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Physical Georgaphy AS > Atmosphere + Weather > Flashcards

Atmosphere + Weather Flashcards

1
Q

(2.1) What is an energy budget?

A
  • refers to the amount of energy entering a system, the amount leaving the system + the transfer of energy within the system
  • commonly considered at a global scale (macro-scale) + local scale (micro-scale)
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2
Q

(2.1) What does microclimate mean?

A

A term sometimes used to describe regional climates - e.g. those associated with large urban areas, coastal areas + mountainous regions

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3
Q

(2.1) What are the components of a daytime budget?

A
  • incoming (shortwave) solar radiation
  • reflected solar radiation
  • surface absorption
  • sensible heat transfer
  • long-wave radiation
  • latent heat (evaporation + condensation)
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4
Q

(2.1) How to express the earth’s surfaces gain of energy?

A

Energy available at surface = incoming solar radiation - (reflected solar radiation + surface absorption + sensible heat transfer + long-wave radiation + latent heat transfer)

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5
Q

(2.1) What components does the night time budget consist of?

A
  • long-wave radiation
  • latent heat transfer
  • absorbed energy returned to earth
  • sensible heat transfer
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6
Q

(2.1) What affects incoming (SW) solar radiation?

A
  • latitude
  • season
  • cloud coverage
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7
Q

(2.1) How do clouds affect incoming solar radiation?

A
  • the less cloud coverage there is, and/or the higher the cloud -> the more radiation reaches the earth’s surface
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8
Q

(2.1) What is albedo?

A
  • the proportion of energy that is reflected back to the atmosphere
  • albedo varies with colour - light materials are more reflective than dark materials
  • grass has an average albedo of 20-30% - so it reflects back 20-30% of the radiation it receives
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9
Q

(2.1) What is surface absorption *

A
  • energy that reaches the earths surface has the potential to heat it
  • much depends on the nature of the surface
  • the heat transferred to the soil + bedrock during the day may be released back to the surface at night - partly offsetting the night-time cooling at the surface
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10
Q

(2.1) What is sensible heat transfer?

A
  • refers to the movement of parcels of air into + out of the area being studied
  • e.g. air that is warmed by the surface may begin to rise (convection) + be replaced by cooler air = convection transfer —> very common in warm areas in early afternoon
  • it is also part of the night time budget - cold air moving into an area may reduce temps - whereas warm air may supply energy + raise temps.
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11
Q

(2.1) What is long wave radiation?

A
  • the radiation of energy from the earth (a cold body) into the atmosphere + some of it eventually into space
  • however there is a downward movement of long wave radiation from particles in the atmosphere
  • the difference between the two flows is the net long-wave balance
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12
Q

(2.1) Explain net long wave radiation

A
  • during the day - outgoing long wave radiation transfer is greater than the incoming long wave radiation transfer = net loss of energy from surface
  • during cloudless night (common in deserts) - little return of long wave radiation from the atmosphere due to lack of clouds = net loss of energy from surface
  • cloudy night - clouds return some long wave radiation to the surface = overall loss of energy reduced
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13
Q

(2.1) What is latent heat transfer?

A
  • when liquid water is turned to water vapour, heat energy is used up
  • when water vapour becomes a liquid, heat is released
  • therefore when water is present at a surface, a proportion of the energy available will be used to evaporate it + less energy will be available to raise local energy levels + temp.
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14
Q

(2.1) Latent heat transfer at night

A
  • during night - water vapour in the air close to the surface condenses to form water (cuz air has been cooled by surface)
  • water condenses = latent heat released
  • this affects the cooling process at the surface
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15
Q

(2.1) What is dew + when does it occur?

A
  • condensation on a surface
  • the air is saturated because the temperature of the surface has dropped enough to cause condensation
  • occasionally condensation occurs because more moisture is introduced - e.g. sea breeze - while the temp. remains constant
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16
Q

(2.1) What happens to absorbed energy back into the earth?

A
  • insulation received by the earth will be reradiated as long wave radiation
  • some of this will be absorbed by water vapour + other greenhouse gases
  • thereby raising temperatures
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17
Q

2.1 Why do surface temperatures change?

A
  • during the day - the ground heats the air by radiation, conduction + convection
  • the ground radiates energy + as the air receives more radiation than it emits, the air is warmed
  • air close to the ground is also warmed through conduction - air movement at the surface is slower due to friction with the surface so there is more time for it be heated
  • the combined effect of radiation + conduction makes the air warmer + makes it rises due to convection
  • at night - the ground is cooled as a result of radiation
  • heat is transferred from the air to the ground
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18
Q

(2.2) What can incoming solar radiation be referred to as?

A

Insolation

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19
Q

(2.2) what is convection?

