Microphysical characteristics of sea fog over the east coast of Leizhou Peninsula, China

Microphysical properties of sea fog and correlations of these properties were analyzed based on the measurements from a comprehensive field campaign carried out from 15 March to 18 April 2010 on Donghai Island (2135N, 110325E) in Zhanjiang, Guangdong Province, China. There were four types of circulation pattern in favor of sea fog events in this area identified, and the synoptic weather pattern was found to influence the microphysical properties of the sea fogs. Those influenced by a warm sector in front of a cold front or the anterior part of low pressure were found to usually have a much longer duration, lower visibility, greater liquid water content, and bigger fog droplet sizes. A fog droplet number concentration of N1 cm－3 and liquid water content of L0.001 gm3 can be used to define sea fogs in this area. The type of fog droplet size distribution of the sea fog events was mostly monotonically-decreasing, with the spectrum width always being 20 m. The significant temporal variation of N was due in large part to the number concentration variation of fog droplets with radius 3 m. A strong collection process appeared when droplet spectrum width was 10 m, which subsequently led to the sudden increase of droplet spectrum width. The dominant physical process during the sea fog events was activation with subsequent condensational growth or reversible evaporation processes, but turbulent mixing also played an important role. The collection process occurred, but was not vital.