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Impacts of the Sahel-Sahara Interface Reforestation on West African Climate: Intra-Annual Variability and Extreme Temperature Events

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Atmospheric and Climate Sciences 2019年第1期9卷 35-61页

作者： Ibrahima Diba moctar camara Arona Diedhiou Laboratoire d’Océanographie des Sciences de l’Environnement et du Climat (LOSEC) UFR Sciences et Technologies Université A. SECK de Ziguinchor Ziguinchor Sénégal IRD CNRS Grenoble INP IGE Université Grenoble Alpes Grenoble France

The impacts of the reforestation of the Sahel-Sahara interface on the seasonal distribution of the surface temperature and thermal extremes are studied in the Sahel (West African region lying between 11°N and 18°N). We performed a simulation with the standard version of the RegCM4 model followed by another one using the altered version of the same model taking into account an incorporated forest. The impacts of the vegetation change are assessed by analyzing the difference between the two runs. The reforestation may influence strongly the frequency of warm days (TG90P) and very warm days (TX90P) by decreasing it over the reforested zone from March to May (MAM) and the entire Sahel during the June-August (JJA) period. These TG90P and TX90P indices decrease may be due to the strengthening of the atmospheric moisture content over the whole Sahel region and the weakening of the sensible heat flux over the reforested zone. The analysis also shows a decrease of the TN90P indice (warm nights) over the Sahel during the wet season (JJA) which could be partly associated with the strengthening of the evapotranspiration over the whole Sahel domain. The analysis of additional thermal indices shows an increase of the tropical nights over the entire Sahel from December to February (DJF) and during the warm season (MAM). The strengthening of the tropical night is partly associated with an increase of the surface net downward shortwave flux over the reforested zone. When considering the heat waves, an increase (a decrease) of these events is recorded over the southern Sahel during JJA and SON periods (over the whole Sahelian region during DJF), respectively. Changes in latent heat flux appear to be largely responsible for these extreme temperatures change. This work shows that the vegetation change may impact positively some regions like the reforested area by reducing the occurrence of thermal extremes;while other Sahel regions (eastern part of the central Sahel) could suff

关键词： RegCM4 Reforestation Heat Waves Sahel

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Spatial Distribution of Cordex Regional Climate Models Biases over West Africa

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International Journal of Geosciences 2015年第9期6卷 1018-1031页

作者： Alioune Badara Sarr moctar camara Ibrahima Diba Laboratoire d’Océanographie des Sciences de l’Environnement et du Climat (LOSEC) Université Assane SECK de Ziguinchor Ziguinchor Senegal

The objective of this work is to analyze the spatial distribution of biases of nine (9) regional climate models (RCMs) and their ensemble average used under the framework of COordinated Regional climate Downscaling EXperiment (CORDEX) project over West Africa during the summer period. We assessed the ability of RCMs to represent adequately West African summer rainfall by analyzing some statistical parameters such as the relative bias, the standard deviation, the root mean square error (RMSE) and the correlation coefficient between observation data (GPCP used as reference) and regional climate models outputs. We first analyzed the relative bias between GPCP climatology and the other available observed data (CRU, CMAP, UDEL, GPCC, TRMM and their ensemble mean). This analysis highlights the big uncertainty on the quality of these observed rainfall data over West Africa which may be largely due to the rarity of?in situ?measurement data over this region. The statistical analysis with respect to GPCP rainfall shows the presence of large relative bias values over most part of West Africa for engaged RCMs. However their ensemble mean outperforms individual RCMs by exhibiting the weakest relative change. The RMSE values are weak over West Africa except over and off the Guinea highlands for RCMs and the Era-interim reanalysis. The spatial distribution of the coefficient of correlation between the observation data and RCMs shows that all models (except HIRHAM) present positive values over the Northern Sahel and the Gulf of Guinea. The model of the DMI exhibits the weakest values of correlation coefficient. This study shows that RCMs simulate West African climate in a satisfactory way despite the fact that they exhibit systematic biases.

关键词： CORDEX Regional Climate Models Rainfall

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Intra-Seasonal Variability of Aerosols and Their Radiative Impacts on Sahel Climate during the Period 2000-2010 Using AERONET Data

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International Journal of Geosciences 2013年第1期4卷 267-273页

作者： Mamadou Simina Drame moctar camara Amadou T. Gaye Laboratoire d’Océanographie des Sciences de l’Environnement et du Climat UFR des Sciences et Technologies Université de Ziguinchor Ziguinchor Sénégal Laboratoire de Physique de l’Atmosphère et de l’Océan Siméon Fongang Université Cheikh Anta Diop Dakar-Fann Sénégal

