Analysis of the Dynamics and Water Vapor Conditions of SummerPrecipitation Anomalies in North China in Recent 60 Years
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Tianjin Climate Center

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    Abstract:

    In order to understand the causes of summer precipitation anomalies in North China and improve climate monitoring and prediction technology, based on the summer precipitation data in North China and NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data from 1961 to 2021, using the methods of correlation, synthesis and circulation anomaly reconstruction, the circulation background of summer (June -August) precipitation anomaly in North China and the relationship between East Asian subtropical summer monsoon, North China dynamic rise index and summer precipitation in North China are analyzed. The results show that: (1) the circulation conditions of abnormal precipitation in North China in summer are that the high ridge of Ural Mountain at 500hPa in summer is stronger, the Baikal Lake trough is deeper, the subtropical high in the Northwest Pacific is north by west near the Korean Peninsula, and North China is in the circulation situation of "high in the East and low in the west", so the dynamic rising conditions are favorable. At the same time, the 850hPa Indian monsoon is stronger, the East Asian subtropical summer monsoon is significantly stronger, and the water vapor source in North China is sufficient. (2) The East Asian subtropical summer monsoon index and North China dynamic rise index defined in this paper have a good indication of summer precipitation anomalies in North China. When the two indexes are stronger, the summer precipitation in North China is abnormally more. If both indexes are weak, the summer precipitation in North China is abnormally less. If the two indexes are inconsistent, the summer precipitation in North China is basically normal. (3) The abnormally more or less summer rainfall in North China is the result of the synergy of the East Asian subtropical summer monsoon and the dynamic upward movement in North China. The subtropical summer monsoon in East Asia is stronger (the dynamic upward movement in North China is stronger), the Baikal trough in the 500hPa layer is deepened, the subtropical high in the Northwest Pacific is north by west, and North China is under the control of the circulation of "high in the East and low in the West", so the dynamic upward conditions are favorable. At the same time, the Indian summer monsoon at 850hPa and the subtropical summer monsoon in East Asia are relatively strong, which will strengthen the water vapor transmission of the west wind in the tropical Indian Ocean and the south wind in the subtropical region of East Asia, and the water vapor source in North China is sufficient. The above situation will cause abnormally more summer precipitation in North China. On the contrary, the summer precipitation in North China will be abnormally less. (4) From April to May in the early stage, the Baikal trough in the 500hPa layer deepened, the subtropical high in the Northwest Pacific was northerly, and the southerly wind in East Asia in the 850hPa layer was significantly stronger, which can be used as a climate monitoring and prediction index for the abnormally more summer precipitation in North China.

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History
  • Received:July 15,2022
  • Revised:March 08,2023
  • Adopted:April 06,2023
  • Online: April 06,2023
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