Quantitative Analysis of Water Vapor Sources for Rainstorm Days in Beijing During Warm Seasons of 2009-2013

LU Tingting; CUI Xiaopeng

doi:10.16032/j.issn.1004-4965.2025.005

Abstract：With the help of the FLEXPART model as well as a quantitative analysis of water vapor source contribution,the present study investigated the water vapor sources,transport paths,and quantitative contribution to rainstorm events in Beijing during warm seasons(May-September)from 2009 to 2013.Key findings are as follows.Air parcels originated from widely distributed initial source regions with varying transport paths.Lower-altitude air parcels exhibited enhanced moisture uptake capacity,particularly those originating from or traversing water surfaces.Air parcels underwent multiple moisture uptake and release processes en route to Beijing,with the most pronounced exchanges occurring over the continental and coastal areas of Central China and North China.Dominant moisture contributions(65.8％)to Beijing rainstorms originated from the continental and coastal areas of Central and North China.Secondary contributions included Western Asia-Northwest China-Tibetan Plateau(7.34％)and South China continental/coastal regions(8.16％).The total amount of water vapor absorbed by the target air parcel from the continental and coastal areas of North China and Central China was the largest.While the proportion of water vapor released in Beijing was only 6.9％,due to the huge amount of water vapor absorbed in the continental and coastal areas of Central and North China,the contribution of this area to the rainstorm days was much higher than that other areas.The Western Asia-Northwest China-Tibetan Plateau region ranked second in total moisture uptake but exhibited substantial transport losses,reducing its effective contribution to levels comparable with South China.Although the total amount of water vapor uptake in the continental and coastal areas of South China was equivalent to that in the south of Russia near Lake Baikal,due to the relatively low loss along the way,the contribution of water vapor of the former was significantly higher than that of the latter.