Objective Classification and Environmental Characteristics of Different High-Wind Types in the Mid- and Lower Reaches of the Yangtze River Basin

This study develops an objective attribution framework, integrating a two-step K-means clustering procedure with a random forest algorithm, to classify the weather systems responsible for high winds over the mid- and lower reaches of the Yangtze River from 2020 to 2023. The analysis utilizes hourly automatic weather station observations, ERA5 reanalysis, and merged precipitation data. Four dominant HW types are identified: cold-air (CAHWs, 40.3%), tropical-cyclone (TCHWs, 27.9%), convective-system (CSHWs, 22.2%), and a residual “other” category (9.6%). Three main types exhibit distinct spatiotemporal distributions and environmental characteristics. CAHWs occur mainly in spring, autumn, and winter, concentrated in three sub-regions within the terrain channel or above the lake surface. CAHWs are characterized by non-precipitating northerlies associated with deformation frontogenesis and modulated by boundary layer processes, including terrain channeling and surface friction. TCHWs are confined to coastal areas in July and September, primarily controlled by tropical cyclone motion and land-sea distribution. CSHWs peak in afternoons from March to October and can be further divided into precipitating (PCSHWs, 40.3%) and non-precipitating (NPSCHWs, 59.7%) types. NPCSHWs typically occur in precipitation-free zones within 50 km of convective systems producing moderate to heavy rainfall, whereas PCSHWs form in smaller convective systems along the periphery of precipitation regions rather than within heavy-rainfall cores. PCSHWs are associated with higher instability, stronger low-level shear, and weaker inhibition than NPCSHWs, indicating a more organized convective environment.