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首页> 外文期刊>Geoscience and Remote Sensing Letters, IEEE >Estimating the Optimal Broadband Emissivity Spectral Range for Calculating Surface Longwave Net Radiation
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Estimating the Optimal Broadband Emissivity Spectral Range for Calculating Surface Longwave Net Radiation

机译：计算表面长波净辐射的最佳宽带发射光谱范围的估算

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摘要

Surface broadband emissivity (BBE) in the thermal infrared spectrum is essential for calculating the surface total longwave net radiation in land surface models. However, almost all narrowband emissivities estimated from satellite observations are in the 3–14-$muhbox{m}$ spectral region. Previous studies converted these narrowband emissivities to BBE over different spectral ranges, such as 3–14, 8–12, 8–13.5, and 8–14 $muhbox{m}$ . Errors in the calculated total longwave net radiation must be quantified systematically using these BBEs. Moreover, the best spectral range for longwave net radiation must be determined. The key to addressing these issues is the use of the realistic emissivity spectra. By applying modern radiative transfer tools, we derived the emissivity spectra of water, snow, and minerals at 1–200 $muhbox{m}$ . Using these emissivity spectra, we first investigated the accuracy of replacing all-wavelength surface longwave net radiation with the surface longwave net radiation in the 3–100-, 4–100-, 2.5–100-, 2.5–200-, and 1–200-$muhbox{m}$ spectral domains. Surface longwave net radiation at 2.5–200 $muhbox{m}$ was found to be optimal, with a bias and root mean square (rms) of less than 0.928 and 0.993 $hbox{W/m}^{2}$, respectively. We calculated the errors when estimating surface longwave net radiation at 2.5–200 $muhbox{m}$ with BBE in different spectral ranges. The results show that- BBE at 8–13.5 $muhbox{m}$ had the lowest error and the corresponding bias and rms were less than 0.002 and 1.453 $hbox{W/m}^{2}$, respectively. When the 2.5–200-$muhbox{m}$ surface longwave net radiation calculated by the 8–13.5-$muhbox{m}$ BBE was used to replace the all-wavelength surface longwave net radiation, the average bias and rms were 1.473 and 2.746 $hbox{W/m}^{2}$, respectively. Using the most representative emissivity spectra, we derived the conversion formulas for calculating BBE at 8–13.5 $muhbox{m}$ from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Moderate Resolution Imaging Spectrometer (MODIS) narrowband emissivity products.
机译：热红外光谱中的表面宽带发射率（BBE）对于计算陆地表面模型中的表面总长波净辐射至关重要。但是，根据卫星观测估计的几乎所有窄带发射率都在3–14-muhbox {m} $光谱范围内。先前的研究将这些窄带发射率在3–14、8–12、8–13.5和8–14 $ muhbox {m} $的不同光谱范围内转换为BBE。必须使用这些BBE系统地量化所计算的总长波净辐射中的误差。此外，必须确定长波净辐射的最佳光谱范围。解决这些问题的关键是使用实际的发射率光谱。通过应用现代的辐射传递工具，我们得出了水，雪和矿物质在1–200 $ muhbox {m} $处的发射光谱。使用这些发射率光谱，我们首先研究了在3-100、4-100、2.5-100、2.5-200和1-中用表面长波净辐射代替全波长表面长波净辐射的准确性。 200- $ muhbox {m} $频谱域。发现在2.5–200 $ muhbox {m} $处的表面长波净辐射最佳，其偏差和均方根（rms）分别小于0.928和0.993 $ hbox {W / m} ^ {2} $ 。当使用不同光谱范围的BBE估计2.5–200 $ muhbox {m} $的表面长波净辐射时，我们计算了误差。结果表明，BBE在8–13.5 $ muhbox {m} $处具有最低的误差，相应的偏差和均方根分别小于0.002和1.453 $ hbox {W / m} ^ {2} $。当使用8–13.5- $ muhbox {m} $ BBE计算的2.5–200– $ muhbox {m} $表面长波净辐射代替全波长的表面长波净辐射时，平均偏差和rms为1.473和2.746 $ hbox {W / m} ^ {2} $。使用最具代表性的发射率光谱，我们从先进的星载热发射和反射辐射计（ASTER）和中分辨率成像光谱仪（MODIS）窄带发射率产品中得出了用于计算8–13.5 $ muhbox {m} $的BBE的转换公式。

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