Weather and Climate

Formation Of Precipitation

The puzzle of raindrop formation has already been noted. The simple growth of cloud droplets by condensation is apparently an inadequate mechanism and more complex processes have to be envisaged. Various early theories of raindrop growth can be discounted. Proposals were that differently charged droplets could coalesce by electrical attraction, but it appears that distances between drops are too great and the difference between the electrical charges too small for this to happen. It was...

Surface pressure conditions

Tropical Easterly Jet Stream Map

The most permanent features of the mean sea-level pressure maps are the oceanic subtropical high-pressure cells Figures 7.9 and 7.10 . These anticyclones are located at about 30 latitude, suggestively situated below the mean subtropical jet stream. They move a few degrees equatorward in winter and poleward in summer in response to the seasonal expansion and contraction of the two circumpolar vortices. In the northern hemisphere, the subtropical ridges of high pressure weaken over the heated...

Warm airmasses

Mapa Hemisferio Oriental Para Imprimir

These have their origins in the subtropical high-pressure cells and, during the summer season, in the bodies of warm surface air that characterize the heart of large land areas. The tropical (T) sources are (1) maritime (mT), originating in the oceanic subtropical high-pressure cells (2) continental (cT), either originating from the continental parts of these subtropical cells (e.g. as does the North African Harmattan) or (3) associated with regions of generally light variable winds, assisted...

Atmospheric motion principles

When you have read this chapter you will Know the basic laws of horizontal motion in the atmosphere, Know how the Coriolis force arises and its effects, Be able to define the geostrophic wind, Know how friction modifies wind velocity in the boundary layer, Understand the principles of divergence convergence and vorticity and their roles in atmospheric processes, Understand the thermodynamic, dynamic and topographic factors that lead to distinctive local wind regimes. The atmosphere is in...

Atmospheric Energy And Horizontal Heat Transport

Poleward Heat Transfer

So far, we have given an account of the earth's heat budget and its components. We have already referred to two forms of energy internal or heat energy, due to the motion of individual air molecules, and latent energy, which is released by condensation of water vapour. Two other forms of energy are important geopotential energy due to gravity and height above the surface, and kinetic energy associated with air motion. Geopotential and internal energy are interrelated, since the addition of heat...

The frontalwave depression

Initial Stage Mid Latitude Cyclones

A depression also termed a low or cyclone see Note 2 is an area of relatively low pressure, with a more or less circular isobaric pattern. It covers an area 1500 to 3000 km in diameter and usually has a life span of four to seven days. Systems with these characteristics, which are prominent on daily weather maps, are referred to as synoptic-scale features. The mid-latitude depression is usually associated with the convergence of contrasting Figure 9.7 Four stages in the typical development of a...

The Mediterranean

Global Mediterranean Type Climate

The characteristic west coast climate of the subtropics is the Mediterranean type with hot, dry summers and mild, relatively wet winters. It is interposed between the temperate maritime type and the arid subtropical desert climate. The boundary between the temperate maritime climate of western Europe and that of the Mediterranean can be delimited on the basis of the seasonality of rainfall. However, another diagnostic feature is the relatively sharp increase in solar radiation across a zone...

Land and sea breezes

Sea Land Breezes Typical Scales

Another thermally induced wind regime is the land and sea breeze see Figure 6.11 . The vertical expansion of the air column that occurs during daytime heating over the more rapidly heated land see Chapter 3B.5 tilts the isobaric surfaces downward at the coast, causing onshore winds at the surface and a compensating offshore movement aloft. Typical land-sea pressure differences are of the order of 2 mb. At night, the air over the sea is warmer and the situation is reversed, although this...

A Hurricanes and typhoons

Cumulonimbus Clouds Air Circulation

The most notorious type of cyclone is the hurricane or typhoon . Some eighty or so cyclones each year are responsible, on average, for 20,000 fatalities, as well as causing immense damage to property and a serious shipping hazard, due to the combined effects of high winds, high seas, flooding from the heavy rainfall and coastal storm surges. Considerable attention has been given to forecasting their development and movement, so their origin and structure are beginning to be understood....

Central And Southern Africa

Blank Convergent Divergent Boundary

The annual climatic regime over West Africa has many similarities to that over South Asia, the surface airflow being determined by the position of the leading edge of a monsoon trough see Figure 11.2 . This airflow is southwesterly to the south of the trough and easterly to northeasterly to its north Figure 11.38 . The major difference between the circulations of the two regions is due largely to the differing geography of the land to sea distribution and to the lack of a large mountain range...

Memberry 2001 Monsoon Tropical Cyclones. Part 1 Weather

Academica Sinica 1957-8 On the general circulation over eastern Asia. Tellus 9, 432-46 10, 58-75 and 299-312. Anthes, R. A. 1982 Tropical cyclones their evolution, structure, and effects. Met. Monogr. 19 41 , Amer. Met. Soc., Boston, MA, 208pp. Augstein, E. et al. 1973 Mass and energy transport in an undisturbed trade wind flow. Monthly Weather Review 101, 101-11. Avila, L. A. 1990 Atlantic tropical systems of 1989. Monthly Weather Review 118, 1178-85. Barnston, A. G. 1995 Our improving...

Surface Receipt Of Solar Radiation And Its Effects

Solar Radiation Element Climatology

1 Energy transfer within the earth-atmosphere system So far, we have described the distribution of solar radiation as if it were all available at the earth's surface. This is, of course, unrealistic because of the effect of the atmosphere on energy transfer. Heat energy can be transferred by three mechanisms 1 Radiation Electromagnetic waves transfer energy both heat and light between two bodies, without the necessary aid of an intervening material medium, at a speed of300 X 106m s-1 i.e. the...

