التوزيع الزماني و المكاني للأمطار على جنوب غرب المملكة العربية السعودية

الملخص EN

Rainfall in the Kingdom of Saudi Arabia differs from season to season, year to year, and between the regions.

The objective of this research is to study the spatial and temporal distributions over southwest region of Saudi Arabia.

The study of monthly rainfall, seasonally and annually over southwest region of Saudi Arabia shows that, the largest amount of rain was in spring, followed by summer.

The winter and autumn seasons received less rainfall in the region.

It was also found that the mountain areas received the largest amount of rain in comparing with the other lower relief areas.

This study showed that the highest rate of annual rain was in the year 1997 at all stations except Bisha and Najran of which the highest annual average of rain was in the years 1982 and 1996 respectively, while the lowest annual average of the rain was over Najran in 1981 where no rain record.

In addition, it was found that the trend of rain decreased with time during the years (1978-2008) at all stations; while the trend of rain increased with time at Gazan and Najran during the same period.

From the spatial distribution of rainfall over the southwest region, it was found that highest values of rainfall concentrated in the central region, especially over the highest stations.

The gradient values of rain were high in the spring and summer, concentrated over the central region.

On the other hand, rainfall gradient values were weak in the winter and autumn, which indicated that there was no difference in the amount of the rainfall between the stations.

The period of occurrence of rainfall over region can be classified into two periods, the first period in spring and the second period occurs in summer.