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Evaluation of GOMOS limb scattering measurements
Ghassan Taha(1), Glen Jaross(1)
, Didier Fussen(2)
, Filip Vanhellemont(2)
, and Richard McPeters(3)
(1)
Science Systems and Applications, Inc.,
10210 Greenbelt Road, Suite 400,
Lanham, MD 20706,
United States
(2) Belgian Institute for Space Aeronomy, Avenue Circulaire 3 , B-1180 Brussels , Belgium
(3) NASA Goddard Space Flight Center, Laboratory for Atmospheres, Code 613.3, Greenbelt, MD 20771 , United States
Abstract
As part of its routine measurements, GOMOS measures the solar limb scattering above and below the star to correct for background radiation. If corrected for gain and offset, and calibrated, GOMOS spectral radiances, in theory, could be used to retrieve various gaseous species as well as aerosol extinction. The information content is similar to that obtained by other limb scatter sensors, such as SCIAMACHY and ODIN/OSIRIS, with one important difference; each GOMOS image contains a stellar signal, sensor pointing and hence the vertical profile registration of atmospheric species should be superior to other limb sensors.
In this work, we are analyzing a subset of GOMOS bright limb measurements with solar zenith angle less than 80o, and within 150 km of SAGE II. A radiative transfer model, with input from SAGE measurements of ozone and aerosol, as well as NCEP temperature and pressure, is used to model and investigate the quality of GOMOS limb radiances, as well as studying the accuracy and sensitivity of various altitude registration techniques, such as maximum correlation, RSAS, or ozone knee methods. Inaccuracies in altitude registration are often a major uncertainty component for trace gas profile retrievals, and hence hinder the scientific value of such measurements. Pointing errors have been identified as the largest contributor to Ozone Mapping and Profiler Suite (OMPS) limb precision errors between the tropopause and the ozone peak. Thus, its one of OMPS main priorities to test and validate altitude registration techniques, and adopt the most accurate one.
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