大气科学2017，Vol.41Issue(6)：1125-1140,16.DOI:10.3878/j.issn.1006-9895.1703.17112
长江中游和下游夏季降水季节内振荡的差异
Differences in Intraseasonal Summer Rainfall Oscillation between the Middle and Lower Reaches of the Yangtze River
摘要
Abstract
The most significant climatological intraseasonal oscillation (ISO) periods of summer rainfall over the middle and lower reaches of the Yangtze River (M-LYR) are investigated by using the gauge-based daily precipitation analysis data of China and the NCAR/NCEP reanalysis data from 1979 to 2013.It is found that the oscillation periods of summer rainfall at the intraseasonal timescale show remarkable difference between the MYR and LYR.The 10-30-day oscillation is the primary mode over the MYR,while the longer period of 30-60-day dominates the LYR.The phase composite analysis is applied to reveal evolutions of intraseasonal circulation and vertical structure associated with these two periods of climatological ISO precipitation over the Yangtze River.In the upper troposphere at 200 hPa,it shows that a wave train over the mid-high latitudes propagates eastward,affecting the summer rainfall over MYR,while the southwestward propagation of the weakened Okhotsk blocking high is associated with the 30-60-day rainfall oscillation over LYR.The vertical structures of wind vorticity and divergence/convergence exhibit different features during their moving toward the Yangtze River.10-30-day anomalous vorticity and divergence/convergence move southward toward the MYR;however,the 30-60-day anomalies move northward from the tropics.Atmospheric moisture from the South China Sea and from north of the Yangtze River converges over MYR,leading to favorable condition for the occurrence of rainfall.In contrast,the moisture in the LYR primarily comes from the tropics.Large amounts of atmospheric moisture originate from the eastern Indian Ocean,move through the Bay of Bengal and the South China Sea,converge with moisture transported westward from the western tropical Pacific,and then move northward,reaching the LYR.The results explain from the perspective of upper-level circulation and vertically integrated moisture flux why the 10-30-day oscillation mode of rainfall over MYR propagates southward,while the 30-60-day oscillation mode of rainfall over LYR propagates northward.关键词
长江中下游/夏季降水/季节内振荡/最显著周期Key words
Middle-lower reaches of the Yangtze River/Summer rainfall/Intraseasonal oscillation (ISO)/Most significant period分类
天文与地球科学引用本文复制引用
许乐心,张人禾,齐艳军..长江中游和下游夏季降水季节内振荡的差异[J].大气科学,2017,41(6):1125-1140,16.基金项目
国家重点基础研究发展计划项目(973计划)2015CB453203,国家重点研发计划2016YFA0600602、 2016YFA0601504,国家自然科学基金项目41675068,中国气象科学研究院基本科研业务费2015Z001 National Basic Research Program of China (973 Program) (Grant 2015CB453203),National Key Research and Development Program Approved by Ministry of Science and Technology (Grants 2016YFA0600602,2016YFA0601504),National Nature Science Foundation of China (Grant 41675068),Basic Research Fund of the Chinese Academy of Meteorological Sciences (Grant 2015Z001) （973计划）
