2013年长江中下游地区高温热浪及可能成因

Analysis and Possible Cause of Heatwave over South China in 2013 Summer

利用1971～2013年中国800余站点的逐日温度资料和NCEP/NCAR再分析资料,采用气候诊断方法,初步分析了2013年夏季长江中下游地区异常高温热浪天气发生的可能原因。结果表明：2013年夏季7、8两月,105°E以东的长江流域大部分地区地面气温较常年平均偏高2℃～4℃;超过35℃的高温日数较气候平均多20 d以上。导致2013年夏季7、8两月长江中下游地区的异常高温热浪天气的一个特殊原因,是南亚季风区和东亚热带季风区异常强的对流活动,使对流层上层南亚高压偏东偏强、对流层中层西太平洋副热带高压偏北偏西偏强和长江流域异常的下沉运动;同时,西风带及中高纬环流系统配置不利于冷空气南下,是长江中下游地区发生持续的异常高温天气的另一个因子。

Using the daily temperature data of more than 800 sites in China from 1971 to 2013 and the NCEP / NCAR reanalysis data,and the Climate diagnosis method,the possible cause of the heat wave anomalies are analyzed in the summer of 2013 in the middle and lower reaches of the Yangtze river. The results showed that： in July and August of 2013,the average surface temperature is more than 2 ℃ to 4 ℃ in most area of Yangtze river. In most regions of the east of105°E and between 25°N to 35°N,the days abnormal with maximum temperatures of 35 ℃ or above which is more than climate average is 20 days. In July and August of 2013,the special reason of the extreme summer condition in the middle and lower reaches of the Yangtze river is the active convection in the south Asian monsoon region and the east Asian monsoon region. It made Tibetan high pressure more enhanced and expand eastward in higher troposphere,western Pacific subtropical high expand northward and westward and more enhanced,and the abnormal downward flow. At the same time,the system configuration of westerlies and middle high latitude condition against cold air down south is the another factor of the persistent extreme summer conditions in the middle and lower reaches of the Yangtze river region.