Characteristics of rapid (24 h) cold wave events and circulation patterns in Jiangsu Province

Based on the daily minimum temperature data and NCEP/NCAR reanalysis data from the conventional meteorological stations in Jiangsu Province from 1951 to 2023, the basic characteristics and main circulation types of rapid (24 h) cold wave events (referred to as fast cold wave events, the same below) in Jiangsu Province are analyzed. The results show that: (1) The frequency of rapid cold wave events decreases from north to south, and the spatial difference is obvious. The intensity of cold wave events is high in the northwest and southeast of Jiangsu province, and slightly smaller in the southwest of Jiangsu. The number of cold wave events decreases with the increase of the affected area, and the cold wave events are all regional, mainly of general intensity; (2) The events are mainly concentrated in winter, with the highest in January, the extreme value of cooling occurres in December, and the average intensity is the strongest in March and the weakest in January. The frequency and intensity of rapid cold wave events are relatively more and stronger before 1970s, and then show a trend of decreasing and weakening volatility, and then increasing and strengthening after the beginning of the 21st century; (3) The rapid cold wave events are mainly divided into the north-low-south-high type and the west-low-east-high type; (4) The intensity of cold air in the north-low-south-high circulation type is stronger, and most of the cold air in the west-low and east-high circulation type is relatively weaker, but a very small number of west-low-east-high circulation types can also cause strong rapid cold wave events.