The Center for Atmospheric Sciences | » Limb Scattering Radiative Transfer Model Development in Support of the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler Mission

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  • Limb Scattering Radiative Transfer Model Development in Support of the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler Mission

    My recent work has been funded by NASA through a sub-contract with SSAI, which has supported radiative transfer model improvements relevant for the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) sensor.  This sensor launched aboard the Suomi NPP satellite in October 2011, and the current acting leader for the OMPS LP algorithm team is Dr. P.K. Bhartia at NASA Goddard Space Flight Center.  This work began in cooperation with Dr. Bhartia’s predecessor, Dr. Didier Rault (formerly of NASA Langley Research Center), and has been assisted by Dr. Dave Flittner (also of NASA Langley Research Center) and Ernest Nyaku (current graduate student at Hampton University).

    To understand the OMPS LP measurements and achieve the primary goal of this mission (determining the vertical profile of ozone and aerosols in the upper troposphere and stratosphere), we require a radiative transfer (RT) model that can accurately simulate the scattered ultraviolet, visible and near-infrared radiation in the limb of a specified atmosphere.  (In a “limb scattering” observation, the observer is outside the atmosphere, and looks toward the horizon along a line of sight that intersects the planetary atmosphere, but not the surface.)  Recent improvements in our limb scattering RT model were presented in a poster at the 7th Atmospheric Limb Conference (Bremen, Germany, June 2013).  That poster is available in the link below, and its abstract follows:

    Loughman_Poster_June2013_Bremen_LimbWorkshop

    The Gauss-Seidel Limb Scattering (GSLS) radiative transfer (RT) model has been compared with several other limb scattering RT models in previous studies, including Siro, MCC++, CDIPI, LIMBTRAN, and SASKTRAN. To address deficiencies in the GSLS radiance calculations revealed in earlier comparisons, several recent changes have been added that improve the accuracy and flexibility of the GSLS model, including:

    1. Introduction of variable atmospheric and surface properties along the limb line of sight (LOS).

    2. Improved treatment of the variation of the extinction coefficient within atmospheric layers.

    3. Re-introduction of the ability to simulate vector (polarized) radiances, and proper treatment of extinction in the uppermost atmosphere.

    4. Addition of the ability to model multiple aerosol types within the model atmosphere.

    These model improvements are verified by comparison to standard radiance tables whenever possible, demonstrating significant improvement in cases for which previous versions of the GSLS model performed poorly. The GSLS model is imbedded in the retrieval algorithm used to process data from the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP), which was launched on the Suomi NPP satellite in October 2011. The significance of the GSLS RT model improvements for the OMPS LP retrievals is fairly minor, except for the problem of tangent height registration.