A model for accurately calculating hyper-spectral, middle-shortwave infrared radiative transfer for remote sensing  

作　　者：BAI WenGuang ZHANG Peng ZHANG WenJian MA Gang QI ChengLi 

机构地区：[1]School of Atmosphere Physics, Nanjing University of Information Science & Technology, Nanjing 210044, China [2]National Satellite Meteorology Center, Beijing 100081, China

出　　处：《Science China Earth Sciences》2018年第3期317-326,共10页中国科学（地球科学英文版）

基　　金：supported by the National High Technology Research and Development Program(Grant No.2015AA123704);the National Natural Science Foundation of China(Grant No.41475031);the Special Fund for Scientific Research(Meteorology)in the Public Interest(Grant Nos.GYHY201506074&GYHY201506002)

摘　　要：Although the calculation of radiative transfer in the middle-shortwave infrared band is important in the field of optical remote sensing, studies in this area of research are rare in China. Both solar reflection and atmospheric emission should be considered when calculating radiative transfer in the middle-shortwave infrared band. This paper presents a new radiative transfer model based on the doubling and adding method. The new model uses approximate calculations of direct solar reflection,multiple scattering, and thermal emissions for a finitely thin atmospheric layer and considers both the solar and thermal sources of radiation. To verify its accuracy, the calculation results produced by the model for four typical scenarios(single layer at night,multi-layer aerosols, double-layer with ice and water clouds, and multi-layer with clouds and aerosols) were compared with those of the DISORT model. With the exception of a few channels, the absolute deviation between the two models was less than2×10^(-6) K. For the same calculation, the computation speed of the new model was approximately two to three times faster than that of the DISORT model. Sensitivity studies were performed to evaluate the error resulting from using simplified calculation methods in the new model. The results obtained in this study indicated that atmospheric thermal emission made a significant contribution to the measured radiance in the strong-absorption band(2230–2400 cm^(-1)), whereas solar radiation could be neglected in this region. However, neglecting solar radiation in the window region(2400–2580 cm^(-1)) introduced error on the order of dozens of K. Employing the average-layer temperature method simplified the calculation of thermal radiation but caused a larger error in the strong-absorption band than in the window region. In the doubling and adding method, the calculation error decreased as the value used for minimum optical thickness decreased. Under the condition of satisfying the requirement of calculation precision, we can conAlthough the calculation of radiative transfer in the middle-shortwave infrared band is important in the field of optical remote sensing, studies in this area of research are rare in China. Both solar reflection and atmospheric emission should be considered when calculating radiative transfer in the middle-shortwave infrared band. This paper presents a new radiative transfer model based on the doubling and adding method. The new model uses approximate calculations of direct solar reflection, multiple scattering, and thermal emissions for a finitely thin atmospheric layer and considers both the solar and thermal sources of radiation. To verify its accuracy, the calculation results produced by the model for four typical scenarios （single layer at night, multi-layer aerosols, double-layer with ice and water clouds, and multi-layer with clouds and aerosols） were compared with those of the DISORT model. With the exception of a few channels, the absolute deviation between the two models was less than 2~ 10-6 K. For the same calculation, the computation speed of the new model was approximately two to three times faster than that of the DISORT model. Sensitivity studies were performed to evaluate the error resulting from using simplified calculation methods in the new model. The results obtained in this study indicated that atmospheric thermal emission made a significant contribution to the measured radiance in the strong-absorption band （2230-2400 cm-1）, whereas solar radiation could be neglected in this region. However, neglecting solar radiation in the window region （2400-2580 cm 1） introduced error on the order of dozens of K. Employing the average-layer temperature method simplified the calculation of thermal radiation but caused a larger error in the strong-absorption band than in the window region. In the doubling and adding method, the calculation error decreased as the value used for minimum optical thickness decreased. Under the condition of satisfying the requirement of calculation precision, we ca

关 键 词：Doubling and adding method Radiative transfer calculation Middle-shortwave infrared band Light scattering byclouds and aerosols 

分 类 号：P407[天文地球—大气科学及气象学]