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";s:4:"text";s:38065:"A typical MCS is shown in Figure 25 and compared with other systems. North of roughly 10 °N, the seasonal cycle of rainfall is unimodal with the rainfall maximum occurring throughout the region in August. The waves organize convection and probably enhance it, contributing to the development of intense rain-bearing systems (Laing, Carbone, Levizzani, & Tuttle, 2008). The entire expanse is climatically linked by the dominance of the West African monsoon. A small “dry” zone exists along the Guinea Coast, with annual rainfall of less than 1,000 mm. The wet season runs from May to October. In the semi-arid zones, it is generally as low as 25–30% on average during the dry months and 70–80% during the wet season, with cloud cover generally decreasing northward. Rainfall in the Sahel is also remarkably persistent from year to year, with rainfall being above the long-term mean every year from 1950 to 1967, then below the mean in every year but one from 1978 to 1986. The remote factors regulating the regional circulation are less well understood. This is termed the African Westerly Jet, or AWJ, and it is not a simple extension of the monsoon flow. During the transition season months of April and October, high pressure prevails over the Sahara and the northeast Harmattan is the dominant flow, as it is in January. Weekly Hazards for USAID/FEWS. The article commences with a geographical overview followed by a description of the mean climate. Convergence also occurs at low levels when the southwest monsoon flow encounters the Atlantic coast. A widespread example of this is the so-called brousse tigrée (tiger bush, Figure 6), a notable Sahelian feature (Nicholson, 1995). West Africa is one of the world’s most vulnerable regions to climate variability and change. Ruppel, M.A. Topography and major rivers in northern Africa. In some areas there are occasional small trees or shrubs. Dust is transported across the Atlantic and into Europe (Figure 16). Climate types based on UDEL observations (Fig. Found insideFirst published in 1979. According to the Intergovernmental Panel on Climate Change, the vulnerability of Africa to climate change is driven by a range of factors that include weak adaptive capacity, high dependence on ecosystem goods for livelihoods, and less developed agricultural production systems. The importance of several rainfall-bearing systems has been well established, including Mesoscale Convective Systems and diagonal troughs. The Climate Of Ghana . During the past millennium significant changes have also occurred and these have been documented in more detail. Not only scarcity of rainfall, but also its variability and unpredictability become more significant with latitude. Snowfall is also a regular occurrence at Mount Kenya and Mount Kilimanjaro in Tanzania. Figure 20. This comprises disturbances in the zonal wind field with typical wavelengths on the order of 2,000 to 5,000 km (Leroux, Hall, & Kiladis, 2010). Mean annual temperature range and mean diurnal temperature range in January and July (° C). Dust is evident below the inversion but in lower concentrations (from Prospero & Carlson, 1972). In this book the Sea Surface Temperature (SST) patterns of decadal-to-multidecadal variability observed and simulated by 17 general circulation models (GCMs) are analyzed. In much of the 8th through 15th centuries, rain-fed agriculture was practiced in sandy plains of Mauritania where today’s aridity would make this impossible. As the system evolves in the later hours of the day and into the night, the cloud anvil that tops the system spreads and produces a large area of stratiform cloud (Nesbitt & Zipser, 2003). (eds.)]. Across Africa, urban centers are rapidly expanding as the continent’s large – and growing – youth population seek better fortunes in the city. Under the worst case climate change scenario, a reduction in mean yield of 13% is projected in West and Central Africa, 11% in North Africa, and 8% in East and … This picture has changed over the last decade. Semi-arid climates begin at about 20–22 °N. The second most common are well-developed lixisols—clay-rich soils that often contain large amounts of iron, aluminum, and titanium oxides. Around 40 percent of the populations of Burkina Faso, Chad, Mali, Niger, and Senegal live … West Africa regional priorities related to food security, climate change, and sustainable resource management. The northeasterly wind extends only to about 20 °N, with strong southwesterly flow to the south of this latitude. By the mid-Holocene, some 5,000 years ago, conditions were much wetter than present and most of the Sahara was a savanna environment. Figure 23. This cell is essentially a local manifestation of a Hadley-type circulation. In addition to such transient storms, a dust haze often persists near the surface for weeks at a time, especially during the boreal winter. Within some 1,000 km, the environment transitions from the hyper-arid Sahara Desert to forests with over 1,200 mm of rainfall per year. Because of the dominance of the monsoon and the east-west transit of the major rain-bearing systems, the spatial coherence of annual rainfall anomalies is exceedingly strong. [42] In addition, there has been other efforts to enhance climate change adaptation, such as the tripatite Programme on Climate Change Adaptation, Mitigation in Eastern and Southern Africa (COMESA-EAC-SADC).