关键词: 深秋定义, 深秋暴雨, 锋面系统, 锋生, 湖北省

Abstract: Based on the national station observation and NCEP reanalysis data from 1962 to 2020, combined with the human comfort index, the late autumn season in Hubei Province was defined for the first time, and the characteristics of heavy rain in late autumn in Hubei Province were revealed by the synthetic and comparative methods.The results showed that the daily average temperature range of late autumn in Hubei Province was 10~16 ℃. The beginning date of late autumn in Hubei Province was October 27, and the end date was November 24. The three modes of EOF decomposition of heavy rain days in late autumn of Hubei province included the regional heavy rain cases in late autumn of Hubei province, which showed that the southern Jianghan Plain, the eastern northeast of Hubei Province and the southeast of Hubei Province were the areas with high incidence of heavy rain. The number of heavy rain days in late autumn in Hubei Province changed significantly, and the value of high and low alternated significantly. Morlet wavelet analysis showed that there were obvious periodic oscillation signals of 2~3 years, quasi-6 years and 12~13 years in the late autumn rainstorm in Hubei Province, among which quasi-6 years was the most prominent, and the oscillation phenomenon of 12~13 years had increased since the 1990s. The main influencing systems of the late autumn rainstorm process included the Western Pacific subtropical high, the East Asian trough and the southern branch trough of the Gulf of Bangladesh. Near the surface, the front shape of the southwest warm and humid air climbing on the cold mat was formed, when the westerly shortwave trough moved eastwards to approach or superimpose on the frontal system, the frontogenesis was strengthened, which was different from the trigger model that the short-wave trough was close to or superimposed on the inactive Plum rain front and carried cold air into the surface “warm inverted trough” under the background field of the saddle-shaped large-scale circulation in the typical Plum rain front process. The frontal system of the heavy rain in late autumn had a small slope and weak upward movement, which mainly occurred in the middle and upper troposphere. The tropospheric θse was distributed from low to high from bottom to top, and the atmospheric junction was in a stable state. However, the frontal system of the heavy rain in Plum rain front had a large slope, and the tropospheric θse was distributed in a “sandwich” pattern of high-low-high.

Key words: climatology definition of late autumn, rainstorm in late autumn, frontal system, frontogenesis, Hubei Province