The Analysis of Summer Precipitation Modes and Its Characteristics of Water Vapor Transportation in Hydroelectric Basins of Chongqing

Hydroelectric is one of the crucial forms of electricity generation in Chongqing， studying the intensity and distribution of summer precipitation in the Chongqing hydropower basin holds significant importance for providing reliable meteorological support for summer power generation.Currently， research efforts primarily concentrate on the Southwest region or the Sichuan Basin， with limited focus on individual hydropower basins， as a result， the potential for providing refined electricity meteorological services is restricted.In this study， by using EOF analysis， regression analysis， synthesis analysis and other methods， the summer precipitation modes and causes in hydroelectric basins of Chongqing were analyzed based on the precipitation data from 115 meteorological observation stations in Chongqing's hydroelectric basins from 1981 to 2022， as well as ERA5 reanalysis data.Furthermore， the characteristics of water vapor transport for each precipitation mode were explored.The results show that there are two main precipitation modes in the summer in the major hydroelectric basins of Chongqing： the region-wide consistent mode and the north-south reverse mode.The circulation characteristics of the consistent excessive mode in region-wide consistent mode are mainly characterized by large amplitude in the mid-high latitude geopotential height field， a stronger and southward-shifted mid-latitude westerly jet， a stronger and southward-shifted South Asian high， and a westward-shifted subtropical high， the consistent low mode are opposite.Simultaneously， there are abnormal southwest water vapor transport and convergence within the basin， which collectively result in excessive precipitation in the basin.In addition， there are four water vapor channels that influence the region-wide consistent mode， they are the southerly channel in the western Bay of Bengal， the southerly channel in the northern part of the Indochina Peninsula， the westerly channel on the eastern side of the Tibetan plateau， and the easterly channel west of the Philippines， with the eastern channel west of the Philippines having the most significant impact.The circulation characteristics of the more north and less south mode in north-south reverse mode are primarily characterized by a west-high-east-low geopotential height field in the mid-high latitudes， a northward-shifted mid-latitude westerly jet， an eastern-type South Asian high in the mid-low latitudes， and a tendency for the subtropical high to extend westward and northward.Meanwhile， there is a strong northward water vapor flux within the basin， with water vapor convergence in the northern part and water vapor divergence in the southern part， more south and less north mode are opposite.Additionally， there are two water vapor channels that influence the north-south reverse mode， they are the southerly channel in the central part of the basin and the southerly channel in the eastern part of the Philippines， exhibiting consistent changes.