The southern westerlies

Heavy Rainfall West Southern Alps

The strong zonal airflow in the belt of the southern westerlies, which is apparent only on mean monthly maps, is associated with a major frontal zone characterized Figure 10.33 Main climatological features of Australasia and the southwest Pacific. Areas with gt 100 mm January and gt 50 mm July mean monthly precipitation for Australia are also shown. Source After Steiner, from Salinger et al. 1995 , copyright John Wiley amp Sons Ltd. Reproduced with permission. Figure 10.33 Main climatological...

Laws Of Horizontal Motion

There are four controls on the horizontal movement of air near the earth's surface the pressure-gradient force, the Coriolis force, centripetal acceleration, and frictional forces. The primary cause of air movement is the development of a horizontal pressure gradient through spatial differences in surface heating and consequent changes in air density and pressure. The fact that such a gradient can persist rather than being destroyed by air motion towards the low pressure results from the effect...

The vertical variation of pressure systems

Vertical Motion Low High Pressure System

The air pressure at the surface, or at any level in the atmosphere, depends on the weight of the overlying air column. In Chapter 2B, we noted that air pressure is proportional to air density and that density varies inversely with air temperature. Accordingly, increasing the temperature of an air column between the surface and, say, 3 km will reduce the air density and therefore lower the air pressure at the surface without affecting the pressure at 3 km altitude. Correspondingly, if we compare...

Circulations in the vertical and horizontal planes

Atmospheric Cells Monsoon Regions

There are two possible ways in which the atmosphere can transport heat and momentum. One is by circulation in the vertical plane as indicated in Figure 7.18, which shows three meridional cells in each hemisphere. The low-latitude Hadley cells were considered to be analogous to the convective circulations set up when a pan of water is heated over a flame and are referred to as thermally direct cells. Warm air near the equator was thought to rise and generate a low-level flow towards the equator,...

Cloud electrification and lightning

Cloud Charge Particle

Two general hypotheses help to account for thunderstorm electrification. One involves induction in the presence of an electric field, the other is non-inductive charge transfer. The ionosphere at 30 to 40 km altitude is positively charged owing to the action of cosmic and solar ultraviolet radiation in ionization and the earth's surface is negatively charged during fine weather. Thus cloud droplets can acquire an induced positive charge on their lower side and negative charge on their upper...

Above the thermocline a Vertical

Meteorological And Oceanographic Process

The major atmosphere-ocean interactive processes (Figure 7.26) involve heat exchanges, evaporation, density changes and wind shear. The effect of these processes is to produce a vertical oceanic layering that is of great climatic significance 1 At the ocean surface, winds produce a thermally mixed surface layer averaging a few tens of metres deep poleward of latitude 60 , 400 m at latitude 40 and 100 to 200 m at the equator. 2 Below the relatively warm mixed layer is the thermocline, a layer in...

Adiabatic Temperature Changes

Saturation Temperature Pressure

When an air parcel moves to an environment of lower pressure without heat exchange with surrounding air its volume increases. Volume increase involves work and the consumption of energy this reduces the heat available per unit volume and hence the temperature. Such a temperature change, involving no subtraction or addition of heat, is termed adiabatic. Vertical displacements of air are the major cause of adiabatic temperature changes. Near the earth's surface, most temperature changes are...

The pressuregradient force

The pressure-gradient force has vertical and horizontal components but, as already noted, the vertical component is more or less in balance with the force of gravity. Horizontal differences in pressure arise from thermal heating contrasts or mechanical causes such as mountain barriers and these differences control the horizontal movement of an airmass. The horizontal pressure gradient serves as the motivating force that causes air to move from areas of high pressure towards areas where it is...

Fundamentals Of The

In the GCM, all dynamic and thermodynamic processes and the radiative and mass exchanges that have been treated in Chapters 2 to 7 are modelled using five basic sets of equations. The basic equations describing the atmosphere are 1 The three dimensional equations of motion i.e. conservation of momentum see Chapter 6A,B . 2 The equation of continuity i.e. conservation of mass or the hydrodynamic equation, p. 118 . 3 The equation of continuity for atmospheric water vapour i.e. conservation of...

Frontal waves

The typical geometry of an airmass interface, or front, resembles a wave form Figure 9.7 . Similar wave patterns are, in fact, found to occur on the interfaces between many different media for example, waves on the sea surface, ripples on beach sand, eolian sanddunes, etc. Unlike these wave forms, however, the frontal waves in the atmosphere are usually unstable that is, they suddenly originate, increase in size, and then gradually dissipate. Numerical model calculations show that in middle...

Tropical Disturbances

Synoptic Scale Meaning

It was not until the 1940s that detailed accounts were given of types of tropical disturbances other than the long-recognized tropical cyclone. Our view of tropical weather systems was revised radically following the advent of operational meteorological satellites in the 1960s. Special programmes of meteorological measurements at the surface and in the upper air, together with aircraft and ship observations, have been carried out in the Pacific and Indian Oceans, the Caribbean Sea and the...

Topographic effects

Precipitation England

In various parts of Europe, topography has a marked effect on the climate, not only of the uplands themselves but also of adjacent areas. Apart from the more obvious effects on temperatures, precipitation amounts and winds, the major mountain masses also affect the movement of frontal systems. Frictional drag over mountain barriers increases the slope of cold fronts and decreases the slope of warm fronts, so that the latter are slowed down and the former accelerated. The Scandinavian mountains...

Mesoscale Convective Systems

Mesoscale Convection System Simulaton

Mesoscale convective systems MCSs are intermediate in size and life span between synoptic disturbances and individual cumulonimbus cells see Figure 9.26 . Figure 9.27 shows the movement of clusters of convective cells, each cell about 1 km in diameter, as they crossed southern Britain with a cold front. Each individual cell may be short-lived, but cell clusters may persist for hours, strengthening or weakening due to orographic and other factors. MCSs occur seasonally in middle latitudes...

