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Geography 308 > Module 3 Water > Flashcards

Module 3 Water Flashcards

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1
Q

How much water vapour is in the earths atmosphere?

A

Highly variable, can range from 0 to 4%

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2
Q

What are the four types of unit we use for humditity?

A

Vapour pressure (Pa / mbar)
Absolute humidity (kg/m3 or mol/m3)
Mixing ratio (kg H2O/kg dry air)
Relative humidity

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3
Q

Explain what vapour pressure means

A

is the pressure measured in Pascals or millibars exerted by water vapour (H2O gas) in the atmosphere. This is a partial pressure as in if you had a jar of air, water vapour would exert this amount of pressure.

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4
Q

Explain what absolute humidity is?

A

Is a measure how many H20 g molecules are in a volume of air, measured in kg.m^3 or mol/m^3

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5
Q

Whats a mixing ratio?

A

Describes what percentage of the air is water vapour, is kg h2O/Kg dry air

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6
Q

What’s relative humidity?

A

Is the amount of water vapor in the air over the maximum amount of water vapour that can be in the air.

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7
Q

What is virtual temperature?

A

Is a increase of temperature to account for a decrease in density when air becomes moist- allows you to get the correct density of air, the equation for this is Tv= (1+0.61r)

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8
Q

Describe latent heat of fusion

A

Is the heat (energy) that it takes for a solid to become a liquid (for ex ice to water) without changing the temperature

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9
Q

Describe latent heat of vaporisation

A

Is the energy required to do a phase change from liquid to gas without changing the temperature

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10
Q

How does water vapour contribute to global warming?

A

Water vapour allows short wave radiation to get through it but traps longwave radiation as it absorbs it, this causes global warming

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11
Q

Describe what evaporation is?

A

Is losing water molecules to the atmopshere, this due to their high energy levels which cause them to escape into the atmosphere

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12
Q

Describe condensation

A

Is when water molecules lose their and precipitate out of the atmosphere.

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13
Q

Describe net evaporation

A

Net evaporation is when more water molecules are evaporating than condensing

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14
Q

Describe saturation

A

The point at which number of water molecules evaporating is equal to the number of water molecules condensing, is when water and atmosphere are at equilibrium.

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15
Q

What is net condensation, describe a situation where you might get it

A

Is when there’s more water molecules condensing than evaporating, this could because the temperature of the air was initially high but then cooled, causing the water molecules to lose energy and ppt out of the atmosphere increasing the rate of condensation compared to evaporation.

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16
Q

What is saturation vapour pressure?

A

Is the vapor pressure of a system at equilibrium (saturation) no net movement of condensation or evaporation.

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17
Q

Describe saturation vapour pressures relationship with temperature?

A

As temperature increases saturation avpour pressure will also increase, this is because the higehr the temp the more water molecules are evaporating and consequently condensing

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18
Q

How does saturation vapour pressure over ice get affected?

A

Is lower as there’s much less water molecules escaping out of ice due to the bonds in ice being stronger.

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19
Q

What is the clausius claperyon eqn?

A

Allows you to calculate the saturation vapour pressure at any temperature.

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20
Q

What is the vapour pressure deficit?

A

Is a factor that drives evaporation. Describes how when there’s less water vapour (and pressure of that vapour) present in the atmosphere than the amount present when the system is at equilibrium (the saturation vapour pressure) evaporation will happen more and the greater the difference the greater the evaporation rate

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21
Q

How does availability of water control the net evaporation rate?

A

You can have a vapour pressure deficit in a desert, but if there’s no source of water evaporation won’t happen. You need both dry air and a place to get moisture from.

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22
Q

Can plants be a good source of water for evaporation?

A

Yes, they do transpiration- 90% of their water intake is transpired. This provide moisture to the atmosphere and contributes greatly to evaporation.

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23
Q

How does turbulence effect evaporation?

A

It can increase evaporation as if heavy winds are blowing they are more likely to pick up water molecules and replace them with dry air.

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24
Q

Where do we get the energy in order to evaporate water?

