Numerical Errors in Coupling Micro- and Macrophysics in the Community Atmosphere Model

Tuesday, 16 December 2014
David J Gardner1, Peter Caldwell1, Jean M Sexton2 and Carol S Woodward1, (1)Lawrence Livermore National Laboratory, Livermore, CA, United States, (2)Southern Methodist University, Dallas, TX, United States
In this study, we investigate numerical errors in version 2 of the Morrison-Gettelman microphysics scheme (MG2) and its coupling to a development version of the macrophysics (condensation/evaporation) scheme used in version 5 of the Community Atmosphere Model (CAM5). Our analysis is performed using a modified version of the Kinematic Driver (KiD) framework, which combines the full macro- and microphysics schemes from CAM5 with idealizations of all other model components. The benefit of this framework is that its simplicity makes diagnosing problems easier and its efficiency allows us to test a variety of numerical schemes. Initial results suggest that numerical convergence requires time steps much shorter than those typically used in CAM5.