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How Earth Works > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

Atmospheric pressure

A
  • primary impact of airflow is to move heat energy around the globe to moderate temperature on Earth
  • airflow affects global and local air quality and pollution levels
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2
Q

Air pressure

A
  • the force that air molecules exert on a surface due to their weight
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3
Q

Factors that influence air pressure

A
  • atmospheric pressure is most closely associated with temperature and density of air
  • air temperature: when air close to earth’s surface is warmed a great deal, it causes air molecules to scatter and density thus decreases, resulting in low atmospheric pressure
  • air density: density of air molecules is greater closer to the Earth’s surface (air pressure is relatively high), with increased altitude, the density of air molecules becomes progressively less, resulting in progressively lower air pressure
  • low atmospheric pressure results when air is forced to rise vigorously
  • high atmospheric pressure associated with high atmospheric pressure because cold air is dense and sinks
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4
Q

Measuring and mapping air pressure

A
  • air pressure measured in millibars (mb) with a barometer
  • to observe how air pressure changes with altitude, look at 3 separate locations at different elevations
    1. sea level: average pressure of air = 1013.25mb
    2. Denver colorado: average pressure of air = 840 mb
    3. top of mt everest: average pressure of air = 320 mb
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5
Q

Air density, altitude, and atmosphere pressure

A
  • at low altitudes, air molecules are held close to Earth by gravity and thus are denser, resulting in high atmospheric pressure
  • density of air molecules is low at high altitudes and air pressure is relatively low
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6
Q

Measurement of atmospheric pressure

A
  • the pressure of the atmosphere is measured by the height of a column of mercury that can be supported by that pressure
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7
Q

Atmospheric pressure and altitude

A
  • average atmospheric pressure decreases with increasing elevation and altitude above the Earth’s surface
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8
Q

Atmospheric pressure systems

A
  • air pressure varies horizontally across the earth’s surface with distinct zones of high air pressure and distinct zones of low air pressure
  • when air is warmed in the atmosphere it expands, decreasing its density and causing it to rise
  • low-pressure system: a circulating body of air where relatively less pressure exists on the earth’s surface because warm air ascends (rising away from the surface) in the system’s core
  • high-pressure system: a circulating body of air that exerts relatively high pressure on the surface of the earth because cool air descends (sinking toward the surface) in the centre of the system
  • when warm air rises at the low-pressure system, air from the high-pressure system will move in to replace it, creating wind
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9
Q

Low-pressure systems

A
  • a rotating column of air where air converges at the surface and subsequently lifts
  • referred to as cyclones
  • View from the side: the vertical flow of air consists of rising air with the most vigorous upward flow in the centre of the system, resulting in the central part having the lowest pressure
  • NH: the horizontal flow of air around the centre of a low is counterclockwise as the air flows toward the core, due to the Coriolis effect
  • SH: the horizontal flow of air is clockwise, flowing inward, because of the rising air at the centre of the system creating a void into which air must flow
  • LP systems are generally associated with cloudy or stormy weather because rising air cools
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10
Q

Cyclones

A
  • low-pressure systems
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11
Q

High-pressure systems

A
  • a rotating column of air that descends toward the surface of the earth where it diverges
  • referred to as anticyclones
  • vertical flow of descending air which diverges (spreads out) at the surface
  • air sinks most vigorously in the centre of a high, so the highest pressure is in the central part of the system
  • NH: horizontal airflow around the center of the system is clockwise
  • SH: horizontal airflow around the center of the system is counterclockwise (opposite to LP systems)
  • HP systems are generally associated with fair weather because descending air warms as it approaches the surface
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12
Q

Anticyclones

A
  • high-pressure systems
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13
Q

Atmospheric pressure systems

A
  • In LP systems, air converges at the surface, rises, and forms clouds
  • In HP systems, air descends from above and diverges at the surface. No clouds are formed in warming air so these are generally associated with clear skies
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14
Q

Atmospheric pressure map of the North Atlantic

A
  • red arrows represent direction of the winds
  • L = LP system
  • H = HP system
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15
Q

