Role of low-level jet evolution in vertical aerosol redistribution: a Doppler wind lidar study over East China

Low-level jets (LLJs) play an important role in aerosol transport and boundary-layer processes. This study utilizes coherent Doppler wind lidar observations to investigate the relationship between LLJ evolution and vertical aerosol redistribution during two dust episodes over Hefei, East China. Results show that changes in LLJ core height are associated with distinct aerosol distribution patterns during the two dust events. In the April 2021 event, the northwesterly jet core exhibits a dynamic vertical migration, descending from 2.5 to 0.3 km before reascending to 1.0 km during the surface PM 10 peak (410 µg m −3 ). The descending jet is accompanied by enhanced vertical wind shear (>0.04 s −1 ) near the lower jet interface and increased spectral width, together with a downward shift in the enhanced backscatter region. These changes coincide with the rapid increase in surface PM 10 concentration, suggesting that enhanced dynamical variability and mixing conditions may have contributed to the downward redistribution of dust. Conversely, the March 2022 event is characterized by a relatively stable LLJ core and persistent lower tropospheric stability, which is associated with the persistence of aerosols within an elevated layer. Persistent wind shear and enhanced spectral width below the LLJ core coincided with the enhanced backscatter region. The PM 10 peak occurred at 16:00 LT (UTC+8 h) on 14 March 2022, approximately 8 h after the inferred onset of frontal influence, coinciding with weakening lower tropospheric stability and changes in the backscatter structure above the site. Wind hodographs show a clockwise rotation of wind vectors that is qualitatively consistent with a possible contribution from inertial oscillation during LLJ evolution. Overall, the observations suggest two contrasting aerosol redistribution processes associated with LLJ evolution: rapid downward redistribution during jet descent and delayed surface influence when aerosols remain elevated under stable conditions. The results provide an observational basis for refining boundary-layer parameterizations in numerical weather prediction and air quality models.