Abstract:Extreme precipitation struck Zhejiang Province induced by Typhoon Lekima in 2019. It was found that the spiral rainbelt staggering on the coast of Zhejiang Province during the daytime of 9 August, and rainfall was enhanced significantly due to inner-core convection during Lekima’s landing period over the night. Rainfall centers were significantly related to the near-shore of Tiantai Mountain, Kuocang Mountain and Yandang Mountain in Zhejiang Province. Based on analysis of GPM (Global Precipitation Measure) retrieval cloud parameters, Lekima’s spiral rainbands were dominant by mixed cumulus-stratus precipitation, while eyewall was dominated by tropical warm cloud precipitation. With larger effective diameter of raindrops and the higher density of raindrop particles, extreme rainfall intensity was formed in Lekima’s eyewall. Spiral rainbelt was enhanced due to the low-level frontogenesis and coast convergence during the landing of Lekima. Lekima’s inner-core convection was more intense on the left direction, leading to heavier rainfall on the left side of typhoon’s landing position. By comparing precipitation rate evolution between mountainous and plain areas via statistics with minute-interval automatic weather station observation, it was preliminarily proved that the topographic rainfall enhancing mechanism and the asymmetric inner-core convective structure have almost the same impact on precipitation intensity, both favoring the asymmetrical rainfall concentrating on the left side to Lekima’s forwarding direction.