A

Transfer of heat by the movement of a gas or liquid

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20
Q

(2.2) what is conduction?

A

The transfer of heat by contact

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21
Q

(2.2) How much insolation gets absorbed by the Earth’s surface?

A
  • only 46%

because…
- 19% is absorbed by atmospheric gases
- 23% is reflected by clouds + water droplets
- 8% is reflected by atmosphere
- 6% reflected by earth’s surface

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22
Q

(2.2) how much energy received by Earth is re-radiated?

A
  • 8% reflected by atmosphere
  • 14% re-radiated as long wave
  • 22% of latent heat transfer (evaporation + condensation)

= 32%

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23
Q

(2.2) What causes an energy imbalance?

A
  • an excess of radiation (positive budget) in the tropics
  • a deficit of radiation (negative balance) at higher latitudes
  • neither of these regions are getting hotter or colder so energy transfers equalise this energy imbalance
  • this results in a second energy budget in the atmosphere —> horizontal transfer between low latitudes + high latitudes to compensate for differences in global insolation
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24
Q

Latitudes diagram

A
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25
Q

Energy budget diagram

A
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26
Q

How is heat transferred?

A
  • ocean currents —> warm ocean currents move heat from the tropics to the poles + cold ocean currents work in the opposite direction
  • trade winds —> transfer large amounts of heat from the tropics to the poles
  • storms —> tropical cyclones transfer large amounts of heat energy from the tropics to the subtropics + temperate zones
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27
Q

(2.2) what are wind belts?

A
  • air blows from high pressure (over 1013 mb) to low pressure (below 1013mb) + redistributes heat around the earth - sensible heat transfer
  • winds between tropics converge on inter tropical convergence zones
  • winds blow inwards + rise (forming low pressure) —> rising air stimulates latent heat, causing convection
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28
Q

(2.2) What are annual temperature patterns

A
  • January = highest temps over land (above 30°c) found in Australia + Southern Africa, lowest temps (below -40) are found over Siberia, Greenland + Canadian artic
  • July = maximum temp found over the Sahara, Near East, northern India, southern USA + Mexico
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29
Q

(2.2) what causes annual temperature patterns?

A
  • there is little season variation at the equator
  • but in mid or high latitudes - larger seasonal variation occurs due to decrease in insolation from the equator to the poles
  • there is also a time lag between overhead sun + period of maximum insolation - because the air is heated from below not above
  • over oceans the lag time is greater - due to differences in specific heat capacities
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30
Q

(2.2) what influences atmospheric transfer?

A
  • pressure variations —> air blows from high pressure to low pressure = redistributing heat globally
  • ocean currents —> warm currents raise the temp of overlying air, cold currents cool the air above
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31
Q

What do pressure variations imply?

A
  • Decline in pressure indicates poorer weather
  • rising pressure means better weather
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32
Q

What is surface pressure?

A
  • low pressure in equatorial regions, as warm air rises + leaves the surface
  • warm air spreads + gets denser + cooler = sinks
  • higher pressures seen in polar regions, where cool air descends onto the surface + meets warm air from equator
33
Q

Why are surface wind belts uneven?

A
  • uneven due to seasonal variation in insolation
  • summer in the northern hemisphere causes cooling in the southern hemisphere
  • therefore increasing difference between polar + equatorial air
34
Q

(2.2) what do atmospheric transfers (winds) do?

A
  • the winds follow the tri-cellular model (Hadley, Ferrell, polar)
  • as the Hadley cell starts at the ICTZ (thermal equator) which shifts north in July, moving winds with it
  • in India this causes a reversal of winds from southerlies in July to northerlies in January
  • this causes the monsoon as southerly winds are moist from the Bay of Bengal
  • where as northerly winds came from the himalaya
35
Q

(2.2) How are ocean currents made?

A
  • created by differences in salt concentration + temperature
  • the water warms in the Gulf of Mexico + drifts north into the Atlantic - hitting the UK
  • sea ice starts to form, which is fresh water
  • this means remaining water is saltier + cleaner + sinks to the bottom, dragging more warm water under to replace it
  • this mechanism drives the current - called the Thermo-halide current
36
Q

(2.2) Land temperature distribution

A
  • low reflectivity = more absorption of radiation
  • lower specific heat capacity = set amount of energy raises land temp by more than
  • less water = less energy lost by evaporation
37
Q

(2.2) sea temperature distribution

A
  • high reflectivity = less absorption of radiation
  • sun rays penetrate deep = convection current distribute heat deeply
  • high specific heat capacity = set amount of energy raises temp by less
  • large amounts of energy used for evaporation
38
Q

(2.2) general air movements

A
  • air flows from high pressure areas to low pressure areas
  • the Coriolis effect deflects winds - air is deflected to the right in the northern hemisphere + to the left in the southern hemisphere
  • these wind patterns form the General Circulation Model
39
Q

Diagram of Coriolis effect

A
40
Q

What does the General Circulation Model show?

