Abstract: To make clear the spatio-temporal distribution characteristics of convective initiation ( CI) on hail days and recognize the key areas and periods for hail warnings in Guizhou Province , using the identification results of convective initiation (CI) on 110 hail days , this study analyzes the distinct characteristics of CI under different synoptic patterns and their relationships with topographic factors . The results show that :(1) Temporally , CI exhibits a pattern of " high frequency in spring with double peaks in the afternoon and nighttime . " A significant seasonal evolution has been observed in the relationship between CI echo top height and critical thermodynamic stratification . Spatially , the most active CI zone is located along the eastern transitional slopes of the Wumeng Mountains , presenting an evolutionary pattern of " being triggered over western mountainous terrain followed by eastward development along the topographic gradient. " In spring , CI progresses northeastward from western high- altitude source regions , while in summer , it remains active in the southwestern mountains and the junction areas of Sichuan , Yunnan and Guizhou , with new centers emerging in lower-elevation hilly areas . (2) Synoptically , hail days in Guizhou are dominated by upper-level trough patterns and pre-frontal hail patterns . The northwestern airflow and shear line patterns reflect the coupling characteristics between cold air intrusion and topographic channels , whereas the upper-level trough and pre-frontal hail patterns demonstrate the stepped triggering feature along northwest- southeast oriented terrain . (3) The spatial distribution of CI has a significantly positive correlation with elevation , slope direction and terrain incision depth . Based on the distribution characteristics of CI on hail days , this study reveals the triggering mechanisms of hailstorm convective initiation in Guizhou under the coupling of terrain and circulation .