Articles

G. 1979 Recent advances in climate theory based on simple climate models. Prog. Phys. Geog. 3, 259-86. Bosart, L. 1985 Weather forecasting. In Houghton, D. D. ed. Handbook of Applied Meteorology, Wiley, New York, pp. 205-79. Browning, K. A. 1980 Local weather forecasting. Proc. Roy. Soc. Lond. Sect. A 371, 179-211. Carson, D. J. 1999 Climate modelling achievements and prospects. Quart. J. Roy. Met. Soc, 125, 1-27. Cullen, M. J. P. 1993 The Unified Forecast Climate model. Met. Mag....

Tropical cloud clusters

Herman Miller Equa Parts Sheet

Mesoscale convective systems MCSs are widespread in tropical and subtropical latitudes. The mid-latitude mesoscale convective complexes discussed in Chapter 9.I are an especially severe category of MCS. Satellite studies of cold high cloud-top signatures show that tropical systems typically extend over a 3000 to 6000 km2 area. They are common over tropical South America and the maritime continent of Indonesia-Malaysia and adjacent western equatorial Pacific Ocean warm pool. Other land areas...

Orographic precipitation

Precipitation Hills

Orographic precipitation is commonly regarded as a distinct type, but this requires careful qualification. Mountains are not especially efficient in causing moisture to be removed from airstreams crossing them, yet because precipitation falls repeatedly in more or less the same locations, the cumulative totals are large. An orographic barrier may produce several effects, depending on its alignment and size. They include 1 forced ascent on a smooth mountain slope, producing adiabatic cooling,...

Simpler models

Surface And Upper Air Report

Because GCMs require massive computer resources, other approaches to modelling climate have developed. A variant of the GCM is the statistical-dynamical model (SDM), in which only zonally averaged features are analysed, and north-south energy and momentum exchanges are not treated explicitly but are represented statistically through parameterization. Simpler still are the energy balance model (EBM) and the radiative convective model (RCM). The EBM assumes a global radiation balance and...

Short green crops

Crop Height And Transpiration

Short green crops, up to a metre or so in height, supplied with sufficient water and exposed to similar solar radiation conditions, all have a similar net radiation Rn balance. This is largely because of the small range of albedos, 20 to 30 per cent for short green crops compared with 9 to 18 per cent for forests. Canopy structure appears to be the primary reason for this albedo difference. General figures for rates of energy dispersal at noon on a June day in a 20-cm high stand of grass in the...

Teleconnections

Mapa Por Proyeccion Polar

Teleconnections are defined as linkages over great distances of atmospheric and oceanic variables clearly the linkages between climatic conditions in the eastern and western tropical Pacific Ocean represent a 'canonical' teleconnection. Figure 11.52 illustrates the coincidence of ENSO events with regional climates that are wetter or drier than normal. In Chapter 7C.1, we have referred to Walker's observed teleconnection between ENSO events and the lower than normal monsoon rainfall over South...

Pressure and wind conditions

Above Sea Level

The dominant features of the mean North Atlantic pressure pattern are the Icelandic Low and the Azores High. These are present at all seasons (see Figure 7.9), although their location and relative intensity change considerably. The upper flow in this sector undergoes little seasonal change in pattern, but the westerlies decrease in strength by over half from winter to summer. The other major pressure system influencing European climates is the Siberian winter anticyclone, the occurrence of...

The thermal low

These lows occur almost exclusively in summer, resulting from intense daytime heating of continental areas. Figure 7.1C illustrates their vertical structure. The most impressive examples are the summer low-pressure cells over Arabia, the northern part of the Indian subcontinent and Arizona. The Iberian Peninsula is another region commonly affected by such lows. They occur over southwestern Spain on 40 to 60 per cent of days in July and August. Typically, their intensity is only 2 to 4 mb and...

B 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 westeast 'seesaw' in winter temperatures between western Europe and western Greenland associated with the north-south change in pressure gradient over the North Atlantic. The North Atlantic Oscillation (NAO) is a north-south oscillation in the pressure field between the Icelandic...

Pressure systems

Pressure Systems Map Asia

The mean pressure pattern for the middle troposphere displays a prominent trough over eastern North America in both summer and winter see Figures 7.3A and 7.4A . In part, this is a lee trough caused by the effect of the western mountain ranges on the upper westerlies, but at least in winter the strong baroclinic zone along the East Coast of the continent is a major contributory factor. As a result of this mean wave pattern, cyclones tend to move southeastward over the Midwest, carrying...

A Continental and oceanic influences

Fog Effect

The large annual temperature range in the interior of the continent shown in Figure 3.24 demonstrates the pattern of continentality of North America. The figure illustrates the key role of the distance from the ocean in the direction of the prevailing westerly winds. The topographic barriers of the western Cordilleras limit the inland penetration of maritime airstreams. On a more local scale, inland water bodies such as Hudson Bay and the Great Lakes have a small moderating influence -cooling...

The subArctic

Subarctic Weather

The longitudinal differences in mid-latitude climates persist into the northern polar margins, giving rise to maritime and continental subtypes, modified by the extreme radiation conditions in winter and summer. For example, radiation receipts in summer along the Arctic coast of Siberia compare favourably, by virtue of the long daylight, with those in lower mid-latitudes. The maritime type is found in coastal Alaska, Iceland, northern Norway and adjoining parts of Russia. Winters are cold and...

Condensation Levell

Mixing Condensation Level

Figure 5.4 Schematic adiabatic chart used to determine the convective condensation level see p. 91 . T0 represents the early morning temperature Tp T2 and T3 illustrate daytime heating of the surface air. downward it will warm at the dry adiabatic rate the parcel will always be warmer and less dense than the surrounding air, and tend to return to its former position unless prevented from doing so . However, if local surface heating causes the environmental lapse rate near the surface to exceed...