A

We get it from the sun, during times of the day we have an excess of energy (ie in the day we gain energy) which is then used to evaporate water.

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25
Q

List the four factors that control net evaporation rate

A

Vapour Pressure Deficit
Availability of water
Turbulence (mixing)
Available energy

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26
Q

Describe the difference between boiling and evaporation

A

Evaporations is water molecules turning into their gas form at the surface of the liquid, whereas boiling is water turning into vapour through the entire water volume at a specific temp

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27
Q

How is boiling point temperature determined?

A

This is the temperature when the saturation vapour pressure is equal to the atmospheric pressure, the air molecules on top of the liquid aren’t exerting a higher pressure and therefore the water molecules are not held down by it and all release into the atmopshere.

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28
Q

Does boiling point increase or decrease at higher elevations?

A

BP decreases at higher elevations because atmospheric pressure decreases at high elevations which make sit easier to be equal to it.

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29
Q

What is dewpoint temperature?

A

The temperature to which air must be cooled, at a constant pressure, to reach saturation, any further cooling beyond this point would result in net condensation

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30
Q

What is relative humidity?

A

Relative humidity reports how close the air is to saturation

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31
Q

How does relative humidity and absolute humidity fluctuate during the day?

A

Relative humidity is high during the morning, absolute humidity is high during the night. This is because the air much cooler in the morning meaning closer to saturation so relative humidity is higher. Absolute humidity is higher at night as air is warmer, so it can hold more water vapour.

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32
Q

Define vapour pressure deficit mathematically

A

Saturation vapour pressure-actual vapor pressure

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33
Q

Define dew point depression mathematically

A

Difference between air temperature and the dew-point temperature
air temp-dew point temp

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34
Q

What is psycherometry?

A

A way to measure humidity, you compare wet and dry thermometer, if a vapour pressure deficit is there evaopartion will transpire which will com off the wet thermometer reducing its temp compared to the dry one.

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35
Q

Why do humid environemnts fell hotter?

A

We feel hotter due to a gain of energy, because we can’t sweat and evaporate that sweat to cool ursleve soff in a humid enviornment and water vapour traps heat we feel hotter.

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36
Q

Whats a humidex?

A

“Humidex” which basically takes into account how effective our body’s cooling mechanism is at different temperatures.

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37
Q

If there’s net condensation what might this indicate about the air mass?

A

most processes that result in condensation involve some sort of cooling of an air mass, so this would indicate that the air mass got colder

38
Q

What is dew? Describe how its formed

A

Is condensed water droplets, it’s formed during night time as the ground cools, if the ground surface drops to temperature below the dew point temperature than dew will form

39
Q

What happens if the temperature drops very far below the dewpoint temperature?

A

The condensed water will freeze into ice

40
Q

Describe how frost is formed (on the ground)

A

This is happens when the dewpoint is below 0 and the ground cools to that dewpoint, the water vapour doesn’t condense as water but instead leaves the air as frost.

41
Q

How does condensation work in the atmosphere?

A

The atmosphere doesn’t have any surfaces for water to condense on, it should fall back onto the ground however there’s tiny surfaces called aerosols in the atmosphere which stay up in it due to the force of wind. Water vapour condenses on them.

42
Q

Why can’t water droplets condense on eachother?

A

They can but the droplet formed would be very small and wouldn’t be able to get bigger. This is due to curvature of the small water droplets, water droplets evaporate more easily off a curved surface as hydrogen bonds are harder to form on it. Because of this they are more likely to evaporate than condense on a curved surface

43
Q

Is the saturation vapour pressure higher on a curved or flat surface?

A

Curved, as curved surfaces are bad at holding H bonds.

44
Q

What relative humidity would have to be reached in order to condensate water droplets on other water droplets?

A

that for a very small droplet, relative humidity must be MUCH HIGHER than 100% to get condensation to occur, this would still, be unlikely though as at that RH the water droplets are still more likely to condense on aerosols.

45
Q

If aerosols are also particles, how do they stop the effect of curvature?

A

Aerosols are big particles usually, so they behave like a flat surface. For small aerosols, if a few water molecules condense it’ll behave like a big one as well.

