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Sample records for winter monsoon strength

  1. Winter/Summer Monsoon Experiment

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Winter/Summer Monsoon Experiment (MONEX) was conducted during the First Global GARP (Global Atmospheric Research Program) Experiment (FGGE). An international...

  2. Late Holocene anti-phase change in the East Asian summer and winter monsoons

    Science.gov (United States)

    Kang, Shugang; Wang, Xulong; Roberts, Helen M.; Duller, Geoff A. T.; Cheng, Peng; Lu, Yanchou; An, Zhisheng

    2018-05-01

    Changes in East Asian summer and winter monsoon intensity have played a pivotal role in the prosperity and decline of society in the past, and will be important for future climate scenarios. However, the phasing of changes in the intensity of East Asian summer and winter monsoons on millennial and centennial timescales during the Holocene is unclear, limiting our ability to understand the factors driving past and future changes in the monsoon system. Here, we present a high resolution (up to multidecadal) loess record for the last 3.3 ka from the southern Chinese Loess Plateau that clearly demonstrates the relationship between changes in the intensity of the East Asian summer and winter monsoons, particularly at multicentennial scales. At multimillennial scales, the East Asian summer monsoon shows a steady weakening, while the East Asian winter monsoon intensifies continuously. At multicentennial scales, a prominent ∼700-800 yr cycle in the East Asian summer and winter monsoon intensity is observed, and here too the two monsoons are anti-phase. We conclude that multimillennial changes are driven by Northern Hemisphere summer insolation, while multicentennial changes can be correlated with solar activity and changing strength of the Atlantic meridional overturning circulation.

  3. 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.

  4. Air pollution episodes associated with East Asian winter monsoons

    Energy Technology Data Exchange (ETDEWEB)

    Hien, P.D., E-mail: pdhien@gmail.com [Vietnam Atomic Energy Agency, 59 Ly Thuong Kiet str. Hanoi (Viet Nam); Loc, P.D.; Dao, N.V. [National Hydro-Meteorological Center, 62-A2 Nguyen Chi Thanh str. Hanoi (Viet Nam)

    2011-11-01

    A dozen multi-day pollution episodes occur from October to February in Hanoi, Vietnam due to prolonged anticyclonic conditions established after the northeast monsoon surges (cold surges). These winter pollution episodes (WPEs) account for most of the 24-h PM{sub 10} exceedances and the highest concentrations of gaseous pollutants in Hanoi. In this study, WPEs were investigated using continuous air quality monitoring data and information on upper-air soundings and air mass trajectories. The 24-h pollutant concentrations are lowest during cold surges; concurrently rise thereafter reaching the highest levels toward the middle of a monsoon cycle, then decline ahead of the next cold surge. Each monsoon cycle usually proceeds through a dry phase and a humid phase as Asiatic continental cold air arrives in Hanoi through inland China then via the East China Sea. WPEs are associated with nighttime radiation temperature inversions (NRTIs) in the dry phase and subsidence temperature inversions (STIs) in the humid phase. In NRTI periods, the rush hour pollution peak is more pronounced in the evening than in the morning and the pollution level is about two times higher at night than in daytime. In STI periods, broad morning and evening traffic peaks are observed and pollution is as high at night as in daytime. The close association between pollution and winter monsoon meteorology found in this study for the winter 2003-04 may serve as a basis for advance warning of WPEs and for forecasting the 24-h pollutant concentrations. - Highlights: {yields} Dozen pollution episodes from Oct. to Feb in Hanoi associated with anticyclones after monsoon surges. {yields} 24-h concentrations of PM{sub 10}, SO{sub 2}, NO{sub 2}, CO rise after surge and decline ahead of the next. {yields} Episodes caused by nighttime radiation and subsidence inversions in dry and humid monsoon phases. {yields} Distinct diurnal variations of pollutant concentrations observed in the two periods. {yields} Close

  5. Vertical distribution of mesozooplankton in the central and eastern Arabian Sea during the winter monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Padmavati, G.; Haridas, P.; Nair, K.K.C.; Gopalakrishnan, T.C.; Shiney, P.; Madhupratap, M.

    The vertical distribution of mesozooplankton in the central and eastern Arabian Sea was investigated during the winter monsoon in 1995. Samples were analysed from discrete depth zones defined according to oxygen and temperature profiles of the water...

  6. Wet scavenging of organic and elemental carbon during summer monsoon and winter monsoon seasons

    Science.gov (United States)

    Sonwani, S.; Kulshrestha, U. C.

    2017-12-01

    In the era of rapid industrialization and urbanization, atmospheric abundance of carbonaceous aerosols is increasing due to more and more fossil fuel consumption. Increasing levels of carbonaceous content have significant adverse effects on air quality, human health and climate. The present study was carried out at Delhi covering summer monsoon (July -Sept) and winter monsoon (Dec-Jan) seasons as wind and other meteorological factors affect chemical composition of precipitation in different manner. During the study, the rainwater and PM10 aerosols were collected in order to understand the scavenging process of elemental and organic carbon. The Rain water samples were collected on event basis. PM10 samples were collected before rain (PR), during rain (DR) and after rain (AR) during 2016-2017. The collected samples were analysed by the thermal-optical reflectance method using IMPROVE-A protocol. In PM10, the levels of organic carbon (OC) and its fractions (OC1, OC2, OC3 and OC4) were found significantly lower in the AR samples as compared to PR and DR samples. A significant positive correlation was noticed between scavenging ratios of organic carbon and rain intensity indicating an efficient wet removal of OC. In contrast to OCs, the levels of elemental carbon and its fractions (EC1, EC2, and EC3) in AR were not distinct during PR and DR. The elemental carbon showed very week correlation with rain intensity in Delhi region which could be explained on the basis of hydrophobic nature of freshly emitted carbon soot. The detailed results will be discussed during the conference.

  7. Variability of East Asian winter monsoon in Quaternary climatic extremes in North China.

    NARCIS (Netherlands)

    Lu, H.; van Huissteden, J.; Zhou, J.

    2000-01-01

    In order to examine high-frequency variations of East Asian winter monsoon in Quaternary climate extremes, two typical loess-paleosol sequences in the Chinese Loess Plateau were investigated. Sandy layers in the loess deposits, the "Upper sand" and "Lower sand" (layers L9 and L15, respectively),

  8. Mesoscale process-induced variation of the West India coastal current during the winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Jineesh, V.K.; Muraleedharan, K.R.; Lix, J.K.; Revichandran, C.; HareeshKumar, P.V.; NaveenKumar, K.R.

    Analysis of sea level anomaly from the merged altimeter data reveals the existence of a large anticyclonic eddy in the southeastern Arabian Sea during the winter monsoon The eddy moves westward with an average speed of ~15 km day1 corresponding...

  9. Robust Projected Weakening of Winter Monsoon Winds Over the Arabian Sea Under Climate Change

    Science.gov (United States)

    Parvathi, V.; Suresh, I.; Lengaigne, M.; Izumo, T.; Vialard, J.

    2017-10-01

    The response of the Indian winter monsoon to climate change has received considerably less attention than that of the summer monsoon. We show here that all Coupled Model Intercomparison Project Phase 5 (CMIP5) models display a consistent reduction (of 6.5% for Representative Concentration Pathways 8.5 and 3.5% for 4.5, on an average) of the winter monsoon winds over the Arabian Sea at the end of 21st century. This projected reduction weakens but remains robust when corrected for overestimated winter Arabian Sea winds in CMIP5. This weakening is driven by a reduction in the interhemispheric sea level pressure gradient resulting from enhanced warming of the dry Arabian Peninsula relative to the southern Indian Ocean. The wind weakening reduces winter oceanic heat losses to the atmosphere and deepening of convective mixed layer in the northern Arabian Sea and hence can potentially inhibit the seasonal chlorophyll bloom that contributes substantially to the Arabian Sea annual productivity.

  10. Late holocene primary productivity and sea surface temperature variations in the northeastern Arabian Sea: Implications for winter monsoon variability.

    Digital Repository Service at National Institute of Oceanography (India)

    Boll, A; Luckge, A; Munz, P.; Forke, S.; Schulz, H.; Ramaswamy, V.; Rixen, T.; Gaye, B.; Emeis, K.-C.

    Pakistan are indicated from 400 B.C. to 250 A.D. by reduced productivity and relatively high SST. At about 250 A.D., the intensity of the winter monsoon increased off Pakistan as indicated by a trend to lower SST. We infer that monsoon conditions were...

  11. Hydrography and biogeochemistry of the north western Bay of Bengal and the north eastern Arabian Sea during winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Balachandran, K.K.; Laluraj, C.M.; Jyothibabu, R.; Madhu, N.V.; Muraleedharan, K.R.; Vijay, J.G.; Maheswaran, P.A.; Ashraf, T.T.M.; Nair, K.K.C.; Achuthankutty, C.T.

    The north eastern Arabian Sea and the north western Bay of Bengal within the Indian exclusive economic zone were explored for their environmental characteristics during the winter monsoons of 2000 and 2001 respectively. The two regions were found...

  12. The progression of the boreal winter monsoon through the western Maritime Continent as differentiated by ENSO phase

    Directory of Open Access Journals (Sweden)

    S.-Y. Lee

    2016-08-01

    Full Text Available 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.

  13. Pulleniatina Minimum Events in the Andaman Sea (NE Indian Ocean): Implications for winter monsoon and thermocline changes

    Digital Repository Service at National Institute of Oceanography (India)

    Sijinkumar, A.V.; Nath, B.N.; Possnert, G.; Aldahan, A.

    of Post Graduate Studies & Research in Geology, Govt. College Kasaragod, Kerala, 671123, India 2 Department of Geology, United Arab Emirates University, Al Ain, UAE 1. Introduction A Pulleniatina minimum event (PME) refers to the sudden decrease... is most abundant when winter sea surface temperatures (SST) are relatively high (Bé and Tolderlund 1971; Ravelo and Fairbanks 1992). The Holocene PME has also been attributed to the intensification of the winter monsoon and consequently to decreased SST...

  14. Numerical Simulation of the Direct Radiative Effects of Dust Aerosol on the East Asian Winter Monsoon

    Directory of Open Access Journals (Sweden)

    Hui Sun

    2015-01-01

    Full Text Available Variations of the East Asian winter monsoon (EAWM induced by dust aerosol are studied by using a regional climate model (RegCM4/Dust. Dust coupled and uncoupled experiments are carried out for the past decade (2000–2009. The coupled RegCM4 captures three centers of dust mixing ratio (DMR located in the Taklamakan Desert, western Inner Mongolia, and northern Xinjiang, respectively, with maximum values greater than 500 µg kg−1 in winter. The surface total radiation change induced by dust is negative, and its central value of −8 W m−2 results in surface temperature cooling by 1.5°C in winter. Dust induced radiation change at the top of the atmosphere (TOA is also negative in Northern China, except over the Tibetan Plateau (TP, and up to −5 W m−2 in Central China. Dust cooling effects increase the sea level pressure (SLP gradient between land and ocean, the cold surge frequency, and the East Asian jet stream (EAJ intensity and then enhance the EAWM. The dry and cold wind pervade most areas of East Asia, suppressing large-scale precipitation and eventually leading to a rainfall decrease of about 10–30% in Northern China and the middle Yangtze River Valley.

  15. The 10-30-day intraseasonal variation of the East Asian winter monsoon: The temperature mode

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    Yao, Suxiang; Sun, Qingfei; Huang, Qian; Chu, Peng

    2016-09-01

    East Asia is known for its monsoon characteristics, but little research has been performed on the intraseasonal time scale of the East Asian winter monsoon (EAWM). In this paper, the extended reanalysis (ERA)-Interim sub-daily data are used to study the surface air temperature intraseasonal oscillation (ISO) of the EAWM. The results show that the air temperature (2-m level) of the EAWM has a dominant period of 10-30 days. Lake Baikal and south China are the centers of the air temperature ISO. An anomalous low frequency (10-30-day filtered) anticyclone corresponds to the intraseasonal cold air. The 10-30-day filtered cold air spreads from Novaya Zemlya to Lake Baikal and even to South China. The ISO of the Arctic Oscillation (AO) index influences the temperature of the EAWM by stimulating Rossby waves in middle latitude, causing meridional circulation, and eventually leads to the temperature ISO of the EAWM. RegCM4 has good performance for the simulation of the air temperature ISO. The simulated results indicate that the plateau is responsible for the southward propagation of the intraseasonal anticyclone. The anticyclone could not reach South China when there was no plateau in western China and its upper reaches.

  16. Intrusion of the Bay of Bengal water into the Arabian Sea during winter monsoon and associated chemical and biological response

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Narvekar, J.; Kumar, A.; Shaji, C.; Anand, P.; Sabu, P.; Rijomon, G.; Josia, J.; Jayaraj, K.A.; Radhika, A.; Nair, K.K.C.

    : Physicochemical properties. Citation: Prasanna Kumar, S., et al. (2004), Intrusion of the Bay of Bengal water into the Arabian Sea during winter monsoon and associated chemical and biological response, Geophys. Res. Lett., 31, L15304, doi:10.1029/2004GL020247. 1...

  17. Convective and stratiform components of a Winter Monsoon Cloud Cluster determined from geosynchronous infrared satellite data

    Science.gov (United States)

    Goldenberg, Stanley B.; Houze, Robert A., Jr.; Churchill, Dean D.

    1990-01-01

    The horizontal precipitation structure of cloud clusters observed over the South China Sea during the Winter Monsoon Experiment (WMONEX) is analyzed using a convective-stratiform technique (CST) developed by Adler and Negri (1988). The technique was modified by altering the method for identifying convective cells in the satellite data, accounting for the extremely cold cloud tops characteristic of the WMONEX region, and modifying the threshold infrared temperature for the boundary of the stratiform rain area. The precipitation analysis was extended to the entire history of the cloud cluster by applying the modified CST to IR imagery from geosynchronous-satellite observations. The ship and aircraft data from the later period of the cluster's lifetime make it possible to check the locations of convective and stratiform precipitation identified by the CST using in situ observations. The extended CST is considered to be effective for determining the climatology of the convective-stratiform structure of tropical cloud clusters.

  18. East Asian winter monsoon forecasting schemes based on the NCEP's climate forecast system

    Science.gov (United States)

    Tian, Baoqiang; Fan, Ke; Yang, Hongqing

    2017-12-01

    The East Asian winter monsoon (EAWM) is the major climate system in the Northern Hemisphere during boreal winter. In this study, we developed two schemes to improve the forecasting skill of the interannual variability of the EAWM index (EAWMI) using the interannual increment prediction method, also known as the DY method. First, we found that version 2 of the NCEP's Climate Forecast System (CFSv2) showed higher skill in predicting the EAWMI in DY form than not. So, based on the advantage of the DY method, Scheme-I was obtained by adding the EAWMI DY predicted by CFSv2 to the observed EAWMI in the previous year. This scheme showed higher forecasting skill than CFSv2. Specifically, during 1983-2016, the temporal correlation coefficient between the Scheme-I-predicted and observed EAWMI was 0.47, exceeding the 99% significance level, with the root-mean-square error (RMSE) decreased by 12%. The autumn Arctic sea ice and North Pacific sea surface temperature (SST) are two important external forcing factors for the interannual variability of the EAWM. Therefore, a second (hybrid) prediction scheme, Scheme-II, was also developed. This scheme not only involved the EAWMI DY of CFSv2, but also the sea-ice concentration (SIC) observed the previous autumn in the Laptev and East Siberian seas and the temporal coefficients of the third mode of the North Pacific SST in DY form. We found that a negative SIC anomaly in the preceding autumn over the Laptev and the East Siberian seas could lead to a significant enhancement of the Aleutian low and East Asian westerly jet in the following winter. However, the intensity of the winter Siberian high was mainly affected by the third mode of the North Pacific autumn SST. Scheme-I and Scheme-II also showed higher predictive ability for the EAWMI in negative anomaly years compared to CFSv2. More importantly, the improvement in the prediction skill of the EAWMI by the new schemes, especially for Scheme-II, could enhance the forecasting skill of

  19. How autumn Eurasian snow anomalies affect east asian winter monsoon: a numerical study

    Science.gov (United States)

    Luo, Xiao; Wang, Bin

    2018-03-01

    Previous studies have found that snow Eurasian anomalies in autumn can affect East Asian winter monsoon (EAWM), but the mechanisms remain controversial and not well understood. The possible mechanisms by which Eurasian autumn snow anomalies affect EAWM are investigated by numerical experiments with a coupled general circulation model and its atmospheric general circulation model component. The leading empirical orthogonal function mode of the October-November mean Eurasian snow cover is characterized by a uniform anomaly over a broad region of central Eurasia (40°N-65°N, 60°E-140°E). However, the results from a 150-ensemble mean simulation with snow depth anomaly specified in October and November reveal that the Mongolian Plateau and Vicinity (MPV, 40°-55°N, 80°-120°E) is the key region for autumn snow anomalies to affect EAWM. The excessive snow forcing can significantly enhance EAWM and the snowfall over the northwestern China and along the EAWM front zone stretching from the southeast China to Japan. The physical process involves a snow-monsoon feedback mechanism. The excessive autumn snow anomalies over the MPV region can persist into the following winter, and significantly enhance winter snow anomalies, which increase surface albedo, reduce incoming solar radiation and cool the boundary layer air, leading to an enhanced Mongolian High and a deepened East Asian trough. The latter, in turn, strengthen surface northwesterly winds, cooling East Asia and increasing snow accumulation over the MPV region and the southeastern China. The increased snow covers feedback to EAWM system through changing albedo, extending its influence southeastward. It is also found that the atmosphere-ocean coupling process can amplify the delayed influence of Eurasian snow mass anomaly on EAWM. The autumn surface albedo anomalies, however, do not have a lasting "memory" effect. Only if the albedo anomalies are artificially extended into December and January, will the EAWM be

  20. Multivariate forecast of winter monsoon rainfall in India using SST anomaly as a predictor: Neurocomputing and statistical approaches

    OpenAIRE

    Chattopadhyay, Goutami; Chattopadhyay, Surajit; Jain, Rajni

    2009-01-01

    In this paper, the complexities in the relationship between rainfall and sea surface temperature (SST) anomalies during the winter monsoon (November-January) over India were evaluated statistically using scatter plot matrices and autocorrelation functions.Linear as well as polynomial trend equations were obtained and it was observed that the coefficient of determination for the linear trend was very low and it remained low even when polynomial trend of degree six was used. An exponential regr...

  1. The Indian winter monsoon and its response to external forcing over the last two and a half centuries

    Science.gov (United States)

    Munz, Philipp M.; Lückge, Andreas; Siccha, Michael; Böll, Anna; Forke, Sven; Kucera, Michal; Schulz, Hartmut

    2017-09-01

    The Indian winter monsoon (IWM) is a key component of the seasonally changing monsoon system that affects the densely populated regions of South Asia. Cold winds originating in high northern latitudes provide a link of continental-scale Northern Hemisphere climate to the tropics. Western disturbances associated with the IWM play a critical role for the climate and hydrology in northern India and the western Himalaya region. It is vital to understand the mechanisms and teleconnections that influence IWM variability to better predict changes in future climate. Here we present a study of regionally calibrated winter (January) temperatures and according IWM intensities, based on a planktic foraminiferal record with biennial (2.55 years) resolution. Over the last 250 years, IWM intensities gradually weakened, based on the long-term trend of reconstructed January temperatures. Furthermore, the results indicate that IWM is connected on interannual- to decadal time scales to climate variability of the tropical and extratropical Pacific, via El Niño Southern Oscillation and Pacific Decadal Oscillation. However, our findings suggest that this relationship appeared to begin to decouple since the beginning of the twentieth century. Cross-spectral analysis revealed that several distinct decadal-scale phases of colder climate and accordingly more intense winter monsoon centered at the years 1800, 1890 and 1930 can be linked to changes of the North Atlantic Oscillation.

  2. Interdecadal changes in the East Asian winter monsoon and their possible causes

    Science.gov (United States)

    Yun, Junghee; Ha, Kyung-Ja

    2017-04-01

    Using Ensemble Empirical Mode Decomposition (EEMD) for detecting the interdecadal changes in the East Asian winter monsoon (EAWM), this study investigates that the intensity of the EAWM experienced remarkable transition around mid-1980s and late 2000s: a strong period (P1, 1960-1986), a weak period (P2, 1987-2007), and a strong period (P3, 2008-2013). The EAWM is influenced by a distinctive cold (warm) temperature anomaly, and cold (warm) sea surface temperature (SST) anomalies are present over the North Pacific (NP) during P1 (P2). In contrast with P1, the EAWM is characterized by a large temperature difference between Eurasian continent and NP, and a negative Pacific Decadal Oscillation (PDO)-like SST pattern is found over the NP during P3. During three periods, the Siberian high (SH) plays an important role in deciding the intensity of the EAWM. In addition, the EAWM exists under the influence of an enhanced atmospheric circulation associated with a positive North Pacific Oscillation (NPO) and a negative PDO during P2 and P3, respectively. Accordingly, to recognize the impacts of this climate variability on the weakening (strengthening) EAWM, the combined effect of the SH and NPO (SH and PDO) is explored during P1 and P2 (P2 and P3). Consequently, while the atmospheric variabilities such as SH and NPO are the dominant contributors to the weakening of EAWM after the mid-1980s, the SST variability such as PDO contributes to the strengthening of EAWM along with the SH variability in recent decade.

  3. Quantitative Estimation of the Impact of European Teleconnections on Interannual Variation of East Asian Winter Temperature and Monsoon

    Science.gov (United States)

    Lim, Young-Kwon; Kim, Hae-Dong

    2014-01-01

    The impact of European teleconnections including the East AtlanticWest Russia (EA-WR), the Scandinavia (SCA), and the East Atlantic (EA) on East Asian winter temperature variability was quantified and compared with the combined effect of the Arctic Oscillation (AO), the Western Pacific (WP), and the El-Nino Southern Oscillation (ENSO), which are originated in the Northern Hemispheric high-latitudes or the Pacific. Three European teleconnections explained 22-25 percent of the total monthly upper-tropospheric height variance over Eurasia. Regression analysis revealed warming by EA-WR and EA and cooling by SCA over mid-latitude East Asia during their positive phase and vice versa. Temperature anomalies were largely explained by the advective temperature change process at the lower troposphere. The average spatial correlation over East Asia (90-180E, 10-80N) for the last 34 winters between observed and reconstructed temperature comprised of AO, WP and ENSO effect (AWE) was approximately 0.55, and adding the European teleconnection components (ESE) to the reconstructed temperature improved the correlation up to approximately 0.64. Lower level atmospheric structure demonstrated that approximately five of the last 34 winters were significantly better explained by ESE than AWE to determine East Asian seasonal winter temperatures. We also compared the impact between EA-WR and AO on the 1) East Asian winter monsoon, 2) cold surge, and 3) the Siberian high. These three were strongly coupled, and their spatial features and interannual variation were somewhat better explained by EA-WR than AO. Results suggest that the EA-WR impact must be treated more importantly than previously thought for a better understanding of East Asian winter temperature and monsoon variability.

  4. ENSO and East Asian winter monsoon relationship modulation associated with the anomalous northwest Pacific anticyclone

    Science.gov (United States)

    Kim, Ji-Won; An, Soon-Il; Jun, Sang-Yoon; Park, Hey-Jin; Yeh, Sang-Wook

    2017-08-01

    Using observational datasets and numerical model experiments, the mechanism on the slowly varying change in the relationship between the El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) is investigated. The decadal-window (11-, 15-, and 21-year) moving correlations show a significant change in the boreal wintertime ENSO-EAWM relationship between two sub-periods of 1976‒1992 and 1997‒2013. Such recent change in ENSO-EAWM relationship is mainly attributed to the changes in the intensity and zonal location of the anomalous lower-tropospheric northwest Pacific anticyclone (NWP-AC). NWP-AC commonly develops near the region of the Philippine Sea during the ENSO's peak phase and plays an important role of bridging the tropical convection and mid-latitude teleconnection. On one hand, the intensity of the NWP-AC is influenced by the interdecadal variation in a linkage between ENSO and the Indian Ocean sea surface temperature (SST) variability, referring that a strong connection between the Pacific and Indian Oceans results in the strengthening of NWP-AC response to ENSO. On the other hand, the zonal displacement of the NWP-AC is associated with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). That is, the tropical Pacific mean state (i.e., zonal SST gradient between climatologically warm western Pacific and cold eastern Pacific)—strengthened by either the negative PDO phase or the positive AMO phase—drives the anomalous ENSO-induced convection to be shifted to the west. With this westward shift, the zonal center of the NWP-AC also migrates westward over the Philippine Islands and exerts stronger connection between ENSO and EAWM. In contrast, the relaxed zonal SST contrast associated with either the positive PDO phase or the negative AMO phase tends to exhibit weaker ENSO-EAWM relationship via both of eastward shifted zonal centers of the anomalous ENSO-induced convection and the NWP-AC. Finally, a

  5. Aerosol optical and physical properties during winter monsoon pollution transport in an urban environment.

    Science.gov (United States)

    Verma, S; Bhanja, S N; Pani, S K; Misra, A

    2014-04-01

    We analysed aerosol optical and physical properties in an urban environment (Kolkata) during winter monsoon pollution transport from nearby and far-off regions. Prevailing meteorological conditions, viz. low temperature and wind speed, and a strong downdraft of air mass, indicated weak dispersion and inhibition of vertical mixing of aerosols. Spectral features of WinMon aerosol optical depth (AOD) showed larger variability (0.68-1.13) in monthly mean AOD at short-wavelength (SW) channels (0.34-0.5 μm) compared to that (0.28-0.37) at long-wavelength (LW) channels (0.87-1.02 μm), thereby indicating sensitivity of WinMon AOD to fine aerosol constituents and the predominant contribution from fine aerosol constituents to WinMon AOD. WinMon AOD at 0.5 μm (AOD 0. 5) and Angstrom parameter ( α) were 0.68-0.82 and 1.14-1.32, respectively, with their highest value in December. Consistent with inference from spectral features of AOD, surface aerosol loading was primarily constituted of fine aerosols (size 0.23-3 μm) which was 60-70 % of aerosol 10- μm (size 0.23-10 μm) concentration. Three distinct modes of aerosol distribution were obtained, with the highest WinMon concentration at a mass median diameter (MMD) of 0.3 μm during December, thereby indicating characteristics of primary contribution related to anthropogenic pollutants that were inferred to be mostly due to contribution from air mass originating in nearby region having predominant emissions from biofuel and fossil fuel combustion. A relatively higher contribution from aerosols in the upper atmospheric layers than at the surface to WinMon AOD was inferred during February compared to other months and was attributed to predominant contribution from open burning emissions arising from nearby and far-off regions. A comparison of ground-based measurements with Moderate Resolution Imaging Spectroradiometer (MODIS) data showed an underestimation of MODIS AOD and α values for most of the days. Discrepancy in

  6. The Glacial-Interglacial summer monsoon recorded in southwest Sulawesi speleothems: Evidence for sea level thresholds driving tropical monsoon strength

    Science.gov (United States)

    Kimbrough, A. K.; Gagan, M. K.; Dunbar, G. B.; Krause, C.; Di Nezio, P. N.; Hantoro, W. S.; Cheng, H.; Edwards, R. L.; Shen, C. C.; Sun, H.; Cai, B.; Rifai, H.

    2016-12-01

    Southwest Sulawesi lies within the Indo-Pacific Warm Pool (IPWP), at the center of atmospheric convection for two of the largest circulation cells on the planet, the meridional Hadley Cell and zonal Indo-Pacific Walker Circulation. Due to the geographic coincidence of these circulation cells, southwest Sulawesi serves as a hotspot for changes in tropical Pacific climate variability and Australian-Indonesian summer monsoon (AISM) strength over glacial-interglacial (G-I) timescales. The work presented here spans 386 - 127 ky BP, including glacial terminations IV ( 340 ky BP) and both phases of TIII (TIII 248 ky BP and TIIIa 217 ky BP). This record, along with previous work from southwest Sulawesi spanning the last 40 kyr, reveals coherent climatic features over three complete G-I cycles. The multi-stalagmite Sulawesi speleothem δ18O record demonstrates that on G-I timescales, the strength of the AISM is most sensitive to changes in sea level and its impact on the regional distribution of land and shallow ocean. Stalagmite δ18O and trace element (Mg/Ca) data indicate a rapid increase in rainfall at glacial terminations and wet interglacials. TIV, TIII, TIIIa, and TI are each characterized by an abrupt 3‰ decrease in δ18O that coincides with sea level rise and flooding of the Sunda and Sahul shelves. Strong evidence for a sea level (flooding/exposure) threshold is found throughout the southwest Sulawesi record. This is most clearly demonstrated over the period 230 - 212 ky BP (MIS 7d-7c), when a sea level fall to only -80 to -60 m for 10 kyr results in a weakened AISM and glacial conditions, followed by a full termination. Taken together, both glaciations and glacial terminations imply a sea level threshold driving the AISM between two primary levels of intensity (`interglacial' & `glacial'). These massive, sea-level driven shifts in AISM strength are superimposed on precession-scale variability associated with boreal fall insolation at the equator, indicating

  7. Contrasting effects of winter and summer climate on alpine timberline evolution in monsoon-dominated East Asia

    Science.gov (United States)

    Cheng, Ying; Liu, Hongyan; Wang, Hongya; Piao, Shilong; Yin, Yi; Ciais, Philippe; Wu, Xiuchen; Luo, Yao; Zhang, Caina; Song, Yaqiong; Gao, Yishen; Qiu, Anan

    2017-08-01

    Alpine timberline is particularly sensitive to global climate change, with the danger of losing essential ecosystem services in high elevational regions. Its evolution is generally linked to annual average thermal regimes, and is regarded as an indicator of climate warming. However, the effect of uneven seasonal climate change stressed by the Hijioka et al. (2014) on alpine timberline dynamics in terms of both position migration and species composition remains unclear. Here, we documented approximately 6000 years of postglacial alpine timberline evolution on Mt. Tabai in the monsoon-dominated East Asian subtropical-temperate transition. We analyzed three high-resolution lacustrine sediment sequences located below, within, and above the current alpine timberline, an ecotone between the forest line and treeline, respectively. The timberline position appears to have varied coincidently with the temperature effect of cold East Asian Winter Monsoon (EAWM), implying that enhanced EAWM shortened the duration of the growing season and reduced forest survival at the alpine timberline. Unlike position migration, however, timberline species composition depends on summer precipitation. We found that drought-tolerant herb and shrub species were much more sensitive to variations in the water-bearing East Asian Summer Monsoon (EASM) than mesophytic trees at the alpine timberline. Our results suggest that prediction of future timberline dynamics should consider uneven seasonal climate changes.

  8. The role of the Asian winter monsoon in the rapid propagation of abrupt climate changes during the last deglaciation

    Science.gov (United States)

    Chu, Guoqiang; Sun, Qing; Zhu, Qingzeng; Shan, Yabing; Shang, Wenyu; Ling, Yuan; Su, Youliang; Xie, Manman; Wang, Xishen; Liu, Jiaqi

    2017-12-01

    High-resolution temperature records spanning the last deglaciation from low latitudes are scarce; however, they are important for understanding the rapid propagation of abrupt climate events throughout the Northern Hemisphere and the tropics. Here, we present a branched GDGTs-based temperature reconstruction from the sediments of Maar Lake Huguangyan in tropical China. The record reveals that the mean temperature during the Oldest Dryas was 17.8 °C, which was followed by a two-step increase of 2-3 °C to the Bølling-Allerød, a decrease to 19.8 °C during the Younger Dryas, and a rapid warming at the onset of the Holocene. The Oldest Dryas was about 2 °C warmer than the Younger Dryas. The reconstructed temperature was weighted towards the wintertime since the lake is monomictic and the mixing process in winter supplies nutrients from the lake bottom to the entire water column, greatly promoting biological productivity. In addition, the winter-biased temperature changes observed in the study are more distinctive than the summer-biased temperature records from extra-tropical regions of East Asia. This implies that the temperature decreases during abrupt climatic events were mainly a winter phenomenon. Within the limits of the dating uncertainties, the broadly similar pattern of winter-weighted temperature change observed in both tropical Lake Huguangyan and in Greenland ice cores indicates the occurrence of tightly-coupled interactions between high latitude ice sheets and land areas in the tropics. We suggest that the winter monsoon (especially cold surges) could play an important role in the rapid transmission of the temperature signal from the Arctic to the tropics.

  9. Indian summer monsoon and winter hydrographic variations over past millennia resolved by clay sedimentation

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.; Dayal, A.M.; Basavaiah, N.; Kader, U.S.A.

    Ocean. For example, a large hydrological imbalance due to precipitation – evaporation (P-E) and fluvial influx associated with hydrometeorological regimes in two adjacent basins (the Bay of Bengal, P>>E due to higher fluvial runoff and precipitation...; the Arabian Sea, excess evaporation and loss of fresh water; E>>P) leads to an inter-basin transfer. During boreal summer (June though September), Indian Monsoon Current advects high salinity Arabian Sea Waters into BOB [Vinayachandran et al., 1999]. Upon...

  10. Link between western Arabian sea surface temperature and summer monsoon strength and high-latitude abrupt climate events

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    to other months (Hastenrath and Lamb, 1979). During the SW monsoon the western Arabian Sea gains heat whereas the eastern Arabian Sea loses heat to the atmosphere. Modern Sea Surface Temperature (SST) varies from 23.2 to 28.4 ?C at the location of ODP... to the atmosphere. Such air-sea interactions were highly unstable during the last glacial period. This winter surface-water cooling extended up to the Arabian coast during the last glacial period, in contrast to the present-day winter cooling which is restricted...

  11. The decline of winter monsoon velocity in the South China Sea through the 20th century: Evidence from the Sr/Ca records in corals

    Science.gov (United States)

    Liu, Yajing; Peng, Z.; Chen, T.; Wei, G.; Sun, W.; Sun, R.; He, J.; Liu, Gaisheng; Chou, C.-L.; Zartman, R.E.

    2008-01-01

    A modern massive Porites coral was collected from the Longwan Bay (19??20???N, 110??39???E) on the east coast of the Hainan Island, China. The coral was sectioned vertical to the growth axis into discs of double density-bands representing annual growth. The samples were analyzed for the Sr/Ca ratio by inductively coupled plasma atomic emission spectrometry. The history of winter sea-surface temperature (SST) is reconstructed using the Sr/Ca ratio in winter bands of corals. The winter SST at Xisha in the middle of the South China Sea (SCS) is weakly correlated with the instrument-measured winter monsoon velocity (WMV) with a correlation coefficient of 0.19. The winter SST data from corals at Longwan Bay, Hainan, in the northern SCS are moderately correlated with the WMV (r = 0.40). Interestingly we found that the difference of winter SSTs between the two sites (Xisha and Longwan Bay, Hainan) (the X-H index) is significantly negatively correlated with the WMV (r = - 0.73). This negative correlation may be related to the intrusion of the warm Kuroshio Current into the SCS through the Luzon Strait promoted by the strong northeastern monsoon winds in the winter. Using the relationship between our coralline data and observed WMV, the calculated winter monsoon velocity (WMVc) was obtained for 87??years. This data set in combination with the instrument-measured data between 1993 and 1998 generate a record of WMVc for a period of 93??years from 1906 to 1998. The WMVc in the 20th century shows significant interannual and decadal variability with a trend of persistent decline in the whole 20th century at the rate of decrease of - 0.02 (m/s)/a. The lowest wind velocity occurred during the last two decades of the 20th century. The WMVc has decreased significantly by about 30% from the early to the late of 20th century. The 20th century decline of winter monsoon velocity evidenced from the SCS coral records is consistent with the atmosphere-ocean general circulation models

  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. Anthropogenic aerosol effects on East Asian winter monsoon: The role of black carbon-induced Tibetan Plateau warming

    Science.gov (United States)

    Jiang, Yiquan; Yang, Xiu-Qun; Liu, Xiaohong; Yang, Dejian; Sun, Xuguang; Wang, Minghuai; Ding, Aijun; Wang, Tijian; Fu, Congbin

    2017-06-01

    This study investigates anthropogenic aerosol effects on East Asian winter monsoon (EAWM) with Community Atmospheric Model version 5. In winter, the anthropogenic aerosol optical depth is the largest over southern East Asia and adjacent oceans. The associated EAWM change, however, is the most significant in northern East Asia, which is characterized by a significant surface cooling in northern East Asia and an acceleration of the jet stream around 40°N, indicating an intensification of the EAWM northern mode. Such an intensification is attributed to anthropogenic black carbon (BC)-induced Tibetan Plateau (TP) warming. The BC is mostly transported from northern South Asia by wintertime westerly and southwesterly and then deposited on snow, giving rise to a reduction of surface albedo and an increase of surface air temperature via the snow-albedo feedback. The TP warming increases meridional temperature gradient and lower tropospheric baroclinicity over northern East Asia, leading to the jet stream acceleration around 40°N and the westward shift of East Asian major trough via the transient eddy-mean flow feedback. Such upper tropospheric pattern favors more cold air outbreak, leading to a large surface cooling in northern East Asia. In southern East Asia, the effect of nonabsorbing aerosols is dominant. The solar flux at surface is significantly reduced directly by scattering of nonabsorbing aerosols and indirectly by intensification of short wave cloud forcing. Accordingly, the surface air temperature in southern East Asia is reduced. The precipitation is also significantly reduced in South China and Indo-China Peninsula, where the aerosol indirect effect is the largest.

  14. Long range transport of caesium isotopes from temperate latitudes to the equatorial zone during the winter monsoon period

    International Nuclear Information System (INIS)

    Pham Duy Hien; Nguyen Thanh Binh; Vuong Thu Bac; Truong Y; Nguyen Trong Ngo.

    1993-01-01

    An air radioactivity monitoring study carried out in Dalat, Vietnam since 1986 has revealed distinct peaks of caesium isotope concentrations in air and fallout during December-January, when the monthly average air temperature was lowest and dry fallout dominated. These peaks provide evidence of the intrusion of more radioactive cold air masses from temperate northern latitudes during the development of large-scale anti cyclones, frequently observed in the most active winter monsoon period. High dry fallout velocity (about 10 cm/s) determined from the measured concentrations, clearly demonstrates one of the most relevant features of cold air masses: behind the cold front, vertical air motion is descending. The role of other processes, such as injection of radioactive air from stratosphere and local resuspension of soil dust, has been shown to be insignificant. The interpretation of the experimental results was based on the analysis of environmental -meteorological factors as well as the behaviour of other naturally-occurring radionuclides. (author). 7 refs, 2 figs

  15. Comparison of the Impact of the Arctic Oscillation and East Atlantic - West Russia Teleconnection on Interannual Variation in East Asian Winter Temperatures and Monsoon

    Science.gov (United States)

    Lim, Young-Kwon; Kim, Hae-Dong

    2014-01-01

    The large-scale impacts of the Arctic Oscillation (AO) and the East Atlantic/West Russia (EA/WR) teleconnection on the East Asian winter climate anomalies are compared for the past 34 winters focusing on 1) interannual monthly to seasonal temperature variability, 2) East Asian winter monsoon (EAWM), and 3) the Siberian high (SH) and cold surge. Regression analysis reveals warming by AO and EA/WR over mid-latitude East Asia during their positive phase and vice versa. The EA/WR impact is found to be comparable to the AO impact in affecting the East Asian temperature and monsoon. For example, warm (cold) months over mid-latitude East Asia during the positive (negative) AO are clearly seen when the AO and EA/WR are in the same phase. Near zero correlation is found between temperature and the AO phase when both teleconnections are in an opposite phase. The well-known negative relationship between SH and the AO phase is observed significantly more often when the AO is in the same phase with the EA/WR. Also, the indices of EAWM, cold surge, and SH are found to be more highly negative-correlated with the EA/WR rather than with the AO. The advective temperature change and associated circulation demonstrate that the anomalous large-scale field including the SH over the mid-latitude Asian inland is better represented by the EA/WR, influencing the East Asian winter climates. These results suggest that the impact of EA/WR should be considered more important than previously thought for a better understanding of East Asian winter temperature and monsoon variability.

  16. Partial least regression approach to forecast the East Asian winter monsoon using Eurasian snow cover and sea surface temperature

    Science.gov (United States)

    Yu, Lulu; Wu, Zhiwei; Zhang, Renhe; Yang, Xin

    2017-06-01

    Seasonal prediction of the East Asian (EA) winter monsoon (EAWM) is of great significance yet a challenging issue. In this study, three statistical seasonal prediction models for the EAWM are established using three leading modes of the Eurasian snow cover (ESC), the first leading mode of sea surface temperature (SST) and the four leading modes of the combination of the ESC and SST in preceding autumn, respectively. These leading modes are identified by the partial-least square (PLS) regression. The first PLS (PLS1) mode for the ESC features significantly anomalous snow cover in Siberia and Tibetan Plateau regions. The ESC second PLS (PLS2) mode corresponds to large areas of snow cover anomalies in the central Siberia, whereas the third PLS (PLS3) mode a meridional seesaw pattern of ESC. The SST PLS1 mode basically exhibits an El Niño-Southern Oscillation developing phase in equatorial eastern Pacific and significant SST anomalies in North Atlantic. A strong EAWM tends to emerge in a La Niña year concurrent with cold SST anomalies in the North Atlantic, and vice versa. After a 35-year training period (1967-2001), three PLS seasonal prediction models are constructed and the 11-year hindcast is performed for the period of 2002-2012, respectively. The PLS model based on combination of the autumn ESC and SST exhibits the best hindcast skill among the three models, its correlation coefficient between the observation and the hindcast reaching 0.86. This indicates that this physical-based PLS model may provide another practical tool for the EAWM. In addition, the relative contribution of the ESC and SST is also examined by assessing the hindcast skills of the other two PLS models constructed solely by the ESC or SST. Possible physical mechanisms are also discussed.

  17. 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).

  18. Role of Madden-Julian Oscillation in Modulating Monsoon Retreat

    Science.gov (United States)

    Singh, Madhu; Bhatla, R.

    2018-01-01

    The Madden-Julian oscillation (MJO) is the major fluctuation in tropical weather on a seasonal scale. The impact of MJO on different epochs, viz., onset, advance and active break is well known. There can be several MJO events in a season and it may enhance/suppress the retreat process. The present study aims to find the MJO-modulated retreat of monsoon. The results suggest that the fastest retreat of monsoon occurred in the years 2007 and 2008, while slowest retreat of monsoon occurred in the year 1979. The retreat features of the Indian summer monsoon (ISM) are investigated with the MJO phase and amplitude variations. The daily MJO indices for the retreat period 1979-2016 are used. The results reveal that the MJO strength decreases during the transition phase (i.e., summer monsoon to winter monsoon transition). The monsoon retreat is most favored by strong MJO phase 4 and phase 5. The fastest retreat of monsoon occurred in the years 2007 and 2008, while the slowest retreat of monsoon occurred in the year 1979. There exists a weak positive correlation between the MJO amplitude and the retreat period of monsoon. The monsoon retreat is most favored by strong MJO phase 4 and phase 5. The MJO amplitude variations during MJO phases 1-8 suggest that the MJO amplitude decreases with increase in retreat period. The MJO-modulated retreat results in slow retreat of monsoon, whereas fast and normal retreat of monsoon is seen on rare occasions. Weak MJO events lead to normal retreat of monsoon.

  19. Variations in particulate matter over Indo-Gangetic Plains and Indo-Himalayan Range during four field campaigns in winter monsoon and summer monsoon: Role of pollution pathways

    Science.gov (United States)

    Sen, A.; Abdelmaksoud, A. S.; Nazeer Ahammed, Y.; Alghamdi, Mansour ِA.; Banerjee, Tirthankar; Bhat, Mudasir Ahmad; Chatterjee, A.; Choudhuri, Anil K.; Das, Trupti; Dhir, Amit; Dhyani, Pitamber Prasad; Gadi, Ranu; Ghosh, Sanjay; Kumar, Kireet; Khan, A. H.; Khoder, M.; Maharaj Kumari, K.; Kuniyal, Jagdish Chandra; Kumar, Manish; Lakhani, Anita; Mahapatra, Parth Sarathi; Naja, Manish; Pal, Dharam; Pal, S.; Rafiq, Mahammad; Romshoo, Shakil Ahmad; Rashid, Irfan; Saikia, Prasenjit; Shenoy, D. M.; Sridhar, Vijay; Verma, Nidhi; Vyas, B. M.; Saxena, Mohit; Sharma, A.; Sharma, S. K.; Mandal, T. K.

    2017-04-01

    Both in-situ and space-borne observations reveal an extremely high loading of particulates over the Indo-Gangetic Plains (IGP), all year around. With a burgeoning population and combustion sources (fossil fuels (FFs) and biofuels (BFs)) in close proximity to each other, the IGP is widely regarded as a hotspot for anthropogenic aerosol emission in South Asia. The deteriorating air quality over this region, particularly during winters, is a cause of major concern, since the pollutants undergo long range transport from their source regions to the Indo-Himalayan Range (IHR), Bay of Bengal (BoB) and other remote areas, polluting their pristine atmospheric conditions. Seasonal reversal in winds over the Indian mainland leads to an outflow of continental pollutants into the BoB during winters and a net advection of desert dust aerosols into the IGP from southwest Asia (SW-Asia), northwest India (NW-India) and northern Africa (N-Africa) during summers. Through the course of this study, four observational campaigns were conducted for sampling the ambient PM2.5 and PM10 during winter and summer seasons of 2014-2015, at multiple locations (18 sites) in the IGP, IHR, and semi-arid/arid sites towards their south and west, in order to accurately determine the inter-seasonal and inter-annual changes in the aerosol loading at the sites. We have also utilized data from Moderate Resolution Imaging Spectroradiometer (MODIS) on-board Earth Observing System (EOS) Terra satellite for estimating the columnar Aerosol Optical Depth at 550 nm (AOD550) and data from EOS Terra and Aqua satellites for discovering openly burning fires in the vicinity of sampling sites. Determination of the major source regions and key transport pathways during both seasons have also been attempted, using back-trajectory cluster analyses, as well as receptor models such as PSCF and CWT.

  20. Increasing persistent haze in Beijing: potential impacts of weakening East Asian winter monsoons associated with northwestern Pacific sea surface temperature trends

    Science.gov (United States)

    Pei, Lin; Yan, Zhongwei; Sun, Zhaobin; Miao, Shiguang; Yao, Yao

    2018-03-01

    Over the past decades, Beijing, the capital city of China, has encountered increasingly frequent persistent haze events (PHE). While the increased pollutant emissions are considered as the most important reason, changes in regional atmospheric circulations associated with large-scale climate warming also play a role. In this study, we find a significant positive trend of PHE in Beijing for the winters from 1980 to 2016 based on updated daily observations. This trend is closely related to an increasing frequency of extreme anomalous southerly episodes in North China, a weakened East Asian trough in the mid-troposphere and a northward shift of the East Asian jet stream in the upper troposphere. These conditions together depict a weakened East Asian winter monsoon (EAWM) system, which is then found to be associated with an anomalous warm, high-pressure system in the middle-lower troposphere over the northwestern Pacific. A practical EAWM index is defined as the seasonal meridional wind anomaly at 850 hPa in winter over North China. Over the period 1900-2016, this EAWM index is positively correlated with the sea surface temperature anomalies over the northwestern Pacific, which indicates a wavy positive trend, with an enhanced positive phase since the mid-1980s. Our results suggest an observation-based mechanism linking the increase in PHE in Beijing with large-scale climatic warming through changes in the typical regional atmospheric circulation.

  1. Penetration of Atlantic westerly winds into the C. and E. Asian monsoonal system.

    NARCIS (Netherlands)

    Vandenberghe, J.; Renssen, H.; van Huissteden, J.; Nugteren, G; Konert, M.; Lu, H.; Dodonov, A.; Zhou, L.; Buylaart, J.P.

    2006-01-01

    The geographical position of the convergence zone where the western Atlantic climate system meets the Asian (winter) monsoonal system depends on their relative strength. These individual strengths are determined by the intensities of the air pressure gradients over the North Atlantic, and the

  2. Penetration of Atlantic westerly winds into Central and East Asian monsoonal system.

    NARCIS (Netherlands)

    Vandenberghe, J.F.; Renssen, H.; van Huissteden, J.; Nugteren, G.D.; Konert, M.; Lu, H.; Dodonov, A.; Buylaart, J.P.

    2006-01-01

    The geographical position of the convergence zone where the western Atlantic climate system meets the Asian (winter) monsoonal system depends on their relative strength. These individual strengths are determined by the intensities of the air pressure gradients over the North Atlantic, and the

  3. Long-range atmospheric transport of terrestrial biomarkers by the Asian winter monsoon: Evidence from fresh snow from Sapporo, northern Japan

    Science.gov (United States)

    Yamamoto, Shinya; Kawamura, Kimitaka; Seki, Osamu

    2011-07-01

    Molecular distributions of terrestrial biomarkers were investigated in fresh snow samples from Sapporo, northern Japan, to better understand the long-range atmospheric transport of terrestrial organic matter by the Asian winter monsoon. Stable carbon (δ 13C) and hydrogen (δD) isotope ratios of C 22-C 28n-alkanoic acids were also measured to decipher their source regions. The snow samples are found to contain higher plant-derived n-alkanes, n-alkanols and n-alkanoic acids as major components. Relative abundances of these three biomarker classes suggest that they are likely derived from higher plants in the Asian continent. The C 27/C 31 ratios of terrestrial n-alkanes in the snow samples range from 1.3 to 5.5, being similar to those of the plants growing in the latitudes >40°N of East Asia. The δ 13C values of the n-alkanoic acids in the snow samples (-33.4 to -27.6‰) are similar to those of typical C 3 gymnosperm from Sapporo (-34.9 to -29.3‰). However, the δD values of the n-alkanoic acids (-208 to -148‰) are found to be significantly depleted with deuterium (by ˜72‰) than those of plant leaves from Sapporo. Such depletion can be most likely interpreted by the long-range atmospheric transport of the n-alkanoic acids from vegetation in the latitudes further north of Sapporo because the δD values of terrestrial higher plants tend to decrease northward in East Asia reflecting the δD of precipitation. Together with the results of backward trajectory analyses, this study suggests that the terrestrial biomarkers in the Sapporo snow samples are likely transported from Siberia, Russian Far East and northeast China to northern Japan by the Asian winter monsoon.

  4. Dune mobility and aridity at the desert margin of northern China at a time of peak monsoon strength

    Science.gov (United States)

    Mason, J.A.; Lu, H.; Zhou, Y.; Miao, X.; Swinehart, J.B.; Liu, Z.; Goble, R.J.; Yi, S.

    2009-01-01

    Wind-blown sands were mobile at many sites along the desert margin in northern China during the early Holocene (11.5-8 ka ago), based on extensive new numerical dating. This mobility implies low effective moisture at the desert margin, in contrast to growing evidence for greater than modern monsoon precipitation at the same time in central and southern China. Dry conditions in the early Holocene at the desert margin can be explained through a dynamic link between enhanced diabatic heating in the core region of the strengthened monsoon and increased subsidence in drylands to the north, combined with high evapotranspiration rates due to high summer temperatures. After 8 ka ago, as the monsoon weakened and lower temperatures reduced evapotranspiration, eolian sands were stabilized by vegetation. Aridity and dune mobility at the desert margin and a strengthened monsoon can both be explained as responses to high summer insolation in the early Holocene. ?? 2009 Geological Society of America.

  5. Winter precipitation and snow accumulation drive the methane sink or source strength of Arctic tussock tundra.

    Science.gov (United States)

    Blanc-Betes, Elena; Welker, Jeffrey M; Sturchio, Neil C; Chanton, Jeffrey P; Gonzalez-Meler, Miquel A

    2016-08-01

    Arctic winter precipitation is projected to increase with global warming, but some areas will experience decreases in snow accumulation. Although Arctic CH4 emissions may represent a significant climate forcing feedback, long-term impacts of changes in snow accumulation on CH4 fluxes remain uncertain. We measured ecosystem CH4 fluxes and soil CH4 and CO2 concentrations and (13) C composition to investigate the metabolic pathways and transport mechanisms driving moist acidic tundra CH4 flux over the growing season (Jun-Aug) after 18 years of experimental snow depth increases and decreases. Deeper snow increased soil wetness and warming, reducing soil %O2 levels and increasing thaw depth. Soil moisture, through changes in soil %O2 saturation, determined predominance of methanotrophy or methanogenesis, with soil temperature regulating the ecosystem CH4 sink or source strength. Reduced snow (RS) increased the fraction of oxidized CH4 (Fox) by 75-120% compared to Ambient, switching the system from a small source to a net CH4 sink (21 ± 2 and -31 ± 1 mg CH4  m(-2)  season(-1) at Ambient and RS). Deeper snow reduced Fox by 35-40% and 90-100% in medium- (MS) and high- (HS) snow additions relative to Ambient, contributing to increasing the CH4 source strength of moist acidic tundra (464 ± 15 and 3561 ± 97 mg CH4  m(-2)  season(-1) at MS and HS). Decreases in Fox with deeper snow were partly due to increases in plant-mediated CH4 transport associated with the expansion of tall graminoids. Deeper snow enhanced CH4 production within newly thawed soils, responding mainly to soil warming rather than to increases in acetate fermentation expected from thaw-induced increases in SOC availability. Our results suggest that increased winter precipitation will increase the CH4 source strength of Arctic tundra, but the resulting positive feedback on climate change will depend on the balance between areas with more or less snow accumulation than they are currently

  6. The effect of winter sports participation on high school football players: strength, power, agility, and body composition.

    Science.gov (United States)

    Wroble, R R; Moxley, D R

    2001-02-01

    In this study, football players (N = 57) in grades 9-11 from 3 high schools chose to participate in 1 of 2 groups. Group WC (N = 39) participated in off-season strength training only. Group SP (N = 18) participated in both a winter sport (either wrestling or basketball) and an identical strength training program. All participants were tested at the close of football season (Pre) and at the end of the winter sports season (Post), a period of 4 months. Body composition (weight [W] and body fat percentage [BF]), strength (calculated 1RM [1 repetition maximum] max for barbell bench press [BP] and squat [SQ]), power (vertical jump [VJ] and seated shot put [UP]), and agility (18.3-m agility run [AG]) were measured. Both groups WC and SP increased significantly in W and BF and improved significantly in BP and VJ (p training.

  7. Monsoon oscillations regulate fertility of the Red Sea

    KAUST Repository

    Raitsos, Dionysios E.

    2015-02-16

    Tropical ocean ecosystems are predicted to become warmer, more saline, and less fertile in a future Earth. The Red Sea, one of the warmest and most saline environments in the world, may afford insights into the function of the tropical ocean ecosystem in a changing planet. We show that the concentration of chlorophyll and the duration of the phytoplankton growing season in the Red Sea are controlled by the strength of the winter Arabian monsoon (through horizontal advection of fertile waters from the Indian Ocean). Furthermore, and contrary to expectation, in the last decade (1998-2010) the winter Red Sea phytoplankton biomass has increased by 75% during prolonged positive phases of the Multivariate El Niño-Southern Oscillation Index. A new mechanism is reported, revealing the synergy of monsoon and climate in regulating Red Sea greenness. © 2015 The Authors.

  8. North Atlantic, ITCZ, and Monsoonal Climate Links

    Science.gov (United States)

    Haug, G. H.; Deplazes, G.; Peterson, L. C.; Brauer, A.; Mingram, J.; Dulski, P.; Sigman, D. M.

