Variations in Meteorological and Hydrological Quantities due to Climate Change and a Study of Predicted Rainfall Amounts from Climate Change Effects Compared with Observed Values in the Chao Phraya River Basin

Abstract

This study presents the impact of climate change in key meteorological parameters in the Chao Phraya River Basin. Including maximum temperature, minimum temperature and rainfall using output from the Hadley Center’s Generalized Circulation Model (GCM) called “HadCM3 (10) (13)” with an approximate spatial resolution of 180x180 km. This model is listed in Coupled Model Intercomparison Project Phase 5 (CIMP 5) of AR5. The calculations use greenhouse gas emission scenario based on a balanced development pattern that combines both fossil fuels and renewal energy (A1B). The data will be downscaled to study area using the PRECIS regional climate model with approximately 25x25 km resolution. The bias correction technique will be applied using average adjustments based on measurement. Data from 41 meteorological stations in the study and nearby areas from Thai Meteorological Department (TMD) will be used in this study. The study found that during the 20-Year period between 2017-2036, the monthly average maximum and minimum temperatures in the study area are likely to increase by approximately 0.50-2.0 degrees Celsius compared to the 30-year average period of 1981-2010. Monthly rainfall under climate change during 20-year period between 2017-2036, averaged every 5 years shows significant deviations both above and below the 30-year average period of 1981-2010 by 10-50 mm per month. The runoff under climate change was conducted using rainfall – runoff relationship. The results showed significant variations between 5-year average periods during the 20-year time frame of 2017-2036. The comparison of predicted monthly average rainfall for the 5-year period of 2017-2021 under climate change scenarios with observed values from the Nakhon Luang, Lower Pasak and Khlong Priao-Sao Hai Irrigation Projects in the Chao Phraya River Basin showed significant differences.