湖南省夏季高温热浪时空分布特征及其成因

Spatial-Temporal Characteristics and Causes of Summer Heat Waves in Hunan Province

利用1960~2014年夏季(6~8月)湖南省77个气象站逐日最高气温资料,对该地区高温热浪的时空分布特征进行分析研究。研究结果表明:湖南省大部分地区常年遭受高温热浪袭击,年均发生1.53次,部分地区年均出现2次以上。高频次、高强度的高温热浪主要集中于湘中偏东(衡阳盆地一带)地区,株洲、长沙、益阳等地为次大值区,湘西地区高温热浪的发生频次及强度则低于全省平均值。近年来,湖南高温热浪的影响范围不断扩大,炎热程度不断增强。近55年高温热浪频次及强度具有显著的阶段性特征,20世纪80年代以前呈减少(减弱)趋势,此后呈增多(增强)趋势,21世纪以来高温热浪增多增强尤其明显。对一次持续时间长、影响范围广的极端高温热浪过程研究发现:南亚高压东伸扩展,西太副高异常偏西、偏北且稳定少动,下沉运动强盛等条件的配合有利于湖南省持续性高温的发生。

A comprehensive understanding of heatwaves is of great importance for making scientifically-based emergency plans to reduce their consequent disastrous impacts. Based on daily maximum temperature observations in summer over Hunan Province during 1960-2014, the spatial and temporal distribution characteristics of heatwaves and the possible synoptic causes are discussed. The major conclusions are as follows. High occurrence frequency and intensity of heatwaves are commonly observed in eastern Hunan （near Hengyang Basin）, while heat waves are less frequent and with weak intensity in western Hunan. The areas affected by heatwaves are expanding and the intensity of heat waves is also enhancing, whereas the spatial difference in heatwaves has narrowed. The heatwave frequency （intensity） displays obvious stage changes, which decreased （weakened） before 1980s but turned to increase （strengthen） since the 1990s. After entering the 21st century, more frequent and stronger heatwaves take place. The analysis of a heat wave event with extremely high temperature showed that a stable and strong western subtropical high with its position shifting westward and northward, eastward extending South Asian high, and strong and persistent downdrafts are all favorable for the occurrence of high temperature in Hunan.