Academic literature on the topic 'Southern Westerly Wind belt'

Nationalism: Past as Prologue began as a single volume being compiled by Ad Akande, a scholar from South Africa, who proposed it to me as co-author about two years ago. The original idea was to examine how the damaging roots of nationalism have been corroding political systems around the world, and creating dangerous obstacles for necessary international cooperation. Since I (Bruce E. Johansen) has written profusely about climate change (global warming, a.k.a. infrared forcing), I suggested a concerted effort in that direction. This is a worldwide existential threat that affects every living t

The Mediterranean region has a highly distinctive climate due to its position between 30 and 45°N to the west of the Euro-Asian landmass. With respect to the global atmospheric system, it lies between subtropical high pressure systems to the south, and westerly wind belts to the north. In winter, as these systems move equatorward, the Mediterranean basin lies under the influence of, and is exposed to, the westerly wind belt, and the weather is wet and mild. In the summer, as shown in Figure 3.1, the Mediterranean lies under subtropical high pressure systems, and conditions are hot and dry, with an absolute drought that may persist for more than two or three months in drier regions. Climates such as this are relatively rare, and the Mediterranean shares its winter wet/summer dry conditions with locations as distant as central Chile, the southern tip of Cape Province in South Africa, southwest Australia in the Southern Hemisphere, and central California in the Northern Hemisphere. All have in common their mid-latitude position, between subtropical high pressure systems and westerly wind belts. They all lie on the westerly side of continents so that, in winter, when the westerly wind belts dominate over their locations, they are exposed to rain-bearing winds. In the Köppen classification (Köppen 1936), these climates are known as Mediterranean (Type Cs, which is subdivided in turn into maritime Csb and continental Csa). The influence of the Mediterranean Sea means that the Mediterranean-type climate of the region extends much further into the continental landmass than elsewhere, and is not restricted to a narrow ocean-facing strip. Nevertheless, within the Mediterranean region climate is modified by position and topographic influences can be important. The proximity of the western Mediterranean to the Atlantic Ocean gives its climate a maritime flavour, with higher rainfall and milder temperatures throughout the year. The eastern Mediterranean lies closer to the truly continental influences of central Europe and Asia. Its climate is drier, and temperatures are hotter in summer and colder in winter than in the west. Annual rainfall is typically around 750 mm in Rome, but only around 400 mm in Athens.

The literature on aeolian processes and on aeolian morphological and sedimentological features has shown a dramatic increase during the last decade. A variety of textbooks, extensive reviews, and special issues of journal volumes devoted to aeolian research have been published (Nordstrom et al. 1990; Pye and Tsoar 1990; Kozarski 1991; Pye 1993; Pye and Lancaster 1993; Cooke et al. 1993; Lancaster 1995; Tchakerian 1995; Livingstone and Warren 1996; Goudie et al. 1999). However, not surprisingly the majority of these studies discuss aeolian processes and phenomena in the extensive warm arid regions of the world. The results of aeolian research in the less extensive, but still impressive, cold arid environments of the world are only available in a diversity of articles. At best they are only briefly mentioned in textbooks on aeolian geomorphology (Koster 1988, 1995; McKenna-Neuman 1993). Likewise, the literature with respect to wind-driven deposits in western Europe is scattered and not easily accessible. The aeolian geological record for Europe, as reflected in the ‘European sand belt’ in the north-western and central European Lowlands, which extends from Britain to the Polish–Russian border, is known in great detail (Koster 1988; van Geel et al. 1989; Böse 1991). Zeeberg (1998) showed that extensive aeolian deposits progress with two separate arms into the Baltic Region, and into Belorussia and northernmost Ukraine. Recently, Mangerud et al. (1999) concluded that the sand belt extends even to the Pechora lowlands close to the north-western border of the Ural mountain range in Russia. Sand dunes and cover sands are widespread and well developed in this easternmost extension of the European sand belt. The northerly edges of this sand belt more or less coincide with the maximal position of the Late Weichselian (Devensian, Vistulian) ice sheet, while the southern edges grade into coverloams or sandy loess and loess (Mücher 1986; Siebertz 1988; Antoine et al. 1999). However, along these southern edges the dune fields and sand sheets regionally are derived from different sources, such as the sands of the Keuper Formation or the floodplains of the Rhine and Main rivers.

