institute of Scientific and Technical Information of China (English)

    Yen Yi Loo; Lawal Billa; Ajit Singh

    2015-01-01

    Global warming and climate change is one of the most extensively researched and discussed topical issues affecting the environment. Although there are enough historical evidence to support the theory that climate change is a natural phenomenon, many research scientists are widely in agreement that the increase in temperature in the 20th century is anthropologically related. The associated effects are the variability of rainfall and cyclonic patterns that are being observed globally. In Southeast Asia the link between global warming and the seasonal atmospheric flow during the monsoon seasons shows varying degree of fuzziness. This study investigates the impact of climate change on the seasonality of monsoon Asia and its effect on the variability of monsoon rainfall in Southeast Asia. The comparison of decadal variation of precipitation and temperature anomalies before the 1970s found general increases which were mostly varying. But beyond the 1970s, global precipitation anomalous showed increases that almost corresponded with increases in global temperature anomalies for the same period. There are frequent changes and a shift westward of the Indian summer monsoon. Although precipitation is observed to be 70%below normal levels, in some areas the topography affects the intensity of rainfall. These shifting phenomenon of other monsoon season in the region are impacting on the variability of rainfall and the onset of monsoons in Southeast Asia and is predicted to delay for 15 days the onset of the monsoon in the future. The variability of monsoon rainfall in the SEA region is observed to be decadal and the frequency and intensity of intermittent flooding of some areas during the monsoon season have serious consequences on the human, financial, infrastructure and food security of the region.

  12. Effectiveness of the Viet Nam produced, mouse brain-derived, inactivated Japanese encephalitis vaccine in Northern Viet Nam.

    Directory of Open Access Journals (Sweden)

    Florian Marks

    Full Text Available BACKGROUND: Japanese encephalitis (JE is a flaviviral disease of public health concern in many parts of Asia. JE often occurs in large epidemics, has a high case-fatality ratio and, among survivors, frequently causes persistent neurological sequelae and mental disabilities. In 1997, the Vietnamese government initiated immunization campaigns targeting all children aged 1-5 years. Three doses of a locally-produced, mouse brain-derived, inactivated JE vaccine (MBV were given. This study aims at evaluating the effectiveness of Viet Nam's MBV. METHODOLOGY: A matched case-control study was conducted in Northern Viet Nam. Cases were identified through an ongoing hospital-based surveillance. Each case was matched to four healthy controls for age, gender, and neighborhood. The vaccination history was ascertained through JE immunization logbooks maintained at local health centers. PRINCIPAL FINDINGS: Thirty cases and 120 controls were enrolled. The effectiveness of the JE vaccine was 92.9% [95% CI: 66.6-98.5]. Confounding effects of other risk variables were not observed. CONCLUSIONS: Our results strongly suggest that the locally-produced JE-MBV given to 1-5 years old Vietnamese children was efficacious.

  13. Hydrography of the Wadge bank - premonsoon and monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    RamaRaju, V.S.; Rao, T.V.N.; RameshBabu, V.; Anto, A.F.

    and central parts of the region during pre-monsoon. The low saline Bay of Bengal waters are present in the southeastern part of the Wadge Bank and high saline waters of Arabian Sea intrude from northwest indicating the withdrawal of the North Equatorial...

  14. Morphodynamics of tidal inlets in a tropical monsoon area

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Verhagen, H.J.; Wang, Z.B.

    2007-01-01

    Morphodynamics of a tidal inlet system on a micro-tidal coast in a tropical monsoon influenced region is modelled and discussed. Influences of river flow and wave climate on the inlet morphology are investigated with the aid of process-based state-of-the-art numerical models. Seasonal and episodic b

  15. Holocene vegetation variation in the Daihai Lake region of north-central China: a direct indication of the Asian monsoon climatic history

    Science.gov (United States)

    Xiao, Jule; Xu, Qinghai; Nakamura, Toshio; Yang, Xiaolan; Liang, Wendong; Inouchi, Yoshio

    2004-07-01

    DH99a sediment core recovered at the center of Daihai Lake in north-central China was analyzed at 4-cm intervals for pollen assemblage and concentration. The pollen record spanning the last ca 10,000 yr revealed a detailed history of vegetation and climate changes over the Daihai Lake region during the Holocene. From ca 10,250 to 7900 cal yr BP, arid herbs and shrubs dominated the lake basin in company with patches of mixed pine and broadleaved forests, indicating a mild and dry climatic condition. Over this period, the woody plants displayed an increasing trend, which may suggest a gradual increase in warmth and humidity. The period between ca 7900 and 4450 cal yr BP exhibits large-scale covers of mixed coniferous and broadleaved forests, marking a warm and humid climate. Changes in the composition of the forests indicate that both temperature and precipitation displayed obvious fluctuations during this period, i.e., cool and humid ca 7900- 7250 cal yr BP, warm and slightly humid ca 7250- 6050 cal yr BP, warm and humid between ca 6050 and 5100 cal yr BP, mild and slightly humid ca 5100- 4800 cal yr BP, and mild and humid ca 4800- 4450 cal yr BP. The period can be viewed as the Holocene optimum (characterized by a warm and moist climate) of north-central China, with the maximum (dominated both by warmest temperatures and by richest precipitations) occurring from ca 6050 to 5100 cal yr BP. During the period of ca 4450- 2900 cal yr BP, the woody plants declined, and the climate generally became cooler and drier than the preceding period. This period is characterized by a cold, dry episode from ca 4450 to 3950 cal yr BP, a warm, slightly humid interval between ca 3950 and 3500 cal yr BP and a mild, slightly dry episode from ca 3500 to 2900 cal yr BP, and appears to be a transition from warm and humid to cold and dry climatic conditions. Since ca 2900 cal yr ago, the forests disappeared and the vegetation density decreased, reflecting a cool and dry climate. However, a

  16. Meteorological results of monsoon-88 Expedition (pre-monsoon period)

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Krishnamurthy, L.; Babu, M.T.

    Mean atmospheric circulation, moisture budget and net heat exchange were studied during a pre-monsoon period (18th March to 3rd May, 1988), making use of the data collected on board "Akademik Korolev" in the central equatorial and southern Arabian...

  17. Comparison of East Asian winter monsoon indices

    Directory of Open Access Journals (Sweden)

    Gao Hui

    2007-01-01

    Full Text Available Four East Asian winter monsoon (EAWM indices are compared in this paper. In the research periods, all the indices show similar interannual and decadal-interdecadal variations, with predominant periods centering in 3–4 years, 6.5 years and 9–15 years, respectively. Besides, all the indices show remarkable weakening trends since the 1980s. The correlation coefficient of each two indices is positive with a significance level of 99%. Both the correlation analyses and the composites indicate that in stronger EAWM years, the Siberian high and the higher-level subtropical westerly jet are stronger, and the Aleutian low and the East Asia trough are deeper. This circulation pattern is favorable for much stronger northwesterly wind and lower air temperature in the subtropical regions of East Asia, while it is on the opposite in weaker EAWM years. Besides, EAWM can also exert a remarkable leading effect on the summer monsoon. After stronger (weaker EAWM, less (more summer precipitation is seen over the regions from the Yangtze River valley of China to southern Japan, while more (less from South China Sea to the tropical western Pacific.

  18. On the role of convective systems over the northwest Pacific and monsoon activity over the Indian subcontinent

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Babu, A.K.; Reason, C.

    .e. years with well below average rainfall) as compared to excess monsoon years (years with well above average rainfall). Based on these previously found associations involving various characteristics of convective activity in the region, this study seeks... and also on the quantum of monsoon rainfall for several contrasting monsoon years. 2. Data Data for convective systems in the northwest Pacific Ocean (NWP) were acquired from the UNISYS website (http://weather.unisys.com) and originate from the Joint...

  19. Mid-Pliocene East Asian monsoon climate simulated in the PlioMIP

    Directory of Open Access Journals (Sweden)

    R. Zhang

    2013-09-01

    Full Text Available Based on simulations with 15 climate models in the Pliocene Model Intercomparison Project (PlioMIP, the regional climate of East Asia (focusing on China during the mid-Pliocene is investigated in this study. Compared to the pre-industrial, the multi-model ensemble mean (MMM of all models shows the East Asian summer winds (EASWs largely strengthen in monsoon China, and the East Asian winter winds (EAWWs strengthen in south monsoon China but slightly weaken in north monsoon China in the mid-Pliocene. The MMM of all models also illustrates a warmer and wetter mid-Pliocene climate in China. The simulated weakened mid-Pliocene EAWWs in north monsoon China and intensified EASWs in monsoon China agree well with geological reconstructions. However, there is a large model–model discrepancy in simulating mid-Pliocene EAWW, which should be further addressed in the future work of PlioMIP.

  20. Analyzing Seasonal Variation of Clouds over the Asian Monsoon Regions and the Tibetan Plateau Region using CloudSat/CALIPSO Data%用CloudSat/CALIPSO资料分析亚洲季风区和青藏高原地区云的季节变化特征

    Institute of Scientific and Technical Information of China (English)

    汪会; 罗亚丽; 张人禾

    2011-01-01

    occurrence frequency, vertical location, physical thickness, distance between cloud layers, and vertical distribution of radar reflectivity) are contrasted among four regions: East AsianMonsoon Region (EAMR), Indian Monsoon Region (IMR), the Western North Pacific Monsoon Region (WNPMR), and the Tibetan Plateau Region (TPR). The geographical distribution of low-level clouds over the Asian monsoon regions and its correlation with atmospheric stability of the lower troposphere (LTS) are also analyzed The major findings are as follows: (1) During the period, the total cloud amounts are 69% (EAMR), 72% (IMR), 83% (WNPMR), and 69% (TPR), respectively, to which single-layer clouds contribute 56% (IMR and WNPMR) to 77% (TPR). The multi-layer clouds are mostly double-layered or triple-layered (fractions≥95%). In the IMR, the total cloud amount in summer (greater than 90%) is significantly larger than in winter (about 50%); the total cloud amounts are larger during spring and summer 090%) than autumn and winter (about 50%) in the EAMR and TPR; the seasonal variation is negligible over the WNPMR (2) Clouds located above 10 km containing small ice crystals prevail in the tropical monsoon regions (IMR and WNPMR) all the year round. Marine boundary layer clouds are common during each season in the WNPMR, in contrast to the IMR where low-level clouds occur mainly during summer. The EAMR clouds are located mostly below 10 km from autumn to spring. Although more clouds are present in the upper troposphere during summer than other seasons over the EAMR, their occurrences and vertical locations are lower than those in the IMR and WNPMR (cloud amount of 60%- 70% from 12 to 16 km heights). The TPR clouds are mostly located in the height range of 4 - 11 km, with cloud particles at the same height covering a wide range of size. (3) The geographical distributions of low-level clouds in the Asian monsoon region are similar between spring and autumn, and significantly distinct between summer and

  1. Violation of Bans on Tobacco Advertising and Promotion at Points of Sale in Viet Nam: Trend from 2009 - 2015.

    Science.gov (United States)

    Huong, Le Thi Thanh; Long, Tran Khanh; Son, Phung Xuan; Huyen, Do Phuc; Linh, Phan Thuy; Bich, Nguyen Ngoc; Lam, Nguyen Xuan; Anh, Le Vu; Tuyet-Hanh, Tran Thi

    2016-01-01

    Comprehensive bans on tobacco advertising and promotion were introduced through tobacco control legislation in Viet Nam, but it has been established that violations of the bans are very common. This study was conducted to explore the trend in violations of bans on tobacco advertising and promotion at points of sale in Viet Nam in the past six years and to explore any differences in the violation situations before and after the Law on Tobacco Control came into effect on 1st May 2013. Quantitative data were collected through observation of violations of the bans on tobacco advertising and promotion at points of sale in 10 provinces throughout Viet Nam in four survey rounds (2009, 2010, 2011, and 2015). Variation in violation prevalence over time was examined by chi-square test using a Bonferini method. Binary logistic regression was employed to identify the factors that may have influences on different types of violation. A level of significance of padvertising increased while violations on promotion ban and on displaying tobacco decreased through time. Some factors associated with the tobacco advertising and promotion bans included surveyed years, types of points of sale, regions and areas where the points of sale were located. The enforcement of the bans did not improve even after the issuance and the enactment of the Law on Tobacco Control. This suggests that the monitoring and enforcement of bans on tobacco advertising and promotion at points of sale should be strengthened. Penalties should be strictly applied for violators as indicated in the current tobacco control legislation.

  2. Gridded daily Indian monsoon rainfall for 14 seasons: Merged TRMM and IMD gauge analyzed values

    Indian Academy of Sciences (India)

    Ashis K Mitra; I M Momin; E N Rajagopal; S Basu; M N Rajeevan; T N Krishnamurti

    2013-10-01

    Indian monsoon is an important component of earth’s climate system. Daily rainfall data for longer period is vital to study components and processes related to Indian monsoon. Daily observed gridded rainfall data covering both land and adjoining oceanic regions are required for numerical model validation and model development for monsoon. In this study, a new gridded daily Indian rainfall dataset at 1° × 1° latitude/longitude resolution covering 14 monsoon seasons (1998–2011) are described. This merged satellite gauge rainfall dataset (NMSG) combines TRMM TMPA rainfall estimates with gauge information from IMD gridded data. Compared to TRMM and GPCP daily rainfall data, the current NMSG daily data has more information due to inclusion of local gauge analysed values. In terms of bias and skill scores this dataset is superior to other daily rainfall datasets. In a mean climatological sense and also for anomalous monsoon seasons, this merged satellite gauge data brings out more detailed features of monsoon rainfall. The difference of NMSG and GPCP looks significant. This dataset will be useful to researchers for monsoon intraseasonal studies and monsoon model development research.

  3. See-saw relationship of the Holocene East Asian-Australian summer monsoon

    Science.gov (United States)

    Eroglu, Deniz; McRobie, Fiona H.; Ozken, Ibrahim; Stemler, Thomas; Wyrwoll, Karl-Heinz; Breitenbach, Sebastian F. M.; Marwan, Norbert; Kurths, Jürgen

    2016-09-01

    The East Asian-Indonesian-Australian summer monsoon (EAIASM) links the Earth's hemispheres and provides a heat source that drives global circulation. At seasonal and inter-seasonal timescales, the summer monsoon of one hemisphere is linked via outflows from the winter monsoon of the opposing hemisphere. Long-term phase relationships between the East Asian summer monsoon (EASM) and the Indonesian-Australian summer monsoon (IASM) are poorly understood, raising questions of long-term adjustments to future greenhouse-triggered climate change and whether these changes could `lock in' possible IASM and EASM phase relationships in a region dependent on monsoonal rainfall. Here we show that a newly developed nonlinear time series analysis technique allows confident identification of strong versus weak monsoon phases at millennial to sub-centennial timescales. We find a see-saw relationship over the last 9,000 years--with strong and weak monsoons opposingly phased and triggered by solar variations. Our results provide insights into centennial- to millennial-scale relationships within the wider EAIASM regime.

  4. See–saw relationship of the Holocene East Asian–Australian summer monsoon

    Science.gov (United States)

    Eroglu, Deniz; McRobie, Fiona H.; Ozken, Ibrahim; Stemler, Thomas; Wyrwoll, Karl-Heinz; Breitenbach, Sebastian F. M.; Marwan, Norbert; Kurths, Jürgen

    2016-01-01

    The East Asian–Indonesian–Australian summer monsoon (EAIASM) links the Earth's hemispheres and provides a heat source that drives global circulation. At seasonal and inter-seasonal timescales, the summer monsoon of one hemisphere is linked via outflows from the winter monsoon of the opposing hemisphere. Long-term phase relationships between the East Asian summer monsoon (EASM) and the Indonesian–Australian summer monsoon (IASM) are poorly understood, raising questions of long-term adjustments to future greenhouse-triggered climate change and whether these changes could ‘lock in' possible IASM and EASM phase relationships in a region dependent on monsoonal rainfall. Here we show that a newly developed nonlinear time series analysis technique allows confident identification of strong versus weak monsoon phases at millennial to sub-centennial timescales. We find a see–saw relationship over the last 9,000 years—with strong and weak monsoons opposingly phased and triggered by solar variations. Our results provide insights into centennial- to millennial-scale relationships within the wider EAIASM regime. PMID:27666662

  5. See-saw relationship of the Holocene East Asian-Australian summer monsoon.

    Science.gov (United States)

    Eroglu, Deniz; McRobie, Fiona H; Ozken, Ibrahim; Stemler, Thomas; Wyrwoll, Karl-Heinz; Breitenbach, Sebastian F M; Marwan, Norbert; Kurths, Jürgen

    2016-09-26

    The East Asian-Indonesian-Australian summer monsoon (EAIASM) links the Earth's hemispheres and provides a heat source that drives global circulation. At seasonal and inter-seasonal timescales, the summer monsoon of one hemisphere is linked via outflows from the winter monsoon of the opposing hemisphere. Long-term phase relationships between the East Asian summer monsoon (EASM) and the Indonesian-Australian summer monsoon (IASM) are poorly understood, raising questions of long-term adjustments to future greenhouse-triggered climate change and whether these changes could 'lock in' possible IASM and EASM phase relationships in a region dependent on monsoonal rainfall. Here we show that a newly developed nonlinear time series analysis technique allows confident identification of strong versus weak monsoon phases at millennial to sub-centennial timescales. We find a see-saw relationship over the last 9,000 years-with strong and weak monsoons opposingly phased and triggered by solar variations. Our results provide insights into centennial- to millennial-scale relationships within the wider EAIASM regime.

  6. FEATURES AND COMPARISONS OF THE QUASI-BIENNIAL VARIATIONS IN THE ASIA-PACIFIC MONSOON SUBSYSTEMS

    Institute of Scientific and Technical Information of China (English)

    ZHENG Bin; LI Chun-hui; LIN Ai-lan; GU De-jun

    2009-01-01

    The National Centers for Environmental Prediction (NCEP) reanalysis data Climate Diagnostics Center Merged Analysis of Precipitation (CMAP) results,and NOAA Extended Reconstructed Sea Surface Temperature (SST),have been utilized in this paper to study the quasi-biennial variations in Asia-Pacific monsoon subsystems and associated SST anomalies (SSTA) and wind anomalies. Four monsoon indices are computed fi,om NCEP/National Center for Atmospheric Research (NCAR) reanalysis to represent the South Asian monsoon (SAM),South China Sea summer monsoon (SCSSM),Western North Pacific monsoon (WNPM) and East Asian monsoon (EAM),respectively. The quasi-biennial periods are very significant in Asia-Pacific monsoons (as discovered by power spectrum analysis),and for SAM and EAM---with moderate effects by EI Ni(n)o-Southern Oscillation (ENSO)---the quasi-biennial periods are the most important factor. For SCSSM and WNPM (once again due to the effects of ENSO),the quasi-biennial periods are of secondary durations. There are obvious interdecadal variations in the quasi-biennial modes of the Asia-Pacific monsoon,so in the negative phase the biennial modes will not be significant or outstanding. The wind anomalies and SSTA associated with the biennial modes are very different in the SAM. WNPM and EAM regions. Since the WNPM and SCSSM are very similar in the biennial modes,they can be combined into one subsystem,called SCS/WNPM.

  7. Impact of convection over the equatorial trough on the summer monsoon activity over India

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Shenoi, S.S.C.; Schulz, J.

    Project (GPCP). Most (about 73%) of the break in monsoon (BM) events were associated with the convective activity (rainfall more than 30 mm/pentad) over the equatorial trough (ET) region. The association between these events and the convective activity...

  8. Global association of the Madden-Julian Oscillation with monsoon lows and depressions

    Science.gov (United States)

    Haertel, Patrick; Boos, William R.

    2017-08-01

    Previous research has revealed that monsoon lows and depressions are modulated on intraseasonal time scales in a few regions, including India, Australia, and the East Pacific. This study examines whether such modulation occurs on a global scale and, in particular, how the Madden-Julian Oscillation (MJO) is associated with changes in synoptic-scale vortices across all monsoon regions. The spatial climatology of monsoon disturbances is largely insensitive to MJO amplitude. However, monsoon disturbance frequency (MDF) varies substantially with MJO phase, with regional perturbations of 25 to 90% of the seasonal mean value across the tropics. In off-equatorial locations, MDF maxima occur in locations where the MJO enhances low level cyclonic vorticity, typically near the western edge of midlevel moisture perturbations. In contrast, equatorial MDF perturbations are in phase with MJO moisture and rainfall anomalies, with maxima in regions with strong low level zonal wind convergence.

  9. Subseasonal features of the Asian summer monsoon in the NCEP climate forecast system

    Institute of Scientific and Technical Information of China (English)

    Song YANG; WEN Min; R Wayne HIGGINS

    2008-01-01

    The operational climate forecast system (CFS) of the US National Centers for Environmental Prediction provides climate predic-tions over the world, and CFS products are becoming an important source of information for regional climate predictions in many Asian countries where monsoon climate dominates. Recent studies have shown that, on monthly-to-seasonal time-scales, the CFS is highly skillful in simulating and predicting the variability of the Asian monsoon. The higher-frequency variability of the Asian summer monsoon in the CFS is analyzed, using output from a version with a spectral triangular truncation of 126 waves in horizon-tal and 64 sigma layers in vertical, focusing on synoptic, quasi-biweekly, and intraseasonal time-scales. The onset processes of different regional monsoon components were investigated within Asia. Although the CFS generally overestimates variability of mon-soon on these time-scales, it successfully captures many major features of the variance patterns, especially for the synoptic time-scale. The CFS also captures the timing of summer monsoon onsets over India and the Indo-China Peninsula. However, it encoun-ters difficulties in simulating the onset of the South China Sea monsoon. The success and failure of the CFS in simulating the onset of monsoon precipitation can also be seen from the associated features of simulated atmospheric circulation processes. Overall, the CFS is capable of simulating the synoptic-to-intraseasonal variability of the Asian summer monsoon with skills. As for seasonal-to-interannual time-scales shown previously, the model is expected to possess a potential for skillful predictions of the high-frequencyvariability of the Asian monsoon.

  10. Effects of increased CO{sub 2} levels on monsoons

    Energy Technology Data Exchange (ETDEWEB)

    Cherchi, Annalisa; Masina, Simona; Navarra, Antonio [Centro Euro-Mediterraneo per i Cambiamenti Climatici and Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Alessandri, Andrea [Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy)

    2011-07-15

    Increased atmospheric carbon dioxide concentration provided warmer atmospheric temperature and higher atmospheric water vapor content, but not necessarily more precipitation. A set of experiments performed with a state-of-the-art coupled general circulation model forced with increased atmospheric CO{sub 2} concentration (2, 4 and 16 times the present-day mean value) were analyzed and compared with a control experiment to evaluate the effect of increased CO{sub 2} levels on monsoons. Generally, the monsoon precipitation responses to CO{sub 2} forcing are largest if extreme concentrations of carbon dioxide are used, but they are not necessarily proportional to the forcing applied. In fact, despite a common response in terms of an atmospheric water vapor increase to the atmospheric warming, two out of the six monsoons studied simulate less or equal summer mean precipitation in the 16 x CO{sub 2} experiment compared to the intermediate sensitivity experiments. The precipitation differences between CO{sub 2} sensitivity experiments and CTRL have been investigated specifying the contribution of thermodynamic and purely dynamic processes. As a general rule, the differences depending on the atmospheric moisture content changes (thermodynamic component) are large and positive, and they tend to be damped by the dynamic component associated with the changes in the vertical velocity. However, differences are observed among monsoons in terms of the role played by other terms (like moisture advection and evaporation) in shaping the precipitation changes in warmer climates. The precipitation increase, even if weak, occurs despite a weakening of the mean circulation in the monsoon regions (''precipitation-wind paradox''). In particular, the tropical east-west Walker circulation is reduced, as found from velocity potential analysis. The meridional component of the monsoon circulation is changed as well, with larger (smaller) meridional (vertical) scales. (orig.)

  11. Characteristics of Thermal and Geopotential Height Differences Between Continent and Ocean and Its Role in the Strength of the Asian Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    Andrea Silverman; SUN Jilin

    2005-01-01

    The interdecadal factors affecting the summer monsoon winds over Somalia and the South China Sea were studied. Global geopotential heights and wind velocity fields of the 850-hPa and 200-hPa pressure levels, as well as sea surface temperature anomaly data and correlation coefficients were analyzed. The monsoons over Somalia and the South China Sea were found to be two different monsoon systems, operating on different mechanisms and being affected by different oceanatmosphere interactions. The intensity of the Asian subtropical summer monsoon is influenced by the intensity of the summer monsoon over Somalia in the month of June and by the intensity of the summer monsoon over the South China Sea in the months of June and July. The summer monsoon wind strength over Somalia is affected by regional factors, such as the heating of the Tibetan plateau, and by global mechanisms, such as the subtropical heat exchange with Antarctica. The summer monsoon over the South China Sea is affected by different ocean-atmosphere interactions. The Somalia and subtropical summer monsoons have wind blowing down the pressure gradient from area over ocean to that over land, like typical summer monsoons. The South China Sea summer monsoon has winds that blow down the pressure gradient from area over land to that over ocean. The South China Sea summer monsoon is affected by the Kuroshio Current off the east coast of Japan.

