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Meteorology > Wind > Flashcards

Wind Flashcards

1
Q

Do the poles or the equator receive more heat?

A

The equator

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2
Q

What does air do as it is heated throughout the day?

A

Rise within the atmosphere

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3
Q

Describe the Low Latitude meteorological band

A

Low Latitudes (0° to 30°).

Circulation is dominated by warm air rising at the equator
Air then cools in the upper troposphere, diverges and moves towards 30° and sinks
At the lower levels, air converges around 0° into a region known as the ITCZ
This is known as the Hadley Cell

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4
Q

Which Latitude is the equator on?

A

0°

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5
Q

Describe the Mid Latitude meteorological band

A

Mid Latitudes (30° to 60°)

At the polar front (60°), where warmer tropical air meets colder polar air, air converges and rises to create condensation, cloud formation and precipitation.
The polar front moves seasonally between 45° in the winter and 65° in the summer.
This is the Ferrell Cell.

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6
Q

What is wind?

A

Wind is movement of air over the surface of the Earth, from an area of relatively high pressure to one of relatively low pressure.

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7
Q

How is pressure displayed on a meteorological chart?

A

Isobars

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8
Q

What are isobars?

A

Continuous lines joining places of equal pressure, normally at MSL.

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9
Q

What is the pressure gradient?

A

How close or far apart the isobars are. If isobars are close together, there is a rapid pressure change. If isobars are apart there is a slack pressure change.

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10
Q

What is the gradient wind?

A

A theory that wind that flows from high to low pressure.

The pressure gradient exerts a force perpendicular to the isobars, from high to low pressure, proportional to the gradient.

The steeper the gradient the stronger the wind.

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11
Q

If there is a steeper pressure gradient, is the wind faster or slower?

A

Faster

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12
Q

What is the name given to the Geostrophic Force?

A

Coriolis Effect

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13
Q

As windspeed increases, is it more or less affected by the Coriolis Effect?

A

As windspeed increases, it is more affected by the Coriolis Effect

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14
Q

What is the geostrophic wind?

A

The theoretical wind that blows along isobars as a result of the coriolis effect.

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15
Q

How does wind flow around a Low Pressure system in the northern hemisphere?

A

Wind flows ANTI-CLOCKWISE around a low-pressure system in the northern hemisphere.

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16
Q

How does wind flow around a High Pressure system in the northern hemisphere?

A

Wind flows CLOCKWISE around a high-pressure system in the northern hemisphere.

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17
Q

What is wind measured in?

A

Knots (KT) most commonly

But also
Kilometres per hour (KMH)
Metres per second (MPS)

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18
Q

What is wind direction given a compass bearing in relation to?

A

In a METAR, wind direction is given a compass bearing in relation to TRUE NORTH.

However, readings to aircraft from an anemometer in a VCR are given in relation to MAGNETIC NORTH.

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19
Q

What instrument measures wind speed and direction at ground level?

A

Anemometer (speed)
Wind Vane (direction)

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20
Q

What are the names given to a sudden increase or decrease in wind speed?

A

Gust - sudden increase
Lull - sudden decrease

21
Q

What is a wind speed increase that lasts for a few minutes called?

A

Squall (SQ)

22
Q

What is the name given to a prolonged high wind speed?

A

Gale. A wind is a gale if it has a mean value of at least 34kts or is gusting to 43kts or greater

23
Q

What is a clockwise change in wind direction called?

A

Veer

24
Q

What is an anti-clockwise change in wind direction called?

A

Back

25
Q

What is Buys Ballots Law?

A

In the northern hemisphere, if you stand with your back to the wind, the low pressure lies to your left.

26
Q

What happens to wind direction as speed increases?

A

Wind veers as speed increases.

27
Q

What does surface heating do to wind?

A

Surface heating causes turbulence which evens out the land irregularities, reducing friction and causing the surface wind to veer and increase.

For example a clear and sunny day.

28
Q

What does surface cooling do to wind?

A

Surface cooling reduces turbulence, which increases friction, causing the surface wind to back and decrease.

For example a dull/cloudy day or night.

29
Q

What happens to the speed and direction of wind in the friction layer?

A

In the friction layer, wind speed decreases and therefore backs

30
Q

If friction is decreased, what happens to windspeed and direction?

A

If friction is decreased, windspeed increases and veers.

31
Q

What plays an important part in determining weather patterns on a small scale?

A

Local Geography

32
Q

Describe a Sea Breeze?

A

Land experiences a more rapid temperature rise than the sea due to its different specific heat capacity.

Land transfers this heat energy to the air and causes it to rise.

Air over the sea rushes in to replace the rising land air.

The established wind will begin to veer as speed increases and will no longer blow at right angles toward the coast.

33
Q

What happens to a Sea Breeze at the end of the day?

A

As insolation decreases, a sea breeze will back and decrease.

34
Q

Describe a Land Breeze

A

Land experiences a more rapid temperature drop than the sea due to its different specific heat capacity.

This can produce a weak circulation opposite to a Sea Breeze, known as a Land Breeze.

35
Q

What are Anabatic winds?

A

Winds that flow uphill, due to insolation on a hillside causing air to rise up the hill.

36
Q

What are Katabatic winds?

A

Winds that flow downhill, due to surface cooling on a hillside causing air to fall down the hill as it gets colder.

They occur in areas of high ground with long, gentle slopes and are more pronounced if there is a covering of snow or ice.

37
Q

What are Valley Winds?

A

Winds that flow along a valley as a result of either Anabatic or Katabatic winds.

38
Q

What are mountain waves?

A

Air rises to cross an obstruction and descends immediately beyond it but continues to rise and fall with gradually decreasing amplitude.

39
Q

How are mountain waves often indicated?

A

By the presence of lenticular clouds.

40
Q

What is a Rotor?

A

A second type of cloud from a mountain wave that is downwind of a ridge. It indicates maxiumum turbulence and flight in the vicinity is NOT advisable.

41
Q

What are the Fohn Winds?

A

A warm, dry wind that blows down the leeside of hills or mountains.

42
Q

What causes the Fohn Winds?

A

A combination of rising terrain and the difference between the DALR and SALR.

43
Q

Describe the Fohn Winds

A

Air rises on the windward side and cools at the DALR. Upon reaching the dew point it cools at the SALR.

If the temperature reduction is significant, rain may begin to fall on the windward side.

The drier air now descends on the leeward side at the SALR. But since it is drier, it will have a lower dew point.

This means the air will become unsaturated sooner and will fall further at the DALR.

The result is a net gain in temperature and so, a warm, dry wind that blows down the leeside of hills or mountains.

44
Q

What is a thermal wind?

A

A wind that blows due to a difference in temperature between adjacent atmospheric areas

45
Q

Why do the Earth’s permanent bands of weather exist?

A

These bands exist because they have a different temperature to the adjacent bands.

46
Q

What causes the Jet Stream?

A

At the boundary of the Earth’s different air masses and temperature bands, a thermal wind blows from warm air to cold air.

These high and fast winds are subject to the Coriolis effect (geostrophic force) causing them to bend to the right in the Northern Hemisphere.

So the Jet Stream is created and blows from West to East in the Northern Hemisphere

47
Q

What is the average difference in specific heat capacities of land and water?

A

Water requires 5x more energy to heat up than land.

Therefore water has a 5x higher specific heat capacity and land heats up 5x faster.

48
Q

What is the name of the upper level wind?

A

Geostrophic wind

Meteorology (15 decks)

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