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Earth Systems > Atmosphere 2 > Flashcards

Atmosphere 2 Flashcards

1
Q

What is Adiabatic Cooling?

A
  • Decrease in temperature of a parcel of air caused by a pressure decrease and volume increases exerted on the parcel.
  • Importantly, cooling is not achieved by conduction or any mechanism other than the pressure/volume change, so overall, no heat is lost/gained by the system
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2
Q

What is the Dry Adiabatic Lapse rate?

A

When the temperature decreases by about 10 Deg C for every 1 km you go up

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3
Q

What is the Saturated Adiabatic Lapse rate?

A

If the air is moist it cools a bit slower, about 6 DegC every km

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4
Q

What happens to the air with increasing altitude?

A

Air gets cooler and thinner (lower pressure) with increasing altitude.

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5
Q

If you are at the base of a mountain and the temperature is 25 Deg C, what will the temperature be at the top of the mountain which is 3000 m above you? (assume dry adiabatic lapse rate)

A

Temperature decreases by 10 Deg C every 1km up, so here it will drop from 25 Deg C to 25 Deg C – (3 x 10 Deg C) = – 5 Deg C

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6
Q

The temperature at the base of a cloud 2000 m above you is -5 Deg C. What is the temperature where you are? (assume saturated adiabatic lapse rate)

A

The temperature increases by 6oC every km you descend, so here it will go up from – 5 Deg C to – 5 Deg C + (2 x 6) = 7 Deg C.

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7
Q

What happens to a parcel or pocket of air that has been moved to a new altitude?

A

It will cool or heat following the adiabatic lapse rates -> it doesn’t have time to conduct/transmit heat.

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8
Q

What is an Environmental Lapse Rate?

A
  • Temperature profiles for a given location have time to conduct/transmit heat and depend on many local factors (including terrain, vegetation, humidity).
  • So most locations have their own unique heating and cooling profiles = ENVIRONMENTAL LAPSE RATES
  • The rate at which the air temperature changes with height in the atmosphere surrounding a cloud or a rising parcel of air
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9
Q

What determines the atmospheric stability?

A
  • Imagine a parcel of air is moved between different altitudes (via wind, volcanic eruption, bird burp etc.)
  • How that pocket of newly moved air behaves relative to the Environmental Lapse Rate determines whether we get stable/still or unstable/dispersive conditions.
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10
Q

What happens when the Environmental Lapse rate is larger than the Adiabatic Lapse rate?

A
  • Unstable conditions
  • A parcel of air cools slower than surrounding air. At increasing altitude the parcel is always warmer than surrounding air so keeps rising - ELR > ALR
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11
Q

What happens when the Environmental Lapse rate is smaller than the Adiabatic Lapse rate?

A
  • Stable conditions
  • A parcel of air cools faster than surrounding air. At increasing altitude the parcel is always cooler than surrounding air so it sinks back down - ELR < ALR
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12
Q

What is Temperature inversion?

A

A reversal of the normal behaviour of temperature in the troposphere, in which a layer of cool air at the surface is overlain by a layer of warmer air. (Under normal conditions air temperature usually decreases with height.)

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13
Q

What would a temperature inversion look like on a ELR vs ALR chart?

A
  • On really cold nights, air above ground conducts radiation from the day, becomes hotter and the inverse of a normal temperature profile results. An extremely stable profile develops. - ELR «&laquo_space;ALR
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14
Q

What is meant by “Neutral Conditions” in a ELR vs ALR chart?

A

When a parcel of air cools at exactly the same rate as surrounding air. Stays where it is. - ELR = ALR

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15
Q

At sea level (0 m), the air temperature is 10oC. A parcel of air is lifted from 0 m to 600 m above sea level. If the local Environmental Lapse Rate is 4 Deg C per km, will the parcel rise, sink or fall at its new height? (assume the parcel follows the dry lapse rate)

A
  • Step 1 : let’s calculate what the ambient temp will be at 600 m using the ELR: 10 Deg C – (4 x 0.6), which = 7.6 Deg C
  • Step 2: let’s calculate what the air parcel temp will be at 600 m using the ALR: 10 Deg C – (10x 0.6), which = 4 Deg C
  • Step 3: So, the air parcel temperature is lower than the surrounding air temperature so the parcel will sink
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16
Q

Why is the stability of air important?

A

The stability of air is a critical factor in determining how smoke plumes and air pollutants behave

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17
Q

What are four important air pollutants?

A
  • Particulates (from fires, fuel combustion)
  • Sulfur dioxides (from burning coal)
  • Nitrogen dioxides (from motor vehicles)
  • Volatile organic compounds (from fuel combustion)
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18
Q

What pollution movements causes unstable air conditions?

A
  • Rapid mixing into air

* Pollutants dispersed quickly

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19
Q

What pollution movements causes stable air conditions?

