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Tiando, Damien Sinonmatohou, Shougeng Hu, Xin Fan, and Muhammad Rashid Ali. "Tropical Coastal Land-Use and Land Cover Changes Impact on Ecosystem Service Value during Rapid Urbanization of Benin, West Africa." International Journal of Environmental Research and Public Health 18, no. 14 (July 11, 2021): 7416. http://dx.doi.org/10.3390/ijerph18147416.
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West African coastal areas including the Beninese coastal zones have undergone an intensification of socio-economic activity in the last few decades that has been strongly driven by the effects of rapid urbanization. This has led to land-use and land cover changes that represent threats to the sustainability of various ecosystem functions. Such dynamics of land use and land cover changes pose challenges to coastal zone management. Correct assessment is vital for policymakers and planners to ensure efficient and sustainable use of the coastal ecosystem services, and it remains crucial to achieving sustainable coastal zone management. This study examines changes in land-use and land cover (LULC) and their impacts on ecosystem services value (ESV) fluctuations in the tropical coastal region of Benin, West Africa. We employed Globe Land 30 image data for the years 2010 and 2020, and the ESV fluctuations during the study period were evaluated using the benefit transfer approach (BTA) with corresponding local coefficients values and the GIS techniques. The results reveal that (1) in the current urbanizing coastal area, the LULC types have changed significantly, with obvious reductions in forest land and waterbodies and a considerable increase in artificial surfaces; (2) the total ESV decreased by 8.51% from USD 7.1557 million in 2010 to USD 6.5941 million in 2020; (3) the intensity of LULC in the coastal region has increased over the last 10 years; (4) regions with high land-use intensity have a high rate of ESV change; and (5) provisioning services are the greatest contributors of ESV (51% in 2010; 41% in 2020), followed by supporting services (37% in 2010; 35% in 2020) and regulating services (25% in 2010; 30% in 2020). Uncontrolled changes in LULC from forest land and waterbodies are the main causes of the loss in total ESV, necessitating urgent measures to improve the coastal ecosystem sustainability through effective planning and policies.
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Kounta, Lala, Xavier Capet, Julien Jouanno, Nicolas Kolodziejczyk, Bamol Sow, and Amadou Thierno Gaye. "A model perspective on the dynamics of the shadow zone of the eastern tropical North Atlantic – Part 1: the poleward slope currents along West Africa." Ocean Science 14, no. 5 (September 10, 2018): 971–97. http://dx.doi.org/10.5194/os-14-971-2018.
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Abstract. The West African seaboard is one of the upwelling sectors that has received the least attention, and in situ observations relevant to its dynamics are particularly scarce. The current system in this sector is not well known and understood, e.g., in terms of seasonal variability, across-shore structure, and forcing processes. This knowledge gap is addressed in two studies that analyze the mean seasonal cycle of an eddy-permitting numerical simulation of the tropical Atlantic. Part 1 is concerned with the circulation over the West African continental slope at the southernmost reach of the Canary Current system, between ∼8 and 20∘ N. The focus is on the depth range most directly implicated in the wind-driven circulation (offshore and coastal upwellings and Sverdrup transport) located above the potential density σt=26.7 kg m−3 in the model (approx. above 250 m of depth). In this sector and for this depth range, the flow is predominantly poleward as a direct consequence of positive wind stress curl forcing, but the degree to which the magnitude of the upper ocean poleward transport reflects Sverdrup theory varies with latitude. The model poleward flow also exhibits a marked semiannual cycle with transport maxima in spring and fall. Dynamical rationalizations of these characteristics are offered in terms of wind forcing of coastal trapped waves and Rossby wave dynamics. Remote forcing by seasonal fluctuations of coastal winds in the Gulf of Guinea plays an instrumental role in the fall intensification of the poleward flow. The spring intensification appears to be related to wind fluctuations taking place at shorter distances north of the Gulf of Guinea entrance and also locally. Rossby wave activity accompanying the semiannual fluctuations of the poleward flow in the coastal waveguide varies greatly with latitude, which in turn exerts a major influence on the vertical structure of the poleward flow. Although the realism of the model West African boundary currents is difficult to determine precisely, the present in-depth investigation provides a renewed framework for future observational programs in the region.
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Honfoga, B. G., and G. J. M. van den Boom. "Food-Consumption Patterns in Central West Africa, 1961 to 2000, and Challenges to Combating Malnutrition." Food and Nutrition Bulletin 24, no. 2 (January 2003): 167–82. http://dx.doi.org/10.1177/156482650302400210.
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We discuss food-consumption patterns in Central West Africa from 1961 to 2000 and some implications for combating malnutrition. The availability of food in the region improved in the 1960s, declined sharply in the 1970s and the early 1980s, and has shown a modest positive trend since the mid-1980s. Notwithstanding obvious progress over the past decades and in the region as a whole, food availability today remains below the required levels for large parts of the population and appears unstable over time, particularly in the Sahelian zone. On average, diets in this zone contain fewer than 2,200 kcal, compared with almost 2,500 kcal in the coastal zone. Conversely, protein deficiency is more common in the coastal zone, where a typical diet contains only 45 g of protein, compared with 60 g in the Sahelian zone. Furthermore, consumption is showing a dietary shift toward cereals, while yield growth lags far behind population growth. The associated import dependency and pressure on land seem to gain significance regardless of the region's agro-ecological capacity to increase and to substitute cereal imports for locally produced food. Moreover, food consumption appears responsive to income changes (calorie-income elasticity ranges from 0.25 to 0.62), while, in turn, it has a significant impact on nutritional outcomes (stunting-calorie elasticity of −1.42). We conclude that combating malnutrition requires first broad-spectrum income growth, and next specific policies that promote the yield and the contribution to diets of nutritious food produced within the region.
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Juo, A. S. R., and L. P. Wilding. "Soils of the lowland forests of West and Central Africa." Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 104 (1996): 15–29. http://dx.doi.org/10.1017/s0269727000006102.
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The forest zone of West and Central Africa comprises the coastal and adjacent inland regions bounded the semi-deciduous forests in the west and the equatorial forests in central Africa and the Congo basin. Sedimentary plains, developed mostly on weathered sandy materials, lie along the coastal stretches and cover vast areas of the Congo basin. Behind the coast the plain rises gradually to hills and plateaus of much lower elevation than those of the highlands of East Africa. Two great rivers, the Niger and the Congo, which discharge huge volumes of fresh water to the Atlantic Ocean, are major contributors to the hydrological cycles of the rain forests ecosystems of the Guinea–Congo Region. The Niger originates from the forested highlands of Guinea and discharges its waters into the Bight of Benin by way of a large delta in southern Nigeria. The Congo basin occupies an immense area of 750 000 km2, surrounded by Pre-Cambrian uplands. The alluvial floor of the saucer-shaped basin is flat, and marshes and swamps comprise a large proportion of the total area. The highlands and plateaus along the rim are low to the west and north and higher to the south. To the east, they merge with the mountains of the Great Rift Valley of East Africa (Gann & Duignan 1972; Hance 1975; Grove 1978; Hamilton 1989).
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Barusseau, Jean-Paul, Raphaël Certain, Robert Vernet, and Jean-François Saliège. "Morphosedimentological record and human settlements as indicators of West-African Late Holocene climate variations in the littoral zone of the Iwik peninsula (Banc d’Arguin – Mauritania)." Bulletin de la Société Géologique de France 180, no. 5 (September 1, 2009): 449–56. http://dx.doi.org/10.2113/gssgfbull.180.5.449.
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Abstract The geomorphological, sedimentological and archaeological studies of coastal features in the Iwik-Aouatil area show two categories of coastal sedimentary units: very extensive sand flats and linear relief features covered by a thin veneer of anthropogenic Anadara senilis shell-middens. These units provide an opportunity to discuss the return to arid conditions in western Sahara during the Late Holocene, when climate changes induced the alternating occurrence of more or less dry episodes, from around 5 ka until today. These constructions reflect the global climate change within the general framework known for the region. Two different processes occurred: (1) constant deposition of wide sand-flats and (2) construction of sedimentary ridges at specific moments. These processes demonstrate the existence of (1) constant sand discharge during the whole period as sand availability is not a limiting factor and (2) a substantially increased sand influx during the 4.2-3.2 ka episode. Because of sea-level stability in the Banc d’Arguin area during the Late Holocene, the variability of morphogenetic agents is considered to be the likely cause of fluctuations, influencing sand input rate and implying that either sand was delivered in greater abundance (aridity crisis and stronger winds) or littoral drift was more powerful (stronger waves and more frequent storms in the northern part of the Atlantic ocean), or both simultaneously. The action of these two driving forces in the depositional processes observed in the Iwik-Aouatil coastal plain is evaluated with respect to the occurrence of episodes of rapid climate changes (RCCs) and North Atlantic Oscillation (NAO) changes. A climate pattern combining episodes of RCC and NAO positive (NAO+) index during the 4.5-3.2 ka period is convenient for both sand supply, which accelerates the southwestward migration of barchan’s lines, and sand transportation, which improves the efficiency of the littoral drift.
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Gaki - Papanastassiou, K., E. Karymbalis, H. Maroukian, and K. Tsanakas. "GEOMORPHIC EVOLUTION OF WESTERN (PALIKI) KEPHALONIA ISLAND (GREECE) DURING THE QUATERNARY." Bulletin of the Geological Society of Greece 43, no. 1 (January 19, 2017): 418. http://dx.doi.org/10.12681/bgsg.11193.
