近45 a浙江连阴雨时空分布的环流特征及成因

利用1973—2017年浙江省63个常规气象观测站的日降水资料及NCEP/NCAR提供的月平均海温场、风场、高度场和湿度场以及射出长波辐射(OLR)场等再分析资料,运用EOF和距平合成以及t检验等方法,分析了近45 a浙江省2—4月总连阴雨日数的时空分布与全省一致连阴雨分布型的大气环流场及海温场,OLR场等的分布特征,并探讨其成因。结果表明:浙江省2—4月总连阴雨日数空间分布主要有全省一致型、南北相异型两种类型。当欧亚大陆中高纬度为乌拉尔山脊偏强(弱),鄂霍次克海地区槽偏强(弱),副高强度偏强(弱),易发全省一致偏多(少)型连阴雨;浙江上空OLR为负距平区易发生全省一致偏多型连阴雨,浙江上空OLR为正距平区易发生全省一致偏少型连阴雨;全省一致偏多型赤道中东太平洋海温明显偏暖,而全省一致偏少型赤道中东太平洋海温明显偏冷;赤道西太平洋海温为反位相。厄尔尼诺次年,全省一致偏多型连阴雨易发生;拉尼娜次年,全省一致偏少型连阴雨易发生。

Circulation characteristics and causes of time-space distribution of continuous rainy weather in Zhejiang Province over the past 45 years

In this study,using the daily precipitation data collected at 63 conventional meteorological observatories in Zhejiang Province from 1973 to 2017 and the sea surface temperature field,wind field,height field,humidity field and outgoing long-wave radiation (OLR) field provided by NCEP/NCAR,the EOF,anomalies Synthetic and t-test methods are used to analyze the time and space distribution of total rainy days in February to April in Zhejiang Province,as well as the atmospheric circulation field,previous sea surface temperature,and the distribution characteristics of the same OLR field in continuous rainy weather.Based on the analysis,we then explore the causes.The results show that the spatial distribution of the total number of rainy days in Zhejiang Province from February to April is generally divided into two categories:in the first,the distribution is the same around the province,while in the second the distribution is different between the north and south.When the high ridge of the Ural Mountains is strong (weak),the Okhotsk sea trough in the middle and high latitudes of the Eurasian continent and western Pacific subtropical high are also strong (weak),which causes the consistently strong (low)density rain in the province.OLR is a negative anomaly area in Zhejiang Province,which is prone to the same pattern of continuous rainy weather in the province.When the OLR is a positive anomaly area in Zhejiang Province,it is prone to cause the weather of consistently less rain than average in the province.In addition,when the weather of continuously more rain appears in the province,then the SST of the Equatorial Middle East Pacific in the early period and same period are significantly higher;otherwise,the SST of the Equatorial Middle East Pacific in the early period and same period are significantly lower.The SST in the western equatorial Pacific is the anti-phase.In the following year of El Niño,the weather phenomenon of continuously more rain typically appears in the province.In the following year of La Nina,the weather phenomenon of continuously less rain usually appears.