TOPOGRAPHIC, SEASONAL AND ARIDITY INFLUENCES ON RAINFALL VARIABILITY IN WESTERN SAUDI ARABIA

In the Western region of Saudi Arabia, rainfall is characterized by variability in space and time. The mean annual and seasonal rainfall are investigated on the basis of the records of 30 stations over the course of 35 years revealing a positive relationship with elevation. Four representative stations with complete records are selected to determine the aridity index of the area. The results show that the spatial variation of annual rainfall moderately reflects the effect of topography. Seasonal isohyet maps are more practical than annual ones in arid regions due to the interaction between different sources of moisture. Seasonal maps can also be helpful in identifying recharge and flood estimation. The aridity index classifies the study area as underlying desert conditions and water deficit except the mountainous areas which could be described as semi arid. The results are important for future climate and water studies in Western Saudi Arabia.