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Proceedings Paper

Long-term monitoring of surface reflectance, NDVI, and clouds from space: What contribution can we expect due to the effect of instrument spectral response variations?
Author(s): Alexander P. Trishchenko; Josef Cihlar; Zhanqing Li; Byongjun Hwang
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Paper Abstract

Since the satellites provide frequent and global observations of atmospheric and terrestrial environment, attempts have been made to use satellite data for long-term monitoring of land reflectances, vegetation indices and clouds properties. Although the construction and characteristics of spaceborne instruments may be quite similar, they are not identical among all missions, even for the same type of instrument like AVHRR. Consequently, the effect of varying spectral response may create an artificial noise imposed upon a subtle natural variability. We report the results of a study on the sensitivity of Normalized Difference Vegetation Index (NDVI), surface and cloud reflectance to differences in instrument spectral response functions (SRF) for various satellite sensors. They include AVHRR radiometers onboard NOAA satellites NOAA-6 - NOAA-16, the Moderate Resolution Imaging Spectroradiometer (MODIS), the VEGETATION sensor (VGT) and the Global Imager (GLI). We also analyzed the SRF effects for several geostationary satellites used for cloud studies, such as GOES-8 - 12, METEOSAT-2 - 7, GMS -1 - 5. The results obtained here demonstrate that the effect of instrument spectral response function cannot be ignored in long-term monitoring studies that employ space observations from different sensors. The SRF effect introduces differences in observed reflectances and retrieved quantities that may be comparable or exceed the range of natural variability and possible systematic trends, the contribution from the calibration, atmospheric and other corrections. Some modeling results were validated against real satellite observations with good agreement.

Paper Details

Date Published: 5 September 2002
PDF: 12 pages
Proc. SPIE 4815, Atmospheric Radiation Measurements and Applications in Climate, (5 September 2002); doi: 10.1117/12.482310
Show Author Affiliations
Alexander P. Trishchenko, Canada Ctr. for Remote Sensing (Canada)
Josef Cihlar, Canada Ctr. for Remote Sensing (Canada)
Zhanqing Li, Univ. of Maryland/College Park (United States)
Byongjun Hwang, Intermap Technologies Corp. (Canada)

Published in SPIE Proceedings Vol. 4815:
Atmospheric Radiation Measurements and Applications in Climate
Joseph A. Shaw, Editor(s)

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