A
  • Pollution descends to ground

* In extreme conditions, a temperature inversion exists

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20
Q

What pollution movement causes neutral air conditions?

A

Pollution goes laterally, vertical movement depends on terrain

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21
Q

How would you find the amount of moisture in a pocket of air on a es vs T graph, when only given the Dew point temperature.

A
  • The es vs T graph has a blue, curved line running through it and hence you need only line up the given temperature to the line and then where ever that point is on the y-axis is the amount of moisture in the pocket.
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22
Q

Why does air move?

A

The fundamental reason that the air in our atmosphere moves is due to temperature gradients between the equator and the poles.

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23
Q

What form of heat do we get from the sun?

A
  • Radiation

- The radiation is absorbed by clouds, atmospheric gases and the Earths surface

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24
Q

Why do some parts of the Earth receive more heat radiation than others?

A
  • This is mainly due to the curvature of the Earth
  • This curvature means that at higher latitudes, the radiation from the sun is spread over a much larger surface area, while the same amount of energy is much more concentrated near the equator.
25
Q

Why do the poles not get as much heat as the equator?

A
  • Due to the curvature of the Earth and because the radiation has to travel through a greater depth of atmosphere nearer the poles, in comparison to the equator
  • Therefore, more radiation is lost to scattering and absorption to gases and particles in the atmosphere
26
Q

Why do the polar regions not get sunlight for certain parts of the year?

A
  • The tilt of the Earth means that the polar regions do not see daylight during the winter
  • This means that in these regions, during winter, the Earth is continuously sending out heat to space without any compensating heat from the sun
27
Q

Why is snow and ice important?

A
  • Snow, ice and thick clouds reflect a lot of the sun’s radiation back into space
28
Q

What does “ Albedo” mean?

A
  • The reflectivity of the underlying surface of ice or snow, which is an important factor in determining how much of the sun’s radiation is used for heating the Earth.
29
Q

What does the combined work of ice/snow albedo, dark winters in the polar regions, the curvature of the Earth and atmospheric absorption of radiation have to do with the temperature gradient?

A
  • The combined effect of all these processes sets up a thermal gradient between the equator and the poles
  • In fact, the global radiation is such that poleward of 40 degrees latitude, the outgoing heat radiation from the Earth, exceeds the incoming heat radiation from the sun.
30
Q

What is Global Circulation?

A
  • An air conditioning system that redistributes the heat and stops the equator from becoming hotter and hotter and the poles from becoming colder and colder, which would inevitably lead to the earth becoming uninhabitable
31
Q

How does Global Circulation work?

A

Global Circulation takes the form of three large atmospheric cells, which exist in both the Northern and Southern hemispheres.
- Convection processes cause the hot air at the equator to rise and cold air at the poles to sink, and we get a general circulation pattern

32
Q

What effect does the Earths rotation have on Global Circulation?

A
  • The Earths rotations means we get some important additional processes affecting air movement, such as:
  • The Coriolis Effect
33
Q

What is the Coriolis effect?

A
  • An effect whereby a mass moving in a rotating system experiences a force acting perpendicular to the direction of motion and to the axis of rotation. On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather system
34
Q
  • Equator vs pole in a race around the globe, who uses more energy to move their air?
A
  • It’s a dead heat – they both take exactly the same time to get round (24 hours).
  • But the equator needs to go a lot faster to keep up
  • This is the key – air near the equator is moving much, much faster (west to east) than air at the poles
35
Q

What happens to the air moving from the equator to the north pole?

A

The air that moves from the equator to the North Pole (due to convection) is deflected to the right due to the Coriolis Effect

36
Q

What happens to the air moving from the equator to the South pole?

A

The air that moves from the equator to the South Pole (due to convection) is deflected to the left due to the Coriolis Effect

37
Q

What are the Trade winds?

A
  • Due to convection combined with Coriolis Effect we get prevailing NORTH EASTERLY winds around the Equator in the Northern Hemisphere And prevailing SOUTH EASTERLY winds around the Equator in the Southern Hemisphere, these are known as the Trade Winds
38
Q

Does the rate of deflection change as you move away from the equator?

A
  • Rate of Coriolis Effect is negligible near equator and increases exponentially as we move to the poles
  • Hence, instead of linear Coriolis Effect we get a curved pattern of increasing effect as we move away from the equator
39
Q

What happens to the convection patterns at about 30 degrees latitude?

A
  • The deflection is so strong that by about 30 degrees latitude convection patterns stop there and return back to the Equator
40
Q

What is the result of combining the Coriolis effect with the Convection Currents?

A

It results in 3 broad weather cells in both the Northern and Southern Hemisphere:

  1. Hadley Cell (Largest)
  2. Ferrel Cell
  3. Polar Cell (Smallest)
41
Q

What direction does the wind move in, in the Hadley Cell?

