2013年长江中下游地区夏季高温事件的环流特征及成因

Circulation characteristics and causes of the summer extreme high temperature event in the middle and lower reaches of the Yangtze River of 2013

采用ERA-interim和NCEP CFSR逐日再分析资料以及长江中下游29个测站的逐日温度资料,分析了2013年7月23日—8月14日长江中下游地区夏季异常高温的特点、环流特征及成因。研究结果表明,2013年夏季高温期间西太平洋副热带高压较往年异常偏强,西太平洋副热带高压控制区内大范围异常下沉运动产生的大气绝热加热是高温形成的主要原因。同时,与强大西太平洋副热带高压相联系的异常强大反气旋环流使得长江中下游地区上空的水汽向东北方向大量输出,导致了该区域水汽含量的减少,致使到达地面的太阳短波辐射增加,这是高温形成的又一原因。进一步分析表明,2013年夏季海洋性大陆地区大气热源异常偏强,该地区大气热源的异常增强可能是导致2013年夏季西太平洋副热带高压异常偏强的主要原因。

Based on the ERA-interim,NCEP CFSR daily reanalysis data and daily observation temperature data from 29 stations over middle and low reaches of Yangtze River,the characteristics of the extreme high temperature event,circulation features and its causes over the middle and lower reaches of the Yangtze River during 23 July to 14 August,2013 were analyzed. Results show that the intensity of the Western Pacific Subtropical High（ WPSH） was extremely strong in summer of 2013,and the atmospheric adiabatic heating caused by the enhancing sinking motion in the WPSH controlling zone is the main cause for this high temperature event. Moreover,the extremely enhanced WPSH-related anticyclonic circulation leads to an increasing outflow of the water vapor over the middle and lower reaches of the Yangtze River area to the east,which causes the decreasing of the water vapor content,increasing of downward solar radiation flux at the surface,so this is another cause for this high temperature event. Further analysis indicates that an anomalous enhanced atmospheric heating source over the Maritime Continent is probably the main reason why the WPSH is extremely strong in summer of 2013.