Weather Characteristics and Formation Mechanism of Summer Heavy Fog in Chengdu Shuangliu Airport
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Graphical Abstract
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Abstract
Based on the NCEP 1°×1° reanalysis data and automatic observing data of Chengdu Shuangliu airport,characteristics of meteorological elements of summer heavy fog were analyzed statistically. By using the method of composition analysis,the heavy fog events occurred from 2003 to 2015 were also studied. The results show that the summer heavy fog in Chengdu Shuangliu Airport is radiation fog with shorter duration. Southerly and southwesterly wind with low speed is found during the occurrence of heavy fog. The heavy fog occurs in the negative vorticity areas behind precipitation system. The presence of pre- precipitation provides the water vapor for the fog event. The relative humidity is above 80% at 20 o'clock last night,and generally more than 92% when heavy fog occurs. Under stable high- pressure system situation,the invasion of dry air in the middle and high troposphere makes configuration of dry upper- level and wet lower- level maintained in Shuangliu airport. Downdraft benefits subsidence warming in upper air and radiative cooling near the ground,which form isotherm or inversion structure. These all lead to the setting- up of stable stratification,which is favorable for formation of fog.
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