A semi-implicit semi-Lagrangian regional climate model: The Canadian RCM

A new regional climate model (RCM) is presented in this paper and its perfo rmance is investigated through a pair of 60-day simulations. This new model is based on the dynamical formulation of the Cooperative Centre for Resear ch in Mesometeorology (CCRM) mesoscale nonhydrostatic community model and o n the complete subgrid-scale physical parameterization package of the secon d-generation Canadian Centre for Climate modeling and analysis General Circ ulation Model (CCCma GCMII). The main feature of the Canadian RCM (CRCM) co mes from the very efficient semi-implicit and semi-Lagrangian (SISL) numeri cal scheme used for the integration of the fully elastic nonhydrostatic Eul er equations. The efficiency of the SISL scheme allows the use of longer ti me steps (at least by a factor of 5) for the integration of this model (e.g ., the 45-km resolution version of the model uses a 15-min time step). A co mplete description of the numerical formulation of the model is presented w ith a review of the principal characteristics of the physical package. A pa ir of two-month-long winter simulations is also analyzed to investigate the behavior of the model and to evaluate the potential of the SISL integratio n scheme in the context of regional climate simulation. The two integration s, produced with a 45-km resolution version of the model, developed realist ic small-scale details from the low-resolution GCMII fields used to initial ize and drive the RCM.