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Sample records for greater summer precipitation

  1. Recent summer precipitation trends in the Greater Horn of Africa and the emerging role of Indian Ocean sea surface temperature

    Energy Technology Data Exchange (ETDEWEB)

    Williams, A.P. [Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM (United States); University of California, Geography Department, Santa Barbara, CA (United States); Funk, Chris [University of California, Geography Department, Santa Barbara, CA (United States); U.S. Geological Survey, Earth Resources Observation and Science (EROS), Sioux Falls, SD (United States); Michaelsen, Joel [University of California, Geography Department, Santa Barbara, CA (United States); Rauscher, Sara A. [Los Alamos National Laboratory, Theoretical Division, Los Alamos, NM (United States); Robertson, Iain; Loader, Neil J. [Swansea University, Department of Geography, College of Science, Swansea (United Kingdom); Wils, Tommy H.G. [Rotterdam University, Department of Geography, Rotterdam (Netherlands); Koprowski, Marcin [Nicolaus Copernicus University, Laboratory of Dendrochronology, Institute of Ecology and Environment Protection, Torun (Poland); Eshetu, Zewdu [Ethiopian Institute of Agricultural Research, Forestry Research Centre, Addis Ababa (Ethiopia)

    2012-11-15

    We utilize a variety of climate datasets to examine impacts of two mechanisms on precipitation in the Greater Horn of Africa (GHA) during northern-hemisphere summer. First, surface-pressure gradients draw moist air toward the GHA from the tropical Atlantic Ocean and Congo Basin. Variability of the strength of these gradients strongly influences GHA precipitation totals and accounts for important phenomena such as the 1960s-1980s rainfall decline and devastating 1984 drought. Following the 1980s, precipitation variability became increasingly influenced by the southern tropical Indian Ocean (STIO) region. Within this region, increases in sea-surface temperature, evaporation, and precipitation are linked with increased exports of dry mid-tropospheric air from the STIO region toward the GHA. Convergence of dry air above the GHA reduces local convection and precipitation. It also produces a clockwise circulation response near the ground that reduces moisture transports from the Congo Basin. Because precipitation originating in the Congo Basin has a unique isotopic signature, records of moisture transports from the Congo Basin may be preserved in the isotopic composition of annual tree rings in the Ethiopian Highlands. A negative trend in tree-ring oxygen-18 during the past half century suggests a decline in the proportion of precipitation originating from the Congo Basin. This trend may not be part of a natural cycle that will soon rebound because climate models characterize Indian Ocean warming as a principal signature of greenhouse-gas induced climate change. We therefore expect surface warming in the STIO region to continue to negatively impact GHA precipitation during northern-hemisphere summer. (orig.)

  2. An underestimated role of precipitation frequency in regulating summer soil moisture

    International Nuclear Information System (INIS)

    Wu Chaoyang; Chen, Jing M; Pumpanen, Jukka; Cescatti, Alessandro; Marcolla, Barbara; Blanken, Peter D; Ardö, Jonas; Tang, Yanhong; Magliulo, Vincenzo; Georgiadis, Teodoro; Soegaard, Henrik; Cook, David R; Harding, Richard J

    2012-01-01

    Soil moisture induced droughts are expected to become more frequent under future global climate change. Precipitation has been previously assumed to be mainly responsible for variability in summer soil moisture. However, little is known about the impacts of precipitation frequency on summer soil moisture, either interannually or spatially. To better understand the temporal and spatial drivers of summer drought, 415 site yr measurements observed at 75 flux sites world wide were used to analyze the temporal and spatial relationships between summer soil water content (SWC) and the precipitation frequencies at various temporal scales, i.e., from half-hourly, 3, 6, 12 and 24 h measurements. Summer precipitation was found to be an indicator of interannual SWC variability with r of 0.49 (p < 0.001) for the overall dataset. However, interannual variability in summer SWC was also significantly correlated with the five precipitation frequencies and the sub-daily precipitation frequencies seemed to explain the interannual SWC variability better than the total of precipitation. Spatially, all these precipitation frequencies were better indicators of summer SWC than precipitation totals, but these better performances were only observed in non-forest ecosystems. Our results demonstrate that precipitation frequency may play an important role in regulating both interannual and spatial variations of summer SWC, which has probably been overlooked or underestimated. However, the spatial interpretation should carefully consider other factors, such as the plant functional types and soil characteristics of diverse ecoregions. (letter)

  3. Assessing the applicability of WRF optimal parameters under the different precipitation simulations in the Greater Beijing Area

    Science.gov (United States)

    Di, Zhenhua; Duan, Qingyun; Wang, Chen; Ye, Aizhong; Miao, Chiyuan; Gong, Wei

    2018-03-01

    Forecasting skills of the complex weather and climate models have been improved by tuning the sensitive parameters that exert the greatest impact on simulated results based on more effective optimization methods. However, whether the optimal parameter values are still work when the model simulation conditions vary, which is a scientific problem deserving of study. In this study, a highly-effective optimization method, adaptive surrogate model-based optimization (ASMO), was firstly used to tune nine sensitive parameters from four physical parameterization schemes of the Weather Research and Forecasting (WRF) model to obtain better summer precipitation forecasting over the Greater Beijing Area in China. Then, to assess the applicability of the optimal parameter values, simulation results from the WRF model with default and optimal parameter values were compared across precipitation events, boundary conditions, spatial scales, and physical processes in the Greater Beijing Area. The summer precipitation events from 6 years were used to calibrate and evaluate the optimal parameter values of WRF model. Three boundary data and two spatial resolutions were adopted to evaluate the superiority of the calibrated optimal parameters to default parameters under the WRF simulations with different boundary conditions and spatial resolutions, respectively. Physical interpretations of the optimal parameters indicating how to improve precipitation simulation results were also examined. All the results showed that the optimal parameters obtained by ASMO are superior to the default parameters for WRF simulations for predicting summer precipitation in the Greater Beijing Area because the optimal parameters are not constrained by specific precipitation events, boundary conditions, and spatial resolutions. The optimal values of the nine parameters were determined from 127 parameter samples using the ASMO method, which showed that the ASMO method is very highly-efficient for optimizing WRF

  4. Summer precipitation influences the stable oxygen and carbon isotopic composition of tree-ring cellulose in Pinus ponderosa.

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    Roden, John S; Ehleringer, James R

    2007-04-01

    The carbon and oxygen isotopic composition of tree-ring cellulose was examined in ponderosa pine (Pinus ponderosa Dougl.) trees in the western USA to study seasonal patterns of precipitation inputs. Two sites (California and Oregon) had minimal summer rainfall inputs, whereas a third site (Arizona) received as much as 70% of its annual precipitation during the summer months (North American monsoon). For the Arizona site, both the delta(18)O and delta(13)C values of latewood cellulose increased as the fraction of annual precipitation occurring in the summer (July through September) increased. There were no trends in latewood cellulose delta(18)O with the absolute amount of summer rain at any site. The delta(13)C composition of latewood cellulose declined with increasing total water year precipitation for all sites. Years with below-average total precipitation tended to have a higher proportion of their annual water inputs during the summer months. Relative humidity was negatively correlated with latewood cellulose delta(13)C at all sites. Trees at the Arizona site produced latewood cellulose that was significantly more enriched in (18)O compared with trees at the Oregon or California site, implying a greater reliance on an (18)O-enriched water source. Thus, tree-ring records of cellulose delta(18)O and delta(13)C may provide useful proxy information about seasonal precipitation inputs and the variability and intensity of the North American monsoon.

  5. Spatial variations of summer precipitation trends in South Korea, 1973-2005

    International Nuclear Information System (INIS)

    Chang, Heejun; Kwon, Won-Tae

    2007-01-01

    We have investigated the spatial patterns of trends in summer precipitation amount, intensity, and heavy precipitation for South Korea between 1973 and 2005. All stations show increasing trends in precipitation amount during the summer months, with the highest percentage of significant increase in June precipitation for the northern and central western part of South Korea. There is a significant increase in August precipitation for stations in the southeastern part of South Korea. Only a few stations exhibited significant upward trends in September precipitation. There is a weak to moderate spatial autocorrelation with the highest Moran's I value in June precipitation amount and August precipitation intensity. The number of days with daily precipitation exceeding 50 and 30 mm during the summer has increased at all stations. Observed trends are likely to be associated with changes in large-scale atmospheric circulation, sea surface temperature anomalies, and orography, but detailed causes of these trends need further investigation

  6. Dendroclimatic Reconstruction of Summer Temperatures in Irik Valley, Mount Elbrus (Greater Caucasus

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    Iulian Horia HOLOBÂCĂ

    2014-11-01

    Full Text Available Recent evidence suggests an acceleration of glacier retreat in Greater Caucasus after 1980. For the same period a significant summer temperature warming trend and little or no change in precipitation variation have been observed. In this paper we seek to find similar past climatic conditions using a dendroclimatic reconstruction of summer temperatures from upper treeline sites after the Little Ice Age (LIA. Dendroclimatological sampling of Scots pine (Pinus sylvestris has been made in Irik Valley, near Elbrus glacier, and a tree-ring width (TRW chronology has been used to reconstruct May – August (MJJA temperatures back to 1830. Three warm periods were identified in the MJJA temperatures reconstructed data (1830 - 1900, but we cannot appreciate if they had the same intensity as the recent warm period

  7. Early-Holocene decoupled summer temperature and monsoon precipitation in southwest China

    Science.gov (United States)

    Wu, D.; Chen, F.; Chen, X.; Lv, F.; Zhou, A.; Chen, J.; Abbott, M. B.; Yu, J.

    2017-12-01

    Proxy based reconstructions of Holocene temperature have shown that both the timing and magnitude of the thermal maximum vary substantially between different regions; the simulations results from climate models also show that summers were substantially cooler over regions directly influenced by the presence of the Laurentide ice sheet during the early Holocene, whereas other regions of the Northern Hemisphere were dominated by orbital forcing. However, for lack of summer temperature reconstruction in the low latitude regions like southwestern China dominated by the Indian summer monsoon, the Holocene summer temperature variations and it underlying forcing mechanism are ambiguous. Here we present a well-dated record of pollen-based quantitative summer temperature (mean July; MJT) over the last 14000 years from Xingyun Lake, Yunnan Province, southwest China. It was found that MJT decreased during the YD event, then increased slowly until 7400 yr BP, and decreased thereafter. The MJT shows a pattern with middle Holocene maximum of MJT, indicating a different changing pattern with the carbonate oxygen isotope record (d18O) from the same core during the early Holocene (11500-7400 yr BP), which has the similar variation with speleothem d18O record from Dongge cave, both indicate the variation of monsoon precipitation with the highest precipitation occurred during the early Holocene. Therefore, we propose that the variation of summer temperature and precipitation in southwest China was decoupled during the early Holocene. However, both MJT and monsoon precipitation decreased after the middle Holocene following the boreal summer insolation. We suggest that the high precipitation with strong summer monsoon and hence higher cloud cover may depress the temperature increasing forced by increasing summer insolation during the early Holocene; while melting ice-sheet in the high latitude regions had strongly influenced the summer temperature increase during the deglacial period

  8. Observed variability of summer precipitation pattern and extreme events in East China associated with variations of the East Asian summer monsoon: VARIABILITY OF SUMMER PRECIPITATION AND EXTREME EVENT IN EAST CHINA

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lei [School of Atmospheric Sciences, Nanjing University, China; Pacific Northwest National Laboratory, Richland WA USA; Qian, Yun [Pacific Northwest National Laboratory, Richland WA USA; Zhang, Yaocun [School of Atmospheric Sciences, Nanjing University, China; Zhao, Chun [Pacific Northwest National Laboratory, Richland WA USA; Leung, L. Ruby [Pacific Northwest National Laboratory, Richland WA USA; Huang, Anning [School of Atmospheric Sciences, Nanjing University, China; Xiao, Chuliang [Cooperative Institute for Limnology and Ecosystems Research, School of Natural Resources and Environment, University of Michigan, Ann Arbor MI USA

    2015-11-09

    This paper presents a comprehensive analysis of interannual and interdecadal variations of summer precipitation and precipitation-related extreme events in China associated with variations of the East Asian summer monsoon (EASM) from 1979-2012. A high-quality daily precipitation dataset covering 2287 weather stations in China is analyzed. Based on the precipitation pattern analysis using empirical orthogonal functions, three sub-periods of 1979-1992 (period I), 1993-1999 (period II) and 2000-2012 (period III) are identified to be representative of the precipitation variability. Similar significant variability of the extreme precipitation indices is found across four sub-regions in eastern China. The spatial patterns of summer mean precipitation, the number of days with daily rainfall exceeding 95th percentile precipitation (R95p) and the maximum number of consecutive wet days (CWD) anomalies are consistent, but opposite to that of maximum consecutive dry days (CDD) anomalies during the three sub-periods. However, the spatial patterns of hydroclimatic intensity (HY-INT) are notably different from that of the other three extreme indices, but highly correlated to the dry events. The changes of precipitation anomaly patterns are accompanied by the change of the EASM regime and the abrupt shift of the position of the west Pacific subtropical high around 1992/1993 and 1999/2000, respectively, which influence the moisture transport that contributes most to the precipitation anomalies. Lastly, the EASM intensity is linked to sea surface temperature anomaly over the tropical Indian and Pacific Ocean that influences deep convection over the oceans.

  9. Seasonal Analysis of Microbial Communities in Precipitation in the Greater Tokyo Area, Japan

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    Satoshi Hiraoka

    2017-08-01

    Full Text Available The presence of microbes in the atmosphere and their transport over long distances across the Earth's surface was recently shown. Precipitation is likely a major path by which aerial microbes fall to the ground surface, affecting its microbial ecosystems and introducing pathogenic microbes. Understanding microbial communities in precipitation is of multidisciplinary interest from the perspectives of microbial ecology and public health; however, community-wide and seasonal analyses have not been conducted. Here, we carried out 16S rRNA amplicon sequencing of 30 precipitation samples that were aseptically collected over 1 year in the Greater Tokyo Area, Japan. The precipitation microbial communities were dominated by Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria and were overall consistent with those previously reported in atmospheric aerosols and cloud water. Seasonal variations in composition were observed; specifically, Proteobacteria abundance significantly decreased from summer to winter. Notably, estimated ordinary habitats of precipitation microbes were dominated by animal-associated, soil-related, and marine-related environments, and reasonably consistent with estimated air mass backward trajectories. To our knowledge, this is the first amplicon-sequencing study investigating precipitation microbial communities involving sampling over the duration of a year.

  10. The role of summer precipitation and summer temperature in establishment and growth of dwarf shrub Betula nana in northeast Siberian tundra

    DEFF Research Database (Denmark)

    Li, Bingxi; Heijmans, Monique M P D; Berendse, Frank

    2016-01-01

    It is widely believed that deciduous tundra-shrub dominance is increasing in the pan-Arctic region, mainly due to rising temperature. We sampled dwarf birch (Betula nana L.) at a northeastern Siberian tundra site and used dendrochronological methods to explore the relationship between climatic...... variables and local shrub dominance. We found that establishment of shrub ramets was positively related to summer precipitation, which implies that the current high dominance of B. nana at our study site could be related to high summer precipitation in the period from 1960 to 1990. The results confirmed...... that early summer temperature is most influential to annual growth rates of B. nana. In addition, summer precipitation stimulated shrub growth in years with warm summers, suggesting that B. nana growth may be co-limited by summer moisture supply. The dual controlling role of temperature and summer...

  11. Interdecadal variations of East Asian summer monsoon northward propagation and influences on summer precipitation over East China

    Science.gov (United States)

    Jiang, Z.; Yang, S.; He, J.; Li, J.; Liang, J.

    2008-08-01

    The interdecadal variation of northward propagation of the East Asian Summer Monsoon (EASM) and summer precipitation in East China have been investigated using daily surface rainfall from a dense rain gauge network in China for 1957 2001, National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, European Center for Medium-Range Weather Forecast (ECMWF) reanalysis, and Global Mean Sea Level Pressure Dataset (GMSLP2) from Climatic Research Unit (CRU). Results in general show a consistent agreement on the interdecadal variability of EASM northward propagations. However, it appears that the interdecadal variation is stronger in NCEP than in ECMWF and CRU datasets. A newly defined normalized precipitation index (NPI), a 5-day running mean rainfall normalized with its standard deviation, clearly depicts the characteristics of summer rainbelt activities in East China in terms of jumps and durations during its northward propagations. The EASM northward propagation shows a prominent interdecadal variation. EASM before late 1970s had a rapid northward advance and a northern edge beyond its normal position. As a result, more summer rainfall occurred for the North China rainy season, Huaihe-River Mei-Yu, and South China Mei-Yu. In contrast, EASM after late 1970s had a slow northward movement and a northern edge located south of its normal position. Less summer precipitation occurred in East China except in Yangtze River basin. The EASM northernmost position (ENP), northernmost intensity (ENI), and EASM have a complex and good relationship at interdecadal timescales. They have significant influences on interdecadal variation of the large-scale precipitation anomalies in East China.

  12. Rising Mediterranean Sea Surface Temperatures Amplify Extreme Summer Precipitation in Central Europe

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    Volosciuk, Claudia; Maraun, Douglas; Semenov, Vladimir A.; Tilinina, Natalia; Gulev, Sergey K.; Latif, Mojib

    2016-08-01

    The beginning of the 21st century was marked by a number of severe summer floods in Central Europe associated with extreme precipitation (e.g., Elbe 2002, Oder 2010 and Danube 2013). Extratropical storms, known as Vb-cyclones, cause summer extreme precipitation events over Central Europe and can thus lead to such floodings. Vb-cyclones develop over the Mediterranean Sea, which itself strongly warmed during recent decades. Here we investigate the influence of increased Mediterranean Sea surface temperature (SST) on extreme precipitation events in Central Europe. To this end, we carry out atmosphere model simulations forced by average Mediterranean SSTs during 1970-1999 and 2000-2012. Extreme precipitation events occurring on average every 20 summers in the warmer-SST-simulation (2000-2012) amplify along the Vb-cyclone track compared to those in the colder-SST-simulation (1970-1999), on average by 17% in Central Europe. The largest increase is located southeast of maximum precipitation for both simulated heavy events and historical Vb-events. The responsible physical mechanism is increased evaporation from and enhanced atmospheric moisture content over the Mediterranean Sea. The excess in precipitable water is transported from the Mediterranean Sea to Central Europe causing stronger precipitation extremes over that region. Our findings suggest that Mediterranean Sea surface warming amplifies Central European precipitation extremes.

  13. Preliminary Studies on Summer Precipitation Patterns in China%我国夏季降水类型初探

    Institute of Scientific and Technical Information of China (English)

    李鸾

    2008-01-01

    [Objective]Study on the spatial distribution of summer precipitation patterns and interannnal and interdacadal variability.[Method]The summer precipitation patterns were obtained from standard field of summer precipitation data for 160 observation stations in China during 1951-2000 by the utilization of empirical orthogonal function(EOF),and characteristics of interannual and interdecadal variability were analyzed.[Result]The summer precipitation mainly distributes in eastern part of China;The Ist,2nd and 3rd EOF modes of spatial distribution are especially remarkable as well consistent with the results of previous reports about three rainfall patterns from analysis on the percentages of precipitation anomaly of summer.[Conclusion]There exists interannnal and interdecadal variability for summer precipitation in China.

  14. The link between Tibetan Plateau monsoon and Indian summer precipitation: a linear diagnostic perspective

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    Ge, Fei; Sielmann, Frank; Zhu, Xiuhua; Fraedrich, Klaus; Zhi, Xiefei; Peng, Ting; Wang, Lei

    2017-12-01

    The thermal forcing of the Tibetan Plateau (TP) is analyzed to investigate the formation and variability of Tibetan Plateau Summer Monsoon (TPSM), which affects the climates of the surrounding regions, in particular the Indian summer monsoon precipitation. Dynamic composites and statistical analyses indicate that the Indian summer monsoon precipitation is less/greater than normal during the strong/weak TPSM. Strong (weak) TPSM is associated with an anomalous near surface cyclone (anticyclone) over the western part of the Tibetan Plateau, enhancing (reducing) the westerly flow along its southern flank, suppressing (favoring) the meridional flow of warm and moist air from the Indian ocean and thus cutting (providing) moisture supply for the northern part of India and its monsoonal rainfall. These results are complemented by a dynamic and thermodynamic analysis: (i) A linear thermal vorticity forcing primarily describes the influence of the asymmetric heating of TP generating an anomalous stationary wave flux. Composite analysis of anomalous stationary wave flux activity (after Plumb in J Atmos Sci 42:217-229, 1985) strongly indicate that non-orographic effects (diabatic heating and/or interaction with transient eddies) of the Tibetan Plateau contribute to the generation of an anomalous cyclone (anti-cyclone) over the western TP. (ii) Anomalous TPSM generation shows that strong TPSM years are related to the positive surface sensible heating anomalies over the eastern TP favoring the strong diabatic heating in summer. While negative TPSM years are associated with the atmospheric circulation anomalies during the preceding spring, enhancing northerly dry-cold air intrusions into TP, which may weaken the condensational heat release in the middle and upper troposphere, leading to a weaker than normal summer monsoon over the TP in summer.

  15. Variability of East Asian summer monsoon precipitation during the Holocene and possible forcing mechanisms

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    Lu, Fuzhi; Ma, Chunmei; Zhu, Cheng; Lu, Huayu; Zhang, Xiaojian; Huang, Kangyou; Guo, Tianhong; Li, Kaifeng; Li, Lan; Li, Bing; Zhang, Wenqing

    2018-03-01

    Projecting how the East Asian summer monsoon (EASM) rainfall will change with global warming is essential for human sustainability. Reconstructing Holocene climate can provide critical insight into its forcing and future variability. However, quantitative reconstructions of Holocene summer precipitation are lacking for tropical and subtropical China, which is the core region of the EASM influence. Here we present high-resolution annual and summer rainfall reconstructions covering the whole Holocene based on the pollen record at Xinjie site from the lower Yangtze region. Summer rainfall was less seasonal and 30% higher than modern values at 10-6 cal kyr BP and gradually declined thereafter, which broadly followed the Northern Hemisphere summer insolation. Over the last two millennia, however, the summer rainfall has deviated from the downward trend of summer insolation. We argue that greenhouse gas forcing might have offset summer insolation forcing and contributed to the late Holocene rainfall anomaly, which is supported by the TraCE-21 ka transient simulation. Besides, tropical sea-surface temperatures could modulate summer rainfall by affecting evaporation of seawater. The rainfall pattern concurs with stalagmite and other proxy records from southern China but differs from mid-Holocene rainfall maximum recorded in arid/semiarid northern China. Summer rainfall in northern China was strongly suppressed by high-northern-latitude ice volume forcing during the early Holocene in spite of high summer insolation. In addition, the El Niño/Southern Oscillation might be responsible for droughts of northern China and floods of southern China during the late Holocene. Furthermore, quantitative rainfall reconstructions indicate that the Paleoclimate Modeling Intercomparison Project (PMIP) simulations underestimate the magnitude of Holocene precipitation changes. Our results highlight the spatial and temporal variability of the Holocene EASM precipitation and potential forcing

  16. Record dry summer in 2015 challenges precipitation projections in Central Europe

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    Orth, René; Zscheischler, Jakob; Seneviratne, Sonia I.

    2016-06-01

    Central Europe was characterized by a humid-temperate climate in the 20th century. Climate change projections suggest that climate in this area will shift towards warmer temperatures by the end of the 21st century, while projected precipitation changes are highly uncertain. Here we show that the 2015 summer rainfall was the lowest on record since 1901 in Central Europe, and that climate models that perform best in the three driest years of the historical time period 1901-2015 project stronger drying trends in the 21st century than models that perform best in the remaining years. Analyses of precipitation and derived soil moisture reveal that the 2015 event was drier than both the recent 2003 or 2010 extreme summers in Central Europe. Additionally there are large anomalies in satellite-derived vegetation greenness. In terms of precipitation and temperature anomalies, the 2015 summer in Central Europe is found to lie between historical climate in the region and that characteristic of the Mediterranean area. Even though the models best capturing past droughts are not necessarily generally more reliable in the future, the 2015 drought event illustrates that potential future drying trends have severe implications and could be stronger than commonly assumed from the entire IPCC AR5 model ensemble.

  17. The boreal winter Madden-Julian Oscillation's influence on summertime precipitation in the greater Caribbean

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    Curtis, Scott; Gamble, Douglas W.

    2016-07-01

    Precipitation totals in the greater Caribbean are known to be affected by interannual variability. In particular, dry conditions in the spring-summer have been physically linked to the positive phase of North Atlantic Oscillation (NAO) in the literature. In this study, it was found through regression analysis that an active Madden-Julian Oscillation (MJO) in winter geographically focused over the Maritime Continent contributes to a positive NAO in March via the generation of Rossby waves in the Northern Hemisphere. Specifically, a negative Pacific-North American pattern develops in the winter and transitions to an Atlantic pattern in spring. The positive NAO is a transient feature of this evolving wave train, but a center of significant positive 200 hPa geopotential heights is entrenched over the southeast U.S. throughout the February to May time period and is manifested as high pressure at the surface. The southern flank of this system increases the speeds of the trade winds and leads to a cooling of the Caribbean sea surface temperatures and, thus, convection suppression and reduced precipitation. Thus, this study advances our understanding of the climate of the greater Caribbean by using climate teleconnections to relate the MJO to rainfall in the region.

  18. Application and Study of Precipitation Schemes in Weather Simulation in Summer and Winter over China

    Institute of Scientific and Technical Information of China (English)

    XU Guoqiang; WAN Qilin; HUANG Liping; XUE Jishan; CHEN Dehui

    2006-01-01

    Through simulation of summer and winter precipitation cases in China, the cloud precipitation schemes of model were examined. Results indicate that it is discrepant between convective precipitation simulated by the Kain-Fritsch (KF) scheme and Betts-Miller (BM) scheme in summer, the former scheme is better than the latter in this case. The ambient atmosphere may be varied by different convective schemes. The air is wetter and the updraft is stronger in the KF scheme than in the BM scheme, which can induce the more grid scale precipitation in the KF scheme, i.e., the different cumulus schemes may have the different and important effect on the grid scale precipitation. However, there is almost no convective rain in winter in northern China, so the effect of cumulus precipitation on the grid scale precipitation can be disregarded.Therefore, the gird scale precipitation is primary in the winter of northern China.

  19. Tree Rings Show Recent High Summer-Autumn Precipitation in Northwest Australia Is Unprecedented within the Last Two Centuries.

    Directory of Open Access Journals (Sweden)

    Alison J O'Donnell

    Full Text Available An understanding of past hydroclimatic variability is critical to resolving the significance of recent recorded trends in Australian precipitation and informing climate models. Our aim was to reconstruct past hydroclimatic variability in semi-arid northwest Australia to provide a longer context within which to examine a recent period of unusually high summer-autumn precipitation. We developed a 210-year ring-width chronology from Callitris columellaris, which was highly correlated with summer-autumn (Dec-May precipitation (r = 0.81; 1910-2011; p < 0.0001 and autumn (Mar-May self-calibrating Palmer drought severity index (scPDSI, r = 0.73; 1910-2011; p < 0.0001 across semi-arid northwest Australia. A linear regression model was used to reconstruct precipitation and explained 66% of the variance in observed summer-autumn precipitation. Our reconstruction reveals inter-annual to multi-decadal scale variation in hydroclimate of the region during the last 210 years, typically showing periods of below average precipitation extending from one to three decades and periods of above average precipitation, which were often less than a decade. Our results demonstrate that the last two decades (1995-2012 have been unusually wet (average summer-autumn precipitation of 310 mm compared to the previous two centuries (average summer-autumn precipitation of 229 mm, coinciding with both an anomalously high frequency and intensity of tropical cyclones in northwest Australia and the dominance of the positive phase of the Southern Annular Mode.

  20. Tree Rings Show Recent High Summer-Autumn Precipitation in Northwest Australia Is Unprecedented within the Last Two Centuries

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    O'Donnell, Alison J.; Cook, Edward R.; Palmer, Jonathan G.; Turney, Chris S. M.; Page, Gerald F. M.; Grierson, Pauline F.

    2015-01-01

    An understanding of past hydroclimatic variability is critical to resolving the significance of recent recorded trends in Australian precipitation and informing climate models. Our aim was to reconstruct past hydroclimatic variability in semi-arid northwest Australia to provide a longer context within which to examine a recent period of unusually high summer-autumn precipitation. We developed a 210-year ring-width chronology from Callitris columellaris, which was highly correlated with summer-autumn (Dec–May) precipitation (r = 0.81; 1910–2011; p < 0.0001) and autumn (Mar–May) self-calibrating Palmer drought severity index (scPDSI, r = 0.73; 1910–2011; p < 0.0001) across semi-arid northwest Australia. A linear regression model was used to reconstruct precipitation and explained 66% of the variance in observed summer-autumn precipitation. Our reconstruction reveals inter-annual to multi-decadal scale variation in hydroclimate of the region during the last 210 years, typically showing periods of below average precipitation extending from one to three decades and periods of above average precipitation, which were often less than a decade. Our results demonstrate that the last two decades (1995–2012) have been unusually wet (average summer-autumn precipitation of 310 mm) compared to the previous two centuries (average summer-autumn precipitation of 229 mm), coinciding with both an anomalously high frequency and intensity of tropical cyclones in northwest Australia and the dominance of the positive phase of the Southern Annular Mode. PMID:26039148

  1. Evaluation of Real-Time Convection-Permitting Precipitation Forecasts in China During the 2013-2014 Summer Season

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    Zhu, Kefeng; Xue, Ming; Zhou, Bowen; Zhao, Kun; Sun, Zhengqi; Fu, Peiling; Zheng, Yongguang; Zhang, Xiaoling; Meng, Qingtao

    2018-01-01

    Forecasts at a 4 km convection-permitting resolution over China during the summer season have been produced with the Weather Research and Forecasting model at Nanjing University since 2013. Precipitation forecasts from 2013 to 2014 are evaluated with dense rain gauge observations and compared with operational global model forecasts. Overall, the 4 km forecasts show very good agreement with observations over most parts of China, outperforming global forecasts in terms of spatial distribution, intensity, and diurnal variation. Quantitative evaluations with the Gilbert skill score further confirm the better performance of the 4 km forecasts over global forecasts for heavy precipitation, especially for the thresholds of 100 and 150 mm d-1. Besides bulk characteristics, the representations of some unique features of summer precipitation in China under the influence of the East Asian summer monsoon are further evaluated. These include the northward progression and southward retreat of the main rainband through the summer season, the diurnal variations of precipitation, and the meridional and zonal propagation of precipitation episodes associated with background synoptic flow and the embedded mesoscale convective systems. The 4 km forecast is able to faithfully reproduce most of the features while overprediction of afternoon convection near the southern China coast is found to be a main deficiency that requires further investigations.

  2. Anthropogenic changes of summer precipitation in North Rhine - Westphalia, Germany

    Science.gov (United States)

    Brücher, T.; Ulbrich, U.

    2003-04-01

    A transient low resolution (T42) greenhouse gas run of the ECHAM4/OPYC3 GCM, and a nested run of the regional climate model HIRLAM/RCA1 (40 km resolution) are considered with respect to summer rainfall. The area of investigation is the flat part (< 200 m above sea level) of North Rhine-Westphalia, Germany, and the model grid points close to / within this area, respectively. For the time period representing present day climate, the precipitation amounts simulated by the GCM are in good agreement with oberserved values, whereas the nested regional model produces too large rainfall sums (+25%). With respect to intensity classes on a daily basis, both models underestimate the observed frequency of intense events and overestimate the number of days with a low precipitation amount. For the GCM, we take account of these systematic errors by defining a non-linear transfer function. This function is subsequently applied to the model's output from the scenario period. For future climate, both models show a significant reduction of the total summer precipitation. This reduction is caused by an increased number of dry days, which eventually dominates over a simultaneous increase in the number of days with intense precipitation. Average rainfalls are computed for periods between 5 to 30 days. For all averaging periods considered. The frequency of periods with less than 2 mm precipitation per day is found to rise (by up to 200%) compared to present day climate. There are less periods with more than 3 mm of rain. The decline amounts up to 50%. Thus, the models give no evidence for a grouping of heavy rainfall events.

  3. Intensification of extreme European summer precipitation in a warmer climate

    DEFF Research Database (Denmark)

    Christensen, O. B.; Christensen, J. H.

    2004-01-01

    Heavy and/or extended precipitation episodes with subsequent surface runoff can inflict catastrophic property damage and loss of human life. Thus, it is important to determine how the character of such events could change in response to greenhouse gas-induced global warming. Impacts of climate...... warming on severe precipitation events in Europe on a diurnal time scale were investigated with a high-resolution regional climate model for two of the greenhouse gas emission scenarios constructed by the Intergovernmental Panel on Climate Change (IPCC; Nakicenovic, N., et al., 2000, IPCC special report...... models both originating from fully transient climate change simulations. Here, we show that although the summer time precipitation decreases over a substantial part of Europe in the scenarios analysed, an increase in the amount of precipitation exceeding the present-day 99th and in most cases even the 95...

  4. Relationships between the West Asian subtropical westerly jet and summer precipitation in northern Xinjiang

    Science.gov (United States)

    Zhao, Yong; Wang, MinZhong; Huang, AnNing; Li, HongJun; Huo, Wen; Yang, Qing

    2014-05-01

    The relation between the spatial and temporal variations of the West Asian subtropical westerly jet (WASWJ) and the summer precipitation in northern Xinjiang has been explored using the NCEP/NCAR reanalysis data and the summer precipitation data at 43 stations in northern Xinjiang during 1961 to 2007. Results show that the position of the WASWJ is more important than its strength in influencing the summer precipitation in northern Xinjiang. When the jet position is further south, the anomalous southwesterly flow crossing the Indian subcontinent along the southern foothill of the Tibetan Plateau is favorable for the southwestward warm and wet air penetrating from low latitudes into Central Asia and northern Xinjiang and more rainfall formation. Further analysis shows that the interannual variations of the jet position are well correlated with the Arctic Oscillation (AO). In the weak AO years, the middle to upper troposphere becomes colder than normal and results in an anomalous cyclonic circulation at 200 hPa over Western and Central Asia, which enhances the westerly wind over middle and low latitudes and leads to the WASWJ located further south.

  5. Predictability of summer extreme precipitation days over eastern China

    Science.gov (United States)

    Li, Juan; Wang, Bin

    2017-08-01

    Extreme precipitation events have severe impacts on human activity and natural environment, but prediction of extreme precipitation events remains a considerable challenge. The present study aims to explore the sources of predictability and to estimate the predictability of the summer extreme precipitation days (EPDs) over eastern China. Based on the region- and season-dependent variability of EPDs, all stations over eastern China are divided into two domains: South China (SC) and northern China (NC). Two domain-averaged EPDs indices during their local high EPDs seasons (May-June for SC and July-August for NC) are therefore defined. The simultaneous lower boundary anomalies associated with each EPDs index are examined, and we find: (a) the increased EPDs over SC are related to a rapid decaying El Nino and controlled by Philippine Sea anticyclone anomalies in May-June; (b) the increased EPDs over NC are accompanied by a developing La Nina and anomalous zonal sea level pressure contrast between the western North Pacific subtropical high and East Asian low in July-August. Tracking back the origins of these boundary anomalies, one or two physically meaningful predictors are detected for each regional EPDs index. The causative relationships between the predictors and the corresponding EPDs over each region are discussed using lead-lag correlation analyses. Using these selected predictors, a set of Physics-based Empirical models is derived. The 13-year (2001-2013) independent forecast shows significant temporal correlation skills of 0.60 and 0.74 for the EPDs index of SC and NC, respectively, providing an estimation of the predictability for summer EPDs over eastern China.

  6. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    Science.gov (United States)

    Gong, Zhiqiang; Dogar, Muhammad Mubashar Ahmad; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-09-01

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection. The differences of summer precipitation modes of the empirical orthogonal function and the bias of atmospheric circulations over EA-NWP are analyzed to determine the reason for the precipitation prediction errors. Results indicate that the BCC_CSM could not reproduce the positive-negative-positive meridional tripole pattern from south to north that differs markedly from that observed over the last 20 years. This failure can be attributed to the bias of the BCC_CSM hindcasts of the summer EAP teleconnection and the low predictability of 500 hPa at the mid-high latitude lobe of the EAP. Meanwhile, the BCC_CSM hindcasts' deficiencies of atmospheric responses to SST anomalies over the Indonesia maritime continent (IMC) resulted in opposite and geographically shifted geopotential anomalies at 500 hPa as well as wind and vorticity anomalies at 850 hPa, rendering the BCC_CSM unable to correctly reproduce the EAP teleconnection pattern. Understanding these two problems will help further improve BCC_CSM's summer precipitation forecasting ability over EA-NWP.

  7. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    KAUST Repository

    Gong, Zhiqiang

    2017-04-05

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection. The differences of summer precipitation modes of the empirical orthogonal function and the bias of atmospheric circulations over EA-NWP are analyzed to determine the reason for the precipitation prediction errors. Results indicate that the BCC_CSM could not reproduce the positive-negative-positive meridional tripole pattern from south to north that differs markedly from that observed over the last 20 years. This failure can be attributed to the bias of the BCC_CSM hindcasts of the summer EAP teleconnection and the low predictability of 500 hPa at the mid-high latitude lobe of the EAP. Meanwhile, the BCC_CSM hindcasts\\' deficiencies of atmospheric responses to SST anomalies over the Indonesia maritime continent (IMC) resulted in opposite and geographically shifted geopotential anomalies at 500 hPa as well as wind and vorticity anomalies at 850 hPa, rendering the BCC_CSM unable to correctly reproduce the EAP teleconnection pattern. Understanding these two problems will help further improve BCC_CSM\\'s summer precipitation forecasting ability over EA-NWP.

  8. Diurnal variation of summer precipitation over the Tibetan Plateau. A cloud-resolving simulation

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jianyu; Zhang, Bing; Wang, Minghuan [China Meteorological Administration, Wuhan (China). Wuhan Inst. of Heavy Rain; Wang, Huijuan [Weather Modification Office of Hubei Province, Wuhan (China)

    2012-07-01

    In this study, the Weather Research and Forecasting model was used to simulate the diurnal variation in summer precipitation over the Tibetan Plateau (TP) at a cloudresolving scale. Compared with the TRMM, precipitation data shows that the model can well simulate the diurnal rainfall cycle with an overall late-afternoon maximum precipitation in the central TP and a nighttime maximum in the southern edge. The simulated diurnal variations in regional circulation and thermodynamics are in good correspondence with the precipitation diurnal cycles in the central and southern edge of TP, respectively. A possible mechanism responsible for the nocturnal precipitation maximum in the southern edge has been proposed, indicating the importance of the TP in regulating the regional circulation and precipitation. (orig.)

  9. 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.

  10. Relationships between δ18O in summer precipitation and temperature and moisture trajectories at Muztagata, western China

    Institute of Scientific and Technical Information of China (English)

    YU; Wusheng; YAO; Tandong; TIAN; Lide; LI; Zhen; SUN; Weizhen; WANG; Yu

    2006-01-01

    Based on summer observations of stable isotope of precipitation at Muztagata, western China, during 2002―2003, this paper presents the relationship between δ18O in precipitation and air temperature, and discusses the effect of moisture transport on δ18O in precipitation. Results show that air temperature correlates positively with δ18O in precipitation, and the temperature effect controls the δ18O of precipitation in this area. The Muztagata region exhibits high δ18O values in summer precipitation, similar to those shown at stations in adjacent regions. According to the results of our model set up to trace the moisture trajectories, the westerlies and local moisture circulation contribute to variations of oxygen isotopes in precipitation. In addition, the impacts of the moisture transport distance, the moisture transport level, and the incursion of the polar air mass also influence the variations of δ18O in precipitation. The moisture origins and transport mechanisms also contribute to the variation of δ18O in precipitation at Muztagata.

  11. Assessment and correction of BCC_CSM's performance in capturing leading modes of summer precipitation over North Asia

    KAUST Repository

    Gong, Zhiqiang

    2017-11-07

    This article examines the ability of Beijing Climate Center Climate System Model (BCC_CSM) in demonstrating the prediction accuracy and the leading modes of the summer precipitation over North Asia (NA). A dynamic-statistic combined approach for improving the prediction accuracy and the prediction of the leading modes of the summer precipitation over NA is proposed. Our results show that the BCC_CSM can capture part of the spatial anomaly features of the first two leading modes of NA summer precipitation. Moreover, BCC_CSM regains relationships such that the first and second mode of the empirical orthogonal function (EOF1 and EOF2) of NA summer precipitation, respectively, corresponds to the development of the El Niño and La Niña conditions in the tropical East Pacific. Nevertheless, BCC_CSM exhibits limited prediction skill over most part of NA and presents a deficiency in reproducing the EOF1\\'s and EOF2\\'s spatial pattern over central NA and EOF2\\'s interannual variability. This can be attributed as the possible reasons why the model is unable to capture the correct relationships among the basic climate elements over the central NA, lacks in its ability to reproduce a consistent zonal atmospheric pattern over NA, and has bias in predicting the relevant Sea Surface Temperature (SST) modes over the tropical Pacific and Indian Ocean regions. Based on the proposed dynamic-statistic combined correction approach, compared with the leading modes of BCC_CSM\\'s original prediction, anomaly correlation coefficients of corrected EOF1/EOF2 with the tropical Indian Ocean SST are improved from 0.18/0.36 to 0.51/0.62. Hence, the proposed correction approach suggests that the BCC_CSM\\'s prediction skill for the summer precipitation prediction over NA and its ability to capture the dominant modes could be certainly improved by choosing proper historical analogue information.

  12. Spatio-Temporal Variability of Summer Precipitation in Mexico under the Influence of the MJO, with Emphasis on the Bimodal Pattern

    Science.gov (United States)

    Perdigón, J.; Romero-Centeno, R.; Barrett, B.; Ordoñez-Perez, P.

    2017-12-01

    In many regions of Mexico, precipitation occurs in a very well defined annual cycle with peaks in May-June and September-October and a relative minimum in the middle of the rainy season known as the midsummer drought (MSD). The MJO is the most important mode of intraseasonal variability in the tropics, and, although some studies have shown its evident influence on summer precipitation in Mexico, its role in modulating the bimodal pattern of the summer precipitation cycle is still an open question. The spatio-temporal variability of summer precipitation in Mexico is analyzed through composite analysis according to the phases of the MJO, using the very high resolution CHIRPS precipitation data base and gridded data from the CFSR reanalysis to analyzing the MJO influence on the atmospheric circulation over Mexico and its adjacent basins. In general, during MJO phases 8-2 (4-6) rainfall is above-normal (below-normal), although, in some cases, the summer rainfall patterns during the same phase present considerable differences. The atmospheric circulation shows low (high) troposphere southwesterly (northeasterly) wind anomalies in southern Mexico under wetter conditions compared with climatological patterns, while the inverse pattern is observed under drier conditions. Composite anomalies of several variables also agreed well with those rainfall anomalies. Finally, a MJO complete cycle that reinforces (weakens) the bimodal pattern of summer rainfall in Mexico was found.

  13. Multi-pentad prediction of precipitation variability over Southeast Asia during boreal summer using BCC_CSM1.2

    Science.gov (United States)

    Li, Chengcheng; Ren, Hong-Li; Zhou, Fang; Li, Shuanglin; Fu, Joshua-Xiouhua; Li, Guoping

    2018-06-01

    Precipitation is highly variable in space and discontinuous in time, which makes it challenging for models to predict on subseasonal scales (10-30 days). We analyze multi-pentad predictions from the Beijing Climate Center Climate System Model version 1.2 (BCC_CSM1.2), which are based on hindcasts from 1997 to 2014. The analysis focus on the skill of the model to predict precipitation variability over Southeast Asia from May to September, as well as its connections with intraseasonal oscillation (ISO). The effective precipitation prediction length is about two pentads (10 days), during which the skill measured by anomaly correlation is greater than 0.1. In order to further evaluate the performance of the precipitation prediction, the diagnosis results of the skills of two related circulation fields show that the prediction skills for the circulation fields exceed that of precipitation. Moreover, the prediction skills tend to be higher when the amplitude of ISO is large, especially for a boreal summer intraseasonal oscillation. The skills associated with phases 2 and 5 are higher, but that of phase 3 is relatively lower. Even so, different initial phases reflect the same spatial characteristics, which shows higher skill of precipitation prediction in the northwest Pacific Ocean. Finally, filter analysis is used on the prediction skills of total and subseasonal anomalies. The results of the two anomaly sets are comparable during the first two lead pentads, but thereafter the skill of the total anomalies is significantly higher than that of the subseasonal anomalies. This paper should help advance research in subseasonal precipitation prediction.

  14. New summer areas and mixing of two greater sandhill crane populations in the Intermountain West

    Science.gov (United States)

    Collins, Daniel P.; Grisham, Blake A.; Conring, Courtenay M.; Knetter, Jeffrey M.; Conway, Warren C.; Carleton, Scott A.; Boggie, Matthew A.

    2016-01-01

    Population delineation throughout the annual life cycle for migratory birds is needed to formulate regional and national management and conservation strategies. Despite being well studied continentally, connectivity of sandhill crane Grus canadensis populations throughout the western portion of their North American range remains poorly described. Our objectives were to 1) use global positioning system satellite transmitter terminals to identify summer distributions for the Lower Colorado River Valley Population of greater sandhill cranes Grus canadensis tabida and 2) determine whether intermingling occurs among any of the western greater sandhill crane populations: Rocky Mountain Population, Lower Colorado River Valley Population, and Central Valley Population. Capture and marking occurred during winter and summer on private lands in California and Idaho as well as on two National Wildlife Refuges: Cibola and Sonny Bono Salton Sea National Wildlife Refuges. A majority of marked greater sandhill cranes summered in what is established Lower Colorado River Valley Population breeding areas in northeastern Nevada and southwestern Idaho. A handful of greater sandhill cranes summered outside of traditional breeding areas in west-central Idaho around Cascade Reservoir near Donnelly and Cascade, Idaho. For example, a greater sandhill crane colt captured near Donnelly in July 2014 survived to winter migration and moved south to areas associated with the Rocky Mountain Population. The integration of the greater sandhill crane colt captured near Donnelly provides the first evidence of potential intermingling between the Lower Colorado River Population and Rocky Mountain Population. We suggest continued marking and banding efforts of all three western populations of greater sandhill cranes will accurately delineate population boundaries and connectivity and inform management decisions for the three populations.

  15. Investigation of Microphysical Parameters within Winter and Summer Type Precipitation Events over Mountainous [Complex] Terrain

    International Nuclear Information System (INIS)

    Stalker, James R.; Bossert, James E.

    1997-10-01

    In this study we investigate complex terrain effects on precipitation with RAMS for both in winter and summer cases from a microphysical perspective. We consider a two dimensional east-west topographic cross section in New Mexico representative of the Jemez mountains on the west and the Sangre de Cristo mountains on the east. Located between these two ranges is the Rio Grande Valley. In these two dimensional experiments, variations in DSDs are considered to simulate total precipitation that closely duplicate observed precipitation

  16. Changes in urban-related precipitation in the summer over three city clusters in China

    Science.gov (United States)

    Zhao, Deming; Wu, Jian

    2017-09-01

    The impacts of urban surface expansion on the summer precipitations over three city clusters [Beijing-Tianjin-Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD)] in eastern China under different monsoonal circulation backgrounds were explored using the nested fifth-generation Penn State/NCAR Mesoscale Model version 3.7 (MM5 V3.7), including the urban-related thermal and dynamical parameters. Ten-year integrations were performed using satellite image data from 2000 and 2010 to represent the urban surface distributions and expansions in China. Changes in the precipitation revealed obvious subregional characteristics, which could be explained by the influences of the vertical wind velocity and moisture flux. With urban-related warming, vertical wind motion generally intensified over urban surface-expanded areas. Meanwhile, the increase in impervious surface areas induced rapid rainwater runoff into drains, and the Bowen ratio increased over urban areas, which further contributed to changes in the local moisture fluxes in these regions. The intensities of the changes in precipitation were inconsistent over the three city clusters, although the changes in vertical motion and local evaporation were similar, which indicates that the changes in precipitation cannot be solely explained by the changes in the local evaporation-related moisture flux. The changes in precipitation were also influenced by the changes in the East Asian summer monsoon (EASM) circulation and the corresponding moisture flux, which are expressed in marked subregional characteristics. Therefore, the influence of urban-related precipitation over the three city clusters in China, for which changes in moisture flux from both the impacted local evaporation and EASM circulation should be considered, varied based on the precipitation changes of only a single city.

  17. Sensitivity of U.S. summer precipitation to model resolution and convective parameterizations across gray zone resolutions

    Science.gov (United States)

    Gao, Yang; Leung, L. Ruby; Zhao, Chun; Hagos, Samson

    2017-03-01

    Simulating summer precipitation is a significant challenge for climate models that rely on cumulus parameterizations to represent moist convection processes. Motivated by recent advances in computing that support very high-resolution modeling, this study aims to systematically evaluate the effects of model resolution and convective parameterizations across the gray zone resolutions. Simulations using the Weather Research and Forecasting model were conducted at grid spacings of 36 km, 12 km, and 4 km for two summers over the conterminous U.S. The convection-permitting simulations at 4 km grid spacing are most skillful in reproducing the observed precipitation spatial distributions and diurnal variability. Notable differences are found between simulations with the traditional Kain-Fritsch (KF) and the scale-aware Grell-Freitas (GF) convection schemes, with the latter more skillful in capturing the nocturnal timing in the Great Plains and North American monsoon regions. The GF scheme also simulates a smoother transition from convective to large-scale precipitation as resolution increases, resulting in reduced sensitivity to model resolution compared to the KF scheme. Nonhydrostatic dynamics has a positive impact on precipitation over complex terrain even at 12 km and 36 km grid spacings. With nudging of the winds toward observations, we show that the conspicuous warm biases in the Southern Great Plains are related to precipitation biases induced by large-scale circulation biases, which are insensitive to model resolution. Overall, notable improvements in simulating summer rainfall and its diurnal variability through convection-permitting modeling and scale-aware parameterizations suggest promising venues for improving climate simulations of water cycle processes.

  18. Regional-scale relationships between aerosol and summer monsoon circulation, and precipitation over northeast Asia

    Science.gov (United States)

    Yoon, Soon-Chang; Kim, Sang-Woo; Choi, Suk-Jin; Choi, In-Jin

    2010-08-01

    We investigated the regional-scale relationships between columnar aerosol loads and summer monsoon circulation, and also the precipitation over northeast Asia using aerosol optical depth (AOD) data obtained from the 8-year MODIS, AERONET Sun/sky radiometer, and precipitation data acquired under the Global Precipitation Climatology Project (GPCP). These high-quality data revealed the regional-scale link between AOD and summer monsoon circulation, precipitation in July over northeast Asian countries, and their distinct spatial and annual variabilities. Compared to the mean AOD for the entire period of 2001-2008, the increase of almost 40-50% in the AOD value in July 2005 and July 2007 was found over the downwind regions of China (Yellow Sea, Korean peninsula, and East Sea), with negative precipitation anomalies. This can be attributable to the strong westerly confluent flows, between cyclone flows by continental thermal low centered over the northern China and anticyclonic flows by the western North Pacific High, which transport anthropogenic pollution aerosols emitted from east China to aforementioned downwind high AOD regions along the rim of the Pacific marine airmass. In July 2002, however, the easterly flows transported anthropogenic aerosols from east China to the southwestern part of China in July 2002. As a result, the AOD off the coast of China was dramatically reduced in spite of decreasing rainfall. From the calculation of the cross-correlation coefficient between MODIS-derived AOD anomalies and GPCP precipitation anomalies in July over the period 2001-2008, we found negative correlations over the areas encompassed by 105-115°E and 30-35°N and by 120-140°E and 35-40°N (Yellow Sea, Korean peninsula, and East Sea). This suggests that aerosol loads over these regions are easily influenced by the Asian monsoon flow system and associated precipitation.

  19. Effects of air-sea coupling over the North Sea and the Baltic Sea on simulated summer precipitation over Central Europe

    Science.gov (United States)

    Ho-Hagemann, Ha Thi Minh; Gröger, Matthias; Rockel, Burkhardt; Zahn, Matthias; Geyer, Beate; Meier, H. E. Markus

    2017-12-01

    This study introduces a new approach to investigate the potential effects of air-sea coupling on simulated precipitation inland over Central Europe. We present an inter-comparison of two regional climate models (RCMs), namely, the COSMO-CLM (hereafter CCLM) and RCA4 models, which are configured for the EURO-CORDEX domain in the coupled and atmosphere-only modes. Two versions of the CCLM model, namely, 4.8 and 5.0, join the inter-comparison being almost two different models while providing pronouncedly different summer precipitation simulations because of many changes in the dynamics and physics of CCLM in version 5.0. The coupling effect on the prominent summer dry bias over Central Europe is analysed using seasonal (JJA) mean statistics for the 30-year period from 1979 to 2009, with a focus on extreme precipitation under specific weather regimes. The weather regimes are compared between the coupled and uncoupled simulations to better understand the mechanism of the coupling effects. The comparisons of the coupled systems with the atmosphere-only models show that coupling clearly reduces the dry bias over Central Europe for CCLM 4.8, which has a large dry summer bias, but not for CCLM 5.0 and RCA4, which have smaller dry biases. This result implies that if the atmosphere-only model already yields reasonable summer precipitation over Central Europe, not much room for improvement exists that can be caused by the air-sea coupling over the North Sea and the Baltic Sea. However, if the atmosphere-only model shows a pronounced summer dry bias because of a lack of moisture transport from the seas into the region, the considered coupling may create an improved simulation of summer precipitation over Central Europe, such as for CCLM 4.8. For the latter, the benefit of coupling varies over the considered timescales. The precipitation simulations that are generated by the coupled system COSTRICE 4.8 and the atmosphere-only CCLM 4.8 are mostly identical for the summer mean

  20. Climatic change of summer temperature and precipitation in the Alpine region - a statistical-dynamical assessment

    Energy Technology Data Exchange (ETDEWEB)

    Heimann, D.; Sept, V.

    1998-12-01

    Climatic changes in the Alpine region due to increasing greenhouse gas concentrations are assessed by using statistical-dynamical downscaling. The downscaling procedure is applied to two 30-year periods (1971-2000 and 2071-2100, summer months only) of the output of a transient coupled ocean/atmosphere climate scenario simulation. The downscaling results for the present-day climate are in sufficient agreement with observations. The estimated regional climate change during the next 100 years shows a general warming. The mean summer temperatures increase by about 3 to more than 5 Kelvin. The most intense climatic warming is predicted in the western parts of the Alps. The amount of summer precipitation decreases in most parts of central Europe by more than 20 percent. Only over the Adriatic area and parts of eastern central Europe an increase in precipitation is simulated. The results are compared with observed trends and results of regional climate change simulations of other authors. The observed trends and the majority of the simulated trends agree with our results. However, there are also climate change estimates which completely contradict with ours. (orig.) 29 refs.

  1. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    KAUST Repository

    Gong, Zhiqiang; Dogar, Muhammad Mubashar; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-01-01

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection

  2. Large-scale connection between aerosol optical depth and summer monsoon circulation, and precipitation over northeast Asia

    Science.gov (United States)

    Kim, Sang-Woo; Yoon, Soon-Chang; Choi, Suk-Jin; Choi, In-Jin

    2010-05-01

    We investigated the large-scale connection between columnar aerosol loads and summer monsoon circulation, and also the precipitation over northeast Asia using aerosol optical depth (AOD) data obtained from the 8-year MODIS, AERONET Sun/sky radiometer, and precipitation data acquired under the Global Precipitation Climatology Project (GPCP). These high-quality data revealed the large-scale link between AOD and summer monsoon circulation, precipitation in July over northeast Asian countries, and their distinct spatial and annual variabilities. Compared to the mean AOD for the entire period of 2001-2008, the increase of almost 40-50% in the AOD value in July 2005 and July 2007 was found over the downwind regions of China (Yellow Sea, Korean peninsula, and East Sea), with negative precipitation anomalies. This can be attributable to the strong westerly confluent flows, between cyclone flows by continental thermal low centered over the northern China and anti-cyclonic flows by the western North Pacific High, which transport anthropogenic pollution aerosols emitted from east China to aforementioned downwind high AOD regions along the rim of the Pacific marine airmass. In July 2002, however, the easterly flows transported anthropogenic aerosols from east China to the southwestern part of China in July 2002. As a result, the AOD off the coast of China was dramatically reduced in spite of decreasing rainfall. From the calculation of the cross-correlation coefficient between MODIS-derived AOD anomalies and GPCP precipitation anomalies over the period 2001-2008, we found negative correlations over the areas encompassed by 105-115E and 30-35N and by 120-140E and 35-40N (Yellow Sea, Korean peninsula, and East Sea). This suggests that aerosol loads over these regions are easily influenced by the Asian monsoon flow system and associated precipitation.

  3. Spatio-temporal variation of precipitation in the Three-River Headwater Region from 1961 to 2010

    Institute of Scientific and Technical Information of China (English)

    YI Xiangsheng; LI Guosheng; YIN Yanyu

    2013-01-01

    Based on a monthly dataset of precipitation time series (1961-2010) from 12 meteorological stations across the Three-River Headwater Region (THRHR) of Qinghai Province,China,the spatio-temporal variation and abrupt change analysis of precipitation were examined by using moving average,linear regression,spline interpolation,the Mann-Kendall test and so on.Major conclusions were as follows.(1) The long-term annual and seasonal precipitation in the study area indicated an increasing trend with some oscillations during 1961-2010; however,the summer precipitation in the Lantsang (Lancang) River Headwater Region (LARHR),and the autumn precipitation in the Yangtze River Headwater Region (YERHR) of the THRHR decreased in the same period.(2) The amount of annual precipitation in the THRHR and its three sub-headwater regions was greater in the 1980s and 2000s.The springs were fairly wet after the 1970s,while the summers were relatively wet in the 1960s,1980s and 2000s.In addition,the amount of precipitation in the autumn was greater in the 1970s and 1980s,but it was relatively less for the winter precipitation,except in the 1990s.(3) The normal values of spring,summer,winter and annual precipitation in the THRHR and its three sub-headwater regions all increased,but the normal value of summer precipitation in the LARHR had a negative trend and the normal value of winter precipitation declined in general.(4) The spring and winter precipitation increased in most of the THRHR.The summer,autumn and annual precipitation increased mainly in the marginal area of the west and north and decreased in the regions of Yushu,Zaduo,Jiuzhi and Banma.(5) The spring and winter precipitation in the THRHR and its three sub-headwater regions showed an abrupt change,except for the spring precipitation in the YARHR.The abrupt changes of spring precipitation were mainly in the late 1980s and early 1990s,while the abrupt changes of winter precipitation were primary in the mid-to late 1970s

  4. Interdecadal change in the summer SST-precipitation relationship around the late 1990s over the South China Sea

    Science.gov (United States)

    Chen, Jiepeng; Wang, Xin; Zhou, Wen; Wen, Zhiping

    2017-11-01

    An interdecadal change in the air-sea interaction over the South China Sea (SCS) after the late 1990s has been identified using a local contemporaneous precipitation-sea surface temperature (SST) and precipitation-SST tendency relationship. During 1979-1998, there is a negative precipitation-SST relationship over the SCS, with a larger magnitude over the northeastern SCS (NESCS) than over the southwestern SCS (SWSCS). The remote effect of warmer SST over the tropical Indian Ocean plays a crucial role in a strong anticyclone and suppressed rainfall over the SCS and western North Pacific. Due to greater mixed-layer depth over the SWSCS than over the NESCS, entrainment heat flux makes a larger contribution to a positive precipitation-SST tendency over the SWSCS than over the NESCS. The cloud-radiation effect has a dominant and positive contribution to the SST tendency over the NESCS, whereas it has a negative contribution to SST tendency over the SWSCS. In contrast, the precipitation-SST correlation becomes weakly negative over the NESCS and significantly positive over the SWSCS during 1999-2013. The CESM-CAM5 model demonstrates that cooler SST over the tropical central-eastern Pacific (TCEP) triggers a weak anticyclone, slightly suppressing rainfall over the SCS. The cloud-radiation effect still contributes mostly to a positive SST tendency over the NESCS. Warmer SST over the SWSCS induces an increase in surface evaporation and low-level moisture convergence and causes enhanced rainfall. That offsets the remote effect of TCEP SST and results in a negative precipitation-SST tendency with negative cloud-radiation feedback. The interdecadal change in remote forcing to SCS rainfall around the late 1990s is related to the evolution of TCEP SST anomalies from the preceding winter to summer, which is possibly modulated by the phase of the Pacific Decadal Oscillation.

  5. Time variation of the effect of geographical factors on spatial distribution of summer precipitation over the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Moliba Bankanza, Jacques Celestin

    2011-01-01

    Roč. 115, 1-2 (2011), s. 51-70 ISSN 0324-6329 Institutional research plan: CEZ:AV0Z30420517 Keywords : multivariate regression * precipitation models * summer precipitation * geographic influence * environmental variables * temporal variability * Czech Republic Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.364, year: 2011 http://owww.met.hu/download.php?id=2&vol=115&no=1-2&a=4

  6. Combined Effects of Synoptic-Scale Teleconnection Patterns on Summer Precipitation in Southern China

    Directory of Open Access Journals (Sweden)

    Chao Wang

    2018-04-01

    Full Text Available Using ERA-Interim daily reanalysis and precipitation data, the combined effects of East Asia-Pacific (EAP and Silk Road (SR teleconnection patterns on summer precipitation in Southern China were investigated on synoptic to sub-monthly timescales. Combined EAP and SR patterns lead to more persistent and extreme precipitation in the Yangtze River Valley (YRV and exhibit an obvious zonal advance between the South Asia High (SAH and Western Pacific Subtropical High (WPSH prior to its onset. During typical combined events, an overlap between the SAH and WPSH remains in a favorable position for Persistent Extreme Precipitation (PEP. Furthermore, SR-induced acceleration of the westerly jet stream and extra positive vorticity advection provide persistent upper-level divergence for YRV precipitation. An anomalous EAP-related cyclone/anticyclone pair over East Asia induces enhanced low-level southwesterlies to the northern anticyclone flank and northerlies from the mid-latitudes, advecting anomalously abundant moisture toward the YRV, resulting in clear moisture convergence. Moreover, the strong ascent of warmer/moister air along a quasi-stationary front may be crucial for PEP. During decay, the SAH and WPSH diverge from each other and retreat to their normal positions, and the strong ascent of warmer/moister air rapidly weakens to dissipation, terminating PEP in the YRV.

  7. Few apparent short-term effects of elevated soil temperature and increased frequency of summer precipitation on the abundance and taxonomic diversity of desert soil micro- and meso-fauna

    Science.gov (United States)

    Darby, B.J.; Neher, D.A.; Housman, D.C.; Belnap, J.

    2011-01-01

    Frequent hydration and drying of soils in arid systems can accelerate desert carbon and nitrogen mobilization due to respiration, microbial death, and release of intracellular solutes. Because desert microinvertebrates can mediate nutrient cycling, and the autotrophic components of crusts are known to be sensitive to rapid desiccation due to elevated temperatures after wetting events, we studied whether altered soil temperature and frequency of summer precipitation can also affect the composition of food web consumer functional groups. We conducted a two-year field study with experimentally-elevated temperature and frequency of summer precipitation in the Colorado Plateau desert, measuring the change in abundance of nematodes, protozoans, and microarthropods. We hypothesized that microfauna would be more adversely affected by the combination of elevated temperature and frequency of summer precipitation than either effect alone, as found previously for phototrophic crust biota. Microfauna experienced normal seasonal fluctuations in abundance, but the effect of elevated temperature and frequency of summer precipitation was statistically non-significant for most microfaunal groups, except amoebae. The seasonal increase in abundance of amoebae was reduced with combined elevated temperature and increased frequency of summer precipitation compared to either treatment alone, but comparable with control (untreated) plots. Based on our findings, we suggest that desert soil microfauna are relatively more tolerant to increases in ambient temperature and frequency of summer precipitation than the autotrophic components of biological soil crust at the surface.

  8. The Interdecadal Variability of Summer Precipitation over the South of China and its Response to Asian Monsoon at the Turning Points of Global Warming

    Science.gov (United States)

    Wang, Huan; Li, Dongliang

    2017-04-01

    Under the background of global warming, decadal variability of the summer precipitation in the South of China and the Asian monsoon experienced mutations at around the end of 1970s, the beginning of 1990s and 21st century. We examined the external and internal forcings which may cause the mutations and diagnosed the mechanism. Human emission of CO2 has always been the fatal reason for global warming, and it is also the primary reason for the precipitation increasing over Yangtze-Huai river basin at the end of the 1970s. The Yangtze-Huai river basin and South China demonstrated more summer rainfall after 1993. This can be explained by the weakening of the Asian summer monsoon caused by the positive anomaly of summer SST over northwest Pacific Ocean and Indian Ocean. A significant trend in the enhancement of sensible heat over the TP has exerted some considerable influence on the reinforce of the EASM, accompanied by the northward migration of the summer precipitation belt shifting northward at the beginning of 21st century.

  9. 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

  10. Future changes in summer mean and extreme precipitation frequency in Japan by d4PDF regional climate simulations

    Science.gov (United States)

    Okada, Y.; Ishii, M.; Endo, H.; Kawase, H.; Sasaki, H.; Takayabu, I.; Watanabe, S.; Fujita, M.; Sugimoto, S.; Kawazoe, S.

    2017-12-01

    Precipitation in summer plays a vital role in sustaining life across East Asia, but the heavy rain that is often generated during this period can also cause serious damage. Developing a better understanding of the features and occurrence frequency of this heavy rain is an important element of disaster prevention. We investigated future changes in summer mean and extreme precipitation frequency in Japan using large ensemble dataset which simulated by the Non-Hydrostatic Regional Climate Model with a horizontal resolution of 20km (NHRCM20). This dataset called database for Policy Decision making for Future climate changes (d4PDF), which is intended to be utilized for the impact assessment studies and adaptation planning to global warming. The future climate experiments assume the global mean surface air temperature rise 2K and 4K from the pre-industrial period. We investigated using this dataset future changes of precipitation in summer over the Japanese archipelago based on observational locations. For mean precipitation in the present-day climate, the bias of the rainfall for each month is within 25% even considering all members (30 members). The bias at each location is found to increase by over 50% on the Pacific Ocean side of eastern part of Japan and interior locations of western part of Japan. The result in western part of Japan depends on the effect of the elevations in this model. The future changes in mean precipitation show a contrast between northern and southern Japan, with the north showing a slight increase but the south a decrease. The future changes in the frequency of extreme precipitation in the national average of Japan increase at 2K and 4K simulations compared with the present-day climate, respectively. The authors were supported by the Social Implementation Program on Climate Change Adaptation Technology (SI-CAT), the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.

  11. Cluster analysis on summer precipitation field over Qinghai-Tibet Plateau from 1961 to 2004%1961-2004年青藏高原夏季降水的时空分布

    Institute of Scientific and Technical Information of China (English)

    卢鹤立; 邵全琴; 刘纪远; 王军邦; 陈沈斌; 陈卓奇

    2008-01-01

    The summer day-by-day precipitation data of 97 meteorological stations on the Qinghai-Tibet Plateau from 1961 to 2004 were selected to analyze the temporal-spatial dis- tribution through accumulated variance, correlation analysis, regression analysis, empirical orthogonal function, power spectrum function and spatial analysis tools of GIS. The result showed that summer precipitation occupied a relatively high proportion in the area with less annual precipitation on the Plateau and the correlation between summer precipitation and annual precipitation was strong. The altitude of these stations and summer precipitation ten- dency presented stronger positive correlation below 2000 m, with correlation value up to 0.604 (a=0.01). The subtracting tendency values between 1961-1983 and 1984-2004 at five altitude ranges (2000-2500 m, 2500-3000 m, 3500-4000 m, 4000-4500 m and above 4500 m) were above zero and accounted for 71.4% of the total. Using empirical orthogonal function, summer precipitation could be roughly divided into three precipitation pattern fields: the Southeast Plateau Pattern Field, the Northeast Plateau Pattern field and the Three Rivers' Headstream Regions Pattern Field. The former two ones had a reverse value from the north to the south and opposite line was along 35°N. The potential cycles of the three pattern fields were 5.33a, 21.33a and 2.17a respectively, tested by the confidence probability of 90%. The station altitudes and summer precipitation potential cycles presented strong negative corre- lation in the stations above 4500 m, with correlation value of -0.626 (a=0.01). In Three Rivers Headstream Regions summer precipitation cycle decreased as the altitude rose in the sta- tions above 3500 m and increased as the altitude rose in those below 3500 m. The empirical orthogonal function analysis in June precipitation, July precipitation and August precipitation showed that the June precipitation pattern field was similar to the July's, in which

  12. Predictable patterns of the Asian and Indo-Pacific summer precipitation in the NCEP CFS

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Jianyin [CMA Institute of Tropical and Marine Meteorology, Guangzhou, Guangdong (China); Yang, Song; Kumar, Arun [NOAA/NWS/NCEP Climate Prediction Center, Camp Springs, MD (United States); Hu, Zeng-Zhen [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); Huang, Bohua [George Mason University, Department of Climate Dynamics, Fairfax, VA (United States); Zhang, Zuqiang [CMA National Climate Center, Beijing (China)

    2009-06-15

    The predictable patterns of the Asian and Indo-Pacific summer precipitation in the NCEP climate forecast system (CFS) are depicted by applying a maximized signal-to-noise empirical orthogonal function analysis. The CFS captures the two most dominant modes of observed climate patterns. The first most dominant mode is characterized by the climate features of the onset years of El Nino-Southern Oscillation (ENSO), with strong precipitation signals over the tropical eastern Indian and western Pacific oceans, Southeast Asia, and tropical Asian monsoon regions including the Bay of Bengal and the South China Sea. The second most dominant mode is characterized by the climate features of the decay years of ENSO, with weakening signals over the western-central Pacific and strengthening signals over the Indian Ocean. The CFS is capable of predicting the most dominant modes several months in advance. It is also highly skillful in capturing the air-sea interaction processes associated with the precipitation features, as demonstrated in sea surface temperature and wind patterns. (orig.)

