Comment on egusphere-2023-1843

Abstract

Abstract. The UMBC Hyper-Angular Rainbow Polarimeter (HARP2) will be onboard NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, scheduled for launch in January 2024. In this study we systematically evaluate the retrievability and uncertainty of aerosol and ocean parameters from HARP2 multi-angle polarimeter (MAP) measurements. To reduce the computational demand of MAP-based retrievals and maximize data processing throughput, we developed improved neural network (NN) forward models for space-borne HARP2 measurements over a coupled atmosphere and ocean system within the FastMAPOL retrieval algorithm. A cascading retrieval scheme is further implemented in FastMAPOL, which leverages a series of NN models of varying size, speed, and accuracy to optimize performance. A full day of global synthetic HARP2 data was generated and used to test various retrieval parameters including aerosol microphysical and optical properties, aerosol layer height, ocean surface wind speed, and ocean chlorophyll-a concentration. To assess retrieval quality, pixel-wise retrieval uncertainties were derived from the Jacobians of the cost function and evaluated against the difference between the retrieval parameters and truth based on a Monte Carlo error propagation method. We found that the fine-mode aerosol properties can be retrieved well from the HARP2 data, though the coarse-mode aerosol properties are more uncertain. Larger uncertainties are also associated with a reduced number of available viewing angles, which typically occurs near the scan edge of the HARP2 instrument. Results of the performance assessment demonstrate that the algorithm is a viable approach for operational application to HARP2 data after PACE launch.

Authors 17

1. Meng Gao corresponding

   Goddard Space Flight Center · National Aeronautics and Space Administration · Science Systems and Applications (United States)

   Affiliation as printed

   Ocean Ecology Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

   Science Systems and Applications, Inc., Greenbelt, MD, USA

2. B. A. Franz

   Goddard Space Flight Center · National Aeronautics and Space Administration

   Affiliation as printed

   Ocean Ecology Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

3. Peng‐Wang Zhai

   University of Maryland, Baltimore County

   Affiliation as printed

   University of Maryland, Baltimore County, Baltimore, MD 21250, USA

4. Kirk David Knobelspiesse

   Goddard Space Flight Center · National Aeronautics and Space Administration

   Affiliation as printed

   Ocean Ecology Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

5. A. M. Sayer

   Goddard Space Flight Center · National Aeronautics and Space Administration

   Affiliation as printed

   Ocean Ecology Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

6. Xiaoguang Xu

   University of Maryland, Baltimore County

   Affiliation as printed

   University of Maryland, Baltimore County, Baltimore, MD 21250, USA

7. Vanderlei J. Martins

   University of Maryland, Baltimore County

   Affiliation as printed

   University of Maryland, Baltimore County, Baltimore, MD 21250, USA

8. Brian Cairns

   Goddard Institute for Space Studies

   Affiliation as printed

   NASA Goddard Institute for Space Studies, New York, NY 10025, USA

9. Patricia Castellanos

   Goddard Space Flight Center

   Affiliation as printed

   Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

10. Guangliang Fu Aachen Netherlands Institute for Space Research (SRON

    Space Research Organisation Netherlands

    Affiliation as printed

    Netherlands Institute for Space Research (SRON, NWO-I), Leiden, Netherlands

11. Neranga Hannadige

    University of Maryland, Baltimore County

    Affiliation as printed

    University of Maryland, Baltimore County, Baltimore, MD 21250, USA

12. Otto Hasekamp Aachen Netherlands Institute for Space Research (SRON

    Space Research Organisation Netherlands

    Affiliation as printed

    Netherlands Institute for Space Research (SRON, NWO-I), Leiden, Netherlands

13. Yongxiang Hu

    Langley Research Center

    Affiliation as printed

    MS 475 NASA Langley Research Center, Hampton, VA 23681-2199, USA

14. Amir I. Ibrahim

    Goddard Space Flight Center · National Aeronautics and Space Administration

    Affiliation as printed

    Ocean Ecology Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

15. Frederick S. Patt

    Goddard Space Flight Center · National Aeronautics and Space Administration

    Affiliation as printed

    Ocean Ecology Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

    Science Applications International Corp., Greenbelt, MD, USA

16. Anin Puthukkudy

    University of Maryland, Baltimore County

    Affiliation as printed

    University of Maryland, Baltimore County, Baltimore, MD 21250, USA

17. P. Jeremy Werdell

    Goddard Space Flight Center · National Aeronautics and Space Administration

    Affiliation as printed

    Ocean Ecology Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA