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Earth Systems > Atmosphere 1 > Flashcards

Atmosphere 1 Flashcards

1
Q

Basically, what is the atmosphere?

A
  • A collection of mostly stable gases existing to a height of 1000 km above the Earth’s surface, held together by gravity
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2
Q

What are the main gases that make up the atmosphere?

A
  1. Nitrogen (N2) - 78.1%
  2. Oxygen (O2) - 20.9%
  3. Argon (Ar) - 0.93%
  4. Neon (Ne) - 0.0018%
  5. Water vapour (H2O) - 0.5 - 4%
  6. Carbon dioxide (CO2) - 0.04%
  7. Helium (He) - 0.0005%
  8. Methane (CH4) - 0.00017%
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3
Q

What is the difference between the Ancient atmosphere and today’s atmosphere?

A

Ancient Atmosphere:
- 4.5 to 3 billion years ago
- Rich in CO2, H2O and depleted in N2 and O2
Today’s Atmosphere:
- billion years ago to today
- Depleted in CO2, H2O and rich in N2 and O2

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4
Q

What would have caused the changes to atmospheric gas concentrations over time?

A
  1. Decrease in H2O
  2. Decrease in CO2
  3. Increase in O2
  4. Increase in N2
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5
Q

What would have caused a decrease in H2O in the ancient atmosphere?

A
  • Water condenses

* Oceans start filling up

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6
Q

What would have caused a decrease in CO2 in the ancient atmosphere?

A
  • Oceans absorb CO2

* Plants start photosynthesising

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7
Q

What would have caused an increase in O2 in the ancient atmosphere?

A
  • Plants on the scene

* Lithosphere saturated in O2 – banded iron formation (pic)

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8
Q

What would have caused an increase in N2 in the ancient atmosphere?

A

• Light, relatively abundant, unreactive and simply left behind

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9
Q

What are State Variables?

A

Variables that define the state of the atmosphere:
• Temperature
• Pressure
• Density

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10
Q

What is temperature?

A
  • Temperature is the concentration of heat in a body, measured according to an arbitrary scale such as the Celsius or Kelvin scales
    • Symbol: T
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11
Q

What is pressure?

A
  • Pressure is the force exerted per unit area of any real or imaginary surface because of bombardment by molecules of contiguous fluid (the air in this case).
    • Symbol: p
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12
Q

What is the SI unit for Temperature and how do you convert it?

A
  • unit: Kelvin scale in K Celsius scale in Deg C
  • temperature in K equals temperature in Deg C + 273. In particular, 0 Deg C = 273 K.
  • Global mean temperature at the sea-level is 15 Deg C
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13
Q

What is the SI unit for Pressure and how do you convert it?

A
  • Unit: Pascal or Pa
  • 1 Pascal = 1 Newton m-2
  • 1 hectopascals = 100 Pascals
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14
Q

What does 1 standard atmospheric pressure equal Pa, hPa and mbar?

A

= 101,325 Pa
= 1013.25 hPa (hectopascals)
= 1013.25 mbar (millibars)

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15
Q

What is Density?

A

Density is the mass concentration expressed as mass per unit volume.
• Symbol: p (Greek symbol, not the English letter “p”), pronounced as ‘rho’

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16
Q

What is the SI unit for density?

A
  • Unit: kg m-3

* For T = 15 Deg C, p (symbol for pressure) = 1013.25 hPa, the average density of the dry air is 1.22 kg m-3.

17
Q

What is the Equation of State?

A
  • The relationship between temperature, pressure and volume is governed by the ideal gas law, which is also known as the equation of state.
18
Q

What does the Equation of State look like?

A 
pV = nRT
Where:
p = pressure
V = Volume
n = Mass
R = Constant
T = Temperature
19
Q

What happens to the Equation of State when working with the atmosphere?

A

For the atmosphere, we normally modify the equation slightly to:
p = RdpT
Where:
p = pressure in Pa
p (the greek symbol for density, appearing after the equals in the equation) = density in Kg m^-3
T = Temperature in Kelvin
Rd = The gas constant for dry air, which has a numerical value of 287 J K^-1 Kg^-1

20
Q

What is Hydrostatic Pressure?

A
  • Pressure that is exerted by the air at equilibrium at a given location due to gravity
21
Q

What happens to the Hydrostatic Pressure in the Atmosphere?

A

For the hydrostatic pressure of the atmosphere:
• pressure decreases with height
• the rate of decrease in pressure also decreases with height since the air density decreases.

22
Q

What happens to temperature as you get higher into the atmosphere?

A

The temperature will decrease linearly as you get higher into the atmosphere.

23
Q

What is The Lapse Rate?

A
  • The rate of decrease is known as the lapse rate.
    • The lapse rate measures the rate of change in temperature in the vertical direction, and has a typical value of 6.5 Deg C km-1
24
Q

What are the key things to look for as you go up in altitude?

A
  • Lower pressure
  • Lower Temperature
  • Lower density
25
Q

Why is Water Vapour in the Atmosphere important?

A
  • Essential to the formation of precipitation
  • The energy involved in raising water from the surface and returning it back to the ground – the latent heat of vaporisation – is an important energy pathway in the atmosphere
  • It contributes to the greenhouse effect – water vapour is a powerful greenhouse gas
26
Q

What is Relative Humidity?

A

The ratio of the amount of water vapour in the air compared to the maximum amount of water vapour required for saturation at that particular temperature

27
Q

What is the equation for Relative Humidity?

A
  • Since the amount of water vapour is directly proportional to the vapour pressure, the relative humidity is commonly defined as:
  • Rh = vapour pressure/saturation vapour pressure
    or: e/es
28
Q

Does an air column with 50% relative humidity at 20 Deg C have more moisture that an air column with 50% relative humidity at 35 Deg C?

A

No, it will have less moisture because “humidity” is the amount of water in the air, therefore, if the temperature is higher there will be more moisture in the 35 deg c.

29
Q

What is the Dew Point?

A
  • Dew-point temperature (or dew-point for short), Td , is the temperature to which air would have to be cooled for saturation to occur. It tells us the actual water vapour content.
30
Q

What is the difference between the Dew point and the Relative Humidity?

A
  • Dew-point is a good measure of the level of moisture in the air, while the relative humidity is not
31
Q

What happens to the relative humidity when the temperature increases?

A

When the temperature increases it warms the air particles and therefore increases the amount of space in the atmosphere for water. This means that as the temperature increases the relative humidity goes down.

32
Q

What happens to the relative humidity when the temperature decreases?

A

When the temperature decreases the amount of heat and energy in the air particles decreases and therefore there is less space between them. This means that the water molecules have less room and hence, eventually the water will condense and turn into precipitation. The point at which all the space is gone and the relative humidity is 100% is the Dew point.

Earth Systems (13 decks)

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