第八届全国中尺度气象学研讨会

Isolated convection initiation (ICI) over complex terrain under weak synoptic forcing remains poorly understood because the coupled effects of terrain-induced dynamical lifting, surface thermal forcing, and soil moisture (SM) modulation have not been disentangled. This study combines 5-year radar-based ICI climatology and convection-permitting semi-idealized simulation over the Dabie Mountains (DBM) in East China. ICI occurs predominantly in August on the leeside slope from noon to early afternoon, indicative of terrain-anchored local thermal convection. Semi-idealized simulations reveal a hierarchical control: terrain-induced flow deflection establishes persistent leeside convergence zones that predetermine ICI location, while surface sensible heating (SSH) and surface latent heating (SLH) jointly determine whether deep convection develops. Removing the DBM eliminates ICI entirely, whereas removing surrounding mountains amplifies DBM’s isolated dynamical influence, confirming that the DBM itself sustains preferred ICI locations. Suppressing SSH strongly inhibits convection through weakened thermally induced convergence, whereas suppressing SLH nearly eliminates precipitation by destroying moisture supply and instability despite sufficient dynamical lifting, demonstrating that both SSH and SLH are indispensable. Under abundant background moisture, SM modulates precipitation intensity rather than ICI location through a thermodynamic–dynamical compensation effect: drier soils enhance SSH-driven ascent and precipitation despite less favorable thermodynamic profiles, whereas wetter soils increase instability but reduce precipitation by suppressing dynamical lifting. These findings establish a hierarchical framework in which terrain-induced dynamical lifting controls ICI location, whereas the balance between SSH-driven ascent and SLH-maintained instability governs precipitation intensity, providing critical insights for improving ICI prediction and nowcasting over moisture-rich mountainous regions.

convection initiation; isolated convection; complex terrain; soil moisture; leeside convergence; weak synoptic forcing