Using a monthly precipitation dataset of 160 stations over China and a daily and monthly National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset from 1961 ...Using a monthly precipitation dataset of 160 stations over China and a daily and monthly National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset from 1961 to 2006, we here define an East Asian land-sea atmospheric heat source difference index ILSQD and investigate its relationship to summer rainfall in China and East Asian general circulation. The results show that ILSQD more closely reflects the anomalous variations in summer monsoon phenomena; in the high-index (HI) cases, the strong low-level southerlies over East China and the strong high-level westerlies over middle latitudes indicate an active summer monsoon, and vice versa in the low-index (LI) cases. This index also reflects summer rainfall anomalies over East China; in the HI (LI) cases rainfall increases (decreases) over North China and at the same time decreases (increases) over the mid-lower Yangtze River valley and the southern Yangtze River. Hence, ILSQD can be utilized as a summer monsoon index. There is also remarkable correlation between ILSQD in March and the following summer rainfall over the mid-lower Yangtze River valley. Finally, the Community Atmospheric Model Version 3.1 (CAM3.1) of NCAR is used to run numerical experiments, which verify that the anomalous summer precipitation in simulations is similar to that of diagnosis analysis based on the anomalous summer atmospheric heating forcing. Similarly, the atmospheric heating rate in March can force summer rainfall anomalies in the simulations just as observed in the data.展开更多
Investigating the temporal and spatial distributions of the atmospheric heat sources(AHS)over the Tibetan Plateau-Tropical Indian Ocean(TP-TIO)region is of great importance for the understanding of the evolution and d...Investigating the temporal and spatial distributions of the atmospheric heat sources(AHS)over the Tibetan Plateau-Tropical Indian Ocean(TP-TIO)region is of great importance for the understanding of the evolution and development of the South Asian summer monsoon(SASM).This study used the Japanese 55-year Reanalysis(JRA-55)data from 1979 to 2016 and adopted statistical methods to study the characteristics of the AHS between the TP and TIO,and theirs link to the SASM on an interannual scale.The results indicated that the monthly variations of the AHS in the two regions were basically anti-phase,and that the summer AHS in the TP was obviously stronger than that in the TIO.There were strong AHS and atmospheric moisture sink(AMS)centers in both the eastern and western TP in summer.The AHS center in the east was stronger than that in the west,and the AMS centers showed the opposite pattern.In the TIO,a strong AHS center in the northwest-southeast direction was located near 10°S,90°E.Trend analysis showed that summer AHS in the TIO was increasing significantly,especially before 1998,whereas there was a weakening trend in the TP.The difference of the summer AHS between the TP and TIO(hereafter IQ)was used to measure the thermal contrast between the TP and the TIO.The IQ showed an obvious decreasing trend.After 1998,there was a weak thermal contrast between the TP and the TIO,which mainly resulted from the enhanced AHS in the TIO.The land-sea thermal contrast,the TIO Hadley circulation in the southern hemisphere and the SASM circulation all weakened,resulting in abnormal circulation and abnormal precipitation in the Bay of Bengal(BOB).展开更多
为对东亚夏季风强弱年青藏高原、东亚及太平洋地区热力作用以及不同区域热力差进行对比研究,对进一步研究关键区热力差异对东亚季风的影响提供一些参考,采用相关分析,合成分析等统计方法。结果表明:东亚夏季风偏强时,孟加拉湾、华南、...为对东亚夏季风强弱年青藏高原、东亚及太平洋地区热力作用以及不同区域热力差进行对比研究,对进一步研究关键区热力差异对东亚季风的影响提供一些参考,采用相关分析,合成分析等统计方法。结果表明:东亚夏季风偏强时,孟加拉湾、华南、南海及热带西太平洋大气热源异常偏强,印度东部、青藏高原、中南半岛及中纬度西太平洋地区大气热源异常偏弱;且高原东部与东亚关键区热力差偏大,垂直方向上热力差在600 h Pa达到最大,东亚关键区与热带西太平洋热力差偏小,热力差在250 h Pa左右达到最大;高原东部与热带西太平洋热力差为负,热力差在400 h Pa达到最大。反之亦然。东亚夏季风强度变化对高原与热带西太平洋上空高层大气热源影响更大,对东亚关键区上空低层大气热源影响更大。展开更多