This paper presents a study using in situ measurements (AERONET data) to characterize the intra-seasonal variability of aerosols and their shortwave radiative impacts on Sahel (11N - 18N and 20W - 15E) climate using a long time series (2000 to 2010) from AERONET data. We first used the MISR aerosol optical depth (AOD) averaged between 2000 and 2010 to identify dust maxima regions. They are mainly located over Eastern Mauritania-Northern Mali and Eastern Niger-Western Tchad (near the Bodele depression). Moreover the aerosol loading is stronger during the spring (MAM) and particularly during the summer (JJA). The analysis of AERONET data at 4 Sahelian stations (Dakar, Agoufou, Banizoumbou and Ouagadougou) shows that Sahel is under dust influence all year long. The dust season is mainly located between March and October, with two peaks of AOD recorded in March and June;while the maximum of biomass burning activity is recorded in winter (December to February). The radiative forcing of aerosols on the Sahelian climate results mainly in a cooling as well as at the surface than at the top of the atmosphere (TOA) but the forcing is stronger at the surface and particularly during the summer (JJA) and spring (MAM) periods. Although there is not a sharp difference between DJF and SON periods from a station to another one when considering the aerosol loading (AOD), the radiative forcing is stronger at the surface and weaker at the TOA during DJF for most stations. The analysis of the force effectiveness (ratio between AOD and the radiative forcing) suggests that the BOA radiative forcing is mainly influenced by the nature of aerosols.

关键词： AERONET Aerosol Optical Depth Radiative Forcing

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An experimental investigation of transient cavitation control on a hydrofoil using hemispherical vortex generators

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Journal of Hydrodynamics 2021年第6期33卷 1139-1147页

作者： Ebrahim Kadivar Takaho Ochiai Yuka Iga Ould el moctar Ship Technology Ocean Engineering and Transport SystemsUniversity of Duisburg-EssenDuisburgGermany Institute of Fluid Scienece Tohoku UniversitySendaiJapan

Unsteady cavitation causes noise,damage,and performance decline in the marine engineering and fluid machinery ***,finding a method to control the cavitation and its destructive effects is important for the industrial *** this work,we proposed a passive method to control the unsteady behavior of transient cavitation at the medium Reynolds *** this aim,we performed an experimental study using a high-speed camera to analyze the effects of hemispherical vortex generators(VGs)on the cavitation dynamics around a hydrofoil *** addition,the pressure pulsations induced by the collapse of the cavity structures in the wake region of the hydrofoil were captured with a pressure transducer mounted on the wall downstream of the *** results showed that the instability behaviors of the cavity structures on the hydrofoil were mitigated using the proposed cavitation passive control *** addition,the pressure pulsations in the wake region of the hydrofoil were reduced *** can be concluded that the suppression of cavitation instabilities can improve the operating life and reliability of the marine and hydraulic systems.

关键词： Hydrodynamic cavitation cavitation passive control hemispherical vortex generators pressure pulsations high speed observation

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Study of Ground Deformation Caused by Underground Tunneling with Physical Model Test

Study of Ground Deformation Caused by Underground Tunneling ...

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作者： SANA moctar 绍兴文理学院

学位级别：硕士

隧道施工期间的地面变形主要是由施工产生的地层损失所引起的。本文首先利用Peck公式研究了双隧道施工过程中的地层变形,然后引入了物理模型试验,以模拟排水法在隧道施工过程中引起的地层损失。目的是模拟隧道施工过程中因地层损失引起... 详细信息

隧道施工期间的地面变形主要是由施工产生的地层损失所引起的。本文首先利用Peck公式研究了双隧道施工过程中的地层变形,然后引入了物理模型试验,以模拟排水法在隧道施工过程中引起的地层损失。目的是模拟隧道施工过程中因地层损失引起的地层沉降,探讨不同地层损失率下的变形规律。在第一部分中,从第一条隧道开挖过程中现场采集的监测数据中,采用Peck公式通过对称法获得第二条隧道的变形曲线。最后,使用叠加法获得最终曲线。对获得的各种曲线的分析表明,叠加法会出现较大的变形,其峰值位于隧道的中心。该方法适用性较好,可预测双隧道施工期间的变形。此外,为了更好地理解我们的研究,实验过程如下:首先建立物理模型,为其配备隧道模型,位移传感器,然后使用干燥的石英砂填充模型箱,最后通过排水法模拟隧道沉降过程。在模拟结束时获得的结果表明,影响地层沉降的直接因素都与地层的损失有关,此外,地层的表面和内部的沉降随地层损失的增加而增加。地层沉降槽的曲线呈正态分布,地层损失引起的地表下陷槽范围约为3d,地层内部沉降槽的宽度随深度的增加而减小。此外,定义了地层沉降槽的体积传递率,即地层沉降槽的体积与地层损失的比值,发现地层沉降槽的体积传递率与地层深度成反比,与地层损失率成正比。在地铁隧道施工中,地面变形是不希望发生的,也是不可避免的影响。因此,最好的选择是研究现象,以便更好地理解问题。对该物理模型的研究非常有启发性,因为它可以很好地理解地层损失的概念,定义不同变形速率下的地面变形并推导几种变形规律以预测隧道施工期间的沉降。