Agriculture is the mainstay of Kenya’s economic development and accounts for about 30% of the country’s gross domestic product, 60% of export earnings, and 70% of the labor force. This sector is the largest source of employment (Government of Kenya, 1995). More than 85% of the population survives in one way or the other on agricultural activities (crops and livestock). Agriculture in Kenya is mainly rain-fed, with little irrigation. About 46% of the rural population live below the poverty line, with 70% of them below food poverty line. Like many parts of the tropics, the majority of agricultural activities in Kenya are rain dependent. Small-scale farmers, pastoralists, and wildlife are most often affected by drought, with crops withering and livestock as well as wildlife dying. Drought of more than one season overwhelms the social fabric, as crops, livestock, wild animals, and humans die. Such droughts affect pastoral communities (e.g., the Masai in Kenya and Tanzania) by killing livestock and game animals, forcing these communities to invade the nearby towns and cities to find remnants of patches of grass still left there or grass growing at the roadsides. The death of game animals affects ecotourism. Interannual climate variability that often leads to the recurrence of climate extremes such as droughts has far-reaching impacts on agricultural production. Figure 18.1 shows below-normal rainfall during different years that are often associated with droughts in Kenya. These rainfall deficits are caused by the anomalies in the circulation patterns that can extend from local or regional to very large scales. Some patterns that are responsible for spatial and temporal distribution of rainfall in Kenya include the Intertropical Convergence Zone (ITCZ), subtropical anticyclones, monsoonal wind systems, tropical cyclones, easterly/westerly wave perturbations, subtropical jet streams, East African low-level jet stream, extratropical weather systems, teleconnection with El Niño/Southern Oscillation (ENSO), and quasi-biennial oscillation (Ogallo, 1988, 1991, 1994). In addition, complex physical features such as large inland lakes, mountains, and complex orographic patterns (e.g., the Great Rift Valley) influence rainfall patterns. Lake Victoria in western Kenya is also one of the largest freshwater lakes in the world and has its own strong circulation patterns in space and time.

We live in the Quaternary period and are a product of its wide fluctuations in climate and rapid environmental change. From at least the Mid-Miocene, about 25 million years ago, the expansion of the Southern Ocean has supported a powerful westerly wind system. These winds prevent tropical heat from reaching the Antarctic region, which in turn has allowed the gradual refrigeration of the world’s oceans as ice built up on Antarctica (and eventually formed an ice shelf over the sea; Nunn 1999). Earlier in the Tertiary, when the ocean column was warm from top to bottom, seasonal cooling was offset by rising warm water, and the ocean currents effectively transported heat to the poles. For the last 2 million years the main mass of the oceans has remained at maximum density, around 4°C, with warmer surface waters of the tropical and temperate regions floating only in the upper few hundred metres above the thermocline. The Quaternary is the period of refrigerated ocean which marks an ice age, with the Earth in such a delicate thermal equilibrium that relatively minor changes in the amount of solar radiation received by a given hemisphere in a given season cause major fluctuations of ice volume in terrestrial ice caps. The marked asymmetry of land and sea in the two hemispheres means that the effects of changes in the season of closest approach to the sun, of the degree of tilt of the planet and the eccentricity of the orbit, cause instability in the long-term climate. The Quaternary is defined by successive expansions and retreats of ice caps, with the maximum episodes of ice and of warmth (the interstadials) each lasting around 10 000 years. Intermediate times are cooler than present, and these persist for around 100 000 years. The lock-up of ice is reflected by global changes in sea level, ocean levels falling about 125 m during glacial maxima and rising up to 6 m above present during some interglacials. The Antarctic ice cap retains about 75 m of the ocean’s water even during the interglacial phases.