A
  • between the Hadley + Ferrel cells there are significant differences in air pressure
  • this creates strong, permanent waves of air about 10 km up (100-300kph) - jet streams
  • there are 2 jet streams in each hemisphere -> one between 20°-30° + one 30°-50°
  • jet streams are in waves -> e.g. Rossby waves moves around major mountain ranges - Andes, himalaya, alps etc.
41
Q

(2.2) General circulation diagram

A
42
Q

(2.2) Rossby wave diagram

A
43
Q

(2.3) atmospheric moisture states

A
  • evaporation, condensation + sublimation
  • energy is taken in (latent heat) by evaporation + released by condensation
  • hoar frost is an example of sublimation (vapour to solid)
44
Q

(2.3) Factors effecting evaporation

A
  • Initial humidity of the air —> if the air is very dry then strong evaporation occurs; if it saturated then very little occurs
  • supply of heat —> the hotter the air, the more evaporation
  • wind strength —> under calm conditions the air becomes saturated rapidly
45
Q

(2.3) factors affecting condensation

A
  • adiabatic cooling —> decrease in pressure, expand + cool
  • radiative cooling of the air
  • contact cooling of air when it rests over a cold surface
46
Q

(2.3) Characteristics of mist + fog

A
  • cloud at ground level (cloud=collection of water droplets)
  • mist occurs when visibility is between 1000m + 5000m
  • fog is thicker - occurs where visibility is below 1000m
47
Q

(2.3) why does mist/fog form at ground level?

A
  • air can only hold a certain amount of moisture
  • colder air can hold less moisture than warmer air
  • once this maximum amount of moisture is reached - air is saturated + water vapour in the air turns to liquid
  • this causes clouds to form
48
Q

(2.3) How do clouds of fog/mist form?

A
  • air must be cooled close to the ground
    —> e.g. advection fog = as warm, moist air passes over a cold surface it is chilled = condensation
    —> e.g. radiation fog = when ground loses at heat at night by long wave radiation + therefore the air above is cooled causing condensation + fog
  • more water vapour must have been added to the atmosphere close to the ground
    —> can occur over warm, wet surfaces e.g. large lakes = water is evaporated from the warm surface of the lake + condenses in the cold air above to form fog
    —> for mist or fog to form, condensation nuclei are needed (e.g. dust or salt particles) - more common in urban or coastal areas so more mist/fog occurs there
49
Q

(2.3) How does dew form?

A
  • dew is the condensation of water on a surface —> water vapour in the air has turned into water droplets on a surface
  • normally occurs because the surface is cold + has caused the air to cool + therefore become more saturated (reach dew point) + so condensation has occurred
50
Q

(2.3) What is temperature inversions?

A
  • normally air temp decreases with altitude - however there are some situations where there is a abnormal layer of warm air above the colder air in the troposphere
  • this often happens at night in calm conditions - so sometimes called nocturnal inversions
51
Q

(2.3) Why do temperature inversions occur?

A
  • during the day the ground is heated by the sun’s short wave radiation + then after a short time, it heats the air above it when it emits long wave radiation
  • at the night the ground surface + air lose the heat energy they have absorbed during the day - however the ground loses heat energy faster than air as it is more efficient conductor of heat
  • by the end of the night the ground is very cold + the air directly above it will be cool too due to close proximity to surface
  • however, the air layer above thus will still be warm as it has cooled slower than the ground surface - causing a temp inversion
52
Q

(2.3) What impact can temperature inversions have?

A
  • temp inversions will act as a lid on pollutants
  • causing them to remain in the lower atmosphere next to the earth’s surface
53
Q

(2.3) What is a sea breeze?

A
  • on a warm summer day along the coast, the differential heating of land + sea leads to the development of local winds = sea breeze
  • the land is heated quicker than the sea + so the air above the land is warmer than the air above the sea during the day
  • as air above is heated by radiation from the sun it expands + begins to rise, being lighter then the surrounding air
  • to replace the rising air, cooler air is drawn in from above the surface of the sea - this is a sea breeze
54
Q

(2.3) What is land breeze?

A
  • occurs at night when the land cools faster then the sea
  • this creates a situation which is the opposite to day time - air above the sea is warmer than air above land
  • the warmer air above the sea rise + expands - pulling in air from the cooler land surface
55
Q

(2.3) how do clouds form?

A
  • air rises + cools (adiabatic cooling)
  • humidity increases to 100% + saturation occurs
  • air which is still warmer than the surrounding air will continue to rise —> creating to tall (thunder) clouds - this air is unstable
56
Q

(2.3) what are the types of clouds?

