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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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Atmos. Meas. Tech., 10, 3677-3695, 2017
https://doi.org/10.5194/amt-10-3677-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
09 Oct 2017
Deriving the slit functions from OMI solar observations and its implications for ozone-profile retrieval
Kang Sun1, Xiong Liu1, Guanyu Huang1, Gonzalo González Abad1, Zhaonan Cai1, Kelly Chance1, and Kai Yang2 1Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA
2Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA
Abstract. The Ozone Monitoring Instrument (OMI) has been successfully measuring the Earth's atmospheric composition since 2004, but the on-orbit behavior of its slit functions has not been thoroughly characterized. Preflight measurements of slit functions have been used as a static input in many OMI retrieval algorithms. This study derives on-orbit slit functions from the OMI irradiance spectra assuming various function forms, including standard and super-Gaussian functions and a stretch to the preflight slit functions. The on-orbit slit functions in the UV bands show U-shaped cross-track dependences that cannot be fully represented by the preflight ones. The full widths at half maximum (FWHM) of the stretched preflight slit functions for detector pixels at large viewing angles are up to 30 % larger than the nadir pixels for the UV1 band, 5 % larger for the UV2 band, and practically flat in the VIS band. Nonetheless, the on-orbit changes of OMI slit functions are found to be insignificant over time after accounting for the solar activity, despite of the decaying of detectors and the occurrence of OMI row anomaly. Applying the derived on-orbit slit functions to ozone-profile retrieval shows substantial improvements over the preflight slit functions based on comparisons with ozonesonde validations.

Citation: Sun, K., Liu, X., Huang, G., González Abad, G., Cai, Z., Chance, K., and Yang, K.: Deriving the slit functions from OMI solar observations and its implications for ozone-profile retrieval, Atmos. Meas. Tech., 10, 3677-3695, https://doi.org/10.5194/amt-10-3677-2017, 2017.
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Short summary
This study derives on-orbit slit functions from the OMI irradiance spectra. The results differ from the widely used preflight slit functions. The on-orbit changes of OMI slit functions are insignificant over time after accounting for the solar activity. Applying the derived on-orbit slit functions to ozone-profile retrieval shows substantial improvements over the preflight slit functions based on comparisons with ozonesonde validations.
This study derives on-orbit slit functions from the OMI irradiance spectra. The results differ...
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