Recent Trends in Surface Air Temperature over Al-Taif, Saudi Arabia

Variability 0f surface air temperature and distribution over 36 year’s period (1978 to 2013) in Al-Taif, Saudi Arabia, has been studied using Regression Analysis and Theil-Sen nonparametric test. The monthly mean of mean (Tmmean), maximum (Tmmax) and minimum (Tmmin) temperatures levels and their trends have been investigated. The trends in deviations from the reference period (1978–2013) are analyzed and the results showed the following particular findings: • The number of hot days increased by 2.0088 days per year which means that there is 72.317 hot days increased during the last 36 years. The frequency of the hot nights increased by 0.3703 nights per year, this means that there are 13.3308 hot nights increased during the last 36 years. The number of cold nights increased by 0.0587 nights per year this implies that there is 2.113 nights has decreased during the entire period. The number of cold days decreased by -0.2241 day per year which implies that there is 8.064 cold days has decreased during the entire period. • The highest and lowest values of Tdmax are 40.79°C in July 2011 and 31.96°C in February 1999. • The highest and lowest values of Tdmin are 36.9°C in July 2013 and 25.73°C in January 1992. • The monthly mean of daily mean temperature (Tmmean) have increased during the entire period with annual increase 0.0155°C, 0.0636°C, 0.0202°C, 0.0192°C, 0.0333°C, 0.0271°C, 0.0308°C, 0.0497°C, 0.023°C, 0.0248°C, 0.0167°C and -0.0007°C for January to December with major increases in February, August, May and July. • The monthly mean of daily mean temperature (Tmmean) have increased with 0.558°C, 2.2896°C, 0.7272°C, 0.6912°C, 1.1988°C, 0.9756°C, 1.8088°C, 1.7892°C, 0.828°C, 0.8928°C, 0.6012°C in January to November respectively while it decreases with -0.0252°C in December during the full period. • The annual mean of Tdmean is increasing by 0.0269°C per year which implies that over the last 36 years the annual mean temperature has increased by 0.9684°C. • The annual deviations of monthly mean temperature (Tmmean) from the overall mean temperature show major decreasing trends (cooling) in the period (1978 to 1997) and major increasing (warming) trends in the period (1998 to 2013). • The maximum of Tmmax was 37.59°C in July while a minimum of 18.15°C was found in December. • Tmmax have increased in all months with annual increase of, 0.0434°C, 0.1036°C, 0.0629°C, 0.0486°C, 0.0616°C, 0.0478°C, 0.0533°C, 0.0681°C, 0.047°C, 0.0583°C, 0.0416°C and 0.0145°C for the months January to December. The higher increases were in August and February and less increase were in January and November. • The annual mean of daily maximum temperature (Tamax) show an annual increasing trend of 0.0542°C which implies that over the last 36 years the annual mean of daily maximum temperature of Al-Taif has increased by 1.9512°C. • The annual deviation of Tmmax from overall mean temperature show negative trends during the interval (1978 to 1997) and shows major positive trends in the period (1998 to 2013). The maximum cooling was found in the years 1982 and 1992 with 1.55°C and 1.53°C while the maximum warming was recorded in the year 1999 and 2010 with 1.389°C and 1.12°C respectively. • The Tmmin varied between a minimum of 5.63°C in January and a maximum of 25.45°C in July which means that the ratio between the hottest to the coldest Tmmin 4.52. • The increasing trends in the Tmmin values were observed in all months of the year with an annual decrease (cooling) of -0.0117°C, -0.0236°C, -9.00E-05°C, -0.0006°C, -0.0031°C, -0.0046°C and -0.0125°C for Jan., Mar., May, Oct., Nov. and Dec. and has increased (warming) with an annual value of 0.0307°C, 0.0161°C, 0.0201°C and 0.0384°C for Feb., Jun., Jul. and Sep. which implies that the Tmmin has decreased with the values of -0.4212°C, -0.8496°C, -0.0032°C, -0.0216°C, -0.1116°C, -0.1656°C and -0.45°C for Jan., Mar., May, Oct., Nov. and Dec. and has increased with 1.1052°C, 0.5796°C, 0.7236°C, 1.3824°C and 0.126°C for Feb., Jun., Jul. and Sep. during the last 36 years respectively. • The annual mean of daily minimum temperature (Tamin) showed significant increasing trend with an annual rise of 0.0044°C which implies that over the last 36 years the annual mean of daily minimum temperature of Al-Taif has increased by 0.1584°C • The annual deviations from overall mean of (Tamin) show negative trends (cooling) during the periods (1982-1984, 1986, 1989, 1992, 1996-2002 and 2004) and positive trends (warming) in the periods (1978 to 1981, 1985, 1987-1988, 1990-1991, 1993-1995, 2003, and 2005-2013). • The increasing trend in the annual and the monthly mean of daily mean (Tdmean), daily maximum (Tdmax) and daily minimum (Tdmin) temperatures (Tmmin) determined by regression method have been confirmed by the nonparametric Theil-Sen method. This study showed that Al-Taif is vulnerable to the considerable warming temperature trend which requires specific attention towards the energy demands for extra cooling, medical preparedness and water resources.