Dynamical downscaling of the western North Pacific from CCSM4 simulations during the last glacial maximum and late 20th century using the WRF model: model configuration and validation

Abstract. Using the Weather Research and Forecasting (WRF) model (version 3.5.1), dynamical downscaling of the Community Climate System Model, version 4 (CCSM4), simulations of the last glacial maximum (LGM) and 20th century (ensemble member #6) run were conducted to simulate ten years of climate over the western North Pacific during the LGM and modern climates, respectively. This paper describes the downscaling procedures for the Weather Research and Forecasting (WRF) model experiments and the quantitative and qualitative model validations comparing with the CCSM4 LGM and 20th century simulations results.

Results of the dynamical downscaling of the CCSM4 LGM paleoclimate and twentieth century using the WRF model show not only that the WRF model is capable of long-term simulations in the paleoclimate state of LGM, but also that the WRF model can correct biases in the general circulation model (GCM), producing more realistic spatial distributions of the pressure-level variables. The downscaling of a GCM model using the WRF model (36 km) for the regional climate simulation is considered computationally cost-effective and reliable from the perspectives of model thermodynamics in general, although there are some model errors still existing with dynamic variables.