Space observations of cold-cloud phase change
Name
Lindzen_Space observations.pdf
Size
2.64 MB
Format
Adobe PDF
Checksum (MD5)
ffdd75bcb027a569413be362abe3cfe4
Author(s)
Choi, Yong-Sang
Lindzen, Richard Siegmund
Ho, Chang-Hoi
Kim, Jinwon
Date Issued
May 2010
Journal
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Citation
Choi, Y.-S. et al. “Space Observations of Cold-cloud Phase Change.” Proceedings of the National Academy of Sciences 107.25 (2010): 11211–11216. ©2010 by the National Academy of Sciences
Version
Final published version
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[superscript -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.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1073/pnas.1006241107
