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Chinese Agricultural Science Bulletin ›› 2023, Vol. 39 ›› Issue (14): 85-94.doi: 10.11924/j.issn.1000-6850.casb2022-0356

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Analysis of Precipitation and Circulation Characteristics of Autumn Flood in the Middle Reaches of the Yellow River in 2021

JIN Lijun(), LIU Jing, WANG Peng   

  1. Hydrological Bureau of YRCC, Zhengzhou 450004
  • Received:2022-04-26 Revised:2022-06-28 Online:2023-05-09 Published:2023-05-09

Abstract:

To improve the ability of precipitation forecasting in autumn in the middle reaches of the Yellow River, so as to provide reference for agricultural production and even disaster prevention and mitigation in this area, this study used the daily precipitation data of hydrological and meteorological stations, the daily subtropical high ridge line and west extension ridge point data of the National Climate Center, and the reanalysis data of NCEP/NCAR, to analyze the characteristics of autumn precipitation in the middle reaches of the Yellow River in 2021 and the daily evolution characteristics of the circulation situation. The results showed that the autumn flood in the middle reaches of the Yellow River in 2021 was caused by six strong precipitation processes, with the characteristics of long lasting days, stable rain band, strong rain intensity and high overlap of falling areas. During the autumn flood season, the ridge line of the subtropical high was relatively stable. The seasonal southward fall of the subtropical high was abnormally late, and the west extension ridge was westward. The blocking situation prevailed in the middle and high latitudes of Eurasia. The heavy precipitation process in the middle reaches of the Yellow River mainly occurred in the situation of double resistance height in the weakening collapse period when the resistance height of Ural Mountain reached the peak period, and in the situation of single resistance height formed by Ural Mountain. The stronger strength and easterly position of the South Asian high were the main reasons for the formation of the jet stream at 40°—45° N and 110°—140° E of 200 hPa. The low-level jet was not significant in the early stage and its location was southerly, but it expanded northward after late September. The appropriate configuration of high and low-level jet provided a favorable circulation background for the development of upward movement during the occurrence of sustained heavy precipitation in the middle reaches of the Yellow River. In the autumn flood season, the water vapor mainly came from the Western Pacific, which was transported by the abnormally strong easterly air flow on the south side of the subtropical high and the strong southwest air flow on the northwest side of the subtropical high.

Key words: autumn flood, subtropical high, high resistance, jet, circulation characteristics, the middle reaches of the Yellow River