A regional FY-3A VIRR radiance-bias correction scheme for assimilation

Data assimilation is important to the improvement of numerical weather prediction (NWP). Recently, much progress has been made in the direct assimilation of satellite radiance in NWP. In order to use radiance from the infrared channels of the visible and infrared radiometer (VTRR) on FY-3A, biases between the observed radiances and those simulated from model must be corrected. Using the radiosonde data as the input of rapid radiant transfer model CRTM, the simulation error of infrared channels observation of VIRR is analyzed. Based on the analytic results, a regional VIRR radiance bias correction scheme for FY-3A is developed by taking into account both instrument characteristics and observed bias for different types of ground objects in China. The preliminary test result is encouraging, and the scheme is expected to be used in the operational NWP data assimilation system in China.