FY 2F红外亮温资料模拟与偏差分析

为了实现西太平洋及东亚区域FY-2F可见红外自旋扫描辐射计(VISSR)资料的直接同化,本文利用飓风天气预报模式(WRF For Hurricane,HWRF)和快速辐射传输模式(Community Radiative Transfer Model,CRTM)对FY-2F的亮温资料进行了模拟。在有云情况下,中高纬度锋面云系模拟的相对较好,而低纬热带云团模拟偏差较大。对于晴空条件下模拟的红外1、2、4通道(IR1、2、4)亮温,受陆地下垫面发射率不均匀的影响模拟偏差较大,且辐射传输模式平均而言低估了地表发射率。海洋下垫面的资料模拟情况要明显好于陆地。IR4通道在白天受太阳短波影响观测亮温偏高。去除受云污染的资料仅保留晴空观测资料,通过格点统计插值(Community Gridpoint Statistical Interpolation,GSI)质量控制和偏差订正,IR2通道平均偏差减小约50%,IR3通道平均偏差从3.7 K减小到0.34 K。而IR1通道质量较好,偏差订正前后几乎没有变化。

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.