The cold front

Weather Frontal Depression Plan View

The weather conditions observed at cold fronts are equally variable, depending upon the stability of the warm sector air and the vertical motion relative to the frontal zone. The classical cold front model is of the ana-type, and the cloud is usually cumulonimbus. Figure 9.15 illustrates the warm conveyor belt associated with such a frontal zone and the line convection. Over the British Isles, air in the warm sector is rarely unstable, so that nimbostratus occurs more frequently at the cold...

Midlatitude Disturbances

Theoretical ideas about the atmosphere and its weather systems evolved in part through the needs of nineteenth-century mariners for information about winds and storms, especially predictions of future behaviour. At low levels in the westerly belt approximately 40 to 70 latitude there is a complex pattern of moving high and low pressure systems, while between 6000 m and 20,000 m there is a coherent westerly airflow. Dove 1827 and 1828 and Fitz Roy 1863 supported the 'opposing current' theory of...

SUMMARY

Ideal airmasses are defined in terms of barotropic conditions, where isobars and isotherms are assumed to be parallel to each other and to the surface. The character of an airmass is determined by the nature of the source area, changes due to airmass movement, and its age. On a regional scale, energy exchanges and vertical mixing lead to a measure of equilibrium between surface conditions and those of the overlying air, particularly in quasi-stationary high-pressure systems. Airmasses are...

Southern Africa

Mammal Teeth Types Diagram

Southern Africa lies between the South Atlantic and Indian Ocean subtropical high-pressure cells in a region subject to the interaction of tropical easterly and extratropical westerly airflows. Both of these high-pressure cells shift west and intensify see Figure 7.10 in the southern winter. Because the South Atlantic cell always extends 3 latitude further north than the Indian Ocean cell, it brings low-level westerlies to Angola and Zaire at all seasons and high-level westerlies to central...

Atmosphere Weather and Climate

Atmosphere Weather And Climate 2003

Chorley Taylor amp Francis Croup LONDON AND NEW YORK First published 1968 by Methuen amp Co. Ltd Eighth edition 2003 by Routledge 11 New Fetter Lane, London EC4P 4EE Simultaneously published in the USA and Canada by Routledge 29 West 35th Street, New York, NY 10001 Routledge is an imprint of the Taylor amp Francis Group This edition published in the Taylor amp Francis e-Library, 2004. 1968, 1971, 1976, 1982, 1987, 1992, 1998, 2003 Roger G. Barry and Richard J....

The Asian Monsoon

Meridional Circulation Over India

The name monsoon is derived from the Arabic word mausim, which means season, referring to large-scale seasonal reversals of the wind regime. The Asiatic seasonal wind reversal is notable for its vast extent and the penetration of its influence beyond tropical latitudes Figure 11.14 . However, such seasonal shifts of the surface winds occur in many regions that are not traditionally considered as monsoonal. Although there is an overlap between these traditional regions and those experiencing...

Winter Monsoon Season

Japan Shurin Weather

Figure 11.36 A Seasonal variation of daily normals at Nagoya, southern Japan, suggesting six natural seasons. B Average ten-day precipitation amounts for a station in southern Japan, indicating in black the proportion of rainfall produced by typhoon circulations. The latter reaches a maximum during the Shurin season. Sources A From Maejima 1967 B after Saito 1959 , from Trewartha 98I . during late July and August, giving a period of more settled sunny weather. The secondary precipitation...

Condensation Level

Nickel Antimony Phase Diagram

Figure 5.2 illustrates an important property of the tephigram. A line along a dry adiabat 6 through the dry-bulb temperature of the surface air TA , an isopleth of saturation mixing ratio xs through the dew-point Td , and a saturated adiabat 6w through the wet-bulb temperature Tw , all intersect at a point corresponding to saturation for the airmass. This relationship, known Figure 5.2 Graph showing the relationships between temperature T , potential temperature 6 , wet-bulb potential...

A Zonal index variations

Air Circulation Index Cycle

Variations of three to eight weeks' duration are observed in the strength of the zonal westerlies, averaged around the hemisphere. They are rather more noticeable in the winter months, when the general circulation is strongest. The nature of the changes is illustrated schematically in Figure 7.23. The mid-latitude westerlies develop waves, and the troughs and ridges become accentuated, ultimately splitting up into a cellular pattern with pronounced meridional flow at certain longitudes. The...

Oceanicity and continentality

Winter temperatures in northwest Europe are some 11 C or more above the latitudinal average see Figure 3.18 , a fact usually attributed to the presence of the North Atlantic current. There is, however, a complex interaction between the ocean and the atmosphere. The current, which originates from the Gulf Stream off Florida strengthened by the Antilles current, is primarily a wind-driven current initiated by the prevailing south-westerlies. It flows at a velocity of 16 to 32 km per day and thus,...

Frontal Characteristics

Frontal Depression Unstable

The character of frontal weather depends upon the vertical motion in the airmasses. If the air in the warm sector is rising relative to the frontal zone the fronts are usually very active and are termed ana-fronts, whereas sinking of the warm air relative to the cold airmasses gives rise to less intense kata-fronts Figure 9.11 . Figure 9.9 Stages in the life cycle of a marine extratropical depression showing I Incipient frontal depression II Frontal fracture III Bent-back warm front and frontal...

Upper wind conditions

Diy Box Joint Router Jig Plans

It is often observed that clouds at different levels move in different directions. The wind speeds at these levels may also differ markedly, although this is not so evident to the casual observer. The gradient of wind velocity with height is referred to as the (vertical) wind shear, and in the free air, above the friction level, the amount of shear depends upon the vertical temperature profile. This important relationship is illustrated in Figure 7.6. The diagram shows hypothetical contours of...

