Turner D S
Appl Opt. 2000 Nov 1;39(31):5663-70. doi: 10.1364/ao.39.005663.
An underlying assumption of data assimilation models is that the radiative transfer model used by them can simulate observed radiances with zero bias and small error. For practical reasons a fast parameterized radiative transfer model is used instead of a highly accurate line-by-line model. These fast models usually replace the spectral integration of the product of the transmittance and the Planck function with a monochromatic equivalent, namely, the product of a spectrally averaged transmittance and a spectrally averaged Planck function. The error of using this equivalent form is commonly assumed to be negligible. However, this error is not necessarily negligible and introduces a systematic height-dependent bias to the assimilation scheme. Although the bias could be corrected by a separate bias correction scheme, it is more effective to correct its source, the fast radiative transfer model. I examine the magnitude of error when the monochromatic-equivalent approach is used and demonstrate how a fast parameterized radiative model with Planck-weighted mean transmittances can effectively reduce if not eliminate these errors at source. I focus on channel 12 of the High-Resolution Infrared Radiation Sounder onboard the National Oceanic and Atmospheric Administration (NOAA)-14 satellite that, among all the channels of this instrument, displays the largest error.
数据同化模型的一个基本假设是，它们所使用的辐射传输模型能够以零偏差和小误差模拟观测到的辐射亮度。出于实际原因，使用的是快速参数化辐射传输模型而非高精度的逐线模型。这些快速模型通常用单色等效物替代透过率与普朗克函数乘积的光谱积分，即光谱平均透过率与光谱平均普朗克函数的乘积。通常认为使用这种等效形式的误差可以忽略不计。然而，这种误差不一定可以忽略不计，并且会给同化方案带来与高度相关的系统偏差。虽然可以通过单独的偏差校正方案来校正偏差，但校正其源头——快速辐射传输模型会更有效。我研究了使用单色等效方法时的误差大小，并展示了一个具有普朗克加权平均透过率的快速参数化辐射模型如何能够在源头有效减少（如果不能消除）这些误差。我关注的是美国国家海洋和大气管理局（NOAA）-14卫星上高分辨率红外辐射探测器的第12通道，在该仪器的所有通道中，这个通道显示出的误差最大。