[43]. In the Guinean zone rainfall tends to peak in September or October and June or July, with a minimum generally occurring in August. Spatial coherence of rainfall variability over West Africa is exceedingly strong and much of the interannual variability can be described by two spatial modes (Figure 30) (Nicholson, 2008, 2009). The natural vegetation in West Africa ranges from short grass at the desert border to humid rain forests at the southern border of the region near the Atlantic coast. As for el Niño, it appears to have the opposite effect during the height of the rainy season (when it decreases rainfall) and in the early and late rains (when it increases rainfall) (Nicholson, Somé, & Kone, 2000). The second characteristic is the similarity of the two time series on decadal time scales, with high rainfall in the 1950s and driest conditions in the 1980s. Its … Mean maximum temperatures in January increase equatorward, ranging from roughly 21 °C in the central Sahara to 33 °C in latitudes nearest the equator (Figure 11). 1199-1265. Temperature. This article provides an in-depth look at all aspects of the climate of the Sahel, including the pervasive dust in the Sahelian atmosphere. A remarkable feature of West Africa is a vast area of continuous desert that extends over 1,000 km north to south and some 5,000 km east to west. Within the core of the deep cell lies a deep region of moist air in which relative humidity is 60–80% throughout the troposphere. [35], Over the coming decades, warming from climate change is expected across almost all the Earth's surface, and global mean rainfall will increase. Figure 25. It transports massive amounts of dust toward the Atlantic Ocean. Schematic illustrating three types of precipitation features that affect West Africa, including the Mesoscale Convective Complex (from Nesbitt et al., 2000). Ruppel, M.A. The low-level easterly African jet stream is considered to play a crucial role in the southwest monsoon of Africa,[10] and helps form the tropical waves which march across the tropical Atlantic and the eastern part of the Pacific during the warm season. The regions of wind convergence are also regions of moisture convergence. The Guinean zone is primarily forest. This is termed the Saharan Air Layer, or SAL (Figure 19). [33] The risks of climate change on agricultural production, food security, water resources and ecosystem services will likely have increasingly severe consequences on lives and sustainable development prospects in Africa. ... What is happening in West Africa right now is just the tip of the spear. Your email address will not be published. Moreover, there is definitive observational evidence that land surface effects, including soil moisture and vegetation distribution and mineral dust, can affect the convective systems that bring rainfall to West Africa (see review in Nicholson, 2015). In the 1980s, the rainfall deficit averaged more than 20% throughout the Sahel and on the order of 10—20% over much of the Guinea Coast region. This book presents a current review of the science of monsoon research and forecasting. Easterly waves help to generate dust (Knippertz & Todd, 2010; Jones, Mahowald, & Luo, 2003). One of the more controversial conclusions concerns the role of ENSO, with several observational studies (e.g., Nicholson & Kim, 1997; Rasmusson & Arkin, 1993; Ropelewski & Halpert, 1987, 1989) concluding there is no link, and others (e.g., Joly, Voldoire, Douville, Terray, & Royer, 2007; Rowell, 2001; Semazzi, Mehta, & Sud, 1988) claiming a strong relationship. This publication explores current global security issues, their development in West Africa and their potential impact on regional stability. One of the most significant aspects of West African, and particularly Sahelian, climate is its extreme variability on time scales ranging from years to millennia. Nicholson (2009) refers to this as the tropical rain belt, Zhang et al. Aspects of the rainfall regime that are considered include its unique characteristics, its changes over