  12. Coherent tropical-subtropical Holocene see-saw moisture patterns in the Eastern Hemisphere monsoon systems

    Science.gov (United States)

    Wang, Yongbo; Bekeschus, Benjamin; Handorf, Dörthe; Liu, Xingqi; Dallmeyer, Anne; Herzschuh, Ulrike

    2017-08-01

    The concept of a Global Monsoon (GM) has been proposed based on modern precipitation observations, but its application over a wide range of temporal scales is still under debate. Here, we present a synthesis of 268 continental paleo-moisture records collected from monsoonal systems in the Eastern Hemisphere, including the East Asian Monsoon (EAsM), the Indian Monsoon (IM), the East African Monsoon (EAfM), and the Australian Monsoon (AuM) covering the last 18,000 years. The overall pattern of late Glacial to Holocene moisture change is consistent with those inferred from ice cores and marine records. With respect to the last 10,000 years (10 ka), i.e. a period that has high spatial coverage, a Fuzzy c-Means clustering analysis of the moisture index records together with ;Xie-Beni; index reveals four clusters of our data set. The paleoclimatic meaning of each cluster is interpreted considering the temporal evolution and spatial distribution patterns. The major trend in the tropical AuM, EAfM, and IM regions is a gradual decrease in moisture conditions since the early Holocene. Moisture changes in the EAsM regions show maximum index values between 8 and 6 ka. However, records located in nearby subtropical areas, i.e. in regions not influenced by the intertropical convergence zone, show an opposite trend compared to the tropical monsoon regions (AuM, EAfM and IM), i.e. a gradual increase. Analyses of modern meteorological data reveal the same spatial patterns as in the paleoclimate records such that, in times of overall monsoon strengthening, lower precipitation rates are observed in the nearby subtropical areas. We explain this pattern as the effect of a strong monsoon circulation suppressing air uplift in nearby subtropical areas, and hence hindering precipitation. By analogy to the modern system, this would mean that during the early Holocene strong monsoon period, the intensified ascending airflows within the monsoon domains led to relatively weaker ascending or

  13. Interannual variability of South American monsoon circulation

    Science.gov (United States)

    Alonso Gan, Manoel; Rafaele Araújo Lima, Jeane

    2016-04-01

    The South America Monsoon System (SAMS) is responsible for influencing the atmospheric circulation and precipitation over most of tropical South America (SA) during the summer season. Studies for aiming to understand the temporal variability of this system have great value to the scientific community, because the processes that control the monsoon climate are not totally clear. Thus, the main objective of this research is to investigate the possible large-scale climatic factors and the remote interaction mechanisms, which may be associated with summer season interannual variability focusing on identifying the main differences between dry and wet extremes rainy season in the South-eastern Amazon Basin (SAB), Central-West (WC) and Southeast (SE) of Brazil, which are areas influenced by the summer monsoon regime. For such analyzes, Pearson correlations, quantile method and composite analysis were used during the period from 1979 to 2014. The correlation between precipitation anomaly in SAB and the sea surface temperature anomaly (SSTA) and wind at 850hPa and 300hPa indicate El Niño-Southern Oscillation (ENSO) influence. Precipitation anomalies in WC did not show significant correlation with SSTA. However, a pattern similar to ENSO Modoki type was observed in the composite analysis. At 850 hPa, the presence of an anomalous cyclonic (anticyclonic) circulation was observed over the central region of SA during wet (dry) summers seasons. Over SE region of Brazil, a dipole SSTA pattern over the South Atlantic was identified, as well the presence of anomalous circulations with an equivalent barotropic structure over these SSTA areas. This pattern is more evident in case of dry summer on the SE. At 300 hPa, the wave train between 30°S-60°S was observed presenting a feature curvature from 120°W reaching SA, similar to the Pacific-South American pattern (PSA). Analysis of the summer interannual variability indicated the manifestation of wet summers more frequently than dry

  14. Arabian Peninsula-North Pacific Oscillation and its association with the Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using correlation and EOF analyses on sea level pressure from 57-year NCEP-NCAR reanalysis data, the Arabian Peninsula-North Pacific Oscillation (APNPO) is identified. The APNPO reflects the co-variability between the North Pacific high and South Asian summer monsoon low. This teleconnec- tion pattern is closely related to the Asian summer monsoon. On interannual timescale, it co-varies with both the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM); on decadal timescale, it co-varies with the EASM: both exhibit two abrupt climate changes in the middle 1960s and the late 1970s respectively. The possible physical process for the connections between the APNPO and Asian summer monsoon is then explored by analyzing the APNPO-related atmospheric circulations. The results show that with a strong APNPO, the Somali Jet, SASM flow, EASM flow, and South Asian high are all enhanced, and an anomalous anticyclone is produced at the upper level over northeast China via a zonal wave train. Meanwhile, the moisture transportation to the Asian monsoon regions is also strengthened in a strong APNPO year, leading to a strong moisture convergence over India and northern China. All these changes of circulations and moisture conditions finally result in an anoma- lous Asian summer monsoon and monsoon rainfall over India and northern China. In addition, the APNPO has a good persistence from spring to summer. The spring APNPO is also significantly corre- lated with Asian summer monsoon variability. The spring APNPO might therefore provide valuable in- formation for the prediction of Asian summer monsoon.

  15. Sea surface height anomaly and upper ocean temperature over the Indian Ocean during contrasting monsoons

    Science.gov (United States)

    Gera, Anitha; Mitra, A. K.; Mahapatra, D. K.; Momin, I. M.; Rajagopal, E. N.; Basu, Swati

    2016-09-01

    Recent research emphasizes the importance of the oceanic feedback to monsoon rainfall over the Asian landmass. In this study, we investigate the differences in the sea surface height anomaly (SSHA) and upper ocean temperature over the tropical Indian Ocean during multiple strong and weak monsoons. Analysis of satellite derived SSHA, sea surface temperature (SST) and ocean reanalysis data reveals that patterns of SSHA, SST, ocean temperature, upper ocean heat content (UOHC) and propagations of Kelvin and Rossby waves differ during strong and weak monsoon years. During strong monsoons positive SSH, SST and UOHC anomalies develop over large parts of north Indian Ocean whereas during weak monsoons much of the north Indian Ocean is covered with negative anomalies. These patterns can be used as a standard tool for evaluating the performance of coupled and ocean models in simulating & forecasting strong and weak monsoons. The rainfall over central India is found to be significantly correlated with SSHA over the regions (Arabian Sea and West central Indian Ocean and Bay of Bengal) where SSHA is positively large during strong monsoons. The SST-SSHA correlation is also very strong over the same area. The study reveals that much convection takes place over these regions during strong monsoons. In contrast during weak monsoons, convection takes place over eastern equatorial region. These changes in SST are largely influenced by oceanic Kelvin and Rossby waves. The Rossby waves initiated in spring at the eastern boundary propagate sub-surface heat content in the ocean influencing SST in summer. The SST anomalies modulate the Hadley circulation and the moisture transport thereby contributing to rainfall over central India. Therefore oceanic Kelvin and Rossby waves influence the rainfall over central India.

  16. Determination of summer monsoon onset and its related large-scale circulation characteristics over Pakistan

    Science.gov (United States)

    Latif, M.; Syed, F. S.

    2016-08-01

    The onset of summer monsoon over the Core Monsoon Region of Pakistan (CMRP) has been investigated in this study using observational daily rainfall and Precipitable Water (PW) data sets. An objective criterion is proposed to define monsoon onset dates by employing Precipitation Index and Normalized Precipitable Water Index techniques. The climatological mean summer monsoon onset dates over CMRP based on daily rainfall data sets are observed to be 1 July and 30 June in the station and gridded data sets, respectively. Whereas the daily PW-based climatological mean onset date is 30 June. The year-wise onset dates determined through station and gridded rainfall data sets are very similar but these dates differ in case of PW-based onsets. The evolution of large-scale circulation anomalies and thermodynamic structure leading monsoon onset over Pakistan shows that a strong positive temperature and geopotential height anomalies appear over the northwestern part of the core region in the upper atmosphere. This warm geopotential height anomaly gets strengthen as the monsoon onset approaches. The temperature anomalies are barotropic whereas the geopotential height anomalies are baroclinic with the presence of low level anticyclone over the Tibetan Plateau. A moisture convergence zone along the foothill of Himalayas and low level moisture convergence zone over the north Arabian Sea set the stage for the moisture carrying monsoon winds to blow inland towards CMRP. The moisture is mainly supplied from the Arabian Sea, as the low pressure system approaches CMRP from the Bay of Bengal.

  17. Deciphering the desiccation trend of the South Asian monsoon hydroclimate in a warming world

    Science.gov (United States)

    Krishnan, R.; Sabin, T. P.; Vellore, R.; Mujumdar, M.; Sanjay, J.; Goswami, B. N.; Hourdin, F.; Dufresne, J.-L.; Terray, P.

    2016-08-01

    Rising propensity of precipitation extremes and concomitant decline of summer-monsoon rains are amongst the most distinctive hydroclimatic signals that have emerged over South Asia since 1950s. A clear understanding of the underlying causes driving these monsoon hydroclimatic signals has remained elusive. Using a state-of-the-art global climate model with high-resolution zooming over South Asia, we demonstrate that a juxtaposition of regional land-use changes, anthropogenic-aerosol forcing and the rapid warming signal of the equatorial Indian Ocean is crucial to produce the observed monsoon weakening in recent decades. Our findings also show that this monsoonal weakening significantly enhances occurrence of localized intense precipitation events, as compared to the global-warming response. A 21st century climate projection using the same high-resolution model indicates persistent decrease of monsoonal rains and prolongation of soil drying. Critical value-additions from this study include (1) realistic simulation of the mean and long-term historical trends in the Indian monsoon rainfall (2) robust attributions of changes in moderate and heavy precipitation events over Central India (3) a 21st century projection of drying trend of the South Asian monsoon. The present findings have profound bearing on the regional water-security, which is already under severe hydrological-stress.

  18. Managing Success in Viet Nam: Macroeconomic Consequences of Large Capital Inflows with Limited Policy Tools

    OpenAIRE

    Menon, Jayant

    2009-01-01

    Viet Nam has experienced spectacular economic growth over the past decade, in part the result of massive foreign direct investment (FDI) inflows. Although much has been written on the impacts of FDI in developing countries, previous studies have generally ignored macroeconomic consequences in cost-benefit assessments. These macroeconomic aspects can be particularly important in transitional economies like Viet Nam, where some of the tools for macroeconomic stabilization may be blunt or unavai...

  19. Osmanlı Devletinin Son Yıllarında Ağnam Vergisine Yapılan Zamlar Rise In Ağnam (Sheep Tax In The Recent Years Of Ottoman State

    Directory of Open Access Journals (Sweden)

    Ünal TAŞKIN

    2013-07-01

    Full Text Available People generally known as rayah in Ottoman State had some responsibilities to state. Among these responsibilities there were tax figures to be paid about agricultural and husbandry facilities. Each rayah doing husbandry facilities made payments in certain rates according to animal breed fed. Known as the tax of sheep and goat in the classical time of state, sheep tax gained a more general meaning and was subject to new regulations. It was initiated to be collected with a method called mukataa and expressing a certain amount determined in advance since the XVII. century of Ottoman State. Called as sheep tax mukataa, this income became one the most important figure of central treasury. Since the XIX. by abandoning the collection in kind method additional taxes with various names were also abolished.The price determined as the amount of tax was too much for some regions of the state because of regional differences in sheep prices. Because of this it was initiated to determine how much income was gained from the milk and wool of sheep and goat according to each region with the new regulation since the second part of the XIX. century. Determined by local administrations seperately, the tax figure of these amounts were determined in central office.As the rise in the taxes caused a negative effect on public, they were read justed towards the end of XIX. century. Reasons such as the current social situation of state, the worry of fund raising and political events caused changes in the encashment of taxes called as ağnam group. In ourwork the eight fold rise in ağnam tax which is accepted as one of the most important sources for recovering budget deficit of Ottoman State is goingto be studied. Osmanlı Devleti’nde reaya genel adıyla bilinen halkın, devletekarşı birtakım mükellefiyetleri vardı. Bu mükellefiyetler içerisinde,tarım ve hayvancılık faaliyetlerinden kaynaklı, ödenmesi gereken vergikalemleri mevcuttu. Hayvanc

  20. Mid-Pliocene East Asian monsoon climate simulated in the PlioMIP

    OpenAIRE

    Zhang, R.; Yan, Q.; Z. S. Zhang; Jiang, D.; B. L. Otto-Bliesner; A. M. Haywood; D. J. Hill; Dolan, A. M.; Stepanek, C.; Lohmann, G.; Contoux, C.; F. Bragg; Chan, W.-L.; Chandler, M. A.; A. Jost

    2013-01-01

    Based on the simulations with fifteen climate models in the Pliocene Model Intercomparison Project (PlioMIP), the regional climate of East Asia (focusing on China) during the mid-Pliocene is investigated in this study. Compared to the pre-industrial, the multi-model ensemble mean (MMM) of all models shows the East Asian summer wind (EASW) largely strengthens in monsoon China, and the East Asian winter wind (EAWW) strengthens in south monsoon China but slightly weakens in north monsoon China i...

  1. What drives the global summer monsoon over the past millennium?

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian [Chinese Academy of Sciences, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Nanjing (China); Wang, Bin [University of Hawaii at Manoa, Department of Meteorology, Honolulu, HI (United States); University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); Yim, So-Young; Lee, June-Yi [University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); Jhun, Jong-Ghap [Seoul National University, School of Earth and Environmental Sciences/Research Institute of Oceanography, Seoul (Korea, Republic of); Ha, Kyung-Ja [Pusan National University, Division of Earth Environmental System, Busan (Korea, Republic of)

    2012-09-15

    The global summer monsoon precipitation (GSMP) provides a fundamental measure for changes in the annual cycle of the climate system and hydroclimate. We investigate mechanisms governing decadal-centennial variations of the GSMP over the past millennium with a coupled climate model's (ECHO-G) simulation forced by solar-volcanic (SV) radiative forcing and greenhouse gases (GHG) forcing. We show that the leading mode of GSMP is a forced response to external forcing on centennial time scale with a globally uniform change of precipitation across all monsoon regions, whereas the second mode represents internal variability on multi-decadal time scale with regional characteristics. The total amount of GSMP varies in phase with the global mean temperature, indicating that global warming is accompanied by amplification of the annual cycle of the climate system. The northern hemisphere summer monsoon precipitation (NHSMP) responds to GHG forcing more sensitively, while the southern hemisphere summer monsoon precipitation (SHSMP) responds to the SV radiative forcing more sensitively. The NHSMP is enhanced by increased NH land-ocean thermal contrast and NH-minus-SH thermal contrast. On the other hand, the SHSMP is strengthened by enhanced SH subtropical highs and the east-west mass contrast between Southeast Pacific and tropical Indian Ocean. The strength of the GSMP is determined by the factors controlling both the NHSMP and SHSMP. Intensification of GSMP is associated with (a) increased global land-ocean thermal contrast, (b) reinforced east-west mass contrast between Southeast Pacific and tropical Indian Ocean, and (c) enhanced circumglobal SH subtropical highs. The physical mechanisms revealed here will add understanding of future change of the global monsoon. (orig.)

  2. The South Asian Monsoon Circulation in Moist Isentropic coordinates

    Science.gov (United States)

    Thazhe Purayil, Sabin; Pauluis, Olivier

    2016-04-01

    The atmospheric circulation and thermodynamic structure during the South Asian Summer Monsoon season is analyzed in isentropic coordinates through the mass transport represented in terms of the potential temperature and equivalent potential temperature. This approach, originally developed to analyze the global meridional circulation, makes it possible to identify the thermodynamic properties of the inflow and outflow of different air mass. To understand the thermodynamic properties of air mass in south Asian monsoon region, we have used three diagnostics; a) the joint distribution of the mass transport as a function of dry and moist entropy, b) the vertical mass flux over the monsoon domain and c) the mass transport and isentropic thickness for different moist ventilation range of tropical atmosphere. The thermodynamic properties of the various air masses, such as the inflow of warm moist air in the boundary layer, upper tropospheric outflow, and midlatitude dry air intrusion are being systematically identified. The isentropic distribution of the vertical mass flux transport in terms of equivalent potential temperature is used to explain the characteristics of ascending and descending air parcels over the Indian subcontinent. Diagnosis based on the isentropic thickness reveals that the regional monsoon circulation and associated precipitation features can be systematically explained by this method. This technique is used to study the evolution of the monsoon flow in the seasonal scale. We used the data from AMIP-type simulations carried out with prescribed Sea Surface Temperature and sea ice for a 25 year period (1981-2005) from the GFDL High-resolution atmospheric model (HiRAM) with an average grid spacing of ~25km over the globe.

  3. Atlantic effects on recent decadal trends in global monsoon

    Science.gov (United States)

    Kamae, Youichi; Li, Xichen; Xie, Shang-Ping; Ueda, Hiroaki

    2017-01-01

    Natural climate variability contributes to recent decadal climate trends. Specifically the trends during the satellite era since 1979 include Atlantic and Indian Ocean warming and Pacific cooling associated with phase shifts of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation, and enhanced global monsoon (GM) circulation and rainfall especially in the Northern Hemisphere. Here we evaluate effects of the oceanic changes on the global and regional monsoon trends by partial ocean temperature restoring experiments in a coupled atmosphere-ocean general circulation model. Via trans-basin atmosphere-ocean teleconnections, the Atlantic warming drives a global pattern of sea surface temperature change that resembles observations, giving rise to the enhanced GM. The tropical Atlantic warming and the resultant Indian Ocean warming favor subtropical deep-tropospheric warming in both hemispheres, resulting in the enhanced monsoon circulations and precipitation over North America, South America and North Africa. The extratropical North Atlantic warming makes an additional contribution to the monsoon enhancement via Eurasian continent warming and resultant land-sea thermal gradient over Asia. The results of this study suggest that the Atlantic multidecadal variability can explain a substantial part of global climate variability including the recent decadal trends of GM.

  4. Spatial monsoon variability with respect to NAO and SO

    Indian Academy of Sciences (India)

    S B Kakade; S S Dugam

    2006-10-01

    In this paper, the simultaneous effect of North Atlantic Oscillation (NAO) and Southern Oscillation (SO) on monsoon rainfall over different homogeneous regions/subdivisions of India is studied. The simultaneous effect of both NAO and SO on Indian summer monsoon rainfall (ISMR) is more important than their individual impact because both the oscillations exist simultaneously throughout the year. To represent the simultaneous impact of NAO and SO, an index called effective strength index (ESI) has been defined on the basis of monthly NAO and SO indices. The variation in the tendency of ESI from January through April has been analyzed and reveals that when this tendency is decreasing, then the ESI value throughout the monsoon season (June-September) of the year remains negative and vice versa. This study further suggests that during the negative phase of ESI tendency, almost all subdivisions of India show above-normal rainfall and vice versa. The correlation analysis indicates that the ESI-tendency is showing an inverse and statistically significant relationship with rainfall over 14 subdivisions of India. Area wise, about 50% of the total area of India shows statistically significant association. Moreover, the ESI-tendency shows a significant relationship with rainfall over north west India, west central India, central north east India, peninsular India and India as a whole. Thus, ESI-tendency can be used as a precursor for the prediction of Indian summer monsoon rainfall on a smaller spatial scale.

  5. The Dynamic Plateau Monsoon Index and Its Association with General Circulation Anomalies

    Institute of Scientific and Technical Information of China (English)

    XUN Xueyi; HU Zeyong; MA Yaoming

    2012-01-01

    Based on monthly ECMWF reanalysis-Interim (ERA-Interim) reanalysis data,along with monthly precipitation and temperature data,the Dynamic Plateau Monsoon Index (DPMI) is defined.The results of a contrast analysis of the DPMI versus the Traditional Plateau Monsoon Index (TPMI) are described.The response of general circulation to northern Qinghai-Xizang Plateau summer monsoon anomalies and the correlation of the DPMI with general circulation anomalies are investigated.The results show that,the DPMI reflected meteorological elements better and depicted climate variation more accurately than the TPMI.In years when the plateau summer monsoon is strong,the low over the plateau and the trough near the eastern coast of Asia are deeper and higher than normal over South China.This correlation corresponds to two anomalous cyclones over the plateau and the eastern coast of Asia and an anomalous anticyclone in South China.The plateau and its adjacent regions are affected by anomalous southwesterly winds that transport more moisture to South China and cause more precipitation.The lower reaches of the Yangtze River appear to receive more precipitation by means of the strong westerly water vapor flow transported from the "large triangle affecting the region".In years when the plateau summer monsoon is weak,these are opposite.The plateau monsoon is closely related to the intensity and position of the South Asian high,and the existence of a teleconnection pattern in the mid-upper levels suggests a possible linl~ge of the East Asian monsoon and the Indian monsoon to the plateau summer monsoon.

  6. Dominating Controls for Wetter South Asian Summer Monsoon in the Twenty-First Century

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Rui; Ashfaq, Moetasim; Rastogi, Deeksha; Leung, Lai-Yung R.; Dominguez, Francina

    2015-04-01

    We analyze a suite of Global Climate Models from the 5th Phase of Coupled Models Intercomparison Project (CMIP5) archives to understand the mechanisms behind a net increase in the South Asian summer monsoon precipitation in response to enhanced radiative forcing during the 21st century despite a robust weakening of dynamics governing the monsoon circulation. Combining the future changes in the contributions from various sources, which contribute to the moisture supply over South Asia, with those in monsoon dynamics and atmospheric moisture content, we establish a pathway of understanding that partly explains these counteracting responses to increase in radiative forcing. Our analysis suggests that both regional (local recycling, Arabian Sea, Bay of Bengal) and remote (mainly Indian Ocean) sources contribute to the moisture supply for precipitation over South Asia during the summer season that is facilitated by the monsoon dynamics. Increase in radiative forcing fuels an increase in the atmospheric moisture content through warmer temperatures. For regional moisture sources, the effect of excessive atmospheric moisture is offset by weaker monsoon circulation and uncertainty in the response of the evapotranspiration over land, so anomalies in their contribution to the total moisture supply are either mixed or muted. In contrast, weakening of the monsoon dynamics has less influence on the moisture supply from remote sources that not only is a dominant moisture contributor in the historical period, but is also the net driver of the positive summer monsoon precipitation response in the 21st century. Our results also indicate that historic measures of the monsoon dynamics may not be well suited to predict the non-stationary moisture driven South Asian summer monsoon precipitation response in the 21st century.

  7. An Assessment of Monsoon Triggered Landslides in Western Nepal

    Science.gov (United States)

    Sudan Acharya, Madhu

    2010-05-01

    Due to heavy monsoon rain, rugged topography and very young mountains, frequent slope failures and soil erosion are very common in Nepal but in most of cases the natural slopes are disturbed by men to construct a road through it and the situation further aggravated by the Monsoon rain. Summer usually tests the disaster response capacity of Nepal, when the monsoons trigger water induced disasters. This year Nepal's Western regions were most severely affected by floods and landslides. Every year, sadly, it is the same story of mostly poor people living in remote villages succumbing to landslides and flooding and those who survive facing hardships brought on by the disaster. The tail end of the monsoon in October has triggered flood and landslides in Nepal which affected a total of 14 districts in the mid and far-west regions, of which Kailali, Bardiya, Banke, Dadeldhura, Accham and Kanchapur district are most affected. The affected areas are geographically scattered and remote, and are therefore difficult to access. In this year (2009), flood and landslides have claimed 62 lives, affecting more than 152,000 individuals from 27,000 families. More than 4,000 families are displaced and are taking shelter in schools, open space and forest areas with no protection from the external elements. In the above context the prevention and mitigation measures for landslides is a great challenge for Nepal. Nepal has been investing its huge amount of resources to stabilize landslides and roadside slope failures, still then it has become unmanageable during Monsoon time. Considering the above facts, an assessment of landslides which were occurred during the Monsoon (July-October 2009), along Khodpe - Jhota - Chainpur road in far western region of Nepal has been carried out based on the field observation of various landslides. The paper presents the causes and mechanisms of failures of different landslides which are mostly triggered by Monsoon rain. It also suggests some low cost

  8. Orbital pacing and ocean circulation-induced collapses of the Mesoamerican monsoon over the past 22,000 y.

    Science.gov (United States)

    Lachniet, Matthew S; Asmerom, Yemane; Bernal, Juan Pablo; Polyak, Victor J; Vazquez-Selem, Lorenzo

    2013-06-04

    The dominant controls on global paleomonsoon strength include summer insolation driven by precession cycles, ocean circulation through its influence on atmospheric circulation, and sea-surface temperatures. However, few records from the summer North American Monsoon system are available to test for a synchronous response with other global monsoons to shared forcings. In particular, the monsoon response to widespread atmospheric reorganizations associated with disruptions of the Atlantic Meridional Overturning Circulation (AMOC) during the deglacial period remains unconstrained. Here, we present a high-resolution and radiometrically dated monsoon rainfall reconstruction over the past 22,000 y from speleothems of tropical southwestern Mexico. The data document an active Last Glacial Maximum (18-24 cal ka B.P.) monsoon with similar δ(18)O values to the modern, and that the monsoon collapsed during periods of weakened AMOC during Heinrich stadial 1 (ca. 17 ka) and the Younger Dryas (12.9-11.5 ka). The Holocene was marked by a trend to a weaker monsoon that was paced by orbital insolation. We conclude that the Mesoamerican monsoon responded in concert with other global monsoon regions, and that monsoon strength was driven by variations in the strength and latitudinal position of the Intertropical Convergence Zone, which was forced by AMOC variations in the North Atlantic Ocean. The surprising observation of an active Last Glacial Maximum monsoon is attributed to an active but shallow AMOC and proximity to the Intertropical Convergence Zone. The emergence of agriculture in southwestern Mexico was likely only possible after monsoon strengthening in the Early Holocene at ca. 11 ka.

  9. Strong winter monsoon wind causes surface cooling over India and China in the Late Miocene

    Directory of Open Access Journals (Sweden)

    H. Tang

    2015-01-01

    Full Text Available Modern Asian winter monsoon characterised by the strong northwesterly wind in East Asia and northeasterly wind in South Asia, has a great impact on the surface temperature of the Asian continent. Its outbreak can result in significant cooling of the monsoon region. However, it is still unclear whether such an impact existed and is detectable in the deep past. In this study, we use temperature reconstructions from plant and mammal fossil data together with climate model results to examine the co-evolution of surface temperature and winter monsoon in the Late Miocene (11–5 Ma, when a significant change of the Asian monsoon system occurred. We find that a stronger-than-present winter monsoon wind might have existed in the Late Miocene due to the lower Asian orography, particularly the northern Tibetan Plateau and the mountains north of it. This can lead to a pronounced cooling in southern China and northern India, which counteracts the generally warmer conditions in the Late Miocene compared to present. The Late Miocene strong winter monsoon was characterised by a marked westerly component and primarily caused by a pressure anomaly between the Tibetan Plateau and Northern Eurasia, rather than by the gradient between the Siberian High and the Aleutian Low. As a result, the close association of surface temperature with winter monsoon strength on inter-annual scale as observed at present may not have established in the Late Miocene.

  10. Global warming and South Indian monsoon rainfall-lessons from the Mid-Miocene.

    Science.gov (United States)

    Reuter, Markus; Kern, Andrea K; Harzhauser, Mathias; Kroh, Andreas; Piller, Werner E

    2013-04-01

    Precipitation over India is driven by the Indian monsoon. Although changes in this atmospheric circulation are caused by the differential seasonal diabatic heating of Asia and the Indo-Pacific Ocean, it is so far unknown how global warming influences the monsoon rainfalls regionally. Herein, we present a Miocene pollen flora as the first direct proxy for monsoon over southern India during the Middle Miocene Climate Optimum. To identify climatic key parameters, such as mean annual temperature, warmest month temperature, coldest month temperature, mean annual precipitation, mean precipitation during the driest month, mean precipitation during the wettest month and mean precipitation during the warmest month the Coexistence Approach is applied. Irrespective of a ~ 3-4 °C higher global temperature during the Middle Miocene Climate Optimum, the results indicate a modern-like monsoonal precipitation pattern contrasting marine proxies which point to a strong decline of Indian monsoon in the Himalaya at this time. Therefore, the strength of monsoon rainfall in tropical India appears neither to be related to global warming nor to be linked with the atmospheric conditions over the Tibetan Plateau. For the future it implies that increased global warming does not necessarily entail changes in the South Indian monsoon rainfall.

