Climatological study of the southwestern region of Saudi Arabia. I. Rainfall analysis

The annual rainfall in the southwestern region of Saudi Arabia was analyzed. The study area was divided into regions and subregions depending on the altitude above mean sea level and mean annual rainfall. The classification was supported by comprehensive statistical analysis. The results showed that spring is the main season for rainfall, followed by summer. The gamma distribution was found to provide the best fit, followed by the normal distribution. The analysis of interannual and relative interannual variability showed that regions I and V (adjacent to and furthest away from the coast, respectively, in the southern part of the study area) can be classified as arid, while regions II, III and IV (between and to the north of regions I and V) are classified as semi-arid.