Research on Fine-Scale Risk Zoning of Hail Disasters in Yunnan Flue-Cured Tobacco Based on Machine Learning

This study explores the thermal, dynamic and environmental conditions for hail formation, and proposes a machine learning method based on random forest models. The methodology incorporates strong convective ingredients such as CAPE, LI, 0°C level height, -20°C level height, along with disaster-prone environmental factors like altitude, slope, and aspect, to objectively analyze hail days. After steps such as training set construction, factor selection, regional modeling, and model training, the Yunnan hail day discrimination model was developed. By integrating DEM elevation data and ERA5 reanalysis-derived convective ingredients, a distribution map of hail days during the climate baseline year over the 1 km × 1 km grid of Yunnan flue-cured tobacco fields was generated. After verification and correction, the natural breakpoint method was used to achieve the refined zoning for hail disaster risk in Yunnan flue-cured tobacco. It was found that the hail disaster risk presents a higher tendency in the north compared to the south, with northern high-altitude areas predominantly at high or moderately high risk, while the low-altitude central and southern mountainous regions display moderate to low risk. Additionally, by employing climatic factors such as average temperature in July, sunshine duration from July to August, and rainfall from April to September, alongside geographical and topographical elements, precise climatic suitability zoning for Yunnan flue-cured tobacco was accomplished. This zoning represents a comprehensive analysis of exposure and vulnerability. Combined with the refined risk zoning of flue-cured tobacco hail disasters, the refined risk zoning of hail disasters in Yunnan flue-cured tobacco was finally achieved. The results indicated an overall east-high, west-low risk pattern: areas east of the Ailao Mountains showed higher risk, while those west exhibited moderate to lower risk. Notably, the high-cold zones in the north-central region and the rainy margins of the south and west demonstrated no risk. This study aims to provide scientific guidance for rational layout and hail prevention work during the field period of Yunnan flue-cured tobacco.