AMT Atmospheric Measurement Techniques AMT Atmos. Meas. Tech. 1867-8548 Copernicus Publications Göttingen, Germany 10.5194/amt-3-1667-2010 Possible shift of spectral response function of the MODIS 6.8 μm water vapor channel causing a cold bias of 2–3 K Sohn B. J. 1 Kim B.-R. 1 Lee S.-S. 1 School of Earth and Environmental Sciences, Seoul National University, Seoul, 151–747, Korea 03 12 2010 3 6 1667 1672 Copyright: © 2010 B. J. Sohn et al. 2010 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://amt.copernicus.org/articles/3/1667/2010/amt-3-1667-2010.html The full text article is available as a PDF file from https://amt.copernicus.org/articles/3/1667/2010/amt-3-1667-2010.pdf

The calibration of the Moderate-resolution Imaging Spectroradiometer (MODIS) 6.8 μm water vapor (WV) channel was assessed by comparing Terra/MODIS measurements with the WV channel brightness temperatures equivalent to Infrared Atmospheric Sounding Interferometer (IASI) measurements for June 2007 and December 2007. IASI spectral information was transferred to the Japanese Multifunctional Transport Satellite (MTSAT)-1R WV channel and then to the MODIS WV channel. Results indicate that the MODIS WV channel is biased low by 2–3 K, possibly caused by the shift of the spectral response function by about +11 cm<sup>−1</sup>. This finding is particularly important because the bias of −3 K can cause about +30% relative errors in the retrieval of upper tropospheric humidity (UTH) over the tropics. In other words, the current MODIS measurements may result in higher UTH values, showing relative errors up to +30%.

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