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Kephalonia Island is located in the Ionian Sea (western Greece). The active subduction zone of the African lithosphere submerging beneath the Eurasian plate is placed just west of the island. The evolution of the island is depended mostly on the geodynamic processes derived from this vigorous margin. The geomorphic evolution of the western part of the island (Paliki peninsula) during the Quaternary was studied, by carrying out detailed field geomorphological mapping focusing on both coastal and fluvial landforms, utilizing aerial photos and satellite image interpretation with the use of GIS technology. The coastal morphology of Paliki includes beachrocks, aeolianites, notches and small fan deltas which were all studied and mapped in detail. The drainage systems of the peninsula comprise an older one on carbonate formations in the northwest and a younger Quaternary one in the south and southeast. Eight marine terraces found primarily on the Pliocene marine formations range in elevation from 2 m to 440 m are tilted to the south. In the Late Pleistocene some of the main drainage networks flowed towards the newly-formed gulf of Argostoli to the east.
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Sylla, Soumaïla, Kouadio Fréderic Kouakou, Christian Bernard Tia, Stanislas Silvain Yao, and Boua Célestin Atse. "The spatial distribution of coastal fish assemblage in Côte d’Ivoire’s Exclusive Economic Zone (EEZ), West Africa." Journal of Applied Biosciences 108, no. 1 (April 19, 2017): 10519. http://dx.doi.org/10.4314/jab.v108i1.5.
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FIELDS-BLACK, EDDA L. "UNTANGLING THE MANY ROOTS OF WEST AFRICAN MANGROVE RICE FARMING: RICE TECHNOLOGY IN THE RIO NUNEZ REGION, EARLIEST TIMES TO c. 1800." Journal of African History 49, no. 1 (March 2008): 1–21. http://dx.doi.org/10.1017/s0021853707003374.
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ABSTRACTThis study focuses on the ancient past of coastal Guinea's Rio Nunez region, a coastal rice-growing region virtually unexplored by studies of West African rice and rice farmers. It argues that coastal cultivators have adapted mangrove rice-farming systems in situ for approximately the past 1,000 years, a historical period pre-dating the European travelers' accounts on which the current literature heavily relies. Rather than diffusing from the interior, these specialized farming systems grew organically out of land-use systems. Using the comparative method of historical linguistics and cultural vocabulary, the study establishes different stages in coastal farmers' experimentation, adaptation and specialization in the coastal environment and approximates historical dates when the different stages occurred. And with botanical and biological studies of mangrove vegetation, the study distinguishes between the softer, spongy roots of white mangroves and hard, twisted roots of red mangroves. The interdisciplinary evidence reveals that knowledge of white mangroves was an early formative stage in cultivators' fabrication of coastal land-use systems. Lastly, from an examination of loanwords, the study discusses the important contributions made by Mande groups, who speak the Susu language in the Rio Nunez region, in intensifying mangrove rice-farming systems indigenous to the coast and extending them from zones of white to those of red mangroves. The interdisciplinary methods and sources enable the study to capture localized experimentation and innovation as continuous processes, thereby breaking with the current literature's emphasis on diffusion from the interior to the coast.
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Havik, Philip J. "Hybridising Medicine: Illness, Healing and the Dynamics of Reciprocal Exchange on the Upper Guinea Coast (West Africa)." Medical History 60, no. 2 (March 14, 2016): 181–205. http://dx.doi.org/10.1017/mdh.2016.3.
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The present article seeks to fill a number of lacunae with regard to the study of the circulation and assimilation of different bodies of medical knowledge in an important cultural contact zone, that is the Upper Guinea Coast. Building upon ongoing research on trade and cultural brokerage in the area, it focuses upon shifting attitudes and practices with regard to health and healing as a result of cultural interaction and hybridisation against the background of growing intra-African and Afro-Atlantic interaction from the fifteenth to the late seventeenth century. Largely based upon travel accounts, missionary reports and documents produced by the Portuguese Inquisition, it shows how forms of medical knowledge shifted and circulated between littoral areas and their hinterland, as well as between the coast, the Atlantic and beyond. It shows that the changing patterns of trade, migration and settlement associated with Mandé influence and Afro-Atlantic exchange had a decisive impact on changing notions of illness and therapeutic trajectories. Over the centuries, cross-cultural, reciprocal borrowing contributed to the development of healing kits employed by Africans and non-African outsiders alike, which were used and brokered by local communities in different locations in the region.
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Guerrera, Francesco, Manuel Martín-Martín, Mario Tramontana, Bertin Nimon, and Kossi Essotina Kpémoua. "Shoreline Changes and Coastal Erosion: The Case Study of the Coast of Togo (Bight of Benin, West Africa Margin)." Geosciences 11, no. 2 (January 21, 2021): 40. http://dx.doi.org/10.3390/geosciences11020040.
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The coastal strip between the Volta River delta and the westernmost portion of Benin (West Africa Margin of Atlantic Basin) is highly populated (e.g., Lomé) due to migrations from inland areas. The coastal zone has proved to be very vulnerable because of the potential development of sometimes catastrophic events related to different and interacting causes, resulting in negative effects on natural ecosystems and socio-economic conditions. The main problem is the marked erosion of large coastal sectors with maximum retreat rates of the order of 5 m/year. The continuous loss of territory leads to a progressive impoverishment of activities and human resources and to the increase of geological risk factors. The coastal erosion is induced both by natural and anthropic causes and can be controlled only by means of prevention programs, detailed scientific studies and targeted technical interventions. The main erosional processes observed in the study area are triggered by the presence of the Lomé port and other human activities on the coastal strip, including the water extraction from the subsoil, which induces subsidence and the use of sediments as inert material. These elements, together with the reduction of the solid supply from Volta River (caused by the realization of the Akosombo dam) are among the main factors that control the medium and long-term evolution of the area. Also relative sea level changes, which take into account also tectonic and/or isostatic components, can contribute to the process. In order to have a real understanding of the coastal dynamics and evolution, it would be necessary to develop a scientific structure through the collaboration of all countries of the Bight of Benin affected by coastal erosion. The aim should be primarily to collect the interdisciplinary quantitative data necessary to develop a scientific knowledge background of the Bight of Benin coastal/ocean system. In conclusion, some proposals are presented to reduce the vulnerability of the coastal area as for example to plan surveys for the realization of appropriate coastal protection works, such as walls, revetments, groins, etc. A possible expansion of the port of Lomè is also considered. Proposals comprise the constitution of a Supranational Scientific Committee as a coordinating structure on erosion for both the study of phenomena and planning interventions.
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Karstensen, J., B. Fiedler, F. Schütte, P. Brandt, A. Körtzinger, G. Fischer, R. Zantopp, J. Hahn, M. Visbeck, and D. Wallace. "Open ocean dead zones in the tropical North Atlantic Ocean." Biogeosciences 12, no. 8 (April 30, 2015): 2597–605. http://dx.doi.org/10.5194/bg-12-2597-2015.
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Abstract. Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day−1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies.
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Schütte, F., P. Brandt, and J. Karstensen. "Occurrence and characteristics of mesoscale eddies in the tropical northeast Atlantic Ocean." Ocean Science Discussions 12, no. 6 (December 18, 2015): 3043–97. http://dx.doi.org/10.5194/osd-12-3043-2015.
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Abstract. Coherent mesoscale features (referred to here as eddies) in the tropical northeast Atlantic (between 12–22° N and 15–26° W) are examined and characterised. The eddies' surface signatures are investigated using 19 years of satellite derived sea level anomaly (SLA) data. Two automated detection methods are applied, the geometrical method based on closed streamlines around eddy cores, and the Okubo–Weiß method based on the relation between vorticity and strain. Both methods give similar results. Mean eddy surface signatures of SLA, sea surface temperature (SST) and salinity (SSS) are obtained from composites of all snapshots around identified eddy cores. Anticyclones/cyclones are associated with elevation/depression of SLA and enhanced/reduced SST and SSS patterns. However, about 20 % of all detected anticyclones show reduced SST and reduced SSS instead. These kind of eddies are classified as anticyclonic mode-water eddies (ACMEs). About 146 ± 4 eddies per year are identified (52 % cyclones, 39 % anticylones, 9 % ACMEs) with rather similar mean radii of about 56 ± 12 km. Based on concurrent in-situ temperature and salinity profile data (from Argo float, shipboard and mooring data) inside of the three eddy types, their distinct differences in vertical structure is determined. Most eddies are generated preferentially in boreal summer and along the West African coast at three distinct coastal headland region and carry South Atlantic Central Water that originates from the northward transport within the Mauretania coastal current system. Westward eddy propagation (on average about 3.00 ± 2.15 km d−1) is confined to distinct corridors with a small meridional deflection dependent on the eddy type (anticyclones – equatorward, cyclones – poleward, ACMEs – no deflection). Heat and salt flux out of the coastal region and across the Cap Verde Frontal Zone, which separates the shadow zone from the ventilated gyre, are calculated.
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Chen, Tsing-Chang. "Characteristics of African Easterly Waves Depicted by ECMWF Reanalyses for 1991–2000." Monthly Weather Review 134, no. 12 (December 1, 2006): 3539–66. http://dx.doi.org/10.1175/mwr3259.1.
