Characteristics of Persistent Heavy Rainfall and Water Vapor Transport in Western Sichuan Plateau
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Abstract:
Based on the routine observational data, NCEP FNL data and the HYSPLIT model, the spatiotemporal distribution, circulation situation, water vapor source and transport path of the persistent heavy rainfall events in the western Sichuan Plateau from 2008 to 2017 are analyzed. The main results are as follows: The total frequency of persistent heavy rainfall events in all observation stations of the western Sichuan Plateau is 337, and the frequency of regional heavy rainfall episodes is 21, in which the transition areas between plateau and basin including Luding, Kangding and Wenchuan have the highest frequency of persistent heavy rainfall. The longest duration of heavy rainfall events is about 3 to 4 days. In this study, the influencing circulation situations contains two troughs and one ridge, one trough and one ridge, and westerly trough. The cyclone over the Bay of Bengal is found to be a crucial weather system, which appears in 16 of the 21 regional persistent heavy rainfall cases. Moreover, all the regional cases in June and July are affected by the Bay of Bengal cyclone. The air masses on the western Sichuan Plateau are mainly accessed through four paths. The southwest and southeast routes originating from the tropical Indian Ocean are 43% and 11%, respectively, and the northwestern routes originating from the North Atlantic, the Mediterranean and the northcentral Iran account for 29%. The northeast path from the Caspian Sea to the Aral Sea accounts for 17%. The initial altitude of air particles of the northerly path is higher than that of the southerly path, and the corresponding temperature and water vapor content are lower. After analyzing the water vapor flux and water vapor flux divergence, the water vapor transport in regional persistent heavy rainfall in the western Sichuan Plateau is classified as three types, namely the S type, the westerly airflow type and the southerly airflow type.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.