Analysis of atmospheric circulation characteristics during Meiyu concentrated period in 2024 in middle and lower reaches of Changjiang River
To enhance the forecast level of heavy rainfall during the Meiyu period,causes of abnormal characteristics and large-scale circulation during the Meiyu concentrated period in 2024 in the middle and lower reaches of the Changjiang River were analyzed by using the daily precipitation station data and NCEP reanalysis data.Additionally,a comparison was made with the characteristics of the Meiyu concentrated period in 2016.The results showed that:① The Meiyu period in the middle and lower reaches of the Changjiang River in 2024 had obvious phased characteristics.The period from June 17th to July 2nd was a Meiyu concentrated period,during which four heavy rainfall events occurred.The main rainfall areas were along the mainstream of the middle and lower reaches of the Changjiang River,as well as in the central-northern parts of the Dongting Lake and Poyang Lake watersheds.After July 2nd,the main rainfall area moved northward to the northern part of the Changjiang River mainstream,so the Meiyu concentrated period ended.The rainfall pattern in the Changjiang River Basin has changed from more in the south and less in the north to more in the north and less in the south.② The coupling of high,middle,and low-level circulation systems was the large-scale circulation background for the formation and maintenance of heavy rainfall in the middle and lower reaches of the Changjiang River during the Meiyu period.During the four rainfall events,a meridional circulation pattern"two troughs and one ridge"was observed at mid-to-high latitudes,while the Western Pacific Subtropical High(WPSH)maintained a stable zonal distribution.Strong water vapor from the Bay of Bengal and the western Pacific Ocean was transported to the middle and lower rea-ches of the Changjiang River by prevailing southwest winds.Cold and warm air converged persistently on both sides of the main-stream of the middle and lower reaches of the Changjiang River.All these factors lead to relentless rainfall and abnormally high precipitation totals during the Meiyu concentrated period.③ The Meiyu concentrated periods in 2024 and 2016 had many common characteristics,including similar characteristics and intensity,both occurring during the decaying phase of El Nino events,accom-panied by a stronger and more westward WPSH,and a stronger southwest warm-moist airflow.The research results can provide references for flood control and disaster reduction efforts during the Meiyu period in the Changjiang River Basin.
heavy rainfallMeiyu concentrated periodatmospheric circulationmiddle and lower reaches of Changjiang River
万方数据
维普