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Abstract Several interesting characteristics of African easterly waves (AEWs) were observed and investigated by previous studies: two separate propagation paths, genesis mechanisms, restriction of vertical development, and the interaction with the African easterly jet (AEJ). However, some aspects of these characteristics have been neglected: the contrast of the AEW population along the two propagation paths, the AEW genesis mechanism over the Saharan thermal low and the role played by the low-level North African circulation in this mechanism, the dynamical mechanism restricting the vertical development of AEWs, and the synoptic relationship and interaction between the AEJ and the AEWs along the two propagation paths. The ECMWF reanalyses for the 1991–2000 period supplemented with those of 1979 were analyzed to explore these AEW features. Major findings of this effort are the following: The population of AEWs along the propagation path north of the AEJ (AEWn) is approximately 2.5 times of that along the propagation path south of the AEJ (AEWs). The AEWn geneses primarily occur over the three convergent centers and the southwestward extension of the Saharan thermal low. Underneath the midtropospheric Saharan high, the baroclinic instability of a shallow, low static stability environment, which may be triggered by the intrusion of dry northerlies over central North Africa, leads to the AEW genesis. Continental-scale upward motion along the Saharan thermal low and the cyclonic-shear side of the AEJ maintains positive vortex stretching below the Saharan high and the western part of the Asian monsoon high. These two regions thus form a favorable environment for the development of AEWs within the near-surface troposphere along the Saharan thermal low and the midtroposphere south of the AEJ. The passage of AEWn (AEWs) across the coastal zone of West Africa is accompanied by a weak (strong) AEJ and weak (strong) Saharan high. The westward propagation and development/maintenance of the two types of AEWs are achieved through vorticity advection by the AEJ, which is the major AEW–AEJ interaction. These findings will facilitate the search for AEW dynamics and aid in assessing the impact of AEW activity on North African climate change.
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Ismaïla, Ndour, Baldé Assiatou, Thiam Ndiaga, Thiaw Modou, Faye Saliou, Fall Massal, and Diop Mika. "Identification and Characterization of Critical Sites for Small Pelagic Fish in the Coastal Marine Area of Senegal, West Africa." Journal of Biology and Life Science 11, no. 1 (September 15, 2019): 18. http://dx.doi.org/10.5296/jbls.v11i1.15131.
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Better management of coastal marine resources generally requires good knowledge of habitats and resources. This need led to the performance of an identification and bioecological characterization study of critical sites for small pelagics in the Senegalese coastal marine zone. Biological and ecological data were collected using beach seines (12 to 28 mm mesh) and surface drifting gillnets (28 to 36 mm mesh) at sites identified by fishermen on the basis of surveys. The results of the study highlight the bioecological characteristics of these sites: (i) the Port-Baie Hann site - a nursery and spawning site with a high diversity for the target species; it is under marine pollution threat; (ii) the Mbodiène-Ngazobil site, with high diversity for target species and the Kafountine-Cap site are nursery and spawning sites under high fishing pressure, (iii) the Diakhanor-Sangomar site - a spawning site under the potential threat of exploration of offshore Sangomar oil in addition to the high fishing pressure. This work is a first flagship contribution to a process that should lead to the development and control of new tools for the effective and sustainable management of small pelagics at national and regional scales.
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Schütte, Florian, Peter Brandt, and Johannes Karstensen. "Occurrence and characteristics of mesoscale eddies in the tropical northeastern Atlantic Ocean." Ocean Science 12, no. 3 (May 13, 2016): 663–85. http://dx.doi.org/10.5194/os-12-663-2016.
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Abstract. Coherent mesoscale features (referred to here as eddies) in the tropical northeastern Atlantic Ocean (between 12–22° N and 15–26° W) are examined and characterized. The eddies' surface signatures are investigated using 19 years of satellite-derived sea level anomaly (SLA) data. Two automated detection methods are applied, the geometrical method based on closed streamlines around eddy cores, and the Okubo–Weiß method based on the relation between vorticity and strain. Both methods give similar results. Mean eddy surface signatures of SLA, sea surface temperature (SST) and sea surface salinity (SSS) anomalies are obtained from composites of all snapshots around identified eddy cores. Anticyclones/cyclones are identified by an elevation/depression of SLA and enhanced/reduced SST and SSS in their cores. However, about 20 % of all anticyclonically rotating eddies show reduced SST and reduced SSS instead. These kind of eddies are classified as anticyclonic mode-water eddies (ACMEs). About 146 ± 4 eddies per year with a minimum lifetime of 7 days are identified (52 % cyclones, 39 % anticyclones, 9 % ACMEs) with rather similar mean radii of about 56 ± 12 km. Based on concurrent in situ temperature and salinity profiles (from Argo float, shipboard, and mooring data) taken inside of eddies, distinct mean vertical structures of the three eddy types are determined. Most eddies are generated preferentially in boreal summer and along the West African coast at three distinct coastal headland regions and carry South Atlantic Central Water supplied by the northward flow within the Mauretanian coastal current system. Westward eddy propagation (on average about 3.00 ± 2.15 km d−1) is confined to distinct zonal corridors with a small meridional deflection dependent on the eddy type (anticyclones – equatorward, cyclones – poleward, ACMEs – no deflection). Heat and salt fluxes out of the coastal region and across the Cape Verde Frontal Zone, which separates the shadow zone from the ventilated subtropical gyre, are calculated.
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Wane, Dahirou, Alban Lazar, Malick Wade, and Amadou Thierno Gaye. "A Climatological Study of the Mechanisms Controlling the Seasonal Meridional Migration of the Atlantic Warm Pool in an OGCM." Atmosphere 12, no. 9 (September 18, 2021): 1224. http://dx.doi.org/10.3390/atmos12091224.
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The tropical Atlantic Warm Pool is one of the main drivers of the marine intertropical convergence zone and the associated coastal Northeast Brazilian and West-African monsoons. Its meridional displacement is driven by the solar cycle, modulated by the atmosphere and ocean interactions, whose nature and respective proportions are still poorly understood. This paper presents a climatological study of the upper ocean and lower atmosphere contributions to the warm pool seasonal migration, using an Ocean General Circulation Model (OGCM). First, we provide quantitative, albeit simple, pieces of evidence on how the large amplitude of migration in the west, compared to the east, is mainly due to the strong east–west contrast of the background meridional SST gradient intensities, which is maintained by equatorial and eastern tropical upwellings. Our main results consist first in identifying a diagnostic equation for the migration speed of the two meridional boundary isotherms of the Warm Pool, expressed in terms of the various mixed-layer heat fluxes. We then evidence and quantify how, in general, the migration is forced by air–sea fluxes, and damped by ocean circulation. However, remarkable controls by the ocean are identified in some specific regions. In particular, in the northwestern part of the Warm Pool, characterized by a large temperature inversion area, the boreal spring northward movement speed depends on the restitution of the solar heating by the thermocline. Additionally, over the southern part of the Warm Pool, our study quantifies the key role of the equatorial upwelling, which, depending on the longitude, significantly accelerates or slows down the summer poleward migration.
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Schrage, Jon M., and Andreas H. Fink. "Nocturnal Continental Low-Level Stratus over Tropical West Africa: Observations and Possible Mechanisms Controlling Its Onset." Monthly Weather Review 140, no. 6 (June 1, 2012): 1794–809. http://dx.doi.org/10.1175/mwr-d-11-00172.1.
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Abstract Some spatiotemporal characteristics and possible mechanisms controlling the onset of the widespread, low-level nocturnal stratiform clouds that formed during May–October 2006 over southern tropical West Africa are investigated using cloudiness observations from surface weather stations, data from various satellite platforms, and surface-based remote sensing profiles at Nangatchori in central Benin. It is found that the continental stratus is lower than the maritime stratus over the Gulf of Guinea and persists well into the noon hours. For the study period, a clear seasonal cycle was documented, as well as a dependence on latitude with the cloudiest zone north of the coastal zone and south of approximately 9°N. It is also shown that nonprecipitating clear and cloudy nights observed at Nangatchori in central Benin often reflect clearer and cloudier than normal conditions over a wide region of southern West Africa. At Nangatchori, on average the stratus developed at 0236 UTC (about local time) with an extremely low cloud base at 172 m (above ground level) when averaged over all cloudy nights. About 2–3 h before cloudiness onset, a distinct nighttime low-level jet formed that promoted static destabilization and a low Richardson number flow underneath it. The ensuing vertical upward mixing of moisture that accumulated under the near-surface inversion after sunset caused the cloud formation. It is argued that a strong shear underneath the nighttime low-level jet is the major process for cloud formation, but the low-level static stability and the time scale of the shear-driven mixing are other potential factors.
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Wolters, E. L. A., B. J. J. M. van den Hurk, and R. A. Roebeling. "Evaluation of rainfall retrievals from SEVIRI reflectances over West Africa using TRMM-PR and CMORPH." Hydrology and Earth System Sciences 15, no. 2 (February 3, 2011): 437–51. http://dx.doi.org/10.5194/hess-15-437-2011.