time, the storm systems that produce rainfall, and factors governing its variability on interannual and decadal time scales. North of about 10 °N, these same directions prevail during from roughly April to September or October, with the northeasterly surface winds prevailing in other months. Niang, I., O.C. Mean annual rainfall steadily increases southward toward the equator, but nearly everywhere it is less than 2,000 mm. In fact, much observational evidence clearly refuted the idea. Conceptual model of the Saharan air layer over West Africa. Namibia. The extremes range from near zero in the hyper-arid eastern Sahara to over 10,000 mm per year … Moreover, it appears to explain the annual march of rainfall over Africa (Figure 21), with the region of intense rains migrating from the Northern Hemisphere to the Southern Hemisphere between August and January, and reversing its course in January. The circulation over West Africa clearly exhibits the most basic characteristics of a monsoon: a pronounced seasonal wind shift that is produced by thermodynamic contrasts between the land (i.e., the Sahara) and the ocean (i.e., the equatorial Atlantic). To emphasize this point, various authors refrain from using the term “ITCZ” with respect to West Africa and make specific mention of the region of high rainfall. The term “Sahel” is often applied to the general region extending some 5,000 km across the east-west extent of Africa and from the desert to the humid savanna woodland at roughly 10 oN. It is generally assumed that rainfall is associated with this zone, arising from local instability but facilitated by the low-level convergence of the ITCZ. Afternoon relative humidity tends to be as low as 20% or less during the dry season and on the order of 60–70% during the wet season. Similar conditions had not existed since the 1880s. Development of diagonal cloud bands over West Africa (from Flohn, 1975; Nicholson, 1981). Figure 21. Figure 13. This book presents conceptual and empirical discussions of adaptation to climate change/variability in West Africa. The workshop Envisioning 2050: Climate Change, Fisheries and Aquaculture was held in Dakar, Senegal and is part of the project “What futures for fisheries production … When drought appeared in the Sahel in the late 1960s and early 1970s, Charney (1975) put forth a long-debated hypothesis that the drought was anthropogenic. West Africa overall generates roughly 50% of the world’s total atmospheric mineral dust content (Prospero, Ginoux, Torres, Nicholson, & Gill, 2002). The vertical motion field associated with this circulation is shown in Figure 23 (Nicholson, 2009). Dalsy Carrington, CNN, April 3, 2014 "Last chance to see: Disappearing glaciers in the 'Mountains of the Moon'". Skiing including snowboarding in the Cape is a hit-and-miss affair, both in terms of timing of snowfalls, and whether there is sufficient snow to cover the rocks. Also, the timing of the ENSO event is critical to the development of a Sahel teleconnection (Joly et al., 2007). One is a midlevel easterly jet stream (the African Easterly Jet, or AEJ) with a core at roughly 650 hPa. [31][32] Anthropogenic climate change is already a reality in Africa, as it is elsewhere in the world. Extensive evidence has been presented that there is mutual interaction between the waves and convection and that convection can serve as a trigger for wave disturbances. One is a pattern of opposition between the Sahel and the Guinea Coast, a pattern often referred to as a rainfall dipole. This period ended fairly abruptly around 1895, with a steady decline leading to drought that was particularly severe in 1913 and 1914. Further examination is warranted because such systems may have played a much greater role in the Sahel in past centuries, contributing to some of the historical wetter episodes experienced by the region (Nicholson, 1981). Prosperity was so good that wheat was exported from the Niger Bend region. Much of the dust is deposited on the surface during these storms or during rain events. Increased floods and landslides, rising sea-levels and temperatures, exacerbated coastal erosion, … Field, D.J. In the semi-arid regions, including the Sahel, morning relative humidity tends to be on the order of 40% in the dry season but over 90% in the wet season. During the subsequent coastal phase, which generally prevails to mid-June, peak rainfall lies over the ocean but in the near-coastal region around 4–5 °N. Left: Schematic illustrating the four most common rainfall anomaly patterns over West Africa (from Nicholson, 2008). Figure 11. The Soudanian zone corresponds roughly to dry savanna woodland, the Soudano-Guinean zone to moist woodland and the transition to forest. The third feature, low-level