当前位置： 首页»科研成果» 2013 Estimating the Optimal Broadband Emissivity Spectral Range for Calculating Surface Longwave Net Radiation 程洁、梁顺林、姚云军、张晓通

 

Jie Cheng, Member, IEEE, Shunlin Liang, Senior Member, IEEE, Yunjun Yao, and Xiaotong Zhang

 

College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China;

State Key Laboratory of Remote Sensing Science, Jointly Sponsored by Beijing Normal University and the Institute of Remote Sensing Applications of Chinese Academy of Sciences, Beijing 100875, China;

Department of Geographical Sciences, University of Maryland, College Park, MD 20742 USA.

 

Abstract

Surface broadband emissivity (BBE) in the thermal infrared spectrum is essential for calculating the surface total longwave net radiation in land surfacemodels. However, almost all narrowband emissivities estimated from satellite observations are in the 3–14-μm 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 μm. 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 μm. Using these emissivity spectra, we first investigated the accuracy of replacing allwavelength 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-μm spectral domains. Surface longwave net radiation at 2.5–200 μm was found to be optimal, with a bias and root mean square (rms) of less than 0.928 and 0.993 W/m2, respectively. We calculated the errors when estimating surface longwave net radiation at 2.5–200 μm with BBE in different spectral ranges. The results show that BBE at 8–13.5 μm had the lowest error and the corresponding bias and rms were less than 0.002 and 1.453 W/m2, respectively. When the 2.5–200-μmsurface longwave net radiation calculated by the 8–13.5-μm BBE was used to replace the allwavelength surface longwave net radiation, the average bias and rms were 1.473 and 2.746 W/m2, respectively. Using the most representative emissivity spectra, we derived the conversion formulas for calculating BBE at 8–13.5 μm from the Advanced Spaceborne

Thermal Emission and Reflection Radiometer (ASTER) and the Moderate Resolution Imaging Spectrometer (MODIS) narrowband emissivity products.

 

Key Words: Broadband emissivity (BBE), land surface model, refractive index, remote sensing, surface radiation budget

 

PUBLISHED BY: IEEE GEOSCIENCE AND REMOTE SENSING LETTERS, 2013, 10 (2): 401-405.

 

PDF DOWNLOAD: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=06276235