  11. The footprint of Asian monsoon dynamics in the mass and energy balance of a Tibetan glacier

    Directory of Open Access Journals (Sweden)

    T. Mölg

    2012-08-01

    Full Text Available Determinations of glacier-wide mass and energy balance are still scarce for the remote mountains of the Tibetan Plateau, where field measurements are challenging. Here we run and evaluate a physical, distributed mass balance model for Zhadang glacier (central Tibet, 30° N, based on in-situ measurements over 2009–2011 and an uncertainty estimate by Monte Carlo and ensemble strategies. The model application aims to provide the first quantification of how the Indian Summer Monsoon (ISM impacts an entire glacier over the various stages of the monsoon's annual cycle. We find a strong and systematic ISM footprint on the interannual scale. Early (late monsoon onset causes higher (lower accumulation, and reduces (increases the available energy for ablation primarily through changes in absorbed shortwave radiation. By contrast, only a weak footprint exists in the ISM cessation phase. Most striking though is the core monsoon season: local mass and energy balance variability is fully decoupled from the active/break cycle that defines large-scale atmospheric variability during the ISM. Our results demonstrate quantitatively that monsoon onset strongly affects the ablation season of glaciers in Tibet. However, we find no direct ISM impact on the glacier in the main monsoon season, which has not been acknowledged so far. This result also adds cryospheric evidence that regional modification of the large-scale monsoon flow prevails on the Tibetan Plateau in summer.

  12. The footprint of Asian monsoon dynamics in the mass and energy balance of a Tibetan glacier

    Directory of Open Access Journals (Sweden)

    T. Mölg

    2012-12-01

    Full Text Available Determinations of glacier-wide mass and energy balance are still scarce for the remote mountains of the Tibetan Plateau, where field measurements are challenging. Here we run and evaluate a physical, distributed mass balance model for Zhadang Glacier (central Tibet, 30° N based on in-situ measurements over 2009–2011 and an uncertainty estimate by Monte Carlo and ensemble strategies. The model application aims to provide the first quantification of how the Indian Summer Monsoon (ISM impacts an entire glacier over the various stages of the monsoon's annual cycle. We find a strong and systematic ISM footprint on the interannual scale. Early (late monsoon onset causes higher (lower accumulation, and reduces (increases the available energy for ablation primarily through changes in absorbed shortwave radiation. By contrast, only a weak footprint exists in the ISM cessation phase. Most striking though is the core monsoon season: local mass and energy balance variability is fully decoupled from the active/break cycle that defines large-scale atmospheric variability during the ISM. Our results demonstrate quantitatively that monsoon onset strongly affects the ablation season of glaciers in Tibet. However, we find no direct ISM impact on the glacier in the main monsoon season, which has not been acknowledged so far. This result also adds cryospheric evidence that, once the monsoon is in full swing, regional atmospheric variability prevails on the Tibetan Plateau in summer.

  13. The footprint of Asian monsoon dynamics in the mass and energy balance of a Tibetan glacier

    Science.gov (United States)

    Mölg, T.; Maussion, F.; Yang, W.; Scherer, D.

    2012-12-01

    Determinations of glacier-wide mass and energy balance are still scarce for the remote mountains of the Tibetan Plateau, where field measurements are challenging. Here we run and evaluate a physical, distributed mass balance model for Zhadang Glacier (central Tibet, 30° N) based on in-situ measurements over 2009-2011 and an uncertainty estimate by Monte Carlo and ensemble strategies. The model application aims to provide the first quantification of how the Indian Summer Monsoon (ISM) impacts an entire glacier over the various stages of the monsoon's annual cycle. We find a strong and systematic ISM footprint on the interannual scale. Early (late) monsoon onset causes higher (lower) accumulation, and reduces (increases) the available energy for ablation primarily through changes in absorbed shortwave radiation. By contrast, only a weak footprint exists in the ISM cessation phase. Most striking though is the core monsoon season: local mass and energy balance variability is fully decoupled from the active/break cycle that defines large-scale atmospheric variability during the ISM. Our results demonstrate quantitatively that monsoon onset strongly affects the ablation season of glaciers in Tibet. However, we find no direct ISM impact on the glacier in the main monsoon season, which has not been acknowledged so far. This result also adds cryospheric evidence that, once the monsoon is in full swing, regional atmospheric variability prevails on the Tibetan Plateau in summer.

  14. Workshop on Monsoon Climate Systems: Toward Better Prediction of the Monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Sperber, K R; Yasunari, T

    2005-12-20

    The Earth's monsoon systems are the life-blood of more than two-thirds of the world's population through the rainfall they provide to the mainly agrarian societies they influence. More than 60 experts gathered to assess the current understanding of monsoon variability and to highlight outstanding problems simulating the monsoon.

  15. Understanding land surface response to changing South Asian monsoon in a warming climate

    Directory of Open Access Journals (Sweden)

    M. V. S. Ramarao

    2015-05-01

    Full Text Available Recent studies have drawn attention to a significant weakening trend of the South Asian monsoon circulation and an associated decrease in regional rainfall during the last few decades. While surface temperatures over the region have steadily risen during this period, most of the CMIP (Coupled Model Intercomparison Project global climate models have difficulties in capturing the observed decrease of monsoon precipitation, thus limiting our understanding of the regional land surface response to monsoonal changes. This problem is investigated by performing two long-term simulation experiments, with and without anthropogenic forcing, using a variable resolution global climate model having high-resolution zooming over the South Asian region. The present results indicate that anthropogenic effects have considerably influenced the recent weakening of the monsoon circulation and decline of precipitation. It is seen that the simulated increase of surface temperature over the Indian region during the post-1950s is accompanied by a significant decrease of monsoon precipitation and soil moisture. Our analysis further reveals that the land surface response to decrease of soil moisture is associated with significant reduction in evapotranspiration over the Indian land region. A future projection, based on the representative concentration pathway 4.5 (RCP4.5 scenario of the Intergovernmental panel on Climate Change (IPCC, using the same high-resolution model indicates the possibility for detecting the summer-time soil drying signal over the Indian region during the 21st century, in response to climate change. While these monsoon hydrological changes have profound socioeconomic implications, the robustness of the high-resolution simulations provides deeper insights and enhances our understanding of the regional land surface response to the changing South Asian monsoon.

  16. Shining Light on an mGlu5 Photoswitchable NAM: A Theoretical Perspective.

    Science.gov (United States)

    Dalton, James A R; Lans, Isaias; Rovira, Xavier; Malhaire, Fanny; Gómez-Santacana, Xavier; Pittolo, Silvia; Gorostiza, Pau; Llebaria, Amadeu; Goudet, Cyril; Pin, Jean-Philippe; Giraldo, Jesús

    2016-01-01

    Metabotropic glutamate receptors (mGluRs) are important drug targets because of their involvement in several neurological diseases. Among mGluRs, mGlu5 is a particularly high-profile target because its positive or negative allosteric modulation can potentially treat schizophrenia or anxiety and chronic pain, respectively. Here, we computationally and experimentally probe the functional binding of a novel photoswitchable mGlu5 NAM, termed alloswitch-1, which loses its NAM functionality under violet light. We show alloswitch-1 binds deep in the allosteric pocket in a similar fashion to mavoglurant, the co-crystallized NAM in the mGlu5 transmembrane domain crystal structure. Alloswitch-1, like NAM 2-Methyl-6-(phenylethynyl)pyridine (MPEP), is significantly affected by P655M mutation deep in the allosteric pocket, eradicating its functionality. In MD simulations, we show alloswitch-1 and MPEP stabilize the co-crystallized water molecule located at the bottom of the allosteric site that is seemingly characteristic of the inactive receptor state. Furthermore, both NAMs form H-bonds with S809 on helix 7, which may constitute an important stabilizing interaction for NAM-induced mGlu5 inactivation. Alloswitch-1, through isomerization of its amide group from trans to cis is able to form an additional interaction with N747 on helix 5. This may be an important interaction for amide-containing mGlu5 NAMs, helping to stabilize their binding in a potentially unusual cis-amide state. Simulated conformational switching of alloswitch-1 in silico suggests photoisomerization of its azo group from trans to cis may be possible within the allosteric pocket. However, photoexcited alloswitch-1 binds in an unstable fashion, breaking H-bonds with the protein and destabilizing the co-crystallized water molecule. This suggests photoswitching may have destabilizing effects on mGlu5 binding and functionality.

  17. Mesoscale characteristics of monsoonal convection and associated stratiform precipitation

    Science.gov (United States)

    Keenan, Thomas D.; Rutledge, Steven A.

    1993-01-01

    Observations undertaken on 12 January 1990 at Darwin (Australia) are used to document the structure of a monsoonal rainband in a low convective available potential energy low-shear tropical environment. Dual-Doppler radar analyses are employed to investigate the structure and kinematics of the convective and stratiform regions. A system with the characteristics of a relatively short-lived squall line in which warm rain processes play a significant role in the production of precipitation is evident. Planetary boundary layer cold-pool production is important in the organization and motion of the system. A trailing stratiform region is evident with a mean updraft-downdraft circulation, but is composed of in situ decaying convective cells. A storm-relative mesoscale cyclonic circulation is also observed within the stratiform cloud. This vortex was maintained by thermodynamically induced midlevel convergence, convectively generated storm-scale circulations, and their interaction with the background monsoon flow.

  18. Interactive Aspects of the Indian and the African Summer Monsoon Systems

    Science.gov (United States)

    Sanjeeva Rao, P.; Sikka, D. R.

    2007-09-01

    This study addresses an understanding of the possible mutual interactions of sub-seasonal variability of the two neighboring regional monsoon systems through data analysis. The NCEP/NCAR re-analysis and OLR data for three years was used to reveal the large-scale organization of convective episodes on synoptic (~5 days) and low frequency (15 50 day) scales. It is found that synoptic scale organization over both the sectors is influenced by the eastward migration of large-scale convective episodes associated with the Madden Julian Oscillation (MJO) on the low frequency scale. The organization of convection associated with the African monsoon on the synoptic scale is influenced by the pulsatory character of lower mid-troposphere and upper troposphere wind regimes moving westward over the African sector. Over the Indian region formation of low pressure areas and depressions in the monsoon trough occur in an overlapping manner under an envelope of low frequency seasonal oscillation. We have also found some correspondence between the summer monsoon rainfall over tropical North Africa and India on a decadal basis, which would suggest a common mode of multi-decadal variability in the two monsoon systems. The study points out the need to organize simultaneous field campaigns over the Indian and the African monsoon regions so as to bring out observational features of possible interactions between the two neighboring systems, which could then be validated through modeling studies.

  19. The effects of monsoons and climate teleconnections on the Niangziguan Karst Spring discharge in North China

    Science.gov (United States)

    Zhang, Juan; Hao, Yonghong; Hu, Bill X.; Huo, Xueli; Hao, Pengmei; Liu, Zhongfang

    2017-01-01

    Karst aquifers supply drinking water for 25 % of the world's population, and they are, however, vulnerable to climate change. This study is aimed to investigate the effects of various monsoons and teleconnection patterns on Niangziguan Karst Spring (NKS) discharge in North China for sustainable exploration of the karst groundwater resources. The monsoons studied include the Indian Summer Monsoon, the West North Pacific Monsoon and the East Asian Summer Monsoon. The climate teleconnection patterns explored include the Indian Ocean Dipole, E1 Niño Southern Oscillation, and the Pacific Decadal Oscillation. The wavelet transform and wavelet coherence methods are used to analyze the karst hydrological processes in the NKS Basin, and reveal the relations between the climate indices with precipitation and the spring discharge. The study results indicate that both the monsoons and the climate teleconnections significantly affect precipitation in the NKS Basin. The time scales that the monsoons resonate with precipitation are strongly concentrated on the time scales of 0.5-, 1-, 2.5- and 3.5-year, and that climate teleconnections resonate with precipitation are relatively weak and diverged from 0.5-, 1-, 2-, 2.5-, to 8-year time scales, respectively. Because the climate signals have to overcome the resistance of heterogeneous aquifers before reaching spring discharge, with high energy, the strong climate signals (e.g. monsoons) are able to penetrate through aquifers and act on spring discharge. So the spring discharge is more strongly affected by monsoons than the climate teleconnections. During the groundwater flow process, the precipitation signals will be attenuated, delayed, merged, and changed by karst aquifers. Therefore, the coherence coefficients between the spring discharge and climate indices are smaller than those between precipitation and climate indices. Further, the fluctuation of the spring discharge is not coincident with that of precipitation in most

  20. Climatology of monsoon precipitation over the Tibetan Plateau from 13-year TRMM observations

    Science.gov (United States)

    Aijuan, Bai; Guoping, Li

    2016-10-01

    Based on the 13-year data from the Tropical Rainfall Measuring Mission (TRMM) satellite during 2001-2013, the influencing geographical location of the Tibetan Plateau (Plateau) monsoon is determined. It is found that the domain of the Plateau monsoon is bounded by the latitude between 27° N and 37° N and the longitude between 60° E and 103° E. According to the annual relative precipitation, the Plateau monsoon can be divided into three sections: the Plateau winter monsoon (PWM) over Iran and Afghanistan, the Plateau summer monsoon (PSM) over the central Plateau, and the transiting zone of the Plateau monsoon (TPM) over the south, west, and east edges of the Plateau. In PWM and PSM, the monsoon climatology has a shorter rainy season with the mean annual rainfall of less than 800 mm. In TPM, it has a longer rainy season with the mean annual rainfall of more than 1800 mm. PWM experiences a single-peak monthly rainfall with the peak during January to March; PSM usually undergoes a multi-peak pattern with peaks in the warm season; TPM presents a double-peak pattern, with a strong peak in late spring to early summer and a secondary peak in autumn. The Plateau monsoon also characterizes an asymmetrical seasonal advance of the rain belt. In the east of the Plateau, the rain belt migrates in a south-north orientation under the impact of the tropical and subtropical systems' oscillation. In the west of the Plateau, the rain belt advances in an east-west direction, which is mainly controlled by the regional Plateau monsoon.

  1. Quaternary Lake Deposits of Nam Co, Tibet, with a Discussion of the Connection of Nam Co with Ring Co-Jiuru Co

    Institute of Scientific and Technical Information of China (English)

    朱大岗; 赵希涛; 孟宪刚; 吴中海; 吴珍汉; 冯向阳; 邵兆刚; 刘琦胜; 杨美玲

    2002-01-01

    Shorelines are widespread and lake deposits and lake geomorphology are well developed on the northern Tibetan Plateau. Through field observations of lacustrine deposits of Nam Co-the highest and largest Quaternary lake in Tibet, the authors found four-step shore terraces composed of sands and clays with well-developed horizontal bedding and 3-12 m, 15-22 m, 25-30 m and 35-45 m higher than the lake surface respectively, lacustrine deposits resting on the bedrocks and 60-150 m higher than the lake surface, and up to ~50 levees composed of oblate lakeshore gravels. Moreover they found lacustrine and lakeshore deposits making up the terraces and levees on the bottoms of wide dividing valleys connecting Nam Co with the Rencoyuema, Rencogongma and Jiuru Co northwest of Nam Co (the valley bottoms are 20 m, 90 m and 60 m higher than the above-mentioned three lakes) and on slopes north of it, i.e. terraces II and III of Nam Co. Thus they confirm that Nam Co and Ring Co-Jiuru Co had connected with each other several times, i.e. formed a unified large lake several times, rather than had been different lakes connected only by river channels. From indications such as the distribution of the highest shoreline and lake deposits and geomorphology, the authors conclude that the total area of the old large lakes on the northern Tibetan Plateau is a few times larger than that of the modern lakes and that the last-stage old large lakes formed in the interglacial interval of the last glaciation.

  2. 亚洲季风区过去700年来夏季极端干/湿事件多尺度变化特征分析%Multi-scale Analysis of the Extreme Dry/Wet Events in Asian Monsoon Region in Summer During Last 7 Centuries

    Institute of Scientific and Technical Information of China (English)

    杨萍; 侯威; 颜鹏程

    2016-01-01

    Monsoon failures,mega droughts,and extreme flooding events have repeatedly affected the agrari-an peoples of Asia over the past millennium.A scarcity of long-term instrumental climate data for many remote re-gions of Monsoon Asia impedes progress toward resolving these issues.To better elucidate the spatial complexity of the Asian monsoon,a large-scale,spatially explicit,long-term data set is needed.This context is provided here by our Monsoon Asia Drought Atlas (MADA).The MADA provides a seasonal-to centennial-scale window into the A-sian monsoon’s repeated tendency for extended dry and wet extremes with distinct spatial flavors of response.Re-cently,ensemble empirical mode decomposition (EEMD)method is developed for non-linear and non-stationary signal analysis.The EEMD method is instituted and utilized in several fields such as de-noising,ocean surface measurement,metrology,image processing and so on.The method can work on nature signals (non-linear and nonstationary signals)as well as reducing the speckle noise.The EEMD method is like as a filter bank that the sig-nal is decomposed into several intrinsic mode functions(IMFs)and the frequencies of IMFs are arranged in decrease order (high to low)after the EEMD processing.The scaling mode of the EEMD method is similar to wavelet trans-form,but the signal resolution at different frequency domain is not decrease by down-sampling.In this paper,we propose the EEMD method to extract the multi-scale characters of the variability of extreme dry/wet events in Asian monsoon area.Using the Palmer Drought Severity Index data of MADA from 504 stations in Asian monsoon area in summer from 1300-2005a and EEMD method,we get the series of the number of grids which is especially and seri-ous wet or dry in this region by an interval of 5 years,and analysis the variations of these series.Based the feature of nonlinear/nonstationarity and multi-scale in climatic system,applying EEMD to the series of the number of grids which is

  3. Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006

    Directory of Open Access Journals (Sweden)

    S. Janicot

    2008-09-01

    Full Text Available The AMMA (African Monsoon Multidisciplinary Analysis program is dedicated to providing a better understanding of the West African monsoon and its influence on the physical, chemical and biological environment regionally and globally, as well as relating variability of this monsoon system to issues of health, water resources, food security and demography for West African nations. Within this framework, an intensive field campaign took place during the summer of 2006 to better document specific processes and weather systems at various key stages of this monsoon season. This campaign was embedded within a longer observation period that documented the annual cycle of surface and atmospheric conditions between 2005 and 2007. The present paper provides a large and regional scale overview of the 2006 summer monsoon season, that includes consideration of of the convective activity, mean atmospheric circulation and synoptic/intraseasonal weather systems, oceanic and land surface conditions, continental hydrology, dust concentration and ozone distribution. The 2006 African summer monsoon was a near-normal rainy season except for a large-scale rainfall excess north of 15° N. This monsoon season was also characterized by a 10-day delayed onset compared to climatology, with convection becoming developed only after 10 July. This onset delay impacted the continental hydrology, soil moisture and vegetation dynamics as well as dust emission. More details of some less-well-known atmospheric features in the African monsoon at intraseasonal and synoptic scales are provided in order to promote future research in these areas.

  4. Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006

    Science.gov (United States)

    Janicot, S.; Thorncroft, C. D.; Ali, A.; Asencio, N.; Berry, G.; Bock, O.; Bourles, B.; Caniaux, G.; Chauvin, F.; Deme, A.; Kergoat, L.; Lafore, J.-P.; Lavaysse, C.; Lebel, T.; Marticorena, B.; Mounier, F.; Nedelec, P.; Redelsperger, J.-L.; Ravegnani, F.; Reeves, C. E.; Roca, R.; de Rosnay, P.; Schlager, H.; Sultan, B.; Tomasini, M.; Ulanovsky, A.; Acmad Forecasters Team

    2008-09-01

    The AMMA (African Monsoon Multidisciplinary Analysis) program is dedicated to providing a better understanding of the West African monsoon and its influence on the physical, chemical and biological environment regionally and globally, as well as relating variability of this monsoon system to issues of health, water resources, food security and demography for West African nations. Within this framework, an intensive field campaign took place during the summer of 2006 to better document specific processes and weather systems at various key stages of this monsoon season. This campaign was embedded within a longer observation period that documented the annual cycle of surface and atmospheric conditions between 2005 and 2007. The present paper provides a large and regional scale overview of the 2006 summer monsoon season, that includes consideration of of the convective activity, mean atmospheric circulation and synoptic/intraseasonal weather systems, oceanic and land surface conditions, continental hydrology, dust concentration and ozone distribution. The 2006 African summer monsoon was a near-normal rainy season except for a large-scale rainfall excess north of 15° N. This monsoon season was also characterized by a 10-day delayed onset compared to climatology, with convection becoming developed only after 10 July. This onset delay impacted the continental hydrology, soil moisture and vegetation dynamics as well as dust emission. More details of some less-well-known atmospheric features in the African monsoon at intraseasonal and synoptic scales are provided in order to promote future research in these areas.

  5. Tropical stratospheric circulation and monsoon rainfall

    Science.gov (United States)

    Sikder, A. B.; Patwardhan, S. K.; Bhalme, H. N.

    1993-09-01

    Interannual variability of both SW monsoon (June September) and NE monsoon (October December) rainfall over subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu have been examined in relation to monthly zonal wind anomaly for 10 hPa, 30 hPa and 50 hPa at Balboa (9°N, 80°W) for the 29 year period (1958 1986). Correlations of zonal wind anomalies to SW monsoon rainfall ( r=0.57, significant at 1% level) is highest with the longer lead time (August of the previous year) at 10 hPa level suggesting some predictive value for Coastal Andhra Pradesh. The probabilities estimated from the contingency table reveal non-occurrence of flood during easterly wind anomalies and near non-occurrence of drought during westerly anomalies for August of the previous year at 10 hPa which provides information for forecasting of performance of SW monsoon over Coastal Andhra Pradesh. However, NE monsoon has a weak relationship with zonal wind anomalies of 10 hPa, 30 hPa and 50 hPa for Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu. Tracks of the SW monsoon storms and depressions in association with the stratospheric wind were also examined to couple with the fluctuations in SW monsoon rainfall. It is noted that easterly / westerly wind at 10 hPa, in some manner, suppresses / enhances monsoon storms and depressions activity affecting their tracks.

  6. Improving Energy-Based Estimates of Monsoon Location in the Presence of Proximal Deserts

    CERN Document Server

    Shekhar, Ravi

    2016-01-01

    Two theoretical frameworks have been widely used to understand the response of monsoons to local and remote forcings: the vertically integrated atmospheric energy budget and convective quasi-equilibrium (CQE). Existing forms of these frameworks neglect some of the complexities of monsoons, such as the shallow meridional circulations that advect dry air from adjacent deserts into the middle and lower troposphere of monsoon regions. Here the fidelity of energy budget and CQE theories for monsoon location is assessed in a three-dimensional beta-plane model with boundary conditions representative of an off-equatorial continent with a tropical grassland and an adjacent subtropical desert. Energy budget theories show mixed success for various SST and land surface albedo forcings, with the ITCZ being collocated with the energy flux equator but a non-monotonic relationship existing between ITCZ latitude and cross-equatorial energy transport. Accounting for the off-equatorial position of the unperturbed energy flux eq...

  7. The Onset of the Monsoon over the Bay of Bengal: The Year-to-Year Variations

    Institute of Scientific and Technical Information of China (English)

    YU Wei-Dong; LI Kui-Ping; SHI Jian-Wei; LIU Lin; WANG Hui-Wu; LIU Yan-Liang

    2012-01-01

    In situ buoy observation data spanning four years (2008-2011) were used to demonstrate the year-to-year variations of the monsoon onset processes in the Bay of Bengal (BOB). A significant early (late) monsoon onset event in 2009 (2010) was analyzed in detail. It is found that the year-to-year variations of monsoon onset can be attributed to either the interannual variability in the BoB SST or the irregular activities of the intra-seasonal oscillation (ISO). This finding raises concern over the potential difficulties in simulating or predicting the monsoon onset in the BoB region. This uncertainty largely comes from the unsatisfactory model behavior at the intra-seasonal time scale.

  8. Eurasian Snow Conditions and Summer Monsoon Rainfall over South and Southeast Asia:Assessment and Comparison

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    This study reveals the complex nature of the connection between Eurasian snow and the following summer season's monsoon rainfall by using four different indicators of snow conditions and correlating each of them to summer monsoon rainfall. Using 46 years of historical records of mean winter snow depth,maximum snow depth, and snow starting dates, and 27 years of snow area coverage from remote sensing observations over Eurasia, the authors found diverse correlation patterns between snow conditions and the following warm season's rainfall over South and Southeast Asia. Some of the results contradict the well-known inverse relationships between snow and the summer monsoon. This study provides an easy comparison of results in that it shows the connections between Eurasian snow and monsoon rainfall by using different Eurasian snow indicators based on the best available historical records without discrimination of regional variations in snow conditions.

  9. Genesis of economic relevant fresh groundwater resources in Pleistocene/ Neogene aquifers in Nam Dinh (Red River Delta, Vietnam).

    Science.gov (United States)

    Wagner, F.; Ludwig, R. R.; Noell, U.; Hoang, H. V.; Pham, N. Q.; Larsen, F.; Lindenmaier, F.

    2012-04-01

    In the Southern Red River Delta (Nam Dinh Province, Vietnam), a local lens of low saline pore water of high quality has been identified in unconsolidated Pleistocene and Neogene aquifers, which are regionally known to contain brackish and saline pore waters. Since the 1990ies, ongoing overexploitation of the fresh groundwater results in decreasing GW heads up to 0.6 m/a and the development of a regional abstraction cone. The presented study focuses on distribution and genesis of fresh and saline pore waters and reflects the results in frame of the regional hydrogeological context. Observations of the geological structure and groundwater dynamics combined with hydrochemical and isotopic studies suggest adjacent Triassic hard rock aquifers as the major source for fresh Pleistocene and Neogene groundwater. Salinization status in the economically most relevant Pleistocene aquifer has been studied based on archive and new hydrochemical and geophysical data. Own hydrochemical field studies as well as laboratory measurements of the specific resistivity of dry sediment samples allow the translation of induction logging data from existing monitoring wells into vertical pore water salinity profiles. This approach suggests the regional occurrence of saline pore water in shallow Holocene sediments in the working area, as confirmed by pore water studies in Hoan et al. (2010). Interpretation of induction logging and stable isotope data suggest vertical diffusion of saline pore water in shallow Holocene sediments as a source for high saline pore water in deeper aquifers. Analytical diffusion modeling for a period of 3000 years confirms that vertical diffusion of Holocene paleo-sea water can explain saline pore water in Pleistocene and Neogene aquifers in a stagnant environment. The constant influx of fresh groundwater from adjacent Triassic hard rocks results in flushing of the primary Pleistocene and Neogene pore water and inhibits the infiltration of saline water from marine

  10. GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Tianjun; Turner, Andrew G.; Kinter, James L.; Wang, Bin; Qian, Yun; Chen, Xiaolong; Wu, Bo; Wang, Bin; Liu, Bo; Zou, Liwei; He, Bian

    2016-10-10

    The Global Monsoons Model Inter-comparison Project (GMMIP) has been endorsed by the panel of Coupled Model Inter-comparison Project (CMIP) as one of the participating model inter-comparison projects (MIPs) in the sixth phase of CMIP (CMIP6). The focus of GMMIP is on monsoon climatology, variability, prediction and projection, which is relevant to four of the “Grand Challenges” proposed by the World Climate Research Programme. At present, 21 international modeling groups are committed to joining GMMIP. This overview paper introduces the motivation behind GMMIP and the scientific questions it intends to answer. Three tiers of experiments, of decreasing priority, are designed to examine (a) model skill in simulating the climatology and interannual-to-multidecadal variability of global monsoons forced by the sea surface temperature during historical climate period; (b) the roles of the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation in driving variations of the global and regional monsoons; and (c) the effects of large orographic terrain on the establishment of the monsoons. The outputs of the CMIP6 Diagnostic, Evaluation and Characterization of Klima experiments (DECK), “historical” simulation and endorsed MIPs will also be used in the diagnostic analysis of GMMIP to give a comprehensive understanding of the roles played by different external forcings, potential improvements in the simulation of monsoon rainfall at high resolution and reproducibility at decadal timescales. The implementation of GMMIP will improve our understanding of the fundamental physics of changes in the global and regional monsoons over the past 140 years and ultimately benefit monsoons prediction and projection in the current century.