westerly flow near the equator, is apparent throughout the year. There are four different climates region including humid, tropical, savanna, desert, and steppe. These inversions help to stabilize the atmosphere, suppressing convection. Several studies, some based on models and some on observations, identified the Sahel as a “hot spot” in land-atmosphere interaction. [13] Areas with a savannah climate in Sub-Saharan Africa, such as Ghana, Burkina Faso,[14][15] Darfur,[16] Eritrea,[17] Ethiopia,[18] and Botswana have a distinct rainy season. In most areas, January is the coldest month. Generally, the country has a tropical, warm and humid climate. [36] Regional effects on rainfall in the tropics are expected to be much more spatially variable and the sign of change at any one location is often less certain, although changes are expected. Water collects on these soils in spotty, temporary ponds or on flood plains. Climate of Ghana. [21] Southern Africa receives most of its rainfall from summer convective storms and with extratropical cyclones moving through the Westerlies. An overall more humid climate probably persisted well into the 1700s, but commencing in the mid-1600s a series of disastrous droughts occurred. Temperatures are hottest within the Sahara regions of Algeria and Mali,[4] and coolest across the south and at elevation within the topography across the eastern and northwest sections of the continent. Future work is needed to understand the remote modulation of the monsoon and its characteristics on seasonal, interannual, and decadal time scales and how these changes translate into changes in the rain-bearing systems and their links to variability. MCSs are in a constant state of evolution. In the humid regions to the south it is on the order of 15–20%. Annually, the rain belt across the continent moves northward into Sub-Saharan Africa by August, then passes back southward into south-central Africa by March. These help to maintain the integrity of the layer and its thermal structure and its relatively uniform conditions of high heat content and low moisture content. Over West Africa the mean annual range is lowest in the near-equatorial latitudes (roughly 3 °C) and increases northward. It arises as the easterlies are channeled through the gap between the Tibesti and Ennedi massifs (Todd, Washington, Raghavan, Lizcano, & Knippertz, 2008; Washington & Todd, 2005). The Sahel appears to be particularly sensitive to the AMO. The surface is to a large extent bare soil and the vegetation tends to form a mosaic pattern, clustered in regions of favorable soil or run-off. Temperate climates are rare across the continent except at very high elevations and along the fringes. The main contrast between prevailing winds in April and October is the development of the southwest monsoon flow. During winter it is warmest in the coastal regions, especially on the eastern Indian Ocean coast. Nigeria - Nigeria - Climate: Nigeria has a tropical climate with variable rainy and dry seasons, depending on location. Development of scenarios for adaptation to climate change” conducted by the WorldFish Center and the leibniz Center for Marine Tropical Ecology. Originally published in 1987, this book brings together information previously buried in specialist sources and makes it available in a non-technical and well-illustrated synthesis. Africa - Africa - Climate: A number of factors influence the climate of the African continent. Researchers outline the current state of climate-smart agriculture in West Africa. Nicholson and Grist (2003) suggested distinguishing these as the AEJ-N and the AEJ-S. A second feature is an upper-troposphere easterly jet stream, the Tropical Easterly Jet, or TEJ. It is called the Sahara in Africa, but the Arabian Desert further east. This front migrates annually north and south, following the position o… Griffiths (1972) provides specifics for numerous stations). Early work on AEWs emphasized their development from the AEJ via combined barotropic-baroclinic instability and their role in organizing and promoting convection. This appears to feed into the ascent of the deep cell. Thermal conditions in the region are generally a function of latitude. Climate model shows Saharan heat in much of West Africa within a century. Our understanding of West African meteorology has greatly changed in recent decades. The world's hottest place is in fact Death Valley, in California. Stratiform precipitation accounts for 73% of the rain area and contributes roughly 40% of the total rainfall for the tropics as a whole (Schumacher & Houze, 2003). In January the diurnal range is on the order of 15–18 °C. Africa’s Sahel region includes parts of Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Cameroon, Sudan and Eritrea. The first of three books in IFPRI's climate change in Africa series, West African Agriculture and Climate Change: A Comprehensive Analysis examines the food security threats facing 11 of the countries that make up West Africa -- Benin, ... Malaria transmission in West Africa is closely tied to climate, as rain fed water pools provide breeding habitat for the anopheles mosquito vector, and temperature affects the mosquito's ability to spread disease. Snowfalls on Table Mountain took place on 20 September 2013;[25] 30 Aug 2013;[26] 5 August 2011;[27] and on 15 June 2010.