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Abstract. This paper describes the evaluation of the KNMI Cloud Physical Properties – Precipitation Properties (CPP-PP) algorithm over West Africa. The algorithm combines condensed water path (CWP), cloud phase (CPH), cloud particle effective radius (re), and cloud-top temperature (CTT) retrievals from visible, near-infrared and thermal infrared observations of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) satellites to estimate rain occurrence frequency and rain rate. For the 2005 and 2006 monsoon seasons, it is investigated whether the CPP-PP algorithm is capable of retrieving rain occurrence frequency and rain rate over West Africa with sufficient accuracy, using Tropical Monsoon Measurement Mission Precipitation Radar (TRMM-PR) as reference. As a second goal, it is assessed whether SEVIRI is capable of monitoring the seasonal and daytime evolution of rainfall during the West African monsoon (WAM), using Climate Prediction Center Morphing Technique (CMORPH) rainfall observations. The SEVIRI-detected rainfall area agrees well with TRMM-PR, with the areal extent of rainfall by SEVIRI being ~10% larger than from TRMM-PR. The mean retrieved rain rate from CPP-PP is about 8% higher than from TRMM-PR. Examination of the TRMM-PR and CPP-PP cumulative frequency distributions revealed that differences between CPP-PP and TRMM-PR are generally within +/−10%. Relative to the AMMA rain gauge observations, CPP-PP shows very good agreement up to 5 mm h−1. However, at higher rain rates (5–16 mm h−1) CPP-PP overestimates compared to the rain gauges. With respect to the second goal of this paper, it was shown that both the accumulated precipitation and the seasonal progression of rainfall throughout the WAM is in good agreement with CMORPH, although CPP-PP retrieves higher amounts in the coastal region of West Africa. Using latitudinal Hovmüller diagrams, a fair correspondence between CPP-PP and CMORPH was found, which is reflected by high correlation coefficients (~0.7) for both rain rate and rain occurrence frequency. The daytime cycle of rainfall from CPP-PP shows distinctly different patterns for three different regions in West Africa throughout the WAM, with a decrease in dynamical range of rainfall near the Inter Tropical Convergence Zone (ITCZ). The dynamical range as retrieved from CPP-PP is larger than that from CMORPH. It is suggested that this results from both the better spatio-temporal resolution of SEVIRI, as well as from thermal infrared radiances being partly used by CMORPH, which likely smoothes the daytime precipitation signal, especially in case of cold anvils from convective systems. The promising results show that the CPP-PP algorithm, taking advantage of the high spatio-temporal resolution of SEVIRI, is of added value for monitoring daytime precipitation patterns in tropical areas.
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Adite, Alphonse, Ibrahim ImorouToko, and Adam Gbankoto. "Fish Assemblages in the Degraded Mangrove Ecosystems of the Coastal Zone, Benin, West Africa: Implications for Ecosystem Restoration and Resources Conservation." Journal of Environmental Protection 04, no. 12 (2013): 1461–75. http://dx.doi.org/10.4236/jep.2013.412168.
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Kurekin, Andrey, Benjamin Loveday, Oliver Clements, Graham Quartly, Peter Miller, George Wiafe, and Kwame Adu Agyekum. "Operational Monitoring of Illegal Fishing in Ghana through Exploitation of Satellite Earth Observation and AIS Data." Remote Sensing 11, no. 3 (February 1, 2019): 293. http://dx.doi.org/10.3390/rs11030293.
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Over the last decade, West African coastal countries, including Ghana, have experienced extensive economic damage due to illegal, unreported and unregulated (IUU) fishing activity, estimated at about USD 100 million in losses each year. Illegal, unreported and unregulated fishing poses an enormous threat to the conservation and management of the dwindling fish stocks, causing multiple adverse consequences for fisheries, coastal and marine ecosystems and for the people who depend on these resources. The Integrated System for Surveillance of Illegal, Unlicensed and Unreported Fishing (INSURE) is an efficient and inexpensive system that has been developed for the monitoring of IUU fishing in Ghanaian waters. It makes use of fast-delivery Earth observation data from the synthetic aperture radar instrument on Sentinel-1 and the Multi Spectral Imager on Sentinel-2, detecting objects that differ markedly from their immediate background using a constant false alarm rate test. Detections are matched to, and verified by, Automatic Identification System (AIS) data, which provide the location and dimensions of ships that are legally operating in the region. Matched and unmatched data are then displayed on a web portal for use by coastal management authorities in Ghana. The system has a detection success rate of 91% for AIS-registered vessels, and a fast throughput, processing and delivering information within 2 h of acquiring the satellite overpass. However, over the 17-month analysis period, 75% of SAR detections have no equivalent in the AIS record, suggesting significant unregulated marine activity, including vessels potentially involved in IUU. The INSURE system demonstrated its efficiency in Ghana’s exclusive economic zone and it can be extended to the neighbouring states in the Gulf of Guinea, or other geographical regions that need to improve fisheries surveillance.
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Vinayachandran, Puthenveettil Narayana Menon, Yukio Masumoto, Michael J. Roberts, Jenny A. Huggett, Issufo Halo, Abhisek Chatterjee, Prakash Amol, et al. "Reviews and syntheses: Physical and biogeochemical processes associated with upwelling in the Indian Ocean." Biogeosciences 18, no. 22 (November 23, 2021): 5967–6029. http://dx.doi.org/10.5194/bg-18-5967-2021.
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Abstract. The Indian Ocean presents two distinct climate regimes. The north Indian Ocean is dominated by the monsoons, whereas the seasonal reversal is less pronounced in the south. The prevailing wind pattern produces upwelling along different parts of the coast in both hemispheres during different times of the year. Additionally, dynamical processes and eddies either cause or enhance upwelling. This paper reviews the phenomena of upwelling along the coast of the Indian Ocean extending from the tip of South Africa to the southern tip of the west coast of Australia. Observed features, underlying mechanisms, and the impact of upwelling on the ecosystem are presented. In the Agulhas Current region, cyclonic eddies associated with Natal pulses drive slope upwelling and enhance chlorophyll concentrations along the continental margin. The Durban break-away eddy spun up by the Agulhas upwells cold nutrient-rich water. Additionally, topographically induced upwelling occurs along the inshore edges of the Agulhas Current. Wind-driven coastal upwelling occurs along the south coast of Africa and augments the dynamical upwelling in the Agulhas Current. Upwelling hotspots along the Mozambique coast are present in the northern and southern sectors of the channel and are ascribed to dynamical effects of ocean circulation in addition to wind forcing. Interaction of mesoscale eddies with the western boundary, dipole eddy pair interactions, and passage of cyclonic eddies cause upwelling. Upwelling along the southern coast of Madagascar is caused by the Ekman wind-driven mechanism and by eddy generation and is inhibited by the Southwest Madagascar Coastal Current. Seasonal upwelling along the East African coast is primarily driven by the northeast monsoon winds and enhanced by topographically induced shelf breaking and shear instability between the East African Coastal Current and the island chains. The Somali coast presents a strong case for the classical Ekman type of upwelling; such upwelling can be inhibited by the arrival of deeper thermocline signals generated in the offshore region by wind stress curl. Upwelling is nearly uniform along the coast of Arabia, caused by the alongshore component of the summer monsoon winds and modulated by the arrival of Rossby waves generated in the offshore region by cyclonic wind stress curl. Along the west coast of India, upwelling is driven by coastally trapped waves together with the alongshore component of the monsoon winds. Along the southern tip of India and Sri Lanka, the strong Ekman transport drives upwelling. Upwelling along the east coast of India is weak and occurs during summer, caused by alongshore winds. In addition, mesoscale eddies lead to upwelling, but the arrival of river water plumes inhibits upwelling along this coast. Southeasterly winds drive upwelling along the coast of Sumatra and Java during summer, with Kelvin wave propagation originating from the equatorial Indian Ocean affecting the magnitude and extent of the upwelling. Both El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events cause large variability in upwelling here. Along the west coast of Australia, which is characterized by the anomalous Leeuwin Current, southerly winds can cause sporadic upwelling, which is prominent along the southwest, central, and Gascoyne coasts during summer. Open-ocean upwelling in the southern tropical Indian Ocean and within the Sri Lanka Dome is driven primarily by the wind stress curl but is also impacted by Rossby wave propagations. Upwelling is a key driver enhancing biological productivity in all sectors of the coast, as indicated by enhanced sea surface chlorophyll concentrations. Additional knowledge at varying levels has been gained through in situ observations and model simulations. In the Mozambique Channel, upwelling simulates new production and circulation redistributes the production generated by upwelling and mesoscale eddies, leading to observations of higher ecosystem impacts along the edges of eddies. Similarly, along the southern Madagascar coast, biological connectivity is influenced by the transport of phytoplankton from upwelling zones. Along the coast of Kenya, both productivity rates and zooplankton biomass are higher during the upwelling season. Along the Somali coast, accumulation of upwelled nutrients in the northern part of the coast leads to spatial heterogeneity in productivity. In contrast, productivity is more uniform along the coasts of Yemen and Oman. Upwelling along the west coast of India has several biogeochemical implications, including oxygen depletion, denitrification, and high production of CH4 and dimethyl sulfide. Although weak, wind-driven upwelling leads to significant enhancement of phytoplankton in the northwest Bay of Bengal during the summer monsoon. Along the Sumatra and Java coasts, upwelling affects the phytoplankton composition and assemblages. Dissimilarities in copepod assemblages occur during the upwelling periods along the west coast of Australia. Phytoplankton abundance characterizes inshore edges of the slope during upwelling season, and upwelling eddies are associated with krill abundance. The review identifies the northern coast of the Arabian Sea and eastern coasts of the Bay of Bengal as the least observed sectors. Additionally, sustained long-term observations with high temporal and spatial resolutions along with high-resolution modelling efforts are recommended for a deeper understanding of upwelling, its variability, and its impact on the ecosystem.
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Touré, Amadou, Jonne Rodenburg, Kazuki Saito, Sylvester Oikeh, Koichi Futakuchi, Dieudonné Gumedzoe, and Joel Huat. "Cultivar and Weeding Effects on Weeds and Rice Yields in a Degraded Upland Environment of the Coastal Savanna." Weed Technology 25, no. 3 (September 2011): 322–29. http://dx.doi.org/10.1614/wt-d-10-00172.1.
