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EAS 201 > Ch 7a: Atmosphere > Flashcards

Ch 7a: Atmosphere Flashcards

1
Q

Extent of Atmosphere

A

Thins upward, 500 km merges with vacuum of space, 5% of the volume of Earth.

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2
Q

Atmosphere Pressure and Density

A

gases are highly compressible, density increases downward.

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3
Q

Measuring Pressure:

A

Aneroid barometers, mercury barometers

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4
Q

Average pressure at sea level:

A

760 mm mercury, 101.325 kPa

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5
Q

Temperature measures:

A

average kinetic energy of molecules

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6
Q

Heat refers to:

A

total energy of all molecules

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7
Q

Temperature and Elevation:

A

four layers based on temperature changes: troposphere, stratosphere, mesosphere, thermosphere.

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8
Q

Troposphere:

A

16 km thick at equator, 10 km at poles. Top surface is tropopause. Heated from below, reradiated. Contains most weather

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9
Q

Stratosphere:

A

extends from top of troposphere to ~50km. Temperature increases upward due to absorption of solar UV energy by ozone. Upper boundary is stratopause.

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10
Q

Mesosphere:

A

temperature decreases upwards to ~80km.

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11
Q

Thermosphere:

A

Heating of gas molecules by EMR. Temperature is high, scare molecules so total heat content very low.

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12
Q

Composition of the atmosphere:

A

gases and aerosols.

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13
Q

Gases:

A

mainly nitrogen, oxygen, argon, water vapour.

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14
Q

Aerosols:

A

water droplets, solid particles

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15
Q

Greenhouse Gases, waves

A

incoming solar energy is mainly short wave. Radiated by ground is long wave. Absorbed by 5 greenhouse gases:

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16
Q

5 Greenhouse Gases:

A

carbon dioxide, water vapor, methane, nitorus oxide, ozone.

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17
Q

Absorption of solar energy and gases:

A

different gases absorb different parts of Sun’s energy spectrum. Absorbed energy is converted to heat within atmosphere.

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18
Q

Behavior of water:

A

water can exist in the atmosphere in 3 phases. Phase transformation involves latent heat.

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19
Q

Water Vapor varies between __%-__%.

A

varies between 0.3%-4.0%. Typically quoted as partial pressures. (Dalton’s Law of partial pressures)

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20
Q

Saturation Pressure:

A

dry air in contact with water or ice. Partial pressure of VP increases

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21
Q

When evaporation and condensation are balanced:

A

air is saturated, VP=SVP

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22
Q

Relative Humidity (RH):

A

RH = (VP/SVP) * 100%. Dew point.

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23
Q

RH changes when:

A

water vapour amount or temperature changes

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24
Q

Adiabatic temperature change AKA

A

Adiabatic lapse rates

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25
Q

Adiabatic temperature change

A

as air masses rise, pressure falls and expansion occurs. Temperature decreases at -1C per 100m

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26
Q

Adiabatic cooling of rising air causes condensation

A

condensation releases latent heat energy. Offsets adiabatic cooling.

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27
Q

Total energy of atmosphere is …

A

approx constant. Energy is continuously redistributed through circulation (atmospheric and oceanic)

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28
Q

Atmospheric circulation

A

As air is intensely heated near equator: expansion generates a region of low pressure. Air tends to rise because of its buoyancy. Creates pressure-gradient flow. High P regions to low P regions.

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29
Q

Temperature varies dramatically with …

A

with location and elevation; affects pressure. Significant for weather studies, aviation.

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30
Q

Isobars

A

contours of air pressure

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31
Q

Geostrophic flow:

A

rotating earth, pressure gradient flow is modified by the coriolis effect.

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32
Q

When flow is parallel to isobars:

A

pressure gradient is exactly balanced by Coriolis effect, flow is straight (geostrophic flow)

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33
Q

Near-surface flow

A

Air flow near surface is not exactly geostrophic due to friction.

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34
Q

Distribution of high and low pressure

A

ITCZ, sub-tropical high, subpolar low, converging tropical and polar air masses meet at polar front, polar high.

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35
Q

ITCZ =

A

Inter tropical convergence zone.

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36
Q

Air masses control…

A

control weather conditions. Up to 2000 km wide.

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37
Q

Air masses characterized by:

A

temperature, specific humidity, origin (M or C)

38
Q

Define air fronts

A

they mark boundaries between air masses

39
Q

air masses do not…

A

merge well

40
Q

warm - cold contact

A

High speed winds, strong T and P changes –> jet stream

41
Q

Frontal Zone Classification

A

depends mainly on the direction of air mass movement. Contact region is usually inclined

42
Q

Front types:

A

cold, warm, stationary, occluded

43
Q

Warm Front:

A

warm air advances on cold, warm air mass flows over cold

44
Q

Cold Front:

A

Cold air advances on warm, cold air mass flows under warm

45
Q

Stationary Front:

A

a front that is not moving

46
Q

Occluded Front:

A

when a cold front overtakes a warm front

47
Q

Wind speed and direction:

A

direction wind comes from, typical wind speeds average 10-30 kmh.

