摘要
根据1958-2011年中国东部(105°E以东)316站逐日降水观测资料及环流逐日再分析资料,利用统计分析、物理量诊断等方法,探讨华南前汛期盛期(5月21日至6月10日)中国东部降水异常模态及对应大气环流特征和可能成因。分析发现,华南前汛期盛期中国东部降水异常表现为两个相互独立的降水模态:第一模态为华南全区一致型,当其时间系数为正(负)时,整个华南降水偏多(少),黄河中游降水偏少(多);第二模态为华南沿海东部型,当其时间系数为正(负)时,华南沿海东部降水偏多(少),而长江中下游降水偏少(多)。研究发现,造成华南前汛期盛期两个降水型的环流特征有明显差异:全区一致型降水主要受东亚高空西风急流南北偏移、副热带高压脊东西偏移及低层南海北部异常风场影响;沿海东部型降水主要由东亚高空西风急流强弱及位置异常、副热带高压强弱变化、低层日本以南西太平洋异常风场导致。此外,两个降水型对应环流异常的成因也各不相同。第一模态中高层环流异常由丝绸之路遥相关型导致,低层风场异常在5月下旬由阿拉伯海向下游传播的风场异常波列引起,在6月上旬则由西太平洋西移的异常反气旋(气旋)造成。第二模态的中高层环流异常先后由极地—欧亚遥相关型、环球遥相关型引起,低层风场异常由高层环流异常的动力作用造成。两降水型均存在整层深厚的垂直运动,但第一模态的垂直运动在高层闭合且对应显著的辐合辐散异常,第二模态则不具有上述特征。
Based on daily observed rainfall data at 316 stations in China and the National Centers for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR) reanalysis dataset for 1958-2011, dominant modes of precipitation anomalies over eastern China(to the east of 105°E) during the peak of pre-rainy season in South China(21 May to 10 June) and accompanying circulation as well as possible causes are investigated using statistical and diagnostic methods. Two dominant modes are revealed by empirical orthogonal function(EOF) analysis. The first EOF mode(EOF1) depicts a seesaw in precipitation anomalies between South China and the middle reaches of the Yellow River basin, while the second EOF mode(EOF2) shows a seesaw in precipitation anomalies between the eastern coastal region of South China and the mid-lower reaches of the Yangtze River valley. The major circulation characteristics corresponding to the two modes are different. EOF1 is attributed to the meridional displacement of the East Asian subtropical westerly jet stream(EAJS) and the zonal displacement of the western North Pacific subtropical high(WNPSH), while EOF2 is attributed to the intensity anomalies of the EAJS and the WNPSH. For EOF1, the 200-h Pa Silk Road pattern wave train and the low-level wind anomalies jointly contribute to the corresponding circulation anomalies. For EOF2, the circulation anomalies are first induced by Polar Eurasia pattern and the circumglobal teleconnection. Anomalies in the lower levels are attributed to the dynamic effects of high level anomalies. Differences between the vertical structures of the two modes are also discussed.
出处
《气候与环境研究》
CSCD
北大核心
2016年第6期633-652,共20页
Climatic and Environmental Research
基金
国家自然科学基金项目41375055
国家重点基础研究发展计划项目2014CB954301~~
关键词
华南前汛期盛期
次季节降水
西风急流
丝绸之路遥相关
环球遥相关
Peak of pre-rainy season in South China
Subseasonal precipitation
Westerly jet-stream
Silk Road pattern
Circumglobal teleconnection