  13. An Evaluation of the Predictability of Austral Summer Season Precipitation over South America.

    Science.gov (United States)

    Misra, Vasubandhu

    2004-03-01

    In this study predictability of austral summer seasonal precipitation over South America is investigated using a 12-yr set of a 3.5-month range (seasonal) and a 17-yr range (continuous multiannual) five-member ensemble integrations of the Center for Ocean Land Atmosphere Studies (COLA) atmospheric general circulation model (AGCM). These integrations were performed with prescribed observed sea surface temperature (SST); therefore, skill attained represents an estimate of the upper bound of the skill achievable by COLA AGCM with predicted SST. The seasonal runs outperform the multiannual model integrations both in deterministic and probabilistic skill. The simulation of the January February March (JFM) seasonal climatology of precipitation is vastly superior in the seasonal runs except over the Nordeste region where the multiannual runs show a marginal improvement. The teleconnection of the ensemble mean JFM precipitation over tropical South America with global contemporaneous observed sea surface temperature in the seasonal runs conforms more closely to observations than in the multiannual runs. Both the sets of runs clearly beat persistence in predicting the interannual precipitation anomalies over the Amazon River basin, Nordeste, South Atlantic convergence zone, and subtropical South America. However, both types of runs display poorer simulations over subtropical regions than the tropical areas of South America. The examination of probabilistic skill of precipitation supports the conclusions from deterministic skill analysis that the seasonal runs yield superior simulations than the multiannual-type runs.

  14. 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.

  15. Atmospheric Circulation Patterns over East Asia and Their Connection with Summer Precipitation and Surface Air Temperature in Eastern China during 1961-2013

    Science.gov (United States)

    Li, Shuping; Hou, Wei; Feng, Guolin

    2018-04-01

    Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961-2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in eastern China as well as associated external forcing are investigated. Three patterns of the atmospheric circulation are identified, all with quasi-barotropic structures: (1) the East Asia/Pacific (EAP) pattern, (2) the Baikal Lake/Okhotsk Sea (BLOS) pattern, and (3) the eastern China/northern Okhotsk Sea (ECNOS) pattern. The positive EAP pattern significantly increases precipitation over the Yangtze River valley and favors cooling north of the Yangtze River and warming south of the Yangtze River in summer. The warm sea surface temperature anomalies over the tropical Indian Ocean suppress convection over the northwestern subtropical Pacific through the Ekman divergence induced by a Kelvin wave and excite the EAP pattern. The positive BLOS pattern is associated with below-average precipitation south of the Yangtze River and robust cooling over northeastern China. This pattern is triggered by anomalous spring sea ice concentration in the northern Barents Sea. The anomalous sea ice concentration contributes to a Rossby wave activity flux originating from the Greenland Sea, which propagates eastward to North Pacific. The positive ECNOS pattern leads to below-average precipitation and significant warming over northeastern China in summer. The reduced soil moisture associated with the earlier spring snowmelt enhances surface warming over Mongolia and northeastern China and the later spring snowmelt leads to surface cooling over Far East in summer, both of which are responsible for the formation of the ECNOS pattern.

  16. ENSO variability reflected in precipitation oxygen isotopes across the Asian Summer Monsoon region

    Science.gov (United States)

    Cai, Zhongyin; Tian, Lide; Bowen, Gabriel J.

    2017-10-01

    Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.

  17. Increased temperature and altered summer precipitation have differential effects on biological soil crusts in a dryland ecosystem

    Science.gov (United States)

    Johnson, Shannon L.; Kuske, Cheryl R.; Carney, Travis D.; Housman, David C.; Gallegos-Graves, La Verne; Belnap, Jayne

    2012-01-01

    Biological soil crusts (biocrusts) are common and ecologically important members of dryland ecosystems worldwide, where they stabilize soil surfaces and contribute newly fixed C and N to soils. To test the impacts of predicted climate change scenarios on biocrusts in a dryland ecosystem, the effects of a 2–3 °C increase in soil temperature and an increased frequency of smaller summer precipitation events were examined in a large, replicated field study conducted in the cold desert of the Colorado Plateau, USA. Surface soil biomass (DNA concentration), photosynthetically active cyanobacterial biomass (chlorophyll a concentration), cyanobacterial abundance (quantitative PCR assay), and bacterial community composition (16S rRNA gene sequencing) were monitored seasonally over 2 years. Soil microbial biomass and bacterial community composition were highly stratified between the 0–2 cm depth biocrusts and 5–10 cm depth soil beneath the biocrusts. The increase in temperature did not have a detectable effect on any of the measured parameters over 2 years. However, after the second summer of altered summer precipitation pattern, significant declines occurred in the surface soil biomass (avg. DNA concentration declined 38%), photosynthetic cyanobacterial biomass (avg. chlorophyll a concentration declined 78%), cyanobacterial abundance (avg. gene copies g−1 soil declined 95%), and proportion of Cyanobacteria in the biocrust bacterial community (avg. representation in sequence libraries declined 85%). Biocrusts are important contributors to soil stability, soil C and N stores, and plant performance, and the loss or reduction of biocrusts under an altered precipitation pattern associated with climate change could contribute significantly to lower soil fertility and increased erosion and dust production in dryland ecosystems at a regional scale.

  18. Climate dynamics of South America during summer: Connections between the large-scale circulation and regional precipitation

    Science.gov (United States)

    Lenters, Johh Derick

    1997-05-01

    Relationships between the large-scale circulation and regional precipitation over South America during austral summer are examined using a GCM, linear model, and observational analyses. Emphasis is placed on understanding the origin of upper-tropospheric circulation features such as the Bolivian high and its effects on South American precipitation variability, particularly on the Central Andean Altiplano. Results from the linear model indicate that the Bolivian high and 'Nordeste low' are generated in response to precipitation over the Amazon basin, Central Andes, and South Atlantic convergence zone (SACZ), with African precipitation also playing a crucial role in the formation of the low. The direct mechanical and sensible heating effects of the Andes are minimal, acting only to induce a weak lee trough in midlatitudes and a shallow monsoonal circulation over the Central Andes. In the GCM the effects of the Andes include a strengthening of the Bolivian high and northward shift of the Nordeste low, primarily through changes in the precipitation field. The position of the Bolivian high is primarily determined by Amazonian precipitation and is little affected by the removal of the Andes. Strong subsidence to the west of the high is found to be important for the maintenance of the high's warm core, while large-scale convective overshooting to the east is responsible for a layer of cold air above the high. Observations from eight summer seasons reveal a close relationship between precipitation variability in the Central Andes and the position and intensity of the Bolivian high. The physical mechanisms of this connection are explored using composite, EOF, and correlation techniques. On intraseasonal to interannual timescales, rainy episodes on the Altiplano are found to be associated with warm, moist, poleward flow along the eastern flank of the Andes, often in conjunction with extratropical disturbances and a westward displacement of the SACZ. Corresponding to this

  19. Comparison of aerosol effects on simulated spring and summer hailstorm clouds

    Science.gov (United States)

    Yang, Huiling; Xiao, Hui; Guo, Chunwei; Wen, Guang; Tang, Qi; Sun, Yue

    2017-07-01

    Numerical simulations are carried out to investigate the effect of cloud condensation nuclei (CCN) concentrations on microphysical processes and precipitation characteristics of hailstorms. Two hailstorm cases are simulated, a spring case and a summer case, in a semiarid region of northern China, with the Regional Atmospheric Modeling System. The results are used to investigate the differences and similarities of the CCN effects between spring and summer hailstorms. The similarities are: (1) The total hydrometeor mixing ratio decreases, while the total ice-phase mixing ratio enhances, with increasing CCN concentration; (2) Enhancement of the CCN concentration results in the production of a greater amount of small-sized hydrometeor particles, but a lessening of large-sized hydrometeor particles; (3) As the CCN concentration increases, the supercooled cloud water and rainwater make a lesser contribution to hail, while the ice-phase hydrometeors take on active roles in the growth of hail; (4) When the CCN concentration increases, the amount of total precipitation lessens, while the role played by liquid-phase rainfall in the amount of total precipitation reduces, relatively, compared to that of ice-phase precipitation. The differences between the two storms include: (1) An increase in the CCN concentration tends to reduce pristine ice mixing ratios in the spring case but enhance them in the summer case; (2) Ice-phase hydrometeor particles contribute more to hail growth in the spring case, while liquid water contributes more in the summer case; (3) An increase in the CCN concentration has different effects on surface hail precipitation in different seasons.

  20. Isotope fingerprinting of precipitation associated with western disturbances and Indian summer monsoons across the Himalayas

    Science.gov (United States)

    Jeelani, Ghulam; Deshpande, R. D.

    2017-12-01

    Precipitation samples were collected across the Himalayas from Kashmir (western Himalaya) to Assam (eastern Himalaya) to understand the variation of the stable isotopic content (δ ^{18}O and δ D) in precipitation associated with two dominant weather systems of the region: western disturbances (WDs) and Indian summer monsoon (ISM). Large spatial and temporal variations in isotopic values were noted with δ^{18}O and δ D values ranging from -30.3 to [InlineEquation not available: see fulltext.] and -228 to [InlineEquation not available: see fulltext.], respectively. The d-excess values also exhibit a large range of variation from -30 to [InlineEquation not available: see fulltext.]. In general, heavier isotopic values are observed in most of the samples in Jammu, whereas lighter values are observed in majority of the samples in Uttarakhand. Precipitation at Jammu seems to have undergone intense evaporation while that from Uttarakhand suggest normal Rayleigh fractionation/distillation of the air mass as it moves from the source region to the precipitation site and/or orographic lifting. The d-excess of rainfall in Kashmir has a distinctly higher median value of [InlineEquation not available: see fulltext.] compared to other precipitation sites with a median of [InlineEquation not available: see fulltext.]. Using distinct isotopic signatures, the regions receiving precipitation from two different weather systems have been identified.

  1. Uncertainty of global summer precipitation in the CMIP5 models: a comparison between high-resolution and low-resolution models

    Science.gov (United States)

    Huang, Danqing; Yan, Peiwen; Zhu, Jian; Zhang, Yaocun; Kuang, Xueyuan; Cheng, Jing

    2018-04-01

    The uncertainty of global summer precipitation simulated by the 23 CMIP5 CGCMs and the possible impacts of model resolutions are investigated in this study. Large uncertainties exist over the tropical and subtropical regions, which can be mainly attributed to convective precipitation simulation. High-resolution models (HRMs) and low-resolution models (LRMs) are further investigated to demonstrate their different contributions to the uncertainties of the ensemble mean. It shows that the high-resolution model ensemble means (HMME) and low-resolution model ensemble mean (LMME) mitigate the biases between the MME and observation over most continents and oceans, respectively. The HMME simulates more precipitation than the LMME over most oceans, but less precipitation over some continents. The dominant precipitation category in the HRMs (LRMs) is the heavy precipitation (moderate precipitation) over the tropic regions. The combinations of convective and stratiform precipitation are also quite different: the HMME has much higher ratio of stratiform precipitation while the LMME has more convective precipitation. Finally, differences in precipitation between the HMME and LMME can be traced to their differences in the SST simulations via the local and remote air-sea interaction.

  2. Future Projection of Summer Extreme Precipitation from High Resolution Multi-RCMs over East Asia

    Science.gov (United States)

    Kim, Gayoung; Park, Changyong; Cha, Dong-Hyun; Lee, Dong-Kyou; Suh, Myoung-Seok; Ahn, Joong-Bae; Min, Seung-Ki; Hong, Song-You; Kang, Hyun-Suk

    2017-04-01

    Recently, the frequency and intensity of natural hazards have been increasing due to human-induced climate change. Because most damages of natural hazards over East Asia have been related to extreme precipitation events, it is important to estimate future change in extreme precipitation characteristics caused by climate change. We investigate future changes in extremal values of summer precipitation simulated by five regional climate models participating in the CORDEX-East Asia project (i.e., HadGEM3-RA, RegCM4, MM5, WRF, and GRIMs) over East Asia. 100-year return value calculated from the generalized extreme value (GEV) parameters is analysed as an indicator of extreme intensity. In the future climate, the mean values as well as the extreme values of daily precipitation tend to increase over land region. The increase of 100-year return value can be significantly associated with the changes in the location (intensity) and scale (variability) GEV parameters for extreme precipitation. It is expected that the results of this study can be used as fruitful references when making the policy of disaster management. Acknowledgements The research was supported by the Ministry of Public Safety and Security of Korean government and Development program under grant MPSS-NH-2013-63 and the National Research Foundation of Korea Grant funded by the Ministry of Science, ICT and Future Planning of Korea (NRF-2016M3C4A7952637) for its support and assistant in completion of the study.

  3. A preliminary characterization of the spatial variability of precipitation at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Hevesi, J.A.; Flint, A.L.; Ambos, D.S.

    1994-01-01

    Isohyetal maps of precipitation and numerical models for simulating precipitation are needed to help characterize natural infiltration at Yucca Mountain, Nevada. A geostatistical analysis of measured precipitation accumulated from storm periods. Precipitation was measured during a 3.8 year period from January 1990 to October, 1993 using a network of precipitation gages. A total of 34 winter-type storms and 12 summer-type storm, categorized using synoptic weather records, were analyzed using the 1st and 2nd statistical moments and sample variograms. Average standardized variograms indicated good spatial correlation for both storm types with only slight differences in the general spatial structure. Coefficients of variation and average relative variograms indicated that summer storms are characterized by greater variability as compared to winter storms. Models were fitted to the average summer and winter standarized variograms for each storm using the mean storm depth and the coefficient of variation as scaling parameters. Isohyetal maps of 4 representative storms were created using the standarized models. Results indicate that standarized models can be used to simulate the spatial distribution of precipitation depth, provided that the 1st and 2nd moments are known or can be estimated, and that identifiable deterministic trends can be included in the models. A single, fixed model representing the spatial variability of precipitation at Yucca Mountain is not recommended

  4. Precipitation stable isotope records from the northern Hengduan Mountains in China capture signals of the winter India-Burma Trough and the Indian Summer Monsoon

    Science.gov (United States)

    Yu, Wusheng; Tian, Lide; Yao, Tandong; Xu, Baiqing; Wei, Feili; Ma, Yaoming; Zhu, Haifeng; Luo, Lun; Qu, Dongmei

    2017-11-01

    This project reports results of the first precipitation stable isotope (δ18 O and δD) time series produced for Qamdo in the northern Hengduan Mountains in the southeastern Tibetan Plateau. The data showed that the fluctuations of precipitation stable isotopes at Qamdo during the different seasons revealed various moisture sources. The westerlies and local recycling moisture dominated at the study area before the pre-monsoon and after the post-monsoon seasons, which resulted in similar trends of both precipitation stable isotopes and temperature. The marine moisture was transported to the northern Hengduan Mountains by the winter India-Burma Trough combined with convection. Consequently, stable isotopes in subsequent precipitation were occasionally observed to decrease suddenly. However, δ18 O and δD values of precipitation at Qamdo were lower during the monsoon period and the duration of those low values was longer because of the effects of the Indian Summer Monsoon and the strengthening convection. Our findings indicate that the effects of seasonal precipitation differences caused by various climate systems, including the winter India-Burma Trough and Indian Summer Monsoon, need to be considered when attempting to interpret tree-ring and ice core records for the Hengduan Mountains.

  5. Controls on summer low flow

    Science.gov (United States)

    Graham, C. B.; McNamara, J. P.

    2012-12-01

    Summer low flow has significant impacts on aquatic flora and fauna, municipal water use, and power generation. However, the controls on the minimum annual summer discharge are complex, including a combination of snowmelt dynamics, summer evapotranspiration demand, and spring, summer precipitation patterns and surface - groundwater interactions. This is especially true in the Rocky Mountain West of the United States, where snowpack provides the majority of water available for spring runoff and groundwater replenishment. In this study, we look at summer low flow conditions at four snow dominated catchments (26 km2 - 2200 km2) in South-central Idaho currently feeling the effects of climate change. Measures of snowmelt dynamics, summer evapotranspiration demand and spring and summer precipitation are used to determine the dominant controls on late summer low flow magnitude, timing and duration. These analyses show that the controls vary between watersheds, with significant implications for the impacts of climate change in snow dominated areas of the Rocky Mountain West.

  6. Quantitative diagnosis of moisture sources and transport pathways for summer precipitation over the mid-lower Yangtze River Basin

    Science.gov (United States)

    Wang, Ning; Zeng, Xin-Min; Guo, Wei-Dong; Chen, Chaohui; You, Wei; Zheng, Yiqun; Zhu, Jian

    2018-04-01

    Using a moisture tracking model with 32-year reanalysis data and station precipitation observations, we diagnosed the sources of moisture for summer (June 1-August 31) precipitation in mid-lower reaches of the Yangtze River Basin (YRB). Results indicate the dominant role of oceanic evaporation compared to terrestrial evapotranspiration, and the previously overlooked southern Indian Ocean, as a source region, is found to contribute more moisture than the well-known Arabian Sea or Bay of Bengal. Terrestrial evapotranspiration appears to be important for summer precipitation, especially in early June when moisture contribution is more than 50%. The terrestrial contribution then decreases and is generally less than 40% after late June. The Indian Ocean is the most important oceanic source before mid-July, with its largest contribution during the period of heavy precipitation, while the Pacific Ocean becomes the more important oceanic source after mid-July. To quantitatively analyze paths of moisture transport to YRB, we proposed the Trajectory Frequency Method. The most intense branch of water vapor transport to YRB stretches from the Arabian Sea through the Bay of Bengal, the Indochina Peninsula, the South China Sea, and South China. The other main transport branches are westerly moisture fluxes to the south of the Tibetan Plateau, cross-equatorial flows north of Australia, and separate branches located in the north and equatorial Pacific Ocean. Significant intraseasonal variability for these branches is presented. Additionally, the importance of the South China Sea for moisture transport to YRB, especially from the sea areas, is emphasized.

  7. Two case studies on NARCCAP precipitation extremes

    Science.gov (United States)

    Weller, Grant B.; Cooley, Daniel; Sain, Stephan R.; Bukovsky, Melissa S.; Mearns, Linda O.

    2013-09-01

    We introduce novel methodology to examine the ability of six regional climate models (RCMs) in the North American Regional Climate Change Assessment Program (NARCCAP) ensemble to simulate past extreme precipitation events seen in the observational record over two different regions and seasons. Our primary objective is to examine the strength of daily correspondence of extreme precipitation events between observations and the output of both the RCMs and the driving reanalysis product. To explore this correspondence, we employ methods from multivariate extreme value theory. These methods require that we account for marginal behavior, and we first model and compare climatological quantities which describe tail behavior of daily precipitation for both the observations and model output before turning attention to quantifying the correspondence of the extreme events. Daily precipitation in a West Coast region of North America is analyzed in two seasons, and it is found that the simulated extreme events from the reanalysis-driven NARCCAP models exhibit strong daily correspondence to extreme events in the observational record. Precipitation over a central region of the United States is examined, and we find some daily correspondence between winter extremes simulated by reanalysis-driven NARCCAP models and those seen in observations, but no such correspondence is found for summer extremes. Furthermore, we find greater discrepancies among the NARCCAP models in the tail characteristics of the distribution of daily summer precipitation over this region than seen in precipitation over the West Coast region. We find that the models which employ spectral nudging exhibit stronger tail dependence to observations in the central region.

  8. Mercury Wet Scavenging and Deposition Differences by Precipitation Type.

    Science.gov (United States)

    Kaulfus, Aaron S; Nair, Udaysankar; Holmes, Christopher D; Landing, William M

    2017-03-07

    We analyze the effect of precipitation type on mercury wet deposition using a new database of individual rain events spanning the contiguous United States. Measurements from the Mercury Deposition Network (MDN) containing single rainfall events were identified and classified into six precipitation types. Mercury concentrations in surface precipitation follow a power law of precipitation depth that is modulated by precipitation system morphology. After controlling for precipitation depth, the highest mercury deposition occurs in supercell thunderstorms, with decreasing deposition in disorganized thunderstorms, quasi-linear convective systems (QLCS), extratropical cyclones, light rain, and land-falling tropical cyclones. Convective morphologies (supercells, disorganized, and QLCS) enhance wet deposition by a factor of at least 1.6 relative to nonconvective morphologies. Mercury wet deposition also varies by geographic region and season. After controlling for other factors, we find that mercury wet deposition is greater over high-elevation sites, seasonally during summer, and in convective precipitation.

  9. Sensitivity of convective precipitation to soil moisture and vegetation during break spell of Indian summer monsoon

    Science.gov (United States)

    Kutty, Govindan; Sandeep, S.; Vinodkumar; Nhaloor, Sreejith

    2017-07-01

    Indian summer monsoon rainfall is characterized by large intra-seasonal fluctuations in the form of active and break spells in rainfall. This study investigates the role of soil moisture and vegetation on 30-h precipitation forecasts during the break monsoon period using Weather Research and Forecast (WRF) model. The working hypothesis is that reduced rainfall, clear skies, and wet soil condition during the break monsoon period enhance land-atmosphere coupling over central India. Sensitivity experiments are conducted with modified initial soil moisture and vegetation. The results suggest that an increase in antecedent soil moisture would lead to an increase in precipitation, in general. The precipitation over the core monsoon region has increased by enhancing forest cover in the model simulations. Parameters such as Lifting Condensation Level, Level of Free Convection, and Convective Available Potential Energy indicate favorable atmospheric conditions for convection over forests, when wet soil conditions prevail. On spatial scales, the precipitation is more sensitive to soil moisture conditions over northeastern parts of India. Strong horizontal gradient in soil moisture and orographic uplift along the upslopes of Himalaya enhanced rainfall over the east of Indian subcontinent.

  10. Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

    Science.gov (United States)

    Yi, Yonghong; Kimball, John; Reichle, Rolf H.

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  11. Future changes in Asian summer monsoon precipitation extremes as inferred from 20-km AGCM simulations

    Science.gov (United States)

    Lui, Yuk Sing; Tam, Chi-Yung; Lau, Ngar-Cheung

    2018-04-01

    This study examines the impacts of climate change on precipitation extremes in the Asian monsoon region during boreal summer, based on simulations from the 20-km Meteorological Research Institute atmospheric general circulation model. The model can capture the summertime monsoon rainfall, with characteristics similar to those from Tropical Rainfall Measuring Mission and Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation. By comparing the 2075-2099 with the present-day climate simulations, there is a robust increase of the mean rainfall in many locations due to a warmer climate. Over southeastern China, the Baiu rainband, Bay of Bengal and central India, extreme precipitation rates are also enhanced in the future, which can be inferred from increases of the 95th percentile of daily precipitation, the maximum accumulated precipitation in 5 consecutive days, the simple daily precipitation intensity index, and the scale parameter of the fitted gamma distribution. In these regions, with the exception of the Baiu rainband, most of these metrics give a fractional change of extreme rainfall per degree increase of the lower-tropospheric temperature of 5 to 8.5% K-1, roughly consistent with the Clausius-Clapeyron relation. However, over the Baiu area extreme precipitation change scales as 3.5% K-1 only. We have also stratified the rainfall data into those associated with tropical cyclones (TC) and those with other weather systems. The AGCM gives an increase of the accumulated TC rainfall over southeastern China, and a decrease in southern Japan in the future climate. The latter can be attributed to suppressed TC occurrence in southern Japan, whereas increased accumulated rainfall over southeastern China is due to more intense TC rain rate under global warming. Overall, non-TC weather systems are the main contributor to enhanced precipitation extremes in various locations. In the future, TC activities over southeastern China tend to further

  12. Precipitation and ice core isotopes from the Asian Summer Monsoon region reflect coherent ENSO variability

    Science.gov (United States)

    Cai, Z.; Tian, L.; Bowen, G. J.

    2017-12-01

    Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.

  13. Diurnal phase of late-night against late-afternoon of stratiform and convective precipitation in summer southern contiguous China

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Rucong [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); China Meteorological Administration, LaSW, Chinese Academy of Meteorological Sciences, Beijing (China); Yuan, Weihua [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); Graduate School of the Chinese Academy of Sciences, Beijing (China); Li, Jian [China Meteorological Administration, LaSW, Chinese Academy of Meteorological Sciences, Beijing (China); Fu, Yunfei [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); University of Science and Technology of China, Laboratory of Satellite Remote Sensing and Climate Environment, Hefei, Anhui (China)

    2010-09-15

    Using the tropical rainfall measuring mission (TRMM) Precipitation Radar (PR) observations combined with the surface rain gauge data during 1998-2006, the robust diurnal features of summer stratiform and convective precipitation over the southern contiguous China are revealed by exploring the diurnal variations of rain rate and precipitation profile. The precipitation over the southern contiguous China exhibits two distinguishing diurnal phases: late-night (2200-0600 LST) and late-afternoon (1400-2200 LST), dependent on the location, precipitation type and duration time. Generally, the maximum rain rate and the highest profile of stratiform precipitation occur in the late-afternoon (late-night) over the southeastern (southwestern) China, while most of the stratiform short-duration rain rate tends to present late-afternoon peaks over the southern China. For convective precipitation, the maximum rain rate and the highest profile occur in the late-afternoon over most of the southern contiguous China, while the convective long-duration rain rate exhibits late-night peaks over the southwestern China. Without regional dependence, the convective precipitation exhibits much larger amplitude of diurnal variations in both near surface rain rate and vertical extension compared with stratiform precipitation and the convective rain top rises most rapidly between noon and afternoon. However, there are two distinctive sub-regions. The diurnal phases of precipitation there are very weakly dependent on precipitation type and duration time. Over the eastern periphery of the Tibetan Plateau, the maximum rain rate and the highest profile of either convective or stratiform precipitation occur in the late-night. Over the southeastern coastal regions, both the near surface rain rate and rain top of convective and stratiform precipitation peak in the late-afternoon. (orig.)

  14. The Consequences of Precipitation Seasonality for Mediterranean-Ecosystem Vegetation of South Africa.

    Science.gov (United States)

    Cramer, Michael D; Hoffman, M Timm

    2015-01-01

    Globally, mediterranean-climate ecosystem vegetation has converged on an evergreen, sclerophyllous and shrubby growth form. The particular aspects of mediterranean-climate regions that contribute to this convergence include summer droughts and relatively nutrient-poor soils. We hypothesised that winter-precipitation implies stressful summer droughts and leaches soils due to greater water availability (i.e. balance between precipitation and potential evapotranspiration; P-PET) during cold periods. We conducted a comparative analysis of normalised difference vegetation indices (NDVI) and edaphic and climate properties across the biomes of South Africa. NDVI was strongly correlated with both precipitation and P-PET (r2 = 0.8). There was no evidence, however, that winter-precipitation reduces NDVI in comparison to similar amounts of summer-precipitation. Base saturation (BS), a measure of soil leaching was, however, negatively related to P-PET (r2 = 0.64). This led to an interaction between P-PET and BS in determining NDVI, indicating the existence of a trade-off between water availability and soil nutrients that enables NDVI to increase with precipitation, despite negative consequences for soil nutrient availability. The mechanism of this trade-off is suggested to be that water increases nutrient accessibility. This implies that along with nutrient-depauperate geologies and long periods of time since glaciation, the winter-precipitation may have contributed to the highly leached status of the soils. Since many of the ecophysiological characteristics of mediterranean-ecosystem flora are associated with low nutrient availabilities (e.g. evergreen foliage, sclerophylly, cluster roots), we conclude that mediterranean-climates promote convergence of growth-forms in these regions through high leaching capacity.

  15. Multivariate Regression Analysis and Statistical Modeling for Summer Extreme Precipitation over the Yangtze River Basin, China

    Directory of Open Access Journals (Sweden)

    Tao Gao

    2014-01-01

    Full Text Available Extreme precipitation is likely to be one of the most severe meteorological disasters in China; however, studies on the physical factors affecting precipitation extremes and corresponding prediction models are not accurately available. From a new point of view, the sensible heat flux (SHF and latent heat flux (LHF, which have significant impacts on summer extreme rainfall in Yangtze River basin (YRB, have been quantified and then selections of the impact factors are conducted. Firstly, a regional extreme precipitation index was applied to determine Regions of Significant Correlation (RSC by analyzing spatial distribution of correlation coefficients between this index and SHF, LHF, and sea surface temperature (SST on global ocean scale; then the time series of SHF, LHF, and SST in RSCs during 1967–2010 were selected. Furthermore, other factors that significantly affect variations in precipitation extremes over YRB were also selected. The methods of multiple stepwise regression and leave-one-out cross-validation (LOOCV were utilized to analyze and test influencing factors and statistical prediction model. The correlation coefficient between observed regional extreme index and model simulation result is 0.85, with significant level at 99%. This suggested that the forecast skill was acceptable although many aspects of the prediction model should be improved.

  16. Influence of aerosol-cloud interaction on austral summer precipitation over Southern Africa during ENSO events

    Science.gov (United States)

    Ruchith, R. D.; Sivakumar, V.

    2018-04-01

    In the present study, we are investigating the role of aerosols-and clouds in modulating the austral summer precipitation (December-February) during ENSO events over southern Africa region for the period from 2002 to2012 by using satellite and complimentary data sets. Aerosol radiative forcing (ARF) and Cloud radiative forcing (CRF) shows distinct patterns for El-Nina and La-Nina years. Further analysis were carried out by selecting the four Southern Africa regions where the precipitation shows remarkable difference during El-Nino and La-Nina years. These regions are R1 (33°S-24°S, 18°E-30°E), R2 (17°S-10°S, 24°E-32°E), R3 (19°S-9°S, 33°E-41°E) and R4 (7°S-0°S, 27°E-36°E). Aerosol Optical depth (AOD) shows considerable differences during these events. In region R1, R2 and R3 AOD shows more abundance in El-Nino years as compared to La-Nina years where as in R4 the AOD shows more abundance in La-Nina years. Cloud Droplet Effective radius (CDER) shows higher values during La-Nina years over R1, R2 and R3 regions but in R4 region CDER shows higher values in El-Nino years. Aerosol indirect effect (AIE) is estimated both for fixed cloud liquid water path (CLWP) and for fixed cloud ice path (CIP) bins, ranging from 1 to 300 gm -2 at 25 gm -2 interval over all the selected regions for El-Nino and La-Nina years. The results indicate more influence of positive indirect effect (Twomey effect) over R1 and R3 region during El-Nino years as compared to La-Nina years. This analysis reveals the important role of aerosol on cloud-precipitation interaction mechanism illustrating the interlinkage between dynamics and microphysics during austral summer season over southern Africa.

  17. Effects of Reduced Summer Precipitation on Productivity and Forage Quality of Floodplain Meadows at the Elbe and the Rhine River

    Science.gov (United States)

    Ludewig, Kristin; Donath, Tobias W.; Zelle, Bianka; Eckstein, R. Lutz; Mosner, Eva; Otte, Annette; Jensen, Kai

    2015-01-01

    Background Floodplain meadows along rivers are semi-natural habitats and depend on regular land use. When used non-intensively, they offer suitable habitats for many plant species including rare ones. Floodplains are hydrologically dynamic ecosystems with both periods of flooding and of dry conditions. In German floodplains, dry periods may increase due to reduced summer precipitation as projected by climate change scenarios. Against this background, the question arises, how the forage quantity and quality of these meadows might change in future. Methods We report results of two field trials that investigated effects of experimentally reduced summer precipitation on hay quantity and quality of floodplain meadows at the Rhine River (2011-2012) and at two Elbe tributaries (2009-2011). We measured annual yield, the amount of hay biomass, and contents of crude protein, crude fibre, energy, fructan, nitrogen, phosphorus, and potassium. Results The annual yield decreased under precipitation reduction at the Rhine River. This was due to reduced productivity in the second cut hay at the Rhine River in which, interestingly, the contents of nitrogen and crude protein increased. The first cut at the Rhine River was unaffected by the treatments. At the Elbe tributaries, the annual yield and the hay quantity and quality of both cuts were only marginally affected by the treatments. Conclusion We conclude that the yield of floodplain meadows may become less reliable in future since the annual yield decreased under precipitation reduction at the Rhine River. However, the first and agriculturally more important cut was almost unaffected by the precipitation reduction, which is probably due to sufficient soil moisture from winter/spring. As long as future water levels of the rivers will not decrease during spring, at least the use of the hay from the first cut of floodplain meadows appears reliable under climate change. PMID:25950730

  18. Reconstructions of spring/summer precipitation for the Eastern Mediterranean from tree-ring widths and its connection to large-scale atmospheric circulation

    Energy Technology Data Exchange (ETDEWEB)

    Touchan, Ramzi; Funkhouser, Gary; Hughes, Malcolm K. [The University of Arizona, Laboratory of Tree-Ring Research, Tucson, AZ (United States); Xoplaki, Elena; Luterbacher, Juerg [University of Bern, Institute of Geography and NCCR Climate, Bern (Switzerland); Erkan, Nesat [Southwest Anatolia Forest Research Institute (SAFRI), Antalya (Turkey); Akkemik, Uenal [University of Istanbul, Faculty of Forestry, Department of Forest Botany, Bahcekoey-Istanbul (Turkey); Stephan, Jean [Ministry of Agriculture, Forestry Department, Beirut (Lebanon)

    2005-07-01

    This study represents the first large-scale systematic dendroclimatic sampling focused on developing chronologies from different species in the eastern Mediterranean region. Six reconstructions were developed from chronologies ranging in length from 115 years to 600 years. The first reconstruction (1885-2000) was derived from principal components (PCs) of 36 combined chronologies. The remaining five, 1800-2000, 1700-2000, 1600-2000, 1500-2000 and 1400-2000 were developed from PCs of 32, 18, 14, 9, and 7 chronologies, respectively. Calibration and verification statistics for the period 1931-2000 show good levels of skill for all reconstructions. The longest period of consecutive dry years, defined as those with less than 90% of the mean of the observed May-August precipitation, was 5 years (1591-1595) and occurred only once during the last 600 years. The longest reconstructed wet period was 5 years (1601-1605 and 1751-1755). No long term trends were found in May-August precipitation during the last few centuries. Regression maps are used to identify the influence of large-scale atmospheric circulation on regional precipitation. In general, tree-ring indices are influenced by May-August precipitation, which is driven by anomalous below (above) normal pressure at all atmospheric levels and by convection (subsidence) and small pressure gradients at sea level. These atmospheric conditions also control the anomaly surface air temperature distribution which indicates below (above) normal values in the southern regions and warmer (cooler) conditions north of around 40 N. A compositing technique is used to extract information on large-scale climate signals from extreme wet and dry summers for the second half of the twentieth century and an independent reconstruction over the last 237 years. Similar main modes of atmospheric patterns and surface air temperature distribution related to extreme dry and wet summers were identified both for the most recent 50 years and the last

  19. Evaluation of precipitation forecasts from 3D-Var and hybrid GSI-based system during Indian summer monsoon 2015

    Science.gov (United States)

    Singh, Sanjeev Kumar; Prasad, V. S.

    2018-02-01

    This paper presents a systematic investigation of medium-range rainfall forecasts from two versions of the National Centre for Medium Range Weather Forecasting (NCMRWF)-Global Forecast System based on three-dimensional variational (3D-Var) and hybrid analysis system namely, NGFS and HNGFS, respectively, during Indian summer monsoon (June-September) 2015. The NGFS uses gridpoint statistical interpolation (GSI) 3D-Var data assimilation system, whereas HNGFS uses hybrid 3D ensemble-variational scheme. The analysis includes the evaluation of rainfall fields and comparisons of rainfall using statistical score such as mean precipitation, bias, correlation coefficient, root mean square error and forecast improvement factor. In addition to these, categorical scores like Peirce skill score and bias score are also computed to describe particular aspects of forecasts performance. The comparison results of mean precipitation reveal that both the versions of model produced similar large-scale feature of Indian summer monsoon rainfall for day-1 through day-5 forecasts. The inclusion of fully flow-dependent background error covariance significantly improved the wet biases in HNGFS over the Indian Ocean. The forecast improvement factor and Peirce skill score in the HNGFS have also found better than NGFS for day-1 through day-5 forecasts.

  20. Effects of microphysics parameterization on simulations of summer heavy precipitation in the Yangtze-Huaihe Region, China

    Science.gov (United States)

    Kan, Yu; Chen, Bo; Shen, Tao; Liu, Chaoshun; Qiao, Fengxue

    2017-09-01

    It has been a longstanding problem for current weather/climate models to accurately predict summer heavy precipitation over the Yangtze-Huaihe Region (YHR) which is the key flood-prone area in China with intensive population and developed economy. Large uncertainty has been identified with model deficiencies in representing precipitation processes such as microphysics and cumulus parameterizations. This study focuses on examining the effects of microphysics parameterization on the simulation of different type of heavy precipitation over the YHR taking into account two different cumulus schemes. All regional persistent heavy precipitation events over the YHR during 2008-2012 are classified into three types according to their weather patterns: the type I associated with stationary front, the type II directly associated with typhoon or with its spiral rain band, and the type III associated with strong convection along the edge of the Subtropical High. Sixteen groups of experiments are conducted for three selected cases with different types and a local short-time rainstorm in Shanghai, using the WRF model with eight microphysics and two cumulus schemes. Results show that microphysics parameterization has large but different impacts on the location and intensity of regional heavy precipitation centers. The Ferrier (microphysics) -BMJ (cumulus) scheme and Thompson (microphysics) - KF (cumulus) scheme most realistically simulates the rain-bands with the center location and intensity for type I and II respectively. For type III, the Lin microphysics scheme shows advantages in regional persistent cases over YHR, while the WSM5 microphysics scheme is better in local short-term case, both with the BMJ cumulus scheme.

  1. Diurnal variations of summer precipitation over the regions east to Tibetan Plateau

    Science.gov (United States)

    Wu, Yang; Huang, Anning; Huang, Danqing; Chen, Fei; Yang, Ben; Zhou, Yang; Fang, Dexian; Zhang, Lujun; Wen, Lijuan

    2017-12-01

    Based on the hourly gauge-satellite merged precipitation product with the horizontal resolution of 0.1° latitude/longitude during 2008-2014, diurnal variations of the summer precipitation amount (PA), frequency (PF), and intensity (PI) with different duration time over the regions east to Tibetan Plateau have been systematically revealed in this study. Results indicate that the eight typical precipitation diurnal patterns identified by the cluster analysis display pronounced regional features among the plateaus, basins, plains, hilly and coastal areas. The precipitation diurnal cycles are significantly affected by the sub-grid terrain fluctuations. The PA, PF and PI of the total rainfall show much more pronounced double diurnal peaks with the sub-grid topography standard deviation (SD) decreased. Meanwhile, the diurnal peaks of PA and PF (PI) strengthen (weaken) with the sub-grid topography SD enhanced. Over the elevated mountain ranges, southeastern hilly and coastal regions, the PA and PF diurnal patterns of the total rainfall generally show predominant late-afternoon peaks, which are closely associated with the short-duration (≤slant 3 h) rainfall. Along the Tibetan Plateau to its downstream, the diurnal peaks of PA, PF and PI for the total rainfall all exhibit obvious eastward phase time delay mainly due to the diurnal evolutions of long-duration (> 6 h) rainfall. However, the 4-6 h rainfall leads to the eastward phase time delay of the total rainfall along the Taihang Mountains to its downstream. Further mechanism analysis suggests that the midnight to morning diurnal evolution of the long-duration rainfall is closely associated with the diurnal variations of the upward branches of thermally driven mountain-plain solenoids and the water vapor transport associated with the accelerated nocturnal southwesterly winds. The late-afternoon peak of the short-duration PA over the southeastern hilly and coastal regions is ascribed to the strong local thermal

  2. Summer weather characteristics and periodicity observed over the period 1888-2013 in the region of Belgrade, Serbia

    Science.gov (United States)

    Vujović, Dragana; Todorović, Nedeljko; Paskota, Mira

    2018-04-01

    With the goal of finding summer climate patterns in the region of Belgrade (Serbia) over the period 1888-2013, different techniques of multivariate statistical analysis were used in order to analyze the simultaneous changes of a number of climatologic parameters. An increasing trend of the mean daily minimum temperature was detected. In the recent decades (1960-2013), this increase was much more pronounced. The number of days with the daily minimum temperature greater or equal to 20 °C also increased significantly. Precipitation had no statistically significant trend. Spectral analysis showed a repetitive nature of the climatologic parameters which had periods that roughly can be classified into three groups, with the durations of the following: (1) 6 to 7 years, (2) 10 to 18 years, and (3) 21, 31, and 41 years. The temperature variables mainly had one period of repetitiveness of 5 to 7 years. Among other variables, the correlations of regional fluctuations of the temperature and precipitation and atmospheric circulation indices were analyzed. The North Atlantic oscillation index had the same periodicity as that of the precipitation, and it was not correlated to the temperature variables. Atlantic multidecadal oscillation index correlated well to the summer mean daily minimum and summer mean temperatures. The underlying structure of the data was analyzed by principal component analysis, which detected the following four easily interpreted dimensions: More sunshine-Higher temperature, Precipitation, Extreme heats, and Changeable summer.

  3. Precipitation regime classification for the Mojave Desert: Implications for fire occurrence

    Science.gov (United States)

    Tagestad, Jerry; Brooks, Matthew L.; Cullinan, Valerie; Downs, Janelle; McKinley, Randy

    2016-01-01

    Long periods of drought or above-average precipitation affect Mojave Desert vegetation condition, biomass and susceptibility to fire. Changes in the seasonality of precipitation alter the likelihood of lightning, a key ignition source for fires. The objectives of this study were to characterize the relationship between recent, historic, and future precipitation patterns and fire. Classifying monthly precipitation data from 1971 to 2010 reveals four precipitation regimes: low winter/low summer, moderate winter/moderate summer, high winter/low summer and high winter/high summer. Two regimes with summer monsoonal precipitation covered only 40% of the Mojave Desert ecoregion but contain 88% of the area burned and 95% of the repeat burn area. Classifying historic precipitation for early-century (wet) and mid-century (drought) periods reveals distinct shifts in regime boundaries. Early-century results are similar to current, while the mid-century results show a sizeable reduction in area of regimes with a strong monsoonal component. Such a shift would suggest that fires during the mid-century period would be minimal and anecdotal records confirm this. Predicted precipitation patterns from downscaled global climate models indicate numerous epochs of high winter precipitation, inferring higher fire potential for many multi-decade periods during the next century.

  4. Possible teleconnections between East and South Asian summer monsoon precipitation in projected future climate change

    Science.gov (United States)

    Woo, Sumin; Singh, Gyan Prakash; Oh, Jai-Ho; Lee, Kyoung-Min

    2018-01-01

    The present paper examined the teleconnections between two huge Asian summer monsoon components (South and East Asia) during three time slices in future: near-(2010-2039), mid-(2040-2069) and far-(2070-2100) futures under the RCP4.5 and RCP8.5 scenarios. For this purpose, a high-resolution atmospheric general circulation model is used and integrated at 40 km horizontal resolution. To get more insight into the relationships between the two Asian monsoon components, we have studied the spatial displaying correlation coefficients (CCs) pattern of precipitation over the entire Asian monsoon region with that of South Asia and three regions of East Asia (North China, Korea-Japan and Southern China) separately during the same three time slices. The possible factors responsible for these teleconnections are explored by using mean sea level pressure (MSLP) and wind fields at 850 hPa. The CC pattern of precipitation over South Asia shows an in-phase relationship with North China and an out-of-phase relationship with Korea-Japan, while precipitation variations over Korea-Japan and Southern China exhibit an out-of-phase relationship with South Asia. The CCs analysis between the two Asian blocks during different time slices shows the strongest CCs during the near and far future with the RCP8.5 scenario. The CC pattern of precipitation over Korea-Japan and Southern China with the wind (at 850 hPa) and MSLP fields indicate that the major parts of the moisture over Korea-Japan gets transported from the west Pacific along the western limb of NPSH, while the moisture over Southern China comes from the Bay of Bengal and South China Seas for good monsoon activity.

  5. Aerosol indirect effects on summer precipitation in a regional climate model for the Euro-Mediterranean region

    Science.gov (United States)

    Da Silva, Nicolas; Mailler, Sylvain; Drobinski, Philippe

    2018-03-01

    Aerosols affect atmospheric dynamics through their direct and semi-direct effects as well as through their effects on cloud microphysics (indirect effects). The present study investigates the indirect effects of aerosols on summer precipitation in the Euro-Mediterranean region, which is located at the crossroads of air masses carrying both natural and anthropogenic aerosols. While it is difficult to disentangle the indirect effects of aerosols from the direct and semi-direct effects in reality, a numerical sensitivity experiment is carried out using the Weather Research and Forecasting (WRF) model, which allows us to isolate indirect effects, all other effects being equal. The Mediterranean hydrological cycle has often been studied using regional climate model (RCM) simulations with parameterized convection, which is the approach we adopt in the present study. For this purpose, the Thompson aerosol-aware microphysics scheme is used in a pair of simulations run at 50 km resolution with extremely high and low aerosol concentrations. An additional pair of simulations has been performed at a convection-permitting resolution (3.3 km) to examine these effects without the use of parameterized convection. While the reduced radiative flux due to the direct effects of the aerosols is already known to reduce precipitation amounts, there is still no general agreement on the sign and magnitude of the aerosol indirect forcing effect on precipitation, with various processes competing with each other. Although some processes tend to enhance precipitation amounts, some others tend to reduce them. In these simulations, increased aerosol loads lead to weaker precipitation in the parameterized (low-resolution) configuration. The fact that a similar result is obtained for a selected area in the convection-permitting (high-resolution) configuration allows for physical interpretations. By examining the key variables in the model outputs, we propose a causal chain that links the aerosol

  6. Influence of Western Tibetan Plateau Summer Snow Cover on East Asian Summer Rainfall

    Science.gov (United States)

    Wang, Zhibiao; Wu, Renguang; Chen, Shangfeng; Huang, Gang; Liu, Ge; Zhu, Lihua

    2018-03-01

    The influence of boreal winter-spring eastern Tibetan Plateau snow anomalies on the East Asian summer rainfall variability has been the focus of previous studies. The present study documents the impacts of boreal summer western and southern Tibetan Plateau snow cover anomalies on summer rainfall over East Asia. Analysis shows that more snow cover in the western and southern Tibetan Plateau induces anomalous cooling in the overlying atmospheric column. The induced atmospheric circulation changes are different corresponding to more snow cover in the western and southern Tibetan Plateau. The atmospheric circulation changes accompanying the western Plateau snow cover anomalies are more obvious over the midlatitude Asia, whereas those corresponding to the southern Plateau snow cover anomalies are more prominent over the tropics. As such, the western and southern Tibetan Plateau snow cover anomalies influence the East Asian summer circulation and precipitation through different pathways. Nevertheless, the East Asian summer circulation and precipitation anomalies induced by the western and southern Plateau snow cover anomalies tend to display similar distribution so that they are more pronounced when the western and southern Plateau snow cover anomalies work in coherence. Analysis indicates that the summer snow cover anomalies over the Tibetan Plateau may be related to late spring snow anomalies due to the persistence. The late spring snow anomalies are related to an obvious wave train originating from the western North Atlantic that may be partly associated with sea surface temperature anomalies in the North Atlantic Ocean.

  7. Response of aboveground carbon balance to long-term, experimental shifts in precipitation seasonality is contingent on plant community type in cold-desert rangelands

    Science.gov (United States)

    Reinhardt, K.; McAbee, K.; Germino, M. J.; Bosworth, A.

    2016-12-01

    Semi-arid rangelands have been identified as potential carbon (C) sinks. However, the degree of net C storage or release in water-limited systems is a function of precipitation amount and timing, as well as plant community composition. In northern latitudes of western North America, climate models predict increases in wintertime precipitation and decreases in summertime precipitation. In theory, this should boost C storage in cold-desert ecosystems that have deep-rooted woody plants due to greater wintertime soil water storage that enhances summertime productivity. However, there are few long-term, manipulative field-based studies investigating how shrub- and grass-dominated rangelands will respond to changing precipitation patterns. We measured aboveground C pools and fluxes at leaf, soil, and ecosystem scales over the 2014 growing season on plots that had supplemental precipitation added in either winter or summer for 21 years, in shrub- and exotic-bunchgrass-dominated plots. We hypothesized that increased winter precipitation would stimulate aboveground C uptake and storage relative to ambient conditions, in our cold-desert-adapted plant species. We further hypothesized that long-term gains in aboveground C storage due to precipitation manipulations would be greater in plots containing shrubs. Our hypotheses were generally supported: ecosystem C uptake and long-term biomass accumulation were greater in winter- and summer-irrigated plots compared to control plots in both vegetation communities. However, substantial increases in aboveground biomass occurred only in winter-irrigated plots that contained shrubs. Our findings suggest that increases in winter precipitation will enhance C storage of this widespread ecosystem, provided that the ecosystems have resisted conversion to exotic grassland.

  8. Damped summer warming accompanied with cloud cover increase over Eurasia from 1982 to 2009

    International Nuclear Information System (INIS)

    Tang Qiuhong; Leng Guoyong

    2012-01-01

    The relationship between summer temperature, total cloud cover and precipitation over Eurasia was investigated using observation-based products of temperature and precipitation, and satellite-derived cloud cover and radiation products. We used a partial least squares regression approach to separate the local influences of cloud cover and precipitation on temperature variations. Our results suggest that the variance of summer temperature is partly explained by changes in summer cloudiness. The summer temperature dependence on cloud cover is strong at the high latitudes and in the middle latitude semi-humid area, while the dependence on precipitation is strong in the Central Asia arid area and the southern Asia humid area. During the period 1982–2009, the damped warming in extended West Siberia was accompanied with increases in cloud cover, and the pronounced warming in Europe and Mongolia was associated with a decrease in cloud cover and precipitation. Our results suggest that cloud cover may be the important local factor influencing the summer temperature variation in Eurasia while precipitation plays an important role at the middle latitudes. (letter)

  9. Using damage data to estimate the risk from summer convective precipitation extremes

    Science.gov (United States)

    Schroeer, Katharina; Tye, Mari

    2017-04-01

    model to test whether the relationship between extreme rainfall events and damages is robust enough to estimate a potential underrepresentation of high intensity rainfall events in ungauged areas. Risk-relevant factors of socio-economic vulnerability, land cover, streamflow data, and weather type information are included to improve and sharpen the analysis. Within this study, we first aim to identify which rainfall events are most damaging and which factors affect the damages - seen as a proxy for the vulnerability - related to summer convective rainfall extremes in different catchment types. Secondly, we aim to detect potentially unreported damaging rainfall events and estimate the likelihood of such cases. We anticipate this damage perspective on summertime extreme convective precipitation to be beneficial for risk assessment, uncertainty management, and decision making with respect to weather and climate extremes on the regional-to-local level.

  10. Trends in total and daily precipitation indices in japan from 1901 to 2000

    OpenAIRE

    Nagata, Rena; Zaiki, Masumi

    2008-01-01

    Long-term trends in seasonal precipitation amount and daily precipitation indices were investigated for spring, summer, autumn, and winter with a daily precipitation dataset for Japan from 1901 to 2000. Heavy precipitation in spring and summer has significantly increased along the west coast of Japan. Such changes in precipitation have resulted in the increased heavy precipitation intensity. For autumn and winter, total precipitation significantly decreased in the Kanto district and central J...

  11. Compound extremes of summer temperature and precipitation leading to intensified departures from natural variability.

    Science.gov (United States)

    Mahony, C. R.; Cannon, A. J.

    2017-12-01

    Climate change can drive local climates outside the range of their historical year-to-year variability, straining the adaptive capacity of ecological and human communities. We demonstrate that interactions between climate variables can produce larger and earlier departures from natural variability than is detectable in individual variables. For example, summer temperature (Tx) and precipitation (Pr) are negatively correlated in most terrestrial regions, such that interannual variability lies along an axis from warm-and-dry to cool-and-wet conditions. A climate change trend perpendicular to this axis, towards warmer-wetter conditions, can depart more quickly from the range of natural variability than a warmer-drier trend. This multivariate "departure intensification" effect is evident in all six CMIP5 models that we examined: 23% (9-34%) of the land area of each model exhibits a pronounced increase in 2σ extremesin the Tx-Pr regime relative to Tx or Pr alone. Observational data suggest that Tx-Pr correlations are sufficient to produce departure intensification in distinct regions on all continents. Departures from the historical Tx-Pr regime may produce ecological disruptions, such as in plant-pathogen interactions and human diseases, that could offset the drought mitigation benefits of increased precipitation. Our study alerts researchers and adaptation practitioners to the presence of multivariate climate change signals and compound extremes that are not detectable in individual climate variables.

  12. Diagnosing the leading mode of interdecadal covariability between the Indian Ocean sea surface temperature and summer precipitation in southern China

    Science.gov (United States)

    Liu, Jingpeng; Ren, Hong-Li; Li, Weijing; Zuo, Jinqing

    2018-03-01

    Precipitation in southern China during boreal summer (June to August) shows a substantial interdecadal variability on the timescale longer than 8 years. In this study, based on the analysis of singular value decomposition, we diagnose the leading mode of interdecadal covariability between the observational precipitation in southern China and the sea surface temperature (SST) in the Indian Ocean. Results indicate that there exist a remarkable southern China zonal dipole (SCZD) pattern of interdecadal variability of summer precipitation and an interdecadal Indian Ocean basin mode (ID-IOBM) of SST. It is found that the SCZD is evidently covaried with the ID-IOBM, which may induce anomalous inter-hemispheric vertical circulation and atmospheric Kelvin waves. During the warm phase of the ID-IOBM, an enhanced lower-level convergence and upper-level divergence exist over the tropical Indian Ocean, which is a typical Gill-Matsuno-type response to the SST warming. Meanwhile, the accompanied upper-level outflow anomalies further converge over the Indo-China peninsula, resulting in a lower-level anticyclone that contributes to reduction of the eastward moisture transport from the Bay of Bengal to the west part of southern China. In addition, the Kelvin wave-like pattern, as a response of the warm ID-IOBM phase, further induces the lower-level anticyclonic anomaly over the South China Sea-Philippines. Such an anticyclonic circulation is favorable for more water vapor transport from the East China Sea into the east part of southern China. Therefore, the joint effects of the anomalous inter-hemispheric vertical circulation and the Kelvin wave-like pattern associated with the ID-IOBM may eventually play a key role in generating the SCZD pattern.

  13. Compound summer temperature and precipitation extremes over central Europe

    Science.gov (United States)

    Sedlmeier, Katrin; Feldmann, H.; Schädler, G.

    2018-02-01

    Reliable knowledge of the near-future climate change signal of extremes is important for adaptation and mitigation strategies. Especially compound extremes, like heat and drought occurring simultaneously, may have a greater impact on society than their univariate counterparts and have recently become an active field of study. In this paper, we use a 12-member ensemble of high-resolution (7 km) regional climate simulations with the regional climate model COSMO-CLM over central Europe to analyze the climate change signal and its uncertainty for compound heat and drought extremes in summer by two different measures: one describing absolute (i.e., number of exceedances of absolute thresholds like hot days), the other relative (i.e., number of exceedances of time series intrinsic thresholds) compound extreme events. Changes are assessed between a reference period (1971-2000) and a projection period (2021-2050). Our findings show an increase in the number of absolute compound events for the whole investigation area. The change signal of relative extremes is more region-dependent, but there is a strong signal change in the southern and eastern parts of Germany and the neighboring countries. Especially the Czech Republic shows strong change in absolute and relative extreme events.

  14. The Centennial Trends Greater Horn of Africa precipitation dataset

    Science.gov (United States)

    Funk, Chris; Nicholson, Sharon E.; Landsfeld, Martin F.; Klotter, Douglas; Peterson, Pete J.; Harrison, Laura

    2015-01-01

    East Africa is a drought prone, food and water insecure region with a highly variable climate. This complexity makes rainfall estimation challenging, and this challenge is compounded by low rain gauge densities and inhomogeneous monitoring networks. The dearth of observations is particularly problematic over the past decade, since the number of records in globally accessible archives has fallen precipitously. This lack of data coincides with an increasing scientific and humanitarian need to place recent seasonal and multi-annual East African precipitation extremes in a deep historic context. To serve this need, scientists from the UC Santa Barbara Climate Hazards Group and Florida State University have pooled their station archives and expertise to produce a high quality gridded ‘Centennial Trends’ precipitation dataset. Additional observations have been acquired from the national meteorological agencies and augmented with data provided by other universities. Extensive quality control of the data was carried out and seasonal anomalies interpolated using kriging. This paper documents the CenTrends methodology and data.

  15. Ischemic Heart Disease Hospitalization among Older People in a Subtropical City — Hong Kong: Does Winter Have a Greater Impact than Summer?

    Directory of Open Access Journals (Sweden)

    Pui Hing Chau

    2014-04-01

    Full Text Available Globally, excess winter morbidity from ischemic heart disease (IHD is reported. In subtropical regions, there is a need to quantify the difference in the adverse effect of cold winters compared with hot summers, particularly among the older people. Our objectives were to: (i compare the effect of winter on IHD hospitalizations with that of summer; (ii examine temporal trends in the excess winter hospitalizations; and (iii investigate the effect of age, gender, and meteorological factors on predicting such excess. Inpatient admissions due to IHD as principal cause during June 2000 to February 2009 in public hospitals of Hong Kong were extracted for the population aged ≥65. An Excess Hospitalization in Winter vs. Summer (EHWS Index was used to contrast the adverse effect of weather on hospitalizations in winter vs. summer. Multiple linear regressions were used to investigate the trend and the predictors of such index. It was found that in a subtropical city, greater effect of winter on IHD hospitalizations than summer was observed, particularly among the oldest old (an index of 61.5% (95% CI: 49.5%–74.4% for men aged ≥85 and 32.3% (95% CI: 25.5%–39.5% for women aged ≥85. There was significant increasing trend in the index among those aged ≥85 but the age difference was less prominent among the women. Absolute level of coldness was not a significant factor, whereas the change in temperature was a significant factor, which implies that great fluctuation in temperature within a winter day had greater impact on occurrence of circulatory disease than an absolute temperature threshold.

  16. Precipitation Indices Low Countries

    Science.gov (United States)

    van Engelen, A. F. V.; Ynsen, F.; Buisman, J.; van der Schrier, G.

    2009-09-01

    Since 1995, KNMI published a series of books(1), presenting an annual reconstruction of weather and climate in the Low Countries, covering the period AD 763-present, or roughly, the last millennium. The reconstructions are based on the interpretation of documentary sources predominantly and comparison with other proxies and instrumental observations. The series also comprises a number of classifications. Amongst them annual classifications for winter and summer temperature and for winter and summer dryness-wetness. The classification of temperature have been reworked into peer reviewed (2) series (AD 1000-present) of seasonal temperatures and temperature indices, the so called LCT (Low Countries Temperature) series, now incorporated in the Millennium databases. Recently we started a study to convert the dryness-wetness classifications into a series of precipitation; the so called LCP (Low Countries Precipitation) series. A brief outline is given here of the applied methodology and preliminary results. The WMO definition for meteorological drought has been followed being that a period is called wet respectively dry when the amount of precipitation is considerable more respectively less than usual (normal). To gain a more quantitative insight for four locations, geographically spread over the Low Countries area (De Bilt, Vlissingen, Maastricht and Uccle), we analysed the statistics of daily precipitation series, covering the period 1900-present. This brought us to the following definition, valid for the Low Countries: A period is considered as (very) dry respectively (very) wet if over a continuous period of at least 60 days (~two months) cq 90 days (~three months) on at least two out of the four locations 50% less resp. 50% more than the normal amount for the location (based on the 1961-1990 normal period) has been measured. This results into the following classification into five drought classes hat could be applied to non instrumental observations: Very wet period

  17. Response of biological soil crust diazotrophs to season, altered summer precipitation and year-round increased temperature in an arid grassland of the Colorado Plateau, USA

    Directory of Open Access Journals (Sweden)

    Chris M Yeager

    2012-10-01

    Full Text Available Biological soil crusts (biocrusts, which supply significant amounts of fixed nitrogen into terrestrial ecosystems worldwide (~33 Tg y-1, are likely to respond to changes in temperature and precipitation associated with climate change. Using nifH gene-based surveys, we explored variation in the diazotrophic community of biocrusts of the Colorado Plateau, USA in response to season (autumn vs. spring, as well as field manipulations that increased the frequency of small-volume precipitation events and year-round soil temperature. Abundance of nifH genes in biocrusts ranged from 3x106 – 1x108 g-1 soil, and nifH from heterocystous cyanobacteria closely related to Scytonema hyalinum, Spirirestis rafaelensis, and Nostoc commune comprised > 98% of the total. Although there was no apparent seasonal effect on total nifH gene abundance in the biocrusts, T-RFLP analysis revealed a strong seasonal pattern in nifH composition. Spirirestis nifH abundance was estimated to oscillate 1 to >2 orders of magnitude between autumn (low and spring (high. A year-round increase of soil temperature (2 − 3 °C had little effect on the diazotroph community structure over 2 years. Altered summer precipitation had little impact on diazotroph community structure over the first 1.5 years of the study, when natural background patterns across years and seasons superseded any treatment effects. However, after the second summer of treatments, nifH abundance was 2.6 fold lower in biocrusts receiving altered precipitation. Heterocystous cyanobacteria were apparently more resilient to altered precipitation than other cyanobacteria. The results demonstrate that diazotrophic community composition of biocrusts in this semi-arid grassland undergoes strong seasonal shifts and that the abundance of its dominant members decreased in response to more frequent, small-volume precipitation events.

  18. Response of biological soil crust diazotrophs to season, altered summer precipitation, and year-round increased temperature in an arid grassland of the Colorado Plateau, USA

    Science.gov (United States)

    Yeager, Chris M.; Kuske, Cheryl R.; Carney, Travis D.; Johnson, Shannon L.; Ticknor, Lawrence O.; Belnap, Jayne

    2012-01-01

    Biological soil crusts (biocrusts), which supply significant amounts of fixed nitrogen into terrestrial ecosystems worldwide (~33Tg y-1), are likely to respond to changes in temperature and precipitation associated with climate change. Using nifH gene-based surveys, we explored variation in the diazotrophic community of biocrusts of the Colorado Plateau, USA in response to season (autumn vs. spring), as well as field manipulations that increased the frequency of small volume precipitation events and year-round soil temperature. Abundance of nifH genes in biocrusts ranged from 3×106 to 1×8 g-1 soil, and nifH from heterocystous cyanobacteria closely related to Scytonema hyalinum, Spirirestis rafaelensis, and Nostoc commune comprised >98% of the total. Although there was no apparent seasonal effect on total nifH gene abundance in the biocrusts, T-RFLP analysis revealed a strong seasonal pattern in nifH composition. Spirirestis nifH abundance was estimated to oscillate 1 to >2 orders of magnitude between autumn (low) and spring (high). A year-round increase of soil temperature (2–3°C) had little effect on the diazotroph community structure over 2 years. Altered summer precipitation had little impact on diazotroph community structure over the first 1.5years of the study, when natural background patterns across years and seasons superseded any treatment effects. However, after the second summer of treatments, nifH abundance was 2.6-fold lower in biocrusts receiving altered precipitation. Heterocystous cyanobacteria were apparently more resilient to altered precipitation than other cyanobacteria. The results demonstrate that diazotrophic community composition of biocrusts in this semi-arid grassland undergoes strong seasonal shifts and that the abundance of its dominant members decreased in response to more frequent, small volume precipitation events.

  19. Extreme climate, not extreme weather: the summer of 1816 in Geneva, Switzerland

    Directory of Open Access Journals (Sweden)

    R. Auchmann

    2012-02-01

    Full Text Available We analyze weather and climate during the "Year without Summer" 1816 using sub-daily data from Geneva, Switzerland, representing one of the climatically most severely affected regions. The record includes twice daily measurements and observations of air temperature, pressure, cloud cover, wind speed, and wind direction as well as daily measurements of precipitation. Comparing 1816 to a contemporary reference period (1799–1821 reveals that the coldness of the summer of 1816 was most prominent in the afternoon, with a shift of the entire distribution function of temperature anomalies by 3–4 °C. Early morning temperature anomalies show a smaller change for the mean, a significant decrease in the variability, and no changes in negative extremes. Analyzing cloudy and cloud-free conditions separately suggests that an increase in the number of cloudy days was to a significant extent responsible for these features. A daily weather type classification based on pressure, pressure tendency, and wind direction shows extremely anomalous frequencies in summer 1816, with only one day (compared to 20 in an average summer classified as high-pressure situation but a tripling of low-pressure situations. The afternoon temperature anomalies expected from only a change in weather types was much stronger negative in summer 1816 than in any other year. For precipitation, our analysis shows that the 80% increase in summer precipitation compared to the reference period can be explained by 80% increase in the frequency of precipitation, while no change could be found neither in the average intensity of precipitation nor in the frequency distribution of extreme precipitation. In all, the analysis shows that the regional circulation and local cloud cover played a dominant role. It also shows that the summer of 1816 was an example of extreme climate, not extreme weather.

  20. quantitative precipitation forecasts during the Indian Summer Monsoon

    Indian Academy of Sciences (India)

    65

    the Indian Summer Monsoon: Contiguous Rain Area (CRA) Approach ... 1Centre for Australian Weather and Climate Research, Melbourne, Australia ... are evaluated over India using the Contiguous Rainfall Area (CRA) verification technique.

  1. A statistical intercomparison between "urban" and "rural" precipitation chemistry data from greater Manchester and two nearby secondary national network sites in the United Kingdom

    Science.gov (United States)

    Lee, David S.; Longhurst, James W. S.

    Precipitation chemistry data from a dense urban monitoring network in Greater Manchester, northwest England, were compared with interpolated values from the U.K. secondary national acid deposition monitoring network for the year 1988. Differences were found to be small. However, when data from individual sites from the Greater Manchester network were compared with data from the two nearest secondary national network sites, significant differences were found using simple and complex statistical analyses. Precipitation chemistry at rural sites could be similar to that at urban sites, but the sources of some ions were thought to be different. The synoptic-scale gradients of precipitation chemistry, as shown by the secondary national network, also accounted for some of the differences.

  2. Early summer precipitation in the lower Yangtze River basin for AD 1845-2011 based on tree-ring cellulose oxygen isotopes

    Science.gov (United States)

    Xu, Chenxi; Shi, Jiangfeng; Zhao, Yesi; Nakatsuka, Takeshi; Sano, Masaki; Shi, Shiyuan; Guo, Zhengtang

    2018-04-01

    Precipitation from June to August is generally used to reflect the East Asian summer monsoon (EASM) variability. However, the principal modes of the EASM rainfall are different between May-June (MJ) and July-August due to the seasonal march of East Asian subtropical front. Therefore, it is necessary to study them separately. In this study, we reconstruct a 167-year MJ precipitation time series using tree-ring cellulose δ18O that explains 46.9% of the variance in the lower Yangtze River basin, Southeast China, that extends the meteorological data back more than 100 years and makes the precipitation study at decadal scales possible. The decades with 5 or more anomalously dry or wet years are the 1880s, 1890s, and 1910s, and the 1980s and 2000s have only one anomalous year per decade. MJ precipitation shows a significantly negative relationship with absolute Niño 3.4 sea surface temperature, especially during the developing phases of El Niño-Southern Oscillation, indicating that there is less rainfall during El Niño events. However, the relationship is not uniform throughout the period. Further analyses show that it is stronger when the Pacific Decadal Oscillation is in its positive phases.

  3. Mechanisms and Attribution of Changes in Austral Summer Precipitation Related to the South Atlantic Convergence Zone

    Science.gov (United States)

    Zilli, Marcia Terezinha

    Austral summer (DJF) precipitation over tropical South America (SA) is characterized by the South American Monsoon System (SAMS) and the South Atlantic Convergence Zone (SACZ). The increase in atmospheric temperature and water vapor content over the SA during the last decades of the 20 th century could affect the duration and amplitude of the SAMS and the intensity of the SACZ. This research examines the spatial variability of precipitation trends over SE Brazil, focusing on the SACZ. More specifically, this study investigates trends in precipitation over Southeastern Brazil (SE Brazil) and examines changes in the position and intensity of the SACZ. SE Brazil is the most densely populated region in the country with a large portion of this population living in urban centers. The SACZ is important for agriculture and water supply for millions of people. One of the main goals of this research is to identify mechanisms associated with the observed changes in the characteristics of the SACZ during the last three decades of the 20th century, and examine the relative contribution of natural and anthropogenic forcing to precipitation trends. The first chapter investigates the pattern of spatial variability of precipitation trends over the coastal region of SE Brazil. This study shows that over the southern portion of the study area, precipitation is increasing due to the increase in the frequency and intensity of extreme events. Over the northern portion of the area, while the intensity of extreme events is increasing, the number of precipitating days is decreasing. This spatial pattern of precipitation trends suggests a poleward shift of the SACZ, which is investigated in the second chapter. Chapter 2 focuses on the underlying mechanisms associated with changes in precipitation intensity related to the position of the SACZ. Decadal variations in the mean state of the atmosphere suggest that the observed changes in precipitation over SE Brazil are associated with a

  4. Summer monsoon circulation and precipitation over the tropical Indian Ocean during ENSO in the NCEP climate forecast system

    Science.gov (United States)

    Chowdary, J. S.; Chaudhari, H. S.; Gnanaseelan, C.; Parekh, Anant; Suryachandra Rao, A.; Sreenivas, P.; Pokhrel, S.; Singh, P.

