Thermal to Far Infrared (TIR-FIR) Sea-Surface Effective-Emissivity (IRSSE) Model Version 2

Thermal infrared (IR) environmental satellite data assimilation and remote sensing of the surface and lower troposphere depend on accurate specification of the spectral surface emissivity within clear-sky forward calculations. Over ocean surfaces, accurate modeling of surface-leaving radiances over the sensor scanning swaths is complicated by a quasi-specular bidirectional reflectance distribution function (BRDF). Recent findings at the Joint Center for Satellite Data Assimilation (JCSDA) have also revealed significant zonally varying systematic biases (≈|0.5| K) on a global scale over cold ocean waters, these the result of temperature dependence in the thermal IR optical constants. This paper proposes practical solutions to these problems by modeling thermal IR “effective emissivity” in a manner that accounts for both surface emission and quasi-specular reflectance, along with temperature dependence, while meeting the latency and computational constraints of operational global data assimilation and retrieval systems. We overview the theoretical basis of the model and validate it against ship-based Marine Atmospheric Emitted Radiance Interferometer (MAERI) spectra obtained from cold and warm water ocean campaigns.

热红外（IR）环境卫星数据同化和地表及对流层低层遥感依赖于在晴空正向计算中对光谱表面发射率的精确规定。在海洋表面，由于传感器扫描条带上的准镜面双向反射分布函数（BRDF），对表面辐射亮度的精确模拟变得复杂。联合卫星数据同化中心（JCSDA）的最新研究也揭示了在全球冷海洋水域尺度上存在的显著纬向变化的系统性偏差（约|0.5| K），这些偏差是热红外光学常数温度依赖性的结果。本文通过模拟热红外“有效发射率”并提出实际解决方案，这些解决方案在考虑到表面辐射和准镜面反射的同时，还考虑了温度依赖性，同时满足了全球数据同化和检索系统操作中的延迟和计算约束。我们概述了该模型的理论基础，并通过从冷水和温水海洋考察中获得的基于船舶的海洋大气发射辐射干涉仪（MAERI）光谱对其进行验证。