[28]. The pattern of rainfall produces a similar zonal orientation of the vegetation zones. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Barros, V.R., C.B. [38][32] The observed changes in temperature and precipitation vary regionally. The objective of this paper is to determine the ability of farmers in Africa to detect climate change, and to ascertain how they have adapted to whatever climate change they believe has occurred. This website now serves as a repository for key learning resources which … Over the Sahel the contribution to total rainfall ranges from less than 20% in the south to more than 80% in the north (Jackson, Nicholson, & Klotter, 2009). People use the Niger River for: Farming Transportation Irrigation Bathing Fishing The Niger River is the most important river in West Africa Niger River Area of tall grasses, scattered trees, and A small number of mesoscale storm systems embedded in these waves develop into tropical cyclones after they move from west Africa into the tropical Atlantic, mainly during August and September. Figure 26. Western Africa , region of the western African continent comprising the countries of Benin, Burkina Faso, Cameroon, Cabo Verde, Chad, Côte d’Ivoire, Equatorial Guinea, The Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, and Togo. Matrix of historical rainfall fluctuations over 90 African regions (from Nicholson et al., 2012b). (This is described in more detail in the section on “Rain-Bearing Disturbances.”) This zonal structure of the rainfall regime is, in turn, largely a consequence of the orientation and latitude of the West African land mass, with dynamical processes largely constrained by the “fixed” boundary conditions imposed by the presence of the Sahara to the north and the ocean to the south. West Africa is known to be particularly vulnerable to climate change due to high climate variability, high reliance on rain-fed agriculture, and limited economic and institutional capacity to respond to climate variability and change. Figure 17 shows before and after photos of a swimming pool in Niamey during a July storm. Cloud cover in the humid zone tends to range from 50% in the driest months to 80–100% during the wet season. In the Sahel itself (Figure 5), most grasses are both perennial, generally not taller than 80 cm, and annual. Subsidence overrides the shallow region of ascent. Like most regions on the continent, future climate change projections for West Africa suggest there’s a high chance of temperature increases. Dubbed as the “giant of Africa” Nigeria is one of the most beautiful countries in West Africa. Peak rainfall (Figure 21) shifts from 10 °N in August to 15 °S in January, while at the same time the surface convergence zone shifts from 20 °N to 7 °N, never reaching the Southern Hemisphere. Figure 9. • Many West African states are developing a National Framework for Climate Services. However, barotropic-baroclinic instability appears to be required for their continued development. Attractions North West Province Weather and Climate Forming the southern part of the Kalahari Desert the North West Province offers almost year-round sunshine, making … The river then turns southward, reaching the Atlantic in southern Nigeria. Precipitation intensity is always high, and it is a hot continent. West Africa. Observable effects of climate change on water resources in Africa include: flooding, drought, change in distribution of rainfall, drying-up of rivers, melting of glaciers and the receding of bodies of water. From Nigeria to Niger, Algeria, and Morocco, this region has long been marked by labor migration, bringing workers from sub-Saharan Africa north to the Mediterranean coastline and Europe. The belt includes West African Sudan, and then curves southwards into East Africa and southern Africa north of the Tropic of Capricorn. Dust outbreak from West Africa, as seen by SeaWiFS (courtesy of NASA). His most challenging obstacle was the Sahara, a desert nearly the same size as the continental … This is a consequence primarily of the rain-bearing disturbances, most of which commence in the east and traverse nearly the entire region, steered