Abstract

This comparative study analyzes the general rainfall in Ha'il and Assir based on the maximum daily and annual rainfall over 42 years (1976-2017). The data were collected at seven stations in Ha'il and ten stations in Assir to detect climate change phenomena there. The Shapiro-Wilk Test examined the rainfall data distribution. The Levene and ANOVA Tests examined variances of homogeneity. To analyze the general rainfall trend and its statistical significance, the study adopts the Semi-Averages Ratio, Binomial, and the Student's T-Tests. In Ha'il, the Semi-averages method results, and the Binomial Test showed a maximum annual and daily rainfall decrease. The Student's T-Test confirmed this trend for the daily and annual rainfall in Simira, Al Ha'it, Ha'il, and Al Ghazalah stations, and for the maximum daily rainfall in the stations of Simira, Al Ha'it, Uqlat Bin Jibrin, and Al Ghazala. The results revealed increasing annual rainfall in Sabah Billahmar, Al Tajir, Bani Thawr, and As Sudah. Similar trends were detected for the maximum daily rainfall in Khaybar Al Janoub, Bani Thawr, and An Namas. A rainfall decrease was detected in all other stations in Assir. The results of the Binomial and the Student's T-Tests varied. The rest of the annual rainfall trends have no statistical significance and are just phenomenal. This study concluded that the decreasing and increasing trends of annual and maximum daily rains do not definitively indicate there is climate change in Assir and Ha'il. Despite some decreasing rainfall trends of statistical significance, this did not deny some increasing rainfall trends.

Keywords

Maximum daily rainfall, Annual rainfall, Variability trend, Statistical test.

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