DocumentCode :
918425
Title :
EOS MLS forward model polarized radiative transfer for Zeeman-split oxygen lines
Author :
Schwartz, Michael J. ; Read, William G. ; Van Snyder, W.
Author_Institution :
Jet Propulsion Lab., California Inst. of Technol., Pasadena, CA, USA
Volume :
44
Issue :
5
fYear :
2006
fDate :
5/1/2006 12:00:00 AM
Firstpage :
1182
Lastpage :
1191
Abstract :
This work supplements the Earth Observing System (EOS) Microwave Limb Sounder (MLS) clear-sky unpolarized forward model with algorithms for modeling polarized emission from the Zeeman-split 118.75-GHz O2 spectral line. The model accounts for polarization-dependent emission and for correlation between polarizations with complex, 2×2 intensity and absorption matrices. The oxygen line is split into three Zeeman components by the interaction of oxygen´s electronic spin with an external magnetic field, and the splitting is of order ±0.5 MHz in a typical geomagnetic field. Zeeman splitting is only significant at pressures low enough that collisional broadening (∼1.6 MHz/hPa) is not very large by comparison. The polarized forward model becomes significant for MLS temperature retrievals at pressure below 1.0 hPa and is crucial at pressures below ∼0.03 hPa. Interaction of the O2 molecule with the radiation field depends upon the relative orientation of the radiation polarization mode and the geomagnetic field direction. The model provides both limb radiances and the derivatives of these radiances with respect to atmospheric temperature and composition, as required by MLS temperature retrievals. EOS MLS views the atmospheric limb at 118.75 GHz with a pair of linear-cross-polarized, 100-kHz-resolution, 10-MHz-wide spectrometers. The antennas of the associated receivers are scanned to view rays with tangent heights from the Earth´s surface to 0.001 hPa. Comparisons of the modeled MLS radiances with measurements show generally good agreement in line positions and strengths, however residuals in the line centers at the highest tangent heights are larger than desired and still under investigation.
Keywords :
Zeeman effect; aerospace instrumentation; artificial satellites; atmospheric composition; atmospheric measuring apparatus; atmospheric spectra; atmospheric temperature; oxygen; radiative transfer; 118.75 GHz; Aura stellite; EOS MLS forward model; Earth Observing System; Microwave Limb Sounder; O2; Zeeman splitting; atmospheric composition; atmospheric temperature; collisional broadening; limb radiance; oxygen spectral line; polarized radiative transfer; radiation polarization mode; spectral line position; spectral line strength; Atmospheric modeling; Earth Observing System; Electromagnetic wave absorption; Geomagnetism; Magnetic fields; Multilevel systems; Polarization; Receiving antennas; Spectroscopy; Temperature; Earth Observing System (EOS) Aura; Microwave Limb Sounder (MLS); Zeeman; forward model;
fLanguage :
English
Journal_Title :
Geoscience and Remote Sensing, IEEE Transactions on
Publisher :
ieee
ISSN :
0196-2892
Type :
jour
DOI :
10.1109/TGRS.2005.862267
Filename :
1624598
Link To Document :
بازگشت