Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 6 2004 10.5194/acpd-4-8201-2004 http://www.atmos-chem-phys-discuss.net/4/8201/2004/ http://www.atmos-chem-phys-discuss.net/4/8201/2004/acpd-4-8201-2004.html http://www.atmos-chem-phys-discuss.net/4/8201/2004/acpd-4-8201-2004.pdf 8201 8244 2004-12-15 Intercomparison of satellite retrieved aerosol optical depth over ocean during the period September 1997 to December 2000 G. Myhre gunnar.myhre@geo.uio.no F. Stordal M. Johnsrud D. J. Diner I. V. Geogdzhayev J. M. Haywood B. Holben T. Holzer-Popp A. Ignatov R. Kahn Y. J. Kaufman N. Loeb J. Martonchik M. I. Mishchenko N. R. Nalli L. A. Remer M. Schroedter-Homscheidt D. Tanré O. Torres M. Wang Norwegian Institute for Air Research (NILU), Kjeller, Norway Department of Geosciences, University of Oslo, Oslo, Norway Jet Propulsion Laboratory, California Institute of Technology, Pasadena California, USA NASA Goddard Institute for Space Studies, New York, New York, USA Met Office, Exeter, UK Biospheric Sciences Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Deutsches Fernerkundungsdatenzentrum (DFD), Oberpfaffenhofen, Germany NOAA/NESDIS/Office of Research and Applications/Climate Research and Applications Division, Washington, D.C., USA Laboratory for Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA Center for Atmospheric Sciences, Hampton University, Hampton, VA., USA Laboratoire d’Optique Atmosphérique, Université de Lille/CNRS, Villeneuve d’Ascq, France Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, Maryland, USA University of Maryland-Baltimore County, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Monthly mean aerosol optical depth (AOD) over ocean is compared from a total of 9 aerosol retrievals during a 40 months period. Comparisons of AOD have been made both for the entire period and sub periods. We identify regions where there is large disagreement and good agreement between the aerosol satellite retrievals. Significant differences in AOD have been identified in most of the oceanic regions. Several analyses are performed including spatial correlation between the retrievals as well as comparison with AERONET data. During the 40 months period studied there have been several major aerosol field campaigns as well as events of high aerosol content. It is studied how the aerosol retrievals compare during such circumstances. The differences found in this study are larger than found in a previous study where 5 aerosol retrievals over an 8 months period were compared. However, results in coastal regions are promising especially for aerosol retrievals from satellite instruments dedicated for aerosol research. In depth analyses explaining the differences between AOD obtained in different retrievals are clearly needed. We limit this study to identify differences and similarities and indicate possible sources that affect the quality of the retrievals. This is a necessary first step towards understanding the differences and improving the retrievals.