The sensitivity of the East Asian summer monsoon to soil moisture anomalies over China was investigated based on ensembles of seasonal simulations （March-September） using the NCEP GCM coupled with the Simplified Sim...The sensitivity of the East Asian summer monsoon to soil moisture anomalies over China was investigated based on ensembles of seasonal simulations （March-September） using the NCEP GCM coupled with the Simplified Simple Biosphere Model （NCEP GCM/SSiB）. After a control experiment with free-running soil moisture, two ensembles were performed in which the soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China （YRNC） was double and half that in the control, with the maximum less than the field capacity. The simulation results showed significant sensitivity of the East Asian summer monsoon to wet soil in YRNC. The wetter soil was associated with increased surface latent heat flux and reduced surface sensible heat flux. In turn, these changes resulted in a wetter and colder local land surface and reduced land-sea temperature gradients, corresponding to a weakened East Asian monsoon circulation in an anomalous anticyclone over southeastern China, and a strengthened East Asian trough southward over Northeast China. Consequently, less precipitation appeared over southeastern China and North China and more rainfall over Northeast China. The weakened monsoon circulation and strengthened East Asian trough was accompanied by the convergence of abnormal northerly and southerly flow over the Yangtze River valley, resulting in more rainfall in this region. In the drier soil experiments, less precipitation appeared over YRNC. The East Asian monsoon circulation seems to show little sensitivity to dry soil anomalies in NCEP GCM/SSiB.展开更多
The timing of the South Asian High(SAH) establishment over the Indochina Peninsula(IP) from April to May and its relations to the setup of the subsequent tropical Asian summer monsoon and precipitation over eastern-ce...The timing of the South Asian High(SAH) establishment over the Indochina Peninsula(IP) from April to May and its relations to the setup of the subsequent tropical Asian summer monsoon and precipitation over eastern-central China in summer are investigated by using NCEP/NCAR daily reanalysis data,outgoing longwave radiation(OLR)data and the daily precipitation data from 753 weather stations in China.It is found that the transitions of the zonal wind vertical shear and convection establishment over tropical Asia are earlier(later) in the years of early(late) establishment of SAH.In the lower troposphere,anti-cyclonic(cyclonic) anomaly circulation dominates the equatorial Indian Ocean.Correspondingly,the tropical Asian summer monsoon establishes earlier(later).Furthermore,the atmospheric circulation and the water vapor transport in the years of advanced SAH establishment are significantly different from the delayed years in Asia in summer.Out-of-phase distribution of precipitation in eastern-central China will appear with a weak(strong) SAH and western Pacific subtropical high,strong(weak) ascending motion in the area south of Yangtze River but weak(strong) ascending motion in the area north of it,and cyclonic(anti-cyclonic) water vapor flux anomaly circulation from the eastern-central China to western Pacific.Accordingly,the timing of the SAH establishment at the upper levels of IP is indicative of the subsequent onset of the tropical Asian summer monsoon and the flood-drought pattern over eastern-central China in summer.展开更多
The Twentieth Century Reanalysis （20thCR） dataset released in 2010 covers the period 1871-2010 and is one of the longest reanalysis datasets available worldwide. Using ERA-40, ERA-Interim and NCEP-NCAR reanalysis da...The Twentieth Century Reanalysis （20thCR） dataset released in 2010 covers the period 1871-2010 and is one of the longest reanalysis datasets available worldwide. Using ERA-40, ERA-Interim and NCEP-NCAR reanalysis data, as well as HadSLP2 data and meteorological temperature records over eastern China, the performances of 20thCR in reproducing the spatial patterns and temporal variability of the East Asian winter monsoon （EAWM） are examined. Results indicate that 20thCR data： （1） can accurately reproduce the most typical configuration patterns of all sub-factors differences in the main circulation fields over East Asia involved in the EAWM system, albeit with some in comparison to ERA-40 reanalysis data; （2） is reliable and stable in describing the temporal variability of EAWM since the 1930s; and （3） can describe the high-frequency variability of EAWM better than the low-frequency fluctuations, especially in the early period. In conclusion, caution should be taken when using 20thCR data to study interdecadal variabilities or long-term trends of the EAWM, especially prior to the 1930s.展开更多
