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Space observations of cold-cloud phase change

Title
Space observations of cold-cloud phase change
Authors
Choi Y.-S.Lindzen R.S.Ho C.-H.Kim J.
Ewha Authors
최용상
SCOPUS Author ID
최용상scopus
Issue Date
2010
Journal Title
Proceedings of the National Academy of Sciences of the United States of America
ISSN
0027-8424JCR Link
Citation
vol. 107, no. 25, pp. 11211 - 11216
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
This study examines the vertically resolved cloud measurements from the cloud-aerosol lidar with orthogonal polarization instrument on Aqua satellite from June 2006 through May 2007 to estimate the extent to which the mixed cloud-phase composition can vary according to the ambient temperature, an important concern for the uncertainty in calculating cloud radiative effects. At -20°C, the global average fraction of supercooled clouds in the total cloud population is found to be about 50% in the data period. Between -10 and -40°C, the fraction is smaller at lower temperatures. However, there are appreciable regional and temporal deviations from the global mean(> ± 20%) at the isotherm. In the analysis with coincident dust aerosol data from the same instrument, it appears that the variation in the supercooled cloud fraction is negatively correlated with the frequencies of dust aerosols at the -20°C isotherm. This result suggests a possibility that dust particles lifted to the cold cloud layer effectively glaciate supercooled clouds. Observations of radiative flux from the clouds and earth's radiant energy system instrument aboard Terra satellite, as well as radiative transfer model simulations, show that the 20% variation in the supercooled cloud fraction is quantitatively important in cloud radiative effects, especially in shortwave, which are 10-20 W m-2 for regions of mixed-phase clouds affected by dust. In particular, our results demonstrate that dust, by glaciating supercooled water, can decrease albedo, thus compensating for the increase in albedo due to the dust aerosols themselves. This has important implications for the determination of climate sensitivity.
DOI
10.1073/pnas.1006241107
Appears in Collections:
엘텍공과대학 > 환경공학전공 > Journal papers
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