IMPACT OF CLIMATIC CHANGE ON RIYADH CITY RAINFALL

Warming of the atmosphere affects many things of the global water cycle such as increasing evaporation, changing precipitation patterns and intensity. This study investigates the impact of climate changes on the rainfall in Riyadh, Saudi Arabia. The rainfall data from four stations over approximately fifty years was statistically analyzed to study the changes in the rainfall frequency and the annual total rainfall amount. The study concluded that the general trend of total annual rainfall between (1965 and 2016) can be divided into three distinct periods. The first trend between 1965 and 1997 was obviously increasing; however, the second trend between 1997 and 2012 was decreasing, thereafter the last trend up to 2016 returned to increase. Moreover, studying the changes in rainfall frequency using HYFRAN-PLUS software recommends considering an increment of 21.61% percentage as a correction factor of the currently maximum daily rainfall depth for one hundred year return period. Furthermore, applying Akaike and Bayesian Information Criteria, Gamma Probability Distribution Function (PDF) was the best PDF to statistically represent the return period frequency for three of the four rainfall stations.