The performance of CAM5 physics modules at high spatial resolution

Poster PDF

Description

Rapid development and evaluation of the next generation physics suite for global climate models requires the ability to easily isolate processes and test parameterizations across a range of scales. Current computing capabilities do not allow one to run a global model at resolutions anticipated in ten years. In addition, the performance of the current physics suite when simulating regional-scale atmospheric variability has not been characterized. In parallel with the development of the new computational architectures for climate models, we have adopted a methodology of running and evaluating the performance of global climate model physics parameterizations at a range of spatial scales. As part of a Laboratory Directed Research and Development (LDRD) project under PNNL’s Aerosol Climate Initiative, the physics suite from the Advanced Physics Community Atmosphere Model v.5 (CAM5) is currently being ported to the regional Weather Research and Forecasting (WRF) model. This includes the Zhang and McFarlane scheme for deep convection, the Park and Bretherton scheme for shallow convection, the Morrison and Gettleman scheme for microphysics, the Bretherton and Park scheme for the planetary boundary layer, the Modal Aerosol Model (MAM) representation of aerosols, and a reduced MOZART gas-phase chemistry mechanism. The RRTMG radiation scheme employed by CAM5 is already available in WRF version 3.2, and other groups have coupled the CLM land-use scheme to WRF. While the full MOZART mechanism is available in WRF version 3.2, we are porting a reduced version that is typically employed by CAM5. By porting the CAM5 physics suite to WRF, we will be able to evaluate those parameterizations at multiple spatial scales. The modular nature of WRF will also enable individual CAM5 physics parameterizations to be directly compared to other parameterizations used for research applications in regional models. In this study, we will show the performance and behavior of some of the CAM5 physics parameterizations compared to field campaign data as well as with other parameterizations. When evaluating simulated aerosols, we have employed the strategy of the Aerosol Modeling Testbed, in which the initial and boundary conditions, emissions, meteorology, trace gas chemistry, and emissions for the MAM aerosol module are the same for other aerosol models. In this way, an objective and systematic assessment of the performance of simulating aerosol properties in relation to computational expense can be obtained. A similar approach is also used when evaluating clouds and other meteorological processes.