9 research outputs found
Study of the Impact of the Natural Production of Coastal Marine Aerosols on the Dynamics and Microphysical Behavior of a Convective Cloud
Abstract The atmosphere contains suspended particles of various origins natural or anthropogenic that constitutes the atmospheric aerosol. The aerosol cloud interaction is a fundamental mechanis m that influences the precipitation process. To study the impact of ma rine aerosols, especially those generated in coastal areas, on the dynamics and microphysical behavior of the clouds, two numerical models were coupled. The first, calculates the coastal ma rine aerosol spectrum that could be generated under a given weather condition at the sea surface. The p redicted spectrum is then introduced, as in itial aerosol spectra, to a cloud model with a detailed microphysics. The simulat ions performed have focused on a convective cloud (mixed phase) using distinct initial aerosols spectra of different origins in order to highlight the potential effect of ma rine aerosol naturally produced in surf zone on the dynamics and microphysics of the cloud. The results carried out indicates an important contribution of marine aerosol in the process of precipitation formation by promoting an early start of precipitat ion at lower alt itudes, leading to increased amounts of precipitation reaching the ground
Radar Rainfall Estimation in Morocco: Quality Control and Gauge Adjustment
This study focused on investigating the impact of gauge adjustment on the rainfall estimate from a Moroccan C-band weather radar located in Khouribga City. The radar reflectivity underwent a quality check before deployment to retrieve the rainfall amount. The process consisted of clutter identification and the correction of signal attenuation. Thereafter, the radar reflectivity was converted into rainfall depth over a period of 24 h. An assessment of the accuracy of the radar rainfall estimate over the study area showed an overall underestimation when compared to the rain gauges (bias = −6.4 mm and root mean square error [RMSE] = 8.9 mm). The adjustment model was applied, and a validation of the adjusted rainfall versus the rain gauges showed a positive impact (bias = −0.96 mm and RMSE = 6.7 mm). The case study conducted on December 16, 2016 revealed substantial improvements in the precipitation structure and intensity with reference to African Rainfall Climatology version 2 (ARC2) precipitations
ANALYSE SPATIALE ET TEMPORELLE DES VENTS DE SURFACE A PARTIR DU MODELE ALADIN ET DES DONNEES DE TELEDETECTION SUR LA REGION D'UPWELLING DES CANARIES
International audienceThe quality of surface wind speeds and directions derived from the regional model for weather forecasting "Aire limitée et adaptation dynamique" (ALADIN), in use at the Directorate of Meteorology (DOM) of Morocco, are examined by comparison with the 10-m wind speeds and directions observed by meteorological stations and with satellite wind analysis estimated from QuikSCAT, and new surface wind products, known as Blended wind products, which consist of merged satellite observations and numerical model estimates, over oceanic regions NorthWest of Africa during the period 2003-2006. Overall, the various surface wind sources exhibit good agreement. Highest correlations are found for ALADIN and Blended; however, ALADIN wind speeds and the associated variability tend to be underestimated in comparison with in-situ and satellite estimates. ALADIN wind speed biases are 1m/s, and the associated RMS difference values vary between 1,15m/s and 2,15m/s. Similar good agreements are found for wind direction comparisons. Indeed, for winds higher than 3m/s, the mean and the standard deviation difference values do not exceed 6° and 30°, respectively. However, some large discrepancies between ALADIN and the satellite wind estimates are found at some specific local areas such as Essaouira and the Canary Islands. The former are mainly associated with the impacts of orography.La qualité de la vitesse et la direction du vent de surface issu du modèle régional "Aire Limitée et adaptation dynamique" (ALADIN) pour la prévision météorologique, actuellement opérationnel à la Direction de la météorologie nationale du Maroc, sont étudiés par comparaison avec la vitesse du vent de 10 m et les directions observées par les stations météorologiques et à l'analyse du vent par satellite estimée à partir de QuikSCAT, à partir de nouveaux produits sur les vents de surface, les produits du vent "Blended", fusionnant des observations satellitaires et les estimations du modèle numérique, sur les côtes du nord-ouest de l'Afrique au cours de la période 2003-2006. Sur l'ensemble, le vent de surface des différentes sources présente un bon accord. Les corrélations les plus élevées se trouvent entre ALADIN et "Blended", mais la vitesse du vent ALADIN et la variabilité associée ont tendance à être sous-estimées par rapport aux vents in-situ et les estimations par satellite. Le biais de la vitesse du vent ALADIN est de l'ordre de 1 m/s, et les valeurs associées des différences de RMS varient entre 1,15 m/s et 2,15 m/s. De bons accords similaires sont trouvés dans la comparaison des directions du vent. En effet, pour les vents de plus de 3m/s, la moyenne et les valeurs de la différence de l'écart type ne dépassent pas 6 ° et 30 °, respectivement. Toutefois, certains écarts élevés entre ALADIN et les estimations du vent par satellite sont trouvés sur certains domaines spécifiques locaux telles que Essaouira et les îles Canaries. Ces écarts sont essentiellement liés aux impacts de l'orographie