Advection

A
  • the horizontal movement of air

- from high-pressure system to low-pressure system at the surface

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16
Q

Compass headings and wind directions

A
  • winds named for the direction from which they originate
  • westerly winds, originate in the west and flow toward the east
  • northwind in the NH brings in air from the north toward the south
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17
Q

Atmospheric pressure systems in Europe

A
  • low indicated by cloud cover (spiralling into the low in a counterclockwise direction)
  • high is a clear sky
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18
Q

The variables that influence large scale winds

A

Unequal heating of land surfaces

  • the ultimate cause for all wind patterns on earth results from variations in the amount of solar radiation received between latitudes
  • means that air density (and pressure) differ from place to place
  • surface-air flows from high pressure to low pressure and the atmosphere works to balance the two
  • difference between the tropics and the poles, tropics are much warmer and receive the most direct insolation throughout the year
  • unequal heating causes motion in the process called convection (vertical mixing of fluid material - in this case, its air) because of differences in temperature
  • on a global scale, air heated near the equator results in low air pressure as air rises with the upward-moving part of the convection processes, it travels to higher latitudes in both hemispheres through advection, where air cools and descends as a high-pressure system at some point in the downward part of the convection process
  • the combined process of convection & advection = the first stage of atmospheric circulation on earth, and are the overall method through which heat is distributed around the planet, once air is set in motion like this, the other forces (pressure gradient, Coriolis, frictional) then directly influence the movement of the air

Pressure gradient force

  • the variable that drives the movement of air between 2 different areas of pressure = the pressure gradient force
  • the greater the difference in surface pressures between the 2 regions, the steeper the pressure gradient, and the faster the air flows from high to low to equalize the pressure (faster wind speed)
  • widely spaced isobars = very limited pressure change occurring, the pressure gradient is shallow, light winds
  • isobars closer together = rapid change in surface temperature occurs, a steep pressure gradient, air flows faster, moving toward the centre of the low, to fill the relative void created by the less dense air at the surface, strong winds

Coriolis effect

  • related to the rotation of Earth on its axis
  • objects in the atmosphere, including air, are deflected or pulled sideways as the earth rotates until them
  • NH: direction of deflection for an object moving toward the equator is to the right when viewed from the North Pole
  • SH: direction of deflection for an object moving toward the equator is to the left when viewed from the South Pole
  • when air rises into the upper troposphere (above about 1000m), its speed increases because it flows freely, the air is influenced most by the Coriolis effect once this altitude is reached, causing winds to spiral to the right in the NH and to the left in the SH
  • process most pronounced at higher latitudes, generally results in westerly airflow from west to east
  • in the upper atmosphere of the NH, the wind begins to flow perpendicular to isobars, under the influence of the pressure gradient, as air flows from the high, the Coriolis effect influences the moving air and deflects it from its path, the deflection continues until the pressure gradient and the Coriolis effect are in balance when the air is moving parallel to the isobars
  • net result is that air moves around pressure systems in the upper atmosphere, winds called geostrophic winds

Frictional forces

  • occurs at ground level and operates in direct opposition to the winds
  • force of friction occurs because of the drag and impediments created by features on the surface of the earth (mountains, trees, buildings)
  • these features cause the wind to slow down and move in irregular ways
  • results in airflow that is somewhere between the flow driven by the pressure gradient (perpendicular to isobars), and the Coriolis effect (parallel to isobars)
  • effect of friction is strongest at the surface and diminishes progressively to an altitude of 1000m
  • wind flows at an angle relative to the isobars at ground level, but at higher altitudes, wind follows a geostrophic course parallel to isobars

integrating all major factors:

  • pressure gradient force causes winds to flow at right angles to isobars in the direction of lower pressure
  • now including the Coriolis effect, winds flow parallel to the isobars as geostrophic winds, this process occurs because of the balancing effect that the Coriolis effect & pressure gradient force have on one another
  • the Coriolis effect keeps wind from flowing across isobars, whereas the pressure gradient force stops winds from curving up the pressure slope
  • perplexing pattern because arrows seem to “bend” to the left around the lows in NH, and to the right around highs (contrary to Coriolis effect), opposite in SH
  • when the force of friction is added, the end result is winds that follow an intermediate course relative to the isobars, somewhere between perpendicular and parallel to the lines of equal atmospheric pressure
  • convection loops consist of spiralling masses of descending rising air, linked horizontally by advection
  • surface divergence out of a high and convergence into a low, warm air rises up at the low, cooling and producing precipitation
  • diverges out higher in the atmosphere and moves parallel to the isobars (geostrophic flow)
  • winds converge and sink, creating high pressure at the surface, and then diverging out of the high, heading to a low surface
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19
Q

