A Study On The Characteristics Of Dense Fogs In Jiangsu Province During Autumn And Winter

Based on normal NCEP reanalysis, observation data, wind profiler data and so on, successive fogs of autumn and winter in Jiangsu are analyzed with focus on characteristics, formation and dissipation.The basic circulation in Jiangsu dense fog is summarized.1. We get the basic circulation situation and main impact system in Jiangsu continuous dense fog by comprehensively analyzing the history of Jiangsu fogs. The favorable conditions for developing dense fog are westerly flowing weak temperature advection in the mid-latitude at 500hPa and small wind speed which has big Southerly components to deliver vapor at 700hPa and warm center or warm ridge inland, uniform pressure, field anticyclone in The East China Sea to deliver vapor at 850hPa. The favorable conditions for maintaining dense fog are stable situation and vapor transporting wind, flow field, energy field. The favorable conditions for dissipating dense fog are adjustment of the circulation situation and invasion of cold air,enlarge of The north wind and enhancement of turbulence.2. Get the development characteristics of different dense fog and their thermal and kinetic factors of maintenance by analyzing different types of dense fog. Radiation-advection fog formed by radiation cooling, low-level warm and wet advection changed radiation fog to advection fog. The favorable dynamic conditions for maintaining dense fog were upper- and middle-level convergence and subsidence warming and low-level weak upward movement of flow, and stable temperature inversion layer inhibiting vertical movement. The radiation fog formed by radiation cooling upper- and low-level vapor conditions maintained by middle-level inversion and ground inversion with help of boundary low-level jet. The warm and wet advection fog formed by warm wet advection flowing into Jiangsu from the sea and maintained by vapor from southeast at 925hPa, stable inversion and weak turbulence. The radiation-cooling fog generated in front and behind of the cold front and around frontal zone formed by cool advection. Early vapor accumulation and vapor maintained by the inversion, convergence in the fog area of vapor flux divergence at 1000hPa and divergence at 950hPa were dynamic conditions for maintaining dense fog.3. Get the characteristics of two kinds of fogs through the comparison and analysis by numerical simulation. The continuous fog and three successive fogs are analyzed to get the result: they happen and maintain when circulation are two slots and a ridge at 500hPa and different ground situation.Enhanced reasons were different when the fogs were different, three successive fogs were enhanced by different reasons for different fog types. The vapor source of the continuous process of fog is the East China Sea, and the two parts of vapor source of three successive fogs are Bohai Sea and East China Sea. The fog diminished under different cold air, the cold air which made three successive fogs diminished is stronger and wider range.4. Explore the influences of different schemes and physical processes on formation and development of fogs in Jiangsu. The results show that the radiation is the most important factor in the formation and development of fog. The fog can’t generate without radiation. The effect of clouds for radiation fog is also very obvious. Without the influence of cloud, the strength and scope of the formation of radiation fog becomes small.