J.-L. F. Li,
W.-L. Lee, D. E. Waliser, J. D. Neelin, J. P. Stachnik and T. Lee, 2014:
J. Geophys. Res., 119(7), 3809-3824, doi:10.1002/2013JD021038.
Paper (pdf 6.9 MB)
© Copyright 2014 by the American Geophysical Union.
Abstract. Conventional global climate models (GCMs) often consider radiation interactions only with small-particle/suspended cloud mass, ignoring large-particle/falling and convective core cloud mass. We characterize the radiation and atmospheric circulation impacts of frozen precipitating hydrometeors (i.e., snow), using the National Center for Atmospheric Research coupled GCM, by conducting sensitivity experiments that turn off the radiation interaction with snow. The changes associated with the exclusion of precipitating hydrometeors exhibit a number differences consistent with biases in CMIP3 and CMIP5 (Coupled Model Intercomparison Project Phase 3 and Phase 5), including more outgoing longwave flux at the top of atmosphere and downward shortwave flux at the surface in the heavily precipitating regions. Neglecting the radiation interaction of snow increases the net radiative cooling near the cloud top with the resulting increased instability triggeringmore convection in the heavily precipitating regions of the tropics. In addition, the increased differential vertical heating leads to a weakening of the low-level mean flow and an apparent low-level eastward advection from the warm pool resulting in moisture convergence south of the Intertropical Convergence Zone and north of the South Pacific Convergence Zone (SPCZ). This westerly bias, with effective warm and moist air transport, might be a contributing factor in the model's northeastward overextension of the SPCZ and the concomitant changes in sea surface temperatures, upward motion, and precipitation. Broader dynamical impacts include a stronger local meridional overturning circulation over the middle and east Pacific and commensurate changes in low and upper level winds, large-scale ascending motion, with a notable similarity to the systematic bias in this region in CMIP5 upper level zonal winds.
Citation.
J.-L. F. Li, W.-L. Lee, D. E. Waliser, J. D. Neelin, J. P. Stachnik and T. Lee, 2014:
J. Geophys. Res., 119(7), 3809-3824, doi:10.1002/2013JD021038.
Acknowledgments. We thank Akio Arakawa at UCLA, Sun Won, Qing Yue, Seungwon Lee, Eric Fetzer, and Bin Guan at JPL as well as H.-H. Hsu at Academia Sinica, Taiwan, for useful comments. This work has been supported in part by the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) and Earth Science Data Records Uncertainty (ESDR-ERR) programs and in part by the NOAA NA11OAR4310099 (J.D.N.). The contributions by D.E.W. and J.L.L. to this study were carried out on behalf of the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
An edited version of this paper was published by AGU. Copyright (2014) American Geophysical Union. To view the published open abstract, go to AGU Paper.