    2014-04-01

    This study investigates the El Niño Southern Oscillation (ENSO) teleconnections to tropical Indian Ocean (TIO) and their relationship with the Indian summer monsoon in the coupled general circulation model climate forecast system (CFS). The model shows good skill in simulating the impact of El Niño over the Indian Oceanic rim during its decay phase (the summer following peak phase of El Niño). Summer surface circulation patterns during the developing phase of El Niño are more influenced by local Sea Surface Temperature (SST) anomalies in the model unlike in observations. Eastern TIO cooling similar to that of Indian Ocean Dipole (IOD) is a dominant model feature in summer. This anomalous SST pattern therefore is attributed to the tendency of the model to simulate more frequent IOD events. On the other hand, in the model baroclinic response to the diabatic heating anomalies induced by the El Niño related warm SSTs is weak, resulting in reduced zonal extension of the Rossby wave response. This is mostly due to weak eastern Pacific summer time SST anomalies in the model during the developing phase of El Niño as compared to observations. Both eastern TIO cooling and weak SST warming in El Niño region combined together undermine the ENSO teleconnections to the TIO and south Asia regions. The model is able to capture the spatial patterns of SST, circulation and precipitation well during the decay phase of El Niño over the Indo-western Pacific including the typical spring asymmetric mode and summer basin-wide warming in TIO. The model simulated El Niño decay one or two seasons later, resulting long persistent warm SST and circulation anomalies mainly over the southwest TIO. In response to the late decay of El Niño, Ekman pumping shows two maxima over the southern TIO. In conjunction with this unrealistic Ekman pumping, westward propagating Rossby waves display two peaks, which play key role in the long-persistence of the TIO warming in the model (for more than a

  5. Recent and future extreme precipitation over Ukraine

    Science.gov (United States)

    Vyshkvarkova, Olena; Voskresenskaya, Elena

    2014-05-01

    of Atlantic multidecadal oscillation. Typical space distribution of extreme precipitation (R95p) for seasons and for year is characterized by their southward intensity increasing from North-East and North-West. Summer precipitation extremes are characterized by quite homogeneous distribution. Linear trends of indices of precipitation extremes (R95p, R20mm and R30mm) for period 1951 - 2005 are mainly negative in winter season and positive in summer. To analyze the possible changes of extreme precipitation it was calculated the R95p index for recent climate period (1986 - 2005) and for periods 2046 - 2065 and 2081 - 2100 (as it was recommended by IPCC). Its difference between 1986 - 2005 and 2046 - 2065 shows that intensity of extreme precipitation will decrease in the north-east and increase in the south-west regions, especially in summer season. Magnitude of intensity changes of extreme precipitation will be ± 4 - 5 mm/day. The intensity changes of extreme precipitation since the recent climate period till the end of the century will be some less (2 - 3 mm/day) than in previous period, except summer months. Number of cases with precipitation extremes will be increase in southern regions of Ukraine in summer seasons. In other seasons it will be at the recent climate level.

  6. Interdecadal Change in Extreme Precipitation over South China and Its Mechanism

    Institute of Scientific and Technical Information of China (English)

    NING Liang; QIAN Yongfu

    2009-01-01

    Based on the daily precipitation data taken from 17 stations over South China during the period of 1961 2003, a sudden change in summer extreme precipitation events over South China in the early 1990s along with the possible mechanism connected with the anomalies of the latent heat flux over the South China Sea and the sensible heat flux over the Indochina peninsula are examined. The results show that both the annual and summer extreme precipitation events have obvious interdecadal variations and have increased significantly since the early 1990s. Moreover, the latent heat flux over the South China Sea and the sensible heat flux over the Indochina peninsula also have obvious interdecadal variations consistent with that of the extreme precipitation, and influence different months' extreme precipitation, respectively. Their effects are achieved by the interdecadal increases of the strengthening convection over South China through the South China Sea Summer Monsoon.

  7. Self-organizing map network-based precipitation regionalization for the Tibetan Plateau and regional precipitation variability

    Science.gov (United States)

    Wang, Nini; Yin, Jianchuan

    2017-12-01

    A precipitation-based regionalization for the Tibetan Plateau (TP) was investigated for regional precipitation trend analysis and frequency analysis using data from 1113 grid points covering the period 1900-2014. The results utilizing self-organizing map (SOM) network suggest that four clusters of precipitation coherent zones can be identified, including the southwestern edge, the southern edge, the southeastern region, and the north central region. Regionalization results of the SOM network satisfactorily represent the influences of the atmospheric circulation systems such as the East Asian summer monsoon, the south Asian summer monsoon, and the mid-latitude westerlies. Regionalization results also well display the direct impacts of physical geographical features of the TP such as orography, topography, and land-sea distribution. Regional-scale annual precipitation trend as well as regional differences of annual and seasonal total precipitation were investigated by precipitation index such as precipitation concentration index (PCI) and Standardized Anomaly Index (SAI). Results demonstrate significant negative long-term linear trends in southeastern TP and the north central part of the TP, indicating arid and semi-arid regions in the TP are getting drier. The empirical mode decomposition (EMD) method shows an evolution of the main cycle with 4 and 12 months for all the representative grids of four sub-regions. The cross-wavelet analysis suggests that predominant and effective period of Indian Ocean Dipole (IOD) on monthly precipitation is around ˜12 months, except for the representative grid of the northwestern region.

  8. Observed changes in extreme precipitation in Poland: 1991-2015 versus 1961-1990

    Science.gov (United States)

    Pińskwar, Iwona; Choryński, Adam; Graczyk, Dariusz; Kundzewicz, Zbigniew W.

    2018-01-01

    Several episodes of extreme precipitation excess and extreme precipitation deficit, with considerable economic and social impacts, have occurred in Europe and in Poland in the last decades. However, the changes of related indices exhibit complex variability. This paper analyses changes in indices related to observed abundance and deficit of precipitated water in Poland. Among studied indices are maximum seasonal 24-h precipitation for the winter half-year (Oct.-March) and the summer half-year (Apr.-Sept.), maximum 5-day precipitation, maximum monthly precipitation and number of days with intense or very intense precipitation (respectively, in excess of 10 mm or 20 mm per day). Also, the warm-seasonal maximum number of consecutive dry days (longest period with daily precipitation below 1 mm) was examined. Analysis of precipitation extremes showed that daily maximum precipitation for the summer half-year increased for many stations, and increases during the summer half-year are more numerous than those in the winter half-year. Also, analysis of 5-day and monthly precipitation sums show increases for many stations. Number of days with intense precipitation increases especially in the north-western part of Poland. The number of consecutive dry days is getting higher for many stations in the summer half-year. Comparison of these two periods: colder 1961-1990 and warmer 1991-2015, revealed that during last 25 years most of statistical indices, such as 25th and 75th percentiles, median, mean and maximum are higher. However, many changes discussed in this paper are weak and statistically insignificant. The findings reported in this paper challenge results based on earlier data that do not include 2007-2015.

  9. Forecasting the summer rainfall in North China using the year-to-year increment approach

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A new approach to forecasting the year-to-year increment of rainfall in North China in July-August (JA) is proposed. DY is defined as the difference of a variable between the current year and the preceding year (year-to-year increment). NR denotes the seasonal mean precipitation rate over North China in JA. After analyzing the atmospheric circulation anomalies associated with the DY of NR, five key predictors for the DY of NR have been identified. The prediction model for the DY of NR is established by using multi-linear regression method and the NR is obtained (the current forecasted DY of NR added to the preceding observed NR). The prediction model shows a high correlation coefficient (0.8) between the simulated and the observed DY of NR throughout period 1965-1999, with an average relative root mean square error of 19% for the percentage of precipitation rate anomaly over North China. The prediction model makes a hindcast for 2000-2007, with an average relative root mean square error of 21% for the percentage of precipitation rate anomaly over North China. The model reproduces the downward trend of the percentage of precipitation rate anomaly over North China during 1965-2006. Because the current operational prediction models of the summer precipitation have average forecast scores of 60%-70%, it has been more difficult to forecast the summer rainfall over North China. Thus this new approach for predicting the year-to-year increment of the summer precipitation (and hence the summer precipitation itself) has the potential to significantly improve operational forecasting skill for summer precipitation.

  10. Seasonal and annual precipitation time series trend analysis in North Carolina, United States

    Science.gov (United States)

    Sayemuzzaman, Mohammad; Jha, Manoj K.

    2014-02-01

    The present study performs the spatial and temporal trend analysis of the annual and seasonal time-series of a set of uniformly distributed 249 stations precipitation data across the state of North Carolina, United States over the period of 1950-2009. The Mann-Kendall (MK) test, the Theil-Sen approach (TSA) and the Sequential Mann-Kendall (SQMK) test were applied to quantify the significance of trend, magnitude of trend, and the trend shift, respectively. Regional (mountain, piedmont and coastal) precipitation trends were also analyzed using the above-mentioned tests. Prior to the application of statistical tests, the pre-whitening technique was used to eliminate the effect of autocorrelation of precipitation data series. The application of the above-mentioned procedures has shown very notable statewide increasing trend for winter and decreasing trend for fall precipitation. Statewide mixed (increasing/decreasing) trend has been detected in annual, spring, and summer precipitation time series. Significant trends (confidence level ≥ 95%) were detected only in 8, 7, 4 and 10 nos. of stations (out of 249 stations) in winter, spring, summer, and fall, respectively. Magnitude of the highest increasing (decreasing) precipitation trend was found about 4 mm/season (- 4.50 mm/season) in fall (summer) season. Annual precipitation trend magnitude varied between - 5.50 mm/year and 9 mm/year. Regional trend analysis found increasing precipitation in mountain and coastal regions in general except during the winter. Piedmont region was found to have increasing trends in summer and fall, but decreasing trend in winter, spring and on an annual basis. The SQMK test on "trend shift analysis" identified a significant shift during 1960 - 70 in most parts of the state. Finally, the comparison between winter (summer) precipitations with the North Atlantic Oscillation (Southern Oscillation) indices concluded that the variability and trend of precipitation can be explained by the

  11. Observed precipitation trends in the Yangtze river catchment from 1951 to 2002

    Institute of Scientific and Technical Information of China (English)

    SUBuda; JIANGTong; SHIYafeng; StefanBECKER; MracoGEMMER

    2004-01-01

    The monthly, seasonal, and annual precipitation trends in the Yangtze river catchment have been detected through analysis of 51 meteorological stations' data between 1950-2002 provided by National Meteorological Administration. Results reveal that: 1) Summer precipitation in the Yangtze river catchment shows significant increasing tendency. The Poyanghu lake basin, Dongtinghu lake basin and Taihu lake basin in the middle and lower reaches are the places showing significant positive trends. Summer precipitation in the middle and lower reaches experienced an abrupt change in the year 1992; 2) The monthly precipitation in months just adjoining to summer shows decreasing tendency in the Yangtze river catchment. The upper and middle reaches in Jialingjiang river basin and Hanshui river basin are the places showing significant negative trends; 3) Extreme precipitation events show an increasing tendency in most places, especially in the middle and lower reaches of the Yangtze river catchment.

  12. A skilful prediction scheme for West China autumn precipitation

    Science.gov (United States)

    Wei, Ting; Song, Wenling; Dong, Wenjie; Ke, Zongjian; Sun, Linhai; Wen, Xiaohang

    2018-01-01

    West China is one of the country's largest precipitation centres in autumn. This region's agriculture and people are highly vulnerable to the variability in the autumn rain. This study documents that the water vapour for West China autumn precipitation (WCAP) is from the Bay of Bengal, the South China Sea and the Western Pacific. A strong convergence of the three water vapour transports (WVTs) and their encounter with the cold air from the northern trough over Lake Barkersh-Lake Baikal result in the intense WCAP. Three predictors in the preceding spring or summer are identified for the interannual variability of WCAP: (1) sea surface temperature in the Indo-Pacific warm pool in summer, (2) soil moisture from the Hexi Corridor to the Hetao Plain in summer and (3) snow cover extent over East Europe and West Siberian in spring. The cold SSTAs contribute to an abnormal regional meridional circulation and intensified WVTs. The wet soil results in greater air humidity and anomalous southerly emerging over East Asia. Reduced snow cover stimulates a Rossby wave train that weakens the cold air, favouring autumn rainfall in West China. The three predictors, which demonstrate the influences of air-sea interaction, land surface processes and the cryosphere on the WCAP, have clear physical significance and are independent with each other. We then develop a new statistical prediction model with these predictors and the multilinear regression analysis method. The predicted and observed WCAP shows high correlation coefficients of 0.63 and 0.51 using cross-validation tests and independent hindcasts, respectively.

  13. Observation of atomic oxygen O(1S) green-line emission in the summer polar upper mesosphere associated with high-energy (≥30 keV) electron precipitation during high-speed solar wind streams

    Science.gov (United States)

    Lee, Young-Sook; Kwak, Young-Sil; Kim, Kyung-Chan; Solheim, Brian; Lee, Regina; Lee, Jaejin

    2017-01-01

    The auroral green-line emission at 557.7 nm wavelength as arising from the atomic oxygen O(1S → 1D) transition typically peaks at an altitude of 100 km specifically in the nightside oval, induced by auroral electrons within an energy range of 100 eV-30 keV. Intense aurora is known as being suppressed by sunlight in summer daytime but usually occurs in low electrical background conductivity. However, in the present study in summer (July) sunlit condition, enhancements of O(1S) emission rates observed by using the Wind Imaging Interferometer/UARS were frequently observed at low altitudes below 90 km, where ice particles are created initially as subvisible and detected as polar mesosphere summer echoes, emerging to be an optical phenomenon of polar mesospheric clouds. The intense O(1S) emission occurring in summer exceeds those occurring in the daytime in other seasons both in occurrence and in intensity, frequently accompanied by occurrences of supersonic neutral velocity (300-1500 m s-1). In the mesosphere, ion motion is controlled by electric field and the momentum is transferred to neutrals. The intense O(1S) emission is well associated with high-energy electron precipitation as observed during an event of high-speed solar wind streams. Meanwhile, since the minimum occurrences of O(1S) emission and supersonic velocity are maintained even in the low precipitation flux, the mechanism responsible is not only related to high-energy electron precipitation but also presumably to the local conditions, including the composition of meteoric-charged ice particles and charge separation expected in extremely low temperatures (<150 K).

  14. Simulating the convective precipitation diurnal cycle in a North American scale convection-permitting model

    Science.gov (United States)

    Scaff, L.; Li, Y.; Prein, A. F.; Liu, C.; Rasmussen, R.; Ikeda, K.

    2017-12-01

    A better representation of the diurnal cycle of convective precipitation is essential for the analysis of the energy balance and the water budget components such as runoff, evaporation and infiltration. Convection-permitting regional climate modeling (CPM) has been shown to improve the models' performance of summer precipitation, allowing to: (1) simulate the mesoscale processes in more detail and (2) to provide more insights in future changes in convective precipitation under climate change. In this work we investigate the skill of the Weather Research and Forecast model (WRF) in simulating the summer precipitation diurnal cycle over most of North America. We use 4 km horizontal grid spacing in a 13-years long current and future period. The future scenario is assuming no significant changes in large-scale weather patterns and aims to answer how the weather of the current climate would change if it would reoccur at the end of the century under a high-end emission scenario (Pseudo Global Warming). We emphasize on a region centered on the lee side of the Canadian Rocky Mountains, where the summer precipitation amount shows a regional maximum. The historical simulations are capable to correctly represent the diurnal cycle. At the lee-side of the Canadian Rockies the increase in the convective available potential energy as well as pronounced low-level moisture flux from the southeast Prairies explains the local maximum in summer precipitation. The PGW scenario shows an increase in summer precipitation amount and intensity in this region, consistently with a stronger source of moisture and convective energy.

  15. Changes in seasonal and diurnal precipitation types during summer over South Korea in the late twenty-first century (2081-2100) projected by the RegCM4.0 based on four RCP scenarios

    Science.gov (United States)

    Oh, Seok-Geun; Suh, Myoung-Seok

    2018-01-01

    Changes in seasonal and diurnal precipitation types over South Korea during summer in the late twenty-first century (2081-2100) were projected under four RCP scenarios using the Regional Climate Model (RegCM4.0) with a horizontal resolution of 12.5 km. Two boundary conditions, ERA-Interim and HadGEM2-AO, were used to drive the RegCM4.0 (jointly named RG4_ERA and RG4_HG2, respectively). In general, the RegCM4.0 reproduces the spatial distribution of summer precipitation over Northeast Asia for the current climate (1989-2008) reasonably well. The RG4_HG2 shows larger dry biases over South Korea, when compared with observations, than does the RG4_ERA. These strong dry biases result from the underestimation of convective precipitation (CPR) and are particularly noticeable in late afternoons during July and August. It is related to the performance of HadGEM2-AO which simulated southwesterly winds weakly in that time. However, interestingly, the RG4_HG2 simulates similar increases in the contribution of CPR to total precipitation after mid-July, resulting in comparable performance in the reproduction of heavy precipitation. In the late twenty-first century, a significant increase (decrease) in CPR (NCPR) is generally projected over South Korea, and particularly under the RCP8.5. During June, the total precipitation is affected primarily by changes in NCPR under RCP2.6 and RCP6.0. After mid-July, increasing total precipitation is primarily caused by the distinct increases in CPR in the late afternoons; this pattern is particularly noticeable under RCP8.5, which is associated with more destabilized atmospheric conditions during July and August. Light and heavy precipitation are projected to decrease and increase, respectively, under RCP8.5.

  16. 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

  17. Tropical Atlantic-Korea teleconnection pattern during boreal summer season

    Science.gov (United States)

    Ham, Yoo-Geun; Chikamoto, Yoshimitsu; Kug, Jong-Seong; Kimoto, Masahide; Mochizuki, Takashi

    2017-10-01

    The remote impact of tropical Atlantic sea surface temperature (SST) variability on Korean summer precipitation is examined based on observational data analysis along with the idealized and hindcast model experiments. Observations show a significant correlation (i.e. 0.64) between Korean precipitation anomalies (averaged over 120-130°E, 35-40°N) and the tropical Atlantic SST index (averaged over 60°W-20°E, 30°S-30°N) during the June-July-August (JJA) season for the 1979-2010 period. Our observational analysis and partial-data assimilation experiments using the coupled general circulation model demonstrate that tropical Atlantic SST warming induces the equatorial low-level easterly over the western Pacific through a reorganization of the global Walker Circulation, causing a decreased precipitation over the off-equatorial western Pacific. As a Gill-type response to this diabatic forcing, an anomalous low-level anticyclonic circulation appears over the Philippine Sea, which transports wet air from the tropics to East Asia through low-level southerly, resulting an enhanced precipitation in the Korean peninsula. Multi-model hindcast experiments also show that predictive skills of Korean summer precipitation are improved by utilizing predictions of tropical Atlantic SST anomalies as a predictor for Korean precipitation anomalies.

  18. Response of the Asian summer monsoons to idealized precession and obliquity forcing in a set of GCMs

    Science.gov (United States)

    Bosmans, J. H. C.; Erb, M. P.; Dolan, A. M.; Drijfhout, S. S.; Tuenter, E.; Hilgen, F. J.; Edge, D.; Pope, J. O.; Lourens, L. J.

    2018-05-01

    We examine the response of the Indian and East Asian summer monsoons to separate precession and obliquity forcing, using a set of fully coupled high-resolution models for the first time: EC-Earth, GFDL CM2.1, CESM and HadCM3. We focus on the effect of insolation changes on monsoon precipitation and underlying circulation changes, and find strong model agreement despite a range of model physics, parameterization, and resolution. Our results show increased summer monsoon precipitation at times of increased summer insolation, i.e. minimum precession and maximum obliquity, accompanied by a redistribution of precipitation and convection from ocean to land. Southerly monsoon winds over East Asia are strengthened as a consequence of an intensified land-sea pressure gradient. The response of the Indian summer monsoon is less straightforward. Over south-east Asia low surface pressure is less pronounced and winds over the northern Indian Ocean are directed more westward. An Indian Ocean Dipole pattern emerges, with increased precipitation and convection over the western Indian Ocean. Increased temperatures occur during minimum precession over the Indian Ocean, but not during maximum obliquity when insolation is reduced over the tropics and southern hemisphere during northern hemisphere summer. Evaporation is reduced over the northern Indian Ocean, which together with increased precipitation over the western Indian Ocean dampens the increase of monsoonal precipitation over the continent. The southern tropical Indian Ocean as well as the western tropical Pacific (for precession) act as a moisture source for enhanced monsoonal precipitation. The models are in closest agreement for precession-induced changes, with more model spread for obliquity-induced changes, possibly related to a smaller insolation forcing. Our results indicate that a direct response of the Indian and East Asian summer monsoons to insolation forcing is possible, in line with speleothem records but in

  19. Validation of precipitation over Japan during 1985-2004 simulated by three regional climate models and two multi-model ensemble means

    Energy Technology Data Exchange (ETDEWEB)

    Ishizaki, Yasuhiro [Meteorological Research Institute, Tsukuba (Japan); National Institute for Environmental Studies, Tsukuba (Japan); Nakaegawa, Toshiyuki; Takayabu, Izuru [Meteorological Research Institute, Tsukuba (Japan)

    2012-07-15

    We dynamically downscaled Japanese reanalysis data (JRA-25) for 60 regions of Japan using three regional climate models (RCMs): the Non-Hydrostatic Regional Climate Model (NHRCM), modified RAMS version 4.3 (NRAMS), and modified Weather Research and Forecasting model (TWRF). We validated their simulations of the precipitation climatology and interannual variations of summer and winter precipitation. We also validated precipitation for two multi-model ensemble means: the arithmetic ensemble mean (AEM) and an ensemble mean weighted according to model reliability. In the 60 regions NRAMS simulated both the winter and summer climatological precipitation better than JRA-25, and NHRCM simulated the wintertime precipitation better than JRA-25. TWRF, however, overestimated precipitation in the 60 regions in both the winter and summer, and NHRCM overestimated precipitation in the summer. The three RCMs simulated interannual variations, particularly summer precipitation, better than JRA-25. AEM simulated both climatological precipitation and interannual variations during the two seasons more realistically than JRA-25 and the three RCMs overall, but the best RCM was often superior to the AEM result. In contrast, the weighted ensemble mean skills were usually superior to those of the best RCM. Thus, both RCMs and multi-model ensemble means, especially multi-model ensemble means weighted according to model reliability, are powerful tools for simulating seasonal and interannual variability of precipitation in Japan under the current climate. (orig.)

  20. Intraseasonal SST-precipitation coupling during the Indian Summer Monsoon, and its modulation by the Indian Ocean Dipole

    Science.gov (United States)

    Jongaramrungruang, S.; Seo, H.; Ummenhofer, C.

    2016-02-01

    The Indian Summer Monsoon (ISM) plays a crucial role in shaping the large proportion of the total precipitation over the Indian subcontinent each year. The ISM rainfall exhibits a particularly strong intraseasonal variability, that has profound socioeconomic consequences, such as agricultural planning and flood preparation. However, our understanding of the variability on this time scale is still limited due to sparse data availability in the past. In this study, we used a combination of state-of-the-art high-resolution satellite estimate of rainfall, objectively analyzed surface flux, as well as atmospheric reanalysis product to investigate the nature of the ISM intraseasonal rainfall variability and how it varies year to year. The emphasis is placed on the Bay of Bengal (BoB) where the intraseasonal ocean-atmosphere coupling is most prominent. Results show that the maximum warming of SST leads the onset of heavy precipitation event by 3-5 days, and that surface heat flux and surface wind speed are weak prior to the rain but amplifies and peaks after the rain reaches its maximum. Furthermore, the Indian Ocean Dipole (IOD) significantly affects the observed intraseasonal SST-precipitation relationship. The pre-convection SST warming is stronger and more pronounced during the negative phase of the IOD, while the signal is weaker and less organized in the positive phase. This is explained by the column-integrated moisture budget analysis which reveals that, during the ISM heavy rainfall in the BoB, there is more moisture interchange in the form of enhanced vertical advection from the ocean to atmosphere in negative IOD years as compared to positive IOD years. Knowing the distinction of ISM variabilities during opposite phases of the IOD will help contribute to a more reliable prediction of ISM activities.

  1. Tritium time series in precipitation of Rm. Valcea, Romania.

    Science.gov (United States)

    Varlam, Carmen; Duliu, Octavian G; Faurescu, Ionut; Vagner, Irina; Faurescu, Denisa

    2016-01-01

    Following tritium concentration records in precipitation for the period 1999-2013 and tritium concentration behaviour during this period for the Ramnicu Valcea (Rm. Valcea) location, the tritium level of individual precipitations of the late spring and summer for the 2009-2013 period was investigated. Despite good correlation between monthly mean tritium concentrations and monthly mean precipitations over the 15-year period of observations (Pearson coefficient 0.87), the individual precipitations had no linear correlation between the tritium concentration and the amount of precipitation.

  2. [Chemical characteristics of precipitation in South China Sea].

    Science.gov (United States)

    Xiao, Hong-Wei; Long, Ai-Min; Xie, Lu-Hua; Xiao, Hua-Yun; Liu, Cong-Qiang

    2014-02-01

    Rainwater samples were collected in the summer on "Shiyan 3" during the 2012 South China Sea Sectional Scientific Survey. The concentrations of anion and cation, and pH in precipitation were determined and backward trajectories of air mass were simulated to analyze the chemical characteristics of ions and examine the source of ions. The results indicated that the mean pH value of precipitation was 6.3, with 5.6 of minimal value in summer in South China Sea. The order of anion and cation abundance was Cl(-) > S04(2-) > NO3(-) and Na(+) > Mg(2+) > Ca(2+) > K(+). Cl(-) was the major anion and Na(+) was the major cation, with concentrations of 2 637.5 microeq x L(-1) and 2095.5 microeq x L(-1), respectively, showing that they were the characteristics of marine atmospheric precipitation. There was a good linear relationship between each pair of 7 ions, with correlation coefficient above 0.9, suggesting that they may have a common source. However, the correlation coefficients were lower between NO3(-) and other ions than the others, suggesting that NO3(-) had more complex sources. The concentrations of Ca(2+) and K(+) in precipitation may be related to coral environment in South China Sea. The backward trajectories in 6 stations showed that the air mass was from south and southwest of South China Sea, without passing through above the continent. These results suggested that precipitation affected by human ion source can be ignored in summer in South China Sea.

  3. Low interannual precipitation has a greater negative effect than seedling herbivory on the population dynamics of a short-lived shrub, Schiedea obovata.

    Science.gov (United States)

    Bialic-Murphy, Lalasia; Gaoue, Orou G

    2018-01-01

    Climate projections forecast more extreme interannual climate variability over time, with an increase in the severity and duration of extreme drought and rainfall events. Based on bioclimatic envelope models, it is projected that changing precipitation patterns will drastically alter the spatial distributions and density of plants and be a primary driver of biodiversity loss. However, many other underlying mechanisms can impact plant vital rates (i.e., survival, growth, and reproduction) and population dynamics. In this study, we developed a size-dependent integral projection model (IPM) to evaluate how interannual precipitation and mollusk herbivory influence the dynamics of a Hawaii endemic short-lived shrub, Schiedea obovata (Caryophyllaceae). Assessing how wet season precipitation effects population dynamics it critical, as it is the timeframe when most of the foliar growth occurs, plants flower and fruit, and seedlings establish. Temporal variation in wet season precipitation had a greater effect than mollusk herbivory on S . obovata population growth rate λ, and the impact of interannual precipitation on vital rates shifted across plant ontogeny. Furthermore, wet season precipitation influenced multiple vital rates in contrasting ways and the effect of precipitation on the survival of larger vegetative and reproductively mature individuals contributed the most to variation in the population growth rate. Among all combination of wet season precipitation and herbivory intensities, the only scenario that led to a growing population was when high wet precipitation was associated with low herbivory. Our study highlights the importance of evaluating how abiotic factors and plant-consumer interactions influence an organism across its life cycle to fully understand the underpinning mechanisms that structure its spatial and temporal distribution and abundance. Our results also illustrate that for short-lived species, like S. obovata , seedling herbivory can have

  4. Projected change in East Asian summer monsoon by dynamic downscaling: Moisture budget analysis

    Science.gov (United States)

    Jung, Chun-Yong; Shin, Ho-Jeong; Jang, Chan Joo; Kim, Hyung-Jin

    2015-02-01

    The summer monsoon considerably affects water resource and natural hazards including flood and drought in East Asia, one of the world's most densely populated area. In this study, we investigate future changes in summer precipitation over East Asia induced by global warming through dynamical downscaling with the Weather Research and Forecast model. We have selected a global model from the Coupled Model Intercomparison Project Phase 5 based on an objective evaluation for East Asian summer monsoon and applied its climate change under Representative Concentration Pathway 4.5 scenario to a pseudo global warming method. Unlike the previous studies that focused on a qualitative description of projected precipitation changes over East Asia, this study tried to identify the physical causes of the precipitation changes by analyzing a local moisture budget. Projected changes in precipitation over the eastern foothills area of Tibetan Plateau including Sichuan Basin and Yangtze River displayed a contrasting pattern: a decrease in its northern area and an increase in its southern area. A local moisture budget analysis indicated the precipitation increase over the southern area can be mainly attributed to an increase in horizontal wind convergence and surface evaporation. On the other hand, the precipitation decrease over the northern area can be largely explained by horizontal advection of dry air from the northern continent and by divergent wind flow. Regional changes in future precipitation in East Asia are likely to be attributed to different mechanisms which can be better resolved by regional dynamical downscaling.

  5. Influence of a large late summer precipitation event on food limitation and grasshopper population dynamics in a northern Great Plains grassland.

    Science.gov (United States)

    Branson, David H

    2008-06-01

    The complex interplay between grasshoppers, weather conditions, and plants that cause fluctuations in grasshopper populations remains poorly understood, and little is known about the ecological processes that generate grasshopper outbreaks. Grasshopper populations respond to interacting extrinsic and intrinsic factors, with yearly and decadal weather patterns and the timing of precipitation all potentially important. The effects of initial and increasing grasshopper densities on grasshopper survival and reproductive correlates were examined at a northern mixed-grass prairie site through manipulations of grasshopper densities inside 10-m2 cages. High-quality grass growth occurred after a 9.1-cm mid-August rain. Reduced proportional survival was apparent in the two higher density treatments before the rain, indicative of food-limited density-dependent mortality. However, the large late summer rainfall event mediated the effects of exploitative competition on demographic characteristics because of the high-quality vegetation growth. This led to weaker effects of food limitation on survival and reproduction at the end of the experiment. The results indicate a direct link between weather variation, resource quality and grasshopper population dynamics led to a severe grasshopper outbreak and show that infrequent large precipitation events can have significant effects on population dynamics. Additional research is needed to examine the importance of infrequent large precipitation events on grasshopper population dynamics in grassland ecosystems.

  6. Stable Isotopic Variations in Precipitation in Southwest China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This study analyzes the relationships of stable isotopes in precipitation with temperature, air pressure and humidity at different altitudes, and the potential influencing mechanisms of control factors on the stable isotopes in precipitation in Southwest China. There appear marked negative correlations of the δ18O in precipitation with precipitation amount, vapor pressure and atmospheric precipitable water (PW)at the Mengzi, Simao and Tengchong stations on the synoptic timescale; the marked negative correlations between the δ18O in precipitation and the diurnal mean temperature at 400 hPa, 500 hPa, 700 hPa and 850hPa are different from the temperature effect in middle-high-latitude inland areas. In addition, the notable positive correlation between the δ18O in precipitation and the dew-point deficit △Td at different altitudes is found at the three stations. Precipitation is not the only factor generating an amount effect. Probably,the amount effect is related to the variations of atmospheric circulation and vapor origins. On the annual timescale, the annual precipitation amount weighted-mean δ18O displays negative correlations not only with annual precipitation but also with annual mean temperature at 500 hPa. It can be deduced that, in the years with an abnormally strong summer monsoon, more warm and wet air from low-latitude oceans is transported northward along the vapor channel located in Southwest China and generates abnormally strong rainfall on the way. Meanwhile, the abnormally strong condensation process will release more condensed latent heat in the atmosphere, and this will lead to a rise of atmospheric temperature during rainfall but a decline of δ18O in the precipitation. On the other hand, in the years with an abnormally weak summer monsoon, the precipitation and the atmospheric temperature during rainfalls decrease abnormally but the δ18O in precipitation increases.

  7. Dynamical seasonal prediction of Southern African summer precipitation

    CSIR Research Space (South Africa)

    Yuan, C

    2014-01-01

    Full Text Available Pacific as predictors. More recently, they were replaced by two- and one-tiered dynamical 75 forecast systems, but raw model outputs, such as geopotential height at 850 hPa, are often 76 statistically downscaled to achieve better prediction skills... above-normal years, all have a distinct La Niña signal in the tropical Pacific, and 315 among six successfully predicted below-normal years, all but the 2000/2001 austral summer 316 have a distinct El Niño signal. As a result, composites of SST...

  8. A statistical intercomparison between 'urban' and 'rural' precipitation chemistry data from Greater Manchester and the two nearby secondary national network sites in the United Kingdom

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.S.; Longhurst, J.W.S. (Manchester Polytechnic, Manchester (United Kingdom). Acid Rain Information Centre, Dept. of Environmental and Graphical Studies)

    1992-11-01

    Precipitation chemistry data from a dense urban monitoring network in Greater Manchester, northwest England, were compared with interpolated values from the U.K. secondary national acid deposition monitoring network for the year 1988. Differences were found to be small. However, when data from individual sites from the Greater Manchester network were compared with data from the two nearest secondary national network sites, significant differences were found using simple and complex statistical analyses. Precipitation chemistry at rural sites could be similar to that at urban sites, but the sources of some ions were thought to be different. The synoptic-scale gradients of precipitation chemistry, as shown by the secondary national network, also accounted for some of the differences. 34 refs., 7 figs., 8 tabs.

  9. Sagebrush, greater sage-grouse, and the occurrence and importance of forbs

    Science.gov (United States)

    Pennington, Victoria E.; Schlaepfer, Daniel R.; Beck, Jeffrey L.; Bradford, John B.; Palmquist, Kyle A.; Lauenroth, William K.

    2016-01-01

    Big sagebrush (Artemisia tridentata Nutt.) ecosystems provide habitat for sagebrush-obligate wildlife species such as the Greater Sage-Grouse (Centrocercus urophasianus). The understory of big sagebrush plant communities is composed of grasses and forbs that are important sources of cover and food for wildlife. The grass component is well described in the literature, but the composition, abundance, and habitat role of forbs in these communities is largely unknown. Our objective was to synthesize information about forbs and their importance to Greater Sage-Grouse diets and habitats, how rangeland management practices affect forbs, and how forbs respond to changes in temperature and precipitation. We also sought to identify research gaps and needs concerning forbs in big sagebrush plant communities. We searched for relevant literature including journal articles and state and federal agency reports. Our results indicated that in the spring and summer, Greater Sage-Grouse diets consist of forbs (particularly species in the Asteraceae family), arthropods, and lesser amounts of sagebrush. The diets transition to sagebrush in fall and winter. Forbs provide cover for Greater Sage-Grouse individuals at their lekking, nesting, and brood-rearing sites, and the species has a positive relationship with arthropod presence. The effect of grazing on native forbs may be compounded by invasion of nonnative species and differs depending on grazing intensity. The effect of fire on forbs varies greatly and may depend on time elapsed since burning. In addition, chemical and mechanical treatments affect annual and perennial forbs differently. Temperature and precipitation influence forb phenology, biomass, and abundance differently among species. Our review identified several uncertainties and research needs about forbs in big sagebrush ecosystems. First, in many cases the literature about forbs is reported only at the genus or functional type level. Second, information about forb

  10. A method for deterministic statistical downscaling of daily precipitation at a monsoonal site in Eastern China

    Science.gov (United States)

    Liu, Yonghe; Feng, Jinming; Liu, Xiu; Zhao, Yadi

    2017-12-01

    Statistical downscaling (SD) is a method that acquires the local information required for hydrological impact assessment from large-scale atmospheric variables. Very few statistical and deterministic downscaling models for daily precipitation have been conducted for local sites influenced by the East Asian monsoon. In this study, SD models were constructed by selecting the best predictors and using generalized linear models (GLMs) for Feixian, a site in the Yishu River Basin and Shandong Province. By calculating and mapping Spearman rank correlation coefficients between the gridded standardized values of five large-scale variables and daily observed precipitation, different cyclonic circulation patterns were found for monsoonal precipitation in summer (June-September) and winter (November-December and January-March); the values of the gridded boxes with the highest absolute correlations for observed precipitation were selected as predictors. Data for predictors and predictands covered the period 1979-2015, and different calibration and validation periods were divided when fitting and validating the models. Meanwhile, the bootstrap method was also used to fit the GLM. All the above thorough validations indicated that the models were robust and not sensitive to different samples or different periods. Pearson's correlations between downscaled and observed precipitation (logarithmically transformed) on a daily scale reached 0.54-0.57 in summer and 0.56-0.61 in winter, and the Nash-Sutcliffe efficiency between downscaled and observed precipitation reached 0.1 in summer and 0.41 in winter. The downscaled precipitation partially reflected exact variations in winter and main trends in summer for total interannual precipitation. For the number of wet days, both winter and summer models were able to reflect interannual variations. Other comparisons were also made in this study. These results demonstrated that when downscaling, it is appropriate to combine a correlation

  11. Summer fallow soil management - impact on rainfed winter wheat

    DEFF Research Database (Denmark)

    Li, Fucui; Wang, Zhaohui; Dai, Jian

    2014-01-01

    Summer fallow soil management is an important approach to improve soil and crop management in dryland areas. In the Loess Plateau regions, the annual precipitation is low and varies annually and seasonally, with more than 60% concentrated in the summer months from July to September, which...... is the summer fallow period in the winter wheat-summer fallow cropping system. With bare fallow in summer as a control, a 3-year location-fixed field experiment was conducted in the Loess Plateau to investigate the effects of wheat straw retention (SR), green manure (GM) planting, and their combination on soil...... water retention (WR) during summer fallow, winter wheat yield, and crop water use and nitrogen (N) uptake. The results showed that SR increased soil WR during summer fallow by 20 mm on average compared with the control over 3 experimental years but reduced the grain yield by 8% in the third year...

  12. Spring hydrology determines summer net carbon uptake in northern ecosystems

    International Nuclear Information System (INIS)

    Yi, Yonghong; Kimball, John S; Reichle, Rolf H

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO 2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the normalized difference vegetation index; NDVI) and atmospheric CO 2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (⩾50° N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO 2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO 2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends. (letters)

  13. Hydrological impacts of precipitation extremes in the Huaihe River Basin, China.

    Science.gov (United States)

    Yang, Mangen; Chen, Xing; Cheng, Chad Shouquan

    2016-01-01

    Precipitation extremes play a key role in flooding risks over the Huaihe River Basin, which is important to understand their hydrological impacts. Based on observed daily precipitation and streamflow data from 1958 to 2009, eight precipitation indices and three streamflow indices were calculated for the study of hydrological impacts of precipitation extremes. The results indicate that the wet condition intensified in the summer wet season and the drought condition was getting worse in the autumn dry season in the later years of the past 50 years. The river basin had experienced higher heavy rainfall-related flooding risks in summer and more severe drought in autumn in the later of the period. The extreme precipitation events or consecutive heavy rain day events led to the substantial increases in streamflow extremes, which are the main causes of frequent floods in the Huaihe River Basin. The large inter-annual variation of precipitation anomalies in the upper and central Huaihe River Basin are the major contributor for the regional frequent floods and droughts.

  14. SST and circulation trend biases cause an underestimation of European precipitation trends

    NARCIS (Netherlands)

    Haren, van R.; Oldenborgh, van G.J.; Lenderink, G.; Collins, M.; Hazeleger, W.

    2013-01-01

    Clear precipitation trends have been observed in Europe over the past century. In winter, precipitation has increased in north-western Europe. In summer, there has been an increase along many coasts in the same area. Over the second half of the past century precipitation also decreased in southern

  15. Late-Eighteenth-Century Precipitation Reconstructions from James Madison's Montpelier Plantation.

    Science.gov (United States)

    Druckenbrod, Daniel L.; Mann, Michael E.; Stahle, David W.; Cleaveland, Malcolm K.; Therrell, Matthew D.; Shugart, Herman H.

    2003-01-01

    This study presents two independent reconstructions of precipitation from James Madison's Montpelier plantation at the end of the eighteenth century. The first is transcribed directly from meteorological diaries recorded by the Madison family for 17 years and reflects the scientific interests of James Madison and Thomas Jefferson. In his most active period as a scientist, Madison assisted Jefferson by observing the climate and fauna in Virginia to counter the contemporary scientific view that the humid, cold climate of the New World decreased the size and number of its species. The second reconstruction is generated using tree rings from a forest in the Montpelier plantation and connects Madison's era to the modern instrumental precipitation record. These trees provide a significant reconstruction of both early summer and prior fall precipitation. Comparison of the dendroclimatic and diary reconstructions suggests a delay in the seasonality of precipitation from Madison's era to the mid-twentieth century. Furthermore, the dendroclimatic reconstructions of early summer and prior fall precipitation appear to track this shift in seasonality.

  16. Observed and simulated impacts of the summer NAO in Europe: implications for projected drying in the Mediterranean region

    Energy Technology Data Exchange (ETDEWEB)

    Blade, Ileana; Fortuny, Didac [Universitat de Barcelona, Facultat de Fisica, Departament d' Astronomia i Meteorologia, Barcelona (Spain); Liebmann, Brant [CIRES Climate Diagnostics Center, NOAA/Earth System Research Laboratory, Boulder, CO (United States); Oldenborgh, Geert Jan van [Royal Dutch Meteorological Institute, De Bilt (Netherlands)

    2012-08-15

    Climate models predict substantial summer precipitation reductions in Europe and the Mediterranean region in the twenty-first century, but the extent to which these models correctly represent the mechanisms of summertime precipitation in this region is uncertain. Here an analysis is conducted to compare the observed and simulated impacts of the dominant large-scale driver of summer rainfall variability in Europe and the Mediterranean, the summer North Atlantic Oscillation (SNAO). The SNAO is defined as the leading mode of July-August sea level pressure variability in the North Atlantic sector. Although the SNAO is weaker and confined to northern latitudes compared to its winter counterpart, with a southern lobe located over the UK, it significantly affects precipitation in the Mediterranean, particularly Italy and the Balkans (correlations of up to 0.6). During high SNAO summers, when strong anticyclonic conditions and suppressed precipitation prevail over the UK, the Mediterranean region instead is anomalously wet. This enhanced precipitation is related to the presence of a strong upper-level trough over the Balkans - part of a hemispheric pattern of anomalies that develops in association with the SNAO - that leads to mid-level cooling and increased potential instability. Neither this downstream extension nor the surface influence of the SNAO is captured in the two CMIP3 models examined (HadCM3 and GFDL-CM2.1), with weak or non-existent correlations between the SNAO and Mediterranean precipitation. Because these models also predict a strong upward SNAO trend in the future, the error in their representation of the SNAO surface signature impacts the projected precipitation trends. In particular, the attendant increase in precipitation that, based on observations, should occur in the Mediterranean and offset some of the non-SNAO related drying does not occur. Furthermore, the fact that neither the observed SNAO nor summer precipitation in Europe/Mediterranean region

  17. Wetting and greening Tibetan Plateau in early summer in recent decades

    Science.gov (United States)

    Zhang, Wenxia; Zhou, Tianjun; Zhang, Lixia

    2017-06-01

    The Tibetan Plateau (TP) plays an essential role in the global hydrological cycle. Unlike the well-recognized surface warming, changes in precipitation over the TP and the underlying mechanisms remain ambiguous. A significant increase in the amount of precipitation over the southeastern TP in May over 1979-2014 (13.46% decade-1 of the climatology) is identified in this study, based on homogenized daily rain gauge data. Both the increased precipitation frequency and intensity have contributions. The coherent increases in soil moisture content and vegetation activities further confirm the precipitation trend, indicating a wetting and greening TP in the early summer in recent decades. The moisture budget analysis shows that this wetting trend in the past four decades is dominated by the increased water vapor convergence due to circulation changes, while increases in specific humidity play a minor role. The wetting trend over the TP in May results directly from the earlier onset of the South Asian summer monsoon (ASM) since the late 1970s associated with the phase transition of Interdecadal Pacific Oscillation around the late 1990s. The earlier onset of the ASM triggers low-level southwesterly anomalies over the northern Indian Ocean, promoting moisture convergence and increased precipitation over the TP in May. Specifically, the increased amount of precipitation after the onset of the ASM explains 95% of the increase in the total amount of precipitation in May.

  18. Climatology of extreme daily precipitation in Colorado and its diverse spatial and seasonal variability

    Science.gov (United States)

    Mahoney, Kelly M.; Ralph, F. Martin; Walter, Klaus; Doesken, Nolan; Dettinger, Michael; Gottas, Daniel; Coleman, Timothy; White, Allen

    2015-01-01

    The climatology of Colorado’s historical extreme precipitation events shows a remarkable degree of seasonal and regional variability. Analysis of the largest historical daily precipitation totals at COOP stations across Colorado by season indicates that the largest recorded daily precipitation totals have ranged from less than 60 mm day−1 in some areas to more than 250 mm day−1 in others. East of the Continental Divide, winter events are rarely among the top 10 events at a given site, but spring events dominate in and near the foothills; summer events are most common across the lower-elevation eastern plains, while fall events are most typical for the lower elevations west of the Divide. The seasonal signal in Colorado’s central mountains is complex; high-elevation intense precipitation events have occurred in all months of the year, including summer, when precipitation is more likely to be liquid (as opposed to snow), which poses more of an instantaneous flood risk. Notably, the historic Colorado Front Range daily rainfall totals that contributed to the damaging floods in September 2013 occurred outside of that region’s typical season for most extreme precipitation (spring–summer). That event and many others highlight the fact that extreme precipitation in Colorado has occurred historically during all seasons and at all elevations, emphasizing a year-round statewide risk.

  19. Effects of altered temperature and precipitation on desert protozoa associated with biological soil crusts.

    Science.gov (United States)

    Darby, Brian J; Housman, David C; Zaki, Amr M; Shamout, Yassein; Adl, Sina M; Belnap, Jayne; Neher, Deborah A

    2006-01-01

    Biological soil crusts are diverse assemblages of bacteria, cyanobacteria, algae, fungi, lichens, and mosses that cover much of arid land soils. The objective of this study was to quantify protozoa associated with biological soil crusts and test the response of protozoa to increased temperature and precipitation as is predicted by some global climate models. Protozoa were more abundant when associated with cyanobacteria/lichen crusts than with cyanobacteria crusts alone. Amoebae, flagellates, and ciliates originating from the Colorado Plateau desert (cool desert, primarily winter precipitation) declined 50-, 10-, and 100-fold, respectively, when moved in field mesocosms to the Chihuahuan Desert (hot desert, primarily summer rain). However, this was not observed in protozoa collected from the Chihuahuan Desert and moved to the Sonoran desert (hot desert, also summer rain, but warmer than Chihuahuan Desert). Protozoa in culture began to encyst at 37 degrees C. Cysts survived the upper end of daily temperatures (37-55 degrees C), and could be stimulated to excyst if temperatures were reduced to 15 degrees C or lower. Results from this study suggest that cool desert protozoa are influenced negatively by increased summer precipitation during excessive summer temperatures, and that desert protozoa may be adapted to a specific desert's temperature and precipitation regime.

  20. Paltry past-precipitation: Predisposing prairie dogs to plague?

    Science.gov (United States)

    Eads, David; Biggins, Dean E.

    2017-01-01

    The plague bacterium Yersinia pestis was introduced to California in 1900 and spread rapidly as a sylvatic disease of mammalian hosts and flea vectors, invading the Great Plains in the United States by the 1930s to 1940s. In grassland ecosystems, plague causes periodic, devastating epizootics in colonies of black-tailed prairie dogs (Cynomys ludovicianus), sciurid rodents that create and maintain subterranean burrows. In doing so, plague inhibits prairie dogs from functioning as keystone species of grassland communities. The rate at which fleas transmit Y. pestis is thought to increase when fleas are abundant. Flea densities can increase during droughts when vegetative production is reduced and herbivorous prairie dogs are malnourished and have weakened defenses against fleas. Epizootics of plague have erupted frequently in prairie dogs during years in which precipitation was plentiful, and the accompanying cool temperatures might have facilitated the rate at which fleas transmitted Y. pestis. Together these observations evoke the hypothesis that transitions from dry-to-wet years provide conditions for plague epizootics in prairie dogs. Using generalized linear models, we analyzed a 24-year dataset on the occurrence of plague epizootics in 42 colonies of prairie dogs from Colorado, USA, 1982–2005. Of the 33 epizootics observed, 52% erupted during years with increased precipitation in summer. For the years with increased summer precipitation, if precipitation in the prior growing season declined from the maximum of 502 mm to the minimum of 200 mm, the prevalence of plague epizootics was predicted to increase 3-fold. Thus, reduced precipitation may have predisposed prairie dogs to plague epizootics when moisture returned. Biologists sometimes assume dry conditions are detrimental for plague. However, 48% of epizootics occurred during years in which precipitation was scarce in summer. In some cases, an increased abundance of fleas during dry years might

  1. Declining summer snowfall in the Arctic: causes, impacts and feedbacks

    Energy Technology Data Exchange (ETDEWEB)

    Screen, James A.; Simmonds, Ian [University of Melbourne, School of Earth Sciences, Melbourne, VIC (Australia)

    2012-06-15

    Recent changes in the Arctic hydrological cycle are explored using in situ observations and an improved atmospheric reanalysis data set, ERA-Interim. We document a pronounced decline in summer snowfall over the Arctic Ocean and Canadian Archipelago. The snowfall decline is diagnosed as being almost entirely caused by changes in precipitation form (snow turning to rain) with very little influence of decreases in total precipitation. The proportion of precipitation falling as snow has decreased as a result of lower-atmospheric warming. Statistically, over 99% of the summer snowfall decline is linked to Arctic warming over the past two decades. Based on the reanalysis snowfall data over the ice-covered Arctic Ocean, we derive an estimate for the amount of snow-covered ice. It is estimated that the area of snow-covered ice, and the proportion of sea ice covered by snow, have decreased significantly. We perform a series of sensitivity experiments in which inter-annual changes in snow-covered ice are either unaccounted for, or are parameterized. In the parameterized case, the loss of snow-on-ice results in a substantial decrease in the surface albedo over the Arctic Ocean, that is of comparable magnitude to the decrease in albedo due to the decline in sea ice cover. Accordingly, the solar input to the Arctic Ocean is increased, causing additional surface ice melt. We conclude that the decline in summer snowfall has likely contributed to the thinning of sea ice over recent decades. The results presented provide support for the existence of a positive feedback in association with warming-induced reductions in summer snowfall. (orig.)

  2. Tundra water budget and implications of precipitation underestimation.

    Science.gov (United States)

    Liljedahl, Anna K; Hinzman, Larry D; Kane, Douglas L; Oechel, Walter C; Tweedie, Craig E; Zona, Donatella

    2017-08-01

    Difficulties in obtaining accurate precipitation measurements have limited meaningful hydrologic assessment for over a century due to performance challenges of conventional snowfall and rainfall gauges in windy environments. Here, we compare snowfall observations and bias adjusted snowfall to end-of-winter snow accumulation measurements on the ground for 16 years (1999-2014) and assess the implication of precipitation underestimation on the water balance for a low-gradient tundra wetland near Utqiagvik (formerly Barrow), Alaska (2007-2009). In agreement with other studies, and not accounting for sublimation, conventional snowfall gauges captured 23-56% of end-of-winter snow accumulation. Once snowfall and rainfall are bias adjusted, long-term annual precipitation estimates more than double (from 123 to 274 mm), highlighting the risk of studies using conventional or unadjusted precipitation that dramatically under-represent water balance components. Applying conventional precipitation information to the water balance analysis produced consistent storage deficits (79 to 152 mm) that were all larger than the largest actual deficit (75 mm), which was observed in the unusually low rainfall summer of 2007. Year-to-year variability in adjusted rainfall (±33 mm) was larger than evapotranspiration (±13 mm). Measured interannual variability in partitioning of snow into runoff (29% in 2008 to 68% in 2009) in years with similar end-of-winter snow accumulation (180 and 164 mm, respectively) highlights the importance of the previous summer's rainfall (25 and 60 mm, respectively) on spring runoff production. Incorrect representation of precipitation can therefore have major implications for Arctic water budget descriptions that in turn can alter estimates of carbon and energy fluxes.

  3. Radar-based summer precipitation climatology of the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Bližňák, Vojtěch; Kašpar, Marek; Müller, Miloslav

    2018-01-01

    Roč. 38, č. 2 (2018), s. 677-691 ISSN 0899-8418 R&D Projects: GA ČR GA17-23773S; GA MZe QJ1520265 Institutional support: RVO:68378289 Keywords : weather radar * rain gauges * adjustment * precipitation climatology * Czech Republic Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 3.760, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/joc.5202/full

  4. 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.)

  5. Factors favorable to frequent extreme precipitation in the upper Yangtze River Valley

    Science.gov (United States)

    Tian, Baoqiang; Fan, Ke

    2013-08-01

    Extreme precipitation events in the upper Yangtze River Valley (YRV) have recently become an increasingly important focus in China because they often cause droughts and floods. Unfortunately, little is known about the climate processes responsible for these events. This paper investigates factors favorable to frequent extreme precipitation events in the upper YRV. Our results reveal that a weakened South China Sea summer monsoon trough, intensified Eurasian-Pacific blocking highs, an intensified South Asian High, a southward subtropical westerly jet and an intensified Western North Pacific Subtropical High (WNPSH) increase atmospheric instability and enhance the convergence of moisture over the upper YRV, which result in more extreme precipitation events. The snow depth over the eastern Tibetan Plateau (TP) in winter and sea surface temperature anomalies (SSTAs) over three key regions in summer are important external forcing factors in the atmospheric circulation anomalies. Deep snow on the Tibetan Plateau in winter can weaken the subsequent East Asian summer monsoon circulation above by increasing the soil moisture content in summer and weakening the land-sea thermal contrast over East Asia. The positive SSTA in the western North Pacific may affect southwestward extension of the WNPSH and the blocking high over northeastern Asia by arousing the East Asian-Pacific pattern. The positive SSTA in the North Atlantic can affect extreme precipitation event frequency in the upper YRV via a wave train pattern along the westerly jet between the North Atlantic and East Asia. A tripolar pattern from west to east over the Indian Ocean can strengthen moisture transport by enhancing Somali cross-equatorial flow.

  6. Effect of precipitation bias correction on water budget calculation in Upper Yellow River, China

    International Nuclear Information System (INIS)

    Ye Baisheng; Yang Daqing; Ma Lijuan

    2012-01-01

    This study quantifies the effect of precipitation bias corrections on basin water balance calculations for the Yellow River Source region (YRS). We analyse long-term (1959–2001) monthly and yearly data of precipitation, runoff, and ERA-40 water budget variables and define a water balance regime. Basin precipitation, evapotranspiration and runoff are high in summer and low in winter. The basin water storage change is positive in summer and negative in winter. Monthly precipitation bias corrections, ranging from 2 to 16 mm, do not significantly alter the pattern of the seasonal water budget. The annual bias correction of precipitation is about 98 mm (19%); this increase leads to the same amount of evapotranspiration increase, since yearly runoff remains unchanged and the long-term storage change is assumed to be zero. Annual runoff and evapotranspiration coefficients change, due to precipitation bias corrections, from 0.33 and 0.67 to 0.28 and 0.72, respectively. These changes will impact the parameterization and calibration of land surface and hydrological models. The bias corrections of precipitation data also improve the relationship between annual precipitation and runoff. (letter)

  7. Snow farming: conserving snow over the summer season

    Science.gov (United States)

    Grünewald, Thomas; Wolfsperger, Fabian; Lehning, Michael

    2018-01-01

    Summer storage of snow for tourism has seen an increasing interest in the last years. Covering large snow piles with materials such as sawdust enables more than two-thirds of the initial snow volume to be conserved. We present detailed mass balance measurements of two sawdust-covered snow piles obtained by terrestrial laser scanning during summer 2015. Results indicate that 74 and 63 % of the snow volume remained over the summer for piles in Davos, Switzerland and Martell, Italy. If snow mass is considered instead of volume, the values increase to 83 and 72 %. The difference is attributed to settling and densification of the snow. Additionally, we adapted the one-dimensional, physically based snow cover model SNOWPACK to perform simulations of the sawdust-covered snow piles. Model results and measurements agreed extremely well at the point scale. Moreover, we analysed the contribution of the different terms of the surface energy balance to snow ablation for a pile covered with a 40 cm thick sawdust layer and a pile without insulation. Short-wave radiation was the dominant source of energy for both scenarios, but the moist sawdust caused strong cooling by long-wave emission and negative sensible and latent heat fluxes. This cooling effect reduces the energy available for melt by up to a factor of 12. As a result only 9 % of the net short-wave energy remained available for melt. Finally, sensitivity studies of the parameters thickness of the sawdust layer, air temperature, precipitation and wind speed were performed. We show that sawdust thickness has a tremendous effect on snow loss. Higher air temperatures and wind speeds increase snow ablation but less significantly. No significant effect of additional precipitation could be found as the sawdust remained wet during the entire summer with the measured quantity of rain. Setting precipitation amounts to zero, however, strongly increased melt. Overall, the 40 cm sawdust provides sufficient protection for mid

  8. Future weather types and their influence on mean and extreme climate indices for precipitation and temperature in Central Europe

    Directory of Open Access Journals (Sweden)

    Ulf Riediger

    2014-09-01

    occurrence of warm south-westerlies and a decrease in cold easterlies. Thereby, an increase of extensive areal rainfall events is simulated for specific weather types. Otherwise, warmer and drier summers are projected by the RCM ensemble. Here, a few weather patterns are relevant for very hot conditions with the total number of very hot days where the mean daily temperature greater than 25 °C increases. Thereby, anticyclonic weather patterns are most relevant for non precipitation events and particulary, the number of days with anticyclonic westerlies is expected to double in the future.

  9. Projections of Future Precipitation Extremes Over Europe: A Multimodel Assessment of Climate Simulations

    Science.gov (United States)

    Rajczak, Jan; Schär, Christoph

    2017-10-01

    Projections of precipitation and its extremes over the European continent are analyzed in an extensive multimodel ensemble of 12 and 50 km resolution EURO-CORDEX Regional Climate Models (RCMs) forced by RCP2.6, RCP4.5, and RCP8.5 (Representative Concentration Pathway) aerosol and greenhouse gas emission scenarios. A systematic intercomparison with ENSEMBLES RCMs is carried out, such that in total information is provided for an unprecedentedly large data set of 100 RCM simulations. An evaluation finds very reasonable skill for the EURO-CORDEX models in simulating temporal and geographical variations of (mean and heavy) precipitation at both horizontal resolutions. Heavy and extreme precipitation events are projected to intensify across most of Europe throughout the whole year. All considered models agree on a distinct intensification of extremes by often more than +20% in winter and fall and over central and northern Europe. A reduction of rainy days and mean precipitation in summer is simulated by a large majority of models in the Mediterranean area, but intermodel spread between the simulations is large. In central Europe and France during summer, models project decreases in precipitation but more intense heavy and extreme rainfalls. Comparison to previous RCM projections from ENSEMBLES reveals consistency but slight differences in summer, where reductions in southern European precipitation are not as pronounced as previously projected. The projected changes of the European hydrological cycle may have substantial impact on environmental and anthropogenic systems. In particular, the simulations indicate a rising probability of summertime drought in southern Europe and more frequent and intense heavy rainfall across all of Europe.

  10. Spatio-temporal changes in precipitation over Beijing-Tianjin-Hebei region, China

    Science.gov (United States)

    Zhao, Na; Yue, Tianxiang; Li, Han; Zhang, Lili; Yin, Xiaozhe; Liu, Yi

    2018-04-01

    Changes in precipitation have a large effect on human society and are of primary importance for many scientific fields such as hydrology, agriculture and eco-environmental sciences. The present study intended to investigate the spatio-temporal characteristics of precipitation in Beijing-Tianjin-Hebei (BTH) region by using 316 meteorological stations during the period 1965-2014. Geographical Weighted Regression (GWR) method and High Accuracy Surface Modeling (HASM) method were applied to produce the precipitation patterns at different time scales. Mann-Kendall (MK) statistical test was applied to analyze the precipitation temporal variations. Results indicated that annual precipitation over the past 50 years appeared to be a non-periodic oscillation phenomenon; the number of wet years was approximately the same as that of dry years; significant positive trends were observed in spring during 1978-2014 and summer during 1996-2014; on the whole, precipitation in May, June, September, and December showed increasing trends at the 95% confidence level; and significant positive trends were also identified in July during 2000-2013 and August during 1997-2010, while slight decreasing trends were observed in February and November. Summer (June, July, and August) was the wettest season, accounting for 68.73% of annual totals in BTH. In general, northeastern BTH received the highest range of precipitation while northwestern area had the lowest. It was found that precipitation variation in this region had been closely linked to latitude, Digital Elevation Model (DEM), distance to the sea, and urbanization rate. In addition, land use played an important role in the decadal precipitation changes in BTH.

  11. Properties of Extreme Precipitation and Their Uncertainties in 3-year GPM Precipitation Radar Data

    Science.gov (United States)

    Liu, N.; Liu, C.

    2017-12-01

    Extreme high precipitation rates are often related to flash floods and have devastating impacts on human society and the environments. To better understand these rare events, 3-year Precipitation Features (PFs) are defined by grouping the contiguous areas with nonzero near-surface precipitation derived using Global Precipitation Measurement (GPM) Ku band Precipitation Radar (KuPR). The properties of PFs with extreme precipitation rates greater than 20, 50, 100 mm/hr, such as the geographical distribution, volumetric precipitation contribution, seasonal and diurnal variations, are examined. In addition to the large seasonal and regional variations, the rare extreme precipitation rates often have a larger contribution to the local total precipitation. Extreme precipitation rates occur more often over land than over ocean. The challenges in the retrieval of extreme precipitation might be from the attenuation correction and large uncertainties in the Z-R relationships from near-surface radar reflectivity to precipitation rates. These potential uncertainties are examined by using collocated ground based radar reflectivity and precipitation retrievals.

  12. A 22,000-Year Record of Monsoonal Precipitation from Northern Chile's Atacama Desert.

    Science.gov (United States)

    Betancourt; Latorre; Rech; Quade; Rylander

    2000-09-01

    Fossil rodent middens and wetland deposits from the central Atacama Desert (22 degrees to 24 degrees S) indicate increasing summer precipitation, grass cover, and groundwater levels from 16.2 to 10.5 calendar kiloyears before present (ky B.P.). Higher elevation shrubs and summer-flowering grasses expanded downslope across what is now the edge of Absolute Desert, a broad expanse now largely devoid of rainfall and vegetation. Paradoxically, this pluvial period coincided with the summer insolation minimum and reduced adiabatic heating over the central Andes. Summer precipitation over the central Andes and central Atacama may depend on remote teleconnections between seasonal insolation forcing in both hemispheres, the Asian monsoon, and Pacific sea surface temperature gradients. A less pronounced episode of higher groundwater levels in the central Atacama from 8 to 3 ky B.P. conflicts with an extreme lowstand of Lake Titicaca, indicating either different climatic forcing or different response times and sensitivities to climatic change.

  13. Influence of finite-time Lyapunov exponents on winter precipitation over the Iberian Peninsula

    Science.gov (United States)

    Garaboa-Paz, Daniel; Lorenzo, Nieves; Pérez-Muñuzuri, Vicente

    2017-05-01

    Seasonal forecasts have improved during the last decades, mostly due to an increase in understanding of the coupled ocean-atmosphere dynamics, and the development of models able to predict the atmosphere variability. Correlations between different teleconnection patterns and severe weather in different parts of the world are constantly evolving and changing. This paper evaluates the connection between winter precipitation over the Iberian Peninsula and the large-scale tropospheric mixing over the eastern Atlantic Ocean. Finite-time Lyapunov exponents (FTLEs) have been calculated from 1979 to 2008 to evaluate this mixing. Our study suggests that significant negative correlations exist between summer FTLE anomalies and winter precipitation over Portugal and Spain. To understand the mechanisms behind this correlation, summer anomalies of the FTLE have also been correlated with other climatic variables such as the sea surface temperature (SST), the sea level pressure (SLP) or the geopotential. The East Atlantic (EA) teleconnection index correlates with the summer FTLE anomalies, confirming their role as a seasonal predictor for winter precipitation over the Iberian Peninsula.

  14. Meridional distribution and seasonal variation of stable oxygen isotope ratio of precipitation in the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Kayo Nakamura

    2010-07-01

    Full Text Available The stable oxygen isotope ratio(δ^O in precipitation is known to have important meridional and seasonal variations, but there are almost no measurements of δ^O in precipitation over polar oceans. The present research took advantage of 4 opportunities for in situ observations in summer and winter at high latitudes in the Southern Ocean. In addition, we analyzed samples of precipitation at Syowa Station in 2008 to obtain year-round data. Based on these data, we consider the meridional and seasonal variations of δ^O in precipitation over the Southern Ocean. In general, δ^O decreases with increasing latitude, and is lower in winter than in summer. The latitude gradient is stronger in winter. At 60°S, δ^O is -5.4‰ and -11.3‰ in summer and winter, respectively, while the corresponding figures at 66°S are -10.5‰ and -20.8‰. These results will help us understand the mechanisms of the salinity distribution and its variation in the Antarctic Ocean.

  15. Short-Term Effects of Changing Precipitation Patterns on Shrub-Steppe Grasslands: Seasonal Watering Is More Important than Frequency of Watering Events.

    Science.gov (United States)

    Densmore-McCulloch, Justine A; Thompson, Donald L; Fraser, Lauchlan H

    2016-01-01

    Climate change is expected to alter precipitation patterns. Droughts may become longer and more frequent, and the timing and intensity of precipitation may change. We tested how shifting precipitation patterns, both seasonally and by frequency of events, affects soil nitrogen availability, plant biomass and diversity in a shrub-steppe temperate grassland along a natural productivity gradient in Lac du Bois Grasslands Protected Area near Kamloops, British Columbia, Canada. We manipulated seasonal watering patterns by either exclusively watering in the spring or the fall. To simulate spring precipitation we restricted precipitation inputs in the fall, then added 50% more water than the long term average in the spring, and vice-versa for the fall precipitation treatment. Overall, the amount of precipitation remained roughly the same. We manipulated the frequency of rainfall events by either applying water weekly (frequent) or monthly (intensive). After 2 years, changes in the seasonality of watering had greater effects on plant biomass and diversity than changes in the frequency of watering. Fall watering reduced biomass and increased species diversity, while spring watering had little effect. The reduction in biomass in fall watered treatments was due to a decline in grasses, but not forbs. Plant available N, measured by Plant Root Simulator (PRS)-probes, increased from spring to summer to fall, and was higher in fall watered treatments compared to spring watered treatments when measured in the fall. The only effect observed due to frequency of watering events was greater extractable soil N in monthly applied treatments compared to weekly watering treatments. Understanding the effects of changing precipitation patterns on grasslands will allow improved grassland conservation and management in the face of global climatic change, and here we show that if precipitation is more abundant in the fall, compared to the spring, grassland primary productivity will likely be

  16. Extensive summer water pulses do not necessarily lead to canopy growth of Great Basin and northern Mojave Desert shrubs.

    Science.gov (United States)

    Snyder, K A; Donovan, L A; James, J J; Tiller, R L; Richards, J H

    2004-10-01

    Plant species and functionally related species groups from arid and semi-arid habitats vary in their capacity to take up summer precipitation, acquire nitrogen quickly after summer precipitation, and subsequently respond with ecophysiological changes (e.g. water and nitrogen relations, gas exchange). For species that respond ecophysiologically, the use of summer precipitation is generally assumed to affect long-term plant growth and thus alter competitive interactions that structure plant communities and determine potential responses to climate change. We assessed ecophysiological and growth responses to large short-term irrigation pulses over one to three growing seasons for several widespread Great Basin and northern Mojave Desert shrub species: Chrysothamnus nauseosus, Sarcobatus vermiculatus, Atriplex confertifolia, and A. parryi. We compared control and watered plants in nine case studies that encompassed adults of all four species, juveniles for three of the species, and two sites for two of the species. In every comparison, plants used summer water pulses to improve plant water status or increase rates of functioning as indicated by other ecophysiological characters. Species and life history stage responses of ecophysiological parameters (leaf N, delta15N, delta13C, gas exchange, sap flow) were consistent with several previous short-term studies. However, use of summer water pulses did not affect canopy growth in eight out of nine comparisons, despite the range of species, growth stages, and site conditions. Summer water pulses affected canopy growth only for C. nauseosus adults. The general lack of growth effects for these species might be due to close proximity of groundwater at these sites, co-limitation by nutrients, or inability to respond due to phenological canalization. An understanding of the connections between short-term ecophysiological responses and growth, for different habitats and species, is critical for determining the significance of

  17. The role of the subtropical North Atlantic water cycle in recent US extreme precipitation events

    Science.gov (United States)

    Li, Laifang; Schmitt, Raymond W.; Ummenhofer, Caroline C.

    2018-02-01

    The role of the oceanic water cycle in the record-breaking 2015 warm-season precipitation in the US is analyzed. The extreme precipitation started in the Southern US in the spring and propagated northward to the Midwest and the Great Lakes in the summer of 2015. This seasonal evolution of precipitation anomalies represents a typical mode of variability of US warm-season precipitation. Analysis of the atmospheric moisture flux suggests that such a rainfall mode is associated with moisture export from the subtropical North Atlantic. In the spring, excessive precipitation in the Southern US is attributable to increased moisture flux from the northwestern portion of the subtropical North Atlantic. The North Atlantic moisture flux interacts with local soil moisture which enables the US Midwest to draw more moisture from the Gulf of Mexico in the summer. Further analysis shows that the relationship between the rainfall mode and the North Atlantic water cycle has become more significant in recent decades, indicating an increased likelihood of extremes like the 2015 case. Indeed, two record-high warm-season precipitation events, the 1993 and 2008 cases, both occurred in the more recent decades of the 66 year analysis period. The export of water from the North Atlantic leaves a marked surface salinity signature. The salinity signature appeared in the spring preceding all three extreme precipitation events analyzed in this study, i.e. a saltier-than-normal subtropical North Atlantic in spring followed by extreme Midwest precipitation in summer. Compared to the various sea surface temperature anomaly patterns among the 1993, 2008, and 2015 cases, the spatial distribution of salinity anomalies was much more consistent during these extreme flood years. Thus, our study suggests that preseason salinity patterns can be used for improved seasonal prediction of extreme precipitation in the Midwest.