  11. GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project

    Science.gov (United States)

    Zhou, Tianjun; Turner, Andrew G.; Kinter, James L.; Wang, Bin; Qian, Yun; Chen, Xiaolong; Wu, Bo; Wang, Bin; Liu, Bo; Zou, Liwei; He, Bian

    2016-10-01

    The Global Monsoons Model Inter-comparison Project (GMMIP) has been endorsed by the panel of Coupled Model Inter-comparison Project (CMIP) as one of the participating model inter-comparison projects (MIPs) in the sixth phase of CMIP (CMIP6). The focus of GMMIP is on monsoon climatology, variability, prediction and projection, which is relevant to four of the "Grand Challenges" proposed by the World Climate Research Programme. At present, 21 international modeling groups are committed to joining GMMIP. This overview paper introduces the motivation behind GMMIP and the scientific questions it intends to answer. Three tiers of experiments, of decreasing priority, are designed to examine (a) model skill in simulating the climatology and interannual-to-multidecadal variability of global monsoons forced by the sea surface temperature during historical climate period; (b) the roles of the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation in driving variations of the global and regional monsoons; and (c) the effects of large orographic terrain on the establishment of the monsoons. The outputs of the CMIP6 Diagnostic, Evaluation and Characterization of Klima experiments (DECK), "historical" simulation and endorsed MIPs will also be used in the diagnostic analysis of GMMIP to give a comprehensive understanding of the roles played by different external forcings, potential improvements in the simulation of monsoon rainfall at high resolution and reproducibility at decadal timescales. The implementation of GMMIP will improve our understanding of the fundamental physics of changes in the global and regional monsoons over the past 140 years and ultimately benefit monsoons prediction and projection in the current century.

  12. Surface and upper air meteorological features during onset phase of 2003 monsoon

    Indian Academy of Sciences (India)

    O P Singh; H R Hatwar; Onkari Prasad

    2007-08-01

    The second campaign of the Arabian Sea Monsoon Experiment (ARMEX-II) was conducted in two phases viz., March–April and May–June 2003. In the present work, the buoy and ocean research vessel data collected during the second phase of ARMEX-II have been analysed to bring out the characteristic features of monsoon onset. The results have shown that the thermodynamical features such as build up of lower tropospheric instability and increased height of zero degree isotherm occurred about a week before the monsoon onset over Kerala and adjoining southeast Arabian Sea. There was a sharp fall in the temperature difference between 850 and 500 hPa, and the height of zero degree isotherm about 2–3 days before the monsoon onset. The flux of sensible heat was positive (sea to air) over south Arabian Sea during the onset phase. Over the Bay of Bengal higher negative (air to sea) values of sensible flux prevailed before the monsoon onset which became less negative with the advance of monsoon over that region. The pre-onset period was characterized by large sea surface temperature (SST) gradient over the Arabian Sea with rapid decrease towards north of the warm pool region. The buoy observations have shown that SST remained close to 30.5°C in the warm pool region during the pre-onset period in 2003 but only 2–3 degrees away (north of this region) SSTs were as low as 28.5-29°C. An interesting aspect of sea level pressure (SLP) variability over the Indian seas during the onset phase of summer monsoon 2003 was undoubtedly, the highest SLP in the warm pool region inspite of very high SSTs.

  13. The onset and advance of the Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the daily outgoing longwave radiation (OLR) data from National Oceanic and Atmospheric Administration (NOAA) satellites, the Climate Prediction Center's merged analysis of precipitation (CMAP) data and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset, the mean intraseasonal variability of the Asian summer monsoon (ASM) is investigated by using power spectrum analysis, band-pass filter, and diagnostic analyses. The processes of the onset and advance of monsoon over the southern part of Indochina Peninsula, the east coast of Bay of Bengal, the South China Sea and the Indian subcontinent are explored. It is found that there is an abrupt change in OLR, precipitation and zonal wind during the onset and advance of the ASM. It is also indicated that the southern part of Indochina Peninsula and the adjacent Andaman Sea is the region where the earliest onset of the ASM occurs in the 2nd pentad of May.

  14. Spacebased Observations of the Oceanic Responses to Monsoons in South China Sea and Arabian Sea

    Science.gov (United States)

    Xie, Xiao-Su; Liu, W. Timothy

    2000-01-01

    A large percentage of the world's population and their agrarian economy must endure the vagaries of the monsoons over the tropical oceans between Africa and the Philippines. We know very little about the oceanic responses to changes of the monsoon in the South China Sea (SCS), which is under the influence of the East Asian Monsoon System, and the Arabian Sea (AS), which is dominated by the Indian Monsoon System; oceanic observations are sparse in both regions. Data from spaceborne microwave scatterometers and radiometers have been used to estimate the two major atmospheric forcing, momentum flux and latent heat flux (LHF), which change with the monsoon winds. Spaceborne sensors also observed the surface signatures of the oceanic response: SST and sea level changes (SLC. Sufficient durations of these data have recently become available to allow the meaningful studies of the annual cycles and interannual anomalies. In SCS, the winter monsoon is strong and steady but the summer monsoon is weak and has large intraseasonal fluctuations. In AS, the summer monsoon is much stronger than the winter monsoon. Significant correlations between LHF and SST tendency, and between curl of wind stress and SLC are found in both oceans. In the north SCS, winds are strong and dry, LHF is high, and ocean cooling is also large in fall; LHF is low and the ocean warms up in spring. In AS, LHF and SST tendency have a semi annual period; LHF is high in summer when the wind is strong and in winter when the wind is dry. Along the coast of Oman, the strong summer southwest monsoon causes intense upwelling, low SST and LHF in summer; such wind-driven SST changes is not as obvious along the Vietnam coast because of the weaker summer monsoon. The negative correlation between curl of wind stress and SLC found in the central basins of both SCS and AS agrees with a simple Ekman pumping scenario. Cyclonic winds drive surface divergence and upwelling in the ocean; the rise of the thermocline causes

  15. Southwest monsoon changes indicated by oxygen isotope of ostracode shells from sediments in Qinghai Lake since the late Glacial

    Institute of Scientific and Technical Information of China (English)

    LIU XingQi; SHEN Ji; WANG SuMin; WANG YongBo; LIU WeiGuo

    2007-01-01

    The δ18O records of ostracode shells in sediments of core QH-2000 from Qinghai Lake can be used as a better proxy to reflect monsoon changes. Low monsoon precipitation between 17.5 and 11 cal. Ka BP is indicated by positive δ18O values averaging 2.37‰. A fast shift in δ18O from positive at 11 cal. Ka BP to negative at 10 cal. Ka BP indicates sharp increase of monsoon precipitation. An interval of generally high monsoon precipitation is observed between 10 and 6 cal. Ka BP with δ18O values averaging -2.15‰. Decrease of monsoon precipitation between 6 and 2.5 cal. Ka BP is indicated by positive δ18O values. δ18O keeps positive values averaging 3.0‰ between 2.5 and 0 cal. Ka BP suggesting low high monsoon precipitation. The climatic changes indicated by δ18O records of ostracode shells in sediments of core QH-2000 from Qinghai Lake and our broader regional comparison show that the climate in Qinghai Lake since the late Glacial is probably controlled by southwest monsoon other than southeast monsoon.

  16. TIGERZ I: Aerosols, Monsoon and Synergism

    Science.gov (United States)

    Holben, B. N.; Tripathi, S. N.; Schafer, J. S.; Giles, D. M.; Eck, T. F.; Sinyuk, A.; Smirnov, A.; Krishnmoorthy, K.; Sorokin, M. G.; Newcomb, W. W.; Tran, A. K.; Sikka, D. R.; Goloub, P.; O'Neill, N. T.; Abboud, I.; Randles, C.; Niranjan, K.; Dumka, U. C.; Tiwari, S.; Devara, P. C.; Kumar, S.; Remer, L. A.; Kleidman, R.; Martins, J. V.; Kahn, R.

    2008-12-01

    The Indo-Gangetic Plain of northern India encompasses a vast complex of urban and rural landscapes, cultures that serve as anthropogenic sources of fine mode aerosols mixed with coarse mode particles transported from SW Asia. The summer monsoon and fall Himalayan snowmelt provide the agricultural productivity to sustain an extremely high population density whose affluence is increasing. Variations in the annual monsoon precipitation of 10% define drought, normal and a wet season; the net effects on the ecosystems and quality of life can be dramatic. Clearly investigation of anthropogenic and natural aerosol impacts on the monsoon, either through the onset, monsoon breaks or end points are a great concern to understand and ultimately mitigate. Many national and international field campaigns are being planned and conducted to study various aspects of the Asian monsoon and some coordinated under the Asian Monsoon Years (AMY) umbrella. A small program called TIGERZ conducted during the pre-monsoon of 2008 in North Central India can serve as a model for contributing significant resources to existing field programs while meeting immediate project goals. This poster will discuss preliminary results of the TIGERZ effort including ground-based measurements of aerosol properties in the I-G from AERONET and synergism with various Indian programs, satellite observations and aerosol modeling efforts.

  17. High Resolution δ18O and δ13C Records of AMS 14C Dated Stalagmites From Jinlun and Yilingyan Caves in Guangxi, China: Climate Variability and Controlling Factors in the Monsoonal Region During the Past 2300 Years

    Science.gov (United States)

    Li, H. C.; Lien, W. Y.; Mii, H. S.; Jiang, G. H.; Chou, C. Y.; Chou, P. J.

    2015-12-01

    Jinlun Cave in Mashan County and Yilingyan Cave in Wuming County are ~120km and ~60km north of Nanning in Guangxi Province under influence of both Indian Monsoon and North Western Pacific Monsoon. Several stalagmites have been dated by AMS 14C dating method since 230Th/U is not applicable due to very low U contents. Twenty (20) AMS 14C dates on Stalagmite JL20131005-10 (10-cm long) show "Bomb carbon curve", spanning the past 60 years. Lamination counting further confirms the chronology. Thirty nine (39) AMS 14C dates on Stalagmite JL20131005-12 (33-cm long) reveal 2300-year continuous growth. Stalagmite YLY20130727-12 (10-cm long) from Yilingyan Cave covers a continuous record of past 2300 years. All studied stalagmites in the caves contain low dead carbon fractions. The annual resolution δ18O and δ13C records obtained from the stalagmites allow us to compare the stalagmite δ18O records with the instrumental rainfall and temperature records, Pacific Decadal Oscillation (PDO), Southern Oscillation Index (SOI), and Sunspot variation, etc. The δ18O and δ13C records exhibit relatively good correlation throughout the time, indicating climatic control on vegetation change. Based on the high-resolution δ18O and δ13C records, we interpret that dry climatic conditions and poor vegetation coverage during periods of AD1880~1850, 1700~1600, 1460~1320, 1210~1280, 860~750, 540~420, 300~220, and AD100~0 shown by increased δ18O and δ13C. The δ18O and δ13C were strongly depleted during the Medieval Warm Period (MWP between AD900 and AD1100) and Current Warm Period (CWP, since AD1900), reflecting strongly increased East Asian Summer Monsoon. After AD1900, the δ13C decreased about 6‰, perhaps indicating human impact on surface vegetation. The δ18O records from the study area are comparable to the published WX42B δ18O record of Wanxiang Cave (Zhang et al., 2008) except for the period of AD1400~1850. Our study suggests that AMS 14C dating is an alternative method for

  18. A diagnostic study of monsoon energetics for two contrasting years

    Directory of Open Access Journals (Sweden)

    S. S. V. S. Ramakrishna

    2010-12-01

    Full Text Available In the present study we made an attempt to explain the behavior of the southwest monsoon for two contrasting years, from the view point of energetics. As a test case we selected 2002 and 2003, which were weak and strong monsoon years, respectively, based on rainfall. The energy terms Kψ, Kχ and APE and the conversion terms f∇ψ. ∇χ, −ω'T' are calculated at 850 hPa level and also vertically integrated from 1000 hPa to 100 hPa. The results indicate that, the year of high energy (both KΨ, Kχ i.e. 2002, does not give a good amount of rainfall compared to the good year i.e. 2003. The break period during the year 2002 has been clearly explained using the block diagrams. Periods of highest rainfall coincide with the positive conversions of f∇ψ. ∇χ and −ω'T'. Vertically integrated moisture fluxes during the break period of 2002, 2003 are also analyzed. The main reservoirs (sources and sinks for the monsoon energy are also identified using block diagrams. Negative correlation between daily rainfall and energy terms in the year 2002 indicates its unusual behavior both in terms of energetics as well as precipitation. Positive correlations in the year 2003 represent strong monsoonal behavior. We calculated the climatology of the total kinetic energy at 850 hPa, vertically integrated (1000–100 hPa for 30 years (1980–2009 and rainfall for 103 years (1901–2003 which clearly indicates that the monsoon is indeed a season of high energy for the South Asian region.

    Also the east- west direct thermal circulations are strongly related to the good and bad monsoon years.

  19. The South American monsoon variability over the last millennium in climate models

    Science.gov (United States)

    Rojas, Maisa; Arias, Paola A.; Flores-Aqueveque, Valentina; Seth, Anji; Vuille, Mathias

    2016-08-01

    In this paper we assess South American monsoon system (SAMS) variability in the last millennium as depicted by global coupled climate model simulations. High-resolution proxy records for the South American monsoon over this period show a coherent regional picture of a weak monsoon during the Medieval Climate Anomaly and a stronger monsoon during the Little Ice Age (LIA). Due to the small external forcing during the past 1000 years, model simulations do not show very strong temperature anomalies over these two specific periods, which in turn do not translate into clear precipitation anomalies, in contrast with the rainfall reconstructions in South America. Therefore, we used an ad hoc definition of these two periods for each model simulation in order to account for model-specific signals. Thereby, several coherent large-scale atmospheric circulation anomalies are identified. The models feature a stronger monsoon during the LIA associated with (i) an enhancement of the rising motion in the SAMS domain in austral summer; (ii) a stronger monsoon-related upper-tropospheric anticyclone; (iii) activation of the South American dipole, which results in a poleward shift of the South Atlantic Convergence Zone; and (iv) a weaker upper-level subtropical jet over South America. The diagnosed changes provide important insights into the mechanisms of these climate anomalies over South America during the past millennium.

  20. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    Science.gov (United States)

    Ao, Hong; Roberts, Andrew P.; Dekkers, Mark J.; Liu, Xiaodong; Rohling, Eelco J.; Shi, Zhengguo; An, Zhisheng; Zhao, Xiang

    2016-06-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (∼8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

  1. The South American Monsoon Variability over the Last Millennium in CMIP5/PMIP3 simulations

    Directory of Open Access Journals (Sweden)

    M. Rojas

    2015-12-01

    Full Text Available In this paper we assess South American Monsoon System (SAMS variability throughout the Last Millennium as depicted by the Coupled Modelling Intercomparison Project version 5/Paleo Modelling Intercomparison Project version 3 (CMIP5/PMIP3 simulations. High-resolution proxy records for the South American monsoon over this period show a coherent regional picture of a weak monsoon during the Medieval Climate Anomaly period and a stronger monsoon during the Little Ice Age (LIA. Due to the small forcing during the past 1000 years, CMIP5/PMIP3 model simulations do not show very strong temperature anomalies over these two specific periods, which in turn do not translate into clear precipitation anomalies, as suggested by rainfall reconstructions in South America. However, with an ad-hoc definition of these two periods for each model simulation, several coherent large-scale atmospheric circulation anomalies were identified. The models feature a stronger Monsoon during the LIA associated with: (i an enhancement of the rising motion in the SAMS domain in austral summer, (ii a stronger monsoon-related upper-troposphere anticyclone, (iii activation of the South American dipole, which results to a certain extent in a poleward shift in the South Atlantic Convergence Zone and (iv a weaker upper-level sub tropical jet over South America, this providing important insights into the mechanisms of these climate anomalies over South America during the past millennium.

  2. An improved south Asian summer monsoon index with Monte Carlo test

    Institute of Scientific and Technical Information of China (English)

    Shi Neng; Gu Jun-Qiang; Yi Yan-Ming; Lin Zhen-Min

    2005-01-01

    The Indian monsoon intensity index suggested by Webster and Yang (WY index) is optimized and improved in this paper. At first, the area (40°E-110°E, 0°-20°N) for calculating the zonal wind-shear between 850hPa and 200hPa in the WY index is optimized and adjusted according to the significance test of differences of wind fields. Then the regionally averaged zonal wind is computed over the optimized area. Finally, the optimal linear combination of the zonal winds at the two levels is performed using the regression method, thus defining a new broad-scale circulation index for the interannual variability of the south Asian summer monsoon, i.e. the improved south Asian summer monsoon index. Results indicate that the improved south Asian summer monsoon index has two advantages: its correlation with the All Indian Summer Monsoon Rainfall index is higher than that of WY index, and its computational domain of circulation is also larger than that of WY index. The computational results based on the 1948-98 NCAR/NCEP wind data indicate that the correlation of the improved SASM index with the All Indian Summer Monsoon Rainfall index is higher than that of WY index by 0.27.

  3. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    Science.gov (United States)

    Ao, H.; Roberts, A. P.; Dekkers, M. J.; Liu, X.; Rohling, E. J.; Shi, Z.; An, Z.; Zhao, X.

    2016-12-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (˜8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

  4. Links between Indo-Pacific climate variability and drought in the Monsoon Asia Drought Atlas

    Science.gov (United States)

    Ummenhofer, Caroline C.; D'Arrigo, Rosanne D.; Anchukaitis, Kevin J.; Buckley, Brendan M.; Cook, Edward R.

    2013-03-01

    Drought patterns across monsoon and temperate Asia over the period 1877-2005 are linked to Indo-Pacific climate variability associated with the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). Using the Monsoon Asia Drought Atlas (MADA) composed of a high-resolution network of hydroclimatically sensitive tree-ring records with a focus on the June-August months, spatial drought patterns during El Niño and IOD events are assessed as to their agreement with an instrumental drought index and consistency in the drought response amongst ENSO/IOD events. Spatial characteristics in drought patterns are related to regional climate anomalies over the Indo-Pacific basin, using reanalysis products, including changes in the Asian monsoon systems, zonal Walker circulation, moisture fluxes, and precipitation. A weakening of the monsoon circulation over the Indian subcontinent and Southeast Asia during El Niño events, along with anomalous subsidence over monsoon Asia and reduced moisture flux, is reflected in anomalous drought conditions over India, Southeast Asia and Indonesia. When an IOD event co-occurs with an El Niño, severe drought conditions identified in the MADA for Southeast Asia, Indonesia, eastern China and central Asia are associated with a weakened South Asian monsoon, reduced moisture flux over China, and anomalous divergent flow and subsidence over Indonesia. Insights into the relative influences of Pacific and Indian Ocean variability for Asian monsoon climate on interannual to decadal and longer timescales, as recorded in the MADA, provide a useful tool for assessing long-term changes in the characteristics of Asian monsoon droughts in the context of Indo-Pacific climate variability.

  5. A mechanism for land-ocean contrasts in global monsoon trends in a warming climate

    Energy Technology Data Exchange (ETDEWEB)

    Fasullo, J. [National Center for Atmospheric Research, CAS/NCAR, Boulder, CO (United States)

    2012-09-15

    A central paradox of the global monsoon record involves reported decreases in rainfall over land during an era in which the global hydrologic cycle is both expected and observed to intensify. It is within this context that this work develops a physical basis for both interpreting the observed record and anticipating changes in the monsoons in a warming climate while bolstering the concept of the global monsoon in the context of shared feedbacks. The global-land monsoon record across multiple reanalyses is first assessed. Trends that in other studies have been taken as real are shown to likely be spurious as a result of changes in the assimilated data streams both prior to and during the satellite era. Nonetheless, based on satellite estimates, robust increases in monsoon rainfall over ocean do exist and a physical basis for this land-ocean contrast remains lacking. To address the contrast's causes, simulated trends are therefore assessed. While projections of total rainfall are inconsistent across models, the robust land-ocean contrast identified in observations is confirmed. A feedback mechanism is proposed rooted in the facts that land areas warm disproportionately relative to ocean, and onshore flow is the chief source of monsoonal moisture. Reductions in lower tropospheric relative humidity over land domains are therefore inevitable and these have direct consequences for the monsoonal convective environment including an increase in the lifting condensation level and a shift in the distribution of convection generally towards less frequent and potentially more intense events. The mechanism is interpreted as an important modulating influence on the ''rich-get-richer'' mechanism. Caveats for regional monsoons exist and are discussed. (orig.)

  6. Glacial-interglacial water cycle, global monsoon and atmospheric methane changes

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhengtang; Wu, Haibin [Chinese Academy of Sciences, Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Beijing (China); Zhou, Xin [Chinese Academy of Sciences, Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Beijing (China); University of Science and Technology of China, School of Earth and Space Sciences and Institute of Polar Environment, Hefei (China)

    2012-09-15

    The causes of atmospheric methane (CH{sub 4}) changes are still a major contention, in particular with regards to the relative contributions of glacial-interglacial cycles, monsoons in both hemispheres and the late Holocene human intervention. Here, we explore the CH{sub 4} signals in the Antarctic EPICA Dome C and Vostok ice records using the methods of timeseries analyses and correlate them with insolation and geological records to address these issues. The results parse out three distinct groups of CH{sub 4} signals attributable to different drivers. The first group ({proportional_to}80% variance), well tracking the marine {delta}{sup 18}O record, is attributable to glacial-interglacial modulation on the global water cycle with the effects shared by wetlands at all latitudes, from monsoonal and non-monsoonal regions in both hemispheres. The second group ({proportional_to}15% variance), centered at the {proportional_to}10-kyr semi-precession frequency, is linkable with insolation-driven tropical monsoon changes in both hemispheres. The third group ({proportional_to}5% variance), marked by millennial frequencies, is seemingly related with the combined effect of ice-volume and bi-hemispheric insolation changes at the precession bands. These results indicate that bi-hemispheric monsoon changes have been a constant driver of atmospheric CH{sub 4}. This mechanism also partially explains the Holocene CH{sub 4} reversal since {proportional_to}5 kyr BP besides the human intervention. In the light of these results, we propose that global monsoon can be regarded as a system consisting of two main integrated components, one primarily driven by the oscillations of Inter-Tropical Convergence Zone (ITCZ) in response to the low-latitude summer insolation changes, anti-phase between the two hemispheres (i.e. the ITCZ monsoon component); and another modulated by the glacial-interglacial cycles, mostly synchronous at the global scale (i.e. the glacial-interglacial monsoon

  7. Extreme monsoon precipitation events over South Asia in a warming world

    Science.gov (United States)

    Raghavan, K.; Sabin, T. P.; Mujumdar, M.; Priya, P.

    2012-04-01

    The recent series of flood events over Pakistan and Northwest India during the monsoon seasons of 2010 and 2011 are examples of extreme phenomena during the last century that have evoked considerable interest among various scientific communities. One of the causes for the 2010 intense precipitation over Pakistan has been attributed to the interaction between the tropical monsoon surge and southward intruding extra-tropical circulation anomalies (Hong et al. 2011). On the other hand, it has been hypothesized by Mujumdar et al. (2012) that the westward shift of the West Pacific Subtropical High (WPSH) in response to the strong La Nina conditions during 2010 was instrumental in altering the convection and circulation over the Bay of Bengal and the monsoon trough region, which in turn sustained the moist convective activities over Indo-Pak through transport of moisture from the Arabian Sea. However several aspects of the dynamics of these intense monsoon precipitation events are not adequately understood especially when atmospheric convective instabilities are expected to amplify in the backdrop of the ongoing global warming. Here, we have carried out a set of ensemble simulation experiments using a high-resolution global climate model to understand the evolution of intense monsoon precipitation events over Pakistan and Northwest India as in 2010. The results based on the model simulations indicate that while interactions among the WPSH, the South Asian monsoon trough and sub-tropical westerlies are conducive for development of convective instabilities over the Indo-Pak region, the local convective activities are found to significantly amplify in response to the large build up of moisture associated with global warming. The present results have implications in understanding how extreme monsoon precipitation events in the Indo-Pak region might have responded to past climatic variations.

  8. Turbulent flux modelling with a simple 2-layer soil model and extrapolated surface temperature applied at Nam Co Lake basin on the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    T. Gerken

    2012-04-01

    Full Text Available This paper introduces a surface model with two soil-layers for use in a high-resolution circulation model that has been modified with an extrapolated surface temperature, to be used for the calculation of turbulent fluxes. A quadratic temperature profile based on the layer mean and base temperature is assumed in each layer and extended to the surface. The model is tested at two sites on the Tibetan Plateau near Nam Co Lake during four days during the 2009 Monsoon season. In comparison to a two-layer model without explicit surface temperature estimate, there is a greatly reduced delay in diurnal flux cycles and the modelled surface temperature is much closer to observations. Comparison with a SVAT model and eddy covariance measurements shows an overall reasonable model performance based on RMSD and cross correlation comparisons between the modified and original model. A potential limitation of the model is the need for careful initialisation of the initial soil temperature profile, that requires field measurements. We show that the modified model is capable of reproducing fluxes of similar magnitudes and dynamics when compared to more complex methods chosen as a reference.