    2008-12-01

    Major element chemistry and color data from sediment cores in the anoxic Cariaco Basin off Venezuela record with (sub)annual resolution large and abrupt shifts in the hydrologic cycle of the tropical Atlantic during the last 80 ka. These data suggest a direct connection between the position of the ITCZ over northern South America, the strength of trade winds, and the temperature gradient to the high northern latitudes, ENSO, and monsoonal climate in Asia. The mechanisms behind these decadal-scale ITCZ-monsoon swings can be further explored at major climate transitions such as the onset of Younger Dryas cooling at ~12.7 ka, one of the most abrupt climate changes observed in ice core, lake and marine records in the North Atlantic realm and much of the Northern Hemisphere. Annually laminated sediments from ideally record the dynamics of abrupt climate changes since seasonal deposition immediately responds to climate and varve counts accurately estimate the time of change. We compare sub-annual geochemical data from a lake in Western Germany, which provides one of the best-dated records currently available for this climate transition, with the new the Cariaco Basin record and a new and higher resolution record from Lake Huguang Maar in China, and the Greenland ice core record. The Lake Meerfelder Maar record indicates an abrupt increase in storminess, occurring from one year to the next at 12,678 ka BP, coincident with other observed climate changes in the region. We interpret this shift of the wintertime winds to signify an abrupt change in the North Atlantic westerlies to a stronger and more zonal jet. The observed wind shift provides the atmospheric mechanism for the strong temporal link between North Atlantic overturning and European climate during the last deglaciation, tightly coupled to ITCZ migrations observed in the Cariaco Basin sediments, and a stronger east Asian Monsoon winter monsoon as seen in lake Huguang Maar, when cave stalagmite oxygen isotope data

  9. Winter cooling in the northern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Prasad, T.G.

    The upper thermo-haline structure and the surface meteorological parameters of the central and eastern Arabian Sea during the inter-monsoon (April-May, 1994) and winter monsoon (February-March, 1995) periods, were analysed to understand physical...

  10. Composition, Shell Strength, and Metabolizable Energy of Mulinia lateralis and Ischadium recurvum as Food for Wintering Surf Scoters (Melanitta perspicillata).

    Science.gov (United States)

    Wells-Berlin, Alicia M; Perry, Matthew C; Kohn, Richard A; Paynter, Kennedy T; Ottinger, Mary Ann

    2015-01-01

    Decline in surf scoter (Melanitta perspicillata) waterfowl populations wintering in the Chesapeake Bay has been associated with changes in the availability of benthic bivalves. The Bay has become more eutrophic, causing changes in the benthos available to surf scoters. The subsequent decline in oyster beds (Crassostrea virginica) has reduced the hard substrate needed by the hooked mussel (Ischadium recurvum), one of the primary prey items for surf scoters, causing the surf scoter to switch to a more opportune species, the dwarf surfclam (Mulinia lateralis). The composition (macronutrients, minerals, and amino acids), shell strength (N), and metabolizable energy (kJ) of these prey items were quantified to determine the relative foraging values for wintering scoters. Pooled samples of each prey item were analyzed to determine composition. Shell strength (N) was measured using a shell crack compression test. Total collection digestibility trials were conducted on eight captive surf scoters. For the prey size range commonly consumed by surf scoters (6-12 mm for M. lateralis and 18-24 mm for I. recurvum), I. recurvum contained higher ash, protein, lipid, and energy per individual organism than M. lateralis. I. recurvum required significantly greater force to crack the shell relative to M. lateralis. No difference in metabolized energy was observed for these prey items in wintering surf scoters, despite I. recurvum's higher ash content and harder shell than M. lateralis. Therefore, wintering surf scoters were able to obtain the same amount of energy from each prey item, implying that they can sustain themselves if forced to switch prey.

  11. Composition, shell strength, and metabolizable energy of Mulinia lateralis and Ischadium recurvum as food for wintering surf scoters (Melanitta perspicillata)

    Science.gov (United States)

    Berlin, Alicia; Perry, Matthew C.; Kohn, R.A.; Paynter, K.T.; Ottinger, Mary Ann

    2015-01-01

    Decline in surf scoter (Melanitta perspicillata) waterfowl populations wintering in the Chesapeake Bay has been associated with changes in the availability of benthic bivalves. The Bay has become more eutrophic, causing changes in the benthos available to surf scoters. The subsequent decline in oyster beds (Crassostrea virginica) has reduced the hard substrate needed by the hooked mussel (Ischadium recurvum), one of the primary prey items for surf scoters, causing the surf scoter to switch to a more opportune species, the dwarf surfclam (Mulinia lateralis). The composition (macronutrients, minerals, and amino acids), shell strength (N), and metabolizable energy (kJ) of these prey items were quantified to determine the relative foraging values for wintering scoters. Pooled samples of each prey item were analyzed to determine composition. Shell strength (N) was measured using a shell crack compression test. Total collection digestibility trials were conducted on eight captive surf scoters. For the prey size range commonly consumed by surf scoters (6-12 mm for M. lateralis and 18-24 mm for I. recurvum), I. recurvum contained higher ash, protein, lipid, and energy per individual organism than M. lateralis. I. recurvum required significantly greater force to crack the shell relative to M. lateralis. No difference in metabolized energy was observed for these prey items in wintering surf scoters, despite I. recurvum's higher ash content and harder shell than M. lateralis. Therefore, wintering surf scoters were able to obtain the same amount of energy from each prey item, implying that they can sustain themselves if forced to switch prey.

  12. Composition, Shell Strength, and Metabolizable Energy of Mulinia lateralis and Ischadium recurvum as Food for Wintering Surf Scoters (Melanitta perspicillata.

    Directory of Open Access Journals (Sweden)

    Alicia M Wells-Berlin

    Full Text Available Decline in surf scoter (Melanitta perspicillata waterfowl populations wintering in the Chesapeake Bay has been associated with changes in the availability of benthic bivalves. The Bay has become more eutrophic, causing changes in the benthos available to surf scoters. The subsequent decline in oyster beds (Crassostrea virginica has reduced the hard substrate needed by the hooked mussel (Ischadium recurvum, one of the primary prey items for surf scoters, causing the surf scoter to switch to a more opportune species, the dwarf surfclam (Mulinia lateralis. The composition (macronutrients, minerals, and amino acids, shell strength (N, and metabolizable energy (kJ of these prey items were quantified to determine the relative foraging values for wintering scoters. Pooled samples of each prey item were analyzed to determine composition. Shell strength (N was measured using a shell crack compression test. Total collection digestibility trials were conducted on eight captive surf scoters. For the prey size range commonly consumed by surf scoters (6-12 mm for M. lateralis and 18-24 mm for I. recurvum, I. recurvum contained higher ash, protein, lipid, and energy per individual organism than M. lateralis. I. recurvum required significantly greater force to crack the shell relative to M. lateralis. No difference in metabolized energy was observed for these prey items in wintering surf scoters, despite I. recurvum's higher ash content and harder shell than M. lateralis. Therefore, wintering surf scoters were able to obtain the same amount of energy from each prey item, implying that they can sustain themselves if forced to switch prey.

  13. Characteristics of monsoon low level jet (MLLJ)

    Indian Academy of Sciences (India)

    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.

  14. The asymmetric effects of El Niño and La Niña on the East Asian winter monsoon and their simulation by CMIP5 atmospheric models

    Science.gov (United States)

    Guo, Zhun; Zhou, Tianjun; Wu, Bo

    2017-02-01

    El Niño-Southern Oscillation (ENSO) events significantly affect the year-by-year variations of the East Asian winter monsoon (EAWM). However, the effect of La Niña events on the EAWM is not a mirror image of that of El Niño events. Although the EAWM becomes generally weaker during El Niño events and stronger during La Niña winters, the enhanced precipitation over the southeastern China and warmer surface air temperature along the East Asian coastline during El Niño years are more significant. These asymmetric effects are caused by the asymmetric longitudinal positions of the western North Pacific (WNP) anticyclone during El Niño events and the WNP cyclone during La Niña events; specifically, the center of the WNP cyclone during La Niña events is westward-shifted relative to its El Niño counterpart. This central-position shift results from the longitudinal shift of remote El Niño and La Niña anomalous heating, and asymmetry in the amplitude of local sea surface temperature anomalies over the WNP. However, such asymmetric effects of ENSO on the EAWM are barely reproduced by the atmospheric models of Phase 5 of the Coupled Model Intercomparison Project (CMIP5), although the spatial patterns of anomalous circulations are reasonably reproduced. The major limitation of the CMIP5 models is an overestimation of the anomalous WNP anticyclone/cyclone, which leads to stronger EAWM rainfall responses. The overestimated latent heat flux anomalies near the South China Sea and the northern WNP might be a key factor behind the overestimated anomalous circulations.

  15. Winter vitamin D3 supplementation does not increase muscle strength, but modulates the IGF-axis in young children

    DEFF Research Database (Denmark)

    Mortensen, Charlotte; Mølgaard, Christian; Hauger, Hanne

    2018-01-01

    PURPOSE: To explore whether muscle strength, the insulin-like growth factor axis (IGF-axis), height, and body composition were associated with serum 25-hydroxyvitamin D [25(OH)D] and affected by winter vitamin D supplementation in healthy children, and furthermore to explore potential sex differe...

  16. A solar (irradiance) trigger for millennial-scale abrupt changes in the southwest monsoon?

    Science.gov (United States)

    Higginson, Matthew J.; Altabet, Mark A.; Wincze, Lauren; Herbert, Timothy D.; Murray, David W.

    2004-09-01

    Marine sedimentary records of the last glacial from tropical monsoon latitudes indicate climate fluctuations comparable to rapid changes in δ18O recorded in Greenland. Synchronizing two high-resolution sedimentary records from the Oman and Pakistan margins, we resolve millennial-scale reversals in sea surface temperature (SST) gradient (ΔSST) across the Arabian Sea which directly correspond with the majority of Dansgaard-Oeschger (D-O) events for the last 65 kyr. The relative amplitude of individual monsoon and D-O events appears comparable, suggesting coupled and at least hemispheric forcing. To explore this quasi-cyclic forcing, we compare alkenone-based geologic data with modern satellite-derived ΔSST estimates between sites. Interstadial conditions fall within the range of monsoons during the Holocene, but stadial conditions have no analogs. Following published associations between Eurasian Winter Snow Cover (EWSC) and monsoon rainfall, and El Niño/Southern Oscillation (ENSO) events and anomalous EWSC, we find a good correlation between the Southern Oscillation Index (SOI) and Arabian Sea ΔSST throughout the modern data set. An apparent 11-year cyclicity in the SOI reveals an association between the monsoon, SOI, and solar output variability. The SOI primarily tracks solar total irradiance, but the SOI monsoon linkage becomes nonlinear during excursions of the SOI associated with El Niño Events. Strong El Niños coincide precisely with minimum solar irradiance during the solar cycle, which we attribute to threshold behavior in tropical Pacific SSTs and associated trade wind strength. We propose that both short-term (interannual-decadal) and long-term (centennial-millennial) changes in solar output are consistent with records of ENSO variability, monsoon intensity, and D-O event timing.

  17. Atlantic and Pacific Ocean synergistic forcing of the Mesomerican monsoon over the last two millennia

    Science.gov (United States)

    Lachniet, M. S.; Asmerom, Y.; Polyak, V. J.; Bernal, J. P.

    2015-12-01

    We present a new replicated, high resolution (~2 yrs) and precisely-dated (± 4 yr) wet season hydroclimate reconstruction for the Mesoamerican sector of the North American Monsoon over the past 2250 years. Our new reconstruction is based on two aragonite stalagmites from southwestern Mexico which replicate oxygen isotope variations over the 950-1950 CE interval, and are calibrated to instrumental rainfall variations in the Basin of Mexico. Such data complement existing dendroclimatic reconstructions of early wet season and winter drought severity. Comparisons to indices of ocean-atmosphere circulation show a combined forcing by the North Atlantic Oscillation and the El Niño/Southern Oscillation. Monsoon strengthening coincided with synergistic forcing of a La Niña-like mode and a negative North Atlantic Oscillation, and vice versa for droughts. Although drought is commonly invoked as an stressor leading to societal change, the role of intensified monsoon onto cultural development is rarely explored. We observe that prominent transitions from drought to pluvial conditions are associated with population increases in three of the major highland Mexico civilizations of Teotihuacan, Tula Grande, and the Aztecs. These data suggest a role for ocean-atmosphere dynamics arising from the Atlantic and Pacific Oceans on Mesoamerican monsoon strength.

  18. The Indian Monsoon

    Indian Academy of Sciences (India)

    user

    Her main research interests are monsoon ... His research interests are monsoon variability and prediction and radiation studies. In this article we first consider the importance of prediction of the monsoon, and events such as the intense rainfall event ..... of knowledge to form a forecast of the future, such aids should be.

  19. Glacial to Holocene swings of the Australian-Indonesian monsoon

    Science.gov (United States)

    Mohtadi, Mahyar; Oppo, Delia W.; Steinke, Stephan; Stuut, Jan-Berend W.; de Pol-Holz, Ricardo; Hebbeln, Dierk; Lückge, Andreas

    2011-08-01

    The Australian-Indonesian monsoon is an important component of the climate system in the tropical Indo-Pacific region. However, its past variability, relation with northern and southern high-latitude climate and connection to the other Asian monsoon systems are poorly understood. Here we present high-resolution records of monsoon-controlled austral winter upwelling during the past 22,000 years, based on planktic foraminiferal oxygen isotopes and faunal composition in a sedimentary archive collected offshore southern Java. We show that glacial-interglacial variations in the Australian-Indonesian winter monsoon were in phase with the Indian summer monsoon system, consistent with their modern linkage through cross-equatorial surface winds. Likewise, millennial-scale variability of upwelling shares similar sign and timing with upwelling variability in the Arabian Sea. On the basis of element composition and grain-size distribution as precipitation-sensitive proxies in the same archive, we infer that (austral) summer monsoon rainfall was highest during the Bølling-Allerød period and the past 2,500 years. Our results indicate drier conditions during Heinrich Stadial 1 due to a southward shift of summer rainfall and a relatively weak Hadley cell south of the Equator. We suggest that the Australian-Indonesian summer and winter monsoon variability were closely linked to summer insolation and abrupt climate changes in the northern hemisphere.

  20. Late Holocene (~ 2 ka) East Asian Monsoon variations inferred from river discharge and climate interrelationships in the Pearl River Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Nan, Q.; Li, T.; Chen, J.; Nigam, R.

    -size distributions, TOC contents, and δ13Corg variations appear to be directly related to monsoon precipitation in the sediment source area. An increased East Asian summer monsoon rainfall (EASM) and/or an enhanced East Asian winter monsoon rainfall could...

  1. Himalayan River Terraces as A Landscape Response to Quaternary Summer Monsoon Variability

    Science.gov (United States)

    Jonell, T. N.; Clift, P. D.

    2013-12-01

    In order to interpret marine sedimentary archives as records of the erosional response to Asian monsoon variability, we must first recognize how transport processes affect the storage and release of sediment to the ocean. River terraces, such as found in the Greater Himalaya, provide a pivotal role in the source-to-sink story, because this is where sediment storage occurs and is likely modulated. We investigate the role that climate plays in controlling erosion and sediment flux to the Indus delta and fan by looking at the Indus River system, which is dominated by the strong forcing of the Asian monsoon, as well as winter Westerly winds. Paleoceanographic, speleothem, and lacustrine records indicate that summer monsoon intensity was strong from 29 to 37 ka, decreased after that time until ~16 ka, reached maximum intensity from 8 to 10 ka, and then weakened until ~3 ka. Some lacustrine records, however, indicate a more complex pattern of monsoon variability in the Greater Himalaya, which contrasts with monsoonal forcing in central India. This disagreement suggests that floodplains of major river systems may not experience the same climatic conditions as their mountain sources, resulting in contrasting landscape responses to climate change. High altitude river valleys, at least north ofthe Greater Himalaya, appear to be sensitive to monsoon strength because they lie on the periphery of the present rainfall maximum, in the Himalayan rain shadow. These steep river valleys may be affected by landslide damming during periods of increase moisture transport and strong monsoonal precipitation, where damming provides sediment storage through valley-filling and later sediment release through gradual incision or dam-bursting. The Zanskar River, a major tributary to the upper Indus River, provides a record of the erosional response of mountain river valleys to these extreme phases through river terracing. New OSL ages from alluvial terraces indicate reworking of sediment and

  2. Characteristics of monsoon low level jet (MLLJ) as an index of ...

    Indian Academy of Sciences (India)

    R.Narasimhan(krishtel emaging) 1461 1996 Oct 15 13:05:22

    Temperature and wind data are used to describe variation in the strength of the Monsoon Low. Level Jet (MLLJ) from an ... Figure 1(a). Typical vertical wind speed profiles for some cases in the active phase of monsoon in the year 1965. Figure 1(b). .... axis and is therefore important in the forecasting of. South West monsoon ...

  3. Indian summer monsoon experiments

    OpenAIRE

    Bhat, GS; Narasimha, R

    2007-01-01

    Eight major field experiments have been carried out so far addressing the Indian summer monsoon. While these experiments were international and the impetus was external till 1980, India’s own monsoon programmes evolved since then. In this article, objectives and outcomes from some of these experiments are described. It is shown that monsoon experiments have contributed in several ways. Each experiment enhanced the infrastructure facilities in the country, brought together scientists from diff...

  4. Monsoon-ocean coupling

    OpenAIRE

    Gadgil, Sulochana

    2000-01-01

    The Indian monsoon is maintained by propagation of convective systems of synoptic (lows, depressions, etc.) and planetary scale (tropical convergence zones) from the warm tropical oceans, onto the heated subcontinent. As a result, the monsoon variability on subseasonal scales (between wet and dry spells) and on interannual scales (good monsoons and droughts) is linked to variation of the convective systems over the ocean, where variability in turn depends on the sea surface temperature throug...

  5. The Changing Relationship between Surface Temperatures and Indian Monsoon Rainfall with the Phase of ESI Tendency

    Directory of Open Access Journals (Sweden)

    S. B. Kakade

    2012-01-01

    Full Text Available Effective Strength Index (ESI is the relative strength of NAO and SO. ESI tendency is the algebraic difference between April-ESI and January-ESI and it represents the simultaneous evolution of NAO and SO from winter to spring. During positive (negative phase of ESI tendency, NAO restores positive (negative phase and SO restores negative (positive phase before the beginning of summer season. Thus during contrasting phases (positive and negative of ESI tendency, the evolution of NAO and SO is out of phase. In this paper we have studied the spatial and temporal variability of winter-time temperature field over Europe, Arabian Sea and Bay of Bengal during contrasting phases of ESI tendency. The study reveals that during positive (negative ESI tendency, smaller (larger region of Europe is showing significant winter-time cooling (warming at surface. The relationship between winter-time surface temperature over above regions and Indian summer monsoon rainfall (ISMR also shows spatial and temporal variability. The probable explanation for this change in the relationship is discussed in the paper. Two sets of temperature parameters for two different phases of ESI tendency are found out. Multiple regression equations are developed for the prediction of ISMR in each phase of ESI tendency. The performance of these equations is also discussed in this paper.

  6. Influence of monsoon upwelling on the planktonic foraminifera off Oman during Late Quaternary

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    , these sediments provide an integrated information of the upwelling process and Asian monsoon strengths over geological time. The monsoon system is one of the Earth's most dynamic features, which interacts with global atmospheric circulation that controls... the heat budget in the Arabian Sea. Hence changes in the monsoon system may play an essential role on global climate. The southwest (SW) monsoon system in the Arabian Sea exerts a strong influence upon the climatic conditions in south and southeast...

  7. South Asian summer monsoon variability during the last ~54 kyrs inferred from surface water salinity and river run off proxies

    Digital Repository Service at National Institute of Oceanography (India)

    Gebregiorgis, D.; Hathorne, E.C.; Sijinkumar, A; Nath, B.N.; Nurnberg, D.; Frank, M.

    The past variability of the South Asian Monsoon is mostly known from records of wind strength over the Arabian Sea while high-resolution paleorecords from regions of strong monsoon precipitation are still lacking. Here, we present records of past...

  8. The Indian Monsoon

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 12; Issue 5. The Indian Monsoon - Physics of the Monsoon. Sulochana Gadgil. Series Article Volume 12 Issue 5 May 2007 pp 4-20. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/012/05/0004-0020 ...

  9. 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...

  10. A glimpse of the Quaternary monsoon history from India and adjoining seas

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.; Correge, T.

    . Agriculture in the Indian subcontinent largely depends on monsoon precipitation with about 65% of the total cultivated area, accounting for almost half of the total food grain production, being solely dependent on rains for irrigation (Gadgil et al., 1999... as the Winter Monsoon), that causes heavy rains over the equatorial Indian Ocean and the region further south of the equator (Figure 1). Any change in monsoon precipitation affects the food grain production (Gadgil et al., 1999) and the regional hydrological...

  11. Interactions of Large-Scale Tropical Motion Systems During the 1996-1997 Australian Monsoon

    National Research Council Canada - National Science Library

    Taylor, Sylvia

    1998-01-01

    During the northern winter monsoon, several large-scale tropical motion systems are active in the southern tropical region of the ITCZ and SPCZ, including the maritime continent, northern Australia and the West Pacific...

  12. Observed variability of sea surface salinity and thermal inversions in the Lakshadweep Sea during contrast monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Johnson, Z.; Salgaonkar, G.; Nisha, K.; Rajan, C.K.; Rao, R.R.

    a weak (2002) monsoon. The resultant near-surface thermal inversions also have shown large differences in the life cycle and depth of occurrence between these two winters. Citation: Gopalakrishna, V. V., Z. Johnson, G. Salgaonkar, K. Nisha, C. K...

  13. Nitrogen uptake in the northeastern Arabian Sea during winter cooling

    Digital Repository Service at National Institute of Oceanography (India)

    Kumar, S.; Ramesh, R.; Dwivedi, R.M.; Raman, M.; Sheshshayee, M.S.; DeSouza, W.

    technique are presented. In this relatively underexplored region, productivity is high during winter due to supply of nutrients by convective mixing caused by the cooling of the surface by the northeast monsoon winds. Studies done during different months...

  14. Upstream Subtropical Signals Preceding the Asian Summer Monsoon Circulation.

    Science.gov (United States)

    Yang, Song; Lau, K.-M.; Yoo, S.-H.; Kinter, J. L.; Miyakoda, K.; Ho, C.-H.

    2004-11-01

    In this study, the authors address several issues with respect to the antecedent signals of the large-scale Asian summer monsoon that were earlier identified by Webster and Yang. In particular, they revisit the changes in the subtropical upper-tropospheric westerlies preceding the monsoon, depict the detailed structure of the monsoon's antecedent signals, and investigate the physical processes from the signals to the monsoon. They also explore the teleconnection of these signals to various large-scale climate phenomena and emphasize the importance of the upstream location of the signals relative to the Tibetan Plateau and the monsoon.Before a strong (weak) Asian summer monsoon, the 200-mb westerlies over subtropical Asia are weak (strong) during the previous winter and spring. A significant feature of these signals is represented by the variability of the Middle East jet stream whose changes are linked to the Arctic Oscillation, North Atlantic Oscillation, El Niño Southern Oscillation, and other climate phenomena. When this jet stream intensifies and shifts southeastward, cold air intrudes frequently from eastern Europe into the Middle East and southwestern Asia. As a result, in subtropical Asia, snow and precipitation increase, the ground wetness increases, and surface temperature decreases. A strengthening Middle East jet stream is also accompanied by increases in both stationary wave activity flux and higher-frequency eddy activities. The Tibetan Plateau acts to block these westerly activities propagating eastward and increase the persistence of the low-temperature anomalies, which in turn prolongs the atmospheric signals from winter to spring.A strong link is found between the persistent low-temperature anomalies and the decrease in geopotential height over southern Asia, including the Tibetan Plateau, in spring. The latter indicates a late establishment of the South Asian high, and implies a delay in the atmospheric transition from winter to summer conditions

  15. 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...

  16. Indian monsoon variability in relation to Regional Pressure Index

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    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 ... spatial and temporal scales, for developing the LRF models. .... ability in Indian summer monsoon rainfall on.

  17. Energetics and monsoon bifurcations

    Science.gov (United States)

    Seshadri, Ashwin K.

    2017-01-01

    Monsoons involve increases in dry static energy (DSE), with primary contributions from increased shortwave radiation and condensation of water vapor, compensated by DSE export via horizontal fluxes in monsoonal circulations. We introduce a simple box-model characterizing evolution of the DSE budget to study nonlinear dynamics of steady-state monsoons. Horizontal fluxes of DSE are stabilizing during monsoons, exporting DSE and hence weakening the monsoonal circulation. By contrast latent heat addition (LHA) due to condensation of water vapor destabilizes, by increasing the DSE budget. These two factors, horizontal DSE fluxes and LHA, are most strongly dependent on the contrast in tropospheric mean temperature between land and ocean. For the steady-state DSE in the box-model to be stable, the DSE flux should depend more strongly on the temperature contrast than LHA; stronger circulation then reduces DSE and thereby restores equilibrium. We present conditions for this to occur. The main focus of the paper is describing conditions for bifurcation behavior of simple models. Previous authors presented a minimal model of abrupt monsoon transitions and argued that such behavior can be related to a positive feedback called the `moisture advection feedback'. However, by accounting for the effect of vertical lapse rate of temperature on the DSE flux, we show that bifurcations are not a generic property of such models despite these fluxes being nonlinear in the temperature contrast. We explain the origin of this behavior and describe conditions for a bifurcation to occur. This is illustrated for the case of the July-mean monsoon over India. The default model with mean parameter estimates does not contain a bifurcation, but the model admits bifurcation as parameters are varied.

  18. Nosema ceranae Winter Control: Study of the Effectiveness of Different Fumagillin Treatments and Consequences on the Strength of Honey Bee (Hymenoptera: Apidae) Colonies.

    Science.gov (United States)

    Mendoza, Y; Diaz-Cetti, S; Ramallo, G; Santos, E; Porrini, M; Invernizzi, C

    2017-02-01

    In Uruguay, colonies of honey bees moving to Eucalyptus grandis plantation in autumn habitually become infected with the microsporidian Nosema ceranae , a parasite that attacks the digestive system of bees. Beekeepers attributed to N. ceranae depopulation of the colonies that often occurs at the end of the blooming period, and many use the antibiotic fumagillin to reduce the level of infection. The aim of this study was to compare the effectiveness of four different fumagillin treatments and determine how this antibiotic affects the strength of the colonies during the winter season. The colonies treated with fumagillin in July showed less spore load at the end of applications, being the most effective the following treatments: the four applications sprayed over bees of 30 mg of fumagillin in 100 ml of sugar syrup 1:1, and four applications of 90 mg of fumagillin in 250 ml of sugar syrup 1:1 using a feeder. However, 2 month after the treatment applications, the colonies treated with fumagillin were the same size as the untreated colonies. In September, the colonies treated and not treated with fumagillin did not differ in colony strength (adult bee population and brood area) or spores abundance. Our study demonstrates that fumagillin treatment temporarily decreased the spore load of N. ceranae , but this was not reflected in either the size of the colonies or the probability of surviving the winter regardless of the dose or the administration strategy applied. Given the results obtained, we suggest to not perform the pharmacological treatment under the conditions described in the experiment. En Uruguay las colonias de abejas melíferas que se trasladan a las forestaciones de Eucalyptus grandis en otoño indefectiblemente se infectan con el microsporido Nosema ceranae , parásito que ataca el sistema digestivo de las abejas. Los apicultores atribuyen a N. ceranae el despoblamiento de las colonias que ocurre con frecuencia al terminar el periodo de floraci

  19. Winter to winter recurrence of atmospheric circulation anomalies over East Asia and its impact on winter surface air temperature anomalies.

    Science.gov (United States)

    Zhao, Xia; Yang, Guang

    2017-01-01

    The persistence of atmospheric circulation anomalies over East Asia shows a winter to winter recurrence (WTWR) phenomenon. Seasonal variations in sea level pressure anomalies and surface wind anomalies display significantly different characteristics between WTWR and non-WTWR years. The WTWR years are characterized by the recurrence of both a strong (weak) anomalous Siberian High and an East Asian winter monsoon over two successive winters without persistence through the intervening summer. However, anomalies during the non-WTWR years have the opposite sign between the current and ensuing winters. The WTWR of circulation anomalies contributes to that of surface air temperature anomalies (SATAs), which is useful information for improving seasonal and interannual climate predictions over East Asia and China. In the positive (negative) WTWR years, SATAs are cooler (warmer) over East Asia in two successive winters, but the signs of the SATAs are opposite in the preceding and subsequent winters during the non-WTWR years.

  20. The Plateau Monsoon variation during the past 130 kyr revealed by loess deposit at northeast Qinghai-Tibet (China).

    NARCIS (Netherlands)

    Lu, H.; Wang, X.; Ma, H.; Tan, H.; Vandenberghe, J.; Miao, X.; Li, Z.; Sun, Y.; An, Z.; Cao, G.

    2004-01-01

    Climate in northeast Qinghai-Tibetan Plateau is characterised by the alternation of summer and winter monsoon circulation, which is generated by thermodynamic and kinetic effects of the immense plateau. The Plateau Monsoon system during the recent geological past has been investigated through a 44-m

  1. Winter Weather

    Science.gov (United States)

    ... Education Centers Harwood Training Grants Videos E-Tools Winter Storms Plan. Equip. Train To prevent injuries, illnesses and Fatalities during winter storms. This page requires that javascript be enabled ...

  2. Foretelling the Monsoon

    Indian Academy of Sciences (India)

    Relation between the continental TCZ and the TCZ over Equatorial Indian Ocean · Understanding year-to year (interannual) variation of the monsoon · Slide 40 · IMPACT OF EL NINO/LA NINA · Slide 42 · Variation of ISMR anomalies ( i.e. difference from the average value) normalized by std. deviation from 1979-2004.

  3. The Indian Monsoon

    Indian Academy of Sciences (India)

    user

    trying to predict, such as clouds or a monsoon depression (in which thousands of clouds are embedded) are the culmination of the instabilities of the atmosphere2. They involve nonlinear. Figure 3. Anomalies of the rainfall for June–Septem- ber 2002 for the meteoro- logical subdivisions of In- dia . Blue: Excess (>+19%).

  4. The Indian Monsoon

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 11; Issue 8. The Indian Monsoon - Variations in Space and Time. Sulochana Gadgil. Series Article Volume 11 Issue 8 August 2006 pp 8-21. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/011/08/0008-0021 ...

  5. The Indian Monsoon

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 13; Issue 3. The Indian Monsoon - Links to Cloud systems over the Tropical Oceans. Sulochana Gadgil. Series Article Volume 13 Issue 3 March 2008 pp 218-235. Fulltext. Click here to view fulltext PDF. Permanent link:

  6. The Indian Monsoon

    Indian Academy of Sciences (India)

    Sulochana Gadgil is an honorary Professor at the. Centre for Atmospheric and. Oceanic Sciences at the. Indian Institute of Science. Her main research interests are monsoon dynamics, the coupling of the tropical cloud systems to the oceans. She is interested in evolutionary biology as well and has worked on mathematical ...

  7. The Indian Monsoon

    Indian Academy of Sciences (India)

    Oceanic Sciences at the. Indian Institute of Science. Her main research interests are monsoon dynamics, the coupling of the tropical cloud systems to the oceans. She has also worked with agricultural scientists and farmers to identify farming strategies which are tailored to the rainfall variability experienced over the region.

  8. Foretelling the Monsoon

    Indian Academy of Sciences (India)

    Link of rainfall over the monsoon zone to cloud systems over the surrounding ocean · Slide 31 · Slide 32 · Special Features of Indian longitudes discovered in the first study of satellite imagery · Slide 34 · Slide 35 · Slide 36 · Slide 37 · Relation between the continental TCZ and the TCZ over Equatorial Indian Ocean.

  9. The Indian Monsoon

    Indian Academy of Sciences (India)

    2006-06-23

    Jun 23, 2006 ... spells with little or no rainfall. SERIES I ARTICLE raging monsoon' is high, it is unwise to schedule such events in this period. Planning such an event during this period, rather than a few weeks later, makes sense only if the expected benefit of the earlier date far outweighs this large expected loss. It appears.

  10. The Indian Monsoon

    Indian Academy of Sciences (India)

    The most important facet of weather and climate in a tropical region such as ours, is rainfall. I have considered the observed space-time variation of the rainfall over the. Indian region, in the first articlel in this series. The ulti- mate aim of monsoon meteorology is to gain sufficient insight into the physics of this variation for ...

  11. Winter MVC

    OpenAIRE

    Castellón Gadea, Pasqual

    2013-01-01

    Winter MVC és un framework de presentació basat en Spring MVC que simplifica la metodologia de configuracions. Winter MVC es un framework de presentación basado en Spring MVC que simplifica la metodología de configuraciones. Winter MVC is a presentation framework that simplifies Spring MVC configuration methodology.

  12. Changes in the Indian summer monsoon intensity in Sri Lanka during the last 30 ky - A multiproxy record from a marine sediment core.

    Science.gov (United States)

    Ranasinghage, P. N.; Nanayakkara, N. U.; Kodithuwakku, S.; Siriwardana, S.; Luo, C.; Fenghua, Z.

    2016-12-01

    Indian monsoon plays a vital role in determining climate events happening in the Asian region. There is no sufficient work in Sri Lanka to fully understand how the summer monsoonal variability affected Sri Lanka during the quaternary. Sri Lanka is situated at an ideal location with a unique geography to isolate Indian summer monsoon record from iris counterpart, Indian winter monsoon. Therefore, this study was carried out to investigate its variability and understand the forcing factors. For this purpose a 1.82 m long gravity core, extracted from western continental shelf off Colombo, Sri Lanka by Shiyan 1 research vessel, was used. Particle size, chemical composition and colour reflectance were measured using laser particle size analyzer at 2 cm resolution, X-Ray Fluorescence spectrometer (XRF) at 2 cm resolution, and color spectrophotometer at 1 cm resolution respectively. Radio carbon dating of foraminifera tests by gas bench technique yielded the sediment age. Finally, principal component analysis (PCA) of XRF and color reflectance (DSR) data was performed to identify groups of correlating elements and mineralogical composition of sediments. Particle size results indicate that Increasing temperature and strengthening monsoonal rainfall after around 18000 yrs BP, at the end of last glacial period, enhanced chemical weathering over physical weathering. Proxies for terrestrial influx (XRF PC1, DSR PC1) and upwelling and nutrient supply driven marine productivity (XRF PC3 and DSR PC2) indicate that strengthening of summer monsoon started around 15000 yrs BP and maximized around 8000-10000 yrs BP after a short period of weakening during Younger Dryas (around 11000 yrs BP). The 8.2 cold event was recorded as a period of low terrestrial influx indicating weakening of rainfall. After that terrestrial input was low till around 2000 yrs BP indicating decrease in rainfall. However, marine productivity remained increasing throughout the Holocene indicating an increase in

  13. Monsoon regulation of Lombok Strait internal waves

    Science.gov (United States)

    Matthews, J. P.; Aiki, H.; Masuda, S.; Awaji, T.; Ishikawa, Y.

    2011-05-01

    We use satellite imagery and numerical modeling to investigate the characteristics of Lombok Strait nonlinear internal waves in relation to the dominant monsoon seasonality. Two basic wave types are identified, the first of which represents the well-known arc-like internal wave (AIW) that radiates uniformly away from its generation region near the sill in regular sequences of ranked solitons. This component is best defined to the north of the strait and is the main focus of our paper. A second type (termed here the "irregular internal wave") manifests to the south in association with extensive throughflow plumes and appears in distorted, braided assemblages with orientations that are incompatible with uniform outward motion from the sill. Synthetic aperture radar (SAR) data show that the northward-propagating AIWs are often observed during the boreal winter monsoon, when the southward throughflow weakens. A potential cause of this seasonal behavior is revealed by advanced numerical modeling, which indicates that strong southward throughflows during the southeast monsoon greatly constrain the northward tidal influx, particularly near the surface, thereby inhibiting embryonic wave growth at the leading edge of the intrusion and producing comparatively weak internal wave release. This new mechanism operates alongside other possible seasonal influences on SAR internal wave detection relating, for example, to wind or stratification. Our findings suggest that long-term modifications to the Lombok Strait throughflow, due to evolution of the monsoon and/or the El Niño-Southern Oscillation, could retune the energy, composition, and directionality of internal wavefields radiated from the passage.

  14. Characteristics of monsoon low level jet (MLLJ) as an index of ...

    Indian Academy of Sciences (India)

    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.

  15. Dirtier Air from a Weaker Monsoon

    Science.gov (United States)

    Chin, Mian

    2012-01-01

    particular, a weaker East Asian summer monsoon is characterized by weaker southerly or southwesterly winds, a deficit in rainfall over northern China and larger rainfalls in southern China. By contrast, when the East Asian summer monsoon is strong, the southerly winds and strong rainfalls extend to northern China. The decadal scale decline in the strength of the East Asian summer monsoon since the 1970s would imply an increase in aerosol concentrations in northern China, north of 28deg N, and a decrease in southern China if emissions were kept the same. One obvious reason for this direction of aerosol change is that the reduction of monsoon rainfall in northern China would cause less wet scavenging of aerosols by precipitation. Zhu et al.2 investigated this relationship between aerosol concentrations and the strength of the East Asian summer monsoon and showed that the two parameters have strong negative correlations: the summer aerosol concentrations near the surface over eastern China.

  16. West African monsoon 2012

    OpenAIRE

    Cornforth, Rosalind J.

    2013-01-01

    Living up to its reputation as a highly variable climate system, the West African Monsoon (WAM) 2012 contrasted strikingly with the previous year. In 2011, the West African rainy season was delayed, patchy, and irregular. In 2012, whilst it was anomalously wet in many area, the Guinea coastal countries and some crucial agricultural regions remained very dry, persisting from the previous year. As a result, 2012 generated the third big food crisis to hit the region in the last seven years. The ...

  17. Interannual variability of the onset of the South China Sea summer monsoon

    OpenAIRE

    Luo, Ming; Leung, Yee; Graf, Hans-Friedrich; Herzog, Michael; Zhang, Wei

    2015-01-01

    This article investigates the year-to-year variability of the onset of the South China Sea summer monsoon (SCSSM) and the possible influences exerted by the surface temperature anomalies over land and sea. Early and late monsoon onsets are related to the temperature anomalies in different regions. It is found that an early onset follows negative sea surface temperature (SST) anomalies in the central tropical Pacific (CP) Ocean during the preceding winter and spring, corresponding to a CP La N...

  18. Asian monsoon variability, cyclicities, and forcing mechanisms

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    the high latitude climate and Indian Ocean monsoon records at millennial time scale poses new challenge to address the monsoon variability issue. However, it is not clear yet whether monsoon triggers the high latitude changes or high latitude air...

  19. High Northern Latitude Insolation Forcing of Tropical Monsoons or Monsoon Forcing of High Northern Latitude Ice Volume?

    Science.gov (United States)

    Beck, W.; Zhou, W.; Cheng, L.; Wu, Z.; Xian, F.; Kong, X.; Cottam, T.; An, Z.; White, L.

    2017-12-01

    We show that atmospheric 10Be flux is a quantitative proxy for rainfall, and use it to derive a 530Ka-long record of East Asian summer monsoon rainfall from Chinese Loess. Our record strongly resembles the Red Sea paleosea level and LR04 benthic foram δ18O records, with 53% & 45% of its variance reflected in each of these two global ice volume proxies. This suggests EASM intensity is closely coupled to ice volume by some mechanism. At first glance, this seems to support the claim based on strongly correlated Chinese cave δ18O and 65°N summer solar insolation that Asian monsoon intensity is controlled by high northern latitude insolation. Nevertheless, our 10Be-proxy has only 17% common variance with cave δ18O. Furthermore, Chinese cave δ18O records are very poorly correlated with sea-level/global ice volume, conflicting with both our proxy and Milankovitch theory, if interpreted as a monsoon intensity proxy. We argue that cave δ18O is instead a mixing proxy for monsoon moisture derived from (δ18O depleted) Indian vs Pacific monsoon sectors. We suggest both this mixing ratio and EASM intensity are not governed by high northern latitude insolation, but rather by orbital forcing of the low latitude interhemispheric insolation gradient, which mimics the 65°N insolation pattern. We show this gradient regulates the ratio of Asian monsoon outflow to the Indian vs. North Pacific subtropical highs, providing a coupling to both Hadley and Walker circulations. When outflow strengthens in one of these sectors it weakens in the other, regulating the relative strength of the Trade and Westerly winds in each sector. Trade wind coupling to monsoon strength in each sector controls the ISM/Pacific monsoon moisture mixing ratio and EASM intensity, although intensity is also influenced by other factors. This model provides mechanisms by which the monsoons may influence ice volume. Westerlies strength adjacent to the North Pacific Subtropical High strongly regulates transient

  20. 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

  1. Revisiting Asian monsoon formation and change associated with Tibetan Plateau forcing: I. Formation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Guoxiong; Liu, Yimin; Duan, Anmin; Bao, Qing [Chinese Academy of Sciences, State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Beijing (China); Dong, Buwen [University of Reading, Department of Meteorology, National Centre for Atmospheric Science, Reading (United Kingdom); Liang, Xiaoyun [China Meteorological Administration, National Climate Center, Beijing (China); Yu, Jingjing [China Meteorological Administration, National Meteorological Information Center, Beijing (China)

    2012-09-15

    Numerical experiments with different idealized land and mountain distributions are carried out to study the formation of the Asian monsoon and related coupling processes. Results demonstrate that when there is only extratropical continent located between 0 and 120 E and between 20/30 N and the North Pole, a rather weak monsoon rainband appears along the southern border of the continent, coexisting with an intense intertropical convergence zone (ITCZ). The continuous ITCZ surrounds the whole globe, prohibits the development of near-surface cross-equatorial flow, and collects water vapor from tropical oceans, resulting in very weak monsoon rainfall. When tropical lands are integrated, the ITCZ over the longitude domain where the extratropical continent exists disappears as a consequence of the development of a strong surface cross-equatorial flow from the winter hemisphere to the summer hemisphere. In addition, an intense interaction between the two hemispheres develops, tropical water vapor is transported to the subtropics by the enhanced poleward flow, and a prototype of the Asian monsoon appears. The Tibetan Plateau acts to enhance the coupling between the lower and upper tropospheric circulations and between the subtropical and tropical monsoon circulations, resulting in an intensification of the East Asian summer monsoon and a weakening of the South Asian summer monsoon. Linking the Iranian Plateau to the Tibetan Plateau substantially reduces the precipitation over Africa and increases the precipitation over the Arabian Sea and the northern Indian subcontinent, effectively contributing to the development of the South Asian summer monsoon. (orig.)

  2. Desert Dust and Monsoon Rain

    Science.gov (United States)

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

    2014-01-01

    For centuries, inhabitants of the Indian subcontinent have know that heavy dust events brought on by strong winds occur frequently in the pre-monsoon season, before the onset of heavy rain. Yet scientists have never seriously considered the possibility that natural dust can affect monsoon rainfall. Up to now, most studies of the impacts of aerosols on Indian monsoon rainfall have focused on anthropogenic aerosols in the context of climate change. However, a few recent studies have show that aerosols from antropogenic and natural sources over the Indian subcontinent may affect the transition from break to active monsoon phases on short timescales of days to weeks. Writing in Nature Geoscience, Vinoj and colleagues describe how they have shown that desert dust aerosols over the Arabian Sea and West Asia can strenghten the summer monsoon over the Indial subcontinent in a matter of days.

  3. Picophytoplankton variability: Influence of winter convective mixing and advection in the northeastern Arabian Sea

    Science.gov (United States)

    Bemal, Suchandan; Anil, Arga Chandrashekar; Shankar, D.; Remya, R.; Roy, Rajdeep

    2018-04-01

    The deepening of mixed layer and ensuing changes in optical and physicochemical properties of euphotic zone can influence phytoplankton community dynamics in the northeastern Arabian Sea during winter monsoon. The response of picophytoplankton community to such changes during winter convective mixing is not well understood. Herein, we have compared variations in the picophytoplankton community structure during early (November-December 2012), peak (end-January 2014) and late (mid-February 2015) winter monsoon from three separate cruises in the southern northeastern Arabian Sea. The higher Synechococcus abundance owing to entrainment of nutrients in mixed layer was observed during peak winter monsoon, while the concomitant changes in nitrate concentration, light and oxygen environment restricted Prochlorococcus growth resulting in lower abundance during the same period. This highlights the diverse responses of picophytoplankton groups to physicochemical changes of water column during winter convective mixing. The divinyl chlorophyll b/a ratio (marker for Prochlorococcus ecotypes) indicated prevalence of one low-light adapted ecotype (sensitive to light shock) in sub-surface water, one high-light adapted ecotype in surface water during early winter monsoon and both disappeared during intense mixing period in peak winter monsoon. Subsequently, a distinct low-light adapted ecotype, capable to tolerate light shock, was noticed during late winter monsoon and we argue that this ecotype is introduced to southern northeastern Arabian Sea through advection from north by sub-surface circulation. The total picophytoplankton biomass available to microbial loop is restored during late winter monsoon, when stratification begins, with a higher abundance of Synechococcus and the re-occurrence of Prochlorococcus population in the region. These inferences indicate that variability in picophytoplankton community structure and their contribution to the microbial loop are driven by

  4. Indian summer monsoon rainfall characteristics during contrasting monsoon years.

    Digital Repository Service at National Institute of Oceanography (India)

    Varikoden, H.; RameshKumar, M.R.; Babu, C.A.

    monsoon rainfall. During 2009, Pacific SST was above normal in nino regions, characteristic of the El Nino structure; however, during 2010, the nino regions were clearly below normal temperature, indicating the La Nina pattern. The associated atmospheric...

  5. Atmospheric circulation characteristics associated with the onset of Asian summer monsoon

    Science.gov (United States)

    Li, Chongyin; Pan, Jing

    2006-12-01

    The onset of the Asian summer monsoon has been a focus in the monsoon study for many years. In this paper, we study the variability and predictability of the Asian summer monsoon onset and demonstrate that this onset is associated with specific atmospheric circulation characteristics. The outbreak of the Asian summer monsoon is found to occur first over the southwestern part of the South China Sea (SCS) and the Malay Peninsula region, and the monsoon onset is closely related to intra-seasonal oscillations in the lower atmosphere. These intra-seasonal oscillations consist of two low-frequency vortex pairs, one located to the east of the Philippines and the other over the tropical eastern Indian Ocean. Prior to the Asian summer monsoon onset, a strong low-frequency westerly emerges over the equatorial Indian Ocean and the low-frequency vortex pair develops symmetrically along the equator. The formation and evolution of these low-frequency vortices are important and serve as a good indicator for the Asian summer monsoon onset. The relationship between the northward jumps of the westerly jet over East Asia and the Asian summer monsoon onset over SCS is investigated. It is shown that the northward jump of the westerly jet occurs twice during the transition from winter to summer and these jumps are closely related to the summer monsoon development. The first northward jump (from 25° 28°N to around 30°N) occurs on 8 May on average, about 7 days ahead of the summer monsoon onset over the SCS. It is found that the reverse of meridional temperature gradient in the upper-middle troposphere (500 200 hPa) and the enhancement and northward movement of the subtropical jet in the Southern Hemispheric subtropics are responsible for the first northward jump of the westerly jet.

  6. 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.

  7. The impact of stochastic parametrisations on the representation of the Asian summer monsoon

    Science.gov (United States)

    Strømmen, K.; Christensen, H. M.; Berner, J.; Palmer, T. N.

    2018-03-01

    The impact of the stochastic schemes Stochastically Perturbed Parametrisation Tendencies (SPPT) and Stochastic Kinetic Energy Backscatter Scheme (SKEBS) on the representation of interannual variability in the Asian summer monsoon is examined in the coupled climate model CCSM4. The Webster-Yang index, measuring anomalies of a specified wind-shear index in the monsoon region, is used as a metric for monsoon strength, and is used to analyse the output of three model integrations: one deterministic, one with SPPT, and one with SKEBS. Both schemes show improved variability, which we trace back to improvements in the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). SPPT improves the representation of ENSO and through teleconnections thereby the monsoon, supporting previous work on the benefits of this scheme on the model climate. SKEBS also improves monsoon variability by way of improving the representation of the IOD, in particular by breaking an overly strong coupling to ENSO.

  8. Fluid dynamics of the monsoon

    OpenAIRE

    Gadgil, Sulochana

    1981-01-01

    The monsoonal regions of the world are characterized by a seasonal reversal in the direction of winds associated with the excursion of the equatorial trough (or the ITCZ) in response to the variation in the latitude of maximum insolation. This monsoonal circulation is a planetary scale phenomenon. However, the associated precipitation is critically dependent on the organization of the cumulus clouds (typically a few kilometers in horizontal extent) over the scale of synoptic vortices (typical...

  9. Symmetric instability of monsoon flows

    OpenAIRE

    Krishnakumar, V.; Lau, K.-M.

    2011-01-01

    Using a zonally symmetric multi-level moist linear model, we have examined the possibility of symmetric instability in the monsoon region. Stability analyses with a zonally symmetric model using monthly ECMWF (Jan – Dec) zonal basic flows revealed both unstable as well as neutral modes. In the absence of cumulus heating, the linear stability of the monsoon flow changes dramatically with the emergence of many unstable modes in the month of May and lasting through August; whereas with the inclu...

  10. Enhanced export of carbon by salps during the northeast monsoon period in the northern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Sarin, M.M.; Rengarajan, R.

    ) during the winter monsoon, 10-23 February 1997. The sampling period was characterised by an extensive salp swarm, and salp faecal pellets were the dominant contributors to the particulate matter in the sediment traps. Average sup(234)Th flux out...

  11. Winter Wonderlands

    Science.gov (United States)

    Coy, Mary

    2011-01-01

    Listening to people complain about the hardships of winter and the dreariness of the nearly constant gray sky prompted the author to help her sixth graders recognize and appreciate the beauty that surrounds them for nearly five months of the year in western New York. The author opines that if students could see things more artistically, the winter…

  12. A Large Scale Index to Characterize the Indian Summer Monsoon

    Science.gov (United States)

    Cannon, F. G.; Carvalho, L. V.; Jones, C.; Bookhagen, B.

    2012-12-01

    Seasonal rainfall associated with the Indian summer monsoon is the primary water source for the central and eastern Himalaya, while the western Himalaya receives significant amounts of precipitation during the winter season. Typically, the monsoon season begins in the eastern lowlands during June, migrates northwest across the Ganges plains, is bounded by the Himalayan orographic barrier to the north, and lasts until approximately mid-October. By the end of the monsoon season, the accumulated rainfall contributes to over 80% of the total annual precipitation in the central and eastern Himalayan regions. Consequently, the seasonal variability of mountain runoff depends on the onset, duration, and intensity of the monsoon and short-to-long term variations in these factors play a fundamental role in the region's hydrologic cycle. The objective task of this research is to develop detailed diagnostic analyses to characterize climatological variability of the summer monsoon system over high Asian mountains during 1979-present. Primarily, we apply a combined empirical orthogonal function to seasonal variations in circulation, temperature and moisture. Previous research has shown that important mechanisms of monsoonal variability include low level (surface - 850 hPa) specific humidity, temperature, zonal and meridional wind components, and precipitation. This project utilizes daily CFSR reanalysis data for the aforementioned variables from 1979 to 2010 at a one-degree spatial resolution over the Indian sub-continent (5°-45°N and 60°-90°E). We also employ precipitation data from various sources including APHRODITE, TRMM, GPCP, and station data to comprehensively investigate the validity of our index through various precipitation data acquisition methods. Based on the time coefficient of the second EOF of surface level humidity, temperature, and zonal and meridional wind, we construct the proposed monsoon index and define the onset, demise, and intraseasonal variations

  13. The Origins of ITCZs, Monsoons, and Monsoon Onset

    Science.gov (United States)

    Chao, Winston C.

    2009-01-01

    Intertropical convergence zones (ITCZs), monsoons and monsoon onset are among the most prominent of atmospheric phenomena. Understanding their origins is fundamental to a full understanding of the atmospheric general circulation and has challenged meteorologists for a very long time. There has been important progress in understanding these phenomena in recent years, and in this seminar, recent developments, to which the speaker has contributed, are reviewed. First, contrary to conventional belief, land-sea thermal contrast is not necessary for monsoons to form. Second, monsoon onset occurs when there is a sudden poleward jump of an ITCZ during its annual cycle of latitudinal movement. A monsoon, then, is an ITCZ after its poleward jump. Third, the SST latitudinal maximum is not the most significant, or even a necessary, factor in the formation of an ITCZ; there are other important, if not more important, factors. These factors are the interaction between convection and surface fluxes, the interaction between convection and radiation, and the earth's rotation. Finally, the recent understanding of how ITCZs form has led to a conceptual explanation for the origin of the double ITCZ bias in GCM simulations.

  14. 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

    including, but not limited to, the Mei-Yu/Baiu sudden onset and withdrawal, low-level jet orientation and variability, and orographic forced rainfall. Under anthropogenic climate change many competing factors complicate making robust projections of monsoon changes. Without aerosol effects, increased land-sea temperature contrast suggests strengthened monsoon circulation due to climate change. However, increased aerosol emissions will reflect more solar radiation back to space, which may temper or even reduce the strength of monsoon circulations compared to the present day. A more comprehensive assessment is needed of the impact of black carbon aerosols, which may modulate that of other anthropogenic greenhouse gases. Precipitation may behave independently from the circulation under warming conditions in which an increased atmospheric moisture loading, based purely on thermodynamic considerations, could result in increased monsoon rainfall under climate change. The challenge to improve model parameterizations and include more complex processes and feedbacks pushes computing resources to their limit, thus requiring continuous upgrades of computational infrastructure to ensure progress in understanding and predicting the current and future behavior of monsoons.

  15. Monsoon effect simulation on typhoon rainfall potential - Typhoon Morakot (2009

    Directory of Open Access Journals (Sweden)

    Yi-Ling Chang

    2017-01-01

    Full Text Available A record breaking extreme precipitation event produced 3000 mm day-1 of accumulated rainfall over southern Taiwan in August 2009. The interactions between Typhoon Morakot and the prevailing southwesterly (SW monsoon are the primary mechanism for this heavy precipitation during 5 - 13 August 2009. This extreme precipitation could be produced by the abundant moisture from the SW monsoon associated with the interaction between typhoon and monsoon wind fields, leading to severe property damage. The accurate mapping of extreme precipitation caused from the interaction between a monsoon and typhoon is critical for early warning in Taiwan. This study simulates the heavy rainfall event is based on the Weather Research and Forecast system model (WRF using the three nested domain configuration. Using data assimilation with a virtual meteorological field using the 3D-Var system, such as wind field to alter the SW monsoon strength in the initial condition, the impacts of intensified convergence and water vapor content on the accumulated rainfall are analyzed to quantize the intensification of typhoon rainfall potential. The results showed a positive correlation between the enhanced precipitation and the intensity of low-level wind speed convergence as well as water vapor content. For the Typhoon Morakot case study the rainfall for could attain approximately 2 × 104 mm at 6 hours interval in the southern Taiwan area when 10 × 10-6 s-1 convergence intensified at 850 hPa level around the southern part of the Taiwan Strait. These results suggest that low-level wind speed, convergence and water vapor content play key roles in the typhoon rainfall potential coupled with the SW monsoon.

  16. Decadal Monsoon-ENSO Relationships Reexamined

    Science.gov (United States)

    Yun, Kyung-Sook; Timmermann, Axel

    2018-02-01

    The strength of the El Niño-Southern Oscillation (ENSO)-Indian summer monsoon rainfall (ISMR) relationship shows considerable decadal fluctuations, which have been previously linked to low-frequency climatic processes such as shifts in ENSO's center of action or the Atlantic Multidecadal Oscillation. However, random variability can also cause similar variations in the relationship between climate phenomena. Here we propose a statistical test to determine whether the observed time-evolving correlations between ENSO and ISMR are different from those expected from a simple stochastic null hypothesis model. The analysis focuses on the time evolution of moving correlations, their expected variance, and probabilities for rapid transitions. The results indicate that the time evolution of the observed running correlation between these climate modes is indistinguishable from a system in which the ISMR signal can be expressed as a stochastically perturbed ENSO signal. This challenges previous deterministic interpretations. Our results are further corroborated by the analysis of climate model simulations.

  17. On breaks of the Indian monsoon

    Indian Academy of Sciences (India)

    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 ...

  18. Seasonal sea surface temperature contrast between the Holocene and last glacial period in the western Arabian Sea (Ocean Drilling Project Site 723A): Modulated by monsoon upwelling

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; Malmgren, B.A.

    were noticed within the Holocene period, which is attributed to the intense upwelling during the summer monsoon. This causes a lowering of SST to values similar to those of the winter season in analogy with the present day. A 3 degrees C rise in winter...

