Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulator
Many passive remote-sensing techniques have been developed to retrieve cloud microphysical properties from satellite-based sensors, with the most common approaches being the bispectral and polarimetric techniques. These two vastly different retrieval techniques have been implemented for a variet...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/11/3689/2018/amt-11-3689-2018.pdf |
| _version_ | 1811276157757161472 |
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| author | D. J. Miller D. J. Miller Z. Zhang Z. Zhang S. Platnick A. S. Ackerman F. Werner C. Cornet K. Knobelspiesse |
| author_facet | D. J. Miller D. J. Miller Z. Zhang Z. Zhang S. Platnick A. S. Ackerman F. Werner C. Cornet K. Knobelspiesse |
| author_sort | D. J. Miller |
| collection | DOAJ |
| description | Many passive remote-sensing techniques have been
developed to retrieve cloud microphysical properties from satellite-based
sensors, with the most common approaches being the bispectral and
polarimetric techniques. These two vastly different retrieval techniques
have been implemented for a variety of polar-orbiting and geostationary
satellite platforms, providing global climatological data sets. Prior
instrument comparison studies have shown that there are systematic
differences between the droplet size retrieval products (effective radius)
of bispectral (e.g., MODIS, Moderate Resolution Imaging Spectroradiometer)
and polarimetric (e.g., POLDER, Polarization and Directionality of Earth's
Reflectances) instruments. However, intercomparisons of airborne bispectral
and polarimetric instruments have yielded results that do not appear to be
systematically biased relative to one another. Diagnosing this discrepancy
is complicated, because it is often difficult for instrument intercomparison
studies to isolate differences between retrieval technique sensitivities and
specific instrumental differences such as calibration and atmospheric
correction. In addition to these technical differences the polarimetric
retrieval is also sensitive to the dispersion of the droplet size
distribution (effective variance), which could influence the interpretation
of the droplet size retrieval. To avoid these instrument-dependent
complications, this study makes use of a cloud remote-sensing retrieval
simulator. Created by coupling a large-eddy simulation (LES) cloud model
with a 1-D radiative transfer model, the simulator serves as a test bed for
understanding differences between bispectral and polarimetric retrievals.
With the help of this simulator we can not only compare the two techniques
to one another (retrieval intercomparison) but also validate retrievals
directly against the LES cloud properties. Using the satellite retrieval
simulator, we are able to verify that at high spatial resolution (50 m) the
bispectral and polarimetric retrievals are highly correlated with one
another within expected observational uncertainties. The relatively small
systematic biases at high spatial resolution can be attributed to different
sensitivity limitations of the two retrievals. In contrast, a systematic
difference between the two retrievals emerges at coarser resolution. This
bias largely stems from differences related to sensitivity of the two
retrievals to unresolved inhomogeneities in effective variance and optical
thickness. The influence of coarse angular resolution is found to increase
uncertainty in the polarimetric retrieval but generally maintains a
constant mean value. |
| first_indexed | 2024-04-12T23:52:37Z |
| format | Article |
| id | doaj.art-7e54d0da74904065b07472c675b5a74a |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-04-12T23:52:37Z |
| publishDate | 2018-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-7e54d0da74904065b07472c675b5a74a2022-12-22T03:11:39ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482018-06-01113689371510.5194/amt-11-3689-2018Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulatorD. J. Miller0D. J. Miller1Z. Zhang2Z. Zhang3S. Platnick4A. S. Ackerman5F. Werner6C. Cornet7K. Knobelspiesse8Physics, University of Maryland, Baltimore County, Baltimore, MD, USANASA Goddard Space Flight Center, Greenbelt, MD, USAPhysics, University of Maryland, Baltimore County, Baltimore, MD, USAJoint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD, USANASA Goddard Space Flight Center, Greenbelt, MD, USANASA Goddard Institute for Space Studies, New York, NY, USAJoint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD, USALaboratoire d'Optique Atmosphérique, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, FranceNASA Goddard Space Flight Center, Greenbelt, MD, USAMany passive remote-sensing techniques have been developed to retrieve cloud microphysical properties from satellite-based sensors, with the most common approaches being the bispectral and polarimetric techniques. These two vastly different retrieval techniques have been implemented for a variety of polar-orbiting and geostationary satellite platforms, providing global climatological data sets. Prior instrument comparison studies have shown that there are systematic differences between the droplet size retrieval products (effective radius) of bispectral (e.g., MODIS, Moderate Resolution Imaging Spectroradiometer) and polarimetric (e.g., POLDER, Polarization and Directionality of Earth's Reflectances) instruments. However, intercomparisons of airborne bispectral and polarimetric instruments have yielded results that do not appear to be systematically biased relative to one another. Diagnosing this discrepancy is complicated, because it is often difficult for instrument intercomparison studies to isolate differences between retrieval technique sensitivities and specific instrumental differences such as calibration and atmospheric correction. In addition to these technical differences the polarimetric retrieval is also sensitive to the dispersion of the droplet size distribution (effective variance), which could influence the interpretation of the droplet size retrieval. To avoid these instrument-dependent complications, this study makes use of a cloud remote-sensing retrieval simulator. Created by coupling a large-eddy simulation (LES) cloud model with a 1-D radiative transfer model, the simulator serves as a test bed for understanding differences between bispectral and polarimetric retrievals. With the help of this simulator we can not only compare the two techniques to one another (retrieval intercomparison) but also validate retrievals directly against the LES cloud properties. Using the satellite retrieval simulator, we are able to verify that at high spatial resolution (50 m) the bispectral and polarimetric retrievals are highly correlated with one another within expected observational uncertainties. The relatively small systematic biases at high spatial resolution can be attributed to different sensitivity limitations of the two retrievals. In contrast, a systematic difference between the two retrievals emerges at coarser resolution. This bias largely stems from differences related to sensitivity of the two retrievals to unresolved inhomogeneities in effective variance and optical thickness. The influence of coarse angular resolution is found to increase uncertainty in the polarimetric retrieval but generally maintains a constant mean value.https://www.atmos-meas-tech.net/11/3689/2018/amt-11-3689-2018.pdf |
| spellingShingle | D. J. Miller D. J. Miller Z. Zhang Z. Zhang S. Platnick A. S. Ackerman F. Werner C. Cornet K. Knobelspiesse Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulator Atmospheric Measurement Techniques |
| title | Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulator |
| title_full | Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulator |
| title_fullStr | Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulator |
| title_full_unstemmed | Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulator |
| title_short | Comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics: case studies using a LES–satellite retrieval simulator |
| title_sort | comparisons of bispectral and polarimetric retrievals of marine boundary layer cloud microphysics case studies using a les satellite retrieval simulator |
| url | https://www.atmos-meas-tech.net/11/3689/2018/amt-11-3689-2018.pdf |
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