Intercomparison of Arctic regional climate simulations: Case studies of January and June 1990

Abstract

Advances in regional climate modeling must be strongly based on analysis of physical processes in comparison with data. In a data-poor region such as the Arctic; this procedure may be enhanced by a community-based approach, i.e., through collaborative analysis by several research groups. To illustrate this approach, simulations were performed with two regional climate models, HIRHAM and ARCSyM, over the Arctic basin to 65°N, laterally driven at the boundaries by observational analyses. It was found that both models are able to reproduce reasonably the main features of the large-scale flow and the surface parameters in the Arctic. Distinct differences in the simulations can be attributed to specific characteristics of the boundary layer and surface parameterizations, which result in surface flux differences, and to the lateral moisture forcing, both of which affect moisture availability in the atmosphere. Further disparities are associated with the additional degrees of freedom allowed in the coupled model ARCSyM. Issues of model configuration and experimental design are discussed, including domain size, grid spacing, boundary formulations, model initialization and spin-up, and ensemble approaches. In order to reach definitive conclusions in a regional climate model intercomparison, ensemble simulations with adequate spin-up and equivalent initialization of surface fields will be required. Copyright 2000 by the American Geophysical Union.