Selection of Suitable General Circulation Model Precipitation and Application of Bias Correction Methods: A Case Study from the Western Thailand

Abstract

The General Circulation Models (GCMs) precipitations are generally characterized by the biases and low spatial resolution. These two are the major limiting factors for direct application of GCMs scenarios in the studies of climate change impact assessment. Based on 17 experiments over the two river basins of the western Thailand, Six GCMs were analyzed for their ability to simulate the magnitude and spatial variability of current precipitation. Monthly precipitation scenarios from six GCMs (17 experiments) are downloaded from the IPCC data centre. Three bias-correction techniques namely, scaling, empirical-gamma and gamma-gamma transformations were applied on a daily scale of 9 years (1991–1999) to improve the quality of the selected ECHAM4/OPYC SRES A2 and B2 precipitation for the Mae Ping and Mae Klong River Basins in the Western Thailand. All the three bias correction methods have been compared with observed precipitation based on statistical parameters. Gamma-gamma transformation method is found to be effective in correcting the rainfall frequency and intensity simultaneously as compared to other methods. The bias corrected daily precipitation is useful in studies related to climate change and water resources management at basin level.