2016年四川省持续性高温天气时空变化特征及其成因

利用四川省134个地面站的逐日最高气温资料和ERA-interim再分析资料，对2016年四川省持续性高温天气过程的时空变化规律及其持续期间大尺度环流的异常演变特征进行诊断分析，结果表明:2016年8月11~26日，四川省出现历史罕见的持续大范围高温天气，全省平均最高气温、高温日数和持续高温日数均突破历史同期极值，为1968年以来最大，高温站点占比达76.1%；高温持续期间，副高持续加强并西伸，南亚高压偏强且异常东伸，二者的位置配置致使四川长期处于异常反气旋控制之下，盛行下沉气流，是诱发此次持续性高温的直接原因；东亚东部地区环流平直，伴随位势高度场正异常和偏北的副热带西风急流，致使冷空气南下受阻，同时对流层低层水汽异常辐散伴随强下沉运动，降水偏少，促使高温发展和维持。 

Diagnosis on Characteristics and Mechanisms of Persistent High Temperature Event over Sichuan in 2016

Based on the observed data of 134 meteorological stations and ERA-interim reanalysis data in Sichuan Province (SCP), the spatial-temporal characteristics of persistent high temperature event and its corresponding atmospheric circulation are analyzed. The results showed that an unprecedented persistent high temperature event occurred in SCP from August 11 to 26, 2016, which accompanied with the highest temperature values and the longest duration since 1968. The critical circulation system was the westward-expanding and intensified western Pacific subtropical high. Correspondingly, the intensive South Asia high moved eastward significantly, directly accelerated the movement of the western Pacific subtropical high. Due to the abnormal anticyclone in SCP, downdraft was beneficial to the formation of high temperature. In addition, the synergistic effects of higher geopotential height of East Asia and northerly subtropical westerly airflows blocked cold front southward. Anomalous divergence of water vapor flux in the lower troposphere is coupled with the strong downward motion, which results in less rain and prolonged high temperature. It revealed the characteristics and circulation mechanisms on the typical high temperature episode in SCP.