摘要:
Spatio-temporal change characteristics of the persistent meteorological and hydrological drought in Yunnan from 2009 to 2014 were analyzed based on Dai Palmer drought severity index (Dai-PDSI) and streamflow drought index (SDI).The causes of persistent drought were investigated based on the NCAR/NCEP reanalysis data from various perspectives including:the West Pacific subtropical high,Tibetan high,Southern Branch Trough,tropospheric vertical motion,and vertical distribution of water vapor.The results showed that the persistent drought from 2009 to 2014 was the longest drought in Yunnan since 1961.The driest period was from October,2009 to September,2010,and summer and winter were two driest seasons.The drought in the east of Yunnan was the heaviest and the drought in the southeastern part was slightly light.Hydrologic drought was accompanied by meteorological drought.The heaviest hydrological drought was in Jinsha River and Nanpan River.Secondary hydrological drought occurred in the Lancang River.In terms of strength,hydrologic drought is weaker than meteorological drought.In summer,the atmosphere over Yunnan was controlled continuously by downward flow due to that the West Pacific subtropical high was stronger and westward and the Tibetan high center was westward.In winter,the Southern Branch Trough was weak and could not help to guide the water vapor from Bengal Bay to Yunnan.In other seasons,downward flow prevailed and water vapor was seriously shortage in troposphere.%基于戴-帕尔默干旱强度指数(Dai Palmer drought severity index,Dai-PDSI)和径流干旱指数(streamflow drought index,SDI),分析云南地区2009-2014年持续性气象干旱与水文干旱时空演变特征,并利用NCAR/NCEP再分析资料,从西太平洋副热带高压、青藏高压、南支槽、对流层垂直运动及水汽垂直分布等视角,分析2009-2014年云南持续性干旱的原因.结果表明:①2009-2014年是云南地区自1961年以来最严重的一次持续性极端干旱过程,2009年10月-2010年9月是最干旱的时段;夏季与冬季是干旱最严重的两个季节.②在空间上,云南中东部旱情最重,东南部稍轻.③水文干旱伴随气象干旱而生,金沙江和南盘江出现重度水文干旱,澜沧江出现中等水文干旱,从强度上讲,水文干旱弱于气象干旱.④夏季西太平洋副热带高压偏西偏强,青藏高压持续偏强、中心偏西,云南上空的大气持续受它们控制,盛行下沉气流;冬季南支槽偏弱,不利于引导孟加拉湾水汽北上;在其他季节,大气多以下沉运动为主,对流层水汽严重不足.