The Discovery Of Jet Streams

Late nineteenth-century observers of high-level cloud motion noted the occasional existence of strong upper winds, but their regularity and persistence were not suspected at the time. The recognition that there are coherent bands of very strong winds in the upper troposphere was an operational discovery by Allied bomber pilots flying over Europe and the North Pacific during the Second World War. Flying westward, headwinds were sometimes encountered that approached the air speed of the planes....

C Precipitation and the moisture balance

Longitudinal influences are apparent in the distribution of annual precipitation, although this is in large measure a reflection of the topography. The 600-mm annual isohyet in the United States approximately follows the 100 W meridian (Figure 10.19), and westward to the Rockies is an extensive dry belt in the rain shadow of the western mountain ranges. In the southeast, totals exceed 1250 mm, and 1000 mm or more is received along the Atlantic coast as far north as New Brunswick and...

A The Arctic

Temperature Graph Tundra

At 75 N, the sun is below the horizon for about ninety days, from early November until early February. Winter air temperatures over the Arctic Ocean average about -32 C, but they are usually 10-12 C higher some 1000 m above the surface as a result of the strong radiative temperature inversion. The winter season is generally stormy in the Eurasian sector, where low-pressure systems enter the Arctic Basin from the North Atlantic, whereas anticyclonic conditions predominate north of Alaska over...

Cool ocean currents

Between the western coasts of the continents and the eastern rims of the subtropical high-pressure cells the ocean surface is relatively cold (see Figure 7.33). This is the result of the importation of water from higher latitudes by the dominant currents the slow upwelling (sometimes at the rate of about 1 m in twenty-four hours) of water from intermediate depths due to the Ekman effect (see Chapter 7D.1) and the coastal divergence (see Figure 7.31). This concentration of cold water gently...

Tropical urban climates

A striking feature of recent and projected world population growth is the relative increase in the tropics and subtropics. Today there are thirty-four world cities with more than five million people, twenty-one of which are in the less-developed countries. By ad 2025 it is predicted that, of the thirteen cities that will have populations in the twenty to thirty-million range, eleven will be in less-developed countries (Mexico City, Sao Paulo, Lagos, Cairo, Karachi, Delhi, Bombay, Calcutta,...

Solar Radiation

Main Atmospheric Absorption Bands

The source of the energy injected into our atmosphere is the sun, which is continually shedding part of its mass by radiating waves of electromagnetic energy and high-energy particles into space. This constant emission represents all the energy available to the earth except for a small amount emanating from the radioactive decay of earth minerals . The amount of energy received at the top of the atmosphere is affected by four factors solar output, the sun-earth distance, the altitude of the...

Discussion Topics

Weischet Interpretation Meteosat

Trace the possible paths of a water molecule through the hydrological cycle and consider the measurements that need to be made to determine the quantities of water involved in the various transformations. What processes lead to phase changes of water in the atmosphere and what are some of their consequences What is the significance of clouds in the global water balance Compare the moisture balance of an air column and that of a small drainage basin. What are the various statistics used to...

East Asian And Australian Summer Monsoons

Image Monsoon Through

China has no equivalent to India's hot, pre-monsoon season. The low-level, northeasterly winter monsoon reinforced by subsiding air from the upper westerlies persists in north China, and even in the south it begins to be replaced by maritime tropical air only in April to May. Thus at Guangzhou Canton , mean temperatures rise from only 17 C in March to 27 C in May, some 6 C lower than the mean values over northern India. Westerly depressions are most frequent over China in spring see Figure...

El Nio And The Southern Oscillation

El Ni o episodes of warm coastal currents with accompanying disastrous consequences for marine life and birds recur about every four to seven years and consequently were long known along the west coast of South America. The related Southern Oscillation (SO) of sea-level pressure between Tahiti (normally high pressure) and Jakarta (or Darwin) (normally low pressure) was identified by Sir Gilbert Walker in 1910 and reinvestigated in the mid-1950s by I. Schell and H. Berlage and in the 1960s by A....

Boundary layer

Ekman Boundary Layer Convergence

The last force that has an important effect on air movement is that due to friction from the earth's surface. Towards the surface i.e. below about 500 m for flat terrain , friction begins to reduce the wind velocity below its geostrophic value. The slowing of the wind towards the surface modifies the deflective force, which is dependent on velocity, causing it also to decrease. Initially, the frictional force is opposite to the wind velocity, but in a balanced state - when the velocity and...

Early summer

East Asian Monsoon Domroes And Peng

Generally, during the last week in May the southern branch of the high-level jet begins to break down, becoming intermittent and then gradually shifting northward over the Tibetan Plateau. At 500 mb and below, however, the plateau exerts a blocking effect on the flow and the jet axis there jumps from the south to the north side of the plateau from May to June. Over India, the equatorial trough pushes northward with each weakening of the upper westerlies south of Tibet, but the final burst of...

The Intertropical Convergence

Streamline Convergence

The tendency for the trade wind systems of the two hemispheres to converge in the equatorial low-pressure trough has already been noted see Chapter 7B . Views on the exact nature of this feature have been subject to continual revision. From the 1920s to the 1940s, the frontal concepts developed in mid-latitudes were applied in the tropics, and the streamline confluence of the northeast and southeast trades was identified as the intertropical front ITF . Over continental areas such as West...

The Greenhouse Effect

The natural greenhouse effect of the earth's atmosphere is attributable primarily to water vapour. It accounts for 21 K of the 33 K difference between the effective temperature of a dry atmosphere and the real atmosphere through the trapping of infra-red radiation. Water vapour is strongly absorptive around 2.4-3.1 jUm, 4.5-6.5 jUm and above 16 jUm. The concept of greenhouse gas-induced warming is commonly applied to the effects of the increases in atmospheric carbon dioxide concentrations...

