03 December 2014

Intercomparison of the Cloud Water Phase among Global Climate Models

Summary

0
0
1
248
1420
Uniuversity of Wyoming
11
3
1665
14.0

Normal
0

false
false
false

EN-US
ZH-CN
X-NONE

/* Style Definitions */
table.MsoNormalTable
{mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0in 5.4pt 0in 5.4pt;
mso-para-margin:0in;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:Cambria;
mso-ascii-font-family:Cambria;
mso-ascii-theme-font:minor-latin;
mso-hansi-font-family:Cambria;
mso-hansi-theme-font:minor-latin;
mso-font-kerning:1.0pt;
mso-fareast-language:ZH-CN;}

Mixed-phase clouds with both liquid and ice coexisting play a critical role in modulating the Earth’s radiation flux, and precipitation formation. The ratio of liquid water to ice in mixed-phase clouds, largely determined by the presence of ice nuclei and cloud temperature, alters their radiative properties. In this study, the supercooled liquid fraction of mixed-phase clouds is compared among six state-of-the-art global climate models (GCMs) and with NASA Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP) retrievals. It is found that the GCMs predict vastly different distributions of cloud phase (i.e., liquid versus ice) for a given temperature, and none of them are capable of reproducing the spatial distribution or magnitude of the observed phase partitioning. All the GCMs underestimate liquid water at mixed-phase cloud temperatures, which can affect cloud radaitive forcings, because of the difference in optical properties of liquid versus ice. The sensitivity of the simulated cloud phase in GCMs to the choice of heterogeneous ice nucleation parameterization is investigated. The response to a change in ice nucleation is quite different for each GCM, and the implementation of the same ice nucleation parameterization in all GCMs does not reduce the differences in simulated phase among GCMs. The results suggest that processes subsequent to ice nucleation (e.g., the growth of ice crystals through Wegener-Bergeron-Findeisen process, autoconversion, accretion, and sedimentation) are at least as important in determining phase simulated by GCMs, and thus should be the focus of future studies aimed at reducing uncertainties among GCMs.

Contact
Muge Komurcu
University of Wyoming
Funding
Publications
Komurcu, M, T Storelvmo, I Tan, U Lohmann, Y Yun, J Penner, Y Wang, X Liu, and T Takemura.  2014.  "Intercomparison of the Cloud Water Phase Among Global Climate Models."  doi:10.1002/2013JD021119.
Acknowledgments

M. Komurcu would like to acknowledge David M. Winker, Steven Platnick and Robert Pincus for treasured discussions regarding the uncertainties in satellite retrievals and Eugene E. Clothiaux and Jerry Y. Harrington for providing valuable comments on the influence of crystal habit in retrieval algorithms. This work was supported in part by the facilities and staff of the Yale University Faculty of Arts and Sciences High Performance Computing Center. X. Liu and Y. Wang thank the support by the DOE’s Office of Science/ Biological and Environmental Research, through Earth System Modeling Program. PNNL is operated for DOE by Battelle Memorial Institute under contract DE-AC06-76RLO 1830. T. Takemura is supported by the Funding Program for Next Generation World-Leading Researchers of the Cabinet Office, Government of Japan (GR079). U. Lohmann would like to acknowledge support from the BACCHUS EU FP7-603445 project. We also would like to thank the anonymous reviewers, whose valuable comments helped to clarify and improve the paper. Satellite retrievals used in this study and described in Section 2 are available online. CALIOP retrievals can be downloaded from https://eosweb.larc.nasa.gov/order-data. NCEP Reanalysis 2 products are available online at http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis2.pressure... LWP and IWP data products are available online athttp://ladsweb.nascom.nasa.gov/data/search.html. CloudSat IWP products are available online at http://www.cloudsat.cira.colostate.edu. ISCCP LWP and IWP products are available online from different providers listed in the project description website: http://isccp.giss.nasa.gov/products/obtaining.html