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Atmospheric absorption model for dry air and water vapor at microwave frequencies below 100 GHz derived from spaceborne radiometer observations
Author(s) -
Wentz Frank J.,
Meissner Thomas
Publication year - 2016
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1002/2015rs005858
Subject(s) - water vapor , microwave , radiometer , microwave radiometer , environmental science , materials science , radiative transfer , absorption (acoustics) , remote sensing , atmospheric sciences , satellite , optics , meteorology , physics , geology , composite material , quantum mechanics , astronomy
The Liebe and Rosenkranz atmospheric absorption models for dry air and water vapor below 100 GHz are refined based on an analysis of antenna temperature ( T A ) measurements taken by the Global Precipitation Measurement Microwave Imager (GMI) in the frequency range 10.7 to 89.0 GHz. The GMI T A measurements are compared to the T A predicted by a radiative transfer model (RTM), which incorporates both the atmospheric absorption model and a model for the emission and reflection from a rough‐ocean surface. The inputs for the RTM are the geophysical retrievals of wind speed, columnar water vapor, and columnar cloud liquid water obtained from the satellite radiometer WindSat. The Liebe and Rosenkranz absorption models are adjusted to achieve consistency with the RTM. The vapor continuum is decreased by 3% to 10%, depending on vapor. To accomplish this, the foreign‐broadening part is increased by 10%, and the self‐broadening part is decreased by about 40% at the higher frequencies. In addition, the strength of the water vapor line is increased by 1%, and the shape of the line at low frequencies is modified. The dry air absorption is increased, with the increase being a maximum of 20% at the 89 GHz, the highest frequency considered here. The nonresonant oxygen absorption is increased by about 6%. In addition to the RTM comparisons, our results are supported by a comparison between columnar water vapor retrievals from 12 satellite microwave radiometers and GPS‐retrieved water vapor values.