Analysis of Characteristics of Meteorological Elements of Radiation Fog and Rain Fog in Southwestern Hubei

The circulation conditions and characteristics of ground- and high-level meteorological elements of continuous radiation and rain types of fog in southwestern Hubei are analyzed using boundary detection and automatic ground observatory data. The following results are reported: 1) The inverse overlay of a blocking high-pressure ridge and southern trough benefited the occurrence of rain fog in southwestern Hubei. 2) The ground-level visibility and relative humidity exhibited a significant inverse relationship. Rain fog maintenance was nearly synchronous with the precipitation. 3) Ground-level visibility and cloud droplet concentration were more significant than the rain fog inverse relationship with the occurrence of radiation fog. Visibility and rain fog content also exhibited a significant inverse relationship with the occurrence of radiation fog; however, such a relationship did not exist between visibility and rain fog. Low ground-wind speed or calm wind commonly co-existed with radiation and rain types of fog. 4) The upper inversion layer was stronger, the lower inversion layer was weaker, and multi-inversion layers occurred with radiation fog. The bottom inversion layer of the rain fog was higher than that of radiation fog, although the inversion layer was not always present. However, two­-three inversion layers occurred with rain fog. 5) Low boundary-layer wind speed and weak convective activity benefited both fog types occurring in mountainous regions. 6) The saturated air layer height of radiation fog was lower than that of mist.