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Title: Thin Liquid Water Clouds: Their Importance and Our Challenge

Abstract

Many 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 LWP is small (i.e., <100 gm-2) and, thus, the radiative properties of these clouds must be well understood to capture them correctly in climate models. Here 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 broken (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. Seventeen different algorithms participated and their retrieved LWP, optical depth, and effective radii are evaluated using data from several case studies. 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, andmore » we discuss fruitful avenues for future research.« less

Authors:
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Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
985072
Report Number(s):
PNNL-SA-47822
Journal ID: ISSN 0003-0007; ISSN 1520-0477; KP1205010; TRN: US201016%%1757
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Bulletin of the American Meteorological Society, 88(2):177-190; Journal Volume: 88; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ALGORITHMS; CLASSIFICATION; CLIMATE MODELS; CLOUDS; ENERGY BALANCE; EVALUATION; WATER

Citation Formats

Turner, David D., Vogelmann, A. M., Austin, Richard T., Barnard, James C., Cady-Pereira, Karen, Chiu, C., Clough, Shepard A., Flynn, Connor J., Khaiyer, Mandana M., Liljegren, James C., Johnson, Karen L., Lin, B., Long, Charles N., Marshak, A., Matrosov, S. Y., McFarlane, Sally A., Miller, Mark A., Min, Qilong, Minnis, Patrick, O'Hirok, William, Wang, Zhien, and Wiscombe, Warren J. Thin Liquid Water Clouds: Their Importance and Our Challenge. United States: N. p., 2007. Web. doi:10.1175/BAMS-88-2-177.
Turner, David D., Vogelmann, A. M., Austin, Richard T., Barnard, James C., Cady-Pereira, Karen, Chiu, C., Clough, Shepard A., Flynn, Connor J., Khaiyer, Mandana M., Liljegren, James C., Johnson, Karen L., Lin, B., Long, Charles N., Marshak, A., Matrosov, S. Y., McFarlane, Sally A., Miller, Mark A., Min, Qilong, Minnis, Patrick, O'Hirok, William, Wang, Zhien, & Wiscombe, Warren J. Thin Liquid Water Clouds: Their Importance and Our Challenge. United States. doi:10.1175/BAMS-88-2-177.
Turner, David D., Vogelmann, A. M., Austin, Richard T., Barnard, James C., Cady-Pereira, Karen, Chiu, C., Clough, Shepard A., Flynn, Connor J., Khaiyer, Mandana M., Liljegren, James C., Johnson, Karen L., Lin, B., Long, Charles N., Marshak, A., Matrosov, S. Y., McFarlane, Sally A., Miller, Mark A., Min, Qilong, Minnis, Patrick, O'Hirok, William, Wang, Zhien, and Wiscombe, Warren J. Mon . "Thin Liquid Water Clouds: Their Importance and Our Challenge". United States. doi:10.1175/BAMS-88-2-177.
@article{osti_985072,
title = {Thin Liquid Water Clouds: Their Importance and Our Challenge},
author = {Turner, David D. and Vogelmann, A. M. and Austin, Richard T. and Barnard, James C. and Cady-Pereira, Karen and Chiu, C. and Clough, Shepard A. and Flynn, Connor J. and Khaiyer, Mandana M. and Liljegren, James C. and Johnson, Karen L. and Lin, B. and Long, Charles N. and Marshak, A. and Matrosov, S. Y. and McFarlane, Sally A. and Miller, Mark A. and Min, Qilong and Minnis, Patrick and O'Hirok, William and Wang, Zhien and Wiscombe, Warren J.},
abstractNote = {Many 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 LWP is small (i.e., <100 gm-2) and, thus, the radiative properties of these clouds must be well understood to capture them correctly in climate models. Here 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 broken (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. Seventeen different algorithms participated and their retrieved LWP, optical depth, and effective radii are evaluated using data from several case studies. 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 fruitful avenues for future research.},
doi = {10.1175/BAMS-88-2-177},
journal = {Bulletin of the American Meteorological Society, 88(2):177-190},
number = 2,
volume = 88,
place = {United States},
year = {Mon Feb 19 00:00:00 EST 2007},
month = {Mon Feb 19 00:00:00 EST 2007}
}