  18. Convection index as a tool for trend analysis of intense summer storms in Switzerland

    Science.gov (United States)

    Gaal, Ladislav; Molnar, Peter; Szolgay, Jan

    2013-04-01

    Convective summer thunderstorms are generally responsible for the most devastating floods in urban and small natural catchments. In this study we focus on the identification of the nature and magnitude of changes in the properties of intense summer storms of convective character in Switzerland in the last three decades. The study is based on precipitation records from the SwissMetNet (MeteoSwiss) network at 63 stations that cover altitudes ranging from 200 up to 3300 m a.s.l. over the period 1981-2012 (32 years). Additionally, the same stations also measure the number of lightning strikes within a range of 30 km from each station. In an accompanying contribution we describe the method how intensive summer storms can be reliably selected out of all storms in long and high resolution precipitation time series. On the basis of the statistical distributions and dependence among key storm characteristics at the event scale (total rainfall depth R, storm duration D, and peak intensity I) and using high resolution lightning data as a surrogate we defined a threshold intensity I* that differentiates between the events accompanied with lightning with an acceptably small probability of misclassification. This allowed us to identify intense summer events with convective character as those where I > I* regardless of their duration or total rainfall depth. The current study makes use of the threshold intensity I* for the definition of a seasonal convection index at each station (Llasat, 2001). This index gives us a measure of 'convectiveness', i.e. the total precipitation depth coming from convective storms relative to the total precipitation depth of all summer storms. We computed the convection index at all 63 stations and analyzed the series for trends. We found that the seasonal convection index increases at most of the stations in Switzerland and in approximately 20% of the cases this increase is statistically significant. This is likely a consequence of the fact that the

  19. CLUJ-NAPOCA PRECIPITATION FORECAST USING WSR-98D DOPPLER RADAR

    Directory of Open Access Journals (Sweden)

    Narcis MAIER

    2011-11-01

    Full Text Available CLUJ-NAPOCA precipitation forecast using WSR-98D Doppler radar. Forecasting inundations requires accurate spatial and temporal estimation of rainfalls in an area. Depending on the Z-R relationship (reflectivity-precipitation rate, the thresholds, maximum reflectivity data processing, VIL, cloud height or speed, provided by the WSR-98D affects the estimated precipitation used in the prediction of inundations. How much precipitation receives a watershed during an extreme event and what response will result depends on the basin hydrographic characteristics. A study of summer weather events between the years 2004-2008 and a new method in establishing relations between the radar estimated and recorded precipitations led to the determination of new relations between them which will balance the connections between them.

  20. Are satellite products good proxies for gauge precipitation over Singapore?

    Science.gov (United States)

    Hur, Jina; Raghavan, Srivatsan V.; Nguyen, Ngoc Son; Liong, Shie-Yui

    2018-05-01

    The uncertainties in two high-resolution satellite precipitation products (TRMM 3B42 v7.0 and GSMaP v5.222) were investigated by comparing them against rain gauge observations over Singapore on sub-daily scales. The satellite-borne precipitation products are assessed in terms of seasonal, monthly and daily variations, the diurnal cycle, and extreme precipitation over a 10-year period (2000-2010). Results indicate that the uncertainties in extreme precipitation is higher in GSMaP than in TRMM, possibly due to the issues such as satellite merging algorithm, the finer spatio-temporal scale of high intensity precipitation, and the swath time of satellite. Such discrepancies between satellite-borne and gauge-based precipitations at sub-daily scale can possibly lead to distorting analysis of precipitation characteristics and/or application model results. Overall, both satellite products are unable to capture the observed extremes and provide a good agreement with observations only at coarse time scales. Also, the satellite products agree well on the late afternoon maximum and heavier rainfall of gauge-based data in winter season when the Intertropical Convergence Zone (ITCZ) is located over Singapore. However, they do not reproduce the gauge-observed diurnal cycle in summer. The disagreement in summer could be attributed to the dominant satellite overpass time (about 14:00 SGT) later than the diurnal peak time (about 09:00 SGT) of gauge precipitation. From the analyses of extreme precipitation indices, it is inferred that both satellite datasets tend to overestimate the light rain and frequency but underestimate high intensity precipitation and the length of dry spells. This study on quantification of their uncertainty is useful in many aspects especially that these satellite products stand scrutiny over places where there are no good ground data to be compared against. This has serious implications on climate studies as in model evaluations and in particular, climate

  1. A hydrogeologic framework for characterizing summer streamflow sensitivity to climate warming in the Pacific Northwest, USA

    Science.gov (United States)

    M. Safeeq; G.E. Grant; S.L. Lewis; M.G. Kramer; B. Staab

    2014-01-01

    Summer streamflows in the Pacific Northwest are largely derived from melting snow and groundwater discharge. As the climate warms, diminishing snowpack and earlier snowmelt will cause reductions in summer streamflow. Most regional-scale assessments of climate change impacts on streamflow use downscaled temperature and precipitation projections from general circulation...

  2. Climate signals in a multispecies tree-ring network from central and southern Italy and reconstruction of the late summer temperatures since the early 1700s

    Science.gov (United States)

    Leonelli, Giovanni; Coppola, Anna; Salvatore, Maria Cristina; Baroni, Carlo; Battipaglia, Giovanna; Gentilesca, Tiziana; Ripullone, Francesco; Borghetti, Marco; Conte, Emanuele; Tognetti, Roberto; Marchetti, Marco; Lombardi, Fabio; Brunetti, Michele; Maugeri, Maurizio; Pelfini, Manuela; Cherubini, Paolo; Provenzale, Antonello; Maggi, Valter

    2017-11-01

    A first assessment of the main climatic drivers that modulate the tree-ring width (RW) and maximum latewood density (MXD) along the Italian Peninsula and northeastern Sicily was performed using 27 forest sites, which include conifers (RW and MXD) and broadleaves (only RW). Tree-ring data were compared using the correlation analysis of the monthly and seasonal variables of temperature, precipitation and standardized precipitation index (SPI, used to characterize meteorological droughts) against each species-specific site chronology and against the highly sensitive to climate (HSTC) chronologies (based on selected indexed individual series). We find that climate signals in conifer MXD are stronger and more stable over time than those in conifer and broadleaf RW. In particular, conifer MXD variability is directly influenced by the late summer (August, September) temperature and is inversely influenced by the summer precipitation and droughts (SPI at a timescale of 3 months). The MXD sensitivity to August-September (AS) temperature and to summer drought is mainly driven by the latitudinal gradient of summer precipitation amounts, with sites in the northern Apennines showing stronger climate signals than sites in the south. Conifer RW is influenced by the temperature and drought of the previous summer, whereas broadleaf RW is more influenced by summer precipitation and drought of the current growing season. The reconstruction of the late summer temperatures for the Italian Peninsula for the past 300 years, based on the HSTC chronology of conifer MXD, shows a stable model performance that underlines periods of climatic cooling (and likely also wetter conditions) in 1699, 1740, 1814, 1914 and 1938, and follows well the variability of the instrumental record and of other tree-ring-based reconstructions in the region. Considering a 20-year low-pass-filtered series, the reconstructed temperature record consistently deviates divergence may also be due to the precipitation

  3. Climate signals in a multispecies tree-ring network from central and southern Italy and reconstruction of the late summer temperatures since the early 1700s

    Directory of Open Access Journals (Sweden)

    G. Leonelli

    2017-11-01

    Full Text Available A first assessment of the main climatic drivers that modulate the tree-ring width (RW and maximum latewood density (MXD along the Italian Peninsula and northeastern Sicily was performed using 27 forest sites, which include conifers (RW and MXD and broadleaves (only RW. Tree-ring data were compared using the correlation analysis of the monthly and seasonal variables of temperature, precipitation and standardized precipitation index (SPI, used to characterize meteorological droughts against each species-specific site chronology and against the highly sensitive to climate (HSTC chronologies (based on selected indexed individual series. We find that climate signals in conifer MXD are stronger and more stable over time than those in conifer and broadleaf RW. In particular, conifer MXD variability is directly influenced by the late summer (August, September temperature and is inversely influenced by the summer precipitation and droughts (SPI at a timescale of 3 months. The MXD sensitivity to August–September (AS temperature and to summer drought is mainly driven by the latitudinal gradient of summer precipitation amounts, with sites in the northern Apennines showing stronger climate signals than sites in the south. Conifer RW is influenced by the temperature and drought of the previous summer, whereas broadleaf RW is more influenced by summer precipitation and drought of the current growing season. The reconstruction of the late summer temperatures for the Italian Peninsula for the past 300 years, based on the HSTC chronology of conifer MXD, shows a stable model performance that underlines periods of climatic cooling (and likely also wetter conditions in 1699, 1740, 1814, 1914 and 1938, and follows well the variability of the instrumental record and of other tree-ring-based reconstructions in the region. Considering a 20-year low-pass-filtered series, the reconstructed temperature record consistently deviates < 1 °C from the instrumental

  4. Significantly Increased Extreme Precipitation Expected in Europe and North America from Extratropical Storms

    Science.gov (United States)

    Hawcroft, M.; Hodges, K.; Walsh, E.; Zappa, G.

    2017-12-01

    For the Northern Hemisphere extratropics, changes in circulation are key to determining the impacts of climate warming. The mechanisms governing these circulation changes are complex, leading to the well documented uncertainty in projections of the future location of the mid-latitude storm tracks simulated by climate models. These storms are the primary source of precipitation for North America and Europe and generate many of the large-scale precipitation extremes associated with flooding and severe economic loss. Here, we show that in spite of the uncertainty in circulation changes, by analysing the behaviour of the storms themselves, we find entirely consistent and robust projections across an ensemble of climate models. In particular, we find that projections of change in the most intensely precipitating storms (above the present day 99th percentile) in the Northern Hemisphere are substantial and consistent across models, with large increases in the frequency of both summer (June-August, +226±68%) and winter (December-February, +186±34%) extreme storms by the end of the century. Regionally, both North America (summer +202±129%, winter +232±135%) and Europe (summer +390±148%, winter +318±114%) are projected to experience large increases in the frequency of intensely precipitating storms. These changes are thermodynamic and driven by surface warming, rather than by changes in the dynamical behaviour of the storms. Such changes in storm behaviour have the potential to have major impacts on society given intensely precipitating storms are responsible for many large-scale flooding events.

  5. Potential future changes in the characteristics of daily precipitation in Europe simulated by the HIRHAM regional climate model

    Energy Technology Data Exchange (ETDEWEB)

    May, Wilhelm [Danish Meteorological Institute, Danish Climate Centre, Copenhagen (Denmark)

    2008-05-15

    In this study the potential future changes in various aspects of daily precipitation events over Europe as a consequence of the anticipated future increase in the atmospheric greenhouse gas concentrations are investigated. This is done by comparing two 3-member ensembles of simulations with the HIRHAM regional climate model for the period 1961-1990 and 2071-2100, respectively. Daily precipitation events are characterized by their frequency and intensity, and heavy precipitation events are described via 30-year return levels of daily precipitation. Further, extended periods with and without rainfall (wet and dry spells) are studied, considering their frequency and length as well as the average and extreme amounts of precipitation accumulated during wet spells, the latter again described via 30-year return levels. The simulations show marked changes in the characteristics of daily precipitation in Europe due to the anticipated greenhouse warming. In winter, for instance, the frequency of wet days is enhanced over most of the European continent except for the region on the Norwegian west coast and the Mediterranean region. The changes in the intensity and the 30-year return level of daily precipitation are characterized by a similar pattern except for central Europe with a tendency of decreased 30-year return levels and increased precipitation intensity. In summer, on the other hand, the frequency of wet days is decreased over most of Europe except for northern Scandinavia and the Baltic Sea region. In contrast, the precipitation intensity and the 30-year return level of daily precipitation are increased over entire Scandinavia, central and eastern Europe. The changes in the 30-year return level of daily precipitation are generally stronger than the corresponding changes in the precipitation intensity but can have opposite signs in some regions. Also the distribution of wet days is changed in the future. During summer, for instance, both the frequency and the length

  6. Hot Central-European summer of 2013 in a long-term context

    Czech Academy of Sciences Publication Activity Database

    Lhotka, Ondřej; Kyselý, Jan

    2015-01-01

    Roč. 35, č. 14 (2015), s. 4399-4407 ISSN 0899-8418 Institutional support: RVO:67179843 Keywords : summer of 2013 * climate variability * temperature records * heat waves * effective precipitation * Central Europe Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.609, year: 2015

  7. Seasonal variation of radon daughters concentrations in the atmosphere and in precipitation at the Japanese coast of the Sea of Japan

    International Nuclear Information System (INIS)

    Nishikawa, T.; Okabe, S.; Aoki, M.

    1988-01-01

    The atmospheric radon daughters concentration at Fukui in the Japanese coastal region of the Sea of Japan shows a seasonal variation whose high values appear in summer and low values in winter. On the other hand, the radon daughters concentration in precipitation at Fukui and that in the maritime atmosphere over the Sea of Japan are high in winter and low in summer. It is concluded from these phenomena that the greater part of the continental radon and its daughters are transported by seasonal winds from Siberia and China to Japan across the Sea of Japan in winter. However, when the air masses approach the shore, the cumulonimbus grows and the heavy snowfall scavenges out the radon daughters from the air masses in large quantities at the Japanese coastal region of the Sea of Japan. (author)

  8. Changes of precipitation and extremes and the possible effect of urbanization in the Beijing metropolitan region during 1960-2012 based on homogenized observations

    Science.gov (United States)

    Li, Zhen; Yan, Zhongwei; Tu, Kai; Wu, Hongyi

    2015-09-01

    Daily precipitation series at 15 stations in the Beijing metropolitan region (BMR) during 1960-2012 were homogenized using the multiple analysis of series for homogenization method, with additional adjustments based on analysis of empirical cumulative density function (ECDF) regarding climate extremes. The cumulative density functions of daily precipitation series, the trends of annual and seasonal precipitation, and summer extreme events during 1960-2012 in the original and final adjusted series at Beijing station were comparatively analyzed to show the necessity and efficiency of the new method. Results indicate that the ECDF adjustments can improve the homogeneity of high-order moments of daily series and the estimation of climate trends in extremes. The linear trends of the regional-mean annual and seasonal (spring, summer, autumn, and winter) precipitation series are -10.16, 4.97, -20.04, 5.02, and -0.11 mm (10 yr)-1, respectively. The trends over the BMR increase consistently for spring/autumn and decrease for the whole year/summer; however, the trends for winter decrease in southern parts and increase in northern parts. Urbanization affects local trends of precipitation amount, frequency, and intensity and their geographical patterns. For the urban-influenced sites, urbanization tends to slow down the magnitude of decrease in the precipitation and extreme amount series by approximately -10.4% and -6.0%, respectively; enhance the magnitude of decrease in precipitation frequency series by approximately 5.7%; reduce that of extremes by approximately -8.9%; and promote the decreasing trends in the summer intensity series of both precipitation and extremes by approximately 6.8% and 51.5%, respectively.

  9. Spring Arctic Oscillation-East Asian summer monsoon connection through circulation changes over the western North Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Dao-Yi; Yang, Jing; Hu, Miao [Beijing Normal University, State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing (China); Kim, Seong-Joong [Korea Polar Research Institute, Incheon (Korea, Republic of); Gao, Yongqi [Nansen-Zhu International Research Center, IAP/CAS, Beijing (China); Nansen Environmental and Remote Sensing Center/Bjerknes Center for Climate Research, Bergen (Norway); Guo, Dong [Beijing Normal University, State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing (China); Nansen-Zhu International Research Center, IAP/CAS, Beijing (China); Zhou, Tianjun [State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), IAP/CAS, Beijing (China)

    2011-12-15

    In the present study the links between spring Arctic Oscillation (AO) and East Asian summer monsoon (EASM) was investigated with focus on the importance of the North Pacific atmospheric circulation and sea surface temperature (SST). To reduce the statistical uncertainty, we analyzed high-pass filtered data with the inter-annual time scales, and excluded the El Nino/Southern Oscillation signals in the climate fields using a linear fitting method. The significant relationship between spring AO and EASM are supported by the changes of multi-monsoon components, including monsoon indices, precipitation, and three-dimensional atmospheric circulations. Following a stronger positive spring AO, an anomalous cyclonic circulation at 850 hPa appears in southeastern Asia and the western North Pacific in summer, with the easterly anomalies spanning from the Pacific to Asian continent along 25 N-30 N and the westerly anomalies south of 15 N. At the same time, the summer western North Pacific subtropical high becomes weaker. Consistently, the positive precipitation anomalies are developed over a broad region south of 30 N stretching from southern China to the western Pacific and the negative precipitation anomalies appear in the lower valley of the Yangtze River and southern Japan. The anomalous cyclone in the western North Pacific persisting from spring to summer plays a key role in modulating EASM and monsoon precipitation by a positive air-sea feedback mechanism. During spring the AO-associated atmospheric circulation change produces warmer SSTs between 150 E-180 near the equator. The anomalous sensible and latent heating, in turn, intensifies the cyclone through a Gill-type response of the atmosphere. Through this positive feedback, the tropical atmosphere and SST patterns sustain their strength from spring to summer, that consequently modifies the monsoon trough and the western North Pacific subtropical high and eventually the EASM precipitation. Moreover, the SST response to

  10. Daily δ18O and δD of precipitations from 2007 to 2009 in Guangzhou, South China: Implications for changes of moisture sources

    Science.gov (United States)

    Xie, Luhua; Wei, Gangjian; Deng, Wenfeng; Zhao, Xiaoli

    2011-04-01

    SummaryOxygen and hydrogen stable isotopes ( δ18O and δD) in precipitation collected in every event from 2007 to 2009 in Guangzhou, South China, are presented in this paper. The total correlation between δ18O and δD is obtained as δD = (8.46 ± 0.13) δ18O + (15.0 ± 0.9). More negative δ18O and δD generally occur during summer and autumn, while less negative or even positive δ18O and δD occur during winter and spring. Significant negative correlations between precipitation δ18O and temperature, and between precipitation δ18O and precipitation amount are observed. Regression line changes from year to year are likely due to changes in moisture sources for the precipitation. The moisture contributed by adjacent seas or local evaporation account for the main precipitation during winter and early spring, while summer monsoon brings huge amounts of moisture from remote seas associated with higher temperature and larger precipitation amounts. Seasonal variations of the precipitation D-excess provide more details for changes in moisture sources. Higher D-excess values during winter and early spring are estimated to correspond to a lesser proportion of remote moisture, while lower D-excess values during summer and autumn correspond to larger remote moisture transported by summer monsoons. This generally agrees with the results of model analysis on single isobaric backward trajectories for air parcels during specific time periods. Results of this study imply that precipitation δ18O and δD, as well as some related paleoclimate proxies such as δ18O in speleothem and tree ring, and δD in plant-derived organic compounds and tree ring, currently cannot indicate changes in temperature or precipitation amount separately, but should be comprehensive proxies for monsoon climate.

  11. Method for modeling the deposition of sulfur by precipitation over regional scales

    International Nuclear Information System (INIS)

    Hicks, B.B.; Shannon, J.D.

    1979-01-01

    Radioactive fallout data suggest that the concentration of pollutants in rainfall, while highly variable, might be described on the average by about an inverse half-power dependence on the amount of precipitation. Recent measurements of sulfur concentrations in summer rainfall collected at Argonne National Laboratory tend to support this contention, as do preliminary results derived from operations of the DOE precipitation chemistry network. The concept is extended to develop a bulk removal rate for airborne total sulfur by precipitation for use in regional dispersion modeling

  12. Linkages between ENSO/PDO signals and precipitation, streamflow in China during the last 100 years

    Science.gov (United States)

    Ouyang, R.; Liu, W.; Fu, G.; Liu, C.; Hu, L.; Wang, H.

    2014-09-01

    This paper investigates the single and combined impacts of El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) on precipitation and streamflow in China over the last century. Results indicate that the precipitation and streamflow overall decrease during El Niño/PDO warm phase periods and increase during La Niña/PDO cool phase periods in the majority of China, although there are regional and seasonal differences. Precipitation and streamflow in the Yellow River basin, Yangtze River basin and Pearl River basin are more significantly influenced by El Niño and La Niña events than is precipitation and streamflow in the Songhua River basin, especially in October and November. Moreover, significant influence of ENSO on streamflow in the Yangtze River mainly occurs in summer and autumn while in the Pearl River influence primarily occurs in the winter and spring. The precipitation and streamflow are relatively greater in the warm PDO phase in the Songhua River basin and several parts of the Yellow River basin and relatively less in the Pearl River basin and most parts of Northwest China compared to those in the cool PDO phase, though there is little significance detected by Wilcoxon signed-rank test. When considering the combined influence of ENSO and PDO, the responses of precipitation/streamflow are shown to be opposite in northern China and southern China, with ENSO-related precipitation/streamflow enhanced in northern China and decreased in southern China during the warm PDO phases, and enhanced in southern China and decreased in northern China during the cool PDO phases. It is hoped that this study will be beneficial for understanding the precipitation/streamflow responses to the changing climate and will correspondingly provide valuable reference for water resources prediction and management across China.

  13. Regional simulation of Indian summer monsoon intraseasonal oscillations at gray-zone resolution

    Science.gov (United States)

    Chen, Xingchao; Pauluis, Olivier M.; Zhang, Fuqing

    2018-01-01

    Simulations of the Indian summer monsoon by the cloud-permitting Weather Research and Forecasting (WRF) model at gray-zone resolution are described in this study, with a particular emphasis on the model ability to capture the monsoon intraseasonal oscillations (MISOs). Five boreal summers are simulated from 2007 to 2011 using the ERA-Interim reanalysis as the lateral boundary forcing data. Our experimental setup relies on a horizontal grid spacing of 9 km to explicitly simulate deep convection without the use of cumulus parameterizations. When compared to simulations with coarser grid spacing (27 km) and using a cumulus scheme, the 9 km simulations reduce the biases in mean precipitation and produce more realistic low-frequency variability associated with MISOs. Results show that the model at the 9 km gray-zone resolution captures the salient features of the summer monsoon. The spatial distributions and temporal evolutions of monsoon rainfall in the WRF simulations verify qualitatively well against observations from the Tropical Rainfall Measurement Mission (TRMM), with regional maxima located over Western Ghats, central India, Himalaya foothills, and the west coast of Myanmar. The onset, breaks, and withdrawal of the summer monsoon in each year are also realistically captured by the model. The MISO-phase composites of monsoon rainfall, low-level wind, and precipitable water anomalies in the simulations also agree qualitatively with the observations. Both the simulations and observations show a northeastward propagation of the MISOs, with the intensification and weakening of the Somali Jet over the Arabian Sea during the active and break phases of the Indian summer monsoon.

  14. Polyfluorinated and perfluorinated chemicals in precipitation and runoff from cities across eastern and central China.

    Science.gov (United States)

    Zhao, Lijie; Zhou, Meng; Zhang, Tao; Sun, Hongwen

    2013-02-01

    Twenty-three polychlorinated and perfluorinated compounds (PFCs) were investigated in water phase and particulate matters of 19 precipitation samples (18 snow samples and 1 rain sample) from different cities across eastern and central China collected in February 2010. The PFCs in samples of 9e precipitation events during more than half a year at 1 site in Tianjin and 6 successive samples during 1 precipitation event were measured to elucidate the change of PFC in precipitation. In addition, PFCs in 3 runoffs at different kinds of sites in Tianjin were compared with those in the corresponding precipitation. The results showed that the particulate matters separated from the precipitation contained undetectable PFCs. The total PFC concentration ranged between 4.7 and 152 ng L(-1) in water phase of the precipitation samples, with perfluorooctanoic acid (PFOA) being detected at all of the sampling sites and the dominant PFC at most of the sampling sites. Some potential precursors of environmentally concerned PFCs and their degradation intermediates were measured simultaneously, among which 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), 8:2 FTUCA, and  × (3, 4, 5, 7):3 acid [F(CF(2))xCH(2)CH(2)COOH] were measured for the first time in Chinese precipitations; however, their concentrations were all lower than the limits of detection except that 6:2 FTUCA and 8:2 FTUCA could be detected in 3 and 8 precipitation samples, respectively. No clear seasonal variation in PFC concentrations in precipitation was observed during half a year; however, a relatively greater average concentration of total PFCs was observed during winter and summer compared with spring. The concentration of individual PFCs showed an obvious descending trend in the successive samples of the precipitation event. PFOA and perfluorononanoic acid in runoffs collected from different sites showed the following similar pattern-gas station > highway > university campus-whereas the other

  15. Systematical estimation of GPM-based global satellite mapping of precipitation products over China

    Science.gov (United States)

    Zhao, Haigen; Yang, Bogang; Yang, Shengtian; Huang, Yingchun; Dong, Guotao; Bai, Juan; Wang, Zhiwei

    2018-03-01

    As the Global Precipitation Measurement (GPM) Core Observatory satellite continues its mission, new version 6 products for Global Satellite Mapping of Precipitation (GSMaP) have been released. However, few studies have systematically evaluated the GSMaP products over mainland China. This study quantitatively evaluated three GPM-based GSMaP version 6 precipitation products for China and eight subregions referring to the Chinese daily Precipitation Analysis Product (CPAP). The GSMaP products included near-real-time (GSMaP_NRT), microwave-infrared reanalyzed (GSMaP_MVK), and gauge-adjusted (GSMaP_Gau) data. Additionally, the gauge-adjusted Integrated Multi-Satellite Retrievals for Global Precipitation Measurement Mission (IMERG_Gau) was also assessed and compared with GSMaP_Gau. The analyses of the selected daily products were carried out at spatiotemporal resolutions of 1/4° for the period of March 2014 to December 2015 in consideration of the resolution of CPAP and the consistency of the coverage periods of the satellite products. The results indicated that GSMaP_MVK and GSMaP_NRT performed comparably and underdetected light rainfall events (Pearson linear correlation coefficient (CC), fractional standard error (FSE), and root-mean-square error (RMSE) metrics during the summer. Compared with GSMaP_NRT and GSMaP_MVK, GSMaP_Gau possessed significantly improved metrics over mainland China and the eight subregions and performed better in terms of CC, RMSE, and FSE but underestimated precipitation to a greater degree than IMERG_Gau. As a quantitative assessment of the GPM-era GSMaP products, these validation results will supply helpful references for both end users and algorithm developers. However, the study findings need to be confirmed over a longer future study period when the longer-period IMERG retrospectively-processed data are available.

  16. A comparison of the flood precipitation episode in August 2002 with historic extreme precipitation events on the Czech territory

    Czech Academy of Sciences Publication Activity Database

    Řezáčová, Daniela; Kašpar, Marek; Müller, Miloslav; Sokol, Zbyněk; Kakos, Vilibald; Hanslian, David; Pešice, Petr

    2005-01-01

    Roč. 77, - (2005), s. 354-366 ISSN 0169-8095 R&D Projects: GA AV ČR(CZ) IBS3042101; GA MŽP(CZ) SA/650/4/03 Institutional research plan: CEZ:AV0Z30420517 Keywords : Precipitation * Summer floods * Czech territory * Hydro-meteorological conditions * Extremeness of meteorological quantities * Distribution function Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.481, year: 2005

  17. Variations of net ecosystem production due to seasonal precipitation differences in a tropical dry forest of northwest Mexico

    Science.gov (United States)

    Verduzco, Vivian S.; Garatuza-Payán, Jaime; Yépez, Enrico A.; Watts, Christopher J.; Rodríguez, Julio C.; Robles-Morua, Agustin; Vivoni, Enrique R.

    2015-10-01

    Due to their large extent and high primary productivity, tropical dry forests (TDF) are important contributors to atmospheric carbon exchanges in subtropical and tropical regions. In northwest Mexico, a bimodal precipitation regime that includes winter precipitation derived from Pacific storms and summer precipitation from the North American monsoon (NAM) couples water availability with ecosystem processes. We investigated the net ecosystem production of a TDF ecosystem using a 4.5 year record of water and carbon fluxes obtained from the eddy covariance method complemented with remotely sensed data. We identified a large CO2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO2 efflux occurs prior to vegetation green-up, we infer that respiration is mainly due to decomposition of soil organic matter accumulated from the prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production but can be overwhelmed by the strength of the primary productivity during the NAM. Precipitation characteristics during NAM have significant controls on sustaining carbon fixation in the TDF into the fall season. We identified that a threshold of ~350 to 400 mm of monsoon precipitation leads to a switch in the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m2/yr) to a net sink (-249 g C/m2/yr). This monsoonal precipitation threshold is typically exceeded one out of every 2 years. The close coupling of winter and summer periods with respect to carbon fluxes suggests that the annual carbon balance is dependent on precipitation amounts in both seasons in TDF ecosystems.

  18. 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.

  19. Impact of vegetation feedback at subseasonal & seasonal timescales on precipitation over North America

    Science.gov (United States)

    Kim, Y.; Wang, G.

    2006-05-01

    Soil moisture-vegetation-precipitation feedbacks tend to enhance soil moisture memory in some areas of the globe, which contributes to the subseasonal and seasonal climate prediction skill. In this study, the impact of vegetation on precipitation over North America is investigated using a coupled land-atmosphere model CAM3- CLM3. The coupled model has been modified to include a predictive vegetation phenology scheme and validated against the MODIS data. Vegetation phenology is modeled by updating the leaf area index (LAI) daily in response to cumulative and concurrent hydrometeorological conditions. First, driven with the climatological SST, a large group of 5-member ensembles of simulations from the late spring and summer to the end of year are generated with the different initial conditions of soil moisture. The impact of initial soil moisture anomalies on subsequent precipitation is examined with the predictive vegetation phenology scheme disabled/enabled ("SM"/"SM_Veg" ensembles). The simulated climate differences between "SM" and "SM_Veg" ensembles represent the role of vegetation in soil moisture-vegetation- precipitation feedback. Experiments in this study focus on how the response of precipitation to initial soil moisture anomalies depends on their characteristics, including the timing, magnitude, spatial coverage and vertical depth, and further how it is modified by the interactive vegetation. Our results, for example, suggest that the impact of late spring soil moisture anomalies is not evident in subsequent precipitation until early summer when local convective precipitation dominates. With the summer wet soil moisture anomalies, vegetation tends to enhance the positive feedback between soil moisture and precipitation, while vegetation tends to suppress such positive feedback with the late spring anomalies. Second, the impact of vegetation feedback is investigated by driving the model with the inter-annually varying monthly SST (1983-1994). With the

  20. Projections of East Asian summer monsoon change at global warming of 1.5 and 2 °C

    Science.gov (United States)

    Liu, Jiawei; Xu, Haiming; Deng, Jiechun

    2018-04-01

    Much research is needed regarding the two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 and 2 °C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM) intensity change and associated precipitation change under both warming targets are explored in this study. The multimodel ensemble mean projections by 19 CMIP5 models show small increases in EASM intensity and general increases in summer precipitation at 1.5 and 2 °C warming, but with large multimodel standard deviations. Thus, a novel multimodel ensemble pattern regression (EPR) method is applied to give more reliable projections based on the concept of emergent constraints, which is effective at tightening the range of multimodel diversity and harmonize the changes of different variables over the EASM region. Future changes projected by using the EPR method suggest decreased precipitation over the Meiyu belt and increased precipitation over the high latitudes of East Asia and Central China, together with a considerable weakening of EASM intensity. Furthermore, reduced precipitation appears over 30-40° N of East Asia in June and over the Meiyu belt in July, with enhanced precipitation at their north and south sides. These changes in early summer are attributed to a southeastward retreat of the western North Pacific subtropical high (WNPSH) and a southward shift of the East Asian subtropical jet (EASJ), which weaken the moisture transport via southerly wind at low levels and alter vertical motions over the EASM region. In August, precipitation would increase over the high latitudes of East Asia with more moisture from the wetter area over the ocean in the east and decrease over Japan with westward extension of WNPSH. These monthly precipitation changes would finally contribute to a tripolar pattern of EASM precipitation change at 1.5 and 2 °C warming. Corrected EASM intensity exhibits a slight difference between 1.5 and 2 °C, but a

  1. Numerical simulation on the southern flood and northern drought in summer 2014 over Eastern China

    Science.gov (United States)

    Xu, Lianlian; He, Shengping; Li, Fei; Ma, Jiehua; Wang, Huijun

    2017-12-01

    In summer 2014, Eastern China suffered a typical "southern flood and northern drought" anomalous climate. Observational analyses indicated that the anomalous vertical motion, East Asian subtropical westerly jet stream, and the East Asian summer monsoon (EASM) played important roles in the formation of such precipitation anomaly. Furthermore, using the climate model (IAP-AGCM-4.1) perturbed by simultaneous observed sea surface temperature anomalies (SSTAs) in global scale and four different regions (North Pacific, Indian Ocean, North Atlantic, and Equatorial Pacific), this study investigated the potential contribution of ocean to such "southern flood and northern drought" over Eastern China in summer 2014. The simulations forced by global-scale SSTAs or North Pacific SSTAs displayed the most similarity to the observed "southern flood and northern drought" over Eastern China. It was revealed that the global-scale and North Pacific SSTAs influenced the rainfall over Eastern China via modulating the EASM. The related simulations successfully reproduced the associated atmospheric circulation anomalies. The experiment driven by Indian Ocean SSTAs could also reproduce the similar precipitation anomaly pattern and suggested that the Indian Ocean exerted pronounced influence on the North Pacific Subtropical High. Additionally, the simulations forced by SSTAs in the North Atlantic and Equatorial Pacific successfully reproduced the northern drought but failed to capture the southern flood. The simulations suggested that precipitation anomaly over Eastern China in summer 2014 was a comprehensive effect of global SSTAs and the dominant contribution to the "southern flood and northern drought" pattern came from the North Pacific and Indian Ocean.

  2. Spatial Distribution of Stable Isotopes of Precipitation in Kumamoto, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Anoue, M. T.; Shimada, J. [Graduate School of Science and Technology, Kumamoto University (Japan); Ichiyanagi, K. [Graduate School of Science and Technology, Kumamoto University and Japan Agency for Marine-Earth Science and Technology (Japan)

    2013-07-15

    To understand the spatial distribution of stable isotopic compositions in precipitation, precipitation samples were collected every two weeks from november 2009 to december 2010 at 6 points in Kumamoto, Japan. The {delta}{sup 18}O and {delta}{sup 2}H of precipitation samples were measured by isotope ratio mass spectrometry (Delta-S) with CO{sub 2}/H2{sub O} equivalent method for {delta}{sup 18}O and the chromium reduction method for {delta}2H. The range of {delta}{sup 18}O and d-excess (= {delta}{sup 2}H - 8 {delta}{sup 18}O) in precipitation is from -13.4 per mille to -3.5 per mille and from 2.6 per mille to 35.6 per mille , respectively. Seasonal variability of {delta}{sup 18}O (d-excess) in precipitation was low (high) in winter and high (low) in summer. The seasonal wind of this study area was dominated by south-westerly in summer (from June to August) and north-westerly in winter (from December to February). These wind regimes indicate seasonal variabilities of the water vapour pathway from the origin. In this paper the trend of inland effect to the {delta}{sup 18}O for both south-westerly and north-westerly are also considered. As a result, significant correlation between distances from the coastal line at south-westerly or north-westerly and {delta}{sup 18}O in precipitation was recognized, particularly from 18 February to 7 March and from 29 September to 19 October in 2010 (statistically significant with 5% level). Furthermore, in order to evaluate the course of precipitation, the column total of water vapour flux was considered in the whole period by using JRA-25 and JCDAS. It is interesting that the inland effect corresponded to the column total of water vapour flux at south-westerly (north-westerly). Hence, it is conceivable that the spatial distribution of {delta}{sup 18}O in precipitation was controlled by a column total of water vapour flux in this area. (author)

  3. Precipitates in irradiated Zircaloy

    International Nuclear Information System (INIS)

    Chung, H.M.

    1985-10-01

    Precipitates in high-burnup (>20 MWd/kg U) Zircaloy spent-fuel cladding discharged from commercial boiling- and pressurized-water reactors have been characterized by TEM-HVEM. Three classes of primary precipitates were observed in the irradiated Zircaloys: Zr 3 O (2 to 6 nm), cubic-ZrO 2 (greater than or equal to 10 nm), and delta-hydride (35 to 100 nm). The former two precipitations appears to be irradiation induced in nature. Zr(Fe/sub x/Cr/sub 1-x/) 2 and Zr 2 (Fe/sub x/Ni/sub 1-x/) intermetallics, which are the primary precipitates in unirradiated Zircaloys, were largely dissolved after the high burnup. It seems, therefore, that the influence of the size and distribution of the intermetallics on the corrosion behavior may be quite different for the irradiated Zircaloys

  4. Projected changes in precipitation intensity and frequency over complex topography: a multi-model perspective

    Science.gov (United States)

    Fischer, Andreas; Keller, Denise; Liniger, Mark; Rajczak, Jan; Schär, Christoph; Appenzeller, Christof

    2014-05-01

    Fundamental changes in the hydrological cycle are expected in a future warmer climate. This is of particular relevance for the Alpine region, as a source and reservoir of several major rivers in Europe and being prone to extreme events such as floodings. For this region, climate change assessments based on the ENSEMBLES regional climate models (RCMs) project a significant decrease in summer mean precipitation under the A1B emission scenario by the mid-to-end of this century, while winter mean precipitation is expected to slightly rise. From an impact perspective, projected changes in seasonal means, however, are often insufficient to adequately address the multifaceted challenges of climate change adaptation. In this study, we revisit the full matrix of the ENSEMBLES RCM projections regarding changes in frequency and intensity, precipitation-type (convective versus stratiform) and temporal structure (wet/dry spells and transition probabilities) over Switzerland and surroundings. As proxies for raintype changes, we rely on the model parameterized convective and large-scale precipitation components. Part of the analysis involves a Bayesian multi-model combination algorithm to infer changes from the multi-model ensemble. The analysis suggests a summer drying that evolves altitude-specific: over low-land regions it is associated with wet-day frequency decreases of convective and large-scale precipitation, while over elevated regions it is primarily associated with a decline in large-scale precipitation only. As a consequence, almost all the models project an increase in the convective fraction at elevated Alpine altitudes. The decrease in the number of wet days during summer is accompanied by decreases (increases) in multi-day wet (dry) spells. This shift in multi-day episodes also lowers the likelihood of short dry spell occurrence in all of the models. For spring and autumn the combined multi-model projections indicate higher mean precipitation intensity north of the

  5. Delayed responses of an Arctic ecosystem to an extremely dry summer: impacts on net ecosystem exchange and vegetation functioning

    Science.gov (United States)

    Zona, D.; Lipson, D. A.; Richards, J. H.; Phoenix, G. K.; Liljedahl, A. K.; Ueyama, M.; Sturtevant, C. S.; Oechel, W. C.

    2013-12-01

    The importance and mode of action of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. Summer 2007 in Barrow, Arctic Alaska, experienced unusually high air temperatures (fifth warmest over a 65 yr period) and record low precipitation (lowest over a 65 yr period). These abnormal conditions resulted in strongly reduced net Sphagnum CO2 uptake, but no effect neither on vascular plant development nor on net ecosystem exchange (NEE) from this arctic tundra ecosystem. Gross primary production (GPP) and ecosystem respiration (Reco) were both generally greater during most of this extreme summer. Cumulative ecosystem C uptake in 2007 was similar to the previous summers, showing the capacity of the ecosystem to compensate in its net ecosystem exchange (NEE) despite the impact on other functions and structure such as substantial necrosis of the Sphagnum layer. Surprisingly, the lowest ecosystem C uptake (2005-2009) was observed during the 2008 summer, i.e the year directly following the extremely summer. In 2008, cumulative C uptake was ∼70% lower than prior years. This reduction cannot solely be attributed to mosses, which typically contribute with ∼40% - of the entire ecosystem C uptake. The minimum summer cumulative C uptake in 2008 suggests that the entire ecosystem experienced difficulty readjusting to more typical weather after experiencing exceptionally warm and dry conditions. Importantly, the return to a substantial cumulative C uptake occurred two summers after the extreme event, which suggest a high resilience of this tundra ecosystem. Overall, these results show a highly complex response of the C uptake and its sub-components to atypically dry conditions. The impact of multiple extreme events still awaits further investigation.

  6. Variation among sub-basins of the upper Nelson River in relationships between precipitation, runoff and the Pacific Decadal Oscillation

    International Nuclear Information System (INIS)

    McCullough, G.

    2008-01-01

    In this paper, I examine relationships between precipitation and river discharge in the Nelson River watershed and several global climate indices. Inter-decadal patterns in discharge and precipitation for several sub-basins closely tracked the Pacific Decadal Oscillation (PDO) through much of the 20th century. The PDO explained 53% of the variability in precipitation and 70% in discharge for the Red River (5-y averages) from 1915-1975. However, since 1975, both precipitation and discharge have increased relative to trend of the PDO. Winnipeg River discharge likewise increased relative to the PDO, but diverged earlier, beginning in 1965. The hydrograph of the Saskatchewan River followed the PDO only until mid-century, after which discharge declined relative to the PDO. The decline of discharge in the Saskatchewan River is not matched by consistent declines in precipitation, but may be partly due to consumptive use, mainly irrigation, and losses due to evaporation from large reservoirs created in the 1960s and 1970s. However, the increases in the Red and Winnipeg River are well-explained by increased spring and summer precipitation. For instance, precipitation was 20-30% higher in the decade 1996-2005 than in the previous decade. By examining historical data, we show the runoff coefficient to increase with increasing discharge, and that the proportional increase is greater in the Red than in the Winnipeg River basin. In the Red, the moderate difference in precipitation was amplified into a doubling of annual mean discharge. Comparing the same 2 periods, a smaller 10% increase in precipitation in the Winnipeg River basin explains a 27% increase in discharge. (author)

  7. Quantitative precipitation climatology over the Himalayas by using Precipitation Radar on Tropical Rainfall Measuring Mission (TRMM) and a dense network of rain-gauges

    Science.gov (United States)

    Yatagai, A.

    2010-09-01

    Quantified grid observation data at a reasonable resolution are indispensable for environmental monitoring as well as for predicting future change of mountain environment. However quantified datasets have not been available for the Himalayan region. Hence we evaluate climatological precipitation data around the Himalayas by using Precipitation Radar (PR) data acquired by the Tropical Rainfall Measuring Mission (TRMM) over 10 years of observation. To validate and adjust these patterns, we used a dense network of rain gauges collected by the Asian Precipitation—Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE Water Resources) project (http://www.chikyu.ac.jp/precip/). We used more than 2600 stations which have more than 10-year monthly precipitation over the Himalayan region (75E-105E, 20-36N) including country data of Nepal, Bangladesh, Bhutan, Pakistan, India, Myanmar, and China. The region we studied is so topographically complicated that horizontal patterns are not uniform. Therefore, every path data of PR2A25 (near-surface rain) was averaged in a 0.05-degree grid and a 10-year monthly average was computed (hereafter we call PR). On the other hand, for rain-gauge, we first computed cell averages if each 0.05-degree grid cell has 10 years observation or more. Here we refer to the 0.05-degree rain-gauge climatology data as RG data. On the basis of comparisons between the RG and PR composite values, we defined the parameters of the regressions to correct the monthly climatology value based on the rain gauge observations. Compared with the RG, the PR systematically underestimated precipitation by 28-38% in summer (July-September). Significant correlation between TRMM/PR and rain-gauge data was found for all months, but the correlation is relatively low in winter. The relationship is investigated for different elevation zones, and the PR was found to underestimate RG data in most zones, except for certain zones in

  8. Deficiencies and possibilities for long-lead coupled climate prediction of the Western North Pacific-East Asian summer monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sun-Seon; Ha, Kyung-Ja [Pusan National University, Division of Earth Environmental System, Busan (Korea, Republic of); Lee, June-Yi; Wang, Bin [University of Hawaii, Department of Meteorology and International Pacific Research Center, Honolulu, HI (United States); Schemm, Jae Kyung E. [Climate Prediction Center/NCEP, Camp Springs, MD (United States)

    2011-03-15

    Long-lead prediction of waxing and waning of the Western North Pacific (WNP)-East Asian (EA) summer monsoon (WNP-EASM) precipitation is a major challenge in seasonal time-scale climate prediction. In this study, deficiencies and potential for predicting the WNP-EASM precipitation and circulation one or two seasons ahead were examined using retrospective forecast data for the 26-year period of 1981-2006 from two operational couple models which are the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) and the Bureau of Meteorology Research Center (BMRC) Predictive Ocean-Atmosphere Model for Australia (POAMA). While both coupled models have difficulty in predicting summer mean precipitation anomalies over the region of interest, even for a 0-month lead forecast, they are capable of predicting zonal wind anomalies at 850 hPa several months ahead and, consequently, satisfactorily predict summer monsoon circulation indices for the EA region (EASMI) and for the WNP region (WNPSMI). It should be noted that the two models' multi-model ensemble (MME) reaches 0.40 of the correlation skill for the EASMI with a January initial condition and 0.75 for the WNPSMI with a February initial condition. Further analysis indicates that prediction reliability of the EASMI is related not only to the preceding El Nino and Southern Oscillation (ENSO) but also to simultaneous local SST variability. On other hand, better prediction of the WNPSMI is accompanied by a more realistic simulation of lead-lag relationship between the index and ENSO. It should also be noted that current coupled models have difficulty in capturing the interannual variability component of the WNP-EASM system which is not correlated with typical ENSO variability. To improve the long-lead seasonal prediction of the WNP-EASM precipitation, a statistical postprocessing was developed based on the multiple linear regression method. The method utilizes the MME prediction of the EASMI and

  9. Assessing the impacts of climate change on future precipitation trends based on downscaled cmip5 simulations data

    International Nuclear Information System (INIS)

    Mentgal, A.; Harijan, K.; Uqaili, M.A.

    2017-01-01

    This study investigates future changes in precipitation over the CRB (Columbia River Basin) in both wet (DJF) and dry (JJA) seasons under RCP85 GHG emission scenario. The simulations from four climate models which participated in CMIP5 (Coupled Model Intercomparison Project Phase-5) were downscaled using the BCSD (Bias Correction and Spatial Disaggregation) method. After downscaling, extreme value analysis and MME (Multi Model Ensemble) averaging is performed. This study focuses on computing 2, 5, 10 and 25 years return levels for both winter (DJF) and summer (JJA) seasons. The maximum winter precipitation values for 2, 5, 10 and 25 years return periods have been estimated to be about 112, 127, 148 and 171 mm/day respectively whereas the maximum summer precipitation values for 2, 5, 10 and 25 years return periods are observed to be about 56, 81, 96 and 126 mm/day respectively. The MME average outperformed the individual models in simulating the historical precipitation in both seasons. The MME results showed a consistent and significant increase in the extreme precipitation and decrease in mean precipitation in both future wet and dry seasons. Largest increase in precipitation occurs over the higher elevations of the Cascades Range, Coast Range and the Mountainous Range. (author)

  10. Northern peatland Collembola communities unaffected by three summers of simulated extreme precipitation

    NARCIS (Netherlands)

    Krab, E.J.; Aerts, R.; Berg, M.P.; van Hal, J.R.; Keuper, F.

    2014-01-01

    Extreme climate events are observed and predicted to increase in frequency and duration in high-latitude ecosystems as a result of global climate change. This includes extreme precipitation events, which may directly impact on belowground food webs and ecosystem functioning by their physical impacts

  11. Downscaling GISS ModelE Boreal Summer Climate over Africa

    Science.gov (United States)

    Druyan, Leonard M.; Fulakeza, Matthew

    2015-01-01

    The study examines the perceived added value of downscaling atmosphere-ocean global climate model simulations over Africa and adjacent oceans by a nested regional climate model. NASA/Goddard Institute for Space Studies (GISS) coupled ModelE simulations for June- September 1998-2002 are used to form lateral boundary conditions for synchronous simulations by the GISS RM3 regional climate model. The ModelE computational grid spacing is 2deg latitude by 2.5deg longitude and the RM3 grid spacing is 0.44deg. ModelE precipitation climatology for June-September 1998-2002 is shown to be a good proxy for 30-year means so results based on the 5-year sample are presumed to be generally representative. Comparison with observational evidence shows several discrepancies in ModelE configuration of the boreal summer inter-tropical convergence zone (ITCZ). One glaring shortcoming is that ModelE simulations do not advance the West African rain band northward during the summer to represent monsoon precipitation onset over the Sahel. Results for 1998-2002 show that onset simulation is an important added value produced by downscaling with RM3. ModelE Eastern South Atlantic Ocean computed sea-surface temperatures (SST) are some 4 K warmer than reanalysis, contributing to large positive biases in overlying surface air temperatures (Tsfc). ModelE Tsfc are also too warm over most of Africa. RM3 downscaling somewhat mitigates the magnitude of Tsfc biases over the African continent, it eliminates the ModelE double ITCZ over the Atlantic and it produces more realistic orographic precipitation maxima. Parallel ModelE and RM3 simulations with observed SST forcing (in place of the predicted ocean) lower Tsfc errors but have mixed impacts on circulation and precipitation biases. Downscaling improvements of the meridional movement of the rain band over West Africa and the configuration of orographic precipitation maxima are realized irrespective of the SST biases.

  12. Relations between oxygen stable isotopic ratios in precipitation and relevant meteorological factors in southwest China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The correlations of isotopic ratios in precipitation with temperature, air pressure and humidity at dif- ferent altitudes, in southwest China, are analyzed. There appear marked negative correlations for the δ 18O in precipitation with precipitation amount, vapor pressure and atmospheric precipitable water (PW) at Mengzi, Simao and Tengchong stations on synoptic timescale; the marked negative correlations between the δ 18O in precipitation and the diurnal mean temperature at 400 hPa, 500 hPa, 700 hPa and 850 hPa are different from the temperature effect in middle-high-latitude inland. Moreover, the notable positive correlation between the δ 18O in precipitation and the dew-point deficit △Td at different altitudes is found at the three stations. On annual timescale, the annual precipitation amount weighted mean δ 18O display the negative correlations not only with annual precipitation but also with annual mean temperature at 500 hPa. It can be deduced that, in the years with abnormally strong summer monsoon, more warm and wet air from low-latitude oceans is transported northward along the vapor channel located in southwest China and generates abnormally strong rainfall on the way. Meanwhile, the ab- normally strong condensation process will release more condensed latent heat into atmosphere, and lead to the rise of atmospheric temperature during rainfall, but decline of the δ 18O in precipitation. On the contrary, in the years with abnormally weak summer monsoon, the abnormally weak condensation process will release less condensed latent heat into atmosphere, and lead to the decline of atmos- pheric temperature during rainfall, but increase of the δ 18O in precipitation.

  13. Characteristics and Mechanisms of Zonal Oscillation of Western Pacific Subtropical High in Summer

    Science.gov (United States)

    Guan, W.; Ren, X.; Hu, H.

    2017-12-01

    The zonal oscillation of the western Pacific subtropical high (WPSH) influences the weather and climate over East Asia significantly. This study investigates the features and mechanisms of the zonal oscillation of the WPSH during summer on subseasonal time scales. The zonal oscillation index of the WPSH is defined by normalized subseasonal geopotential height anomaly at 500hPa averaged over the WPSH's western edge (110° - 140°E, 10° - 30°N). The index shows a predominant oscillation with a period of 10-40 days. Large positive index indicates a strong anticyclonic anomaly over East Asia and its coastal region south of 30°N at both 850hPa and 500hPa. The WPSH stretches more westward accompanied by warmer SST anomalies beneath the western edge of the WPSH. Meanwhile, above-normal precipitation is seen over the Yangtze-Huaihe river basin and below-normal precipitation over the south of the Yangtze River. Negative index suggests a more eastward position of WPSH. The anomalies in circulation and SST for negative index are almost the mirror image of those for the positive index. In early summer, the zonal shift of the WPSH is affected by both the East Asia/Pacific (EAP) teleconnection pattern and the Silk road pattern (SRP). The positive (negative) phase of the EAP pattern is characterized by a low-level anticyclonic (cyclonic) anomaly over the subtropical western Pacific, indicating the western extension (eastward retreat) of the WPSH. Comparing with the EAP pattern, the SRP forms an upper-level anticyclonic (cyclonic) anomaly in mid-latitudes of East Asia, and then leads to the westward (eastward) movement of the WPSH. In late summer, the zonal shift of the WPSH is mainly affected by the EAP pattern, because the EAP pattern in late summer is stronger than that in early summer. The zonal shift of the WPSH is also influenced by the subseasonal air-sea interaction locally. During the early stage of WPSH's westward stretch, the local SST anomaly in late summer is

  14. Satellite passive microwave rain rate measurement over croplands during spring, summer and fall

    International Nuclear Information System (INIS)

    Spencer, R.W.

    1984-01-01

    Rain rate algorithms for spring, summer and fall that have been developed from comparisons between the brightness temperatures measured by the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) and rain rates derived from operational WSR-57 radars over land are described. Data were utilized from a total of 25 SMMR passes and 234 radars, resulting in ∼12 000 observations of ∼1600 km 2 areas. Multiple correlation coefficients of 0.63, 0.80 and 0.75 are achieved for the spring, summer and fall algorithms, respectively. Most of this information is in the form of multifrequency contrast in brightness temperature, which is interpreted as a measurement of the degree to which the land-emitted radiation is attenuated by the rain systems. The SMMR 37 GHz channel has more information on rain rate than any other channel. By combining the lower frequency channels with the 37 GHz observations, variations in land and precipitation thermometric temperatures can be removed, leaving rain attenuation as the major effect on brightness temperature. Polarization screening at 37 GHz is found to be sufficient to screen out cases of wet ground, which is only important when the ground is relatively vegetation free. Heavy rain cases are found to be a significant part of the algorithms' success, because of the strong microwave signatures (low brightness temperatures) that result from the presence of precipitation-sized ice in the upper portions of heavily precipitating storms. If IR data are combined with the summer microwave data, an improved (0.85) correlation with radar rain rates is achieved

  15. High-resolution projections of mean and extreme precipitations over China through PRECIS under RCPs

    Science.gov (United States)

    Zhu, Jinxin; Huang, Gordon; Wang, Xiuquan; Cheng, Guanhui; Wu, Yinghui

    2018-06-01

    The impact of global warming on the characteristics of mean and extreme precipitations over China is investigated by using the Providing REgional Climate Impacts for Studies (PRECIS) model. The PRECIS model was driven by the Hadley Centre Global Environment Model version 2 with Earth System components and coupling (HadGEM2-ES). The results of both models are analyzed in terms of mean precipitation and indices of precipitation extremes (R95p, R99p, SDII, WDF, and CWD) over China at the resolution of 25 km under the Representative Concentration Pathways 4.5 and 8.5 (RCP4.5 and RCP8.5) scenarios for the baseline period (1976-2005) and two future periods (2036-2065 and 2070-2099). With improved resolution, the PRECIS model is able to better represent the fine-scale physical process than HadGEM2-ES. It can provide reliable spatial patterns of precipitation and its related extremes with high correlations to observations. Moreover, there is a notable improvement in temporal patterns simulation through the PRECIS model. The PRECIS model better reproduces the regional annual cycle and frequencies of daily precipitation intensity than its driving GCM. Under RCP4.5 and RCP8.5, both the HadGEM2-ES and the precis project increasing annual precipitation over the entire country for two future periods. Precipitation increase in winter is greater than the increase in summer. The results suggest that increased radiative forcing from RCP4.5 to RCP8.5 would further intensify the magnitude of projected precipitation changes by both PRECIS and HadGEM2-ES. For example, some parts of south China with decreased precipitation under RCP4.5 would expect even less precipitation under RCP8.5; regions (northwest, northcentral and northeast China) with increased precipitation under RCP4.5 would expect more precipitation under RCP8.5. Apart from the projected increase in annual total precipitation, the results also suggest that there will be an increase in the days with precipitation higher than

  16. Using GRACE to constrain precipitation amount over cold mountainous basins

    Science.gov (United States)

    Behrangi, Ali; Gardner, Alex S.; Reager, John T.; Fisher, Joshua B.

    2017-01-01

    Despite the importance for hydrology and climate-change studies, current quantitative knowledge on the amount and distribution of precipitation in mountainous and high-elevation regions is limited due to instrumental and retrieval shortcomings. Here by focusing on two large endorheic basins in High Mountain Asia, we show that satellite gravimetry (Gravity Recovery and Climate Experiment (GRACE)) can be used to provide an independent estimate of monthly accumulated precipitation using mass balance equation. Results showed that the GRACE-based precipitation estimate has the highest agreement with most of the commonly used precipitation products in summer, but it deviates from them in cold months, when the other products are expected to have larger errors. It was found that most of the products capture about or less than 50% of the total precipitation estimated using GRACE in winter. Overall, Global Precipitation Climatology Project (GPCP) showed better agreement with GRACE estimate than other products. Yet on average GRACE showed 30% more annual precipitation than GPCP in the study basins. In basins of appropriate size with an absence of dense ground measurements, as is a typical case in cold mountainous regions, we find GRACE can be a viable alternative to constrain monthly and seasonal precipitation estimates from other remotely sensed precipitation products that show large bias.

  17. Characteristics of cloud occurrence using ceilometer measurements and its relationship to precipitation over Seoul

    Science.gov (United States)

    Lee, Sanghee; Hwang, Seung-On; Kim, Jhoon; Ahn, Myoung-Hwan

    2018-03-01

    Clouds are an important component of the atmosphere that affects both climate and weather, however, their contributions can be very difficult to determine. Ceilometer measurements can provide high resolution information on atmospheric conditions such as cloud base height (CBH) and vertical frequency of cloud occurrence (CVF). This study presents the first comprehensive analysis of CBH and CVF derived using Vaisala CL51 ceilometers at two urban stations in Seoul, Korea, during a three-year period from January 2014 to December 2016. The average frequency of cloud occurrence detected by the ceilometers is 54.3%. It is found that the CL51 is better able to capture CBH as compared to another ceilometer CL31 at a nearby meteorological station because it could detect high clouds more accurately. Frequency distributions for CBH up to 13,000 m providing detailed vertical features with 500-m interval show 55% of CBHs below 2 km for aggregated CBHs. A bimodal frequency distribution was observed for three-layers CBHs. A monthly variation of CVF reveals that frequency concentration of lower clouds is found in summer and winter, and higher clouds more often detected in spring and autumn. Monthly distribution features of cloud occurrence and precipitation are depending on seasons and it might be easy to define their relationship due to higher degree of variability of precipitation than cloud occurrence. However, a fluctuation of cloud occurrence frequency in summer is similar to precipitation in trend, whereas clouds in winter are relatively frequent but precipitation is not accompanied. In addition, recent decrease of summer precipitation could be mostly explained by a decrease of cloud occurrence. Anomalous precipitation recorded sometimes is considerably related to corresponding cloud occurrence. The diurnal and daily variations of CBH and CVF from ceilometer observations and the analysis of microwave radiometer measurements for two typical cloudiness cases are also reviewed

  18. Projections of East Asian summer monsoon change at global warming of 1.5 and 2 °C

    Directory of Open Access Journals (Sweden)

    J. Liu

    2018-04-01

    Full Text Available Much research is needed regarding the two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 and 2 °C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM intensity change and associated precipitation change under both warming targets are explored in this study. The multimodel ensemble mean projections by 19 CMIP5 models show small increases in EASM intensity and general increases in summer precipitation at 1.5 and 2 °C warming, but with large multimodel standard deviations. Thus, a novel multimodel ensemble pattern regression (EPR method is applied to give more reliable projections based on the concept of emergent constraints, which is effective at tightening the range of multimodel diversity and harmonize the changes of different variables over the EASM region. Future changes projected by using the EPR method suggest decreased precipitation over the Meiyu belt and increased precipitation over the high latitudes of East Asia and Central China, together with a considerable weakening of EASM intensity. Furthermore, reduced precipitation appears over 30–40° N of East Asia in June and over the Meiyu belt in July, with enhanced precipitation at their north and south sides. These changes in early summer are attributed to a southeastward retreat of the western North Pacific subtropical high (WNPSH and a southward shift of the East Asian subtropical jet (EASJ, which weaken the moisture transport via southerly wind at low levels and alter vertical motions over the EASM region. In August, precipitation would increase over the high latitudes of East Asia with more moisture from the wetter area over the ocean in the east and decrease over Japan with westward extension of WNPSH. These monthly precipitation changes would finally contribute to a tripolar pattern of EASM precipitation change at 1.5 and 2 °C warming. Corrected EASM intensity exhibits a slight difference

  19. The paleoclimate context and future trajectory of extreme summer hydroclimate in eastern Australia

    Science.gov (United States)

    Cook, Benjamin I; Palmer, Jonathan G; Cook, Edward R; Turney, Chris S M; Allen, Kathryn; Fenwick, Pavla; O’Donnell, Alison; Lough, Janice M; Grierson, Pauline F; Ho, Michelle; Baker, Patrick J

    2018-01-01

    Eastern Australia recently experienced an intense drought (Millennium Drought, 2003–2009) and record-breaking rainfall and flooding (austral summer 2010–2011). There is some limited evidence for a climate change contribution to these events, but such analyses are hampered by the paucity of information on long-term natural variability. Analyzing a new reconstruction of summer (December–January–February) Palmer Drought Severity Index (the Australia–New Zealand Drought Atlas; ANZDA, 1500–2012 CE), we find moisture deficits during the Millennium Drought fall within the range of the last 500 years of natural hydroclimate variability. This variability includes periods of multi-decadal drought in the 1500s more persistent than any event in the historical record. However, the severity of the Millennium Drought, which was caused by autumn (March–April–May) precipitation declines, may be underestimated in the ANZDA because the reconstruction is biased towards summer and antecedent spring (September-October-November) precipitation. The pluvial in 2011, however, which was characterized by extreme summer rainfall faithfully captured by the ANZDA, is likely the wettest year in the reconstruction for Coastal Queensland. Climate projections (RCP 8.5 scenario) suggest that eastern Australia will experience long-term drying during the 21st century. While the contribution of anthropogenic forcing to recent extremes remains an open question, these projections indicate an amplified risk of multi-year drought anomalies matching or exceeding the intensity of the Millennium Drought. PMID:29780675

  20. Spatio-temporal trend analysis of precipitation in Guizhou province based on GIS technology

    Science.gov (United States)

    Wu, Jianfeng; Zhang, Fengtai; Pan, Yuanfen; Li, Wei; Cao, Guangjie; An, Youzhi

    2018-02-01

    Precipitation changes are closely related to human production and life. Based on the data of Guizhou Province from 1998 to 2012, the temporal and spatial characteristics of precipitation in Guizhou Province were analyzed from the annual, seasonal and monthly scales by linear trend analysis and ArcGIS kriging spatial interpolation. The results show that the annual precipitation is mainly concentrated in the summer, accounting for 47.6% of the year, followed by spring accounted for 26.9%, autumn accounted for 18.6% in winter accounted for 6.9%. In the time, the precipitation in the study area shows a decreasing trend in the annual scale, seasonal scale and July. The overall spatial precipitation distribution shows a decreasing trend from the east to the west. The precipitation also in the south is higher than the northern region.

  1. Constraining precipitation amount and distribution over cold regions using GRACE

    Science.gov (United States)

    Behrangi, A.; Reager, J. T., II; Gardner, A. S.; Fisher, J.

    2017-12-01

    Current quantitative knowledge on the amount and distribution of precipitation in high-elevation and high latitude regions is limited due to instrumental and retrieval shortcomings. Here we demonstrate how that satellite gravimetry (Gravity Recovery and Climate Experiment, GRACE) can be used to provide an independent estimate of monthly accumulated precipitation using mass balance. Results showed that the GRACE-based precipitation estimate has the highest agreement with most of the commonly used precipitation products in summer, but it deviates from them in cold months, when the other products are expected to have larger error. We also observed that as near surface temperature decreases products tend to underestimate accumulated precipitation retrieved from GRACE. The analysis performed using various products such as GPCP, GPCC, TRMM, and gridded station data over vast regions in high latitudes and two large endorheic basins in High Mountain Asia. Based on the analysis over High Mountain Asia it was found that most of the products capture about or less than 50% of the total precipitation estimated using GRACE in winter. Overall, GPCP showed better agreement with GRACE estimate than other products. Yet on average GRACE showed 30% more annual precipitation than GPCP in the study basin.

  2. Reproducibility of precipitation distributions over extratropical continental regions in the CMIP5

    Science.gov (United States)

    Hirota, Nagio; Takayabu, Yukari

    2013-04-01

    Reproducibility of precipitation distributions over extratropical continental regions in the CMIP5 Nagio Hirota1,2 and Yukari N. Takayabu2 (1) National Institute of Polar Research (NIPR) (2) Atmosphere and Ocean Research Institute (AORI), the University of Tokyo Reproducibility of precipitation distributions over extratropical continental regions by CMIP5 climate models in their historical runs are evaluated, in comparison with GPCP(V2.2), CMAP(V0911), daily gridded gauge data APHRODITE. Surface temperature, cloud radiative forcing, and atmospheric circulations are also compared with observations of CRU-UEA, CERES, and ERA-interim/ERA40/JRA reanalysis data. It is shown that many CMIP5 models underestimate and overestimate summer precipitation over West and East Eurasia, respectively. These precipitation biases correspond to moisture transport associated with a cyclonic circulation bias over the whole continent of Eurasia. Meanwhile, many models underestimate cloud over the Eurasian continent, and associated shortwave cloud radiative forcing result in a significant warm bias. Evaporation feedback amplify the warm bias over West Eurasia. These processes consistently explain the precipitation biases over the Erasian continent in summer. We also examined reproducibility of winter precipitation, but robust results are not obtained yet due to the large uncertainty in observation associated with the adjustment of snow measurement in windy condition. Better observational data sets are necessary for further model validation. Acknowledgment: This study is supported by the PMM RA of JAXA, Green Network of Excellence (GRENE) Program by the Ministry of Education, Culture, Sports, Science and Technology, Japan, and Environment Research and Technology Development Fund (A-1201) of the Ministry of the Environment, Japan.

  3. Decreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland

    Science.gov (United States)

    Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

    2011-09-01

    Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks.

  4. Decreased summer drought affects plant productivity and soil carbon dynamics in Mediterranean woodland

    Science.gov (United States)

    Cotrufo, M. F.; Alberti, G.; Inglima, I.; Marjanović, H.; Lecain, D.; Zaldei, A.; Peressotti, A.; Miglietta, F.

    2011-06-01

    Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. The throughfall manipulation experiment started in 2004 and we report data up to the 2009 growing season. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 50 % and 220 %, respectively, as compared to control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction of precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodland. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long term soil C stocks.

  5. Validation of the HIRHAM-Simulated Indian Summer Monsoon Circulation

    Directory of Open Access Journals (Sweden)

    Stefan Polanski

    2010-01-01

    Full Text Available The regional climate model HIRHAM has been applied over the Asian continent to simulate the Indian monsoon circulation under present-day conditions. The model is driven at the lateral and lower boundaries by European reanalysis (ERA40 data for the period from 1958 to 2001. Simulations with a horizontal resolution of 50 km are carried out to analyze the regional monsoon patterns. The focus in this paper is on the validation of the long-term summer monsoon climatology and its variability concerning circulation, temperature, and precipitation. Additionally, the monsoonal behavior in simulations for wet and dry years has been investigated and compared against several observational data sets. The results successfully reproduce the observations due to a realistic reproduction of topographic features. The simulated precipitation shows a better agreement with a high-resolution gridded precipitation data set over the central land areas of India and in the higher elevated Tibetan and Himalayan regions than ERA40.

  6. Classic Maya civilization collapse related to modest reduction in precipitation

    Science.gov (United States)

    Medina-Elizalde, M.; Rohling, E. J.

    2013-05-01

    The disintegration of the Classic Maya civilization during the Terminal Classic Period (TCP) in the Yucatán Peninsula (YP) and Central America was a complex process that occurred over a ~200-year interval and involved a catastrophic depopulation of the region. While it is well established that the civilization collapse coincided with widespread episodes of drought, their nature and severity remain enigmatic. We present a quantitative analysis that offers a coherent interpretation for four of the most detailed paleoclimate records of the event. The underlying processes driving the patterns and amplitudes of these environmental records during the TCP are evaluated with an isotope mass balance model set up for Lake Chichancanab, located in the YP. We use our hydrological-isotope model (i) to test whether the TCP droughts reflect a persistent summer season southern shift of the intertropical convergence zone and its associated belt of convective activity, away from the YP, and (2) to simulate the development of Lake Chichancanab as a function of weaker perturbations to summer precipitation as reflected by a stalagmite d18O-derived rainfall record from the YP. We conclude that the droughts occurring during the disintegration of the Maya civilization represented up to 40% reduction in annual precipitation, likely due to a reduction in summer season tropical cyclone frequency/intensity. Archaeological and Paleoclimatic records from the Yucatan Peninsula

  7. Robustness of Ensemble Climate Projections Analyzed with Climate Signal Maps: Seasonal and Extreme Precipitation for Germany

    Directory of Open Access Journals (Sweden)

    Susanne Pfeifer

    2015-05-01

    Full Text Available Climate signal maps can be used to identify regions where robust climate changes can be derived from an ensemble of climate change simulations. Here, robustness is defined as a combination of model agreement and the significance of the individual model projections. Climate signal maps do not show all information available from the model ensemble, but give a condensed view in order to be useful for non-climate scientists who have to assess climate change impact during the course of their work. Three different ensembles of regional climate projections have been analyzed regarding changes of seasonal mean and extreme precipitation (defined as the number of days exceeding the 95th percentile threshold of daily precipitation for Germany, using climate signal maps. Although the models used and the scenario assumptions differ for the three ensembles (representative concentration pathway (RCP 4.5 vs. RCP8.5 vs. A1B, some similarities in the projections of future seasonal and extreme precipitation can be seen. For the winter season, both mean and extreme precipitation are projected to increase. The strength, robustness and regional pattern of this increase, however, depends on the ensemble. For summer, a robust decrease of mean precipitation can be detected only for small regions in southwestern Germany and only from two of the three ensembles, whereas none of them projects a robust increase of summer extreme precipitation.

  8. Relating ring width of Mediterranean evergreen species to seasonal and annual variations of precipitation and temperature

    Science.gov (United States)

    Nijland, W.; Jansma, E.; Addink, E. A.; Domínguez Delmás, M.; de Jong, S. M.