  9. 北半球环状模波流相互作用动力学研究进展%Advances on Wave-Flow Interaction Dynamics of NAM

    Institute of Scientific and Technical Information of China (English)

    梁苏洁; 赵南

    2011-01-01

    总结了国内外学者对于北半球环状模(NAM:Northern Hemisphere Annular Mode)及其活动中心形成原因的研究成果.主要从NAM的天气、气候影响,波流相互作用原理对NAM形成的解释,NAM在北太平洋、北大西洋和北极3个区域活动中心的天气尺度波和行星尺度波活动等方面论述.NAM在对流层的变化与天气尺度波有关,北太平洋和北大西洋两个活动中心是天气尺度波活跃的区域,其峰值区表现为风暴轴,其中北大西洋天气尺度波破碎过程会使得NAM指数急剧变化.NAM在平流层的变化和准定常行星波关系密切,冬季准定常行星波会上传并与高纬平流层纬向流发生相互作用,从而引起北极极涡发生改变.准定常行星波将NAM 3个活动中心有机联系起来:对流层准定常行星波的纬向传播会影响北太平洋风暴轴的位置,而风暴轴的变化会影响下游北大西洋波破碎过程,同时准定常行星波的上传可以影响极涡活动.%The progresses in the studies in the recent years of NAM/AO (Northern Hemisphere Anuular Mode / Arctic Oscillation) are reviewed, with the emphases on the influences of the NAM/AO on weather and climate, the physical mechanisms of NAM/AO, the wave-flow interaction theory, and the baroclinic Rossby wave and quasi-stationary planetary wave activities on the NAM/AO' s three regional activity centers. During recent years, many studies show that tropospheric fluctuations of NAM/AO are associated with baroclinic waves, while fluctuations are associated with the quasi-stationary planetary waves in the stratosphere. It is found that the regions where baroclinic wave activities are frequent are the Pacific and Atlantic in the Northern Hemisphere, and the peak value areas are manifested as storm tracks. Besides, the wave breaking is the trigger of NAM/AO events in North Atlantic. On the other hand, the stratospheric zonal winds modify the upward-propagation of the troposphere

  10. Shift in Indian summer monsoon onset during 1976/1977

    Science.gov (United States)

    Sahana, A. S.; Ghosh, Subimal; Ganguly, Auroop; Murtugudde, Raghu

    2015-05-01

    The Indian summer monsoon rainfall (ISMR) contributes nearly 80% of the annual rainfall over India and has a significant influence on the country’s gross domestic product through the agricultural sector. Onset of the ISMR displays substantial interannual variability and controls the crop calendar and hence the agricultural output. This variability is traditionally linked to sea surface temperature (SST) anomalies over the tropical Pacific Ocean. The tropical Pacific SST underwent a regime shift during 1976/77. We report a prominent delay in the Indian summer monsoon (ISM) onset following the regime shift. The onset dates are computed with the Hydrologic Onset and Withdrawal Index, based on vertically integrated moisture transport over the Arabian Sea (AS). The shift in onset is found to be due to the change in moisture availability over the AS. A delay in the development of easterly vertical shear reduces northward-propagating intraseasonal variability during May-June, limiting the moisture supply from the equatorial Indian Ocean (IO) to the AS. This, along with enhanced precipitation over the IO during the pre-monsoon, drives a reduction in moisture availability over the AS region from pre- to post-1976/77, delaying the ISM onset in recent decades. Our findings highlight the need for the re-assessment of the crop calendar in India, which is now based on the mean onset date computed from long-term data, without considering the regime shift or trends in onset.

  11. Transport pathways from the Asian monsoon anticyclone to the stratosphere

    Science.gov (United States)

    Garny, Hella; Randel, William

    2016-04-01

    The upper tropospheric Asian monsoon anticyclone emerges in response to persistent deep convection over India and southeast Asia in northern summer. The monsoon circulation is associated with rapid transport from the surface to the upper troposphere within convective updrafts, leading to tracer anomalies within the anticyclone. Possibly air is transported further into the stratosphere, but the exact pathways of air from the upper tropospheric anticyclone to the stratosphere are currently under debate. While air is thought to be confined to the anticyclone by its surrounding wind jets, large variability in the anticyclone results in shedding of air from the anticyclone to its surrounding, and possibly air might reach the extratropical lower stratosphere by isentropic mixing. On the other hand, positive vertical velocities in the anticyclone region suggests upward transport of air into the tropical lower stratosphere. In this study, we investigate transport pathways of air originating in the upper tropospheric Asian monsoon anticyclone based on isentropic and three-dimensional trajectories. Trajectories are driven by ERA-Interim reanalysis data, and three-dimensional results are based both on kinematic and diabatic transport calculations. Isentropic calculations show that air parcels are typically confined within the anticyclone for 10-20 days, and spread over the tropical belt within a month of their initialization. However, only few parcels (3 % at 360 K, 8 % at 380 K) reach the extratropical stratosphere by isentropic transport. When considering vertical transport we find that 31 % (48 %) of the trajectories reach the stratosphere within 60 days when using vertical velocities or diabatic heating rates to calculate vertical transport, respectively. In both cases, most parcels that reach the stratosphere are transported upward within the anticyclone and enter the stratosphere in the tropics, typically 10-20 days after their initialization at 360 K. This suggests

  12. Eastward propagating MJO during boreal summer and Indian monsoon droughts

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Susmitha; Sahai, A.K.; Goswami, B.N. [Indian Institute of Tropical Meteorology, Climate and Global Modeling Division, Pune (India)

    2009-06-15

    Improved understanding of underlying mechanism responsible for Indian summer monsoon (ISM) droughts is important due to their profound socio-economic impact over the region. While some droughts are associated with 'external forcing' such as the El-Nino and Southern Oscillation (ENSO), many ISM droughts are not related to any known 'external forcing'. Here, we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics. We show that most ISM droughts are associated with at least one very long break (VLB; breaks with duration of more than 10 days) and that the processes responsible for VLBs may also be the mechanism responsible for ISM droughts. Our analysis also reveals that all extended monsoon breaks (whether co-occurred with El-Nino or not) are associated with an eastward propagating Madden-Julian Oscillation (MJO) in the equatorial Indian Ocean and western Pacific extending to the dateline and westward propagating Rossby waves between 10 and 25 N. The divergent Rossby wave associated with the dry phase of equatorial convection propagates westward towards Indian land, couple with the northward propagating dry phase and leads to the sustenance of breaks. Thus, the propensity of eastward propagating MJO during boreal summer is largely the cause of monsoon droughts. While short breaks are not accompanied by westerly wind events (WWE) over equatorial western Pacific favorable for initiating air-sea interaction, all VLBs are accompanied by sustained WWE. The WWEs associated with all VLB during 1975-2005 initiate air-sea interaction on intraseasonal time scale, extend the warm pool eastward allowing the convectively coupled MJO to propagate further eastward and thereby sustaining the divergent circulation over India and the monsoon break. The ocean-atmosphere coupling on interannual time scale (such as El-Nino) can also produce VLB, but not necessary. (orig.)

  13. Eastward propagating MJO during boreal summer and Indian monsoon droughts

    Science.gov (United States)

    Joseph, Susmitha; Sahai, A. K.; Goswami, B. N.

    2009-06-01

    Improved understanding of underlying mechanism responsible for Indian summer monsoon (ISM) droughts is important due to their profound socio-economic impact over the region. While some droughts are associated with ‘external forcing’ such as the El-Niño and Southern Oscillation (ENSO), many ISM droughts are not related to any known ‘external forcing’. Here, we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics. We show that most ISM droughts are associated with at least one very long break (VLB; breaks with duration of more than 10 days) and that the processes responsible for VLBs may also be the mechanism responsible for ISM droughts. Our analysis also reveals that all extended monsoon breaks (whether co-occurred with El-Niño or not) are associated with an eastward propagating Madden-Julian Oscillation (MJO) in the equatorial Indian Ocean and western Pacific extending to the dateline and westward propagating Rossby waves between 10° and 25°N. The divergent Rossby wave associated with the dry phase of equatorial convection propagates westward towards Indian land, couple with the northward propagating dry phase and leads to the sustenance of breaks. Thus, the propensity of eastward propagating MJO during boreal summer is largely the cause of monsoon droughts. While short breaks are not accompanied by westerly wind events (WWE) over equatorial western Pacific favorable for initiating air-sea interaction, all VLBs are accompanied by sustained WWE. The WWEs associated with all VLB during 1975-2005 initiate air-sea interaction on intraseasonal time scale, extend the warm pool eastward allowing the convectively coupled MJO to propagate further eastward and thereby sustaining the divergent circulation over India and the monsoon break. The ocean-atmosphere coupling on interannual time scale (such as El-Niño) can also produce VLB, but not necessary.

  14. The East Asian subtropical summer monsoon: Recent progress

    Science.gov (United States)

    He, Jinhai; Liu, Boqi

    2016-04-01

    The East Asian subtropical summer monsoon (EASSM) is one component of the East Asian summer monsoon system, and its evolution determines the weather and climate over East China. In the present paper, we firstly demonstrate the formation and advancement of the EASSM rainbelt and its associated circulation and precipitation patterns through reviewing recent studies and our own analysis based on JRA-55 (Japanese 55-yr Reanalysis) data and CMAP (CPC Merged Analysis of Precipitation), GPCP (Global Precipitation Climatology Project), and TRMM (Tropical Rainfall Measuring Mission) precipitation data. The results show that the rainy season of the EASSM starts over the region to the south of the Yangtze River in early April, with the establishment of strong southerly wind in situ. The EASSM rainfall, which is composed of dominant convective and minor stratiform precipitation, is always accompanied by a frontal system and separated from the tropical summer monsoon system. It moves northward following the onset of the South China Sea summer monsoon. Moreover, the role of the land-sea thermal contrast in the formation and maintenance of the EASSM is illustrated, including in particular the effect of the seasonal transition of the zonal land-sea thermal contrast and the influences from the Tibetan Plateau and midlatitudes. In addition, we reveal a possible reason for the subtropical climate difference between East Asia and East America. Finally, the multi-scale variability of the EASSM and its influential factors are summarized to uncover possible reasons for the intraseasonal, interannual, and interdecadal variability of the EASSM and their importance in climate prediction.

  15. Respiratory virus laboratory pandemic planning an surveillance in central Viet Nam, 2008-2010

    Directory of Open Access Journals (Sweden)

    Trinh Xuan Mai

    2012-07-01

    Full Text Available Introduction: Laboratory capacity is needed in central Viet Nam to provide early warning to public health authorities of respiratory outbreaks of importance to human health, for example the outbreak of influenza A(H1N1 pandemic in 2009. Polymerase chain reaction (PCR procedures established as part of a capacity-building process were used to conduct prospective respiratory surveillance in a region where few previous studies have been undertaken.Methods: Between October 2008 and September 2010, nose and throat swabs from adults and children (approximately 20 per week presenting with an acute respiratory illness to the Ninh Hoa General Hospital were collected. Same-day PCR testing and result reporting for 13 respiratory viruses were carried out by locally trained scientists.Results: Of 2144 surveillance samples tested, 1235 (57.6% were positive for at least one virus. The most common were influenza A strains (17.9%, with pandemic influenza A(H1N1 2009 and seasonal H3N2 strain accounting for 52% and 43% of these, respectively. Other virus detections included: rhinovirus (12.4%, enterovirus (8.9%, influenza B (8.3%, adenovirus (5.3%, parainfluenza (4.7%, respiratory syncytial virus (RSV (3.9%, human coronavirus (3.0% and human metapneumovirus (0.3%. The detection rate was greatest in the 0–5 year age group. Viral co-infections were identified in 148 (6.9% cases.Discussion: The outbreak in 2009 of the influenza A(H1N1 pandemic strain provided a practical test of the laboratory’s pandemic plan. This study shows that the availability of appropriate equipment and molecular-based testing can contribute to important individual and public health outcomes in geographical locations susceptible to emerging infections.

  16. Impacts of aerosol-monsoon interaction on rainfall and circulation over Northern India and the Himalaya Foothills

    Science.gov (United States)

    Lau, William K. M.; Kim, Kyu-Myong; Shi, Jainn-Jong; Matsui, T.; Chin, M.; Tan, Qian; Peters-Lidard, C.; Tao, W. K.

    2016-11-01

    The boreal summer of 2008 was unusual for the Indian monsoon, featuring exceptional heavy loading of dust aerosols over the Arabian Sea and northern-central India, near normal all-India rainfall, but excessive heavy rain, causing disastrous flooding in the Northern Indian Himalaya Foothills (NIHF) regions, accompanied by persistent drought conditions in central and southern India. Using the NASA Unified-physics Weather Research Forecast (NUWRF) model with fully interactive aerosol physics and dynamics, we carried out three sets of 7-day ensemble model forecast experiments: (1) control with no aerosol, (2) aerosol radiative effect only and (3) aerosol radiative and aerosol-cloud-microphysics effects, to study the impacts of aerosol-monsoon interactions on monsoon variability over the NIHF during the summer of 2008. Results show that aerosol-radiation interaction (ARI), i.e., dust aerosol transport, and dynamical feedback processes induced by aerosol-radiative heating, plays a key role in altering the large-scale monsoon circulation system, reflected by an increased north-south tropospheric temperature gradient, a northward shift of heavy monsoon rainfall, advancing the monsoon onset by 1-5 days over the HF, consistent with the EHP hypothesis (Lau et al. in Clim Dyn 26(7-8):855-864, 2006). Additionally, we found that dust aerosols, via the semi-direct effect, increase atmospheric stability, and cause the dissipation of a developing monsoon onset cyclone over northeastern India/northern Bay of Bengal. Eventually, in a matter of several days, ARI transforms the developing monsoon cyclone into meso-scale convective cells along the HF slopes. Aerosol-Cloud-microphysics Interaction (ACI) further enhances the ARI effect in invigorating the deep convection cells and speeding up the transformation processes. Results indicate that even in short-term (up to weekly) numerical forecasting of monsoon circulation and rainfall, effects of aerosol-monsoon interaction can be

  17. Impacts of aerosol-monsoon interaction on rainfall and circulation over Northern India and the Himalaya Foothills

    Science.gov (United States)

    Lau, William K. M.; Kim, Kyu-Myong; Shi, Jainn-Jong; Matsui, T.; Chin, M.; Tan, Qian; Peters-Lidard, C.; Tao, W. K.

    2017-09-01

    The boreal summer of 2008 was unusual for the Indian monsoon, featuring exceptional heavy loading of dust aerosols over the Arabian Sea and northern-central India, near normal all-India rainfall, but excessive heavy rain, causing disastrous flooding in the Northern Indian Himalaya Foothills (NIHF) regions, accompanied by persistent drought conditions in central and southern India. Using the NASA Unified-physics Weather Research Forecast (NUWRF) model with fully interactive aerosol physics and dynamics, we carried out three sets of 7-day ensemble model forecast experiments: (1) control with no aerosol, (2) aerosol radiative effect only and (3) aerosol radiative and aerosol-cloud-microphysics effects, to study the impacts of aerosol-monsoon interactions on monsoon variability over the NIHF during the summer of 2008. Results show that aerosol-radiation interaction (ARI), i.e., dust aerosol transport, and dynamical feedback processes induced by aerosol-radiative heating, plays a key role in altering the large-scale monsoon circulation system, reflected by an increased north-south tropospheric temperature gradient, a northward shift of heavy monsoon rainfall, advancing the monsoon onset by 1-5 days over the HF, consistent with the EHP hypothesis (Lau et al. in Clim Dyn 26(7-8):855-864, 2006). Additionally, we found that dust aerosols, via the semi-direct effect, increase atmospheric stability, and cause the dissipation of a developing monsoon onset cyclone over northeastern India/northern Bay of Bengal. Eventually, in a matter of several days, ARI transforms the developing monsoon cyclone into meso-scale convective cells along the HF slopes. Aerosol-Cloud-microphysics Interaction (ACI) further enhances the ARI effect in invigorating the deep convection cells and speeding up the transformation processes. Results indicate that even in short-term (up to weekly) numerical forecasting of monsoon circulation and rainfall, effects of aerosol-monsoon interaction can be

  18. Inverse relation between summer and winter monsoon strength during late Holocene: continental molecular isotopic record from the Indian subcontinent

    Science.gov (United States)

    Sanyal, P.; Basu, S.; Pillai, A.; Singh, P.; Ratnam, J.; Sankaran, M.; Amibili, A.

    2015-12-01

    The Indian monsoon shapes the livelihood of ca. 40% of world's population. Despite dedicated efforts, comprehensive picture of monsoon variability has proved elusive largely due to the absence of long-term qualitative high-resolution record from key climatic zones and variability of monsoon with respect to various forcing mechanisms (e.g., solar insolation) and teleconnections (e.g., El Niño-Southern Oscillation, Indian Ocean Dipole). In this study, high-resolution molecular (n-alkane) isotopic (δD and δ13C ratios) reconstruction of mid-late Holocene (~5.0 cal ka) climate has been undertaken using lacustrine sediments from two climatically sensitive regions; (i) Arid Banni grasslands, western India with dominant moisture source derived from Indian summer monsoon (June-September) and (ii) Semi-arid Ennamangalam lake, south India with significant fraction of rainfall received during winter period (October to December) from Northeast (NE) monsoon. The climate reconstruction from western India based on δDn-alkane values shows prevalence of intensified monsoon until ca. 3 cal ka followed by gradual decrease in the precipitation. In contrast, climate reconstruction from south India is characterized by more negative δDn-alkane (intensified precipitation) values during late Holocene (~2.5 cal ka). The compilation of paleoclimate records shows that the precipitation pattern in Banni region responded linearly to gradually changing insolation and additionally amplified by climate systems like ENSO. However, intensified monsoon in South India shows strengthened NE monsoonal precipitation during late Holocene. The spatial inhomogeneity in the palaeohydrological record can be attributed to the persistence of inverse relationship between summer and winter monsoon. In addition, strong positive correlation between δDn-alkane and δ13Cn-alkane values from both region shows that the relative abundance of C3-C4 plants in the contemporary ecosystems are governed by rainfall

  19. Root characteristics of some grass species on the sea dikes in Viet Nam

    NARCIS (Netherlands)

    Trung, L.H.

    2012-01-01

    Between 2009 and 2011, some grass-covered sea dikes were tested with the Wave Overtopping Simulator in the north of Viet Nam. Slope specifications and grass species of sea and estuary dikes were quantitatively observed and investigated. This report is concerned with expressing main characteristics

  20. Root characteristics of some grass species on the sea dikes in Viet Nam

    NARCIS (Netherlands)

    Trung, L.H.

    2012-01-01

    Between 2009 and 2011, some grass-covered sea dikes were tested with the Wave Overtopping Simulator in the north of Viet Nam. Slope specifications and grass species of sea and estuary dikes were quantitatively observed and investigated. This report is concerned with expressing main characteristics o

  1. A contextual ICA stakeholder model approach for the Namibian spatial data infrastructure (NamSDI)

    CSIR Research Space (South Africa)

    Sinvula, KM

    2013-08-01

    Full Text Available In 2011, the Namibian parliament presented and promulgated the Namibian Spatial Data Infrastructure (NamSDI) with the aim of promoting the sharing and improved access and use of geospatial data and services across Namibia. Notable SDI models...

  2. Time to unsuccessful tuberculosis treatment outcome, Cambodia, China, and Viet Nam

    DEFF Research Database (Denmark)

    Hoa, N B; Sokun, C; Wei, C

    2012-01-01

    OBJECTIVE: To determine the frequency and characteristics of patients with unsuccessful tuberculosis (TB) treatment. METHODS: Random selection of TB case registers among all treatment units in Cambodia, two provinces in China, and Viet Nam. The data of two calendar years were analyzed to assess u...

  3. Characterisation of Mycobacterium tuberculosis isolates lacking IS6110 in Viet Nam.

    NARCIS (Netherlands)

    Huyen, M.N.; Tiemersma, E.W.; Kremer, K.; Haas, P. de; Lan, N.T.; Buu, T.N.; Sola, C.; Cobelens, F.G.; Soolingen, D. van

    2013-01-01

    SETTING: The molecular diagnosis of tuberculosis (TB) in Viet Nam is often based on the detection of insertion sequence (IS) 6110 in Mycobacterium tuberculosis. However, 8-11% of M. tuberculosis strains in South-East Asia do not contain this target and this undermines the validity of these molecular

  4. Climate change and development responses on agriculture in Quang Nam Province Vietnam

    DEFF Research Database (Denmark)

    Schroll, Henning; Andersen, Jan; Lund, Søren

    2011-01-01

    The study describes the development of agriculture in Quang Nam Province and the adaptation to climate change. Climate change can be defined as the deviation from the “normal” climate variation and we did not assess the anthropogenic contributions to the climate events. It was not possible...

  5. Characteristics of tuberculosis patients at intake in Cambodia, two provinces in China, and Viet Nam

    Directory of Open Access Journals (Sweden)

    Lauritsen Jens M

    2011-05-01

    Full Text Available Abstract Background The tuberculosis register is a critical data source for the information system of national tuberculosis control programs. From the information in the tuberculosis case register, it is possible to extend the standard analysis of age and sex characteristics among sputum smear-positive cases to all tuberculosis case categories. National tuberculosis programs might utilize such information to identify problems related to referral and access to diagnosis and treatment. Objectives Based on the electronic database we created, our objectives were to provide a detailed description of age and sex characteristics of tuberculosis patients at registration and to provide a comparison of age-specific sex characteristics among incident and prevalent sputum smear-positive cases. Methods A representative sample of tuberculosis case registers from 1 January 2003 to 31 December 2005 was selected in Cambodia, two provinces in China and Viet Nam. Age and sex characteristics of cases in the three separate prevalence surveys in the three jurisdictions (Cambodia: year 2002; China: year 2000; and Viet Nam: year 2006-2007 were obtained for comparison. Results A total 37,635 patients had been registered during the period in the selected units in the three countries. Cases were more frequently male in all three countries with 53%, 71%, and 69% in Cambodia, China, and Viet Nam, respectively. The ratios of the female-to-male odds in the notification system to that in the prevalence survey in smear-positive cases in Cambodia, China and Viet Nam were 2.1, 0.9, and 1.8, respectively. Because of the small proportion of extrapulmonary tuberculosis registered in China, we limited the analysis on age and sex distribution for extrapulmonary cases to Cambodia and Viet Nam. The proportion with extrapulmonary tuberculosis among all cases was 18.5% in Cambodia and 15.7% in Viet Nam, decreasing in frequency with increasing age. Conclusions Characteristics of patients

  6. Atmospheric processes of organic pollutants over a remote lake on the central Tibetan Plateau: implications for regional cycling

    Science.gov (United States)

    Ren, Jiao; Wang, Xiaoping; Wang, Chuanfei; Gong, Ping; Yao, Tandong

    2017-01-01

    Atmospheric processes (air-surface exchange, and atmospheric deposition and degradation) are crucial for understanding the global cycling and fate of organic pollutants (OPs). However, such assessments over the Tibetan Plateau (TP) remain uncertain. More than 50 % of Chinese lakes are located on the TP, which exerts a remarkable influence on the regional water, energy, and chemical cycling. In this study, air and water samples were simultaneously collected in Nam Co, a large lake on the TP, to test whether the lake is a secondary source or sink of OPs. Lower concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were observed in the atmosphere and lake water of Nam Co, while the levels of polycyclic aromatic hydrocarbons (PAHs) were relatively higher. Results of fugacity ratios and chiral signatures both suggest that the lake acted as the net sink of atmospheric hexachlorocyclohexanes (HCHs), following their long-range transport driven by the Indian monsoon. Different behaviours were observed in the PAHs, which primarily originated from local biomass burning. Acenaphthylene, acenaphthene, and fluorene showed volatilization from the lake to the atmosphere, while other PAHs were deposited into the lake due to the integrated deposition process (wet/dry and air-water gas deposition) and limited atmospheric degradation. As the dominant PAH compound, phenanthrene exhibited a seasonal reversal of air-water gas exchange, which was likely related to the melting of the lake ice in May. The annual input of HCHs from the air to the entire lake area (2015 km2) was estimated as 1.9 kg yr-1, while input estimated for ∑ 15PAHs can potentially reach up to 550 kg yr-1. This study highlights the significance of PAH deposition on the regional carbon cycling in the oligotrophic lakes of the TP.

  7. The effect of El-Niño on South Asian Monsoon and agricultural production

    Science.gov (United States)

    Mukherjee, A.

    2015-12-01

    Mukherjee A, Wang S.Y.Abstract:The South Asian Monsoon has a prominent and significant impact on South Asian countries like India, Bangladesh, Nepal, Pakistan, Sri Lanka and it is one of the most studied phenomena in the world. The monsoon is historically known to be influenced by El Niño-Southern Oscillation (ENSO). The inter-annual and inter-decadal variability of seasonal precipitation over India strongly depends upon the ENSO phasing. The average southwest monsoon rainfall received during the years with El Niño was found to be less compared to normal years and the average rainfall during the northeast monsoon is higher in coastal Andhra Pradesh. ENSO is anti-correlated with Indian summer monsoon (ISM). The last prominent effect of ENSO on India's monsoon occurred in 2009 with 23% reduction in annual rainfall, reducing summer sown crops such as rice, sugar cane etc. and pushing up food prices. Climatic resources endowment plays a major role in planning agricultural production in tropical and sub-tropical environment especially under rain-fed agriculture, and so contingent crop planning drawn on this relationship would help to mitigate the effects of ENSO episodes in the region. The unexplored area in this domain of research is the changes in the frequency and intensity of ENSO due to global warming and its impact on ENSO prediction and agricultural management practices. We analyze the last 30 years datasets of Pacific SST, and precipitation and air temperature over Southeast Asia to examine the evolution of ENSO teleconnections with ISM, as well as making estimates of drought indices such as Palmer Drought Severity Index. This research can lead toward better crop management strategies in the South Asian monsoon region.

  8. Spatial and Temporal Dynamics of Lakes in Nam Co Basin, 1991-2011

    Institute of Scientific and Technical Information of China (English)

    Xu Wang; Aiguo Zhou; Ziyong Sun

    2016-01-01

    ABSTRACT:Lakes in Tibet Plateau with little effects of human activities serve as important indicators of climate change. This study analysed remote sensing data and long term climate variables to examine the hydrological response of lakes in Nam Co Basin. The area changes of lakes were extracted by Landsat TM/ETM+and analysed by SRTM 3 DEM. And the ICESat elevation data between 2003 and 2009 were used to observe the lake level of the Nam Co Lake. The results show that the number of new formed glacier lakes increased by 36% and the area of glacier lakes increased by 36.7% (0.97 km2) from 1991 to 2011. At the same time, the surface area of the Nam Co Lake expanded by 3.71%(72.64 km2) of the original size in 1991, with a tendency value of 3.63 km2 per year. The lake level of the Nam Co Lake shows an increase tendency of 0.24 m per year during 2003–2009. These variations appear to be related to an increase in mean annual temperature of 0.06 ºC per year, and an increase in annual precipitation of 2.1 mm per year in summer in the last two decades. The increased number of lakes and increased area of glacial lakes reached a peak at an altitude of 5 500–5 600 m a.s.l.. The number of new formed glacier lakes and the area of glacier lakes tend to higher altitudes. Climate change has an im-portant impact on the variation of the glacier lakes and the Nam Co Lake.