A
  • cumulo = heaped
  • nimbus = rain
  • strato = layer
  • alto = high
  • cirrus = highest
57
Q

(2.3) what is classed as precipitation?

A
  • rain
  • dew
  • hail
  • fog
  • snow
58
Q

(2.3) how does rain form?

A
  • condensation occurs due to cooling onto condensation nuclei’s (or ground dew)
  • droplets grow in size until heavy enough to fall through rising air
59
Q

(2.3) why does precipitation vary?

A
  • heat
  • initial moisture
  • atmospheric temperature
    (These all effect condensation)
60
Q

(2.3) what is the Bergeron theory?

A
  • all rain + snow form in clouds with temps below 0°C (often -40°C)
  • snow will often melt as it falls to form rain
61
Q

(2.3) how do thunderstorms form?

A
  • as clouds form, latent heat released causes further uplift
  • pulled air brings more moisture
  • different movements of air generate static energy
62
Q

(2.3) how does hail form?

A
  • rain forms updraughts preventing it falling so it freezes to form hail
  • if updraughts continue, hail will grow
63
Q

(2.3) how does snow form?

A
  • water vapour sublimates to create crystals
  • mostly air so very light
64
Q

(2.3) when does heaviest snowfall occur?

A
  • when warm, moist air is forced over mountains
  • or warm moist air is forced to mix with cold air on a front
  • rapidly cooling in both cases
65
Q

(2.3) which season is fog common?

A
  • summer + winter due to high pressure conditions (clear skies)
  • clear skies allows cooling of ground to be rapid at night + cools air above
66
Q

(2.3) why does fog disperse as sun rises?

A

temp rises + reabsorbs moisute into air as humidity falls

67
Q

(2.3) what is smog?

A
  • inversion traps pollution in the lower layer
  • where it mixes with fog to form smog
68
Q

(2.3) what are the types of rainfall?

A
  • frontal rain
  • orographic rain
  • conventional rain
69
Q

(2.3) what is frontal rain?

A
  • when cold air meets warm air in a ‘weather front’
  • warm air rises so bumps into the cold air + rises above it
  • the warm air gets cooler as it rises + the water vapour condenses into water
  • this forms a cloud + eventually falls as raindrops
70
Q

(2.3) What is orographic rain?

A
  • when wind pushes air towards a hill + forces it upwards
  • when it reaches the top of the hill it cools down
  • if it has enough moisture, the water vapour will condense into water to form a cloud + eventually fall as raindrops
71
Q

(2.3) what is conventional rain?

A
  • when the sun shines on the ground + heats a shallow layer of air close to it
  • this is air now warmer than the surrounding air, so it rises up into the atmosphere
  • warm air gets cooler as it rises up higher
  • as a result the water vapour condenses into water, forms a cloud + eventually falls as raindrops
72
Q

(2.3) what is conventional rain also known as?

A
  • showers - produces smaller areas of rainfall
  • they are much smaller + more unpredictable because the ground surface varies
  • this means the air close to the ground is heated at different rates - which is why showers can pop up anywhere + be blown around in different directions by the wind
  • tarmac (a darker surface) will heat air more quickly than grass (lighter surface) or water (lake)
73
Q

(2.4) how do urban areas affect their climate?

A
  • anthropogenic heat (people), pollution, cars, acid rain, impermeable surfaces, heat capacity of buildings, reflection etc.
  • in general they increase temperature + can increase rainfall
  • the effect is know as the urban heat island
74
Q

Urban heat island diagram

A
75
Q

How do buildings affect climate?

A
  • heat stored by buildings + re-radiated
  • ground heated by insolation - low albedo of tarmac so less reflected
  • streets collect radiated heat
  • low humidity - lack of vegetation = less evaporation
76
Q

What is the greenhouse effect?

A
  • SW radiation passes through atmosphere
  • LW radiation trapped by clouds formed by pollution
  • small proportion absorbed by ‘green house gases’
  • an increase in the quantity of ‘greenhouse gases’ causes more energy to be trapped + an increase in global average temps
77
Q

Arguments against global warming

A

Naturally causes
- changed by variations in tilt + elipicity of our orbit
- variations in solar output
- change in ocean currents/ continental drift
- volcanic activity

78
Q

Effects of global warming?

A
  • rising sea levels - Netherlands/Bangladesh/Maldives = up to 200 million displaced by 1m rise
  • 1/20 (400 mil) threatened by floods from glacial melting
  • increase in high category hurricanes
  • change in agricultural plan
  • 400 mil at risk of drought if temps rise by 2°C

Physical Georgaphy AS (5 decks)

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