Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley...Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.展开更多
By using the gauged rainfall in 160 stations within China's Mainland and the NCEP/NCAR reanalysis data, the impacts of anomalous SST in Kuroshio and its extension on precipitation in Northeast China were investiga...By using the gauged rainfall in 160 stations within China's Mainland and the NCEP/NCAR reanalysis data, the impacts of anomalous SST in Kuroshio and its extension on precipitation in Northeast China were investigated. The results show that a difference in the meridional circulation such as the East Asia/Pacific teleconnection pattern(EAP)may be responsible for the difference in rainfall between 1998 and 2010. In comparison with 1998, the anomalous meridional circulation pattern in 2010 shifted northeastward, and then the western subtropical high, the mid-latitudinal trough and the northeastern Asia blocking high also shifted northeastward, causing intensified convergence of the cold and warm air masses at the southern region and thus more rainfall in the southwestern region and less in the northwestern region. In 1998, the anomalous cyclone, one component of the meridional pattern, located at the Songhuajiang-Nengjiang River basin, resulted in more rainfall in the majority of the area. The results of observation and the model show that the difference in SSTA in Kuroshio and its extension under the background of different El Ni觡o events is the key point:(1) The anomalous warmth moved westward from the mid-Pacific to the east of the Philippine Sea during the central event, which led the heat resources shifting to the northeast in 2010; subsequently, a shift occurred to the north of the anomalous ascent and decent, followed by a warm SSTA in the region of Kuroshio's extension in 2010 and Kuroshio in 1998.(2) The warm SSTA in the Kuroshio extension causing the Rossby wave activity flux strengthened in 2010, and then the westerly jet shifted northward and extended eastward. A warm SSTA in Kuroshio and cold SSTA in its extension in 1998 caused the westerly jet to shift southward and weaken. As a result,the anomalous anticyclone and cyclone shifted northward in 2010, and the blocking high also shifted northward.展开更多
The relationship between summer rainfall anomalies in northeast China and two types of El Ni?o events is investigated by using observation data and an atmospheric general circulation model(AGCM).It is shown that,for d...The relationship between summer rainfall anomalies in northeast China and two types of El Ni?o events is investigated by using observation data and an atmospheric general circulation model(AGCM).It is shown that,for different types of El Ni?o events,there is different rainfall anomaly pattern in the following summer.In the following year of a typical El Ni?o event,there are remarkable positive rainfall anomalies in the central-western region of northeast China,whereas the pattern of more rainfall in the south end and less rainfall in the north end of northeast China easily appears in an El Ni?o Modoki event.The reason for the distinct difference is that,associated with the different sea surface temperature anomalies(SSTA)along the equatorial Pacific,the large-scale circulation anomalies along east coast of East Asia shift northward in the following summer after El Ni?o Modoki events.Influenced by the anomalous anticyclone in Philippine Sea,southwesterly anomalies over eastern China strengthen summer monsoon and bring more water vapor to northeast China.Meanwhile,convergence and updraft is strengthened by the anomalous cyclone right in northeast China in typical El Ni?o events.These moisture and atmospheric circulation conditions are favorable for enhanced precipitation.However,because of the northward shift,the anomalous anticyclone in the Philippine Sea in typical El Ni?o cases shifts to the south of Japan in Modoki years,and the anomalous cyclone in northeast China in typical El Ni?o cases shifts to the north of northeast China,leading to the"dipole pattern"of rainfall anomalies.According to the results of numerical experiments,we further confirm that the tropical SSTA in different types of El Ni?o event can give rise to observed rainfall anomaly patterns in northeast China.展开更多
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-Q11-03)
文摘Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.
基金National Basic Research Program of China(973 Program)(2012CB417403)National Natural Science Foundation of China(NSFC,41205048)
文摘By using the gauged rainfall in 160 stations within China's Mainland and the NCEP/NCAR reanalysis data, the impacts of anomalous SST in Kuroshio and its extension on precipitation in Northeast China were investigated. The results show that a difference in the meridional circulation such as the East Asia/Pacific teleconnection pattern(EAP)may be responsible for the difference in rainfall between 1998 and 2010. In comparison with 1998, the anomalous meridional circulation pattern in 2010 shifted northeastward, and then the western subtropical high, the mid-latitudinal trough and the northeastern Asia blocking high also shifted northeastward, causing intensified convergence of the cold and warm air masses at the southern region and thus more rainfall in the southwestern region and less in the northwestern region. In 1998, the anomalous cyclone, one component of the meridional pattern, located at the Songhuajiang-Nengjiang River basin, resulted in more rainfall in the majority of the area. The results of observation and the model show that the difference in SSTA in Kuroshio and its extension under the background of different El Ni觡o events is the key point:(1) The anomalous warmth moved westward from the mid-Pacific to the east of the Philippine Sea during the central event, which led the heat resources shifting to the northeast in 2010; subsequently, a shift occurred to the north of the anomalous ascent and decent, followed by a warm SSTA in the region of Kuroshio's extension in 2010 and Kuroshio in 1998.(2) The warm SSTA in the Kuroshio extension causing the Rossby wave activity flux strengthened in 2010, and then the westerly jet shifted northward and extended eastward. A warm SSTA in Kuroshio and cold SSTA in its extension in 1998 caused the westerly jet to shift southward and weaken. As a result,the anomalous anticyclone and cyclone shifted northward in 2010, and the blocking high also shifted northward.
基金National Basic Research Program of China(2012CB417403)National Natural Science Foundation of China(41205048)
文摘The relationship between summer rainfall anomalies in northeast China and two types of El Ni?o events is investigated by using observation data and an atmospheric general circulation model(AGCM).It is shown that,for different types of El Ni?o events,there is different rainfall anomaly pattern in the following summer.In the following year of a typical El Ni?o event,there are remarkable positive rainfall anomalies in the central-western region of northeast China,whereas the pattern of more rainfall in the south end and less rainfall in the north end of northeast China easily appears in an El Ni?o Modoki event.The reason for the distinct difference is that,associated with the different sea surface temperature anomalies(SSTA)along the equatorial Pacific,the large-scale circulation anomalies along east coast of East Asia shift northward in the following summer after El Ni?o Modoki events.Influenced by the anomalous anticyclone in Philippine Sea,southwesterly anomalies over eastern China strengthen summer monsoon and bring more water vapor to northeast China.Meanwhile,convergence and updraft is strengthened by the anomalous cyclone right in northeast China in typical El Ni?o events.These moisture and atmospheric circulation conditions are favorable for enhanced precipitation.However,because of the northward shift,the anomalous anticyclone in the Philippine Sea in typical El Ni?o cases shifts to the south of Japan in Modoki years,and the anomalous cyclone in northeast China in typical El Ni?o cases shifts to the north of northeast China,leading to the"dipole pattern"of rainfall anomalies.According to the results of numerical experiments,we further confirm that the tropical SSTA in different types of El Ni?o event can give rise to observed rainfall anomaly patterns in northeast China.
