杭州空中水资源和降水转化率分析

Research on Atmospheric Water Vapor Resources and Precipitation Conversion Rate in Hangzhou

采用NCEP/NCAR再分析资料和月降水资料,对杭州地区近66年的空中水资源和降水转化率特征进行了分析研究。结果表明:杭州年平均水汽含量为28~30 mm,夏季最高,春、秋季次之,冬季最低。空间分布上,南高北低。时间演变上,年平均和春、秋季水汽含量均呈下降趋势,春季的下降趋势更显著,夏季呈弱上升之势,冬季在20世纪无明显趋势,21世纪后显著减小,其中除冬季外,其余均通过了0.05的显著性检验。杭州平均季节降水转化率最大为冬、春季,其次是夏季,最小为秋季,降水转化率普遍偏低,空中水资源开发潜力巨大。水汽含量与降水的相关性较好,其可作为降水预报的指标之一。除水汽条件外,散度、尤其是涡度等动力场的配置是决定降水转化率高低的重要因素。

Based on the NCEP/NCAR reanalysis data and the monthly precipitation data,the characteristics of atmospheric water vapor resources and precipitation conversion rate in Hangzhou in the last 66 years are studied.The results indicate that the annual average water vapor content is 28~30 mm over Hangzhou.The water vapor content which reaches the maximum in summer and the minimum in winter is somewhere in between in spring and autumn,and the spatial distribution of water vapor is of characteristic of the south-high and north-low in Hangzhou area.The water vapor content of annual mean tends to decrease,which is similar to the evolution trends of both spring and autumn,while the downward trend in spring is more significant.However,the water vapor content presents a weak uptrend in summer.In winter,there is no obvious trend in the twentieth century but a significant downtrend after entering the21 st century.All of these trends above except winter passed the significant test at 0.05 level.The seasonal precipitation conversion rate in Hangzhou is the highest in winter and spring,the next in summer and the lowest in autumn.The precipitation conversion rate is generally low,therefor the development potential of air water resources is huge.There is a close correlation between precipitation and water vapor content which can be used as an indicator of precipitation prediction.In addition,the structures of dynamic factors such as divergence and vorticity play an important role in effecting precipitation conversion rate.