Scale- and Aerosol-Aware Kain-Fritsch Convection Parameterization: Formulations and Tests

Friday, 19 December 2014
Kiran V Alapaty1, John S Kain2, Jerold Allen Herwehe1, O Russell Bullock1, Shaocai Yu1, Xiaoliang Song3, Guang Jun Zhang3 and Laura D Fowler4, (1)U.S. Environmental Protection Agency, Durham, NC, United States, (2)National Oceanic and Atmospheric Administration, National Severe Storms Laboratory, Norman, OK, United States, (3)Scripps Institution of Oceanography, Center for Clouds Chemistry, La Jolla, CA, United States, (4)NCAR, Boulder, CO, United States
Our presentation focuses on the development and testing of a seamless version of the Kain-Fritsch (KF) convection parameterization scheme that works across all spatial scales down to 1 km. To update the KF scheme for multiple scales in the WRF model, first, we proposed a scaling parameter to introduce scale-dependence in the KF scheme for use with various convection parameters, and then we developed new formulations for: (1) the convective adjustment timescale; (2) the entrainment of environmental air; (3) the fallout of condensates from updrafts; and (4) the stabilizing capacity. These scale-dependent formulations make the KF scheme operable at all scales down to about sub-kilometer grid resolution. Additionally, we have introduced methodologies for (5) impacting grid-scale vertical velocity with convective updrafts and downdrafts, (6) eliminating double counting of precipitation due to concurrent usage of grid-scale and subgrid-scale cloud formulations for any grid cell, and (7) including aerosol indirect effects by embedding a double moment convective cloud microphysics within the KF scheme. Results obtained from using the regional WRF and global MPAS models will be presented to demonstrate the effects of these science updates to the KF scheme.