Monitoring and analysis of heavy fog process in expressway section based on the microwave radiometer data

A heavy fog event during January 2014(i.e., 29-30 January) over Hubei is studied. Based on observed data at automatic meteorological monitoring station (sampling every 2 min), the correlation between visibility and meteorological elements (surface temperature, temperature, relative humidity, etc.) were analyzed. Using the microwave radiometer data at 2 stations in Hubei, the temporal and spatial variations of water vapor and liquid water content retrieved from the microwave radiometer data are presented. The results show that during the formation phase of heavy fog, the temperature and the road surface temperature decrease, visibility decreases, and the rate of decline is obvious. During the period of development of heavy fog, the temperature and the road surface temperature change smoothly, the visibility is less than 100 meters. During the extinction stage of heavy fog, the temperature and surface temperature increase, visibility increases and the fog diffuses. Fog occurs under the environment of a specific atmospheric circulation. By analyzing the microwave radiation data, it is found that near-surface inversion is an important condition for the generation of heavy fog, and its evolution has a good corresponding relationship with the development of heavy fog. During the development of dense fog, the water vapor density gradually increase from the surface upward. The near-surface liquid water content raises. The relative humidity saturation area raises in height. The thick fog thickness increases. The fog concentration increases, and the visibility decreases. During the period of the disappearance of heavy fog, the liquid water content and water vapor density are significantly reduced. The relative humidity saturation area is highly reduced. The thick fog thickness is thinned. The fog concentration is reduced and the visibility increases.