A Unified Cloud Parameterization: One Scheme to Represent All Convective Clouds
To simulate the variety of cloud types observed in the atmosphere, climate modelers have historically used different representations for different clouds. This approach causes discontinuities as simulated conditions change such that one cloud scheme turns off and another one turns on. A unified cloud parameterization overcomes this limitation by being general enough that it can be used to represent all cloud types, ensuring smooth transitions of the simulated clouds as environmental conditions change. A team of climate modelers from the National Center for Atmospheric Research, University of Wisconsin–Milwaukee, University of Washington, and Pacific Northwest National Laboratory found improvements in simulated clouds when a statistical interface between cloud properties and cloud processes was introduced in a turbulence scheme to accommodate a diversity of overlapping cloud microphysical conditions within model grid cells. This was allowed to extend throughout the lower atmosphere to simulate all clouds. The researchers expect that alternate methods of accounting for unresolved variability, such as quadrature, could reduce the computation cost of sampling the variability.
Thayer-Calder, K., A. Gettelman, C. Craig, S. Goldhaber, P. A. Bogenschutz, C.-C. Chen, H. Morrison, J. Höft, E. Raut, B. M. Griffin, J. K. Weber, V. E. Larson, M. C. Wyant, M. Wang, Z. Guo, and S. J. Ghan. 2015. “A Unified Parameterization of Clouds and Turbulence using CLUBB and Subcolumns in the Community Atmosphere Model,” Geoscientific Model Development 8, 3801–21. DOI: 105194/gmd-8-3801-2015.