Future Climate Change Scenario at Hot Semi-arid Climate of Ahmedabad (23.04°N, 72.38°E), India Based on Statistical Downscaling by LARS-WG Model

Abstract

General Circulation Models (GCMs) are widely used nowadays to simulate future climate scenarios. However, present GCMs have limited skills in simulating the complex and local climate features and to provide reliable information on precipitation and temperature data which are the principal inputs to hydrologic impact assessment models. Furthermore, the outputs provided by GCMs are too coarse to be used by such hydrologic models, as they require information at much finer scales. Downscaling of GCMs output is, therefore, a necessity. Keeping this in view, the present study aimed at verifying the skills of LARS-WG, a popular downscaling tool, in downscaling weather data in hot semi-arid climate of Ahmedabad and predict and analyze the future changes of temperature (daily maximum and minimum) and precipitation based on IPCC SRA2 scenario generated by seven GCMs’ predictions for the near (2011–2030), medium (2046–2065) and far (2080–2099) future periods. For this purpose, daily rainfall, maximum and minimum temperature data for the study site Ahmedabad for 1969–2013 have been utilized. LARS-WG showed excellent skill in downscaling maximum and minimum temperature and reasonably good skill in downscaling daily rainfall data at Ahmedabad. The downscaled precipitation from the predictions of seven GCMs indicated no coherent change trends among various GCMs’ predictions of precipitation during near, medium and far future periods. Predicted rainfall in monsoon season (JJAS) based on the ensemble mean of seven GCMs showed a decrease in rainfall in near future i.e. 2011–2030 by about 2%; however, during medium future (2046–2065) it is predicted to increase and remain close to the baseline value; and during far future (2080–2099) period it is predicted to increase by about 5% compared to the baseline value. Summer maximum temperature is predicted to increase by 0.7, 2.0 and 4.0 deg. Celsius during 2011–2030, 2046–2065 and 2080–2099 respectively at the study site. Winter minimum temperature is predicted to increase by 1.0, 2.5 and 5.0 deg. Celsius during 2011–2030, 2046–2065 and 2080–2099 respectively at Ahmedabad.