Numerical Simulation and Weather Diagnosis of a Dense Fog in Tianjin Region

A dense fog on 28 Nov 2011 in Tianjin region is simulated and diagnosed with WRF model. A reasonable of micro-physical processes and parameters of the program is selected in the simulation .The results showed that: the selected WRF program can simulate the whole process of the fog .The key reasons about the formation of fog are below: strong warm vapor transportation and the plenty of local atmospheric vapor, a strong low-level temperature advection , the weak convergence of vapor decrease the temperature, below 850hpa the following continued weak wind and atmospheric stratification stability that created a stable circumstance. This fog is one typical advection and radiation fog. With near-surface strong wind, especially around 850hpa cold advection cooling the temperature of high place and turbulent transport and moisture divergence of weak sinking motion warming the temperature of lower place, the progress destroyed the atmosphere stable stratification. The fog weakened and dissipated.