Simulating the climate of South Pacific islands using a high resolution model

摘要

Downscaled regional climate simulations for Fiji and Federated States of Micronesia (FSM) from Coupled Model Intercomparison Project 3 (CMIP3) Global Coupled Models (GCMs) are carried out as part of the Pacific Climate Change Science Program (PCCSP) using the CSIRO stretched-grid Conformal Cubic Atmospheric Model (CCAM) for the period 1980-2000. The model simulations are performed at 60 km and at 8 km horizontal resolutions. The higher resolution is chosen to partly resolve the detailed orography of the countries selected, providing insight into the spatial distribution of temperature and precipitation for an individual island that GCMs are unable to represent. The downscaling is carried out in two steps. First, CCAM simulations are run on a global 60 km grid using bias-corrected sea surface temperatures (SST) and sea ice from six CMIP3 GCMs. Three of these 60 km simulations are then further downscaled to 8 km resolution over the two countries. The focus of this paper is validation of these high-resolution simulations against gridded analyses, satellite rainfall climatologies and available station data for rainfall and temperature for the period 1980-2000. The results show that high resolution orography plays an important role in capturing the current climate. The validation demonstrates that the 8 km simulations are capable of realistically depicting the current climate when the topography influences the wind flow and rainfall (Fiji), performing better than both the GCMs and the 60 km downscaled simulations. However, the performance of the 8 km simulations is similar to the GCM and 60 km simulations when topographical features are not present (FSM).