辽宁夏季干旱环流特征分析

利用辽宁省54站1963—2015年夏季月平均降水量资料及NCEP/NCAR月平均环流场再分析资料,对辽宁夏季降水变化特征及异常年环流特征进行了分析,结合2014和2015年夏季环流场与异常年环流场的对比分析,揭示辽宁夏季干旱环流特征及造成2014、2015年辽宁夏季干旱的环流场因素。研究发现:东亚地区对流层各层大尺度环流系统相互配合是造成辽宁夏季降水异常的主要原因。2014和2015年辽宁夏季干旱的环流场特征均与辽宁夏季异常干旱年情况类似:西太平洋副热带高压脊线位置偏南,且副高西北侧为负的位势高度距平,不利于副高西伸北进;由于副高偏南,辽宁地区西南水汽输送不充足;副热带西风急流轴位于辽宁以南地区上空,且辽宁以南上空200 h Pa纬向风距平为正,以北为负。这种不同高度层大尺度环流配置是造成2014和2015年辽宁夏季干旱的主要环流原因。

Analysis of drought circulation characteristics in summer of Liaoning Province

Based on the monthly mean rainfall data from 54 observational stations in summer during 1963 to 2015 in Liaoning Province and the NCEP/NCAR monthly circulation field reanalysis information, we analyzed the variation characteristics of precipitation in summer and the circulation characteristics in anomaly years. Combined with comparative analysis of circulation field in summer during 2014 to 2015 with the circulation field in abnormal years, we clarified the drought circulation characteristics in summer and the circulation field factors caused drought in summer during 2014 to 2015 in Liaoning. The results showed that: The cooperation of large scale circulation system in different height of troposphere in East Asia was the main reason for the anomaly precipitation in summer in Liaoning. The circulation fields characteristics of drought in summer during 2014 to 2015 in Liaoning were all similar with the condition of anomaly drought in summer. The position of west pacific subtropical ridge line was partial to south, and its northwest side was negative anomaly, so it was unuseful to subtropicalhigh towards west and north. Because the subtropicalhigh was inclined to south, so the southwest water vapor transport was not sufficient in Liaoning region. The subtropical westerly jet axis was located in south of Liaoning and the 200 hPa zonal wind anomaly over the south of Liaoning was positive, northern part was negative. This allocation of large scale circulation in different height of troposphere was the main circulation reason for the summer drought during 2014 to 2015 in Liaoning.