Based on the drought/flood grades of 90 meterological stations over eastern China and summer average sea-level pressure （SLP） during 1850-2008 and BPCCA statistical methods, the coupling relationship between the dro...Based on the drought/flood grades of 90 meterological stations over eastern China and summer average sea-level pressure （SLP） during 1850-2008 and BPCCA statistical methods, the coupling relationship between the drought/flood grades and the East Asian summer SLP is analyzed. The East Asian summer monsoon index which is closely related with interdecadal variation of drought/flood distribution over eastern China is defined by using the key areas of SLP. The impact of the interdecadal variation of the East Asian summer monsoon on the distribution of drought/flood over eastern China in the last 159 years is researched. The results show that there are four typical drought and flood spatial distribution patterns in eastern China, i.e. the distribution of drought/flood in southern China is contrary to the other regions, the distribution of drought/flood along the Huanghe River–Huaihe River Valley is contrary to the Yangtze River Valley and regions south of it, the distribution of drought/flood along the Yangtze River Valley and Huaihe River Valley is contrary to the other regions, the distribution of drought/flood in eastern China is contrary to the western. The main distribution pattern of SLP in summer is that the strength of SLP is opposite in Asian continent and West Pacific. It has close relationship between the interdecadal variation of drought/flood distribution patterns over eastern China and the interdecadal variation of the East Asian summer monsoon which was defined in this paper, but the correlation is not stable and it has a significant difference in changes of interdecadal phase. When the East Asian summer monsoon was stronger （weaker）, regions north of the Yangtze River Valley was more susceptible to drought （flood）, the Yangtze River Valley and regions south of it were more susceptible to flood （drought） before the 1920s; when the East Asian summer monsoon was stronger （weaker）, the regions north of the Yangtze River Valley was prone to flood （drought）, the Yangtze River Valley and regions south of it were prone to drought （flood） after the 1920s. It is indicated that by using the data of the longer period could get much richer results than by using the data of the last 50–60 years. The differences in the interdecadal phase between the East Asian summer monsoon and the drought/flood distributions in eastern China may be associated with the nonlinear feedback, which is the East Asian summer monsoon for the extrinsic forcing of solar activity.展开更多
The characteristics and causes of centennial-scale drought events over eastern China during the past 1500 years were explored based on simulations of the Community Earth System Model （CESM）. The results show that ce...The characteristics and causes of centennial-scale drought events over eastern China during the past 1500 years were explored based on simulations of the Community Earth System Model （CESM）. The results show that centenni- al-scale drought events over eastern China occurred during the periods of 622-735 （Drought period 1, D1） and 1420-1516 （Drought period 2, D2） over the past 1500 years, which is comparable with climate proxy data. In D1, the drought center occurred in northern China and the Yangtze River valley; however, in southern China, precipitation was much more than usual. In D2, decreased precipitation was found across almost the whole region of eastern China. The direct cause of these two drought events was the weakened East Asian summer monsoon, and the specif- ic process was closely linked to the air-sea interaction of the Indo-Pacific Ocean. In DI, regions of maximum cool- ing were observed over the western Pacific, which may have led to anomalous subsidence, weakening the Walker cir- culation, and reducing the northward transport of water vapor. Additionally, upward motion occurred over southern China, strengthening convection and increasing precipitation. In D2, owing to the decrease in the SST, subsidence dominated the North Indian Ocean, blocking the low-level cross-equatorial flow, enhancing the tropical westerly an- omalies, and reducing the northward transport of moisture. Additionally, descending motion appeared in eastern China, subsequently decreasing the precipitation over the whole region of eastern China. The anomalous cooling of the Indo-Pacific Ocean SST may have been caused by the persistently low solar irradiation in D1; whereas, in D2, this characteristic may have been influenced not only by persistently low solar irradiation, but frequent volcanic erup- tions too.展开更多
Based on 481-year records of historical dust storm （DS） and Dryness-Wetness Index （DWI） at 120 sites, spatial distribution characteristics of dryness-wetness （DW） in typical dust storm years （DS years） and in ...Based on 481-year records of historical dust storm （DS） and Dryness-Wetness Index （DWI） at 120 sites, spatial distribution characteristics of dryness-wetness （DW） in typical dust storm years （DS years） and in non-dust storm years （non-DS years） were derived for continental China. In DS years, most of the sites were drier than in normal years while in non-DS years wetter than normal, and the variation of DWI in DS years was larger than that in non-DS years. The relative instability and increased regional difference of atmospheric circulation in DS years might have induced more frequent DS events and dry-wet abnormality in continental China. In DS years the latitudinal （north-south） dry-wet difference was larger than that in non-DS years, that is, north China was even much drier than south China. This might be attributed to increased latitudinal differences of thermal and pressure gradients in DS years, resulting in the southward withdrawal of precipitation and increase of DS events.展开更多
