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.C. A-M. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 703733 (STILLING project). This research was supported by the research projects: Swedish BECC, MERGE, VR (2014-5320)

Corrosion and air pollution from diesel exhaust.

There is widespread public concern, often strongly expressed, over the fumes and black exhaust emitted from diesel vehicles. Such emissions are particularly noticeable in traffic jams, road tunnels, badly ventilated garages and on hilly roads. These emissions are injurious to humans and other living beings; the black dirt and acidic smuts emitted from diesel exhaust are deposited on nearby surfaces corroding metal works, disfiguring buildings and damaging vegetation. With the growing volume and density of road traffic, the problem is becoming increasingly serious. The present study is an investigation into corrosion and atmospheric pollution due to diesel exhaust. In this study an attempt is made towards reducing the concentrations of the undesirable constituents in the exhaust gases by (i) treating the fuel prior to its admission into the cylinder and (ii) treating the exhaust gases before their discharge into the atmosphere. Accordingly, various additives are added in various dosages to the fuel or are injected into the exhaust gas stream in a specially designed afterburner and the effects of these additives on the concentrations of the undesirable constituents in the exhaust are studied. The results of three representative additives, viz: Isoamyl nitrate (X), Aniline (Y) and Cyclohexane (Z) only are reported in this thesis. The effects of additives in the fuel on the cetane No. of the base fuel, the concentrations of CO, formaldehyde, smoke, oxides of nitrogen and the corrosion and deposits due to the exhaust gases are investigated. It is shown that significant reduction in the concentrations of the above mentioned constituents could be brought about by the use of certain additives in their optimum dosages. The side effects of these additives on engine performance (fuel consumption and engine running conditions) are also investigated. The effects of injecting the three representative additives mixed with heated air into the exhaust gas stream in the specially designed afterburner on the concentrations of CO, formaldehyde, smoke, oxides of nitrogen and oxides of sulphur are investigated (this technique has not been attempted with diesel exhaust prior to the present work). It is shown that the injection of these additives into the exhaust gases reduces the concentrations of the undesirable constituents in the exhaust gases except that of oxides of nitrogen, which increased. However, the effects of the additives are only noticeable at higher engine loads where the concentrations of these constituents are generally high. All tests were carried out on a medium speed, four stroke, single cylinder indirect injection compression ignition engine with fixed injection timing

HYDRUS simulations of the effects of dual-drip subsurface irrigation and a physical barrier on water movement and solute transport in soils

Subsurface drip irrigation systems, compared to other irrigation systems, enhance the delivery of water and nutrients directly into the root zone. However, in light-textured soils, certain quantities of water may percolate below the root zone due to the subsurface position of drip lines and/or poor management of irrigation systems. The main objective of this paper is to evaluate three technologies to enhance a spatial distribution of water and solutes in the root zone and to limit downward leaching. The three technologies include (a) a physical barrier, (b) a dual-drip system with concurrent irrigation, and (c) a dual-drip system with sequential irrigation. To achieve this objective, we performed computer simulations using the HYDRUS (2D/3D) software for both bare and vegetated soils. The results indicate that the physical barrier is more efficient than dual-drip systems in enhancing the water distribution in the root zone while preventing downward leaching. On the other hand, the dual-drip system improves water distribution in sandy soils. Additionally, the dual-drip system with sequential irrigation, followed by the dual-drip system with concurrent irrigation, is the most efficient in limiting downward leaching of solutes. © 2013 Springer-Verlag Berlin Heidelberg