  9. Role of Anomalous States of Upper Tropospheric Circulation on Extremely Dry and Wet Summer Monsoon Events

    Science.gov (United States)

    Ahmad, S.; Koike, T.; Nishii, K.; Shrestha, M.

    2011-12-01

    Seasonal changes in wind pattern, monsoon, sometimes result in severe droughts and intense flooding in many parts of the world including South Asian countries like Pakistan. The livelihood of a vast population in Pakistan depends on agriculture and land use is strongly influenced by water-based ecosystems that depend on the monsoon rains. Furthermore, climate change studies undertaken so far reveal that action is essential in order to prevent long term damage to water cycle and thus of great concern to the community and stakeholders. Pakistan Summer Monsoon (PSM) is affected by both the disturbances from the tropical and the extratropical regions; however there is lack of understanding of physical mechanisms of PSM compared to other regional studies i.e. Indian Summer Monsoon (ISM) and South-East Asian Monsoon (SEAM). In our study, we applied heat and vorticity budgets, and wave train analysis to reveal the mechanisms of the extremely dry and wet PSM events associated with the anomalous upper tropospheric conditions. We found that the extremely dry (wet) PSM events were closely related with the anomalous cyclonic (anticyclonic) upper-tropospheric circulation around northwest of Pakistan, and mid-upper tropospheric cooling (warming) anomaly around Pakistan and to its north/northwest. We also found in addition to Rossby wave response due to the suppressed (enhanced) convective activities around monsoon regions, the midlatitude wave energy propagation emanating around cyclonic/anticyclonic anomaly around northwestern Atlantic, northeastern Atlantic, Europe or Mediterranean regions induced/reinforced/maintained the anomalous upper tropospheric cyclonic (anticyclonic) circulation around northwest of Pakistan during extremely dry (wet) PSM events. Therefore, devastating drought (flood) events over the PSM region resulting from weak (strong) convection anomalies are induced by both the tropical and extratropical processes.

  10. Significance of the normalized seasonality of wind field and its rationality for characterizing the monsoon

    Institute of Scientific and Technical Information of China (English)

    李建平; 曾庆存

    2000-01-01

    The significance of the normalized seasonality of wind field is theoretically studied and the intrinsic relationship between its critical value and the definition of the monsoon region is revealed. As a result, the rationality which the monsoon region is characterized by the significant normalized seasonality is proved. Based on this, by use of the NECP/NCAR reanalysis data during 1958-1997, the spatial structure of the significant normalized seasonality of wind field is investigated, and the significant baroclinity of the seasonal variation of the atmospheric general circulation in the vertical direction is verified. Moreover, in the tropics there exists an anti-symmetric distribution between the significant seasonality in the eastern hemisphere and that in the western hemisphere, and the monsoon is linked closely to some important systems such as the subtropical highs, the night jet and the west wind channels.

  11. Characteristics of monsoon low level jet (MLLJ) as an index of monsoon activity

    Indian Academy of Sciences (India)

    N V Sam; K P R Vittal Murty

    2002-12-01

    Temperature and wind data are used to describe variation in the strength of the Monsoon Low Level Jet (MLLJ) from an active phase of the monsoon to a break phase. Also estimated are the characteristics of turbulence above and below MLLJ.

  12. Mechanism of ENSO influence on the South Asian monsoon rainfall in global model simulations

    Science.gov (United States)

    Joshi, Sneh; Kar, Sarat C.

    2017-02-01

    Coupled ocean atmosphere global climate models are increasingly being used for seasonal scale simulation of the South Asian monsoon. In these models, sea surface temperatures (SSTs) evolve as coupled air-sea interaction process. However, sensitivity experiments with various SST forcing can only be done in an atmosphere-only model. In this study, the Global Forecast System (GFS) model at T126 horizontal resolution has been used to examine the mechanism of El Niño-Southern Oscillation (ENSO) forcing on the monsoon circulation and rainfall. The model has been integrated (ensemble) with observed, climatological and ENSO SST forcing to document the mechanism on how the South Asian monsoon responds to basin-wide SST variations in the Indian and Pacific Oceans. The model simulations indicate that the internal variability gets modulated by the SSTs with warming in the Pacific enhancing the ensemble spread over the monsoon region as compared to cooling conditions. Anomalous easterly wind anomalies cover the Indian region both at 850 and 200 hPa levels during El Niño years. The locations and intensity of Walker and Hadley circulations are altered due to ENSO SST forcing. These lead to reduction of monsoon rainfall over most parts of India during El Niño events compared to La Niña conditions. However, internally generated variability is a major source of uncertainty in the model-simulated climate.

  13. Role of west Asian surface pressure in summer monsoon onset over central India

    Science.gov (United States)

    Chakraborty, Arindam; Agrawal, Shubhi

    2017-07-01

    Using rain-gauge measurements and reanalysis data sets for 1948-2015, we propose a mechanism that controls the interannual variation of summer monsoon onset over central India. In May, about a month before the onset, the low level jet over the Arabian Sea is about 40% stronger and about 2.5 degrees northward during years of early onset as compared to years of late onset. A stronger and northward shifted low level jet carries about 50% more moisture in early onset years, which increases low level moist static energy over central India in the pre-monsoon season. The increase in low level moist static energy decreases the stability of the atmosphere and makes it conducive for convection. The strength and position of the low level jet are determined by surface pressure gradient between western Asia and the west-equatorial Indian Ocean. Thus, an anomalous surface pressure low over western Asia in the pre-monsoon season increases this gradient and strengthens the jet. Moreover, a stronger low level jet increases the meridional shear of zonal wind and supports the formation of an onset vortex in a stronger baroclinic atmosphere. These developments are favourable for an early onset of the monsoon over the central Indian region. Our study postulates a new physical mechanism for the interannual variation of onset over central India, the core of the Indian monsoon region and relevant to Indian agriculture, and could be tested for real-time prediction.

  14. Assessment of the Impact of The East Asian Summer Monsoon on the Air Quality Over China

    Science.gov (United States)

    Hao, Nan; Ding, Aijun; Safieddine, Sarah; Valks, Pieter; Clerbaux, Cathy; Trautmann, Thomas

    2016-04-01

    Air pollution is one of the most important environmental problems in developing Asian countries like China. In this region, studies showed that the East Asian monsoon plays a significant role in characterizing the temporal variation and spatial patterns of air pollution, since monsoon is a major atmospheric system affecting air mass transport, convection, and precipitation. Knowledge gaps still exist in the understanding of Asian monsoon impact on the air quality in China under the background of global climate change. For the first time satellite observations of tropospheric ozone and its precursors will be integrated with the ground-based, aircraft measurements of air pollutants and model simulations to study the impact of the East Asian monsoon on air quality in China. We apply multi-platform satellite observations by the GOME-2, IASI, and MOPITT instruments to analyze tropospheric ozone and CO, precursors of ozone (NO2, HCHO and CHOCHO) and other related trace gases over China. Two years measurements of air pollutants including NO2, HONO, SO2, HCHO and CHOCHO at a regional back-ground site in the western part of the Yangtze River Delta (YRD) in eastern China will be presented. The potential of using the current generation of satellite instruments, ground-based instruments and aircraft to monitor air quality changes caused by the East Asian monsoon circulation will be presented. Preliminary comparison results between satellite measurement and limited but valuable ground-based and aircraft measurements will also be showed.

  15. Future projection of mean and variability of the Asian Summer Monsoon and Indian Ocean Climate systems

    Energy Technology Data Exchange (ETDEWEB)

    Annamalai, H [IPRC, University of Hawaii

    2014-09-15

    The overall goal of this project is to assess the ability of the CMIP3/5 models to simulate the Indian-Ocean monsoon systems. The PI along with post-docs investigated research issues ranging from synoptic systems to long-term trends over the Asian monsoon region. The PI applied diagnostic tools such as moist static energy (MSE) to isolate: the moist and radiative processes responsible for extended monsoon breaks over South Asia, precursors in the ENSO-monsoon association, reasons for the drying tendency over South Asia and the possible effect on tropical Indian Ocean climate anomalies influencing certain aspects of ENSO characteristics. By diagnosing various observations and coupled model simulations, we developed working hypothesis and tested them by carrying out sensitivity experiments with both linear and nonlinear models. Possible physical and dynamical reasons for model sensitivities were deduced. On the teleconnection front, the ability of CMIP5 models in representing the monsoon-desert mechanism was examined recently. Further more, we have applied a suite of diagnostics and have performed an in depth analysis on CMIP5 integrations to isolate the possible reasons for the ENSO-monsoon linkage or lack thereof. The PI has collaborated with Dr. K.R. Sperber of PCMDI and other CLIVAR Asian-Australian monsoon panel members in understanding the ability of CMIP3/5 models in capturing monsoon and its spectrum of variability. The objective and process-based diagnostics aided in selecting models that best represent the present-day monsoon and its variability that are then employed for future projections. Two major highlights were an invitation to write a review on present understanding monsoons in a changing climate in Nature Climate Change, and identification of an east-west shift in observed monsoon rainfall (more rainfall over tropical western Pacific and drying tendency over South Asia) in the last six decades and attributing that shift to SST rise over the tropical

  16. Atmospheric circulation processes contributing to a multidecadal variation in reconstructed and modeled Indian monsoon precipitation

    Science.gov (United States)

    Wu, Qianru; Hu, Qi

    2015-01-01

    analysis of the recently reconstructed gridded May-September total precipitation in the Indian monsoon region for the past half millennium discloses significant variations at multidecadal timescales. Meanwhile, paleo-climate modeling outputs from the National Center for Atmospheric Research Community Climate System Model 4.0 show similar multidecadal variations in the monsoon precipitation. One of those variations at the frequency of 40-50 years per cycle is examined in this study. Major results show that this variation is a product of the processes in that the meridional gradient of the atmospheric enthalpy is strengthened by radiation loss in the high-latitude and polar region. Driven by this gradient and associated baroclinicity in the atmosphere, more heat/energy is generated in the tropical and subtropical (monsoon) region and transported poleward. This transport relaxes the meridional enthalpy gradient and, subsequently, the need for heat production in the monsoon region. The multidecadal timescale of these processes results from atmospheric circulation-radiation interactions and the inefficiency in generation of kinetic energy from the potential energy in the atmosphere to drive the eddies that transport heat poleward. This inefficiency creates a time delay between the meridional gradient of the enthalpy and the poleward transport. The monsoon precipitation variation lags that in the meridional gradient of enthalpy but leads that of the poleward heat transport. This phase relationship, and underlining chasing process by the transport of heat to the need for it driven by the meridional enthalpy gradient, sustains this multidecadal variation. This mechanism suggests that atmospheric circulation processes can contribute to multidecadal timescale variations. Interactions of these processes with other forcing, such as sea surface temperature or solar irradiance anomalies, can result in resonant or suppressed variations in the Indian monsoon precipitation.

  17. Pleistocene Indian Monsoon rainfall variability dominated by obliquity

    Science.gov (United States)

    Gebregiorgis, D.; Hathorne, E. C.; Giosan, L.; Collett, T. S.; Nuernberg, D.; Frank, M.

    2015-12-01

    The past variability of the Indian Monsoon is mostly known from records of wind strength over the Arabian Sea while Quaternary proxy records of Indian monsoon precipitation are still lacking. Here we utilize scanning x-ray fluorescence (XRF) data from a sediment core obtained by the IODP vessel JOIDES Resolution in the Andaman Sea (Site 17) to investigate changes in sediment supply from the peak monsoon precipitation regions to the core site. We use Ti/Ca and K/Rb ratios to trace changes in terrigenous flux and weathering regime, respectively, while Zr/Rb ratios suggest grain size variations. The age model of Site 17 is based on correlation of benthic C. wuellerstorfi/C. mundulus δ18O data to the LR04 global benthic δ18O stack at a resolution of ~3 kyr (Lisiecki and Raymo, 2005) for the last 2 Myrs. In its youngest part the age model is supported by five 14C ages on planktic foraminifera and the youngest Toba ash layer (Ali et al., 2015) resulting in a nearly constant sedimentation rate of ~6.5 cm/kyr. Frequency analysis of the 4 mm resolution Ti/Ca, K/Rb, and Zr/Rb time series using the REDFIT program (Schulz and Mudelsee, 2002), reveals the three main Milankovitch orbital cycles above the 90% confidence level. Depth domain spectral analysis reveals the presence of significant cyclicity at wavelengths of 28.5 and 2.8 m corresponding to the ~400 kyr and ~41 kyr cycles, respectively, during the last 2 Myr. These records suggest that Indian monsoon variability has varied in the obliquity and eccentricity bands, the latter in particular after the mid Pleistocene transition (MPT), while strong precession forcing is lacking in this super-high resolution record. Northern summer insolation and Southern Hemisphere latent heat export are out of phase during precessional cycles, but in phase in the obliquity band, which indicates that Indian monsoon precipitation has likely been more sensitive to both NH pull and SH push mechanisms (Clemens and Prell, 2003). References Ali

  18. The progression of the boreal winter monsoon through the western Maritime Continent as differentiated by ENSO phase

    Science.gov (United States)

    Lee, Shao-Yi; McBride, John L.

    2016-08-01

    The impact of global ENSO on the regional monsoon onset over the Maritime Continent is examined, using satellite-derived scatterometer surface winds over the sea channel from the South China Sea, through the Karimata Strait into the Java Sea. An index of monsoon onset, fracsign, is defined based on a positive dot-product between the monthly wind at each gridpoint and the "basis-wind" or climatological wind at the peak of the relevant monsoon season.Rather than being delayed throughout the Maritime Continent during El Niño years, the monsoon is seen to arrive faster at and remain longer over the western Maritime Continent, and therefore delayed for the eastern Maritime Continent. The wind-based diagnostic can be further decomposed into two components that reflect the monsoon wind strength and the location of the wind convergence zone, respectively. During El Niño years, the monsoon strength post-onset is weaker than normal over the eastern maritime continent. However, there is no ENSO-related differentiation in monsoon strength post-onset over the western Maritime Continent.

  19. On the unstable ENSO-Western North Pacific Monsoon relation during the 20th Century

    Science.gov (United States)

    Vega Martín, Inmaculada; Gallego Puyol, David; Ribera Rodriguez, Pedro; Gómez Delgado, Francisco de Paula; Peña-Ortiz, Cristina

    2017-04-01

    The concept of the Western North Pacific Summer Monsoon (WNPSM) appeared for the first time in 1987. Unlike the Indian Summer Monsoon and the East Asian summer monsoon, the WNPSM is an oceanic monsoon driven essentially by the meridional gradient of sea surface temperature. Its circulation is characterized by a northwest-southeast oriented monsoon trough with intense precipitation and low-level southwesterlies and upper-tropospheric easterlies in the region [100°-130° E, 5°-15°N]. Although this monsoon is mainly oceanic, it modulates the precipitation of densely populated areas such as the Philippines. To date, the WNPSM has been quantified by the so-called Western North Pacific Monsoon Index (WNPMI), an index based on wind anomalies over large domains of the Western Pacific. The requirement of continuous observed wind over remote oceanic areas to compute the WNPMI has limited its availability to the 1949-2014 period. In this work we have extended the index by almost 100 years by using historical observations of wind direction taken aboard ships. Our Western North Pacific Directional Index (WNPDI), is defined as the sum of the persistence of the low-level westerly winds in [5°-15°N, 100°-130°E] and easterly winds in [20°-30°N, 110°-140°E]. The new WNPDI index is highly correlated to the existent WNPMI for the concurrent period (1948-2014). (r=+0.88, pCompetitividad through the project INCITE (CGL2013-44530-P, BES-2014-069733).

  20. Systematic errors in Monsoon simulation: importance of the equatorial Indian Ocean processes

    Science.gov (United States)

    Annamalai, H.; Taguchi, B.; McCreary, J. P., Jr.; Nagura, M.; Miyama, T.

    2015-12-01

    H. Annamalai1, B. Taguchi2, J.P. McCreary1, J. Hafner1, M. Nagura2, and T. Miyama2 International Pacific Research Center, University of Hawaii, USA Application Laboratory, JAMSTEC, Japan In climate models, simulating the monsoon precipitation climatology remains a grand challenge. Compared to CMIP3, the multi-model-mean (MMM) errors for Asian-Australian monsoon (AAM) precipitation climatology in CMIP5, relative to GPCP observations, have shown little improvement. One of the implications is that uncertainties in the future projections of time-mean changes to AAM rainfall may not have reduced from CMIP3 to CMIP5. Despite dedicated efforts by the modeling community, the progress in monsoon modeling is rather slow. This leads us to wonder: Has the scientific community reached a "plateau" in modeling mean monsoon precipitation? Our focus here is to better understanding of the coupled air-sea interactions, and moist processes that govern the precipitation characteristics over the tropical Indian Ocean where large-scale errors persist. A series idealized coupled model experiments are performed to test the hypothesis that errors in the coupled processes along the equatorial Indian Ocean during inter-monsoon seasons could potentially influence systematic errors during the monsoon season. Moist static energy budget diagnostics has been performed to identify the leading moist and radiative processes that account for the large-scale errors in the simulated precipitation. As a way forward, we propose three coordinated efforts, and they are: (i) idealized coupled model experiments; (ii) process-based diagnostics and (iii) direct observations to constrain model physics. We will argue that a systematic and coordinated approach in the identification of the various interactive processes that shape the precipitation basic state needs to be carried out, and high-quality observations over the data sparse monsoon region are needed to validate models and further improve model physics.

  1. Three centuries of Myanmar monsoon climate variability inferred from teak tree rings

    Science.gov (United States)

    D'Arrigo, Rosanne; Palmer, Jonathan; Ummenhofer, Caroline C.; Kyaw, Nyi Nyi; Krusic, Paul

    2011-12-01

    Asian monsoon extremes critically impact much of the globe’s population. Key gaps in our understanding of monsoon climate remain due to sparse coverage of paleoclimatic information, despite intensified recent efforts. Here we describe a ring width chronology of teak, one of the first high-resolution proxy records for the nation of Myanmar. Based on 29 samples from 20 living trees and spanning from 1613-2009, this record, from the Maingtha forest reserve north of Mandalay, helps fill a substantial gap in spatial coverage of paleoclimatic records for monsoon Asia. Teak growth is positively correlated with rainfall and Palmer Drought Severity Index variability over Myanmar, during and prior to the May-September monsoon season (e.g., r = 0.38 with Yangon rainfall, 0.001, n 68). Importantly, this record also correlates significantly with larger-scale climate indices, including core Indian rainfall (23°N, 76°E a particularly sensitive index of the monsoon), and the El Niño-Southern Oscillation (ENSO). The teak ring width value following the so-called 1997-98 El Niño of the Century suggests that this was one of the most severe droughts in the past ˜300 years in Myanmar. Evidence for past dry conditions inferred for Myanmar is consistent with tree-ring records of decadal megadroughts developed for Thailand and Vietnam. These results confirm the climate signature related to monsoon rainfall in the Myanmar teak record and the considerable potential for future development of climate-sensitive chronologies from Myanmar and the broader region of monsoon Asia.

  2. The CLIVAR C20C project: which components of the Asian-Australian monsoon circulation variations are forced and reproducible?

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Tianjun; Li, Lijuan [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); Wu, Bo [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); Graduate University of Chinese Academy of Sciences, Beijing (China); Scaife, A.A.; Fereday, D.; Folland, C.K.; Knight, J.R. [Met Office Hadley Centre, Exeter (United Kingdom); Broennimann, S.; Fischer, A.M. [ETH, Institute for Atmospheric and Climate Science, Zurich (Switzerland); Cherchi, A.; Navarra, A. [Centro Euromediterraneo per i Cambiamenti Climatici, Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Jin, K.E.; Kinter, J. [Centre for Ocean-Land-Atmosphere Studies, Calverton (United States); Kucharski, F. [Abdus Salam International Center for Theoretical Physics, Trieste (Italy); Kusunoki, S.; Nakaegawa, T. [Japan Meteorological Agency, Meteorological Research Institute, Tsukuba (Japan); Lau, N.C.; Nath, M.J. [NOAA, Geophysical Fluid Dynamics Laboratory, Princeton (United States); Pegion, P.; Schubert, S. [NASA Goddard Space Flight Center, Greenbelt (United States); Rozanov, E. [ETH, Institute for Atmospheric and Climate Science, Zurich (Switzerland); World Radiation Center, Physical-Meteorological Observatory, Davos (Switzerland); Sporyshev, P. [Voeikov Main Geophysical Observatory, St Petersburg (Russian Federation); Voldoire, A. [CNRM, Meteo France, Toulouse Cedex 1 (France); Wen, Xinyu [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); Beijing University, Department of Atmospheric Sciences, Beijing (China); Yoon, J.H.; Zeng, N. [University of Maryland, Baltimore (United States)

    2009-12-15

    A multi-model set of atmospheric simulations forced by historical sea surface temperature (SST) or SSTs plus Greenhouse gases and aerosol forcing agents for the period of 1950-1999 is studied to identify and understand which components of the Asian-Australian monsoon (A-AM) variability are forced and reproducible. The analysis focuses on the summertime monsoon circulations, comparing model results against the observations. The priority of different components of the A-AM circulations in terms of reproducibility is evaluated. Among the subsystems of the wide A-AM, the South Asian monsoon and the Australian monsoon circulations are better reproduced than the others, indicating they are forced and well modeled. The primary driving mechanism comes from the tropical Pacific. The western North Pacific monsoon circulation is also forced and well modeled except with a slightly lower reproducibility due to its delayed response to the eastern tropical Pacific forcing. The simultaneous driving comes from the western Pacific surrounding the maritime continent region. The Indian monsoon circulation has a moderate reproducibility, partly due to its weakened connection to June-July-August SSTs in the equatorial eastern Pacific in recent decades. Among the A-AM subsystems, the East Asian summer monsoon has the lowest reproducibility and is poorly modeled. This is mainly due to the failure of specifying historical SST in capturing the zonal land-sea thermal contrast change across the East Asia. The prescribed tropical Indian Ocean SST changes partly reproduce the meridional wind change over East Asia in several models. For all the A-AM subsystem circulation indices, generally the MME is always the best except for the Indian monsoon and East Asian monsoon circulation indices. (orig.)

  3. Analysis of Basic Features of the Onset of the Asian Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, a relatively systematic climatological research on the onset of the Asian tropical summer monsoon (ATSM) was carried out. Based on a unified index of the ATSM onset, the advance of the whole ATSM was newly made and then the view that the ATSM firstly breaks out over the tropical eastern Indian Ocean and the middle and southern Indo-China Peninsula was further documented, which was in the 26th pentad (about May 10), then over the South China Sea (SCS) in the 28th pentad. It seems that the ATSM onset over the two regions belongs to the different stages of the same monsoon system. Then, the onset mechanism of ATSM was further investigated by the comprehensive analysis on the land-sea thermodynamic contrast, intraseasonal oscillation, and so on, and the several key factors which influence the ATSM onset were put forward. Based on these results, a possible climatological schematic map that the ATSM firstly breaks out over the tropical eastern Indian Ocean, the Indo-China Peninsula, and the SCS was also presented, namely seasonal evolution of the atmospheric circulation was the background of the monsoon onset; the enhancement and northward advance of the convections, the sensible heating and latent heating over the Indo-China Peninsula and its neighboring areas, the dramatic deepening of the India-Burma trough, and the westerly warm advection over the eastern Tibetan Plateau were the major driving forces of the summer monsoon onset, which made the meridional gradient of the temperature firstly reverse over this region and ascending motion develop. Then the tropical monsoon and precipitation rapidly developed and enhanced. The phase-lock of the 30-60-day and 10-20-day low frequency oscillations originated from different sources was another triggering factor for the summer monsoon onset. It was just the common effect of these factors that induced the ATSM earliest onset over this region.

  4. Prediction of a thermodynamic wave train from the monsoon to the Arctic following extreme rainfall events

    Science.gov (United States)

    Krishnamurti, T. N.; Kumar, Vinay

    2016-06-01

    This study addresses numerical prediction of atmospheric wave trains that provide a monsoonal link to the Arctic ice melt. The monsoonal link is one of several ways that heat is conveyed to the Arctic region. This study follows a detailed observational study on thermodynamic wave trains that are initiated by extreme rain events of the northern summer south Asian monsoon. These wave trains carry large values of heat content anomalies, heat transports and convergence of flux of heat. These features seem to be important candidates for the rapid melt scenario. This present study addresses numerical simulation of the extreme rains, over India and Pakistan, and the generation of thermodynamic wave trains, simulations of large heat content anomalies, heat transports along pathways and heat flux convergences, potential vorticity and the diabatic generation of potential vorticity. We compare model based simulation of many features such as precipitation, divergence and the divergent wind with those evaluated from the reanalysis fields. We have also examined the snow and ice cover data sets during and after these events. This modeling study supports our recent observational findings on the monsoonal link to the rapid Arctic ice melt of the Canadian Arctic. This numerical modeling suggests ways to interpret some recent episodes of rapid ice melts that may require a well-coordinated field experiment among atmosphere, ocean, ice and snow cover scientists. Such a well-coordinated study would sharpen our understanding of this one component of the ice melt, i.e. the monsoonal link, which appears to be fairly robust.

  5. Differences and links between the East Asian and South Asian summer monsoon systems: Characteristics and Variability

    Science.gov (United States)

    Huang, Ronghui; Liu, Yong; Du, Zhencai; Chen, Jilong; Huangfu, Jingliang

    2017-10-01

    This paper analyzes the differences in the characteristics and spatio-temporal variabilities of summertime rainfall and water vapor transport between the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM) systems. The results show obvious differences in summertime rainfall characteristics between these two monsoon systems. The summertime rainfall cloud systems of the EASM show a mixed stratiform and cumulus cloud system, while cumulus cloud dominates the SASM. These differences may be caused by differences in the vertical shear of zonal and meridional circulations and the convergence of water vapor transport fluxes. Moreover, the leading modes of the two systems' summertime rainfall anomalies also differ in terms of their spatiotemporal features on the interannual and interdecadal timescales. Nevertheless, several close links with respect to the spatiotemporal variabilities of summertime rainfall and water vapor transport exist between the two monsoon systems. The first modes of summertime rainfall in the SASM and EASM regions reveal a significant negative correlation on the interannual and the interdecadal timescales. This close relationship may be linked by a meridional teleconnection in the regressed summertime rainfall anomalies from India to North China through the southeastern part over the Tibetan Plateau, which we refer to as the South Asia/East Asia teleconnection pattern of Asian summer monsoon rainfall. The authors wish to dedicate this paper to Prof. Duzheng YE, and commemorate his 100th anniversary and his great contributions to the development of atmospheric dynamics.

