Simulation of Brightness Temperature in Infrared Channel of FY 2F and Bias Analysis
To assimilate the radiance data of FY 2F imagery directly in West Pacific and East Asian, WRF for Hurricane (HWRF) and Community Radiative Transfer Model (CRTM) are used to simulate the brightness temperature (BT) of FY 2F. Under the cloudy condition, the frontal clouds are well simulated in the middle and high latitude while the substantial bias exists in tropical cloud cluster of low latitude. In the clear sky condition, the BT of infrared channel 1, 2, 4 (IR1, 2, 4) are strongly influenced by the surface emission with big biases above the land because of the inhomogeneity and the radiation transfer model under estimates the emissivity of land on average. Meanwhile it performs well above the ocean surface. The observation of IR4 channel are higher than simulated BT because of the influence of sun radiation. The cloudy contamination data are abandoned to keep the clear sky radiance in Community Gridpoint Statistical Interpolation (GSI). After quality control and bias correction of GSI, the bias of IR2 has a reduction of 50% on average and the average bias of IR3 is decreased from 3.7 K to 0.34 K. The quality of IR1 observation is better than other channels, and there is little change of the bias after correction.