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Geography > Moisture in the Atmosphere > Flashcards

Moisture in the Atmosphere Flashcards

1
Q

Water Vapour

A

water as gas. amount of water vapour in atmosphere = humidity. Temp of air affects amount of water vapour

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2
Q

Rain

A

Liquid water found atmosphere when air temperature cool for vapour condense. Water vapour is initially very light and small, and remain suspend in
the air as cloud droplets. They will join together, become heavy and
eventually fall into the ground. Liquid found in atmosphere as clouds or rain

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3
Q

Ice

A

temp of air below 0, water freeze. This how hailstones fall. If water sublimes - becomes snow

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4
Q

Coalescence

A

water droplets bump into each other becoming
bigger as a result of air movement within the cloud.

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5
Q

Types of precipitation:

A

rain snow hail frost sleet

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6
Q

What refers to water in the air

A

Dew point

Condensation level

Humidity

Relative humidity

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7
Q

Specific humidity

A

The mass of the water vapour (in grams) contained in a kilogram of dry air.

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8
Q

Absolute humidity

A

The mass of water vapour (in grams) contained in a cubic metre of dry air.

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9
Q

Relative humidity

A

The proportion of water vapour in an
air parcel compared to the amount of water vapour it
could hold at a given temperature.

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10
Q

Saturated air parcel

A

Relative humidity = 100%. Lots of moisture in air

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11
Q

What affects humidity

A

Temp of air and water present in atmosphere. Warm air holds more moisture

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12
Q

Relative Humidity calculations

A

(Actual amount/Saturation amount) *100 = x%

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13
Q

dew point

A

Temp where air condenses. Higher altitudes = lower dew point temp. Height at which dew pt is reached - condensation level

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14
Q

Why does it rain in the Highveld during the
afternoon?

A

Heating will raise the temperatures and increase evaporation
(also cause convection currents)

Heated air holds more moisture ( expanding air -> more
space to hold moisture) and increases as the day goes on.

By late afternoon the air may be full of moisture and can be
seen as clouds.

Leads to afternoon rainstorms, sometimes have hail too.
(Why? Think convection currents).

When air temperature drop the water condenses and can
cause rain

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15
Q

Cumulous cloud shape

A

Patchy looking

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16
Q

Stratus cloud

A

Layered clouds can form at any height and are the most
common type

17
Q

Nimbus(rain) cloud

A

Nimbostratus and cumilonimbus

18
Q

Cloud formation

A

Condensation and water vapor needed.
Rising currents help to suspend water droplets in the sky

Water droplets will fall when they get to heavy.

Solid surfaces in the sky act as condensation nuclei and help
promote the condensation process

19
Q

Coalescence

A

Air movements in clouds cause tiny droplets to collide

20
Q

Rain formation

A

Coalescence occurs. More turbulent the air, bigger the drops until become too heavy and fall to earth. Avg rain drop 2mm in diameter.

21
Q

How rainfall show on map

A

Colour shading and isohyets - lines on map joining places of equal rainfall.

22
Q

trigger action

A

natural mechanism that causes air to rise

23
Q

Types of rain

A

Convection(heating), Frontal/cyclonic(Sea) and Relief/orographic(Mountain)

24
Q

Convection rain

A

Convection rain is a thunderstorm. Surface heating is trigger action.

25
Q

Steps of convection rain

A

Cumulous stage - hot air rises causing cumulous clouds grow higher. Mature stage - Cumulous clouds reach 7km high. Air gets cold and starts to sink. Both up and down currents are now present. Is now a cumulonimbus cloud. Friction between currents causes electrical imbalance results lightning. Very strong currents result water drops freezing causing hail. Dissipating stage is once everything gets too heavy and falls.

26
Q

Relief rain

A

Mountains force air to rise causing it to condense and result in rain. The mountain is the trigger action

27
Q

Steps of relief rain

A

Moist air blows off an ocean and rises up the mountain
range.

The windward side of the mountain is the side the wind
strikes first and the leeward side is the side the wind is
blowing away from

Air rises, cools and condenses on the windward side.

Turbulence causes coalescence and start to fall as rain.

Most moisture is lost on the wind ward side and little is left
on the leeward side.

The drier side of the mountain is called the rain shadow.

Orographic rain is usually gentle rain that lasts as long as the air
coming in from the ocean is being forced up the mountain.

The cloud responsible is normally Nimbostratus but cumulonimbus
can form if the air rises very quickly.

Drakensberg and Cape fold mountains

28
Q

front

A

boundary between two different kinds of air - usually hot+cold. Fronts develop between warm, moist air masses and dry, cold air masses.

29
Q

frontal rain trigger action

A

trigger action is the front

30
Q

Frontal rain steps

A

When the air masses meet the warm air will rise over the cold air as warm air is less dense and lighter.

Warm air will rise, cool and condense.

A warm front has a very gentle slope

With a variety of clouds. The rain falls

from the Nimbostratus.

A cold front has a steeper slope which

makes warm air rise more quickly.

Cumulonimbus clouds

31
Q

Hail formation

A

Strong convection currents cause up and down currents in the
cumulonimbus clouds.

Water drops carried above freezing level

Begins to fall and collect more water

After each updraft forms a new layer

Continues until hail too heavy and falls. Melts slightly while falling

32
Q

Formation of snow:

A

Water vapour condensing onto condensation nuclei to form ice
crystals. Turning from water vapour to snow without condensing is
called sublimation

Snow crystals float and freeze onto each other getting bigger

They are six sided and fall from nimbostratus clouds.

Increase in size by further sublimation or by collisions (known as
snow flakes)

33
Q

Dew

A

Condensed water droplets seen on grass/plants

34
Q

Dew formation

A

At night land loses heat to terrestrial radiation. The cold land cools the
air above it.

IF the temperature drops below dew point water vapor on the
ground condenses to from dew. Dew most common in spring+autumn in highveld

35
Q

Frost

A

If temperature drops below freezing, instead of water vapor condensing, it sublimates . Bad for certain plants but good for citrus. Protect plants with fans/artificial heating get frost resistant crops.

36
Q

Frost formation in valleys

A

Clear calm and windless nights (wind mixes air)

Land on side of the valley cools and begins to sink to valley floor

Warm air at the bottom of valley rises above the cold sinking air to
form the inversion layer.

Cold air on the valley floor cools and pools in the frost pocket. This is
where fog will develop once dew point temperature is reached.

The water droplets will freeze if the temperature hits freezing point.

Geography (10 decks)

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