Wei Heli, Chen Xiuhong, Rao Ruizhong, Wang Yingjian, Yang Ping
Opt Express. 2007 Jun 25;15(13):8360-70. doi: 10.1364/oe.15.008360.
A fast narrowband transmittance model, referred to as the Fast Fitting Transmittance Model (FFTM), is developed based on rigorous line-by- line (LBL) calculations. Specifically, monochromatic transmittances are first computed from a LBL model in a spectral region from 1 to 25000 cm(-1) for various pressures and temperatures ranging from 0.05 hPa to 1100 hPa and from 200 K to 320 K, respectively. Subsequently, the monochromatic transmittances are averaged over a spectral interval of 1 cm(-1) to obtain narrowband transmittances that are then fitted to various values of absorber amount. A database of fitting coefficients is then created that can be used to compute narrowband transmittances for an arbitrary atmospheric profile. To apply the FFTM to an inhomogeneous atmosphere, the Curtis-Godson (CG) approximation is employed to obtain the weighted effective coefficients. The present method is validated against the LBLRTM and also compared with the high-spectral-resolution measurements acquired by the Atmospheric Infrared Sounder (AIRS) and High-resolution Interferometer Sounder (HIS). With a spectral resolution of 1 cm(-1) and a wide spectral coverage, the FFTM offers a unique combination of numerical efficiency and considerable accuracy for computing moderate- to high-spectral-resolution transmittances involved in radiative transfer simulations and remote sensing applications.
一种快速窄带透过率模型，称为快速拟合透过率模型（FFTM），是基于严格的逐线（LBL）计算开发的。具体而言，首先从LBL模型计算1至25000 cm⁻¹光谱区域内各种压力和温度下的单色透过率，压力范围为0.05 hPa至1100 hPa，温度范围分别为200 K至320 K。随后，将单色透过率在1 cm⁻¹的光谱间隔上进行平均，以获得窄带透过率，然后将其拟合到不同的吸收体含量值。接着创建一个拟合系数数据库，可用于计算任意大气廓线的窄带透过率。为了将FFTM应用于非均匀大气，采用柯蒂斯-戈德森（CG）近似来获得加权有效系数。本方法针对LBLRTM进行了验证，并与大气红外探测器（AIRS）和高分辨率干涉仪探测器（HIS）获取的高光谱分辨率测量结果进行了比较。FFTM具有1 cm⁻¹的光谱分辨率和广泛的光谱覆盖范围，为计算辐射传输模拟和遥感应用中涉及的中高光谱分辨率透过率提供了数值效率和相当精度的独特组合。