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Weeds are a major constraint to rice production in labor-limited, upland rice-based systems in West Africa. The effects of weeding regimes and rice cultivars on weed growth and rice yield were investigated at two upland locations (Abomey-Calavi and Niaouli) in the degraded coastal savanna zone of Benin in 2005 and 2006 with below-average rainfall. Four weeding regimes (hoe weeding at 21 d after sowing [DAS], delayed hoe weeding at 31 DAS, hoe weeding at 21 and 42 DAS, and a no weeding control) were the main plot treatments. Cultivars comprising three interspecific upland rice cultivars (NERICA 1, NERICA 2, and NERICA 7) and the parents (Oryza sativaWAB56-104 andO. glaberrimaCG14) were tested in subplots. The most dominant weed species identified were Jamaican crabgrass,Mariscus, and silver spinach. Rice yield was generally low because of drought stress; none of the experiments had a higher mean yield than 1,400 kg ha−1across cultivars. Across cultivars, the best weeding regimes in terms of weed control and rice yields were single weeding at 31 DAS (W31) and double weeding at 21 and 42 DAS (W21+42). Under these weeding regimes, WAB56-104 out-yielded the three NERICA cultivars. CG14 showed the strongest weed suppressive ability (WSA) in Abomey-Calavi but did not have strong WSA in Niaouli because of lower biomass accumulation. WSA of WAB56-104 was similar to that of the three NERICA cultivars. Single weeding at 31 DAS, together with the use of cultivars with good adaptation to unfavorable rice growing conditions, would increase land and labor productivity of upland rice-based systems in West Africa.
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Amoussou, Toundji O., Vinsoun Millogo, Ana F. Filipe, Chibuye F. Kunda, Dorothé Y. Njé, Vinsoun Millogo, and Elliot H. Alhassan. "Anticipating the Effects of Increasing Rivers’ Water Salinity for Sustainable Conservation of Tilapia Resources in Rural Coastal Zone of Benin, West Africa." Tanzania Journal of Science 47, no. 5 (January 5, 2022): 1890–900. http://dx.doi.org/10.4314/tjs.v47i5.33.
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The current research aimed at using the application of multi-factor models to support fisheries management decisions for successful resources’ conservation. The study was based on the tilapia species Coptodon guineensis, which is among the most widely exploited in Benin coastal zone. In an attempt to suggest conservation strategies, the phenotypic variability of 356 accessions of this species was assessed in relation with water salinity, and several interactions. The fish were collected through small-scale experimental fishing using cast nets and gillnets. The findings indicated that the salinity observed in the sampled rivers is due, at proportions ranging from 0.13% to 47%, to the sea surface salinity (SSS) of the Atlantic Ocean, suggesting a leading inland origin of the salinity of these rivers. The evidence also showed that the tilapia populations have been relatively adapted to the increasing water salinity of the sampled rivers. The fish species*river type and fish species*fish sex interactions had significant effects on phenotypic characteristics rather than river type*fish sex interaction. For an efficient conservation of these populations, two conservation areas (Lake Nokoué and Porto-Novo lagoon vs Lake Toho and Grand-Popo lagoon), could be considered for this tilapia species.
Keywords: Aquatic salinization, population adaptation, growth parameters, interaction patterns
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Gebremichael, Mekonnen, Haowen Yue, and Vahid Nourani. "The Accuracy of Precipitation Forecasts at Timescales of 1–15 Days in the Volta River Basin." Remote Sensing 14, no. 4 (February 15, 2022): 937. http://dx.doi.org/10.3390/rs14040937.
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Medium-range (1–15 day) precipitation forecasts are increasingly available from global weather models. This study presents evaluation of the Global Forecast System (GFS) for the Volta river basin in West Africa. The evaluation was performed using two satellite-gauge merged products: NASA’s Integrated Multi-satellitE Retrievals (IMERG) “Final Run” satellite-gauge merged rainfall observations, and the University of California Santa Barbara’s Climate Hazard’s group Infrared Precipitation with Stations (CHIRPS). The performance of GFS depends on the climate zone, with underestimation bias in the dry Sahel climate, overestimation bias in the wet Guinea Coastal climate, and relatively no bias in the moderately wet Savannah climate. Averaging rainfall over the watershed of the Akosombo dam (i.e., averaging across all three climate zones), the GFS forecast indicates low skill (Kling-Gupta Efficiency KGE = 0.42 to 0.48) for the daily, 1-day, lead GFS forecast, which deteriorates further as the lead time increases. A sharp decrease in KGE occurred between 6 to 10 days. Aggregating the forecasts over long timescales improves the accuracy of the GFS forecasts. On a 15-day accumulation timescale, GFS shows higher skills (KGE = 0.74 to 0.88).
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Niespolo, Elizabeth M., Warren D. Sharp, Graham Avery, and Todd E. Dawson. "Early, intensive marine resource exploitation by Middle Stone Age humans at Ysterfontein 1 rockshelter, South Africa." Proceedings of the National Academy of Sciences 118, no. 16 (April 12, 2021): e2020042118. http://dx.doi.org/10.1073/pnas.2020042118.
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Modern human behavioral innovations from the Middle Stone Age (MSA) include the earliest indicators of full coastal adaptation evidenced by shell middens, yet many MSA middens remain poorly dated. We apply 230Th/U burial dating to ostrich eggshells (OES) from Ysterfontein 1 (YFT1, Western Cape, South Africa), a stratified MSA shell midden. 230Th/U burial ages of YFT1 OES are relatively precise (median ± 2.7%), consistent with other age constraints, and preserve stratigraphic principles. Bayesian age–depth modeling indicates YFT1 was deposited between 119.9 to 113.1 thousand years ago (ka) (95% CI of model ages), and the entire 3.8 m thick midden may have accumulated within ∼2,300 y. Stable carbon, nitrogen, and oxygen isotopes of OES indicate that during occupation the local environment was dominated by C3 vegetation and was initially significantly wetter than at present but became drier and cooler with time. Integrating archaeological evidence with OES 230Th/U ages and stable isotopes shows the following: 1) YFT1 is the oldest shell midden known, providing minimum constraints on full coastal adaptation by ∼120 ka; 2) despite rapid sea-level drop and other climatic changes during occupation, relative shellfish proportions and sizes remain similar, suggesting adaptive foraging along a changing coastline; 3) the YFT1 lithic technocomplex is similar to other west coast assemblages but distinct from potentially synchronous industries along the southern African coast, suggesting human populations were fragmented between seasonal rainfall zones; and 4) accumulation rates (up to 1.8 m/ka) are much higher than previously observed for dated, stratified MSA middens, implying more intense site occupation akin to Later Stone Age middens.
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Taylor, Elliott, Andy Graham, Jose Rios, Jean-Yves Huet, Lindsay Page-Jones, and Gabriel Ivaba. "Angola Coastal Mapping and Tactics for Oil Spill Response." International Oil Spill Conference Proceedings 2017, no. 1 (May 1, 2017): 850–62. http://dx.doi.org/10.7901/2169-3358-2017.1.850.
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ABSTRACT The Angolan oil and gas industry workgroup (ACEPA-Associação das Companhias de Exploração e Produção de Angola) continues to collaborate in the development and completion of oil spill response initiatives as responsible operators and committed participants in the IMO-IPIECA Global Initiative for West, Central and Southern Africa (GI WACAF). Between 2012–2015, a comprehensive program of oil spill response planning, geodatabase development, mapping, and guides were completed for the entire coast of Angola. Low altitude aerial video surveys that combine oblique imagery and a verbal commentary record were recorded as the foundation for mapping coastal sensitivities, ESI characterization, shore zone and backshore operational definition, and shoreline segmentation. Other information added to the coastal geodatabase includes operational and logistical considerations such as land access and boat launch locations, proposed sites for staging, holding of temporary wastes, industrial and human use (fishing, recreational), and nearshore access constraints. A key aspect of the shoreline mapping effort was to build the information into a stand-alone pre-shoreline cleanup assessment technique (SCAT)-database that provides layered information for each of the 1999 shoreline segments. Digital video and high-resolution oblique aerial photos for 2400 km of coastline are geo-referenced and integrated into the GIS system with viewer software that allows the user to “fly” the shoreline. Shoreline attributes for biological, socioeconomic, and human use were used to rank 117 sensitive sites. The 45 highest priority sensitive sites were surveyed and detailed geographic response plans (GRPs) for site protection strategies and tactics were compiled into two atlases. The comprehensive coastal characterization, segmentation, and priority site protection plans provide the Angola government and oil industry with spill preparedness tools that are world-class.
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Falk, Thomas M., Guy G. Teugels, Eddie K. Abban, Wolfgang Villwock, and Lothar Renwrantz. "Phylogeographic patterns in populations of the black-chinned tilapia complex (Teleostei, Cichlidae) from coastal areas in West Africa: support for the refuge zone theory." Molecular Phylogenetics and Evolution 27, no. 1 (April 2003): 81–92. http://dx.doi.org/10.1016/s1055-7903(02)00369-x.
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Fonju, Dr Njuafac Kenedy. "Pre-Colonial and Colonial British Equation of Exploration, Expropriation and Exploitation (3Es) Through Monarchical Hierarchical Orders of Diplomatic Agents in the Gold Coast (Ghana) of West Africa 1621-1957." Scholars Journal of Arts, Humanities and Social Sciences 9, no. 9 (September 9, 2021): 400–416. http://dx.doi.org/10.36347/sjahss.2021.v09i09.004.
