Abstract:

Based on observational data of precipitation fog from 2011 to 2016 in Jiangsu province, we analyzed the synoptic types, the variation of meteorological parameters, and formation mechanisms of precipitation fog events.The results indicated that the main synoptic patterns for precipitation fog events in Jiangsu province include the inverted trough type, the ahead of cold front type, and the bottom of high-pressure type.The inverted trough type occurs most frequently and provides necessary meteorological conditions for the formation of precipitation fog, such as low air pressure, high humidity, low wind speed, ground wind direction shift from east/southeast to north, and high air temperature during the early period.During the formation period of precipitation fog events, positive temperature variability is converted to a weak negative value at 925 hPa over Jiangsu province, indicating that weak and cold air favors the occurrence of precipitation fog events.Weak and cold advection at the bottom of the boundary layer contributes to the condensation of water vapor and the formation of temperature inversion.The strongest temperature inversion corresponds to the lowest visibility.Both the updraft and downdraft with low vertical speeds are observed at the bottom of the boundary layer during precipitation fog events in Jiangsu province.

Key words: Precipitation fog, Synoptic type, Formation mechanism