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Abstract:
Based on the finely resolved CloudSat data products from 2007 to 2010, the microphysical characteristics of precipitating and non-precipitating stratocumulus clouds over Eastern China are investigated in this study, cloud microphysical mechanism evolution during the development of stratocumulus clouds which are divided into five groups based on the magnitude of liquid water path are studied, and the sea-land difference in cloud microphysical properties are also examined. The quantity value of liquid water path in the precipitating stratocumulus clouds is greater than that in the non-precipitating stratocumulus clouds. In non-precipitating stratocumulus clouds, the condensation process is the primary mechanism for hydrometeor particle growth, but this mechanism is inversely proportional to the particle radius, therefore, it is difficult for cloud droplets to form drizzle or raindrops simply through condensational growth. In the vigorous developmental stage of non-precipitating stratocumulus clouds, the relatively feebler coalescence process appeared in the upper layers of clouds. The coalescence process becomes evident in precipitating stratocumulus clouds. When the cloud liquid water path is less than 500 g·m-2, cloud droplets grow in size continuously by the coalescence process as they fall through the entire cloud layer, and the raindrops appear near the cloud base. When the cloud liquid water path becomes larger than 500 g·m-2, the coalescence process occurs mostly in the upper layers. In the middle part of the cloud, the transition from cloud droplets to raindrops is most active, and the maximum values of cloud liquid water content, liquid number concentration and liquid effective radius appear in this level. The difference in cloud microphysical properties between sea and land can be accounted for the difference in updraft strength and aerosol concentration, aerosols produced by anthropogenic activity over land areas can act as the cloud condensation nuclei and promote the cloud droplets condensation process, thus the values of cloud microphysical properties over the land are greater than that over the sea. While in the upper layers of clouds, cloud droplets condensational growth is limited, sufficient moisture over the sea becomes more crucial in the development of non-precipitating stratocumulus clouds. As for precipitating stratocumulus clouds with liquid water path greater than 500 g·m-2, the stronger updrafts in clouds over land can prolong the lifetime of smaller particles and promote particle growth in vicinity of cloud top, meanwhile, the values of cloud microphysical properties are greater over the land.
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