SSM/I Brightness temperatures. Corrections for incidence angle variation.

Fuhrhop, Rolf and Simmer, Clemens (1996) SSM/I Brightness temperatures. Corrections for incidence angle variation. Open Access Journal of Atmospheric and Oceanic Technology, 13 . pp. 246-254. DOI 10.1175/1520-0426(1996)013<0246:SBTCFI>2.0.CO;2.

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Abstract

The incidence angles of the SSM/I radiometers on the DMSP satellites vary from satellite to satellite and exhibit variations of up to 1.5° during one orbit. The effects of these variations on the measured brightness temperatures are investigated on the basis of simulated and measured data for oceanic arm. A deviation of 1° from the nominal incidence angle of 53.0° causes brightness temperature changes of up to 2 K depending on surface and atmospheric conditions. Errors of retrieved geophysical parameters on the order of 5%–10% result when the incidence angle variation is not taken into account. This is a common property of most published statistical algorithms. For total precipitable water and cloud liquid water content the error increases with increasing parameter value. For wind speed the error is largest for low wind speed and decreases with increasing wind speed. Due to the slowly varying latitudinal dependence of the incidence angle, these errors do not cancel out when monthly means are computed.

A correction method is developed on the basis of simulated data and tested successfully with measured data. Observed brightness temperature differences between DMSP F10 and F11 are reduced when using corrected data. If diurnal variations of geophysical parameters are investigated, the incidence angle correction is mandatory to obtain useful results, especially for DMSP F10.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-ME Maritime Meteorology
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/1520-0426(1996)013<0246:SBTCFI>2.0.CO;2
ISSN: 0739-0572
Date Deposited: 18 Feb 2008 17:23
Last Modified: 01 Jun 2018 09:33
URI: http://oceanrep.geomar.de/id/eprint/4916

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