This numerical study focuses on a dense fog event that occurred during the night of 21-22 January 2008 in the Grand Casablanca region, on the northwestern coast of Morocco. This fog event, which lasted for 15 h, is simulated by the mesoscale non-hydrostatic model Meso-NH and analyzed using conventional meteorological observations from two synoptic stations of the region, Meteosat Second Generation (MSG) satellite imagery and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis. Results demonstrate that this fog event included the formation of radiation fog over a continental zone and its extension to the coastal zone through the lowering of low-stratus clouds, which is in agreement with observations and is captured well by the Meso-NH model. Sensitivity experiments show that coastal fog prediction improves with improved sea-surface temperature. Model skill also depends on the adjustment of microphysical parameters when a single-moment microphysical scheme is used, and on reliable initial conditions.

Using a fog event approach, the local meteorological and synoptic characteristics of fogs that formed over the Grand Casablanca (GCB) region during a 9-yr period (2001–09) are investigated. A climatological study of fog, with emphasis on the fog temporal variability and spatial distribution, is carried out on the basis of hourly surface meteorological observations at two synoptic stations in the region. The fog events are classified into fog types, using an objective classification algorithm, and are characterized by their duration, intensity, and times of onset and dissipation. In addition, fog events are classified into two distinct categories (isolated and widespread) on the basis of their spatial extent. K-means cluster analysis is applied to the patterns of mean sea level pressure in ERA-Interim reanalyses at 0000 UTC to determine the synoptic circulation types associated with fog occurrence in the GCB region. Results show that the fog frequency at the inland suburban station is more recurrent than at the coastal urban station. The fog events are predominantly of the advection–radiation type, with a marked tendency of nighttime occurrence during the winter. The spatial distribution analysis points out the localized character of fog and reveals the possibility of different fog types occurring when fog is present near the two stations simultaneously. Furthermore, the interaction between local- and large-scale mechanisms suggests that advective processes associated with sea-breeze circulation during daytime, followed by radiative processes early in the night, often lead to fog formation over the GCB region.

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The present study investigates hydrodynamic lubrication by ferrofluids of finite journal bearings using the Jenkins model. A magnetic field created by displaced finite wire is used. A numerical solution for the modified Reynolds equation using the finite difference method is obtained. Static characteristics of finite journal bearings are analyzed using 2 control parameters: magnetic force coefficient and Jenkins viscosity. The obtained results are compared to those from Neurenger‐Rosensweig model. It is shown that pressure, load capacity, attitude angle, and side leakage increase and friction factor decreases when increasing the value of each control parameter at low and medium eccentricity ratios. However, the Jenkins viscosity parameter decreases the load capacity and increases the friction factor at high eccentricity ratios.

Considering the rotation of ferromagnetic particles, the present study investigates hydrodynamic lubrication by ferrofluids of finite journal bearings using the Shliomis model. A magnetic field created by displaced finite wire is used. A numerical solution for the modified Reynolds equation using the finite difference method is obtained. Static characteristics of finite journal bearings are analysed using three control parameters: rotational viscosity, magnetization and volume concentration of the ferromagnetic particles. It is shown that the pressure, load capacity, attitude angle and side leakage increase and the friction coefficient decreases when increasing the value of each control parameter. Similar trends are also obtained when increasing values of eccentricity for a fixed value of each control parameter except for the decrease of the attitude angle. , 21 H is the magnetic field intensity and M 0 is the equilibrium magnetization given by the Langevin formula 8 : 206 S. LAGHRABLI ET AL.

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