Climatic characteristics of the Jianghuai cyclone and its linkage with precipitation during the Meiyu period from 1961 to 2020

Abstract. This study examines the climatic characteristics of 202 Jianghuai cyclones and their linkage with precipitation during the Meiyu period from 1961 to 2020. The results show that cyclones mainly originate from eastern Hubei Province and south-central Anhui Province. The frequency of Jianghuai cyclone occurrences shows an increasing trend in 1965–1970, 1990–2000, and after 2020. A decreasing trend is observed for 1970–1990 and 2000–2010. There is a positive correlation coefficient of 0.769 between the frequency of cyclone activity and precipitation in the Meiyu period. The percentage of precipitation affected by cyclone activities can reach up to 47 %. The anomalous increase in precipitation caused by cyclones above 27° N can reach a maximum of 7 mm/day. In contrast, precipitation is decreased in southern China because of the strengthening positive geopotential height in the Western Pacific subtropical high (WPSH). Precursor negative geopotential height anomalies for these cyclones emerge over the Mongolian region. The abnormal signal of the negative geopotential height can be traced to day -4 at the 500 hPa level. The WPSH and southwest jet are the dominant factors causing abnormal precipitation during Jianghuai cyclones. The significant water vapor convergence anomalies in the middle and lower reaches of the Yangtze River and the southwestward water vapor transport anomalies provide sufficient water vapor for cyclone development.