Global Atmospheric Circulation
Global atmospheric circulation refers to the large-scale movement of air around the Earth, driven by differences in temperature and pressure. This circulation is responsible for the distribution of heat and moisture across the planet, leading to the formation of distinct climate zones. The circulation is influenced by factors such as the rotation of the Earth, the uneven heating of the Earth's surface, and the properties of air and water.
5 Key excerpts on "Global Atmospheric Circulation"
eBook - ePub30-Second Climate
The 50 most topical events, measures and conditions, each explained in half a minute
- Joanna D Haigh(Author)
- 2019(Publication Date)
- Ivy Press(Publisher)
...They range from the micro-scale processes associated with water-droplet formation through to the planetary-scale circulation of the ocean and atmosphere transporting heat between the warm equator and the cold polar regions. Processes involving radiation happen almost instantaneously, whereas ice sheets can have timescales of millennia. This makes it a challenging task to model the Earth’s climate system. RELATED TEXTS See also GLOBAL CIRCULATION OF THE ATMOSPHERE GLOBAL CIRCULATION OF THE OCEANS THE EARTH’S RADIATION BALANCE THE BIOSPHERE 3-SECOND BIOGRAPHY SYUKURO MANABE 1931– Japanese meteorologist and climatologist, early pioneer of the development of climate models including multiple components (see here) 30-SECOND TEXT Mat Collins The interactions between components of our complex climate system operate on both micro and macro scales. GLOBAL CIRCULATION OF THE ATMOSPHERE the 30-second climate Warm, moist air rises near the equator. As the air cools by expansion, water condenses in the form of deep cumulonimbus clouds. This air then spreads polewards. If the Earth were not rotating the air would drift all the way to the poles, where it would sink as part of a large overturning convection cell. Because the Earth is spinning fastest at the equator, momentum conservation means that as air moves polewards it starts flowing from west to east in the form of subtropical jets at upper levels in the atmosphere. These fast-moving jets eventually become unstable, confining the convection cell, known as the Hadley Circulation, to the tropics and subtropics. In mid-latitudes, the instability spawns horizontal waves that also transport heat and moisture towards the poles through complex circulation patterns that look highly turbulent. These waves become storms or cyclones that are low-pressure systems often associated with fronts, windy conditions and rain...
eBook - ePub- Roger G. Barry, Richard J Chorley(Authors)
- 2009(Publication Date)
- Routledge(Publisher)
...This tendency is certainly increased in the Northern Hemisphere by the arrangement of the continents and oceans. Detailed studies are now beginning to show that the irregular index fluctuations, together with secondary circulation features, such as cells of low and high pressure at the surface or long waves aloft, play a major role in redistributing momentum and energy. Laboratory experiments with rotating ‘dishpans’ of water to simulate the atmosphere, and computer studies using numerical models of the atmosphere’s behavior, demonstrate that a Hadley circulation cannot provide an adequate mechanism for transporting heat poleward. In consequence, the meridional temperature gradient increases and eventually the flow becomes unstable in the Hadley mode, breaking down into a number of cyclonic and anticyclonic eddies. This phenomenon is referred to as baroclinic instability. In energy terms, the potential energy in the zonal flow is converted into potential and kinetic energy of eddies. It is also now known that the kinetic energy of the zonal flow is derived from the eddies, the reverse of the classical picture, which viewed the disturbances within the global wind belts as superimposed detail. The significance of atmospheric disturbances and the variations of the circulation are becoming increasingly evident. The mechanisms of the circulation are, however, greatly complicated by numerous interactions and feedback processes, particularly those involving the oceanic circulation discussed below. North Atlantic Oscillation The relative strength of the Icelandic Low and Azores High was first observed to fluctuate on annual to decadal scales by Sir Gilbert Walker in the 1920s. Fifty years later, van Loon and Rogers discussed the related west–east ‘see-saw’ in winter temperatures between Western Europe and western Greenland associated with the north– south change in pressure gradient over the North Atlantic. The phenomenon at work here is the North Atlantic Oscillation (NAO)...