46
Q

How do impurities in water affect it’s ability to evaporate?

A

It lowers the saturation vapour pressure

47
Q

Where do aerosols come from?

A

Natural sources include things like fires, volcanoes, wind erosion, sea spray, and pollution

48
Q

What are hygroscopic materials and how are they good at condensing?

A

Materials that readily bond with water, because of this water is more likely to condense on them which allows water to condense on hygroscopic aerosols much more readily.

49
Q

List some examples of hygroscopic aerosols

A

ocean is a good source of hygroscopic aerosols… Salt gets blown up into the atmosphere, also marine organisms produce a sulfur gas that breaks down into ionic compounds that are readily soluble.

50
Q

List some examples of aerosols that are good for condensing and why?

A

dust and combustion by products, good as big

51
Q

What is fog?

A

Fog is condensation that occurs in the atmosphere, near the ground.

52
Q

What is radiation fog?

A

This is produced by radiative cooling of earths surface. forms better when skies are clear (as better cooling). Need a bit of wind to blow cooing upwards, otherwise it’ll just cause dew on grass.

53
Q

What is valley fog?

A

Is a form of radiation fog, forms because air cools at high elevations which then causes air to be dens eand run down the hill in the valley- if the cold air is cold enough to reach the dewpoint temp fog occurs.

54
Q

Whats advection fog?

A

Formed when warm, moist air moves over a cold surface, causing cooling. Happens over water bodies and land- in the case of land it’s because the land cools quicker than the ocean so warm air of ocean flows over land.

55
Q

What’s upslope fog?

A

If warm air encounters something that causes it to rise, it will cool and may cause condensation. coastal areas with big mountains get this a lot.

56
Q

What’s mixing fog?

A

Is when two air masses near saturation but at different temps mix which causes condesation- this is due to the fact that it causes the new air mass to become supersaturated with water

57
Q

What are some examples of mixing fog?

A

Jet contrails (as output of jet is warm hot ai), seeing your breath, ad steam fog

58
Q

what role does Fog play in the hydrological cycle?

A

Fog drip has been estimated at >800mm for some regions. In “cloud forests” like in Peru, Costa Rica, fog drip can account for essentially ALL of precipitation.
-Some plants actually have structures that promote condensation.

59
Q

What are the five ways clouds are formed?

A

By convection, orographic lift (air up mountain), convergence (two masses of air colliding), divergence (), and frontal system (fronts meeting, with the cold below the warm causing lift)

60
Q

If the cloud has the prefix cirr, what does that indicate?

A

That it’s a high cloud

61
Q

If a cloud has the prefix alto what does that mean?

A

That it’s a medium heihght cloud

62
Q

If the cloud has no prefix what does that mean?

A

That it’s a low cloud

63
Q

If the cloud has the term cumulus in it what does that mean?

A

That it’s puffy

64
Q

If the cloud has the term stratus what does that mean?

A

The cloud is layered

65
Q

If the cloud has the term nimbus what does that mean?

A

Its a rainy cloud

66
Q

What is an adiabatic process?

A

A thermodynamic process in which temperature changes without a transfer of heat, this is due to reducing pressure which according to the gas law reduces heat.

67
Q

What is the dry adiabatic lapse rate?

A

The rate at which an unsaturated air parcel changes temperature with a change in elevation (pressure), dry refers to no condense water in it. This rate is 10 degrees per km.

68
Q

What’s the saturated adiabatic lapse rate?

A

When water vapour begins to condense it releases latent heat which slows down cooling, so saturated air parcels get colder slower and the more moisture that is in them the slower they cool. This effect reduces with higher elevation because less water vapour will exist at them (as the water will already have condensed out), the rate at which a condensing air parcel chnages temp which is about 6 degrees per km.

69
Q

What is the environmental lapse rate?

A

The actual rate of temperature change with elevation (pressure) at a given time/place.

70
Q

Why isn’t the environmental lapse rate the same as a the dry lapse rate or saturated lapse rate?

A

Because the air is affected by radiative cooling, frontal interactions and the sun.

