Opposing Trends in Wintertime Convective Initiation Environments of East China Driven by Anthropogenic Aerosols and Greenhouse Gases

Winter convection can trigger severe disasters due to low temperature, yet the drivers and mechanisms of regional long-term trends in winter convective initiation remain unclear. Using homogenized radiosonde data, we reveal the spatially divergent trends in wintertime atmospheric unstable conditions, with a significant decrease in the northern part of East China (NEC, north of 33°N, east of 105°E) but an increase in the southern part of East China (SEC, south of 33°N, east of 105°E) during 1979–2020. CMIP6 Detection and Attribution Model Intercomparison Project confirms that these opposing trends are driven by anthropogenic forcings, with aerosols being the primary contributor to the decreases in NEC (33∼66 while greenhouse gases driving the increase in SEC (54∼77. Both CMIP6 and further WRF-Chem experiments indicate that aerosol-induced stabilization primarily results from stronger radiative cooling at the surface than in the lower troposphere, with its effects exhibiting a pronounced north-south contrast across China. In NEC, weak convection confines aerosols, making it the dominant suppressing factor. In SEC, strong convection disperses aerosols to moderate direct cooling, and aerosol-induced drying raises the lifting condensation level, extends the dry adiabatic ascent, and inhibits the level of free convection attainment. Our findings clarify the competing impacts of anthropogenic emissions on regional climate and underscore the need for balanced emissions-control strategies to mitigate disruptions caused by hazardous winter weather.