eBook - ePubThe Great Maya Droughts
Water, Life, and Death
- Richardson B. Gill(Author)
- 2001(Publication Date)
- University of New Mexico Press(Publisher)
...During the winter, cold high pressure systems penetrate as far as the Maya Lowlands, where they are known as nortes. Over the last 3 million years, the low latitudes have been exporting very little warmth to the Arctic, which has retaliated by sending very cold air and water southward, robbing the continents of the warmth they formerly enjoyed, especially during winter (Stanley 1996:184–187). D ISCUSSION The world’s oceans clearly play a major role in climate, especially in northern Europe. The temperature of the sea surface, as we saw in chapter 6, plays a very direct role in atmospheric convection, resulting in precipitation over the ocean and in those coastal areas that depend on ocean breezes for their precipitation, like the Yucatán Peninsula. Oceanography, however, is still in a state of exploration, and the exact flow of the oceans is still being sorted out. The large-scale ocean currents are extremely complex phenomena, consisting of ribbons of flow interlaced with return currents, both horizontally and vertically, which meander over hundreds of miles. The actual flow is not laminar as suggested by the simplified conveyor belt model, but turbulent and labyrinthine. The northward transport of warm water in the North Atlantic occurs through a linked set of gyre flows, rather than along the simple image of the upper limb of the conveyor belt. The scheme presented here of an ocean conveyor belt simplifies the overwhelming complexity of the true ocean to model a concept of the salt diffusion between oceans (Macdonald and Wunsch 1996:436; McCartney 1994:6; Munk 1955). The position of the North Atlantic’s currents is not fixed, but shifts as the climate changes or, perhaps, the climate changes as the currents shift...
eBook - ePubGlobal Climate Change
Turning Knowledge Into Action
- David Kitchen(Author)
- 2016(Publication Date)
- Routledge(Publisher)
...The conveyor starts where cold saline waters in the Arctic descend to the deep ocean and then circulate around the globe before returning to high latitudes as warm surface currents that heat the atmosphere and moderate the climate (Figure 1.18 Figure 1.18 The deep ocean conveyor. In this simplified diagram, cold saline waters descend into the deep ocean at the poles and then circulate around the globe, returning as warm surface currents that heat the atmosphere above them and moderate the climate in the northern Pacific and Atlantic Oceans). Checkpoint 1.18 How does deep ocean circulation affect global climate? Ocean-Atmosphere Interaction On a timescale of years to decades, interactive cycles involving the sun, volcanic activity, the atmosphere, oceans, clouds, aerosols, natural greenhouse gases, and Earth’s albedo have a major impact on regional climate—with often disastrous consequences. The El Niño-Southern Oscillation (ENSO) is a natural climate cycle that involves both the atmosphere and oceans. Every three to seven years, warm water that has gradually accumulated to form a deep pool in the eastern Pacific rises to the surface and flows toward the east, bringing drought and soaring temperatures to some areas and torrential rain and floods to others. In California, for example, intense storms related to El Niño can lead to destructive flooding and loss of both life and property (Figure 1.19). Figure 1.19 El Niño events have a major impact on weather across the globe. This flooding in California is a consequence of the intense rainfall that affects parts of the west coast of the United States The North Atlantic Oscillation (NAO) is a natural cycle driven by changes in atmospheric pressure that control the path of strong winds in the upper atmosphere...
eBook - ePub- Mike Wickson(Author)
- 2014(Publication Date)
- Crowood(Publisher)
...It is worth emphasing that the major greenhouse gas is ordinary water vapour, followed by carbon dioxide. The other gases such as methane, nitrous oxide and CFCs, whilst having a greater effect per molecule, are present in much smaller quantities. Statistics concerned with upper air conditions including wind information in the aviation atmosphere are available only since the early 1900s. For parts of the world where aviation is on a relatively small scale, information is particularly sparse – notably the polar regions. It is incidentally, only since the 1960s that the low level jet stream off the Horn of Africa mentioned in Chapter 11 was discovered. From the foregoing it is clear that changes in climate can occur, but these have in the past been gradual. Further new information for the aviation atmosphere is bound to accrue in the future. This chapter will cover climate on a latitude or zonal basis together with a study of recent past statistics for the main weather factors. Finally an examination will be made of the expected climate and flying weather in the separate world areas. General Circulation In Chapter 6, it was shown that world pressures for a simple globe in an unrefined atmosphere could produce pressure zones based on latitude. These are reproduced at Figure 18.1. This shows the low pressure in the equatorial region with the lifted air producing Hadley cells and the subtropical anticyclones. The high pressure at the poles (caused by the low temperatures and the excess of air at height) and the variable lows in mid-latitudes between the two high pressure inferred from the systems. Four distinct climate zones could be the diagram: Figure 18.1. World Pressures on a Simple Globe Equatorial – Surface air moving in. High temperature causing lifting and instability clouds and weather. Subtropical – Surface air moving out. Air above descending causing stability and no cloud. Dry desert climate. Low and Variable – Surface air moving in...
