普朗克权重订正对风云卫星快速正演精度的改进

本文在逐线积分(LBL)计算卷积大气透过率的基础上,建立了统一框架的快速透过率回归算法用于卫星红外传感器通道辐射快速正演的实现.通过分别对风云二号自旋扫描辐射计VISSR/FY-2F和风云三号红外分光计IRAS/FY-3B的红外通道进行正演,并与LBL积分的通道亮温进行对比分析.结果表明,快速正演模型在窗区红外通道亮温的标准差(STD)远大于垂直探测通道的正演,随着通道探测高度降低,正演偏差随之增大;并且,全部通道正演的STD最大值小于0.4 K.本文还讨论了在卷积通道透过率时引入普朗克函数作为权重因子以改进红外通道的快速正演精度.提出以2350 cm-1与通道光谱响应曲线的相交作为应用启动普朗克订正的必要条件.试验结果表明:普朗克权重订正可以使快速正演模型的精度提高约25%以上,这个订正仅对通道光谱响应与2350 cm-1相交的通道有效,当通道光谱响应与2350 cm-1不相交,普朗克订正效果明显下降.试验还表明,普朗克订正的效果不仅对宽光谱的成像通道有效,对窄光谱垂直探测通道的正演精度改进同样明显.

An improvement in fast radiative transfer calculation of FengYun satellite by Planck weighting correction

A unified regression method to calculate fast transmittance coefficients is used in fast radiative transfer calculation of satellite infrared channel by a convoluted transmittances database from LBL (Line_By_Line) model. Comparison is performed between the fast calculated brightness temperature and LBL calculations for VISSR/FY-2F and IRAS/FY-3B. The examination indicates that STD (Standard Deviation) of fast calculated brightness temperature in window channels are much larger than the values in sounding channels. The lower atmosphere the channel detects, the larger the STD is available. And the largest the STD is less than 0.4 K. In this paper, a discussion is given to the improvement of fast radiative transfer calculation brought about by Planck weighted correction for convoluted channels' transmittances. Analysis shows that overlap between 2350 cm^-1 and spectral response filter of the channel is a requirement to the Planck weighted correction. It is shown that STDs of brightness temperature between LBL calculation and fast computation are decreased by 25% after Planck weighted correction. And the improvement is available only for such channels with an overlap between their filter function and 2350 cm^-1. Also it is indicated that the improvement from Planck weighted correction could be used not only to the imaging channels that have wide spectral coverage, but also to the sounding channels with very narrow spectral fields.
Keywords： Planck weighted correction -1')" href="#">channel at 2350 cm^-1 fast radiative calculation Fengyun satellite