    2011-05-01

    Plant growth in Mediterranean landscapes is limited by the typical summer-dry climate. Forests in these areas are only marginally productive and may be quite susceptible to modern climate change. To improve our understanding of forest sensitivity to annual and seasonal climatic variability, we use tree-ring measurements of two Mediterranean evergreen tree species: Quercus ilex L. and Arbutus unedo L. We sampled 34 stems of these species on three different types of substrates in the Peyne study area in southern France. The resulting chronologies were analysed in combination with 38 yr of monthly precipitation and temperature data to reconstruct the response of stem growth to climatic variability. Results indicate a strong positive response to May and June precipitation, as well as a significant positive influence of early-spring temperatures and a negative growth response to summer heat. Comparison of the data with more detailed productivity measurements in two contrasting years confirms these observations and shows a strong productivity limiting effect of low early-summer precipitation. The results show that tree-ring data from Q.ilex and A.unedo can provide valuable information about the response of these tree species to climate variability, improving our ability to predict the effects of climate change in Mediterranean ecosystems.

  9. Seasonal fluctuations of organophosphate concentrations in precipitation and storm water runoff.

    Science.gov (United States)

    Regnery, Julia; Püttmann, Wilhelm

    2010-02-01

    To investigate seasonal fluctuations and trends of organophosphate (flame retardants, plasticizers) concentrations in rain and snow, precipitation samples were collected in 2007-2009 period at a densely populated urban sampling site and two sparsely populated rural sampling sites in middle Germany. In addition, storm water runoff was sampled from May 2008 to April 2009 at an urban storm water holding tank (SWHT). Samples were analyzed for tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-1-methylethyl) phosphate (TCPP), tris(1,3-dichloro-2-propyl) phosphate (TDCP), tris(2-butoxyethyl) phosphate (TBEP), tri-iso-butyl phosphate (TiBP), and tri-n-butyl phosphate (TnBP) by gas chromatography-mass spectrometry after solid phase extraction. Among the six analyzed organophosphates (OPs), TCPP dominated in all precipitation and SWHT water samples with maximum concentrations exceeding 1000ngL(-1). For all analytes, no seasonal trends were observed at the urban precipitation sampling site, although atmospheric photooxidation was expected to reduce particularly concentrations of non-chlorinated OPs during transport from urban to remote areas in summer months with higher global irradiation. In the SWHT a seasonal trend with decreasing concentrations in summer/autumn is evident for the non-chlorinated OPs due to in-lake degradation but not for the chlorinated OPs. Furthermore, an accumulation of OPs deposited in SWHTs was observed with concentrations often exceeding those observed in wet precipitation. Median concentrations of TCPP (880ngL(-1)), TDCP (13ngL(-1)) and TBEP (77ngL(-1)) at the SWHT were more than twice as high as median concentrations measured at the urban precipitation sampling site (403ngL(-1), 5ngL(-1), and 21ngL(-1) respectively).

  10. Climatic Suitability of Growing Summer Squash (Cucurbita pepo L. as a Medicinal Plant in Iran

    Directory of Open Access Journals (Sweden)

    Mohammad BANNAYAN

    2011-05-01

    Full Text Available Diversification of production by including a broader range of plant species, can significantly contribute to improve health and nutrition, livelihoods, household food security and ecological sustainability. Exploring the climate impact on any given crop is one of the first priorities to find new suitable areas for production and management of new crops. Summer squash (Cucurbita pepo L. is an economically valuable plant with various medicinal potentials. In order to investigate summer squash cultivation feasibility under Irans climate, three main agricultural regions (Azerbaijan, Khorasan and central part of Iran (Fars and Isfahan were selected. These regions suitability for summer squash cultivation were evaluated by considering three vital climate variables encompass temperature, precipitation, and sunshine hours. These regions show distinct and representative climatic conditions of Iran. Annual and growing season average of maximum, minimum, mean temperature, precipitation, and sunshine hours were calculated (May-September for all locations with 44 years historical weather data (1961-2005 for 8 locations (Oroomieh, Tabriz, Khoy, Mashhad, Sabzevar, Birjand, Shiraz and Isfahan, 39 years (1966-2005 for 2 locations (Kashan and Fassa, 28 years (1977-2005 for 4 locations (Ardebil, Abadeh, Bojnurd and Shargh Isfahan and 20 years (1985-2005 for 9 locations (Mahabad, Sarab, Maragheh, Parsabad, Khalkhal, Ferdous, Ghaen, Kashmar and Sarakhs. Climatic demands of summer squash were determined by four years field studies at four different locations in Iran. Our results showed Azerbaijan region has a suitable condition for this crop cultivation especially from precipitation and temperature perspectives. Central part of Iran and Khorasan were also found as partly suitable locations however as they are near to deserts with hotter and drier climate, there might be some other crops considered as priorities in these areas.

  11. Climatic Suitability of Growing Summer Squash (Cucurbita pepo L. as a Medicinal Plant in Iran

    Directory of Open Access Journals (Sweden)

    Mohammad BANNAYAN

    2011-05-01

    Full Text Available Diversification of production by including a broader range of plant species, can significantly contribute to improve health and nutrition, livelihoods, household food security and ecological sustainability. Exploring the climate impact on any given crop is one of the first priorities to find new suitable areas for production and management of new crops. Summer squash (Cucurbita pepo L. is an economically valuable plant with various medicinal potentials. In order to investigate summer squash cultivation feasibility under Iran�s climate, three main agricultural regions (Azerbaijan, Khorasan and central part of Iran (Fars and Isfahan were selected. These regions suitability for summer squash cultivation were evaluated by considering three vital climate variables encompass temperature, precipitation, and sunshine hours. These regions show distinct and representative climatic conditions of Iran. Annual and growing season average of maximum, minimum, mean temperature, precipitation, and sunshine hours were calculated (May-September for all locations with 44 years historical weather data (1961-2005 for 8 locations (Oroomieh, Tabriz, Khoy, Mashhad, Sabzevar, Birjand, Shiraz and Isfahan, 39 years (1966-2005 for 2 locations (Kashan and Fassa, 28 years (1977-2005 for 4 locations (Ardebil, Abadeh, Bojnurd and Shargh Isfahan and 20 years (1985-2005 for 9 locations (Mahabad, Sarab, Maragheh, Parsabad, Khalkhal, Ferdous, Ghaen, Kashmar and Sarakhs. Climatic demands of summer squash were determined by four years field studies at four different locations in Iran. Our results showed Azerbaijan region has a suitable condition for this crop cultivation especially from precipitation and temperature perspectives. Central part of Iran and Khorasan were also found as partly suitable locations however as they are near to deserts with hotter and drier climate, there might be some other crops considered as priorities in these areas.

  12. Geomagnetic control of polar mesosphere summer echoes

    Directory of Open Access Journals (Sweden)

    J. Bremer

    2000-02-01

    Full Text Available Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N, 16.0°E from 1994 until 1997 polar mesosphere summer echoes (PMSE have been investigated in dependence on geomagnetic K indices derived at the Auroral Observatory Tromsø (69.66°N, 18.94°E. During night-time and morning hours a significant correlation between the signal-to-noise ratio (SNR of the radar results and the geomagnetic K indices could be detected with a maximum correlation near midnight. The correlation becomes markedly smaller in the afternoon and early evening hours with a minimum near 17 UT. This diurnal variation is in reasonable agreement with riometer absorption at Ivalo (68.55°N, 27.28°E and can be explained by the diurnal variation of ionization due to precipitating high energetic particles. Therefore, a part of the diurnal PMSE variation is caused by this particle precipitation. The variability of the solar EUV variation, however, has no significant influence on the PMSE during the observation period.Keywords: Ionosphere (auroral ionosphere - Magnetospheric physics (energetic particles, precipitating - Radio science (remote sensing

  13. Nitrogen deposition in precipitation to a monsoon-affected eutrophic embayment: Fluxes, sources, and processes

    Science.gov (United States)

    Wu, Yunchao; Zhang, Jingping; Liu, Songlin; Jiang, Zhijian; Arbi, Iman; Huang, Xiaoping; Macreadie, Peter Ian

    2018-06-01

    Daya Bay in the South China Sea (SCS) has experienced rapid nitrogen pollution and intensified eutrophication in the past decade due to economic development. Here, we estimated the deposition fluxes of nitrogenous species, clarified the contribution of nitrogen from precipitation and measured ions and isotopic composition (δ15N and δ18O) of nitrate in precipitation in one year period to trace its sources and formation processes among different seasons. We found that the deposition fluxes of total dissolved nitrogen (TDN), NO3-, NH4+, NO2-, and dissolved organic nitrogen (DON) to Daya Bay were 132.5, 64.4 17.5, 1.0, 49.6 mmol m-2•yr-1, respectively. DON was a significant contributor to nitrogen deposition (37% of TDN), and NO3- accounted for 78% of the DIN in precipitation. The nitrogen deposition fluxes were higher in spring and summer, and lower in winter. Nitrogen from precipitation contributed nearly 38% of the total input of nitrogen (point sources input and dry and wet deposition) in Daya Bay. The δ15N-NO3- abundance, ion compositions, and air mass backward trajectories implicated that coal combustion, vehicle exhausts, and dust from mainland China delivered by northeast monsoon were the main sources in winter, while fossil fuel combustion (coal combustion and vehicle exhausts) and dust from PRD and southeast Asia transported by southwest monsoon were the main sources in spring; marine sources, vehicle exhausts and lightning could be the potential sources in summer. δ18O results showed that OH pathway was dominant in the chemical formation process of nitrate in summer, while N2O5+ DMS/HC pathways in winter and spring.

  14. Decoupled warming and monsoon precipitation in East Asia over the last deglaciation

    NARCIS (Netherlands)

    Peterse, F.; Prins, M.A.; Beets, C.J.; Troelstra, S.R.; Zheng, H.B.; Gu, Z.Y.; Schouten, S.; Sinninghe Damsté, J.S.

    2011-01-01

    Our understanding of the continental climate development in East Asia is mainly based on loess-paleosol sequences and summer monsoon precipitation reconstructions based on oxygen isotopes (delta O-18) of stalagmites from several Chinese caves. Based on these records, it is thought that East Asian

  15. Impact of atmospheric blocking events on the decrease of precipitation in the Selenga River basin

    Science.gov (United States)

    Antokhina, O.; Antokhin, P.; Devyatova, E.; Vladimir, M.

    2017-12-01

    The periods of prolonged deficiency of hydropower potential (HP) of Angara cascade hydroelectric plant related to low-inflow in Baikal and Angara basins threaten to energy sector of Siberia. Since 1901 was recorded five such periods. Last period began in 1996 and continues today. This period attracts the special attention, because it is the longest and coincided with the observed climate change. In our previous works we found that the reason of observed decrease of HP is low water content of Selenga River (main river in Baikal Basin). We also found that the variations of Selenga water-content almost totally depend of summer atmospheric precipitation. Most dramatic decrease of summer precipitation observed in July. In turn, precipitation in July depends on location and intensity of atmospheric frontal zone which separates mid-latitude circulation and East Asia monsoon system. Recently occur reduction this frontal zone and decrease of East Asia summer monsoon intensity. We need in the understanding of the reasons leading to these changes. In the presented work we investigate the influence of atmospheric blocking over Asia on the East Asian summer monsoon circulation in the period its maximum (July). Based on the analysis of large number of blocking events we identified the main mechanisms of blocking influence on the monsoon and studied the properties of cyclones formed by the interaction of air masses from mid latitude and tropics. It turned out that the atmospheric blockings play a fundamental role in the formation of the East Asia monsoon moisture transport and in the precipitation anomalies redistribution. In the absence of blockings over Asia East Asian monsoon moisture does not extend to the north, and in the presence of blockings their spatial configuration and localization completely determines the precipitation anomalies configuration in the northern part of East Asia. We also found that the weakening monsoon circulation in East Asia is associated with

  16. Trend analysis of air temperature and precipitation time series over Greece: 1955-2010

    Science.gov (United States)

    Marougianni, G.; Melas, D.; Kioutsioukis, I.; Feidas, H.; Zanis, P.; Anandranistakis, E.

    2012-04-01

    In this study, a database of air temperature and precipitation time series from the network of Hellenic National Meteorological Service has been developed in the framework of the project GEOCLIMA, co-financed by the European Union and Greek national funds through the Operational Program "Competitiveness and Entrepreneurship" of the Research Funding Program COOPERATION 2009. Initially, a quality test was applied to the raw data and then missing observations have been imputed with a regularized, spatial-temporal expectation - maximization algorithm to complete the climatic record. Next, a quantile - matching algorithm was applied in order to verify the homogeneity of the data. The processed time series were used for the calculation of temporal annual and seasonal trends of air temperature and precipitation. Monthly maximum and minimum surface air temperature and precipitation means at all available stations in Greece were analyzed for temporal trends and spatial variation patterns for the longest common time period of homogenous data (1955 - 2010), applying the Mann-Kendall test. The majority of the examined stations showed a significant increase in the summer maximum and minimum temperatures; this could be possibly physically linked to the Etesian winds, because of the less frequent expansion of the low over the southeastern Mediterranean. Summer minimum temperatures have been increasing at a faster rate than that of summer maximum temperatures, reflecting an asymmetric change of extreme temperature distributions. Total annual precipitation has been significantly decreased at the stations located in western Greece, as well as in the southeast, while the remaining areas exhibit a non-significant negative trend. This reduction is very likely linked to the positive phase of the NAO that resulted in an increase in the frequency and persistence of anticyclones over the Mediterranean.

  17. A savanna response to precipitation intensity.

    Directory of Open Access Journals (Sweden)

    Ryan S Berry

    Full Text Available As the atmosphere warms, precipitation events are becoming less frequent but more intense. A three-year experiment in Kruger National Park, South Africa, found that fewer, more intense precipitation events encouraged woody plant encroachment. To test whether or not these treatment responses persisted over time, here, we report results from all five years of that experiment. Grass growth, woody plant growth, total fine root number and area and hydrologic tracer uptake by grasses and woody plants were measured in six treated plots (8 m by 8 m and six control plots. Treatment effects on soil moisture were measured continuously in one treated and one control plot. During the fourth year, increased precipitation intensity treatments continued to decrease water flux in surface soils (0-10 cm, increase water flux in deeper soils (20+ cm, decrease grass growth and increase woody plant growth. Greater root numbers at 20-40 cm and greater woody plant uptake of a hydrological tracer from 45-60 cm suggested that woody plants increased growth by increasing root number and activity (but not root area in deeper soils. During the fifth year, natural precipitation events were large and intense so treatments had little effect on precipitation intensity or plant available water. Consistent with this effective treatment removal, there was no difference in grass or woody growth rates between control and treated plots, although woody plant biomass remained higher in treated than control plots due to treatment effects in the previous four years. Across the five years of this experiment, we found that 1 small increases in precipitation intensity can result in large increases in deep (20-130 cm soil water availability, 2 plant growth responses to precipitation intensity are rapid and disappear quickly, and 3 because woody plants accumulate biomass, occasional increases in precipitation intensity can result in long-term increases in woody plant biomass (i.e., shrub

  18. Inter-Comparison and Evaluation of Remote Sensing Precipitation Products over China from 2005 to 2013

    Directory of Open Access Journals (Sweden)

    Qiaolin Zeng

    2018-01-01

    Full Text Available Precipitation is a key aspect of the climate system. In this paper, the dependability of five satellite precipitation products (TRMM [Tropical Rainfall Measuring Mission] 3BV42, PERSIANN [Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks] CDR, GSMaP [Global Satellite Mapping of Precipitation] RENALYSIS, CMORPH [Climate Prediction Center’s morphing technique] BLD and CMORPH_RAW were compared with in situ measurements over China for the period of 2005 to 2013. To completely evaluate these precipitation products, the annual, seasonal and monthly precipitation averages were calculated. Overall, the Huaihe River and Qinlin mountains are shown to have heavy precipitation to the southeast and lighter precipitation to the northwest. The comparison results indicate that Gauge correction (CMORPH_BLD improves the quality of the original satellite products (CMORPH_RAW, resulting in the higher correlation coefficient (CC, the low relative bias (BIAS and root mean square error (RMSE. Over China, the GSMaP_RENALYSIS outperforms other products and shows the highest CC (0.91 and lowest RMSE (0.85 mm/day and all products except for PERSIANN_CDR exhibit underestimation. GSMaP_RENALYSIS gives the highest of probability of detection (81%, critical success index (63% and lowest false alarm ratio (36% while TRMM3BV42 gives the highest of frequency bias index (1.00. Over Tibetan Plateau, CMORPH_RAW demonstrates the poorest performance with the biggest BIAS (4.2 mm/month and lowest CC (0.22 in December 2013. GSMaP_RENALYSIS displays quite consistent with in situ measurements in summer. However, GSMaP_RENALYSIS and CMORPH_RAW underestimate precipitation over South China. CMORPH_BLD and TRMM3BV42 show consistent with high CC (>0.8 but relatively large RMSE in summer.

  19. Characterization of precipitation features over CONUS derived from satellite, radar, and rain gauge datasets (2002-2012)

    Science.gov (United States)

    Prat, O. P.; Nelson, B. R.

    2013-12-01

    We use a suite of quantitative precipitation estimates (QPEs) derived from satellite, radar, surface observations, and models to derive precipitation characteristics over CONUS for the period 2002-2012. This comparison effort includes satellite multi-sensor datasets of TMPA 3B42, CMORPH, and PERSIANN. The satellite based QPEs are compared over the concurrent period with the NCEP Stage IV product, which is a near real time product providing precipitation data at the hourly temporal scale gridded at a nominal 4-km spatial resolution. In addition, remotely sensed precipitation datasets are compared with surface observations from the Global Historical Climatology Network (GHCN-Daily) and from the PRISM (Parameter-elevation Regressions on Independent Slopes Model), which provides gridded precipitation estimates that are used as a baseline for multi-sensor QPE products comparison. The comparisons are performed at the annual, seasonal, monthly, and daily scales with focus on selected river basins (Southeastern US, Pacific Northwest, Great Plains). While, unconditional annual rain rates present a satisfying agreement between all products, results suggest that satellite QPE datasets exhibit important biases in particular at higher rain rates (≥4 mm/day). Conversely, on seasonal scales differences between remotely sensed data and ground surface observations can be greater than 50% and up to 90% for low daily accumulation (≤1 mm/day) such as in the Western US (summer) and Central US (winter). The conditional analysis performed using different daily rainfall accumulation thresholds (from low rainfall intensity to intense precipitation) shows that while intense events measured at the ground are infrequent (around 2% for daily accumulation above 2 inches/day), remotely sensed products displayed differences from 20-50% and up to 90-100%. A discussion on the impact of differing spatial and temporal resolutions with respect to the datasets ability to capture extreme

  20. Hot Central-European summer of 2013 in a long-term context

    Czech Academy of Sciences Publication Activity Database

    Lhotka, Ondřej; Kyselý, Jan

    2015-01-01

    Roč. 35, č. 14 (2015), s. 4399-4407 ISSN 0899-8418 R&D Projects: GA ČR GAP209/10/2265 Institutional support: RVO:68378289 Keywords : summer of 2013 * climate variability * temperature records * heat waves * effective precipitation * Central Europe Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.609, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/joc.4277/abstract

  1. Distribution of tritium in water vapour and precipitation around Wolsung nuclear power plant.

    Science.gov (United States)

    Chae, Jung-Seok; Lee, Sang-Kuk; Kim, Yongjae; Lee, Jung-Min; Cho, Heung-Joon; Cho, Yong-Woo; Yun, Ju-Yong

    2011-07-01

    The distribution of tritium in water vapour and precipitation with discharge of tritiated water vapour and meteorological factors was studied around the Wolsung nuclear power plant (NPP) site during the period 2004-2008. The tritium concentrations in atmospheric water vapour and precipitation had a temporal variation with relatively high values in the early summer. Spatial distribution of tritium concentrations was affected by various factors such as distance from the NPP site, wind direction, tritium discharge into the atmosphere and atmospheric dispersion factor. The annual mean concentrations of atmospheric HTO and precipitation were correlated with the amount of gaseous tritium released from the Wolsung NPP. The tritium concentrations in precipitation decrease exponentially with an increase of the distance from the Wolsung NPP site.

  2. Rainfall variations over the Bay of Bengal and southern Tibetan Plateau and their connections with different tropical forcing during the early and middle summer

    Science.gov (United States)

    Wang, Z.; Yang, S.

    2016-12-01

    Strong rainfall always occurs in the South Asia region during the summer monsoon time (May-September), especially over the Bay of Bengal (BOB) and southern Tibetan Plateau (STP). The latent heating associated with such rainfall drives large-scale circulation and further influences weather and climate anomalies over the world. Few studies have focused on the intraseasonal difference of the rainfall interannual variations. Generally, two precipitation centers appear over the BOB and STP respectively, which are corresponding to the southern and northern upward branches of the South Asian summer monsoon. Our results indicate that the interannual variability of precipitation over the BOB is consistent with that over the STP during the early summer (May-June), but it is contrary during the midsummer (July-August). In early summer, precipitation over the BOB and STP is mainly regulated by the sea surface temperature (SST) anomalies in tropical eastern Pacific (corresponding to the ENSO). Warm SST anomalies in the eastern Pacific weaken upward motion and further precipitation over the BOB and STP through the modulation of zonal walker circulation. However, the tropical forcing exists over the western Maritime Continent (WMC) during midsummer, which induces the contrary variations of rainfall over the BOB and STP. Warm WMC SST anomalies lead to an anticyclone over the BOB, which is unfavourable to the BOB rainfall. While the southwesterlies at the northwest of that anticyclone favor moisture transport to the Tibetan Plateau and thus an enhancement in rainfall over the STP.

  3. Forecasting Monsoon Precipitation Using Artificial Neural Networks

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper explores the application of Artificial Intelligent (AI) techniques for climate forecast. It pres ents a study on modelling the monsoon precipitation forecast by means of Artificial Neural Networks (ANNs). Using the historical data of the total amount of summer rainfall over the Delta Area of Yangtze River in China, three ANNs models have been developed to forecast the monsoon precipitation in the corre sponding area one year, five-year, and ten-year forward respectively. Performances of the models have been validated using a 'new' data set that has not been exposed to the models during the processes of model development and test. The experiment results are promising, indicating that the proposed ANNs models have good quality in terms of the accuracy, stability and generalisation ability.

  4. TEMPERATURE AND PRECIPITATION CHANGES IN TÂRGU-MURES (ROMANIA FROM PERIOD 1951-2010

    Directory of Open Access Journals (Sweden)

    O.Rusz

    2012-03-01

    Full Text Available Temperature and precipitation changes in Târgu Mures (Romania from period 1951-2010. The analysis was made based upon meteorological data collected at Târgu Mures meteorological station (Romania, Mures county, lat. 46°32’N, lon. 24°32’E, elevation 308 m, between 1951 and 2010. Several climatic parameters were studied (for instance, annual and monthly mean temperature, maximum precipitation in 24 hours, number of summer days, etc. Detected inhomogeneities are not related to instrumental causes or geographical relocation. Positive and statistical significant trends (Mann-Kendall test are indicated for: mean annual temperatures, mean temperatures of warm months, average of the maximum and minimum temperatures (annual and warm months data, number of days with mean temperature between 20.1-25.0 °C, number of days with precipitation ≥0 mm, and for all parameters of precipitation of September. The sequential version of Mann-Kendall test show a beginning of a trend in 1956 in the case of mean temperature (at same, the two and three parts regression denote this year like a moment of change, years 1965 and 1992 in the case of annual amount of precipitation. CUSUM charts indicate occurs of changes points at 1988, 2005, 2009 (mean temperature respectively at 1989, 2004 (precipitation, and at 1968, 1992 (daily temperature range. Tendencies of overlapped time series reveal a more important increase at the end of period (mainly for mean temperature. The analysis with RClimDex show for 5 extreme climate indices a significant trend: positive for summer days, warm nights, warm spell duration indicator and negative for cold nights and cold days.

  5. Factors controlling stable isotope composition of European precipitation

    International Nuclear Information System (INIS)

    Rozanski, K.; Sonntag, C.; Muennich, K.O.

    1982-01-01

    The seasonal and spatial variations of stable isotope ratios in present day European precipitation are simulated with a simple multibox model of the mean west-east horizontal transport of the atmospheric water vapour across the European continent. Isotope fractionation during the formation of precipitation leads to an increasing depletion of heavy isotopes in the residual air moisture as it moves towards the centre of the continent. This isotopic depletion is partly compensated, particularly in summer, by evapotranspiration, which is assumed to transfer soil water into the atmosphere without isotope fractionation. The model estimates are based on horizontal water vapour flux data, varying seasonally between 88 and 130 kg m -1 s -1 for the Atlantic coast region, and on the monthly precipitation, evapotranspiration and surface air temperature data available for various locations in Europe. Both continental and seasonal temperature effects observed in the stable isotope composition of European precipitation are fairly well reproduced by the model. The calculations show that the isotopic composition of local precipitation is primarily controlled by regional scale processes, i.e. by the water vapour transport patterns into the continent, and by the average precipitation-evapotranspiration history of the air masses precipitating at a given place. Local parameters such as the surface and/or cloud base temperature or the amount of precipitation modify the isotope ratios only slightly. Implications of the model predictions for the interpretation of stable isotope ratios in earlier periods as they are preserved in ice cores and in groundwater are also discussed. (Auth.)

  6. Summer Session: A Time for Innovation

    Science.gov (United States)

    Mola, Monty

    2013-05-01

    Summer is almost here (at least for those of us who teach semesters). Many of us are taking a well-deserved break to spend time with our families, conduct research, travel, and myriad other activities. Some of us, however, will be teaching summer school. For those of us lucky enough to be teaching this summer, we have one suggestion: Be bold! Summer is the ideal time to try something new with your teaching. We have known for some time that alternative pedagogies and engaging teaching strategies can be more effective than traditional lectures as student learning environments. However, even with headlines in The Washington Post proclaiming that the lecture is dead,2 inroads of physics education research-based curricula have been slow to diffuse into the classrooms for the greater population of college physics instructors.3 Many instructors of traditional physics courses see the use of research-based instructional strategies (RBIS) as desirable but risky and time consuming.3 Assuming a traditional physics course structure, both the where and the when each component takes place can also limit the types of engaging pedagogies used.4

  7. The inter-decadal correlation between summer arctic oscillation and summer drought and moist characteristic of northwest China

    Science.gov (United States)

    Wang, Pengxiang; Zheng, Youfei; Sun, Landong; Ren, Zhenhe; He, Jinhai; Zhang, Qiang

    2007-09-01

    In the context of 1960~2003 summertime rainfall and small-sized pan evaporations from 131 stations distributed over NW China covering Xinjiang, Qinghai, Gansu, Ningxia, Shaanxi as well as western Nei Mongolia, and Arctic Oscillation Indices (AOI) we define a homogenized index for aridity or wetness feature, with which to examine the relations between AOI and NW China aridity-wetness regime, indicating their noticeable relations on an interdecadal basis. It is found that during the decade of summer Arctic oscillation stronger than mean, the sea level pressure field shows positive (negative) anomalies over Asian landmass, a stronger anticyclonic anomaly circulation appears at 700 hPa over Lake Baikal and to the south, westerly (northerly) departure emerges in the westerly (monsoon) portion of NW China, as well as over NW China there appears a structure with a low in the west and a high in the east at the 500 hPa height field, suggestive of east-Asian summer monsoon weaker than normal such that westerly flows prevail in the westerly zone of NW China, leading to rainfall more than mean for a wetter climate while in its monsoon area the northerly winds are dominant, with precipitation less than normal, resulting in a climate drier in comparison to mean and v.v. for the decade with summer AO weaker than normal.

  8. A high-resolved record of the Asian Summer Monsoon from Dongge Cave, China for the past 1200 years

    Science.gov (United States)

    Zhao, Kan; Wang, Yongjin; Edwards, R. Lawrence; Cheng, Hai; Liu, Dianbing; Kong, Xinggong

    2015-08-01

    Two annually-laminated and 230Th-dated stalagmite oxygen isotope (δ18O) records from Dongge Cave, China, provided a high-resolution Asian Summer Monsoon (ASM) history for the past 1200 years. A close similarity between annual band thickness and stable isotope analyses (δ13C and δ18O) suggests the calcite δ18O is most likely a proxy associated with ASM precipitation. The two duplicated stalagmite δ18O records show that the ASM varies at a periodicity of ∼220 years, concordant with a dominant cycle of solar activity. A period of strong ASM activity occurred during the Spörer Minimum (1450-1550 A.D.), followed by a striking drop circa 1580 A.D., potentially consistent with the social unrest in the final decades of China's Ming Dynasty (1368-1644 A.D.). Centennial-scale changes in ASM precipitation over the last millennium match well with changes in tropical Atlantic sea surface temperatures (SSTs) and South American summer monsoon precipitation. Our findings suggest that variations in low-latitude monsoon precipitation are probably driven by shifts in the mean position of the intertropical convergence zone (ITCZ), which is further mediated by solar activity and tropical SSTs.

  9. TREND OF PRECIPITATION VARIATION IN HUBEI PROVINCE SINCE THE 1960S

    Institute of Scientific and Technical Information of China (English)

    CHEN Zheng-hong; QIN Jun

    2003-01-01

    Through linear regression analysis to the trend of annual, seasonal and monthly precipitation of 72 meteorological stations in Hubei Province from 1961 to 1995, it is revealed that: l) annual precipitation was increasing by 61.0mm/10a in the eastern part of Hubei (112°E as a dividing line) and decreasing by 34.9mm/10a in the western part; 2) precipitation in winter and summer (January, February, March, June and July) was increasing in almost whole province which usually with non-uniformity of precipitation distribution from the south to the north. The precipitation in spring, autumn and winter (April, September, November and December) was decreasing in most of the areas which usually with non-uniformity of precipitation distribution from the east to the west. March and December were transition periods between two spatial distribution pattems mentioned above; 3) the eastem part of Hubei has beome one of precipitation increasing centers in China. The results was consistent with the trend that more frequent flood and drought events happened in Hubei Province which are more different in spatial and temporal scales.

  10. Satellite precipitation estimation over the Tibetan Plateau

    Science.gov (United States)

    Porcu, F.; Gjoka, U.

    2012-04-01

    Precipitation characteristics over the Tibetan Plateau are very little known, given the scarcity of reliable and widely distributed ground observation, thus the satellite approach is a valuable choice for large scale precipitation analysis and hydrological cycle studies. However,the satellite perspective undergoes various shortcomings at the different wavelengths used in atmospheric remote sensing. In the microwave spectrum often the high soil emissivity masks or hides the atmospheric signal upwelling from light-moderate precipitation layers, while low and relatively thin precipitating clouds are not well detected in the visible-infrared, because of their low contrast with cold and bright (if snow covered) background. In this work an IR-based, statistical rainfall estimation technique is trained and applied over the Tibetan Plateau hydrological basin to retrive precipitation intensity at different spatial and temporal scales. The technique is based on a simple artificial neural network scheme trained with two supervised training sets assembled for monsoon season and for the rest of the year. For the monsoon season (estimated from June to September), the ground radar precipitation data for few case studies are used to build the training set: four days in summer 2009 are considered. For the rest of the year, CloudSat-CPR derived snowfall rate has been used as reference precipitation data, following the Kulie and Bennartz (2009) algorithm. METEOSAT-7 infrared channels radiance (at 6.7 and 11 micometers) and derived local variability features (such as local standard deviation and local average) are used as input and the actual rainrate is obtained as output for each satellite slot, every 30 minutes on the satellite grid. The satellite rainrate maps for three years (2008-2010) are computed and compared with available global precipitation products (such as C-MORPH and TMPA products) and with other techniques applied to the Plateau area: similarities and differences are

  11. Decreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland

    Directory of Open Access Journals (Sweden)

    M. F. Cotrufo

    2011-09-01

    Full Text Available Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR. Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks.

  12. Assessing the utility of meteorological drought indices in monitoring summer drought based on soil moisture in Chongqing, China

    Science.gov (United States)

    Chen, Hui; Wu, Wei; Liu, Hong-Bin

    2018-04-01

    Numerous drought indices have been developed to analyze and monitor drought condition, but they are region specific and limited by various climatic conditions. In southwest China, summer drought mainly occurs from June to September, causing destructive and profound impact on agriculture, society, and ecosystems. The current study assesses the availability of meteorological drought indices in monitoring summer drought in this area at 5-day scale. The drought indices include the relative moisture index ( M), the standardized precipitation index (SPI), the standardized precipitation evapotranspiration index (SPEI), the composite index of meteorological drought (CIspi), and the improved composite index of meteorological drought (CIwap). Long-term daily precipitation and temperature from 1970 to 2014 are used to calculate 30-day M ( M 30), SPI (SPI30), SPEI (SPEI30), 90-day SPEI (SPEI90), CIspi, and CIwap. The 5-day soil moisture observations from 2010 to 2013 are applied to assess the performance of these drought indices. Correlation analysis, overall accuracy, and kappa coefficient are utilized to investigate the relationships between soil moisture and drought indices. Correlation analysis indicates that soil moisture is well correlated with CIwap, SPEI30, M 30, SPI30, and CIspi except SPEI90. Moreover, drought classifications identified by M 30 are in agreement with that of the observed soil moisture. The results show that M 30 based on precipitation and potential evapotranspiration is an appropriate indicator for monitoring drought condition at a finer scale in the study area. According to M 30, summer drought during 1970-2014 happened in each year and showed a slightly upward tendency in recent years.

  13. Can frequent precipitation moderate drought impact on peatmoss carbon uptake in northern peatlands?

    NARCIS (Netherlands)

    Nijp, J.J.; Limpens, J.; Metselaar, K.; Zee, van der S.E.A.T.M.; Berendse, F.; Robroek, B.J.M.

    2015-01-01

    Northern peatlands represent a large global carbon store that potentially can be destabilised by summer water table drawdown. Precipitation can moderate negative impacts of water table drawdown by rewetting peatmoss (Sphagnum spp.), the ecosystems’ key species. Yet, the frequency for such rewetting

  14. CERN-Fermilab summer school is smash hit

    CERN Multimedia

    2006-01-01

    A new joint CERN-Fermilab summer school is proving more popular than the organizers ever imagined. Interest in the first CERN-Fermilab Hadron Collider Physics Summer School, to be held at Fermilab on 9-18 August, has proved far greater than anyone anticipated, with 300 applications for the planned 100 places. In response, the Organizing Committee, led by Fermilab's Jeffrey Appel and Bogdan Dobrescu, has had to increase the class size to nearly 150 participants. 'The success of this initiative, with an unexpectedly large number of applications, shows both the great anticipation that exists in the world for the start up of the LHC, and the need for greater educational support to enable the hundreds of young researchers to get ready for a full and prompt exploitation of the LHC data,' explains CERN's Michelangelo Mangano, who is a member of the International Advisory Committee (IAC) for the school. 'Fulfilling the expectations of the students will be a great challenge, which we are all eager to tackle.' Fabiol...

  15. Forecasting sagebrush ecosystem components and greater sage-grouse habitat for 2050: learning from past climate patterns and Landsat imagery to predict the future

    Science.gov (United States)

    Homer, Collin G.; Xian, George Z.; Aldridge, Cameron L.; Meyer, Debra K.; Loveland, Thomas R.; O'Donnell, Michael S.

    2015-01-01

    urophasianus) habitat models to evaluate the effects of potential climate-induced habitat change. Under the 2050 IPCC A1B scenario, 11.6% of currently identified nesting habitat was lost, and 0.002% of new potential habitat was gained, with 4% of summer habitat lost and 0.039% gained. Our results demonstrate the successful ability of remote sensing based sagebrush components, when coupled with precipitation, to forecast future component response using IPCC precipitation scenarios. Our approach also enables future quantification of greater sage-grouse habitat under different precipitation scenarios, and provides additional capability to identify regional precipitation influence on sagebrush component response.

  16. Modeling of Future Changes in Seasonal Snowpack and Impacts on Summer Low Flows in Alpine Catchments

    Science.gov (United States)

    Jenicek, Michal; Seibert, Jan; Staudinger, Maria

    2018-01-01

    It is expected that an increasing proportion of the precipitation will fall as rain in alpine catchments in the future. Consequently, snow storage is expected to decrease, which, together with changes in snowmelt rates and timing, might cause reductions in spring and summer low flows. The objectives of this study were (1) to simulate the effect of changing snow storage on low flows during the warm seasons and (2) to relate drought sensitivity to the simulated snow storage changes at different elevations. The Swiss Climate Change Scenarios 2011 data set was used to derive future changes in air temperature and precipitation. A typical bucket-type catchment model, HBV-light, was applied to 14 mountain catchments in Switzerland to simulate streamflow and snow in the reference period and three future periods. The largest relative decrease in annual maximum SWE was simulated for elevations below 2,200 m a.s.l. (60-75% for the period 2070-2099) and the snowmelt season shifted by up to 4 weeks earlier. The relative decrease in spring and summer minimum runoff that was caused by the relative decrease in maximum SWE (i.e., elasticity), reached 40-90% in most of catchments for the reference period and decreased for the future periods. This decreasing elasticity indicated that the effect of snow on summer low flows is reduced in the future. The fraction of snowmelt runoff in summer decreased by more than 50% at the highest elevations and almost disappeared at the lowest elevations. This might have large implications on water availability during the summer.

  17. Regional climate scenarios - A study on precipitation

    International Nuclear Information System (INIS)

    Hesselbjerg Christensen, J.; Boessing Christensen, O.

    2001-01-01

    A set of nested climate change simulations for the Nordic region and Denmark has been revisited. In the present work we have re-examined the results of CCMB and MBC with special emphasis on precipitation intensity frequencies, in particular the more extreme part of the frequency distribution. It has been demonstrated that the role of extreme precipitation events appears to be more realistically described in a high-resolution model, in terms of numerical agreement as well as seasonal variation. This is mainly due to a better simulation of deep low-pressure systems and mesoscale circulation. Generally, the analysis has confirmed the results from CCMB, but furthermore a resolution effect has been identified which seems essential to the understanding of climate change effects on the extreme end of the precipitation intensity distribution. In order to analyse the role of the model resolution we have aggregated both the nested model data and observational records to the GCM grid from the driving AOGCM. It was found that, in spite of changes in absolute numbers, the seasonal behaviour of decay constants does not change appreciably because of the aggregation. The RCM results show a seasonal behaviour very similar to an observed data set. It is therefore concluded that the GCM has an unrealistic simulation of the dependence of heavy precipitation on climate, as manifested in seasonal variation. In contrast, the regional simulations remain close to observation in this respect. Furthermore, they agree on a conclusion that extreme precipitation generally scales with average precipitation (no significant change in decay constants were detected), but that crucial summer season may be an exception, exhibiting an anomalous increase in heavy precipitation due to the anthropogenic greenhouse effect. The analysis has only been performed over Denmark due to lack of daily observational data for other regions. It is, however, necessary to extend the work to other areas, for instance

  18. The unusual wet summer (July) of 2014 in Southern Europe

    Science.gov (United States)

    Ratna, Satyaban B.; Ratnam, J. V.; Behera, Swadhin K.; Cherchi, Annalisa; Wang, Wanqiu; Yamagata, Toshio

    2017-06-01

    Southern Europe (Italy and the surrounding countries) experienced an unusual wet summer in 2014. The monthly rainfall in July 2014 was 84% above (more than three standard deviation) normal with respect to the 1982-2013 July climatology. The heavy rainfall damaged agriculture, and affected tourism and overall economy of the region. In this study, we tried to understand the physical mechanisms responsible for such abnormal weather by using model and observed datasets. The anomalously high precipitation over Italy is found to be associated with the positive sea surface temperature (SST) and convective anomalies in the tropical Pacific through the atmospheric teleconnection. Rossby wave activity flux at upper levels shows an anomalous tropospheric quasi-stationary Rossby wave from the Pacific with an anomalous cyclonic phase over southern Europe. This anomalous cyclonic circulation is barotropic in nature and seen extending to lower atmospheric levels, weakening the seasonal high and causing heavy precipitation over the Southern Europe. The hypothesis is verified using the National Centers for Environmental Prediction (NCEP) coupled forecast system model (CFSv2) seasonal forecasts. It is found that two-month lead forecast of CFSv2 was able to capture the wet summer event of 2014 over Southern Europe. The teleconnection pattern from Pacific to Southern Europe was also forecasted realistically by the CFSv2 system.

  19. Global Precipitation Responses to Land Hydrological Processes

    Science.gov (United States)

    Lo, M.; Famiglietti, J. S.

    2012-12-01

    Several studies have established that soil moisture increases after adding a groundwater component in land surface models due to the additional supply of subsurface water. However, impacts of groundwater on the spatial-temporal variability of precipitation have received little attention. Through the coupled groundwater-land-atmosphere model (NCAR Community Atmosphere Model + Community Land Model) simulations, this study explores how groundwater representation in the model alters the precipitation spatiotemporal distributions. Results indicate that the effect of groundwater on the amount of precipitation is not globally homogeneous. Lower tropospheric water vapor increases due to the presence of groundwater in the model. The increased water vapor destabilizes the atmosphere and enhances the vertical upward velocity and precipitation in tropical convective regions. Precipitation, therefore, is inhibited in the descending branch of convection. As a result, an asymmetric dipole is produced over tropical land regions along the equator during the summer. This is analogous to the "rich-get-richer" mechanism proposed by previous studies. Moreover, groundwater also increased short-term (seasonal) and long-term (interannual) memory of precipitation for some regions with suitable groundwater table depth and found to be a function of water table depth. Based on the spatial distributions of the one-month-lag autocorrelation coefficients as well as Hurst coefficients, air-land interaction can occur from short (several months) to long (several years) time scales. This study indicates the importance of land hydrological processes in the climate system and the necessity of including the subsurface processes in the global climate models.

  20. Influence of aerosol on regional precipitation in North China

    Institute of Scientific and Technical Information of China (English)

    DUAN Jing; MAO JieTai

    2009-01-01

    The possible anthropogenic aerosol effect on regional precipitation is analyzed based on the historical data of precipitation and visibility of North China. At first, the precipitation amounts from 1960 to 1979 are considered as natural background values in our study for relatively less intensive industrial activi-ties and light air pollution during that period of time, then the region is divided into different subregions by applying the clustering method including the significance test of station rainfall correlations to the time series of 10-day mean rainfall amounts in this period. Based on the rule that the precipitation characteristics are similar in the same clustering region, the correlation of precipitation amounts among all stations in each region is thus established. Secondly, for the period from 1990 to 2005, during which, the economy had experienced a rapid development in this region, the variations of visibility at each station are analyzed. The stations with the absolute change in visibility less than 0.1 km/a are used as the reference stations, at which it is assumed that precipitation has not been seriously influ-enced by anthropogenic aerosols. Then the rainfall amounts of reference stations are used to estimate the natural precipitation values of the other stations in each clustering region. The difference between estimated precipitation and measured precipitation amount is thought to result from changes in an-thropogenic aerosols. These changes in precipitation amounts caused by anthropogenic aerosols at each station are calculated using the 10-day mean rainfall values from 1990 to 2005. The analysis re-suits obtained with this method are remarkable if it passes the significance test, and therefore, the suppression of regional precipitation over the region by anthropogenic aerosol is proved. It is found that this effect is most remarkable in summer. The influence of anthropogenic aerosols on convective precipitation possibly plays an important

  1. 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.

  2. Asian summer monsoon prediction in ECMWF System 4 and NCEP CFSv2 retrospective seasonal forecasts

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hye-Mi; Webster, Peter J.; Curry, Judith A.; Toma, Violeta E. [Georgia Institute of Technology, School of Earth and Atmospheric Science, Atlanta, GA (United States)

    2012-12-15

    The seasonal prediction skill of the Asian summer monsoon is assessed using retrospective predictions (1982-2009) from the ECMWF System 4 (SYS4) and NCEP CFS version 2 (CFSv2) seasonal prediction systems. In both SYS4 and CFSv2, a cold bias of sea-surface temperature (SST) is found over the equatorial Pacific, North Atlantic, Indian Oceans and over a broad region in the Southern Hemisphere relative to observations. In contrast, a warm bias is found over the northern part of North Pacific and North Atlantic. Excessive precipitation is found along the ITCZ, equatorial Atlantic, equatorial Indian Ocean and the maritime continent. The southwest monsoon flow and the Somali Jet are stronger in SYS4, while the south-easterly trade winds over the tropical Indian Ocean, the Somali Jet and the subtropical northwestern Pacific high are weaker in CFSv2 relative to the reanalysis. In both systems, the prediction of SST, precipitation and low-level zonal wind has greatest skill in the tropical belt, especially over the central and eastern Pacific where the influence of El Nino-Southern Oscillation (ENSO) is dominant. Both modeling systems capture the global monsoon and the large-scale monsoon wind variability well, while at the same time performing poorly in simulating monsoon precipitation. The Asian monsoon prediction skill increases with the ENSO amplitude, although the models simulate an overly strong impact of ENSO on the monsoon. Overall, the monsoon predictive skill is lower than the ENSO skill in both modeling systems but both systems show greater predictive skill compared to persistence. (orig.)

  3. Relating ring width of Mediterranean evergreen species to seasonal and annual variations of precipitation and temperature

    Directory of Open Access Journals (Sweden)

    W. Nijland

    2011-05-01

    Full Text Available Plant growth in Mediterranean landscapes is limited by the typical summer-dry climate. Forests in these areas are only marginally productive and may be quite susceptible to modern climate change. To improve our understanding of forest sensitivity to annual and seasonal climatic variability, we use tree-ring measurements of two Mediterranean evergreen tree species: Quercus ilex L. and Arbutus unedo L. We sampled 34 stems of these species on three different types of substrates in the Peyne study area in southern France. The resulting chronologies were analysed in combination with 38 yr of monthly precipitation and temperature data to reconstruct the response of stem growth to climatic variability. Results indicate a strong positive response to May and June precipitation, as well as a significant positive influence of early-spring temperatures and a negative growth response to summer heat. Comparison of the data with more detailed productivity measurements in two contrasting years confirms these observations and shows a strong productivity limiting effect of low early-summer precipitation. The results show that tree-ring data from Q.ilex and A.unedo can provide valuable information about the response of these tree species to climate variability, improving our ability to predict the effects of climate change in Mediterranean ecosystems.

  4. Meteorological characteristics and overland precipitation impacts of atmospheric rivers affecting the West coast of North America based on eight years of SSM/I satellite observations

    Science.gov (United States)

    Neiman, P.J.; Ralph, F.M.; Wick, G.A.; Lundquist, J.D.; Dettinger, M.D.

    2008-01-01

    The pre-cold-frontal low-level jet within oceanic extratropical cyclones represents the lower-tropospheric component of a deeper corridor of concentrated water vapor transport in the cyclone warm sector. These corridors are referred to as atmospheric rivers (ARs) because they are narrow relative to their length scale and are responsible for most of the poleward water vapor transport at midlatitudes. This paper investigates landfalling ARs along adjacent north- and south-coast regions of western North America. Special Sensor Microwave Imager (SSM/ I) satellite observations of long, narrow plumes of enhanced integrated water vapor (IWV) were used to detect ARs just offshore over the eastern Pacific from 1997 to 2005. The north coast experienced 301 AR days, while the south coast had only 115. Most ARs occurred during the warm season in the north and cool season in the south, despite the fact that the cool season is climatologically wettest for both regions. Composite SSM/I IWV analyses showed landfalling wintertime ARs extending northeastward from the tropical eastern Pacific, whereas the summertime composites were zonally oriented and, thus, did not originate from this region of the tropics. Companion SSM/I composites of daily rainfall showed significant orographic enhancement during the landfall of winter (but not summer) ARs. The NCEP-NCAR global reanalysis dataset and regional precipitation networks were used to assess composite synoptic characteristics and overland impacts of landfalling ARs. The ARs possess strong vertically integrated horizontal water vapor fluxes that, on average, impinge on the West Coast in the pre-cold-frontal environment in winter and post-cold-frontal environment in summer. Even though the IWV in the ARs is greater in summer, the vapor flux is stronger in winter due to much stronger flows associated with more intense storms. The landfall of ARs in winter and north-coast summer coincides with anomalous warmth, a trough offshore, and

  5. Insights into changes in precipitation patterns in Brazil from oxygen isotope ratios on speleothems

    Science.gov (United States)

    Cruz, F.; Mathias, V.; Stephen, B. J.; Wang, X.; Cheng, H.; Werner, M.; Edwards, R. L.; Karmann, I.; Auler, A. S.

    2008-12-01

    Variations in tropical precipitation on millennial and orbital time scales can reflect a Hadley-cell-related anti- phasing between the Northern and Southern hemispheres due to the influence of insolation on the global summer monsoons. A new δ18O speleothem record from northeastern Brazil shows that insolation- driven changes in monsoon intensity are capable of producing a similar, zonally oriented anti-phasing within the same hemisphere. Comparison of our speleothem record with other precipitation-sensitive proxies from the central Andes and southeastern Brazil shows that precipitation in Northeastern Brazil has been out of phase with insolation and rainfall in the rest of tropical South America south of the equator since the Last Glacial Maximum. Northeastern Brazil experienced humid conditions when summer insolation was reduced and arid conditions when insolation was high. While previous interpretations of past climate change in NE South America have commonly invoked meridional displacements in ITCZ location as the main mechanism for changes in precipitation on millennial time scales, our results suggest that remote monsoon forcing is responsible for much of the observed precipitation changes on orbital time scales during the Holocene. These results demonstrate that orbitally driven out-of-phase relationships in precipitation are not limited to interhemispheric anti-phasing as demonstrated previously, but may well occur within the same hemisphere. Speleothem records also indicate contrasting climatic conditions around the Last Glacial Maximum in Brazil, characterized by marked dry and wet climates in the Nordeste and in southeastern Brazil, respectively. It is likely, however, that these regional differences primarily reflect more distant extratropical teleconnections from the Atlantic Ocean and high northern latitude changes during glacial conditions.

  6. Study of variations of stable isotopes in precipitation: case of Antananarivo

    International Nuclear Information System (INIS)

    Randrianarivola, M.

    2014-01-01

    The isotopic signature of precipitation is the input signal in any study of hydrological cycle. The scientific objective of this work is to better understand the isotopic variations in precipitation and identify their processes. We used the network of measurement GNIP (Global Network of Isotopes in Precipitation) in which data is acquired by the International Atomic Energy Agency through isotope hydrology laboratory at INSTN-Madagascar. Analyzes stable isotopes ( 18O and 2 H), were performed at a monthly time step. We were able to confirm the relative importance of different mechanisms governing the isotopic composition of precipitation. The spatial distribution of abundance ratios of Antananarivo rain is in fact dictated by the temperature which follow indirectly from the effects of altitude and seasonal variations. At the monthly scale, local meteoric water line δ 2 H versus δ 18 O shows the specificity of Antananarivo (deuterium excess of 17.5‰ ). Additionally, seasonal variations in precipitation is related to the temperature such that in summer (d=15‰) and winter (d=18‰) [fr

  7. Warming combined with more extreme precipitation regimes modifies the water sources used by trees.

    Science.gov (United States)

    Grossiord, Charlotte; Sevanto, Sanna; Dawson, Todd E; Adams, Henry D; Collins, Adam D; Dickman, Lee T; Newman, Brent D; Stockton, Elizabeth A; McDowell, Nate G

    2017-01-01

    The persistence of vegetation under climate change will depend on a plant's capacity to exploit water resources. We analyzed water source dynamics in piñon pine and juniper trees subjected to precipitation reduction, atmospheric warming, and to both simultaneously. Piñon and juniper exhibited different and opposite shifts in water uptake depth in response to experimental stress and background climate over 3 yr. During a dry summer, juniper responded to warming with a shift to shallow water sources, whereas piñon pine responded to precipitation reduction with a shift to deeper sources in autumn. In normal and wet summers, both species responded to precipitation reduction, but juniper increased deep water uptake and piñon increased shallow water uptake. Shifts in the utilization of water sources were associated with reduced stomatal conductance and photosynthesis, suggesting that belowground compensation in response to warming and water reduction did not alleviate stress impacts for gas exchange. We have demonstrated that predicted climate change could modify water sources of trees. Warming impairs juniper uptake of deep sources during extended dry periods. Precipitation reduction alters the uptake of shallow sources following extended droughts for piñon. Shifts in water sources may not compensate for climate change impacts on tree physiology. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  8. Investigating NARCCAP Precipitation Extremes via Bivariate Extreme Value Theory (Invited)

    Science.gov (United States)

    Weller, G. B.; Cooley, D. S.; Sain, S. R.; Bukovsky, M. S.; Mearns, L. O.

    2013-12-01

    We introduce methodology from statistical extreme value theory to examine the ability of reanalysis-drive regional climate models to simulate past daily precipitation extremes. Going beyond a comparison of summary statistics such as 20-year return values, we study whether the most extreme precipitation events produced by climate model simulations exhibit correspondence to the most extreme events seen in observational records. The extent of this correspondence is formulated via the statistical concept of tail dependence. We examine several case studies of extreme precipitation events simulated by the six models of the North American Regional Climate Change Assessment Program (NARCCAP) driven by NCEP reanalysis. It is found that the NARCCAP models generally reproduce daily winter precipitation extremes along the Pacific coast quite well; in contrast, simulation of past daily summer precipitation extremes in a central US region is poor. Some differences in the strength of extremal correspondence are seen in the central region between models which employ spectral nudging and those which do not. We demonstrate how these techniques may be used to draw a link between extreme precipitation events and large-scale atmospheric drivers, as well as to downscale extreme precipitation simulated by a future run of a regional climate model. Specifically, we examine potential future changes in the nature of extreme precipitation along the Pacific coast produced by the pineapple express (PE) phenomenon. A link between extreme precipitation events and a "PE Index" derived from North Pacific sea-surface pressure fields is found. This link is used to study PE-influenced extreme precipitation produced by a future-scenario climate model run.

  9. Projected precipitation changes in South America: a dynamical downscaling within CLARIS

    Energy Technology Data Exchange (ETDEWEB)

    Soerensson, Anna A. [Centra de Investigaciones del Mar y la Atmosfera, CONICET/UBA, Buenos Aires (Argentina); Menendez, Claudio G. [Centra de Investigaciones del Mar y la Atmosfera, CONICET/UBA, Buenos Aires (Argentina); Dept. de Ciencias de la Atmosfera y los Oceanos, FCEN, UBA, Buenos Aires (Argentina); Ruscica, Romina; Alexander, Peter [Dept. de Fisica, FCEN, UBA, Buenos Aires (Argentina); Samuelsson, Patrick; Willen, Ulrika [Rossby Centre, SMHI, Norrkoeping (Sweden)

    2010-06-15

    Responses of precipitation seasonal means and extremes over South America in a downscaling of a climate change scenario are assessed with the Rossby Centre Regional Atmospheric Model (RCA). The anthropogenic warming under A1B scenario influences more on the likelihood of occurrence of severe extreme events like heavy precipitation and dry spells than on the mean seasonal precipitation. The risk of extreme precipitation increases in the La Plata Basin with a factor of 1.5-2.5 during all seasons and in the northwestern part of the continent with a factor 1.5-3 in summer, while it decreases in central and northeastern Brazil during winter and spring. The maximum amount of 5-days precipitation increases by up to 50% in La Plata Basin, indicating risks of flooding. Over central Brazil and the Bolivian lowland, where present 5-days precipitation is higher, the increases are similar in magnitude and could cause less impacts. In southern Amazonia, northeastern Brazil and the Amazon basin, the maximum number of consecutive dry days increases and mean winter and spring precipitation decreases, indicating a longer dry season. In the La Plata Basin, there is no clear pattern of change for the dry spell duration. (orig.)

  10. Characteristics and seasonal variations of precipitation phenomena at Syowa Station

    Directory of Open Access Journals (Sweden)

    Hiroyuki Konishi

    1997-03-01

    Full Text Available Long-term observations of precipitating clouds were carried out by a vertical pointing radar, PPI radar and a 37 GHz microwave radiometer at Syowa Station (69°00′S, 39°35′E, Antarctica in 1989. It is concluded from the observations that precipitation near Syowa Station, Antarctica is mainly brought by cloud vortices associated with extratropical cyclones which advance to high latitude while developing to a mature stage. The seasonal variations of clouds and precipitation were analyzed corresponding to the seasonal changes of air temperature and sea ice area. The occurrence frequencies of cloud vortices which brought snowfall to Syowa Station increased in the fall and spring seasons corresponding to activity of the circumpolar trough. However, the activities of cloud systems that bring precipitation weaken in spring when the sea ice area expands to low latitudes, because of less supply of heat and vapor. In 1989,the amount of precipitation in spring brought by a few snowfall events was as large as the amount of precipitation in fall brought by frequent snowfall events. Radar observations revealed that there were three abundant snowfall seasons at Syowa Station and the amount of snowfall was uniform in all seasons except summer. The amounts of precipitation in fall, winter and spring were 74,74 and 53mm respectively.

  11. Effects of Altered Seasonality of Precipitation on Grass Production and Grasshopper Performance in a Northern Mixed Prairie.

    Science.gov (United States)

    Branson, David H

    2017-06-01

    Climatic changes are leading to differing patterns and timing of precipitation in grassland ecosystems, with the seasonal timing of precipitation affecting plant biomass and plant composition. No previous studies have examined how drought seasonality affects grasshopper performance and the impact of herbivory on vegetation. We modified seasonal patterns of precipitation and grasshopper density in a manipulative experiment to examine if seasonality of drought combined with herbivory affected plant biomass, nitrogen content, and grasshopper performance. Grass biomass was affected by both precipitation and grasshopper density treatments, while nitrogen content of grass was higher with early-season drought. Proportional survival was negatively affected by initial density, while survival was higher with early drought than with full-season drought. Drought timing affected the outcome, with early summer drought increasing grass nitrogen content and grasshopper survival, while season-long and late-season drought did not. The results support arguments that our knowledge of plant responses to seasonal short-term variation in climate is limited and illustrate the importance of experiments manipulating precipitation phenology. The results confirm that understanding the season of drought is critical for predicting grasshopper population dynamics, as extreme early summer drought may be required to strongly affect Melanoplus sanguinipes (F.) performance. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

  12. Mercury in precipitation at an urbanized coastal zone of the Baltic Sea (Poland).

    Science.gov (United States)

    Saniewska, Dominika; Bełdowska, Magdalena; Bełdowski, Jacek; Falkowska, Lucyna

    2014-11-01

    Wet deposition is an important source of metals to the sea. The temporal variability of Hg concentrations in precipitation, and the impact of air masses of different origins over the Polish coastal zone were assessed. Samples of precipitation were collected (August 2008-May 2009) at an urbanized coastal station in Poland. Hg analyses were conducted using CVAFS. These were the first measurements of Hg concentration in precipitation obtained in the Polish coastal zone. Since Poland was identified as the biggest emitter of Hg to the Baltic, these data are very important. In the heating and non-heating season, Hg concentrations in precipitation were similar. Hg wet deposition flux dominated in summer, when the production of biomass in the aquatic system was able to actively adsorb Hg. Input of metal to the sea was attributed to regional and distant sources. Maritime air masses, through transformation of Hg(0), were an essential vector of mercury in precipitation.

  13. Spatiotemporal patterns of precipitation extremes in the Poyang Lake basin, China: Changing properties and causes

    Science.gov (United States)

    Xiao, M.

    2016-12-01

    Under the background of climate change, extensive attentions have been paid on the increased extreme precipitation from the public and government. To analyze the influences of large-scale climate indices on the precipitation extremes, the spatiotemporal patterns of precipitation extremes in the Poyang Lake basin have been investigated using the Bayesian hierarchical method. The seasonal maximum one-day precipitation amount (Rx1day) was used to represent the seasonal precipitation extremes. Results indicated that spring Rx1day was affected by El Niño/Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), a positive ENSO event in the same year tends to decrease the spring Rx1day in the northern part of Poyang Lake Basin while increase the spring Rx1day in southeastern Poyang Lake Basin, a positive NAO events in the same year tends to increase the spring Rx1day in the southwest and northwest part of Poyang Lake basin while decrease the spring Rx1day in the eastern part of Poyang Lake basin; summer Rx1day was affected by Indian Ocean Dipole (IOD), positive IOD events in the same year tend to increase the summer Rx1day of northern Poyang Lake basin while decrease summer Rx1day of southern Poyang Lake basin; autumn Rx1day was affected by ENSO, positive ENSO events in the same year tend to mainly increase the autumn Rx1day in the west part of Poyang Lake basin; winter Rx1day was mainly affected by the NAO, positive NAO events in the same year tend to mainly increase the winter Rx1day of southern Poyang Lake basin, while positive NAO events in the previous year tend to mainly increase the winter Rx1day in the central and northeast part of Poyang Lake basin. It is considered that the region with the negative vertical velocity is dominated by more precipitation and vice versa. Furthermore, field patterns of 500 hPa vertical velocity anomalies related to each climate index have further corroborated the influences of climate indices on the seasonal Rx1day, and

  14. Long-term summer sunshine/moisture stress reconstruction from tree-ring widths from Bosnia and Herzegovina

    Directory of Open Access Journals (Sweden)

    S. Poljanšek

    2013-01-01

    Full Text Available We present the first summer sunshine reconstruction from tree-ring data for the western part of the Balkan Peninsula. Summer sunshine is tightly connected with moisture stress in trees, because the moisture stress and therefore the width of annual tree-rings is under the influence of the direct and interactive effects of sunshine duration (temperature, precipitation, cloud cover and evapotranspiration. The reconstruction is based on a calibrated z-scored mean chronology, calculated from tree-ring width measurements from 7 representative black pine (Pinus nigra Arnold sites in Bosnia and Herzegovina (BiH. A combined regression and scaling approach was used for the reconstruction of the summer sunshine. We found a significant negative correlation (r = −0.54, p < 0.0001 with mean June–July sunshine hours from Osijek meteorological station (Croatia. The developed model was used for reconstruction of summer sunshine for the time period 1660–2010. We identified extreme summer events and compared them to available documentary historical sources of drought, volcanic eruptions and other reconstructions from the broader region. All extreme summers with low sunshine hours (1712, 1810, 1815, 1843, 1899 and 1966 are connected with volcanic eruptions.

  15. Augmenting Satellite Precipitation Estimation with Lightning Information

    Energy Technology Data Exchange (ETDEWEB)

    Mahrooghy, Majid [Mississippi State University (MSU); Anantharaj, Valentine G [ORNL; Younan, Nicolas H. [Mississippi State University (MSU); Petersen, Walter A. [NASA Marshall Space Flight Center, Huntsville, AL; Hsu, Kuo-Lin [University of California, Irvine; Behrangi, Ali [Jet Propulsion Laboratory, Pasadena, CA; Aanstoos, James [Mississippi State University (MSU)

    2013-01-01

    We have used lightning information to augment the Precipitation Estimation from Remotely Sensed Imagery using an Artificial Neural Network - Cloud Classification System (PERSIANN-CCS). Co-located lightning data are used to segregate cloud patches, segmented from GOES-12 infrared data, into either electrified (EL) or non-electrified (NEL) patches. A set of features is extracted separately for the EL and NEL cloud patches. The features for the EL cloud patches include new features based on the lightning information. The cloud patches are classified and clustered using self-organizing maps (SOM). Then brightness temperature and rain rate (T-R) relationships are derived for the different clusters. Rain rates are estimated for the cloud patches based on their representative T-R relationship. The Equitable Threat Score (ETS) for daily precipitation estimates is improved by almost 12% for the winter season. In the summer, no significant improvements in ETS are noted.

  16. Can frequent precipitation moderate the impact of drought on peatmoss carbon uptake in northern peatlands?

    NARCIS (Netherlands)

    Nijp, J.J.; Limpens, J.; Metselaar, K.; Zee, van der S.E.A.T.M.; Berendse, F.; Robroek, B.J.M.

    2014-01-01

    Northern peatlands represent a large global carbon store that can potentially be destabilized by summer water table drawdown. Precipitation can moderate the negative impacts of water table drawdown by rewetting peatmoss (Sphagnum spp.), the ecosystem's key species. Yet, the frequency of such

  17. Biotic and abiotic interactions in temporary summer pools of southern Portugal

    OpenAIRE

    Rosado, Joana; Morais, Manuela; Guilherme, Pedro; Ilheu, Maria

    2012-01-01

    In the south of Portugal, the summer season is characterized by reduced precipitation and high air temperatures, which causes the disruption of surface flow and subsequent formation of disconnect pools that may dry out entirely. During this dry period, there is a natural decrease of water quality standards due to the lack of water, leaving temporary rivers very vulnerable. Nevertheless, the remaining pools and surroundings become important in the survival of biological communities. Aquatic...

  18. Analysis of stable isotope ratios (δ18O and δ2H) in precipitation of the Verde River watershed, Arizona 2003 through 2014

    Science.gov (United States)

    Beisner, Kimberly R.; Paretti, Nicholas V.; Tucci, Rachel S.

    2016-04-25

    Stable isotope delta values (δ18O and δ2H) of precipitation can vary with elevation, and quantification of the precipitation elevation gradient can be used to predict recharge elevation within a watershed. Precipitation samples were analyzed for stable isotope delta values between 2003 and 2014 from the Verde River watershed of north-central Arizona. Results indicate a significant decrease in summer isotopic values overtime at 3,100-, 4,100-, 6,100-, 7,100-, and 8,100-feet elevation. The updated local meteoric water line for the area is δ2H = 7.11 δ18O + 3.40. Equations to predict stable isotopic values based on elevation were updated from previous publications in Blasch and others (2006), Blasch and Bryson (2007), and Bryson and others (2007). New equations were separated for samples from the Camp Verde to Flagstaff transect and the Prescott to Chino Valley transect. For the Camp Verde to Flagstaff transect, the new equations for winter precipitation are δ18O = -0.0004z − 8.87 and δ2H = -0.0029z − 59.8 (where z represents elevation in feet) and the summer precipitation equations were not statistically significant. For the Prescott to Chino Valley transect, the new equations for summer precipitation are δ18O = -0.0005z − 3.22 and δ2H = -0.0022z − 27.9; the winter precipitation equations were not statistically significant and, notably, stable isotope values were similar across all elevations. Interpretation of elevation of recharge contributing to surface and groundwaters in the Verde River watershed using the updated equations for the Camp Verde to Flagstaff transect will give lower elevation values compared with interpretations presented in the previous studies. For waters in the Prescott and Chino Valley area, more information is needed to understand local controls on stable isotope values related to elevation.

  19. Summer moisture changes in the Lake Qinghai area on the northeastern Tibetan Plateau recorded from a meadow section over the past 8400 yrs

    Science.gov (United States)

    Li, Xiangzhong; Liu, Xiangjun; He, Yuxin; Liu, Weiguo; Zhou, Xin; Wang, Zheng

    2018-02-01

    Holocene climatic and environmental changes on the northeastern Tibetan Plateau (TP) have been widely discussed based on the climatic records from sedimentary cores. However, differences in the reconstructed climatic history from various studies in this region still exist, probably due to influence of climatic proxies from multiple factors and the chronological uncertainties in lacustrine sediments. Here we present records of terrestrial plant δ13C, soil color and total organic carbon content over the past 8400 years from a well-dated meadow section on the northeastern TP. The terrestrial plant δ13C value serves as a good summer precipitation/moisture indicator in the studied region. Soil color property and TOC content are also able to disentangle the moisture evolution history. All the data show much wet climates at 8400-7400 cal yr BP, dry climates at 7400-6000 cal yr BP and then wet conditions with fluctuation at 6000-3200 cal yr BP. Late Holocene moisture appears to be comparable with moist conditions from 6000 to 3200 cal yr BP. By further comparing the climatic variations in the Lake Qinghai area with records of the reconstructed summer temperature and the Asian Monsoon precipitation, we believe that the pattern of moisture/precipitation evolution in the Lake Qinghai area was not completely consistent with regions around Lake Qinghai, probably due to complicated interaction between the East Asian Summer Monsoon and the Indian Summer Monsoon.

  20. Experimental research on the poly-aluminum chloride for treating the Pi River water in winter and summer

    Science.gov (United States)

    Jia, Rusheng; Bai, Yulin; Yang, Jie

    2018-02-01

    In the beaker experiments that the disposal of low turbidity water, we observed the influence of some factors, such as the dosage of poly-aluminum chloride coagulant, the pH value of raw water, in disposing the high natural organic matters of low turbidity water in winter and summer. we discussed the removal of residual aluminum and UV254 in summer. The experimental results show that when the turbidity is less than 10 NTU, the optimum dosage are 14.4 mg.L-1 and 8.2 mg.L-1 respectively in winter and summer. No matter in winter or summer, the effect of pH value on coagulation treatment is very significant, the best pH value is about 8.1. In summer, with the increase of dosage of poly-aluminum chloride, residual aluminum increased slowly after decrease, turbidity and UV254 after precipitation is similar removal trend. Finally, according to the current market price of poly-aluminum chloride economic analysis, daily differences in pharmaceutical costs about 1600 yuan in summer and winter in the second water plant in Lu’an.

  1. Regional precipitation variability in East Asia related to climate and environmental factors during 1979-2012

    Science.gov (United States)

    Deng, Yinyin; Gao, Tao; Gao, Huiwang; Yao, Xiaohong; Xie, Lian

    2014-01-01

    This paper studies the inter-annual precipitation variations in different regions of East Asia from oceans to interior areas in China during 1979 – 2012. The results computed by Empirical Orthogonal Functions (EOF) demonstrate that the annual precipitation changes are mainly related to the El Niño-Southern Oscillation, East Asian summer monsoon and aerosols. We also found that the increased Sea surface temperature (SST) could explain the precipitation changes over the Northwest Pacific in the dry season (Oct. – May) and the East China Sea and the South China Sea in the rainy season (Jun. – Sep.). The precipitation changes over the ocean unexplained by SST were likely due to the water vapor transport dominated by dynamic factors. With the increased SST, the moisture transported from oceans to interior land was likely redistributed and caused the complicated regional variability of precipitation. Moreover, the impacts of aerosols on cloud and precipitation varied with different pollution levels and different seasons. PMID:25033387

  2. Synoptic Drivers of Precipitation in the Atlantic Sector of the Arctic

    Science.gov (United States)

    Cohen, L.; Hudson, S.; Graham, R.; Renwick, J. A.

