Characteristics of the Macro- and Micro-Structures of Different Grades of Fog in Jiangsu, China

Based on the minute-resolution meteorological elements data observed at 70 automatic weather stations in Jiangsu, the second-resolution sounding data of 3 sounding stations and the fog droplet spectrum data of 21 dense fog events, from January 1, 2013 to December 31, 2023, the spatial and temporal distribution, boundary layer structure and microphysical structure characteristics of the fog at different grades in Jiangsu were analyzed. The results show that in recent years, the number of fog hours in Jiangsu are distributed along the Yangtze River and to the north along the Huaihe River. The average annual fogging time at each station is 318.5h, the strong dense fog and extremely dense fog were mainly concentrated along the Huaihe River and its north, accounting for 16.4% of the total fog hours. The probability of occurrence of fog in Jiangsu is the highest at 05:50, and the probability of occurrence of fog in winter, spring, summer and autumn is the highest at 07:10, 05:50, 05:20 and 05:50, respectively. The temperature structure of fog at different grades between 0 and 1500 m has inversion layer, and with the increase of fog intensity, the inversion intensity increases. And the relative humidity is saturated in the lower layer, but with the increase of fog intensity, the relative humidity of upper layer decreases. With the increase of fog intensity, the number of fog drops of different sizes all increase, and the spectrum of fog drops expands obviously when strong dense fog or extremely dense fog occurs.