Pressure gradient force

A
  • the difference in the barometric pressure that exists between adjacent zones of low and high pressure that results between airflow
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20
Q

Atmospheric convection

A
  1. suns energy heats the ground surface
    - advection
  2. warmed ground heats the air above it
    - convection
  3. warm air rises
  4. rising air cools
  5. cool air sinks
  • convection occurs when one portion of the earth is heated relative to another
  • when this happens a large “bubble” of air lifts from the surface
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21
Q

The Coriolis effect

A
  • the effect created by the Earth’s rotation that causes winds to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
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22
Q

Geostrophic winds

A
  • airflow that moves parallel to isobars because of the combined effect of the pressure gradient force and Coriolis effect
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23
Q

Frictional forces

A
  • force of friction occurs because of the drag and impediments created by features on the surface of the earth (mountains, trees, buildings)
  • these features cause the wind to slow down and move in irregular ways
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24
Q

The effect of friction on wind flow near the Earth’s surface

A
  • compared to winds at higher altitudes, the flow of surface air is significantly modified by features on the earth’s surface
  • friction with the surface slows the wind speed and reduces the Coriolis effect
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25
Q

The factors that influence large-scale atmospheric circulation

A
  • pressure gradient force causes air to flow perpendicular to isobars
  • Coriolis effect causes movement of air parallel to isobars, occurring in the upper atmosphere (above 1000m)
  • in combination with pressure gradient and Coriolis effect, frictional forces result in winds that flow somewhere intermediate between 0 degrees and 90 degrees of isobars, occurring at the surface where friction slows the wind and the Coriolis effect is reduced
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26
Q

Dynamic convection loop

A
  1. converging winds
  2. descends cool air that warms (HP system)
    - anticyclone at the surface
  3. diverging winds
  4. converging winds
    - cyclone at the surface
  5. rising warm air that cools
  6. diverging winds
  • cyclones and anticyclones are linked together in a convection loop consisting of air masses that spiral due to the Coriolis effect
  • air masses move vertically within the high- and low-pressure systems, and horizontally between them
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27
Q

Global pressure and atmospheric circulation

A
  • general circulation of air around the globe, referring to air in both the upper atmosphere and at the surface (the difference in flow of these parts of the atmosphere is noticeable on the ground)
  • primary driver of global circulation is the unequal heating of the tropics and the poles, because of this energy imbalance, the atmosphere works to balance the system through the process of airflow
  • if the earth had uniform character, did not rotate, and it’s axis were not tilted, the circulatory system would be easy to understand
  • low pressure would occur at the equator because air is very warm, and high pressure would occur at the poles because the air is very cold
  • air would rise away from the surface at the equator, within a low pressure system, and would then flow toward the poles by advection
  • one it reaches the poles, the air would descend toward the surface in a high-pressure system where it would then diverge and flow back toward the equator by advection
  • however Earth does not have a uniform character, it does rotate, and it is tilted with respect to the plane of the ecliptic, given these factors the global circulatory system is more complex
    1. Tropical circulation
  • intertropical convergence zone
  • subtropical high-pressure system
    2. Midlatitude Circulation
    3. Polar Circlation
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28
Q

Topical Circulation

A
  • atmospheric circulatory processes are set in motion in this part of the Earth because of the high angle of incidence and extremely warm temperatures
  • convection loop, with air flowing between the equator and about 30 degrees N and S latitude, each of these loops is a hadley cell

-discussion of tropical circulation focuses on the Intertropical convergence zone and Subtropical high-pressure system

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29
Q

Hadley cell

A
  • large-scale convection loop in the tropical latitudes that connects the Intertropical Convergence Zone (ITCZ) and the Subtropical High (STH)
30
Q

