Spatiotemporal distribution characteristics of Convection Initiation based on objective radar identification in Hubei Province

Convection Initiation (CI) is an important precursor to the occurrence of severe convective weather, and its identification and early warning are of great significance for meteorological disaster prevention and mitigation. Using high spatiotemporal resolution radar composite reflectivity mosaic data and surface automatic weather station precipitation data from Hubei Province for the period 2020–2024, this study employed an improved high-resolution grid-based objective CI identification algorithm to construct a CI dataset for Hubei Province. The spatiotemporal distribution characteristics of CI and their relationship with topography were subsequently analyzed. The results are as follows. (1) A total of 107,322 CI number were identified in Hubei Province from 2020 to 2024, with a daily mean CI number of 59 times and a percentage of CI days of 73%. Both the daily mean CI number and the percentage of CI days were highest in 2020 and lowest in 2022. Seasonally, CI activity was most active in summer, followed by autumn and spring, and least active in winter. (2) The monthly variation of CI activity during this period was characterized by a bimodal pattern, with the primary peak observed in June–July, corresponding to the Meiyu season, and a secondary peak noted in October–November, associated with seasonal transition, cold-warm air convergence, and the influence of tropical systems such as typhoons. (3) The diurnal variation of CI was characterized by a single or dominant peak from afternoon to evening, with a secondary peak identified in the late night during summer. Except in autumn, daytime CI occurrences were generally higher than those at night. (4) The distribution of CI was found to be uneven and significantly influenced by underlying surfaces. High-frequency areas were concentrated mainly in the mountainous regions of southwestern Hubei, particularly at the border of Enshi and Yichang. Relatively high-frequency areas included the Mufu Mountains in southeastern Hubei, the Dabie Mountains in northeastern Hubei, mountainous regions in northwestern Hubei, and areas surrounding large lakes and reservoirs, while the central plains and basins were associated with a relatively lower CI number. These findings preliminarily reveal the occurrence and development patterns of CI activity in Hubei Province, contributing to the construction of a localized CI forecasting model, which facilitates the early detection and warning of severe convective weather.