Abstract:The circulation background and characteristics of meteorological element distribution are analyzed on a wide spread radiation fog that occurred in January 2010 over the Central China area. Observation and simulation of the wide spread radiation fog over Hunan are investigated by using a new generation of high resolution Weather Research and Forecasting (WRF) Model. The results show that there are two obvious inversion layers occurring in the evolution process of the radiation fog. One is the subsidence inversion formed by the high altitude systemic northerly airstream, which is located near 700 hPa with the stable atmospheric stratification, and thus low level water vapor can not be propagated upward, and therefore provides high humidity conditions for the fog formation. The other is the radiation inversion formed from the surface cooling effect of radiation, which is the main factor for the formation and development of this fog. However, for the dissipation of the fog the main cause is the surface heating by solar shortwave radiation after sunrise and heat transportation. In addition, it shows that there are better simulation results by using WRF model when T213 data are used as the initial conditions instead of NCEP reanalysis. The overlap zone of the maximum U value below 900 m with large inversion ≥ 5℃ corresponds well with the fog. At the north of the rivers and lakes, moreover after high ridge changed into high rear sector near the surface, the advection fog appears likely due to the effect of water vapor transport by low level southerly flow. There is a gap of the near surface layer of elements between the simulation from WRF model and observations, and the assimilation of observation data must be considered in the simulation.