Intertropical convergence zone ITCZ

A
  • a band of low pressure, calm winds, rising air, and clouds in tropical latitudes where air converges from the southern and northern hemispheres
  • tropical circulatory processes begin at the equator where the air is warmed due to year-round receipt of direct sunlight
  • warming creates a zone of low pressure because warm air is less dense and more buoyant than colder air
  • resulting from the rising air mass is air from higher tropical latitudes in both hemispheres flowing toward the area of low pressure along the surface by advection, converging into a narrow band known as the ITCZ
  • converging winds known as trade winds, north of the ITCZ they are northeasterly, and south of the ITCZ they are southeasterly because the Coriolis effect deflects the minds in the NH to the right and the SH to the left, these two bands form the tropical easterlies
  • where the northeasterly and southeasterly trade winds converge at the ITCZ, the winds can be relatively calm and highly variable because the pressure gradient is weak, this area is known as the doldrums
  • the ITCZ is a region of cloudiness and frequent rain/thunderstorms, due to (1) the trade winds flowing over warm oceans, a great deal of evaporation from these surfaces takes place and the air contains abundant moisture, high levels of atmospheric pressure can be reached because the air is warm and expanding, as well as (2) due to the warmth of the air, the ITCZ is a place where warm air rises, creating a low-pressure surface, as the air rises it cools, and clouds/rainfall are formed because the water condenses at cooler temperatures
  • rising air ascends in the updrafts that occur in the thunderstorms around the ITCZ, putting a huge amount of sensible heat and latent heat of condensation into the upper troposphere, which will then move poleward
  • easy to find the ITCZ because it consists of a band of clouds and thunderstorms over the oceans, less visible over continents (more diffused)
31
Q

Trade winds

A
  • the primary wind system in the tropics that flows toward the Intertropical Convergence Zone on the equatorial side of the Subtropical High-Pressure System (approximately 0 degrees - 30 degrees N and S latitude)
  • these winds flow from the northeast in the northern hemisphere and from the southeast in the southern hemisphere
32
Q

Tropical easterlies

A
  • band of easterly winds that exist where northern and southern trade winds begin to converge
33
Q

The global circulation model

A

page 123 in textbook

34
Q

Subtropical high-pressure system

A
  • band of high air pressure, calm winds, and clear skies that exists at about 25 degrees to 30 degrees N and S latitude
  • as air in the low-pressure ITCZ rises from earths surface, it spirals upward to the upper part of the troposphere, temperature dropping as the air rises (process occurs because air expands as it rises)
  • high-altitude air on the northern side of the ITCZ flows northward by advection, on the southern side it flows south
  • given that the air has cooled, it must sink and does at approx 25-30 degrees N or S latitude
  • zones of sinking air = Subtropical High (STH) Pressure System
  • airflow in the core of the STH is often weak, referred to as horse latitudes
  • descending air in the STH is dry because of its moisture being lost to the precipitation over the equator
  • air is compressed as it descends, making air denser and warmer as it approaches the surface of the Earth
  • creates a high-pressure zone of hot, dry air
  • zone is characterized by deserts
  • STH functions the same as high-pressure systems, as air descends it rotates in a clockwise direction in the NH and counterclockwise in the SH
  • once the downward spiralling airstreams reach the surface, they diverge… as they diverge on the southern side of the STH in the northern hemisphere, they flow back to the ITCZ, forming the northeasterly trade winds… on the northern side of the STH in the southern hemisphere, the airstreams form the southeasterly trade winds
  • at low latitudes this flow to and from the ITCZ and STH forms a convection loop called a hadley cell
35
Q

