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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 (Naero) limit the cloud droplet number concentration (Nd) 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 Nd, 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 Naero conditions, whereas high CLWC to Naero ratios are often seen under low Naero conditions in addition to moderate Naero conditions. [ABSTRACT FROM AUTHOR]

This study aims to explore aerosol-cloud interaction over eastern China (EC) and its adjacent ocean (ECO) in boreal winter by coupling of a spectral-bin cloud microphysics (SBM) and an online aerosol module (MOSAIC) in WRF-Chem, with the support of four-dimensional data assimilation. The evaluation shows that assimilation has an overall positive impact on the simulation, and the coupling system reproduces the satellite-retrieved cloud parameters while exhibiting significantly improved simulation ability compared to the original SBM scheme as well as the bulk microphysical and MOSAIC coupling system. Differences in aerosol composition and physical processes lead to clear discrepancies in the aerosol-cloud interactions of EC and ECO during the simulation period. In EC with the gradual increase of aerosol number concentration (Naero), cloud droplet number concentration (Nd) first increases then decreases and fluctuates around 800 cm-3, while Nd in ECO increases faster initially, but soon its activation is suppressed by aerosol hygroscopicity and high activation threshold of numerous small particles, and almost no additional cloud droplets are produced. In terms of rapid adjustments, more bursty atmospheric supersaturation and lack of subsequent water cause cloud liquid water content (CLWC) in EC to increase explosively with Nd when there are few cloud droplets, but only maintains a low increase rate with further increasing Nd. ECO exhibits a fast increase in CLWC with Nd at high proportion of naturally emitted large aerosol particles, but its CLWC increase gradually stagnates as Nd increases. For non-precipitating clouds with less water content, CLWC in EC increases slowly with Nd, but can maintain a stable trend. While ECO, which relies mainly on large scale water and temperature variations to reach supersaturation, the increase in Nd leads to a decrease in CLWC. [ABSTRACT FROM AUTHOR]