  19. Monsoon onset over Kerala and pre monsoon rainfall peak

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Shenoi, S.S.C.; Shankar, D.

    degrees E, from 1st March to 31 May for the years 1979 to 2001. The monsoon onset dates over Kerala, as declared by India Meteorological Department has been used in the present study. For each year, the midday of the pentad with the rainfall peak...

  20. Multi-decadal modulation of the El Nino-Indian monsoon relationship by Indian Ocean variability

    International Nuclear Information System (INIS)

    Ummenhofer, Caroline C; Sen Gupta, Alexander; Li Yue; Taschetto, Andrea S; England, Matthew H

    2011-01-01

    The role of leading modes of Indo-Pacific climate variability is investigated for modulation of the strength of the Indian summer monsoon during the period 1877-2006. In particular, the effect of Indian Ocean conditions on the relationship between the El Nino-Southern Oscillation (ENSO) and the Indian monsoon is explored. Using an extended classification for ENSO and Indian Ocean dipole (IOD) events for the past 130 years and reanalyses, we have expanded previous interannual work to show that variations in Indian Ocean conditions modulate the ENSO-Indian monsoon relationship also on decadal timescales. El Nino events are frequently accompanied by a significantly reduced Indian monsoon and widespread drought conditions due to anomalous subsidence associated with a shift in the descending branch of the zonal Walker circulation. However, for El Nino events that co-occur with positive IOD (pIOD) events, Indian Ocean conditions act to counter El Nino's drought-inducing subsidence by enhancing moisture convergence over the Indian subcontinent, with an average monsoon season resulting. Decadal modulations of the frequency of independent and combined El Nino and pIOD events are consistent with a strengthened El Nino-Indian monsoon relationship observed at the start of the 20th century and the apparent recent weakening of the El Nino-Indian monsoon relationship.

  1. 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.

  2. 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.

    2013-01-01

    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. PMID:27087778

  3. 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.)

  4. Evaluation of CFSV2 Forecast Skill for Indian Summer Monsoon Sub-Seasonal Characteristics

    Science.gov (United States)

    S, S. A.; Ghosh, S.

    2015-12-01

    Prediction of sub seasonal monsoon characteristics of Indian Summer Monsoon (ISM) is highly crucial for agricultural planning and water resource management. The Climate forecast System version 2 (CFS V2), the state of the art coupled climate model developed by NCEP, is currently being employed for the seasonal and extended range forecasts of ISM. Even though CFSV2 is a fully coupled ocean- atmosphere- land model with advanced physics, increased resolution and refined initialisation, its ISM forecasts, in terms of seasonal mean and variability needs improvement. Numerous works have been done for verifying the CFSV2 forecasts in terms of the seasonal mean, its mean and variability, active and break spells, and El Nino Southern Oscillation (ENSO) - monsoon interactions. Most of these works are based on either rain fall strength or rainfall based indices. Here we evaluate the skill of CFS v2 model in forecasting the various sub seasonal features of ISM, viz., the onset and withdrawal days of monsoon that are determined using circulation based indices, the Monsoon Intra Seasonal Oscillations (MISO), and Indian Ocean and Pacific Ocean sea surface temperatures. The MISO index, we use here, is based on zonal wind at 850 hPa and Outgoing Long wave Radiation (OLR) anomalies. With this work, we aim at assessing the skill of the model in simulating the large scale circulation patterns and their variabilities within the monsoon season. Variabilities in these large scale circulation patterns are primarily responsible for the variabilities in the seasonal monsoon strength and its temporal distribution across the season. We find that the model can better forecast the large scale circulation and than the actual precipitation. Hence we suggest that seasonal rainfall forecasts can be improved by the statistical downscaling of CFSV2 forecasts by incorporating the established relationships between the well forecasted large scale variables and monsoon precipitation.

  5. Dynamics and Composition of the Asian Summer Monsoon Anticyclone

    Science.gov (United States)

    Gottschaldt, K. D.; Schlager, H.; Baumann, R.; Bozem, H.; Cai, D. S.; Eyring, V.; Hoor, P. M.; Graf, P.; Joeckel, P.; Jurkat, T.; Voigt, C.; Grewe, V.; Zahn, A.; Ziereis, H.

    2017-12-01

    This study places trace gas observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) obtained with the HALO research aircraft during the ESMVal campaign into the context of regional, intra-annual variability by hindcasts with the EMAC model. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from the rest of the year. Air uplifted from the lower troposphere to the tropopause layer dominates the eastern part of the ASMA's interior, while the western part is characterized by subsidence down to the mid-troposphere. Soluble compounds are being washed out when uplifted by convection in the eastern part, where lightning simultaneously replenishes reactive nitrogen in the upper troposphere. Net photochemical ozone production is significantly enhanced in the ASMA, contrasted by an ozone depleting regime in the mid-troposphere and more neutral conditions in autumn and winter. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank, and then transported in the southern fringe around the interior region. Observed and simulated tracer-tracer relations reflect photochemical O3 production, as well as in-mixing from the lower troposphere and the tropopause layer. The simulation additionally shows entrainment of clean air from the equatorial region by northerly winds at the western ASMA flank. Although the in situ measurements were performed towards the end of summer, the main ingredients needed for their interpretation are present throughout the monsoon season.Subseasonal dynamical instabilities of the ASMA effectively overcome horizontal transport barriers, occur quite frequently, and are of paramount importance for the trace gas composition of the ASMA and its outflow into regions around the world.

  6. The greening of Northwest Indian subcontinent and reduction of dust abundance resulting from Indian summer monsoon revival.

    Science.gov (United States)

    Jin, Qinjian; Wang, Chien

    2018-03-15

    The trends of both rainfall and circulation strength of the Indian summer monsoon has been reviving since 2002. Here, using observational data, we demonstrate a statistically significant greening over the Northwest Indian Subcontinent and a consequent decline in dust abundance due to the monsoon revival. The enhanced monsoonal rainfall causes an increase in soil moisture, which results in a significant greening in the Northwest Indian Subcontinent. These increases in rainfall, soil moisture, and vegetation together lead to a substantial reduction of the dust abundance in this region, especially the Thar Desert, as shown by a negative trend in satellite-retrieved aerosol optical depth. The monsoonal rainfall-induced trends in vegetation growth and dust abundance in the Northwest Indian Subcontinent have important implications for agriculture production and air quality given the projected increases and a westward expansion of the global summer monsoon rainfall at the end of this century.

  7. WINTER SAECULUM

    Directory of Open Access Journals (Sweden)

    Emil Mihalina

    2017-03-01

    Full Text Available Accumulated imbalances in the economy and on the markets cause specific financial market dynamics that have formed characteristic patterns kept throughout long financial history. In 2008 Authors presented their expectations of key macroeconomic and selected asset class markets developments for period ahead based on Saeculum theory. Use of term Secular describes a specific valuation environment during prolonged period. If valuations as well as selected macro variables are considered as a tool for understanding business cycles then market cycles become much more obvious and easily understandable. Therefore over the long run, certain asset classes do better in terms of risk reward profile than others. Further on, there is no need for frequent portfolio rebalancing and timing of specific investment positions within a particular asset class market. Current stage in cycle development suggests a need for reassessment of trends and prevailing phenomena due to cyclical nture of long lasting Saeculums. Paper reviews developments in recognizable patterns of selected metrics in current Winter Saeculum dominated with prevailing forces of delivering, deflation and decrease in velocity of money.

  8. The Global Monsoon as Seen through the Divergent Atmospheric Circulation.

    Science.gov (United States)

    Trenberth, Kevin E.; Stepaniak, David P.; Caron, Julie M.

    2000-11-01

    A comprehensive description is given of the global monsoon as seen through the large-scale overturning in the atmosphere that changes with the seasons, and it provides a basis for delimiting the monsoon regions of the world. The analysis focuses on the mean annual cycle of the divergent winds and associated vertical motions, as given by the monthly mean fields for 1979-93 reanalyses from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) and European Centre for Medium-Range Weather Forecasts (ECMWF), which are able to reproduce the dominant modes. A complex empirical orthogonal function analysis of the divergent circulation brings out two dominant modes with essentially the same vertical structures in all months of the year. The first mode, which depicts the global monsoon, has a simple vertical structure with a maximum in vertical motion at about 400 mb, divergence in the upper troposphere that is strongest at 150 mb and decays to zero amplitude above 70 mb, and convergence in the lower troposphere with a maximum at 925 mb (ECMWF) or 850 mb (NCEP). However, this mode has a rich three-dimensional spatial structure that evolves with the seasons. It accounts for 60% of the annual cycle variance of the divergent mass circulation and dominates the Hadley circulation as well as three overturning transverse cells. These include the Pacific Walker circulation; an Americas-Atlantic Walker circulation, both of which comprise rising motion in the west and sinking in the east; and a transverse cell over Asia, the Middle East, North Africa, and the Indian Ocean that has rising motion in the east and sinking toward the west. These exist year-round but migrate and evolve considerably with the seasons and have about a third to half of the mass flux of the peak Hadley cell. The annual cycle of the two Hadley cells reveals peak strength in early February and early August in both reanalyses.A second monsoon mode, which accounts for

  9. Latitudinal Gradients in the Stable Carbon and Oxygen Isotopes of Tree-Ring Cellulose Reveal Differential Climate Influences of the North American Monsoon

    Science.gov (United States)

    Szejner, P.; Wright, W. E.; Babst, F.; Belmecheri, S.; Trouet, V.; Ehleringer, J. R.; Leavitt, S. W.; Monson, R. K.

    2015-12-01

    Summer rainfall plays an important role sustaining different types of ecosystems in the Southwestern US. The arrival of the monsoon breaks the early summer hyper-arid period in the region providing unique seasonal conditions for these ecosystems to thrive. It is unknown to what extent monsoon rainfall is used by Ponderosa pine forests, which occupy many mountain ecosystems in the Western US. While these forests clearly rely on winter snowpack to drive much of their annual net primary productivity, the extent to which they supplement winter moisture, with summer monsoon moisture needs to be clarified. It is likely that there are north-south gradients in the degree to which forests rely on monsoon moisture, as the summer monsoon system tends to become diminished as it moves progressively northward. We addressed these gaps in our knowledge about the monsoon by studying stable Carbon and Oxygen isotopes in earlywood and latewood α-cellulose from cores taken from trees in eleven sites along a latitudinal gradient extending from Southern Arizona and New Mexico toward Utah. Here we show evidence that Ponderosa pine trees from most of these sites use monsoon water to support growth during the late summer, and the fractional use of monsoon precipitation is strongest in the southernmost sites. This study provides new physiological evidence on the influence of the North American monsoon and winter precipitation on tree growth in montane ecosystems of the Western US. Using these results, we predict differences in the susceptibility of southern and northern montane forests to future climate change. ACKNOWLEDGMENTS: This work was funded by an NSF Macrosystems Grant #1065790

  10. Winter Weather: Frostbite

    Science.gov (United States)

    ... Safety During Fire Cleanup Wildfires PSAs Related Links Winter Weather About Winter Weather Before a Storm Prepare Your Home Prepare Your Car Winter Weather Checklists During a Storm Indoor Safety During ...

  11. Interannual and Interdecadal Variations of the East Asian Summer Monsoon and Tropical Pacific SSTs. Part I: Roles of the Subtropical Ridge

    OpenAIRE

    Chang, C.-P.; Zhang, Yongsheng; Li, Tim

    2000-01-01

    The interannual relationship between the East Asian summer monsoon and the tropical Pacific SSTs is studied using rainfall data in the Yangtze River Valley and the NCEP reanalysis for 1951–96. The datasets are also partitioned into two periods, 1951–77 and 1978–96, to study the interdecadal variations of this relationship. A wet summer monsoon is preceded by a warm equatorial eastern Pacific in the previous winter and followed by a cold equatorial eastern Pacific in the following fa...

  12. Rapid retreat of the East Asian summer monsoon in the middle Holocene and a millennial weak monsoon interval at 9 ka in northern China

    Science.gov (United States)

    Dong, Jinguo; Shen, Chuan-Chou; Kong, Xinggong; Wu, Chung-Che; Hu, Hsun-Ming; Ren, Haojia; Wang, Yi

    2018-01-01

    Knowledge of hydroclimatic dynamics in the East Asian monsoon region during the Holocene was hindered by few absolutely-dated and decadally-resolved proxy records in northern China. Here we present replicated carbonate δ18O records of six stalagmites with sub-decadal to multi-decadal resolutions from the Lianhua cave to reveal a detailed evolution of the East Asian Summer Monsoon (EASM) intensity in northern China since 11.5 thousand years before present (ka BP, before 1950 CE). Our composite record shows that solar forcing dominated hydroclimatic changes regionally, including an intensified monsoon at the Holocene Optimum from the termination of Younger Dryas to 6.5 ka BP, and a subsequent multi-millennial weakening monsoon, that agrees with cave records in central and southern China. However, the EASM has retreated southwards more rapidly than the Indian summer monsoon after ∼6.5 ka BP, resulting in aridity conditions occurring at 4.0 ka BP in northern China, which is almost 2000-year earlier than that in central and southern China. This north-south asynchroneity is likely related to the different regional responses among the coupling of the EASM, Indian summer monsoon, the solar forcing, and the differences in thermal forcing due to complex geographical configurations. In addition, a relative enrichment of 1‰ in 18O data of the Lianhua record from 9.5 to 8.1 ka BP shows that the Holocene Optimum was punctuated by a millennial-long weakening monsoon interval, which is not registered among previous cave records in central and southern China. The fresh water-induced cold climate conditions in the North Atlantic region could create stronger East Asian winter monsoon, and induce a weakened EASM and a southward shift of rain belt in northern China. Therefore, it shall not be surprised that there are strong heterogeneities among regional hydroclimatic conditions across monsoonal China, given the complex interplay between external and internal forcing mechanisms

  13. 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

  14. Winter-to-Summer Precipitation Phasing in Southwestern North America: A Multi-Century Perspective from Paleoclimatic Model-Data Comparisons

    Science.gov (United States)

    Coats, Sloan; Smerdon, Jason E.; Seager, Richard; Griffin, Daniel; Cook, Benjamin I.

    2015-01-01

    The phasing of winter-to-summer precipitation anomalies in the North American monsoon (NAM) region 2 (113.25 deg W-107.75 deg W, 30 deg N-35.25 deg N-NAM2) of southwestern North America is analyzed in fully coupled simulations of the Last Millennium and compared to tree ring reconstructed winter and summer precipitation variability. The models simulate periods with in-phase seasonal precipitation anomalies, but the strength of this relationship is variable on multidecadal time scales, behavior that is also exhibited by the reconstructions. The models, however, are unable to simulate periods with consistently out-of-phase winter-to-summer precipitation anomalies as observed in the latter part of the instrumental interval. The periods with predominantly in-phase winter-to-summer precipitation anomalies in the models are significant against randomness, and while this result is suggestive of a potential for dual-season drought on interannual and longer time scales, models do not consistently exhibit the persistent dual-season drought seen in the dendroclimatic reconstructions. These collective findings indicate that model-derived drought risk assessments may underestimate the potential for dual-season drought in 21st century projections of hydroclimate in the American Southwest and parts of Mexico.

  15. A vigorous Mesoamerican monsoon during the Last Glacial Maximum driven by orbital and oceanic forcing

    Science.gov (United States)

    Lachniet, M. S.; Asmerom, Y.; Bernal, J. P.; Polyak, V.; Vazquez-Selem, L. V.

    2012-12-01

    The external forcings on global monsoon strength include summer orbital insolation and ocean circulation changes, both of which are key control knobs on Earth's climate. However, few records of the North American Monsoon (NAM) are available to test its sensitivity to variations in the precession-dominated insolation signal and Atlantic Meridional Overturning Circulation (AMOC) for the Last Glacial Maximum (LGM; 21 ± 3 cal ka BP) and deglacial periods. In particular, well-dated and high-resolution records from the southern sector of the NAM, referred to informally as the Mesoamerican monsoon to distinguish it from the more northerly 'core' NAM, are needed to better elucidate paleoclimate change in North America. Here, we present a 22 ka (ka = kilo years) rainfall history from absolutely-dated speleothems from tropical southwestern Mexico that documents a vigorous LGM summer monsoon, in contradiction to previous interpretations, and that the monsoon collapsed during the Heinrich stadial 1 and Younger Dryas cold events. We conclude that a strong Mesoamerican monsoon requires both a large ocean-to-land temperature contrast, driven as today by summer insolation, and a proximal latitudinal position of the Intertropical Convergence Zone, forced by active AMOC.

  16. Evaporation over the Arabian Sea during two contrasting monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sadhuram, Y.

    Monthly mean surface fields of different meteorological parameters and evaporation are studied for the 1979 (poor monsoon) and 1983 (good monsoon) monsoon seasons over the Arabian Sea, in order to understand the role of evaporation on the Indian...

  17. Cyclone trends constrain monsoon variability during late Oligocene sea level highstands (Kachchh Basin, NW India

    Directory of Open Access Journals (Sweden)

    M. Reuter

    2013-09-01

    Full Text Available Climate change has an unknown impact on tropical cyclones and the Asian monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin as a recorder of tropical cyclone activity along the NW Indian coast during the late Oligocene warming period (~ 27–24 Ma. Proxy data providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system at the Oligocene–Miocene boundary. The vast shell concentrations are comprised of a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deeper to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished, each recording a relative storm wave base. (1 A shallow storm wave base is shown by nearshore molluscs, reef corals and Clypeaster echinoids; (2 an intermediate storm wave base depth is indicated by lepidocyclinid foraminifers, Eupatagus echinoids and corallinacean algae; and (3 a deep storm wave base is represented by an Amussiopecten bivalve-Schizaster echinoid assemblage. These wave base depth estimates were used for the reconstruction of long-term tropical storm intensity during the late Oligocene. The development and intensification of cyclones over the recent Arabian Sea is primarily limited by the atmospheric monsoon circulation and strength of the associated vertical wind shear. Therefore, since the topographic boundary conditions for the Indian monsoon already existed in the late Oligocene, the reconstructed long-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~ 26 Ma followed by a period of monsoon weakening during the

  18. Influence of monsoonal winds on chlorophyll-α distribution in the Beibu Gulf.

    Directory of Open Access Journals (Sweden)

    Chunyan Shen

    Full Text Available The influence of seasonal, monsoonal winds on the temporal and spatial variability of chlorophyll-a (chl-a in the Beibu Gulf is studied based on long-term satellite data of sea surface winds, chl-a concentration and sea surface temperature (SST and in-situ observations for the years from 2002 to 2014. The analysis results indicated that under northeasterly monsoonal winds, chl-a concentrations were substantially elevated in most area of the Beibu Gulf, with a high chl-a concentration (>2 mg m-3 patch extending southwestward from the coastal water of the northeastern Gulf, consistent with the winter wind pattern. Meanwhile, the spatial distribution of high chl-a concentration is correlated with low SST in the northeastern Gulf. In the southern Gulf, there was generally low chl-a, except in the coastal waters southwest of Hainan Island. Here, the upwelling cold water prevails outside the mouth of the Beibu Gulf, driven by the southwesterly monsoonal winds and the runoff from the Changhua River, as implied by low observed SST. Correlation analysis indicated the chl-a concentration was strongly modulated by wind speed (r = 0.63, p0.7, p<0.001. Integrated analysis also showed that stratification is weak and mixing is strong in winter as affected by the high wind speed, which suggests that the wind-induced mixing is a dominant mechanism for entrainment of nutrients and the spatial distribution of chl-a in winter.

  19. Principal components of monsoon rainfall

    OpenAIRE

    BEDI, H. S.; BINDRA, M. M. S.

    2011-01-01

    Monsoon rainfall over India during the 120-day period from the beginning of June to the end of September exhibits interesting oscillations over the country. According to an analysis by Sub-bramayya (1968), there is a negative correlation in rainfall between the north-eastern and west-central parts of India. But his analysis does not indicate how much of the total variance of rainfall is explained by different rainfall patterns. We examined this aspect by expressing rainfall as a linear combin...

  20. The Summer Monsoon of 1987.

    Science.gov (United States)

    Krishnamurti, T. N.; Bedi, H. S.; Subramaniam, M.

    1989-04-01

    In this paper we have examined the evolution of a number of parameters we believe were important for our understanding of the drought over India during the summer of 1987. The list of parameters includes monthly means or anomalies of the following fields: sea surface temperatures, divergent circulations, outgoing longwave radiation, streamfunction of the lower and upper troposphere, and monthly precipitation (expressed as a percentage departure from a long-term mean). The El Niño related warm sea surface temperature anomaly and a weaker warm sea surface temperature anomaly over the equatorial Indian Ocean provide sustained convection, as reflected by the negative values of the outgoing longwave radiation. With the seasonal heating, a pronounced planetary-scale divergent circulation evolved with a center along the western Pacific Ocean. The monsoonal divergent circulation merged with that related to the El Niño, maintaining most of the heavy rainfall activity between the equatorial Pacific Ocean and east Asia. Persistent convective activity continued south of India during the entire monsoon season. Strong Hadley type overturnings with rising motions over these warm SST anomaly regions and descent roughly near 20° to 25°S was evident as early as April 1987. The subtropical high pressure areas near 20° to 25°S showed stronger than normal circulations. This was revealed by the presence of a counterclockwise streamfunction anomaly at 850 mb during April 1987. With the seasonal heating, this anomaly moved northwards and was located over the Arabian Sea and India. This countermonsoon circulation anomaly at the low levels was associated with a weaker than normal Somali jet and Arabian Sea circulation throughout this summer. The monsoon remained active along northeast India, Bangladesh, northern lndochina, and central China during the summer monsoon season. This was related to the eastward shift of the divergent circulation. An eastward shift of the upper tropospheric

  1. Relationship between summer monsoon rainfall and cyclogenesis ...

    Indian Academy of Sciences (India)

    In this study, an attempt has been made to examine the relationship between summer monsoon rainfall (June–September) and the total number of depressions, cyclones and severe cyclones (TNDC) over Bay of Bengal during the post-monsoon (October–December) season. The seasonal rainfall of the subdivisions ...

  2. Delivery of halogenated very short-lived substances from the west Indian Ocean to the stratosphere during the Asian summer monsoon

    Directory of Open Access Journals (Sweden)

    A. Fiehn

    2017-06-01

    Full Text Available Halogenated very short-lived substances (VSLSs are naturally produced in the ocean and emitted to the atmosphere. When transported to the stratosphere, these compounds can have a significant influence on the ozone layer and climate. During a research cruise on RV Sonne in the subtropical and tropical west Indian Ocean in July and August 2014, we measured the VSLSs, methyl iodide (CH3I and for the first time bromoform (CHBr3 and dibromomethane (CH2Br2, in surface seawater and the marine atmosphere to derive their emission strengths. Using the Lagrangian particle dispersion model FLEXPART with ERA-Interim meteorological fields, we calculated the direct contribution of observed VSLS emissions to the stratospheric halogen burden during the Asian summer monsoon. Furthermore, we compare the in situ calculations with the interannual variability of transport from a larger area of the west Indian Ocean surface to the stratosphere for July 2000–2015. We found that the west Indian Ocean is a strong source for CHBr3 (910 pmol m−2 h−1, very strong source for CH2Br2 (930 pmol m−2 h−1, and an average source for CH3I (460 pmol m−2 h−1. The atmospheric transport from the tropical west Indian Ocean surface to the stratosphere experiences two main pathways. On very short timescales, especially relevant for the shortest-lived compound CH3I (3.5 days lifetime, convection above the Indian Ocean lifts oceanic air masses and VSLSs towards the tropopause. On a longer timescale, the Asian summer monsoon circulation transports oceanic VSLSs towards India and the Bay of Bengal, where they are lifted with the monsoon convection and reach stratospheric levels in the southeastern part of the Asian monsoon anticyclone. This transport pathway is more important for the longer-lived brominated compounds (17 and 150 days lifetime for CHBr3 and CH2Br2. The entrainment of CHBr3 and CH3I from the west Indian Ocean to the stratosphere during the

  3. 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

  4. Global monsoons in the mid-Holocene and oceanic feedback

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Z.; Kutzbach, J. [Center for Climatic Research, University of Wisconsin-Madison, 1225 W. Dayton Street, Madison, WI 53706 (United States); Harrison, S.P. [Max Planck Institute for Biogeochemistry, P.O. Box 100164, 07701 Jena (Germany); Otto-Bliesner, B. [National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307 (United States)

    2004-03-01

    The response of the six major summer monsoon systems (the North American monsoon, the northern Africa monsoon, the Asia monsoon, the northern Australasian monsoon, the South America monsoon and the southern Africa monsoon) to mid-Holocene orbital forcing has been investigated using a coupled ocean-atmosphere general circulation model (FOAM), with the focus on the distinct roles of the direct insolation forcing and oceanic feedback. The simulation result is also found to compare well with the NCAR CSM. The direct effects of the change in insolation produce an enhancement of the Northern Hemisphere monsoons and a reduction of the Southern Hemisphere monsoons. Ocean feedbacks produce a further enhancement of the northern Africa monsoon and the North American monsoon. However, ocean feedbacks appear to weaken the Asia monsoon, although the overall effect (direct insolation forcing plus ocean feedback) remains a strengthened monsoon. The impact of ocean feedbacks on the South American and southern African monsoons is relatively small, and therefore these regions, especially the South America, experienced a reduced monsoon regime compared to present. However, there is a strong ocean feedback on the northern Australian monsoon that negates the direct effects of orbital changes and results in a strengthening of austral summer monsoon precipitation in this region. A new synthesis is made for mid-Holocene paleoenvironmental records and is compared with the model simulations. Overall, model simulations produce changes in regional climates that are generally consistent with paleoenvironmental observations. (orig.)

  5. The steady enhancement of the Australian Summer Monsoon in the last 200 years.

    Science.gov (United States)

    Gallego, David; García-Herrera, Ricardo; Peña-Ortiz, Cristina; Ribera, Pedro

    2017-11-23

    A new bicentennial series of the Australian monsoon strength based on historical wind observations has allowed for the assessment of the variability of this system since the early 19th century. Our series covers a period in which the scarcity of meteorological observations in the area had precluded the evaluation of long-term climatic trends. Results indicate that the increase in precipitation over Northern Australia reported for the last 60 years is just a manifestation of a much longer lasting trend related to the strengthening of the Australian monsoon that has been occurring since at least 1816.

  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. Changes in the La Niña teleconnection to the Indian summer monsoon during recent period

    Science.gov (United States)

    Aneesh, S.; Sijikumar, S.

    2018-01-01

    The interannual variability of Indian Summer Monsoon (ISM) rainfall is strongly associated with the El Niño-Southern Oscillation (ENSO), experiencing below and above normal rainfall during El Niño and La Niña years respectively. However, during recent La Niña years, particularly after 1980, the above normal ISM rainfall events are decreased compared to pre-1980 years. The strength of prominent monsoon circulations such as monsoon low level jet and tropical easterly jet are also decreased during recent La Niña years compared to pre-1980. In the spatial scale, the decrease in rainfall observes more over the monsoon trough region and the western part of Indian subcontinent. The number of active monsoon rainfall days, which is an identification of the intraseasonal ISM variability, are considerably reduced during post-1980 La Niña years. The warming over the Indian ocean during recent years influence the anomalous cooling observe over the western Indian ocean during La Niña events. The Indian ocean warming leads to an enhancement of convection over the equatorial region. Latent heat release from the enhanced equatorial convection warms the equatorial troposphere and weakens the meridional tropospheric temperature gradient over the monsoon region. These processes degrade the ascending motion over the Indian region, resulting weaker monsoon circulation and reduced rainfall.

  8. A prominent pattern of year-to-year variability in Indian Summer Monsoon Rainfall.

    Science.gov (United States)

    Mishra, Vimal; Smoliak, Brian V; Lettenmaier, Dennis P; Wallace, John M

    2012-05-08

    The dominant patterns of Indian Summer Monsoon Rainfall (ISMR) and their relationships with the sea surface temperature and 850-hPa wind fields are examined using gridded datasets from 1900 on. The two leading empirical orthogonal functions (EOFs) of ISMR over India are used as basis functions for elucidating these relationships. EOF1 is highly correlated with all India rainfall and El Niño-Southern Oscillation indices. EOF2 involves rainfall anomalies of opposing polarity over the Gangetic Plain and peninsular India. The spatial pattern of the trends in ISMR from 1950 on shows drying over the Gangetic Plain projects onto EOF2, with an expansion coefficient that exhibits a pronounced trend during this period. EOF2 is coupled with the dominant pattern of sea surface temperature variability over the Indian Ocean sector, which involves in-phase fluctuations over the Arabian Sea, the Bay of Bengal, and the South China Sea, and it is correlated with the previous winter's El Niño-Southern Oscillation indices. The circulation anomalies observed in association with fluctuations in the time-varying indices of EOF1 and EOF2 both involve distortions of the low-level monsoon flow. EOF1 in its positive polarity represents a southward deflection of moist, westerly monsoon flow from the Arabian Sea across India, resulting in a smaller flux of moisture to the Himalayas. EOF2 in its positive polarity represents a weakening of the monsoon trough over northeastern India and the westerly monsoon flow across southern India, reminiscent of the circulation anomalies observed during break periods within the monsoon season.

  9. Obliquity (41kyr) Paced SE Asian Monsoon Variability Following the Miocene Climate Transition

    Science.gov (United States)

    Heitmann, E. O.; Breecker, D.; Ji, S.; Nie, J.

    2016-12-01

    We investigated Asian monsoon variability during the Miocene, which may provide a good analog for the future given the lack of northern hemisphere ice sheets. In the Miocene Yanwan Section (Tianshui Basin, China) 25cm thick CaCO3-cemented horizons overprint siltstones every 1m. We suggest this rhythmic layering records variations in water availability influenced by the Asian monsoon. We interpret the siltstones as stacked soils that formed in a seasonal climate with a fluctuating water table, evidenced by roots, clay films, mottling, presence of CaCO3 nodules, and stacked carbonate nodule δ13C and δ18O profiles that mimic modern soils. We interpret the CaCO3-cemented horizons as capillary-fringe carbonates that formed in an arid climate with a steady water table and high potential evapotranspiration (PET), evidenced by sharp upper and basal contacts, micrite, sparite, and root-pore cements. The magnetostratigraphy-based age model indicates obliquity-pacing of the CaCO3-cemented horizons suggesting an orbital control on water availability, for which we propose two mechanisms: 1) summer monsoon strength, moderated by the control of obliquity on the cross-equatorial pressure gradient, and 2) PET, moderated by the control of precession on 35oN summer insolation. We use orbital configurations to predict lithology. Coincidence of obliquity minima and insolation maxima drives strong summer monsoons, seasonal variations in water table depth and soil formation. Coincidence of obliquity maxima and insolation minima drives weak summer monsoons, high PET, and carbonate accumulation above a deepened, stable water table. Coincidence of obliquity and insolation minima drives strong monsoons, low PET, and a high water table, explaining the evidence for aquatic plants previously observed in this section. Southern hemisphere control of summer monsoon variability in the Miocene may thus have resulted in large water availability variations in central China.

  10. 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

  11. Winter Weather Emergencies

    Science.gov (United States)

    Severe winter weather can lead to health and safety challenges. You may have to cope with Cold related health ... Although there are no guarantees of safety during winter weather emergencies, you can take actions to protect ...

  12. Winter maintenance performance measure.

    Science.gov (United States)

    2016-01-01

    The Winter Performance Index is a method of quantifying winter storm events and the DOTs response to them. : It is a valuable tool for evaluating the States maintenance practices, performing post-storm analysis, training : maintenance personnel...

  13. Winter weather demand considerations.

    Science.gov (United States)

    2015-04-01

    Winter weather has varied effects on travel behavior. Using 418 survey responses from the Northern Virginia : commuting area of Washington, D.C. and binary logit models, this study examines travel related changes under : different types of winter wea...

  14. Characteristics of monsoon inversions over the Arabian Sea observed by satellite sounder and reanalysis data sets

    Directory of Open Access Journals (Sweden)

    S. Dwivedi

    2016-04-01

    Full Text Available Monsoon inversion (MI over the Arabian Sea (AS is one of the important characteristics associated with the monsoon activity over Indian region during summer monsoon season. In the present study, we have used 5 years (2009–2013 of temperature and water vapour measurement data obtained from satellite sounder instrument, an Infrared Atmospheric Sounding Interferometer (IASI onboard MetOp satellite, in addition to ERA-Interim data, to study their characteristics. The lower atmospheric data over the AS have been examined first to identify the areas where MIs are predominant and occur with higher strength. Based on this information, a detailed study has been made to investigate their characteristics separately in the eastern AS (EAS and western AS (WAS to examine their contrasting features. The initiation and dissipation times of MIs, their percentage occurrence, strength, etc., has been examined using the huge database. The relation with monsoon activity (rainfall over Indian region during normal and poor monsoon years is also studied. WAS ΔT values are  ∼  2 K less than those over the EAS, ΔT being the temperature difference between 950 and 850 hPa. A much larger contrast between the WAS and EAS in ΔT is noticed in ERA-Interim data set vis-à-vis those observed by satellites. The possibility of detecting MI from another parameter, refractivity N, obtained directly from another satellite constellation of GPS Radio Occultation (RO (COSMIC, has also been examined. MI detected from IASI and Atmospheric Infrared Sounder (AIRS onboard the NOAA satellite have been compared to see how far the two data sets can be combined to study the MI characteristics. We suggest MI could also be included as one of the semipermanent features of southwest monsoon along with the presently accepted six parameters.

  15. Impact of aerosols on regional climate in southern and northern China during strong/weak East Asian summer monsoon years

    Science.gov (United States)

    Li, Shu; Wang, Tijian; Solmon, Fabien; Zhuang, Bingliang; Wu, Hao; Xie, Min; Han, Yong; Wang, Xuemei

    2016-04-01

    In this work, we mainly simulate the effects of aerosols on regional climate in southern China (SC) and northern China (NC) and compare the differences of aerosol climatic effects in strong/weak summer monsoon years with a modified regional climate model RegCM4. The results show that the total climatic effects of aerosols cause the decline of averaged air temperature and precipitation of SC and NC in summer. In NC, the strength of temperature drop in strong summer monsoon years is higher than that in weak summer monsoon years, indicating the possible impact from the different changes of radiation, circulation, and precipitation. The decrease of precipitation is more significant in NC in weak summer monsoon years, while it is stronger in SC in strong summer monsoon years due to the difference of aerosol distribution as well as the effects on circulation and cloud microphysics processes. Besides, aerosol effects also cause a decrease of zonal wind at 850 hPa in SC and an increase in NC. The cooling center is more northerly and stronger in strong monsoon year, while it is more southerly and weaker in weak summer monsoon years, which results in the differences of vertical circulation anomaly and meridional wind anomaly at 850 hPa. In weak summer monsoon years, meridional wind at 850 hPa is increased in NC, while it is found to be decreased in SC. In strong summer monsoon years, meridional winds at 850 hPa in both NC and SC are weakened. However, the decrease in SC is much more distinct and clear.

  16. 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.

  17. Winter-to-winter variations in indoor radon

    International Nuclear Information System (INIS)

    Mose, D.G.; Mushrush, G.W.; Kline, S.W.

    1989-01-01

    Indoor radon concentrations in northern Virginia and central Maryland show a strong dependence on weather. Winter tends to be associated with higher than average indoor radon, and summer with lower than average. However, compared to the winter of 1986-1987, the winter of 1987-1988 was warmer and drier. Consequently, winter-to-winter indoor radon decreased by about 25%. This winter-to-winter decrease is unexpectedly large, and simulates winter-to-summer variations that have been reported

  18. Basic mechanism for abrupt monsoon transitions

    Science.gov (United States)

    Levermann, Anders; Schewe, Jacob; Petoukhov, Vladimir; Held, Hermann

    2009-01-01

    Monsoon systems influence the livelihood of hundreds of millions of people. During the Holocene and last glacial period, rainfall in India and China has undergone strong and abrupt changes. Though details of monsoon circulations are complicated, observations reveal a defining moisture-advection feedback that dominates the seasonal heat balance and might act as an internal amplifier, leading to abrupt changes in response to relatively weak external perturbations. Here we present a minimal conceptual model capturing this positive feedback. The basic equations, motivated by observed relations, yield a threshold behavior, robust with respect to addition of other physical processes. Below this threshold in net radiative influx, R c, no conventional monsoon can develop; above R c, two stable regimes exist. We identify a nondimensional parameter l that defines the threshold and makes monsoon systems comparable with respect to the character of their abrupt transition. This dynamic similitude may be helpful in understanding past and future variations in monsoon circulation. Within the restrictions of the model, we compute R c for current monsoon systems in India, China, the Bay of Bengal, West Africa, North America, and Australia, where moisture advection is the main driver of the circulation. PMID:19858472

  19. Stable isotopic characteristic of Taiwan's precipitation: A case study of western Pacific monsoon region

    Science.gov (United States)

    Peng, Tsung-Ren; Wang, Chung-Ho; Huang, Chi-Chao; Fei, Li-Yuan; Chen, Chen-Tung Arthur; Hwong, Jeen-Lian

    2010-01-01

    The stable oxygen and hydrogen isotopic features of precipitation in Taiwan, an island located at the western Pacific monsoon area, are presented from nearly 3,500 samples collected during the past decade for 20 stations. Results demonstrate that moisture sources from diverse air masses with different isotopic signals are the main parameter in controlling the precipitation's isotope characteristics. The air mass from polar continental (Pc) region contributes the precipitation with high deuterium excess values (up to 23‰) and relatively enriched isotope compositions (e.g., - 3.2‰ for δ 18O) during the winter with prevailing northeasterly monsoon. By contrast, air masses from equatorial maritime (Em) and tropical maritime (Tm) supply the precipitation with low deuterium excess values (as low as about 7‰) and more depleted isotope values (e.g., - 8.9‰ and - 6.0‰ for δ 18O of Tm and Em, respectively) during the summer with prevailing southwesterly monsoon. Thus seasonal differences in terms of δ 18O, δD, and deuterium excess values are primarily influenced by the interactions among various precipitation sources. While these various air masses travel through Taiwan, secondary evaporation effects further modify the isotope characteristics of the inland precipitation, such as raindrop evaporation (reduces the deuterium excess of winter precipitation) and moisture recycling (increases the deuterium excess of summer precipitation). The semi-quantitative estimations in terms of evaluation for changes in the deuterium excess suggest that the raindrop evaporation fractions for winter precipitation range 7% to 15% and the proportions of recycling moisture in summer precipitation are less than 5%. Additionally, the isotopic altitude gradient in terms of δ 18O for summer precipitation is - 0.22‰/100 m, greater than - 0.17‰/100 m of winter precipitation. The greater isotopic gradient in summer can be attributed to a higher temperature vs. altitude gradient

  20. 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.

  1. The role of East Asian monsoon system in shaping population divergence and dynamics of a constructive desert shrub Reaumuria soongarica.

    Science.gov (United States)

    Yin, Hengxia; Yan, Xia; Shi, Yong; Qian, Chaoju; Li, Zhonghu; Zhang, Wen; Wang, Lirong; Li, Yi; Li, Xiaoze; Chen, Guoxiong; Li, Xinrong; Nevo, Eviatar; Ma, Xiao-Fei

    2015-10-29

    Both of the uplift of Qinghai-Tibet Plateau (QTP) and the development of East Asian monsoon system (EAMS) could have comprehensively impacted the formation and evolution of Arid Central Asia (ACA). To understand how desert plants endemic to ACA responded to these two factors, we profiled the historical population dynamics and distribution range shift of a constructive desert shrub Reaumuria soongarica (Tamaricaceae) based on species wide investigation of sequence variation of chloroplast DNA and nuclear ribosomal ITS. Phylogenetic analysis uncovered a deep divergence occurring at ca. 2.96 Mya between the western and eastern lineages of R. soongarica, and ecological niche modeling analysis strongly supported that the monsoonal climate could have fragmented its habitats in both glacial and interglacial periods and impelled its intraspecific divergence. Additionally, the population from the east monsoonal zone expanded rapidly, suggesting that the local monsoonal climate significantly impacted its population dynamics. The isolation by distance tests supported strong maternal gene flow along the direction of the East Asian winter monsoon, whose intensification induced the genetic admixture along the latitudinal populations of R. soongarica. Our results presented a new case that the development of EAMS had prominently impacted the intraspecific divergence and population dynamics of this desert plant.

  2. Spatio-Temporal Variation and Monsoon Effect on the Temperature Lapse Rate of a Subtropical Island

    Directory of Open Access Journals (Sweden)

    Ching-An Chiu

    2014-01-01

    Full Text Available Temperature lapse rate (TLR has been widely used in the prediction of mountain climate and vegetation and in many ecological models. The aims of this paper are to explore the spatio-temporal variations and monsoon effects on the TLR in the subtropical island of Taiwan with its steep Central Mountain Region (CMR. A TLR analysis using the 32-year monthly mean air temperatures and elevations from 219 weather stations (sea level to 3852 m a.s.l. was performed based on different geographical regions and monsoon exposures. The results revealed that the average TLR for all of Taiwan is -5.17°C km-1, with a general tendency to be steeper in summer and shallower in winter. The results are also shallower than the typical or global average TLR of -6.5°C km-1. During the prevailing northeast monsoon season (winter, the TLR exhibits a contrast between the windward side (steeper, -5.97°C km-1 and the leeward side (shallower, -4.51°C km-1. From the diagnosis on spatial characteristics of monthly cloud amount and vertical atmospheric profiles, this contrasting phenomenon may be explained by the warming effect of onshore stratus clouds (500 - 2500 m depth on cold and dry Siberian monsoon air on the windward side of the CMR. On the southwestern leeward side of the CMR, the low-level (1500 m, the weak ventilation atmosphere and temperature inversion make the TLR shallower than on the windward side.

  3. The East Asian Summer Monsoon at mid-Holocene: results from PMIP3 simulations

    Directory of Open Access Journals (Sweden)

    W. Zheng

    2013-02-01

    Full Text Available Ten Coupled General Circulation Models (CGCMs participated in the third phase of Paleoclimate Modelling Intercomparison Project (PMIP3 are assessed for the East Asian Summer Monsoon (EASM in both the pre-Industrial (PI, 0 ka and mid-Holocene (MH, 6 ka simulations. Results show that the PMIP3 model median captures well the large-scale characteristics of the EASM, including the two distinct features of the Meiyu rainbelt and the stepwise meridional displacement of the monsoonal rainbelt. At mid-Holocene, the PMIP3 model median shows significant warming (cooling during boreal summer (winter over Eurasia continent that are dominated by the changes of insolation. However, the PMIP3 models fail to simulate a warmer annual mean and winter surface air temperature (TAS over eastern China as derived from proxy records. The EASM at MH are featured by the changes of large-scale circulation over Eastern China while the changes of precipitation are not significant over its sub-domains of the Southern China and the lower reaches of Yangzi River. The inter-model differences for the monsoon precipitation can be associated with different configurations of the changes in large-scale circulation and the water vapour content, of which the former determines the sign of precipitation changes. The large model spread for the TAS over Tibetan Plateau has a positive relationship with the precipitation in the lower reaches of Yangzi River, yet this relationship does not apply to those PMIP3 models in which the monsoonal precipitation is more sensitive to the changes of large-scale circulation. Except that the PMIP3 model median captured the warming of annual mean TAS over Tibetan Plateau, no significant improvements can be concluded when compared with the PMIP2 models results.

  4. Picophytoplankton as tracers of environmental forcing in a tropical monsoonal Bay

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Patil, J.S.; Rajaneesh, K.M.

    In order to better understand the picophytoplankton (PP) dynamics in tropical monsoon influenced coastal regions, samples were collected daily (June–September 2008: monsoon, December 2008: post-monsoon and April 2009: pre-monsoon) from a fixed...

  5. The East African monsoon system: Seasonal climatologies and recent variations: Chapter 10

    Science.gov (United States)

    Funk, Christopher C.; Hoell, Andrew; Shukla, Shraddhanand; Husak, Gregory J.; Michaelsen, J.

    2016-01-01

    This chapter briefly reviews the complex climatological cycle of the East African monsoon system, paying special attention to its connection to the larger Indo-Pacific-Asian monsoon cycle. We examine the seasonal monsoon cycle, and briefly explore recent circulation changes. The spatial footprint of our analysis corresponds with the “Greater Horn of Africa” (GHA) region, extending from Tanzania in the south to Yemen and Sudan in the north. During boreal winter, when northeast trade winds flow across the northwest Indian Ocean and the equatorial moisture transports over the Indian Ocean exhibit strong westerly mean flows over the equatorial Indian Ocean, East African precipitation is limited to a few highland areas. As the Indian monsoon circulation transitions during boreal spring, the trade winds over the northwest Indian Ocean reverse, and East African moisture convergence supports the “long” rains. In boreal summer, the southwesterly Somali Jet intensifies over eastern Africa. Subsidence forms along the westward flank of this jet, shutting down precipitation over eastern portions of East Africa. In boreal fall, the Jet subsides, but easterly moisture transports support rainfall in limited regions of the eastern Horn of Africa. We use regressions with the trend mode of global sea surface temperatures to explore potential changes in the seasonal monsoon circulations. Significant reductions in total precipitable water are indicated in Kenya, Tanzania, Rwanda, Burundi, Uganda, Ethiopia, South Sudan, Sudan, and Yemen, with moisture transports broadly responding in ways that reinforce the climatological moisture transports over the Indian Ocean. Over Kenya, southern Ethiopia and Somalia, regressions with velocity potential indicate increased convergence aloft. Near the surface, this convergence appears to manifest as a surface high pressure system that modifies moisture transports in these countries as well as Uganda, Tanzania, Rwanda, and Burundi. An analysis

  6. Evolution of productivity and monsoonal dynamics in the eastern Arabian Sea during the past 68 ka using dinoflagellate cyst records

    Digital Repository Service at National Institute of Oceanography (India)

    Narale, D.D.; Naidu, P.D.; Anil, A.C.; Godad, S.P.

    of the Arabian Sea. The present-day climatic and oceanographic conditions predominating in the Eastern Arabian Sea (EAS) are influenced by both the South West (SW or summer) and North East (NE or winter) monsoon systems. The EAS experiences moderate upwelling... based on published morphological descriptions (Fensome et al., 1993; Zonneveld, 1997b; Lewis et al., 1999; Matsuoka and Fukuyo, 2000; Rochon et al., 2009; Radi et al., 2013) and modern dinoflagellate cyst determination key by Zonneveld and Pospelova...

  7. 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.

  8. Monsoonal Variations of Supraglacial Lakes, Langtang Khola, Nepal

    Science.gov (United States)

    Miles, E. S.; Willis, I. C.; Arnold, N. S.; Pellicciotti, F.

    2013-12-01

    As Himalayan debris-covered glaciers retreat and thin in response to climate warming, their long, low-gradient tongues and undulating surfaces tend to form supraglacial lakes. The conceptual response of debris-covered valley glaciers progresses from thinning and stagnation to the development of supraglacial ponds, which eventually may coalesce into very large lakes bounded by terminal moraines. Large terminal lakes are a topic of frequent study due to the public safety hazard of glacier lake outburst floods (GLOFs). However, smaller, transient ponds that form on the glacier's surface may play an important role in determining annual mass balance. Development of surpaglacial ponds may be controlled by the magnitudes of surface undulations, meltwater inputs, and the glacier's general surface gradient. These lakes are not necessarily permanent: they enlarge by enhanced ice-cliff ablation, they are advected and deformed by glacial strain, they may disappear due to englacial drainage or prolonged evaporation, and they may not recur in the same locations each year due to changes in surface topography and hydrologic routing. The prevalence and character of such lakes varies greatly throughout the year. In the cold, dry winter (October-March), the debris surface is largely snow-covered and supraglacial lakes are frozen. During the arid premonsoon (April-May), lakes thaw and the debris surface is dry and free of snow. The debris surface becomes nearly-saturated by monsoonal rains (June-September) leading to surface runoff and widespread lake-filling. During this dynamic monsoon period, ponded water substantially alters the glacier's specific energy balance by increasing the effective thermal conductivity between atmosphere and ice, acting as a heat reservoir, and reducing albedo. Additionally, supraglacial ponds often enhance ablation processes in proximal areas by initiating lake-marginal calving and exposing debris-free ice cliffs. Through these processes supraglacial

  9. The monsoon system: Land–sea breeze or the ITCZ?

    Science.gov (United States)

    Gadgil, Sulochana

    2018-02-01

    For well over 300 years, the monsoon has been considered to be a gigantic land-sea breeze driven by the land-ocean contrast in surface temperature. In this paper, this hypothesis and its implications for the variability of the monsoon are discussed and it is shown that the observations of monsoon variability do not support this popular theory of the monsoon. An alternative hypothesis (whose origins can be traced to Blanford's (1886) remarkably perceptive analysis) in which the basic system responsible for the Indian summer monsoon is considered to be the Intertropical Convergence Zone (ITCZ) or the equatorial trough, is then examined and shown to be consistent with the observations. The implications of considering the monsoon as a manifestation of the seasonal migration of the ITCZ for the variability of the Indian summer monsoon and for identification of the monsoonal regions of the world are briefly discussed.

  10. The monsoon system: Land-sea breeze or the ITCZ?

    Science.gov (United States)

    Gadgil, Sulochana

    2018-02-01

    For well over 300 years, the monsoon has been considered to be a gigantic land-sea breeze driven by the land-ocean contrast in surface temperature. In this paper, this hypothesis and its implications for the variability of the monsoon are discussed and it is shown that the observations of monsoon variability do not support this popular theory of the monsoon. An alternative hypothesis (whose origins can be traced to Blanford's (1886) remarkably perceptive analysis) in which the basic system responsible for the Indian summer monsoon is considered to be the Intertropical Convergence Zone (ITCZ) or the equatorial trough, is then examined and shown to be consistent with the observations. The implications of considering the monsoon as a manifestation of the seasonal migration of the ITCZ for the variability of the Indian summer monsoon and for identification of the monsoonal regions of the world are briefly discussed.

  11. 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.

    The hydrography of the Wadge Bank during premonsoon and monsoon seasons is presented. The thermocline slopes downward towards the central region. Upwelling is prominent in the entire region during monsoon and is observed only in the western...

  12. Diagnosis of the Asian summer monsoon variability and the climate prediction of monsoon precipitation via physical decomposition

    Science.gov (United States)

    Lim, Young-Kwon

    This study investigates the space-time evolution of the dominant modes that constitute the Asian summer monsoon (ASM), and, as an ultimate goal, the climate prediction of the ASM rainfall. Precipitation and other synoptic variables during the prominent life cycle of the ASM (May 21 to September 17) are used to show the detailed features of dominant modes, which are identified as the seasonal cycle, the ISO defined by the 40--50 day intraseasonal oscillation including the Madden-Julian oscillation, and the El Nino mode. The present study reveals that the ISO is the second largest component of the ASM rainfall variation. Correlation analysis indicates that ISO explains a larger fraction of the variance of the observed precipitation (without climatology) than the ENSO mode. The dominant ISO signal faithfully explains the northward propagation of the ISO toward the Asian continent causing intraseasonal active/break periods. The interannual variation of the ISO strength suggests that the ENSO exerts some influence on the ISO. The composite convective ISO anomaly and Kelvin-Rossby wave response over the Indian Ocean shows that the ISO tends to be stronger during the early stage of the ASM than normal in El Nino (La Nina) years, indicating greater (smaller) possibility of ISO-related extreme rainfall over India, Bangladesh, and the Bay of Bengal. The ENSO mode reveals that the following factors affect the evolution of the ASM system in El Nino (La Nina) years. (1) The anomalous sea surface temperature and sea level pressure over the Indian Ocean during the early stage of the ASM weaken (enhance) the meridional pressure gradient. (2) As a result, the westerly jet and the ensuing moisture transport toward India and the Bay of Bengal become weak (strong) and delayed (expedited), providing a less (more) favorable condition for regional monsoon onsets. (3) The Walker circulation anomaly results in an enhanced subsidence (ascent) and drought (flood) over the Maritime continent

  13. Transport and Stirring by the Asian Monsoon Anticyclone

    Science.gov (United States)

    Bowman, K. P.; Siu, L. W.

    2016-12-01

    During boreal summer the Asian monsoon anticyclone (AMA) dominates the atmospheric circulation of the northern hemisphere upper troposphere and lower stratosphere (UTLS). The convection that drives the AMA also transports water and pollutants from the lower troposphere to the UTLS. This air can be exported from within the AMA to the global tropical upper troposphere and the northern hemisphere lower stratosphere by large-scale stirring. Here we analyze the mechanisms responsible for stirring air into and out of the AMA by using air parcel trajectories computed with wind fields that have been filtered to remove selected space and time scales. We focus on the role of Rossby waves propagating along the subtropical jet on the northern flank of the AMA, and on the importance of fluctuations in the size and strength of the AMA circulation itself due to variations in convective heating.

  14. Lower tropospheric ozone over India and its linkage to the South Asian monsoon

    Science.gov (United States)

    Lu, Xiao; Zhang, Lin; Liu, Xiong; Gao, Meng; Zhao, Yuanhong; Shao, Jingyuan

    2018-03-01

    Lower tropospheric (surface to 600 hPa) ozone over India poses serious risks to both human health and crops, and potentially affects global ozone distribution through frequent deep convection in tropical regions. Our current understanding of the processes controlling seasonal and long-term variations in lower tropospheric ozone over this region is rather limited due to spatially and temporally sparse observations. Here we present an integrated process analysis of the seasonal cycle, interannual variability, and long-term trends of lower tropospheric ozone over India and its linkage to the South Asian monsoon using the Ozone Monitoring Instrument (OMI) satellite observations for years 2006-2014 interpreted with a global chemical transport model (GEOS-Chem) simulation for 1990-2010. OMI observed lower tropospheric ozone over India averaged for 2006-2010, showing the highest concentrations (54.1 ppbv) in the pre-summer monsoon season (May) and the lowest concentrations (40.5 ppbv) in the summer monsoon season (August). Process analyses in GEOS-Chem show that hot and dry meteorological conditions and active biomass burning together contribute to 5.8 Tg more ozone being produced in the lower troposphere in India in May than January. The onset of the summer monsoon brings ozone-unfavorable meteorological conditions and strong upward transport, which all lead to large decreases in the lower tropospheric ozone burden. Interannually, we find that both OMI and GEOS-Chem indicate strong positive correlations (r = 0.55-0.58) between ozone and surface temperature in pre-summer monsoon seasons, with larger correlations found in high NOx emission regions reflecting NOx-limited production conditions. Summer monsoon seasonal mean ozone levels are strongly controlled by monsoon strengths. Lower ozone concentrations are found in stronger monsoon seasons mainly due to less ozone net chemical production. Furthermore, model simulations over 1990-2010 estimate a mean annual trend of 0

  15. Prediction of monsoon rainfall with a nested grid mesoscale limited ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    mesoscale convective organization associated with monsoon depression. 1. Introduction. Indian monsoon rainfall is dominated by meso- β type disturbances, such as orographic rainfall along the west coast (Western Ghats) of India, and synoptically induced mesoscale convective systems during the passage of monsoon ...

