Recent trends in wind speed across Saudi Arabia, 1978–2013: a break in the stilling

We analyse recent trends and variability of observed near-surface wind speed from 19 stations across Saudi Arabia (SA) for 1978–2013. The raw wind speed data set was subject to a robust homogenization protocol, and the stations were then classified under three categories: (1) coast, (2) inland and (3) mountain stations. The results reveal a statistically significant (p < 0.05) reduction of wind speed of −0.058 m s⁻¹ dec⁻¹ at annual scale across SA, with decreases in winter (−0.100 m s⁻¹ dec⁻¹) and spring (−0.066 m s⁻¹ dec⁻¹) also detected, being non-significant in summer and autumn. The coast, inland and mountain series showed similar magnitude and significance of the declining trends across all SA series, except for summer when a decoupled variability and opposite trends of wind speed between the coast and inland series (significant declines: −0.101 m s⁻¹ dec⁻¹ and −0.065 m s⁻¹ dec⁻¹, respectively) and the high-elevation mountain series (significant increase: +0.041 m s⁻¹ dec⁻¹) were observed. Even though wind speed declines dominated across much of the country throughout the year, only a small number of stations showed statistically significant negative trends in summer and autumn. Most interestingly, a break in the stilling was observed in the last 12-year (2002–2013) period (+0.057 m s⁻¹ dec⁻¹; not significant) compared to the significant slowdown detected in the previous 24-year (1978–2001) period (−0.089 m s⁻¹ dec⁻¹). This break in the slowdown of winds, even followed by a non-significant recovery trend, occurred in all seasons (and months) except for some winter months. Atmospheric circulation plays a key role in explaining the variability of winds, with the North Atlantic Oscillation positively affecting the annual wind speed, the Southern Oscillation displaying a significant negative relationship with winds in winter, spring and autumn, and the Eastern Atlantic negatively modulating winds in summer.