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The present paper brings 111 British pre-colonial and colonial diplomatic agents who moderated the activities of Exploration, Expropriation and Exploitation (3Es) in the Gold Coast (GC) located in the Rich Zone of African Gulf of Guinea (RZAGG) in the West African Region between 1621 and 1957 when GC gained independence as Ghana been the first Black African Country under the President ship of an African legend Pan-Africanist known as Kwame Nkrumah. The history of Ghana is very important in views of its previous Ghana Empire and Kingship system which European imperialist and colonisers destroyed with over ambitions of 3Es in the Centuries that followed culminated with slavery and slave trade dealings of human beings shipped as lodge of woods across the Atlantic Ocean to American plantations. The teaching of African History in the 21st Century entails us to know those agents and goes deep into their archives to search and evaluate their Machiavelli did in the specific countries during their tenure in office. This is because they laid the groundwork and foundation of Western European imperialism, colonialism and neo-colonialism which later cropped up during the second decade of the 20th Century at independence. Our intension is not to bring out all what they did but rather, the identification of principal actors of the period which can be beneficial to the young generation of historians to open up new research avenues by going deeper to illustrate the activities carried out by each of those foreign diplomatic agents in their 3Es instructions and executions. The scrutiny of specialized and secondary sources facilitated us to use a historical analytical approach with visible statistical tables illustrating each of those monarchical actors of Kings and Queens and agents appointed to fulfil their foreign gains from natural and human resources of GC later Ghana at independence.
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Aladejana, Jamiu A., Robert M. Kalin, Ibrahim Hassan, Philippe Sentenac, and Moshood N. Tijani. "Origin and Residence Time of Groundwater in the Shallow Coastal Aquifer of Eastern Dahomey Basin, Southwestern Nigeria, Using δ18O and δD Isotopes." Applied Sciences 10, no. 22 (November 10, 2020): 7980. http://dx.doi.org/10.3390/app10227980.
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This study employed stable isotopes of δ18O and δ2H in conjunction with other hydrological parameters to understand the origin, inferred residence time, and seasonal effect of groundwater in the shallow aquifers of the eastern Dahomey Basin. A total of 230 groundwater samples (97 in the wet season and 133 in the dry season) were collected from the borehole and shallow aquifer between May 2017 and April 2018. Groundwater analysis included major ions and δ18O and δ2H, isotopes data in precipitation from three selected Global Network of Isotope in Precipitation (GNIP) stations across West Africa, Douala in Cameroon, Cotonou in Republic of Benin, and Kano in Nigeria were used in comparative analysis. Results of the hydrochemical model revealed Ca-HCO3 and Na-Cl as dominant water types with other mixing water types such as Ca–SO4, Ca–Cl, Na–SO4, and K–Mg–HCO3, which characterised early stage of groundwater transformation as it infiltrates through vadose zone into the aquifer. δ18O and δ2H precipitation data from the three stations plotted along with the groundwater samples indicate recent meteoric water origin, with little effect of evaporation during the dry season. The plot of Total Dissolved Solids (TDS) against δ18O showed clustering of the water samples between the recharge and the evaporation zone with dry season samples trending towards increased TDS, which is an indication of the subtle effect of evaporation during this period. Tracing groundwater types along the flow paths within the basin is problematic and attributed to the heterogeneity of the aquifer with anthropogenic influences. Moreover, a comparison of the δ18O and δ2H isotopic compositions of groundwater and precipitation in the three selected stations, with their respective deuterium excess (D-excess) values established low evapotranspiration induced isotope enrichment, which could be due to higher precipitation and humidity in the region resulting in low isotope fractionation; hence, little effect of seasonal variations. The study, therefore, suggested groundwater recharge in the shallow aquifer in the eastern Dahomey Basin is of meteoric origin with a short residence time of water flows from soils through the vadose zone to the aquifers.
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Vamberger, Melita, Margaretha D. Hofmeyr, Flora Ihlow, and Uwe Fritz. "In quest of contact: phylogeography of helmeted terrapins (Pelomedusa galeata, P. subrufa sensu stricto)." PeerJ 6 (June 5, 2018): e4901. http://dx.doi.org/10.7717/peerj.4901.
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Based on rangewide sampling and three mitochondrial and two nuclear markers (together up to 1,850 bp and 1,840 bp, respectively), we examine the phylogeography of two helmeted terrapin species (Pelomedusa galeata and P. subrufa sensu stricto) and infer shifts of climatically suitable spaces since the Last Glacial Maximum using a modeling approach. Whilst P. galeata displays significant phylogeographic structuring across its range and consists of two deeply divergent lineages that could represent distinct species, P. subrufa shows no obvious phylogeographic differentiation. This seems to be related to historically stable or fluctuating ranges. One of the lineages within P. galeata appears to be confined to the westernmost, winter-rainfall region of South Africa and deserves special conservational attention due to the scarcity of surface water. The other lineage is distributed further east and is differentiated in three weakly supported subclades with parapatric distribution; one occurring inland, and two along the south and east coasts, respectively. As far as is known, P. subrufa occurs in South Africa only in the northeast of the country (Limpopo, Mpumalanga) and we report the species for the first time from the Lapalala Wilderness Area in the Waterberg region (Limpopo), approximately 350 km further west than previously recorded. We confirmed the occurrence of P. galeata only 80 km south of Lapalala. Thus, a sympatric occurrence of P. galeata and P. subrufa is possible. Another putative contact zone, for the two lineages within P. galeata, must be located in the Western Cape region, and further contact zones are likely for the eastern subclades within P. galeata. The nuclear loci provided no evidence for gene flow across taxa or genetic clusters within taxa. Future investigations should use denser sampling from putative contact zones and more nuclear markers to re-examine this situation. Despite few phylogeographic studies published for southern African biota, it seems likely that differentiation follows general rules, and that climate and physiographic barriers (e.g., the Great Escarpment) have shaped phylogeographic patterns.
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Anandakumar, S., and G. Ramakrishnan. "பழங்குடிகளும் பொது வெளிச்சமூகமும் - ஓர் பார்வை." Shanlax International Journal of Tamil Research 5, no. 3 (January 1, 2021): 49–52. http://dx.doi.org/10.34293/tamil.v5i3.3641.
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India has one of the largest concentrations of tribal population in the world after Africa. The Tribal areas of India are mostly sheltered and remote, as a result of it a very little is known about their conditions and problems. The tribes are more compared not only in relation to the general population, but also compared with scheduled caste, the other acknowledged backward social group with constitutional protection. Tamil Nadu is one of the major states of the southern zone in India, consists of important tribal groups. The tribal areas of Tamil Nadu can be broadly divided into two major geographical dimensions such as the eastern coastal line and the mountainous regions of the north and west. The average elevation of the Eastern Ghats is 2000 feet and the highest peak is 6000 feet. This range is not continuous in Tamil Nadu. The Indian Sub-continent, in the Indian geographical area of Tamil Nadu covers about 1, 30,000 sq kms, representing nearly four percent of the total geographical area. There are more than 40 different tribes in Tamil Nadu. Scholars believe that most languages are closely related to Tamil and belong to the Dravidian language family.
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Adite, Alphonse, Stanislas P. Sonon, and Ghelus L. Gbedjissi. "Feeding ecology of the mangrove oyster, <i>Crassostrea gasar</i> (Dautzenberg, 1891) in traditional farming at the coastal zone of Benin, West Africa." Natural Science 05, no. 12 (2013): 1238–48. http://dx.doi.org/10.4236/ns.2013.512151.
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Tychsen, John, Ole Geertz-Hansen, and Frands Schjøth. "KenSea – tsunami damage modelling for coastal areas of Kenya." Geological Survey of Denmark and Greenland (GEUS) Bulletin 15 (July 10, 2008): 85–88. http://dx.doi.org/10.34194/geusb.v15.5051.
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On 26 December 2004, the eastern part of the Indian Ocean was hit by a tremendous tsunami created by a submarine earthquake of magnitude 9.1 on the Richter scale off the west coast of Sumatra. The tsunami also reached the western part of the Indian Ocean, including the coastal areas of eastern Africa. Along the coast of Kenya (Figs 1, 2) it resulted in a sudden increase in water level comparable to a high tide situation. This rather limited consequence was partly due to the great distance to the epicentre of the earthquake, and partly due to the low tide at the time of the impact. Hence the reefs that fringe two thirds of the coastline reduced the energy of the tsunami waves and protected the coastal areas. During the spring of 2005, staff members from the Geo- logical Survey of Denmark and Greenland (GEUS) carried out field work related to the project KenSea – development of a sensitivity atlas for coastal areas of Kenya (Tychsen 2006; Tychsen et al. 2006). Local fishermen and authorities often asked what would have been the effect if the tsunami had hit the coastal area during a high tide, and to answer the question GEUS and the Kenya Marine and Fisheries Research Institute (KMFRI) initiated a tsunami damage projection project. The aim was to provide an important tool for contingency planning by national and local authorities in the implementation of a national early warning strategy. The tsunami damage projection project used the database of coastal resources – KenSeaBase – that was developed during the KenSea project. The topographical maps of Kenya at a scale of 1:50 000 have 20 m contour lines, which is insufficient for the tsunami run-up simulation modelling undertaken by the new tsunami project. Therefore new sets of aerial photographs were obtained, and new photogrammetric maps with contour lines with an equidistance of 1 m were drawn for a 6–8 km broad coastal zone. The tsunami modelling is based on the assumption that the height of a future tsunami wave would be comparable with the one that reached the coastal area of Kenya in December 2004. Based on the regional geology of the Indian Ocean, it appears that the epicentre for a possible future earthquake that could lead to a new tsunami would most likely be situated in the eastern part of the ocean. Furthermore, based on a seismological assessment it has been estimated that the largest tsunami that can be expected to reach eastern Africa would have a 50% larger amplitude than the 2004 tsunami.It was therefore decided to carry out the simulation modelling with a tsunami wave similar to that of the 2004 event, but with the wave reaching the coast at the highest astronomical tide (scenario 1) and a worst case with a 50% larger amplitude (scenario 2: Fig. 3). The 2004 tsunami documented that the coastal belt of mangrove swamps provided some protection to the coastline by reducing the energy of the tsunami. Hence we included in this study a scenario 3 (Fig. 4), in which the mangrove areas along the coastline were removed. Maps for the three scenarios have been produced and show the areas that would be flooded, the degree of flooding, and the distribution of buildings such as schools and hospitals in the flooded areas. In addition, the force and velocity of the wave were calculated (COWI 2006).