基金jointly supported by the National Natural Science Foundation of China (Grant Nos. 41205059, 41221064 and 41375092)the Special Fund for Public Welfare Industry (Meteorology) (Grant No. GYHY201206017)
文摘The sensitivity of the East Asian summer monsoon to soil moisture anomalies over China was investigated based on ensembles of seasonal simulations （March-September） using the NCEP GCM coupled with the Simplified Simple Biosphere Model （NCEP GCM/SSiB）. After a control experiment with free-running soil moisture, two ensembles were performed in which the soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China （YRNC） was double and half that in the control, with the maximum less than the field capacity. The simulation results showed significant sensitivity of the East Asian summer monsoon to wet soil in YRNC. The wetter soil was associated with increased surface latent heat flux and reduced surface sensible heat flux. In turn, these changes resulted in a wetter and colder local land surface and reduced land-sea temperature gradients, corresponding to a weakened East Asian monsoon circulation in an anomalous anticyclone over southeastern China, and a strengthened East Asian trough southward over Northeast China. Consequently, less precipitation appeared over southeastern China and North China and more rainfall over Northeast China. The weakened monsoon circulation and strengthened East Asian trough was accompanied by the convergence of abnormal northerly and southerly flow over the Yangtze River valley, resulting in more rainfall in this region. In the drier soil experiments, less precipitation appeared over YRNC. The East Asian monsoon circulation seems to show little sensitivity to dry soil anomalies in NCEP GCM/SSiB.
基金Major Program of the Natural Science Researches for Colleges and Universities in Jiangsu Province(14KJA170004)Natural Science Foundation of Jiangsu Province(BK20131432)+1 种基金"Qing Lan"Project of Jiangsu Province"333"Project of Jiangsu Province
文摘The timing of the South Asian High(SAH) establishment over the Indochina Peninsula(IP) from April to May and its relations to the setup of the subsequent tropical Asian summer monsoon and precipitation over eastern-central China in summer are investigated by using NCEP/NCAR daily reanalysis data,outgoing longwave radiation(OLR)data and the daily precipitation data from 753 weather stations in China.It is found that the transitions of the zonal wind vertical shear and convection establishment over tropical Asia are earlier(later) in the years of early(late) establishment of SAH.In the lower troposphere,anti-cyclonic(cyclonic) anomaly circulation dominates the equatorial Indian Ocean.Correspondingly,the tropical Asian summer monsoon establishes earlier(later).Furthermore,the atmospheric circulation and the water vapor transport in the years of advanced SAH establishment are significantly different from the delayed years in Asia in summer.Out-of-phase distribution of precipitation in eastern-central China will appear with a weak(strong) SAH and western Pacific subtropical high,strong(weak) ascending motion in the area south of Yangtze River but weak(strong) ascending motion in the area north of it,and cyclonic(anti-cyclonic) water vapor flux anomaly circulation from the eastern-central China to western Pacific.Accordingly,the timing of the SAH establishment at the upper levels of IP is indicative of the subsequent onset of the tropical Asian summer monsoon and the flood-drought pattern over eastern-central China in summer.
基金supported by the State Key Laboratory of Earth Surface Processes and Resource Ecology(Grant No.2013-KF-05)the National Basic Research Program of China(Grant Nos.2012CB955401 and 2010CB428506)supported by the project"Reconstruction and Observation of Components for the Southern and NorthernAnnular Mode to Investigate the Cause of Polar Climate Change"(PE13010)of the Korea Polar Research Institute
文摘The Twentieth Century Reanalysis （20thCR） dataset released in 2010 covers the period 1871-2010 and is one of the longest reanalysis datasets available worldwide. Using ERA-40, ERA-Interim and NCEP-NCAR reanalysis data, as well as HadSLP2 data and meteorological temperature records over eastern China, the performances of 20thCR in reproducing the spatial patterns and temporal variability of the East Asian winter monsoon （EAWM） are examined. Results indicate that 20thCR data： （1） can accurately reproduce the most typical configuration patterns of all sub-factors differences in the main circulation fields over East Asia involved in the EAWM system, albeit with some in comparison to ERA-40 reanalysis data; （2） is reliable and stable in describing the temporal variability of EAWM since the 1930s; and （3） can describe the high-frequency variability of EAWM better than the low-frequency fluctuations, especially in the early period. In conclusion, caution should be taken when using 20thCR data to study interdecadal variabilities or long-term trends of the EAWM, especially prior to the 1930s.
