Characterizing Free-Atmospheric Wind Fields and Their Statistical Associations with Aerosol Variability in the Huaihe River Basin

Abstract

The Huaihe River Basin (HRB) experiences pronounced seasonal circulation and recurrent aerosol pollution, yet continuous observations of wind structure above the atmospheric boundary layer remain limited. We integrate rotary Rayleigh Doppler wind lidar (RRDWL) measurements and radiosonde profiles with ERA5 re-analysis, MERRA-2 aerosol optical depth (AOD), surface PM2.5 observations, and selected HYSPLIT trajectories to characterize free-atmospheric wind variability and assess its statistical relationships with regional aerosol conditions. During periods of concurrent observation, RRDWL, radiosonde, and ERA5 profiles consistently capture the dominant features of the wind structure between 11 and 30 km, although agreement weakens near the tropopause. ERA5 data for 2017–2023 reveal pronounced seasonal variability, with stronger upper-tropospheric winds in spring, autumn, and winter than in summer. Enhanced boundary-layer ventilation generally coincides with lower surface PM2.5 concentrations, but the strength and direction of this relationship vary among cities and time periods. The observed probability of elevated-PM2.5 episodes is highest under westerly and northwesterly flow, while selected-event trajectories indicate air-mass pathways originating from, or passing through, western and northern sectors. Seasonal AOD distributions reveal substantial spatial and temporal variability in column-integrated aerosol loading. These results provide a vertically resolved, multi-dataset characterization of atmospheric wind variability over a monsoon-influenced basin and establish an observational framework for distinguishing statistical wind–aerosol relationships from mechanistic interpretations of aerosol transport.