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Langfur, Hal. "The Return of the Bandeira: Economic Calamity, Historical Memory, and Armed Expeditions to the Sertão in Minas Gerais, 1750-1808." Americas 61, no. 3 (January 2005): 429–61. http://dx.doi.org/10.1353/tam.2005.0025.
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Historians of colonial Brazil have conventionally located the conclusion of the great era of bandeira-led conquest somewhere near the end of the seventeenth century. The onset of the colony's gold cycle, corresponding with a series of major inland mineral strikes, reoriented those most actively engaged in the bandeira enterprise. Concentrated in the southern coastal captaincy of São Vicente, later, São Paulo, these wilderness adventurers had explored Portuguese America's immense interior and hunted its indigenous inhabitants. When their accompanying search for alluvial riches finally had born fruit, the Paulista backwoodsmen remade themselves into miners and merchants. The bandeirantes had first discovered gold in 1693 in Brazil's southeastern interior, the region that would soon acquire the name Minas Gerais or the General Mines; they made secondary strikes far to the west in Mato Grosso and Goiás in 1718 and 1725. Many then found themselves quickly displaced by the tide of Portuguese fortune-seekers and their African slaves who followed the paths now opened to the mining zones. As gold and then diamonds flooded the Atlantic world in unprecedented quantities, the colony's subsequent historical legacy would accrue not to São Paulo's peripatetic rustics but to those who consolidated control over the flow of riches. During the second half of the eighteenth century, with the mineral washings already in decline, attention would shift still further away from wilderness exploits, supposed to reflect a bygone era, back toward the coastal agricultural export enclaves that had traditionally preoccupied the Portuguese crown. The scholarly concerns of a later era would generally follow suit. As a consequence, the persistence of armed expeditions of exploration and conquest, which continued to roam the unmapped interior of Portuguese America, would go all but unnoticed as a critical feature of the late colonial period.
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Fischer, Gerhard, Johannes Karstensen, Oscar Romero, Karl-Heinz Baumann, Barbara Donner, Jens Hefter, Gesine Mollenhauer, et al. "Bathypelagic particle flux signatures from a suboxic eddy in the oligotrophic tropical North Atlantic: production, sedimentation and preservation." Biogeosciences 13, no. 11 (June 2, 2016): 3203–23. http://dx.doi.org/10.5194/bg-13-3203-2016.
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Abstract. Particle fluxes at the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic for the period December 2009 until May 2011 are discussed based on bathypelagic sediment trap time-series data collected at 1290 and 3439 m water depth. The typically oligotrophic particle flux pattern with weak seasonality is modified by the appearance of a highly productive and low oxygen (minimum concentration below 2 µmol kg−1 at 40 m depth) anticyclonic modewater eddy (ACME) in winter 2010. The eddy passage was accompanied by unusually high mass fluxes of up to 151 mg m−2 d−1, lasting from December 2009 to May 2010. Distinct biogenic silica (BSi) and organic carbon flux peaks of ∼ 15 and 13.3 mg m−2 d−1, respectively, were observed in February–March 2010 when the eddy approached the CVOO. The flux of the lithogenic component, mostly mineral dust, was well correlated with that of organic carbon, in particular in the deep trap samples, suggesting a tight coupling. The lithogenic ballasting obviously resulted in high particle settling rates and, thus, a fast transfer of epi-/meso-pelagic signatures to the bathypelagic traps. We suspect that the two- to three-fold increase in particle fluxes with depth as well as the tight coupling of mineral dust and organic carbon in the deep trap samples might be explained by particle focusing processes within the deeper part of the eddy. Molar C : N ratios of organic matter during the ACME passage were around 18 and 25 for the upper and lower trap samples, respectively. This suggests that some productivity under nutrient (nitrate) limitation occurred in the euphotic zone of the eddy in the beginning of 2010 or that a local nitrogen recycling took place. The δ15N record showed a decrease from 5.21 to 3.11 ‰ from January to March 2010, while the organic carbon and nitrogen fluxes increased. The causes of enhanced sedimentation from the eddy in February/March 2010 remain elusive, but nutrient depletion and/or an increased availability of dust as a ballast mineral for organic-rich aggregates might have contributed. Rapid remineralisation of sinking organic-rich particles could have contributed to oxygen depletion at shallow depth. Although the eddy formed in the West African coastal area in summer 2009, no indications of coastal flux signatures (e.g. from diatoms) were found in the sediment trap samples, confirming the assumption that the suboxia developed within the eddy en route. However, we could not detect biomarkers indicative of the presence of anammox (anaerobic ammonia oxidation) bacteria or green sulfur bacteria thriving in photic zone suboxia/hypoxia, i.e. ladderane fatty acids and isorenieratene derivatives, respectively. This could indicate that suboxic conditions in the eddy had recently developed and/or the respective bacterial stocks had not yet reached detection thresholds. Another explanation is that the fast-sinking organic-rich particles produced in the surface layer did not interact with bacteria from the suboxic zone below. Carbonate fluxes dropped from ∼ 52 to 21.4 mg m−2 d−1 from January to February 2010, respectively, mainly due to reduced contribution of shallow-dwelling planktonic foraminifera and pteropods. The deep-dwelling foraminifera Globorotalia menardii, however, showed a major flux peak in February 2010, most probably due to the suboxia/hypoxia. The low oxygen conditions forced at least some zooplankton to reduce diel vertical migration. Reduced “flux feeding” by zooplankton in the epipelagic could have contributed to the enhanced fluxes of organic materials to the bathypelagic traps during the eddy passage. Further studies are required on eddy-induced particle production and preservation processes and particle focusing.
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Cockcroft, Andrew C. "Jasus lalandii 'walkouts' or mass strandings in South Africa during the 1990s: an overview." Marine and Freshwater Research 52, no. 8 (2001): 1085. http://dx.doi.org/10.1071/mf01100.
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Faunal mass mortalities are a sporadic, but not uncommon, feature of the West and South coasts of South Africa. Five mass mortalities of West Coast rock lobsterJasus lalandii, including three of the most severe ever recorded in South Africa, occurred in the 1990s and resulted in the stranding of about 2263 tonnes of lobster. The bulk (97%) of the loss occurred in the last three years of the decade. The five events occurred within an 80 km stretch of coastline that straddled two fishing zones and resulted from hypoxic conditions associated with highbiomass dinoflagellate blooms. In each case, the quantity of lobsters stranded was directly related to the extent or duration of low-oxygen conditions. Small females constituted the bulk of the lobster stranded in most events. The lobster fisheries in the affected fishing zones suffered severe impacts. Recovery in one zone appears to be extremely slow, whereas the other zone is more resilient. Not only would a continuation of the trend of increasing frequency and severity of lobster strandings devastate the rock-lobster fishing industry and the employment prospects of small fishing communities, but it could also seriously affect the ecology of the region.
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Nekhoroshkov, Pavel, Jacques Bezuidenhout, Inga Zinicovscaia, Nikita Yushin, Konstantin Vergel, and Marina Frontasyeva. "Levels of Elements in Typical Mussels from the Southern Coast of Africa (Namibia, South Africa, Mozambique): Safety Aspect." Water 13, no. 22 (November 15, 2021): 3238. http://dx.doi.org/10.3390/w13223238.
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The soft tissues of mussels are often used as the main food source, especially in coastal areas. Neutron Activation Analysis was used to measure the content of 24 macro- and microelements in the soft tissues and 18 elements in the shells of selected sets of mussels of the species Mytilus galloprovincialis. The mussels were collected in 8 polluted and 4 pristine zones, which included Namibia, the west and east coasts of South Africa, and Mozambique. According to factor analysis Co, Ni, Zn, As, Se, Br, I, Sb could have anthropogenic origin. The concentrations of elements such as Cr, As, Se and partly Zn at polluted stations were above the maximum permissible levels for seafood. The concentrations of Sc, V, Cr, Mn, Co, Ni, Sb, Cs, Th, U in shells and soft tissues of the same mussels were at the close levels. Elements such as Al, Cr, Co, As (partly Zn, Se, and I) are considered to be harmful to human health at the levels of mussels consumption of 200 g/week per person and lower in such zones as Swakopmund, East London, Port Shepstone, Richards Bay, Xai-Xai according to calculated risk quotients and target hazard indices.
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GRIPER-FRIEDMAN, LINDSAY. "The tone system of West African Coastal English." World Englishes 9, no. 1 (March 1990): 63–77. http://dx.doi.org/10.1111/j.1467-971x.1990.tb00687.x.