48
Q

Wind speed indicators: half notch

A

8 kmh, 5 knots

49
Q

Wind speed indicators: full notch

A

16 kmh, 10 knots

50
Q

Wind speed indicators: triangular wedge

A

80 kmh, 50 knots

51
Q

Wind chill

A

skin cools faster in moving air, boundary layer of very slow moving air acts as an insulator.

52
Q

Wind chill equivalent temperature:

A

windchill factor

53
Q

Factors controlling wind speed and direction:

A

pressure gradient, coriolis effect, friction, topography

54
Q

Cyclones:

A

large (500-2000km wide) wheels of air.

55
Q

Cyclones: pressure info

A

Have LOW pressure centre, wind crosses pressure isobars at an angle into the low. Net inflow of air.

56
Q

Cyclones may:

A

contain clouds and ppte, possibly high winds.

57
Q

Cyclones rotate

A

anticlockwise (in the N.H.) around surface LOW pressure centre

58
Q

Anticyclones rotate

A

clockwise (in the N.H.) around surface HIGH pressure centre.

59
Q

Anticyclones: pressure info

A

wind crosses pressure isobars at an angle, net outflow of air.

60
Q

Anticyclones may:

A

contain clearing and little cloud development or ppte.

61
Q

Global wind patterns:

A

trade winds, westerlies, monsoons

62
Q

Regional to local:

A

breezes, katabatic winds, adiabatic winds

63
Q

Tradewinds:

A

easterlies, reliable rarely shift direction

64
Q

ITCZ:

A

(intertropical convergence zone), air moves upwards creating: clouds and rain and tropical forests. Double band of clouds, Doldrums.

65
Q

Doldrums are:

A

equatorial regions of light ocean currents and winds within the intertropical convergence zone

66
Q

Westerlies:

A

in the temperate zone (mid-latitude). Migrating, rotating cyclones. More fickle than the reliable easterly winds. Often controlled by the jetstream.

67
Q

Monsoons winds

A

seasonal migration of pressure belts reverses wind direction. Affect India, Australia, W. Africa. Migration of the ITCZ.

68
Q

Basic causes of cloud formation

A

density differences, frontal confrontation, large scale obstacles, convergence.

69
Q

Cloud development:

A

lifting of air relating to pressure temperature and SVP drops.

70
Q

Clouds occur when–

A

RH increases until 100%, condensation: nucleation of tiny water droplets. Droplets increase size by collision and recirculation in the system by updrafts.

71
Q

Cloud classification based on:

A

shape, altitude or position, vertical development. Amount of possible rain, snow or hail, causal origin.

72
Q

Cloud types:

A

cirrus clouds (>6km), Stratus clouds, cumulus clouds, Altus clouds (2-6km), Nimbus clouds.

73
Q

Severe storms

A

:name given to a weather system that may be an immediate threat to life or property.

74
Q

Snow and freezing rain

A

raindrops also form from melting snowflakes, supercooled liquid raindrops may freeze when falling on a cold surface.

75
Q

Ice:

A

cloud droplets condense on condensation nuclei

76
Q

If T

A

form supercooled cloud droplets

77
Q

If T

A

form ice crystals on ice nuclei

78
Q

Hail:

A

raindrops fallings into air colder than 0C may freeze into ice pellets. Ice pellets that are > 5 mm are called hail stones

79
Q

Thunderstorms:

A

Moist, unstable vertically lifted air masses. Common olong cold fronts where mT meets cP

80
Q

Condensation & latent heat

A

latent heat

81
Q

Air mass thunderstorm:

A

(Local Thunderstorm): most common, often single cell, width=height (10km), duration (60min), occur when wind changes with height are small

82
Q

Organized thunderstorm:

A

rotating supercell or several multicells. Often associated with mid-latitude cyclone cold fronts, well established anvil. Duration (2-6hrs) Wind changes with height are large.

83
Q

Lightning, upper portion:

A

mainly positively charged

84
Q

Lightning, lower portionL

A

mainly negatively charged

85
Q

Electric sparks:

A

charge accumulations > insulation ability of air

86
Q

Tornadoes - waterspouts

A

grey, rotating funnels extending from stormbase downwards. Often small, usually visible for only a few minutes. Can leave a large swath of destruction. Classification based on Fujita Scale

87
Q

Hurricanes

A

Tropical cyclones, winds are > 32.6m/s. Name based on where it formed. Classified on Saffir-Simpson scale

88
Q

Anatomy of a hurricane

A

About 500-1000km wide and last about 7-10 days. Sinking motion in the inner eye (20-40km diam) Low pressure centre. Rising motion and strong winds in the eyewall region.

89
Q

Adiabatic winds:

A

winds moving up a slope

90
Q

Katabatic winds:

A

winds moving down a slope

EAS 201 (11 decks)

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