2013年夏季湖南严重高温干旱及其大气环流异常

Characteristics of Serious High Temperature and Drought and Anomalies of Atmospheric Circulation in Summer of 2013 in Hu'nan Province

利用湖南省97个台站降水、气温资料和NECP/NCAR再分析资料以及NOAA卫星观测的OLR场资料,系统分析了2013年6月30日至8月14日湖南持续高温干旱的时空分布及同期大气环流异常特征。结果表明:2013年夏季是湖南1951年以来降水最少、高温干旱程度最严重的一年。西太平洋副热带高压强度偏强、西伸脊点偏西,湖南处在副高控制下,盛行下沉气流是发生持续高温干旱的直接原因;西太平洋副高内增强的下沉气流,致使多数县市高温日数和极端高温突破历史同期最高记录。位于菲律宾附近的OLR低值带中心偏西,致使副热带地区下沉区偏西,进而造成西太平洋副高偏强偏西。此外,湖南地区上空为水汽输送异常辐散中心,这在一定程度上促使了干旱的发生发展。

Based on daily precipitation and temperature data from 97 meteorological stations in Hu’nan,NCEP/NCAR reanalysis data and the outgoing long-wave radiation （OLR）data provided by NOAA satellite from June to August during 1981 -2013,the temporal and spatial distribution of the persistent and serious high temperature and drought from June 30 to August 14,2013 in Hu’nan and the atmospheric circulation anomalies were analyzed.The results showed that the precipitation in the summer of 2013 was least and high temperature and drought were most serious since 1951.The western Pacific subtropical high was stronger and the position was westward than normal,and the prevailing descending flow over Hu’nan under the control of the western Pacific subtropical high played an impor-tant role to produce the persistent high temperature and drought.The high temperature days and extreme maximum temperature in most counties and cities of Hu’nan broke through the highest record of the same period historically.The position of the low value center of OLR near the Philippines was westward,which caused the descending area of subtropical region toward west,and then resulted in the western Pacific subtropical high was stronger and its position was westward than normal.At the same time,the anomalous divergences of water vapor flux over Hu’nan prompted partly to the development of high temperature and drought.