基于SPI的青海省春季干旱时空演变特征及环流诊断

利用青海省非常年干旱区39个气象站1981—2017年春季逐月气温、降水资料,采用标准化降水指数(SPI),探讨青海省不同功能区春季干旱频率、干旱站次比的时空演变特征,并着重分析影响青海省不同功能区春季旱涝分布的环流异常特征。结果表明:春季青海省干旱发生频率在18.9%~40.5%之间,干旱站次比以4.9%·(10 a)^-1的速率下降,各功能区均呈现增湿特征,增湿幅度最大的地区为青南牧区,其标准化降水指数(SPI)线性倾向率为0.23·(10 a)^-1。春季影响青海省南、北部地区旱涝分布的500 hPa环流系统配置总体一致(偏涝年欧亚中高纬呈“正、负、正”分布形势,中国大部地区形成西低东高的配置,偏旱年相反),但中高纬度极涡强弱对北部地区旱涝分布影响较明显,中低纬度西亚槽对南部地区旱涝形势的影响较大。春季SPI与前冬(前一年12月至当年2月)的副热带西风急流位置存在明显负相关,前冬中东急流指数与SPI的相关性较东亚急流更显著(中东急流指数、东亚急流与SPI相关系数分别为-0.514和-0.332),前冬副热带西风急流位置若较常年偏南,则次年青海省发生春旱的可能性很大。

Spatial and Temporal Evolution and Atmospheric Circulation Diagnosis of Spring Drought Based on SPI in Qinghai Province

Using monthly temperature and precipitation data from 39 meteorological stations in impermanent arid area of Qinghai Province from 1981 to 2017,this paper discussed the spatial and temporal evolution of drought frequency and drought stations proportion in spring in different climatic functional zones based on standardized precipitation index(SPI),and emphatically analyzed the atmospheric circulation anomaly characteristics affecting the distribution of drought and flood in spring.The results show that drought frequency in spring in Qinghai Province ranged from 18.9%to 40.5%,and the drought stations proportion decreased with the rate of 4.9%·(10 a)^-1 in spring.It presented humidification phenomenon in spring in each climatic functional zone,and in the pastoral area in southern Qinghai humidification was most obvious with the linear tendency rate of 0.23·(10 a)^-1 of SPI.The 500 hPa circulation configuration affecting drought and flood distribution in the southern and northern of Qinghai in spring was generally consistent,the middle and high latitudes over Eurasia showed a“+-+”distribution pattern in more rainfall years,and a low-to-high distribution from west to east formed over China.In drought years it showed an opposite characteristic.However,the influence of polar vortex on drought and flood distribution was greater in northern region of Qinghai,and western Asia trough influenced the southern region more.The SPI in spring presented significant negative correlation with subtropical upper-level westerly jet position in previous winter,and the Middle East jet stream index had more significant correlation with SPI than the east Asian jet stream index,and their correlation coefficients were 0.514 and 0.332,respectively.When the subtropical upper-level jet position was farther south than usual in previous winter,there was a high probability of spring drought in the following year in Qinghai Province.