关键词：地层损失室内模型试验排液法沉降槽体

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Effects of seismic devices on transverse responses of piers in the Sutong Bridge

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Earthquake Engineering and Engineering Vibration 2015年第4期14卷 611-623页

作者： Shen Xing Alfredo camara Ye Aijun State Key Laboratory for Disaster Reduction in Civil Engineering Tongji University Department of Civil and Engineering City UniversityLondonUnited Kingdom PhD

The Sutong Bridge in China opened to traffic in 2008, and is an arterial connection between the cities of Nantong and Suzhou. It is a cable-stayed bridge with a main span of 1,088 m. Due to a tight construction schedule and lack of suitable seismic devices at the time, fixed supports were installed between the piers and the girder in the transverse direction. As a result, significant transverse seismic forces could occur in the piers and foundations, especially during a return period of a 2500-year earthquake. Therefore, the piers, foundations and fixed bearings had to be designed extraordinarily strong. However, when larger earthquakes occur, the bearings, piers and foundations are still vulnerable. The recent rapid developments in seismic technology and the performance-based design approach offer a better opportunity to optimize the transverse seismic design for the Sutong Bridge piers. The optimized design can be applied to the Sutong Bridge(as a retrofit), as well as other bridges. Seismic design alternatives utilizing viscous fluid dampers(VFD), or friction pendulum sliding bearings(FPSB), or transverse yielding metallic dampers(TYMD) are thoroughly studied in this work, and the results are compared with those from the current condition with fixed transverse supports and a hypothetical condition in which only sliding bearings are provided on top of the piers(the girder can move "freely" in the transverse direction during the earthquake, except for frictional forces of the sliding bearings). Parametric analyses were performed to optimize the design of these proposed seismic devices. From the comparison of the peak bridge responses in these configurations, it was found that both VFD and TYMD are very effective in the reduction of transverse seismic forces in piers, while at the same time keeping the relative transverse displacements between piers and the box girder within acceptable limits. However, compared to VFD, TYMD do not interact with the longitudinal disp

关键词： Sutong Bridge cable-stayed bridge seismic devices transverse response bridge piers viscous fluid dampers(VFD) friction pendulum sliding bearings(FPSB) transverse yielding metallic dampers(TYMD)

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Hydrogeochemical Characterization of Aquifer Systems and Surface Water/Groundwater Relations in the Lower Senegal River Valley

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Journal of Geoscience and Environment Protection 2024年第6期12卷 232-254页

作者： Abibatou camara Fatou Diop Ngom moctar Diaw Cheikh Tidiane Wade Ibrahima Mall Department of Geology Cheikh Anta Diop University Dakar Senegal Department of Applied Geosciences and Environment Amadou Mahtar Mbow University Dakar Senegal

This study assesses the chemical quality of water resources in the Lower Senegal River valley, based on 35 samples collected in November 2022. Major ion concentrations in surface water and groundwater were analyzed using classical geochemical interpretation diagrams (Piper, GIBBS, etc.) and multivariate geostatistical analyses, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results revealed three types of facies: Ca-Mg-HCO3-type facies, characteristic of poorly mineralized waters such as surface waters and groundwater from dune formations and the alluvial plain close to the hydraulic axis;Na-Cl type facies associated with well waters located in the alluvial plain that tap Inchirian or Nouakchottian shallow reservoirs and Maastrichtian deep borehole waters;and mixed Ca-Cl and Na-HCO3 type facies observed in certain floodplain and dune reservoirs. The results showed a strong correlation between sodium, chlorides, bromides, and electrical conductivity, indicating a significant contribution of these ions to groundwater mineralization. The various sources of water mineralization include mixing processes between surface water or rainwater, or calcite or dolomite dissolution processes (for weakly mineralized waters), basic exchanges or inverse basic exchanges between the aquifer and the water table (for moderately mineralized waters), and evaporation processes, halite dissolution, and paleosalinity during periods of marine transgression and regression (for highly mineralized waters). The study also highlighted the high vulnerability of the alluvial aquifer to pollution from intensive irrigated agriculture, as significant quantities of sulfates and nitrates were measured in some samples. These results also highlight the importance of water quality management in the Lower Senegal Valley, particularly as concerns the protection of the alluvial aquifer against pollution from irrigated agriculture.