  16. Winters fuels report

    International Nuclear Information System (INIS)

    1995-01-01

    The outlook for distillate fuel oil this winter is for increased demand and a return to normal inventory patterns, assuming a resumption of normal, cooler weather than last winter. With industrial production expected to grow slightly from last winter's pace, overall consumption is projected to increase 3 percent from last winter, to 3.4 million barrels per day during the heating season (October 1, 1995-March 31, 1996). Much of the supply win come from stock drawdowns and refinery production. Estimates for the winter are from the Energy Information Administration's (EIA) 4th Quarter 1995 Short-Tenn Energy Outlook (STEO) Mid-World Oil Price Case forecast. Inventories in place on September 30, 1995, of 132 million barrels were 9 percent below the unusually high year-earlier level. Inventories of high-sulfur distillate fuel oil, the principal type used for heating, were 13 percent lower than a year earlier. Supply problems are not anticipated because refinery production and the ready availability of imports should be adequate to meet demand. Residential heating off prices are expected to be somewhat higher than last winter's, as the effects of lower crude oil prices are offset by lower distillate inventories. Heating oil is forecast to average $0.92 per gallon, the highest price since the winter of 1992-93. Diesel fuel (including tax) is predicted to be slightly higher than last year at $1.13 per gallon. This article focuses on the winter assessment for distillate fuel oil, how well last year's STEO winter outlook compared to actual events, and expectations for the coming winter. Additional analyses include regional low-sulfur and high-sulfur distillate supply, demand, and prices, and recent trends in distillate fuel oil inventories

  17. Impact of East Asian Summer Monsoon on Surface Ozone Pattern in China

    Science.gov (United States)

    Li, Shu; Wang, Tijian; Huang, Xing; Pu, Xi; Li, Mengmeng; Chen, Pulong; Yang, Xiu-Qun; Wang, Minghuai

    2018-01-01

    Tropospheric ozone plays a key role in regional and global atmospheric and climate systems. In East Asia, ozone can be affected both in concentration level and spatial pattern by typical monsoon climate. This paper uses three different indices to identify the strength of East Asian summer monsoon (EASM) and explores the possible impact of EASM intensity on the ozone pattern through synthetic and process analysis. The difference in ozone between three strong and three weak monsoon years was analyzed using the simulations from regional climate model RegCM4-Chem. It was found that EASM intensity can significantly influence the spatial distribution of ozone in the lower troposphere. When EASM is strong, ozone in the eastern part of China (28°N - 42° N) is reduced, but the inverse is detected in the north and south. The surface ozone difference ranges from -7 to 7 ppbv during the 3 months (June to August) of the EASM, with the most obvious difference in August. Difference of the 3 months' average ozone ranges from -3.5 to 4 ppbv. Process analysis shows that the uppermost factor controlling ozone level during summer monsoon seasons is the chemistry process. Interannual variability of EASM can impact the spatial distribution of ozone through wind in the lower troposphere, cloud cover, and downward shortwave radiation, which affect the transport and chemical formation of ozone. The phenomenon should be addressed when considering the interaction between ozone and the climate in East Asia region.

  18. A Stalagmite record of Holocene Indonesian-Australian summer monsoon variability from the Australian tropics

    Science.gov (United States)

    Denniston, Rhawn F.; Wyrwoll, Karl-Heinz; Polyak, Victor J.; Brown, Josephine R.; Asmerom, Yemane; Wanamaker, Alan D.; LaPointe, Zachary; Ellerbroek, Rebecca; Barthelmes, Michael; Cleary, Daniel; Cugley, John; Woods, David; Humphreys, William F.

    2013-10-01

    Oxygen isotopic data from a suite of calcite and aragonite stalagmites from cave KNI-51, located in the eastern Kimberley region of tropical Western Australia, represent the first absolute-dated, high-resolution speleothem record of the Holocene Indonesian-Australian summer monsoon (IASM) from the Australian tropics. Stalagmite oxygen isotopic values track monsoon intensity via amount effects in precipitation and reveal a dynamic Holocene IASM which strengthened in the early Holocene, decreased in strength by 4 ka, with a further decrease from ˜2 to 1 ka, before strengthening again at 1 ka to years to levels similar to those between 4 and 2 ka. The relationships between the KNI-51 IASM reconstruction and those from published speleothem time series from Flores and Borneo, in combination with other data sets, appear largely inconsistent with changes in the position and/or organization of the Intertropical Convergence Zone (ITCZ). Instead, we argue that the El Niño/Southern Oscillation (ENSO) may have played a dominant role in driving IASM variability since at least the middle Holocene. Given the muted modern monsoon rainfall responses to most El Niño events in the Kimberley, an impact of ENSO on regional monsoon precipitation over northwestern Australia would suggest non-stationarity in the long-term relationship between ENSO forcing and IASM rainfall, possibly due to changes in the mean state of the tropical Pacific over the Holocene.

  19. Toward enabling winter occupations: testing a winter coat designed for older adults.

    Science.gov (United States)

    Green, Stephanie L; Boger, Jennifer N; Mihailidis, Alex

    2011-02-01

    Previous research indicates that older adults have difficulties using winter clothing, which contributes to their risk of isolation during winter. Research has also shown that a winter coat that requires less flexibility, strength, and dexterity would help support this population. This pilot study evaluated the measured and perceived effectiveness of a winter coat prototype that had a funnel sleeve design. Eight older adults trialed three coats (the participant's own coat, a coat fitted with sleeve gripper, and the prototype coat), which were evaluated though shoulder range of motion measurements and by the participant completing a survey. Less shoulder range of motion was used to put on the prototype coat. Survey findings support range of motion data that Sleeve Gripper has limited utility. A funnel sleeve design may require less range of motion at the shoulder compared to other coats.

  20. Primary sand-dune plant community and soil properties during the west-coast India monsoon

    Directory of Open Access Journals (Sweden)

    Willis A.

    2016-06-01

    Full Text Available A seven-station interrupted belt transect was established that followed a previously observed plant zonation pattern across an aggrading primary coastal dune system in the dry tropical region of west-coast India. The dominant weather pattern is monsoon from June to November, followed by hot and dry winter months when rainfall is scarce. Physical and chemical soil characteristics in each of the stations were analysed on five separate occasions, the first before the onset of monsoon, three during and the last post-monsoon. The plant community pattern was confirmed by quadrat survey. A pH gradient decreased with distance from the shoreline. Nutrient concentrations were deficient, increasing only in small amounts until the furthest station inland. At that location, there was a distinct and abrupt pedological transition zone from psammite to humic soils. There was a significant increase over previous stations in mean organic matter, ammonium nitrate and soil-water retention, although the increase in real terms was small. ANOVA showed significant variation in electrical conductivity, phosphorus, calcium, magnesium and sodium concentrations over time. There was no relationship between soil chemistry characteristics and plant community structure over the transect. Ipomoea pes-caprae and Spinifex littoreus were restricted to the foredunes, the leguminous forb Alysicarpus vaginalis and Perotis indica to the two stations furthest from the strand. Ischaemum indicum, a C4 perennial grass species adopting an ephemeral strategy was, in contrast, ubiquitous to all stations.

  1. Annual variations of monsoon and drought detected by GPS: A case study in Yunnan, China.

    Science.gov (United States)

    Jiang, Weiping; Yuan, Peng; Chen, Hua; Cai, Jianqing; Li, Zhao; Chao, Nengfang; Sneeuw, Nico

    2017-07-19

    The Global Positioning System (GPS) records monsoonal precipitable water vapor (PWV) and vertical crustal displacement (VCD) due to hydrological loading, and can thus be applied jointly to diagnose meteorological and hydrological droughts. We have analyzed the PWV and VCD observations during 2007.0-2015.0 at 26 continuous GPS stations located in Yunnan province, China. We also obtained equivalent water height (EWH) derived from the Gravity Recovery And Climate Experiment (GRACE) and precipitation at these stations with the same period. Then, we quantified the annual variations of PWV, precipitation, EWH and VCD and provided empirical relationships between them. We found that GPS-derived PWV and VCD (positive means downward movement) are in phase with precipitation and GRACE-derived EWH, respectively. The annual signals of VCD and PWV show linearly correlated amplitudes and a two-month phase lag. Furthermore, the results indicate that PWV and VCD anomalies can also be used to explore drought, such as the heavy drought during winter/spring 2010. Our analysis results verify the capability of GPS to monitor monsoon variations and drought in Yunnan and show that a more comprehensive understanding of the characteristics of regional monsoon and drought can be achieved by integrating GPS-derived PWV and VCD with precipitation and GRACE-derived EWH.

  2. Mesoscale model forecast verification during monsoon 2008

    Indian Academy of Sciences (India)

    There have been very few mesoscale modelling studies of the Indian monsoon, with focus on the verification and intercomparison of the operational real time forecasts. With the exception of Das et al (2008), most of the studies in the literature are either the case studies of tropical cyclones and thunderstorms or the sensitivity ...

  3. Circulation characteristics of a monsoon depression during ...

    Indian Academy of Sciences (India)

    It requires the objective comparison of high and low-resolution analysis datasets in assessing the specific convective features of a monsoon depression. For this purpose, reanalysis datasets of NCAR/NCEP (National Center for Atmospheric Research/National Centers for Environmental Prediction) at a horizontal resolution ...

  4. Relationship between summer monsoon rainfall and cyclogenesis ...

    Indian Academy of Sciences (India)

    S; 120. ◦. –160. ◦. E) are useful to predict TNDC during post-monsoon (October–. December) season. The influence of ENSO (El-Nino. Southern Oscillation) and IOD (Indian ... 1984). Following this methodology, the correlations with the first differences (current season minus previous season) in rainfall and TNDC are used in.

  5. Circulation characteristics of a monsoon depression during ...

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    to produce the structure of convective organization as well as prominent synoptic features associ- ated with monsoon depression. Comparison and error verifications have been done with the help of available upper-air station data. The objective verification reveals the efficiency of the analysis scheme. 1. Introduction.

  6. Mid-Holocene monsoons: a multi-model analysis of the inter-hemispheric differences in the responses to orbital forcing and ocean feedbacks

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Y. [University of Bristol, School of Geographical Sciences, Bristol (United Kingdom); Laboratoire des Sciences du Climat et de l' Environment, CEA/CNRS/UVSQ, Saclay (France); Harrison, S.P. [University of Bristol, School of Geographical Sciences, Bristol (United Kingdom); Macquarie University, School of Biological Sciences, North Ryde, NSW (Australia)

    2012-09-15

    The response of monsoon circulation in the northern and southern hemisphere to 6 ka orbital forcing has been examined in 17 atmospheric general circulation models and 11 coupled ocean-atmosphere general circulation models. The atmospheric response to increased summer insolation at 6 ka in the northern subtropics strengthens the northern-hemisphere summer monsoons and leads to increased monsoonal precipitation in western North America, northern Africa and China; ocean feedbacks amplify this response and lead to further increase in monsoon precipitation in these three regions. The atmospheric response to reduced summer insolation at 6 ka in the southern subtropics weakens the southern-hemisphere summer monsoons and leads to decreased monsoonal precipitation in northern South America, southern Africa and northern Australia; ocean feedbacks weaken this response so that the decrease in rainfall is smaller than might otherwise be expected. The role of the ocean in monsoonal circulation in other regions is more complex. There is no discernable impact of orbital forcing in the monsoon region of North America in the atmosphere-only simulations but a strong increase in precipitation in the ocean-atmosphere simulations. In contrast, there is a strong atmospheric response to orbital forcing over northern India but ocean feedback reduces the strength of the change in the monsoon although it still remains stronger than today. Although there are differences in magnitude and exact location of regional precipitation changes from model to model, the same basic mechanisms are involved in the oceanic modulation of the response to orbital forcing and this gives rise to a robust ensemble response for each of the monsoon systems. Comparison of simulated and reconstructed changes in regional climate suggest that the coupled ocean-atmosphere simulations produce more realistic changes in the northern-hemisphere monsoons than atmosphere-only simulations, though they underestimate the

  7. Employment and winter construction

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan de Place; Larsen, Jacob Norvig

    2011-01-01

    Reduced seasonal building activity in the construction sector is often assumed to be related to hard winter conditions for building activities and poor working conditions for construction workers, resulting in higher costs and poor quality of building products, particularly in the northern...... hemisphere. Can climatic conditions alone explain the sizeable difference in reduction in building activity in the construction sector in European countries in the winter months, or are other factors such as technology, economic cycles and schemes for financial compensation influential as well? What...... possibilities exist for reducing seasonal variation in employment? In addition to a literature review related to winter construction, European and national employment and meteorological data were studied. Finally, ministerial acts, ministerial orders or other public policy documents related to winter...

  8. Deer Wintering Areas

    Data.gov (United States)

    Vermont Center for Geographic Information — Deer winter habitat is critical to the long term survival of white-tailed deer (Odocoileus virginianus) in Vermont. Being near the northern extreme of the...

  9. Winter Bottom Trawl Survey

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The standardized NEFSC Winter Bottom Trawl Survey was initiated in 1992 and covered offshore areas from the Mid-Atlantic to Georges Bank. Inshore strata were covered...

  10. Decadal variability in snow depth anomaly over Eurasia and its association with all India summer monsoon rainfall and seasonal circulations

    CERN Document Server

    Singh, G P

    2003-01-01

    The Historical Soviet Daily Snow Depth (HSDSD) version II data set has been used in the computation of winter and spring snow depth anomalies over west (25 deg. E to 70 deg. E, 35 deg. N to 65 deg. N) and east (70 deg. E to 160 deg. E, 35 deg. N to 65 deg. N) Eurasia. It is noticed that winter snow depth anomaly over east Eurasia is positively correlated while west Eurasia is negatively correlated with subsequent Indian summer monsoon rainfall (ISMR). The DJF snow depth anomaly shows highest and inverse correlation coefficient (CC) with ISMR over a large area of west Eurasia in a recent period of study i.e. 1975-1995. On the basis of standardised winter (mean of December, January and February) snow depth anomaly over west Eurasia, the years 1966, 1968, 1979 and 1986 are identified as high snow years and the years 1961 and 1975 as low snow years. The characteristics of seasonal monsoon circulation features have been studied in detail during contrasting years of less (more) snow depth in winter/spring seasons f...

  11. Summer climate of Madagascar and monsoon pulsing of its vortex

    Science.gov (United States)

    Jury, Mark R.

    2016-02-01

    This study analyzes the climate of Madagascar (12°-26°S, 43°-50°E) and its relation to the Indian Ocean during austral summer (Dec-Mar). Moisture converges onto a standing easterly wave and floods are prevalent in late summer. All-island daytime land temperatures exceed 38 °C in October and are ~4 °C above sea temperatures during summer. Analysis of thermally induced diurnal convection and circulation revealed inflow during the afternoon recirculated from the southeastern mountains and the warm Mozambique Channel. Summer rainfall follows latent and sensible heat flux during the first half of the day, and gains a surplus by evening via thunderstorms over the western plains. At the inter-annual time-scale, 2.3 years oscillations in all-island rainfall appear linked with the stratospheric quasi-biennial oscillation and corresponding 80 Dobson Unit ozone fluctuations during flood events. Wet spells at frequencies from 11-27 days derive from locally-formed tropical cyclones and NW-cloud bands. Flood case studies exhibit moisture recycling in the confluence zone between the sub-tropical anticyclone and the lee-side vortex. Hovmoller analysis of daily rainfall reinforces the concept of local generation and pulsing by cross-equatorial (Indian winter) monsoon flow rather than zonal atmospheric waves. Since the surface water budget is critical to agriculture in Madagascar, this study represents a further step to understand its meso-scale summer climate.

  12. Easterly wave activity and associated heavy rainfall during the pre-monsoon season of 2005

    Science.gov (United States)

    Sawaisarje, G. K.; Khare, Prakash; Chaudhari, Hemantkumar S.; Puviarasan, N.; Ranalkar, M. R.

    2017-12-01

    Waves in easterlies are a tropical disturbance, which are moving from east to west or west-northwest (WNW). Over the Indian region, easterly waves occur mainly in winter, pre-monsoon and post-monsoon seasons. These easterly waves have attracted the attention of many researchers due to the associated heavy rainfall, lightning and thunder squalls. Influence of easterly waves is less explored during pre-monsoon season. It is seen that during years 2001-2015, a total of 80 cases of trough in easterlies were witnessed by southern peninsular India in the pre-monsoon season. The maxima occurred in March (43 cases), followed by April (25 cases) and May (12 cases). It is observed that the year 2005 witnessed the longest spell of easterly waves for 18 days during 24 March to 10 April 2005, which is quite unusual. The event has claimed a death toll of 55 people in the two states of Tamil Nadu and Kerala, and heavy rains associated with this event damaged many houses and huts in Tamil Nadu. The unusual nature of the event has prompted us to undertake the study in details. In all, the event witnessed six systems as troughs in easterlies with their movement westwards from south Andaman Sea region to Lakshadweep and southeast Arabian Sea and Sri Lanka and adjoining Cape Comorin area. An attempt has been made to study the event of easterly waves during the year 2005 by exploring winds, temperature advection, vorticity, moisture convergence and potential instability. The causative reason is due to culmination of positive temperature advection, its multiple interactions with deep convective clouds and moisture incursion from anticyclonic flow close to eastern coast of south peninsular region of India. Observing the waves with the internal mechanism makes the study useful for operational forecasting and provides a better understanding of easterly waves.

  13. Tibet, the Himalaya, Asian monsoons and biodiversity – In what ways are they related?

    Directory of Open Access Journals (Sweden)

    Robert A. Spicer

    2017-10-01

    Full Text Available Prevailing dogma asserts that the uplift of Tibet, the onset of the Asian monsoon system and high biodiversity in southern Asia are linked, and that all occurred after 23 million years ago in the Neogene. Here, spanning the last 60 million years of Earth history, the geological, climatological and palaeontological evidence for this linkage is reviewed. The principal conclusions are that: 1 A proto-Tibetan highland existed well before the Neogene and that an Andean type topography with surface elevations of at least 4.5 km existed at the start of the Eocene, before final closure of the Tethys Ocean that separated India from Eurasia. 2 The Himalaya were formed not at the start of the India–Eurasia collision, but after much of Tibet had achieved its present elevation. The Himalaya built against a pre-existing proto-Tibetan highland and only projected above the average height of the plateau after approximately 15 Ma. 3 Monsoon climates have existed across southern Asia for the whole of the Cenozoic, and probably for a lot longer, but that they were of the kind generated by seasonal migrations of the Inter-tropical Convergence Zone. 4 The projection of the High Himalaya above the Tibetan Plateau at about 15 Ma coincides with the development of the modern South Asia Monsoon. 5 The East Asia monsoon became established in its present form about the same time as a consequence of topographic changes in northern Tibet and elsewhere in Asia, the loss of moisture sources in the Asian interior and the development of a strong winter Siberian high as global temperatures declined. 6 New radiometric dates of palaeontological finds point to southern Asia's high biodiversity originating in the Paleogene, not the Neogene.

  14. Holocene Summer Monsoon Variability- Evidence from Marine Sediment of western Continental Shelf of Sri Lanka

    Science.gov (United States)

    Ranasinghage, P. N.; Ratnayake, K. M.; Dassanayake, D. M. K. K.; Mohtadi, M.; Hewawasam, T.; Jinadasa, S. U. P.; Jayawardena, S.; Siriwardana, S.

    2016-12-01

    decreasing precipitation during 2000-4000 cal yrs BP has also been observed in Arabian Sea close to the west coast of India. Although monsoonal wind strength is increased, change in its direction, which decreases orographic effect, or weakening of convergence in the vicinity of Sri Lanka, could be possible reasons for this phenomenon.

  15. Strong Central Asian seasonality from Eocene oysters indicates early monsoons and aridification

    Science.gov (United States)

    Bougeois, Laurie; de Rafélis, Marc; Tindall, Julia; Proust, Jean-Noël; Reichart, Gert-Jan; de Nooijer, Lennart; Guo, ZhaoJie; Ormukov, Cholponbek; Dupont-Nivet, Guillaume

    2017-04-01

    Climate models suggest that the onset of Asian monsoons and aridification have been governed by Tibetan plateau uplift, global climate changes and the retreat to the west of the vast epicontinental Proto-Paratethys sea during the warm Eocene greenhouse period (55-34 million years ago). However, the role of the Proto-Paratethys sea on climate remains to be quantified by accurate and precise reconstructions. By applying a novel intra-annual geochemical multi-proxy methodology on Eocene oyster shells of the Proto-Paratethys sea and comparing results to climate simulations and sedimentology analyses, we show that the Central Asian region was generally arid with a high seasonal contrast characterized by hot and arid summers and wetter winters. Hotter and more arid summers despite the presence of the Proto-Paratethys may be explained by warmer Eocene global conditions with a strong anticyclonic Hadley cell descending at Central Asian latitudes and a stronger Foehn effect from the emerging Tibetan Plateau to the south. This implies that the shallow sea did not have a strong dampening thermal effect on the monsoonal circulation in contrast to previous circulation models results but in agreement with recent evidence for Eocene summer monsoons. Enhanced winter precipitations, relative to modern, is linked to a westerly moisture source coming from the Proto-Paratethys sea at that time. Additional bulk sediment stable isotope data from marine limestones and pedogenic carbonates suggest a gradual decrease in this westerly moisture source, which is in line with the retreat of the Proto-Paratethys followed by the Oligo-Miocene orogeny of the Central Asian ranges (Tian Shan and Pamir) shielding the westerlies.

  16. Decadal variability in snow depth anomaly over Eurasia and its association with all India summer monsoon rainfall and seasonal circulations

    International Nuclear Information System (INIS)

    Singh, G.P.

    2003-05-01

    The Historical Soviet Daily Snow Depth (HSDSD) version II data set has been used in the computation of winter and spring snow depth anomalies over west (25 deg. E to 70 deg. E, 35 deg. N to 65 deg. N) and east (70 deg. E to 160 deg. E, 35 deg. N to 65 deg. N) Eurasia. It is noticed that winter snow depth anomaly over east Eurasia is positively correlated while west Eurasia is negatively correlated with subsequent Indian summer monsoon rainfall (ISMR). The DJF snow depth anomaly shows highest and inverse correlation coefficient (CC) with ISMR over a large area of west Eurasia in a recent period of study i.e. 1975-1995. On the basis of standardised winter (mean of December, January and February) snow depth anomaly over west Eurasia, the years 1966, 1968, 1979 and 1986 are identified as high snow years and the years 1961 and 1975 as low snow years. The characteristics of seasonal monsoon circulation features have been studied in detail during contrasting years of less (more) snow depth in winter/spring seasons followed by excess (deficient) rainfall over India using National Center for Environmental Prediction (NCEP) / National Center for Atmospheric Research (NCAR) reanylised data for the period 1948-1995. The composite difference of temperature, wind, stream function and velocity potential during the years of high and low snow years at upper and lower levels have been studied in detail. The temperature at lower level shows maximum cooling up to 6 deg. C during DJF and this cooling persists up to 500hPa by 2 deg. C which gives rise to anomalous cyclonic circulation over the Caspian Sea and this may be one of the causes of the weakening of the summer monsoon circulation over Indian sub-continent. The stream function difference fields show westerly dominated over Arabian Sea at upper level in weak monsoon years. Velocity potential difference field shows complete phase reversal in the dipole structure from the deficient to excess Indian summer monsoon rainfall. (author)

  17. Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

    Science.gov (United States)

    Lachkar, Zouhair; Lévy, Marina; Smith, Shafer

    2018-01-01

    The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from -50 to +50 %) on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Ocean Modeling System (ROMS) coupled to a nitrogen-based nutrient-phytoplankton-zooplankton-detritus (NPZD) ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years), the OMZ response is much slower (i.e., a timescale of decades). Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased ventilation. The enhanced ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100-200 m) of the western and central Arabian Sea, leading to intermittent expansions of marine habitats and a more frequent alternation of hypoxic and oxic conditions there. The increased

  18. Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2018-01-01

    Full Text Available The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs. This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from −50 to +50 % on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Ocean Modeling System (ROMS coupled to a nitrogen-based nutrient–phytoplankton–zooplankton–detritus (NPZD ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years, the OMZ response is much slower (i.e., a timescale of decades. Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased ventilation. The enhanced ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100–200 m of the western and central Arabian Sea, leading to intermittent expansions of marine habitats and a more frequent alternation of hypoxic and oxic conditions there

  19. Nitrogen Uptake in the Northeastern Arabian Sea during Winter Cooling

    Directory of Open Access Journals (Sweden)

    S. Kumar

    2010-01-01

    Full Text Available The uptake of dissolved inorganic nitrogen by phytoplankton is an important aspect of the nitrogen cycle of oceans. Here, we present nitrate (NO3- and ammonium (NH4+ uptake rates in the northeastern Arabian Sea using 15N tracer technique. In this relatively underexplored region, productivity is high during winter due to supply of nutrients by convective mixing caused by the cooling of the surface by the northeast monsoon winds. Studies done during different months (January and late February-early March of the northeast monsoon 2003 revealed a fivefold increase in the average euphotic zone integrated NO3- uptake from January (2.3 mmolN m−2d−1 to late February-early March (12.7 mmolN m−2d−1. The f-ratio during January appeared to be affected by the winter cooling effect and increased by more than 50% from the southernmost station to the northern open ocean stations, indicating hydrographic and meteorological control. Estimates of NO3- residence time suggested that NO3- entrained in the water column during January contributed to the development of blooms during late February-early March.

  20. Development of summer monsoon and onset of continuous rains over central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    rains happening during the last phase of monsoon development as a consequence of and after (2-5 weeks) the establishment of monsoon circulation or monsoon front. Summer monsoon front, as the term 'monsoon' originally meant, is to be delineated from...

  1. Orbital-scale nonlinear response of East Asian summer monsoon to its potential driving forces in the late Quaternary

    Science.gov (United States)

    Yi, Liang; Shi, Zhengguo; Tan, Liangcheng; Deng, Chenglong

    2018-03-01

    We conducted a statistical study to characterize the nonlinear response of the East Asian summer monsoon (EASM) to its potential forcing factors over the last 260 ka on orbital timescales. We find that both variation in solar insolation and global ice volume were responsible for the nonlinear forcing of orbital-scale monsoonal variations, accounting for 80% of the total variance. Specifically, EASM records with dominated precession variance exhibit a more sensitive response to changes in solar insolation during intervals of enhanced monsoon strength, but are less sensitive during intervals of reduced monsoon strength. In the case of global ice volume with 100-ka variance, this difference is not one of sensitivity but rather a difference in baseline conditions, such as the relative areas of land and sea which affected the land-sea thermal gradient. We therefore suggest that EASM records with dominated precession variance recorded the signal of a shift in the location of the Inter-tropical Convergence Zone, and the associated changes in the incidence of torrential rainfall; while for proxies with dominated 100-ka variance, it recorded changes in the land-sea thermal gradient via its effects on non-torrential precipitation.

  2. 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

  3. The nuclear winter

    International Nuclear Information System (INIS)

    Velikhow, Y.P.

    1986-01-01

    Nuclear winter is an example of possible secondary effects, and if we speak of secondary we are thinking of small-scale second-order effects, but a nuclear winter is not a second-order effect. If you calculate the amount of heat produced by a nuclear explosion, it is a very small amount which does not have any chance of changing the Earth's climate, but a nuclear explosion drives or stars some new mechanism - the mechanism of nuclear winter - after 100 megatons of dust are transferred to the upper atmosphere. Another example of such amplification is radioactive fall-out, especially long-life radioactive fall-out after the possible elimination of the nuclear power industry, nuclear storage and distribution of storage waste around the globe. This is a very powerful amplification mechanism

  4. Fast Adjustments of the Asian Summer Monsoon to Anthropogenic Aerosols

    Science.gov (United States)

    Li, Xiaoqiong; Ting, Mingfang; Lee, Dong Eun

    2018-01-01

    Anthropogenic aerosols are a major factor contributing to human-induced climate change, particularly over the densely populated Asian monsoon region. Understanding the physical processes controlling the aerosol-induced changes in monsoon rainfall is essential for reducing the uncertainties in the future projections of the hydrological cycle. Here we use multiple coupled and atmospheric general circulation models to explore the physical mechanisms for the aerosol-driven monsoon changes on different time scales. We show that anthropogenic aerosols induce an overall reduction in monsoon rainfall and circulation, which can be largely explained by the fast adjustments over land north of 20∘N. This fast response occurs before changes in sea surface temperature (SST), largely driven by aerosol-cloud interactions. However, aerosol-induced SST feedbacks (slow response) cause substantial changes in the monsoon meridional circulation over the oceanic regions. Both the land-ocean asymmetry and meridional temperature gradient are key factors in determining the overall monsoon circulation response.

  5. Isomap nonlinear dimensionality reduction and bimodality of Asian monsoon convection

    Science.gov (United States)

    Hannachi, A.; Turner, A. G.

    2013-04-01

    It is known that the empirical orthogonal function method is unable to detect possible nonlinear structure in climate data. Here, isometric feature mapping (Isomap), as a tool for nonlinear dimensionality reduction, is applied to 1958-2001 ERA-40 sea-level pressure anomalies to study nonlinearity of the Asian summer monsoon intraseasonal variability. Using the leading two Isomap time series, the probability density function is shown to be bimodal. A two-dimensional bivariate Gaussian mixture model is then applied to identify the monsoon phases, the obtained regimes representing enhanced and suppressed phases, respectively. The relationship with the large-scale seasonal mean monsoon indicates that the frequency of monsoon regime occurrence is significantly perturbed in agreement with conceptual ideas, with preference for enhanced convection on intraseasonal time scales during large-scale strong monsoons. Trend analysis suggests a shift in concentration of monsoon convection, with less emphasis on South Asia and more on the East China Sea.

  6. The effects of El Niño-Southern Oscillation on the winter haze pollution of China

    Science.gov (United States)

    Zhao, Shuyun; Zhang, Hua; Xie, Bing

    2018-02-01

    It has been reported in previous studies that El Niño-Southern Oscillation (ENSO) influenced not only the summer monsoon, but also the winter monsoon over East Asia. This contains some clues that ENSO may affect the winter haze pollution of China, which has become a serious problem in recent decades, through influencing the winter climate of East Asia. In this work, we explored the effects of ENSO on the winter (from December to February) haze pollution of China statistically and numerically. Statistical results revealed that the haze days of southern China tended to be fewer (more) than normal in El Niño (La Niña) winter, whereas the relationships between the winter haze days of northern and eastern China and ENSO were not significant. Results from numerical simulations also showed that ENSO influenced the winter atmospheric anthropogenic aerosol content over southern China more obviously than it did over northern and eastern China. Under the emission level of aerosols for the year 2010, winter atmospheric anthropogenic aerosol content over southern China was generally greater (less) than normal in El Niño (La Niña) winter. This was because the transport of aerosols from South and Southeast Asia to southern China was enhanced (weakened), which masked the better (worse) scavenging conditions for aerosols in El Niño (La Niña) winter. The frequency distribution of the simulated daily surface concentrations of aerosols over southern China indicated that the region tended to have fewer clean and moderate (heavy) haze days, but more heavy (moderate) haze days in El Niño (La Niña) winter.

  7. Deep learning for predicting the monsoon over the homogeneous ...

    Indian Academy of Sciences (India)

    Moumita Saha

    2017-06-12

    Jun 12, 2017 ... forecast of the monsoon at a long lead time which supports the government to implement appropriate .... e.gov.in). • The central India monsoon having the LPA of. 976.4 mm with std of 14%. • The north-east India monsoon having the LPA of 1324.6 mm ...... north-east China and north-west Russia, and the.

  8. 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.

  9. Titan's Emergence from Winter

    Science.gov (United States)

    Flasar, F. Michael; Achterberg, Richard; Jennings, Donald; Schinder, Paul

    2011-01-01

    We summarize the changes in Titans thermal structure derived from Cassini CIRS and radio-occultation data during the transition from winter to early spring. Titan's surface, and middle atmosphere show noticeable seasonal change, whereas that in most of the troposphere is mated. This can be understood in terms of the relatively small radiative relaxation time in the middle atmosphere and much larger time scale in the troposphere. The surface exhibits seasonal change because the heat capacity in an annual skin depth is much smaller than that in the lowest scale height of the troposphere. Surface temperatures rise 1 K at raid and high latitudes in the winter northern hemisphere and cool in the southern hemisphere. Changes in in the middle atmosphere are more complicated. Temperatures in the middle stratosphere (approximately 1 mbar) increase by a few kelvin at mid northern latitudes, but those at high latitudes first increase as that region moves out of winter shadow, and then decrease. This probably results from the combined effect of increased solar heating as the suit moves higher in the sky and the decreased adiabatic warming as the sinking motions associated with the cross-equatorial meridional cell weaken. Consistent with this interpretation, the warm temperatures observed higher up at the winter polar stratopause cool significantly.

  10. Sea surface temperature variability over North Indian Ocean - A study of two contrasting monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sathyendranath, S.; Viswambharan, N.K.; Rao, L.V.G.

    Using the satellite derived sea surface temperature (SST) data for 1979 (bad monsoon) and 1983 (good monsoon), the SST variability for two contrasting monsoon seasons is studied. The study indicates that large negative anomalies off the Somali...

  11. The Rise of the Hindu Kush and its Role in the South Asian Monsoon

    Science.gov (United States)

    Molnar, P. H.; Bendick, R. O.; Boos, W. R.

    2017-12-01

    The emergence of the Hindu Kush to its mean elevation of 3000 m since 10 Ma may have profoundly affected summer rainfall over the Indian subcontinent - the South Asian Monsoon. General Circulation Model runs of climate with different surface heights suggest that the Hindu Kush in Afghanistan may be the most important high terrain that affects the timing and strength of the South Asian monsoon [Chakraborty, Nanjundiah, and Srinivasan, 2002, 2006]. That high terrain, more than the Tibetan Plateau and the Himalaya, blocks warm dry air, with low moist static energy, from mixing with warm moist air from the Bay of Bengal and over India, and therefore enables a moist static energy maximum to be generated by local sources in the northern edges of the Indian subcontinent, facilitating a strong monsoon circulation. Boos and Hurley [2013] showed that if the Hindu Kush is smoothed too much, so that its maximum height is only 1000 m, nearly all General Circulation Model runs yield atmospheric temperature profiles inconsistent with those of monsoons. Fault plane solutions of earthquakes show underthrusting of the Tajik Depression beneath the Hindu Kush, and GPS velocities require 30-35 mm/yr of convergence between India and the Depression. Some of that convergence might be absorbed by subduction of lithosphere with thin crust, but GPS measurements suggest at least 10 and more likely 20 mm/yr of shortening across the Hindu Kush. For a belt 300 km wide with a mean elevation of its crest of 3 km, isostatic balance of 900 km^2 of excess elevation calls for 6000 km^2 of excess crust in a transect across the Hindu Kush. If crust 30-40 km in thickness were shortened horizontally at 20 (10) km/Myr, then 10-7.5 (20-15) Myr would be needed to build the entire range. If a range 1000 m high would have had little effect on the South Asian Monsoon, and if a height of 2000 m were necessary, at current rates of convergence only a few million years would be needed to raise the Hindu Kush from a

  12. Asian Eocene monsoons as revealed by leaf architectural signatures

    Science.gov (United States)

    Spicer, Robert A.; Yang, Jian; Herman, Alexei B.; Kodrul, Tatiana; Maslova, Natalia; Spicer, Teresa E. V.; Aleksandrova, Galina; Jin, Jianhua

    2016-09-01

    The onset and development of the Asian monsoon systems is a topic that has attracted considerable research effort but proxy data limitations, coupled with a diversity of definitions and metrics characterizing monsoon phenomena, have generated much debate. Failure of geological proxies to yield metrics capable of distinguishing between rainfall seasonality induced by migrations of the Inter-tropical Convergence Zone (ITCZ) from that attributable to topographically modified seasonal pressure reversals has frustrated attempts to understand mechanisms underpinning monsoon development and dynamics. Here we circumvent the use of such single climate parameter metrics in favor of detecting directly the distinctive attributes of different monsoon regimes encoded in leaf fossils. Leaf form adapts to the prevailing climate, particularly under the extreme seasonal stresses imposed by monsoons, so it is likely that fossil leaves carry a unique signature of past monsoon regimes. Leaf form trait spectra obtained from fossils from Eocene basins in southern China were compared with those seen in modern leaves growing under known climate regimes. The fossil leaf trait spectra, including those derived from previously published fossil floras from northwestern India, were most similar to those found in vegetation exposed to the modern Indonesia-Australia Monsoon (I-AM), which is largely a product of seasonal migrations of the ITCZ. The presence of this distinctive leaf physiognomic signature suggests that although a monsoon climate existed in Eocene time across southern Asia the characteristics of the modern topographically-enhanced South Asia Monsoon had yet to develop. By the Eocene leaves in South Asia had become well adapted to an I-AM type regime across many taxa and points to the existence of a pervasive monsoon climate prior to the Eocene. No fossil trait spectra typical of exposure to the modern East Asia monsoon were seen, suggesting the effects of this system in southern

  13. Energetics of Indian winter monsoon P. Kumar@ and A. P. Dimri ...

    Indian Academy of Sciences (India)

    31

    2004-2007 over the study region; (a) SLP has contour interval of 3 hPa, (b) geopotential. 12 height (900hPa); contour interval of 30 m, (c) specific humidity bias at 500 hPa; contour. 13 interval of 0.5 g/Kg and (d) specific humidity bias at 900 hPa; contour interval of 1 g/Kg. 14. Fig.5. Temperature bias climatology at 300 hPa ...

  14. Report of a Workshop for the Winter Monsoon Experiment, 14-15 June 1982, Monterey, California.

    Science.gov (United States)

    1983-03-01

    Fort Collins, Colorado 80523 15. Professor Robert Houze Department of Atmospheric Sciences #AK-40 University of Washington Seattle, Washington 98195 16...moderate intensity, there was the expected enhancement of tropical convection during the surge episodes in December 1978 ( Houze et al., 1981b; Johnson...and Priegnitz, 1981). Houze et al. found a greater modulation of equatorial convection and rainfall by the cold surges over water areas than over the

  15. Energetics of Indian winter monsoon P. Kumar@ and A. P. Dimri ...

    Indian Academy of Sciences (India)

    31

    which leads to easterlies losing its omega angular momentum due to friction with surface (i.e., due. 3 to complex terrain). In summer the horizontal flux of relative angular momentum is opposite to. 4 the horizontal flux of omega angular momentum (Peixoto and Oort, 1992; Rao, 2001; Dimri,. 5. 2007). But it is observed that ...

  16. Unusual blooms of green Noctiluca miliaris (Dinophyceae) in the Arabian Sea during the winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Gomes, H.R.; Matondkar, S.G.P.; Parab, S.G.; Goes, J.I.; Pednekar, S.; Al-Azri, A.R.N.; Thoppil, P.G.

    blooms using phytoplankton taxonomic and pigment data from cruises undertaken in 2003-2004 and 2007 as well as ocean color satellite data. Our findings indicate that N. miliaris blooms are becoming an annual and widespread feature in the Arabian Sea. Aqua...

  17. Distribution of mesopelagic micronekton in the Arabian Sea during the winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Karuppasamy, P.K.; Muraleedharan, K.R.; DineshKumar, P.K.; Nair, M.

    and nitrite were obtained using an autoanalyser (SKALAR, Model 51001-1), following the principles of Grasshoff et al. 198322. The acoustic detection of DSL was made by two scientific Echo sounders: Simrad, EK 400 and EK 200 (38 and 120 KHz). The gear... for the temperature, salinity, dissolved oxygen, nitrate and nitrite contour. KARUPPASAMY et al. : MESOPELAGIC MICRONEKTON IN THE ARABIAN SEA 229 Biodiversity indices Diversity is a concise expression of how individuals of a community are distributed...

  18. Dust-induced episodic phytoplankton blooms in the Arabian Sea during winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Banerjee, P.; PrasannaKumar, S.

    Biosphere-Atmosphere Transfer Scheme (BATS) [Dickinson et al., 1993]. For our present study we compared the simulated τdu with τdu from MODIS/Aqua. Implicit in this comparison is the assumption that a successful simulation of τdu means a proper treatment...

  19. 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

  20. Waves in the Red Sea: Response to monsoonal and mountain gap winds

    KAUST Repository

    Ralston, David K.

    2013-08-01

    An unstructured grid, phase-averaged wave model forced with winds from a high resolution atmospheric model is used to evaluate wind wave conditions in the Red Sea over an approximately 2-year period. The Red Sea lies in a narrow rift valley, and the steep topography surrounding the basin steers the dominant wind patterns and consequently the wave climate. At large scales, the model results indicated that the primary seasonal variability in waves was due to the monsoonal wind reversal. During the winter, monsoon winds from the southeast generated waves with mean significant wave heights in excess of 2. m and mean periods of 8. s in the southern Red Sea, while in the northern part of the basin waves were smaller, shorter period, and from northwest. The zone of convergence of winds and waves typically occurred around 19-20°N, but the location varied between 15 and 21.5°N. During the summer, waves were generally smaller and from the northwest over most of the basin. While the seasonal winds oriented along the axis of the Red Sea drove much of the variability in the waves, the maximum wave heights in the simulations were not due to the monsoonal winds but instead were generated by localized mountain wind jets oriented across the basin (roughly east-west). During the summer, a mountain wind jet from the Tokar Gap enhanced the waves in the region of 18 and 20°N, with monthly mean wave heights exceeding 2. m and maximum wave heights of 14. m during a period when the rest of the Red Sea was relatively calm. Smaller mountain gap wind jets along the northeast coast created large waves during the fall and winter, with a series of jets providing a dominant source of wave energy during these periods. Evaluation of the wave model results against observations from a buoy and satellites found that the spatial resolution of the wind model significantly affected the quality of the wave model results. Wind forcing from a 10-km grid produced higher skills for waves than winds from a

  1. Variation in the Indian summer monsoon intensity during the Bolling-Allerod and Holocene

    Digital Repository Service at National Institute of Oceanography (India)

    Kessarkar, P.M.; Rao, V.P.; Naqvi, S.W.A.; Karapurkar, S.G.

    denitrification [Kessarkar et al. 2010.]. Increase in the monsoon strength during 11.5-10.8 ka BP has been reported by Overpeck [1996], and more humid conditions around 11 ka BP have been recorded by Cancer et al. [2005] in the Nilgiris (western Peninsular.... Devol, T. Yoshinari, D. A. Jayakumar, S. W. A. Naqvi, (1998), Isotopic composition of nitrate in the central Arabian Sea and eastern tropical North Pacific: A tracer for mixing and nitrogen cycles, Limnol. Oceanogr., 43, 1680-1689. Cancer, L., D. L...

  2. Investigating monsoon and post-monsoon variabilities of bacterioplankton communities in a mangrove ecosystem.

    Science.gov (United States)

    Ghosh, Anwesha; Bhadury, Punyasloke

    2018-02-01

    In mangrove environments, bacterioplankton communities constitute an important component of aquatic biota and play a major role in ecosystem processes. Variability of bacterioplankton communities from Sundarbans mangrove, located in the Indian subcontinent in South Asia and sits on the apex of Bay of Bengal, was investigated over monsoon and post-monsoon seasons. The study was undertaken in two stations in Sundarbans using 16S rRNA clone library and Illumina MiSeq approaches with focus on the functionally important members that participate in coastal biogeochemical cycling. Out of 544 sequenced clones, Proteobacteria dominated the study area (373 sequences) with persistence of two major classes, namely, Gammaproteobacteria and Alphaproteobacteria across both monsoon and post-monsoon seasons in both stations. Several sequences belonging to Sphingomonadales, Chromatiales, Alteromonadales, Oceanospirillales, and Bacteroidetes were encountered that are known to play important roles in coastal carbon cycling. Some sequences showed identity with published uncultured Planctomycetes and Chloroflexi highlighting their role in nitrogen cycling. The detection of two novel clades highlighted the existence of indigenous group of bacterioplankton that may play important roles in this ecosystem. The eubacterial V3-V4 region from environmental DNA extracted from the above two stations, followed by sequencing in Illumina MiSeq system, was also targeted in the study. A congruency between the clone library and Illumina approaches was observed. Strong variability in bacterioplankton community structure was encountered at a seasonal scale in link with precipitation. Drastic increase in sediment associated bacteria such as members of Firmicutes and Desulfovibrio was found in monsoon hinting possible resuspension of sediment-dwelling bacteria into the overlying water column. Principal component analysis (PCA) revealed dissolved ammonium and dissolved nitrate to account for maximum

  3. Editorial - The winter Atomiades

    CERN Multimedia

    Staff Association

    2011-01-01

    As we wrote in our previous editorial, the Staff Association gives direct support to sports events, such as the Atomiades, a section of the Association of Sports Communities of European Research Institutes, which brings together sportsmen and women from 38 European research centres in 13 countries (Austria, Belgium, Czech Republic, United Kingdom, Finland, France, Germany, Hungary, Italy, Luxemburg, the Netherlands, Russia, and Switzerland). The summer Atomiades take place between the months of June and September every three years. Thirteen such events have taken place since 1973, the last one in June 2009 in Berlin. As far as the winter Atomiades are concerned, also organized every three years, and alternating with the summer Atomiades, there have been eleven since 1981, the last one at the end of January this year in neighbouring France. The following article tells the wonderful adventure of the CERN staff who took part in this event. A positive outcome for CERN skiers at the winter Atomiades The 11t...

  4. Spatio-temporal variability of summer monsoon rainfall over Orissa ...

    Indian Academy of Sciences (India)

    on the performance of monsoon rainfall over India. The southwest sector of a monsoon depression gets more rainfall due to maximum low level conver- gence and vertical motion (Rajamani and Rao. 1981). Dhar et al (1981) have noted a significant relationship of tropical disturbances (depression and cyclonic storms) only ...

  5. Indian Summer Monsoon influence on the Arabian Peninsula Summer Climate

    Science.gov (United States)

    Attada, Raju; Prasad Dasari, Hari; Omar, Knio; Hoteit, Ibrahim

    2017-04-01

    The Indian Summer Monsoon (ISM) is as an integral component of the atmospheric global circulation. During summer, the mid-latitude zone of baroclinic waves in the Middle East region are pushed northward under the influence of ISM. We investigate the impact of ISM on the atmospheric circulation over the Arabian Peninsula on interannual time scale. We analyze various atmospheric variables derived from ECMWF reanalysis. We apply a composite analysis to study the circulation variability over the Middle East during extreme monsoon years. The extreme (strong and weak) monsoon years are identified based on All India Precipitation Index during 1979-2015. Our analysis reveals that ISM is a fundamental driver of the summer circulation over the Middle East. More specifically, during extreme monsoons: (i) the lower tropospheric winds are enhanced and dominated by persistent northerlies along with intensified subsidence due to adiabatic warming, (ii) A prominent baroclinic structure in circulation anomalies are observed, (iii) a meridional shift of the upper tropospheric jet stream (subtropical jet) is noticeable during weak monsoon years; this shift favors a strong Rossby wave response and has a consequent impact on summer circulations over the Middle East, (iv) the upper tropospheric wind anomalies show a well organized train of Rossby waves during strong monsoon years, and (v) Intensification of thermal signal during strong monsoon over West Asia has been noticed. We will present these findings and further discuss the monsoon dynamics controlling the summer Arabian Peninsula circulation.

  6. The monsoon system: Land–sea breeze or the ITCZ?

    Indian Academy of Sciences (India)

    Sulochana Gadgil

    2018-01-27

    Jan 27, 2018 ... ocean contrast is one of the main drivers of the monsoon rainfall, in the 5th Assessment Report of the Inter-governmental Panel on Climate Change. (IPCC Climate Change 2013), the likely enhance- ment of monsoon rainfall has been attributed to increased land–sea contrast, and more abundant.

  7. Glacial to Holocene swings of the Australian-Indonesian monsoon

    NARCIS (Netherlands)

    Mohtadi, M.; Oppo, D.W.; Steinke, S.; Stuut, J.B.W.; De Pol-Holz, R.; Hebbeln, D.; Lückge, A.; Stuut, J.B.W.; De-Pol-Holz, R.

    2011-01-01

    The Australian-Indonesian monsoon is an important component of the climate system in the tropical Indo-Pacific region(1). However, its past variability, relation with northern and southern high-latitude climate and connection to the other Asian monsoon systems are poorly understood. Here we present

  8. Spatio-temporal variability of summer monsoon rainfall over Orissa ...

    Indian Academy of Sciences (India)

    The summer monsoon rainfall over Orissa occurs mostly due to low pressure systems (LPS)developing over the Bay of Bengal and moving along the monsoon trough.A study is hence undertaken to find out characteristic features of the relationship between LPS over different regions and rainfall over Orissa during the ...

  9. Rainfall analysis for Indian monsoon region using the merged rain ...

    Indian Academy of Sciences (India)

    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 ...

  10. Hydrography of the eastern Arabian Sea during summer monsoon ...

    Indian Academy of Sciences (India)

    Arabian Sea, between the onset and wane of the 1995 southwest monsoon; Deep-Sea Res. II 50 2049–2075. Bruce J G, Johnson D R and Kindle J C 1994 Evidence for eddy formation in the eastern Arabian Sea during the northeast monsoon; J. Geophys. Res. 99 7651–7664. Durand F, Shetye S R, Vialard J, Shankar D, ...

  11. Seasonal forecasting of Bangladesh summer monsoon rainfall using ...

    Indian Academy of Sciences (India)

    In this paper, the development of a statistical forecasting method for summer monsoon rainfall over. Bangladesh is described. Predictors for Bangladesh summer monsoon (June–September) rainfall were identified from the large scale ocean–atmospheric circulation variables (i.e., sea-surface temperature, surface air ...

  12. Spatial monsoon variability with respect to NAO and SO

    Indian Academy of Sciences (India)

    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 ...

  13. Occurrence of heavy rainfall around the confluence line in monsoon ...

    Indian Academy of Sciences (India)

    It is well known that heavy rainfall occurs in the southwestern sector of the monsoon depressions due to strong convergence in that sector. By examining the rainfall distribution associated with the monsoon disturbances (lows and depressions) in one of the central Indian river basins, `Godavari', the author found that when ...

  14. Seasonal forecasting of Bangladesh summer monsoon rainfall using ...

    Indian Academy of Sciences (India)

    In this paper, the development of a statistical forecasting method for summer monsoon rainfall over Bangladesh is described. Predictors for Bangladesh summer monsoon (June–September) rainfall were identified from the large scale ocean–atmospheric circulation variables (i.e., sea-surface temperature, surface air ...

  15. Occurrence of heavy rainfall around the confluence line in monsoon ...

    Indian Academy of Sciences (India)

    monsoon disturbances and its importance in causing floods. G NAGESWARA RAO. Department of Meteorology & Oceanography, Andhra University, Visakhapatnam 530003, India. e-mail: raongantasala@yahoo.com. It is well known that heavy rainfall occurs in the southwestern sector of the monsoon depressions due to.

  16. Monsoon signatures in recent corals from the Laccadive Islands

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.A.S.

    as changes in the growth rates. One probable cause for the higher growth rates in the non-monsoon season could be the nutrient deficient environment. In the monsoon season an increase in the availability of the nutrients and particulate organic matter might...

  17. Prediction of monsoon rainfall with a nested grid mesoscale limited ...

    Indian Academy of Sciences (India)

    ... days in the month of August 1997 and one week in September 1997 during three monsoon depressions and one cyclonic storm in the Bay of Bengal. The model results are compared with observations. The study shows that the model can capture mesoscale convective organization associated with monsoon depression.

  18. Impact of Climate Change on India's Monsoonal Climate: Present ...

    Indian Academy of Sciences (India)

    Expected Future Changes in Rainfall and Temperature over India under IPCC SRES A1B GHG Scenarios · Expected Future Change in Monsoon Rainfall and Annual Surface Temp for 2020's, 2050's and 2080's · Likely Future Paradox of Monsoon-ENSO Links · High-Resolution Regional Climate Change Scenarios.

  19. The monsoon system: Land–sea breeze or the ITCZ?

    Indian Academy of Sciences (India)

    Sulochana Gadgil

    2018-01-27

    –sea breeze driven by the land–ocean contrast in surface temperature. In this paper, this hypothesis and its implications for the variability of the monsoon are discussed and it is shown that the observations of monsoon ...

  20. Winter is losing its cool

    Science.gov (United States)

    Feng, S.

    2017-12-01

    Winter seasons have significant societal impacts across all sectors ranging from direct human health to ecosystems, transportation, and recreation. This study quantifies the severity of winter and its spatial-temporal variations using a newly developed winter severity index and daily temperature, snowfall and snow depth. The winter severity and the number of extreme winter days are decreasing across the global terrestrial areas during 1901-2015 except the southeast United States and isolated regions in the Southern Hemisphere. These changes are dominated by winter warming, while the changes in daily snowfall and snow depth played a secondary role. The simulations of multiple CMIP5 climate models can well capture the spatial and temporal variations of the observed changes in winter severity and extremes during 1951-2005. The models are consistent in projecting a future milder winter under various scenarios. The winter severity is projected to decrease 60-80% in the middle-latitude Northern Hemisphere under the business-as-usual scenario. The winter arrives later, ends earlier and the length of winter season will be notably shorter. The changes in harsh winter in the polar regions are weak, mainly because the warming leads to more snowfall in the high latitudes.

  1. Does Aerosol Weaken or Strengthen the South Asian Monsoon?

    Science.gov (United States)

    Lau, William K.

    2010-01-01

    Aerosols are known to have the ability to block off solar radiation reaching the earth surface, causing it to cool - the so-called solar dimming (SDM) effect. In the Asian monsoon region, the SDM effect by aerosol can produce differential cooling at the surface reducing the meridional thermal contrast between land and ocean, leading to a weakening of the monsoon. On the other hand, absorbing aerosols such as black carbon and dust, when forced up against the steep slopes of the southern Tibetan Plateau can produce upper tropospheric heating, and induce convection-dynamic feedback leading to an advance of the rainy season over northern India and an enhancement of the South Asian monsoon through the "Elevated Heat Pump" (EHP) effect. In this paper, we present modeling results showing that in a coupled ocean-atmosphere-land system in which concentrations of greenhouse gases are kept constant, the response of the South Asian monsoon to dust and black carbon forcing is the net result of the two opposing effects of SDM and EHP. For the South Asian monsoon, if the increasing upper tropospheric thermal contrast between the Tibetan Plateau and region to the south spurred by the EHP overwhelms the reduction in surface temperature contrast due to SDM, the monsoon strengthens. Otherwise, the monsoon weakens. Preliminary observations are consistent with the above findings. We find that the two effects are strongly scale dependent. On interannual and shorter time scales, the EHP effect appears to dominate in the early summer season (May-June). On decadal or longer time scales, the SDM dominates for the mature monsoon (July-August). Better understanding the physical mechanisms underlying the SDM and the EHP effects, the local emission and transport of aerosols from surrounding deserts and arid-regions, and their interaction with monsoon water cycle dynamics are important in providing better prediction and assessment of climate change impacts on precipitation of the Asian monsoon

  2. 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

    2017-11-01

    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.

  3. Stable isotopes in precipitation recording South American summer monsoon and ENSO variability: observations and model results

    Science.gov (United States)

    Vuille, M.; Werner, M.

    2005-09-01

    The South American Summer Monsoon (SASM) is a prominent feature of summertime climate over South America and has been identified in a number of paleoclimatic records from across the continent, including records based on stable isotopes. The relationship between the stable isotopic composition of precipitation and interannual variations in monsoon strength, however, has received little attention so far. Here we investigate how variations in the intensity of the SASM influence δ18O in precipitation based on both observational data and Atmospheric General Circulation Model (AGCM) simulations. An index of vertical wind shear over the SASM entrance (low level) and exit (upper level) region over the western equatorial Atlantic is used to define interannual variations in summer monsoon strength. This index is closely correlated with variations in deep convection over tropical and subtropical South America during the mature stage of the SASM. Observational data from the International Atomic Energy Agency-Global Network of Isotopes in Precipitation (IAEA-GNIP) and from tropical ice cores show a significant negative association between δ18O and SASM strength over the Amazon basin, SE South America and the central Andes. The more depleted stable isotopic values during intense monsoon seasons are consistent with the so-called ’‘amount effect‘’, often observed in tropical regions. In many locations, however, our results indicate that the moisture transport history and the degree of rainout upstream may be more important factors explaining interannual variations in δ18O. In many locations the stable isotopic composition is closely related to El Niño-Southern Oscillation (ENSO), even though the moisture source is located over the tropical Atlantic and precipitation is the result of the southward expansion and intensification of the SASM during austral summer. ENSO induces significant atmospheric circulation anomalies over tropical South America, which affect both SASM

  4. Middle Holocene Organic Carbon and Biomarker Records from the South Yellow Sea: Relationship to the East Asian Monsoon

    Science.gov (United States)

    Zou, Liang; Hu, Bangqi; Li, Jun; Dou, Yanguang; Xie, Luhua; Dong, Liang

    2018-03-01

    The East Asian monsoon system influences the sedimentation and transport of organic matter in East Asian marginal seas that is derived from both terrestrial and marine sources. In this study, we determined organic carbon (OC) isotope values, concentrations of marine biomarkers, and levels of OC and total nitrogen (TN) in core YSC-1 from the central South Yellow Sea (SYS). Our objectives were to trace the sources of OC and variations in palaeoproductivity since the middle Holocene, and their relationships with the East Asian monsoon system. The relative contributions of terrestrial versus marine organic matter in core sediments were estimated using a two-end-member mixing model of OC isotopes. Results show that marine organic matter has been the main sediment constituent since the middle Holocene. The variation of terrestrial organic carbon concentration (OCter) is similar to the EASM history. However, the variation of marine organic carbon concentration (OCmar) is opposite to that of the EASM curve, suggesting OCmar is distinctly influenced by terrestrial material input. Inputs of terrestrial nutrients into the SYS occur in the form of fluvial and aeolian dust, while concentrations of nutrients in surface water are derived mainly from bottom water via the Yellow Sea circulation system, which is controlled by the East Asian winter monsoon (EAWM). Variations in palaeoproductivity represented by marine organic matter and biomarker records are, in general, consistent with the recent EAWM intensity studies, thus, compared with EASM, EAWM may play the main role to control the marine productivity variations in the SYS.

