湖南夏秋季持续性区域气象干旱的时空特征

Spatio-temporal Characteristics of Persistent Regional Meteorological Drought in Summer and Autumn in Hunan

基于逐日气象干旱综合指数和持续性区域干旱识别方法,对1961—2017年湖南夏秋季持续性区域干旱事件进行识别,在此基础上分析干旱事件发生频率、持续时间、强度等时空特征。结果表明:近57 a来,湖南夏秋季持续性区域干旱平均每年发生1.4次,其年代际变化特征明显,21世纪00年代干旱频次虽少,但累积强度最大、持续日数最长,而20世纪90年代干旱事件相对偏少、偏弱。持续性区域干旱事件以夏秋连旱为主,7月28日至10月14日是高发时段。干旱持续时间主要集中在15~30 d,最长可达183 d,且持续时间少于40 d的多为一般干旱,重度及以上干旱一般持续110 d以上。持续性区域干旱事件主要表现为全省型、西北部型和南部型3种空间分布形态,全省型的干旱最多,且多为较重及以上等级。持续性区域干旱事件呈北少南多的空间分布特征,累积强度由西北向东南逐步增强,湘西北区域干旱程度较轻,洞庭湖区、湘中和湘南大部干旱程度较重。

Based on daily MCI and identification method of persistent regional drought events,the persistent regional drought events in summer and autumn were identified in Hunan Province from 1961 to 2017.And on this basis,the spatio-temporal characteristics of evaluation indexes including frequency,duration,intensity and start date,end date of persistent regional drought evens were analyzed.The results show that the persistent regional drought events occurred 1.4 times per year on average in Hunan Province in summer and autumn from 1961 to 2017,and the annual variation trend of drought events wasn’t obvious.The decadal variation characteristic was obvious,the drought frequency was the least in the 2000s,but the accumulative intensity of drought was the strongest and lasting days of drought were the longest.The drought events were fewer and weaker in the 1990s.The continuous droughts from summer to autumn dominated in Hunan Province,and occurred more frequently from July 28 to October 14.The drought events persisted mainly from 15 d to 30 d,and the longest lasted 183 d.The duration of general drought events was less than 40 days,while for severe drought events and above it was more than 110 days.The spatial distributions of persistent regional drought events mainly appeared three patterns including the whole province pattern,northwestern pattern and southern pattern in Hunan Province.The drought events with the whole province pattern were the most,and drought grades reached mostly heavy level and above.The persistent regional drought events were less in the north and more in the south of Hunan Province,and the accumulative intensity of drought increased gradually from northwest to southeast.The drought degree in northwestern Hunan was lighter,while in Dongting Lake,central and southern Hunan it was heavier.