Impact des vents sur l'upwelling au sud du Maroc ; apport du modèle ROMS forcé par les données ALADIN et QuikSCAT
International audienceLa présence du Courant des Canaries dans le domaine océanique du Sud du Maroc a un effet majeur sur la température de la surface marine au large et à la côte, et sur l'upwelling des Canaries. L'objectif de notre étude était de simuler le comportement des courants par le modèle ROMS (Regional Ocean Modelling System) avec deux forçages par le vent issus du modèle de méso-échelle ALADIN et du diffusiomètre QuikSCAT. À cet effet, le recours au modèle numérique ALADIN a permis de mettre en évidence la sensibilité des courants d'upwelling aux variations spatiales et temporelles des vents côtiers. La majorité des zones côtières à températures froides représentant l'upwelling ont pu être reproduites. L'utilisation d'ALADIN semble améliorer les corrélations avec les observations pour l'upwelling de la côte nord, avec des valeurs de 60% à 70%. Le modèle ROMS forcé par des données ALADIN ou QuikSCAT reproduit bien la dynamique de cette région d'upwelling. Cette étude montre aussi que la présence des îles Canaries perturbe le Courant des Canaries et génère de l'activité méso-échelle. Cette activité est également associée aux principaux caps de la côte marocaine et résulte généralement de l'influence de la topographie côtière, et des conditions atmosphériques synoptiques. Enfin, entre les zones côtières et l'océan ouvert, le contraste de température de la surface marine répond aux fluctuations du vent et à l'impact de la dynamique atmosphérique
Une formulation parabolique pour la propagation en profondeur finie des ondes de gravité en surface
This paper deals with the parabolic formulation of propagation equations of gravity waves in surface in terms of angular capability with respect to the privileged propagation direction. This parabolic formulation is obtained by splitting the Berkhoff equation operator into two parabolic operators representing progressive and regressive wave propagation. The use of Pade approximants permits to derive simultaneously parabolic equations for the transmitted waves and the reflected waves. Two well-known reference examples, which represent the propagation of the wave when a caustic occur, are studied numerically and the results are compared with those of the literature. (C) 2001 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS.Cet article présente une formulation parabolique des équations de propagation, en profondeur finie, des ondes de gravité en surface en terme de capacité angulaire par rapport à la direction de propagation privilégiée. Cette formulation est obtenue par factorisation de l’opérateur de l’équation de Berkhoff en deux opérateurs représentant les ondes progressives et régressives. L’utilisation des approximants de Padé permet d’accéder simultanément à des équations paraboliques pour les ondes transmises et pour les ondes réfléchies. Deux exemples de propagation de la houle en présence d’une bosse circulaire et d’une bosse elliptique sont étudiés numériquement. La comparaison des résultats avec ceux de la littérature prouve la supériorité de cette équation parabolique vis-à-vis de celle de Radde
Remote Lab Experiments in Mechanic: The Compound Pendulum
In the teaching of experimental sciences, practical work plays a crucial role since it allows learners to transfer the knowledge acquired in theoretical courses into practical skills. For this purpose, laboratories allow learning by experience and aim at involving students, which reinforces learning receptivity. Recent years have seen an increasing use of online labs, including both virtual and remote labs, Remote labs, providing online interfaces to physical labs, allow students to conduct experiments with real-world equipment anywhere and at any time. This paper proposes a model of design, development and implementation of a remote manipulation in an E-Lab. It is the compound pendulum which is part of the handling offered to the students of the 1st year of university in the field of physical sciences. The aim of this paper is to make this approach available to allow more experiments on a digital platform in order to allow learning for all, independently of time and place
Offshore Wind Energy Resource in the Kingdom of Morocco: Assessment of the Seasonal Potential Variability Based on Satellite Data