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Nguyen, Hanh, Chris D. Thorncroft, and Chidong Zhang. "Guinean coastal rainfall of the West African Monsoon." Quarterly Journal of the Royal Meteorological Society 137, no. 660 (July 25, 2011): 1828–40. http://dx.doi.org/10.1002/qj.867.
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Snoussi, Maria, and El Hafid Tabet Aoul. "Integrated coastal zone management programme northwest African region case." Ocean & Coastal Management 43, no. 12 (January 2000): 1033–45. http://dx.doi.org/10.1016/s0964-5691(00)00071-5.
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Dada, Olusegun, Rafael Almar, Pierre Morand, and Frederic Menard. "“Towards West African coastal social-ecosystems sustainability: Interdisciplinary approaches”." Ocean & Coastal Management 211 (October 2021): 105746. http://dx.doi.org/10.1016/j.ocecoaman.2021.105746.
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Alemna, David. "Monetary Convergence Across the Economic Community of West African States: Lessons for the Envisioned West African Monetary Union." Complexity, Governance & Networks 7, no. 1 (May 2, 2022): 50. http://dx.doi.org/10.20377/cgn-108.
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Since its inauguration, the Economic Community of West African States has stressed its desire to advance regional integration through the establishment of a common single currency (the Eco). This policy has been considered advantageous given the economic benefits derived from the existence of one of the oldest sub-regional monetary unions across French-speaking West African Economies. For this reason, the West African Monetary Zone was created as a suggested second monetary zone consisting of English-speaking countries in the region in anticipation that in the long run, the two would converge. While empirical studies into the feasibility of achieving monetary integration in West Africa have provided some understanding of causal notions and possible effects, very few studies embrace complexity theory or attempt to use complexity-related conceptual notions in the identification and interpretation of patterns produced in longitudinal applications. Using both empirical and theoretical methods, this paper provides a unique longitudinal application of Dynamic Patterns Synthesis as an exploratory tool for observing the potential complexities that the proposed single currency arrangement across West Africa is likely to pose. The findings highlight multiple conjunctural causation in observing convergence and unpredictability across the Monetary Zone. These observations suggest more time is needed to achieve an established single currency.
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Sokolova, Flera K., and Anna V. Lyalina. "MIGRATION ATTRACTIVENESS OF THE COASTAL ZONE OF RUSSIA’S NORTH-WEST: LOCAL GRADIENTS." Baltic Region 13, no. 4 (2021): 54–78. http://dx.doi.org/10.5922/2079-8555-2021-4-4.
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A well-acknowledged driver of change, population movement intensifies the development of coastal territories. The Russian North-West holds a vast coastal zone. Granting access to the Baltic, the White, and the Barents Seas, it is an area of geostrategic importance where much of the country’s coastal economy — one of the national priorities — is located. Push and pull factors are enormously diverse in the area, as are migration flows forming attraction poles for migrants. There is little research on the issue despite its social and practical significance. Thus, research is required to examine how the coastal factor can benefit the migration attractiveness and human resources of Russian coastal territories of geostrategic importance. This study aims to delineate coastal territories and investigate local migration flows compared to those recorded in inland regions. The research draws on the concept of coastalisation, employing universal, geographical, and statistical research methods. It uses documentary sources and official 2011—2020 statistics. The findings show that the coastal position and maritime economic activity are relevant factors for migration attractiveness. Saint Petersburg and the coastal municipalities of the Leningrad and Kaliningrad regions are more attractive to migrants than more northerly territories. However, there are attraction poles farther north too, and the coastal zone of the Arkhangelsk region attracts more migrants than its inland part. The study demonstrates the growing polarisation of migration space in the coastal areas and especially agglomerations. Changes in the age structure of immigration flows have caused social factors in attractiveness to migrants to replace employment-related factors.
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Tule, Moses K., Taiwo Ajilore, and Augustine Ujunwa. "Monetary Policy Contagion in the West African Monetary Zone." Foreign Trade Review 54, no. 4 (November 2019): 375–98. http://dx.doi.org/10.1177/0015732519874219.
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The study utilized quarterly time series data for Nigeria and three selected West African Monetary Zone (WAMZ) countries for the period 1980–2016 to verify whether monetary policy shocks emanating from Nigeria are an important source of macroeconomic fluctuations in WAMZ economies. The study complemented the Global vector autoregressive method with the Diebold–Yilmaz (2009) connectedness weights computation for the analysis. Inferences from generalized impulse response function (GIRF) analysis indicated that an unanticipated Nigerian monetary policy shock depreciates the Nigeria–USA exchange rate, stimulates growth, decelerates inflation and expands the money stock in the short run for Nigeria. In Ghana, Nigeria’s monetary policy shocks similarly depreciates the exchange rate, slows growth with high inflationary impact in the short run. In the Gambia, unanticipated shocks emanating from Nigeria strengthens the Gambia–USA exchange rate, depresses growth and inflationary pressures. Sierra Leone shares the appreciation of its currency with the Gambia, in addition to an economic expansion and rising inflation. Money supply also increases to accommodate the expanding demand. These results validated the thesis that there exist considerable geographical linkages within the WAMZ regions through which macroeconomic fluctuations are transmitted. For policy, monetary authorities in the region should collectively address the question of how to stabilize the economy in response to monetary policy shocks emanating from Nigeria. JEL Codes: E52, E32, E65, F02
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Rust, I. C. "Environmental geology of the coastal zone: a South African perspective." South African Journal of Marine Science 10, no. 1 (June 1991): 397–405. http://dx.doi.org/10.2989/02577619109504647.
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Oi Edia, Edia, Sebastien Brosse, Allassane Ouattara, Germain Gourene, Peter Winterton, and Sithan Lek-Ang. "Aquatic Insect Assemblage Patterns in Four West-African Coastal Rivers." Journal of Biological Sciences 7, no. 7 (September 15, 2007): 1130–38. http://dx.doi.org/10.3923/jbs.2007.1130.1138.
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Harvey, Simon K., and Matthew J. Cushing. "Is West African Monetary Zone (WAMZ) a common currency area?" Review of Development Finance 5, no. 1 (June 2015): 53–63. http://dx.doi.org/10.1016/j.rdf.2015.05.001.
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Danekina, V. N. "LANDSCAPE-ECOLOGICAL PLANNING OF THE COASTAL ZONE OF SOUTH-WEST CRIMEA." Proceedings of the International conference “InterCarto/InterGIS” 1, no. 23 (January 1, 2017): 277–85. http://dx.doi.org/10.24057/2414-9179-2017-1-23-277-285.
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Baitalik, Anirban, and Sankar Majumdar. "Coastal Tourism Destinations in West Bengal: Historical Background and Development." International Journal of Social Sciences and Management 2, no. 3 (July 25, 2015): 267–72. http://dx.doi.org/10.3126/ijssm.v2i3.12910.
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Coastal tourism has become a major facet of modern life. Further, tourism development in the coastal zone has become a constant since the end of World War II. Coastal tourism is a process involving tourists and the people and places they visit, particularly the coastal environment and its natural and cultural resources. Most coastal tourism takes place along the shore and in the water immediately adjacent to the shoreline. In India Goa, Kerala, Karnataka were emerged spontaneously as a coastal tourism destination in the 1960s, its unique selling points being its natural coastal beauty. But the history of coastal tourism is not very old in West Bengal. The coastal stretch of West Bengal with a length of about 350 kilometer comprises the two districts- Purba Medinipur and Dakshin Chabbisparagana. In West Bengal there are many popular coastal tourism destinations, but coastal tourism in West Bengal started in 1980s. Present study focuses on historical background and development of the coastal tourism destinations in West Bengal.Int. J. Soc. Sci. Manage. Vol-2, issue-3: 267-272 DOI: http://dx.doi.org/10.3126/ijssm.v2i3.12910
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Rauch, Manuel, Jan Bliefernicht, Patrick Laux, Seyni Salack, Moussa Waongo, and Harald Kunstmann. "Seasonal Forecasting of the Onset of the Rainy Season in West Africa." Atmosphere 10, no. 9 (September 8, 2019): 528. http://dx.doi.org/10.3390/atmos10090528.
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Seasonal forecasts for monsoonal rainfall characteristics like the onset of the rainy seasons (ORS) are crucial for national weather services in semi-arid regions to better support decision-making in rain-fed agriculture. In this study an approach for seasonal forecasting of the ORS is proposed using precipitation information from a global seasonal ensemble prediction system. It consists of a quantile–quantile-transformation for eliminating systematic differences between ensemble forecasts and observations, a fuzzy-rule based method for estimating the ORS date and graphical methods for an improved visualization of probabilistic ORS forecasts. The performance of the approach is tested for several climate zones (the Sahel, Sudan and Guinean zone) in West Africa for a period of eleven years (2000 to 2010), using hindcasts from the Seasonal Forecasting System 4 of ECMWF. We indicated that seasonal ORS forecasts can be skillful for individual years and specific regions (e.g., the Guinean coasts), but also associated with large uncertainties. A spatial verification of the ORS fields emphasizes the importance of selecting appropriate performance measures (e.g., the anomaly correlation coefficient) to avoid an overestimation of the forecast skill. The graphical methods consist of several common formats used in seasonal forecasting and a new index-based method for a quicker interpretation of probabilistic ORS forecast. The new index can also be applied to other seasonal forecast variables, providing an important alternative to the common forecast formats used in seasonal forecasting. Moreover, the forecasting approach proposed in this study is not computationally intensive and is therefore operational applicable for forecasting centers in tropical and subtropical regions where computing power and bandwidth are often limited.