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Optically Thin Liquid Water Clouds: Their Importance and Our ChallengeMany of the clouds important to the Earth's energy balance, from the tropics to the Arctic, are optically thin and contain liquid water. Longwave and shortwave radiative fluxes are very sensitive to small perturbations of the cloud liquid water path (LWP) when the liquid water path is small (i.e., < g/sq m) and, thus, the radiative properties of these clouds must be well understood to capture them correctly in climate models. We review the importance of these thin clouds to the Earth's energy balance, and explain the difficulties in observing them. In particular, because these clouds are optically thin, potentially mixed-phase, and often (i.e., have large 3-D variability), it is challenging to retrieve their microphysical properties accurately. We describe a retrieval algorithm intercomparison that was conducted to evaluate the issues involved. The intercomparison included eighteen different algorithms to evaluate their retrieved LWP, optical depth, and effective radii. Surprisingly, evaluation of the simplest case, a single-layer overcast cloud, revealed that huge discrepancies exist among the various techniques, even among different algorithms that are in the same general classification. This suggests that, despite considerable advances that have occurred in the field, much more work must be done, and we discuss potential avenues for future work.
Document ID
20080006488
Acquisition Source
Langley Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Turner, D. D. (Wisconsin Univ. Madison, WI, United States)
Vogelmann, A. M. (Brookhaven National Lab. Upton, NY, United States)
Austin, R. T. (Colorado State Univ. CO, United States)
Barnard, J. C. (Pacific Northwest National Lab. United States)
Cady-Pereira, K. (Atmospheric and Environmental Research, Inc. United States)
Chiu, J. C. (Maryland Univ. Baltimore County Baltimore, MD, United States)
Clough, S. A. (Atmospheric and Environmental Research, Inc. United States)
Flynn, C. (Pacific Northwest National Lab. United States)
Khaiyer, M. M. (AS and M, Inc. Hampton, VA, United States)
Liljegren, J. (Argonne National Lab. IL, United States)
Johnson, K. (Brookhaven National Lab. Upton, NY, United States)
Lin, B. (NASA Langley Research Center Hampton, VA, United States)
Long, C. (Pacific Northwest National Lab. United States)
Marshak, A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Matrosov, S. Y. (National Oceanic and Atmospheric Administraion United States)
McFarlane, S. A. (Pacific Northwest National Lab. United States)
Miller, M. (Brookhaven National Lab. Upton, NY, United States)
Min, Q. (State Univ. of New York Albany, NY, United States)
Minnis, P. (NASA Langley Research Center Hampton, VA, United States)
O'Hirok, W. (California Univ. Santa Barbara, CA, United States)
Wang, Z. (Wyoming Univ. Laramie, WY, United States)
Wiscombe, W. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2006
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Public Use Permitted.

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