Exploring aerosol-cloud interactions in liquid-phase clouds over eastern China and its adjacent ocean using the WRF-Chem-SBM model

Abstract. This study aims to explore aerosol-cloud interactions in liquid-phase clouds over eastern China (EC) and its adjacent ocean (ECO) in winter based on WRF-Chem-SBM model which couples a spectral-bin cloud microphysics (SBM) and online aerosol module (MOSAIC) as well as the four-dimensional assimilation approach. The model evaluation demonstrates that assimilation has a predominantly favorable impact on the simulation, and the model reasonably reproduces the satellite-retrieved cloud parameters. Differences in meteorological, topographic and aerosol conditions lead to differences in EC and ECO aerosol-cloud processes. Multiple atmospheric supersaturation pathways and abundant aerosols in EC enable more aerosols to be activated, but limited water content makes them difficult to grow into large droplets. While atmospheric supersaturation pathway and aerosol number concentration (N_aero) limit the cloud droplet number concentration (N_d) in ECO, the relatively abundant water content enables more large cloud droplets to exist here. EC and ECO cloud liquid water content (CLWC) exhibit close variation trends with N_d, but differences in aerosols, supersaturation pathways, and water vapor conditions result in distinctions in CLWC variations and the differentiation between precipitation and non-precipitation clouds in the two regions. Meteorological conditions suitable for EC cloud development include (1) weak winds and strong surface radiative forcing cooling, (2) moist air brought by strong easterly winds, (3) cooling and topographic uplift caused by strong northerly winds, and (4) strong updrafts. Meteorological conditions suitable for ECO cloud development include (1) aerosol-rich and not excessively dry airflow from moderate westerly wind, (2) cooling caused by northerly winds, and (3) updrafts. In general, the effect of cooling on aerosol activation is more pronounced compared to humidification in EC and ECO. Moreover, the aerosol conditions suitable for aerosol activation and CLWC increase are similar overall, with the difference being that aerosol activation is strongest under moderate N_aero conditions, whereas high CLWC to N_aero ratios are often seen under low N_aero conditions in addition to moderate N_aero conditions.