    2017-12-01

    Precipitation in the Arctic has been shown to be increasing in recent decades, from both observational and modelling studies, with largest trends seen in autumn and winter. This trend is attributed to a combination of the warming atmosphere and reduced sea ice extent. The seasonality of precipitation in the Arctic is important as it largely determines whether the precipitation falls as snow or rain. This study assesses the spatial and temporal variability of the synoptic drivers of precipitation in the Atlantic (European) sector of the Arctic. This region of the Arctic is of particular interest as it has the largest inter-annual variability in sea ice extent and is the primary pathway for moisture transport into the Arctic from lower latitudes. This study uses the ECMWF ERA-I reanalysis total precipitation to compare to long-term precipitation observations from Ny Ålesund, Svalbard to show that the reanalysis captures the synoptic variability of precipitation well and that most precipitation in this region is synoptically driven. The annual variability of precipitation in the Atlantic Arctic shows strong regionality. In the Svalbard and Barents Sea region, most of the annual total precipitation occurs during autumn and winter (Oct-Mar) (>60% of annual total), while the high-Arctic (> 80N) and Kara Sea receives most of the annual precipitation ( 60% of annual total) during summer (July-Sept). Using a synoptic classification developed for this region, this study shows that winter precipitation is driven by winter cyclone occurrence, with strong correlations to the AO and NAO indices. High precipitation over Svalbard is also strongly correlated with the Scandinavian blocking pattern, which produces a southerly flow in the Greenland Sea/Svalbard area. An increasing occurrence of these synoptic patterns are seen for winter months (Nov and Jan), which may explain much of the observed winter increase in precipitation.

  3. Transient regional climate change: analysis of the summer climate response in a high-resolution, century-scale, ensemble experiment over the continental United States

    Science.gov (United States)

    Diffenbaugh, Noah S.; Ashfaq, Moetasim; Scherer, Martin

    2013-01-01

    Integrating the potential for climate change impacts into policy and planning decisions requires quantification of the emergence of sub-regional climate changes that could occur in response to transient changes in global radiative forcing. Here we report results from a high-resolution, century-scale, ensemble simulation of climate in the United States, forced by atmospheric constituent concentrations from the Special Report on Emissions Scenarios (SRES) A1B scenario. We find that 21st century summer warming permanently emerges beyond the baseline decadal-scale variability prior to 2020 over most areas of the continental U.S. Permanent emergence beyond the baseline annual-scale variability shows much greater spatial heterogeneity, with emergence occurring prior to 2030 over areas of the southwestern U.S., but not prior to the end of the 21st century over much of the southcentral and southeastern U.S. The pattern of emergence of robust summer warming contrasts with the pattern of summer warming magnitude, which is greatest over the central U.S. and smallest over the western U.S. In addition to stronger warming, the central U.S. also exhibits stronger coupling of changes in surface air temperature, precipitation, and moisture and energy fluxes, along with changes in atmospheric circulation towards increased anticylonic anomalies in the mid-troposphere and a poleward shift in the mid-latitude jet aloft. However, as a fraction of the baseline variability, the transient warming over the central U.S. is smaller than the warming over the southwestern or northeastern U.S., delaying the emergence of the warming signal over the central U.S. Our comparisons with observations and the Coupled Model Intercomparison Project Phase 3 (CMIP3) ensemble of global climate model experiments suggest that near-term global warming is likely to cause robust sub-regional-scale warming over areas that exhibit relatively little baseline variability. In contrast, where there is greater

  4. Regionalization of precipitation characteristics in Iran's Lake Urmia basin

    Science.gov (United States)

    Fazel, Nasim; Berndtsson, Ronny; Uvo, Cintia Bertacchi; Madani, Kaveh; Kløve, Bjørn

    2018-04-01

    Lake Urmia in northwest Iran, once one of the largest hypersaline lakes in the world, has shrunk by almost 90% in area and 80% in volume during the last four decades. To improve the understanding of regional differences in water availability throughout the region and to refine the existing information on precipitation variability, this study investigated the spatial pattern of precipitation for the Lake Urmia basin. Daily rainfall time series from 122 precipitation stations with different record lengths were used to extract 15 statistical descriptors comprising 25th percentile, 75th percentile, and coefficient of variation for annual and seasonal total precipitation. Principal component analysis in association with cluster analysis identified three main homogeneous precipitation groups in the lake basin. The first sub-region (group 1) includes stations located in the center and southeast; the second sub-region (group 2) covers mostly northern and northeastern part of the basin, and the third sub-region (group 3) covers the western and southern edges of the basin. Results of principal component (PC) and clustering analyses showed that seasonal precipitation variation is the most important feature controlling the spatial pattern of precipitation in the lake basin. The 25th and 75th percentiles of winter and autumn are the most important variables controlling the spatial pattern of the first rotated principal component explaining about 32% of the total variance. Summer and spring precipitation variations are the most important variables in the second and third rotated principal components, respectively. Seasonal variation in precipitation amount and seasonality are explained by topography and influenced by the lake and westerly winds that are related to the strength of the North Atlantic Oscillation. Despite using incomplete time series with different lengths, the identified sub-regions are physically meaningful.

  5. Urban acid deposition in Greater Manchester

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.S.; Longhurst, J.W.S.; Gee, D.R.; Hare, S.E. (Manchester Polytechnic, Manchester (UK). Acid Rain Information Centre)

    1989-08-01

    Data are presented from a monitoring network of 18 bulk precipitation collectors and one wet-only collector in the urban area of Greater Manchester, in the north west of England. Weekly samples were analysed for all the major ions in precipitation along with gaseous nitrogen dioxide concentrations from diffusion tubes. Statistical analysis of the data shows significant spatial variation of non marine sulphate, nitrate, ammonium, acidity and calcium concentrations, and nitrogen dioxide concentrations. Calcium is thought to be responsible for the buffering of acidity and is of local origin. Wet deposition is the likely removal process for calcium in the atmosphere and probably by below cloud scavenging. Nitrate and ammonium concentrations and depositions show close spatial, temporal and statistical association. Examination of high simultaneous episodes of nitrate and ammonium deposition shows that these depositions cannot be explained in terms of trajectories and it is suggested that UK emissions of ammonia may be important. Statistical analysis of the relationships between nitrate and ammonium depositions, concentrations and precipitation amount suggest that ammonia from mesoscale sources reacts reversibly with nitric acid aerosol and is removed by below cloud scavenging. High episodes of the deposition of non marine sulphate are difficult to explain by trajectory analysis alone, perhaps suggesting local sources. In a comparison between wet deposition and bulk deposition, it was shown that only 15.2% of the non marine sulphur was dry deposited to the bulk precipitation collector. 63 refs., 86 figs., 31 tabs.

  6. My Summer with Science Policy

    Science.gov (United States)

    Murray, Marissa

    This past summer I interned at the American Institute of Physics and helped research and write articles for the FYI Science Policy Bulletin. FYI is an objective digest of science policy developments in Washington, D.C. that impact the greater physical sciences community. Over the course of the summer, I independently attended, analyzed, and reported on a variety of science, technology, and funding related events including congressional hearings, government agency advisory committee meetings, and scientific society events. I wrote and co-wrote three articles on basic energy research legislation, the National Institute of Standards and Technology improvement act, and the National Science Foundation's big ideas for future investment. I had the opportunity to examine some challenging questions such as what is the role of government in funding applied research? How should science priorities be set? What is the right balance of funding across different agencies and programs? I learned about how science policy is a two-way street: science is used to inform policy decisions and policy is made to fund and regulate the conduct of science. I will conclude with how my summer working with FYI showed me the importance of science advocacy, being informed, and voting. Society of Physics Students.

  7. Impact of Climate Change Adaptation Strategies on Winter Wheat and Cropping System Performance across Precipitation Gradients in the Inland Pacific Northwest, USA

    Directory of Open Access Journals (Sweden)

    Tai M. Maaz

    2017-05-01

    Full Text Available Ecological instability and low resource use efficiencies are concerns for the long-term productivity of conventional cereal monoculture systems, particularly those threatened by projected climate change. Crop intensification, diversification, reduced tillage, and variable N management are among strategies proposed to mitigate and adapt to climate shifts in the inland Pacific Northwest (iPNW. Our objectives were to assess these strategies across iPNW agroecological zones and time for their impacts on (1 winter wheat (WW (Triticum aestivum L. productivity, (2 crop sequence productivity, and (3 N fertilizer use efficiency. Region-wide analysis indicated that WW yields increased with increasing annual precipitation, prior to maximizing at 520 mm yr−1 and subsequently declining when annual precipitation was not adjusted for available soil water holding capacity. While fallow periods were effective at mitigating low nitrogen (N fertilization efficiencies under low precipitation, efficiencies declined as annual precipitation exceeded 500 mm yr−1. Variability in the response of WW yields to annual precipitation and N fertilization among locations and within sites supports precision N management implementation across the region. In years receiving <350 mm precipitation yr−1, WW yields declined when preceded by crops rather than summer fallow. Nevertheless, WW yields were greater when preceded by pulses and oilseeds rather than wheat across a range of yield potentials, and when under conservation tillage practices at low yield potentials. Despite the yield penalty associated with eliminating fallow prior to WW, cropping system level productivity was not affected by intensification, diversification, or conservation tillage. However, increased fertilizer N inputs, lower fertilizer N use efficiencies, and more yield variance may offset and limit the economic feasibility of intensified and diversified cropping systems.

  8. Distributing urban resilience to extreme precipitation events with green infrastructure

    Science.gov (United States)

    Montalto, F. A.; Catalano De Sousa, M.; Yu, Z.

    2013-12-01

    New urban green spaces are being designed to manage stormwater, but their performance in a changing climate is untested. Key questions pertain to the ability of these systems to mitigate flood and sewer overflow concerns during impact of extreme events on, and to withstand (biologically and physically) increased frequency and intensity of drought and flood conditions. In this presentation, we present field data characterizing performance of a bioretention area, a stormwater treatment wetland, and a green roof under Hurricane Irene (2011), Superstorm Sandy (2012), and a variety of extreme precipitation events during the summer of 2013. Specifically, we characterize the fate and volume of incident runon and/or precipitation to the facilities during these extreme events, and compare them to long term monitored performance metrics. We also present laboratory test results documenting how vegetation in these facilities stands up to simulated flood and drought conditions. The results are discussed in the context of predicted climate change, specifically associated with the amount and timing of precipitation.

  9. Developing future precipitation events from historic events: An Amsterdam case study.

    Science.gov (United States)

    Manola, Iris; van den Hurk, Bart; de Moel, Hans; Aerts, Jeroen

    2016-04-01

    Due to climate change, the frequency and intensity of extreme precipitation events is expected to increase. It is therefore of high importance to develop climate change scenarios tailored towards the local and regional needs of policy makers in order to develop efficient adaptation strategies to reduce the risks from extreme weather events. Current approaches to tailor climate scenarios are often not well adopted in hazard management, since average changes in climate are not a main concern to policy makers, and tailoring climate scenarios to simulate future extremes can be complex. Therefore, a new concept has been introduced recently that uses known historic extreme events as a basis, and modifies the observed data for these events so that the outcome shows how the same event would occur in a warmer climate. This concept is introduced as 'Future Weather', and appeals to the experience of stakeholders and users. This research presents a novel method of projecting a future extreme precipitation event, based on a historic event. The selected precipitation event took place over the broader area of Amsterdam, the Netherlands in the summer of 2014, which resulted in blocked highways, disruption of air transportation, flooded buildings and public facilities. An analysis of rain monitoring stations showed that an event of such intensity has a 5 to 15 years return period. The method of projecting a future event follows a non-linear delta transformation that is applied directly on the observed event assuming a warmer climate to produce an "up-scaled" future precipitation event. The delta transformation is based on the observed behaviour of the precipitation intensity as a function of the dew point temperature during summers. The outcome is then compared to a benchmark method using the HARMONIE numerical weather prediction model, where the boundary conditions of the event from the Ensemble Prediction System of ECMWF (ENS) are perturbed to indicate a warmer climate. The two

  10. Did Aboriginal vegetation burning affect the Australian summer monsoon?

    Science.gov (United States)

    Balcerak, Ernie

    2011-08-01

    For thousands of years, Aboriginal Australians burned forests, creating grasslands. Some studies have suggested that in addition to changing the landscape, these burning practices also affected the timing and intensity of the Australian summer monsoon. Different vegetation types can alter evaporation, roughness, and surface reflectivity, leading to changes in the weather and climate. On the basis of an ensemble of experiments with a global climate model, Notaro et al. conducted a comprehensive evaluation of the effects of decreased vegetation cover on the summer monsoon in northern Australia. They found that although decreased vegetation cover would have had only minor effects during the height of the monsoon season, during the premonsoon season, burning-induced vegetation loss would have caused significant decreases in precipitation and increases in temperature. Thus, by burning forests, Aboriginals altered the local climate, effectively extending the dry season and delaying the start of the monsoon season. (Geophysical Research Letters, doi:10.1029/2011GL047774, 2011)

  11. Centennial- to decadal-scale monsoon precipitation variations in the upper Hanjiang River region, China over the past 6650 years

    Science.gov (United States)

    Tan, Liangcheng; Cai, Yanjun; Cheng, Hai; Edwards, Lawrence R.; Gao, Yongli; Xu, Hai; Zhang, Haiwei; An, Zhisheng

    2018-01-01

    The upper Hanjiang River region is the recharge area of the middle route of South-to-North Water Transfer Project. The region is under construction of the Hanjiang-Weihe River Water Transfer Project in China. Monsoon precipitation variations in this region are critical to water resource and security of China. In this study, high-resolution monsoon precipitation variations were reconstructed in the upper Hanjiang River region over the past 6650 years from δ18O and δ13C records of four stalagmites in Xianglong cave. The long term increasing trend of stalagmite δ18O record since the middle Holocene is consistent with other speleothem records from monsoonal China. This trend follows the gradually decreasing Northern Hemisphere summer insolation, which indicates that solar insolation may control the orbital-scale East Asian summer monsoon (EASM) variations. Despite the declined EASM intensity since the middle Holocene, local precipitation may not have decreased remarkably, as revealed by the δ13C records. A series of centennial- to decadal-scale cyclicity was observed, with quasi-millennium-, quasi-century-, 57-, 36- and 22-year cycles by removing the long-term trend of stalagmite δ18O record. Increased monsoon precipitation during periods of 4390-3800 a BP, 3590-2960 a BP, 2050-1670 a BP and 1110-790 a BP had caused four super-floods in the upper reach of Hanjiang River. Dramatically dry climate existed in this region during the 5.0 ka and 2.8 ka events, coinciding with notable droughts in other regions of monsoonal China. Remarkably intensified and southward Westerly jet, together with weakened summer monsoon, may delay the onset of rainy seasons, resulting in synchronous decreasing of monsoon precipitation in China during the two events. During the 4.2 ka event and the Little Ice Age, the upper Hanjiang River region was wet, which was similar to the climate conditions in central and southern China, but was the opposite of drought observed in northern China. We

  12. Role of atmospheric heating over the South China Sea and western Pacific regions in modulating Asian summer climate under the global warming background

    Science.gov (United States)

    He, Bian; Yang, Song; Li, Zhenning

    2016-05-01

    The response of monsoon precipitation to global warming, which is one of the most significant climate change signals at the earth's surface, exhibits very distinct regional features, especially over the South China Sea (SCS) and adjacent regions in boreal summer. To understand the possible atmospheric dynamics in these specific regions under the global warming background, changes in atmospheric heating and their possible influences on Asian summer climate are investigated by both observational diagnosis and numerical simulations. Results indicate that heating in the middle troposphere has intensified in the SCS and western Pacific regions in boreal summer, accompanied by increased precipitation, cloud cover, and lower-tropospheric convergence and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS and western Pacific and continental South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The result highlights the important role of air-sea interaction in understanding the changes in Asian climate.

  13. Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

    Directory of Open Access Journals (Sweden)

    A. A. Namgaladze

    Full Text Available The seasonal effects in the thermosphere and ionosphere responses to the precipitating electron flux and field-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions have been investigated using the global numerical model of the Earth's upper atmosphere. Two variants of the calculations have been performed both for the IMF By < 0. In the first variant, the model input data for the summer and winter precipitating fluxes and field-aligned currents have been taken as geomagnetically symmetric and equal to those used earlier in the calculations for the equinoctial conditions. It has been found that both ionospheric and thermospheric disturbances are more intensive in the winter cusp region due to the lower conductivity of the winter polar cap ionosphere and correspondingly larger electric field variations leading to the larger Joule heating effects in the ion and neutral gas temperature, ion drag effects in the thermospheric winds and ion drift effects in the F2-region electron concentration. In the second variant, the calculations have been performed for the events of 28–29 January, 1992 when precipitations were weaker but the magnetospheric convection was stronger than in the first variant. Geomagnetically asymmetric input data for the summer and winter precipitating fluxes and field-aligned currents have been taken from the patterns derived by combining data obtained from the satellite, radar and ground magnetometer observations for these events. Calculated patterns of the ionospheric convection and thermospheric circulation have been compared with observations and it has been established that calculated patterns of the ionospheric convection for both winter and summer hemispheres are in a good agreement with the observations. Calculated patterns of the thermospheric circulation are in a good agreement with the average circulation for the Southern (summer Hemisphere obtained

  14. Sensitivity of temperate desert steppe carbon exchange to seasonal droughts and precipitation variations in Inner Mongolia, China.

    Science.gov (United States)

    Yang, Fulin; Zhou, Guangsheng

    2013-01-01

    Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO₂ flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm) was close to the long-term average (183.9±47.6 mm), while the precipitation in 2008 (136.3 mm) and 2010 (141.3 mm) was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO₂ throughout the study period, with a net ecosystem carbon dioxide exchange (NEE) of -7.2, -22.9, and 26.0 g C m⁻² yr⁻¹ in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEE(sat)) and the temperature sensitivity coefficient of ecosystem respiration (R(eco)) exhibited significant variations. The values of NEE(sat) were -2.6, -2.9, and -1.4 µmol CO₂ m⁻² s⁻¹ in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP) and R(eco), and the drought sensitivity of GPP was greater than that of R(eco). The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution.

  15. Sensitivity of temperate desert steppe carbon exchange to seasonal droughts and precipitation variations in Inner Mongolia, China.

    Directory of Open Access Journals (Sweden)

    Fulin Yang

    Full Text Available Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO₂ flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm was close to the long-term average (183.9±47.6 mm, while the precipitation in 2008 (136.3 mm and 2010 (141.3 mm was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO₂ throughout the study period, with a net ecosystem carbon dioxide exchange (NEE of -7.2, -22.9, and 26.0 g C m⁻² yr⁻¹ in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEE(sat and the temperature sensitivity coefficient of ecosystem respiration (R(eco exhibited significant variations. The values of NEE(sat were -2.6, -2.9, and -1.4 µmol CO₂ m⁻² s⁻¹ in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP and R(eco, and the drought sensitivity of GPP was greater than that of R(eco. The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution.

  16. Climate Drivers of Spatiotemporal Variability of Precipitation in the Source Region of Yangtze River

    Science.gov (United States)

    Du, Y.; Berndtsson, R.; An, D.; Yuan, F.

    2017-12-01

    Variability of precipitation regime has significant influence on the environment sustainability in the source region of Yangtze River, especially when the vegetation degradation and biodiversity reduction have already occurred. Understanding the linkage between variability of local precipitation and global teleconnection patterns is essential for water resources management. Based on physical reasoning, indices of the climate drivers can provide a practical way of predicting precipitation. Due to high seasonal variability of precipitation, climate drivers of the seasonal precipitation also varies. However, few reports have gone through the teleconnections between large scale patterns with seasonal precipitation in the source region of Yangtze River. The objectives of this study are therefore (1) assessment of temporal trend and spatial variability of precipitation in the source region of Yangtze River; (2) identification of climate indices with strong influence on seasonal precipitation anomalies; (3) prediction of seasonal precipitation based on revealed climate indices. Principal component analysis and Spearman rank correlation were used to detect significant relationships. A feed-forward artificial neural network(ANN) was developed to predict seasonal precipitation using significant correlated climate indices. Different influencing climate indices were revealed for precipitation in each season, with significant level and lag times. Significant influencing factors were selected to be the predictors for ANN model. With correlation coefficients between observed and simulated precipitation over 0.5, the results were eligible to predict the precipitation of spring, summer and winter using teleconnections, which can improve integrated water resources management in the source region of Yangtze River.

  17. Influence of precipitation on the Portevin-Le Chatelier effect in Al-Mg alloys

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In the alloy with solute content higher than the limiting solubility,the solute atoms that have failed to dissolve will precipitate from the solid solution and form precipitations.In this study, the Portevin-Le Chatelier(PLC) effects in annealed 5456 and 5052 aluminum alloys with different precipitation contents have been investigated under different applied strain rates.The results suggest that precipitations have significant effect on the PLC effect and the more the precipitations are, the greater the ...

  18. Simulated impacts of land cover change on summer climate in the Tibetan Plateau

    International Nuclear Information System (INIS)

    Li Qian; Xue Yongkang

    2010-01-01

    The Tibetan Plateau (TP) is a key region of land-atmosphere interactions with severe eco-environment degradation. This study uses an atmospheric general circulation model, NCEP GCM/SSiB, to present the major TP summer climate features for six selected ENSO years and preliminarily assess the possible impact of land cover change on the summer circulation over the TP. Compared to Reanalysis II data, the GCM using satellite derived vegetation properties generally reproduces the main 6-year-mean TP summer circulation features despite some discrepancies in intensity and geographic locations of some climate features. Two existing vegetation maps with very different land cover conditions over the TP, one with bare ground and one with vegetation cover, derived from satellite derived data, are tested and produce clearer climate signals due to land cover change. It shows that land cover change from vegetated land to bare ground decreases the radiation absorbed by the surface and results in weaker surface thermal effects, which lead to lower atmospheric temperature, as well as weaker vertical ascending motion, low-layer cyclonic, upper level anticyclonic, and summer monsoon circulation. These changes in circulation cause a decrease in the precipitation in the southeastern TP.

  19. Southern Hemisphere origins for interannual variations of Tibetan Plateau snow cover in boreal summer

    Science.gov (United States)

    Wu, Z.

    2017-12-01

    The climate response to the Tibetan Plateau (TP) snow cover (TPSC) has been receiving extensive concern. However, relatively few studies have devoted to revealing the potential factors that can contribute to the TPSC variability on the interannual time scale. Especially during the boreal summer, snow cover can persist over the TP at high elevations, which exerts profound influences on the local and remote climate change. The present study finds that May Southern Hemisphere (SH) annular mode (SAM), the dominating mode of atmospheric circulation variability in the SH extratropics, exhibits a significant positive relationship with the boreal summer TPSC interannual variability. Observational analysis and numerical experiments manifest that the signal of May SAM can be "prolonged" by a meridional Indian Ocean tripole (IOT) sea surface temperature anomaly (SSTA) via atmosphere-ocean interaction. The IOT SSTA pattern persists into the following summer and excites anomalous local-scale zonal vertical circulation. Subsequently, a positive (or negative) tropical dipole rainfall (TDR) mode is induced with deficient (or sufficient) precipitation in tropical western Indian Ocean and sufficient (or deficient) precipitation in eastern Indian Ocean-Maritime continent. Rossby wave source diagnosis reveals that the wave energies, generated by the latent heat release of the TDR mode, propagate northward into western TP. As a response, abnormal cyclonic circulation and upward movement are triggered and prevail over western TP, providing favorable dynamical conditions for more TPSC, and vice versa. Hence, the IOT SSTA plays an "ocean bridge" role and the TDR mode acts as an "atmosphere bridge" role in the process of May SAM impacting the following summer TPSC variability. The results of our work may provide new insight about the cross-equatorial propagation of the SAM influence. Keywords Southern Hemisphere annular mode; Tibetan Plateau snow cover; Rossby wave source

  20. Oak Forest Responses to Episodic-Seasonal-Drought, Chronic Multi-year Precipitation Change and Acute Drought Manipulations in a Region With Deep Soils and High Precipitation

    Science.gov (United States)

    Hanson, Paul J.; Wullschleger, Stan D.; Todd, Donald E.; Auge, Robert M.; Froberg, Mats; Johnson, Dale W.

    2010-05-01

    Implications of episodic-seasonal drought (extremely dry late summers), chronic multi-year precipitation manipulations (±33 percent over 12 years) and acute drought (-100 percent over 3 years) were evaluated for the response of vegetation and biogeochemical cycles for an upland-oak forest. The Quercus-Acer forest is located in eastern Tennessee on deep acidic soils with mean annual temperatures of 14.2 °C and abundant precipitation (1352 mm y-1). The multi-year observations and chronic manipulations were conducted from 1993 through 2005 using understory throughfall collection troughs and redistribution gutters and pipes. Acute manipulations of dominant canopy trees (Quercus prinus; Liriodendron tulipifera) were conducted from 2003 through 2005 using full understory tents. Regional and severe late-summer droughts were produced reduced stand water use and photosynthetic carbon gain as expected. Likewise, seedlings and saplings exhibited reduced survival and cumulative growth reductions. Conversely, multi-year chronic increases or decreases in precipitation and associated soil water deficits did not reduce large tree basal area growth for the tree species present. The resilience of canopy trees to chronic-change was the result of a disconnect between carbon allocation to tree growth (an early-season phenomenon) and late-season drought occurrence. Acute precipitation exclusion from the largest canopy trees also produced limited physiological responses and minimal cumulative growth reductions. Lateral root water sources were removed through trenching and could not explain the lack of response to extreme soil drying. Therefore, deep rooting the primary mechanism for large-tree resilience to severe drought. Extensive trench-based assessments of rooting depth suggested that ‘deep' water supplies were being obtained from limited numbers of deep fine roots. Observations of carbon stocks in organic horizons demonstrated accumulation with precipitation reductions and

  1. Stable isotope distribution in precipitation in Romania and its relevance for palaeoclimatic studies

    Science.gov (United States)

    Perşoiu, Aurel; Nagavciuc, Viorica; Bădăluţă, Carmen

    2014-05-01

    A surge of recent studies in Romania have targeted various aspects of palaeoclimate (based on stable isotopes in ice, speleothems, tree rings), mineral water origin, wine and other juices provenance. However, while much needed, these studies lack a stable isotope in precipitation background, with only two LMWL's being published so far. In this paper we discuss the links between the stable isotopic composition of precipitation (δ18O and δ2H), climate (air temperature, precipitation amount and large scale circulation) and their relevance for the palaeocllimatic interpretation of stable isotope values in cave ice, cryogenic calcite and tree rings from different sites in Romania. Most of the precipitation in Romania is delivered by the Westerlies, bringing moisture from the North Atlantic; however, their influence is greatly reduced in the eastern half of the country where local evaporative sources play an important role in the precipitation balance. The SW is dominated by water masses from the Mediterranean Sea, while the SE corner clearly draws most of the moisture from the Black Sea and strongly depleted North Atlantic vapor masses. In 2012, Romania experienced the worst draught in 60 years, possibly due to a northward shift of the jest stream associated to blocking conditions in summer, which led to a more northern penetration of the Mediterranean-derived air masses, as well increased precipitation of re-evaporated waters. We have further analyzed cave drip water (δ18O and δ2H), cryogenic cave calcite (δ18O and δ13C) and tree rings (δ18O and δ13C) from selected sites across NW Romania, where the water isotopes in precipitation showed the best (and easiest to understand, given the climatic conditions in 2012) correlation with climatic parameters. Our results that 1) δ18O and δ2H in cave ice are a good proxy for late summer through early winter air temperature; 2) δ13C in cryogenic cave calcite are possible indicators of soil humidity and 3) δ18O in pine

  2. Importance of resolution and model configuration when downscaling extreme precipitation

    Directory of Open Access Journals (Sweden)

    Adrian J. Champion

    2014-07-01

    Full Text Available Dynamical downscaling is frequently used to investigate the dynamical variables of extra-tropical cyclones, for example, precipitation, using very high-resolution models nested within coarser resolution models to understand the processes that lead to intense precipitation. It is also used in climate change studies, using long timeseries to investigate trends in precipitation, or to look at the small-scale dynamical processes for specific case studies. This study investigates some of the problems associated with dynamical downscaling and looks at the optimum configuration to obtain the distribution and intensity of a precipitation field to match observations. This study uses the Met Office Unified Model run in limited area mode with grid spacings of 12, 4 and 1.5 km, driven by boundary conditions provided by the ECMWF Operational Analysis to produce high-resolution simulations for the Summer of 2007 UK flooding events. The numerical weather prediction model is initiated at varying times before the peak precipitation is observed to test the importance of the initialisation and boundary conditions, and how long the simulation can be run for. The results are compared to raingauge data as verification and show that the model intensities are most similar to observations when the model is initialised 12 hours before the peak precipitation is observed. It was also shown that using non-gridded datasets makes verification more difficult, with the density of observations also affecting the intensities observed. It is concluded that the simulations are able to produce realistic precipitation intensities when driven by the coarser resolution data.

  3. Precipitation of uranium concentrates by hydrogen peroxide

    International Nuclear Information System (INIS)

    Barbosa Filho, O.

    1986-12-01

    An experimental study on the (UO 4 .xH 2 ) uranyl peroxide precipitation from a uranium process strip solution is presented. The runs were performed in a batch reactor, in laboratory scale. The main objective was to assess the possibility of the peroxide route as an alternative to a conventional ammonium diuranate process. The chemical composition of process solution was obtained. The experiments were conducted according to a factorial design, aiming to evaluate the effects of initial pH, precipitation pH and H 2 O 2 /UO 2 2+ ratio upon the process. The responses were measured in terms of the efficiency of U precipitation, the content of U in the precipitates and the distribution of impurities in the precipitates. The results indicated that the process works is satisfactory on the studied conditions and depending on conditions, it is possible to achieve levels of U precipitation efficiency greater than 99.9% in reaction times of 2 hours. The precipitates reach grades around 99% U 3 O 8 after calcination (900 0 C) and impurities fall below the limit for penalties established by the ASTM and the Allied Chemical Standards. The precipitates are composed of large aggregates of crystals of 1-4 μm, are fast settling and filtering, and are free-flowing when dry. (Author) [pt

  4. Spatio-Temporal Analysis of the Accuracy of Tropical Multisatellite Precipitation Analysis 3B42 Precipitation Data in Mid-High Latitudes of China

    Science.gov (United States)

    Cai, Yancong; Jin, Changjie; Wang, Anzhi; Guan, Dexin; Wu, Jiabing; Yuan, Fenghui; Xu, Leilei

    2015-01-01

    Satellite-based precipitation data have contributed greatly to quantitatively forecasting precipitation, and provides a potential alternative source for precipitation data allowing researchers to better understand patterns of precipitation over ungauged basins. However, the absence of calibration satellite data creates considerable uncertainties for The Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) 3B42 product over high latitude areas beyond the TRMM satellites latitude band (38°NS). This study attempts to statistically assess TMPA V7 data over the region beyond 40°NS using data obtained from numerous weather stations in 1998–2012. Comparative analysis at three timescales (daily, monthly and annual scale) indicates that adoption of a monthly adjustment significantly improved correlation at a larger timescale increasing from 0.63 to 0.95; TMPA data always exhibits a slight overestimation that is most serious at a daily scale (the absolute bias is 103.54%). Moreover, the performance of TMPA data varies across all seasons. Generally, TMPA data performs best in summer, but worst in winter, which is likely to be associated with the effects of snow/ice-covered surfaces and shortcomings of precipitation retrieval algorithms. Temporal and spatial analysis of accuracy indices suggest that the performance of TMPA data has gradually improved and has benefited from upgrades; the data are more reliable in humid areas than in arid regions. Special attention should be paid to its application in arid areas and in winter with poor scores of accuracy indices. Also, it is clear that the calibration can significantly improve precipitation estimates, the overestimation by TMPA in TRMM-covered area is about a third as much as that in no-TRMM area for monthly and annual precipitation. The systematic evaluation of TMPA over mid-high latitudes provides a broader understanding of satellite-based precipitation estimates, and these data are

  5. Spatio-temporal analysis of the accuracy of tropical multisatellite precipitation analysis 3B42 precipitation data in mid-high latitudes of China.

    Directory of Open Access Journals (Sweden)

    Yancong Cai

    Full Text Available Satellite-based precipitation data have contributed greatly to quantitatively forecasting precipitation, and provides a potential alternative source for precipitation data allowing researchers to better understand patterns of precipitation over ungauged basins. However, the absence of calibration satellite data creates considerable uncertainties for The Tropical Rainfall Measuring Mission (TRMM Multisatellite Precipitation Analysis (TMPA 3B42 product over high latitude areas beyond the TRMM satellites latitude band (38°NS. This study attempts to statistically assess TMPA V7 data over the region beyond 40°NS using data obtained from numerous weather stations in 1998-2012. Comparative analysis at three timescales (daily, monthly and annual scale indicates that adoption of a monthly adjustment significantly improved correlation at a larger timescale increasing from 0.63 to 0.95; TMPA data always exhibits a slight overestimation that is most serious at a daily scale (the absolute bias is 103.54%. Moreover, the performance of TMPA data varies across all seasons. Generally, TMPA data performs best in summer, but worst in winter, which is likely to be associated with the effects of snow/ice-covered surfaces and shortcomings of precipitation retrieval algorithms. Temporal and spatial analysis of accuracy indices suggest that the performance of TMPA data has gradually improved and has benefited from upgrades; the data are more reliable in humid areas than in arid regions. Special attention should be paid to its application in arid areas and in winter with poor scores of accuracy indices. Also, it is clear that the calibration can significantly improve precipitation estimates, the overestimation by TMPA in TRMM-covered area is about a third as much as that in no-TRMM area for monthly and annual precipitation. The systematic evaluation of TMPA over mid-high latitudes provides a broader understanding of satellite-based precipitation estimates, and these

  6. Spatiotemporal characteristics and water budget of water cycle elements in different seasons in northeast China

    International Nuclear Information System (INIS)

    Zhou Jie; Zhao Jun-Hu; He Wen-Ping; Zhi-Qiang Gong

    2015-01-01

    In this paper, we study the spatiotemporal characteristics of precipitable water, precipitation, evaporation, and water–vapor flux divergence in different seasons over northeast China and the water balance of that area. The data used in this paper is provided by the European Center for Medium-Range Weather Forecasts (ECMWF). The results show that the spatial distributions of precipitable water, precipitation, and evaporation feature that the values of elements above in the southeastern area are larger than those in the northwestern area; in summer, much precipitation and evaporation occur in the Changbai Mountain region as a strong moisture convergence region; in spring and autumn, moisture divergence dominates the northeast of China; in winter, the moisture divergence and convergence are weak in this area. From 1979 to 2010, the total precipitation of summer and autumn in northeast China decreased significantly; especially from 1999 to 2010, the summer precipitation always demonstrated negative anomaly. Additionally, other elements in different seasons changed in a truly imperceptible way. In spring, the evaporation exceeded the precipitation in northeast China; in summer, the precipitation was more prominent; in autumn and winter, precipitation played a more dominating role than the evaporation in the northern part of northeast China, while the evaporation exceeded the precipitation in the southern part.The Interim ECMWF Re-Analysis (ERA-Interim) data have properly described the water balance of different seasons in northeast China. Based on ERA-Interim data, the moisture sinks computed through moisture convergence and moisture local variation are quite consistent with those computed through precipitation and evaporation, which proves that ERA-Interim data can be used in the research of water balance in northeast China. On a seasonal scale, the moisture convergence has a greater influence than the local moisture variation on a moisture sink, and the latter is

  7. Spatiotemporal characteristics and water budget of water cycle elements in different seasons in northeast China

    Institute of Scientific and Technical Information of China (English)

    周杰; 赵俊虎; 何文平; 龚志强

    2015-01-01

    In this paper, we study the spatiotemporal characteristics of precipitable water, precipitation, evaporation, and water–vapor flux divergence in different seasons over northeast China and the water balance of that area. The data used in this paper is provided by the European Center for Medium-Range Weather Forecasts (ECMWF). The results show that the spatial distributions of precipitable water, precipitation, and evaporation feature that the values of elements above in the southeastern area are larger than those in the northwestern area;in summer, much precipitation and evaporation occur in the Changbai Mountain region as a strong moisture convergence region;in spring and autumn, moisture divergence dominates the northeast of China;in winter, the moisture divergence and convergence are weak in this area. From 1979 to 2010, the total precipitation of summer and autumn in northeast China decreased significantly; especially from 1999 to 2010, the summer precipitation always demonstrated negative anomaly. Additionally, other elements in different seasons changed in a truly imperceptible way. In spring, the evaporation exceeded the precipitation in northeast China; in summer, the precipitation was more prominent;in autumn and winter, precipitation played a more dominating role than the evaporation in the northern part of northeast China, while the evaporation exceeded the precipitation in the southern part. The Interim ECMWF Re-Analysis (ERA-Interim) data have properly described the water balance of different seasons in northeast China. Based on ERA-Interim data, the moisture sinks computed through moisture convergence and moisture local variation are quite consistent with those computed through precipitation and evaporation, which proves that ERA-Interim data can be used in the research of water balance in northeast China. On a seasonal scale, the moisture convergence has a greater influence than the local moisture variation on a moisture sink, and the latter is

  8. Analysis on Climatic Characteristics of the Precipitation Anomaly in Southwest China in Recent 60 Years

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Rong; PANG; Jing; QIN; Jun

    2012-01-01

    [Objective]The research aimed to analyze temporal-spatial distribution characteristics of the precipitation anomaly in southwest China from 1951 to 2010. [Method] Based on monthly precipitation data at 44 stations of southwest China and 160 stations of China from 1951 to 2010, by using EOF analysis, wavelet analysis and composite analysis, monthly and seasonal change rules of the precipitation in southwest China were analyzed. Corresponding spatial-temporal distribution characteristics of the precipitation in drought and flood years were studied. Temporal-spatial distribution characteristics of the precipitation anomaly in southwest China in recent 60 years were revealed. [Result]Seasonal distribution of the precipitation in southwest China was uneven and was typical single-peak type. Precipitation concentrated from May to September, and peak appeared in July. In recent years, rainfall in autumn significantly became less, while that in other seasons had no obvious change. Precipitation in summer had the cycle of 14 years, another for 6 years and 3-4 years of periodic oscillations. In wet years, precipitation in southwest China had same phase with that in southern China, and anti-phase with that in the junction of Qinghai, Gansu, Xinjiang and Tibet. In dry years, precipitation in southwest China had same phase with that in the eastern part of northwest China and northern China. [Conclusion]The research provided reference basis for prediction and pre-warning of the precipitation in the zone.

  9. Mobility of radiocaesium in boreal forest ecosystems: Influence of precipitation chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Steinnes, E. [Department of Chemistry, Norwegian University of Science and Technology (Norway); Gjelsvik, R.; Skuterud, L.; Thoerring, H. [Norwegian Radiation Protection Authority (Norway)

    2014-07-01

    Mobility and plant uptake of Cs in soils is generally limited by the presence of clay minerals in the soil. However, cations supplied by precipitation may substantially influence the mobility of radiocaesium in natural surface soil and subsequent transfer to food chains. The chemical composition of precipitation shows substantial variation among different areas in Norway for two main reasons. At sites close to the coast the atmospheric supply of marine cations and anions is many-fold greater than in regions shielded from marine influence by mountains. The southernmost part of the country has been, and still is, substantially affected by soil acidification due to long-range atmospheric transport of acidifying substances from areas elsewhere in Europe. This may explain a much higher greater uptake of {sup 137}Cs from the Chernobyl accident in moose in this region than elsewhere (Steinnes et al., 2009), in spite of the fact that some areas farther north received substantially greater fallout. Similarly a much greater transfer of {sup 137}Cs to natural birch forest vegetation is evident from the more acidified soils in the south than in comparable ecosystems elsewhere in the country (Thoerring et al., 2012). Repeated recordings of activity levels in natural surface soils showed faster leaching of Chernobyl {sup 137}Cs relative to inland areas not only in the south but also in coastal areas farther north (Gjelsvik and Steinnes, 2013), indicating that the amounts of marine cations in precipitation also has an appreciable effect on the Cs leaching. The geographical leaching differences still became less prominent with time. Recent lysimeter experiments with undisturbed soil columns obtained from an area receiving high radiocaesium deposition from the Chernobyl accident, applying precipitation with ionic composition characteristic of the different regions mentioned above, did not change the current depth distribution of {sup 137}Cs. However, acidic precipitation increased

  10. Auroral ionospheric quiet summer time conductances

    International Nuclear Information System (INIS)

    Brekke, A.; Hall, C.

    1988-01-01

    The auroral zone E-region conductivities and conductances have been studied for 7 quiet time summer days. The Hall- and Pedersen conductances are found to follow the solar zenith variations in a rather regular fashion, and empirical formulas for these conductances are obtained. The choice of proper collision frequency models is found to be of great importance when deriving the conductances, and it is argued that some of the different results presented by other authors may be due to different models of the collision frequencies. The Hall- to Pedersen conductance ratios can only be used as an indicator of the energy of the precipitating auroral particles when the contribution from the background solar ionization is subtracted. When this is done this ratio takes much higher values than previously reported

  11. Impact of anthropogenic aerosols from global, East Asian, and non-East Asian sources on East Asian summer monsoon system

    Science.gov (United States)

    Wang, Qiuyan; Wang, Zhili; Zhang, Hua

    2017-01-01

    The impact of the total effects due to anthropogenic aerosols from global, East Asian, and non-East Asian sources on East Asian summer monsoon (EASM) system is studied using an aerosol-climate online model BCC_AGCM2.0.1_CUACE/Aero. The results show that the summer mean net all-sky shortwave fluxes averaged over East Asian monsoon region (EAMR) at the top of the atmosphere (TOA) and surface reduce by 4.8 and 5.0 W m- 2, respectively, due to the increases of global aerosol emissions in 2000 relative to 1850. Changes in radiations and their resulting changes in heat and water transport and cloud fraction contribute together to the surface cooling over EAMR in summer. The increases in global anthropogenic aerosols lead to a decrease of 2.1 K in summer mean surface temperature and an increase of 0.4 hPa in summer mean surface pressure averaged over EAMR, respectively. It is shown that the changes in surface temperature and pressure are significantly larger over land than ocean, thus decreasing the contrast of land-sea surface temperature and pressure. This results in the marked anomalies of north and northeast winds over eastern and southern China and the surrounding oceans in summer, thereby weakening the EASM. The summer mean precipitation averaged over the EAMR reduces by 12%. The changes in non-East Asian aerosol emissions play a more important role in inducing the changes of local temperature and pressure, and thus significantly exacerbate the weakness of the EASM circulation due to local aerosol changes. The weakening of circulation due to both is comparable, and even the effect of non-local aerosols is larger in individual regions. The changes of local and non-local aerosols contribute comparably to the reductions in precipitation over oceans, whereas cause opposite changes over eastern China. Our results highlight the importance of aerosol changes outside East Asia in the impact of the changes of anthropogenic aerosols on EASM.

  12. Mood Sensitivity to Seasonal Changes in African College Students Living in the Greater Washington D.C. Metropolitan Area

    Directory of Open Access Journals (Sweden)

    Alvaro Guzman

    2007-01-01

    Full Text Available The purpose of this study was to estimate the degree of seasonality and prevalence of winter- and summer-type seasonal affective disorder (SAD in African immigrant college students in comparison with African American peers. A convenience sample of 246 African immigrants and 599 African Americans studying in Washington, D.C. completed the Seasonal Pattern Assessment Questionnaire (SPAQ, which was used to calculate a global seasonality score (GSS and to estimate the prevalence of winter- and summer-type SAD. Degree of seasonality was related to a complex interaction between having general awareness of SAD, ethnicity, and gender. A greater percentage of African students reported experiencing a problem with seasonal changes relative to African American students, and had summer SAD, but the groups did not differ on GSS and winter SAD. African students reported more difficulties with seasonal changes than their African American peers, which could represent a manifestation of incomplete acclimatization to a higher latitude and temperate climate. As Africans also had a greater rate of summer SAD, this argues against acclimatization to heat.

  13. Linkage Between Hourly Precipitation Events and Atmospheric Temperature Changes over China during the Warm Season

    Science.gov (United States)

    Miao, Chiyuan; Sun, Qiaohong; Borthwick, Alistair G. L.; Duan, Qingyun

    2016-01-01

    We investigated changes in the temporospatial features of hourly precipitation during the warm season over mainland China. The frequency and amount of hourly precipitation displayed latitudinal zonation, especially for light and moderate precipitation, which showed successive downward change over time in northeastern and southern China. Changes in the precipitation amount resulted mainly from changes in frequency rather than changes in intensity. We also evaluated the linkage between hourly precipitation and temperature variations and found that hourly precipitation extreme was more sensitive to temperature than other categories of precipitation. A strong dependency of hourly precipitation on temperature occurred at temperatures colder than the median daily temperature; in such cases, regression slopes were greater than the Clausius-Clapeyron (C-C) relation of 7% per degree Celsius. Regression slopes for 31.6%, 59.8%, 96.9%, and 99.1% of all stations were greater than 7% per degree Celsius for the 75th, 90th, 99th, and 99.9th percentiles for precipitation, respectively. The mean regression slopes within the 99.9th percentile of precipitation were three times the C-C rate. Hourly precipitation showed a strong negative relationship with daily maximum temperature and the diurnal temperature range at most stations, whereas the equivalent correlation for daily minimum temperature was weak. PMID:26931350

  14. Inter-comparison of statistical downscaling methods for projection of extreme precipitation in Europe

    DEFF Research Database (Denmark)

    Sunyer Pinya, Maria Antonia; Hundecha, Y.; Lawrence, D.

    impact studies. Four methods are based on change factors and four are bias correction methods. The change factor methods perturb the observations according to changes in precipitation properties estimated from the Regional Climate Models (RCMs). The bias correction methods correct the output from...... the RCMs. The eight methods are used to downscale precipitation output from fifteen RCMs from the ENSEMBLES project for eleven catchments in Europe. The performance of the bias correction methods depends on the catchment, but in all cases they represent an improvement compared to RCM output. The overall...... results point to an increase in extreme precipitation in all the catchments in winter and in most catchments in summer. For each catchment, the results tend to agree on the direction of the change but differ in the magnitude. These differences can be mainly explained due to differences in the RCMs....

  15. Temperature and precipitation history of the Arctic

    DEFF Research Database (Denmark)

    Miller, G. H.; Brigham-Grette, J.; Alley, R. B.

    2010-01-01

    in the tilt of Earth’s axis, but for the past 700 ka, glacial cycles have been longer, lasting w100 ka, separated by brief, warm interglaciations, when sea level and ice volumes were close to present. The cause of the shift from 41 ka to 100 ka glacial cycles is still debated. During the penultimate...... interglaciation, w130 to w120 ka ago, solar energy in summer in the Arctic was greater than at any time subsequently. As a consequence, Arctic summers werew5 C warmer than at present, and almost all glaciers melted completely except for the Greenland Ice Sheet, and even it was reduced in size substantially from...... as 20 C lower than at present. Ice recession was well underway 16 ka ago, and most of the Northern Hemisphere ice sheets had melted by 6 ka ago. Solar energy reached a summer maximum (9% higher than at present) w11 ka ago and has been decreasing since then, primarily in response to the precession...

  16. Stable isotopes reveal sources of precipitation in the Qinghai Lake Basin of the northeastern Tibetan Plateau

    International Nuclear Information System (INIS)

    Cui, Bu-Li; Li, Xiao-Yan

    2015-01-01

    The use of isotopic tracers is an effective approach for characterizing the moisture sources of precipitation in cold and arid regions, especially in the Tibetan Plateau (TP), an area of sparse human habitation with few weather and hydrological stations. This study investigated stable isotope characteristics of precipitation in the Qinghai Lake Basin, analyzed moisture sources using data sets from NCEP–NCAR, and calculated vapor contributions from lake evaporation to the precipitation in the basin using a two-component mixing model. Results showed that the Local Meteoric Water Line (LMWL) was defined as δ 2 H = 7.86 δ 18 O + 15.01, with a slope of less than 8, indicating that some non-equilibrium evaporation processes occurred when the drops fell below the cloud base. Temperature effects controlled δ 18 O and δ 2 H in precipitation in the basin, with high values in summer season and low values in winter season. Moisture in the basin was derived predominantly from the Southeast Asian Monsoon (SEAM) from June to August and the Westerly Circulation (WC) from September through May. Meanwhile, the transition in atmospheric circulation took place in June and September. The SEAM strengthened gradually, while the WC weakened gradually in June, and inversely in September. However, the Southwest Asian Monsoon (SWAM) did not reach the Qinghai Lake Basin due to the barrier posed by Tanggula Mountain. High d-excess (> 10‰) and significant altitude and lake effects of δ 18 O in precipitation suggested that the vapor evaporated from Qinghai Lake, strongly influenced annual precipitation, and affected the regional water cycle in the basin distinctly. The monthly contribution of lake evaporation to basin precipitation ranged from 3.03% to 37.93%, with an annual contribution of 23.42% or 90.54 mm, the majority of which occurred in the summer season. The findings demonstrate that the contribution of evaporation from lakes to atmospheric vapor is fundamental to water cycling

  17. Stable isotopes reveal sources of precipitation in the Qinghai Lake Basin of the northeastern Tibetan Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Bu-Li, E-mail: cuibuli@ieecas.cn [State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi' an 710061 (China); College of Resources Science and Technology, Beijing Normal University, Beijing 100875 (China); Li, Xiao-Yan [State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875 (China); College of Resources Science and Technology, Beijing Normal University, Beijing 100875 (China)

    2015-09-15

    The use of isotopic tracers is an effective approach for characterizing the moisture sources of precipitation in cold and arid regions, especially in the Tibetan Plateau (TP), an area of sparse human habitation with few weather and hydrological stations. This study investigated stable isotope characteristics of precipitation in the Qinghai Lake Basin, analyzed moisture sources using data sets from NCEP–NCAR, and calculated vapor contributions from lake evaporation to the precipitation in the basin using a two-component mixing model. Results showed that the Local Meteoric Water Line (LMWL) was defined as δ{sup 2}H = 7.86 δ{sup 18}O + 15.01, with a slope of less than 8, indicating that some non-equilibrium evaporation processes occurred when the drops fell below the cloud base. Temperature effects controlled δ{sup 18}O and δ{sup 2}H in precipitation in the basin, with high values in summer season and low values in winter season. Moisture in the basin was derived predominantly from the Southeast Asian Monsoon (SEAM) from June to August and the Westerly Circulation (WC) from September through May. Meanwhile, the transition in atmospheric circulation took place in June and September. The SEAM strengthened gradually, while the WC weakened gradually in June, and inversely in September. However, the Southwest Asian Monsoon (SWAM) did not reach the Qinghai Lake Basin due to the barrier posed by Tanggula Mountain. High d-excess (> 10‰) and significant altitude and lake effects of δ{sup 18}O in precipitation suggested that the vapor evaporated from Qinghai Lake, strongly influenced annual precipitation, and affected the regional water cycle in the basin distinctly. The monthly contribution of lake evaporation to basin precipitation ranged from 3.03% to 37.93%, with an annual contribution of 23.42% or 90.54 mm, the majority of which occurred in the summer season. The findings demonstrate that the contribution of evaporation from lakes to atmospheric vapor is

  18. 18O, 2H and 3H isotopic composition of precipitation and shallow groundwater in Olkiluoto

    International Nuclear Information System (INIS)

    Hendriksson, N.; Karhu, J.; Niinikoski, P.

    2014-12-01

    The isotopic composition of oxygen and hydrogen in local precipitation is a key parameter in the modelling of local water circulation. This study was initiated in order to provide systematic monthly records of the isotope content of atmospheric precipitation in the Olkiluoto area and to establish the relation between local rainfall and newly formed groundwater. During January 2005 - December 2012, a total of 85 cumulative monthly rainfall samples and 68 shallow groundwater samples were collected and the isotopic composition of oxygen and hydrogen was recorded for all those samples. Tritium values are available for 79 precipitation and 65 groundwater samples. Based on the 8-year monitoring, the long-term weighted annual mean isotope values of precipitation and the mean values of shallow groundwater are -11.59 per mille and -11.27 per mille for δ 18 O, - 82.3 per mille and -80.3 per mille for δ 2 H and 9.8 and 9.1 TU for tritium, respectively. Based on these data, the mean stable isotope ratios of groundwater represent the long-term mean annual isotopic composition of local precipitation. The precipitation data were used to establish the local meteoric water line (LMWL) for the Olkiluoto area. The line is formulated as: δ 2 H = 7.45 star δ 18 O + 3.82. The isotope time series reveal a change in time. The increasing trend for the δ 18 O and δ 2 H values may be related to climatic variability while the gradual decline observed in the 3 H data is attributed to the still continuing decrease in atmospheric 3 H activity in the northern hemisphere. The systematic seasonal and long-term tritium trends suggest that any potential ground-level tritium release from the Olkiluoto nuclear power plants is insignificant. The d-excess values of Olkiluoto precipitation during the summer period indicated that a notable amount of re-cycled Baltic Sea water may have contributed to precipitation in the Finnish southern coast. Preliminary estimates of the evaporated Baltic Sea water

  19. Evaluation of precipitation extremes over the Asian domain: observation and modelling studies

    Science.gov (United States)

    Kim, In-Won; Oh, Jaiho; Woo, Sumin; Kripalani, R. H.

    2018-04-01

    In this study, a comparison in the precipitation extremes as exhibited by the seven reference datasets is made to ascertain whether the inferences based on these datasets agree or they differ. These seven datasets, roughly grouped in three categories i.e. rain-gauge based (APHRODITE, CPC-UNI), satellite-based (TRMM, GPCP1DD) and reanalysis based (ERA-Interim, MERRA, and JRA55), having a common data period 1998-2007 are considered. Focus is to examine precipitation extremes in the summer monsoon rainfall over South Asia, East Asia and Southeast Asia. Measures of extreme precipitation include the percentile thresholds, frequency of extreme precipitation events and other quantities. Results reveal that the differences in displaying extremes among the datasets are small over South Asia and East Asia but large differences among the datasets are displayed over the Southeast Asian region including the maritime continent. Furthermore, precipitation data appear to be more consistent over East Asia among the seven datasets. Decadal trends in extreme precipitation are consistent with known results over South and East Asia. No trends in extreme precipitation events are exhibited over Southeast Asia. Outputs of the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulation data are categorized as high, medium and low-resolution models. The regions displaying maximum intensity of extreme precipitation appear to be dependent on model resolution. High-resolution models simulate maximum intensity of extreme precipitation over the Indian sub-continent, medium-resolution models over northeast India and South China and the low-resolution models over Bangladesh, Myanmar and Thailand. In summary, there are differences in displaying extreme precipitation statistics among the seven datasets considered here and among the 29 CMIP5 model data outputs.

  20. Prediction of Summer Extreme Precipitation over the Middle and Lower Reaches of the Yangtze River Basin

    Science.gov (United States)

    Liu, L.; Ning, L.; Liu, J.; Yan, M.; Sun, W.

    2017-12-01

    Abstract: Summer extreme precipitation (SEP) often causes severe landslide, debris flow and floods over the middle and lower reaches of the Yangtze River Basin(MLYRB), so skillful prediction of the SEP is critical to the future climate adaptions and mitigations. In this work, the characteristic region over the MLYRB (27°N-32°N,108°1-118°E) is defined by the spatial mode of the rotated empirical orthogonal functions (REOF) of SEP over the China from 1961 to 2014. A physics-based empirical model (PEM) of SEP predictions is built with two preceding predictors with significant physical influences on the SEP over the MLYRB. The first predictor is the spring sea surface temperature (SST) over the Northern Indian Ocean (20°S-20°N,50°E-95°E), and the second predictor is the spring sea surface pressure (SLP) over the Aleutian Island (50°N-70°N,160°E-160°W). Analyses of physical mechanism show that when the spring SST over the Northern Indian Ocean is higher, the South Asian High (SAH) extends to the east and the western Pacific sub-tropical high (WPSH) extends to the west, therefore, the generated secondary circulation induces anomalous upward motions and more water vapor transportation to the MLYRB, resulting more SEP. Meanwhile, when the spring SLP over the Aleutian Island is lower, the also WPSH extends to the west, which leads to a negative omega anomaly centered the MLYRB and more water vapor transportation to the MLYRB, resulting in more SEP. The regression model is built using the data from a training period from 1961 to 1999 with correlation coefficient skill of 0.57 (p<0.01) for prediction of SEP in 1961-1999. The independent forecast of the PEM shows that it is skillful in SEP prediction with the correlation coefficient between observed SEP and model-simulated SEP over the validation period 2000-2014 is 0.51 (p<0.05). This finding shows that the preceding spring SST and SLP can provide useful information for prediction of SEP, and the methodology

  1. Exposure to extreme heat and precipitation events associated with increased risk of hospitalization for asthma in Maryland, U.S.A.

    Science.gov (United States)

    Soneja, Sutyajeet; Jiang, Chengsheng; Fisher, Jared; Upperman, Crystal Romeo; Mitchell, Clifford; Sapkota, Amir

    2016-04-27

    Several studies have investigated the association between asthma exacerbations and exposures to ambient temperature and precipitation. However, limited data exists regarding how extreme events, projected to grow in frequency, intensity, and duration in the future in response to our changing climate, will impact the risk of hospitalization for asthma. The objective of our study was to quantify the association between frequency of extreme heat and precipitation events and increased risk of hospitalization for asthma in Maryland between 2000 and 2012. We used a time-stratified case-crossover design to examine the association between exposure to extreme heat and precipitation events and risk of hospitalization for asthma (ICD-9 code 493, n = 115,923). Occurrence of extreme heat events in Maryland increased the risk of same day hospitalization for asthma (lag 0) by 3 % (Odds Ratio (OR): 1.03, 95 % Confidence Interval (CI): 1.00, 1.07), with a considerably higher risk observed for extreme heat events that occur during summer months (OR: 1.23, 95 % CI: 1.15, 1.33). Likewise, summertime extreme precipitation events increased the risk of hospitalization for asthma by 11 % in Maryland (OR: 1.11, 95 % CI: 1.06, 1.17). Across age groups, increase in risk for asthma hospitalization from exposure to extreme heat event during the summer months was most pronounced among youth and adults, while those related to extreme precipitation event was highest among ≤4 year olds. Exposure to extreme heat and extreme precipitation events, particularly during summertime, is associated with increased risk of hospitalization for asthma in Maryland. Our results suggest that projected increases in frequency of extreme heat and precipitation event will have significant impact on public health.

  2. pH and its frequency distribution patterns of Acid Precipitation in Japan

    International Nuclear Information System (INIS)

    Kitamura, Moritsugu; Katou, Takunori; Sekiguchi, Kyoichi

    1991-01-01

    The pH data was collected at the 29 stations in Phase-I study of Acid Precipitation Survey over Japan by Japan Environment Agency in terms of frequency distribution patterns. This study was undertaken from April 1984 to March 1988, which was the first survey of acid precipitation over Japan with identical sampling procedures and subsequent chemical analyses. While the annual mean pH at each station ranged from 4.4 to 5.5, the monthly mean varied more widely, from 4.0 to 7.1. Its frequency distribution pattern was obtained for each station, and further grouped into four classes: class I; a mode at the rank of pH 4.5∼4.9, class II; bimodes above and below this pH region, class III; a mode at a higher pH region, class IV; a mode at a lower pH region. The bimodal pattern was suggestive of precipitation with and without incorporation of significant amounts of basic aerosol of anthropogenic origin during descent of rain droplet. The patterns of the stations were also classified on a basis of summer-winter difference into another four classes. Winter pH values were appreciably lower than summer pHs in western parts of Japan and on Japan Sea coast, we attribute the winter pH to probable contribution of acidic pollutants transported by strong winter monsoon from Eurasian Continent. At most stations in northern and eastern Japan, the pH was higher in winter months reflecting more incorporation of basic materials, e.g., NH 4 + and Ca 2+ . (author)

  3. Study of precipitation phenomena during the creep of austenitic stainless steels

    International Nuclear Information System (INIS)

    Le May, I.; Bassett, B.J.; White, W.E.

    1975-01-01

    Creep-rupture data for two austenitic stainless steels, AISI Types 310 and 316, are presented, together with observations of precipitation taking place during creep. While the effects of creep deformation on precipitation in the Type 310 were negligible, ferrite precipitation was considerably greater in the Type 316 undergoing creep than in unstressed material. Ferrite precipitation appears to promote grain boundary cavitation and internal cracking, thus reducing creep resistance and a correlation has been noted between increased ferrite precipitation and apparent further weakening of the Type 316 over the temperature range 730 to 800 0 C approximately, as evidenced by breaks in the isostress lines on a plot of log (time to rupture) versus temperature

  4. Risk assessment of precipitation extremes in northern Xinjiang, China

    Science.gov (United States)

    Yang, Jun; Pei, Ying; Zhang, Yanwei; Ge, Quansheng

    2018-05-01

    This study was conducted using daily precipitation records gathered at 37 meteorological stations in northern Xinjiang, China, from 1961 to 2010. We used the extreme value theory model, generalized extreme value (GEV) and generalized Pareto distribution (GPD), statistical distribution function to fit outputs of precipitation extremes with different return periods to estimate risks of precipitation extremes and diagnose aridity-humidity environmental variation and corresponding spatial patterns in northern Xinjiang. Spatiotemporal patterns of daily maximum precipitation showed that aridity-humidity conditions of northern Xinjiang could be well represented by the return periods of the precipitation data. Indices of daily maximum precipitation were effective in the prediction of floods in the study area. By analyzing future projections of daily maximum precipitation (2, 5, 10, 30, 50, and 100 years), we conclude that the flood risk will gradually increase in northern Xinjiang. GEV extreme value modeling yielded the best results, proving to be extremely valuable. Through example analysis for extreme precipitation models, the GEV statistical model was superior in terms of favorable analog extreme precipitation. The GPD model calculation results reflect annual precipitation. For most of the estimated sites' 2 and 5-year T for precipitation levels, GPD results were slightly greater than GEV results. The study found that extreme precipitation reaching a certain limit value level will cause a flood disaster. Therefore, predicting future extreme precipitation may aid warnings of flood disaster. A suitable policy concerning effective water resource management is thus urgently required.

  5. Anticyclonic atmospheric circulation as an analogue for the warm and dry mid-Holocene summer climate in central Scandinavia

    Directory of Open Access Journals (Sweden)

    K. Antonsson

    2008-10-01

    Full Text Available Climate reconstructions from central Scandinavia suggest that annual and summer temperatures were rising during the early Holocene and reached their maximum after 8000 cal yr BP. The period with highest temperatures was characterized by increasingly low lake-levels and dry climate, with driest and warmest conditions at about 7000 to 5000 cal yr BP. We compare the reconstructed climate pattern with simulations of a climate model for the last 9000 years and show that the model, which is predominantly driven by solar insolation patterns, suggests less prominent mid-Holocene dry and warm period in Scandinavia than the reconstructions. As an additional explanation for the reconstructed climate, we argue that the trend from the moist early Holocene towards dry and warm mid-Holocene was caused by a changing atmospheric circulation pattern with a mid-Holocene dominance of summer-time anticyclonic circulation. An extreme case of the anticyclonic conditions is the persistent blocking high, an atmospheric pressure pattern that at present often causes long spells of particularly dry and warm summer weather, or "Indian summers". The argument is tested with daily instrumental temperature and precipitation records in central Sweden and an objective circulation classification based on surface air pressure over the period 1900–2002. We conclude that the differences between the precipitation and temperature climates under anticyclonic and non-anticyclonic conditions are significant. Further, warm and dry combination, as indicated by mid-Holocene reconstructions, is a typical pattern under anticyclonic conditions. These results indicate that the presented hypothesis for the mid-Holocene climate is likely valid.

  6. The Relationships Between Insoluble Precipitation Residues, Clouds, and Precipitation Over California's Southern Sierra Nevada During Winter Storms

    Science.gov (United States)

    Creamean, Jessie M.; White, Allen B.; Minnis, Patrick; Palikonda, Rabindra; Spangenberg, Douglas A.; Prather, Kimberly A.

    2016-01-01

    Ice formation in orographic mixed-phase clouds can enhance precipitation and depends on the type of aerosols that serve as ice nucleating particles (INP). The resulting precipitation from these clouds is a viable source of water, especially for regions such as the California Sierra Nevada. Thus, a better understanding of the sources of INP that impact orographic clouds is important for assessing water availability in California. This study presents a multi-site, multi-year analysis of single particle insoluble residues in precipitation samples that likely influenced cloud ice and precipitation formation above Yosemite National Park. Dust and biological particles represented the dominant fraction of the residues (64% on average). Cloud glaciation, determined using GOES satellite observations, not only depended on high cloud tops (greater than 6.2 km) and low temperatures (less than -26 C), but also on the composition of the dust and biological residues. The greatest prevalence of ice-phase clouds occurred in conjunction with biologically-rich residues and mineral dust rich in calcium, followed by iron and aluminosilicates. Dust and biological particles are known to be efficient INP, thus these residues are what likely influenced ice formation in clouds above the sites and subsequent precipitation quantities reaching the surface during events with similar meteorology. The goal of this study is to use precipitation chemistry information to gain a better understanding of the potential sources of INP in the south-central Sierra Nevada, where cloud-aerosol-precipitation interactions are under-studied and where mixed-phase orographic clouds represent a key element in the generation of precipitation and thus the water supply in California.

  7. Rapid decadal convective precipitation increase over Eurasia during the last three decades of the 20th century.

    Science.gov (United States)

    Ye, Hengchun; Fetzer, Eric J; Wong, Sun; Lambrigtsen, Bjorn H

    2017-01-01

    Convective precipitation-localized, short-lived, intense, and sometimes violent-is at the root of challenges associated with observation, simulation, and prediction of precipitation. The understanding of long-term changes in convective precipitation characteristics and their role in precipitation extremes and intensity over extratropical regions are imperative to future water resource management; however, they have been studied very little. We show that annual convective precipitation total has been increasing astonishingly fast, at a rate of 18.4%/°C, of which 16% is attributable to an increase in convective precipitation occurrence, and 2.4% is attributable to increased daily intensity based on the 35 years of two (combined) historical data sets of 3-hourly synoptic observations and daily precipitation. We also reveal that annual daily precipitation extreme has been increasing at a rate of about 7.4%/°C in convective events only. Concurrently, the overall increase in mean daily precipitation intensity is mostly due to increased convective precipitation, possibly at the expanse of nonconvective precipitation. As a result, transitional seasons are becoming more summer-like as convective becomes the dominant precipitation type that has accompanied higher daily extremes and intensity since the late 1980s. The data also demonstrate that increasing convective precipitation and daily extremes appear to be directly linearly associated with higher atmospheric water vapor accompanying a warming climate over northern Eurasia.

  8. Diagnosing GCM errors over West Africa using relaxation experiments. Part I: summer monsoon climatology and interannual variability

    Science.gov (United States)

    Pohl, Benjamin; Douville, Hervé

    2011-10-01

    The CNRM atmospheric general circulation model Arpege-Climat is relaxed towards atmospheric reanalyses outside the 10°S-32°N 30°W-50°E domain in order to disentangle the regional versus large-scale sources of climatological biases and interannual variability of the West African monsoon (WAM). On the one hand, the main climatological features of the monsoon, including the spatial distribution of summer precipitation, are only weakly improved by the nudging, thereby suggesting the regional origin of the Arpege-Climat biases. On the other hand, the nudging technique is relatively efficient to control the interannual variability of the WAM dynamics, though the impact on rainfall variability is less clear. Additional sensitivity experiments focusing on the strong 1994 summer monsoon suggest that the weak sensitivity of the model biases is not an artifact of the nudging design, but the evidence that regional physical processes are the main limiting factors for a realistic simulation of monsoon circulation and precipitation in the Arpege-Climat model. Sensitivity experiments to soil moisture boundary conditions are also conducted and highlight the relevance of land-atmosphere coupling for the amplification of precipitation biases. Nevertheless, the land surface hydrology is not the main explanation for the model errors that are rather due to deficiencies in the atmospheric physics. The intraseasonal timescale and the model internal variability are discussed in a companion paper.

  9. Diagnosing GCM errors over West Africa using relaxation experiments. Part I: summer monsoon climatology and interannual variability

    Energy Technology Data Exchange (ETDEWEB)

    Pohl, Benjamin [Meteo-France/CNRS, CNRM/GAME, Toulouse (France); CNRS/Universite de Bourgogne, Centre de Recherches de Climatologie, Dijon (France); Douville, Herve [Meteo-France/CNRS, CNRM/GAME, Toulouse (France)

    2011-10-15

    The CNRM atmospheric general circulation model Arpege-Climat is relaxed towards atmospheric reanalyses outside the 10 S-32 N 30 W-50 E domain in order to disentangle the regional versus large-scale sources of climatological biases and interannual variability of the West African monsoon (WAM). On the one hand, the main climatological features of the monsoon, including the spatial distribution of summer precipitation, are only weakly improved by the nudging, thereby suggesting the regional origin of the Arpege-Climat biases. On the other hand, the nudging technique is relatively efficient to control the interannual variability of the WAM dynamics, though the impact on rainfall variability is less clear. Additional sensitivity experiments focusing on the strong 1994 summer monsoon suggest that the weak sensitivity of the model biases is not an artifact of the nudging design, but the evidence that regional physical processes are the main limiting factors for a realistic simulation of monsoon circulation and precipitation in the Arpege-Climat model. Sensitivity experiments to soil moisture boundary conditions are also conducted and highlight the relevance of land-atmosphere coupling for the amplification of precipitation biases. Nevertheless, the land surface hydrology is not the main explanation for the model errors that are rather due to deficiencies in the atmospheric physics. The intraseasonal timescale and the model internal variability are discussed in a companion paper. (orig.)

