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

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Atmos. Meas. Tech., 9, 1743-1753, 2016
https://doi.org/10.5194/amt-9-1743-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
20 Apr 2016
Cirrus cloud optical and microphysical property retrievals from eMAS during SEAC4RS using bi-spectral reflectance measurements within the 1.88  µm water vapor absorption band
Kerry Meyer1,2, Steven Platnick2, G. Thomas Arnold3,2, Robert E. Holz4, Paolo Veglio4, John Yorks2, and Chenxi Wang5 1Goddard Earth Sciences Technology and Research (GESTAR), Universities Space Research Association, Columbia, Maryland, 21046, USA
2NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA
3Science Systems and Applications, Inc., Lanham, Maryland, 20706, USA
4Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, Madison, Wisconsin, 53706, USA
5Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, 20740, USA
Abstract. Previous bi-spectral imager retrievals of cloud optical thickness (COT) and effective particle radius (CER) based on the Nakajima and King (1990) approach, such as those of the operational MODIS cloud optical property retrieval product (MOD06), have typically paired a non-absorbing visible or near-infrared wavelength, sensitive to COT, with an absorbing shortwave or mid-wave infrared wavelength sensitive to CER. However, in practice it is only necessary to select two spectral channels that exhibit a strong contrast in cloud particle absorption. Here it is shown, using eMAS observations obtained during NASA's SEAC4RS field campaign, that selecting two absorbing wavelength channels within the broader 1.88 µm water vapor absorption band, namely the 1.83 and 1.93 µm channels that have sufficient differences in ice crystal single scattering albedo, can yield COT and CER retrievals for thin to moderately thick single-layer cirrus that are reasonably consistent with other solar and IR imager-based and lidar-based retrievals. A distinct advantage of this channel selection for cirrus cloud retrievals is that the below-cloud water vapor absorption minimizes the surface contribution to measured cloudy top-of-atmosphere reflectance, in particular compared to the solar window channels used in heritage retrievals such as MOD06. This reduces retrieval uncertainty resulting from errors in the surface reflectance assumption and reduces the frequency of retrieval failures for thin cirrus clouds.

Citation: Meyer, K., Platnick, S., Arnold, G. T., Holz, R. E., Veglio, P., Yorks, J., and Wang, C.: Cirrus cloud optical and microphysical property retrievals from eMAS during SEAC4RS using bi-spectral reflectance measurements within the 1.88  µm water vapor absorption band, Atmos. Meas. Tech., 9, 1743-1753, https://doi.org/10.5194/amt-9-1743-2016, 2016.
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Short summary
Cirrus cloud optical and microphysical properties are retrieved from remote sensing solar reflectance measurements at two narrow wavelength channels within the broader water vapor absorption band at 1.88 µm. Results from this technique compare well with other solar reflectance, IR, and lidar-based retrievals. This approach is complementary to traditional remote sensing techniques and can extend cloud retrieval capabilities for thin cirrus clouds.
Cirrus cloud optical and microphysical properties are retrieved from remote sensing solar...
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