Certain parts of the Mediterranean lands are drylands— notably south-east Spain, the North African littoral, and parts of the Levant. This means that there is potential for aeolian processes to operate locally, especially where the vegetation cover has been depleted by human activities. Although water erosion is probably the most pervasive cause of land degradation in the Mediterranean lands (Chapter 20), susceptible soils in the drier portions of the region have been subject to accelerated wind erosion. This forms part of the phenomenon of desertification. Deforestation, high stocking levels of domestic animals, cultivation, and miscellaneous recreational pressures, have all helped to create this problem in North Africa (Sghaier and Seiwert 1993), the Levant (Massri et al. 2002) and in the semi-arid lands of Spain (Lopez et al. 2001). However, the GLASOD (Global Assessment of Soil Degradation) survey of wind erosion severity (Middleton and Thomas 1997: 32–3) suggests that at present, with the exception of parts of North Africa, the Levant, and Sicily, wind erosion severity is generally low in the Mediterranean region. In addition, the Mediterranean lands are in close proximity to the world’s greatest arid zone— the Sahara-Arabian belt—and so are subject to dust incursions from winds from that region: the ‘ghibli’ of Tripolitania, the ‘chili’ of Tunisia, the ‘khamsin’ of Egypt, and the ‘sirocco’ and ‘leveche’ of southern Europe. This has important geochemical implications (Kocak et al. 2004a, b). Knowledge of the dynamics of aeolian dust and sand transport comes from two main sources. The first of these is contemporary process monitoring, including data from dust traps, climatological stations, and remote sensing. The second is the long-term sedimentary record from such environments as caves, the sea-floor, lakes, bogs, and loess deposits. There are, however, problems with gaps in the stratigraphic record, and uncertainties and limitations with respect to developing accurate geochronologies. Atmospheric dust comprised of mineral aerosol derived by deflation of desert surfaces, much of it from the Sahara (Middleton and Goudie 2001; Goudie and Middleton, 2006), is a feature of the Mediterranean basin, and it impacts upon the environment in a number of ways (Goudie and Middleton 2001).

Southeast Asia lies between the continental influence of the rest of Asia to the north and the more oceanic influence of the Indian and Pacific Oceans to the south and the east respectively. While its overall net energy balance is very much determined by its latitudinal position, which is approximately between 20°N and 10°S, the locational factors referred to above largely give the regional climate its distinctive character. Within the broad latitudinal extent defined above, the Southeast Asian region has often been conveniently separated into two sub-areas: continental and insular Southeast Asia. In some ways these sub-regions represent a valid delineation into the more seasonal climatic region influenced by the monsoon system of winds and the uniformly humid equatorial climate. The former comprises Myanmar, Thailand, Lao PDR, Cambodia, and Viet Nam, while the latter includes Malaysia, Singapore, Indonesia, and the Philippines. The continental Southeast Asia experiences greater seasonality, more extremes in both temperature and rainfall, and more pronounced dry spells; whereas the insular parts, termed the ‘maritime continent’ (Ramage 1968), with a much greater expanse of sea than land (the sea area of Indonesia, for example, is four times its land area), have more equable climate. The northern and southern continental interactions in winter and summer and the differential heating due to the asymmetric character of the two sub-regions give rise to the monsoon development (Hastenrath 1991), which, to a large extent, influences the rainfall characteristics of the region as a whole. In a sense, more than temperature variations, this monsoonal influence gives the Southeast Asian climate its distinctive character. Figure 5.2 shows the two monsoon wind systems that affect Southeast Asia. In addition to these annual reversals of the monsoon winds, the seasonal migration of the Intertropical Convergence Zone (ITCZ)—closest to the Equator during the northern hemispheric winter and farthest north during summer—is a significant factor in influencing the monthly weather regime of the region. Being a belt of low-pressure trough coinciding with the band of highest surface temperature, the ITCZ attracts the moist easterlies from both hemispheres towards its trough resulting in uplift of air, intense convection, and precipitation. This whole process provides a mechanism for the transfer of latent heat from the low to the higher latitudes (Houze et al. 1981; Hastenrath 1991).

Abstract The best way to understand the general atmosphere system is to collect and analyze data, identify the variables that occur in the upper and lower classes, and compare them with other values in favor of comparing them to other studies and research. Studies have been conducted in this research by analyzing the wind speed and direction and comparing it with the surface roughness to reach a concept by dividing the regions of Iraq on the basis of the surface roughness that affects the wind speed near the surface. The research aims to know the effect of air flow on the nature of the earth's