Abstract

The Ping Basin is the major basin in Northern Thailand with drainage area of 35,000 km2. Climate trend of Ping Basin for current period (1961-2010) and projected trend (2011-2059) are discussed for maximum and minimum temperature and precipitation. Current trend was analyzed from actual representative three stations data and averaging at basin level. Measures of the variability analysis included temporal variability, trend, anomaly, coefficient of variation (C.V) and index. The basin showed high temporal climate variability throughout the study period (1961-2059). The current period showed significant positive trend of minimum temperature and negative trend of maximum temperature while no significant trend in precipitation with high variability, fluctuation and inconsistency. Minimum temperature of Ping increased at a faster rate than that of Thailand. In the first two decades (1961-80), maximum temperature increased by 1.5°C and decreased by 1°C in the later decades (1981-2010) while minimum temperature dropped by 2.3°C in the period of 1961-80 and increased by 1.53°C in the years 1981-2010 as compared to the long term 50 years normal temperature of 1961-2010. Intercomparison of 5 GCMs at 50 km spatial scale in projecting future trends indicated that all the five models show similar prediction of future mean temperature while ECHAM5 had the most robust prediction power of rainfall. Projected trend (2011-2059) from ECHAM4 PRECIS RCM debiased, calibrated and validated at finer 20 km spatial scale shows precipitation will increase as compared to current intensity and minimum temperature will significantly increase at a higher rate (R2=0.76 at the rate of 0.042°C\annum) than maximum temperature (R2=0.5 at the rate of 0.038°C\annum). Our findings are consistent with projections for Mekong Basin.

Keywords: Climate trend; Projection; GCM intercomparison; Ping basin; Mekong region