  5. Monsoon Variability in the Arabian Sea from Global 0.08 deg HYCOM Simulations

    Science.gov (United States)

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Monsoon Variability in the Arabian Sea from Global 0.08...of the prevailing winds associated with the Indian Monsoon . Predictability of the monsoon circulation however is uncertain due to incomplete...understanding of the physical processes operating on the monsoon and at other time scales, particularly interannual and intraseasonal. Therefore, the long

  6. Weakening of the North American monsoon with global warming

    Science.gov (United States)

    Pascale, Salvatore; Boos, William R.; Bordoni, Simona; Delworth, Thomas L.; Kapnick, Sarah B.; Murakami, Hiroyuki; Vecchi, Gabriel A.; Zhang, Wei

    2017-11-01

    Future changes in the North American monsoon, a circulation system that brings abundant summer rains to vast areas of the North American Southwest, could have significant consequences for regional water resources. How this monsoon will change with increasing greenhouse gases, however, remains unclear, not least because coarse horizontal resolution and systematic sea-surface temperature biases limit the reliability of its numerical model simulations. Here we investigate the monsoon response to increased atmospheric carbon dioxide (CO2) concentrations using a 50-km-resolution global climate model which features a realistic representation of the monsoon climatology and its synoptic-scale variability. It is found that the monsoon response to CO2 doubling is sensitive to sea-surface temperature biases. When minimizing these biases, the model projects a robust reduction in monsoonal precipitation over the southwestern United States, contrasting with previous multi-model assessments. Most of this precipitation decline can be attributed to increased atmospheric stability, and hence weakened convection, caused by uniform sea-surface warming. These results suggest improved adaptation measures, particularly water resource planning, will be required to cope with projected reductions in monsoon rainfall in the American Southwest.

  7. Variation in the Asian monsoon intensity and dry-wet conditions since the Little Ice Age in central China revealed by an aragonite stalagmite

    Science.gov (United States)

    Yin, J.-J.; Yuan, D.-X.; Li, H.-C.; Cheng, H.; Li, T.-Y.; Edwards, R. L.; Lin, Y.-S.; Qin, J.-M.; Tang, W.; Zhao, Z.-Y.; Mii, H.-S.

    2014-10-01

    This paper focuses on the climate variability in central China since AD 1300, involving: (1) a well-dated, 1.5-year resolution stalagmite δ18O record from Lianhua Cave, central China (2) links of the δ18O record with regional dry-wet conditions, monsoon intensity, and temperature over eastern China (3) correlations among drought events in the Lianhua record, solar irradiation, and ENSO (El Niño-Southern Oscillation) variation. We present a highly precise, 230Th / U-dated, 1.5-year resolution δ18O record of an aragonite stalagmite (LHD1) collected from Lianhua Cave in the Wuling Mountain area of central China. The comparison of the δ18O record with the local instrumental record and historical documents indicates that (1) the stalagmite δ18O record reveals variations in the summer monsoon intensity and dry-wet conditions in the Wuling Mountain area. (2) A stronger East Asian summer monsoon (EASM) enhances the tropical monsoon trough controlled by ITCZ (Intertropical Convergence Zone), which produces higher spring quarter rainfall and isotopically light monsoonal moisture in the central China. (3) The summer quarter/spring quarter rainfall ratio in central China can be a potential indicator of the EASM strength: a lower ratio corresponds to stronger EASM and higher spring rainfall. The ratio changed from 1 after 1950, reflecting that the summer quarter rainfall of the study area became dominant under stronger influence of the Northwestern Pacific High. Eastern China temperatures varied with the solar activity, showing higher temperatures under stronger solar irradiation, which produced stronger summer monsoons. During Maunder, Dalton and 1900 sunspot minima, more severe drought events occurred, indicating a weakening of the summer monsoon when solar activity decreased on decadal timescales. On an interannual timescale, dry conditions in the study area prevailed under El Niño conditions, which is also supported by the spectrum analysis. Hence, our record

  8. SPATIO-TEMPORAL ESTIMATION OF INTEGRATED WATER VAPOUR OVER THE MALAYSIAN PENINSULA DURING MONSOON SEASON

    Directory of Open Access Journals (Sweden)

    S. Salihin

    2017-10-01

    Full Text Available This paper provides the precise information on spatial-temporal distribution of water vapour that was retrieved from Zenith Path Delay (ZPD which was estimated by Global Positioning System (GPS processing over the Malaysian Peninsular. A time series analysis of these ZPD and Integrated Water Vapor (IWV values was done to capture the characteristic on their seasonal variation during monsoon seasons. This study was found that the pattern and distribution of atmospheric water vapour over Malaysian Peninsular in whole four years periods were influenced by two inter-monsoon and two monsoon seasons which are First Inter-monsoon, Second Inter-monsoon, Southwest monsoon and Northeast monsoon.

  9. Decontamination and winter conditions

    International Nuclear Information System (INIS)

    Quenild, C.; Tveten, U.

    1984-12-01

    The report deals with two decontamonation experiments under winter conditions. A snow-covered parking lot was contaminated, and the snow was subsequently removed using standard snow-moving equipment. The snow left behind was collected and the content of contaminant was determined. A non-radioactive contaminant was used. A decontamination factor exceeding 100 was obtained. Although the eksperimental conditions were close to ideal, it is reason to believe that extremely efficient removal of deposited materials on a snow surface is achivable. In another investigation, run-off from agricultural surface, contaminated while covered with snow, was measured A lycimeter was used in this experiment. A stable layer of ice and snow was allowed to form before contamination. The run-off water was collected at each thaw period until all snow and ice was gone. Cs-134 was used as contaminant. Roughly 30% of the Cs-134 with which the area was contaminated ran off with the melt water. Following a reactor accident situation, this would have given a corresponding reduction in the long term doses. Both of these experiments show that consequence calculation assumptions, as they are currently applied to large accident assessment, tend to overestimate the consequences resulting from accidents taking place under winter conditions

  10. Winter School Les Houches

    CERN Document Server

    Lannoo, Michel; Bastard, Gérald; Voos, Michel; Boccara, Nino

    1986-01-01

    The Winter School held in Les Houches on March 12-21, 1985 was devoted to Semiconductor Heterojunctions and Superlattices, a topic which is recognized as being now one of the most interesting and active fields in semiconductor physics. In fact, following the pioneering work of Esaki and Tsu in 1970, the study of these two-dimensional semiconductor heterostructures has developed rapidly, both from the point of view of basic physics and of applications. For instance, modulation-doped heterojunctions are nowadays currently used to investigate the quantum Hall effect and to make very fast transistors. This book contains the lectures presented at this Winter School, showing in particular that many aspects of semiconductor heterojunctions and super­ lattices were treated, extending from the fabrication of these two-dimensional systems to their basic properties and applications in micro-and opto-electron­ ics. Among the subjects which were covered, one can quote as examples: molecular beam epitaxy and metallorgani...

  11. On the Feasibility of Tracking the Monsoon History by Using Ancient Wind Direction Records

    Science.gov (United States)

    Gallego, D.; Ribera, P.; Peña-Ortiz, C.; Vega, I.; Gómez, F. D. P.; Ordoñez-Perez, P.; Garcia-Hererra, R.

    2015-12-01

    In this work, we use old wind direction records to reconstruct indices for the West African Monsoon (WAM) and the Indian Summer Monsoon (ISM). Since centuries ago, ships departing from the naval European powers circumnavigated Africa in their route to the Far East. Most of these ships took high-quality observations preserved in logbooks. We show that wind direction observations taken aboard ships can be used to track the seasonal wind reversal typical of monsoonal circulations. The persistence of the SW winds in the 20W-17W and 7N-13N region is highly correlated with the WAM strength and Sahel's precipitation. It has been possible to build a WAM index back to the 19th Century. Our results show that in the Sahel, the second half of the 19thCentury was significantly wetter than present day. The relation of the WAM with the ENSO cycle, and the Atlantic Multidecadal Oscillation was low and instable from the 1840s to the 1970s, when they abruptly suffered an unprecedented reinforcement which last up to the present day. The persistence of the SSW wind in the 60E-80E and 8N-12N area has been used to track the ISM onset since the 1880s. We found evidences of later than average onset dates during the 1900-1925 and 1970-1990 periods and earlier than average onset between 1940 and 1965. A significant relation between the ISM onset and the PDO restricted to shifts from negative to positive PDO phases has been found. The most significant contribution of our study is the fact that we have shown that it is possible to build consistent monsoon indices of instrumental character using solely direct observations of wind direction. Our indices have been generated by using data currently available in the ICOADS 2.5 database, but a large amount of wind observations for periods previous to the 20thcentury still remain not explored in thousands of logbooks preserved in British archives. The interest of unveil these data to track the monsoons for more than 200 -or even 300 years- it is

  12. 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

  13. Arabian Sea mini warm pool and the monsoon onset vortex

    Digital Repository Service at National Institute of Oceanography (India)

    Vinayachandran, P.N.; Shankar, D.; Kurian, J.; Durand, F.; Shenoi, S.S.C.

    and lead to the formation of a monsoon onset vortex7?11. Recently, a major field experiment, called the Arabian Sea Monsoon Experiment (ARMEX), was conducted un- der the Indian Climate Research Program (ICRP) to in- vestigate the role of high SST... consolidated account of what has been known and what should be the future direction. This need is the motivation for this review. Recent reviews have synthesized our current knowl- edge of the basin-scale monsoon circulation of the Indian Ocean12...

  14. Regional analysis of convective systems during the West African monsoon

    Science.gov (United States)

    Guy, Bradley Nicholas

    The West African monsoon (WAM) occurs during the boreal summer and is responsible for a majority of precipitation in the northern portion of West Africa. A distinct shift of precipitation, often driven by large propagating mesoscale convective systems, is indicated from satellite observations. Excepting the coarser satellite observations, sparse data across the continent has prevented understanding of mesoscale variability of these important systems. The interaction between synoptic and mesoscale features appears to be an important part of the WAM system. Without an understanding of the mesoscale properties of precipitating systems, improved understanding of the feedback mechanism between spatial scales cannot be attained. Convective and microphysical characteristics of West African convective systems are explored using various observational data sets. Focus is directed toward meso -alpha and -beta scale convective systems to improve our understanding of characteristics at this spatial scale and contextualize their interaction with the larger-scale. Ground-based radar observations at three distinct geographical locations in West Africa along a common latitudinal band (Niamey, Niger [continental], Kawsara, Senegal [coastal], and Praia, Republic of Cape Verde [maritime]) are analyzed to determine convective system characteristics in each domain during a 29 day period in 2006. Ancillary datasets provided by the African Monsoon Multidisciplinary Analyses (AMMA) and NASA-AMMA (NAMMA) field campaigns are also used to place the radar observations in context. Results show that the total precipitation is dominated by propagating mesoscale convective systems. Convective characteristics vary according to environmental properties, such as vertical shear, CAPE, and the degree of synoptic forcing. Data are bifurcated based on the presence or absence of African easterly waves. In general, African easterly waves appear to enhance mesoscale convective system strength

  15. Seasonal phytoplankton blooms associated with monsoonal influences and coastal environments in the sea areas either side of the Indochina Peninsula

    Science.gov (United States)

    Tang, Dan Ling; Kawamura, Hiroshi; Shi, Ping; Takahashi, Wataru; Guan, Lei; Shimada, Teruhisa; Sakaida, Futoki; Isoguchi, Osamu

    2006-03-01

    The Gulf of Thailand (GoT) is a semienclosed sea on the west and southwest side of the Indochina Peninsula and connects with the near-coastal waters of the South China Sea (SCS) on the east and northeast side of the Malay Peninsula. The objective of the present study is to understand dynamic features of the phytoplankton biology in the GoT and the nearby SCS, on both sides of the Indochina Peninsula, using remote-sensing measurements of chlorophyll-a (Chl a), sea surface temperature (SST), and surface vector winds obtained during the period from September 1997 to March 2003. Results show that seasonal variations of the phytoplankton blooms are primarily controlled by the monsoonal winds and related coastal environments. The GoT and the near-coastal SCS have a peak in the averaged monthly Chl a in December and January, which is associated with the winter northeaster monsoon. The near-coastal SCS have another big peak in the averaged monthly Chl a in summer (July to September), which is associated with the summer southwest monsoon. The offshore bloom in the GoT occurs in its southern part and enhances the December-January peak of averaged monthly Chl a. By contrast, the offshore bloom in the nearby SCS is observed northeast of the Peninsula, and represents the primary source of the July-September peak Chl a. Here the coastal upwelling associated with the offshore Ekman transport caused by the coastal surface winds parallel to the Vietnam east coast gives physical conditions favorable to the development of offshore phytoplankton blooms. The Mekong River discharge waters flow in different directions, depending on the monsoon winds, and contributes to seasonal blooms on both sides of the Peninsula.

  16. Measurements for winter road maintenance

    OpenAIRE

    Riehm, Mats

    2012-01-01

    Winter road maintenance activities are crucial for maintaining the accessibility and traffic safety of the road network at northerly latitudes during winter. Common winter road maintenance activities include snow ploughing and the use of anti-icing agents (e.g. road salt, NaCl). Since the local weather is decisive in creating an increased risk of slippery conditions, understanding the link between local weather and conditions at the road surface is critically important. Sensors are commonly i...

  17. Numerical study of summertime dynamical and physical changes in the southern South China Sea due to the monsoons and its impacts on primary productivity

    Science.gov (United States)

    Daryabor, Farshid; Abu Samah, Azizan; Hai Ooi, See

    2016-04-01

    The ecosystem off the east coast of Peninsular Malaysia is controlled by multiple physical processes during the monsoons (winter and summer) , including the air-sea interaction (such as net heat and surface freshwater fluxes), the small-scale eddies off the southern South China Sea (SSCS), and the monsoon wind induced coastal upwelling. Using high-resolution Regional Ocean Modeling System (ROMS), in-situ observations and remote sensing data, this paper attempts to study the hydrodynamics of the shelf and coastal processes as well as thermohaline circulation in response to changes in the hydrological seasonal cycle especially in the summer monsoon. In addition, we investigate its impacts on the spatial patterns of chlorophyll biomass which acts as a proxy for primary productivity in the SSCS. This study looks into not only the detailed small-scale-circulation such as localized eddies but also the link between the southern South China Sea and the Indian Ocean through the Straits of Malacca and the Java Sea. The flow through the Strait of Malacca and the Java Sea is not only important for navigational purpose but also has an influence on the seasonal spatial and temporal variations of primary productivity in the region. Keywords: southern South China Sea; summer monsoon; coastal upwelling; primary productivity

  18. Winter fuels report

    Energy Technology Data Exchange (ETDEWEB)

    1990-11-29

    The Winter Fuels Report is intended to provide concise, timely information to the industry, the press, policymakers, consumers, analysts, and state and local governments on the following topics: distillate fuel oil net production, imports and stocks for all PADD's and product supplied on a US level; propane net product supplied on a US level; propane net production, imports and stocks for Petroleum Administration for Defense Districts (PADD) I, II, and III; natural gas supply and disposition and underground storage for the United States and consumption for all PADD's; residential and wholesale pricing data for propane and heating oil for those states participating in the joint Energy Information Administration (EIA)/State Heating Oil and Propane Program; crude oil and petroleum price comparisons for the United States and selected cities; and US total heating degree-days by city. 27 figs, 12 tabs.

  19. Winter fuels report

    Energy Technology Data Exchange (ETDEWEB)

    1995-02-17

    The Winter Fuels Report is intended to provide consise, timely information to the industry, the press, policymakers, consumers, analysts, and State and local governments on the following topics: Distillate fuel oil net production, imports and stocks on a US level and for all Petroleum Administration for Defense Districts (PADD) and product supplied on a US level; Natural gas supply and disposition and underground storage for the US and consumption for all PADD`s as well as selected National average prices; Residential and wholesale pricing data for heating oil and propane for those States participating in the joint Energy Information Administration (EIA)/State Heating Oil and Propane Program; Crude oil and petroleum price comparisons for the US and selected cities; and A 6-10 Day and 30-Day outlook for temperature and precipitation and US total heating degree days by city.

  20. Winter fuels report

    International Nuclear Information System (INIS)

    1995-01-01

    The Winter Fuels Report is intended to provide concise, timely information to the industry, the press, policymakers, consumers, analysts, and State and local governments on the following topics: distillate fuel oil net production, imports and stocks on a US level and for all Petroleum Administration for Defense Districts (PADD) and product supplied on a US level; propane net production, imports and stocks on a US level and for PADD's I, II, and III; natural gas supply and disposition and underground storage for the US and consumption for all PADD's, as well as selected National average prices; residential and wholesale pricing data for heating oil and propane for those States participating in the joint Energy Information Administration (EIA)/State Heating Oil and Propane Program; crude oil and petroleum price comparisons for the US and selected cities; and a 6-10 day, 30-Day, and 90-Day outlook for temperature and precipitation and US total heating degree-days by city

  1. Stamena winter wheat variety

    Directory of Open Access Journals (Sweden)

    Mišić Todor

    2001-01-01

    Full Text Available Stamena is a winter wheat variety developed at the Institute of Field and Vegetable Crops in Novi Sad, Yugoslavia. It was released by the Federal Commission for varietals Approval in 1999. Stamena was developed by crossing genetically divergent and highly productive parents Lasta and Rodna (Breeders: T. Mišić. N. Mladenov, Z. Jerković and R. Jevtić. Spike is white, smooth, awn less, medium compact with 18-21 spike lets. The grain is vitreous and dark red (Triticum aestivum L. ssp. vulgar e var. lutescens. Stamena is a medium early variety, 1 day earlier than Partizanka and 3 days earlier than Jugoslavija (Table 4. It has excellent resistance to winterkilling, as in very winter hardy Partizanka. The average stem height is 78 cm, with a good resistance to lodging. Stamena has field resistance to leaf rust (Pucce, recondita tritict, horizontal resistance, which is the type of resistance that modern wheat breeding is interested in. The resistance to stem rust (Pucce, graminis tritict is good and to powdery mildew (Erysiphegraminis tritici very good. The 1000 grain mass is about 32 g and volume grain mass 81.3 kg/hi. (Table 2. Stamena is classified in the subgroup A-l. It has excellent milling and baking quality and it belong to the 1st technological group (quality enhancer. The quantity of dry gluten is about 9%. The variety Stamena is a very productive, with the genetic potential for grain above 11 t/ha suitable for growing on fertile and less fertile soils. It has started to be grown commercially in 2000.

  2. Monsoon regime in the Indian Ocean and zooplankton variability

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.

    The monsoonal effects on zooplankton lead to characteristic zoogeographic patterns in the open ocean and coastal waters. The evaluation of zooplankton variability in the Indian Ocean is presented in three sections: the open ocean, coastal waters...

  3. Dinoflagellates in a mesotrophic, tropical environment influenced by monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A; Patil, J.S.; Hegde, S.; DeSilva, M.S.; Chourasia, M.

    The changes in dinoflagellate community structure in both e the water column and sediment in a mesotrophic, tropical port environment were investigated in this study. Since the South West Monsoon (SWM) is the main source of climatic variation...

  4. Atlantic effects on recent decadal trends in global monsoon

    OpenAIRE

    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 part...

  5. 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.)

  6. Suitability of Starch Syrups for Winter Feeding of Honeybee Colonies

    Directory of Open Access Journals (Sweden)

    Semkiw Piotr

    2016-12-01

    Full Text Available Three different starch syrups available on the Polish market for winter feeding of bees were evaluated for two consecutive beekeeping seasons (2012/2013 and 2013/2014. Sugar syrup and inverted sucrose syrup were used as the control. Winter feeding was conducted at two times: earlier and later in the season. After supplementation of winter feeding was stopped, we measured colony strength (number of combs covered by bees and brood area. After overwintering (spring 2013 and 2014, we estimated the influence of these foods on: bee mortality during overwintering (number of dead bees in winter debris, food consumption, colony strength and brood area in spring (two measurements in three-week intervals, development dynamics and honey yield from spring flow. An analysis of the results for the parameters assessed before overwintering, after its end and during spring development did not show significant differences between bee colonies fed with different types of food. No relevant difficulties concerning food crystallisation were encountered. The analysed syrups turned out to be as suitable for winter feeding of bees as sugar and inverted sucrose syrups.

  7. Causal evidence between monsoon and evolution of rhizomyine rodents.

    Science.gov (United States)

    López-Antoñanzas, Raquel; Knoll, Fabien; Wan, Shiming; Flynn, Lawrence J

    2015-03-11

    The modern Asian monsoonal systems are currently believed to have originated around the end of the Oligocene following a crucial step of uplift of the Tibetan-Himalayan highlands. Although monsoon possibly drove the evolution of many mammal lineages during the Neogene, no evidence thereof has been provided so far. We examined the evolutionary history of a clade of rodents, the Rhizomyinae, in conjunction with our current knowledge of monsoon fluctuations over time. The macroevolutionary dynamics of rhizomyines were analyzed within a well-constrained phylogenetic framework coupled with biogeographic and evolutionary rate studies. The evolutionary novelties developed by these rodents were surveyed in parallel with the fluctuations of the Indian monsoon so as to evaluate synchroneity and postulate causal relationships. We showed the existence of three drops in biodiversity during the evolution of rhizomyines, all of which reflected elevated extinction rates. Our results demonstrated linkage of monsoon variations with the evolution and biogeography of rhizomyines. Paradoxically, the evolution of rhizomyines was accelerated during the phases of weakening of the monsoons, not of strengthening, most probably because at those intervals forest habitats declined, which triggered extinction and progressive specialization toward a burrowing existence.

  8. Optimal Cross Hedging Winter Canola

    OpenAIRE

    Kim, Seon-Woong; Brorsen, B. Wade; Yoon, Byung-Sam

    2014-01-01

    Winter canola in the southern Great Plains has shown large price fluctuations and there have been questions about which futures market could be used to reduce price risk. Our results indicate that the optimal futures contract to cross hedge winter canola is soybean oil futures.

  9. 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.

    2017-10-01

    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.

  10. Winter fuels report

    Energy Technology Data Exchange (ETDEWEB)

    1990-10-04

    The Winter Fuels Report is intended to provide concise, timely information to the industry, the press, policymakers, consumers, analysts, and state and local governments on the following topics: distillate fuel oil net production, imports and stocks for all PADD's and product supplied on a US level; propane net production, imports and stocks for Petroleum Administration for Defense Districts (PADD) I, II, and III; natural gas supply and disposition, underground storage, and consumption for all PADD's; residential and wholesale pricing data for propane and heating oil for those states participating in the joint Energy Information Administration (EIA)/State Heating Oil and Propane Program; crude oil price comparisons for the United States and selected cities; and US total heating degree-days by city. This report will be published weekly by the EIA starting the first week in October 1990 and will continue until the first week in April 1991. The data will also be available electronically after 5:00 p.m. on Thursday during the heating season through the EIA Electronic Publication System (EPUB). 12 tabs.

  11. Klaus Winter (1930 - 2015)

    CERN Multimedia

    2015-01-01

    We learned with great sadness that Klaus Winter passed away on 9 February 2015, after a long illness.   Klaus was born in 1930 in Hamburg, where he obtained his diploma in physics in 1955. From 1955 to 1958 he held a scholarship at the Collège de France, where he received his doctorate in nuclear physics under the guidance of Francis Perrin. Klaus joined CERN in 1958, where he first participated in experiments on π+ and K0 decay properties at the PS, and later became the spokesperson of the CHOV Collaboration at the ISR. Starting in 1976, his work focused on experiments with the SPS neutrino beam. In 1984 he joined Ugo Amaldi to head the CHARM experiment, designed for detailed studies of the neutral current interactions of high-energy neutrinos, which had been discovered in 1973 using the Gargamelle bubble chamber at the PS. The unique feature of the detector was its target calorimeter, which used large Carrara marble plates as an absorber material. From 1984 to 1991, Klau...

  12. Winter fuels report

    Energy Technology Data Exchange (ETDEWEB)

    1995-01-13

    The Winter Fuels Report is intended to provide concise, timely information to the industry, the press, policymakers, consumers, analysts, and State and local governments on the following topics: distillate fuel oil net production, imports and stocks on a US level and for all Petroleum Administration for Defense Districts (PADD) and product supplied on a US level; propane net production, imports and stocks on a US level and for PADD`s I, II, and III; natural gas supply and disposition and underground storage for the US and consumption for all PADD`s, as well as selected National average prices; residential and wholesale pricing data for heating oil and propane for those States participating in the joint Energy Information Administration (EIA)/State Heating Oil and Propane Program; crude oil and petroleum price comparisons for the US and selected cities; and a 6-10 day, 30-Day, and 90-Day outlook for temperature and precipitation and US total heating degree-days by city.

  13. Nature and sources of suspended particulate organic matter in a tropical estuary during the monsoon and pre-monsoon: Insights from stable isotopes (delta 13C POC, delta 15 N TPN) and carbohydrate signature compounds

    Digital Repository Service at National Institute of Oceanography (India)

    Khodse, V.B.; Bhosle, N.B.

    during the monsoon than the pre-monsoon. Conversely, during the pre-monsoon, monosaccharide composition did not vary much and was mostly dominated by glucose. Monosaccharide abundance and ratios suggest that organic matter was subjected to extensive...

  14. Climate and smoke: an appraisal of nuclear winter.

    Science.gov (United States)

    Turco, R P; Toon, O B; Ackerman, T P; Pollack, J B; Sagan, C

    1990-01-12

    The latest understanding of nuclear winter is reviewed. Considerable progress has been made in quantifying the production and injection of soot by large-scale fires, the regional and global atmospheric dispersion of the soot, and the resulting physical, environmental, and climatic perturbations. New information has been obtained from laboratory studies, field experiments, and numerical modeling on a variety of scales (plume, mesoscale, and global). For the most likely soot injections from a full-scale nuclear exchange, three-dimensional climate simulations yield midsummer land temperature decreases that average 10 degrees to 20 degrees C in northern mid-latitudes, with local cooling as large as 35 degrees C, and subfreezing summer temperatures in some regions. Anomalous atmospheric circulations caused by solar heating of soot is found to stabilize the upper atmosphere against overturning, thus increasing the soot lifetime, and to accelerate interhemispheric transport, leading to persistent effects in the Southern Hemisphere. Serious new environmental problems associated with soot injection have been identified, including disruption of monsoon precipitation and severe depletion of the stratospheric ozone layer in the Northern Hemisphere. The basic physics of nuclear winter has been reaffirmed through several authoritative international technical assessments and numerous individual scientific investigations. Remaining areas of uncertainty and research priorities are discussed in view of the latest findings.

  15. Winter Safety Tips for Older Adults

    Science.gov (United States)

    Winter Safety Tips for Older Adults Expert Information from Healthcare Professionals Who Specialize in the Care of ... thick clothing. Think about getting your thermals! –Essential winter wears: hats, gloves or preferably mittens, winter coat, ...

  16. Essential Outdoor Sun Safety Tips for Winter

    Science.gov (United States)

    ... Vitamin D Essential Outdoor Sun Safety Tips for Winter Winter sports enthusiasts are at increased risk for overexposure ... associated with sun exposure. "It's easy to associate winter with frostbite and windburn, but most people are ...

  17. Indian Monsoon and denitrification change in the Laxmi Basin (IODP Exp. 355 Site U1456) of the Eastern Arabian Sea during the last 800 kyrs

    Science.gov (United States)

    Kim, J. E.; Khim, B. K.; Ikehara, M.; Lee, J.

    2017-12-01

    The Arabian Sea is a famous site for the basin-wide denitrification in the globe. The Western Arabian Sea has been acknowledged by its upwelling-induced denitrification related to the Indian Monsoon system (Altabet et al., 1999). It was recently reported that the denitrification in the Eastern Arabian Sea (IODP Exp. 355 Site U1456) has been persistent and consistent during the mid-Pleistocene as reflected in the bulk sediment δ15N values (Tripathi et al., 2017). Based on the age model reconstructed by δ18O stratigraphy of planktonic foraminifera (Globigerinoides ruber) together with shipboard biostratigraphic and paleomagnetic data at Site U1456 drilled in the Laxmi Basin of the Eastern Arabian Sea, the glacial-interglacial fluctuations of denitrification in association with the development of oxygen minimum zone (OMZ) were resolved in the context of Indian Monsoon activity. One of striking features in the Eastern Arabian Sea is that the δ15N values of bulk sediment show clear and consistent denitrification with minimum δ15N values exceeding 6‰ even during glacial periods, when its western counterpart experienced a temporal collapse of OMZ and denitrification. The Eastern Arabian Sea is fed not only by the upwelling-induced productivity in the western margin during the summer monsoon but also by the high productivity during the winter monsoon, both of which maintain the increased productivity affecting the OMZ through the consumption of dissolved oxygen by the degradation of sinking organic particles. The Eastern Arabian Sea is further influenced by the clockwise surface currents, intermediate water ventilation change by the blockage of Antarctic Intermediate Water, limited inflow from the Red Sea/Persian Gulf, and the freshwater salinity stratification due to nearby riverine discharges, all of which make the denitrification process more complicated than the Western Arabian Sea. Nonetheless, the glacial-interglacial denitrification change in the Eastern

  18. Multiscale characterization and prediction of monsoon rainfall in India using Hilbert-Huang transform and time-dependent intrinsic correlation analysis

    Science.gov (United States)

    Adarsh, S.; Reddy, M. Janga

    2017-07-01

    In this paper, the Hilbert-Huang transform (HHT) approach is used for the multiscale characterization of All India Summer Monsoon Rainfall (AISMR) time series and monsoon rainfall time series from five homogeneous regions in India. The study employs the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) for multiscale decomposition of monsoon rainfall in India and uses the Normalized Hilbert Transform and Direct Quadrature (NHT-DQ) scheme for the time-frequency characterization. The cross-correlation analysis between orthogonal modes of All India monthly monsoon rainfall time series and that of five climate indices such as Quasi Biennial Oscillation (QBO), El Niño Southern Oscillation (ENSO), Sunspot Number (SN), Atlantic Multi Decadal Oscillation (AMO), and Equatorial Indian Ocean Oscillation (EQUINOO) in the time domain showed that the links of different climate indices with monsoon rainfall are expressed well only for few low-frequency modes and for the trend component. Furthermore, this paper investigated the hydro-climatic teleconnection of ISMR in multiple time scales using the HHT-based running correlation analysis technique called time-dependent intrinsic correlation (TDIC). The results showed that both the strength and nature of association between different climate indices and ISMR vary with time scale. Stemming from this finding, a methodology employing Multivariate extension of EMD and Stepwise Linear Regression (MEMD-SLR) is proposed for prediction of monsoon rainfall in India. The proposed MEMD-SLR method clearly exhibited superior performance over the IMD operational forecast, M5 Model Tree (MT), and multiple linear regression methods in ISMR predictions and displayed excellent predictive skill during 1989-2012 including the four extreme events that have occurred during this period.

  19. Assessing response of local moisture conditions in central Brazil to variability in regional monsoon intensity using speleothem 87Sr/86Sr values

    Science.gov (United States)

    Wortham, Barbara E.; Wong, Corinne I.; Silva, Lucas C. R.; McGee, David; Montañez, Isabel P.; Troy Rasbury, E.; Cooper, Kari M.; Sharp, Warren D.; Glessner, Justin J. G.; Santos, Roberto V.

    2017-04-01

    Delineating the controls on hydroclimate throughout Brazil is essential to assessing potential impact of global climate change on water resources and biogeography. An increasing number of monsoon reconstructions from δ18O records provide insight into variations in regional monsoon intensity over the last millennium. The strength, however, of δ18O as a proxy of regional climate limits its ability to reflect local conditions, highlighting the need for comparable reconstructions of local moisture conditions. Here, speleothem 87Sr/86Sr values are developed as a paleo-moisture proxy in central Brazil to complement existing δ18O-based reconstructions of regional monsoon intensity. Speleothem 87Sr/86Sr values are resolved using laser ablation and conventional solution mass spectrometry at high resolution relative to existing (non-δ18O-based) paleo-moisture reconstructions to allow comparisons of centennial variability in paleo-monsoon intensity and paleo-moisture conditions. Variations in speleothem 87Sr/86Sr values from Tamboril Cave are interpreted to reflect varying extents of water interaction with the carbonate host rock, with more interaction resulting in greater evolution of water isotope values from those initially acquired from the soil to those of the carbonate bedrock. Increasing speleothem 87Sr/86Sr values over the last millennium suggest progressively less interaction with the carbonate host rock likely resulting from higher infiltration rates, expected under wetter conditions. Increasingly wetter conditions over the last millennium are consistent with an overall trend of increasing monsoon intensity (decreasing δ18O values) preserved in many existing δ18O records from the region. Such a trend, however, is absent in δ18O records from our site (central Brazil) and Cristal Cave (southeast Brazil), suggesting the existence of divergent (relevant to δ18Oprecip) shifts in the climate patterns within and outside the core monsoon region.

  20. Application of vegetation information on the Tibetan Plateau to improve East Asian summer monsoon prediction

    Science.gov (United States)

    Wu, L.; Zhang, J.

    2010-12-01

    The summer monsoon is the most important climate feature in East Asia. Its unusual behaviors may lead to occurrence of extensive drought/flood disasters in East Asia, which can cause serious consequences on the natural environment and the human society. It is well known that the slowly varying oceanic processes provide the primary source for East Asian summer monsoon (EASM) predictability. In addition to the ocean, land surface can also provide a critical memory function in the climate system at the monthly and longer time scales. However, the memory inherent in the land surface is less well understood or applied toward EASM prediction. Here we investigate the role of vegetation on the Tibetan Plateau for the EASM variation and prediction using observational data. We discuss the possible mechanism explaining the relationship between TP vegetation and EASM. A statistical model is further developed to predict the EASM strength by combination of El Nino-Southern Oscillation (ENSO) and the TP vegetation greenness. Hindcast for the period 1982-2006 shows that the use of the TP vegetation information can largely improve the EASM prediction skill compared to that using ENSO alone.

  1. Centennial-scale solar forcing of the South American Monsoon System recorded in stalagmites.

    Science.gov (United States)

    Novello, Valdir F; Vuille, Mathias; Cruz, Francisco W; Stríkis, Nicolás M; de Paula, Marcos Saito; Edwards, R Lawrence; Cheng, Hai; Karmann, Ivo; Jaqueto, Plínio F; Trindade, Ricardo I F; Hartmann, Gelvam A; Moquet, Jean S

    2016-04-21

    The South American Monsoon System (SAMS) is generally considered to be highly sensitive to Northern Hemisphere (NH) temperature variations on multi-centennial timescales. The direct influence of solar forcing on moisture convergence in global monsoon systems on the other hand, while well explored in modeling studies, has hitherto not been documented in proxy data from the SAMS region. Hence little is known about the sensitivity of the SAMS to solar forcing over the past millennium and how it might compete or constructively interfere with NH temperature variations that occurred primarily in response to volcanic forcing. Here we present a new annually-resolved oxygen isotope record from a 1500-year long stalagmite recording past changes in precipitation in the hitherto unsampled core region of the SAMS. This record details how solar variability consistently modulated the strength of the SAMS on centennial time scales during the past 1500 years. Solar forcing, besides the previously recognized influence from NH temperature changes and associated Intertropical Convergence Zone (ITCZ) shifts, appears as a major driver affecting SAMS intensity at centennial time scales.

  2. Reconstruction of Monsoon Driven South China Sea Surface Ocean Circulation using Coral Δ14C

    Science.gov (United States)

    Goodkin, N.; Bolton, A.; Karnauskas, K. B.; Hughen, K. A.; Griffin, S.; Druffel, E. R. M.

    2016-12-01

    The need to improve our understanding of annual and decadal climate behavior in the South China Sea is increasingly important, as this region includes the largest population density globally but encompasses few climate records. Here we present a record of annually resolved Δ14C from a coral collected off the coast of Nha Trang, Vietnam (12°12'49.90″N, 109°18'17.51″E), that reveals a significant correlation to regional winter sea level pressure (SLP) and sea surface temperature (SST), and extends back more than 400 years. Coral Δ14C during thermonuclear bomb testing indicates the presence of wet-season (summer) upwelling, demonstrated by low Δ14C values for both baseline and peak values relative to other records in the region (Bolton et al., 2016, Radiocarbon). However, annually resolved pre-bomb Δ14C correlates significantly to regional dry-season (winter) SLP and SST, indicating that annual variability is driven by changes to the East Asian Winter Monsoon (EAWM) and subsequent down-welling at this site. Spectral density is focused at 25, 11.8, 7, 4, and 3.2 years per cycle reflecting a range of influences on surface advection variability including the EAWM (D'Arrigo et al., 2005, GRL) and the El Nino Southern Oscillation (ENSO). Spectral power at all of these frequencies decreases following the Little Ice Age ( 1600-1850?) to today, indicating that wind driven surface advection was more variable when hemispheric temperatures were cooler. Decadal variance in the past 100 years is significantly correlated to variance records of the Arctic Oscillation (AO, Thompson and Wallace, 1989, GRL), suggesting that increasing variance in the EAWM may be tied to increasing variance of the AO during the Little Ice Age and vice versa.

  3. Indian Monsoon Low-Pressure Systems Feed Up-and-Over Moisture Transport to the Southwestern Tibetan Plateau

    Science.gov (United States)

    Dong, Wenhao; Lin, Yanluan; Wright, Jonathon S.; Xie, Yuanyu; Xu, Fanghua; Xu, Wenqing; Wang, Yan

    2017-11-01

    As an integral part of the South Asian summer monsoon system, monsoon low-pressure systems (LPSs) bring large amounts of precipitation to agrarian north and central India during their passage across the subcontinent. In this study, we investigate the role of LPSs in supplying moisture from north and central India to the southwestern Tibetan Plateau (SWTP) and quantify the contribution of these systems to summer rainfall over the SWTP. The results show that more than 60% of total summer rainfall over the SWTP is related to LPS occurrence. LPSs are associated with a 15% rise in average daily rainfall and a 10% rise in rainy days over the SWTP. This relationship is maintained primarily through up-and-over transport, in which convectively lifted moisture over the Indian subcontinent is swept over the SWTP by southwesterly winds in the middle troposphere. LPSs play two roles in supplying up-and-over moisture transport. First, these systems elevate large amounts of water vapor and condensed water to the midtroposphere. Second, the circulations associated with LPSs interact with the background westerlies to induce southwesterly flow in the midtroposphere, transporting elevated moisture and condensate over the Himalayan Mountains. Our findings indicate that LPSs are influential in extending the northern boundary of the South Asian monsoon system across the Himalayas into the interior of the SWTP. The strength of this connection depends on both LPS characteristics and the configuration of the midtropospheric circulation, particularly the prevailing westerlies upstream of the SWTP.

  4. Influence of the North American monsoon on Southern California tropospheric ozone levels during summer in 2013 and 2014

    Science.gov (United States)

    Granados-Muñoz, Maria Jose; Johnson, Matthew S.; Leblanc, Thierry

    2017-06-01

    The impact of the North American (NA) monsoon on tropospheric ozone variability in Southern California is investigated using lidar measurements at Jet Propulsion Laboratory-Table Mountain Facility, California, and the chemical-transport model GEOS-Chem. Routine lidar observations obtained in July-August 2013-2014 reveal a consistent ozone enhancement of 23 ppbv in the free troposphere (6-9 km), when ozone-rich air is transported along the western edge of the upper level anticyclone associated with the NA monsoon from regions where maximum lightning-induced NOx production occurs. When the high-pressure system shifts to the southeast, a zonal westerly flow of the air parcels reaching the Table Mountain Facility (TMF) occurs, prohibiting the lightning-induced ozone enhanced air to reach TMF. This modulation of tropospheric ozone by the position of the NA monsoon anticyclone could have implications on long-term ozone trends associated with our changing climate, due to the expected widening of the tropical belt affecting the strength and position of the anticyclone.

  5. 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.

  6. The meaning of nuclear winter

    International Nuclear Information System (INIS)

    Geiger, H.J.

    1987-01-01

    In this paper the author reviews the history and origins of the basic ideas underlying nuclear winter; and findings and predictions of several groups regarding this topic. The author reviews some of the further developments and scientific analyses regarding nuclear winter since the initial announcements of 1983, touching on some of the revisions and controversies and trying to indicate the current status of the field

  7. Rocky Mountain hydroclimate: Holocene variability and the role of insolation, ENSO, and the North American Monsoon

    Science.gov (United States)

    Anderson, Lesleigh

    2012-01-01

    Over the period of instrumental records, precipitation maximum in the headwaters of the Colorado Rocky Mountains has been dominated by winter snow, with a substantial degree of interannual variability linked to Pacific ocean–atmosphere dynamics. High-elevation snowpack is an important water storage that is carefully observed in order to meet increasing water demands in the greater semi-arid region. The purpose here is to consider Rocky Mountain water trends during the Holocene when known changes in earth's energy balance were caused by precession-driven insolation variability. Changes in solar insolation are thought to have influenced the variability and intensity of the El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North American Monsoon and the seasonal precipitation balance between rain and snow at upper elevations. Holocene records are presented from two high elevation lakes located in northwest Colorado that document decade-to-century scale precipitation seasonality for the past ~ 7000 years. Comparisons with sub-tropical records of ENSO indicate that the snowfall-dominated precipitation maxima developed ~ 3000 and 4000 years ago, coincident with evidence for enhanced ENSO/PDO dynamics. During the early-to-mid Holocene the records suggest a more monsoon affected precipitation regime with reduced snowpack, more rainfall, and net moisture deficits that were more severe than recent droughts. The Holocene perspective of precipitation indicates a far broader range of variability than that of the past century and highlights the non-linear character of hydroclimate in the U.S. west.

  8. Flip flop of Day-night and Summer-Winter Surface Urban Heat Island Intensity in India.

    Science.gov (United States)

    Shastri, Hiteshri; Barik, Beas; Ghosh, Subimal; Venkataraman, Chandra; Sadavarte, Pankaj

    2017-01-09

    The difference in land surface temperature (LST) between an urban region and its nearby non-urban region, known as surface urban heat island intensity (SUHII), is usually positive as reported in earlier studies. India has experienced unprecedented urbanization over recent decades with an urban population of 380 million. Here, we present the first study of the diurnal and seasonal characteristics of SUHII in India. We found negative SUHII over a majority of urban areas during daytime in pre-monsoon summer (MAM), contrary to the expected impacts of urbanization. This unexpected pattern is associated with low vegetation in non-urban regions during dry pre-monsoon summers, leading to reduced evapotranspiration (ET). During pre-monsoon summer nights, a positive SUHII occurs when urban impacts are prominent. Winter daytime SUHII becomes positive in Indo-Gangetic plain. We attribute such diurnal and seasonal behaviour of SUHII to the same of the differences in ET between urban and non-urban regions. Higher LST in non-urban regions during pre-monsoon summer days results in intensified heatwaves compared to heatwaves in cities, in contrast to presumptions made in the literature. These observations highlight the need for re-evaluation of SUHII in India for climate adaptation, heat stress mitigation, and analysis of urban micro-climates.

  9. Driving forces of Indian summer monsoon on Milankovitch and sub-Milankovitch time scales: A review

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    of the SW monsoon fluctuates with periodicities of 100 ka and 23 ka. These periodicities of SW monsoon were attributed to the orbitally induced changes in solar radiation and surface boundary conditions (Milankovitch Theory). Recent high-resolution studies...

  10. Diatom community dynamics in a tropical, monsoon-influenced environment: West coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    Diatom communities are influenced by environmental perturbations, such as the monsoon system that impact the niche opportunities of species. To discern the influence of the monsoon system on diatom community structure, we sampled during two...

  11. Comparison between phytoplankton bio-diversity and various indices for winter monsoon and inter monsoon periods in north-eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Motwani, G.; Raman, M.; Matondkar, P.; Parab, S.G.; Pednekar, S.; Solanki, H.

    cyanobacteria, dominated the shallow coastal waters Resultant indices were correlated with phytoplankton cell counts and it was found that Shannons index better represents the diversity than other indices Cell counts were also correlated with in situ chlorophyll...

  12. The 9.2 ka event in Asian summer monsoon area: the strongest millennial scale collapse of the monsoon during the Holocene

    Science.gov (United States)

    Zhang, Wenchao; Yan, Hong; Dodson, John; Cheng, Peng; Liu, Chengcheng; Li, Jianyong; Lu, Fengyan; Zhou, Weijian; An, Zhisheng

    2018-04-01

    Numerous Holocene paleo-proxy records exhibit a series of centennial-millennial scale rapid climatic events. Unlike the widely acknowledged 8.2 ka climate anomaly, the likelihood of a significant climate excursion at around 9.2 cal ka BP, which has been notably recognized in some studies, remains to be fully clarified in terms of its magnitude and intensity, as well as its characteristics and spatial distributions in a range of paleoclimatic records. In this study, a peat sediment profile from the Dajiuhu Basin in central China was collected with several geochemical proxies and a pollen analysis carried out to help improve understanding of the climate changes around 9.2 cal ka BP. The results show that the peat development was interrupted abruptly at around 9.2 cal ka BP, when the chemical weathering strength decreased and the tree-pollen declined. This suggests that a strong drier regional climatic event occurred at around 9.2 cal ka BP in central China, which was, in turn, probably connected to the rapid 9.2 ka climate event co-developing worldwide. In addition, based on the synthesis of our peat records and the other Holocene hydrological records from Asian summer monsoon (ASM) region, we further found that the 9.2 ka event probably constituted the strongest abrupt collapse of the Asian monsoon system during the full Holocene interval. The correlations between ASM and the atmospheric 14C production rate, the North Atlantic drift ice records and Greenland temperature indicated that the weakened ASM event at around 9.2 cal ka BP could be interpreted by the co-influence of external and internal factors, related to the changes of the solar activity and the Atlantic Meridional Overturning Circulation (AMOC).

  13. The 9.2 ka event in Asian summer monsoon area: the strongest millennial scale collapse of the monsoon during the Holocene

    Science.gov (United States)

    Zhang, Wenchao; Yan, Hong; Dodson, John; Cheng, Peng; Liu, Chengcheng; Li, Jianyong; Lu, Fengyan; Zhou, Weijian; An, Zhisheng

    2017-06-01

    Numerous Holocene paleo-proxy records exhibit a series of centennial-millennial scale rapid climatic events. Unlike the widely acknowledged 8.2 ka climate anomaly, the likelihood of a significant climate excursion at around 9.2 cal ka BP, which has been notably recognized in some studies, remains to be fully clarified in terms of its magnitude and intensity, as well as its characteristics and spatial distributions in a range of paleoclimatic records. In this study, a peat sediment profile from the Dajiuhu Basin in central China was collected with several geochemical proxies and a pollen analysis carried out to help improve understanding of the climate changes around 9.2 cal ka BP. The results show that the peat development was interrupted abruptly at around 9.2 cal ka BP, when the chemical weathering strength decreased and the tree-pollen declined. This suggests that a strong drier regional climatic event occurred at around 9.2 cal ka BP in central China, which was, in turn, probably connected to the rapid 9.2 ka climate event co-developing worldwide. In addition, based on the synthesis of our peat records and the other Holocene hydrological records from Asian summer monsoon (ASM) region, we further found that the 9.2 ka event probably constituted the strongest abrupt collapse of the Asian monsoon system during the full Holocene interval. The correlations between ASM and the atmospheric 14C production rate, the North Atlantic drift ice records and Greenland temperature indicated that the weakened ASM event at around 9.2 cal ka BP could be interpreted by the co-influence of external and internal factors, related to the changes of the solar activity and the Atlantic Meridional Overturning Circulation (AMOC).

  14. Role of time series sediment traps in understanding the Indian summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.

    "Monsoon", meaning “season” is from the Arabic word "mausim", defining the seasonally changing wind pattern. The Indian summer monsoon system is driven by the differential atmospheric pressure between land and ocean. Boreal cooling of the land mass... otherwise would have made the continents preventing heating up during summer. Ancient Greeks and Roman were very familiar with the monsoon wind system in their navigation. Monsoons have a direct impact on the socio- economic fabric of the vast...

  15. 20th century intraseasonal Asian monsoon dynamics viewed from Isomap

    Directory of Open Access Journals (Sweden)

    A. Hannachi

    2013-10-01

    Full Text Available The Asian summer monsoon is a high-dimensional and highly nonlinear phenomenon involving considerable moisture transport towards land from the ocean, and is critical for the whole region. We have used daily ECMWF reanalysis (ERA-40 sea-level pressure (SLP anomalies on the seasonal cycle, over the region 50–145° E, 20° S–35° N, to study the nonlinearity of the Asian monsoon using Isomap. We have focused on the two-dimensional embedding of the SLP anomalies for ease of interpretation. Unlike the unimodality obtained from tests performed in empirical orthogonal function space, the probability density function, within the two-dimensional Isomap space, turns out to be bimodal. But a clustering procedure applied to the SLP data reveals support for three clusters, which are identified using a three-component bivariate Gaussian mixture model. The modes are found to appear similar to active and break phases of the monsoon over South Asia in addition to a third phase, which shows active conditions over the western North Pacific. Using the low-level wind field anomalies, the active phase over South Asia is found to be characterised by a strengthening and an eastward extension of the Somali jet. However during the break phase, the Somali jet is weakened near southern India, while the monsoon trough in northern India also weakens. Interpretation is aided using the APHRODITE gridded land precipitation product for monsoon Asia. The effect of large-scale seasonal mean monsoon and lower boundary forcing, in the form of ENSO, is also investigated and discussed. The outcome here is that ENSO is shown to perturb the intraseasonal regimes, in agreement with conceptual ideas.

  16. 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.)

  17. 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.

  18. Characteristics of the East Asian Winter Climate Associated with the Westerly Jet Stream and ENSO

    Science.gov (United States)

    Yang, Song; Lau, K.-M.; Kim, K.-M.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    In this study, the influences of the East Asian jet stream (EAJS) and El Nino/Southern Oscillation (ENSO) on the interannual variability of the East Asian winter climate are examined with a focus on the relative climate impacts of the two phenomena. Although the variations of the East Asian winter monsoon and the temperature and precipitation of China, Japan, and Korea are emphasized, the associated changes in the broad-scale atmospheric circulation patterns over Asia and the Pacific and in the extratropical North Pacific sea surface temperature (SST) are also investigated. It is demonstrated that there is no apparent relationship between ENSO and the interannual variability of EAJS core. The EAJS and ENSO are associated with distinctly different patterns of atmospheric circulation and SST in the Asian-Pacific regions. While ENSO causes major climate signals in the Tropics and over the North Pacific east of the dateline, the EAJS produces significant changes in the atmospheric circulation over East Asia and western Pacific. In particular, the EAJS explains larger variance of the interannual signals of the East Asian trough, the Asian continental high, the Aleutian low, and the East Asian winter monsoon. When the EAJS is strong, all these atmospheric systems intensify significantly. The response of surface temperature and precipitation to EAJS variability and ENSO is more complex. In general, the East Asian winter climate is cold (warm) and dry (wet) when the EAJS is strong (weak) and it is warm during El Nino years. However, different climate signals are found during different La Nina years. In terms of linear correlation, both the temperature and precipitation of northern China, Korea, and central Japan are more significantly associated with the EAJS than with ENSO.

  19. Long-term changes of South China Sea surface temperatures in winter and summer

    Science.gov (United States)

    Park, Young-Gyu; Choi, Ara

    2017-07-01

    Utilizing available atmospheric and oceanographic reanalysis data sets, the long-term trend in South China Sea (SCS) sea surface temperature (SST) between 1950 and 2008 and the governing processes are investigated. Both winter and summer SST increased by comparable amounts, but the warming patterns and the governing processes were different. Strong warming in winter occurred in a deep central area, and during summer in the southern region. In winter the net heat flux into the sea increased, contributing to the warming. The spatial pattern of the heat flux, however, was different from that of the warming. Heat flux increased over the coastal area where warming was weaker, but decreased over the deeper area where warming was stronger. The northeasterly monsoon wind weakened lowering the shoreward Ekman transport and the sea surface height gradient. The cyclonic gyre which transports cold northern water to the south weakened, thereby warming the ocean. The effect was manifested more strongly along the southward western boundary current inducing warming in the deep central part. In summer however, the net surface heat flux decreased and could not contribute to the warming. Over the southern part of the SCS, the weakening of the southwesterly summer monsoon reduced southeastward Ekman transport, which is parallel to the mean SST gradient. Southeastward cold advection due to Ekman transport was reduced, thereby warming the surface near the southeastern boundary of the SCS. Upwelling southeast of Vietnam was also weakened, raising the SST east of Vietnam contributing to the southern summer warming secondarily. The weakening of the winds in each season was the ultimate cause of the warming, but the responses of the ocean that lead to the warming were different in winter and summer.

  20. Late quaternary variability of the Arabian Sea monsoon and oxygen minimum zone

    NARCIS (Netherlands)

    Reichart, G.-J.

    1997-01-01

    The Monsoon Among the first Europeans observing the Asiatic monsoon was Alexander the Great during his campaign to the mouth of the Indus (325 B.C.). The oldest known records of the Arabian Sea monsoonal climate, however, are shipping documents, dated about 2300 B.C., which refer to the use

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

    NARCIS (Netherlands)

    Ao, H.; Roberts, A.P.; Dekkers, M.J.; 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

  2. Late quaternary variability of the Arabian Sea monsoon and oxygen minimum zone

    NARCIS (Netherlands)

    Reichart, Gert-Jan

    1997-01-01

    The Monsoon Among the first Europeans observing the Asiatic monsoon was Alexander the Great during his campaign to the mouth of the Indus (325 B.C.). The oldest known records of the Arabian Sea monsoonal climate, however, are shipping documents, dated about 2300 B.C., which refer to the use of the

  3. Impact of monsoon rainfall on the total foodgrain yield over India

    Indian Academy of Sciences (India)

    The Asian monsoon climate is significantly dom- inated by Indian summer monsoon rainfall (ISMR). Every year more than 80% of annual rainfall is received over only the Indian land grid points called all India summer monsoon rainfall index (hereafter. AISMR) followed by Parthasarathy et al. (1995). Within a short span of 4 ...

