Historical Reconstruction of Hydroclimatic Data Based on the Control Runs of GCMs over Sabah and Sarawak, Malaysia

The historical reconstruction of hydroclimate conditions over Sabah and Sarawak states of Malaysia was performed as a first step for the assessment study of climate change impact on water resources. The outputs of ECHAM5 GCM simulation from Max Planck Institute for Meteorology of Germany were downscaled to fine grid resolution data by means of a Regional Hydroclimate Model (RegHCM). The RegHCM, which is a coupled non-hydrostatic atmospheric and upscaled land surface process model, has been customized for Sabah and Sarawak region. A sequence of three model domains, respectively at 81km, 27km, and 9km grid resolutions, was used. The GCM output datasets in the 200–300 km spatial resolution during the historical period of 1970–2000 were downscaled into the 9 km grid resolution that is required for water resources analysis at the watershed scale. The detailed soil and land cover maps provided by Malaysian government have been processed for preparation of required model parameters: such as, roughness height, emissivity, albedo, leaf area index (LAI), soil hydraulic conductivity, and soil rooting depth. Sea surface temperature data in the GCMs was used in the downscaling exercise in order that the historical simulations are consistent with corresponding future simulations.