A
  • Low latitude air movement toward the equator that with heating, rises vertically, with poleward movement in the upper atmosphere. This forms a convection cell that dominates tropical and sub tropical climates.
  • This is where the Trade winds occur
42
Q

What direction does the wind move in, in the Ferrel Cell?

A

A mid-latitude mean atmospheric circulation cell for weather.
- In this cell the air flows poleward and eastward near the surface and equatorward and westward at higher levels. Meaning that the flow in the opposite direction the the other cells

43
Q

What direction does the wind move in, in the Polar Cell?

A
  • Air rises, diverges, and travels toward the poles. Once over the poles, the air sinks, forming the polar highs.
  • At the surface air diverges outward from the polar highs. Surface winds in the polar cell are easterly (polar easterlies).
44
Q

What gives us our Climatic Zones?

A
  • The Circulatory Cells not only transport heat from the equator to the poles, but also result in semi-permanent areas of high and low pressure due to the rising and descending parts of the circulation cells giving us our Climactic Zones.
45
Q

What causes an area of low pressure?

A
  • Where air is rising, an area of low pressure is created and so these areas see a lot of rainfall
  • This is why the largest areas of rain forest are found near the equator
46
Q

What causes an area of high pressure?

A
  • Where air is descending, an area of high pressure forms, giving largely clear skies and little rain fall which leads to the desert regions
  • However, not all deserts are hot, e.g Antarctica sits under the descending branch of the Polar Cell and is also classes as a desert, and because it has less rainfall than the Sahara, it is the largest and driest desert overall.
47
Q

What areas does air move to?

A
  • Air always moves from areas of high pressure to low pressure, to even out the distribution of molecules
  • High pressure being areas where air particles are dense and there are a lot of them
  • Low pressure being areas where air particles are not as frequent and have space to move around
48
Q

What is the Pressure Force Gradient?

A
  • The process of air movement from high to low pressure

- Pressure gradients are important factors in controlling wind direction

49
Q

How is the Pressure Force Gradient scaled?

A

Pressure gradients are defined by ISOBARS (lines of equal pressure). The closer spaced, the faster the gradient.

50
Q

In a Pressure Force Gradient, where are the Isobars closest and most far apart?

A

The Isobars are closest at the side of Low pressure and most far apart as you get closer to the area of High pressure.

51
Q

What sort of pressure gradients develop in the Hadley Cell?

A

In the Hadley cell There are two main locations:

  • The first is near the equator where there is a low pressure because all the hot air is rising and so there is a lot of space between air particles
  • The second is near the border between the Ferrel cell and the Hadley cell. This is where there is a High pressure because all the air is cooling down and condensing.
52
Q

What effect does the Pressure Force Gradient have on the Coriolis Effect?

A
  • We have low pressure zones near the equator as air leaves a vacuum as it rises, and high pressure zones at the end of Hadley Cells where air is forced back down
  • This means that the Coriolis force and the pressure force are opposite because the Pressure gradient takes air from high to low pressure, where the Coriolis takes air from low to high
53
Q

What results from the opposition of the Pressure Force Gradient and the Coriolis Effect?

A
  • The wind direction is exactly balanced between the two forces and wind flows parallel to the isobars.
54
Q

What are Geostrophic Winds?

A
  • Air under the influence of both the pressure gradient force and Coriolis force tends to move parallel to isobars in conditions where friction is low (1000 meters above the surface of the Earth) and isobars are straight.
  • These types of patterns happen in the upper troposphere, where pressure gradients, Coriolis and gravity are the main forces at play.
55
Q

What is Frictional Force?

A
  • Near the Earth’s surface friction or resistance as air drags along the Earth
    • Friction is the opposite direction to wind direction -> it slows the Coriolis Effect on wind
56
Q

What effect does Frictional Force have on wind?

A
  • Due to friction, wind does not flow parallel to isobars in the lower troposphere but hits them at angles depending on balance between all forces as well as wind speed
57
Q

Draw a diagram of wind direction and Isobars at different levels of the Troposphere.

A

https://docs.google.com/document/d/11SlS_6djE3BGAezT2-FeVRTdxG1P1jVyj-u3X2L5qDo/edit?usp=sharing

58
Q

What are Cyclones?

A
  • Cyclones are systems of low air pressure in the middle (the eye) and high pressure on the outside
59
Q

Why do Cyclones spin in a particular direction?

A
  • With no Coriolis Effect, the high pressure air heads straight for the eye
  • But with the Coriolis Effect, the high pressure air is bent as it heads for the eye
  • Due to the Coriolis effect and Convection Currents the moving air is either deflected to the right or to the left depending on which atmosphere it is in.

Earth Systems (13 decks)

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