光学厚度预报因子对风云四号卫星扫描辐射计r红外通道快速正演精度的影响分析

摘要

The fast radiative transmission model can quickly calculate the transmittances coefficients by extending a series of optical depth core functions and channel spectral characteristics, so as to obtain an accuracy that is compatible with the line-by-line model.In this paper, four fast forward operators are established to predict the optical depth ( OD) of mixed gas, water vapor line absorption and water va-por continuum absorption of RTTOV v7, v8, v9 and CRTM v2.1 in 6 infrared channels of AGRI in FY-4 .The largest STDs of all the four fast operators are less than 0 .6 K in brightness temperature of AGRI.The STD of water vapor, CO2 and channel transmittances simulation in RTTOV v9 are the smallest among the four models.And the errors are less in lower levels than that of higher levels in the channel transmittances simulation.Experiments were also conducted using standard atmospheric profiles to calculate the Jacobine and OD of the mixed gas, water vapor absorption and water vapor continuum absorption .The OD errors of the mixed gas decrease with the new information of the deviations of real atmosphere profiles and the reference ones in v9.Simulations of OD of water vapor are improved by 19 water vapor line absorption profiles and 4 water vapor continuum absorption ones in v9.%快速辐射传输模式利用光学厚度预报因子与卫星通道光谱特征系数可实现通道透过率的快速计算,并达到与逐线积分模式相当的正演精度.针对FY-4 AGRI的6个红外通道,分别建立了基于RTTOVv7、v8、v9和CRT-Mv2.1(以下简称四种模式)光学厚度预报因子的快速正演算子,与逐线积分模式的结果对比,分析了四种快速正演算子中均匀混合气体、水汽线吸收和水汽连续吸收预报因子对正演误差的影响.分析表明,四种快速正演模式计算通道亮温与逐线模式结果相比,在温度探测通道的最大标准差要小于0.6K.v9模式在水汽和温度通道的正演误差远小于其他三个模式;四个模式在窗区通道的误差基本相当.v9模式预报因子中,引入实时大气与参考大气的整层离差减小了均匀混合气体光学厚度的正演误差.