5月南亚高压与云南地区夏季降水的关系

应用1961—2012年NCEP/NCAR月平均再分析资料和云南124个测站逐月降水资料,分析了5月南亚高压与云南夏季降水的关系,发现高压脊线位置与降水有显著的相关。利用滤波处理和合成分析方法,分析了5月南亚高压脊线位置变化及其异常与云南夏季降水异常的联系。结果表明:5月南亚高压脊线位置偏北(南)时,夏季云南降水偏多(少);5月南亚高压脊线位置和云南夏季降水都存在显著的年代际变化,去除年代际变化影响之后两者之间的年际变化相关较为显著。5月南亚高压脊线位置偏北年,夏季南亚高压强度偏弱、范围偏小,500 hPa上西太平洋副高东移南压、强度减弱。低层700 hPa上副高西伸加强、云南上空出现明显的风场辐合,反之亦然。5月脊线位置偏北年,夏季南海和西太平洋向云南输送水汽,而脊线偏南年没有明显的水汽来源。

Relationship between South Asia High in May and summer rainfall in Yunnan

Based on the NCEP/NCAR monthly reanalysis data and monthly rainfall data from 124 stations in Yunnan during 1961-2012, correlations between the South Asia High (SAH)in May and summer rainfall in Yunnan are analyzed, which found that a significant correlation exists between the position of ridge line and rainfall. With filtering and synthetic analysis methods, the linkage of the position variation and anomaly of ridge line of SAH in May with summer rainfall anomaly in Yunnan is analyzed. The results show that when the ridge line position of SAH in May locates northward (southward), the summer rainfall in Yunnan is more (less);both the ridge line position of SAH in May and summer rainfall in Yunnan have significant inter-decadal variation, removing which, their inter-annual variation correlation would be more obvious. During the northerly-location years of the ridge line position of SAH in May, its intensity and range become weaker and smaller, the West Pacific Subtropical High at 500hPa moves southeastward and becomes weaker, the subtropical high at 700hPa at low level moves westward and becomes stronger, and the significant wind convergence appears above Yunnan, and vice versa. Furthermore,in the northerly-location years, the vapor from the South Sea and the West Pacific transports to Yunnan in summer, while in the southerly-location years, no obvious vapor transportation occurs.