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A Climatology of Cloud & Radiative Properties Derived from GMS-5 Data Over the Tropical Western Pacific

Nordeen, M.L.(a), Doelling, D.R.(a), Khaiyer, M.M.(a), Rapp, A.D.(a), and Minnis, P.(b), Analytical Services & Materials, Inc. (a), National Aeronautics and Space Administration-Langley Research Center (b)
Twelfth Atmospheric Radiation Measurement (ARM) Science Team Meeting

Satellite derived cloud and radiative properties can provide continuous spatial and temporal coverage over the Tropical Western Pacific (TWP). The TWP is an area with few meteorological stations, but is an interesting region in global climate studies. Starting with the Nauru99 Intensive Operational Period (IOP) (June-July 1999), two years of hourly Geostationary Meteorological Satellite (GSM-5) images are used in the Layered Bispectral Threshold Method (LBTM) to provide cloud and radiation properties. The cloud properties are gridded onto a 20x50 1-degree resolution domain extending from 10N to 10S and 130E to 180E. LBTM uses ECMWF profiles to estimate cloud top height based on the IR temperature and the emmisivity correction derived from the visible optical depth. Results are stratified into low (less than 2 km), mid (2 to 6 km) and high clouds (greater than 6 km). Since the TWP is an area of high variability of humidity, correlated K's along with Meteorological Ozone Atmosphere (MOA) skin temperatures are used to vary IR cloud threshold. Broadband shortwave and longwave fluxes are estimated from GMS-5 narrowband fluxes by an empirical relationship based on coincident CERES and GMS-5 measurements during the same time period. Given the broadband fluxes, the TOA radiative forcing fluxes are computed. Seasonal cycle of the monthly mean properties will be presented of the greater TWP grid as well as for the ARM sites of Manus and Nauru. Cloud amount and height are validated against surface and ship-based instruments. Higher resolution LBTM results from a 0.3 degree centered on Manus and Nauru ARM sites will be performed. This will give an idea whether the ARM sites are representative of the surrounding oceans due to island effects. Preliminary results from a 3 channel algorithm based on the GMS-5 0.63, 11.0 and 12.0 micron channels will be presented. The 3 channel algorithm should improve the thin cloud retrievals.

Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).