基金National Natural Science Foundation of China No.40890053 Special Scientific Fund for Non-profit Public Industry （Meteorology） No.GYHY200906016 No.GYHY201006038
文摘Based on the drought/flood grades of 90 meterological stations over eastern China and summer average sea-level pressure （SLP） during 1850-2008 and BPCCA statistical methods, the coupling relationship between the drought/flood grades and the East Asian summer SLP is analyzed. The East Asian summer monsoon index which is closely related with interdecadal variation of drought/flood distribution over eastern China is defined by using the key areas of SLP. The impact of the interdecadal variation of the East Asian summer monsoon on the distribution of drought/flood over eastern China in the last 159 years is researched. The results show that there are four typical drought and flood spatial distribution patterns in eastern China, i.e. the distribution of drought/flood in southern China is contrary to the other regions, the distribution of drought/flood along the Huanghe River–Huaihe River Valley is contrary to the Yangtze River Valley and regions south of it, the distribution of drought/flood along the Yangtze River Valley and Huaihe River Valley is contrary to the other regions, the distribution of drought/flood in eastern China is contrary to the western. The main distribution pattern of SLP in summer is that the strength of SLP is opposite in Asian continent and West Pacific. It has close relationship between the interdecadal variation of drought/flood distribution patterns over eastern China and the interdecadal variation of the East Asian summer monsoon which was defined in this paper, but the correlation is not stable and it has a significant difference in changes of interdecadal phase. When the East Asian summer monsoon was stronger （weaker）, regions north of the Yangtze River Valley was more susceptible to drought （flood）, the Yangtze River Valley and regions south of it were more susceptible to flood （drought） before the 1920s; when the East Asian summer monsoon was stronger （weaker）, the regions north of the Yangtze River Valley was prone to flood （drought）, the Yangtze River Valley and regions south of it were prone to drought （flood） after the 1920s. It is indicated that by using the data of the longer period could get much richer results than by using the data of the last 50–60 years. The differences in the interdecadal phase between the East Asian summer monsoon and the drought/flood distributions in eastern China may be associated with the nonlinear feedback, which is the East Asian summer monsoon for the extrinsic forcing of solar activity.
基金Supported by the National Key Research and Development Program of China(2016YFA0600401)Natural Science Foundation of Jiangsu Higher Education Institutions(14KJA170002)+1 种基金National Natural Science Foundation of China(41371209,41420104002,and41501210)Priority Academic Program Development of Jiangsu Higher Education Institutions(164320H116)
文摘The characteristics and causes of centennial-scale drought events over eastern China during the past 1500 years were explored based on simulations of the Community Earth System Model （CESM）. The results show that centenni- al-scale drought events over eastern China occurred during the periods of 622-735 （Drought period 1, D1） and 1420-1516 （Drought period 2, D2） over the past 1500 years, which is comparable with climate proxy data. In D1, the drought center occurred in northern China and the Yangtze River valley; however, in southern China, precipitation was much more than usual. In D2, decreased precipitation was found across almost the whole region of eastern China. The direct cause of these two drought events was the weakened East Asian summer monsoon, and the specif- ic process was closely linked to the air-sea interaction of the Indo-Pacific Ocean. In DI, regions of maximum cool- ing were observed over the western Pacific, which may have led to anomalous subsidence, weakening the Walker cir- culation, and reducing the northward transport of water vapor. Additionally, upward motion occurred over southern China, strengthening convection and increasing precipitation. In D2, owing to the decrease in the SST, subsidence dominated the North Indian Ocean, blocking the low-level cross-equatorial flow, enhancing the tropical westerly an- omalies, and reducing the northward transport of moisture. Additionally, descending motion appeared in eastern China, subsequently decreasing the precipitation over the whole region of eastern China. The anomalous cooling of the Indo-Pacific Ocean SST may have been caused by the persistently low solar irradiation in D1; whereas, in D2, this characteristic may have been influenced not only by persistently low solar irradiation, but frequent volcanic erup- tions too.
文摘Based on 481-year records of historical dust storm （DS） and Dryness-Wetness Index （DWI） at 120 sites, spatial distribution characteristics of dryness-wetness （DW） in typical dust storm years （DS years） and in non-dust storm years （non-DS years） were derived for continental China. In DS years, most of the sites were drier than in normal years while in non-DS years wetter than normal, and the variation of DWI in DS years was larger than that in non-DS years. The relative instability and increased regional difference of atmospheric circulation in DS years might have induced more frequent DS events and dry-wet abnormality in continental China. In DS years the latitudinal （north-south） dry-wet difference was larger than that in non-DS years, that is, north China was even much drier than south China. This might be attributed to increased latitudinal differences of thermal and pressure gradients in DS years, resulting in the southward withdrawal of precipitation and increase of DS events.