Midlatitude circulation

A
  • primary purpose of midlatitude circulation is to mix the cool solar air from high latitudes with the warm tropical air from lower latitudes
  • midlatitudes are the regions where these contrasting air masses converge
  • the focal point of midlatitude circulation is the polar front, which on average occurs at about 60 degrees N and S latitudes
  • polar front is the contact in the midlatitudes between warm tropical air and colder polar air
  • in the NH, midlatitudes are north of the STH, as descending air reaches the surface it diverges out of the high, with air on the southern side flowing toward the ITCZ in the form of northeasterly trade winds, whereas air on the north side of the STH flows northward in association with Ferrel cells that are located between the STH and the polar front, these winds are southwesterly, flowing toward the polar front and converging with air flowing southward from the highest latitudes, this southwesterly flow of air contributes to the westerlies in mid-latitudes
  • midlatitude westerlies flow at high speeds, reaching 350km/h-450km/h in the upper troposphere
  • these winds reach these speeds due to a distinct temperature gradient along the polar front (temperature gradient is weak during summer months, strengths toward winter)
  • resulting river of rapidly moving air is the polar front jet stream occurring at altitudes of 10km-12km (band of clouds form along this line)
  • polar jet stream found above the polar front because it is the area of the greatest horizontal temperature gradient, very cold on the poleward side of the jet stream and relatively warmer on the equatorial side of the jet stream, this difference in temp creates a pressure gradient force with lower relative pressure over the warm air, causing an increase in horizontal wind speed with height
  • the Coriolis effect balances the horizontal pressure gradient force and results in a very strong high altitude stream of air that flows from the west above the polar front, this is the jet stream, the greater the contrast across the front, the stronger the polar front jet stream will be
  • the smooth westward flow of upper-air circulatory systems frequently develop distinct undulations called Rossby waves, these rossby waves along the polar front are the mechanisms through which significant temperature differences on either side of the front are moderated (especially during winter months)
  • at any given location in the midlatitudes, the flow of the polar jet stream essentially follows a smooth west-east path for several weeks, this circulatory pattern is called the zonal flow because cold arctic air is confined to a small zone at very high latitudes
  • as the temperature contrast on either side of the polar front increases, the midaltitude atmosphere responds by forming an undulation in the jet stream, beginning the Rossby wave
  • the core of this undulation becomes a midlatitude cyclone rotating counterclockwise
  • with the continued development of the Rossby wave, westerly winds are no longer flowing directly west to east but now have northerly and southerly components as well due to the counterclockwise circulation
  • in contrast to zonal flow, the variable flow associated with a developing Rossby wave is called meridional flow because the air frequently flows parallel to the meridians
  • with the meridional flow, warm air on the east side of the wave pushes poleward because winds are southerly, and cold air from the north plunges southward on the west side of the system where the winds are northerly
  • an influx of cold air into a region is called an arctic outbreak and can result in extremely cold air reaching latitudes far south of its origin, as time progresses it can be pinched off from the main body of arctic air, resulting in the re-establishment of zonal flow conditions
  • this pool of cold air can exist for several weeks gradually warming because of higher angle of insolation at these somewhat lower latitudes
36
Q

The polar front in the Northern Hemisphere

A

pg. 125
- the polar front is the boundary between warm air (to the south) and cold polar air (to the north)
- air from the STH flows toward the polar front

37
Q

Rossby waves

A
  • undulations that develop in the polar front jet stream when significant temperature differences exist between tropical and polar air masses
38
Q

The polar front jet stream

A
  • river of high-speed air in the upper atmosphere that flows along the polar front
39
Q

Zonal flow

A
  • jet stream pattern that is tightly confined to the high latitudes and is thus circular to semicircular in polar view, where winds flow from west to east
40
Q

Meridional flow

A
  • jet stream pattern that develops when strong Rossby waves exist and the polar front jet stream flows parallel to the meridians in many places
41
Q

Development of Rossby waves in the midlatitudes of the Northern Hemisphere

A

a. polar jet stream with small undulations
b. Rossby waves develop, causing north-south motion of large masses of warm/cold air
c. cells of cold air break off from the larger air mass, forming isolated cyclones of cold air

42
Q

Polar circulation

A
  • atmospheric circulation in the polar regions is associated with a simple circulatory loop known as the polar cell
  • air that flows northward at the polar front cools considerably and descends at very high latitudes, producing a weak high-pressure system
  • this system is called the polar high and consists of a mass of descending air that rotates clockwise in the NH and counterclockwise in the SH
  • these rotating systems direct cold dry air toward the polar front in the form of polar easterlies, strongest in the NH where large landmasses exist
  • polar high tends to be located over the northern continental regions and makes northernmost canada and siberia bitterly cold/dry during the winter
43
Q