Condensation nuclei

Kohler Curve

Remarkably, condensation occurs with utmost difficulty in clean air moisture needs a suitable surface upon which it can condense. If clean air is cooled below its dew-point it becomes supersaturated i.e. relative humidity exceeding 100 per cent . To maintain a pure water drop of radius 10-7 cm 0.001 mm requires a relative humidity of 320 per cent, and for one of radius 10-5 cm 0.1 mm only 101 per cent. Usually, condensation occurs on a foreign surface this can be a land or plant surface in the...

Mean upperair patterns

Global Waerming Wheatrher Pattern

The patterns of pressure and wind in the middle troposphere are less complicated in appearance than at the surface as a result of the diminished effects of the landmasses. Rather than using pressure maps at a particular height, it is convenient to depict the height of a selected pressure surface this is termed a contour chart by analogy with topographic relief map see Note 1 . Figure 7.3 and 7.4 show that in the middle troposphere of the southern hemisphere there is a vast circumpolar Figure...

Further Reading Books

Carleton 2001 Synoptic and Dynamic Climatology, Routledge, London, 604pp. Advanced level text chapter 3 treats the global circulation. Bearman, G. ed. 1989 Ocean Circulation, The Open University, Pergamon Press, Oxford, 238pp. Bottomley, M., Folland, C. K, Hsiung, J., Newell, R. E., and Parker, D.E. 1990 Global Ocean Surface Temperature Atlas, Meteorological Office, London, 20pp. 313 plates. Corby, G. A. ed. 1970 The Global Circulation of the Atmosphere, Roy. Met. Soc.,...

The General Circulation

We next consider the mechanisms maintaining the general circulation of the atmosphere - the large-scale patterns of wind and pressure that persist throughout the year or recur seasonally. Reference has already been made to one of the primary driving forces, the imbalance of radiation between lower and higher latitudes (see Figure 3.25), but it is also important to appreciate the significance of energy transfers in the atmosphere. Energy is continually undergoing changes of form, as shown...

The Atmosphere

The atmosphere, vital to terrestrial life, envelops the earth to a thickness of only 1 per cent of the earth's radius. It had evolved to its present form and composition at least 400 million years ago by which time a considerable vegetation cover had developed on land. At its base, the atmosphere rests on the ocean surface which, at present, covers some 70 per cent of the surface of the globe. Although air and water share somewhat similar physical properties, they differ in one important...

Discovery Of The Tropopause And Stratosphere

Early scientific exploration of the upper atmosphere began with manned balloon flights in the mid-nineteenth century. Notable among these was the ascent by J. Glaisher and H. T. Coxwell in 1862. Glaisher last consciousness due to lack of oxygen at about 8800-m altitude and they barely survived the hypoxia. In 1902 L. Teisserenc de Bort in France reported a totally unexpected finding that temperatures ceased decreasing at altitudes of around 12 km. Indeed, at higher elevations temperatures were...

Fronts Jet Streams And The Tropopause 1990 Qeii

E. 1952 Characteristics of air masses over the British Isles. Meteorological Office, Geophysical Memoirs 11 87 , 34pp. Bennetts, D. A., Grant, J. R. and McCallum, E. 1988 An introductory review of fronts Part I Theory and observations. Met. Mag. 117, 357-70. Blanchard, D. O. 1990 Mesoscale convective patterns of the southern High Plains. Bull. Amer. Met. Soc., 71 7 , 994-1005. Boucher, R. J. and Newcomb, R. J. 1962 Synoptic interpretation of some TIROS vortex patterns a preliminary...

D Heat islands

Heat Island Chandler

The net effect of urban thermal processes is to make city temperatures in mid-latitudes generally higher than in the surrounding rural areas. This is most pronounced after sunset during calm, clear weather, when cooling rates in the rural areas greatly exceed those in the urban areas. The energy balance differences that cause this effect depend on the radiation geometry and thermal Table 12.2 Energy budget figures W m-2 for the Cincinnati region during the summer of 1968. Table 12.2 Energy...

Tropical weather and climate

When you have read this chapter you will Understand the characteristics and significance of the intertropical convergence zone, Be familiar with the principal weather systems that occur in low latitudes and their distribution, Know some of the diurnal and local effects that influence tropical weather, Know where and how tropical cyclones tend to occur, Understand the basic mechanisms and characteristics of El Ni o and La Ni a events. Tropical climates are of especial geographical interest...

The earths rotational deflective Coriolis force

Coriolis Effect Chemistry

The Coriolis force arises from the fact that the movement of masses over the earth's surface is referenced to a moving co-ordinate system i.e. the latitude and Figure 6.1 The Coriolis deflecting force operating on an object moving outward from the centre of a rotating turntable. Figure 6.1 The Coriolis deflecting force operating on an object moving outward from the centre of a rotating turntable. longitude grid, which 'rotates' with the earth . The simplest way to visualize how this deflecting...

Reaction System Support Structure

Plate2 The TIROS-N spacecraft, having a length of 3.71 m and a weight of 1421 kg. The four instruments of particular meteorological importance are shown in the numbered boxes. 1. Visible and infra-red detector - discerns clouds, land-sea boundaries, snow and ice extent and temperatures of clouds, earth's surface and sea surface. 2. Infra-red detector - permits calculation of temperatures profile from the surface to the 10-mb level, as well as the water vapour and ozone contents of the...

The temperate west coast and Cordillera

Cordillera Climate Chart

The oceanic circulation of the North Pacific closely resembles that of the North Atlantic. The drift from the Kuroshio current off Japan is propelled by the westerlies towards the west coast of North America and it acts as a warm current between 40 and 60 N. Sea-surface temperatures are several degrees lower than in comparable latitudes off western Europe, however, due to the smaller volume of warm water involved. In addition, in contrast to the Norwegian Sea, the shape of the Alaskan coastline...

