Aerosol Correction for Improving OMPS/LP Ozone Retrieval

The Ozone Mapping and Profiler Suite Limb Profiler (OMPS/LP) on board the Suomi National Polar-orbiting Partnership (S-NPP) satellite was launched on October 28, 2011. The LP instrument measures the radiance scattered from the Earth's atmosphere in limb viewing mode from 290 nm to 1000 nm, and retrieves ozone profiles from the tropopause to 60 km.

The recently released OMPS/LP Version 2 data product contains ozone profile retrievals covering the entire OMPS mission since the start of regular measurements in January 2012. The Version 2 data product incorporates several important changes to the ozone retrieval algorithm. One of the primary changes from Version 1 was to turn off the aerosol retrieval module that was originally used in order to better diagnose any ozone retrieval errors. However, aerosols, including polar stratospheric clouds (PSC) and polar mesospheric clouds (PMC), have a detectable effect on OMPS/LP data. Our analysis shows that ignoring the aerosol contribution can produce an ozone density bias of up to 10% in the region of maximum aerosol extinction. Therefore, implementing an aerosol correction is necessary to improve the quality of the retrieved ozone concentration profile.

In this presentation, we discuss the Aerosol Scattering Index (ASI) for detecting aerosols/PMC/PSC. The ASI is defined as the difference between measured radiance and calculated radiance (assuming no aerosols), normalized at 45 km. Since ASI varies with wavelength, latitude and altitude, we initially assume no aerosol profiles in calculating the ASI values with a radiative transfer forward model. We then include a nominal aerosol profile to see if it significantly reduces the radiance residuals. We also discuss the effect of aerosol size distribution on the ozone profile retrieval process. Finally, we present an aerosol/PMC/PSC correction scheme to improve the retrieved ozone profiles.