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Cirrus Cloud Radiative and Microphysical Properties from Ground Observations and In Situ Measurements During FIRE 1991 and Their Application to Exhibit Problems in Cirrus Solar Radiative Transfer ModelingMeasurements from the FIRE 1991 cirrus cloud field experiment in the central United States are presented and analyzed. The first part focuses on cirrus microphysical properties. Aircraft 2D-probe in situ data at different cloud altitudes were evaluated for cirrus cases on four different days. Also presented are simultaneous data samples from balloonborne videosondes. Only these balloonsondes could detect the smaller crystals. Their data suggest (at least for midlatitude altitudes below 10 km) that ice crystals smaller than 15 microns in size are rare and that small ice crystals not detected by 2D-probe measurements are radiatively of minor importance, as overlooked 2D-probe crystals account for about 10% of the total extinction. The second part focuses on the link between cirrus cloud properties and radiation. With cloud macrophysical properties from surface remote sensing added to the microphysical data and additional radiation measurements at the surface, testbeds for radiative transfer models were created. To focus on scattering processes, model evaluations were limited to the solar radiative transfer by comparing calculated and measured transmissions of sunlight at the surface. Comparisons under cloud-free conditions already reveal a model bias of about +45 W/sq m for the hemispheric solar downward broadband flux. This discrepancy, which is (at least in part) difficult to explain, has to be accounted for in comparisons involving clouds. Comparisons under cirrus cloud conditions identify as the major obstacle in cirrus solar radiative transfer modeling the inability of one-dimensional radiative transfer models to account for horizontal inhomogeneities. The successful incorporation of multidimensional radiative transfer effects will depend not only on better models but critically on the ability to measure and to define characteristic inhomogeneity scales of cloud fields. The relative minor error related to the microphysical treatment is in part a reflection of the improved understanding on solar scattering on ice crystals over the last decade and of the available wealth on ice-crystal size and shape data for this study. In absence of this information, uncertainties from microphysical cirrus model assumptions will remain high.
Document ID
19990041054
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Kinne, Stefan
(NASA Ames Research Center Moffett Field, CA United States)
Akerman, T. P.
(Pennsylvania State Univ. University Park, PA United States)
Shiobara, M.
(Meteorological Research Inst. Tsukuba, Japan)
Uchiyama, A.
(Meteorological Research Inst. Tsukuba, Japan)
Heymsfield, A. J.
(National Center for Atmospheric Research Boulder, CO United States)
Miloshevich, L.
(National Center for Atmospheric Research Boulder, CO United States)
Wendell, J.
(National Oceanic and Atmospheric Administration Boulder, CO United States)
Eloranta, E. W.
(Wisconsin Univ. Madison, WI United States)
Purgold, C.
(NASA Langley Research Center Hampton, VA United States)
Bergstrom, R. W.
(Bay Area Environmental Research Inst. San Francisco, CA United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1997
Publication Information
Publication: Journal of the Atmospheric Sciences
Publisher: American Meteorological Society
Volume: 54
Subject Category
Meteorology And Climatology
Funding Number(s)
CONTRACT_GRANT: NCC2-940
Distribution Limits
Public
Copyright
Other

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