B Warm and cold spells

Two types of synoptic condition are of particular significance for temperatures in the interior of North America. One is the cold wave caused by a northerly outbreak of cP air, which in winter regularly penetrates deep into the central and eastern United States and occasionally affects even Florida and the Gulf Coast, injuring frost-sensitive crops. Cold waves are arbitrarily defined as a temperature drop of at least 11 C in twenty-four hours over most of the United States, and at least 9 C in...

Heat Budget Of The Earth

Annual Radiation Budget Latitude

We can now summarize the net effect of the transfers of energy in the earth-atmosphere system averaged over the globe and over an annual period. The incident solar radiation averaged over the globe is where r radius of the earth and 4nr2 is the surface area of a sphere. This figure is approximately 342 W m-2, or 11 X 109J m-2yr-1 109J 1GJ for convenience we will regard it as 100 units. Referring to Figure 3.21, incoming radiation is absorbed in the stratosphere 3 units , by ozone mainly, and 20...

Bifurcation In Climate And Weather

Subtropical High Pressure Belt

MT WILHELM * < CENTRAL Figure 4.19 The relationship between precipitation (broken line) and relief in the 800 tropics and mid-latitudes. (A) The highly saturated airmasses over the Central Highlands of Papua New Guinea give seasonal maximum precipitations on the windward slopes of the mountains with changes in the monsoonal circulation (B) Across the Jungfrau massif in the Swiss -400 T Alps the precipitation is much less than in A (A) and is closely correlated with the 0 topography on the...

British airflow patterns and their climatic characteristics

Climatic Types And Their Charateristics

The daily weather maps for the British Isles sector 50 to 60 N, 2 E to 10 W from 1873 to the present day have been classified by H. H. Lamb according to the airflow direction or isobaric pattern. He identified seven major categories westerly W , northwesterly NW , northerly N , easterly E and southerly S types Figure 10.2 Continentality in Europe. The indices of Gorczynski dashes and Berg solid lines are explained in the text. Source Partly after Bluthgen 1966 . Figure 10.2 Continentality in...

The centripetal acceleration

Surface Friction Coriolis Wind

Observations in the free atmosphere above the level affected by surface friction up to about 500 to 1000 m show that the wind blows more or less at right angles to the pressure gradient i.e. parallel to the isobars with, for the northern hemisphere, high pressure on the right and low pressure on the left when viewed downwind. This implies that for steady motion the pressure-gradient force is balanced exactly by the Coriolis deflection acting in the diametrically opposite direction Figure 6.3A ....

Wave disturbances

Several types of wave travel westward in the equatorial and tropical tropospheric easterlies the differences between them probably result from regional and seasonal variations in the structure of the tropical atmosphere. Their wavelength is about 2000 to 4000 km, and they have a life span of one to two weeks, travelling some 6 to 7 longitude per day. The first wave type to be described in the tropics was the easterly wave of the Caribbean area. This system is quite unlike a mid-latitude...

Fmamjj Asond Month

Figure 3.16 Annual variation of temperature at different depths in soil at Kaliningrad, European Russia (above) and in the water of the Bay of Biscay (at approximately 47 N, I2 W) (below), illustrating the relatively deep penetration of solar energy into the oceans as distinct from that into land surfaces. The bottom figure shows the temperature deviations from the annual mean for each depth. Sources Geiger (1965) and Sverdrup (1945). raise the temperature of an approximately 30 m thick air...

Diurnal variations

Diurnal weather variations are particularly evident at coastal locations in the trade wind belt and in the Indonesia-Malaysian Archipelago. Land and sea breeze regimes (see Chapter 6C.2) are well developed, as the heating of tropical air over land can be up to five times that over adjacent water surfaces. The sea breeze normally sets in between 08 00 and 11 00 hours, reaching a maximum velocity of 6 to 15 m s-1 about 13 00 to 16 00 and subsiding around 20 00. It may be up to 1000 to 2000 m in...

Potential Evapotranspiration Precipitation

Global Temperature Semi Log Plot

Figure 4.7 The average annual moisture budget for stations in western, central and eastern Britain determined by Thornthwaite's method. When potential evaporation exceeds precipitation soil moisture is used at Berkhamsted in central England and Southend on the east coast, this is depleted by July to August. Autumn precipitation excess over potential evaporation goes into replenishing the soil moisture until field capacity is reached. Source From Howe 1956 . Reprinted from Weather, by permission...

Experimental Investigation Of Heat Transfer Vehrencamp

R. 1991 'Heat island' in a humid tropical city and its relationship with potential evaporation. Theoret. and App. Climatology 43, 137-47. Anderson, G. E. 1971 Mesoscale influences on wind fields. J. App. Met. 10, 377-86. Atkinson, B. W. 1968 A preliminary examination of the possible effect of London's urban area on the distribution of thunder rainfall 1951-60. Trans. Inst. Brit. Geog. 44, 97-118. Atkinson, B. W. 1977 Urban Effects on Precipitation An Investigation of London's...

Acknowledgements

J. Dunn for his considerable contribution to the first edition the late Professor F. Kenneth Hare of the University of Toronto, Ontario, for his thorough and authoritative criticism of the preliminary text and his valuable suggestions Alan Johnson, formerly of Barton Peveril School, Eastleigh, Hampshire, for helpful comments on Chapters 2 to 6 and to Dr C. Desmond Walshaw, formerly of the Cavendish Laboratory, Cambridge, and R. H. A. Stewart of the Nautical...

From Precipitation Lands On Lands

AND GROUND ICE 70 OF ALL FRESH WATER CONTINENTS (Percentages refer to fresh water total) Figure 4.1 The hydrological cycle and water storage of the globe. The exchanges in the cycle are referred to 100 units, which equal the mean annual global precipitation of 1130 mm. The percentage storage figures for atmospheric and continental water are percentages of all fresh water. The saline ocean waters make up 97 per cent of all water. The horizontal advection of water vapour...