  4. Isotopic cycling in a tropical treeline environment: North American monsoon dynamics at Nevado de Colima, Mexico

    Science.gov (United States)

    Hartsough, Peter Christopher

    High elevation sites are especially sensitive to environmental change. One way to get a longer perspective on global change in mountain regions is paleoenvironmental records from tree rings. Data on the response of high elevation species to climatic events is sparse and records used for reconstruction often necessarily come from lower elevation, higher latitude stations. We have set up a unique field site where we are co-monitoring tree growth and weather in real time. In May 2001 we established a monitoring site at 3770m (12,370ft) on Nevado de Colima (19° 34.8'N, 103° 37.3'W) at the western end of the trans-volcanic belt in Southwestern Mexico. The monitoring site consists of an automated weather station and two dendrometer networks for the simultaneous measurement of climate and tree growth parameters. Although we have experienced several equipment setbacks due to the challenging environment, important results relating to growth dynamics and response to climate have surfaced. This field site, near the edge of the tropics, is an important monitoring location for both intra and extra tropical circulation systems. Historical records in the area are of short duration (less than 60 years) so determining the nature of decadal or longer scale fluctuations requires the use of proxy records. Mexican Mountain Pines (Pinus hartwegii Lindl.) growing on Nevado de Colima are under the influence of several large-scale climate features---most notably the North American Monsoon and ENSO. Dendrochronology studies in the region have shown a sensitivity of tree growth to warm season precipitation. The North American Monsoon is still a poorly understood system and an historical perspective is needed for increased confidence in predictive models and forecasting. Careful measurement of tree growth over the five years of the project has led to a clearly defined dormant period over the relatively arid winter. Dendrometer data have shown onset of growth to be closely tied to soil

  5. The impact of monsoon winds and mesoscale eddies on thermohaline structures and circulation patterns in the northern South China Sea

    Science.gov (United States)

    Zhao, Ruixiang; Zhu, Xiao-Hua; Guo, Xinyu

    2017-07-01

    We deployed 5 pressure-recording inverted echo sounders (PIES) along a section in the northern South China Sea (NSCS), and estimated well the distributions of temperature, salinity and velocity across the section. Applying the empirical orthogonal function (EOF) method, we found that variability of the estimates is dominated by two modes: one named the seasonal mode affecting strongly on the hydrographic distribution with explained variability of temperature/salinity by 62.9/72.2%; the other named the eddy mode, corresponding to the arrival of mesoscale eddies, affecting strongly on the circulation pattern with explained variability of velocity by 63.2%. Temporal variation of the seasonal mode is highly correlated with the monsoon winds southeast of Vietnam, suggesting a nonlocal forcing mechanism. Case studies looking at the structures and evolutions of three captured eddies, whose impacts were well quantified by the eddy mode. The monsoon (eddies) significantly affects temperature, salinity and velocity shallower than 635 m (860 m), 160 m (150 m) and 1055 m (920 m), respectively. The monsoon (eddies) can induce maximum temperature, salinity and velocity anomalies up to -1.6 to 2.1 °C (-2.5 to 2.2 °C), -0.11 to 0.14 psu (-0.13 to 0.27 psu) and -0.31 to 0.46 m/s (-0.40 to 0.38 m/s), respectively. Mean volume transport (VT) across the section is 1.0 Sv (1 Sv= 1 ×106 m3 s-1, positive to the northeast). Seasonal VT (with eddy impacts removed) is -4.6 Sv, 11.4 Sv, -5.1 Sv and -4.1 Sv for spring, summer, autumn and winter, respectively.

  6. Differences of atmospheric boundary layer characteristics between pre-monsoon and monsoon period over the Erhai Lake

    Science.gov (United States)

    Xu, Lujun; Liu, Huizhi; Du, Qun; Wang, Lei; Yang, Liu; Sun, Jihua

    2018-01-01

    The differences in planetary boundary layer characteristics, in particular atmospheric boundary layer height (ABLH), humidity, and local circulations in pre-monsoon and monsoon period over the Erhai Lake, were simulated by the lake-atmosphere coupled model WRF v3.7.1. No lake simulations were also conducted to investigate lake effects over complex topography. During pre-monsoon period, local circulation was fully developed under weak synoptic system. The ABLH ran up to 2300 m or so. During monsoon period, temperature difference between land and lake became smaller, resulting in weaker local circulations. The height of circulation reduced by 500 m, and ABLH ran up to 1100 m during the day. Enhanced soil moisture and low surface temperature due to monsoon rainfalls in July could be the main reason for the slightly lower ABLH over the Erhai Lake area. Specific humidity of the boundary layer increased 8.8 g kg-1 or so during monsoon period. The Erhai Lake enlarged thermal contrast between valley and mountain slope in the Dali Basin. The lake reduced air temperature by 2 3 °C during daytime and increased air temperature by nearly 2 °C in the evening. Due to its small roughness length and large thermal capacity, the Erhai Lake enlarged lake-land temperature difference and local wind speed. A cyclonic circulation was maintained by the combination of mountain breeze and land breeze in the south of the lake. The lake decreased air temperature, increased specific humidity, and reduced ABLH during daytime, whereas the opposite effect is presented at night.

  7. The role of the Indian monsoon onset in the West African monsoon onset: observations and AGCM nudged simulations

    Energy Technology Data Exchange (ETDEWEB)

    Flaounas, Emmanouil [LATMOS/IPSL, Universite Pierre et Marie Curie, Paris cedex 05 (France); Janicot, Serge [LOCEAN/IPSL, IRD, Universite Pierre et Marie Curie, Paris (France); Bastin, Sophie [LATMOS/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Roca, Remy [LMD/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Mohino, Elsa [LOCEAN/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Universidad de Sevilla, Sevilla (Spain)

    2012-03-15

    In spring the inland penetration of the West African Monsoon (WAM) is weak and the associated rainband is located over the Guinean coast. Then within a few days deep convection weakens considerably and the rainband reappears about 20 days after over the Sahel, where it remains until late September signalling the summer rainy season. Over the period 1989-2008 a teleconnection induced by the Indian monsoon onset is shown to have a significant impact on the WAM onset, by performing composite analyses on both observational data sets and atmospheric general circulation model simulations ensembles where the model is nudged to observations over the Indian monsoon sector. The initiation of convective activity over the Indian subcontinent north of 15 N at the time of the Indian monsoon onset results in a westward propagating Rossby wave establishing over North Africa 7-15 days after. A back-trajectory analysis shows that during this period, dry air originating from the westerly subtropical jet entrance is driven to subside and move southward over West Africa inhibiting convection there. At the same time the low-level pressure field over West Africa reinforces the moisture transport inland. After the passage of the wave, the dry air intrusions weaken drastically. Hence 20 days after the Indian monsoon onset, convection is released over the Sahel where thermodynamic conditions are more favourable. This scenario is very similar in the observations and in the nudged simulations, meaning that the Indian monsoon onset is instrumental in the WAM onset and its predictability at intraseasonal scale. (orig.)

  8. Relationship between summer monsoon rainfall and cyclogenesis over Bay of Bengal during post-monsoon (October-December) season

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Maneesha, K.

    –Indonesia region (05◦–15◦S; 120◦–160◦E) are useful to predict TNDC during post-monsoon (October– December) season. The influence of ENSO (El-Nino Southern Oscillation) and IOD (Indian Ocean Dipole) on the cyclogenesis over Bay of Bengal were reported earlier...-monsoon (October–December) season for the period, 1984–2013. El-Nino Modoki (Sumesh and Ramesh Kumar 2013) in the cyclogenesis over north Indian Ocean were reported earlier. Li et al. (2015) studied the inter-annual variability of cyclones over Bay of Bengal during...

  9. Asian monsoons and aridification response to Paleogene sea retreat and Neogene westerly shielding indicated by seasonality in Paratethys oysters

    Science.gov (United States)

    Bougeois, Laurie; Dupont-Nivet, Guillaume; de Rafélis, Marc; Tindall, Julia C.; Proust, Jean-Noël; Reichart, Gert-Jan; de Nooijer, Lennart J.; Guo, Zhaojie; Ormukov, Cholponbelk

    2018-03-01

    Asian climate patterns, characterised by highly seasonal monsoons and continentality, are thought to originate in the Eocene epoch (56 to 34 million years ago - Ma) in response to global climate, Tibetan Plateau uplift and the disappearance of the giant Proto-Paratethys sea formerly extending over Eurasia. The influence of this sea on Asian climate has hitherto not been constrained by proxy records despite being recognised as a major driver by climate models. We report here strongly seasonal records preserved in annual lamina of Eocene oysters from the Proto-Paratethys with sedimentological and numerical data showing that monsoons were not dampened by the sea and that aridification was modulated by westerly moisture sourced from the sea. Hot and arid summers despite the presence of the sea suggest a strong anticyclonic zone at Central Asian latitudes and an orographic effect from the emerging Tibetan Plateau. Westerly moisture precipitating during cold and wetter winters appear to have decreased in two steps. First in response to the late Eocene (34-37 Ma) sea retreat; second by the orogeny of the Tian Shan and Pamir ranges shielding the westerlies after 25 Ma. Paleogene sea retreat and Neogene westerly shielding thus provide two successive mechanisms forcing coeval Asian desertification and biotic crises.

  10. Mapping forests in monsoon Asia with ALOS PALSAR 50-m mosaic images and MODIS imagery in 2010.

    Science.gov (United States)

    Qin, Yuanwei; Xiao, Xiangming; Dong, Jinwei; Zhang, Geli; Roy, Partha Sarathi; Joshi, Pawan Kumar; Gilani, Hammad; Murthy, Manchiraju Sri Ramachandra; Jin, Cui; Wang, Jie; Zhang, Yao; Chen, Bangqian; Menarguez, Michael Angelo; Biradar, Chandrashekhar M; Bajgain, Rajen; Li, Xiangping; Dai, Shengqi; Hou, Ying; Xin, Fengfei; Moore, Berrien

    2016-02-11

    Extensive forest changes have occurred in monsoon Asia, substantially affecting climate, carbon cycle and biodiversity. Accurate forest cover maps at fine spatial resolutions are required to qualify and quantify these effects. In this study, an algorithm was developed to map forests in 2010, with the use of structure and biomass information from the Advanced Land Observation System (ALOS) Phased Array L-band Synthetic Aperture Radar (PALSAR) mosaic dataset and the phenological information from MODerate Resolution Imaging Spectroradiometer (MOD13Q1 and MOD09A1) products. Our forest map (PALSARMOD50 m F/NF) was assessed through randomly selected ground truth samples from high spatial resolution images and had an overall accuracy of 95%. Total area of forests in monsoon Asia in 2010 was estimated to be ~6.3 × 10(6 )km(2). The distribution of evergreen and deciduous forests agreed reasonably well with the median Normalized Difference Vegetation Index (NDVI) in winter. PALSARMOD50 m F/NF map showed good spatial and areal agreements with selected forest maps generated by the Japan Aerospace Exploration Agency (JAXA F/NF), European Space Agency (ESA F/NF), Boston University (MCD12Q1 F/NF), Food and Agricultural Organization (FAO FRA), and University of Maryland (Landsat forests), but relatively large differences and uncertainties in tropical forests and evergreen and deciduous forests.

  11. Large-scale response of the Eastern Mediterranean thermohaline circulation to African monsoon intensification during sapropel S1 formation

    Science.gov (United States)

    Tesi, T.; Asioli, A.; Minisini, D.; Maselli, V.; Dalla Valle, G.; Gamberi, F.; Langone, L.; Cattaneo, A.; Montagna, P.; Trincardi, F.

    2017-03-01

    The formation of Eastern Mediterranean sapropels has periodically occurred during intensification of northern hemisphere monsoon precipitation over North Africa. However, the large-scale response of the Eastern Mediterranean thermohaline circulation during these monsoon-fuelled freshening episodes is poorly constrained. Here, we investigate the formation of the youngest sapropel (S1) along an across-slope transect in the Adriatic Sea. Foraminifera-based oxygen index, redox-sensitive elements and biogeochemical parameters reveal - for the first time - that the Adriatic S1 was synchronous with the deposition of south-eastern Mediterranean S1 beds. Proxies of paleo thermohaline currents indicate that the bottom-hugging North Adriatic Dense Water (NAdDW) suddenly decreased at the sapropel onset simultaneously with the maximum freshening of the Levantine Sea during the African Humid Period. We conclude that the lack of the "salty" Levantine Intermediate Water hampered the preconditioning of the northern Adriatic waters necessary for the NAdDW formation prior to the winter cooling. Consequently, a weak NAdDW limited in turn the Eastern Mediterranean Deep Water (EMDWAdriatic) formation with important consequences for the ventilation of the Ionian basin as well. Our results highlight the importance of the Adriatic for the deep water ventilation and the interdependence among the major eastern Mediterranean water masses whose destabilization exerted first-order control on S1 deposition.

  12. Seasonal prediction of Indian summer monsoon: Sensitivity to ...

    Indian Academy of Sciences (India)

    In the present study, the assessment of the Community Atmosphere Model (CAM) developed at National Centre for Atmospheric Research (NCAR) for seasonal forecasting of Indian Summer Monsoon (ISM) with different persistent SST is reported. Towards achieving the objective, 30-year model climatology has been ...

  13. Gridded daily Indian monsoon rainfall for 14 seasons: Merged ...

    Indian Academy of Sciences (India)

    grid consists of around 1250 grid points. Daily IMD analysed rainfall values at these 1250 grids are con- sidered as proxy gauge data for our 1. ◦ lat./long. resolution merged satellite gauge rainfall analysis for the Indian monsoon region. Since the basic gauge analysed data is at 0.5. ◦ lat./long. resolution, we decided to make ...

  14. Measurements of carbon dioxide and heat fluxes during monsoon ...

    Indian Academy of Sciences (India)

    An increase in carbon dioxide (CO2) concentrations in the atmosphere due to anthropogenic activities is responsible for global warming and hence in recent years, CO2 measurement network has expanded globally. In the monsoon season (July–September) of year 2011, we carried out measurements of CO2 and water ...

  15. Simulation of Indian summer monsoon using the Japan ...

    Indian Academy of Sciences (India)

    2Interdisciplinary Programme in Climate Studies, Indian Institute of Technology, Mumbai 400 076, India. ∗. Corresponding author. e-mail: ... ecosystems of the country and finally, on the economy of the country. Thus, the prediction of southwest monsoon is important for the national economy and government's various.

  16. Atlantic effects on recent decadal trends in global monsoon

    Science.gov (United States)

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

    2017-11-01

    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.

  17. Impact of Climate Change on India's Monsoonal Climate: Present ...

    Indian Academy of Sciences (India)

    Table of contents. Impact of Climate Change on India's Monsoonal Climate: Present Status and Outstanding Issues · Slide 2 · Slide 3 ... GFDL CM2.1 Global Coupled Ocean-Atmosphere Model Water Hosing Experiment with 1 Sv equivalent of Freshening Control Expt: 100 yrs After Hosing: 300 yrs · Uncertainties · Slide 28.

  18. Global surface temperature in relation to northeast monsoon rainfall ...

    Indian Academy of Sciences (India)

    est among the public/farmers and in government circles in recent years, in view of the frequent fail- ure of northeast monsoon rainfall (NEMR) over. Tamil Nadu and the consequent water scarcity condition. The study of interannual variability of. NEMR is therefore essential in the understanding and prediction of the same.

  19. Monsoon sensitivity to aerosol direct radiative forcing in the ...

    Indian Academy of Sciences (India)

    Aerosol forcing remains a dominant uncertainty in climate studies. The impact of aerosol direct radiative forcing on Indian monsoon is extremely complex and is strongly dependent on the model, aerosol distribution and characteristics specified in the model, modelling strategy employed as well as on spatial and temporal ...

  20. Towards understanding the unusual Indian monsoon in 2009

    Indian Academy of Sciences (India)

    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 ...

  1. Subseasonal variability during the South China Sea summer monsoon onset

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Renguang [Center for Ocean-Land-Atmosphere Studies, 4041 Powder Mill Road, Suite 302, Calverton, MD (United States)

    2010-04-15

    Analysis of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) data for the period 1998-2007 reveals large subseasonal fluctuations in sea surface temperature (SST) of the South China Sea during the summer monsoon onset. These subseasonal SST changes are closely related to surface heat flux anomalies induced by surface wind and cloud changes in association with the summer monsoon onset. The SST changes feed back on the atmosphere by modifying the atmospheric instability. The results suggest that the South China Sea summer monsoon onset involves ocean-atmosphere coupling on subseasonal timescales. While the SST response to surface heat flux changes is quick and dramatic, the time lag between the SST anomalies and the atmospheric convection response varies largely from year to year. The spatial-temporal evolution of subseasonal anomalies indicates that the subseasonal variability affecting the South China Sea summer monsoon onset starts over the equatorial western Pacific, propagates northward to the Philippine Sea, and then moves westward to the South China Sea. The propagation of these subseasonal anomalies is related to the ocean-atmosphere interaction, involving the wind-evaporation and cloud-radiation effects on SST as well as SST impacts on lower-level convergence over the equatorial western Pacific and atmospheric instability over the Philippine Sea and the South China Sea. (orig.)

  2. Simulation of Indian summer monsoon using the Japan ...

    Indian Academy of Sciences (India)

    Simulation of Indian summer monsoon using the Japan Meteorological Agency's seasonal ensemble prediction system. Kailas Sonawane1,∗. , O P Sreejith1, D R Pattanaik1,. Mahendra Benke1, Nitin Patil2 and D S Pai1. 1India Meteorological Department, Pune 411 005, India. 2Interdisciplinary Programme in Climate ...

  3. Monsoon sensitivity to aerosol direct radiative forcing in the ...

    Indian Academy of Sciences (India)

    4Divecha Centre for Climate Change, Indian Institute of Science, Bangalore 560 012, India. ∗. Corresponding author. ... of the lower atmosphere over the warm oceanic region in the south reduces the land–ocean temperature contrast and weakens the .... to the Himalayas act to reduce monsoon rainfall over India itself, with ...

  4. Anomalous behaviour of the Indian summer monsoon 2009

    Indian Academy of Sciences (India)

    Presence of El Ni˜no like conditions in the Pacific and warming over the equatorial Indian Ocean altered ... soons, with the annual march of climate punctuated ... tation from its equatorial position to continental. Keywords. Indian summer monsoon drought; circulation; SST. J. Earth Syst. Sci. 120, No. 5, October 2011, pp.

  5. Unusual rainfall shift during monsoon period of 2010 in Pakistan ...

    African Journals Online (AJOL)

    Process control charts suggest that monsoon pattern was not normal which made one-fifth of the country to be inundated. In this study, our main concern was to ... Abeyant policies by the Pakistan Irrigation Department (PID) caused destruction in Jacobabad which was not a normal Indus waterway. The first week of August ...

  6. Seasonal prediction of summer monsoon rainfall over cluster ...

    Indian Academy of Sciences (India)

    phases of ESI-tendency. Kakade and Kulkarni (2014) have developed separate LRF equations for predicting summer monsoon rainfall departures (%) for all India and its homogeneous regions during contrasting phases of ESI-tendency. While obtaining independent pre- dictors, first the cluster regions of various meteoro-.

  7. Climatology of gravity wave activity during the West African Monsoon

    Science.gov (United States)

    Kafando, P.; Chane-Ming, F.; Petitdidier, M.

    2008-12-01

    Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001-2006) above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E) and Ouagadougou (12.35° N; 1.51° W). Monthly total energy density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly total energy density calculated with temperature only supports that observed small-scale temperature and wind perturbations are mostly associated with gravity waves in the lower stratosphere especially for large values during the wet season. Above the two sites, monthly evolution of gravity wave total energy density reveals a maximum intensity of gravity wave activity in July during the West African Monsoon period. Indicators of convective activity such as mean Outgoing Longwave Radiation (OLR) and Tropical Rainfall Measuring Mission (TRMM) rain rates reveal to be adequate monsoon proxies to be compared to gravity wave energy intensity during the West African Monsoon.

  8. Climatology of gravity wave activity during the West African Monsoon

    Directory of Open Access Journals (Sweden)

    P. Kafando

    2008-12-01

    Full Text Available Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001–2006 above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E and Ouagadougou (12.35° N; 1.51° W. Monthly total energy density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly total energy density calculated with temperature only supports that observed small-scale temperature and wind perturbations are mostly associated with gravity waves in the lower stratosphere especially for large values during the wet season. Above the two sites, monthly evolution of gravity wave total energy density reveals a maximum intensity of gravity wave activity in July during the West African Monsoon period. Indicators of convective activity such as mean Outgoing Longwave Radiation (OLR and Tropical Rainfall Measuring Mission (TRMM rain rates reveal to be adequate monsoon proxies to be compared to gravity wave energy intensity during the West African Monsoon.

  9. Dynamics and composition of the Asian summer monsoon anticyclone

    Science.gov (United States)

    Gottschaldt, Klaus-Dirk; Schlager, Hans; Baumann, Robert; Sinh Cai, Duy; Eyring, Veronika; Graf, Phoebe; Grewe, Volker; Jöckel, Patrick; Jurkat-Witschas, Tina; Voigt, Christiane; Zahn, Andreas; Ziereis, Helmut

    2018-04-01

    This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The observations were obtained during the Earth System Model Validation (ESMVal) campaign in September 2012. Observed and simulated tracer-tracer relations reflect photochemical O3 production as well as in-mixing from the lower troposphere and the tropopause layer. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from those in the rest of the year, and the measurements reflect the main processes acting throughout the monsoon season. Net photochemical O3 production is significantly enhanced in the ASMA, where uplifted precursors meet increased NOx, mainly produced by lightning. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank and then transported in the southern fringe around the interior region. Radial transport barriers of the circulation are effectively overcome by subseasonal dynamical instabilities of the anticyclone, which occur quite frequently and are of paramount importance for the trace gas composition of the ASMA. Both the isentropic entrainment of O3-rich air and the photochemical conversion of uplifted O3-poor air tend to increase O3 in the ASMA outflow.

  10. Dynamics and predictability of Asian Monsoon and nonlinear dimensionality reduction

    Science.gov (United States)

    Hannachi, Abdel; Turner, Andy

    2013-04-01

    The Asian summer monsoon is a high dimensional and highly nonlinear phenomenon involving considerable moisture transport into land from ocean, and is critical for the whole region. We have used the European Reanalysis ERA-40 sea-level pressure (SLP) anomalies, with respect to the seasonal cycle, over the region (50E-145E, 20S-35N) to study the nonlinearity of the Asian monsoon using Isomap. We have focussed on the two-dimensional embedding of the SLP anomalies. Unlike the unimodality obtained from the empirical orthogonal function space, the probability density function, within the two-dimensional Isomap space, turns out to be bimodal. A clustering procedure is applied and reveals that the data support three clusters, which are identified using a three-component bivariate Gaussian mixture model. The modes are found to be associated respectively with the break and the active phases of the monsoon in addition to a third phase: the China sea active phase. Using the low-level wind field anomalies the active phase is found to be characterised by a strengthening and an eastward extension of the Somali jet whereas during the break phase the Somali jet is weakened and reversed by an easterly flow emanating from the West Pacific. The effect of large scale seasonal mean monsoon and lower boundary forcing is also investigated and discussed.

  11. Unusual rainfall shift during monsoon period of 2010 in Pakistan ...

    African Journals Online (AJOL)

    Arslan

    2013-09-04

    Sep 4, 2013 ... Floods due to “blocking event” in the jet stream during 2010 caused intense rainfall and flash floods in northern Pakistan which resulted to riverine flooding in southern Pakistan. In the beginning of July. 2010, changes in summer monsoon rainfall patterns caused the most severe flooding in Pakistan history.

  12. Summer monsoon intraseasonal oscillation over eastern Arabian Sea

    Indian Academy of Sciences (India)

    The time evolution of atmospheric parameters on intraseasonal time scale in the eastern Arabian. Sea (EAS) is studied during the summer monsoon seasons of 1998–2003 using Tropical Rainfall. Measuring Mission Microwave Imager (TMI) data. This is done using the spectral and wavelet analysis. Analysis shows that ...

  13. Long range prediction of Indian summer monsoon rainfall

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 116; Issue 1. Long range prediction of Indian summer monsoon ... In recent years NCEP/NCAR reanalysis has improved the geographical coverage and availability of the data and this can be easily updated. In this study using NCEP/NCAR reanalysis data on ...

  14. Gridded daily Indian monsoon rainfall for 14 seasons: Merged ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Home; Journals; Journal of Earth System Science; Volume 122; Issue 5 ... Indian monsoon is an important component of earth's climate system. ... the office of Indian Academy of Sciences, including those of the staff, the journals, various programmes, and Current Science, has changed from 'ias.ernet.in' (or ...

  15. Active and break spells of the Indian summer monsoon

    Indian Academy of Sciences (India)

    et al 2006) for identifying the active and break spells. The threshold used for identifying the spells was one-half of the standard deviation of the. IMR index. Gadgil and Joseph (2003) have defined breaks (and active spells) on the basis of the daily rainfall over the monsoon trough zone. They defined a break (active) day as a ...

  16. Is an onset vortex important for monsoon onset over Kerala?

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sankar, S.; Reason, C.

    two independent SST data sets. The role of SST, convection, integrated columnar water vapour and the low-level jet in the setting up of the monsoon onset over Kerala (MOK) is examined. It is found that the MOV which forms over the SEAS region upsets...

  17. Vertical structure of atmosphere in pre-monsoon season over ...

    Indian Academy of Sciences (India)

    This paper discusses the variation of dry bulb and dew point temperature (T and Td) on the days with and without thunderstorm (TSD and NTSD) over Bangalore during pre-monsoon season. The thermo-dynamic parameters like convective available potential energy (CAPE), convective inhibition energy (CIN), precipitable ...

  18. Retrieval of vertical wind profiles during monsoon from satellite ...

    Indian Academy of Sciences (India)

    large number of radiosonde observations of wind profiles over the Indian Ocean during the monsoon months. It has been found that the first ... include several sources of both systematic and random errors. Among them cloud top height .... highly correlated with the pseudo-winds at levels between 850mb and 600mb (r ј 0:8) ...

  19. Page 1 Interannual variability of Indian summer monsoon 81 ...

    Indian Academy of Sciences (India)

    Ocean to the north west of Australia and south western Pacific Ocean). Thus, over the Indian seas, it can be said that SST variations do not exhibit significant differences between the extreme categories of the Indian summer monsoon. The distribution of sea level pressure difference between the flood and drought.

  20. Deep learning for predicting the monsoon over the homogeneous ...

    Indian Academy of Sciences (India)

    Moumita Saha

    2017-06-12

    Jun 12, 2017 ... forecast of the monsoon at a long lead time which supports the government to implement appropriate policies for the economic growth of the ... at an appropriate lead month will be beneficial for planning proper agricultural ..... motivation of minimizing the reconstruction error of the input (the prime working ...

  1. Measurements of carbon dioxide and heat fluxes during monsoon ...

    Indian Academy of Sciences (India)

    Measurements of carbon dioxide and heat fluxes during monsoon-2011 season over rural site of India by eddy covariance technique. M N Patil∗. , T Dharmaraj, R T Waghmare, T V Prabha and J R Kulkarni. Indian Institute of Tropical Meteorology, Dr Homi Bhabha Road, Pune 411 008, India. ∗. Corresponding author.

  2. Increased particle flux to the deep ocean related to monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Ittekkot, V.; Manganini, S.J.; Ramaswamy, V.; Haake, B.; Degens, E.T.; Desai, B.N.; Honjo, S.

    . To assess the impact of monsoon-driven processes on the downward particle flux variations in the open ocean we deployed three moored arrays consisting of six time-series sediment traps at selected locations in the western, central and eastern parts...

  3. Gridded daily Indian monsoon rainfall for 14 seasons: Merged ...

    Indian Academy of Sciences (India)

    opportunities to learn more about weather and cli- mate systems of tropics and monsoons. Since 1997,. TRMM has provided rainfall data for research and application activities related to hydro-meteorology. TRMM archived and real-time data provided by. NASA GES DISC have been used widely around the world (Liu et al.

  4. Linking Indian rivers vs Bay of Bengal monsoon Activity

    Digital Repository Service at National Institute of Oceanography (India)

    Rajamani, V.; Mohanty, U.C.; Ramesh, R.; Bhat, G.S.; Vinayachandran, P.N.; Sengupta, D.; PrasannaKumar, S.; Kolli, R.K.

    : tsnarayana@vsnl.net MEETING REPORT Linking Indian rivers vs Bay of Bengal monsoon activity* In a popular article on ?Interlinking ri v ers: Is it the solution?? ( The Hindu , 26 August 2005), V. Rajamani brought ou t a poss i ble...

  5. Characteristics of monsoon waves off Uran, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nayak, B.U.; Chandramohan, P.; Mandal, S.

    Waves were measured off Uran in the Dharamtar creek (lat. 18 degrees 50 minutes and long. 72 degrees 55 minutes) during monsoon months from 26 June to 20 September 1984 using a Datawell wave rider buoy. The wave records were analysed using Tucker...

  6. Summer monsoon onset over Kerala: New definition and prediction

    Indian Academy of Sciences (India)

    with appropriate lag in time. The composite outgo- ing long wave radiation fields over the north Indian. Ocean (figure not shown) show rapid buildup of convective activity over the southeast Arabian Sea and east Bay of Bengal with the approach of the monsoon. Krishnamurti and Ramanathan (1982) examined observational ...

  7. Impact of vegetation on the simulation of seasonal monsoon rainfall ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 118; Issue 5. Impact of vegetation on the simulation of seasonal monsoon rainfall over the Indian subcontinent using a regional model. Surya K Dutta Someshwar Das S C Kar U C Mohanty P C Joshi. Volume 118 Issue 5 October 2009 pp 413-440 ...

  8. Moisture source for summer monsoon rainfall over India

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Rao, D.P.

    Southwest monsoon plays a vital role in India's economy as the major income comes from agriculture. What could be the moisture source for this copious amount of rainfall over the Indian sub-continent?. This has been studied in detail and noticed...

  9. Multi-model ensemble schemes for predicting northeast monsoon ...

    Indian Academy of Sciences (India)

    Northeast monsoon; multi-model ensemble; rainfall; prediction; principal component regression; single value decomposition. J. Earth Syst. Sci. 120, No. 5, October 2011, pp. 795–805 c Indian Academy of Sciences. 795 ... Rakecha 1983; Krishnan 1984; Raj and Jamadar. 1990; Sridharan and Muthusamy 1990; Singh and.

  10. Large-scale control of the Arabian Sea monsoon inversion in August

    Science.gov (United States)

    Wu, Chi-Hua; Wang, S.-Y. Simon; Hsu, Huang-Hsiung

    2017-12-01

    The summer monsoon inversion in the Arabian Sea is characterized by a large amount of low clouds and August as the peak season. Atmospheric stratification associated with the monsoon inversion has been considered a local system influenced by the advancement of the India-Pakistan monsoon. Empirical and numerical evidence from this study suggests that the Arabian Sea monsoon inversion is linked to a broader-scale monsoon evolution across the African Sahel, South Asia, and East Asia-Western North Pacific (WNP), rather than being a mere byproduct of the India-Pakistan monsoon progression. In August, the upper-tropospheric anticyclone in South Asia extends sideways corresponding with the enhanced precipitation in the subtropical WNP, equatorial Indian Ocean, and African Sahel while the middle part of this anticyclone weakens over the Arabian Sea. The increased heating in the adjacent monsoon systems creates a suppression effect on the Arabian Sea, suggesting an apparent competition among the Africa-Asia-WNP monsoon subsystems. The peak Sahel rainfall in August, together with enhanced heating in the equatorial Indian Ocean, produces a critical effect on strengthening the Arabian Sea thermal inversion. By contrast, the WNP monsoon onset which signifies the eastward expansion of the subtropical Asian monsoon heating might play a secondary or opposite role in the Arabian Sea monsoon inversion.

  11. Potential modulations of pre-monsoon aerosols during El Niño: impact on Indian summer monsoon

    Science.gov (United States)

    Fadnavis, S.; Roy, Chaitri; Sabin, T. P.; Ayantika, D. C.; Ashok, K.

    2017-10-01

    The potential role of aerosol loading on the Indian summer monsoon rainfall during the El Niño years are examined using satellite-derived observations and a state of the art fully interactive aerosol-chemistry-climate model. The Aerosol Index (AI) from TOMS (1978-2005) and Aerosol Optical Depth (AOD) from MISR spectroradiometer (2000-2010) indicate a higher-than-normal aerosol loading over the Indo-Gangetic plain (IGP) during the pre-monsoon season with a concurrent El Niño. Sensitivity experiments using ECHAM5-HAMMOZ climate model suggests that this enhanced loading of pre-monsoon absorbing aerosols over the Indo-Gangetic plain can reduce the drought during El Niño years by invoking the `Elevated-Heat-Pump' mechanism through an anomalous aerosol-induced warm core in the atmospheric column. This anomalous heating upshot the relative strengthening of the cross-equatorial moisture inflow associated with the monsoon and eventually reduces the severity of drought during El Niño years. The findings are subject to the usual limitations such as the uncertainties in observations, and limited number of El Niño years (during the study period).

  12. How can aerosols affect the Asian summer monsoon? Assessment during three consecutive pre-monsoon seasons from CALIPSO satellite data

    Directory of Open Access Journals (Sweden)

    J. Kuhlmann

    2010-05-01

    Full Text Available The impact of aerosols above and around the Tibetan Plateau on the Asian Summer Monsoon during pre-monsoon seasons March-April-May 2007, 2008, and 2009 is investigated by means of remote sensing and radiative transfer modelling. Four source regions are found to be responsible for the high aerosol loading around the Tibetan Plateau: the Taklamakan Desert, the Ganges Plains, the Indus Plains, and the Arabian Sea. CALIPSO lidar satellite data, providing vertically resolved images of aerosols, shows aerosol concentrations to be highest in the lower 5 km of the atmosphere with only little amounts reaching the Tibetan Plateau altitude. Using a radiative transfer model we find that aerosol plumes reduce shortwave radiation throughout the Monsoon region in the seasonal average by between 20 and 30 W/m2. Peak shortwave heating in the lower troposphere reaches 0.2 K/day. In higher layers this shortwave heating is partly balanced by longwave cooling. Although high-albedo surfaces, such as deserts or the Tibetan Plateau, increase the shortwave heating by around 10%, the overall effect is strongest close to the aerosol sources. A strong elevated heating which could influence large-scale monsoonal circulations as suggested by previous studies is not found.

  13. IDRC Bulletin — Winter 2017

    International Development Research Centre (IDRC) Digital Library (Canada)

    2018-01-16

    Jan 16, 2018 ... In this issue, read the research results from our Safe and Inclusive Cities program and don't forget that the Joint Canada-Israel Health Research Program 2018 call is now open. IDRC Bulletin logo IDRC Bulletin — Winter 2017. Featured this month. View of Port-au-Prince in Haiti, March 30, 2016. Safe and ...

  14. Learning through a Winter's Tale

    Science.gov (United States)

    Vidotto, Kristie

    2010-01-01

    In this article, the author shares her experience during the final semester of Year 11 Theatre Studies when she performed a monologue about Hermione from "The Winter's Tale". This experience was extremely significant to her because it nearly made her lose faith in one of the most important parts of her life, drama. She believes this…

  15. Winter School on Coding Theory

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 8; Issue 8. Winter School on Coding Theory. Information and Announcements Volume 8 Issue 8 August 2003 pp 111-111. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/008/08/0111-0111. Resonance ...

  16. Nuclear Winter: The Continuing Debate.

    Science.gov (United States)

    1987-03-23

    prospect of human annihilation. Speculation about the environmental results of a ’long darkness’ were considered by Paul Ehrlich .10 The term nuclear winter...Washington D.C., 1983 The Cold and the Dark: The World after Nuclear War, by Paul Ehrlich , et al. New York: Norton, 1984. (QH545 N83 C66 1983k Caldicott

  17. Using idealized snow forcing to test teleconnections with the Indian summer monsoon in the Hadley Centre GCM

    Energy Technology Data Exchange (ETDEWEB)

    Turner, A.G. [University of Reading, NCAS-Climate, Walker Institute for Climate System Research, Department of Meteorology, Reading (United Kingdom); Slingo, J.M. [University of Reading, NCAS-Climate, Walker Institute for Climate System Research, Department of Meteorology, Reading (United Kingdom); Met Office, Exeter (United Kingdom)

    2011-05-15

    Anomalous heavy snow during winter or spring has long been regarded as a possible precursor of deficient Indian monsoon rainfall during the subsequent summer. However previous work in this field is inconclusive, in terms of the mechanism that communicates snow anomalies to the monsoon summer, and even the region from which snow has the most impact. In this study we explore these issues in coupled and atmosphere-only versions of the Hadley Centre model. A 1050-year control integration of the HadCM3 coupled model, which well represents the seasonal cycle of snow cover over the Eurasian continent, is analysed and shows evidence for weakened monsoons being preceded by strong snow forcing (in the absence of ENSO) over either the Himalaya/Tibetan Plateau or north/west Eurasia regions. However, empirical orthogonal function (EOF) analysis of springtime interannual variability in snow depth shows the leading mode to have opposite signs between these two regions, suggesting that competing mechanisms may be possible. To determine the dominant region, ensemble integrations are carried out using HadAM3, the atmospheric component of HadCM3, and a variety of anomalous snow forcing initial conditions obtained from the control integration of the coupled model. Forcings are applied during spring in separate experiments over the Himalaya/Tibetan Plateau and north/west Eurasia regions, in conjunction with climatological SSTs in order to avoid the direct effects of ENSO. With the aid of idealized forcing conditions in sensitivity tests, we demonstrate that forcing from the Himalaya region is dominant in this model via a Blanford-type mechanism involving reduced surface sensible heat and longwave fluxes, reduced heating of the troposphere over the Tibetan Plateau and consequently a reduced meridional tropospheric temperature gradient which weakens the monsoon during early summer. Snow albedo is shown to be key to the mechanism, explaining around 50% of the perturbation in sensible

  18. Tracing the strength of the southwest monsoon using boron isotopes in the eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Naidu, P.D.; Foster, G.L.; Martínez-Boti, M.A.

    , was further calculated using pH, SST, salinity and TA (derived from salinity using the local modern day relationship between salinity and alkalinity from the GLODAP dataset) [Key et al., 2004]. We have used the R version 2.15.3 for these calculations (R... precipitation on the Western Ghats drains into the EAS through numerous rivers and streams. Modern observations indicate that pCO2sw in the Arabian Sea as a whole is in excess of that in the atmosphere, therefore acting as a significant source of carbon...

  19. Precipitation, temperature, and teleconnection signals across the combined North American, Monsoon Asia, and Old World Drought Atlases

    Science.gov (United States)

    Smerdon, J. E.; Baek, S. H.; Coats, S.; Williams, P.; Cook, B.; Cook, E. R.; Seager, R.

    2017-12-01

    The tree-ring-based North American Drought Atlas (NADA), Monsoon Asia Drought Atlas (MADA), and Old World Drought Atlas (OWDA) collectively yield a near-hemispheric gridded reconstruction of hydroclimate variability over the last millennium. To test the robustness of the large-scale representation of hydroclimate variability across the drought atlases, the joint expression of seasonal climate variability and teleconnections in the NADA, MADA, and OWDA are compared against two global, observation-based PDSI products. Predominantly positive (negative) correlations are determined between seasonal precipitation (surface air temperature) and collocated tree-ring-based PDSI, with average Pearson's correlation coefficients increasing in magnitude from boreal winter to summer. For precipitation, these correlations tend to be stronger in the boreal winter and summer when calculated for the observed PDSI record, while remaining similar for temperature. Notwithstanding these differences, the drought atlases robustly express teleconnection patterns associated with the El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). These expressions exist in the drought atlas estimates of boreal summer PDSI despite the fact that these modes of climate variability are dominant in boreal winter, with the exception of the Atlantic Multidecadal Oscillation. ENSO and NAO teleconnection patterns in the drought atlases are particularly consistent with their well-known dominant expressions in boreal winter and over the OWDA domain, respectively. Collectively, our findings confirm that the joint Northern Hemisphere drought atlases robustly reflect large-scale patterns of hydroclimate variability on seasonal to multidecadal timescales over the 20th century and are likely to provide similarly robust estimates of hydroclimate variability prior to the existence of widespread instrumental data.

  20. Impact of biomass burning aerosol on the monsoon circulation transition over Amazonia

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Fu, Rong; Yu, Hongbin; Qian, Yun; Dickinson, Robert; Silva Dias, Maria Assuncao F.; da Silva Dias, Pedro L.; Fernandes, Katia

    2009-05-30

    Ensemble simulations of a regional climate model (RegCM3) forced by aerosol radiative forcing suggest that biomass burning aerosols can work against the seasonal monsoon circulation transition, thus re-enforce the dry season rainfall pattern for Southern Amazonia. Strongly absorbing smoke aerosols warm and stabilize the lower troposphere within the smoke center in southern Amazonia (where aerosol optical depth > 0.3). These changes increase the surface pressure in the smoke center, weaken the southward surface pressure gradient between northern and southern Amazonia, and consequently induce an anomalous moisture divergence in the smoke center and an anomalous convergence occurs in northwestern Amazonia (5°S-5°N, 60°W-40 70°W). The increased atmospheric thermodynamic stability, surface pressure, and divergent flow in Southern Amazonia may inhibit synoptic cyclonic activities propagated from extratropical South America, and re-enforce winter-like synoptic cyclonic activities and rainfall in southeastern Brazil, Paraguay and northeastern Argentina.

  1. Summer monsoon onset-induced changes of autotrophic pico- and nanoplankton in the largest monsoonal estuary along the west coast of India.

    Science.gov (United States)

    Mohan, Arya P; Jyothibabu, R; Jagadeesan, L; Lallu, K R; Karnan, C

    2016-02-01

    This study presents the response of autotrophic pico- and nanoplankton to southwest monsoon-associated hydrographical transformations in the Cochin backwaters (CBW), the largest monsoonal estuary along the west coast of India. By the onset of the southwest monsoon, the euhaline/mesohaline conditions in the downstream/upstream of CBW usually transform into oligohaline/limnohaline. The flow cytometer analysis revealed the dominance of picoeukaryotes > Synechococcus > nanoautotrophs, with Prochlorococcus either very low or entirely absent. Synechococcus abundance was high during the pre-southwest monsoon (10(6) L(-1)), which dwindled with heavy fresh water influx during the southwest monsoon (10(5) L(-1)). The drastic drop in salinity and faster flushing of the CBW during the southwest monsoon replaced the euhaline/mesohaline strain of Synechococcus with an oligohaline/limnohaline strain. Epifluorescence microscopy analyses showed that, among the two strains of Synechococcus, the phycoerythrin-rich (PE-rich) one was dominant in the mesohaline/euhaline conditions, whereas the phycocyanin-rich (PC-rich) strain dominated in oligohaline/limnohaline conditions. Although Synechococcus abundance diminished during the southwest monsoon, the total abundance of picoplankton community remained virtually unchanged in the upstream due to an increase in the abundance of picoeukaryotes. On the other hand, the autotrophic nanoplankton abundance increased from pre-monsoon levels of av. 3.8 × 10(6)-av. 9.5 × 10(6) L(-1) at the onset of the southwest monsoon. Utilizing suitable multivariate analyses, the study illustrated the differential response and niche preference of various smaller communities of autotrophs to the southwest monsoon-associated hydrographical ramifications in a large monsoonal estuary, which may be applicable to similar such estuaries situated along the Indian coastline.

  2. Winter movement dynamics of black brant

    Science.gov (United States)

    Lindberg, Mark S.; Ward, David H.; Tibbitts, T. Lee; Roser, John

    2007-01-01

    Although North American geese are managed based on their breeding distributions, the dynamics of those breeding populations may be affected by events that occur during the winter. Birth rates of capital breeding geese may be influenced by wintering conditions, mortality may be influenced by timing of migration and wintering distribution, and immigration and emigration among breeding populations may depend on winter movement and timing of pair formation. We examined factors affecting movements of black brant (Branta bernicla nigricans) among their primary wintering sites in Mexico and southern California, USA, (Mar 1998–Mar 2000) using capture–recapture models. Although brant exhibited high probability (>0.85) of monthly and annual fidelity to the wintering sites we sampled, we observed movements among all wintering sites. Movement probabilities both within and among winters were negatively related to distance between sites. We observed a higher probability both of southward movement between winters (Mar to Dec) and northward movement between months within winters. Between-winter movements were probably most strongly affected by spatial and temporal variation in habitat quality as we saw movement patterns consistent with contrasting environmental conditions (e.g., La Niña and El Niño southern oscillation cycles). Month-to-month movements were related to migration patterns and may also have been affected by differences in habitat conditions among sites. Patterns of winter movements indicate that a network of wintering sites may be necessary for effective conservation of brant.

  3. Wintering ecology of adult North American ospreys

    Science.gov (United States)

    Washburn, Brian E.; Martell, Mark S.; Bierregaard, Richard O.; Henny, Charles J.; Dorr, Brian S.; Olexa, Thomas J.

    2014-01-01

    North American Ospreys (Pandion haliaetus) typically migrate long distances to their wintering grounds in the tropics. Beyond the general distribution of their wintering range (i.e., the Caribbean, South America, and Central America), very little is known about the wintering ecology of these birds. We used satellite telemetry to determine the duration of wintering period, to examine the characteristics of wintering areas used by Ospreys, and to quantify space use and activity patterns of wintering Ospreys. Adult Ospreys migrated to wintering sites and exhibited high wintering site fidelity among years. Overall, Ospreys wintered on river systems (50.6%) more than on lakes (19.0%), and use of coastal areas was (30.4%) intermediate. Ospreys remained on their wintering grounds for an average of 154 d for males and 167 d for females. Locations of wintering Ospreys obtained via GPS-capable satellite telemetry suggest these birds move infrequently and their movements are very localized (i.e., 2 and 1.4 km2, respectively. Overall, our findings suggest wintering adult North American Ospreys are very sedentary, demonstrating a pattern of limited daily movements and high fidelity to a few select locations (presumably roosts). We suggest this wintering strategy might be effective for reducing the risk of mortality and maximizing energy conservation.

  4. North American Monsoon Response to Eemian Climate Forcings and its Effect on Rocky Mountain Forests

    Science.gov (United States)

    Insel, N.; Berkelhammer, M. B.

    2017-12-01

    The key to recognizing and predicting future changes in regional climate and ecosystems lies in understanding the causes and characteristics of paleovariations. The Last Interglacial (LIG: 130-116 ka) is the most recent period in Earth history when temperatures are believed to have exceeded those of today. In this study, we are focusing on the response of the North American monsoon (NAM) to shifts in orbital forcings during LIG. In particular, we are using regional climate model (RegCM) simulations under LIG (115ka, 125 ka and 135 ka) and modern forcings to evaluate changes in the strength, timing, duration, and amount of moisture transported from different sources during the NAM season. Understanding these variations is critical to forecast seasonal supply of water to the southwestern U.S. under current warming conditions. In addition, cellulose extracted stable isotopes from Rocky Mountain Eemian wood samples provides both a tool to diagnose the model simulations and to evaluate the response of western U.S. tree species to changes in temperature and moisture availability. Our preliminary results indicate enhanced summer precipitation, wind shifts and changes in NAM characteristics in response to increased Northern Hemisphere insolation. The following features were observed: (1) The NAM strengthens and extends slightly more northward during the Eemian due to a shift in upper-level divergence. (2) The onset and duration of the NAM seems to be similar between modern and Eemian simulations. (3) Consistent with modern observations, simulations suggest a western NAM region in Arizona that receives most of its monsoonal moisture from the Gulf of California, while the eastern NAM region in New Mexico obtains most of its summer rains from the Gulf of Mexico. In the Eemian, we see a spatial shift from more depleted to more enriched source waters throughout the monsoon season. These changes in the summer climate are confirmed by the tree ring isotope data, which show a

  5. Multidecadal changes in the Etesians-Indian Summer Monsoon teleconnection along the 20th Century

    Science.gov (United States)

    Gómez-Delgado, F. de Paula; Vega, Inmaculada; Gallego, David; Peña-Ortiz, Cristina; Ribera, Pedro; García-Herrera, Ricardo

    2017-04-01

    In this work we made use of historical winds record taken aboard ships to reconstruct a series of the prevalent summer northerly winds (Etesian winds) over the Eastern Mediterranean for the entire 20th century. Previous studies have shown a significant link between the frequency and strength of these winds and the strength of the Indian Summer Monsoon (ISM), but this relationship had only been studied in detail for the second half of the 20th century due to the absence of long and continous series of observed wind in the Eastern Mediterranean for previous periods. In this work, a new climatic index, the so-called " Etesian Wind Index " (EWI), is defined as the percentage of days with prevalent northerly wind (wind blowing from 305° to 35°) in a fixed region [20E-30E, 32N-37N]. By using historical wind observations, we have been able to compute this index for the summer (JJAS) since 1880 and analyze the long term variability of the Etesians, as well as to research into its relation with the ISM at an unprecedent temporal coverage. A running coverage analysis revealed a strong and significant positive correlation between the EWI and the strength of the ISM for the period 1960-1980, more markedly in July and August. This result is in accordance with other recent studies. However, we have found that the correalation fades out in the first half of the 20th century (1900-1950) and in the period 1980-2012, even showing significant negative values around the subperiod 1920-1950. Similar indices to the EWI were computed using two different 20th century reanalysis datasets (ERA20C and 20CR-V2C). Despite the fact that both indices show some discrepancies with the EWI before 1950, the correlation analysis with the ISM revealed similar results, pointing out a strong loss of the EWI-ISM correlation in the first half of the 20th century and from 1980 onwards, as well as a marked positive correlated period between 1960 and 1980, specially in August. In this study, we show that

  6. 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.

  7. Classification guide: Sochi 2014 Paralympic Winter Games

    OpenAIRE

    2014-01-01

    The Sochi 2014 Paralympic Winter Games classification guide is designed to provide National Paralympic Committees (NPCs) and International Federations (IFs) with information about the classification policies and procedures that will apply to the Sochi 2014 Paralympic Winter Games.

  8. Multi-scale Interactions of Desert Dust, Rainfall and Circulation during the South Asian Summer Monsoon

    Science.gov (United States)

    Lau, W. K. M.

    2017-12-01

    Desert dust is an intrinsic component of the Indian monsoon system. Every year, during the pre- monsoon season (April-May), large amount of dust aerosols are transported from the deserts in the Middle East and as far as North Africa to the Indian subcontinent, by prevailing westerleis in the mid-to- upper troposphere. During June-July, in spite of wash-out by monsoon rain, desert dusts continue to be transported and replenished by increasing low-level monsoon westerlies across the northern Arabian Sea, and accumulate to great height ( 5 km) against the steep southern slopes of the Tibetan Plateau, over central and northern India. The interactions of dusts with monsoon dynamics are extremely complex. From pre-monsoon (AM) through the entire monsoon season (JJAS), dust aerosol emission, transport and washout are closely intertwined with monsoon winds and rainfall fluctuations, associated with active and inactive monsoon spells, and effects of orography. Meanwhile, dusts in the atmosphere absorb solar radiation, heat the atmosphere, cool the ocean and land surfaces on large-scales, while interacting with clouds through microphysical processes on convective scales. Additionally dust deposited on snow cover in Himalayas and the Tibetan Plateau (HTP) darkens the snow surface, accelerates melting of mountain snowpack, and warms the land surface of the HTP, which is a key driver of the SASM. These complex processes are underpinned by changes in land-sea thermal contrast, moist stability energy, convective potential, and strong interactions with monsoon dynamics and orographty. In this talk, I will show examples, from observations, and model simulations, key processes and underlying mechanisms involving dust interactions with monsoon rainfall and circulation in affecting intraseasonal and interannual variability of the SASM. Roles of dust-monsoon feedback processes in monsoon climate will also be discussed.

  9. Deglacial Tropical Atlantic subsurface warming links ocean circulation variability to the West African Monsoon.

    Science.gov (United States)

    Schmidt, Matthew W; Chang, Ping; Parker, Andrew O; Ji, Link; He, Feng

    2017-11-13

    Multiple lines of evidence show that cold stadials in the North Atlantic were accompanied by both reductions in Atlantic Meridional Overturning Circulation (AMOC) and collapses of the West African Monsoon (WAM). Although records of terrestrial change identify abrupt WAM variability across the deglaciation, few studies show how ocean temperatures evolved across the deglaciation. To identify the mechanism linking AMOC to the WAM, we generated a new record of subsurface temperature variability over the last 21 kyr based on Mg/Ca ratios in a sub-thermocline dwelling planktonic foraminifera in an Eastern Equatorial Atlantic (EEA) sediment core from the Niger Delta. Our subsurface temperature record shows abrupt subsurface warming during both the Younger Dryas (YD) and Heinrich Event 1. We also conducted a new transient coupled ocean-atmosphere model simulation across the YD that better resolves the western boundary current dynamics and find a strong negative correlation between AMOC strength and EEA subsurface temperatures caused by changes in ocean circulation and rainfall responses that are consistent with the observed WAM change. Our combined proxy and modeling results provide the first evidence that an oceanic teleconnection between AMOC strength and subsurface temperature in the EEA impacted the intensity of the WAM on millennial time scales.

  10. Winter temperatures over the Korean Peninsula and East Asia: development of a new index and its application to seasonal forecast

    Science.gov (United States)

    Kim, Seon Tae; Sohn, Soo-Jin; Kug, Jong-Seong

    2017-09-01

    This study proposes a new index for monitoring and predicting winter temperatures of the Korean Peninsula based on the dominant atmospheric winter teleconnection patterns. The utilization of this index is further extended to the East Asian Winter Monsoon (EAWM) index because the new index is found to well represent the main feature of the EAWM circulation. Among the teleconnection patterns, the East Atlantic (EA) and Western Pacific (WP) patterns are found to be most strongly correlated with winter temperatures via their partial association with changes in sea level pressure (SLP) around the Korean Peninsula, i.e., the EA and WP patterns are associated with SLP variation over the Siberian High region and the Kuroshio extension region to the east of Japan, respectively. On the basis of this relationship, the two regions representing the northwest-to-southeast SLP gradients are determined to define the new index. It is found that the new index can represent the Korean winter temperatures consistently well regardless of their considerable decadal changes. When compared with the existing SLP-based EAWM indices, the new index shows the best performance in delineating winter air temperatures, not only in the Korean Peninsula but also in the entire East Asian region. We also assess the prediction skill of the new index with seasonal coupled forecast models of the APEC Climate Center of Korea and its capability to predict winter temperatures. This assessment shows that the new index has potential for operationally predicting and monitoring winter temperatures in Korea and the whole of East Asia.

  11. 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

  12. Connections Between Stratospheric Pollution and the Asian Summer Monsoon

    Science.gov (United States)

    Bauer, Susanne E.; Tsigaridis, Konstas

    2015-01-01

    The Asian Monsoon leads to rapid vertical transport of gases and aerosols into the upper troposphere. Some of the pollution might be transported above cloud levels, which will allow it to spread globally and possibly at some occasions reach into the stratosphere. In this study we will use the GISS climate model to investigate the interactions between pollution and convective transport as well as secondary aerosol formation. Pollution resulting from anthropogenic activity as well as from natural sources such as small and large volcanic eruptions, dust storms and forest fires will be quantified. This modeling study will be accompanied by satellite observations from space that monitor aerosol optical thickness (AOT), and absorption AOT (AAOT) in two and three dimensions. Our goal is a better process level understanding of the evolution of natural and anthropogenic aerosol plumes in conjunction with the Asian Monsoon. Hence, we aim to explain their large-scale expansion, which eventually determines their impacts on climate.

  13. Spatiotemporal patterns and trends of Indian monsoonal rainfall extremes.

    Science.gov (United States)

    Malik, Nishant; Bookhagen, Bodo; Mucha, Peter J

    2016-02-28

    In this study, we provide a comprehensive analysis of trends in the extremes during the Indian summer monsoon (ISM) months (June to September) at different temporal and spatial scales. Our goal is to identify and quantify spatiotemporal patterns and trends that have emerged during the recent decades and may be associated with changing climatic conditions. Our analysis primarily relies on quantile regression that avoids making any subjective choices on spatial, temporal, or intensity pattern of extreme rainfall events. Our analysis divides the Indian monsoon region into climatic compartments that show different and partly opposing trends. These include strong trends towards intensified droughts in Northwest India, parts of Peninsular India, and Myanmar; in contrast, parts of Pakistan, Northwest Himalaya, and Central India show increased extreme daily rain intensity leading to higher flood vulnerability. Our analysis helps explain previously contradicting results of trends in average ISM rainfall.

  14. Leadership in American Indian Communities: Winter Lessons

    Science.gov (United States)

    Metoyer, Cheryl A.

