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)
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
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)
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)
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
6
Q
(2.1) What affects incoming (SW) solar radiation?
A
- latitude
- season
- cloud coverage
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
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
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
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.
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
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
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.
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
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
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
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
18
Q
(2.2) What can incoming solar radiation be referred to as?
A
Insolation
19
Q
(2.2) what is convection?
A
Transfer of heat by the movement of a gas or liquid
20
Q
(2.2) what is conduction?
A
The transfer of heat by contact
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
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%
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
24
Q
Latitudes diagram
A
25
Energy budget diagram
26
How is heat transferred?
- 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
27
(2.2) what are wind belts?
- 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
28
(2.2) What are annual temperature patterns
- 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
29
(2.2) what causes annual temperature patterns?
- 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
30
(2.2) what influences atmospheric transfer?
- 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
31
What do pressure variations imply?
- Decline in pressure indicates poorer weather
- rising pressure means better weather
32
What is surface pressure?
- 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
Why are surface wind belts uneven?
- 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
(2.2) what do atmospheric transfers (winds) do?
- 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
(2.2) How are ocean currents made?
- 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
(2.2) Land temperature distribution
- 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
(2.2) sea temperature distribution
- 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
(2.2) general air movements
- 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
Diagram of Coriolis effect
40
What does the General Circulation Model show?
- 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
(2.2) General circulation diagram
42
(2.2) Rossby wave diagram
43
(2.3) atmospheric moisture states
- 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
(2.3) Factors effecting evaporation
- 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
(2.3) factors affecting condensation
- adiabatic cooling —> decrease in pressure, expand + cool
- radiative cooling of the air
- contact cooling of air when it rests over a cold surface
46
(2.3) Characteristics of mist + fog
- 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
(2.3) why does mist/fog form at ground level?
- 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
(2.3) How do clouds of fog/mist form?
- **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
(2.3) How does dew form?
- 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
(2.3) What is temperature inversions?
- 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
(2.3) Why do temperature inversions occur?
- 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
(2.3) What impact can temperature inversions have?
- temp inversions will act as a lid on pollutants
- causing them to remain in the lower atmosphere next to the earth’s surface
53
(2.3) What is a sea breeze?
- 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
(2.3) What is land breeze?
- 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
(2.3) how do clouds form?
- 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
(2.3) what are the types of clouds?
- cumulo = heaped
- nimbus = rain
- strato = layer
- alto = high
- cirrus = highest
57
(2.3) what is classed as precipitation?
- rain
- dew
- hail
- fog
- snow
58
(2.3) how does rain form?
- 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
(2.3) why does precipitation vary?
- heat
- initial moisture
- atmospheric temperature
(These all effect condensation)
60
(2.3) what is the Bergeron theory?
- 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
(2.3) how do thunderstorms form?
- as clouds form, latent heat released causes further uplift
- pulled air brings more moisture
- different movements of air generate static energy
62
(2.3) how does hail form?
- rain forms updraughts preventing it falling so it freezes to form hail
- if updraughts continue, hail will grow
63
(2.3) how does snow form?
- water vapour sublimates to create crystals
- mostly air so very light
64
(2.3) when does heaviest snowfall occur?
- 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
(2.3) which season is fog common?
- summer + winter due to high pressure conditions (clear skies)
- clear skies allows cooling of ground to be rapid at night + cools air above
66
(2.3) why does fog disperse as sun rises?
temp rises + reabsorbs moisute into air as humidity falls
67
(2.3) what is smog?
- inversion traps pollution in the lower layer
- where it mixes with fog to form smog
68
(2.3) what are the types of rainfall?
- frontal rain
- orographic rain
- conventional rain
69
(2.3) what is frontal rain?
- 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
(2.3) What is orographic rain?
- 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
(2.3) what is conventional rain?
- 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
(2.3) what is conventional rain also known as?
- 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
(2.4) how do urban areas affect their climate?
- 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
Urban heat island diagram
75
How do buildings affect climate?
- 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
What is the greenhouse effect?
- 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
Arguments against global warming
Naturally causes
- changed by variations in tilt + elipicity of our orbit
- variations in solar output
- change in ocean currents/ continental drift
- volcanic activity
78
Effects of global warming?
- 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
