Latitudinally and Seasonally Dependent Zenith-Angle Corrections for Geostationary Satellite IR Brightness Temperatures
Open Access
- 1 April 2001
- journal article
- Published by American Meteorological Society in Journal of Applied Meteorology and Climatology
- Vol. 40 (4) , 689-703
- https://doi.org/10.1175/1520-0450(2001)040<0689:lasdza>2.0.co;2
Abstract
The equivalent brightness temperature Tb recorded by geosynchronous infrared (geo-IR) “window” channel (10.7–11.5 μm) satellite sensors is shown to depend on the zenith angle (local angle from the zenith to the satellite for a pixel’s ground location) in addition to the mix of clouds and surface that would be observed from a direct overhead viewpoint (nadir view). This zenith-angle dependence is characterized, and two corrections are developed from a collection of half-hourly geo-IR pixel data that have been parallax corrected and averaged to a 0.5° × 0.5° latitude/longitude grid for each geosynchronous satellite separately. First, composites of collocated Tb over tropical regions from the Geostationary Operational Environmental Satellite (GOES)-8/GOES-10 and the Meteosat-5/Meteosat-7 satellite pairs are used to produce robust estimates of isotropic zenith-angle corrections as a function of zenith angle and grid-box-averaged Tb. The corrections range from zero for a zenith angle of ∼26.5° to incr... Abstract The equivalent brightness temperature Tb recorded by geosynchronous infrared (geo-IR) “window” channel (10.7–11.5 μm) satellite sensors is shown to depend on the zenith angle (local angle from the zenith to the satellite for a pixel’s ground location) in addition to the mix of clouds and surface that would be observed from a direct overhead viewpoint (nadir view). This zenith-angle dependence is characterized, and two corrections are developed from a collection of half-hourly geo-IR pixel data that have been parallax corrected and averaged to a 0.5° × 0.5° latitude/longitude grid for each geosynchronous satellite separately. First, composites of collocated Tb over tropical regions from the Geostationary Operational Environmental Satellite (GOES)-8/GOES-10 and the Meteosat-5/Meteosat-7 satellite pairs are used to produce robust estimates of isotropic zenith-angle corrections as a function of zenith angle and grid-box-averaged Tb. The corrections range from zero for a zenith angle of ∼26.5° to incr...Keywords
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