关键词： Senegal River Valley Groundwater Pollution Agriculture Alluvial Aquifer

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Remote ischemic preconditioning as treatment for non-ischemic gastrointestinal disorders: Beyond ischemia-reperfusion injury

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World Journal of Gastroenterology 2014年第13期20卷 3572-3581页

作者： Carlos Rodrigo camara-Lemarroy Departamento de Medicina Interna Hospital Universitario "Dr. José E. González"Universidad Autónoma de Nuevo LeónMonterreyNL 64460México

Common gastrointestinal diseases such as radiation enteritis(RE),acute pancreatitis,inflammatory bowel diseases(IBD)and drug-induced hepatotoxicity share pathophysiological mechanisms at the molecular level,mostly involving the activation of many pathways of the immune response,ultimately leading to tissue *** oxidative stress,inflammatory cytokine release,inflammatory cell infiltration and activation and the up-regulation of inflammatory transcription factors participate in the pathophysiology of these complex *** varies in each specific disease,but at least in the cases of RE and IBD immunosuppressors are ***,full therapeutic responses are not always *** pathophysiology of ischemiareperfusion(IR)injury shares many of these *** and repetitive periods of ischemia in an organ or limb have been shown to protect against subsequent major IR injury in distant organs,a phenomenon called remote ischemic preconditioning(RIP).This procedure has been shown to protect the gut,pancreas and liver by modulating many of the same inflammatory *** RIP is safe and tolerable,and has shown to be effective in some recent clinical trials,I suggest that RIP could be used as a physiologicallyrelevant adjunct treatment for non-ischemic gastrointestinal inflammatory conditions.

关键词： Ischemia reperfusion Ischemic preconditioning Remote ischemic preconditioning Acute pancreatitis Radiation enteritis Inflammatory bowel diseases Hepatotoxicity Inflammation

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Contaminated open fracture and crush injury: a murine model

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Bone Research 2015年第1期3卷 31-39页

作者： Shawn R Gilbert Justin camara Richard camara Lynn Duffy Ken Waites Hyunki Kim Kurt Zinn Department of Surgery University of Alabama at Birmingham AL USA Loma Linda School of Medicine Loma LindaCAUSA Departments of Pathology University of Alabama at BirminghamAL USA Department of Radiology University of Alabama at BirminghamAL USA

Modern warfare has caused a large number of severe extremity injuries, many of which become infected. In more recent conflicts, a pattern of co-infection with Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus has emerged. We attempted to recreate this pattern in an animal model to evaluate the role of vascularity in contaminated open fractures. Historically, it has been observed that infected bones frequently appear hypovascular, but vascularity in association with bone infection has not been examined in animal models. Adult rats underwent femur fracture and muscle crush injury followed by stabilization and bacterial contamination with A. baumannii complex and methicillin-resistant Staphylococcus *** and perfusion were assessed by micro CT angiography and SPECT scanning, respectively, at 1, 2 and 4 weeks after injury. Quantitative bacterial cultures were also obtained. Multi-bacterial infections were successfully created, with methicillin-resistant S. aureus predominating. There was overall increase in blood flow to injured limbs that was markedly greater in bacteria-inoculated limbs. Vessel volume was greater in the infected group. Quadriceps atrophy was seen in both groups, but was greater in the infected group. In this animal model, infected open fractures had greater perfusion and vascularity than non-infected limbs.

关键词： MRSA Contaminated open fracture and crush injury a murine model

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Impact of land uses on water quality in Malaysia: a review

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Ecological Processes 2019年第1期8卷 128-137页

作者： Moriken camara Nor Rohaizah Jamil Ahmad Fikri Bin Abdullah Faculty of Environmental Studies Universiti Putra Malaysia UPM43400 SerdangSelangorMalaysia Department of Biological and Agricultural Engineering Faculty of EngineeringUniversiti Putra Malaysia(UPM)43400SerdangSelangorMalaysia.

Land use changes in urbanization,industrialization,and agricultural processes will continue to have negative impacts on water quality at all *** impact of land use changes on water quality is generally studied by analyzing the relationships between land use and water quality ***,the purpose of this research was to review and analyze the main relationships between land use and water quality,as well as to visualize the major sources and processes of water quality pollution in *** achieve our goal,we evaluated the significance of both land use and water quality attributes used in the past studies and correlated them to understand their relationship from another angle of *** results revealed that 87%of the reviewed studies indicated urban land use as a major source of water pollution,while 82%indicated agricultural land use,77%indicated forest land use,and 44%indicated other land ***,the results of correlation analysis showed that agricultural and forest-related activities more affected water quality through their significant positive correlation with physical and chemical indicators of water quality,while urban development activities had a greater impact on water quality through altering hydrological processes such as runoff and *** findings would provide decision-makers with useful information for managing water pollution processes rather than sources only.

关键词： Land use Water quality Malaysia

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