Saudi Arabia has an extremely dry climate, but in the southwest region, comparatively, more rainfall events occur within the effects of topography and seasonality.
This article focuses on studying and analysing the rainfall variability in Asir area. Data for rainfall variability was collected from the Metrological Station in Abha and Khamis Mushait for the period from 1978 to 2014. Statiscal analyses were carried to determine variability in annual rainfall among years for each station separately. The mean, standard deviation, and coefficient of variation were used to calculate the rainfall variability on long-term annual basis.
Present results for Abha and khamis separately: Abha showed rainfall varied and fluctuated over the time, with lower value of 84.8 mm in 2009, and higher value of 639.5 in 1983.and mean of 254.0.mm over the years, and Khamis showed rainfall varied with lower value of 34.1 in 2009, and higher value of 355.9 in 1997and mean of 178.7mm. The average annual rainfall reached more than 202.9 mm. Variation among the years was high with a coefficient of variation for equal to 0.64 and the standard deviation was 110.2 and the standard error of the mean was 102.8.