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Evaluation of Dynamical Downscaling in a Fully Coupled Regional Earth System Model

Presentation Date
Friday, December 17, 2021 at 11:25am
Convention Center - Room 280-282



Regional earth system models (RESMs) provide the capability to dynamically downscale larger data sets from global reanalyses or earth system models. The dynamical downscaling leverages the RESM benefits including prescribed initial and boundary conditions, ability to run at higher spatial and temporal resolutions, and the flexibility to target specific physics and parameterizations best suited for the regional environment of interest. Dynamical downscaling in a fully coupled RESM has a slightly different application in that the surface state and fluxes are provided by the coupled component models and not the source global dataset as would be the case in an atmosphere-only simulation. This study provides an evaluation of the results from dynamically downscaled simulations from the CESM Decadal Prediction Large Ensemble (CESM-DPLE) using the Regional Arctic System Model (RASM), with the Weather Research and Forecasting (WRF) model for the atmosphere, for a pan-Arctic domain. The CESM-DPLE dataset provides three-dimensional atmospheric fields for the initial conditions, boundary updates, and nudging for the top half of the WRF model. The results indicate that the top half of the atmosphere is constrained to and follows the larger CESM-DPLE dataset. Meanwhile the lower part of the atmosphere, and most critically the surface state and fluxes, can freely evolve and are more dependent on the RASM physics than on the CESM-DPLE forcing dataset.

Funding Program Area(s)