Abstract
<title>Abstract</title> <p>This study comprehensively investigates the spatiotemporal characteristics, diurnal variations, and topographic modulation of convective initiation (CI) over Hunan Province and its surrounding regions using 2025 operational FY-4B Level-2 CI and Atmospheric Motion Vector (AMV) products, and further evaluate the practical early warning performance of FY-4B CI products based on a typical severe convective case. The statistical results show that CI activities exhibit significant seasonal heterogeneity, with an active warm season from March to October and the annual maximum CI frequency occurring in July. Spatially, high CI occurrences are mainly concentrated in southern and southwestern Hunan and multi-provincial border mountainous areas, whereas central and northern Hunan present relatively low CI frequency. This study establishes two identification schemes to differentiate developing and decaying CI. Adopting stricter discrimination criteria reduces the proportion of developing CI from 80.54% to 65.90%, and its spatial distribution is highly consistent with total CI, confirming the reliable indicative capability of FY-4B CI for subsequent convective evolution. The regional average CI diurnal peak appears at 06:00 UTC with distinct spatial divergence, which is consistent with the diurnal variation of mesoscale convective systems observed by radar. CI frequency increases with elevation within 0–1000 m, peaks at altitudes above 1000 m, and slightly decreases beyond 1200 m, indicating that moderate mountainous terrain favors local CI via orographic lifting and thermal heterogeneity. Case analysis of a severe hail event demonstrates that FY-4B CI can provide 1–2 hours of advanced early warning signals. However, a small fraction of CI signals decay afterward, underscoring the necessity of distinguishing sustainably developing CI to reduce the false alarm rate of early warnings.</p>