  6. Prediction of a thermodynamic wave train from the monsoon to the Arctic following extreme rainfall events

    Science.gov (United States)

    Krishnamurti, T. N.; Kumar, Vinay

    2017-04-01

    This study addresses numerical prediction of atmospheric wave trains that provide a monsoonal link to the Arctic ice melt. The monsoonal link is one of several ways that heat is conveyed to the Arctic region. This study follows a detailed observational study on thermodynamic wave trains that are initiated by extreme rain events of the northern summer south Asian monsoon. These wave trains carry large values of heat content anomalies, heat transports and convergence of flux of heat. These features seem to be important candidates for the rapid melt scenario. This present study addresses numerical simulation of the extreme rains, over India and Pakistan, and the generation of thermodynamic wave trains, simulations of large heat content anomalies, heat transports along pathways and heat flux convergences, potential vorticity and the diabatic generation of potential vorticity. We compare model based simulation of many features such as precipitation, divergence and the divergent wind with those evaluated from the reanalysis fields. We have also examined the snow and ice cover data sets during and after these events. This modeling study supports our recent observational findings on the monsoonal link to the rapid Arctic ice melt of the Canadian Arctic. This numerical modeling suggests ways to interpret some recent episodes of rapid ice melts that may require a well-coordinated field experiment among atmosphere, ocean, ice and snow cover scientists. Such a well-coordinated study would sharpen our understanding of this one component of the ice melt, i.e. the monsoonal link, which appears to be fairly robust.

  7. Competing influences of greenhouse warming and aerosols on Asian summer monsoon circulation and rainfall

    Science.gov (United States)

    Lau, William Ka-Ming; Kim, Kyu-Myong

    2017-05-01

    In this paper, we have compared and contrasted competing influences of greenhouse gases (GHG) warming and aerosol forcing on Asian summer monsoon circulation and rainfall based on CMIP5 historical simulations. Under GHG-only forcing, the land warms much faster than the ocean, magnifying the pre-industrial climatological land-ocean thermal contrast and hemispheric asymmetry, i.e., warmer northern than southern hemisphere. A steady increasing warm-ocean-warmer-land (WOWL) trend has been in effect since the 1950's substantially increasing moisture transport from adjacent oceans, and enhancing rainfall over the Asian monsoon regions. However, under GHG warming, increased atmospheric stability due to strong reduction in mid-tropospheric and near surface relative humidity coupled to an expanding subsidence areas, associated with the Deep Tropical Squeeze (DTS, Lau and Kim, 2015b) strongly suppress monsoon convection and rainfall over subtropical and extratropical land, leading to a weakening of the Asian monsoon meridional circulation. Increased anthropogenic aerosol emission strongly masks WOWL, by over 60% over the northern hemisphere, negating to a large extent the rainfall increase due to GHG warming, and leading to a further weakening of the monsoon circulation, through increasing atmospheric stability, most likely associated with aerosol solar dimming and semi-direct effects. Overall, we find that GHG exerts stronger positive rainfall sensitivity, but less negative circulation sensitivity in SASM compared to EASM. In contrast, aerosols exert stronger negative impacts on rainfall, but less negative impacts on circulation in EASM compared to SASM.

  8. Contrasting influences of aerosols on cloud properties during deficient and abundant monsoon years.

    Science.gov (United States)

    Patil, Nitin; Dave, Prashant; Venkataraman, Chandra

    2017-03-24

    Direct aerosol radiative forcing facilitates the onset of Indian monsoon rainfall, based on synoptic scale fast responses acting over timescales of days to a month. Here, we examine relationships between aerosols and coincident clouds over the Indian subcontinent, using observational data from 2000 to 2009, from the core monsoon region. Season mean and daily timescales were considered. The correlation analyses of cloud properties with aerosol optical depth revealed that deficient monsoon years were characterized by more frequent and larger decreases in cloud drop size and ice water path, but increases in cloud top pressure, with increases in aerosol abundance. The opposite was observed during abundant monsoon years. The correlations of greater aerosol abundance, with smaller cloud drop size, lower evidence of ice processes and shallower cloud height, during deficient rainfall years, imply cloud inhibition; while those with larger cloud drop size, greater ice processes and a greater cloud vertical extent, during abundant rainfall years, suggest cloud invigoration. The study establishes that continental aerosols over India alter cloud properties in diametrically opposite ways during contrasting monsoon years. The mechanisms underlying these effects need further analysis.

  9. Consistent increase in Indian monsoon rainfall and its variability across CMIP-5 models

    Directory of Open Access Journals (Sweden)

    A. Menon

    2013-01-01

    Full Text Available The possibility of an impact of global warming on the Indian monsoon is of critical importance for the large population of this region. Future projections within the Coupled Model Intercomparison Project Phase 3 (CMIP-3 showed a wide range of trends with varying magnitude and sign across models. Here the Indian summer monsoon rainfall is evaluated in 20 CMIP-5 models for the period 1850 to 2100. In the new generation of climate models a consistent increase in seasonal mean rainfall during the summer monsoon periods arises. All models simulate stronger seasonal mean rainfall in the future compared to the historic period under the strongest warming scenario RCP-8.5. Increase in seasonal mean rainfall is the largest for the RCP-8.5 scenario compared to other RCPs. The interannual variability of the Indian monsoon rainfall also shows a consistent positive trend under unabated global warming. Since both the long-term increase in monsoon rainfall as well as the increase in interannual variability in the future is robust across a wide range of models, some confidence can be attributed to these projected trends.

  10. The role of potential vorticity anomalies in the Somali Jet on Indian Summer Monsoon Intraseasonal Variability

    Science.gov (United States)

    Rai, P.; Joshi, M.; Dimri, A. P.; Turner, A. G.

    2017-08-01

    The climate of the Indian subcontinent is dominated by rainfall arising from the Indian summer monsoon (ISM) during June to September. Intraseasonal variability during the monsoon is characterized by periods of heavy rainfall interspersed by drier periods, known as active and break events respectively. Understanding and predicting such events is of vital importance for forecasting human impacts such as water resources. The Somali Jet is a key regional feature of the monsoon circulation. In the present study, we find that the spatial structure of Somali Jet potential vorticity (PV) anomalies varies considerably during active and break periods. Analysis of these anomalies shows a mechanism whereby sea surface temperature (SST) anomalies propagate north/northwestwards through the Arabian Sea, caused by a positive feedback loop joining anomalies in SST, convection, modification of PV by diabatic heating and mixing in the atmospheric boundary layer, wind-stress curl, and ocean upwelling processes. The feedback mechanism is consistent with observed variability in the coupled ocean-atmosphere system on timescales of approximately 20 days. This research suggests that better understanding and prediction of monsoon intraseasonal variability in the South Asian monsoon may be gained by analysis of the day-to-day dynamical evolution of PV in the Somali Jet.

  11. Monsoon signatures in recent corals from the Laccadive Islands

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.A.S.

    have reduced water transparency, thereby curtailing the growth rates. Scanning electron microscopy clearly showed the presence of lithogenic and biogenic material in the monsoonal bands and their absence in the non-monsoonal bands. This indicates...

  12. Thrusts and Prospects on Understanding and Predicting Asian Monsoon Climate

    Institute of Scientific and Technical Information of China (English)

    WANG Bin

    2008-01-01

    Development of monsoon climate prediction through integrated research efforts to improve our understanding of monsoon variability and predictability is a primary goal of the Asian Monsoon Years (2007-2011) and International Monsoon Study under the leadership of the World Climate Research Programme.The present paper reviews recent progress in Asian monsoon research focusing on (1) understanding and modeling of the monsoon variability, (2) determining the sources and limits of predictability, and (3) assessing the current status of climate prediction, with emphasis on the weekly to interannual time scales. Particular attention is paid to identify scientific issues and thrust areas, as well as potential directions to move forward in an attempt to stimulate future research to advance our understanding of monsoon climate dynamics and improve our capability to forecast Asian monsoon climate variation.

  13. On the recent strengthening of the relationship between ENSO and northeast monsoon rainfall over South Asia

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pankaj; Rupa Kumar, K.; Sahai, A.K. [Indian Institute of Tropical Meteorology, Pune (India); Rajeevan, M. [India Meteorological Department, Pune (India)

    2007-05-15

    The southeastern parts of India and Sri Lanka receive substantial rainfall from the northeast monsoon (NEM) during October through December. The interannual variability in NEM rainfall is known to be significantly influenced by the El-Nino/Southern Oscillation (ENSO). Unlike the southwest monsoon (SWM), the NEM rainfall is enhanced during the warm ENSO events, and vice versa. In the context of the recent weakening of the inverse relationship between Southwest Monsoon (SWM) and ENSO, we examine the secular variations in the positive relationship between ENSO and NEM rainfall over South Asia, showing that their relationship has strengthened over the recent years. Based on the analysis of GISST, IMD/CRU precipitation and NCEP/NCAR reanalysis data, we suggest that this secular variation of the relationship is due to epochal changes in the tropospheric circulation associated with ENSO over the region. (orig.)

  14. Impact of Anthropogenic Climate Change on the East Asian Summer Monsoon

    Science.gov (United States)

    Burke, Claire; Stott, Peter

    2017-07-01

    The East Asian summer monsoon (EASM) is important for bringing rainfall to large areas of China. Historically, variations in the EASM have had major impacts including flooding and drought. We present an analysis of the impact of anthropogenic climate change on EASM rainfall in Eastern China using a newly updated attribution system. Our results suggest that anthropogenic climate change has led to an overall decrease in total monsoon rainfall over the past 65 years, and an increased number of dry days. However the model also predicts that anthropogenic forcings have caused the most extreme heavy rainfall events to become shorter in duration and more intense. With the potential for future changes in aerosol and greenhouse gas emissions, historical trends in monsoon rainfall may not be indicative of future changes, although extreme rainfall is projected to increase over East Asia with continued warming in the region.

  15. Analysis of spatial and temporal extreme monsoonal rainfall over South Asia using complex networks

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Nishant [Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam (Germany); University of Potsdam, Institute of Physics, Potsdam-Golm (Germany); Bookhagen, Bodo [University of California Santa Barbara, Department of Geography, Santa Barbara, CA (United States); Marwan, Norbert [Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam (Germany); Kurths, Juergen [Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam (Germany); Humboldt University, Department of Physics, Berlin (Germany)

    2012-08-15

    We present a detailed analysis of summer monsoon rainfall over the Indian peninsular using nonlinear spatial correlations. This analysis is carried out employing the tools of complex networks and a measure of nonlinear correlation for point processes such as rainfall, called event synchronization. This study provides valuable insights into the spatial organization, scales, and structure of the 90th and 94th percentile rainfall events during the Indian summer monsoon (June-September). We furthermore analyse the influence of different critical synoptic atmospheric systems and the impact of the steep Himalayan topography on rainfall patterns. The presented method not only helps us in visualising the structure of the extreme-event rainfall fields, but also identifies the water vapor pathways and decadal-scale moisture sinks over the region. Furthermore a simple scheme based on complex networks is presented to decipher the spatial intricacies and temporal evolution of monsoonal rainfall patterns over the last 6 decades. (orig.)

  16. Sea breeze Initiated Rainfall over the east Coast of India during the Indian Southwest Monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, M; Warrior, H; Raman, S; Aswathanarayana, P A; Mohanty, U C; Suresh, R

    2006-09-05

    Sea breeze initiated convection and precipitation is investigated along the east coast of India during the Indian southwest monsoon season. The sea breeze circulations are observed approximately 70 to 80% of the days during the summer months (June to August) along the Chennai coast. Observations of average sea breeze wind speeds are stronger at a rural location as compared to the wind speeds observed inside the urban region of Chennai. The sea breeze circulation is shown to be the dominant mechanism for initiating rainfall during the Indian southwest monsoon season. Roughly 80% of the total rainfall observed during the southwest monsoon over Chennai is directly related to the convection initiated by sea breeze circulation.

  17. Evaluation of multi-satellite rainfall products over India during monsoon

    Science.gov (United States)

    Mitra, Ashis K.; Prakash, Satya; Pai, D. S.; Srivastava, A. K.

    2016-05-01

    Simulation and prediction of Indian monsoon rainfall at scales from days-to-season is a challenging task for numerical modelling community worldwide. Gridded estimates of daily rainfall data are required for both land and oceanic regions for model validation, process studies and in turn for model development. Due to recent developments in satellite meteorology, it has become possible to produce realistic near real-time gridded rainfall datasets at operational basis by combining satellite estimates with rain gauge values and other available in-situ observations. Microwave and space based radar based estimates of rainfall has revolutionised the preparation of rainfall datasets especially for tropics. However, a variety of multi-satellite products are available over Indian monsoon region from a variety of sources. Popular products like TRMM TMPA3B42 (RT and V7), GsMaP, CPC/RFE, GPCP and GPM are available to end users in various space/time scales for applications and model validation. In this study, we show the representation and skill of monsoon rainfall from a variety of multi-satellite products over the Indian region. The bias and skill of multi-satellite rainfall are evaluated against gauge based observations. It was found that the TRMM based TMPA was one of the best dataset for Indian monsoon region. Attempt is made to compare the latest GPM based data with other products. The GPM based rainfall product is seen to be superior compared to TRMM.

  18. Wind stress, curl and vertical velocity in the Bay of Bengal during southwest monsoon, 1984

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, M.T.; Heblekar, A.K.; Murty, C.S.

    Wind distribution observed during southwest monsoon of 1984 has used to derive the mean wind stress for the season at every 1 degree square grid and curl over the Bay of Bengal. Two regions of maximum wind stress are present over the Bay of Bengal...

  19. Impacts of the East Asian Monsoon on springtime dust concentrations over China: IMPACTS OF MONSOON ON DUST

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Sijia [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Russell, Lynn M. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Yang, Yang [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Xu, Li [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Lamjiri, Maryam A. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; DeFlorio, Michael J. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Miller, Arthur J. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Ghan, Steven J. [Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Liu, Ying [Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Singh, Balwinder [Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA

    2016-07-12

    We use 150 year preindustrial simulations of the Community Earth System Model to quantify the impacts of the East Asian Monsoon strength on interannual variations of springtime dust concentrations over China. The simulated interannual variations in March-April-May (MAM) dust column concentrations range between 20–40% and 10–60% over eastern and western China, respectively. The dust concentrations over eastern China correlate negatively with the East Asian Monsoon (EAM) index, which represents the strength of monsoon, with a regionally averaged correlation coefficient of 0.64. Relative to the strongest EAM years, MAMdust concentrations in the weakest EAM years are higher over China, with regional relative differences of 55.6%, 29.6%, and 13.9% in the run with emissions calculated interactively and of 33.8%, 10.3%, and 8.2% over eastern, central, and western China, respectively, in the run with prescribed emissions. Both interactive run and prescribed emission run show the similar pattern of climate change between the weakest and strongest EAM years. Strong anomalous northwesterly and westerly winds over the Gobi and Taklamakan deserts during the weakest EAM years result in larger transport fluxes, and thereby increase the dust concentrations over China. These differences in dust concentrations between the weakest and strongest EAM years (weakest-strongest) lead to the change in the net radiative forcing by up to 8 and 3Wm2 at the surface, compared to 2.4 and +1.2Wm2 at the top of the atmosphere over eastern and western China, respectively.

  20. Gender dimensions of Viet Nam's comprehensive macroeconomic and structural reform policies

    OpenAIRE

    Packard, Le Anh Tu

    2006-01-01

    From a gender perspective, Viet Nam is an interesting case study because it is widely seen as a 'globalization' success story where historically the social and political status of women have been high compared with women's status in many other developing countries. At the same time, there is concern that women's status may be eroding during the country's rapid transition to a market economy. Thus, it is of interest to examine the relationship between gender equality and economic performance, ...

  1. Player or referee? Aid effectiveness and the governance of health policy development: Lessons from Viet Nam.

    Science.gov (United States)

    Dodd, Rebecca; Olivé, Jean-Marc

    2011-01-01

    Viet Nam is one of the brightest stars in the constellation of developing countries. Its remarkable achievements in reducing poverty and improving health and education outcomes are well known, and as a result it has enjoyed generous aid programmes. Viet Nam also has a reputation for taking a strong lead in disciplining its donors and pushing for more efficient and effective forms of aid delivery, both at home and internationally. This article discusses how efforts to improve the effectiveness of aid intersect with policy-making processes in the health sector. It presents a quantitative review of health aid flows in Viet Nam and a qualitative analysis of the aid environment using event analysis, participant observation and key informant interviews. The analysis reveals a complex and dynamic web of incentives influencing the implementation of the aid effectiveness agenda in the health sector. There are contradictory forces within the Ministry of Health, within government as a whole, within the donor community and between donors and government. Analytical frameworks drawn from the study of policy networks and governance can help explain these tensions. They suggest that governance of health aid in Viet Nam is characterised by multiple, overlapping 'policy networks' which cut across the traditional donor-government divide. The principles of aid effectiveness make sense for some of these communities, but for others they are irrational and may lead to a loss of influence and resources. However, sustained engagement combined with the building of strategic coalitions can overcome individual and institutional incentives. This article suggests that aid reform efforts should be understood not as a technocratic agenda but as a political process with all the associated tensions, perverse incentives and challenges. Partners thus need to recognise - and find new ways of making sense of - the complexity of forces affecting aid delivery.

  2. Oseltamivir resistance among influenza viruses: surveillance in northern Viet Nam, 2009–2012

    Directory of Open Access Journals (Sweden)

    Nguyen Thi Kim Phuong

    2013-06-01

    Full Text Available Introduction: Antiviral resistance has been reported in seasonal influenza A viruses and avian influenza A(H5N1 viruses in Viet Nam, raising concerns about the efficacy of treatment. Methods: We analysed specimens from two sources during the period 2009–2012: influenza-positive samples from influenza-like illness patients at sentinel clinics in northern Viet Nam and isolates from patients with confirmed A(H5N1 infections. Pyrosequencing was used to detect mutations: H275Y [for A(H1N1 and A(H5N1], E119V [for A(H3N2] and I117V [for A(H5N1]. A neuraminidase inhibition assay was used to determine the Inhibitory Concentration 50 (IC50 values for all influenza A and B isolates. Results: There were 341 influenza A positive samples identified; influenza A(H1N1pdm09 was identified most frequently (n = 215. In 2009, oseltamivir resistance was observed in 100% (19 of 19 of seasonal A(H1N1 isolates and 1.4% (3/215 of A(H1N1pdm09 isolates. This H275Y mutation was not found in influenza subtypes A(H5N1 or A(H3N2 isolates. Discussion: In Viet Nam, seasonal and A(H5N1 influenza vaccines are not currently available; thus, effective treatment is required. The presence of oseltamivir-resistant viruses is therefore a concern. Active surveillance for oseltamivir resistance among influenza viruses circulating in Viet Nam should be continued.

  3. Reappraisal of Asian Summer Monsoon Indices and the Long-Term Variation of Monsoon

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Webster and Yang monsoon index (WYI)-the zonal wind shear between 850 and 200 hPa was calculated and modified on the basis of NCEP/NCAR reanalysis data. After analyzing the circulation and divergence fields of 150-100 and 200 hPa, however, we found that the 200-hPa level could not reflect the real change of the upper-tropospheric circulation of Asian summer monsoon, especially the characteristics and variation of the tropical easterly jet which is the most important feature of the upper-tropospheric circulation. The zonal wind shear U850-U(150+100) is much larger than U850-U200, and thus it can reflect the strength of monsoon more appropriately. In addition, divergence is the largest at 150 hPa rather than 200 hPa, so 150 hPa in the upper-troposphere can reflect the coupling of the monsoon system. Therefore,WYI is redefined as DHI, i.e., IDH=U*850 - U*(150+100), which is able to characterize the variability of not only the intensity of the center of zonal wind shear in Asia, but also the monsoon system in the upper and lower troposphere. DHI is superior to WYI in featuring the long-term variation of Asian summer monsoon as it indicates there is obvious interdecadal variation in the Asian summer monsoon and the climate abrupt change occurred in 1980. The Asian summer monsoon was stronger before 1980 and it weakened after then due to the weakening of the easterly in the layer of 150-100 hPa, while easterly at 200 hPa did not weaken significantly. After the climate jump year in general, easterly in the upper troposphere weakened in Asia, indicating the weakening of summer monsoon; the land-sea pressure difference and thermal difference reduced, resulting in the weakening of monsoon; the corresponding upper divergence as well as the water vapor transport decreased in Indian Peninsula, central Indo-China Peninsula, North China, and Northeast China, indicating the weakening of summer monsoon as well. The difference between NCEP/NCAR and ERA-40 reanalysis data in

  4. Historical perspectives on typhoons and tropical storms in the natural and socio-economic system of Nam Dinh (Vietnam)

    Science.gov (United States)

    Kleinen, John

    2007-02-01

    This contribution starts with a brief introduction of the effects of typhoons and tropical storms on Vietnam, focusing in particular on the coastal region of Nam Dinh, a province in the northern part of the country and part of the Red River Delta. The magnitude of damage caused by a natural disaster is not solely determined by the direct physical impact of the event, but also depends on the socio-economic and political circumstances that shape a person or a groups' daily life. Such conditions define where and how people live and work. An overview of the major events since the 19th century shows how important it is to study these events in historical perspective. This paper briefly considers various conceptualizations and definitions of vulnerability. It analyses the destruction caused by a natural disaster in terms of peoples' vulnerability in a deltaic region. A distinction is made between collective vulnerability and individual vulnerability, each leading to different levels of perception of the disaster. The levels overlap in the discussion because they are interwoven and dependent on one another.

  5. Identifying factors for job motivation of rural health workers in North Viet Nam.

    Science.gov (United States)

    Dieleman, Marjolein; Cuong, Pham Viet; Anh, Le Vu; Martineau, Tim

    2003-11-05

    BACKGROUND: In Viet Nam, most of the public health staff (84%) currently works in rural areas, where 80% of the people live. To provide good quality health care services, it is important to develop strategies influencing staff motivation for better performance. METHOD: An exploratory qualitative research was carried out among health workers in two provinces in North Viet Nam so as to identify entry points for developing strategies that improve staff performance in rural areas. The study aimed to determine the major motivating factors and it is the first in Viet Nam that looks at health workers' job perception and motivation. Apart from health workers, managers at national and at provincial level were interviewed as well as some community representatives. RESULTS: The study showed that motivation is influenced by both financial and non-financial incentives. The main motivating factors for health workers were appreciation by managers, colleagues and the community, a stable job and income and training. The main discouraging factors were related to low salaries and difficult working conditions. CONCLUSION: Activities associated with appreciation such as performance management are currently not optimally implemented, as health workers perceive supervision as control, selection for training as unclear and unequal, and performance appraisal as not useful. The kind of non-financial incentives identified should be taken into consideration when developing HRM strategies. Areas for further studies are identified.

  6. Identifying factors for job motivation of rural health workers in North Viet Nam

    Directory of Open Access Journals (Sweden)

    Anh Le

    2003-11-01

    Full Text Available Abstract Background In Viet Nam, most of the public health staff (84% currently works in rural areas, where 80% of the people live. To provide good quality health care services, it is important to develop strategies influencing staff motivation for better performance. Method An exploratory qualitative research was carried out among health workers in two provinces in North Viet Nam so as to identify entry points for developing strategies that improve staff performance in rural areas. The study aimed to determine the major motivating factors and it is the first in Viet Nam that looks at health workers' job perception and motivation. Apart from health workers, managers at national and at provincial level were interviewed as well as some community representatives. Results The study showed that motivation is influenced by both financial and non-financial incentives. The main motivating factors for health workers were appreciation by managers, colleagues and the community, a stable job and income and training. The main discouraging factors were related to low salaries and difficult working conditions. Conclusion Activities associated with appreciation such as performance management are currently not optimally implemented, as health workers perceive supervision as control, selection for training as unclear and unequal, and performance appraisal as not useful. The kind of non-financial incentives identified should be taken into consideration when developing HRM strategies. Areas for further studies are identified.

  7. Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

    Directory of Open Access Journals (Sweden)

    G. H. Miller

    2007-08-01

    Full Text Available The moisture balance across northern and central Australia is dominated by changes in the strength of the Australian Summer Monsoon. Lake-level records that record changes in monsoon strength on orbital timescales are most consistent with a Northern Hemisphere insolation control on monsoon strength, a result consistent with recent modeling studies. A weak Holocene monsoon relative to monsoon strength 65–60 ka, despite stronger forcing, suggests a changed monsoon regime after 60 ka. Shortly after 60 ka humans colonized Australia and all of Australia's largest mammals became extinct. Between 60 and 40 ka Australian climate was similar to present and not changing rapidly. Consequently, attention has turned toward plausible human mechanisms for the extinction, with proponents for over-hunting, ecosystem change, and introduced disease. To differentiate between these options we utilize isotopic tracers of diet preserved in eggshells of two large, flightless birds to track the status of ecosystems before and after human colonization. More than 800 dated eggshells of the Australian emu (Dromaius novaehollandiae, an opportunistic, dominantly herbivorous feeder, provide a 140-kyr dietary reconstruction that reveals unprecedented reduction in the bird's food resources about 50 ka, coeval in three distant regions. These data suggest a tree/shrub savannah with occasionally rich grasslands was converted abruptly to the modern desert scrub. The diet of the heavier, extinct Genyornis newtoni, derived from >550 dated eggshells, was more restricted than in co-existing Dromaius, implying a more specialized feeding strategy. We suggest that generalist feeders, such as Dromaius, were able to adapt to a changed vegetation regime, whereas more specialized feeders, such as Genyornis, became extinct. We speculate that ecosystem collapse across arid and semi-arid zones was a consequence of systematic burning by early humans

  8. Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

    Science.gov (United States)

    Miller, G. H.; Magee, J. W.; Fogel, M. L.; Gagan, M. K.

    2007-08-01

    The moisture balance across northern and central Australia is dominated by changes in the strength of the Australian Summer Monsoon. Lake-level records that record changes in monsoon strength on orbital timescales are most consistent with a Northern Hemisphere insolation control on monsoon strength, a result consistent with recent modeling studies. A weak Holocene monsoon relative to monsoon strength 65-60 ka, despite stronger forcing, suggests a changed monsoon regime after 60 ka. Shortly after 60 ka humans colonized Australia and all of Australia's largest mammals became extinct. Between 60 and 40 ka Australian climate was similar to present and not changing rapidly. Consequently, attention has turned toward plausible human mechanisms for the extinction, with proponents for over-hunting, ecosystem change, and introduced disease. To differentiate between these options we utilize isotopic tracers of diet preserved in eggshells of two large, flightless birds to track the status of ecosystems before and after human colonization. More than 800 dated eggshells of the Australian emu (Dromaius novaehollandiae), an opportunistic, dominantly herbivorous feeder, provide a 140-kyr dietary reconstruction that reveals unprecedented reduction in the bird's food resources about 50 ka, coeval in three distant regions. These data suggest a tree/shrub savannah with occasionally rich grasslands was converted abruptly to the modern desert scrub. The diet of the heavier, extinct Genyornis newtoni, derived from >550 dated eggshells, was more restricted than in co-existing Dromaius, implying a more specialized feeding strategy. We suggest that generalist feeders, such as Dromaius, were able to adapt to a changed vegetation regime, whereas more specialized feeders, such as Genyornis, became extinct. We speculate that ecosystem collapse across arid and semi-arid zones was a consequence of systematic burning by early humans. We also suggest that altered climate feedbacks linked to changes

  9. Extended Range Prediction of Indian Summer Monsoon: Current status

    Science.gov (United States)

    Sahai, A. K.; Abhilash, S.; Borah, N.; Joseph, S.; Chattopadhyay, R.; S, S.; Rajeevan, M.; Mandal, R.; Dey, A.