基金supported by National Natural Science Foundation of China (Grant Nos.90711003,40505014,40805035 and 40633018)
文摘Using a monthly precipitation dataset of 160 stations over China and a daily and monthly National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset from 1961 to 2006, we here define an East Asian land-sea atmospheric heat source difference index ILSQD and investigate its relationship to summer rainfall in China and East Asian general circulation. The results show that ILSQD more closely reflects the anomalous variations in summer monsoon phenomena; in the high-index (HI) cases, the strong low-level southerlies over East China and the strong high-level westerlies over middle latitudes indicate an active summer monsoon, and vice versa in the low-index (LI) cases. This index also reflects summer rainfall anomalies over East China; in the HI (LI) cases rainfall increases (decreases) over North China and at the same time decreases (increases) over the mid-lower Yangtze River valley and the southern Yangtze River. Hence, ILSQD can be utilized as a summer monsoon index. There is also remarkable correlation between ILSQD in March and the following summer rainfall over the mid-lower Yangtze River valley. Finally, the Community Atmospheric Model Version 3.1 (CAM3.1) of NCAR is used to run numerical experiments, which verify that the anomalous summer precipitation in simulations is similar to that of diagnosis analysis based on the anomalous summer atmospheric heating forcing. Similarly, the atmospheric heating rate in March can force summer rainfall anomalies in the simulations just as observed in the data.
基金Strategic Priority Research Program of Chinese Academy of Sciences(XDA20060501)2019 Non-funded Science and Technology Research Project of Zhanjiang(20051817454-6338)2020 Guangdong Ocean University College Student Innovation and Entrepreneurship Project(580520153)
文摘Investigating the temporal and spatial distributions of the atmospheric heat sources(AHS)over the Tibetan Plateau-Tropical Indian Ocean(TP-TIO)region is of great importance for the understanding of the evolution and development of the South Asian summer monsoon(SASM).This study used the Japanese 55-year Reanalysis(JRA-55)data from 1979 to 2016 and adopted statistical methods to study the characteristics of the AHS between the TP and TIO,and theirs link to the SASM on an interannual scale.The results indicated that the monthly variations of the AHS in the two regions were basically anti-phase,and that the summer AHS in the TP was obviously stronger than that in the TIO.There were strong AHS and atmospheric moisture sink(AMS)centers in both the eastern and western TP in summer.The AHS center in the east was stronger than that in the west,and the AMS centers showed the opposite pattern.In the TIO,a strong AHS center in the northwest-southeast direction was located near 10°S,90°E.Trend analysis showed that summer AHS in the TIO was increasing significantly,especially before 1998,whereas there was a weakening trend in the TP.The difference of the summer AHS between the TP and TIO(hereafter IQ)was used to measure the thermal contrast between the TP and the TIO.The IQ showed an obvious decreasing trend.After 1998,there was a weak thermal contrast between the TP and the TIO,which mainly resulted from the enhanced AHS in the TIO.The land-sea thermal contrast,the TIO Hadley circulation in the southern hemisphere and the SASM circulation all weakened,resulting in abnormal circulation and abnormal precipitation in the Bay of Bengal(BOB).
文摘为对东亚夏季风强弱年青藏高原、东亚及太平洋地区热力作用以及不同区域热力差进行对比研究,对进一步研究关键区热力差异对东亚季风的影响提供一些参考,采用相关分析,合成分析等统计方法。结果表明:东亚夏季风偏强时,孟加拉湾、华南、南海及热带西太平洋大气热源异常偏强,印度东部、青藏高原、中南半岛及中纬度西太平洋地区大气热源异常偏弱;且高原东部与东亚关键区热力差偏大,垂直方向上热力差在600 h Pa达到最大,东亚关键区与热带西太平洋热力差偏小,热力差在250 h Pa左右达到最大;高原东部与热带西太平洋热力差为负,热力差在400 h Pa达到最大。反之亦然。东亚夏季风强度变化对高原与热带西太平洋上空高层大气热源影响更大,对东亚关键区上空低层大气热源影响更大。
