There are few observational and numerical studies of the summertime low-level jet (LLJ) over the Persian Gulf, known as the shamal. In this study, the Weather Research and Forecasting (WRF) model accurately simulates the LLJ's vertical structure, nocturnal features and strong diurnal variation of the wind. The casestudy period is divided into a period during which the shamal is spatially extended (strong winds over the Gulf and Iraq) and a period during which it is less spatially extended (strong flow only over the Gulf). Orography, mountain slope and land/sea breeze are found to be key factors for the shamal diurnal variation of wind speed and wind direction; the Blackadar mechanism appears to be secondary to the heating in forcing the shamal. The Zagros Mountains not only channel the northwesterly winds but also provide a barrier for the easterly monsoon airflow, which maximizes the wind speed. Only during the less extensive period does the Zagros Mountains slope significantly affect the shamal wind intensity and direction. Both shallow and steep mountain slope sensitivity studies feature a jet-like flow over the Persian Gulf. The steep slopes cause larger wind speeds; however, the shallow slopes reveal a stronger diurnally varying wind direction due to larger heating and cooling of the sloping terrain. It is also shown that, during the less extensive period, the land breeze and the lower friction over the sea increase the intensity of the nocturnal jet over the Gulf. Copyright c 2011 Royal Meteorological SocietyKey Words: blocking; inertial oscillation; land/sea breeze; shamal

Among the parameters that must be considered for an offshore wind farm development, the stability conditions of the marine atmospheric boundary layer (MABL) are of significant importance. Atmospheric stability is a vital parameter in wind resource assessment (WRA) due to its direct relation to wind and turbulence profiles. A better understanding of the stability conditions occurring offshore and of the interaction between MABL and wind turbines is needed. Accurate simulations of the offshore wind and stability conditions using mesoscale modelling techniques can lead to a more precise WRA. However, the use of any mesoscale model for wind energy applications requires a proper validation process to understand the accuracy and limitations of the model. For this validation process, the weather research and forecasting (WRF) model has been applied over the North Sea during March 2005. The sensitivity of the WRF model performance to the use of different horizontal resolutions, input datasets, PBL parameterisations, and nesting options was examined. Comparison of the model results with other modelling studies and with high quality observations recorded at the offshore measurement platform FINO1 showed that the ERA-Interim reanalysis data in combination with the 2.5-level MYNN PBL scheme satisfactorily simulate the MABL over the North Sea.

This is a numerical study of the effects of the Nile Delta (ND) man-made greening on local climate. We compared a control simulation, which employs the present-day ND vegetation, with a desertification experiment. It was found that the low surface albedo of the agricultural ND increases net radiation, which in turn raises potential evapotranspiration (PET). This suggests that agricultural use increases the water demand by enhancing PET. Non-local effects are also observed on a frontal system over the eastern Mediterranean Sea that shifted farther away from the coast. This shift is attributed to a stronger land breeze in the present-day land-cover.