Analysis of the Micro-Meteorologic Element During the Advection Fog Period in the South of Tianjin City

The micro-meteorological elements of an advection fog, which occurred in Feb. 2006, were analyzed by using data from the Tianjin Meteorological Boundary Layer Tower. The results show that temperature inversion and higher humidity are due to the warm and moist south-west advection, which provides the necessary conditions for the formation and maintaining of the advection fog. The advection fog comes under the weak unstable condition. There are double-inverse temperatures during the fog period with wind speed decreasing and wind direction shearing. The fog dissipates from higher to lower layers with dry and cold air coming from the northwest associated with a cold front. The long-lasting fog at lower layers is due to the subsidence inverse of cold air. There is a close correlation between the characteristics of temperature profile and thickness of fog.