  10. 3800 Years of Quantitative Precipitation Reconstruction from the Northwest Yucatan Peninsula

    Science.gov (United States)

    Carrillo-Bastos, Alicia; Islebe, Gerald A.; Torrescano-Valle, Nuria

    2013-01-01

    Precipitation over the last 3800 years has been reconstructed using modern pollen calibration and precipitation data. A transfer function was then performed via the linear method of partial least squares. By calculating precipitation anomalies, it is estimated that precipitation deficits were greater than surpluses, reaching 21% and <9%, respectively. The period from 50 BC to 800 AD was the driest of the record. The drought related to the abandonment of the Maya Preclassic period featured a 21% reduction in precipitation, while the drought of the Maya collapse (800 to 860 AD) featured a reduction of 18%. The Medieval Climatic Anomaly was a period of positive phases (3.8–7.6%). The Little Ice Age was a period of climatic variability, with reductions in precipitation but without deficits. PMID:24391940

  11. Precipitation in Madeira island and atmospheric rivers in the winter seasons

    Science.gov (United States)

    Couto, Flavio T.; Salgado, Rui; João Costa, Maria; Prior, Victor

    2016-04-01

    This study aims to analyse the distribution of the daily accumulated precipitation in the Madeira's highlands over a 10-year period, as well as the main characteristics associated with atmospheric rivers (ARs) affecting the island during 10 winter seasons, and their impact in the rainfall amounts recorded near the mountain crest in the south-eastern part of the island. The period between September 2002 and November 2012 is considered for the analysis. The ARs have been identified from the total precipitable water vapour field extracted from the Atmospheric Infrared Sounder (AIRS). The AIRS observations were downloaded for a domain covering large part of the North Atlantic Ocean. The precipitable water vapour field from the European Centre for Medium-range Weather Forecasts (ECMWF) analysis was also used aiming to support the AIRS data when there was no satellite information over the island. The daily accumulated precipitation at surface showed generally drier summers, while the highest accumulated precipitation are recorded mainly during the winter, although some significant events may occur also in autumn and spring seasons. The patterns of the precipitable water vapour field when ARs reach the island were investigated, and even if great part of the atmospheric rivers reaches the island in a dissipation stage, some rivers are heavy enough to reach the Madeira Island. In this situation, the water vapour transport could be observed in two main configurations and transporting significant water vapour amounts toward the Madeira from the tropical region. This study lead to conclude that the atmospheric rivers, when associated to high values of precipitable water vapour over the island can provide favourable conditions to the development of precipitation, sometimes associated with high amounts. However, it was also found that many cases of high to extreme accumulated precipitation at the surface were not associated to this kind of moisture transport.

  12. Atmospheric Rivers and Their Role in Extreme Precipitation in the Midwest U.S.

    Science.gov (United States)

    2013-03-01

    located in the warm sector of extratropical cyclones (warm conveyor belt) and can be characterized by strong winds (low level jet) and large water...the associated synoptic-scale extratropical cyclone and subsequent frontal processes of each planetary wave, resulting in narrow regions of moisture...normal falls during AR storms during the winter on the West Coast. During the summer, precipitation enhancements were not as significant (mostly due

  13. Met UM Upper-tropospheric summer jet teleconnections: A model assessment

    Science.gov (United States)

    Joao Carvalho, Maria; Rodriguez, Jose; Milton, Sean

    2017-04-01

    The upper tropospheric jet stream has been documented to act as a waveguide (Hoskins and Ambrizzi, 1993) and supporting quasi-stationary Rossby waves (Schubert et al. 2011). These have been associated with remote effects in surface level weather such as rainfall anomalies in the East Asian Summer Monsoon as well as extreme temperature events. The goal of this work was to analyse the intraseasonal to interannual upper level boreal summer jet variability and its coupling with low level atmospheric dynamics within the Met Office Unified Model using climate runs. Using the Wallace and Gutzler (1981) proposed approach to find teleconnection patterns on the 200 hPa level wind, lead-lag correlation and Empirical Orthogonal Function analysis on the upper-level jet and relating the results with surface weather variables as well as dynamical variables, it was found that the model presents too strong jet variability, particularly in the tropical region and. In addition, the model presents high teleconnectivity hotspots with higher importance in areas such as the Mediterranean and Caspian Sea which are important source areas for Rossby Waves. Further to this, the model was found to produce an area of teleconnectivity between the tropical Atlantic and western Africa which is not observed in the reanalysis but coexists with long lasting precipitation biases. As comparison for the model results, ERA-Interim circulation and wind data and the TRMM precipitation dataset were used. In order to assess the relative importance of relevant model parameters in the biases and process errors, work is currently underway using perturbed model parameter ensembles.

  14. Can frequent precipitation moderate the impact of drought on peatmoss carbon uptake in northern peatlands?

    Science.gov (United States)

    Nijp, Jelmer J; Limpens, Juul; Metselaar, Klaas; van der Zee, Sjoerd E A T M; Berendse, Frank; Robroek, Bjorn J M

    2014-07-01

    Northern peatlands represent a large global carbon store that can potentially be destabilized by summer water table drawdown. Precipitation can moderate the negative impacts of water table drawdown by rewetting peatmoss (Sphagnum spp.), the ecosystem's key species. Yet, the frequency of such rewetting required for it to be effective remains unknown. We experimentally assessed the importance of precipitation frequency for Sphagnum water supply and carbon uptake during a stepwise decrease in water tables in a growth chamber. CO2 exchange and the water balance were measured for intact cores of three peatmoss species (Sphagnum majus, Sphagnum balticum and Sphagnum fuscum) representative of three hydrologically distinct peatland microhabitats (hollow, lawn and hummock) and expected to differ in their water table-precipitation relationships. Precipitation contributed significantly to peatmoss water supply when the water table was deep, demonstrating the importance of precipitation during drought. The ability to exploit transient resources was species-specific; S. fuscum carbon uptake increased linearly with precipitation frequency for deep water tables, whereas carbon uptake by S. balticum and S. majus was depressed at intermediate precipitation frequencies. Our results highlight an important role for precipitation in carbon uptake by peatmosses. Yet, the potential to moderate the impact of drought is species-specific and dependent on the temporal distribution of precipitation. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  15. Linking precipitation, evapotranspiration and soil moisture content for the improvement of predictability over land

    Science.gov (United States)

    Catalano, Franco; Alessandri, Andrea; De Felice, Matteo

    2013-04-01

    Climate change scenarios are expected to show an intensification of the hydrological cycle together with modifications of evapotranspiration and soil moisture content. Evapotranspiration changes have been already evidenced for the end of the 20th century. The variance of evapotranspiration has been shown to be strongly related to the variance of precipitation over land. Nevertheless, the feedbacks between evapotranspiration, soil moisture and precipitation have not yet been completely understood at present-day. Furthermore, soil moisture reservoirs are associated to a memory and thus their proper initialization may have a strong influence on predictability. In particular, the linkage between precipitation and soil moisture is modulated by the effects on evapotranspiration. Therefore, the investigation of the coupling between these variables appear to be of primary importance for the improvement of predictability over the continents. The coupled manifold (CM) technique (Navarra and Tribbia 2005) is a method designed to separate the effects of the variability of two variables which are connected. This method has proved to be successful for the analysis of different climate fields, like precipitation, vegetation and sea surface temperature. In particular, the coupled variables reveal patterns that may be connected with specific phenomena, thus providing hints regarding potential predictability. In this study we applied the CM to recent observational datasets of precipitation (from CRU), evapotranspiration (from GIMMS and MODIS satellite-based estimates) and soil moisture content (from ESA) spanning a time period of 23 years (1984-2006) with a monthly frequency. Different data stratification (monthly, seasonal, summer JJA) have been employed to analyze the persistence of the patterns and their characteristical time scales and seasonality. The three variables considered show a significant coupling among each other. Interestingly, most of the signal of the

  16. Potential influences of neglecting aerosol effects on the NCEP GFS precipitation forecast

    Science.gov (United States)

    Jiang, Mengjiao; Feng, Jinqin; Li, Zhanqing; Sun, Ruiyu; Hou, Yu-Tai; Zhu, Yuejian; Wan, Bingcheng; Guo, Jianping; Cribb, Maureen

    2017-11-01

    Aerosol-cloud interactions (ACIs) have been widely recognized as a factor affecting precipitation. However, they have not been considered in the operational National Centers for Environmental Predictions Global Forecast System model. We evaluated the potential impact of neglecting ACI on the operational rainfall forecast using ground-based and satellite observations and model reanalysis. The Climate Prediction Center unified gauge-based precipitation analysis and the Modern-Era Retrospective analysis for Research and Applications Version 2 aerosol reanalysis were used to evaluate the forecast in three countries for the year 2015. The overestimation of light rain (47.84 %) and underestimation of heavier rain (31.83, 52.94, and 65.74 % for moderate rain, heavy rain, and very heavy rain, respectively) from the model are qualitatively consistent with the potential errors arising from not accounting for ACI, although other factors cannot be totally ruled out. The standard deviation of the forecast bias was significantly correlated with aerosol optical depth in Australia, the US, and China. To gain further insight, we chose the province of Fujian in China to pursue a more insightful investigation using a suite of variables from gauge-based observations of precipitation, visibility, water vapor, convective available potential energy (CAPE), and satellite datasets. Similar forecast biases were found: over-forecasted light rain and under-forecasted heavy rain. Long-term analyses revealed an increasing trend in heavy rain in summer and a decreasing trend in light rain in other seasons, accompanied by a decreasing trend in visibility, no trend in water vapor, and a slight increasing trend in summertime CAPE. More aerosols decreased cloud effective radii for cases where the liquid water path was greater than 100 g m-2. All findings are consistent with the effects of ACI, i.e., where aerosols inhibit the development of shallow liquid clouds and invigorate warm-base mixed

  17. Potential influences of neglecting aerosol effects on the NCEP GFS precipitation forecast

    Directory of Open Access Journals (Sweden)

    M. Jiang

    2017-11-01

    Full Text Available Aerosol–cloud interactions (ACIs have been widely recognized as a factor affecting precipitation. However, they have not been considered in the operational National Centers for Environmental Predictions Global Forecast System model. We evaluated the potential impact of neglecting ACI on the operational rainfall forecast using ground-based and satellite observations and model reanalysis. The Climate Prediction Center unified gauge-based precipitation analysis and the Modern-Era Retrospective analysis for Research and Applications Version 2 aerosol reanalysis were used to evaluate the forecast in three countries for the year 2015. The overestimation of light rain (47.84 % and underestimation of heavier rain (31.83, 52.94, and 65.74 % for moderate rain, heavy rain, and very heavy rain, respectively from the model are qualitatively consistent with the potential errors arising from not accounting for ACI, although other factors cannot be totally ruled out. The standard deviation of the forecast bias was significantly correlated with aerosol optical depth in Australia, the US, and China. To gain further insight, we chose the province of Fujian in China to pursue a more insightful investigation using a suite of variables from gauge-based observations of precipitation, visibility, water vapor, convective available potential energy (CAPE, and satellite datasets. Similar forecast biases were found: over-forecasted light rain and under-forecasted heavy rain. Long-term analyses revealed an increasing trend in heavy rain in summer and a decreasing trend in light rain in other seasons, accompanied by a decreasing trend in visibility, no trend in water vapor, and a slight increasing trend in summertime CAPE. More aerosols decreased cloud effective radii for cases where the liquid water path was greater than 100 g m−2. All findings are consistent with the effects of ACI, i.e., where aerosols inhibit the development of shallow liquid clouds and

  18. How well do the GCMs/RCMs capture the multi-scale temporal variability of precipitation in the Southwestern United States?

    Science.gov (United States)

    Jiang, Peng; Gautam, Mahesh R.; Zhu, Jianting; Yu, Zhongbo

    2013-02-01

    SummaryMulti-scale temporal variability of precipitation has an established relationship with floods and droughts. In this paper, we present the diagnostics on the ability of 16 General Circulation Models (GCMs) from Bias Corrected and Downscaled (BCSD) World Climate Research Program's (WCRP's) Coupled Model Inter-comparison Project Phase 3 (CMIP3) projections and 10 Regional Climate Models (RCMs) that participated in the North American Regional Climate Change Assessment Program (NARCCAP) to represent multi-scale temporal variability determined from the observed station data. Four regions (Los Angeles, Las Vegas, Tucson, and Cimarron) in the Southwest United States are selected as they represent four different precipitation regions classified by clustering method. We investigate how storm properties and seasonal, inter-annual, and decadal precipitation variabilities differed between GCMs/RCMs and observed records in these regions. We find that current GCMs/RCMs tend to simulate longer storm duration and lower storm intensity compared to those from observed records. Most GCMs/RCMs fail to produce the high-intensity summer storms caused by local convective heat transport associated with the summer monsoon. Both inter-annual and decadal bands are present in the GCM/RCM-simulated precipitation time series; however, these do not line up to the patterns of large-scale ocean oscillations such as El Nino/La Nina Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Our results show that the studied GCMs/RCMs can capture long-term monthly mean as the examined data is bias-corrected and downscaled, but fail to simulate the multi-scale precipitation variability including flood generating extreme events, which suggests their inadequacy for studies on floods and droughts that are strongly associated with multi-scale temporal precipitation variability.

  19. Seasonal variations of stable isotope in precipitation and moisture transport at Yushu,eastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Precipitation δ 18O at Yushu, eastern Tibetan Plateau, shows strong fluctuation and lack of clear seasonality. The seasonal pattern of precipitation stable isotope at Yushu is apparently different from either that of the southwest monsoon region to the south or that of the inland region to the north. This different seasonal pattern probably reflects the shift of different moisture sources. In this paper, we present the spatial comparison of the seasonal patterns of precipitation δ 18O, and calculate the moisture transport flux by using the NCAR/NCEP reanalysis data. This allows us to discuss the relation between moisture transport flux and precipitation δ 18O. This study shows that both the southwest monsoon from south and inland air mass transport from north affected the seasonal precipitation δ 18O at Yushu, eastern Tibetan Plateau. Southwest monsoon brings the main part of the moisture, but southwest transport flux is weaker than in the southern part of the Tibetan Plateau. However, contribution of the inland moisture from north or local evaporation moisture is enhanced. The combined effect is the strong fluctuation of summer precipitation δ 18O at Yushu and comparatively poor seasonality.

  20. Temperature sensitivity of extreme precipitation events in the south-eastern Alpine forelands

    Science.gov (United States)

    Schroeer, Katharina; Kirchengast, Gottfried

    2016-04-01

    How will convective precipitation intensities and patterns evolve in a warming climate on a regional to local scale? Studies on the scaling of precipitation intensities with temperature are used to test observational and climate model data against the hypothesis that the change of precipitation with temperature will essentially follow the Clausius-Clapeyron (CC) equation, which corresponds to a rate of increase of the water holding capacity of the atmosphere by 6-7 % per Kelvin (CC rate). A growing number of studies in various regions and with varying approaches suggests that the overall picture of the temperature-precipitation relationship is heterogeneous, with scaling rates shearing off the CC rate in both upward and downward directions. In this study we investigate the temperature scaling of extreme precipitation events in the south-eastern Alpine forelands of Austria (SEA) based on a dense rain gauge net of 188 stations, with sub-daily precipitation measurements since about 1990 used at 10-min resolution. Parts of the study region are European hot-spots for severe hailstorms and the region, which is in part densely populated and intensively cultivated, is generally vulnerable to climate extremes. Evidence on historical extremely heavy short-time and localized precipitation events of several hundred mm of rain in just a few hours, resulting in destructive flash flooding, underline these vulnerabilities. Heavy precipitation is driven by Mediterranean moisture advection, enhanced by the orographic lifting at the Alpine foothills, and hence trends in positive sea surface temperature anomalies might carry significant risk of amplifying future extreme precipitation events. In addition, observations from the highly instrumented subregion of south-eastern Styria indicate a strong and robust long-term warming trend in summer of about 0.7°C per decade over 1971-2015, concomitant with a significant increase in the annual number of heat days. The combination of these

  1. Variability of the North Atlantic summer storm track: mechanisms and impacts on European climate

    International Nuclear Information System (INIS)

    Dong, Buwen; Sutton, Rowan T; Woollings, Tim; Hodges, Kevin

    2013-01-01

    The summertime variability of the extratropical storm track over the Atlantic sector and its links to European climate have been analysed for the period 1948–2011 using observations and reanalyses. The main results are as follows. (1) The dominant mode of the summer storm track density variability is characterized by a meridional shift of the storm track between two distinct paths and is related to a bimodal distribution in the climatology for this region. It is also closely related to the Summer North Atlantic Oscillation (SNAO). (2) A southward shift is associated with a downstream extension of the storm track and a decrease in blocking frequency over the UK and northwestern Europe. (3) The southward shift is associated with enhanced precipitation over the UK and northwestern Europe and decreased precipitation over southern Europe (contrary to the behaviour in winter). (4) There are strong ocean–atmosphere interactions related to the dominant mode of storm track variability. The atmosphere forces the ocean through anomalous surface fluxes and Ekman currents, but there is also some evidence consistent with an ocean influence on the atmosphere, and that coupled ocean–atmosphere feedbacks might play a role. The ocean influence on the atmosphere may be particularly important on decadal timescales, related to the Atlantic Multidecadal Oscillation (AMO). (letter)

  2. Arsenic immobilization by calcium-arsenic precipitates in lime treated soils

    International Nuclear Information System (INIS)

    Moon, Deok Hyun; Dermatas, Dimitris; Menounou, Nektaria

    2004-01-01

    Lime-based stabilization/solidification (S/S) can be an effective remediation alternative for the immobilization of arsenic (As) in contaminated soils and sludges. However, the exact immobilization mechanism has not been well established. Based on previous research, As immobilization could be attributed to sorption and/or inclusion in pozzolanic reaction products and/or the formation of calcium-arsenic (Ca-As) precipitates. In this study, suspensions of lime-As and lime-As-kaolinite were studied in an attempt to elucidate the controlling mechanism of As immobilization in lime treated soils. Aqueous lime-As suspensions (slurries) with varying Ca/As molar ratios (1:1, 1.5:1, 2:1, 2.5:1 and 4:1) were prepared and soluble As concentrations were determined. X-Ray diffraction (XRD) analyses were used to establish the resulting mineralogy of crystalline precipitate formation. Depending on the redox state of the As source, different As precipitates were identified. When As (III) was used, the main precipitate formation was Ca-As-O. With As(V) as the source, Ca 4 (OH) 2 (AsO 4 ) 2 ·4H 2 O formed at Ca/As molar ratios greater than 1:1. A significant increase in As (III) immobilization was observed at Ca/As molar ratios greater than 1:1. Similarly, a substantial increase in As (V) immobilization was noted at Ca/As molar ratios greater than or equal to 2.5:1. This observation was also confirmed by XRD. Lime-As-kaolinite slurries were also prepared at different Ca/As molar ratios. These slurries were used to specifically investigate the possibility of forming pozzolanic reaction products. Such products would immobilize As by sorption and/or inclusion along with the formations of different As precipitates. Toxicity Characteristic Leaching Procedure (TCLP) tests were used to evaluate As leachability in these slurries. XRD analyses revealed no pozzolanic reaction product formation. Instead, As immobilization was found to be precipitation controlled. The same Ca-As precipitate, Ca

  3. PoPSat: The Polar Precipitation Satellite Mission

    Science.gov (United States)

    Binder, Matthias J.; Agten, Dries; Arago-Higueras, Nadia; Borderies, Mary; Diaz-Schümmer, Carlos; Jamali, Maryam; Jimenez-Lluva, David; Kiefer, Joshua; Larsson, Anna; Lopez-Gilabert, Lola; Mione, Michele; Mould, Toby JD; Pavesi, Sara; Roth, Georg; Tomicic, Maja

    2017-04-01

    enables the required optimal instrument resolution for precipitation events occurring within the troposphere, between 8 and 12 km altitude. Additionally, with an 18° instrument half-cone angle capability, both phased-array radars can provide a 300 km swath width at this altitude. This results in an optimal atmospheric layer coverage of 91% for latitudes above 50° N after 72 hr. A required total system power of 1021 W of the satellite will be sustained using 7.2 m2 of solar arrays, housed on the sunward side of the spacecraft. The mission has an expected total cost of an M-class mission for a nominal lifetime of 5 years. The PoPSat mission has been developed by 15 students of Team Blue supported by a group of experts at the Alpbach Summer School 2016, a ten-days design challenge organised by FFG and ESA and devoted to 'Satellite Observations of the Global Water Cycle'. PoPSat was selected by the jury to be further developed at the Post-Alpbach design challenge at the ESA Redu Centre for an additional four days, with 15 students out of all 4 teams from the Alpbach Summer School. Post-Alpbach Tutors: A. Hahne, J. Huesing, A. Ivanov, G. Kargl, H. Rott, J. Vennekens

  4. 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.)

  5. Precipitation Dynamics and Feedback mechanisms of the Arabian Desert

    Science.gov (United States)

    Burger, Roelof; Kucera, Paul; Piketh, Stuart; Axisa, Duncan; Chapman, Michael; Krauss, Terry; Ghulam, Ayman

    2010-05-01

    The subtropical Arabian desert extends across the entire Peninsula. The Arabian desert finds itself in the downward branch of the Hadley cell with persistent subsidence. This stabilizes the atmosphere and lowers the relative humidity. The result is a strongly capped convective boundary layer and an extremely dry mid troposphere. Most of the area experience very little rainfall, generally below 100 mm per year, resulting in the largest uninterrupted sand desert in the world. However, local factors such as an unbroken 1000 km escarpment along the Red Sea, rocky mountains between 2000 and 3000 m, and gravel plains cut by wadis, causes micro climates with significant altered precipitation characteristics. Altitude oases with annual rainfall between 200 mm and 500 mm are found on the Asir mountains in the south west and over the Jebel Akdhar mountains on the Gulf coast of Oman. This region receives most of its rainfall in the Northern Hemisphere summer driven by a monsoon trough and the ITCZ. During summer, moist surface winds from the Red Sea converges with dry easterlies triggering convection along the Asir escarpment on a daily basis. Clear mornings grow into a layer of Altocumulus stratiformis cumulogenites by noon, which usually last until sunset. This cloud deck interacts with large severe convective cells which grow to the top of the troposphere by mid afternoon. The north experience a mediterranean climate with eastward propagating midlatitude cyclones causing wintertime rainfall. Characteristic cloud bands form over the northern interior. Vertically layered embedded convective cells that are not coupled with the surface propagate on north easterly tracks. This result in another oasis with annual rainfall exceeding 200 mm. Surface based convection causes isolated thunderstorms during spring and early summer, but cloud bases increase as the season progress until the evaporating downdraft causes dust storms. In-situ measurements, WRF model runs, radiosonde ascends

  6. Key drivers of precipitation isotopes in Windhoek, Namibia (2012-2016)

    Science.gov (United States)

    Kaseke, K. F.; Wang, L.; Wanke, H.

    2017-12-01

    Southern African climate is characterized by large variability with precipitation model estimates varying by as much as 70% during summer. This difference between model estimates is partly because most models associate precipitation over Southern Africa with moisture inputs from the Indian Ocean while excluding inputs from the Atlantic Ocean. However, growing evidence suggests that the Atlantic Ocean may also contribute significant amounts of moisture to the region. This four-year (2012-2016) study investigates the isotopic composition (δ18O, δ2H and δ17O) of event-scale precipitation events, the key drivers of isotope variations and the origins of precipitation experienced in Windhoek, Namibia. Results indicate large storm-to-storm isotopic variability δ18O (25‰), δ2H (180‰) and δ17O (13‰) over the study period. Univariate analysis showed significant correlations between event precipitation isotopes and local meteorological parameters; lifted condensation level, relative humidity (RH), precipitation amount, average wind speed, surface and air temperature (p < 0.05). The number of significant correlations between local meteorological parameters and monthly isotopes was much lower suggesting loss of information through data aggregation. Nonetheless, the most significant isotope driver at both event and monthly scales was RH, consistent with the semi-arid classification of the site. Multiple linear regression analysis suggested RH, precipitation amount and air temperature were the most significant local drivers of precipitation isotopes accounting for about 50% of the variation implying that about 50% could be attributed to source origins. HYSLPIT trajectories indicated that 78% of precipitation originated from the Indian Ocean while 21% originated from the Atlantic Ocean. Given that three of the four study years were droughts while two of the three drought years were El Niño related, our data also suggests that δ'17O-δ'18O could be a useful tool to

  7. Evaluation of NASA's MERRA Precipitation Product in Reproducing the Observed Trend and Distribution of Extreme Precipitation Events in the United States

    Science.gov (United States)

    Ashouri, Hamed; Sorooshian, Soroosh; Hsu, Kuo-Lin; Bosilovich, Michael G.; Lee, Jaechoul; Wehner, Michael F.; Collow, Allison

    2016-01-01

    This study evaluates the performance of NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) precipitation product in reproducing the trend and distribution of extreme precipitation events. Utilizing the extreme value theory, time-invariant and time-variant extreme value distributions are developed to model the trends and changes in the patterns of extreme precipitation events over the contiguous United States during 1979-2010. The Climate Prediction Center (CPC) U.S.Unified gridded observation data are used as the observational dataset. The CPC analysis shows that the eastern and western parts of the United States are experiencing positive and negative trends in annual maxima, respectively. The continental-scale patterns of change found in MERRA seem to reasonably mirror the observed patterns of change found in CPC. This is not previously expected, given the difficulty in constraining precipitation in reanalysis products. MERRA tends to overestimate the frequency at which the 99th percentile of precipitation is exceeded because this threshold tends to be lower in MERRA, making it easier to be exceeded. This feature is dominant during the summer months. MERRA tends to reproduce spatial patterns of the scale and location parameters of the generalized extreme value and generalized Pareto distributions. However, MERRA underestimates these parameters, particularly over the Gulf Coast states, leading to lower magnitudes in extreme precipitation events. Two issues in MERRA are identified: 1) MERRA shows a spurious negative trend in Nebraska and Kansas, which is most likely related to the changes in the satellite observing system over time that has apparently affected the water cycle in the central United States, and 2) the patterns of positive trend over the Gulf Coast states and along the East Coast seem to be correlated with the tropical cyclones in these regions. The analysis of the trends in the seasonal precipitation extremes indicates that

  8. Assessment of the performance of CORDEX-South Asia experiments for monsoonal precipitation over the Himalayan region during present climate: part I

    Science.gov (United States)

    Ghimire, S.; Choudhary, A.; Dimri, A. P.

    2018-04-01

    Analysis of regional climate simulations to evaluate the ability of 11 Coordinated Regional Climate Downscaling Experiment in South Asia experiments (CORDEX-South Asia) along with their ensemble to produce precipitation from June to September (JJAS) over the Himalayan region have been carried out. These suite of 11 combinations come from 6 regional climate models (RCMs) driven with 10 initial and boundary conditions from different global climate models and are collectively referred here as 11 CORDEX South Asia experiments. All the RCMs use a similar domain and are having similar spatial resolution of 0.44° ( 50 km). The set of experiments are considered to study precipitation sensitivity associated with the Indian summer monsoon (ISM) over the study region. This effort is made as ISM plays a vital role in summertime precipitation over the Himalayan region which acts as driver for the sustenance of habitat, population, crop, glacier, hydrology etc. In addition, so far the summer monsoon precipitation climatology over the Himalayan region has not been studied with the help of CORDEX data. Thus this study is initiated to evaluate the ability of the experiments and their ensemble in reproducing the characteristics of summer monsoon precipitation over Himalayan region, for the present climate (1970-2005). The precipitation climatology, annual precipitation cycles and interannual variabilities from each simulation have been assessed against the gridded observational dataset: Asian Precipitation-Highly Resolved Observational Data Integration Towards the Evaluation of Water Resources for the given time period. Further, after the selection of the better performing experiment the frequency distribution of precipitation was also studied. In this study, an approach has also been made to study the degree of agreement among individual experiments as a way to quantify the uncertainty among them. The experiments though show a wide variation among themselves and individually over

  9. Regional tree growth and inferred summer climate in the Winnipeg River basin, Canada, since AD 1783

    Science.gov (United States)

    St. George, Scott; Meko, David M.; Evans, Michael N.

    2008-09-01

    A network of 54 ring-width chronologies is used to estimate changes in summer climate within the Winnipeg River basin, Canada, since AD 1783. The basin drains parts of northwestern Ontario, northern Minnesota and southeastern Manitoba, and is a key area for hydroelectric power production. Most chronologies were developed from Pinus resinosa and P. strobus, with a limited number of Thuja occidentalis, Picea glauca and Pinus banksiana. The dominant pattern of regional tree growth can be recovered using only the nine longest chronologies, and is not affected by the method used to remove variability related to age or stand dynamics from individual trees. Tree growth is significantly, but weakly, correlated with both temperature (negatively) and precipitation (positively) during summer. Simulated ring-width chronologies produced by a process model of tree-ring growth exhibit similar relationships with summer climate. High and low growth across the region is associated with cool/wet and warm/dry summers, respectively; this relationship is supported by comparisons with archival records from early 19th century fur-trading posts. The tree-ring record indicates that summer droughts were more persistent in the 19th and late 18th century, but there is no evidence that drought was more extreme prior to the onset of direct monitoring.

  10. Multi-scale heterogeneity in the temporal origin of water taken up by trees water uptake inferred using stable isotopes

    Science.gov (United States)

    Allen, S. T.; Kirchner, J. W.; Braun, S.; Siegwolf, R. T.; Goldsmith, G. R.

    2017-12-01

    Xylem water isotopic composition can reveal how water moves through soil and is subsequently taken up by plants. By examining how xylem water isotopes vary across distinct climates and soils, we test how these site characteristics control critical-zone water movement and tree uptake. Xylem water was collected from over 900 trees at 191 sites across Switzerland during a 10-day period in mid-summer 2015. Sites contained oak, beech and/or spruce trees and ranged in elevation from 260 to 1870 m asl with mean annual precipitation from 700 to 2060 mm. Xylem water samples were analyzed for 2H and 18O using isotope ratio mass spectrometry. Patterns in the temporal origin of xylem water showed regional differences. For example, trees in the southern and alpine regions had xylem water isotopic signatures that more closely resembled summer precipitation. The isotopic spatial range observed for mid-summer xylem waters was similar to the seasonal range of precipitation; that is, mid-summer xylem water at some sites resembled summer precipitation, and at other sites resembled winter precipitation. Xylem water from spruces, oaks, and beeches at the same sites did not differ from each other, despite these species having different rooting habits. Across all sites and species, precipitation amount correlated positively with xylem δ18O. In higher-precipitation areas, summer rain apparently displaces or mixes with older (winter) stored waters, thus reducing the winter-water isotopic signal in xylem water. Alternatively, in areas with limited precipitation, xylem water more closely matched winter water, indicating greater use of older stored water. We conclude that regional variations in precipitation deficits determine variations in the turnover rate of plant-available soil water and storage.

  11. Field significance of performance measures in the context of regional climate model evaluation. Part 2: precipitation

    Science.gov (United States)

    Ivanov, Martin; Warrach-Sagi, Kirsten; Wulfmeyer, Volker

    2018-04-01

    A new approach for rigorous spatial analysis of the downscaling performance of regional climate model (RCM) simulations is introduced. It is based on a multiple comparison of the local tests at the grid cells and is also known as `field' or `global' significance. The block length for the local resampling tests is precisely determined to adequately account for the time series structure. New performance measures for estimating the added value of downscaled data relative to the large-scale forcing fields are developed. The methodology is exemplarily applied to a standard EURO-CORDEX hindcast simulation with the Weather Research and Forecasting (WRF) model coupled with the land surface model NOAH at 0.11 ∘ grid resolution. Daily precipitation climatology for the 1990-2009 period is analysed for Germany for winter and summer in comparison with high-resolution gridded observations from the German Weather Service. The field significance test controls the proportion of falsely rejected local tests in a meaningful way and is robust to spatial dependence. Hence, the spatial patterns of the statistically significant local tests are also meaningful. We interpret them from a process-oriented perspective. While the downscaled precipitation distributions are statistically indistinguishable from the observed ones in most regions in summer, the biases of some distribution characteristics are significant over large areas in winter. WRF-NOAH generates appropriate stationary fine-scale climate features in the daily precipitation field over regions of complex topography in both seasons and appropriate transient fine-scale features almost everywhere in summer. As the added value of global climate model (GCM)-driven simulations cannot be smaller than this perfect-boundary estimate, this work demonstrates in a rigorous manner the clear additional value of dynamical downscaling over global climate simulations. The evaluation methodology has a broad spectrum of applicability as it is

  12. Future Projections of Precipitation Characteristics in East Asia Simulated by the MRI CGCM2

    Institute of Scientific and Technical Information of China (English)

    Akio KITOH; Masahiro HOSAKA; Yukimasa ADACHI; Kenji KAMIGUCHI

    2005-01-01

    Projected changes in precipitation characteristics around the mid-21st century and end-of-the-century are analyzed using the daily precipitation output of the 3-member ensemble Meteorological Research Institute global ocean-atmosphere coupled general circulation model (MRI-CGCM2) simulations under the Special Report on Emissions Scenarios (SRES) A2 and B2 scenarios. It is found that both the frequency and intensity increase in about 40% of the globe, while both the frequency and intensity decrease in about 20% of the globe. These numbers differ only a few percent from decade to decade of the 21st century and between the A2 and B2 scenarios. Over the rest of the globe (about one third), the precipitation frequency decreases but its intensity increases, suggesting a shift of precipitation distribution toward more intense events by global warming. South China is such a region where the summertime wet-day frequency decreases but the precipitation intensity increases. This is related to increased atmospheric moisture content due to global warming and an intensified and more westwardly extended North Pacific subtropical anticyclone,which may be related with an El Ni(n)o-like mean sea surface temperature change. On the other hand, a decrease in summer precipitation is noted in North China, thus augmenting a south-to-north precipit ation contrast more in the future.

  13. On the relationship between atmospheric rivers (ARs) and heavy precipitation over Japan

    Science.gov (United States)

    Yatagai, A. I.; Takayabu, Y. N.

    2016-12-01

    Atmospheric Rivers (ARs) are known as the water-vapor rich part of the broader warm conveyor belt. Recently, several AR detection algorithms are proposed, and structures and that of statistical features are studied globally. Since Japan is a humid country located in the north of the warm pool, ARs, middle tropospheric fast moisture transport, might be an important moisture source for heavy precipitation events in Japan. The purpose of this study is to develop an algorithm of detection of ARs over Japan, and to investigate the possible relationship between them and Japanese heavy precipitation events. Since high spatial correlations were obtained between ERA-Interim reanalysis PW and that of SSM/I (microwave images), we used daily PW (0.75 degree grid) for detection of the ARs. Using 36 years (1979-2014) ERA-Interim, we defined daily smoothed PW climatology. Then, we detected AR area with daily anomaly of PW exceeding 10 mm. However, we exclude round-shaped (caused by Typhoon etc) area and the case of moisture transport not exceeding 30N/30S. The daily AR events over Japan (123-146E, 24-46N) are; 1013 cases for winter (DJF), 1722 for spring (MAM), 2229 for summer (JJA) and 1870 for autumn (SON) during the 36 years. They successfully include Hiroshima disaster event (19 August 2014, Hirota et al., 2015) and Amami heavy precipitation event (20 October 2010). The summer with large AR appearance (1998 and 2010) had negative SOI (La Nina), and lowest appearance year (1992) was the year of El Nino (positively significant SOI). Totally, more ARs come over Japan area in La Nina years, however, the seasonal statistics between SOI and the number of AR is not straightforward, indicating that it is difficult to explain ARs over Japan with only tropical inter-annual variability. We use APHRO-JP (Kamiguchi et al., 2010) daily gridded (0.05 degree) precipitation (1979-2011) over Japanese land areas for comparison. Among the 32 years (1979-2011), we had 82 cases of heavy

  14. Seasonal Precipitation Variability Effects on Carbon Exchange in a Tropical Dry Forest of Northwest Mexico

    Science.gov (United States)

    Verduzco, V.; Garatuza-Payan, J.; Yépez, E. A.; Watts, C. J.; Rodriguez, J. C.; Robles-Morua, A.; Vivoni, E. R.

    2015-12-01

    The Tropical Dry Forest (TDF) cover a large area in tropical and subtropical regions in the Americas and its productivity is thought to have an important contribution to the atmospheric carbon fluxes. However, due to this ecosystem complex dynamics, our understanding about the mechanisms controlling net ecosystem exchange is limited. In this study, five years of continue water and carbon fluxes measurements from eddy covariance complemented with remotely sensed vegetation greenness were used to investigate the ecosystem carbon balance of a TDF in the North American Monsoon region under different hydro climatic conditions. We identified a large CO2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO2 efflux occurs prior to vegetation green-up, we infer a predominant heterotrophic control owed to high decomposition of accumulated labile soil organic matter from prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production over the year, but can be overwhelmed by the strength of the primary productivity during the monsoon season. Precipitation characteristics during the monsoon have significant controls on sustaining carbon fixation in the TDF ecosystem into the fall season. A threshold of ~350 to 400 mm of summer precipitation was identify to switch the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m2/yr) to a net sink (-249 g C/m2/yr). This research points at the needs for understanding the potential effects of changing seasonal precipitation patterns on ecosystem dynamics and carbon sequestration in subtropical regions.

  15. A study of precipitation phenomena during the creep of austenitic stainless steels

    International Nuclear Information System (INIS)

    Le May, I.; White, W.E.; Bassett, B.J.

    1975-01-01

    Creep-rupture data for two austenitic stainless steels, AISI Types 310 and 316, are presented, together with observations of precipitation taking place during creep. While the effects of creep deformation on precipitation in the Type 310 were negligible, ferrite precipitation was considerably greater in the Type 316 undergoing creep than in unstressed material. Ferrite precipitation appears to promote grain boundary cavitation and internal cracking, thus reducing creep resistance, and a correlation has been noted between increased ferrite precipitation and apparent further weakening of the Type 316 over the temperature range 730 0 C to 800 0 C approximately, as evidenced by breaks in the isostress lines on a plot of log (time to rupture) versus temperature. (author)

  16. Analytical flow duration curves for summer streamflow in Switzerland

    Science.gov (United States)

    Santos, Ana Clara; Portela, Maria Manuela; Rinaldo, Andrea; Schaefli, Bettina

    2018-04-01

    This paper proposes a systematic assessment of the performance of an analytical modeling framework for streamflow probability distributions for a set of 25 Swiss catchments. These catchments show a wide range of hydroclimatic regimes, including namely snow-influenced streamflows. The model parameters are calculated from a spatially averaged gridded daily precipitation data set and from observed daily discharge time series, both in a forward estimation mode (direct parameter calculation from observed data) and in an inverse estimation mode (maximum likelihood estimation). The performance of the linear and the nonlinear model versions is assessed in terms of reproducing observed flow duration curves and their natural variability. Overall, the nonlinear model version outperforms the linear model for all regimes, but the linear model shows a notable performance increase with catchment elevation. More importantly, the obtained results demonstrate that the analytical model performs well for summer discharge for all analyzed streamflow regimes, ranging from rainfall-driven regimes with summer low flow to snow and glacier regimes with summer high flow. These results suggest that the model's encoding of discharge-generating events based on stochastic soil moisture dynamics is more flexible than previously thought. As shown in this paper, the presence of snowmelt or ice melt is accommodated by a relative increase in the discharge-generating frequency, a key parameter of the model. Explicit quantification of this frequency increase as a function of mean catchment meteorological conditions is left for future research.

  17. Ranking GCM Estimates of Twentieth Century Precipitation Seasonality in the Western U.S. and its Influence on Floristic Provinces.

    Science.gov (United States)

    Cole, K. L.; Eischeid, J. K.; Garfin, G. M.; Ironside, K.; Cobb, N. S.

    2008-12-01

    Floristic provinces of the western United States (west of 100W) can be segregated into three regions defined by significant seasonal precipitation during the months of: 1) November-March (Mediterranean); 2) July- September (Monsoonal); or, 3) May-June (Rocky Mountain). This third region is best defined by the absence of the late spring-early summer drought that affects regions 1 and 2. Each of these precipitation regimes is characterized by distinct vegetation types and fire seasonality adapted to that particular cycle of seasonal moisture availability and deficit. Further, areas where these regions blend from one to another can support even more complex seasonal patterns and resulting distinctive vegetation types. As a result, modeling the effects of climates on these ecosystems requires confidence that GCMs can at least approximate these sub- continental seasonal precipitation patterns. We evaluated the late Twentieth Century (1950-1999 AD) estimates of annual precipitation seasonality produced by 22 GCMs contained within the IPCC Fourth Assessment (AR4). These modeled estimates were compared to values from the PRISM dataset, extrapolated from station data, over the same historical period for the 3 seasonal periods defined above. The correlations between GCM estimates and PRISM values were ranked using 4 measures: 1) A map pattern relationship based on the correlation coefficient, 2) A map pattern relationship based on the congruence coefficient, 3) The ratio of simulated/observed area averaged precipitation based on the seasonal precipitation amounts, and, 4) The ratio of simulated/observed area averaged precipitation based on the seasonal precipitation percentages of the annual total. For each of the four metrics, the rank order of models was very similar. The ranked order of the performance of the different models quantified aspects of the model performance visible in the mapped results. While some models represented the seasonal patterns very well, others

  18. Can frequent precipitation moderate drought impact on peatmoss carbon uptake in northern peatlands?

    Science.gov (United States)

    Nijp, Jelmer; Limpens, Juul; Metselaar, Klaas; van der Zee, Sjoerd; Berendse, Frank; Robroek, Bjorn

    2014-05-01

    Northern peatlands represent one of the largest global carbon stores that can potentially be released by water table drawdown during extreme summer droughts. Small precipitation events may moderate negative impacts of deep water levels on carbon uptake by sustaining photosynthesis of peatmoss (Sphagnum spp.), the key species in these ecosystems. We experimentally assessed the importance of the temporal distribution of precipitation for Sphagnum water supply and carbon uptake during a stepwise decrease in water levels in a growth chamber. CO2 exchange and the water balance were measured for intact cores of three peatmoss species representative of three contrasting habitats in northern peatlands (Sphagnum fuscum, S. balticum and S. majus). For shallow water levels, capillary rise was the most important source of water for peatmoss photosynthesis and precipitation did not promote carbon uptake irrespective of peatmoss species. For deep water levels, however, precipitation dominated over capillary rise and moderated adverse effects of drought on carbon uptake by peat mosses. The ability to use the transient water supply by precipitation was species-specific: carbon uptake of S. fuscum increased linearly with precipitation frequency for deep water levels, whereas S. balticum and S. majus showed depressed carbon uptake at intermediate precipitation frequencies. Our results highlight the importance of precipitation for carbon uptake by peatmosses. The potential of precipitation to moderate drought impact, however, is species specific and depends on the temporal distribution of precipitation and water level. These results also suggest that modelling approaches in which water level depth is used as the only state variable determining water availability in the living moss layer and (in)directly linked to Sphagnum carbon uptake may have serious drawbacks. The predictive power of peatland ecosystem models may be reduced when deep water levels prevail, as precipitation

  19. Distinguishing Southern Africa precipitation response by strength of El Niño events

    Science.gov (United States)

    Pomposi, C.; Funk, C. C.; Shukla, S.; Magadzire, T.

    2017-12-01

    The El Niño Southern Oscillation (ENSO) is a leading mode of interannual precipitation variability and the main source of skill for seasonal climate predictions. Interannual precipitation variability linked to ENSO can have drastic impacts on agricultural systems and food resources in the semi-arid tropics, highlighting the need for increased information regarding ENSO's links to sub-seasonal to seasonal precipitation variations. The present work describes a case study on recent precipitation variability during warm ENSO events (i.e. El Niño) for the austral summer rainy season (December-February) in Southern Africa. Using a blending of observational and model data, it is found that the probability distribution of precipitation varies according to the strength of El Niño events. Strong El Niño events show a much clearer tendency for drying than moderate or weak events, which have smaller absolute magnitude anomalies and larger spatial heterogeneity in the precipitation response. A dynamical exploration of the various precipitation responses is also completed. The techniques utilized can be easily expanded to study likelihood of drought during El Niño for a variety of other regions and also provides information about El Niño strength and its influence on regional teleconnections. Finally, this presentation will describe the channels by which seasonal forecasting information is disseminated in the region and utilized by the Famine Early Warning Systems Network to help mitigate the impacts of potential food insecurity crises.

  20. Molecular records of continental air temperature and monsoon precipitation variability in East Asia spanning the past 130,000 years

    NARCIS (Netherlands)

    Peterse, F.; Martínez-García, A.; Zhou, B.; Beets, C.J.; Prins, M.A.; Zheng, H.; Eglinton, T.I.

    2014-01-01

    Our current understanding of past changes in East Asian summer monsoon (EASM) precipitation intensity derives from several loess–paleosol sequences and oxygen isotope (δ18O) records of well-dated stalagmites. Although temperature is generally presumed to have had minimal impact on EASM records, past

  1. Interdecadal change of the controlling mechanisms for East Asian early summer rainfall variation around the mid-1990s

    Science.gov (United States)

    Yim, So-Young; Wang, Bin; Kwon, MinHo

    2014-03-01

    East Asian (EA) summer monsoon shows considerable differences in the mean state and principal modes of interannual variation between early summer (May-June, MJ) and late summer (July-August, JA). The present study focuses on the early summer (MJ) precipitation variability. We find that the interannual variation of the MJ precipitation and the processes controlling the variation have been changed abruptly around the mid-1990s. The rainfall anomaly represented by the leading empirical orthogonal function has changed from a dipole-like pattern in pre-95 epoch (1979-1994) to a tripole-like pattern in post-95 epoch (1995-2010); the prevailing period of the corresponding principal component has also changed from 3-5 to 2-3 years. These changes are concurrent with the changes of the corresponding El Nino-Southern Oscillation (ENSO) evolutions. During the pre-95 epoch, the MJ EA rainfall anomaly is coupled to a slow decay of canonical ENSO events signified by an eastern Pacific warming, which induces a dipole rainfall feature over EA. On the other hand, during the post-95 epoch the anomalous MJ EA rainfall is significantly linked to a rapid decay of a central Pacific warming and a distinct tripolar sea surface temperature (SST) in North Atlantic. The central Pacific warming-induced Philippine Sea anticyclone induces an increased rainfall in southern China and decreased rainfall in central eastern China. The North Atlantic Oscillation-related tripolar North Atlantic SST anomaly induces a wave train that is responsible for the increase northern EA rainfall. Those two impacts form the tripole-like rainfall pattern over EA. Understanding such changes is important for improving seasonal to decadal predictions and long-term climate change in EA.

  2. Tree ring evidence of a 20th century precipitation surge in the monsoon shadow zone of the western Himalaya, India

    Science.gov (United States)

    Yadav, Ram R.

    2011-01-01

    The present study is the first attempt to develop an annual (August-July) precipitation series back to AD 1330 using a tree ring data network of Himalayan cedar (Cedrus deodara (Roxb.) G. Don) from the Lahaul-Spiti region in the western Himalaya, India. The rainfall reconstruction reveals high magnitude multidecadal droughts during the 14th and 15th centuries and thenceforth a gradual increase in precipitation. Increasingly wet conditions during the 20th century are consistent with other long-term precipitation reconstructions from high Asia and reflect a large-scale intensification of the hydrological cycle, coincident with what is anticipated due to global warming. Significant relationships between reconstructed precipitation and precipitation records from central southwest Asia, east of the Caspian Sea, ENSO (NINO4-SST) variability and summer monsoon rainfall over central northeast India underscore the utility of our data in synoptic climatology.

  3. ANALYSIS OF PROJECTED FREQUENCY AND INTENSITY CHANGES OF PRECIPITATION IN THE CARPATHIAN REGION

    Directory of Open Access Journals (Sweden)

    KIS ANNA

    2015-03-01

    Full Text Available Precipitation is the major atmospheric source of surface water, thus, in order to build appropriate adaptation strategies for various economic sections related to water resources it is essential to provide projections for precipitation tendencies as exact as possible. Extreme precipitation events are especially important from this point of view since they may result in different environmental, economical, and/or even human health damages. Excessive precipitation for instance may induce floods, flash-floods, landslides, traffic accidents. On the other hand, lack of precipitation is not favorable either: long dry periods affect agricultural production quite negatively, and hence, food safety can be threatened. Several precipitation-related indices (i.e., describing drought or intensity, exceeding different percentile-based or absolute threshold values are analyzed for the Carpathian region for 1961–2100. For this purpose 11 completed regional climate model simulations are used from the ENSEMBLES database. Before the thorough analysis, a percentile-based bias correction method was applied to the raw data, for which the homogenized daily gridded CarpatClim database (1961–2010 served as a reference. Absolute and relative seasonal mean changes of climate indices are calculated for two future time periods (2021–2050 and 2071–2100 and for three subregions within the entire Carpathian region, namely, for Slovakia, Hungary and Romania. According to our results, longer dry periods are estimated for the summer season, mainly in the southern parts of the domain, while precipitation intensity is likely to increase. Heavy precipitation days and high percentile values are projected to increase, especially, in winter and autumn.

  4. Effects of El Nino Modoki on winter precipitation in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Do-Woo [Korea Meteorological Administration, National Institute of Meteorological Research, Seoul (Korea, Republic of); Choi, Ki-Seon [Korea Meteorological Administration, National Typhoon Center, Jeju (Korea, Republic of); Byun, Hi-Ryong [Pukyong National University, Department of Environmental Atmospheric Sciences, Nam-gu, Busan (Korea, Republic of)

    2012-04-15

    This study compares the impacts of El Nino Modoki and El Nino on precipitation over Korea during the boreal winters from 1954 to 2009. Precipitation in Korea tends to be equal to or greater than the normal level during an El Nino Modoki winter, whereas there is no significant change during an El Nino winter. Greater than normal precipitation during El Nino Modoki was also found over the lower reaches of the Yangtze River, China and much of southern Japan. The latitudes of these regions are 5-10 further north than in southern China, where precipitation increases during El Nino. The following two anomalous atmospheric circulations were found to be causes that led to different precipitation distributions over East Asia. First, an atmospheric wave train in the lower troposphere, which propagated from the central tropical Pacific (cyclonic) through the southern Philippine Sea (anticyclonic) to East Asia (cyclonic), reached the southern China and northern Philippine Sea during El Nino, whereas it reached Korea and southern Japan during El Nino Modoki. Second, an anomalous local meridional circulation, which consists of air sinking in the tropics, flowing poleward in the lower troposphere, and rising in the subtropics, developed between the southern Philippine Sea and northern Philippine Sea during El Nino. During El Nino Modoki, however, this circulation expanded further to the north and was formed between the southern Philippine Sea and regions of Korea and southern Japan. (orig.)

  5. Seizure precipitants (triggering factors) in patients with epilepsy.

    Science.gov (United States)

    Ferlisi, Monica; Shorvon, Simon

    2014-04-01

    adult epilepsy clinic population: (a) to identify the frequency of seizure precipitants (triggering factors) and their relative frequency in those with psychiatric disorders, and in those in remission or with active epilepsy, differences in frequency with regard to gender, seizure duration, number of drugs taken; (b) to determine which precipitants patients most commonly report; and (c) to identify differences in the distribution of precipitants among generalized, temporal, and extratemporal epilepsies. Consecutive patients attending a tertiary-care epilepsy clinic were prospectively and an open personal interview to identify and characterize seizure precipitants. Information about the epilepsy and clinical characteristics of patients was collected during the interview and from medical records. Of 104 patients, 97% cited at least one precipitant. Stress, sleep deprivation, and fatigue were the most frequently reported precipitants. Patients with psychological comorbidities reported a greater percentage of seizures with seizure precipitants. Patients with idiopathic generalized epilepsy seemed to be more sensitive to seizures during awakening and sleep deprivation, patients with extratemporal epilepsy reported more frequent seizures during sleep. There were no differences in frequency or type of seizure precipitants with regard to gender, seizure duration or frequency, and the number of antiepileptic drugs taken. The findings may have implications for the better management of epilepsy by increasing a focus on nonpharmacological therapy. The implications of the findings for nosology and causation of epilepsy are also briefly discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. Influence of winter season climate variability on snow-precipitation ratio in the western United States

    Science.gov (United States)

    Mohammad Safeeq; Shraddhanand Shukla; Ivan Arismendi; Gordon E. Grant; Sarah L. Lewis; Anne Nolin

    2015-01-01

    In the western United States, climate warming poses a unique threat to water and snow hydrology because much of the snowpack accumulates at temperatures near 0 °C. As the climate continues to warm, much of the region's precipitation is expected to switch from snow to rain, causing flashier hydrographs, earlier inflow to reservoirs, and reduced spring and summer...

  7. Precipitation behavior of carbides in high-carbon martensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Qin-tian; Li, Jing; Shi, Cheng-bin; Yu, Wen-tao; Shi, Chang-min [University of Science and Technology, Beijing (China). State Key Laboratory of Advanced Metallurgy; Li, Ji-hui [Yang Jiang Shi Ba Zi Group Co., Ltd, Guangdong (China)

    2017-01-15

    A fundamental study on the precipitation behavior of carbides was carried out. Thermo-calc software, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, X-ray diffractometry and high-temperature confocal laser scanning microscopy were used to study the precipitation and transformation behaviors of carbides. Carbide precipitation was of a specific order. Primary carbides (M7C3) tended to be generated from liquid steel when the solid fraction reached 84 mol.%. Secondary carbides (M7C3) precipitated from austenite and can hardly transformed into M23C6 carbides with decreasing temperature in air. Primary carbides hardly changed once they were generated, whereas secondary carbides were sensitive to heat treatment and thermal deformation. Carbide precipitation had a certain effect on steel-matrix phase transitions. The segregation ability of carbon in liquid steel was 4.6 times greater that of chromium. A new method for controlling primary carbides is proposed.

  8. Modelling of spatio-temporal precipitation relevant for urban hydrology with focus on scales, extremes and climate change

    DEFF Research Database (Denmark)

    Sørup, Hjalte Jomo Danielsen

    -correlation lengths for sub-daily extreme precipitation besides having too low intensities. Especially the wrong spatial correlation structure is disturbing from an urban hydrological point of view as short-term extremes will cover too much ground if derived directly from bias corrected regional climate model output...... of precipitation are compared and used to rank climate models with respect to performance metrics. The four different observational data sets themselves are compared at daily temporal scale with respect to climate indices for mean and extreme precipitation. Data density seems to be a crucial parameter for good...... happening in summer and most of the daily extremes in fall. This behaviour is in good accordance with reality where short term extremes originate in convective precipitation cells that occur when it is very warm and longer term extremes originate in frontal systems that dominate the fall and winter seasons...

  9. Utilization of summer legumes as bioenergy feedstocks

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, Keri B.; Bauer, Philip J.; Ro, Kyoung S. [United States Department of Agriculture, ARS, Coastal Plains Soil, Water, and Plant Research Center, 2611 W. Lucas St. Florence, SC 29501 (United States)

    2010-12-15

    Sunn hemp (Crotolaria juncea), is a fast growing, high biomass yielding tropical legume that may be a possible southeastern bioenergy crop. When comparing this legume to a commonly grown summer legume - cowpeas (Vigna unguiculata), sunn hemp was superior in biomass yield (kg ha{sup -1}) and subsequent energy yield (GJ ha{sup -1}). In one year of the study after 12 weeks of growth, sunn hemp had 10.7 Mg ha{sup -1} of biomass with an energy content of 19.0 Mg ha{sup -1}. This resulted in an energy yield of 204 GJ ha{sup -1}. The energy content was 6% greater than that of cowpeas. Eventhough sunn hemp had a greater amount of ash, plant mineral concentrations were lower in some cases of minerals (K, Ca, Mg, S) known to reduce thermochemical conversion process efficiency. Pyrolytic degradation of both legumes revealed that sunn hemp began to degrade at higher temperatures as well as release greater amounts of volatile matter at a faster rate. (author)

  10. Differential Heating in the Indian Ocean Differentially Modulates Precipitation in the Ganges and Brahmaputra Basins

    Directory of Open Access Journals (Sweden)

    Md Shahriar Pervez

    2016-10-01

    Full Text Available Indo-Pacific sea surface temperature dynamics play a prominent role in Asian summer monsoon variability. Two interactive climate modes of the Indo-Pacific—the El Niño/Southern Oscillation (ENSO and the Indian Ocean dipole mode—modulate the amount of precipitation over India, in addition to precipitation over Africa, Indonesia, and Australia. However, this modulation is not spatially uniform. The precipitation in southern India is strongly forced by the Indian Ocean dipole mode and ENSO. In contrast, across northern India, encompassing the Ganges and Brahmaputra basins, the climate mode influence on precipitation is much less. Understanding the forcing of precipitation in these river basins is vital for food security and ecosystem services for over half a billion people. Using 28 years of remote sensing observations, we demonstrate that (i the tropical west-east differential heating in the Indian Ocean influences the Ganges precipitation and (ii the north-south differential heating in the Indian Ocean influences the Brahmaputra precipitation. The El Niño phase induces warming in the warm pool of the Indian Ocean and exerts more influence on Ganges precipitation than Brahmaputra precipitation. The analyses indicate that both the magnitude and position of the sea surface temperature anomalies in the Indian Ocean are important drivers for precipitation dynamics that can be effectively summarized using two new indices, one tuned for each basin. These new indices have the potential to aid forecasting of drought and flooding, to contextualize land cover and land use change, and to assess the regional impacts of climate change.

  11. Differential heating in the Indian Ocean differentially modulates precipitation in the Ganges and Brahmaputra basins

    Science.gov (United States)

    Pervez, Md Shahriar; Henebry, Geoffrey M.

    2016-01-01

    Indo-Pacific sea surface temperature dynamics play a prominent role in Asian summer monsoon variability. Two interactive climate modes of the Indo-Pacific—the El Niño/Southern Oscillation (ENSO) and the Indian Ocean dipole mode—modulate the amount of precipitation over India, in addition to precipitation over Africa, Indonesia, and Australia. However, this modulation is not spatially uniform. The precipitation in southern India is strongly forced by the Indian Ocean dipole mode and ENSO. In contrast, across northern India, encompassing the Ganges and Brahmaputra basins, the climate mode influence on precipitation is much less. Understanding the forcing of precipitation in these river basins is vital for food security and ecosystem services for over half a billion people. Using 28 years of remote sensing observations, we demonstrate that (i) the tropical west-east differential heating in the Indian Ocean influences the Ganges precipitation and (ii) the north-south differential heating in the Indian Ocean influences the Brahmaputra precipitation. The El Niño phase induces warming in the warm pool of the Indian Ocean and exerts more influence on Ganges precipitation than Brahmaputra precipitation. The analyses indicate that both the magnitude and position of the sea surface temperature anomalies in the Indian Ocean are important drivers for precipitation dynamics that can be effectively summarized using two new indices, one tuned for each basin. These new indices have the potential to aid forecasting of drought and flooding, to contextualize land cover and land use change, and to assess the regional impacts of climate change.

  12. How predictable is the northern hemisphere summer upper-tropospheric circulation?

    Energy Technology Data Exchange (ETDEWEB)

    Lee, June-Yi; Wang, Bin [University of Hawaii/IPRC, International Pacific Research Center, Honolulu, HI (United States); Ding, Q. [University of Washington, Department of Earth and Space Sciences and Quaternary Research Center, Seattle, WA (United States); Ha, K.J.; Ahn, J.B. [Pusan National University, Division of Earth Environmental System, Busan (Korea, Republic of); Kumar, A. [NCEP/CPC, Camp Springs, MD (United States); Stern, B. [Princeton University, NOAA/GFDL, Princeton, NJ (United States); Alves, O. [Bureau of Meteorology, Centre for Australia Weather and Climate Research (CAWCR), Melbourne, VIC (Australia)

    2011-09-15

    The retrospective forecast skill of three coupled climate models (NCEP CFS, GFDL CM2.1, and CAWCR POAMA 1.5) and their multi-model ensemble (MME) is evaluated, focusing on the Northern Hemisphere (NH) summer upper-tropospheric circulation along with surface temperature and precipitation for the 25-year period of 1981-2005. The seasonal prediction skill for the NH 200-hPa geopotential height basically comes from the coupled models' ability in predicting the first two empirical orthogonal function (EOF) modes of interannual variability, because the models cannot replicate the residual higher modes. The first two leading EOF modes of the summer 200-hPa circulation account for about 84% (35.4%) of the total variability over the NH tropics (extratropics) and offer a hint of realizable potential predictability. The MME is able to predict both spatial and temporal characteristics of the first EOF mode (EOF1) even at a 5-month lead (January initial condition) with a pattern correlation coefficient (PCC) skill of 0.96 and a temporal correlation coefficient (TCC) skill of 0.62. This long-lead predictability of the EOF1 comes mainly from the prolonged impacts of El Nino-Southern Oscillation (ENSO) as the EOF1 tends to occur during the summer after the mature phase of ENSO. The second EOF mode (EOF2), on the other hand, is related to the developing ENSO and also the interdecadal variability of the sea surface temperature over the North Pacific and North Atlantic Ocean. The MME also captures the EOF2 at a 5-month lead with a PCC skill of 0.87 and a TCC skill of 0.67, but these skills are mainly obtained from the zonally symmetric component of the EOF2, not the prominent wavelike structure, the so-called circumglobal teleconnection (CGT) pattern. In both observation and the 1-month lead MME prediction, the first two leading modes are accompanied by significant rainfall and surface air temperature anomalies in the continental regions of the NH extratropics. The MME

  13. {sup 18}O, {sup 2}H and {sup 3}H isotopic composition of precipitation and shallow groundwater in Olkiluoto

    Energy Technology Data Exchange (ETDEWEB)

    Hendriksson, N. [Geological Survey of Finland, Espoo (Finland); Karhu, J.; Niinikoski, P. [Univ. of Helsinki (Finland)

    2014-12-15

    The isotopic composition of oxygen and hydrogen in local precipitation is a key parameter in the modelling of local water circulation. This study was initiated in order to provide systematic monthly records of the isotope content of atmospheric precipitation in the Olkiluoto area and to establish the relation between local rainfall and newly formed groundwater. During January 2005 - December 2012, a total of 85 cumulative monthly rainfall samples and 68 shallow groundwater samples were collected and the isotopic composition of oxygen and hydrogen was recorded for all those samples. Tritium values are available for 79 precipitation and 65 groundwater samples. Based on the 8-year monitoring, the long-term weighted annual mean isotope values of precipitation and the mean values of shallow groundwater are -11.59 per mille and -11.27 per mille for δ{sup 18}O, - 82.3 per mille and -80.3 per mille for δ{sup 2}H and 9.8 and 9.1 TU for tritium, respectively. Based on these data, the mean stable isotope ratios of groundwater represent the long-term mean annual isotopic composition of local precipitation. The precipitation data were used to establish the local meteoric water line (LMWL) for the Olkiluoto area. The line is formulated as: δ{sup 2}H = 7.45 star δ{sup 18}O + 3.82. The isotope time series reveal a change in time. The increasing trend for the δ{sup 18}O and δ{sup 2}H values may be related to climatic variability while the gradual decline observed in the {sup 3}H data is attributed to the still continuing decrease in atmospheric {sup 3}H activity in the northern hemisphere. The systematic seasonal and long-term tritium trends suggest that any potential ground-level tritium release from the Olkiluoto nuclear power plants is insignificant. The d-excess values of Olkiluoto precipitation during the summer period indicated that a notable amount of re-cycled Baltic Sea water may have contributed to precipitation in the Finnish southern coast. Preliminary estimates

  14. Flood forecasting and uncertainty of precipitation forecasts

    International Nuclear Information System (INIS)

    Kobold, Mira; Suselj, Kay

    2004-01-01

    The timely and accurate flood forecasting is essential for the reliable flood warning. The effectiveness of flood warning is dependent on the forecast accuracy of certain physical parameters, such as the peak magnitude of the flood, its timing, location and duration. The conceptual rainfall - runoff models enable the estimation of these parameters and lead to useful operational forecasts. The accurate rainfall is the most important input into hydrological models. The input for the rainfall can be real time rain-gauges data, or weather radar data, or meteorological forecasted precipitation. The torrential nature of streams and fast runoff are characteristic for the most of the Slovenian rivers. Extensive damage is caused almost every year- by rainstorms affecting different regions of Slovenia' The lag time between rainfall and runoff is very short for Slovenian territory and on-line data are used only for now casting. Forecasted precipitations are necessary for hydrological forecast for some days ahead. ECMWF (European Centre for Medium-Range Weather Forecasts) gives general forecast for several days ahead while more detailed precipitation data with limited area ALADIN/Sl model are available for two days ahead. There is a certain degree of uncertainty using such precipitation forecasts based on meteorological models. The variability of precipitation is very high in Slovenia and the uncertainty of ECMWF predicted precipitation is very large for Slovenian territory. ECMWF model can predict precipitation events correctly, but underestimates amount of precipitation in general The average underestimation is about 60% for Slovenian region. The predictions of limited area ALADIN/Si model up to; 48 hours ahead show greater applicability in hydrological forecasting. The hydrological models are sensitive to precipitation input. The deviation of runoff is much bigger than the rainfall deviation. Runoff to rainfall error fraction is about 1.6. If spatial and time distribution

  15. Variability in rainfall over tropical Australia during summer and relationships with the Bilybara High

    Science.gov (United States)

    Reason, C. J. C.

    2018-04-01

    Variability in summer rainfall over tropical Australia, defined here as that part of the continent north of 25° S, and its linkages with regional circulation are examined. In particular, relationships with the mid-level anticyclone (termed the Bilybara High) that exists over the northwestern Australia/Timor Sea region between August and April are considered. This High forms to the southwest of the upper-level anticyclone via a balance between the upper-level divergence over the region of tropical precipitation maximum and planetary vorticity advection and moves south and strengthens during the spring and summer. It is shown that variations in the strength and position of the Bilybara High are related to anomalies in precipitation and temperature over large parts of tropical Australia as well as some areas in the south and southeast of the landmass. Some of the interannual variations in the High are related to ENSO, but there are also a number of neutral years with large anomalies in the High and hence in rainfall. On decadal time scales, a strong relationship exists between the leading mode of tropical Australian rainfall and the Bilybara High. On both interannual and decadal scales, the relationships between the High and the regional rainfall involve changes in the monsoonal northwesterlies blowing towards northern Australia, and further south, in the easterly trade winds over the region.

  16. Simulation of the summer circulation over South America by two regional climate models. Part I: Mean climatology

    Science.gov (United States)

    Fernandez, J. P. R.; Franchito, S. H.; Rao, V. B.

    2006-09-01

    This study investigates the capabilities of two regional models (the ICTP RegCM3 and the climate version of the CPTEC Eta model - EtaClim) in simulating the mean climatological features of the summer quasi-stationary circulations over South America. Comparing the results with the NCEP/DOE reanalysis II data it is seen that the RegCM3 simulates a weaker and southward shifted Bolivian high (BH). But, the Nordeste low (NL) is located close to its climatological position. In the EtaClim the position of the BH is reproduced well, but the NL is shifted towards the interior of the continent. To the east of Andes, the RegCM3 simulates a weaker low level jet and a weaker basic flow from the tropical Atlantic to Amazonia while they are stronger in the EtaClim. In general, the RegCM3 and EtaClim show, respectively a negative and positive bias in the surface temperature in almost all regions of South America. For both models, the correlation coefficients between the simulated precipitation and the GPCP data are high over most of South America. Although the RegCM3 and EtaClim overestimate the precipitation in the Andes region they show a negative bias in general over the entire South America. The simulations of upper and lower level circulations and precipitation fields in EtaClim were better than that of the RegCM3. In central Amazonia both models were unable to simulate the precipitation correctly. The results showed that although the RegCM3 and EtaClim are capable of simulating the main climatological features of the summer climate over South America, there are areas which need improvement. This indicates that the models must be more adequately tuned in order to give reliable predictions in the different regions of South America.

  17. 76 FR 22350 - Fisheries of the Northeastern United States; Recreational Management Measures for the Summer...

    Science.gov (United States)

    2011-04-21

    ... increase is to permit greater commercial and recreational harvest opportunity while preventing overfishing... that overfishing the summer flounder, scup, and black sea bass resources in 2011 is unlikely to occur...

  18. Coastal Fog Sustains Summer Baseflow in Northern Californian Watershed

    Science.gov (United States)

    Chung, M.; Dufour, A.; Leonardson, R.; Thompson, S. E.; Dawson, T. E.

    2015-12-01

    The Mediterranean climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. During summer, frequently the only water inputs occur as occult precipitation, in the form of fog and dew. In this study, we characterized the role of coastal fog, a dominant feature of Northern Californian coastal ecosystems and a widespread phenomenon associated with deep marine upwelling in west coast, arid, and Mediterranean climates worldwide. We monitored fog occurrence and intensity, throughfall following canopy interception of fog, soil moisture, streamflow, and meteorological variables, and made visual observations of the spatial extent of fog using time-lapse imagery in Upper Pilarcitos Creek Watershed (managed by San Francisco Public Utilities Commission as part of the San Francisco area water supply). We adopted a stratified sampling design that captured the watershed's elevation gradient, forest-edge versus interior locations, and different vegetation cover. The point-scale observations of throughfall inputs and transpiration suppression, estimated from the Penman equation, were upscaled using such watershed features and the observed fog "footprint" identified from the time-lapse images. When throughfall input and fog-induced transpiration suppression were incorporated into the operational watershed model, they improved estimates of summer baseflow, which remained persistently higher than could be explained without the fog effects. Fog, although providing relatively small volumetric inputs to the water balance, appears to offer significant relief of water stress throughout the terrestrial and aquatic components of the coastal Californian ecosystem and thus should be accounted for when assessing water stress availability in dry ecosystems.