This study provides a first estimate of the offshore wind power potential along the Moroccan Atlantic shelf based on remotely sensed data. An in-depth knowledge of wind potential characteristics allows assessment of the offshore wind energy project. Based on consistent daily satellite data retrieved from the Advanced Scatterometer (ASCAT) spanning the period from 2008 to 2017, the seasonal wind characteristics were statistically analyzed using the climatological Weibull distribution functions and an assessment of the Moroccan potential coastal wind energy resources was qualitatively analyzed across a range of sites likely to be suitable for possible exploitation. Also, an atlas of wind power density (WPD) at a height of 80 m was provided for the whole Moroccan coast. An examination of the bathymetrical conditions of the study area was carried out since bathymetry is among the primary factors that need to be examined with the wind potential during offshore wind project planning. The results were presented based on the average wind intensity and the prevailing direction, and also the wind power density was shown at monthly, seasonal and interannual time scale. The analysis indicated that the coastal wind regime of the southern area of Morocco has the greatest energy potential, with an average power density which can reach in some places a value around 450 W/m2 at heights of 10 m and 80 m above sea level (a.s.l) (wind turbine hub height) more particularly in the south of the country
On the temporal memory of coastal upwelling off NW Africa
25 pages, 16 figures, supporting Information http://onlinelibrary.wiley.com/doi/10.1002/2013JC009559/suppinfoWe use a combination of satellite, in situ, and numerical data to provide a comprehensive view of the seasonal coastal upwelling cycle off NW Africa in terms of both wind forcing and sea surface temperature (SST) response. Wind forcing is expressed in terms of both instantaneous (local) and time-integrated (nonlocal) indices, and the ocean response is expressed as the SST difference between coastal and offshore waters. The classical local index, the cross-shore Ekman transport, reproduces reasonably well the time-latitude distribution of SST differences but with significant time lags at latitudes higher than Cape Blanc. Two nonlocal indices are examined. One of them, a cumulative index calculated as the backward averaged Ekman transport that provides the highest correlation with SST differences, reproduces well the timing of the SST differences at all latitudes (except near Cape Blanc). The corresponding time lags are close to zero south of Cape Blanc and range between 2 and 4 months at latitudes between Cape Blanc and the southern Gulf of Cadiz. The results are interpreted based on calculations of spatial and temporal auto and cross correlations for wind forcing and SST differences. At temporal scales of 2–3 weeks, the alongshore advection of alongshore momentum compensates for interfacial friction, allowing the upwelling jet and associated frontal system to remain active. We conclude that the coastal jet plays a key role in maintaining the structure of coastal upwelling, even at times of relaxed winds, by introducing a seasonal memory to the system in accordance with the atmospheric-forcing annual cycleThis work has been supported by project TIC-MOC (CTM2011–28867) of the Spanish Ministerio de Ciencia e Innovación. Partial funding from the Institut de Recherche pour le Développement, UMR EME 212, is also gratefully acknowledged. Aïssa Benazzouz was partially supported by the 50th Anniversary Young African fellowship program of the Intergovernmental Oceanographic Commission. Evan Mason was supported by a Spanish government JAE-Doc grant (CSIC), cofinanced by FSE. Jesus Peña-Izquierdo was funded through a FPI doctoral grant linked to project MOC2 (CTM2008-06438-C02- 01) of the Spanish Ministerio de Ciencia e Innovación. The SST data were provided by GHRSST and the U.S. National Oceanographic Data Center, in a project partly supported by the NOAA Climate Data Record (CDR). QuikSCAT and CCMP global wind were obtained from the NASA Physical Oceanography Distributed Active Archive Center at the Jet Propulsion Laboratory. ROMS development at UCLA is supported by the Office of Naval Research (currently grant N00014-08-1–0597), the applications here shown were partially supported by the National Center for Supercomputing Applications under grant OCE030007 and utilized the ABE systemPeer reviewe
An improved coastal upwelling index from sea surface temperature using satellite-based approach - The case of the Canary Current upwelling system
17 pages, 16 figures, 3 tablesA new methodology to derive an SST-based upwelling index was based on a rigorous spatial analysis of satellite SST fields and their variability, by referring to previous works, from Wooster et al. (1976) to Santos et al. (2011). The data was precautiously processed by considering data quality aspects (including cloud cover) and the best way to derive accurate coastal SST and its offshore reference. The relevance of the developed index was evaluated by comparing its spatial and seasonal consistency against two wind-based indices as well as with the previous SST-based indices, largely superseding these later ones in term of overall quality and spatio-temporal dynamic. Our index adequately describes the spatio-temporal variability of the coastal upwelling intensity in the Canary Current upwelling system and has the advantage of describing complementary aspects of the coastal dynamics of the region that were not covered by Ekman-based indices.The proposed methodology is generic and can be easily applicable to various coastal upwelling systems, especially the four major eastern boundary upwelling ecosystems. © 2014 Elsevier Ltd.We thank the 50th Anniversary Young African fellowship programme of IOC (Intergovernmental Oceanographic Commission) as well as the French Institute of Research for Development (IRD) for partially supporting this workPeer Reviewe