Polar high

A
  • zone of atmospheric pressure at high latitudes
44
Q

Polar easterlies

A
  • band of easterly winds at high latitudes
45
Q

Seasonal migration of the pressure systems

A
  • a distinct seasonal component exists in associated with global atmospheric pressure
  • during the spring/fall equinoxes, the sun is directly overhead the equator, resulting in it receiving the most intense radiation, and the ITCZ is generally located here
  • during winter in the NH, the subsolar point is located at the tropic of capricorn bc the sun is directly overhead at that latitude, this zone receives the most intense radiation and is where the ITCZ is generally located
  • with the coming of the northern hemisphere spring equinox, the ITCZ follows the subsolar point back to the equator, and then migrates into the NH during april/may, reaching the tropic of cancer by later june, then as days shorten in july/august the ITCZ migrates back to the south
  • ITCZ movement over land generally follows seasonal movements but there’s a one-two month lag over large ocean areas (making it a wavy curve)
  • all large pressure systems move seasonally, because they maintain a more or less consistent distance from one another
46
Q

Monsoonal Winds

A
  • monsoon is an important outcone of the seasonal migration of air pressure systems
  • monsoon is a cyclical shift of the prevailing wind direction that occurs at the subcontinetal scale over the course of a year
  • related to seasonal migration of the ITCZ as well as maritime vs continental effect
  • 2 major monsoon systems: south asia, east asia
  • 2 minor monsoon systems: australia and west african
  • other areas where monsoon patterns devleop: southwestern USA
  • monsoon prnounced in south asia as it is where the most seasonal fluctation of the ITCZ occurs
  • winter monsoon occurs because the pressure gradient slopes steeply from the very strong siberian high-pressure system toward the ITCZ
  • reverse direction of surface winds during summer causes the summer monsoon, the reversal occuring because temperatures over asian landmess increase due to high angle of incidence in the summer
47
Q

Monsoon

A
  • the seasonal change in wind direction that occurs in the subtropical locations due to the migration of the intertropical convergence zone (ITCZ) and the subtropical high (STH) pressure system
48
Q

Local Wind Systems

A
  • local wind systems result from temperature differences created by proximity to large bodies of water, topographic variation or other geographical features
49
Q

Land-Sea breezes

A
  • land-sea systems localized along shores of major water bodies
  • winds form due to difference heating/cooling of continents and water (maritime vs continental effect)
  • during the day: air over land heats more rapidly and the warm air rises, resulting in a small zone of low pressure forming over the land near the shore, but air over water is relatively high in pressure bc air is cooler/denser, so it sinks, this difference creates the sea breeze
  • pattern reverses at night because air over land cools more rapidly at night, so the pressure systems reverse creating the land breeze
50
Q

Sea breeze

A
  • daytime circulatory system along coasts where winds flow from a zone of high pressure over water to a zone of relatively low pressure over land
51
Q

Land breeze

A
  • nighttime circulatory system along coasts where winds from a zone of high pressure over land flow to a zone of relatively low pressure over water
52
Q

Coastal wind systems and the maritime vs continental effect

A

daytime sea breeze

  1. heated air rises over warmer land, causing lower pressure
  2. cooler air sinks over water, causing higher pressure
  3. cooler air flows inland toward lower pressure

nighttime land breeze

  1. heated air rises over warmer water, causing lower pressure
  2. cooler air sinks over land, causing higher pressure
  3. air flows offshore toward lower pressure
53
Q

Topographic winds

A
  • valley breeze
  • mountain breeze
  • Katabatic winds
  • chinook winds
54
Q

Valley breeze

A
  • upslope airflow that develops when mountain slopes heat up due to re-radiation and conduction over the course of the day
  • a zone of relatively low pressure develops on the mountain slopes, wheras high pressure is found in the lowlands below
  • resulting: air pressure can flow upslope to fill the pressure void created by the upward movement of air over the heated slopes
55
Q

Local wind flow caused by differences in elevation

A

.

