Gaoyuan qixiang (Feb 2022)
Analysis on the Temporal and Spatial Evolution Characteristics of Water Vapor Transport and Budget over the Source Region of the Three-River
Abstract
The Source Region of the Three-River （SRTR） lies in the hinterland of the Qinghai-Xizang （Tibetan） Plateau （QXP） and is one of the sensitive regions to climate change in East Asia.It is of great significance to study the distribution， transport， and budget of water vapor for understanding the characteristics of the regional precipitation.This research is based on the ERA5 reanalysis data of the European Centre for Medium-Range Weather Forecasts （ECMWF） from 1980 to 2019， combined with the data of 9 radiosonde stations in the National Meteorological Data Center from 1981 to 2010.The temporal and spatial variation characteristics of water vapor distribution， water vapor transport flux and budget of each boundary over the SRTR and its surrounding areas are analyzed.The results show that there are significant differences in the spatial distribution of water vapor content， which presents a high value region in the southeastern QXP and a low value region in the northwest of the QXP.The distribution and value of water vapor content are different in four seasons， which exhibit the largest in summer， followed by autumn and spring， and the least in winter.The annual cycle of water vapor content manifests the single peak over the SRTR and the Brahmaputra River basin.Water vapor is mainly concentrated in June to August and its maximum appears in July with a value of 41.6 mm.The inter-annual variation shows an increasing trend with a rate of 0.4 mm·（10a）-1.The Arabian Sea and the Bay of Bengal are the main sources of water vapor over the SRTR， followed by the western airflow from the middle latitude and the northwestern airflow.Three kinds of airflows form obvious convergence of water vapor transport flux over the Brahmaputra Grand Canyon.There are seasonal discrepancies in the intensity of water vapor transport.Among the water vapor import boundaries， the western boundary has the largest import （815.3×106 kg·s-1）， followed by the southern boundary （724.9×106 kg·s-1） and the seasonal variations of the two boundaries are significant.The northern boundary has less import （317.9×106 kg·s-1）， while the eastern boundary is the export boundary of water vapor flux， and the maximum water vapor export is in September with a value of 140.5×106 kg·s-1.The net water vapor import is greater than the export， thus the water vapor flux is in surplus， which is about to affect the variations of precipitation and the regional water cycle over the SRTR.
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