Tarek Merabtene

Assessment of Seasonal and Annual Rainfall Trends and Variability in Sharjah City, UAE

Although a few studies on rainfall spatial and temporal variability in the UAE have been carried out, evidence of the impact of climate change on rainfall trends has not been reported. This study aims at assessing the significance of long-term rainfall trends and temporal variability at Sharjah City, UAE. Annual rainfall and seasonal rainfall extending over a period of 81 years (1934–2014) recorded at Sharjah International Airport have been analyzed. To this end, several parametric and nonparametric statistical measures have been applied following systematic data quality assessment. The analyses revealed that the annual rainfall trend decreased from −3u2009mm to −9.4u2009mm per decade over the study periods. The decreasing annual rainfall trend is mainly driven by the significant drop in winter rainfall, particularly during the period from 1977 to 2014. The results also indicate that high probability extreme events have shifted toward low frequency (12.7 years) with significant variations in monthly rainfall patterns and periodicity. The findings of the present study suggest reevaluating the derivation of design rainfall for infrastructure of Sharjah City and urge developing an integrated framework for its water resources planning and risk under climate change impacts scenarios.

Impact of surface ocean acidification on the CO2 absorption rate

The rising level of atmospheric CO2 and consequently the acidification of the surface ocean affect the CO2 absorption rate. However, there are no mathematical models to describe the impacts of acidification on the rate of CO2 absorption. Therefore, the objective of this study was to develop simple mathematical models to describe the dependence of the CO2 absorption rate on the pH of the surface ocean. The developed models predict that the CO2 absorption rate is enhanced with acidification directly proportional to the increase in the abundance of * 23 H CO in the surface ocean. In addition, the models predict that the increasing rate of CO2 absorption reflects the increasing rate of increase of CO2 in the atmosphere.

Wave transformation and hydrodynamic characteristics of wave-breaking models coupled with Boussinesq equations

ABSTRACT This paper investigates the different wave transformation and hydrodynamic characteristics of three different wave-breaking models – friction-type, eddy viscosity-type and surface roller-type models – coupled with the weakly nonlinear Boussinesq equations with improved linear dispersion characteristics based on comparisons between predicted and measured wave-breaking phenomena. The experimental cases consider not only different breaker types but also different bathymetry conditions, i.e. uniform slopes and a uniform slope with a submerged breakwater. Although all of the properly calibrated wave-breaking models yield equally good predictions of wave heights, mean water levels and trough levels of breaking and broken waves, the models show clear differences in their predictions of the undertow velocity, near-bottom wave orbital velocity profile, wave skewness, and wave asymmetry. The importance of such differences in the predictive capabilities of these widely used wave-breaking models should be highlighted, particularly when extending the model to the prediction of coastal morphodynamics around the surf zone.

Potential impact of global warming on whiting in a semi-enclosed gulf

In this article, the potential impact of the rising atmospheric CO2 level on whiting in the semi-enclosed Arabian Gulf is considered. Chemical equilibrium models were developed to assess the spatial and temporal distributions of aragonite and calcite saturation indices (ΩAragonite and Ωcalcite) due to acidification resulting from increasing atmospheric CO2 level. The models accounted for the spatial and temporal distributions of salinity and temperature in the surface water of the gulf, which vary in the range of 36-43 psu and 15°C to 32°C. The spatial variations of CaCO3 saturation revealed that the southern part of the gulf along the coastlines of the UAE, Qatar and Bahrain experiences the highest CaCO3 saturation levels and corresponds to the observed whiting phenomenon. Potential acidification and erosion of the whiting phenomenon in the gulf threaten the ecosystem, which deserves significant additional attention from the scientific community and decision makers in the region.

Risk analysis for drought management of water resources systems

The increasing scarcity of water resources in many regions in the world reveals that the robustness of todays water supply systems may not be enhanced and conflict may not be alleviated unless optimal management based on risk analysis is considered. The present study introduces the application of an integrated risk analysis model to determine optimal management strategies that minimize drought damages and threat of water shortage. The newly developed risk model uses a global risk index, referred to as the drought risk index (DRI), as objective function when evaluating optimal management strategies and assess the susceptibility of the water supply system to drought scenarios. Genetic algorithm is used as optimal search procedure to minimize the DRI objective function by clustering the search of the optimal water supply solutions inside a defined acceptable risk space. The application of the model to the water resources system in Fukuoka City, western Japan, was found a highly efficient tool toward an improved performance of actual water resources during drought.