    2010-01-01

    Winter lessons, or stories told in the winter, were one of the ways in which tribal elders instructed and directed young men and women in the proper ways to assume leadership responsibilities. Winter lessons stressed the appropriate relationship between the leader and the community. The intent was to remember the power and purpose of that…

  15. Monsoon and primary acute angle closure in malaysia.

    Science.gov (United States)

    Ch'ng, T W; Mosavi, S A A; Noor Azimah, A A; Azlan, N Z; Azhany, Y; Liza-Sharmini, A T

    2013-10-01

    Acute angle closure (AAC) without prompt treatment may lead to optic neuropathy. Environmental factor such as climate change may precipitate pupillary block, the possible mechanism of AAC. To determine the association of northeast monsoon and incidence of AAC in Malaysia. A retrospective study was conducted on AAC patients admitted to two main tertiary hospitals in Kelantan, Malaysia between January 2001 and December 2011. The cumulative number of rainy day, amount of rain, mean cloud cover and 24 hours mean humidity at the estimated day of attack were obtained from the Department of Meteorology, Malaysia. A total 73 cases of AAC were admitted with mean duration of 4.1SD 2.0 days. More than half have previous history of possibility of AAC. There was higher incidence of AAC during the northeast monsoon (October to March). There was also significant correlation of number of rainy day (r=0.718, pclimate as the potential risk factor. Prompt treatment to arrest pupillary block and reduction of the intraocular pressure is important to prevent potential glaucomatous damage. Public awareness of AAC and accessibility to treatment should be part of preparation to face the effect of northeast monsoon.

  16. Atmospheric water budget over the South Asian summer monsoon region

    Science.gov (United States)

    Unnikrishnan, C. K.; Rajeevan, M.

    2018-04-01

    High resolution hybrid atmospheric water budget over the South Asian monsoon region is examined. The regional characteristics, variability, regional controlling factors and the interrelations of the atmospheric water budget components are investigated. The surface evapotranspiration was created using the High Resolution Land Data Assimilation System (HRLDAS) with the satellite-observed rainfall and vegetation fraction. HRLDAS evapotranspiration shows significant similarity with in situ observations and MODIS satellite-observed evapotranspiration. Result highlights the fundamental importance of evapotranspiration over northwest and southeast India on atmospheric water balance. The investigation shows that the surface net radiation controls the annual evapotranspiration over those regions, where the surface evapotranspiration is lower than 550 mm. The rainfall and evapotranspiration show a linear relation over the low-rainfall regions (budget shows annual, seasonal, and intra-seasonal variations. Evapotranspiration does not show a high intra-seasonal variability as compared to other water budget components. The coupling among the water budget anomalies is investigated. The results show that regional inter-annual evapotranspiration anomalies are not exactly in phase with rainfall anomalies; it is strongly influenced by the surface conditions and other atmospheric forcing (like surface net radiation). The lead and lag correlation of water budget components show that the water budget anomalies are interrelated in the monsoon season even up to 4 months lead. These results show the important regional interrelation of water budget anomalies on south Asian monsoon.

  17. Monsoon convection dynamics and nonlinear dimensionality reduction vis Isomap

    Science.gov (United States)

    Hannachi, A.; Turner, A.

    2012-04-01

    The Asian summer monsoon is a high dimensional and highly nonlinear phenomenon involving considerable moisture transport into land from ocean, and is critical for the whole region. We have used the European Reanalysis ERA-40 sea-level pressure (SLP) anomalies, with respect to the seasonal cycle, over the region (50E-145E, 20S-35N) to study the nonlinearity of the Asian monsoon using Isomap. We have focussed on the two-dimensional embedding of the SLP anomalies. Unlike the unimodality obtained from the empirical orthogonal function space, the probability density function computed within the two-dimensional Isomap space is shown to be bimodal. A clustering procedure is applied and reveals that the data support three clusters, which are identified using a three-component bivariate Gaussian mixture model. Two modes are associated with an active phase over India/Bay of Bengal and East China sea respectively, whereas the third mode is associated witha break over East/South China sea. Using the low-level wind field anomalies the (first mode) active phase is found to be characterised by a strengthening and an eastward extension of the Somali jet whereas during the (second mode) break phase the Somali jet is weakened and reversed by an easterly flow emanating from the West Pacific. The effect of large scale seasonal mean monsoon and lower boundary forcing is also investigated and discussed.

  18. Subseasonal Predictability of Boreal Summer Monsoon Rainfall from Ensemble Forecasts

    Directory of Open Access Journals (Sweden)

    Nicolas Vigaud

    2017-10-01

    Full Text Available Subseasonal forecast skill over the broadly defined North American (NAM, West African (WAM and Asian (AM summer monsoon regions is investigated using three Ensemble Prediction Systems (EPS at sub-monthly lead times. Extended Logistic Regression (ELR is used to produce probabilistic forecasts of weekly and week 3–4 averages of precipitation with starts in May–Aug, over the 1999–2010 period. The ELR tercile category probabilities for each model gridpoint are then averaged together with equal weight. The resulting Multi-Model Ensemble (MME forecasts exhibit good reliability, but have generally low sharpness for forecasts beyond 1 week; Multi-model ensembling largely removes negative values of the Ranked Probability Skill Score (RPSS seen in individual forecasts, and broadly improves the skill obtained in any of the three individual models except for the AM. The MME week 3–4 forecasts have generally higher RPSS and comparable reliability over all monsoon regions, compared to week 3 or week 4 forecast separately. Skill is higher during La Niña compared to El Niño and ENSO-neutral conditions over the 1999–2010 period, especially for the NAM. Regionally averaged RPSS is significantly correlated with the Maden-Julian Oscillation (MJO for the AM and WAM. Our results indicate potential for skillful predictions at subseasonal time-scales over the three summer monsoon regions of the Northern Hemisphere.

  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. CLIVAR Asian-Australian Monsoon Panel Report to Scientific Steering Group-18

    Energy Technology Data Exchange (ETDEWEB)

    Sperber, Ken R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hendon, Harry H. [Bureau of Meteorology Research Centre (BMRC), Melbourne, VIC (Australia)

    2011-05-04

    These are a set of slides on CLIVAR Asian-Australian Monsoon Panel Report to Scientific Steering Group-18. These are the major topics covered within: major activities over the past year, AAMP Monsoon Diagnostics/Metrics Task Team, Boreal Summer Asian Monsoon, Workshop on Modelling Monsoon Intraseasonal Variability, Workshop on Interdecadal Variability and Predictability of the Asian-Australian Monsoon, Evidence of Interdecadal Variability of the Asian-Australian Monsoon, Development of MJO metrics/process-oriented diagnostics/model evaluation/prediction with MJOTF and GCSS, YOTC MJOTF, GEWEX GCSS, AAMP MJO Diabatic Heating Experiment, Hindcast Experiment for Intraseasonal Prediction, Support and Coordination for CINDY2011/DYNAMO, Outreach to CORDEX, Interaction with FOCRAII, WWRP/WCRP Multi-Week Prediction Project, Major Future Plans/Activities, Revised AAMP Terms of Reference, Issues and Challenges.

  1. 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

    2015-01-01

    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. PMID:25733889

  2. 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.

  3. Distributional characteristics of surface-layer mesozooplankton in the Bay of Bengal during the 2005 winter monsoon.

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, V.; Ramaiah, N.

    naturals. Publicaciones del Insitute de Biologia Aplicada 9 (1951) 5-27. 18 Pielou, E. C., Species-diversity and pattern-diversity in the study of ecological succession. J Theor. Biol. 10 (1966) 370-383. 19 Tranter, D. J., Kerr, J. D., Seasonal variations...., Biogeographic inferences of shifting copepod distribution during 1997- 1999 El Niño and La Niña in the California Current, 158, in: ‘Contributions to the Study of East Pacific Crustaceans 4 (1), edited by Hendrickx M.E., Instituto de Ciencias del Mary...

  4. Diurnal variability of heat fluxes over the coastal waters off Visakhapatnam during post-monsoon and winter seasons

    Digital Repository Service at National Institute of Oceanography (India)

    Ramu, Ch V.; Bharathi, G.; Sadhuram, Y.; Prasad, K.V.S.R.

    ). This was due to the enhanced heat loss because of the strong winds noticed on those days. Relationship between Bowen Ratio (B) and sea– air temperature difference (Ts - Ta) Hsu12 proposed a relationship B = a (Ts – Ta)b for unstable conditions, where...

  5. Myctophid and pelagic shrimp assemblages in the oxygen minimum zone of the Andaman Sea during the winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Karuppasamy, P.K.; LaluRaj, C.M.; Muraleedharan, K.R.; Nair, M.

    & Maheswari Nair3 1 PG and Research Department of Zoology, Periyar EVR College, Tiruchirappalli-23, Tamil Nadu, India 2 National Centre for Antarctic & Ocean Research, Goa, India 3 National Institute of Oceanography, Regional Center, Kochi-682018, India [E... in the open ocean; display a high diversity that can be used as an indicator of biogeographic distinctness of a specific area. Many micronekton species demonstrate ontogenetic migrations as well, living in epipelagic layers (0-200 m) as larvae or early...

  6. Effect of freshwater influx on phytoplankton in the Mandovi estuary (Goa, India) during monsoon season: Chemotaxonomy

    Digital Repository Service at National Institute of Oceanography (India)

    Parab, S.G.; Matondkar, S.G.P.; Gomes, H.R.; Goes, J.I.

    stages of the monsoon was recorded, and this data is discussed in relation to environmental changes in the Mandovi estuary during the monsoon season. Keywords: Phytoplankton; Pigment Analysis; Monsoon; Freshwater Runoff; CHEMTAX 1. Introduction... by both salinity and nutrients [8]. As an al- ternative and complement to microscopic examination, the accessory pigments estimated by High Performance Liquid-Chromatography (HPLC) provide accurate class- specific differentiation of the phytoplankton...

  7. Long range forecasting of summer monsoon rainfall from SST in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Murthy, T.V.R.

    southwest monsoon season (June- September). As India's economy mainly depends on agriculture, monsoon rainfall is very important for the country.Besidesagriculture,itis the mainsourceforfresh water to millions of people living in the country. Floods... and droughts associated with strong and weak monsoons greatly influence the economy of the country. Most of the droughts and floods are associated with EI-Nino and La- Nina respectively (Webster andYang3 and krishna Kumar et al\\. The relationship between ENSO...

  8. The Australian Monsoon and its Mesoscale Convective Systems

    Science.gov (United States)

    Mapes, Brian E.

    1992-01-01

    The 1987 Australian monsoon was observed with satellites, rawinsondes, radar and aircraft. These data are presented, with theory filling the gaps, in illustration of its dynamics. The engine of the monsoon is its embedded mesoscale convective systems (MCSs). Ten MCSs were explored with airborne Doppler radar. They all exhibited multicellular convection, in lines or arcs along the edges of cold pools, aging and evolving into areas of stratiform precipitation. This temporal evolution can be divided into three stages: "convective," "intermediary," and "stratiform." Doppler radar divergence profiles for each stage show remarkable consistency from one MCS to the next. Convective areas had low-level convergence, with its peak elevated off the surface, and divergence above ~8 km altitude. Intermediary areas had very little divergence through the lower troposphere, but strong convergence near 10 km altitude, associated with upper-tropospheric ascent. Stratiform areas had midlevel convergence between divergent layers. These divergence profiles indicate thermal forcing of the monsoon by the convection, in a form more useful than heating profiles. The response of the atmosphere to thermal forcing is considered in chapter 2. Thermal disturbances travel through a stratified fluid at a speed proportional to their vertical depth. A heat source with complex vertical structure excites disturbances ("buoyancy bores"), of many depths, that separate themselves out with distance from the heat source. Hence the deeper components of a heat source can be found at greater distances from the heat source, at any given moment and also in the limit of long time in a rotating or dissipative fluid. Low-level dynamical processes initiate deep convection within the active cyclonic areas of the monsoon trough, despite the warm core aloft and the consequent (small) decrease in CAPE. In 1987, four tropical cyclones were generated in the monsoon by this runaway positive feedback loop. Two forcing

  9. Understanding the Unusual 2017 Monsoon and Floods in South Asia

    Science.gov (United States)

    Akanda, A. S.; Palash, W.; Hasan, M. A.; Nusrat, F.

    2017-12-01

    Driven primarily by the South Asian Monsoon, the Ganges-Brahmaputra-Meghna (GBM) river basin system collectively drains intense precipitation for an area of more than 1.5 million square kilometers during the wet summer season. Bangladesh, being the lowest riparian country in the system, experiences recurrent floods and immense suffering to its population. The 2017 monsoon season was quite unusual in terms of the characteristics of the precipitation received in the basin. The monsoon was spread out over a much larger time span (April-October) compared to the average monsoon season (June-September). Although the monsoon does not typically start until June in Bangladesh, the 2017 season started much earlier in April with unusually heavy precipitation in the Meghna basin region and caused major damage to agriculture in northeastern Bangladesh. The rainfall continued in several record-breaking pulses, compared to the typical one or two large waves. One of the largest pulses occurred in early August with very high in intensity and volume, causing ECMWF to issue a major warning about widespread flooding in Bangladesh, Northern India, and Eastern Nepal. This record flood event impacted over 40 million people in the above regions, causing major damage to life and infrastructure. Although the Brahmaputra rose above the danger level several times this season, the Ganges was unusually low, thus sparing downstream areas from disastrous floods. However, heavy precipitation continued until October, causing urban flooding in Dhaka and Chittagong - and worsening sanitation and public health conditions in southern Bangladesh - currently undergoing a terrible humanitarian crisis involving Rohingya refugees from the Myanmar. Despite marked improvement in flood forecasting systems in recent years, the 2017 floods identified critical gaps in our understanding of the flooding phenomena and limitations of dissemination in these regions. In this study, we investigate 1) the unusual

  10. Reconstructing Monsoon Variations in India - Evidence from Speleothems

    Science.gov (United States)

    Breitenbach, S. F.; Lechleitner, F.; Plessen, B.; Marwan, N.; Cheng, H.; Adkins, J. F.; Haug, G. H.

    2012-12-01

    Indian summer monsoon (ISM) rainfall is of vital importance for ca. one fifth of the world's population, yet little is known about the factors governing its variability. Changing seasonality and/or rainfall intensity have profound impacts on the well-being of Asian agriculture-based societies. Most proxy-records from the Indian realm lack temporal resolution and age control sufficient to allow detailed analysis of high-frequency ISM rainfall variations. Low spatial coverage further restricts understanding spatial differences and the interactions between subsystems of the Asian summer monsoon, limiting understanding, not to mention reliable forecasting. Here, we summarize available information on rainfall changes over India, as reflected in speleothems. Suitable stalagmites offer highly precise chronologies and multi-proxy time series. Oxygen isotope and greyscale time series can track ISM intensity. Using published and new records from NE India, we present evidence for significant rainfall changes during the Holocene. Available proxy records show that while long-term ISM rainfall pattern changed in concert with supra-regional variations of the Asian summer monsoon, sub-decadal-scale ISM variations are influenced by local and regional influences. Complex network analysis of Indian and Chinese proxy data reveals that during the Medieval Warm Period ISM and East Asian summer monsoon (EASM) were more tightly linked, with a seemingly strong ISM influence on the EASM. During the cooler Little Ice Age however, the ISM and EASM connection weakened and local effects exerted influence on both sub-systems of the Asian monsoon. In order to allow detailed insights in spatio-temporal variations of the ISM and external teleconnections, precisely dated high-resolution time series must be obtained from various places in the Indian peninsula and beyond. Only a combination of high temporal and spatial coverage will allow assessments of the likelihood of drought recurrence in a given

  11. Influence of Latent Heating over the Asian and Western Pacific Monsoon Region on Sahel Summer Rainfall.

    Science.gov (United States)

    He, Shan; Yang, Song; Li, Zhenning

    2017-08-09

    There has been an interdecadal shift towards a less humid state in Sahel summer rainfall since the 1960s. The decreased Sahel summer rainfall was associated with enhanced summer latent heating over the South Asian and western Pacific summer monsoon region and anomalous zonal-vertical cell of the Asian summer monsoon circulation, indicating that the latent heating plays a significant role in the change in Sahel rainfall. The effects of the latent heating over different monsoon domains on the Sahel rainfall are investigated through several model experiments. Results show that the remote monsoon heating mainly affects Sahel rainfall by generating changes in the zonal-vertical atmospheric circulation.

  12. GEM in the marine atmosphere and air-sea exchange of Hg during late autumn and winter cruise campaigns over the marginal seas of China

    Science.gov (United States)

    Wang, Yan; Liu, Ruhai; Li, Yanping; Cui, Xueqing; Zhou, Jianping; Liu, Shixuan; Zhang, Yuqing

    2017-07-01

    East Asia is one of the primary sources of atmospheric gaseous elemental mercury (GEM) among the world. In this study, GEM concentrations were measured during two cruises in late autumn and winter of 2012 and 2013 which passed through the marginal seas of China. The results show that the mean GEM concentration was 1.65 ng/m3 from the South China Sea to the Yellow Sea during the 2012 cruise. While the mean GEM concentration was 2.38 ng/m3 in the South Yellow Sea, and 1.75 ng/m3 in the North Yellow and Bohai Seas during the 2013 cruise. High GEM contents were detected when the steering wind was offshore. There is a significant positive relationship between GEM and air temperature for these two cruises. Low GEM content was presented when the cold northerly monsoon prevailed while air masses mainly came from the clean northern oceanic region. Dissolved gaseous mercury (DGM) concentration in the surface water of the south Yellow and Bohai seas were 74.4 ± 28 pg/L. DGM concentrations were correlated with water temperature (r = 0.244, p polluted air and low wind speed. High flux values were caused by the northerly monsoon which carried remote clean air to the sea, with large wind speeds. The northerly monsoon is an important factor affecting the GEM transport offshore to marginal sea and the cycle of mercury in the sea in late autumn and winter.

  13. Communicating Certainty About Nuclear Winter

    Science.gov (United States)

    Robock, A.

    2013-12-01

    I have been spending much of my time in the past several years trying to warn the world about the continuing danger of nuclear weapons, and that the solution is a rapid reduction in the nuclear arsenal. I feel that a scientist who discovers dangers to society has an ethical duty to issue a warning, even if the danger is so scary that it is hard for people to deal with. The debate about nuclear winter in the 1980s helped to end the nuclear arms race, but the planet still has enough nuclear weapons, even after reductions planned for 2017 under the New START treaty, to produce nuclear winter, with temperatures plunging below freezing in the summer in major agricultural regions, threatening the food supply for most of the planet. New research by myself, Brian Toon, Mike Mills, and colleagues over the past six years has found that a nuclear war between any two countries, such as India and Pakistan, using 50 atom bombs each of the size dropped on Hiroshima could produce climate change unprecedented in recorded human history, and a world food crisis because of the agricultural effects. This is much less than 1% of the current global arsenal. Communicating certainty - what we know for sure - has been much more effective than communicating uncertainty. The limited success I have had has come from persistence and serendipity. The first step was to do the science. We have published peer-reviewed articles in major journals, including Science, Nature, Proceedings of the National Academy of Sciences, Journal of Geophysical Research, Atmospheric Chemistry and Physics, Physics Today, and Climatic Change. But policymakers do not read these journals. Through fairly convoluted circumstances, which will be described in this talk, we were able to get papers published in Scientific American and the Bulletin of Atomic Scientists. I have also published several encyclopedia articles on the subject. As a Lead Author of Chapter 8 (Radiative Forcing) of the recently published Fifth Assessment

  14. 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.

  15. STUDIES ON THE RESISTANCE TO WINTERING OF THE ITALIAN BEES APIS MELLIFERA LIGUSTICA REARED IN ROMANIA

    Directory of Open Access Journals (Sweden)

    MONICA PÂRVU

    2009-10-01

    Full Text Available The study was conducted on bee families of Apis mellifera carpatica and Apis mellifera ligustica breeds. The bees were housed in multi-storey hives. The experimental period was of 6 months. The resistance to wintering was evaluated on the basis of several apicultural indicators: mortality, feed intake during the winter, general state of the family. Mortality was 35% during wintering for the Carpathian bee and 52% for the Italian bee. The differences were very significant (p≤0.001. When wintering finished all bee families were in good strength. The general state of the bee family was as follows: the Carpathian bee had a strong family when wintering started and ended with a median power; it had a large number of young bees and sufficient reserves; no diarrhoea or mould were noticed; relative humidity was 74%. The Italian bee had a strong family when wintering started and ended with half of the power because of the high mortality during the winter; no diarrhoea or mould were noticed; relative humidity was 69%.

  16. Direct radiative effects of dust aerosols emitted from the Tibetan Plateau on the East Asian summer monsoon - a regional climate model simulation

    Science.gov (United States)

    Sun, Hui; Liu, Xiaodong; Pan, Zaitao

    2017-11-01

    While dust aerosols emitted from major Asian sources such as Taklimakan and Gobi deserts have been shown to have strong effect on Asian monsoon and climate, the role of dust emitted from Tibetan Plateau (TP) itself, where aerosols can directly interact with the TP heat pump because of their physical proximity both in location and elevation, has not been examined. This study uses the dust-coupled RegCM4.1 regional climate model (RCM) to simulate the spatiotemporal distribution of dust aerosols originating within the TP and their radiative effects on the East Asian summer monsoon (EASM) during both heavy and light dust years. Two 20-year simulations with and without the dust emission from TP showed that direct radiative cooling in the mid-troposphere induced by the TP locally produced dust aerosols resulted in an overall anticyclonic circulation anomaly in the low troposphere centered over the TP region. The northeasterly anomaly in the EASM region reduces its strength considerably. The simulations found a significant negative correlation between the TP column dust load produced by local emissions and the corresponding anomaly in the EASM index (r = -0.46). The locally generated TP dust can cause surface cooling far downstream in Bohai Gulf and the China-North Korea border area through stationary Rossby wave propagation. Although dust from within TP (mainly Qaidam Basin) is a relatively small portion of total Asian aerosols, its impacts on Asian monsoon and climate seems disproportionately large, likely owning to its higher elevation within TP itself.

  17. Winter therapy for the accelerators

    CERN Document Server

    Corinne Pralavorio

    2016-01-01

    Hundreds of people are hard at work during the year-end technical stop as all the accelerators are undergoing maintenance, renovation and upgrade operations in parallel.   The new beam absorber on its way to Point 2 before being lowered into the LHC tunnel for installation. The accelerator teams didn’t waste any time before starting their annual winter rejuvenation programme over the winter. At the end of November, as the LHC ion run was beginning, work got under way on the PS Booster, where operation had already stopped. On 14 December, once the whole complex had been shut down, the technical teams turned their attention to the other injectors and the LHC. The year-end technical stop (YETS) provides an opportunity to carry out maintenance work on equipment and repair any damage as well as to upgrade the machines for the upcoming runs. Numerous work projects are carried out simultaneously, so good coordination is crucial. Marzia Bernardini's team in the Enginee...

  18. 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.

  19. Tropical cyclone influence on the long-term variability of Philippine summer monsoon onset

    Science.gov (United States)

    Kubota, Hisayuki; Shirooka, Ryuichi; Matsumoto, Jun; Cayanan, Esperanza O.; Hilario, Flaviana D.

    2017-12-01

    The long-term variability of Philippine summer monsoon onset from 1903 to 2013 was investigated. The onset date is defined by daily rainfall data at eight stations in the northwestern Philippines. Summer monsoons tended to start earlier in May after the mid-1990s. Other early onset periods were found during the 1900s, 1920s, and 1930s, and an interdecadal variability of summer monsoon onset was identified. Independent surface wind data observed by ships in the South China Sea (SCS) revealed prevailing westerly wind in May during the early monsoon onset period. To identify atmospheric structures that trigger Philippine summer monsoon onset, we focused on the year 2013, conducting intensive upper-air observations. Tropical cyclone (TC) Yagi traveled northward in the Philippine Sea (PS) in 2013 and triggered the Philippine monsoon onset by intensifying moist low-level southwesterly wind in the southwestern Philippines and intensifying low-level southerly wind after the monsoon onset in the northwestern Philippines. The influence of TC was analyzed by the probability of the existence of TC in the PS and the SCS since 1951, which was found to be significantly correlated with the Philippine summer monsoon onset date. After the mid-1990s, early monsoon onset was influenced by active TC formation in the PS and the SCS. However, the role of TC activity decreased during the late summer monsoon periods. In general, it was found that TC activity in the PS and the SCS plays a key role in initiating Philippine summer monsoon onset. [Figure not available: see fulltext.

  20. Aerosol and rainfall variability over the Indian monsoon region: distributions, trends and coupling

    Directory of Open Access Journals (Sweden)

    R. Gautam

    2009-09-01

    Full Text Available 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.

  1. Realtime chemical characterization of post monsoon organic aerosols in a polluted urban city: Sources, composition, and comparison with other seasons.

    Science.gov (United States)

    Chakraborty, Abhishek; Mandariya, Anil Kumar; Chakraborti, Ruparati; Gupta, Tarun; Tripathi, S N

    2018-01-01

    Real time chemical characterization of non-refractory submicron aerosols (NR-PM 1 ) was carried out during post monsoon (September-October) via Aerosol Mass Spectrometer (AMS) at a polluted urban location of Kanpur, India. Organic aerosol (OA) was found to be the dominant species with 58% contribution to total NR-PM 1 mass, followed by sulfate (16%). Overall, OA was highly oxidized (average O/C = 0.66) with the dominance of oxidized OAs (60% of total OA) as revealed by source apportionment. Oxidized nature of OA was also supported by very high OC/EC ratios (average = 8.2) obtained from simultaneous offline filter sampling. High and low OA loading periods have very dramatic effects on OA composition and oxidation. OA O/C ratios during lower OA loading periods were on average 30% higher than the same from high loading periods with significant changes in types and relative contribution from oxidized OAs (OOA). Comparison of OA sources and chemistry among post monsoon and other seasons revealed significant differences. Characteristics of primary OAs remain very similar, but features of OOAs showed substantial changes from one season to another. Winter had lowest OOA contribution to total OA but similar overall O/C ratios as other seasons. This reveals that processing of primary OAs, local atmospheric chemistry, and regional contributions can significantly alter OA characteristics from one season to another. This study provides interesting insights into the seasonal variations of OA sources and evolution in a very polluted and complex environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Monsoon Circulations and Tropical Heterogeneous Chlorine Chemistry in the Stratosphere

    Science.gov (United States)

    Kinnison, Doug; Solomon, Susan; Garcia, Rolando; Bandoro, Justin; Wilka, Catherine; Neeley, Ryan, III; Schmidt, Anja; Barnes, John; Vernier, Jean-Paul; Höpfner, Michael; Mills, Michael

    2017-04-01

    Heterogeneous chlorine chemistry on and in liquid polar stratospheric particles is thought to play a significant role in polar and subpolar ozone depletion. Previous studies have not provided evidence for heterogeneous chlorine chemistry occurring in the tropical stratosphere. Using the current best understanding of liquid stratospheric particle chemistry in a state-of-the-art numerical model, we examine whether such processes should be expected to affect tropical composition, particularly at and slightly above the cold tropical tropopause, in association with the Asian and North American summer (June-July-August) monsoons. The Specified Dynamics version of the Community Earth System Model version 1 (CESM1) Whole Atmosphere Community Climate Model (WACCM) is used in this study. This model is nudged to externally specified dynamical fields for temperature, zonal and meridional winds, and surface pressure fields from the NASA Modern Era Retrospective Analysis for Research and Applications (MERRA). Model simulations suggest that transport processes associated with the summer monsoons bring increased abundances of hydrochloric acid (HCl) into contact with liquid sulfate aerosols in the cold tropical lowermost stratosphere, leading to heterogeneous chemical activation of chlorine species. The calculations indicate that the spatial and seasonal distributions of chlorine monoxide (ClO) and chlorine nitrate (ClONO2) near the monsoon regions of the northern hemisphere tropical and subtropical lowermost stratosphere could provide indicators of heterogeneous chlorine processing. In the model, these processes impact the local ozone budget and decrease ozone abundances, implying a chemical contribution to longer-term northern tropical ozone profile changes at 16-19 km.

  3. Southwest monsoon influences the water quality and waste assimilative capacity in the Mandovi estuary (Goa state, India)

    Digital Repository Service at National Institute of Oceanography (India)

    VishnuRadhan, R.; Sagayadoss, J.; Seelan, E.; Vethamony, P.; Shirodkar, P.V.; Zainudin, Z.; Shirodkar, S.

    suspended solids (TSS) and turbidity during southwest (SW) monsoon relative to other seasons. The WQI suggested that an increase in nutrients, turbidity and TSS during SW monsoon increase the WQI values beyond 2, rendering the water at some locations...

  4. Holocene moisture and East Asian summer monsoon evolution in the northeastern Tibetan Plateau recorded by Lake Qinghai and its environs: A review of conflicting proxies

    Science.gov (United States)

    Chen, Fahu; Wu, Duo; Chen, Jianhui; Zhou, Aifeng; Yu, Junqing; Shen, Ji; Wang, Sumin; Huang, Xiaozhong

    2016-12-01

    ostracod δ18O record, which is widely used as a proxy of effective moisture and summer monsoon intensity in lake sediments, at least in Lake Qinghai, and which exhibits light values in the early Holocene and heavier values thereafter, cannot be used to reflect the strength of the EASM or the intensity of monsoon precipitation - as is also the case for leaf wax δ2H records. Rather, we argue that as is the case of the Chinese speleothem δ18O record, which also is often interpreted as an EASM proxy, it reflects variation in the δ18O of precipitation. Overall, we suggest that the EASM significantly affected precipitation in the northeastern Tibetan Plateau during the Holocene; and that it increased in strength during the early Holocene, reached a maximum during the middle Holocene and decreased during the late Holocene.

  5. Physical and biological characteristics of the winter-summer transition in the Central Red Sea

    KAUST Repository

    Zarokanellos, Nikolaos

    2017-07-25

    The Central Red Sea (CRS) lies between two distinct hydrographic and atmospheric regimes. In the southern Red Sea, seasonal monsoon reversal regulates the exchange of water between the Red Sea and the Indian Ocean. In the northern Red Sea, intermediate and occasionally deep water are formed during winter to sustain the basin\\'s overturning circulation. Highly variable mesoscale eddies and the northward flowing eastern boundary current (EBC) determine the physical and biogeochemical characteristics of the CRS. Ship-based and glider observations in the CRS between March and June 2013 capture key features of the transition from winter to summer and depict the impact of the eddy activity on the EBC flow. Less saline and relatively warmer water of Indian Ocean origin reaches the CRS via the EBC. Initially, an anticyclonic eddy with diameter of 140 km penetrating to 150m depth with maximum velocities up to 30–35 cm s prevails in the CRS. This anticyclonic eddy appears to block or at least redirect the northward flow of the EBC. Dissipation of the eddy permits the near-coastal, northward flow of the EBC and gives place to a smaller cyclonic eddy with a diameter of about 50 km penetrating to 200 m depth. By the end of May, as the northerly winds become stronger and persistent throughout the basin, characteristic of the summer southwest monsoon wind regime, the EBC, and its associated lower salinity water became less evident, replaced by the saltier surface water that characterizes the onset of the summer stratification in the CRS.

  6. 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

  7. Climatology of gravity wave activity during the West African Monsoon

    OpenAIRE

    Kafando, P.; Chane-Ming, Fabrice; Petitdidier, Monique

    2008-01-01

    Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001–2006) above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E) and Ouagadougou (12.35° N; 1.51° W). Monthly total energy density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly total energy density...

  8. Indian monsoon cycles through the last twelve million years

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.

    (Sishir Ritu, ~14th January) up till “Karka-Sankranti” with Sun over tropics of Cancer (Varsha Ritu,~14th July), which results into rains over India, then Sun returns back (“Dakshinyana”) towards tropics of Capricorn (Fig.1A). The Sun is apparently... of Cancer during Varsha-Ritu (June/July) as described in the “Surya-Siddhanta” (~400 years A.D.?). (B) Somewhat analogous, what is described in (A), is the modern monsoon – a combination of Hadley-Cell, ITCZ, differential solar heating, pressure, outgoing...

  9. Continental drift and plateau uplift control origination and evolution of Asian and Australian monsoons.

    Science.gov (United States)

    Liu, Xiaodong; Dong, Buwen; Yin, Zhi-Yong; Smith, Robin S; Guo, Qingchun

    2017-01-13

    Evolutions of Asian and Australian monsoons have important significance for understanding the past global change but are still a controversial subject. Here, we explore systematically the effects of plate movement and plateau uplift on the formation and evolution of the Asian and Australian monsoons by numerical simulations based on land-sea distributions and topographic conditions for five typical geological periods during the Cenozoic. Our results suggest that the timings and causes of formation of the monsoons in South Asia, East Asia and northern Australia are different. The Indian Subcontinent, which was located in the tropical Southern Hemisphere in the Paleocene, was influenced by the austral monsoon system simulated at that time. Once it moved to the tropical Northern Hemisphere in the Eocene, the South Asian monsoon established and remained persistently thereafter. However, the monsoons of East Asia and northern Australia did not appear until the Miocene. The establishment of the simulated low-latitude South Asian (northern Australian) monsoon appeared to have strongly depended on the location of mainland India (Australia), associated with northward plate motion, without much relation to the plateau uplift. On the contrary, the establishment of the mid-latitude East Asian monsoon was mainly controlled by the uplift of Tibetan plateau.

  10. Changes in Global Monsoon Circulations: Evidence of a diminishing global hydrological cycle?

    Science.gov (United States)

    Chase, T. N.; Knaff, J. A.; Pielke, R. A.

    2001-05-01

    We examined changes in several independent intensity indices of four major tropical monsoonal circulations from approximately 1950-1998. These intensity indices included upper-level divergence at several standard levels, land surface precipitation in the monsoon regions and ocean surface pressure. These values were averaged seasonally over appropriate regions of southeastern Asian, western Africa, eastern Africa and Australia/Maritime continent and adjacent ocean areas. As a consistency check we also examined two secondary indices: mean sea level pressure trends averaged over each monsoon region and low level convergence at several levels both from the NCEP reanalysis. We find that in each of the four regions examined, a consistent picture emerges indicating significantly diminished monsoonal circulations over the period of record, evidence of a diminished global hydrological cycle since 1950. Trends since 1978, the period of strongest surface warming, are insignificant and uncorrelated with the surface warming. When strong ENSO years are removed from the time series the trends still show a general, significant reduction of monsoon intensity indicating that ENSO variability is not the direct cause for the observed weakening. A comparison with general circulation model simulations of the effects of rising CO2 shows an increase in monsoonal activity with rising global surface temperature except in the case of the Australian/Maritime continent monsoon. When the effects of aerosols are included the simulated southeastern Asian summer monsoon is also reduced in intensity.

  11. The Response of the North American Monsoon to Increased Greenhouse Gas Forcing

    Science.gov (United States)

    Cook, B. I.; Seager, R.

    2013-01-01

    [1] We analyze the response of the North American Monsoon (NAM) to increased greenhouse gas (GHG) forcing (emissions scenario RCP 8.5) using new simulations available through the Coupled Model Intercomparison Project version 5 (CMIP5). Changes in total monsoon season rainfall with GHG warming are small and insignificant. The models do, however, show significant declines in early monsoon season precipitation (June-July) and increases in late monsoon season (September-October) precipitation, indicating a shift in seasonality toward delayed onset and withdrawal of the monsoon. Early in the monsoon season, tropospheric warming increases vertical stability, reinforced by reductions in available surface moisture, inhibiting precipitation and delaying the onset of the monsoon. By the end of the monsoon season, moisture convergence is sufficient to overcome the warming induced stability increases, and precipitation is enhanced. Even with no change in total NAM rainfall, shifts in the seasonal distribution of precipitation within the NAM region are still likely to have significant societal and ecological consequences, reinforcing the need to not only understand the magnitude, but also the timing, of future precipitation changes.

  12. Monitoring bifurcation of Monsoon system through satellite imagery and synoptic data

    International Nuclear Information System (INIS)

    Qureshi, J.; Mahmood, S.A.; Awan, S.A.

    2005-01-01

    The Monsoon phenomenon in Pakistan has quite a unique impact on the weather of our country. In this context summer monsoon are of prime importance considering the water availability in Pakistan. The monsoon conditions are best developed in sub-tropics, as in East and South-East Asia. This Study is an attempt to monitor the summer Monsoon systems affecting most of the Pakistan territory during the primary seasons and causing Large scale heavy rainfall. Monsoon low pressure areas which produce heavy rainfall spells and flooding activity over south Asia are reflective of a specific characteristic from inception to recurvature and dissipation. A study carried out in the monsoon season is indicative of a north westerly track of all the monsoon lows and then after two or three days a point of inflexion has reached before recurvature in easterly and north easterly direction and resulting in quick dissipation. The life of the monsoon low is particularly very short one after the recurvature and it has almost double the speed after recurvature visa vie prior to recurvature. The interesting feature is detected with comparison of surface low pressure center from synoptic charts, satellite image for associated cloud center and upper air convergence center confirming their by north westerly till of the storm structure. (author)

  13. A brief survey on climate change effects on the Indian Monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Bala, G

    2007-02-06

    Each year, Indian summer monsoon season begins in June and ends in September. Surface winds blow from the southwest during this season. The Indian summer monsoon typically covers large areas of India with western and central India receiving more than 90% of their total annual precipitation during this period, and southern and northwestern India receiving 50%-75% of their total annual rainfall. Overall, monthly totals average 200-300 mm over the country as a whole, with the largest values observed during the heart of the monsoon season in July and August. In all total, India receives about 870 mm of rainfall in a normal summer monsoon season. This summary discusses the effects of climate change on the frequency, mean rainfall, duration and the variability of the Indian Monsoon. East Asian Monsoon in the southeastern part of Asia is not discussed in this summary. Changes in monsoon characteristics are mainly inferred from climate model simulations submitted to the Intergovernmental Panel on Climate Change (IPCC)'s Fourth Assessment Report (AR4). It should be cautioned that there is a large range in the results from these models. For instance, the range of mean monsoon precipitation as simulated by the AR4 models over India is from 500 mm to 900 mm for the present-day climate (Kirpalani et al. 2006).

  14. The value of C sub(e) for the Arabian Sea during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, A.S.; Sadhuram, Y.; Krishna, V.V.G.

    We estimate, from the moisture budget the bulk aerodynamic coefficient for latent heat flux (C sub(e)) during the monsoon season over the central Arabian Sea. The average value of C sub(e) under active monsoon conditions was found to be 2.25 x 10...

  15. Monsoon wind and maritime trade: A case study of historical evidence from Orissa, India

    Digital Repository Service at National Institute of Oceanography (India)

    Tripati, S.; Raut, L.N.

    Monsoon plays a predominant role in the daily life of the people of South Asia. The use of monsoon wind in the Indian Ocean for maritime trade was a boon to the sailing ships to reach overseas countries. It is believed that Hippalus discovered...

  16. Characteristics of monsoon low level jet (MLLJ) as an index of ...

    Indian Academy of Sciences (India)

    R.Narasimhan(krishtel emaging) 1461 1996 Oct 15 13:05:22

    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. 1. Introduction. P. V. Joseph and P. L. Raman (IJMG 1966) pointed out the existence of a low-level jet or the. Monsoon Low Level Jet (MLLJ) stream over penin- sular India.

  17. Modelling the impacts of deforestation on monsoon rainfall in West Africa

    International Nuclear Information System (INIS)

    Abiodun, B J; Pal, J S; Afiesimama, E A; Gutowski, W J; Adedoyin, A

    2010-01-01

    The study found that deforestation causes more monsoon moisture to be retained in the mid-troposphere, thereby reducing the northward transport of moisture needed for rainfall over West Africa. Hence, deforestation has dynamical impacts on the West African monsoon and rainfall.

  18. The East Asian summer monsoon variability over the last 145 years inferred from the Shihua Cave record, North China.

    Science.gov (United States)

    Li, Xianglei; Cheng, Hai; Tan, Liangcheng; Ban, Fengmei; Sinha, Ashish; Duan, Wuhui; Li, Hanying; Zhang, Haiwei; Ning, Youfeng; Kathayat, Gayatri; Edwards, R Lawrence

    2017-08-01

    The precipitation variability associated with the East Asian summer monsoon (EASM) has profound societal implications. Here, we use precisely dated and seasonally-resolved stalagmite oxygen isotope (δ 18 O) records from Shihua Cave, North China to reconstruct the EASM variability over the last 145 years. Our record shows a remarkable weakening of the EASM strength since the 1880s, which may be causally linked to the warming of the tropical Pacific and Indian Oceans. The δ 18 O record also exhibits a significant ~30-year periodicity, consistent with the instrumental, historical and proxy-based rainfall records from North China, plausibly driven by the Pacific Decadal Oscillation (PDO). Together, these observations imply that ~30-year periodicity is a persistent feature of the EASM, which remains significant with or without anthropogenic forcing. If indeed, the EASM rainfall in North China might decline significantly in the near future, which may affect millions of people in this region.

  19. The Strength Compass

    DEFF Research Database (Denmark)

    Ledertoug, Mette Marie

    In the Ph.D-project ͚Strengths-based Learning - Children͛s character strengths as a means to their learning potential͛ 750 Danish children have assessed ͚The Strength Compass͛ in order to identify their strengths and to create awareness of strengths. This was followed by a strengths-based interve......In the Ph.D-project ͚Strengths-based Learning - Children͛s character strengths as a means to their learning potential͛ 750 Danish children have assessed ͚The Strength Compass͛ in order to identify their strengths and to create awareness of strengths. This was followed by a strengths...

  20. Indian summer monsoon variability during the Holocene as recorded in sediments of the Arabian Sea: Timing and implications

    Digital Repository Service at National Institute of Oceanography (India)

    Thamban, M.; Kawahata, H.; Rao, V.P.

    . Ocean. Of the two monsoons, the summer (southwest) monsoons are vital to the Indian subcontinent for rainfall and related oceanic processes like upwelling and produc- tivity in the Arabian Sea (Singhvi et al., 2007). The role of summer monsoons as a... flourished and vanished in tandem with climate fluc- tuations. Further, the South Asian monsoons greatly af- fect the hydrography of the Indian Ocean, as well as terrigenous input from the land to the northern Indian 1010 M. Thamban et al. subcontinent have...

  1. Evolution of the South-East Monsoon System - An Investigation of the Dynamical Controls on the Monsoon System Over Geologic Time Scales.

    Science.gov (United States)

    Farnsworth, A.; Lunt, D. J.

    2014-12-01

    The South-East Asian monsoon is a fundamental feature in the global climate system cycling energy, moisture and momentum from tropical to extra-tropical latitudes. Societies rely extensively on precipitation during the monsoon season to sustain population centres and economic activity such as agriculture. However the current monsoon system has not always been in its current configuration varying extensively throughout geological time. However little is known about the driving factors behind its creation and evolution. A series of numerical model simulation (HadCM3L) using state of the art reconstructed paleogeographies have been employed to investigate the evolution of the S.E. Asian monsoon system for each geological stage (32 simulations in total) since the beginning of the Cretaceous. Two methodologies, i) a fixed regional precipitation signal based on the current monsoon regions modern areal extent and ii) a migrating regional construct based on the modern day monsoon regions back rotated through time are investigated. These two methodologies allow an examination of the evolution of tropical precipitation over time in the region. The large-scale processes (paleogeography, CO2) of the monsoon system and the regional dynamics (e.g. sea surface temperatures, regional atmospheric circulation, oceanic heat transport, land-sea temperature differential) that control them are also examined with numerical results compared against available proxy data. Preliminary results indicate a downward trend in global precipitation since the late Eocene with significant change at the E/O boundary. In addition, tropical precipitation (40°N - 40°S) has seen a downward trend in rainfall since the mid-Cretaceous. S.E. Asia is shown to be influenced by changes in topographical features/ location, CO2 concentrations, and the regional atmospheric circulation playing a key role in modification of the monsoon system which drive variability on tectonic time scales.

  2. Declining pre-monsoon dust loading over South Asia: Signature of a changing regional climate.

    Science.gov (United States)

    Pandey, Satyendra K; Vinoj, V; Landu, K; Babu, S Suresh

    2017-11-22

    Desert dust over the Indian region during pre-monsoon season is known to strengthen monsoon circulation, by modulating rainfall through the elevated heat pump (EHP) mechanism. In this context, an insight into long term trends of dust loading over this region is of significant importance in understanding monsoon variability. In this study, using long term (2000 to 2015) aerosol measurements from multiple satellites, ground stations and model based reanalysis, we show that dust loading in the atmosphere has decreased by 10 to 20% during the pre-monsoon season with respect to start of this century. Our analysis reveals that this decrease is a result of increasing pre-monsoon rainfall that in turn increases (decreases) wet scavenging (dust emissions) and slowing circulation pattern over the Northwestern part of the sub-continent.

  3. Trends and oscillations in the Indian summer monsoon rainfall over the last two millennia.

    Science.gov (United States)

    Sinha, Ashish; Kathayat, Gayatri; Cheng, Hai; Breitenbach, Sebastian F M; Berkelhammer, Max; Mudelsee, Manfred; Biswas, Jayant; Edwards, R L

    2015-02-17

    Observations show that summer rainfall over large parts of South Asia has declined over the past five to six decades. It remains unclear, however, whether this trend is due to natural variability or increased anthropogenic aerosol loading over South Asia. Here we use stable oxygen isotopes in speleothems from northern India to reconstruct variations in Indian monsoon rainfall over the last two millennia. We find that within the long-term context of our record, the current drying trend is not outside the envelope of monsoon's oscillatory variability, albeit at the lower edge of this variance. Furthermore, the magnitude of multi-decadal oscillatory variability in monsoon rainfall inferred from our proxy record is comparable to model estimates of anthropogenic-forced trends of mean monsoon rainfall in the 21st century under various emission scenarios. Our results suggest that anthropogenic-forced changes in monsoon rainfall will remain difficult to detect against a backdrop of large natural variability.

  4. Relative role of pre-monsoon conditions and intraseasonal oscillations in determining early-vs-late indian monsoon intensity in a GCM

    Science.gov (United States)

    Ghosh, Rohit; Chakraborty, Arindam; Nanjundiah, Ravi S.

    2018-01-01

    The aim of this paper is to identify relative roles of different land-atmospheric conditions, apart from sea surface temperature (SST), in determining early vs. late summer monsoon intensity over India in a high resolution general circulation model (GCM). We find that in its early phase (June-July; JJ), pre-monsoon land-atmospheric processes play major role to modulate the precipitation over Indian region. These effects of pre-monsoon conditions decrease substantially during its later phase (August-September; AS) for which the interannual variation is mainly governed by the low frequency northward propagating intraseasonal oscillations. This intraseasonal variability which is related to mean vertical wind shear has a significant role during the early phase of monsoon as well. Further, using multiple linear regression, we show that interannual variation of early and late monsoon rainfall over India is best explained when all these land-atmospheric parameters are taken together. Our study delineates the relative role of different processes affecting early versus later summer monsoon rainfall over India that can be used for determining its subseasonal predictability.

  5. Transport of sulfonamide antibiotics in crop fields during monsoon season.

    Science.gov (United States)

    Park, Jong Yol; Ruidisch, Marianne; Huwe, Bernd

    2016-11-01

    Previous studies have documented the occurrence of veterinary sulfonamide antibiotics in groundwater and rivers located far from pollution sources, although their transport and fate is relatively unknown. In mountainous agricultural fields, the transport behaviour can be influenced by climate, slope and physico-chemical properties of the sulfonamides. The objective of this research is to describe the transport behaviour of three sulfonamide antibiotics (sulfamethoxazole, sulfadimethoxine and sulfamethazine) in sloped agricultural fields located in the Haean catchment, South Korea. During dry and monsoon seasons, a solute transport experiment was conducted in two typical sandy loam agricultural fields after application of antibiotics and potassium bromide as conservative tracers. Field measurement and modelling revealed that frequency and amount of runoff generation indicate a relation between slope and rain intensity during monsoon season. Since the steepness of slope influenced partitioning of precipitation between runoff and subsurface flow, higher loss of sulfonamide antibiotics and bromide by runoff was observed at the steeper sloped field. Bromide on topsoil rapidly infiltrated at high infiltration rates. On the contrary, the sulfonamides were relatively retarded in the upper soil layer due to adsorption onto soil particles. Presence of furrows and ridges affected the distribution of sulfonamide antibiotics in the subsurface due to gradient from wetter furrows to drier ridges induced by topography. Modelling results with HydroGeoSphere matched with background studies that describe physico-chemical properties of the sulfonamides interaction between soil and the antibiotic group, solute transport through vadose zone and runoff generation by storm events.

  6. Decadal Prediction and Stochastic Simulation of Hydroclimate Over Monsoonal Asia

    Energy Technology Data Exchange (ETDEWEB)

    Ghil, Michael [Univ. of California, Los Angeles, CA (United States); Robertson, Andrew W. [IRI, Chicago, IL (United States); Cook, Edward R. [LDEO Tree Ring Lab., New York, NY (United States); D’Arrigo, Rosanne [LDEO Tree Ring Lab., New York, NY (United States); Lall, Upmanu [Columbia Water Center, New York, NY (United States); Smyth, Padhraic J. [Univ. of California, Irvine, CA (United States)

    2015-01-18

    We developed further our advanced methods of time series analysis and empirical model reduction (EMR) and applied them to climatic time series relevant to hydroclimate over Monsoonal Asia. The EMR methodology was both generalized further and laid on a rigorous mathematical basis via multilayered stochastic models (MSMs). We identified easily testable conditions that imply the existence of a global random attractor for MSMs and allow for non-polynomial predictors. This existence, in turn, guarantees the numerical stability of the MSMs so obtained. We showed that, in the presence of low-frequency variability (LFV), EMR prediction can be improved further by including information from selected times in the system’s past. This prediction method, dubbed Past-Noise Forecasting (PNF), was successfully applied to the Madden-Julian Oscillation (MJO). Our time series analysis and forecasting methods, based on singular-spectrum analysis (SSA) and its enhancements, were applied to several multi-centennial proxy records provided by the Lamont team. These included the Palmer Drought Severity Index (PDSI) for 1300–2005 from the Monsoonal Asia Drought Atlas (MADA), and a 300-member ensemble of pseudo-reconstructions of Indus River discharge for 1702–2005. The latter was shown to exhibit a robust 27-yr low-frequency mode, which helped multi-decadal retroactive forecasts with no look-ahead over this 300-year interval.

  7. Analysis of Vegetation Index Variations and the Asian Monsoon Climate

    Science.gov (United States)

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

    2012-01-01

    Vegetation growth depends on local climate. Significant anthropogenic land cover and land use change activities over Asia have changed vegetation distribution as well. On the other hand, vegetation is one of the important land surface variables that influence the Asian Monsoon variability through controlling atmospheric energy and water vapor conditions. In this presentation, the mean and variations of vegetation index of last decade at regional scale resolution (5km and higher) from MODIS have been analyzed. Results indicate that the vegetation index has been reduced significantly during last decade over fast urbanization areas in east China, such as Yangtze River Delta, where local surface temperatures were increased significantly in term of urban heat Island. The relationship between vegetation Index and climate (surface temperature, precipitation) over a grassland in northern Asia and over a woody savannas in southeast Asia are studied. In supporting Monsoon Asian Integrated Regional Study (MAIRS) program, the data in this study have been integrated into Giovanni, the online visualization and analysis system at NASA GES DISC. Most images in this presentation are generated from Giovanni system.

  8. Recent and possible future variations in the North American Monsoon

    Science.gov (United States)

    Hoell, Andrew; Funk, Chris; Barlow, Mathew; Shukla, Shraddhanand

    2016-01-01

    The dynamics and recent and possible future changes of the June–September rainfall associated with the North American Monsoon (NAM) are reviewed in this chapter. Our analysis as well as previous analyses of the trend in June–September precipitation from 1948 until 2010 indicate significant precipitation increases over New Mexico and the core NAM region, and significant precipitation decreases over southwest Mexico. The trends in June–September precipitation have been forced by anomalous cyclonic circulation centered at 15°N latitude over the eastern Pacific Ocean. The anomalous cyclonic circulation is responsible for changes in the flux of moisture and the divergence of moisture flux within the core NAM region. Future climate projections using the Coupled Model Intercomparison Project Phase 5 (CMIP5) models, as part of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5), support the observed analyses of a later shift in the monsoon season in the presence of increased greenhouse gas concentrations in the atmosphere under the RCP8.5 scenario. The CMIP5 models under the RCP8.5 scenario predict significant NAM-related rainfall decreases during June and July and predict significant NAM-related rainfall increases during September and October.

  9. Hybrid insolation forcing of Pliocene monsoon dynamics in West Africa

    Science.gov (United States)

    Kuechler, Rony R.; Dupont, Lydie M.; Schefuß, Enno

    2018-01-01

    The Pliocene is regarded as a potential analogue for future climate with conditions generally warmer-than-today and higher-than-preindustrial atmospheric CO2 levels. Here we present the first orbitally resolved records of continental hydrology and vegetation changes from West Africa for two Pliocene time intervals (5.0-4.6 Ma, 3.6-3.0 Ma), which we compare with records from the last glacial cycle (Kuechler et al., 2013). Our results indicate that changes in local insolation alone are insufficient to explain the full degree of hydrologic variations. Generally two modes of interacting insolation forcings are observed: during eccentricity maxima, when precession was strong, the West African monsoon was driven by summer insolation; during eccentricity minima, when precession-driven variations in local insolation were minimal, obliquity-driven changes in the summer latitudinal insolation gradient became dominant. This hybrid monsoonal forcing concept explains orbitally controlled tropical climate changes, incorporating the forcing mechanism of latitudinal gradients for the Pliocene, which probably increased in importance during subsequent Northern Hemisphere glaciations.

  10. Hybrid insolation forcing of Pliocene monsoon dynamics in West Africa

    Directory of Open Access Journals (Sweden)

    R. R. Kuechler

    2018-01-01

    Full Text Available The Pliocene is regarded as a potential analogue for future climate with conditions generally warmer-than-today and higher-than-preindustrial atmospheric CO2 levels. Here we present the first orbitally resolved records of continental hydrology and vegetation changes from West Africa for two Pliocene time intervals (5.0–4.6 Ma, 3.6–3.0 Ma, which we compare with records from the last glacial cycle (Kuechler et al., 2013. Our results indicate that changes in local insolation alone are insufficient to explain the full degree of hydrologic variations. Generally two modes of interacting insolation forcings are observed: during eccentricity maxima, when precession was strong, the West African monsoon was driven by summer insolation; during eccentricity minima, when precession-driven variations in local insolation were minimal, obliquity-driven changes in the summer latitudinal insolation gradient became dominant. This hybrid monsoonal forcing concept explains orbitally controlled tropical climate changes, incorporating the forcing mechanism of latitudinal gradients for the Pliocene, which probably increased in importance during subsequent Northern Hemisphere glaciations.

  11. Monsoon signatures in trace gas records from Cape Rama, India

    International Nuclear Information System (INIS)

    Bhattacharya, S.K.; Jani, R.A.; Borole, D.V.; Francey, R.J.; Allison, C.E.; Masarie, K.A.