  19. Seasonal prediction of East Asian summer rainfall using a multi-model ensemble system

    Science.gov (United States)

    Ahn, Joong-Bae; Lee, Doo-Young; Yoo, Jin‑Ho

    2015-04-01

    Using the retrospective forecasts of seven state-of-the-art coupled models and their multi-model ensemble (MME) for boreal summers, the prediction skills of climate models in the western tropical Pacific (WTP) and East Asian region are assessed. The prediction of summer rainfall anomalies in East Asia is difficult, while the WTP has a strong correlation between model prediction and observation. We focus on developing a new approach to further enhance the seasonal prediction skill for summer rainfall in East Asia and investigate the influence of convective activity in the WTP on East Asian summer rainfall. By analyzing the characteristics of the WTP convection, two distinct patterns associated with El Niño-Southern Oscillation developing and decaying modes are identified. Based on the multiple linear regression method, the East Asia Rainfall Index (EARI) is developed by using the interannual variability of the normalized Maritime continent-WTP Indices (MPIs), as potentially useful predictors for rainfall prediction over East Asia, obtained from the above two main patterns. For East Asian summer rainfall, the EARI has superior performance to the East Asia summer monsoon index or each MPI. Therefore, the regressed rainfall from EARI also shows a strong relationship with the observed East Asian summer rainfall pattern. In addition, we evaluate the prediction skill of the East Asia reconstructed rainfall obtained by hybrid dynamical-statistical approach using the cross-validated EARI from the individual models and their MME. The results show that the rainfalls reconstructed from simulations capture the general features of observed precipitation in East Asia quite well. This study convincingly demonstrates that rainfall prediction skill is considerably improved by using a hybrid dynamical-statistical approach compared to the dynamical forecast alone. Acknowledgements This work was carried out with the support of Rural Development Administration Cooperative Research

  20. Summer Matters: Advocating for Summer Learning That Can Weather Political Seasons

    Science.gov (United States)

    McQuade, Aaron

    2015-01-01

    Research has shown that an idle summer is not just boring; it can cost a student as much as two to three months of educational progress. Summer is critical to each child's development, both mind and body. Any meaningful attempts to get at America's equity divide and the consequent gap in opportunities for kids must include summer education as a…

  1. Prediction of early summer rainfall over South China by a physical-empirical model

    Science.gov (United States)

    Yim, So-Young; Wang, Bin; Xing, Wen

    2014-10-01

    In early summer (May-June, MJ) the strongest rainfall belt of the northern hemisphere occurs over the East Asian (EA) subtropical front. During this period the South China (SC) rainfall reaches its annual peak and represents the maximum rainfall variability over EA. Hence we establish an SC rainfall index, which is the MJ mean precipitation averaged over 72 stations over SC (south of 28°N and east of 110°E) and represents superbly the leading empirical orthogonal function mode of MJ precipitation variability over EA. In order to predict SC rainfall, we established a physical-empirical model. Analysis of 34-year observations (1979-2012) reveals three physically consequential predictors. A plentiful SC rainfall is preceded in the previous winter by (a) a dipole sea surface temperature (SST) tendency in the Indo-Pacific warm pool, (b) a tripolar SST tendency in North Atlantic Ocean, and (c) a warming tendency in northern Asia. These precursors foreshadow enhanced Philippine Sea subtropical High and Okhotsk High in early summer, which are controlling factors for enhanced subtropical frontal rainfall. The physical empirical model built on these predictors achieves a cross-validated forecast correlation skill of 0.75 for 1979-2012. Surprisingly, this skill is substantially higher than four-dynamical models' ensemble prediction for 1979-2010 period (0.15). The results here suggest that the low prediction skill of current dynamical models is largely due to models' deficiency and the dynamical prediction has large room to improve.

  2. Concentrations of tritium in atmospheric moisture and precipitation of Mt. Hakkoda

    International Nuclear Information System (INIS)

    Kimura, Hideki; Kon, Takezumi; Sasaki, Mamoru

    2000-01-01

    A large-scale spent nuclear fuel reprocessing plant in Japan is now under construction in Rokkasho Village, Aomori Prefecture. The 3 H will be one of the major radionuclides released from the plant. To grasp the behavior of 3 H in the environment in Aomori Prefecture, we surveyed 3 H concentrations in the atmospheric moisture and the precipitation samples at Mt. Hakkoda. Additional atmospheric moisture samples were collected at Rokkasho Village and Aomori City. The relatively high 3 H concentration in the atmospheric moisture and the precipitation samples at Mt. Hakkoda were observed from spring to summer. The 3 H concentrations in the precipitation were similar to those in the atmospheric moisture. The temporal variation patterns of 3 H concentrations in the atmospheric moisture were similar in relatively wide region that covers from Mt. Hakkoda to Aomori City and Rokkasho Village. The 3 H concentration in atmospheric moisture at the top of Mt. Hakkoda positively correlated with the ozone concentration. It suggested that 3 H originated from the stratosphere, and showed that ozone might be used as an indictor of background 3 H. (author)

  3. School's out: what are urban children doing? The Summer Activity Study of Somerville Youth (SASSY

    Directory of Open Access Journals (Sweden)

    Goldberg Jeanne

    2010-03-01

    Full Text Available Abstract Background Research indicates that in the United States, children experience healthier BMI and fitness levels during school vs. summer, but research is limited. The primary goal of this pilot study was to assess where children spend their time during the months that school is not in session and to learn about the different types of activities they engage in within different care settings. A secondary goal of this pilot study was to learn what children eat during the summer months. Methods A nine-week summer study of 57 parents of second and third grade students was conducted in an economically, racial/ethnically and linguistically diverse US urban city. Weekly telephone interviews queried time and activities spent on/in 1 the main caregiver's care 2 someone else's care 3 vacation 4 and camp. Activities were categorised as sedentary, light, moderate, or vigorous (0-3 scale. For each child, a mean activity level was calculated and weighted for proportion of time spent in each care situation, yielding a weighted activity index. On the last phone call, parents answered questions about their child's diet over the summer. Two post-study focus groups were conducted to help interpret findings from the weekly activity interviews. Results The mean activity index was 1.05 ± 0.32 and differed between gender (p = 0.07, education (p = 0.08 and primary language spoken in the household (p = 0.01. Children who spent a greater percentage of time in parent care had on average a lower activity index (β = -0.004, p = 0.01 while children who spent a greater percentage of time in camp had a higher activity index (β = 0.004, p = 0.03. When stratified into type of camp, percentage of time spent in active camp was also positively associated with mean activity index (β = 0.005, p = Conclusions Summer activities and some dietary behaviours are influenced by situation of care and socio-demographic characteristics. In particular, children who spend a greater

  4. Atmospheric Dynamics Leading to West European Summer Hot Temperatures Since 1851

    Directory of Open Access Journals (Sweden)

    M. Carmen Alvarez-Castro

    2018-01-01

    Full Text Available Summer hot temperatures have many impacts on health, economy (agriculture, energy, and transports, and ecosystems. In Western Europe, the recent summers of 2003 and 2015 were exceptionally warm. Many studies have shown that the genesis of the major heat events of the last decades was linked to anticyclonic atmospheric circulation and to spring precipitation deficit in Southern Europe. Such results were obtained for the second part of the 20th century and projections into the 21st century. In this paper, we challenge this vision by investigating the earlier part of the 20th century from an ensemble of 20CR reanalyses. We propose an innovative description of Western-European heat events applying the dynamical system theory. We argue that the atmospheric circulation patterns leading to the most intense heat events have changed during the last century. We also show that the increasing temperature trend during major heatwaves is encountered during episodes of Scandinavian Blocking, while other circulation patterns do not yield temperature trends during extremes.

  5. Secondary precipitation in an Al-Mg-Si-Cu alloy

    International Nuclear Information System (INIS)

    Buha, J.; Lumley, R.N.; Crosky, A.G.; Hono, K.

    2007-01-01

    Interruption of a conventional T6 heat treatment at 177 deg. C for the Al-Mg-Si-Cu alloy 6061 after a short period of time (20 min), by inserting a dwell period at a lower temperature (e.g. 65 deg. C), promotes secondary precipitation of Guinier-Preston (GP) zones. As a consequence, a much greater number of precursors to the β'' precipitates are produced so that a finer and denser dispersion of this phase is formed when T6 ageing is resumed. This change in microstructure causes significant and simultaneous improvements in tensile properties and fracture toughness. Secondary precipitation of GP zones occurs through a gradual evolution of a large number of Mg-Si(-Cu)-vacancy co-clusters formed during the initial ageing at 177 deg. C. The precise mechanism of secondary precipitation has been revealed by three-dimensional atom probe microscopy supplemented by transmission electron microscopy and differential scanning calorimetry

  6. Future increases in Arctic precipitation linked to local evaporation and sea-ice retreat.

    Science.gov (United States)

    Bintanja, R; Selten, F M

    2014-05-22

    Precipitation changes projected for the end of the twenty-first century show an increase of more than 50 per cent in the Arctic regions. This marked increase, which is among the highest globally, has previously been attributed primarily to enhanced poleward moisture transport from lower latitudes. Here we use state-of-the-art global climate models to show that the projected increases in Arctic precipitation over the twenty-first century, which peak in late autumn and winter, are instead due mainly to strongly intensified local surface evaporation (maximum in winter), and only to a lesser degree due to enhanced moisture inflow from lower latitudes (maximum in late summer and autumn). Moreover, we show that the enhanced surface evaporation results mainly from retreating winter sea ice, signalling an amplified Arctic hydrological cycle. This demonstrates that increases in Arctic precipitation are firmly linked to Arctic warming and sea-ice decline. As a result, the Arctic mean precipitation sensitivity (4.5 per cent increase per degree of temperature warming) is much larger than the global value (1.6 to 1.9 per cent per kelvin). The associated seasonally varying increase in Arctic precipitation is likely to increase river discharge and snowfall over ice sheets (thereby affecting global sea level), and could even affect global climate through freshening of the Arctic Ocean and subsequent modulations of the Atlantic meridional overturning circulation.

  7. Sources of uncertainty in future changes in local precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Rowell, David P. [Met Office Hadley Centre, Exeter (United Kingdom)

    2012-10-15

    This study considers the large uncertainty in projected changes in local precipitation. It aims to map, and begin to understand, the relative roles of uncertain modelling and natural variability, using 20-year mean data from four perturbed physics or multi-model ensembles. The largest - 280-member - ensemble illustrates a rich pattern in the varying contribution of modelling uncertainty, with similar features found using a CMIP3 ensemble (despite its limited sample size, which restricts it value in this context). The contribution of modelling uncertainty to the total uncertainty in local precipitation change is found to be highest in the deep tropics, particularly over South America, Africa, the east and central Pacific, and the Atlantic. In the moist maritime tropics, the highly uncertain modelling of sea-surface temperature changes is transmitted to a large uncertain modelling of local rainfall changes. Over tropical land and summer mid-latitude continents (and to a lesser extent, the tropical oceans), uncertain modelling of atmospheric processes, land surface processes and the terrestrial carbon cycle all appear to play an additional substantial role in driving the uncertainty of local rainfall changes. In polar regions, inter-model variability of anomalous sea ice drives an uncertain precipitation response, particularly in winter. In all these regions, there is therefore the potential to reduce the uncertainty of local precipitation changes through targeted model improvements and observational constraints. In contrast, over much of the arid subtropical and mid-latitude oceans, over Australia, and over the Sahara in winter, internal atmospheric variability dominates the uncertainty in projected precipitation changes. Here, model improvements and observational constraints will have little impact on the uncertainty of time means shorter than at least 20 years. Last, a supplementary application of the metric developed here is that it can be interpreted as a measure

  8. Contrasting the co-variability of daytime cloud and precipitation over tropical land and ocean

    Science.gov (United States)

    Jin, Daeho; Oreopoulos, Lazaros; Lee, Dongmin; Cho, Nayeong; Tan, Jackson

    2018-03-01

    The co-variability of cloud and precipitation in the extended tropics (35° N-35° S) is investigated using contemporaneous data sets for a 13-year period. The goal is to quantify potential relationships between cloud type fractions and precipitation events of particular strength. Particular attention is paid to whether the relationships exhibit different characteristics over tropical land and ocean. A primary analysis metric is the correlation coefficient between fractions of individual cloud types and frequencies within precipitation histogram bins that have been matched in time and space. The cloud type fractions are derived from Moderate Resolution Imaging Spectroradiometer (MODIS) joint histograms of cloud top pressure and cloud optical thickness in 1° grid cells, and the precipitation frequencies come from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) data set aggregated to the same grid.It is found that the strongest coupling (positive correlation) between clouds and precipitation occurs over ocean for cumulonimbus clouds and the heaviest rainfall. While the same cloud type and rainfall bin are also best correlated over land compared to other combinations, the correlation magnitude is weaker than over ocean. The difference is attributed to the greater size of convective systems over ocean. It is also found that both over ocean and land the anti-correlation of strong precipitation with weak (i.e., thin and/or low) cloud types is of greater absolute strength than positive correlations between weak cloud types and weak precipitation. Cloud type co-occurrence relationships explain some of the cloud-precipitation anti-correlations. Weak correlations between weaker rainfall and clouds indicate poor predictability for precipitation when cloud types are known, and this is even more true over land than over ocean.

  9. Arctic daily temperature and precipitation extremes: Observed and simulated physical behavior

    Science.gov (United States)

    Glisan, Justin Michael

    Simulations using a six-member ensemble of Pan-Arctic WRF (PAW) were produced on two Arctic domains with 50-km resolution to analyze precipitation and temperature extremes for various periods. The first study used a domain developed for the Regional Arctic Climate Model (RACM). Initial simulations revealed deep atmospheric circulation biases over the northern Pacific Ocean, manifested in pressure, geopotential height, and temperature fields. Possible remedies to correct these large biases, such as modifying the physical domain or using different initial/boundary conditions, were unsuccessful. Spectral (interior) nudging was introduced as a way of constraining the model to be more consistent with observed behavior. However, such control over numerical model behavior raises concerns over how much nudging may affect unforced variability and extremes. Strong nudging may reduce or filter out extreme events, since the nudging pushes the model toward a relatively smooth, large-scale state. The question then becomes---what is the minimum spectral nudging needed to correct biases while not limiting the simulation of extreme events? To determine this, we use varying degrees of spectral nudging, using WRF's standard nudging as a reference point during January and July 2007. Results suggest that there is a marked lack of sensitivity to varying degrees of nudging. Moreover, given that nudging is an artificial forcing applied in the model, an important outcome of this work is that nudging strength apparently can be considerably smaller than WRF's standard strength and still produce reliable simulations. In the remaining studies, we used the same PAW setup to analyze daily precipitation extremes simulated over a 19-year period on the CORDEX Arctic domain for winter and summer. We defined these seasons as the three-month period leading up to and including the climatological sea ice maximum and minimum, respectively. Analysis focused on four North American regions defined using

  10. Assessment of satellite-based precipitation estimates over Paraguay

    Science.gov (United States)

    Oreggioni Weiberlen, Fiorella; Báez Benítez, Julián

    2018-04-01

    Satellite-based precipitation estimates represent a potential alternative source of input data in a plethora of meteorological and hydrological applications, especially in regions characterized by a low density of rain gauge stations. Paraguay provides a good example of a case where the use of satellite-based precipitation could be advantageous. This study aims to evaluate the version 7 of the Tropical Rainfall Measurement Mission Multi-Satellite Precipitation Analysis (TMPA V7; 3B42 V7) and the version 1.0 of the purely satellite-based product of the Climate Prediction Center Morphing Technique (CMORPH RAW) through their comparison with daily in situ precipitation measurements from 1998 to 2012 over Paraguay. The statistical assessment is conducted with several commonly used indexes. Specifically, to evaluate the accuracy of daily precipitation amounts, mean error (ME), root mean square error (RMSE), BIAS, and coefficient of determination (R 2) are used, and to analyze the capability to correctly detect different precipitation intensities, false alarm ratio (FAR), frequency bias index (FBI), and probability of detection (POD) are applied to various rainfall rates (0, 0.1, 0.5, 1, 2, 5, 10, 20, 40, 60, and 80 mm/day). Results indicate that TMPA V7 has a better performance than CMORPH RAW over Paraguay. TMPA V7 has higher accuracy in the estimation of daily rainfall volumes and greater precision in the detection of wet days (> 0 mm/day). However, both satellite products show a lower ability to appropriately detect high intensity precipitation events.

  11. Precipitation and evapotranspiration at the mountain lysimeter station Stoderzinken

    Science.gov (United States)

    Herndl, Markus; Winkler, Gerfried; Birk, Steffen

    2014-05-01

    Alpine water resources are highly important for the Austrian drinking water supply. In particular, the Northern Calcareous Alps contribute substantially to both the regional and the national drinking water supply. To analyse water balance, runoff and recharge in a representative mountain pasture area in the Northern Calcareous Alps a lysimeter station was established at the mountain Stoderzinken (1830 m a.s.l.) in 2005. This work examines the water balance at the lysimeter station during one summer period. Precipitation and evapotranspiration are determined using various approaches in order to identify potential errors in the measurement or interpretation of the data and thus to assess the uncertainties in the water balance components. For this purpose, data of rain gauges and a distrometer was compared with the precipitation calculated from the water balance of the lysimeter. Furthermore evapotranspiration was calculated using the HAUDE and PENMAN-MONTEITH equations for comparison. Already in previous seasons the distrometer was found to be prone to errors, which was confirmed when compared to the rain gauge data. In contrast, precipitation rates calculated from the lysimeter data were found to agree better with the rain gauge data but showed a trend to higher values. However, the approach to calculate precipitation from the lysimeter data turned out to be unsuitable for time periods with significant contribution of snow melt. Evapotranspiration calculated from lysimeter data are in good agreement with the results from the above-mentioned (semi-)empirical equations during dry periods. Furthermore the differences to the evapotranspiration calculated from the climate data correlate with the amount of precipitation. These results suggest that in alpine catchments the uncertainty in the precipitation data constitutes the major source of error in the calculation of evapotranspiration from the water balance of the lysimeter. However, it should be noted that these

  12. A New Inter-Hemispheric Teleconnection Increases Predictability of Winter Precipitation in Southwestern US

    Science.gov (United States)

    Mamalakis, A.; Yu, J. Y.; Randerson, J. T.; AghaKouchak, A.; Foufoula-Georgiou, E.

    2017-12-01

    Early and reliable prediction of seasonal precipitation in the southwestern US (SWUS) remains a challenge with significant implications for the economy, water security and ecosystem management of the region. Traditional drivers of winter precipitation in the SWUS have been linked to the El Niño-Southern Oscillation (ENSO), decadal/multidecadal oscillations of the sea surface temperature in northern Pacific and Atlantic oceans, and persistent high-pressure ridges over the Gulf of Alaska. However, ENSO as well as other climate modes exhibit weak statistical relationships with precipitation and low predictability as lead time increases. Grounded on the hypothesis that still undiscovered relationships between large-scale atmosphere-ocean dynamics and SWUS precipitation might exist, here we followed a diagnostic approach by which instead of restricting ourselves to the established teleconnections, we analyzed systematically the correlation of global sea surface temperature (SST) and geopotential height (GPH) with winter precipitation amounts in all climatic divisions in the SWUS, for 1950-2015. Our results show that late-summer persistent SST and GPH anomalies in the subtropical southwestern Pacific are strongly connected with winter precipitation in most climatic divisions, exhibiting higher correlation values than ENSO, and thus increasing the potential for earlier and more accurate precipitation prediction. Cross validation and 30-year running average analysis starting in 1950 suggest an amplification of the detected teleconnections over the past three to four decades. The latter is most likely a result of the reported expansion of the tropics, which has started after the 1980s, and allows SST or GPH variability at lower latitudes to affect the meridional atmospheric circulation. Our work highlights the need to understand the dynamic nature of the coupled atmosphere-ocean system in a changing climate for improving future predictions of regional precipitation.

  13. Changes in atmospheric circulation between solar maximum and minimum conditions in winter and summer

    Science.gov (United States)

    Lee, Jae Nyung

    2008-10-01

    Statistically significant climate responses to the solar variability are found in Northern Annular Mode (NAM) and in the tropical circulation. This study is based on the statistical analysis of numerical simulations with ModelE version of the chemistry coupled Goddard Institute for Space Studies (GISS) general circulation model (GCM) and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The low frequency large scale variability of the winter and summer circulation is described by the NAM, the leading Empirical Orthogonal Function (EOF) of geopotential heights. The newly defined seasonal annular modes and its dynamical significance in the stratosphere and troposphere in the GISS ModelE is shown and compared with those in the NCEP/NCAR reanalysis. In the stratosphere, the summer NAM obtained from NCEP/NCAR reanalysis as well as from the ModelE simulations has the same sign throughout the northern hemisphere, but shows greater variability at low latitudes. The patterns in both analyses are consistent with the interpretation that low NAM conditions represent an enhancement of the seasonal difference between the summer and the annual averages of geopotential height, temperature and velocity distributions, while the reverse holds for high NAM conditions. Composite analysis of high and low NAM cases in both the model and observation suggests that the summer stratosphere is more "summer-like" when the solar activity is near a maximum. This means that the zonal easterly wind flow is stronger and the temperature is higher than normal. Thus increased irradiance favors a low summer NAM. A quantitative comparison of the anti-correlation between the NAM and the solar forcing is presented in the model and in the observation, both of which show lower/higher NAM index in solar maximum/minimum conditions. The summer NAM in the troposphere obtained from NCEP/NCAR reanalysis has a dipolar zonal structure with maximum

  14. [Temporal and spatial variation of the optimal sowing dates of summer maize based on both statistical and processes models in Henan Province, China].

    Science.gov (United States)

    Tan, Mei-xiu; Wang, Jing; Yu, Wei-dong; He, Di; Wang, Na; Dai, Tong; Sun, Yan; Tang, Jian-zhao; Chang, Qing

    2015-12-01

    Sowing date is one of the vital factors for determining crop yield. In this study, temporal and spatial variation of optimal sowing date of summer maize was analyzed by statistical model and the APSIM-Maize model in Henan Province, China. The results showed that average summer maize optimal sowing dates ranged from May 30 to June 13 across Henan Province with earlier sowing before June 8 in the southern part and later sowing from June 4 to June 13 in the northern part. The optimal sowing date in mountain area of western Henan Province should be around May 30. Late-maturing variety Nongda 108 should be planted at least two days earlier than middle-maturing variety Danyu 13. Under climate warming background, maize sowing should be postponed for at least 3 days if maize harvesting date could be delayed for a week. It was proposed that sowing should be delayed for about a week for a yearly less precipitation pattern while advanced for about a week for a yearly more precipitation pattern compared to the normal one. Across Henan Province, the optimal sowing dates of summer maize showed no significant change trend in 1971-2010, while the potential sowing period had been extended for some regions, such as south from Zhumadian, Yichuan, Nei-xiang and Nanyang in the middle part of Henan, Linzhou in the northern Henan and Sanmenxia in the western Henan, as a result from advanced maturity of winter wheat due to increasing temperature and winter wheat cultivar change. Optimal sowing dates at 76.7% of the study stations showed no significant difference between the two methods. It was recommended that the northern Henan should sow maize immediately after any rainfall and replant afterward, while the southern Henan should not sow maize until that there were valid precipitation (3.9 mm and 8.3 mm for upper south and south parts, respectively) during sowing period, both required enough precipitation during key water requirement period and optimal temperature during grain

  15. Precipitation and measurements of precipitation

    NARCIS (Netherlands)

    Schmidt, F.H.; Bruin, H.A.R. de; Attmannspacher, W.; Harrold, T.W.; Kraijenhoff van de Leur, D.A.

    1977-01-01

    In Western Europe, precipitation is normal phenomenon; it is of importance to all aspects of society, particularly to agriculture, in cattle breeding and, of course, it is a subject of hydrological research. Precipitation is an essential part in the hydrological cycle. How disastrous local

  16. Quantitative transmission electron microscopy and atom probe tomography study of Ag-dependent precipitation of Ω phase in Al-Cu-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Song; Ying, Puyou [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Wang, Jian; Li, Junlin [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

    2017-02-27

    The close association between the Ω precipitation and various Ag additions is systematically investigated by quantitative transmission electron microscopy and atom probe tomography analysis. Our results suggest that the precipitation of Ω phase is strongly dependent on Ag variations. Increasing the bulk Ag content favors a denser Ω precipitation and hence leads to a greater age-hardening response of Al-Cu-Mg-Ag alloy. This phenomenon, as proposed by proximity histograms, is directly related to the greater abundance of Ag solutes within Ω precursors. This feature lowers its nucleation barrier and increases the nucleation rate of Ω phase, finally contributes to the enhanced Ω precipitation. Also, it is noted that increasing Ag remarkably restricts the precipitation of θ' phase.

  17. ENSO, IOD and Indian Summer Monsoon in NCEP climate forecast system

    Energy Technology Data Exchange (ETDEWEB)

    Pokhrel, Samir; Chaudhari, H.S.; Saha, Subodh K.; Dhakate, Ashish; Yadav, R.K.; Salunke, Kiran; Mahapatra, S.; Rao, Suryachandra A. [Indian Institute of Tropical Meteorology, Pashan, Pune (India)

    2012-11-15

    El Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Indian Summer Monsoon rainfall features are explored statistically and dynamically using National Centers for Environment Prediction (NCEP) Climate Forecast System (CFSv1) freerun in relation to observations. The 100 years of freerun provides a sufficiently long homogeneous data set to find out the mean state, periodicity, coherence among these climatic events and also the influence of ENSO and IOD on the Indian monsoon. Differences in the occurrence of seasonal precipitation between the observations and CFS freerun are examined as a coupled ocean-atmosphere system. CFS simulated ENSO and IOD patterns and their associated tropical Walker and regional Hadley circulation in pure ENSO (PEN), pure IOD (PIO) and coexisting ENSO-IOD (PEI) events have some similarity to the observations. PEN composites are much closer to the observation as compared to PIO and PEI composites, which suggest a better ENSO prediction and its associated teleconnections as compared to IOD and combined phenomenon. Similar to the observation, the model simulation also show that the decrease in the Indian summer monsoon rainfall during ENSO phases is associated with a descending motion of anomalous Walker circulation and the increase in the Indian summer monsoon rainfall during IOD phase is associated with the ascending branch of anomalous regional Hadley circulation. During co-existing ENSO and IOD years, however, the fate of Indian summer monsoon is dictated by the combined influence of both of them. The shift in the anomalous descending and ascending branches of the Walker and Hadley circulation may be somewhat attributed to the cold (warm) bias over eastern (western) equatorial Indian Ocean basin, respectively in the model. This study will be useful for identifying some of the limitations of the CFS model and consequently it will be helpful in improving the model to unravel the realistic coupled ocean-atmosphere interactions

  18. Hydrological Utility and Uncertainty of Multi-Satellite Precipitation Products in the Mountainous Region of South Korea

    Directory of Open Access Journals (Sweden)

    Jong Pil Kim

    2016-07-01

    Full Text Available Satellite-derived precipitation can be a potential source of forcing data for assessing water availability and managing water supply in mountainous regions of East Asia. This study investigates the hydrological utility of satellite-derived precipitation and uncertainties attributed to error propagation of satellite products in hydrological modeling. To this end, four satellite precipitation products (tropical rainfall measuring mission (TRMM multi-satellite precipitation analysis (TMPA version 6 (TMPAv6 and version 7 (TMPAv7, the global satellite mapping of precipitation (GSMaP, and the climate prediction center (CPC morphing technique (CMORPH were integrated into a physically-based hydrologic model for the mountainous region of South Korea. The satellite precipitation products displayed different levels of accuracy when compared to the intra- and inter-annual variations of ground-gauged precipitation. As compared to the GSMaP and CMORPH products, superior performances were seen when the TMPA products were used within streamflow simulations. Significant dry (negative biases in the GSMaP and CMORPH products led to large underestimates of streamflow during wet-summer seasons. Although the TMPA products displayed a good level of performance for hydrologic modeling, there were some over/underestimates of precipitation by satellites during the winter season that were induced by snow accumulation and snowmelt processes. These differences resulted in streamflow simulation uncertainties during the winter and spring seasons. This study highlights the crucial need to understand hydrological uncertainties from satellite-derived precipitation for improved water resource management and planning in mountainous basins. Furthermore, it is suggested that a reliable snowfall detection algorithm is necessary for the new global precipitation measurement (GPM mission.

  19. Relations between precipitation, groundwater withdrawals, and changes in hydrologic conditions at selected monitoring sites in Volusia County, Florida, 1995--2010

    Science.gov (United States)

    Murray, Louis C.

    2012-01-01

    precipitation conditions than during wetter than average conditions. For precipitation-averaged hydrologic conditions, water-level changes in the surficial aquifer system were statistically correlated solely with precipitation or were more highly correlated with precipitation than with groundwater withdrawals. Changes in Upper Floridan aquifer water levels and in water-surface stage (stage) at Indian and Scoggin Lakes tended to be highly correlated with both precipitation and withdrawals. The greater influence of withdrawals on stage changes, relative to changes in nearby surficial aquifer system water levels, indicates that these karstic lakes may be better connected hydraulically with the underlying Upper Floridan aquifer than is the surficial aquifer system at the other monitoring sites. At most sites, and for both aquifers, the 2-month moving average of precipitation or groundwater withdrawals included as an explanatory variable in the regression models indicates that water-level changes are not only influenced by stressor conditions across the current month, but also by those of the previous month. The relations between changes in water levels, precipitation, and groundwater withdrawals varied seasonally and in response to a period of drought. Water-level changes tended to be most highly correlated with withdrawals during the spring, when relatively large increases contributed to water-level declines, and during the fall when reduced withdrawal rates contributed to water-level recovery. Water-level changes tended to be most highly (or solely) correlated with precipitation in the winter, when withdrawals are minimal, and in the summer when precipitation is greatest. Water-level changes measured during the drought of October 2005 to June 2008 tended to be more highly correlated with groundwater withdrawals at Upper Floridan aquifer sites than at surficial aquifer system sites, results that were similar to those for precipitation-averaged conditions. Also, changes in stage at

  20. Trends in Summer Season Climate for Eastern Europe and Southern Russia in the Early 21st Century

    OpenAIRE

    Lebedeva, Maria G.; Krymskaya, Olga V.; Lupo, Anthony R.; Chendev, Yury G.; Petin, Alexandr N.; Solovyov, Alexandr B.

    2016-01-01

    The goal of this research is to evaluate changes in temperature and precipitation in the Central Chernozem Region of southwestern Russia during the summer and relate these to large-scale circulation types and synoptic circulation processes. Some of these circulation regimes result in extreme weather conditions over the region. Using a classification system for Northern Hemisphere large-scale flow regimes and observations of weather within the Central Chernozem Region, the role of individual s...

  1. Snow cover and End of Summer Snowline statistics from a simple stochastic model

    Science.gov (United States)

    Petrelli, A.; Crouzy, B.; Perona, P.

    2012-04-01

    One essential parameter characterizing snow cover statistics is the End Of Summer Snowline (EOSS), which is also a good indicator of actual climatic trends in mountain regions. EOSS is usually modelled by means of spatially distributed physically based models, and typically require heavy parameterization. In this paper we validate the simple stochastic model proposed by Perona et al. (2007), by showing that the snow cover statistics and the position of EOSS can in principle be explained by only four essential (meteorological) parameters. Perona et al. (2007) proposed a model accounting for stochastic snow accumulation in the cold period, and deterministic melting dynamics in the warm period, and studied the statistical distribution of the snowdepth on the long term. By reworking the ensemble average of the steady state evolution equation we single out a relationship between the snowdepth statistics (including the position of EOSS) and the involved parameters. The validation of the established relationship is done using 50 years of field data from 73 Swiss stations located above 2000 m a.s.l. First an estimation of the meteorological parameters is made. Snow height data are used as a precipitation proxy, using temperature data to estimate SWE during the precipitation event. Thresholds are used both to separate accumulation from actual precipitation and wind transport phenomena, and to better assess summer melting rate, considered to be constant over the melting period according to the simplified model. First results show that data for most of the weather stations actually scales with the proposed relationship. This indicates that, on the long term, the effect of spatial and temporal noise masks most of the process detail so that minimalist models suffice to obtain reliable statistics. Future works will test the validity of this approach at different spatial scales, e.g., regional, continental and planetary. Reference: P. Perona, A. Porporato, and L. Ridolfi, "A

  2. A study on the intra-annual variation and the spatial distribution of precipitation amount and duration over Greece on a 10 day basis

    Science.gov (United States)

    Bartzokas, A.; Lolis, C. J.; Metaxas, D. A.

    2003-02-01

    The intra-annual variation of precipitation amount and duration and their spatial distribution during the year are studied on a 10 day basis for the Greek region, using S-mode and T-mode factor analysis. (i) For the intra-annual variation of precipitation amount, two modes were revealed: the first shows one broad maximum during the conventional winter in stations affected by the sea; the second presents two maxima, the first during late autumn-early winter and the second during late spring, corresponding to the northern mainland stations. (ii) For the spatial distribution of precipitation, three main patterns were revealed: the first one is the winter pattern, with the maximum over the west windward area; the second is the summer pattern, with a maximum over the north inland region; and the third is the autumn pattern, with the maximum over northwestern Greece. (iii) For precipitation duration, two types of intra-annual variation were revealed. The first one is similar to the first of the analysis for precipitation amount; the second presents two maxima, the first during the beginning of December and the second during the middle of February, corresponding to the areas of northwestern and northeastern Greece. (iv) For the spatial distribution of precipitation duration, three main patterns were revealed: the first is the summer pattern, which is similar to the second of the analysis for precipitation amount; the second is the winter pattern, with the spatial maximum located over the eastern mainland and western Crete; finally, the third one is the autumn pattern, with the maximum in northwestern Greece. During the third 10 day period of October and the second 10 day period of February, precipitation seems to present singularities, possibly due to fluctuations in atmospheric circulation. The above intra-annual variations and spatial distribution patterns are connected to the seasonal variations of the depression trajectories, the atmospheric instability, the influence

  3. Extreme Precipitation events over North China in August 2010 and their link to eastward-propagating wave-trains across Eurasia: observations and monthly forecasting

    NARCIS (Netherlands)

    Orsolini, Y.J.; Zhang, L.; Peters, D.H.W.; Fraedrich, K.; Zhu, X.; Schneidereit, A.; van den Hurk, B.J.J.M.

    2015-01-01

    Over the Far East in summer, climate is strongly influenced by the fluctuating Western Pacific Subtropical High (WPSH), and strong precipitation is often associated with southeasterly low-level wind that brings moist air from the southern China seas. The WPSH intraseasonal variability is partly

  4. Spatiotemporal Variability and Covariability of Temperature, Precipitation, Soil Moisture, and Vegetation in North America for Regional Climate Model Applications

    Science.gov (United States)

    Castro, C. L.; Beltran-Przekurat, A. B.; Pielke, R. A.

    2007-05-01

    Previous work has established that the dominant modes of Pacific SSTs influence the summer climate of North America through large-scale forcing, and this effect is most pronounced during the early part of the season. It is hypothesized, then, that land surface influences become more dominant in the latter part of the season as remote teleconnection influences diminish. As a first step toward investigation of this hypothesis in a regional climate model (RCM) framework, the statistically signficant spatiotemporal patterns of variability and covariability in North American precipitation (specified by the standardized precipitation index, or SPI), soil moisture, and vegetation are determined for timescales from a month to six months. To specify these respective data we use: CPC gauge- derived precipitation (1950-2000), Variable Infiltration Capacity (VIC) Model and NOAH Model NLDAS soil moisture and temperature, and the Global Inventory Modeling and Mapping Studies Normalized Difference Vegetation Index (GIMMS-NDVI). The principal statistical tool used is multiple taper frequency singular value decomposition (MTM-SVD), and this is supplemented by wavelet analysis for specific areas of interest. The significant interannual variability in all of these data occur at a timescale of about 7 to 9 years and appears to be the integrated effect of remote SST forcing from the Pacific. Considering the entire year, the spatial pattern for precipitation resembles the typical ENSO winter signature. If the summer season is considered seperately, the out of phase relationship between precipitation anomalies in the central U.S. and core monsoon region is apparent. The largest soil moisture anomalies occur in the central U.S., since precipitation in this region has a consistent relationship to Pacific SSTs for the entire year. This helps to explain the approximately 20 year periodicity in drought conditions there. Unlike soil moisture, the largest anomalies in vegetation occur in the

  5. The Contribution of Extreme Precipitation to the Total Precipitation in China

    Institute of Scientific and Technical Information of China (English)

    SUN Jian-Qi

    2012-01-01

    Using daily precipitation data from weather stations in China, the variations in the contribution of extreme precipitation to the total precipitation are analyzed. It is found that extreme precipitation accounts for approximately one third of the total precipitation based on the overall mean for China. Over the past half century, extreme precipitation has played a dominant role in the year-to-year variability of the total precipitation. On the decadal time scale, the extreme precipitation makes different contributions to the wetting and drying regions of China. The wetting trends of particular regions are mainly attributed to increases in extreme precipitation; in contrast, the drying trends of other regions are mainly due to decreases in non-extreme precipitation.

  6. Impacts of boreal hydroelectric reservoirs on seasonal climate and precipitation recycling as simulated by the CRCM5: a case study of the La Grande River watershed, Canada

    Science.gov (United States)

    Irambona, C.; Music, B.; Nadeau, D. F.; Mahdi, T. F.; Strachan, I. B.

    2018-02-01

    Located in northern Quebec, Canada, eight hydroelectric reservoirs of a 9782-km2 maximal area cover 6.4% of the La Grande watershed. This study investigates the changes brought by the impoundment of these reservoirs on seasonal climate and precipitation recycling. Two 30-year climate simulations, corresponding to pre- and post-impoundment conditions, were used. They were generated with the fifth-generation Canadian Regional Climate Model (CRCM5), fully coupled to a 1D lake model (FLake). Seasonal temperatures and annual energy budget were generally well reproduced by the model, except in spring when a cold bias, probably related to the overestimation of snow cover, was seen. The difference in 2-m temperature shows that reservoirs induce localized warming in winter (+0.7 ± 0.02 °C) and cooling in the summer (-0.3 ± 0.02 °C). The available energy at the surface increases throughout the year, mostly due to a decrease in surface albedo. Fall latent and sensible heat fluxes are enhanced due to additional energy storage and availability in summer and spring. The changes in precipitation and runoff are within the model internal variability. At the watershed scale, reservoirs induce an additional evaporation of only 5.9 mm year-1 (2%). We use Brubaker's precipitation recycling model to estimate how much of the precipitation is recycled within the watershed. In both simulations, the maximal precipitation recycling occurs in July (less than 6%), indicating weak land-atmosphere coupling. Reservoirs do not seem to affect this coupling, as precipitation recycling only decreased by 0.6% in July.

  7. Quantitative measurement of precipitation using radar in comparison with ground-level measurements, taking orographic influences into account; Quantitative Niederschlagsmessung mit Radar im Vergleich mit Bodenmessungen in orographisch gegliedertem Gelaende

    Energy Technology Data Exchange (ETDEWEB)

    Gysi, H. [Radar-Info, Karlsruhe (Germany)

    1998-01-01

    The methods of correction applied to the determination of the spatial distribution of precipitation on the basis of the volumes established by the Karlsruhe C-band precipitation radar distinctly enhance the quality of statements regarding precipitation intensities and their time integration both in summer and winter. (orig./KW) [Deutsch] Die fuer die Bestimmung der raeumlichen Niederschlagsverteilung aus Volumendaten des Karlsruher C-Band Niederschlagradars angewandten Korrekturverfahren verbessern sowohl im Sommer als auch im Winter deutlich die Qualitaet und quantitative Aussagekraft der dargestellten Niederschlagsintensitaeten und deren zeitlichen Integrationen. (orig./KW)

  8. 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

  9. Elevated heat pump effects of dust aerosol over Northwestern China during summer

    Science.gov (United States)

    Tang, Yaoguo; Han, Yongxiang; Ma, Xiaoyan; Liu, Zhaohuan

    2018-05-01

    The Elevated Heat Pump (EHP) effect demonstrates a significant interaction between the aerosol climatic effect and the monsoon, both are important for climate research. In Northwestern China, the influence of EHP mechanism is still lacking in research. In this study, the EHP effects in Northwestern China are investigated by three sensitivity tests using a WRF-Chem model coupled with the Shao dust emission scheme. Results show that: 1) the anomalous circulation caused by dust aerosols are proved to the existence of EHP effect in Northwestern China; 2) three updrafts over the desert are transported eastward at high altitude and subside in Northeastern China, forming a complete secondary circulation with low-level easterly flow from Badain Jaran and Tengger to Taklimakan; 3) a northeasternerly anomaly flow from Northeastern China can affect the intensity of East Asian summer monsoon (EASM), and increase precipitation in the middle and lower reaches of the Yangtze River and decrease precipitation in Northeastern China. 4) We present a conceptual model of EHP in Northwestern China to provide a better understanding of the climatic effects of dust aerosols.

  10. Chemical composition and seasonal variation of acid deposition in Guangzhou, South China: Comparison with precipitation in other major Chinese cities

    International Nuclear Information System (INIS)

    Huang Deyin; Xu Yigang; Peng Pingan; Zhang Huihuang; Lan Jiangbo

    2009-01-01

    With the aim of understanding the origin of acid rains in South China, we analyzed rainwaters collected from Guangzhou, China, between March 2005 and February 2006. The pH of rainwater collected during the monitoring period varied from 4.22 to 5.87; acid rain represented about 94% of total precipitation during this period. The rainwater was characterized by high concentrations of SO 4 2- , NO 3 - , Ca 2+ , and NH 4 + . SO 4 2- and NO 3 - , the main precursors of acid rain, were related to the combustion of coal and fertilizer use/traffic emissions, respectively. Ca 2+ and NH 4 + act as neutralizers of acid, accounting for the decoupling between high SO 4 2- concentrations and relatively high pH in the Guangzhou precipitation. The acid rain in Guangzhou is most pronounced during spring and summer. A comparison with acid precipitation in other Chinese cities reveals a decreasing neutralization capacity from north to south, probably related to the role and origin of alkaline bases in precipitation. - A north-to-south decreasing trend in the neutralization capacity of precipitation in China

  11. Summer precipitation variability over Southeastern South America in a global warming scenario

    Energy Technology Data Exchange (ETDEWEB)

    Junquas, C. [UPMC/CNRS, Laboratoire de Meteorologie Dynamique, Institut Pierre Simon Laplace, Ecole Polytechnique, Paris (France); UMI-IFAECI CNRS-CONICET-UBA, Centro de Investigaciones del Mar y la Atmosfera (CIMA), DCAO/FCEyN, Buenos Aires (Argentina); Vera, C. [UMI-IFAECI CNRS-CONICET-UBA, Centro de Investigaciones del Mar y la Atmosfera (CIMA), DCAO/FCEyN, Buenos Aires (Argentina); Li, L.; Le Treut, H. [UPMC/CNRS, Laboratoire de Meteorologie Dynamique, Institut Pierre Simon Laplace, Ecole Polytechnique, Paris (France)

    2012-05-15

    December-January-February (DJF) rainfall variability in southeastern South America (SESA) is studied in 18 coupled general circulation models from the WCRP/CMIP3 dataset, for present climate and the SRES-A1B climate change scenario. The analysis is made in terms of properties of the first leading pattern of rainfall variability in the region, characterized by a dipole-like structure with centers of action in the SESA and South Atlantic Convergence Zone (SACZ) regions. The study was performed to address two issues: how rainfall variability in SESA would change in a future climate and how much of that change explains the projected increasing trends in the summer mean rainfall in SESA identified in previous works. Positive (negative) dipole events were identified as those DJF seasons with above (below) normal rainfall in SESA and below (above) normal rainfall in the SACZ region. Results obtained from the multi-model ensemble confirm that future rainfall variability in SESA has a strong projection on the changes of seasonal dipole pattern activity, associated with an increase of the frequency of the positive phase. In addition, the frequency increase of positive dipole phase in the twenty first century seems to be associated with an increase of both frequency and intensity of positive SST anomalies in the equatorial Pacific, and with a Rossby wave train-like anomaly pattern linking that ocean basin to South America, which regionally induces favorable conditions for moisture transport convergence and rainfall increase in SESA. (orig.)

  12. Simulated precipitation diurnal cycles over East Asia using different CAPE-based convective closure schemes in WRF model

    Science.gov (United States)

    Yang, Ben; Zhou, Yang; Zhang, Yaocun; Huang, Anning; Qian, Yun; Zhang, Lujun

    2018-03-01

    Closure assumption in convection parameterization is critical for reasonably modeling the precipitation diurnal variation in climate models. This study evaluates the precipitation diurnal cycles over East Asia during the summer of 2008 simulated with three convective available potential energy (CAPE) based closure assumptions, i.e. CAPE-relaxing (CR), quasi-equilibrium (QE), and free-troposphere QE (FTQE) and investigates the impacts of planetary boundary layer (PBL) mixing, advection, and radiation on the simulation by using the weather research and forecasting model. The sensitivity of precipitation diurnal cycle to PBL vertical resolution is also examined. Results show that the precipitation diurnal cycles simulated with different closures all exhibit large biases over land and the simulation with FTQE closure agrees best with observation. In the simulation with QE closure, the intensified PBL mixing after sunrise is responsible for the late-morning peak of convective precipitation, while in the simulation with FTQE closure, convective precipitation is mainly controlled by advection cooling. The relative contributions of different processes to precipitation formation are functions of rainfall intensity. In the simulation with CR closure, the dynamical equilibrium in the free troposphere still can be reached, implying the complex cause-effect relationship between atmospheric motion and convection. For simulations in which total CAPE is consumed for the closures, daytime precipitation decreases with increased PBL resolution because thinner model layer produces lower convection starting layer, leading to stronger downdraft cooling and CAPE consumption. The sensitivity of the diurnal peak time of precipitation to closure assumption can also be modulated by changes in PBL vertical resolution. The results of this study help us better understand the impacts of various processes on the precipitation diurnal cycle simulation.

  13. The hydrological cycle in the high Pamir Mountains: how temperature and seasonal precipitation distribution influence stream flow in the Gunt catchment, Tajikistan

    Science.gov (United States)

    Pohl, E.; Knoche, M.; Gloaguen, R.; Andermann, C.; Krause, P.

    2014-12-01

    Complex climatic interactions control hydrological processes in high mountains that in their turn regulate the erosive forces shaping the relief. To unravel the hydrological cycle of a glaciated watershed (Gunt River) considered representative of the Pamirs' hydrologic regime we developed a remote sensing-based approach. At the boundary between two distinct climatic zones dominated by Westerlies and Indian summer monsoon, the Pamir is poorly instrumented and only a few in situ meteorological and hydrological data are available. We adapted a suitable conceptual distributed hydrological model (J2000g). Interpolations of the few available in situ data are inadequate due to strong, relief induced, spatial heterogeneities. Instead we use raster data, preferably from remote sensing sources depending on availability and validation. We evaluate remote sensing-based precipitation and temperature products. MODIS MOD11 surface temperatures show good agreement with in situ data, perform better than other products and represent a good proxy for air temperatures. For precipitation we tested remote sensing products as well as the HAR10 climate model data and the interpolation-based APHRODITE dataset. All products show substantial differences both in intensity and seasonal distribution with in-situ data. Despite low resolutions, the datasets are able to sustain high model efficiencies (NSE ≥0.85). In contrast to neighbouring regions in the Himalayas or the Hindukush, discharge is dominantly the product of snow and glacier melt and thus temperature is the essential controlling factor. 80% of annual precipitation is provided as snow in winter and spring contrasting peak discharges during summer. Hence, precipitation and discharge are negatively correlated and display complex hysteresis effects that allow to infer the effect of inter-annual climatic variability on river flow. We infer the existence of two subsurface reservoirs. The groundwater reservoir (providing 40% of annual

  14. Dependence between sea surge, river flow and precipitation in south and west Britain

    Directory of Open Access Journals (Sweden)

    C. Svensson

    2004-01-01

    northwards has slightly stronger flow-surge dependence in summer than in winter, whereas dependence is stronger in winter than in summer for the southern part of the study area. Keywords: : Britain, dependence, sea surge, river flow, precipitation, mid-latitude cyclone, seasonality, time lag

  15. Forced decadal changes in the East Asian summer monsoon: the roles of greenhouse gases and anthropogenic aerosols

    Science.gov (United States)

    Tian, Fangxing; Dong, Buwen; Robson, Jon; Sutton, Rowan

    2018-02-01

    Since the mid-1990s precipitation trends over eastern China display a dipole pattern, characterized by positive anomalies in the south and negative anomalies in the north, named as the Southern-Flood-Northern-Drought (SFND) pattern. This work investigates the drivers of decadal changes of the East Asian summer monsoon (EASM), and the dynamical mechanisms involved, by using a coupled climate model (specifically an atmospheric general circulation model coupled to an ocean mixed layer model) forced by changes in (1) anthropogenic greenhouse gases (GHG), (2) anthropogenic aerosol (AA) and (3) the combined effects of both GHG and AA (All Forcing) between two periods across the mid-1990s. The model experiment forced by changes in All Forcing shows a dipole pattern of response in precipitation over China that is similar to the observed SFND pattern across the mid-1990s, which suggests that anthropogenic forcing changes played an important role in the observed decadal changes. Furthermore, the experiments with separate forcings indicate that GHG and AA forcing dominate different parts of the SFND pattern. In particular, changes in GHG increase precipitation over southern China, whilst changes in AA dominate in the drought conditions over northern China. Increases in GHG cause increased moisture transport convergence over eastern China, which leads to increased precipitation. The AA forcing changes weaken the EASM, which lead to divergent wind anomalies over northern China and reduced precipitation.

  16. Intensity changes in future extreme precipitation: A statistical event-based approach.

    Science.gov (United States)

    Manola, Iris; van den Hurk, Bart; de Moel, Hans; Aerts, Jeroen

    2017-04-01

    Short-lived precipitation extremes are often responsible for hazards in urban and rural environments with economic and environmental consequences. The precipitation intensity is expected to increase about 7% per degree of warming, according to the Clausius-Clapeyron (CC) relation. However, the observations often show a much stronger increase in the sub-daily values. In particular, the behavior of the hourly summer precipitation from radar observations with the dew point temperature (the Pi-Td relation) for the Netherlands suggests that for moderate to warm days the intensification of the precipitation can be even higher than 21% per degree of warming, that is 3 times higher than the expected CC relation. The rate of change depends on the initial precipitation intensity, as low percentiles increase with a rate below CC, the medium percentiles with 2CC and the moderate-high and high percentiles with 3CC. This non-linear statistical Pi-Td relation is suggested to be used as a delta-transformation to project how a historic extreme precipitation event would intensify under future, warmer conditions. Here, the Pi-Td relation is applied over a selected historic extreme precipitation event to 'up-scale' its intensity to warmer conditions. Additionally, the selected historic event is simulated in the high-resolution, convective-permitting weather model Harmonie. The initial and boundary conditions are alternated to represent future conditions. The comparison between the statistical and the numerical method of projecting the historic event to future conditions showed comparable intensity changes, which depending on the initial percentile intensity, range from below CC to a 3CC rate of change per degree of warming. The model tends to overestimate the future intensities for the low- and the very high percentiles and the clouds are somewhat displaced, due to small wind and convection changes. The total spatial cloud coverage in the model remains, as also in the statistical

  17. High spatial-temporal resolution and integrated surface and subsurface precipitation-runoff modelling for a small stormwater catchment

    Science.gov (United States)

    Hailegeorgis, Teklu T.; Alfredsen, Knut

    2018-02-01

    Reliable runoff estimation is important for design of water infrastructure and flood risk management in urban catchments. We developed a spatially distributed Precipitation-Runoff (P-R) model that explicitly represents the land cover information, performs integrated modelling of surface and subsurface components of the urban precipitation water cycle and flow routing. We conducted parameter calibration and validation for a small (21.255 ha) stormwater catchment in Trondheim City during Summer-Autumn events and season, and snow-influenced Winter-Spring seasons at high spatial and temporal resolutions of respectively 5 m × 5 m grid size and 2 min. The calibration resulted in good performance measures (Nash-Sutcliffe efficiency, NSE = 0.65-0.94) and acceptable validation NSE for the seasonal and snow-influenced periods. The infiltration excess surface runoff dominates the peak flows while the contribution of subsurface flow to the sewer pipes also augments the peak flows. Based on the total volumes of simulated flow in sewer pipes (Qsim) and precipitation (P) during the calibration periods, the Qsim/P ranges from 21.44% for an event to 56.50% for the Winter-Spring season, which are in close agreement with the observed volumes (Qobs/P). The lowest percentage of precipitation volume that is transformed to the total simulated runoff in the catchment (QT) is 79.77%. Computation of evapotranspiration (ET) indicated that the ET/P is less than 3% for the events and snow-influenced seasons while it is about 18% for the Summer-Autumn season. The subsurface flow contribution to the sewer pipes are markedly higher than the total surface runoff volume for some events and the Summer-Autumn season. The peakiest flow rates correspond to the Winter-Spring season. Therefore, urban runoff simulation for design and management purposes should include two-way interactions between the subsurface runoff and flow in sewer pipes, and snow-influenced seasons. The developed urban P-R model is

  18. Radiation-use efficiency in summer rape

    International Nuclear Information System (INIS)

    Morrison, M.J.; Stewart, D.W.

    1995-01-01

    The radiation-use efficiency (RUE) is a parameter that represents a crop canopy's ability to convert intercepted solar energy to dry matter. The RUE is used in simulation models and can vary with crop type and environment. The objective was to examine the effects of varying row width and seeding rate on the amount of intercepted photosynthetically active radiation (IPAR) and the RUE in summer rape (Brassica napus L.). 'Westar' summer rape was seeded at rates of 1.5, 3.0, 6.0, and 12.0 kg ha-1 in rows spaced 15 or 30 cm apart. Plant sampling was done at key growth stages, and the leaf and pod areas and total plant dry weights were determined. After flowering, plants intercepted more PAR when grown in 15-cm-wide rows than 30-cm-wide rows. For both row widths, as seeding rate increased from 1.5 to 12.0 kg ha-1, IPAR increased. The RUE was greater for plants grown in 15-cm-wide rows than for those grown in 30-cm rows; however, RUE decreased with increasing seeding rate. The mean RUE value was 2.83 g MJ-1 PAR. When the pod area was added to the leaf area, the IPAR increased and the RUE decreased

  19. Chemical and isotopic variations of precipitation in the Los Alamos Region, New Mexico

    International Nuclear Information System (INIS)

    Adams, A.I.; Goff, F.; Counce, D.

    1995-02-01

    Precipitation collectors were installed at 14 locations on the Pajarito Plateau and surrounding areas to study variations in chemistry, stable isotopes and tritium for the years 1990 to 1993. The volume of precipitation was measured and samples were collected and analyzed every three to four months. All precipitation samples contain 18 O) results record seasonal variations in precipitation as the weather patterns shift from sources in the Pacific Ocean to sources in the Gulf of Mexico. The stable isotope results also show isotopic variations due to elevation differences among the collection points. The tritium contents ( 3 H) in rain samples vary from 6.54 T.U. to 141 T.U. Contouring of high tritium values (e.g. >20 T.U.) from each collection period clearly shows that Laboratory activities release some tritium to the atmosphere. The effect of these releases are well below the limits set by the Environmental Protection Agency for drinking water (about 6200 T.U.). The magnitude of the releases is apparently greatest during the summer months. However, anomalous tritium values are detected as far north as Espahola, New Mexico for many collection periods. Tritium releases by the Laboratory are not constant; thus, the actual amount of tritium in each release has been diluted in the composite samples of our three to four month collection periods

  20. Salts-based size-selective precipitation: toward mass precipitation of aqueous nanoparticles.

    Science.gov (United States)

    Wang, Chun-Lei; Fang, Min; Xu, Shu-Hong; Cui, Yi-Ping

    2010-01-19

    Purification is a necessary step before the application of nanocrystals (NCs), since the excess matter in nanoparticles solution usually causes a disadvantage to their subsequent coupling or assembling with other materials. In this work, a novel salts-based precipitation technique is originally developed for the precipitation and size-selective precipitation of aqueous NCs. Simply by addition of salts, NCs can be precipitated from the solution. After decantation of the supernatant solution, the precipitates can be dispersed in water again. By means of adjusting the addition amount of salt, size-selective precipitation of aqueous NCs can be achieved. Namely, the NCs with large size are precipitated preferentially, leaving small NCs in solution. Compared with the traditional nonsolvents-based precipitation technique, the current one is simpler and more rapid due to the avoidance of condensation and heating manipulations used in the traditional precipitation process. Moreover, the salts-based precipitation technique was generally available for the precipitation of aqueous nanoparticles, no matter if there were semiconductor NCs or metal nanoparticles. Simultaneously, the cost of the current method is also much lower than that of the traditional nonsolvents-based precipitation technique, making it applicable for mass purification of aqueous NCs.

  1. The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset

    Science.gov (United States)

    Huffman, George J.; Adler, Robert F.; Arkin, Philip; Chang, Alfred; Ferraro, Ralph; Gruber, Arnold; Janowiak, John; McNab, Alan; Rudolf, Bruno; Schneider, Udo

    1997-01-01

    The Global Precipitation Climatology Project (GPCP) has released the GPCP Version 1 Combined Precipitation Data Set, a global, monthly precipitation dataset covering the period July 1987 through December 1995. The primary product in the dataset is a merged analysis incorporating precipitation estimates from low-orbit-satellite microwave data, geosynchronous-orbit -satellite infrared data, and rain gauge observations. The dataset also contains the individual input fields, a combination of the microwave and infrared satellite estimates, and error estimates for each field. The data are provided on 2.5 deg x 2.5 deg latitude-longitude global grids. Preliminary analyses show general agreement with prior studies of global precipitation and extends prior studies of El Nino-Southern Oscillation precipitation patterns. At the regional scale there are systematic differences with standard climatologies.

  2. 3rd CERN-Fermilab Hadron Collider Physics Summer School

    CERN Multimedia

    2008-01-01

    August 12-22, 2008, Fermilab The school web site is http://cern.ch/hcpss with links to the academic programme and the application procedure. The APPLICATION DEADLINE IS 29 FEBRUARY 2008. The goal of the CERN-Fermilab Hadron Collider Physics Summer Schools is to offer students and young researchers in high-energy physics a concentrated syllabus on the theory and experimental challenges of hadron collider physics. The third session of the summer school will focus on exposing young post-docs and advanced graduate students to broader theories and real data beyond what they’ve learned at their home institutions. Experts from across the globe will lecture on the theoretical and experimental foundations of hadron collider physics, host parallel discussion sessions and answer students’ questions. This year’s school will also have a greater focus on physics beyond the Standard Model, as well as more time for questions at the end of each lecture. The 2008 School will be held at ...

  3. 3rd CERN-Fermilab HadronCollider Physics Summer School

    CERN Multimedia

    EP Department

    2008-01-01

    August 12-22, 2008, Fermilab The school web site is http://cern.ch/hcpss with links to the academic programme and the application procedure. The APPLICATION DEADLINE IS 29 FEBRUARY 2008. The goal of the CERN-Fermilab Hadron Collider Physics Summer Schools is to offer students and young researchers in high-energy physics a concentrated syllabus on the theory and experimental challenges of hadron collider physics. The third session of the summer school will focus on exposing young post-docs and advanced graduate students to broader theories and real data beyond what they’ve learned at their home institutions. Experts from across the globe will lecture on the theoretical and experimental foundations of hadron collider physics, host parallel discussion sessions and answer students’ questions. This year’s school will also have a greater focus on physics beyond the Standard Model, as well as more time for questions at the end of each lecture. The 2008 School will be held at Fermilab. Further enquiries should ...

  4. Novel Stable Isotope Methods for Assessing Changes in Seasonality of Precipitation from Sediments of Ombrotrophic Peatlands

    Science.gov (United States)

    Nichols, J. E.; Booth, R. K.; Jackson, S. T.; Pendall, E. G.; Walcott, M.; Bradley, R.; Pilcher, J.; Huang, Y.

    2007-12-01

    The seasonality of precipitation is a key but often elusive climate parameter in paleoclimate reconstructions. Sediments from ombrotrophic peatlands are excellent archives of past changes in precipitation/evaporation balance. Here we show that these peatland sediments can also be used to assess changes in the seasonality of precipitation. We have recently determined that distributions of Sphagnum and vascular plant biomarkers sensitively record changes in hydrologic balance (Nichols et al., 2006, Org. Geochem. 37, 1505-1513), but biomarker distributions alone do not offer detailed information for the changes in seasonal precipitation. In this study, we combine biomarker and compound-specific H and C isotope ratios to create a more comprehensive picture of the changing climate affecting these sensitive ombrotrophic systems. We present here two sets of downcore data from sites in Arctic Europe as well as Eastern North America. Basic paleohydrology is established using a ratio of Sphagnum to vascular plant biomarkers (C23 and C29 n-alkanes, respectively. We further describe paleohydrology using novel stable isotope proxies based on δD and δ13C measurements of Sphagnum and vascular plant biomarkers. Because Sphagnum has no vascular system and loses water directly by evaporation, Sphagnum biomarkers enriched in deuterium indicate an evaporative growing season (summer). Vascular plants use their root systems to take up water stored within the peatland, so deuterium-depleted vascular plant biomarkers should indicate increased winter recharge of the peatland. A methanotrophic symbiont living inside the Sphagnum's hyaline (water-holding) cells is more active when the Sphagnum is wet and therefore provides more 13C depleted (methane- derived) carbon dioxide for biomass production when the growing season is less evaporative. Hence, 13C depleted Sphagnum biomarkers indicate increased methanotrophy and therefore a wetter summer. We corroborate our stable isotope proxies by

  5. [Characteristics of precipitation pH and conductivity at Mt. Huang].

    Science.gov (United States)

    Shi, Chun-e; Deng, Xue-liang; Wu, Bi-wen; Hong, Jie; Zhang, Su; Yang, Yuan-jian

    2013-05-01

    To understand the general characteristics of pH distribution and pollution in precipitation at Mt. Huang, statistical analyses were conducted for the routine measurements of pH and conductivity (K) at Mt. Huang during 2006-2011. The results showed that: (1) Over the period of study, the annual volume weighted mean (VWM) precipitation pH varied from 4.81 to 5.57, with precipitation acidity strengthening before 2009 and weakening thereafter. The precipitation acidity showed evident seasonal variations, with the VWM pH lowest in winter (4.78), and highest in summer (5.33). The occurrence frequency of acid rain was 46% , accounting for 45% of total rainfalls and with the most frequent pH falling into weak acid to neutral rain. (2) The annual VWM K varied from 16.91 to 27.84 microS x cm(-1), with no evident trend. As for ions pollution, the precipitation was relatively clean at Mt. Huang, with the most frequent K range being below 15 microS x cm(-1), followed by 15-25 microS x cm(-1). From February 2010 to December 2011, precipitation samples were collected on daily basis for ions analysis, as well as pH and K measurement in lab. Detailed comparisons were conducted between the two sets of pH and K, one set from field measurement and the other from lab measurement. The results indicated: (1) The lab measured pH (K) was highly correlated with the field pH (K); however, the lab pH tended to move towards neutral comparing with the corresponding field pH, and the shift range was closely correlated with the field pH and rainfall. The shift range of K from field to lab was highly correlated with the total ion concentration of precipitation. The field K showed evident negative correlation with the field pH with a correlation coefficient of -0.51. (2) When sampling with nylon-polyethylene bags, the statistics showed smaller bias between two sets of pH, with higher correlation coefficient between two sets of K. Furthermore, the lab K also showed evident negative correlation with

  6. Detection of spatio-temporal variability of air temperature and precipitation based on long-term meteorological station observations over Tianshan Mountains, Central Asia

    Science.gov (United States)

    Xu, Min; Kang, Shichang; Wu, Hao; Yuan, Xu

    2018-05-01

    As abundant distribution of glaciers and snow, the Tianshan Mountains are highly vulnerable to changes in climate. Based on meteorological station records during 1960-2016, we detected the variations of air temperature and precipitation by using non-parametric method in the different sub-regions and different elevations of the Tianshan Mountains. The mutations of climate were investigated by Mann-Kendall abrupt change test in the sub-regions. The periodicity is examined by wavelet analysis employing a chi-square test and detecting significant time sections. The results show that the Tianshan Mountains experienced an overall rapid warming and wetting during study period, with average warming rate of 0.32 °C/10a and wet rate of 5.82 mm/10a, respectively. The annual and seasonal spatial variation of temperature showed different scales in different regions. The annual precipitation showed non-significant upward trend in 20 stations, and 6 stations showed a significant upward trend. The temperatures in the East Tianshan increased most rapidly at rates of 0.41 °C/10a. The increasing magnitudes of annual precipitation were highest in the Boertala Vally (8.07 mm/10a) and lowest in the East Tianshan (2.64 mm/10a). The greatest and weakest warming was below 500 m (0.42 °C/10a) and elevation of 1000-1500 m (0.23 °C/10a), respectively. The increasing magnitudes of annual precipitation were highest in the elevation of 1500 m-2000 m (9.22 mm/10a) and lowest in the elevation of below 500 m (3.45 mm/10a). The mutations of annual air temperature and precipitation occurred in 1995 and 1990, respectively. The large atmospheric circulation influenced on the mutations of climate. The significant periods of air temperature were 2.4-4.1 years, and annual precipitation was 2.5-7.4 years. Elevation dependency of temperature trend magnitude was not evidently in the Tianshan Mountains. The annual precipitation wetting trend was amplified with elevation in summer and autumn. The strong

  7. Monitoring of Calcite Precipitation in Hardwater Lakes with Multi-Spectral Remote Sensing Archives

    Directory of Open Access Journals (Sweden)

    Iris Heine

    2017-01-01

    Full Text Available Calcite precipitation is a common phenomenon in calcium-rich hardwater lakes during spring and summer, but the number and spatial distribution of lakes with calcite precipitation is unknown. This paper presents a remote sensing based method to observe calcite precipitation over large areas, which are an important prerequisite for a systematic monitoring and evaluation of restoration measurements. We use globally archived satellite remote sensing data for a retrospective systematic assessment of past multi-temporal calcite precipitation events. The database of this study consists of 205 data sets that comprise freely available Landsat and Sentinel 2 data acquired between 1998 and 2015 covering the Northeast German Plain. Calcite precipitation is automatically identified using the green spectra and the metric BGR area, the triangular area between the blue, green and red reflectance value. The validation is based on field measurements of CaCO3 concentrations at three selected lakes, Feldberger Haussee, Breiter Luzin and Schmaler Luzin. The classification accuracy (0.88 is highest for calcite concentrations ≥0.7 mg/L. False negative results are caused by the choice of a conservative classification threshold. False positive results can be explained by already increased calcite concentrations. We successfully transferred the developed method to 21 other hardwater lakes in Northeast Germany. The average duration of lakes with regular calcite precipitation is 37 days. The frequency of calcite precipitation reaches from single time detections up to detections nearly every year. False negative classification results and gaps in Landsat time series reduce the accuracy of frequency and duration monitoring, but in future the image density will increase by acquisitions of Sentinel-2a (and 2b. Our study tested successfully the transfer of the classification approach to Sentinel-2 images. Our study shows that 15 of the 24 lakes have at least one phase of

  8. Evolution patterns of El Niño and characteristics of typhoon precipitation over East Asia

    Science.gov (United States)

    Moon, Young-Il; Kim, Jong-Suk; Son, Chan-Young; Yoon, Sun-Kwon

    2013-04-01

    Many studies have been conducted on the characteristics of the activity of a tropical cyclone (TC) in the Pacific region regarding the effect of El Niño. Also, recent research has shown that change in the abnormal pattern of sea surface temperature (SST), which is higher than usual in the northwest Pacific region, has progressed considerably, and specifically, that there has been an increase in the frequency of the occurrence of the Central Pacific (CP) El Niño, which has a higher temperature characteristic than usual in the CP region. Consequently, this study conducted a comparative analysis of changes in TC genesis, TC track, and TC intensity focusing on typhoons that affected the Korean peninsula according to three evolutionary patterns (prolonged, abrupt, and symmetric-decay) of the abnormal SST in the CP region. As a result of the analysis, for the years of prolonged-decay and symmetric-decay, precipitation from typhoons during the summer on the Korean peninsula was found to rise markedly compared with usual levels. In the case of the years of abrupt-decay, a reducing pattern of precipitation during the summer appeared throughout the Korean peninsula, and an analysis showed a statistically significant change in the Han River basin and some parts of the southern basin. Such a change should show the obviously changing characteristics of local rainfall owing to change in the air circulation pattern, which is subsequent to change in the activity characteristic of typhoons according to the evolution pattern of the surface of the Pacific. The results are expected to be utilized in the future as basic information for reducing damage by typhoons and establishing realistic solutions concerning the management of water resources in a changing change. Keywords: Evolution patterns of CP El Niño, Tropical cyclone, Summer rainfall

  9. Biotic Iron Precipitation in Sand Filtration Systems by Gallionella ferruginea: Morphology and content of Exopolymers

    DEFF Research Database (Denmark)

    Søgaard, Erik Gydesen; Simonsen, Charlotte

    conditions for principally biotic or abiotic iron precipitation is not well defined. An rH2 greater than 14 e.g. corresponding to an Eh a little above zero at slightly acidic pH is stated to be the best condition for biotic iron precipitation (Degremont, 1991). Abiotic iron precipitation is performed at a p...... are built with the purpose of biotic iron precipitation in order to reduce frequency of backwashing filtration systems. This is possibly due to the fact that biologically precipitated iron has a much denser structure than the corresponding abiotic precipitates (Søgaard et al. 2000). Both kinds of iron......-Peskir J. (2000) Conditions and rates of biotic and abiotic iron precipitation in selected Danish freshwater plants and microscopic analysis of precipitate morphology. Water Research, 34, 10, 2675-2682 Søgaard E.G., Aruna R., Abraham-Peskir, J. and Bender Koch, C. (2001) Conditions for iron precipitation...

  10. Summer rainfall over the southwestern Tibetan Plateau controlled by deep convection over the Indian subcontinent

    Science.gov (United States)

    Dong, Wenhao; Lin, Yanluan; Wright, Jonathon S.; Ming, Yi; Xie, Yuanyu; Wang, Bin; Luo, Yong; Huang, Wenyu; Huang, Jianbin; Wang, Lei; Tian, Lide; Peng, Yiran; Xu, Fanghua

    2016-01-01

    Despite the importance of precipitation and moisture transport over the Tibetan Plateau for glacier mass balance, river runoff and local ecology, changes in these quantities remain highly uncertain and poorly understood. Here we use observational data and model simulations to explore the close relationship between summer rainfall variability over the southwestern Tibetan Plateau (SWTP) and that over central-eastern India (CEI), which exists despite the separation of these two regions by the Himalayas. We show that this relationship is maintained primarily by ‘up-and-over' moisture transport, in which hydrometeors and moisture are lifted by convective storms over CEI and the Himalayan foothills and then swept over the SWTP by the mid-tropospheric circulation, rather than by upslope flow over the Himalayas. Sensitivity simulations confirm the importance of up-and-over transport at event scales, and an objective storm classification indicates that this pathway accounts for approximately half of total summer rainfall over the SWTP. PMID:26948491