Fog Numerical Simulation Of Its Observations

In this study, the mechanism of the dense fog occurred in Beijing and the area around it at 12~14, December, 2002 was simulated by MM5 initiated with NCEP reanalysis data. The mechanism of formation and maintenance of the fog are analyzed.It showed that MM5 could well simulate the occurrence and development of the dense fog. The results of simulation in formation and dissipation of the fog are coincided with the real situation. In the same time, the physical process of formation and development is also discussed. Sensitive experiments are performed for understanding the role of radiation. The results showed that long wave radiation cooling is very important for the formation of the fog, in addition to steady atmospheric stratification and plenty of moisture. The process of fog microphysics near the ground, and the stronger radiation cooling at the top of the fog, result in the burst development of fog. The fog dissipation was influenced most by shortwave radiation. In addition, the sustentation of the deep inversion play a decisive role in the course of prolonged fog.Heavy fog occurred at xi' an area , Shanxi province at 18~19, December, 2004 also was studied. A tri-combination droplets spectral meter was used for sampling fog spectra, the Particle Measuring System (PMS) and visibility instrument was used to obtain particle concentration and fog visibility. The evolution of macrostructure and microstructure are analyzed, and the relation between the macrostructure and microstructure are also studied based on the data from the tri-combination droplets spectral meter, PMS and visibility instrument. The connection between the surge in the fog microstructure and the physical development, the characteristicof fog spectra in differ seedtime are analyzed, and the course of fog was simulated by MM5.