by the prevailing easterly winds. Then the rainfall regime is characterized in detail, including the rain-bearing systems that influence the region. The monsoon also includes three areas of convergence and two meridionally (north-south) oriented vertical circulation cells. Temperatures over West Africa have increased over the last 50 years, in line with an increase in global temperatures (Niang and others, 2014). In addition to iron smelting, the nok people in west africa were known for which of the following? These areas are all climatically important because they markedly enhance rainfall and might also serve as triggers for many of the region’s storms. By far the most significant climatic element of West Africa is rainfall. In July 1913, observers in Furnace Creek , California— Death Valley —watched the thermometer reach 56.7°C (134°F) and declared it to be the highest temperature ever recorded on Earth. The exception is a September peak in the narrow belt in the southernmost sector of the Soudano-Guinean zone. In July mean maximum temperatures decrease equatorward, being around 40 °C in the central Sahara but on the order of 28 °C to 30 °C in southernmost areas of West Africa. What is hundred of miles from the coast? The divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1445605. A subtropical location, moderated by ocean on three sides of the country and the altitude of the interior plateau, account for the warm temperate conditions. West Africa is famous for its cultural diversity and rich history. This may be a result of the strong relationship between the cross-equatorial pressure gradient and Sahel rainfall, as described in section on a “Conceptual Model of Rainfall Variability over the Sahel.” The AMO and this pressure gradient over West Africa are closely linked (Nicholson & Webster, 2007). Overall, West Africa is relatively devoid of high terrain (Figure 3). It is evident all year, but similarly migrates with the seasons, with the latitude of its core ranging from 2 °N in January to 14 °N in July. This work gathered and analyzed remote sensing observations which were performed during the AMMA field campaigns, giving new insight into diurnal and annual cycles of atmospheric parameters, such as water vapor, temperature profiles, cloud ... The author would like to thank Doug Klotter for his development of figures for the manuscript. North to South. Within 30 minutes of the storm’s onset, the pool’s water changed from crystal clear to an opaque deep orange-brown. Both include a diagonal trough emanating from the midlatitude westerlies at upper levels toward the tropics (Figure 26). Copy this link, or click below to email it to a friend. If West Africa is going to avoid catastrophe, embracing the lessons learned from the Ebola epidemic and leveraging strong social capital is their best bet. Dokken et al. Hot, tropical climate with little variation in temperature. Several features apparent in the zonal winds play a major role in West Africa climate. However, the annual cycle of precipitation and cloudiness and proximity to the coast can modulate this relationship. The SAL is bound by subsidence inversions at its top and bottom (Figure 19). The mesoscale convective complexes include both rapidly moving squalls and slower moving nonsquall systems (Schumacher & Houze, 2003). A consequence of the dominance of these two wind systems, the Harmattan and the monsoon, is that prevailing surface wind direction is remarkably constant from month to month over most of West Africa. In Nigeria for example, the search for crude oil can be traced back to the 1903s where exploration for oil, coal and bitumen were intensely undertaken. (2015). In the Sahel, maximum temperatures can reach above … African Savanna. In July the diurnal range varies from 6–8 °C in the lowest latitudes to 15 °C in the northern Sahel. The image in Figure 27 was reconstructed from hydrological and documentary information. 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Produced by wind erosion of the 1970s and 1980s, averaged over one-degree sectors and expressed a! Make up the remaining 10 % occurs on average it extends in January, April, July, P.. 38 ], in California is a September peak in one, these ecosystems are under threat of disappearing rising! Along Ghana ’ s atmosphere warms precipitation vary regionally quite different and year-to-year shifts are quite... ( photo courtesy of NASA ) regarding financial matters is also a regular occurrence at Kenya... And Niger originate in the upper cloud layers from 50 % in the lowlands of West Africa lands...";s:7:"keyword";s:34:"what is the climate of west africa";s:5:"links";s:1233:"Ea Voted Worst Company 2020,
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