1960—2016年中国北方半干旱区盛夏降水时空变化及其水汽输送特征分析

基于气象台站降水观测资料,本文分析了1960—2016年半干旱区盛夏（7、8月）降水量时空变化特征,探讨了典型降水量时空分布型与大气环流及水汽输送的关系。结果表明,1960—2016年半干旱区7月和8月降水量的主导空间模态均可归纳为“区域一致型”和“区内反向型”。“区域一致型”时间序列显示1960—2016年7、8月降水量均呈减少趋势,但8月减少趋势更明显。这一时间序列与大气环流及水汽通量输送之间相关性分析显示,欧亚遥相关以及中纬度西风气流与7月降水量变化密切相关;而西太平洋副热带高压是影响半干旱区8月降水量变化的主要原因。相较而言,“区内反向型”年际变率较小但年代际变化明显,当北方半干旱区受反气旋性环流控制时,易形成北方半干旱区西部地区降水偏多而东部地区偏少的格局。

Spatial and temporal variations in summer precipitation over the semi-arid region of northern China during 1960-2016 and their links with atmospheric circulation

Based on precipitation observations from meteorological stations, the spatial and temporal variations of precipitation in the semi-arid region of northern China during 1960-2016 were analyzed by using EOF method. The research showed that the dominant spatial modes of summer precipitation in semi-arid region of northern China from 1960 to 2016 could be summarized as the regional in-phase type and the sub-regional out-of-phase type. The time series of regional in-phase type showed that the summer precipitation in semi-arid region generally decreased from 1960 to 2016, but the decrease trend in August was more remarkable than that in July. The sub-regional out-of-phase type showed that the interannual variability of precipitation in July and August was relatively small, but the inter-decadal variability was larger. The correlation analysis between the regional in-phase type time coefficients and the atmospheric circulation as well as water vapor transport variables showed that the Eurasian teleconnection and the mid-latitudes westerlies are closely correlated with the precipitation variations in July, while the Western Pacific Subtropical High (WPSH) is the main factor affecting the interannual variations of August precipitation in the semi-arid region. The correlation analysis of sub-regional out-of-phase type time coefficients showed that when the anticyclonic circulation controls the semi-arid northern China, it is easy to form a distribution pattern with more precipitation in the west and relatively lower precipitation in the east of the semi-arid area in northern China.