Abstract
Abstract. This paper reports initial results from an Ozone Mapping and Profiler Suite (OMPS) Nadir Mapper cloud pressure and cloud fraction algorithm. The OMPS cloud products are intended for use in OMPS ozone or other trace-gas algorithms. We developed the OMPS cloud products using a heritage algorithm developed for the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite. The cloud pressure algorithm utilizes the filling-in of ultraviolet solar Fraunhofer lines by rotational Raman scattering. The OMPS cloud products are evaluated by comparison with OMI cloud products that have been compared in turn with other collocated satellite data including cloud optical thickness profiles derived from a combination of measurements from the CloudSat radar and MODerate-resolution Imaging Spectroradiometer (MODIS). We find that the probability density functions (PDFs) of effective cloud fraction retrieved from OMPS and OMI measurements are very similar. The PDFs of the OMPS and OMI cloud pressures are comparable. However, OMPS retrieves somewhat higher pressures on average. The current NASA total ozone retrieval algorithm makes use of a monthly gridded cloud pressure climatology developed from OMI. This climatology captures much of the variability associated with the relevant cloud pressures. However, the use of actual cloud pressures retrieved with OMPS in place of the OMI climatology changes OMPS total column ozone estimates locally (presumably in the correct direction) only in areas with large differences between climatological and actual cloud pressures. The ozone differences can be up to 5% in such areas.
Highlights
The Ozone Mapping and Profiler Suite (OMPS), flying on the Suomi National Polar-orbiting Partnership (NPP) satellite, launched by the US National Aeronautics and Space Administration (NASA) on 28 October 2011, consists of two nadir sensors and a limb profiler
The launch of the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite within the “A-Train” (Afternoon Train) Constellation has provided a unique opportunity to compare cloud pressures derived from solar backscatter measurements with other nearly coincident cloud measurements including cloud optical thickness profiles retrieved from the CloudSat radar and MODerate-resolution Imaging Spectroradiometer (MODIS) radiances
Small differences in the probability density functions (PDFs) of effective cloud fraction (ECF) for ECF > 0.1–0.2 could be explained by the fact that a significant fraction of the OMI smallest-size pixels near nadir are excluded from the comparison due to the row anomaly
Summary
The Ozone Mapping and Profiler Suite (OMPS), flying on the Suomi National Polar-orbiting Partnership (NPP) satellite, launched by the US National Aeronautics and Space Administration (NASA) on 28 October 2011, consists of two nadir sensors and a limb profiler. The launch of the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite within the “A-Train” (Afternoon Train) Constellation has provided a unique opportunity to compare cloud pressures derived from solar backscatter measurements with other nearly coincident cloud measurements including cloud optical thickness profiles retrieved from the CloudSat radar and MODerate-resolution Imaging Spectroradiometer (MODIS) radiances. The OMPS and OMI instruments are similar in some respects, there are substantial differences in the detailed specifications of these instruments including spectral and spatial resolutions It was not clear at the onset whether OMPS would achieve the same level of performance as OMI with respect to the RRS cloud retrieval. The OMI swath width for comparison is 2600 km, and it provides 60 pixels in the cross-track direction with a nadir footprint size of ∼ 12 km × 24 km
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