Variation Of Pressure And Wind Velocity With Height

Both pressure and wind characteristics change with height. Above the level of surface frictional effects (about 500 to 1000 m), the wind increases in speed and becomes more or less geostrophic. With further height increase, the reduction of air density leads to a general increase in wind speed (see Chapter 6A.1). At 45 N, a geostrophic wind of 14 m s-1 at 3 km is equivalent to one of 10 m s-1 at the surface for the same pressure gradient. There is also a seasonal variation in wind speeds aloft,...

Modification of the heat budget

Oke Energy Balance

The energy balance of the built surface is similar to soil surfaces described above, except for the heat production resulting from energy consumption by combustion, which in some cities may even exceed Rn during the winter. Although Rn may not be greatly different from that in nearby rural areas except during times of significant pollution heat storage by surfaces is greater 20 to 30 per cent of Rn by day , leading to greater nocturnal values of H LE is much less in city centres. After long,...

The trade winds

The trades (or tropical easterlies) are important because of their great extent, affecting almost half the globe (see Figure 7.13). They originate at low latitudes on the margins of the subtropical high-pressure cells, and their constancy of direction and speed (about 7 m s-1) is remarkable. Trade winds, like the westerlies, are strongest during the winter half-year, which suggests they are both controlled by the same fundamental mechanism. The two trade wind systems tend to converge in the...

The semiarid southwestern United States

Both the mechanisms and patterns of the climate in areas dominated by the subtropical high-pressure cells are not well documented. The inhospitable nature of these arid regions inhibits data collection, and yet the study of infrequent meteorological events requires a close network of stations maintaining continuous records over long periods. This difficulty is especially apparent in the interpretation of desert precipitation data, because much of the rain falls in local storms irregularly...

Planetaryscale motions in the atmosphere and ocean

When you have read this chapter you will Learn how and why pressure patterns and wind velocity change with altitude, Become familiar with the relationships between surface and mid-tropospheric pressure patterns, Know the features of the major global wind belts, Be familiar with the basic concepts of the general circulation of the atmosphere, Understand the basic structure of the oceans, their circulation and role in climate, Know the nature and role of the thermohaline circulation. In this...

Solar radiation and the global energy budget

When you have read this chapter you will Know the characteristics of solar radiation and the electromagnetic spectrum, Know the effects of the atmosphere on solar and terrestrial radiation, Understand the cause of the atmospheric greenhouse effect, Understand the earth's heat budget and the importance of horizontal transfers of energy as sensible and latent heat. This chapter describes how radiation from the sun enters the atmosphere and reaches the surface. The effects on solar radiation of...

Rock and sand

The energy exchanges of dry desert surfaces are relatively simple. A representative diurnal pattern of energy exchange over desert surfaces is shown in Figure 12.3. The 2-m air temperature varies between 17 and 29 C, although the surface of the dry lake-bed reaches 57 C at midday. Rn reaches a maximum at about 13 00 hours when most of the heat is transferred to the air by turbulent convection in the early morning the heating goes into the ground. At night, this soil heat is returned to the...

C Pollution distribution and impacts

Plume Lofting

Polluted atmospheres often display well-marked physical features around urban areas that are very dependent upon environmental lapse rates, particularly the presence of temperature inversions, and on wind speed. A pollution dome develops as pollution accumulates under an inversion that forms the urban boundary layer Figure 12.23A . A wind speed as low as 2 m s-1 is sufficient to displace the Cincinnati pollution dome downwind, and a wind speed of 3.5 m s-1 will disperse it into a plume. Figure...

Weather and climate in middle and high latitudes

When you have read this chapter you will Be familiar with the major factors determining climate in many regions of middle and high latitudes, and the subtropical margins, Appreciate the role of major topographic barriers in determining regional climate, Be aware of the contrasts between climatic conditions in the Arctic and Antarctic. In Chapters 7 and 8, the general structure of the atmospheric circulation has been outlined and the behaviour and origin of extratropical cyclones examined. The...

Nature Of The Source Area

Frontal Zone Cross Section

The basic idea of airmass formation is that radiative and turbulent transfers of energy and moisture, between the land or ocean surface and the atmosphere, give rise to Figure 9.1 A schematic height cross-section for the northern hemisphere showing barotropic airmasses and a baroclinic frontal zone (assuming that density decreases with height only). Figure 9.1 A schematic height cross-section for the northern hemisphere showing barotropic airmasses and a baroclinic frontal zone (assuming that...

The lee cyclone

Westerly airflow that is forced over a north-south mountain barrier undergoes vertical contraction over the ridge and expansion on the lee side. This vertical movement creates compensating lateral expansion and contraction, respectively. Hence there is a tendency for divergence and anticyclonic curvature over the crest, and convergence and cyclonic curvature in the lee of the barrier. Wave troughs may be set up in this way on the lee side of low hills (see Figure 6.13) as well as major mountain...

The Global Climate System

Undoubtedly the most important outcome of work in the second half of the twentieth century was the recognition of the existence of the global climate system (see Box 1.1). The climate system involves not just the atmosphere elements, but the five major GLOBAL ATMOSPHERIC RESEARCH PROGRAMME (GARP) AND THE WORLD CLIMATE RESEARCH PROGRAMME (WCRP) The idea of studying global climate through co-ordinated intensive programmes of observation emerged through the World Meteorological Organization (WMO...

Terrestrial Infrared Radiation And The Greenhouse Effect

Radiation from the sun is predominantly short-wave, whereas that leaving the earth is long-wave, or infra-red, radiation see Figure 3.1 . The infra-red emission from the surface is slightly less than that from a black body at the same temperature and, accordingly, Stefan's Law see p. 33 is modified by an emissivity coefficient e , which is generally between 0.90 and 0.95, i.e. F eoT4. Figure 3.1 shows that the atmosphere is highly absorbent to infra-red radiation due to the effects of water...