    2014-12-01

    The main focus of this study is to develop forecast consensus in the extended range prediction (ERP) of monsoon Intraseasonal oscillations using a suit of different variants of Climate Forecast system (CFS) model. In this CFS based Grand MME prediction system (CGMME), the ensemble members are generated by perturbing the initial condition and using different configurations of CFSv2. This is to address the role of different physical mechanisms known to have control on the error growth in the ERP in the 15-20 day time scale. The final formulation of CGMME is based on 21 ensembles of the standalone Global Forecast System (GFS) forced with bias corrected forecasted SST from CFS, 11 low resolution CFST126 and 11 high resolution CFST382. Thus, we develop the multi-model consensus forecast for the ERP of Indian summer monsoon (ISM) using a suite of different variants of CFS model. This coordinated international effort lead towards the development of specific tailor made regional forecast products over Indian region. Skill of deterministic and probabilistic categorical rainfall forecast as well the verification of large-scale low frequency monsoon intraseasonal oscillations has been carried out using hindcast from 2001-2012 during the monsoon season in which all models are initialized at every five days starting from 16May to 28 September. The skill of deterministic forecast from CGMME is better than the best participating single model ensemble configuration (SME). The CGMME approach is believed to quantify the uncertainty in both initial conditions and model formulation. Main improvement is attained in probabilistic forecast which is because of an increase in the ensemble spread, thereby reducing the error due to over-confident ensembles in a single model configuration. For probabilistic forecast, three tercile ranges are determined by ranking method based on the percentage of ensemble members from all the participating models falls in those three categories. CGMME further

  10. A new centennial index to study the Western North Pacific Monsoon decadal variability

    Science.gov (United States)

    Vega, Inmaculada; Gómez-Delgado, F. de Paula; Gallego, David; Ribera, Pedro; Peña-Ortiz, Cristina; García-Herrera, Ricardo

    2016-04-01

    The concept of the Western North Pacific Summer Monsoon (WNPSM) appeared for the first time in 1987. It is, unlike the Indian Summer Monsoon (ISM) and the East Asian summer monsoon (EASM), an oceanic monsoon mostly driven by the meridional gradient of sea surface temperature. Its circulation is characterized by a northwest-southeast oriented monsoon trough with intense precipitation and low-level southwesterlies and upper-tropospheric easterlies in the region [100°-130° E, 5°-15°N]. Up to now, the primary index to characterize the WNPSM has been the Western North Pacific Monsoon Index (WNPMI) which covers the 1949-2013 period. The original WNPMI was defined as the difference of 850-hPa westerlies between two regions: D1 [5°-15°N, 100°-130°E] and D2 [20°-30°N, 110°-140°E]. Both domains are included in the main historical ship routes circumnavigating Asia for hundreds of years. Many of the logbooks of these ships have been preserved in historical archives and they usually contain daily observations of wind force and direction. Therefore, it has been possible to compute a new index of instrumental character, which reconstructs the WNPSM back to the middle of the 19th Century, by using solely historical wind direction records preserved in logbooks. We define the monthly Western North Pacific Directional Index (WNPDI) as the sum of the persistence of the low-level westerly winds in D1 and easterly winds in D2. The advantages of this new index are its nature (instrumental) and its length (1849-2013), which is 100 years longer than the WNPMI (which was based on reanalysis data). Our WNPDI shows a high correlation (r=+0.87, pCompetitividad through the project INCITE (CGL2013-44530-P, BES-2014-069733).

  11. Impact of irrigation on the South Asian summer monsoon

    Science.gov (United States)

    Saeed, Fahad; Hagemann, Stefan; Jacob, Daniela

    2009-10-01

    The Indian subcontinent is one of the most intensely irrigated regions of the world and state of the art climate models do not account for the representation of irrigation. Sensitivity studies with the regional climate model REMO show distinct feedbacks between the simulation of the monsoon circulation with and without irrigation processes. We find that the temperature and mean sea level pressure, where the standard REMO version without irrigation shows a significant bias over the areas of Indus basin, is highly sensitive to the water used for irrigation. In our sensitivity test we find that removal of this bias has caused less differential heating between land and sea masses. This in turns reduces the westerlies entering into land from Arabian Sea, hence creating conditions favorable for currents from Bay of Bengal to intrude deep into western India and Pakistan that have been unrealistically suppressed before. We conclude that the representation of irrigated water is unavoidable for realistic simulation of south Asian summer monsoon and its response under global warming.

  12. Evidence for signiifcant climate impacts in monsoonal Asia at 8.2 ka from multiple proxies and model simulations

    Institute of Scientific and Technical Information of China (English)

    MORRILL Carrie; WAGNER Amy J; OTTO-BLIESNER Bette L; ROSENBLOOM Nan

    2011-01-01

    Given the likelihood of future reductions in the strength of the Atlantic Meridional Overturning Circulation (AMOC), it is important to document how changes in the AMOC have altered climate patterns in the past and to assess the skill of coupled climate models in reproducing these teleconnections. Of past abrupt changes in the AMOC, the 8.2 ka event provides a particularly useful case study because its duration, magnitude of AMOC reduction and background climate state are closest to conditions expected in the future. In this research, we present an expanded proxy synthesis of the 8.2 ka event in monsoonal Asia, including new high-resolution lake and bog records, more sites from the East Asia monsoon region and proxies of winter monsoon strength. We compare proxy evidence with a new simulation of the 8.2 ka event using the Community Climate System Model version 3 (CCSM3) and prescribing North Atlantic freshwater forcing according to the latest reconstructions. We ifnd clear and objectively-determined evidence for 8.2 ka climate anomalies at nearly all of the fourteen proxy sites, emphasizing the strong and widespread impacts of the event in monsoonal Asia during both summer and winter seasons. The model simulation corroborates that these anomalies, described generally as a weakening of the summer monsoon and strengthening of the winter monsoon, were likely caused by a reduction of the AMOC. Examination of regional anomalies in East Asia reveals some spatial heterogeneity, however, that in the model simulation is caused by contraction of the seasonal migration of the subtropical monsoon front. The duration of climate anomalies at 8.2 ka in monsoonal Asia, both in proxy records and the model simulation, generally matches the duration of the event in Greenland ice core δ18O, further supporting a tight connection to the North Atlantic.

  13. Towards understanding the unusual Indian monsoon in 2009

    Indian Academy of Sciences (India)

    P A Francis; Sulochana Gadgil

    2010-08-01

    The Indian summer monsoon season of 2009 commenced with a massive deficit in all-India rainfallof 48% of the average rainfall in June. The all-India rainfall in July was close to the normal but that in August was deficit by 27%. In this paper, we first focus on June 2009, elucidating the special features and attempting to identify the factors that could have led to the large deficit in rainfall. In June 2009, the phase of the two important modes, viz., El Niño and Southern Oscillation (ENSO) and the equatorial Indian Ocean Oscillation (EQUINOO) was unfavourable. Also, the eastern equatorial Indian Ocean (EEIO) was warmer than in other years and much warmer than the Bay. In almost all the years, the opposite is true, i.e., the Bay is warmer than EEIO in June. It appears that this SST gradient gave an edge to the tropical convergence zone over the eastern equatorial Indian Ocean, in competition with the organized convection over the Bay. Thus, convection was not sustained for more than three or four days over the Bay and no northward propagations occurred. We suggest that the reversal of the sea surface temperature (SST) gradient between the Bay of Bengal and EEIO, played a critical role in the rainfall deficit over the Bay and hence the Indian region. We also suggest that suppression of convection over EEIO in association with the El Niño led to a positive phase of EQUINOO in July and hence revival of the monsoon despite the El Niño. It appears that the transition to a negative phase of EQUINOO in August and the associated large deficit in monsoon rainfall can also be attributed to the El Niño.

  14. Response of Asian Summer Monsoon to CO2 Doubling

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jian; LIU Qinyu; HUANG Fei

    2011-01-01

    Based on simulations of the IPCC 20C3M and SRES A1B experiments in ten coupled models,the Asian summer monsoon (ASM) response to CO2 doubling and the different responses among models are examined.Nine models show the similar results that the weakening of land-ocean thermal contrast caused by the CO2 doubling contributes to a weaker large-scale ASM circulation.Further analysis in this study also shows that the major ASM components,such as the Somali cross-equatorial flow,the low level India-South China Sea monsoon trough,and the upper level tropical easterly jet stream,weaken as CO2 doubles.However,the ASM rainfall increases as a result of the increased moisture from the warmer Indian Ocean and the South China Sea,and the enhanced northward moisture transport over the ASM region.For the response of enhanced northward moisture transport over South Asia,the positive contribution of moisture content increase in the Indian Ocean is dominant and the negative contribution of the weaker monsoon circulation is secondary at 850 hPa,but both have positive contribution to the total moisture transport along the East China coast.The paradox of the weaker ASM circulation and the increasing precipitation in CO2 doubling is confirmed.It is found that strengthening of northward moisture transport could intensify the precipitation and atmospheric heat source over the north Arabian Sea and East China,and result in enhanced southwesterly at 850hPa as global warming occurs.All ten models show significant enhanced southwesterly response over the north Arabian Sea,and six of them show enhanced southwesterly response along the East China coast.

  15. Three million years of monsoon variability over the northern Sahara

    Energy Technology Data Exchange (ETDEWEB)

    Larrasoana, J.C.; Roberts, A.P.; Rohling, E.J.; Winklhofer, M. [School of Ocean and Earth Science, Southampton Oceanography Centre, University of Southampton, European Way, Southampton SO14 3ZH (United Kingdom); Wehausen, R. [Institut fuer Chemie und Biologie des Meeres (ICBM), Carl-von-Ossietzky-Universitaet, 26111, Oldenburg (Germany)

    2003-12-01

    We present a 3 million year record of aeolian dust supply into the eastern Mediterranean Sea, based on hematite contents derived from magnetic properties of sediments from Ocean Drilling Program Site 967. Our record has an average temporal resolution of {proportional_to}400 years. Geochemical data validate this record of hematite content as a proxy for the supply of aeolian dust from the Sahara. We deduce that the aeolian hematite in eastern Mediterranean sediments derives from the eastern Algerian, Libyan, and western Egyptian lowlands located north of the central Saharan watershed ({proportional_to}21 N). In corroboration of earlier work, we relate dust flux minima to penetration of the African summer monsoon front to the north of the central Saharan watershed. This would have enhanced soil humidity and vegetation cover in the source regions, in agreement with results from ''green Sahara'' climate models. Our results indicate that this northward monsoon penetration recurred during insolation maxima throughout the last 3 million years. As would be expected, this orbital precession-scale mechanism is modulated on both short ({proportional_to}100-kyr) and long ({proportional_to}400-kyr) eccentricity time scales. We also observe a strong expression of the {proportional_to}41-kyr (obliquity) cycle, which we discuss in terms of high- and low-latitude mechanisms that involve Southern Hemisphere meridional temperature contrasts and shifts in the latitudes of the tropics, respectively. We also observe a marked increase in sub-Milankovitch variability around the mid-Pleistocene transition ({proportional_to}0.95 Ma), which suggests a link between millennial-scale climate variability, including monsoon dynamics, and the size of northern hemisphere ice sheets. (orig.)

  16. Dynamics of Tropical Waves and Monsoons.

    Science.gov (United States)

    1981-04-01

    large-scale rainband in the Baum season. J Vet’,’,r 1o,. large-scale baroclinic forcing. Japon . 52. 448-451. -72 953 MONTHLY % EATHInR REVIEV% V L l 08...monsoon circulation large orographic structures such as the Himalavas. tan importance emanating from the social -economi- and 4) the perturbation of

  17. Warm Indian Ocean, Weak Asian Monsoon

    Science.gov (United States)

    Koll Roxy, Mathew; Ritika, Kapoor; Terray, Pascal; Murtugudde, Raghu; Ashok, Karumuri; Nath Goswami, Buphendra

    2015-04-01

    There are large uncertainties looming over the status and fate of the South Asian monsoon in a changing climate. Observations and climate models have suggested that anthropogenic warming in the past century has increased the moisture availability and the land-sea thermal contrast in the tropics, favoring an increase in monsoon rainfall. In contrast, we notice that South Asian subcontinent experienced a relatively subdued warming during this period. At the same time, the tropical Indian Ocean experienced a nearly monotonic warming, at a rate faster than the other tropical oceans. Using long-term observations and coupled model experiments, we suggest that the enhanced Indian Ocean warming along with the suppressed warming of the subcontinent weaken the land-sea thermal contrast throughout the troposphere, dampen the monsoon Hadley circulation, and reduce the rainfall over South Asia. As a result, the summer monsoon rainfall during 1901-2012 shows a significant weakening trend over South Asia, extending from Pakistan through central India to Bangladesh.

  18. Planetary Boundary Layer Patterns, Height Variability and their Controls over the Indian Subcontinent with respect to Monsoon

    Science.gov (United States)

    Sathyanadh, A.; Karipot, A.; Prabhakaran, T.

    2016-12-01

    Planetary boundary layer (PBL) height and its controlling factors undergo large variations at different spatio-temporal scales over land regions. In the present study, Modern Era Retrospective analysis for Research and Applications (MERRA) data products are used to investigate variations of PBL height and its controls in relation to different phases of Indian monsoon. MERRA PBL height validations carried out against those estimated from radiosonde and Global Positioning System Radio Occultation atmospheric profiles revealed fairly good agreement. Different PBL patterns are identified in terms of maximum height, its time of occurrence and growth rate, and they vary with respect to geographical locations, terrain characteristics and monsoon circulation. The pre-monsoon boundary layers are the deepest over the region, often exceeding 4 km and grow at a rate of approximately 400 m hr-1. Large nocturnal BL depths, possibly related to weakly convective residual layers, are another feature noted during dry conditions. Monsoon BLs are generally shallower, except where rainfall is scanty. The break-monsoon periods have slightly deeper BLs than the active monsoon phase. The controlling factors for the observed boundary layer behaviour are investigated using supplementary MERRA datasets. Evaporative fraction is found to have dominant control on the PBL height varying with seasons and regions. The characteristics and controls of wet and dry boundary layer regimes over inland and coastal locations are different. The fractional diffusion (ratio of non-local and total diffusion) coefficient analyses indicated that enhanced entrainment during monsoon contributes to reduction in PBLH unlike in the dry period. The relationship between controls and PBLH are better defined over inland than coastal regions. The wavelet cross spectral analysis revealed temporal variations in dominant contributions from the controlling factors at different periodicities during the course of the year.

  19. Observed and Forecasted Intraseasonal Activity of Southwest Monsoon Rainfall over India During 2010, 2011 and 2012

    Science.gov (United States)

    Pattanaik, D. R.; Rathore, L. S.; Kumar, Arun

    2013-12-01

    The monsoon seasons of 2010 and 2011, with almost identical seasonal total rainfall over India from June to September, are associated with slightly different patterns of intraseasonal rainfall fluctuations. Similarly, the year 2012, with relatively less rainfall compared to 2010 and 2011, also witnessed different intraseasonal rainfall fluctuations, leading to drought-like situations over some parts of the country. The present article discusses the forecasting aspect of monsoon activity over India during these 3 years on an extended range time scale (up to 3 weeks) by using the multimodel ensemble (MME), based on operational coupled model outputs from the ECMWF monthly forecasting system and the NCEP's Climate Forecast System (CFS). The average correlation coefficient (CC) of weekly observed all-India rainfall (AIR) and the corresponding MME forecast AIR is found to be significant, above the 98 % level up to 2 weeks (up to 18 days) with a slight positive CC for the week 3 (days 19-25) forecast. However, like the variation of observed intraseasonal rainfall fluctuations during 2010, 2011 and 2012 monsoon seasons, the MME forecast skills of weekly AIR are also found to be different from one another, with the 2012 monsoon season indicating significant CC (above 99 % level) up to week 2 (12-18 days), and also a comparatively higher CC (0.45) during the week 3 forecast (days 19-25). The average CC between observed and forecasted weekly AIR rainfall over four homogeneous regions of India is found to be the lowest over the southern peninsula of India (SPI), and northeast India (NEI) is found to be significant only for the week 1 (days 5-11) forecast. However, the CC is found to be significant over northwest India (NWI) and central India (CEI), at least above the 90 % level up to 18 days, with NWI having slightly better skill compared to the CEI. For the individual monsoon seasons of 2010, 2011 and 2012, there is some variation in CC and other skill scores over the four

  20. Linking hemispheric radiation budgets, ITCZ shifts, and monsoons

    Science.gov (United States)

    McGee, D.; Donohoe, A.; Marshall, J.; Ferreira, D.

    2014-12-01

    We explore the relationship between the Intertropical Convergence Zone (ITCZ), hemispheric heat budgets, and monsoon strength in past climates. Modern seasonal and interannual variability in the globally-averaged position of the ITCZ (as estimated by the tropical precipitation centroid) reflects the interhemispheric heat balance, with the ITCZ's displacement toward the warmer hemisphere directly proportional to atmospheric heat transport into the cooler hemisphere. Model simulations suggest that ITCZ shifts are likely to have obeyed the same relationship with interhemispheric heat transport in response to past changes in orbital parameters, ice sheets, and ocean circulation. This relationship implies that even small (±1 degree) shifts in the mean (annually and zonally averaged) ITCZ require large changes in hemispheric heat budgets, placing tight bounds on mean ITCZ shifts in past climates. To test this energetic argument, we use the observed relationship between mean ITCZ position and tropical sea surface temperature (SST) gradients in combination with proxy-based estimates of past SST gradients to show that mean ITCZ shifts for the mid-Holocene, Heinrich Stadial 1 and Last Glacial Maximum are not likely to have been more than 1 degree latitude from its present mean position. In exploring these results, we provide brief descriptions of the estimated radiation budgets of past climates that help demonstrate how different climate forcings change the interhemispheric heat balance and thus the ITCZ's global-mean position. We also address the seeming inconsistency between the small ITCZ shifts indicated by energetic constraints and the large changes in monsoon rainfall suggested by proxy data. We compare global-average and regional-scale tropical precipitation in observations and explore their responses to a variety of forcings (orbital changes, ice sheets, hosing) in models. These comparisons make clear that monsoon precipitation can change substantially even in the

  1. The global monsoon division combining the k-means clustering method and low-level cross-equatorial flow

    Science.gov (United States)

    Jiang, Ning; Qian, Weihong; Leung, Jeremy Cheuk-Hin

    2016-10-01

    The global monsoon domain has been recently determined utilizing two criteria: difference of local maximum and minimum pentad-mean precipitation rates exceeding 4 mm day-1, and wind reversal of low-level cross-equatorial flow. In this paper, 22 major dry-wet alteration regions under six categories were first derived through the k-means clustering method from the climatological evolution of global precipitation. Considering the seasonal influences of the low-level cross-equatorial flow in these major dry-wet alternation regions, the global monsoon was objectively divided into 16 major regions under five climatological precipitation categories. Nine monsoon regions are distributed between Asia and Australia while four regions are from Africa to the Southwest Indian Ocean and three regions in Americas. Precipitation trends during rainy seasons of 1981-2010 were examined in the 16 monsoon regions. Four regions with decreasing trends of precipitation are located in Africa and the Southwest Indian Ocean while three regions with increasing trends are situated in Americas. Six regions of increasing precipitation trends are concentrated in Asia and the biggest increasing trend is found in south China.

  2. Daily atmospheric variability in the South American monsoon system

    Energy Technology Data Exchange (ETDEWEB)

    Krishnamurthy, V. [Institute of Global Environment and Society (IGES), Center for Ocean-Land-Atmosphere Studies (COLA), Calverton, MD (United States); George Mason University, Department of Atmospheric, Oceanic and Earth Sciences, Fairfax, VA (United States); Misra, Vasubandhu [Florida State University, Department of Meteorology and Center for Ocean-Atmospheric Prediction Studies, Tallahassee, FL (United States)

    2011-08-15

    The space-time structure of the daily atmospheric variability in the South American monsoon system has been studied using multichannel singular spectrum analysis of daily outgoing longwave radiation. The three leading eigenmodes are found to have low-frequency variability while four other modes form higher frequency oscillations. The first mode has the same time variability as that of El Nino-Southern Oscillation (ENSO) and exhibits strong correlation with the Pacific sea surface temperature (SST). The second mode varies on a decadal time scale with significant correlation with the Atlantic SST suggesting an association with the Atlantic multidecadal oscillation (AMO). The third mode also has decadal variability but shows an association with the SST of the Pacific decadal oscillation (PDO). The fourth and fifth modes describe an oscillation that has a period of about 165 days and is associated with the North Atlantic oscillation (NAO). The sixth and seventh modes describe an intraseasonal oscillation with a period of 52 days which shows strong relation with the Madden-Julian oscillation. There exists an important difference in the variability of convection between Amazon River Basin (ARB) and central-east South America (CESA). Both regions have similar variations due to ENSO though with higher magnitude in ARB. The AMO-related mode has almost identical variations in the two regions, whereas the PDO-related mode has opposite variations. The interseasonal NAO-related mode also has variations of opposite sign with comparable magnitudes in the two regions. The intraseasonal variability over the CESA is robust while it is very weak over the ARB region. The relative contributions from the low-frequency modes mainly determine the interannual variability of the seasonal mean monsoon although the interseasonal oscillation may contribute in a subtle way during certain years. The intraseasonal variability does not seem to influence the interannual variability in either region

  3. Study of snow-monsoon relationship and changes in rainfall and temperature characteristics in India

    Science.gov (United States)

    Mamgain, Ashu

    In the recent past, there are indications of changes in the surface air temperature, extreme weather events, snow and Indian summer monsoon. This thesis analyses the above weather phenomena based on observed data and climate model simulations for the present as well as the near future. Earlier studies show a strong negative relationship between Eurasian snow cover/depth and Indian summer monsoon rainfall. Limitations of such studies are that both the parameters snow and rainfall were seasonally averaged over large areas. Indian summer monsoon has its own characteristics of evolution such as onset, active, break and withdrawal phases which have been studied extensively. However, the evolution of Eurasian snow is yet to be examined. Further, it is interesting to explore the characteristics of evolution of snow over the different regions of Eurasia and their relationship with the evolution characteristics of summer monsoon. In this thesis, a detailed examination has been done on the starting and the ending dates of snowfall over different regions of Eurasia and attempts have been made to explore any relationship with onset of Indian summer monsoon. It is observed that the regions where snowfall starts early, it ends late. Further, in those regions maximum snow depth also occurs late. In some years, more snowfall in East Eurasia is followed by less snowfall in West Eurasia. Also snow depths particularly in the northernmost and southwest regions of East Eurasia are opposite in phase. The results of this study indicate a weak relationship between snow starting dates in Eurasia and summer monsoon onset dates in the Kerala coast. However, the relationship between the northernmost Eurasian snow depth and the summer monsoon precipitation in the Peninsular India is significant. Today, regional weather/climate models are increasingly used to study several atmospheric phenomena. The Regional Climate Model, RegCM3 has been successfully integrated to simulate the salient features

  4. Model Interpretation of Climate Signals: Application to the Asian Monsoon Climate

    Science.gov (United States)

    Lau, William K. M.

    2002-01-01

    This is an invited review paper intended to be published as a Chapter in a book entitled "The Global Climate System: Patterns, Processes and Teleconnections" Cambridge University Press. The author begins with an introduction followed by a primer of climate models, including a description of various modeling strategies and methodologies used for climate diagnostics and predictability studies. Results from the CLIVAR Monsoon Model Intercomparison Project (MMIP) were used to illustrate the application of the strategies to modeling the Asian monsoon. It is shown that state-of-the art atmospheric GCMs have reasonable capability in simulating the seasonal mean large scale monsoon circulation, and response to El Nino. However, most models fail to capture the climatological as well as interannual anomalies of regional scale features of the Asian monsoon. These include in general over-estimating the intensity and/or misplacing the locations of the monsoon convection over the Bay of Bengal, and the zones of heavy rainfall near steep topography of the Indian subcontinent, Indonesia, and Indo-China and the Philippines. The intensity of convection in the equatorial Indian Ocean is generally weaker in models compared to observations. Most important, an endemic problem in all models is the weakness and the lack of definition of the Mei-yu rainbelt of the East Asia, in particular the part of the Mei-yu rainbelt over the East China Sea and southern Japan are under-represented. All models seem to possess certain amount of intraseasonal variability, but the monsoon transitions, such as the onset and breaks are less defined compared with the observed. Evidences are provided that a better simulation of the annual cycle and intraseasonal variability is a pre-requisite for better simulation and better prediction of interannual anomalies.

  5. From monsoon to marine productivity in the Arabian Sea: insights from glacial and interglacial climates

    Science.gov (United States)

    Le Mézo, Priscilla; Beaufort, Luc; Bopp, Laurent; Braconnot, Pascale; Kageyama, Masa

    2017-07-01

    The current-climate Indian monsoon is known to boost biological productivity in the Arabian Sea. This paradigm has been extensively used to reconstruct past monsoon variability from palaeo-proxies indicative of changes in surface productivity. Here, we test this paradigm by simulating changes in marine primary productivity for eight contrasted climates from the last glacial-interglacial cycle. We show that there is no straightforward correlation between boreal summer productivity of the Arabian Sea and summer monsoon strength across the different simulated climates. Locally, productivity is fuelled by nutrient supply driven by Ekman dynamics. Upward transport of nutrients is modulated by a combination of alongshore wind stress intensity, which drives coastal upwelling, and by a positive wind stress curl to the west of the jet axis resulting in upward Ekman pumping. To the east of the jet axis there is however a strong downward Ekman pumping due to a negative wind stress curl. Consequently, changes in coastal alongshore stress and/or curl depend on both the jet intensity and position. The jet position is constrained by the Indian summer monsoon pattern, which in turn is influenced by the astronomical parameters and the ice sheet cover. The astronomical parameters are indeed shown to impact wind stress intensity in the Arabian Sea through large-scale changes in the meridional gradient of upper-tropospheric temperature. However, both the astronomical parameters and the ice sheets affect the pattern of wind stress curl through the position of the sea level depression barycentre over the monsoon region (20-150° W, 30° S-60° N). The combined changes in monsoon intensity and pattern lead to some higher glacial productivity during the summer season, in agreement with some palaeo-productivity reconstructions.

  6. Clay mineralogical and geochemical proxies of the East Asian summer monsoon evolution in the South China Sea during Late Quaternary