    2002-01-01

    Concentrations of trace gases CO 2 , CH 4 , CO, N 2 O and H 2 , and the stable carbon and oxygen isotopic composition of CO 2 have been measured in air samples collected from Cape Rama, a coastal station on the west coast of India, since 1993. The data show clear signatures of continental and oceanic air mass resulting in complex seasonal variation of trace gas characteristics. The regional atmospheric circulation in the Indian Ocean and Arabian Sea undergoes biannual reversal in low-level winds associated with the yearly migration of the inter-tropical convergence zone (ITCZ). From June to September, the wind is from the equatorial Indian Ocean to the Indian subcontinent (southwest monsoon) and brings in pristine marine air. From December to February, dry continental winds blow from the northeast and transport continental emissions to the ocean (northeast monsoon). Detailed transport and chemical modelling will be necessary to interpret these records, however the potential to identify and constrain the regional trace gas emissions appears to be high. (author)

  12. ENSO influence on the Asian summer monsoon anticyclone as derived from the satellite observations, reanalysis and model simulations

    Science.gov (United States)

    Yan, Xiaolu; Konopka, Paul; Ploeger, Felix; Tao, Mengchu; Bian, Jianchun; Mueller, Rolf

    2017-04-01

    El Nino and La Nina are opposite phases of El Nino-Southern Oscillation (ENSO). The extremes of ENSO patterns have impacts not only on ocean processes, but also on global weather and climate. The ENSO activities typically show pronounced features in boreal winter time, but some prolonged events may last for months or years. In this study we analyze the influence of ENSO on the atmospheric composition in the tropical and extra-tropical UTLS region in the months following strong ENSO events. In particular, we are interested in the impact of ENSO on the Asian summer monsoon (ASM) anticyclone. Using the Multivariate ENSO Index (MEI), we define two composites starting from strong El Nino and La Nina winters (|MEI|>0.9) and analyze the anomalies caused by them in the following months. To quantify the differences in dynamics, the velocity potential (VP) and the stream function (SF) are calculated based on ERA-Interim reanalysis from 1979 to 2015. SF shows that during winter the horizontal flow in the tropical UTLS is dominated by two equatorially symmetric anticyclones resembling the well-known Matsuno-Gill solution. In summer, the anticyclone in the North Hemisphere is shifted to the ASM region. VP shows that the centers of the divergent part of the flow lie in the West Tropical Pacific and Central Pacific for La Nina and El Nino winters, respectively. These centers move northwestwards during spring and summer. The anticyclone, subtropical jet and the divergent part of the flow after La Nina winters are significantly stronger than after El Nino winters. Based on the MLS measurements of CO, H2O and O3 from 2004 to 2015, we also discuss the respective anomalies at the tropopause level for the El Nino/La Nina composites. EL Nino composite of CO shows higher values in the tropical region not only during winter but also during spring and summer. La Nina composite of H2O shows low anomaly over Maritime Continent which spread over the whole tropics until summer. The H2O

  13. Effects of Land Use on the Predictability of Land-Atmosphere Fluxes and Moisture Transport in the North American Monsoon Region

    Science.gov (United States)

    Bohn, T. J.; Mascaro, G.; White, D. D.; Vivoni, E. R.

    2014-12-01

    Southern Arizona and New Mexico receive 40-60% of their annual rainfall in the summer, as part of the North American Monsoon (NAM). Modeling studies suggest that 15-25% of this rainfall first falls on Mexican land, is transpired by vegetation, and subsequently is transported northward across the border to the US. The main source regions in Mexico include two primary landcover types in Sonora and Sinaloa: subtropical scrub and tropical deciduous forests in the foothills of the Sierra Madre Occidental; and large expanses of irrigated agriculture along the Gulf of California. The foothill ecosystems, known for their rapid greening and large transpiration rates at the onset of the monsoon, are under threat from deforestation for grazing activities. On the other hand, irrigated agriculture in both the winter and summer has shifted the seasonality of evaporative fluxes and introduced socio-economic factors into their interannual variability and predictability. In this study, we examine the differences in spatial and temporal characteristics of evapotranspiration yielded by current and pre-industrial land cover / land use. To this end, we employ the Variable Infiltration Capacity (VIC) land surface model at 1/16 degree resolution, driven by gridded meteorological observations and MODIS LAI, NDVI, and albedo products, across the NAM region (Arizona, New Mexico, and northern Mexico). We compare the magnitude and timing of land-atmosphere fluxes given by both pre-industrial and current land cover/use, as well as the land cover under several possible alternative land use scenarios. We identify the regions where the largest changes in magnitude and timing of evapotranspiration have occurred, as well as the regions and land use changes that could produce the largest changes in future evapotranspiration under different scenarios. Finally, we explore the consequences these effects have for the predictability of monsoon moisture transport.

  14. The interdecadal change of the leading mode of the winter precipitation over China

    Science.gov (United States)

    Ge, Jingwen; Jia, Xiaojing; Lin, Hai

    2016-10-01

    The interdecadal change of the leading mode of the mean winter precipitation over China has been investigated using observational data for the period from 1960 to 2012. The leading empirical orthogonal function (EOF) mode (EOF1) of the winter precipitation over China displays a mono-sign pattern over southeastern China, accounting for 49.7 % of the total variance in the precipitation. Both the El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) can impact EOF1. A positive (negative) EOF1 is accompanied by warm (cold) ENSO events and weak (strong) EAWM, and the latters can cause anomalous southerlies (northerlies) along the coast of southeastern China, accompanied by the transportation of water vapor from the Bay of Bengal and the South China Sea favoring a wet (dry) winter over southeastern China. An abrupt transition of the EOF1 is observed around the mid-1980s. Therefore, the data are divided into two subperiods, i.e., 1960-1987 (P1) and 1988-2009 (P2). Significant differences in the large scale atmospheric circulation and sea surface temperature anomalies associated with EOF1 during these two subperiods are observed. EOF1 is closely related to the mid- to high-latitude atmospheric circulation in P1, while its relationship to the tropics obviously increases during P2. The partial regression analysis results show that the interdecadal change of EOF1 is caused by both the interdecadal changes of the EAWM and ENSO around the mid-1980s. In P1, the lower-level anomalous southerlies along the coastal southeastern China accompanied by water vapor transportation that causes above-average precipitation are related to an anti-cyclonic system centered over the mid-latitude western North Pacific associated with EAWM. In P2, the influence of the EAWM is weaker, and the southerly anomaly over the coastal southeastern China is mainly caused by the anticyclone over Philippines, which is related to the ENSO.

  15. 33 CFR 100.109 - Winter Harbor Lobster Boat Race, Winter Harbor, ME.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Winter Harbor Lobster Boat Race, Winter Harbor, ME. 100.109 Section 100.109 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY REGATTAS AND MARINE PARADES SAFETY OF LIFE ON NAVIGABLE WATERS § 100.109 Winter Harbor...

  16. Competing Atmospheric and Surface-Driven Impacts of Absorbing Aerosols on the East Asian Summer Monsoon

    Science.gov (United States)

    Persad, G.; Paynter, D.; Ming, Y.; Ramaswamy, V.

    2015-12-01

    Absorbing aerosols, by attenuating shortwave radiation within the atmosphere and reemitting it as longwave radiation, redistribute energy both vertically within the surface-atmosphere column and horizontally between polluted and unpolluted regions. East Asia has the largest concentrations of anthropogenic absorbing aerosols globally, and these, along with the region's scattering aerosols, have both reduced the amount of solar radiation reaching the Earth's surface regionally ("solar dimming") and increased shortwave absorption within the atmosphere, particularly during the peak months of the East Asian Summer Monsoon (EASM). We here analyze how atmospheric absorption and surface solar dimming compete in driving the response of EASM circulation to anthropogenic absorbing aerosols, which dominates, and why—issues of particular importance for predicting how the EASM will respond to projected changes in absorbing and scattering aerosol emissions in the future. We probe these questions in a state-of-the-art general circulation model (GCM) using a combination of realistic and idealized aerosol perturbations that allow us to analyze the relative influence of absorbing aerosols' atmospheric and surface-driven impacts on EASM circulation. In combination, our results make clear that, although absorption-driven dimming has a less detrimental effect on EASM circulation than purely scattering-driven dimming, aerosol absorption is still a net impairment to EASM strength when both its atmospheric and surface effects are considered. Because atmospheric heating is not efficiently conveyed to the surface, the surface dimming and associated cooling from even a pure absorber is sufficient to counteract its atmospheric heating, resulting in a net reduction in EASM strength. These findings elevate the current understanding of the impacts of aerosol absorption on the EASM, improving our ability to diagnose EASM responses to current and future regional changes in aerosol emissions.

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

    Directory of Open Access Journals (Sweden)

    C. V. Srinivas

    2015-09-01

    Full Text Available 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

  18. Late Pleistocene-Holocene vegetation and Indian summer monsoon record from the Lahaul, Northwest Himalaya, India

    Science.gov (United States)

    Rawat, Suman; Gupta, Anil K.; Sangode, S. J.; Srivastava, Priyeshu; Nainwal, H. C.

    2015-04-01

    The high resolution Holocene paleomonsoon records from Northwest (NW) Himalaya are limited. The carbon isotope (δ13C), Total organic carbon (TOC) and pollen analysis were therefore carried out from a peat-lake sediment sequence developed in alpine meadows of the Chandra valley, Lahaul, NW Himalaya, in order to reconstruct centennial to millennial scale vegetational changes and Indian summer monsoon (ISM) variability during the Holocene. The chronology of peat-lake sediments is constrained with 9 AMS 14C dates. The recovered non-arboreal pollen (NAP) suggested that during Holocene alpine desert-steppe, meadows and shrubs growing along the stream had developed in the Lahaul valley whereas arboreal pollens (AP) e.g. Pinus, Quercus, Cedrus and Ulmus presently growing in the southern hill slopes of Pir Panjal range indicated moisture carrying monsoonal air flow from the South. The increased δ13C and low TOC values between ∼12,880 and 11,640 calibrated years before present (cal yr BP) suggested weakening of ISM and low organic carbon production corresponding to the Younger Dryas (YD) cold event. The gradual depletion in carbon isotope ratio from ∼11,640 to 8810 cal yr BP indicated enhanced precipitation in the Chandra valley in response of increased ISM strength in early Holocene. The short spell of cold and dry climate with gradual decrease in ISM intensity between ca 10,398 and 9778 cal yr BP is closely linked with Bond event-7. The other prominent cold-dry events recorded in present study are (i) ∼8810 to 8117 cal yr BP roughly corresponding to global 8.2 ka cold event, (ii) ∼4808 to 4327 cal yr BP closely preceding the global 4.2 ka cold-arid period, and (iii) ∼1303 to 1609 cal AD corresponding to Little Ice Age (LIA) event. The expansion of thermophillous broad leaved taxa viz. Betula utilis, Alnus nepalensis, Quercus semicarpifolia and Juglans regia and effective growth of meadow vegetation such as grasses, Caryophyllaceae and Artemisia along with

  19. 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

  20. Animals in Winter. Young Discovery Library Series.

    Science.gov (United States)

    de Sairigne, Catherine

    This book is written for children 5 through 10. Part of a series designed to develop their curiosity, fascinate them and educate them, this volume introduces the habits of a variety of animals during the winter. Topics include: (1) surviving during winter, including concepts such as migration, hibernation, and skin color change; (2) changing…

  1. How to Have a Healthy Winter | Poster

    Science.gov (United States)

    Without a doubt, winter is here. Between the icy weather and the recent hustle and bustle of the holidays, everyone is at an increased risk of getting sick. With that in mind, Occupational Health Services has a few simple tips for staying healthy this winter.

  2. Belichten Zantedeschia in winter biedt perspectief

    NARCIS (Netherlands)

    Leeuwen, van P.J.; Trompert, J.P.T.

    2011-01-01

    Zantedeschia produceert in de Nederlandse winter geen bloemen. In de praktijk wordt met assimilatiebelichting wel bloei in de winter verkregen met de cultivar 'Crystal Blush'. Onderzoek door PPO laat zien welke hoeveelheid licht nodig is en dat ook gekleurde Zantedeschia's van een goede kwaliteit

  3. Nuclear Winter: Scientists in the Political Arena

    Science.gov (United States)

    Badash, Lawrence

    2001-03-01

    The nuclear winter phenomenon is used to illustrate the many paths by which scientific advice reaches decision makers in the United States government. Because the Reagan administration was hostile to the strategic policy that the scientific discovery seemed to demand, the leading proponent of nuclear winter, Carl Sagan, used his formidable talent for popularization to reach a larger audience.

  4. 43 CFR 423.37 - Winter activities.

    Science.gov (United States)

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Winter activities. 423.37 Section 423.37 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE....37 Winter activities. (a) You must not tow persons on skis, sleds, or other sliding devices with a...

  5. 36 CFR 1002.19 - Winter activities.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Winter activities. 1002.19... RECREATION § 1002.19 Winter activities. (a) Skiing, snowshoeing, ice skating, sledding, innertubing.... (c) Failure to abide by area designations or activity restrictions established under this section is...

  6. 36 CFR 2.19 - Winter activities.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Winter activities. 2.19... RESOURCE PROTECTION, PUBLIC USE AND RECREATION § 2.19 Winter activities. (a) Skiing, snowshoeing, ice... designations or activity restrictions established under this section is prohibited. ...

  7. Chapter 7: Migration and winter ecology

    Science.gov (United States)

    Deborah M. Finch; Jeffrey F. Kelly; Jean-Luc E. Cartron

    2000-01-01

    The willow flycatcher (Empidonax traillii) is a Neotropical migrant that breeds in North America, but winters in Central and northern South America. Little specific information is known about migration and wintering ecology of the southwestern willow flycatcher (E. t. extimus) (Yong and Finch 1997). Our report applies principally...

  8. Interim Report 'Winter smog and traffic'.

    NARCIS (Netherlands)

    Bloemen, H.; Blom, T.; Bogaard, van den C.; Boluyt, N.; Bree, van L.; Brunekreef, B.; Hoek, G.; Zee, van der S.

    1994-01-01

    This report presents a halfway score of the research project "Winter smog and Traffic", one of the themes of the research programme "Air Pollution and Health". A state of the art is presented of the health effects associated with exposure to winter smog and of the toxicological effects caused by the

  9. [Effects of irrigation mode on winter wheat yield and water- and nutrient use efficiencies under maize straw returning to field].

    Science.gov (United States)

    Dang, Jian-you; Pei, Xue-xia; Zhang, Jing; Wang, Jiao-ai; Cao, Yong; Zhang, Ding-yi

    2011-10-01

    In 2008-2010, a field experiment was conducted to study the effects of different irrigation modes on the grain yield, dry matter translocation, water use efficiency (WUE), and nutrient use efficiency (NUE) of winter wheat under maize straw returning to the field in a semi-arid and semi-humid monsoon region of Linfen, Shanxi Province of Northwest China. Irrigation at wintering time promoted tillering, irrigation at jointing stage increased the total tiller number and the fertile spike rate per tiller, whereas irrigation at booting stage promoted the dry matter accumulation in spike and increased the 1000-kernel mass. When the irrigation was implemented at two growth stages and the second irrigation time was postponed, both the dry matter translocation to leaf and the kernels per spike increased. Irrigation twice throughout the whole growth season induced a higher NUE and higher dry matter accumulation in spike, as compared to irrigation once. The irrigation amount at wintering time and the total irrigation amount had lesser effects on the tillering and the dry matter accumulation in spike. Increasing irrigation amount at jointing stage or booting stage more benefited the nutrient uptake, dry matter accumulation and translocation, and grain WUE, which in turn made the yield-formation factors be more balance and the grain yield be higher. It was concluded that to guarantee the irrigation amount at wintering time could achieve stabilized yield, and the optimal irrigation mode was irrigation at wintering time plus an additional irrigation at jointing stage (900 m3 hm(-2)), which could satisfy the water demand of winter wheat at its mid and later growth stage and increase the WUE of grain, and realize water-saving and high-yielding cultivation.

  10. Change in the relationship between the Australian summer monsoon circulation and boreal summer precipitation over Central China in the late 1990s

    Science.gov (United States)

    Yang, Ruowen; Wang, Jian; Zhang, Tianyu; He, Shengping

    2017-09-01

    Recent study revealed a close connection between the Australian summer monsoon (ASM) and boreal summer precipitation over Central China (SPCC). This study further revealed a strengthening of the ASM-SPCC relationship around the late 1990s. It is found that the relationship between the ASM and the SPCC during 1979-1997 (1998-2014) relationship is statistically insignificant (significant). Further analysis indicated that during 1998-2014, the weakened ASM is concurrent with significant positive sea surface temperature (SST) in the Indian Ocean and South China Sea, which could persist into the following boreal summer and further lead to intensified East Asian summer monsoon, strengthened western North Pacific subtropical high, and anomalous ascending motion over Central China. Consequently, more moisture is transported from the western Pacific northward to Central China where significant anomalous convergence appears. Therefore, the ASM could potentially influence the SPCC during 1998-2014. By contrast, the ASM-related SST and atmospheric circulation anomalies in boreal winter are statistically insignificant during 1979-1997. Such an interdecadal change might be attributed to the interdecadal warming that occurred in the Indian Ocean and South China Sea around the late 1990s. This study might be useful for the prediction of the SPCC.

  11. Aluminium toxicity in winter wheat

    Directory of Open Access Journals (Sweden)

    Szabó A.

    2015-01-01

    Full Text Available Aluminium is the most frequent metal of the earth crust; it occurs mainly as biologically inactive, insoluble deposit. Environmental problems, industrial contaminations and acid rains increase the soil acidity, leading to the mobilization of Al. Half of the world’s potential arable lands are acidic; therefore, Al-toxicity decreases crop productivity. Wheat is a staple food for 35% of the world population. The effects of Al-stress (0.1 mM were studied on winter wheat; seedlings were grown hydroponically, at acidic pH. After two weeks, the root weight was decreased; a significant difference was found in the P- and Ca-content. The shoot weight and element content changed slightly; Al-content in the root was one magnitude higher than in the shoot, while Al-translocation was limited. The root plasma membrane H+-ATPase has central role in the uptake processes; Al-stress increased the Mg2+-ATPase activity of the microsomal fraction.

  12. Aerosols cause intraseasonal short-term suppression of Indian monsoon rainfall.

    Science.gov (United States)

    Dave, Prashant; Bhushan, Mani; Venkataraman, Chandra

    2017-12-11

    Aerosol abundance over South Asia during the summer monsoon season, includes dust and sea-salt, as well as, anthropogenic pollution particles. Using observations during 2000-2009, here we uncover repeated short-term rainfall suppression caused by coincident aerosols, acting through atmospheric stabilization, reduction in convection and increased moisture divergence, leading to the aggravation of monsoon break conditions. In high aerosol-low rainfall regions extending across India, both in deficient and normal monsoon years, enhancements in aerosols levels, estimated as aerosol optical depth and absorbing aerosol index, acted to suppress daily rainfall anomaly, several times in a season, with lags of a few days. A higher frequency of prolonged rainfall breaks, longer than seven days, occurred in these regions. Previous studies point to monsoon rainfall weakening linked to an asymmetric inter-hemispheric energy balance change attributed to aerosols, and short-term rainfall enhancement from radiative effects of aerosols. In contrast, this study uncovers intraseasonal short-term rainfall suppression, from coincident aerosol forcing over the monsoon region, leading to aggravation of monsoon break spells. Prolonged and intense breaks in the monsoon in India are associated with rainfall deficits, which have been linked to reduced food grain production in the latter half of the twentieth century.

  13. Leaf unfolding of Tibetan alpine meadows captures the arrival of monsoon rainfall.

    Science.gov (United States)

    Li, Ruicheng; Luo, Tianxiang; Mölg, Thomas; Zhao, Jingxue; Li, Xiang; Cui, Xiaoyong; Du, Mingyuan; Tang, Yanhong

    2016-02-09

    The alpine meadow on the Tibetan Plateau is the highest and largest pasture in the world, and its formation and distribution are mainly controlled by Indian summer monsoon effects. However, little is known about how monsoon-related cues may trigger spring phenology of the vast alpine vegetation. Based on the 7-year observations with fenced and transplanted experiments across lower to upper limits of Kobresia meadows in the central plateau (4400-5200 m), we found that leaf unfolding dates of dominant sedge and grass species synchronized with monsoon onset, regardless of air temperature. We also found similar patterns in a 22-year data set from the northeast plateau. In the monsoon-related cues for leaf unfolding, the arrival of monsoon rainfall is crucial, while seasonal air temperatures are already continuously above 0 °C. In contrast, the early-emerging cushion species generally leafed out earlier in warmer years regardless of precipitation. Our data provide evidence that leaf unfolding of dominant species in the alpine meadows senses the arrival of monsoon-season rainfall. These findings also provide a basis for interpreting the spatially variable greening responses to warming detected in the world's highest pasture, and suggest a phenological strategy for avoiding damages of pre-monsoon drought and frost to alpine plants.

  14. Predicting summer monsoon of Bhutan based on SST and teleconnection indices

    Science.gov (United States)

    Dorji, Singay; Herath, Srikantha; Mishra, Binaya Kumar; Chophel, Ugyen

    2018-02-01

    The paper uses a statistical method of predicting summer monsoon over Bhutan using the ocean-atmospheric circulation variables of sea surface temperature (SST), mean sea-level pressure (MSLP), and selected teleconnection indices. The predictors are selected based on the correlation. They are the SST and MSLP of the Bay of Bengal and the Arabian Sea and the MSLP of Bangladesh and northeast India. The Northern Hemisphere teleconnections of East Atlantic Pattern (EA), West Pacific Pattern (WP), Pacific/North American Pattern, and East Atlantic/West Russia Pattern (EA/WR). The rainfall station data are grouped into two regions with principal components analysis and Ward's hierarchical clustering algorithm. A support vector machine for regression model is proposed to predict the monsoon. The model shows improved skills over traditional linear regression. The model was able to predict the summer monsoon for the test data from 2011 to 2015 with a total monthly root mean squared error of 112 mm for region A and 33 mm for region B. Model could also forecast the 2016 monsoon of the South Asia Monsoon Outlook of World Meteorological Organization (WMO) for Bhutan. The reliance on agriculture and hydropower economy makes the prediction of summer monsoon highly valuable information for farmers and various other sectors. The proposed method can predict summer monsoon for operational forecasting.

  15. 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.

  16. Initial results from the StratoClim aircraft campaign in the Asian Monsoon in summer 2017

    Science.gov (United States)

    Rex, M.

    2017-12-01

    The Asian Monsoon System is one of the Earth's largest and most energetic weather systems. Monsoon rainfall is critical to feeding over a billion people in Asia and the monsoon circulation affects weather patterns over the entire northern hemisphere. The Monsoon also acts like an enormous elevator, pumping vast amounts of air and pollutants from the surface up to the tropopause region at levels above 16km altitude, from where air can ascend into the stratosphere, where it spreads globally. Thus the monsoon affects the chemical composition of the global tropopause region and the stratosphere, and hence plays a key role for the composition of the UTS. Dynamically the monsoon circulation leads to the formation of a large anticyclone at tropopause levels above South Asia - the Asian Monsoon Anticyclone (AMA). Satellite images show a large cloud of aerosols directly above the monsoon, the Asian Tropopause Aerosol Layer (ATAL). In July to August 2017 the international research project StratoClim carried out the first in-situ aircraft measurements in the AMA and the ATAL with the high altitude research aircraft M55-Geophysica. Around 8 scientific flights took place in the airspaces of Nepal, India and Bangladesh and have horizontally and vertically probed the AMA and have well characterized the ATAL along flight patterns that have been carefully designed by a theory, modelling and satellite data analysing team in the field. The aircraft campaign has been complemented by launches of research balloons from ground stations in Nepal, Bangladesh, China and Palau. The presentation will give an overview of the StratoClim project, the aircraft and balloon activities and initial results from the StratoClim Asian Monsoon campaign in summer 2017.

  17. Toward a 530,000-year Hydroclimate History for the Southern Half of the Australasian Monsoon

    Science.gov (United States)

    Gagan, M. K.; Scroxton, N. G.; Kimbrough, A. K.; Krause, C.; Hantoro, W. S.; Ayliffe, L. K.; Dunbar, G. B.; Cheng, H.; Edwards, R. L.; Hellstrom, J. C.; Shen, C. C.; Scott-Gagan, H.; Suwargadi, B. W.; Rifai, H.

    2015-12-01

    Speleothem 18O/16O records have revealed key aspects of past hydroclimates in the northern Australasian monsoon domain on orbital to millennial scales, but much less is known about the southern half of the monsoon system. We aim to develop a hydroclimate history for the southern Australasian monsoon based on speleothems from southwest Sulawesi and Flores, Indonesia (latitudes 5-9oS), which extend back to ~530 kyr BP and 90 kyr BP, respectively. To date, the 18O/16O record for Sulawesi covers glacial terminations TIV (~340 kyr BP), TIII (~245 kyr BP) and TI (~18 kyr BP). The details of each termination are different, however two important hydroclimate patterns are emerging. First, the 18O/16O record shows sharp weakening of the monsoon immediately before each termination. This surprisingly robust pattern marks a southern extension of the northern 'weak monsoon interval', and reinforces the idea that southward monsoon displacement is a fundamental feature of terminations. Second, monsoon intensification around Sulawesi lags the rise in atmospheric CO2 and Antarctic temperature by several thousand years, but parallels the 18O/16O decrease in atmospheric O2. Our finding extends that of Wang et al. (2008) and Cheng et al. (2009) who noted the influence of the low-latitude hydrological cycle on the 18O/16O of tropical transpiration, and its potential for correlating ice core and paleomonsoon records. Further south, the 90-kyr 18O/16O record for Flores shows clear precession-scale antiphasing with China, and southerly positioning of the summer monsoon rainfall belt during Heinrich stadials. Heinrich stadials 5, 4, 2 and 1 occur during wetter intervals in Flores that accompanied relatively high southern summer insolation. Intriguingly, these events are associated with abrupt atmospheric CH4 signals that may be due to increased Southern Hemisphere CH4 production related to intensification of monsoon rainfall over southern tropical land areas (Rhodes et al., 2014).

  18. 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

  19. Black Carbon and West African Monsoon precipitation: observations and simulations

    Directory of Open Access Journals (Sweden)

    J. Huang

    2009-11-01

    Full Text Available We have recently investigated large-scale co-variability between aerosol and precipitation and other meteorological variables in the West African Monsoon (WAM region using long term satellite observations and reanalysis data. In this study we compared the observational results to a global model simulation including only direct radiative forcing of black carbon (BC. From both observations and model simulations we found that in boreal cold seasons anomalously high African aerosols are associated with significant reductions in cloud amount, cloud top height, and surface precipitation. These results suggest that the observed precipitation reduction in the WAM region is caused by radiative effect of BC. The result also suggests that the BC effect on precipitation is nonlinear.

  20. Black carbon and West African Monsoon precipitation. Observations and simulations

    International Nuclear Information System (INIS)

    Huang, J.; Adams, A.; Zhang, C.; Wang, C.

    2009-01-01

    We have recently investigated large-scale co-variability between aerosol and precipitation and other meteorological variables in the West African Monsoon (WAM) region using long term satellite observations and reanalysis data. In this study we compared the observational results to a global model simulation including only direct radiative forcing of black carbon (BC). From both observations and model simulations we found that in boreal cold seasons anomalously high African aerosols are associated with significant reductions in cloud amount, cloud top height, and surface precipitation. These results suggest that the observed precipitation reduction in the WAM region is caused by radiative effect of BC. The result also suggests that the BC effect on precipitation is nonlinear. (orig.)

  1. Sensitivity studies on the impacts of Tibetan Plateau snowpack pollution on the Asian hydrological cycle and monsoon climate

    Science.gov (United States)

    Qian, Y.; Flanner, M.; Leung, R.; Wang, W.

    2012-04-01

    The Tibetan Plateau (TP) has long been identified to be critical in regulating the Asian monsoon climate and hydrological cycle. In this modeling study a series of numerical experiments with a global climate model are designed to simulate radiative effect of black carbon (BC) and dust in snow, and to assess the relative impacts of anthropogenic CO2 and carbonaceous particles in the atmosphere and snow on the snowpack over the TP and subsequent impacts on the Asian monsoon climate and hydrological cycle. Simulations results show a large BC content in snow over the TP, especially the southern slope. Because of the high aerosol content in snow and large incident solar radiation in the low latitude and high elevation, the TP exhibits the largest surface radiative flux changes induced by aerosols (e.g. BC, Dust) in snow compared to any other snow-covered regions in the world. Simulation results show that the aerosol-induced snow albedo perturbations generate surface radiative flux changes of 5-25 W m-2 during spring, with a maximum in April or May. BC-in-snow increases the surface air temperature by around 1.0oC averaged over the TP and reduces spring snowpack over the TP more than pre-industrial to present CO2 increase and carbonaceous particles in the atmosphere. As a result, runoff increases during late winter and early spring but decreases during late spring and early summer (i.e. a trend toward earlier melt dates). The snowmelt efficacy, defined as the snowpack reduction per unit degree of warming induced by the forcing agent, is 1-4 times larger for BC-in-snow than CO2 increase during April-July, indicating that BC-in-snow more efficiently accelerates snowmelt because the increased net solar radiation induced by reduced albedo melts the snow more efficiently than snow melt due to warming in the air. The TP also influences the South (SAM) and East (EAM) Asian monsoon through its dynamical and thermal forcing. Simulation results show that during boreal spring

  2. Sensitivity studies on the impacts of Tibetan Plateau snowpack pollution on the Asian hydrological cycle and monsoon climate

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Yun; Flanner, M G; Leung, Lai-Yung R; Wang, Weiguo

    2011-03-02

    The Tibetan Plateau (TP), the highest and largest plateau in the world, has long been identified to be critical in regulating the Asian monsoon climate and hydrological cycle. The snowpack and glaciers over the TP provide fresh water to billions of people in Asian countries, but the TP glaciers have been retreating extensively at a speed faster than any other part of the world. In this study a series of experiments with a global climate model are designed to simulate black carbon (BC) and dust in snow and their radiative forcing and to assess the relative impacts of anthropogenic CO2 and carbonaceous particles in the atmosphere and snow, respectively, on the snowpack over the TP, as well as their subsequent impacts on the Asian monsoon climate and hydrological cycle. Results show a large BC content in snow over the TP, especially the southern slope, with concentration larger than 100 µk/kg. Because of the high aerosol content in snow and large incident solar radiation in the low latitude and high elevation, the TP exhibits the largest surface radiative forcing induced by aerosols (e.g. BC, Dust) in snow compared to other snow-covered regions in the world. The aerosol-induced snow albedo perturbations generate surface radiative forcing of 5-25 W m-2 during spring, with a maximum in April or May. BC-in-snow increases the surface air temperature by around 1.0°C averaged over the TP and reduces snowpack over the TP more than that induced by pre-industrial to present CO2 increase and carbonaceous particles in the atmosphere during spring. As a result, runoff increases during late winter and early spring but decreases during late spring and early summer (i.e. a trend toward earlier melt dates). The snowmelt efficacy, defined as the snowpack reduction per unit degree of warming induced by the forcing agent, is 1-4 times larger for BC-in-snow than CO2 increase during April-July, indicating that BC-in-snow more efficiently

  3. Large-Scale Control of the Arabian Sea Summer Monsoon Inversion and Low Clouds: A New Perspective

    Science.gov (United States)

    Wu, C. H.; Wang, S. Y.; Hsu, H. H.; Hsu, P. C.

    2016-12-01

    The Arabian Sea undergoes a so-called summer monsoon inversion that reaches the maximum intensity in August associated with a large amount of low-level clouds. The formation of inversion and low clouds was generally thought to be a local system influenced by the India-Pakistan monsoon advancement. New empirical and numerical evidence suggests that, rather than being a mere byproduct of the nearby monsoon, the Arabian Sea monsoon inversion is coupled with a broad-scale monsoon evolution connected across the Africa Sahel, South Asia, and the East Asia-western North Pacific (WNP). Several subseasonal variations occur in tandem: The eastward expansion of the Asian-Pacific monsoonal heating likely suppresses the India-Pakistan monsoon while enhancing low-level thermal inversion of Arabian Sea; the upper-tropospheric anticyclone in South Asia weakens in August smoothing zonal contrast in geopotential heights (10°N-30°N); the subtropical WNP monsoon trough in the lower troposphere that signals the revival of East Asian summer monsoon matures in August; the Sahel rainfall peaks in August accompanied by an intensified tropical easterly jet. The occurrence of the latter two processes enhances upper-level anticyclones over Africa and WNP and this, in turn, induces subsidence in between over the Arabian Sea. Numerical experiments demonstrate the combined effect of the African and WNP monsoonal heating on the enhancement of the Arabian Sea monsoon inversion. Connection is further found in the interannual and decadal variations between the East Asian-WNP monsoon and the Arabian Sea monsoon inversion. In years with reduced low clouds of Arabian Sea, the East Asian midlatitude jet stream remains strong in August while the WNP monsoon trough appears to be weakened. The Arabian Sea inversion (ridge) and WNP trough pattern which forms a dipole structure, is also found to have intensified since the 21st century.

  4. 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

  5. Intra- and inter-seasonal variability of nutrients in a tropical monsoonal estuary (Zuari, India).

    Digital Repository Service at National Institute of Oceanography (India)

    Anand, S.S.; Sardessai, S.; Muthukumar, C.; Mangalaa, K.R.; Sundar, D.; Parab, S.G.; DileepKumar, M.

    monsoon (June to September) that leads to peak river discharges (Shetye et al., 2007) and hence these rivers are referred as monsoon rivers. Monsoonal estuaries are highly unique in that they do not reach steady state at any time unlike the temperate...). This period recorded the highest salinity (34.2) in the estuary with the maximal seasonal mean of 29.9±3.1 in the year (Table 4). A gradual increase in temperature was found until May in which it was nearly steady. Although some wavy pattern could be seen...

  6. Origins and interrelationship of Intraseasonal rainfall variations around the Maritime Continent during boreal winter

    Science.gov (United States)

    Cao, Xi; Wu, Renguang

    2018-04-01

    Large intraseasonal rainfall variations are identified over the southern South China Sea (SSCS), tropical southeastern Indian Ocean (SEIO), and east coast of the Philippines (EPHI) in boreal winter. The present study contrasts origins and propagations and investigates interrelations of intraseasonal rainfall variations on the 10-20- and 30-60-day time scales in these regions. Different origins are identified for intraseasonal rainfall anomalies over the SSCS, SEIO, and EPHI on both time scales. On the 10-20-day time scale, strong northerly or northeasterly wind anomalies related to the East Asian winter monsoon (EAWM) play a major role in intraseasonal rainfall variations over the SSCS and EPHI. On the 30-60-day time scale, both the intraseasonal signal from the tropical Indian Ocean and the EAWM-related wind anomalies contribute to intraseasonal rainfall variations over the SSCS, whereas the EAWM-related wind anomalies have a major contribution to the intraseasonal rainfall variations over the EPHI. No relation is detected between the intraseasonal rainfall variations over the SEIO and the EAWM on both the 10-20-day and 30-60-day time scales. The anomalies associated with intraseasonal rainfall variations over the SSCS and EPHI propagate northwestward and northeastward, respectively, on the 10-20- and 30-60-day time scales. The intraseasonal rainfall anomalies display northwestward and northward propagation over the Bay of Bengal, respectively, on the 10-20- and 30-60-day time scales.

  7. Seasonal prediction of summer monsoon rainfall over cluster ...

    Indian Academy of Sciences (India)

    is defined as the algebraic difference between monthly indices of NAO and SO. The anomalies from the annual mean have been calculated for each month and these anomaly series are then divided by the standard deviation. These series are called as ESI series of respective month. ESI-tendency from winter to spring is ...

  8. Transport pathways of CO in the African upper troposphere during the monsoon season: a study based upon the assimilation of spaceborne observations

    Directory of Open Access Journals (Sweden)

    B. Barret

    2008-06-01

    Full Text Available The transport pathways of carbon monoxide (CO in the African Upper Troposphere (UT during the West African Monsoon (WAM is investigated through the assimilation of CO observations by the Aura Microwave Limb Sounder (MLS in the MOCAGE Chemistry Transport Model (CTM. The assimilation setup, based on a 3-D First Guess at Assimilation Time (3-D-FGAT variational method is described. Comparisons between the assimilated CO fields and in situ airborne observations from the MOZAIC program between Europe and both Southern Africa and Southeast Asia show an overall good agreement around the lowermost pressure level sampled by MLS (~215 hPa. The 4-D assimilated fields averaged over the month of July 2006 have been used to determine the main dynamical processes responsible for the transport of CO in the African UT. The studied period corresponds to the second AMMA (African Monsoon Multidisciplinary Analyses aircraft campaign. At 220 hPa, the CO distribution is characterized by a latitudinal maximum around 5° N mostly driven by convective uplift of air masses impacted by biomass burning from Southern Africa, uplifted within the WAM region and vented predominantly southward by the upper branch of the winter hemisphere Hadley cell. Above 150 hPa, the African CO distribution is characterized by a broad maximum over northern Africa. This maximum is mostly controlled by the large scale UT circulation driven by the Asian Summer Monsoon (ASM and characterized by the Asian Monsoon Anticyclone (AMA centered at 30° N and the Tropical Easterly Jet (TEJ on the southern flank of the anticyclone. Asian pollution uplifted to the UT over large region of Southeast Asia is trapped within the AMA and transported by the anticyclonic circulation over Northeast Africa. South of the AMA, the TEJ is responsible for the tranport of CO-enriched air masses from India and Southeast Asia over Africa. Using the high time resolution provided by the 4-D assimilated fields, we give evidence

  9. Reconstruction of East Asian Monsoon variability 6.5ka-present using organic and inorganic geochemical proxies in the Pearl River Estuary, China

    Science.gov (United States)

    Strong, David; Yu, Fengling; Pancost, Richard; Flecker, Rachel; Valdes, Paul; Wilkinson, Ian; Rees, John; Leng, Melanie; Lloyd, Jeremy; Garrett, Edmund

    2010-05-01

    The East Asian Monsoon (EAM) is one of the most significant contributors, both environmentally and socioeconomically, to the densely-populated East Asia region in which over one third of the world's population reside. Additionally, the EAM is a key system in global atmospheric circulation. Thus, understanding past changes in the EAM is of pivotal importance for assessing the impact of future climate change. Previous EAM reconstructions have mainly focused on lake and cave records. However, these records record a small, regional-scale signal of paleoprecipitation and are thus susceptible to local responses and might not record continental-scale climate. Multiproxy studies from marginal marine systems such as estuaries and semi-enclosed seas have shown great potential to reconstruct past variability in the climate system, particularly aspects of the hydrological cycle and temperature, on a continental scale. The Pearl River was chosen for this study as it possesses a large (400,000km2) drainage basin. The latitudinal orientation of the basin between the tropics and subtropics (22° to 26° N), its susceptibility to both summer (humid) and winter (dry) monsoon winds, and its location within the modern summer Inter-Tropical Convergence Zone (ITCZ) area make the basin very sensitive to variability in the EAM system. Here we present results for a suite of inorganic geochemical proxies for paleosalinity (such as foraminiferal oxygen isotope ratios, δ18O) and organic geochemical proxies for fluvial sediment flux (such as the concentration ratio of terrestrial to marine biomarkers), testing both modern (spatial) and Holocene (temporal) variability. The anticipated spatial variability of inorganic and organic proxies is observed, with terrestrial signals dominating in the upper estuary but becoming weaker towards the open sea; however, some proxies appear to record this transition with greater fidelity than others, with the n-alcohol-based proxy being the strongest and

  10. The oceanography of winter leads

    Science.gov (United States)

    Morison, J. H.; McPhee, M. G.; Curtin, T. B.; Paulson, C. A.

    1992-07-01

    Leads in pack ice have long been considered important to the thermodynamics of the polar regions. A winter lead affects the ocean around it because it is a density source. As the surface freezes, salt is rejected and forms more dense water which sinks under the lead. This sets up a circulation with freshwater flowing in from the sides near the surface and dense water flowing away from the lead at the base of the mixed layer. If the mixed layer is fully turbulent, this pattern may not occur; rather, the salt rejected at the surface may simply mix into the surface boundary layer. In either event the instability produced at the surface of leads is the primary source of unstable buoyancy flux and, as such, exerts a strong influence on the mixed layer. Here as many as possible of the disparate and almost anecdotal observations of lead oceanography are assembled and combined with theoretical arguments to predict the form and scale of oceanographic disturbances caused by winter leads. The experimental data suggest the velocity disturbances associated with lead convection are about 1-5 cm s-1. These appear as jets near the surface and the base of the mixed layer when ice velocities across the lead are less than about 5 cm s-1. The salinity disturbances are about 0.01 to 0.05 psu. Scaling arguments suggest that the geostrophic currents set up by the lead density disturbances are also of the order of 1-5 cm s-1. The disturbances are most obvious when freezing is rapid and ice velocity is low because the salinity and velocity disturbances in the upper ocean are not smeared out by turbulence. In this vein, lead convection may be characterized at one extreme as free convection in which the density disturbance forces the circulation. At the other extreme, lead convection may be characterized as forced convection in which the density disturbance is mixed rapidly by boundary layer turbulence. The lead number Lo, which is the ratio of the pressure term to the turbulence term in the

  11. Half a Century of Schladming Winter Schools

    International Nuclear Information System (INIS)

    Pietschmann, H.

    2012-01-01

    The Schladming Winter Schools have started as early as in 1962. Over the times the yearly Schools have closely followed the actual developments in nuclear, particle, or more generally, in theoretical physics. Several new achievements have first been dealt with in length in the lectures at the Schladming Winter School. It has seen very prominent lecturers, among them a series of Nobel laureates (some of them reporting on their works even before they got their Nobel prizes). I will try to highlight the role of the Schladming Winter Schools in pro- mulgating new developments of theoretical physics in depth at the lectures given over the past 50 years. (author)

  12. The relationship between the Sahelian and previous 2nd Guinean rainy seasons: a monsoon regulation by soil wetness?

    Directory of Open Access Journals (Sweden)

    N. Philippon

    2002-04-01

    Full Text Available The correlation of 0.61 found between observed July–September Sahelian rainfall in year 0 and September–November Guinean rainfall in year - 1, led us to explore the statistical relationships between precipitation, soil moisture and near surface Moist Static Energy (MSE gradients in West Africa. These analyses were performed over successive 30-year periods and specifically, the most recent period between 1968–1998. It is shown from observations, National Centers for Environmental Predictions and National Center for Atmospheric Research (NCEP/NCAR reanalyses and from the Global Soil Wetness Project (GSWP database, that wet Sahelian rainy seasons are preceded by abnormally wet soils over the Sudan-Guinean belt during northern winter. Such moisture anomalies tend to hold during the dry season, then generate increasing MSE gradients just above the continent by March–April. These gradients have been shown to be of prime importance for monsoon dynamics and associated rainfall.Key words. Hydrology (soil moisture – Meteorology and atmospheric dynamics (climatology

  13. 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.

  14. Unusial winter 2011/2012 in Slovakia

    Czech Academy of Sciences Publication Activity Database

    Faško, P.; Lapin, M.; Matejovič, P.; Pecho, Jozef

    2012-01-01

    Roč. 15, č. 1 (2012), s. 19-26 ISSN 1335-339X Institutional support: RVO:68378289 Keywords : winter characteristics * climate variabilit * climate change * global warming Subject RIV: DG - Athmosphere Sciences, Meteorology

  15. Habitat characteristics of wintering Wood Warbler Phylloscopus ...

    African Journals Online (AJOL)

    Habitat characteristics of wintering Wood Warbler Phylloscopus sibilatrix in the Centre Region of Cameroon: conservation implications. Taku Awa II, Tsi A Evaristus, Robin C Whytock, Tsetagho Guilain, John Mallord ...

  16. VT Mean Winter Precipitation - 1971-2000

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) ClimatePrecip_PRECIPW7100 includes mean winter precipitation data (October through March) for Vermont (1971-2000). It's a raster dataset derived...

  17. Overview of climatic effects of nuclear winter

    International Nuclear Information System (INIS)

    Jones, E.M.; Malone, R.C.

    1985-01-01

    A general description of the climatic effects of a nuclear war are presented. This paper offers a short history of the subject, a discussion of relevant parameters and physical processes, and a description of plausible nuclear winter scenario. 9 refs

  18. Geochemical evidence on the source regions of Tibetan Plateau dusts during non-monsoon period in 2008/09

    Science.gov (United States)

    Li, C.; Kang, S.; Zhang, Q.; Gao, S.

    2012-12-01

    Geochemical characteristics, source regions and related transport patterns of dust over the Tibetan Plateau (TP) are still unclear. To address these issues, major (Na, Mg, Al, K and Ca), trace (e.g. Li, Cr, Ni, As, Cd, Cs, Pb and U) and rare earth elements of dust samples from five snow-pits over the TP and its fringe areas during the non-monsoon period in 2008/2009 were analyzed. The results indicate that rare earth element compositions of snow-pit dust are similar to those of the upper continental crust. Enrichment factors of all the elements of snow-pit dust are identical to those of the pollution elements (e.g. Cu and Ni) and elements like Li, As and Cs that are concentrated in surface soils. In contrast, concentrations of some typical pollution elements (e.g. Cr and Cd) of snow pit dust are lower than those of dusts derived from the Sahara Desert and the Thar Desert surrounding the TP. Additionally, the compositions of rare earth elements and high field strength elements (Hf, Zr and Nb) of snow-pit dust are also similar to those of surface soils and different from dusts of these two deserts. The combined evidence, including dust transport patterns around the TP, supports the conclusion that the TP itself is the main source region of snow-pit dusts of the inner TP. It is unlikely that those particle-bound pollutants are transported into the TP from outside sources during the non-monsoon period. Ratios of Ce/Sm against Eu/Sm for the snow-pit dust, fine dust from the Sahara desert (A), and ratios of Ce/Er against Eu/Er for the snow-pit dust, fine dust from the Thar Desert (B). Dust from Sahasa cannot penetrate into the TP and transport only along the Himalayas at south and the Tianshan at north due to their high elevation

  19. Evaluation of the ECMWF Sub-seasonal to Seasonal Precipitation Forecasts during the Peak of West Africa Monsoon in Nigeria

    Directory of Open Access Journals (Sweden)

    Eniola Olaniyan

    2018-02-01

    Full Text Available Motivated by the increasing needs for reliable seasonal climate forecasts for enhanced living and protection of property, this study evaluates the predictive skill of the European Center for Medium-range Weather Forecast's Sub-seasonal to Seasonal (ECMWF-S2S precipitation forecasts during the peak of West Africa Monsoon in Nigeria. It investigates the ability of the ECMWF-S2S model to reproduce the atmospheric dynamics that influence the monsoon variability in West-Africa. Rain gauge values of 46 meteorological stations and 10-member ensemble of ECMWF-S2S forecasts from the Ensemble Prediction System (EPS version of the ECMWF were subjected to quantitative statistical analyses. Results show that the model has weak capability in predicting wind strength at 700 mb level to depict the African Easterly Jet (AEJ. However, irrespective of the ENSO phases, ECMWF-S2S model is capable of adequately and reliably predicting the latitudinal positions of the Inter-Tropical Discontinuity (ITD, mean sea level pressure component of the thermal lows and sea surface temperature (SST anomalies over the Pacific and Atlantic Oceans. On inter-annual time-scales, results also show that ECMWF-S2S model performs best over the Savannah in forecasting of rainfall anomalies (synchronization = 75% and over the Sahel in the prediction of rainfall accumulation. The model may however not be able to forecast extreme precipitation reliably because the disagreement between the model's ensemble members increases as higher rainfall accumulation values are attained. The implication here is that the reproducibility of the atmospheric dynamic by the model is a better measure of rainfall prediction than the actual quantitative rainfall forecasts especially in areas south of latitude 10°N. The study therefore suggests considering some climate driving mechanisms as predictability sources for the ECMWF-S2S model to enable the atmospheric dynamics to be better represented in the model.

  20. Drought and Winter Drying (Pest Alert)

    Science.gov (United States)

    USDA Forest Service

    Drought and winter drying have periodically caused major damage to trees. Drought reduces the amount of water available in the soil. In the case of winter drying, the water may be in the soil, but freezing of the soil makes the water unavailable to the tree. In both cases, more water is lost through transpiration than is available to the plant. Symptoms of drought and...

  1. Coming to grips with nuclear winter

    International Nuclear Information System (INIS)

    Scherr, S.J.

    1985-01-01

    This editorial examines the politics related to the concept of nuclear winter which is a term used to describe temperature changes brought on by the injection of smoke into the atmosphere by the massive fires set off by nuclear explosions. The climate change alone could cause crop failures and lead to massive starvation. The author suggests that the prospect of a nuclear winter should be a deterrent to any nuclear exchange

  2. Wet winter pore pressures in railway embankments

    OpenAIRE

    Briggs, Kevin M; Smethurst, Joel A; Powrie, William; O'Brien, Anthony S

    2013-01-01

    This paper demonstrates the influence of extreme wet winter weather on pore water pressures within clay fill railway embankments, using field monitoring data and numerical modelling. Piezometer readings taken across the London Underground Ltd network following the wet winter of 2000/2001 were examined, and showed occurrences of hydrostatic pore water pressure within embankments but also many readings below this. A correlation was found between the maximum pore water pressures and the permeabi...

  3. An overview of the diurnal cycle of the atmospheric boundary layer during the West African monsoon season: results from the 2016 observational campaign

    Science.gov (United States)

    Kalthoff, Norbert; Lohou, Fabienne; Brooks, Barbara; Jegede, Gbenga; Adler, Bianca; Babić, Karmen; Dione, Cheikh; Ajao, Adewale; Amekudzi, Leonard K.; Aryee, Jeffrey N. A.; Ayoola, Muritala; Bessardon, Geoffrey; Danuor, Sylvester K.; Handwerker, Jan; Kohler, Martin; Lothon, Marie; Pedruzo-Bagazgoitia, Xabier; Smith, Victoria; Sunmonu, Lukman; Wieser, Andreas; Fink, Andreas H.; Knippertz, Peter

    2018-03-01

    deep, and easterly winds above; the depth and strength of the monsoon flow show great day-to-day variability. Within the monsoon layer, a nocturnal low-level jet forms in approximately the same layer as the LLC. Its strength and duration is highly variable from night to night. This unique data set will allow us to test some new hypotheses about the processes involved in the development of LLCs and their interaction with the boundary layer and can also be used for model evaluation.

  4. Environmental changes associated with monsoon induced upwelling, off central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DeSousa, S.N.; Sawkar, K.; Rao, P.V.S.S.D.P.

    Coastal upwelling of nutrients during and after the southwest monsoon has been considered to support rich pelagic and demersal fisheries off the west coast of India. Studies indicate occurrence of coastal upwelling assoicated with Ekman transport...

  5. Hydrography and circulation in the northwestern Bay of Bengal during the retreat of southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Sarma, Y.V.B.; Babu, M.T.; Rao, D.P.

    The distribution of temperature and salinity in the upper 500 m of the northwestern Bay of Bengal, adjoining the East Coast of India, during the retreat of southwest monsoon (September) of 1983 is presented. This study reveals coastal upwelling...

  6. Coastal processes at the southern tip of India during summer monsoon 2005

    Digital Repository Service at National Institute of Oceanography (India)

    Smitha, B.R.; VimalKumar, K.G.; Sanjeevan, V.N.

    In situ temperature and wind data, during summer monsoon 2005, bring out some interesting features like, the existence of a purely wind driven upweiling system at the southern tip (ST), very adjacent to another remotely forced upweiling system...

  7. The Upper Ocean Response to the Monsoon in the Arabian Sea

    National Research Council Canada - National Science Library

    Fischer, Albert

    2000-01-01

    ... in heat, associated with the propagation of mesoscale eddies. During the southwest monsoon a coastal filament exports recently upwelled water from the Omani coast to the site of the array, 600 km offshore...

  8. Diurnal Variation over the Tropical Monsoon Regions During Northern Summer 1991

    National Research Council Canada - National Science Library

    Jimenez, Greg

    1997-01-01

    This study examines diurnal variation of convection over western India, the Bay of Bengal, Indochina and the northern South China Sea during the 1991 northern summer monsoon using combined Japanese (GMS) and Indian (INSAT...

  9. Spectral characteristics of the nearshore waves off Paradip, India during monsoon and extreme events

    Digital Repository Service at National Institute of Oceanography (India)

    Aboobacker, V.M.; Vethamony, P.; Sudheesh, K.; Rupali, S.P.

    and directional wave energy spectra distinctly separate out the wave conditions that prevailed off Paradip in the monsoon, fair weather and extreme weather events during the above period. Frequency-energy spectra during extreme events are single peaked...

  10. High CO2 emissions from the tropical Godavari estuary (India) associated with monsoon river discharges

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V.S.S.; Kumar, N.A.; Prasad, V.R.; Venkataramana, V.; Appalanaidu, S.; Sridevi, B.; Kumar, B.S.K.; Bharati, M.D.; Subbaiah, C.V.; Acharyya, T.; Rao, G.D.; Viswanadham, R.; Gawade, L.; Manjary, D.T.; Kumar, P.P.; Rajeev, K.; Reddy, N.P.C.; Sarma, V.V.; Kumar, M.D.; Sadhuram, Y.; Murty, T.V.R.

    Estuaries have been under sampled to establish them as sources or sinks of the atmospheric carbon dioxide. Such poor coverage is well known for tropical, particularly monsoon driven, estuaries. In an attempt to study the variability in CO sub(2...

  11. Bacterial domination over Archaea in ammonia oxidation in a monsoon-driven tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Vipindas, P.V.; Anas, A.; Jasmin, C.; Lallu, K.R.; Fausia, K.H.; Balachandran, K.K.; Muraleedharan, K.R.; Nair, S.

    Autotrophic ammonia oxidizing microorganisms,which are responsible for the rate-limiting step of nitrification in most aquatic systems, have not been studied in tropical estuaries. Cochin estuary (CE) is one of the largest, productive, and monsoon...

  12. Monsoon induced seasonal variability of sheltered versus exposed beaches along the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoi, S.S.C.; Murty, C.S.; Veerayya, M.

    . The second function reveals the significant erosional/accretional phases with a well defined cyclicity of one year associated with monsoonal wind and wave climate. The second spatial function efficiently expresses a"pivot point" for the seasonal shore...

  13. Role of distinct flavours of IOD events on Indian summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Anil, N.; RameshKumar, M.R.; Sajeev, R.; Saji, P.K.

    The summer monsoon contributes to about 75 % of mean annual rainfall over the various meteorological subdivisions of India. The role of ocean–atmosphere phenomena such as Indian Ocean Dipole (IOD) and El Nino-Southern Oscillation (ENSO...

  14. 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...

  15. 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.

    High resolution climate records of the ice age terminations from monsoon-dominated regions reveal the interplay of regional and global driving forces. Speleothem records from Chinese caves indicate that glacial terminations were interrupted...

  16. Attenuation of surface waves due to monsoon rains: A model study for the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Kumar, B.P.; Sarma, Y.V.B.

    The dynamic interaction of intense rain with waves based on momentum exchange is applied to a second generation wave model to predict wave attenuation during monsoon. The scheme takes into account the characteristics of rain and wave parameters...

  17. Multidecadal Weakening of Indian Summer Monsoon Circulation Induces an Increasing Northern Indian Ocean Sea Level

    Science.gov (United States)

    Swapna, P.; Jyoti, J.; Krishnan, R.; Sandeep, N.; Griffies, S. M.

    2017-10-01

    North Indian Ocean sea level has shown significant increase during last three to four decades. Analyses of long-term climate data sets and ocean model sensitivity experiments identify a mechanism for multidecadal sea level variability relative to global mean. Our results indicate that North Indian Ocean sea level rise is accompanied by a weakening summer monsoon circulation. Given that Indian Ocean meridional heat transport is primarily regulated by the annual cycle of monsoon winds, weakening of summer monsoon circulation has resulted in reduced upwelling off Arabia and Somalia and decreased southward heat transport, and corresponding increase of heat storage in the North Indian Ocean. These changes in turn lead to increased retention of heat and increased thermosteric sea level rise in the North Indian Ocean, especially in the Arabian Sea. These findings imply that rising North Indian Ocean sea level due to weakening of monsoon circulation demands adaptive strategies to enable a resilient South Asian population.

  18. Daily variations in pathogenic bacterial populations in a monsoon influenced tropical environment

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, L.; Anil, A; Naik, S.D.; Gaonkar, C.C.

    Changing climatic conditions have influenced the monsoon pattern in recent years. Variations in bacterial population in one such tropical environment were observed everyday over two years and point out intra and inter annual changes driven...

  19. Nutrient biogeochemistry of the eastern Arabian Sea during the southwest monsoon retreat

    Digital Repository Service at National Institute of Oceanography (India)

    George, R; Muraleedharan, K.R; Martin, G.D.; Sabu, P.; Gerson, V.J.; Dineshkumar, P.K.; Nair, S.M.; Chandramohanakumar, N.; Nair, K.K.C

    Hydrography of the eastern Arabian Sea and associated chemical and biological responses were studied during the withdrawal phase of summer monsoon 2003. The shelf region off the southwest coast of India (10 degrees N-15 degrees N) continued...

  20. Air Sea Interaction Over the Indian Ocean During the Contrasting Monsoon Years 2002 and 2003

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar; Sankar; Fennig; Pai, S.; Schulz

    The air sea interaction processes over the Indian Ocean are studied using the satellite data from the Tropical Rainfall Measuring Mission Satellite for two contrasting monsoon years, namely 2002 (deficit) and 2003 (normal). The moisture transport...