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Proceedings Paper

Extending GACP aerosol climatology beyond NOAA-9 AVHRR lifetime
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Paper Abstract

We present an improved version of GACP (Global Aerosol Climatology Project) algorithm which uses channel 1 and 2 radiances of the Advanced Very High Resolution Radiometer (AVHRR) to retrieve aerosol optical thickness and Angstrom exponent over the ocean. We specifically discuss recent changes in the algorithm as well as the results of a sensitivity study analyzing the effect of several sources of retrieval errors not addressed previously. Uncertainties in the AVHRR radiance calibration (particularly in the deep- space count value) may be among the major factors potentially limiting the retrieval accuracy. On the other hand, the performance of two-channel algorithms weakly depends on a specific choice of the aerosol size distribution function. The updated algorithm is applied to a 10-year period of observations (July 1983 - Aug 1994), which includes data from NOAA-7, NOAA-9 (February 1985 - November 1988),and NOAA-11 satellites. The results are posted on the world wide web at The NOAA-9 record shows no discernable long-term trends in the global and hemisphere averages of the optical thickness and Angstrom exponent. On the other hand, there is a discontinuity in the Angstrom exponent values derived from NOAA-9 and NOAA-11 data and a significant temporal trend in the NOAA-11 record. The latter are unlikely to be related to the Pinatubo eruption and may be indicative of a serious calibration problem.

Paper Details

Date Published: 31 January 2002
PDF: 12 pages
Proc. SPIE 4539, Remote Sensing of Clouds and the Atmosphere VI, (31 January 2002); doi: 10.1117/12.454422
Show Author Affiliations
Igor V. Geogdzhayev, NASA Goddard Institute for Space Studies and Columbia Univ. (United States)
Michael I. Mishchenko, NASA Goddard Institute for Space Studies (United States)

Published in SPIE Proceedings Vol. 4539:
Remote Sensing of Clouds and the Atmosphere VI
Klaus Schaefer; Olga Lado-Bordowsky; Adolfo Comeron; Michel R. Carleer; Janet S. Fender, Editor(s)

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