Research on Assimilation of Surface Observation Data in GRAPES Model

Numerical experiments about the precipitation occurred in Sichuan Province in early July 2012 were carried out by using operational mesoscale numerical model GRAPES-MESO (Version 3.1) with four kinds of surface observation data assimilation and the control experiment. The results are as follows: different degree of false precipitation and missing precipitation was discovered among the five numerical simulations of different area and different magnitude of precipitation. Among all these simulations, the severity of false and missing precipitation in the control experiment and the assimilation of horizontal wind were more than the others; the reliebility of each simulation decreased with increasing simulation time; the assimilation impact of four assimilation methods were instable as the time of simulation increased, the method assimilating all of surface observation factors were relatively stable; in the beginning and the end of simulation, the scheme that assimilating all the observation data had the relatively obvious effect, assimilation of horizontal wind had the little effect; during the middle period of simulation, all the simulation scheme became instable; with the increasing of simulation time, the difference among all of the simulations decreased, but increased between the simulation and the observation.