56
Q

Mountain breeze

A
  • downslope airflow that develops when the mountain slopes cool off at night and relatively low pressure exists in valleys
  • reverse of the valley breeze
57
Q

Katabatic winds

A
  • downslope airflow that evolves when pools of cold air develop over ice caps and subsequently descend into valleys
  • more extreme version of mountain breezes, in cold places like greenland, antarctica
  • most common during winter months when extremely cold air accumulates over higher-altitude regions covered by ice sheets, which then flows downhill under the force of gravity
58
Q

Chinook winds

A
  • downslope airflow that results when a zone of high pressure exists on one side of a mountain range and a zone of low pressure exists on the other side
  • only occur when a steep pressure gradient develops along the range, which requires a high-pressure system on the side of the range that faces the oncoming winds (windward side)
  • on the leeward side a low-pressure system must exist
  • the resulting airflow moves downslope the leeward side, resulting in dry air warming as it descends
59
Q

Windward side

A
  • the side of a mountain that faces oncoming winds
60
Q

Leeward side

A
  • the side of a mountain range that faces away from prevailing winds
61
Q

Human Interactions: Harnessing Wind Energy

A

*

62
Q

Oceanic Circulation

A

Gyres and Thermohaline Circulation
- heat energy is moved through oceanic circulation
- tropical easterly winds produce easterly oceanic currents in the low latitudes
- high speed westerly winds in the SH produce the west-wind drift
- Coriolis effect plays a major role in oceanic current movement, ocean currents in NH generally move clockwise, moving warm tropical water into higher latitudes, ocean currents in the SH circulate counterclockwise , delivering cold water from antarctic latitudes to the equatorial region where it warms and then flows west as the south equatorial current
- primary difference between oceanic and atmospheric circulatory processes is that the continents block the movement of water, resulting in distinct circulatory systems called gyres
- a slow mix of water occurs vertically between the layers of the ocean, these currents together making the Thermohaline Circulation, or oceanic conveyer belt, linking all the worlds oceans
generated bc of different regional differences in water density that evolve through variations in temperature and salinity
- generally, water at the surface of the ocean is warmer/less salty
- in the western part of the tropical atlantic basin, as a part of the north atlantic gyre, warm water flows northward in the gulf stream, as it flows to higher latitudes, evaporation occurs which increases the salinity of the current and the surface waters gradually cool as they continue northward
- decreasing temperature and high salinity results in water density sinking in the northern atlantic
- sinking water becomes a down-dwelling current
- downward motion enhanced by development of sea ice at high latitudes which pushes more salt into the water below the ice and increases salinity of the water and its density
- resulting downwelling current flows at great depths to the southern part of the atlantic basin and then flows to the east between Antarctica and Australia to the pacific ocean where it flows northward toward Alaska
- as water moves into the tropical regions of the pacific it warms and becomes an upwelling current that moves back to the surface

El Nino

  • anomaly in oceanic circulation
  • the reversal of “normal” flow in the tropical pacific ocean
  • “normal” circulatory pattern in the pacific ocean reverses every 3-8 years, apparent cause is the normally strong tropical easterlies weaken, allowing a distinct westerly flow to develop in surface ocean waters - called el nino
  • reversal of surface flow usually occurs around christmastime
  • el nino brings intense storms to the normally dry parts of south america and drought to the western pacific, this weather reversal occurs because the atmospheric pressure in the eastern pacific is relatively low, and relatively high in the western pacific
63
Q

Gyres

A
  • large oceanic circulatory systems that form because currents are deflected by landmasses
64
Q

Thermohaline Circulation

A
  • the global oceanic circulatory system that is driven by differences in salinity
65
Q

Global oceanic circulation

A
  • oceanic currents fundamentally move in the same direction as the winds
66
Q

Downwelling current

A
  • a current that sinks to great depths within the ocean because water temperature drops and salinity increases
67
Q

Upwelling current

A
  • a current that ascends. to the surface of the ocean because water temperature increases and salinity increases
68
Q

Surface and deep water circulation loop in the world oceans

A
  • combined processes that drive the circulation of ocean currents around the world
69
Q

polar front

A
  • the contact in the midlatitudes between warm tropical air and colder polar air
70
Q

westerlies

A
  • midlatitude winds that generally flow from west to east

How Earth Works (7 decks)

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