71
Q

What does atmospheric stability refer to?

A

How stable the atmosphere will be under different conditions

72
Q

What does it mean if the atmosphere is absolutely stable?

A

If the ELR cools slower than both the DALR and SALR, this means that any rising parcel of air whether saturated or not will cool faster than the air surrounding it which means it won’t rise

73
Q

What causes a stable atmosphere?

A

Anything that causes cooling near the surface such as radiative cooling and advection will decrease the ELR

74
Q

What is subsidence?

A

Is air that sinks, causing the top of it to cool more than the bottom as it’s higher up in elevation, this causes a stable atmosphere

75
Q

What does it mean if the atmosphere is absolutely unstable?

A

If the ELR cools faster than the DALR and SALR, the atmosphere is absolutely unstable, and the air rises quickly.

76
Q

What does it mean if the atmosphere is conditionally unstable?

A

If the ELR is between the DALR and SALR, atmosphere is conditionally unstable (i.e. DALR > ELR > SALR)
here air parcel will fall back to the surface unless they reach a height in which they start condensing which then makes them unstable as they cool slower and therefore rise more.

77
Q

What causes instability in the atmosphere?

A

Surface heating and advection (in this case of cold air over a warm land surface) are pretty straightforward.
-Cloud radiation cooling is maybe less obvious.
-clouds emit a lot of radiation, and in some cases, it’s enough to cool down the upper troposphere enough to lead to instability. Also a lifting layer of air

78
Q

What does it mean if the atmopshere is neutral?

A

ELR equals SALR or DALR

79
Q

What is the lifting condensation level?

A

The lifting condensation level (LCL) is the height at which a parcel of air cools to its dew point.

80
Q

How are cloud heights measured?

A

by a laser ceiolmeter

81
Q

What are CCN’s?

A

cloud condensation nuclei, are the aerosols in the air that water vapour condense on and these are what can form clouds.

82
Q

Is there a max that cloud droplets can grow?

A

Yes, 10 micrometers

83
Q

How do cloud droplets stay aloft?

A

Due to terminal velocity, the force of gravity and the force of friction being exerted on the droplet reach equilibrium making the droplet in air have an acceleration of 0, larger droplets fall faster than smaller droplets. If the updraft velocity in the cloud exceeds it, the cloud will stay afloat. If it doesn’t it will fall.

84
Q

How do cloud droplets grow?

A

They can grow by smashing into eachother, the larger they grow the more their terminal velocity, if it exceeds the updraft the droplet will fall out as rain. Usually happens in warm clouds.

85
Q

Whats the bergeron findeisen process?

A

Is how ice crystals grow, they usually can only grow between 20 to 40 degrees below freezing anything below or above will be water or ice. As the saturation vapor pressure over ice is lower, water vapour will be attracted towards it and the ice crystals will grow using the water vapour.

86
Q

What happens when the ice crystals grow too big they start falling?

A

Gravity causes ice crystals to fall out of cloud, as they fall out of cloud they gather more water vapour though coallesence, wind will break them into smaller pieces and each of those small pieces can act as CCN, other will aggregate to form snowflakes.

87
Q

Why isn’t all precipitation that comes from the middle area f a cloud deposit as snow?

A

Because when the crystal fall they reach the warmer cloud layer where they might melt, , if atmosphere is cold enough they’ll retain form a ssnowflake, if not they will melt and turn back into raindrops.

88
Q

Whats a hydrometeors?

A

Any product of condensation or deposition of atmospheric water vapor

89
Q

What is virga?

A

When small raindrops or raindrops that enter dry air evaporate before they can hit the ground.

90
Q

What effects the precipitation we see at the ground?

A

them temperature profile, if cold- deposits as snow, if very cold -deposits as ice pellets or freezing rain, if warm deposits as rain

91
Q

What is hail and hows it formed?

A

When you have a cloud with stong updrafts and a particles bounces around it in collecting water droplets which eventually create a mass big enough that it falls out of the cloud. The murky parts if hail come from trapped oxygen due to fast freezing,

Geography 308 (4 decks)

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