Wind Flashcards

1
Q

What measures surface wind

A

Anemometer

, 10m or 30ft agl

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2
Q

Gust

A

Sudden change in wind speed by 10kts in less than a min

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3
Q

Calm

A

1kt or less

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4
Q

Gale force

A

34-47kts

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5
Q

Storm force

A

48 - 63kts

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6
Q

Hurricane force

A

Greater than or equal to 64

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7
Q

Squall

A

Gust lasting more than 1 min

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8
Q

Lull

A

Sudden drop in wind speed

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9
Q

What happens to the surface wind in the northern hemisphere

A

Backed and slacks

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10
Q

Sea breeze wind speed

A

10 - 5kts

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11
Q

Anabatic

A

Winds going up the mountain, low pressure which is caused by convection, air comes in and goes up the mountain

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12
Q

Katabatic wind

A

Typical at night, surface cools, get denser, falls down the mountain

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13
Q

Geostrophic wind

A

The CF and PGF are equal and opposite and the wind gets deflected 90 degrees so wind travels parallel to the isobars

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14
Q

Ballots law

A

Back to the wind, low pressure will be on your left

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15
Q

Gradient wind

A

Wind coming out a high/low pressure

Coming out a high due to centrifugal for acting in the same direction, the the wind is faster

Wind around a low is slower due to the centrifugal force and the corolis acting the opposite direction

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16
Q

Deflection of the wind over the sea and % of the 3000ft wind

A

10 degrees, 70%

17
Q

Deflection of the wind over the land by day and % of the 3000ft wind

A

30 degrees, 50%

18
Q

Deflection of the wind over the land by night and % of the 3000ft wind

A

45 degrees, 25 %

19
Q

Diurnal variation

A

Durning the day, thermal activity on the surface causes fast high level air to get mixed with slow surface air to get a faster overall wind speed

Durning the night, less thermal air, no rising air, less mixing

20
Q

Sea breeze formation

A

Surface heating on the land causes a low pressure to form and thus causing a PGF, goes in opposite direction in the night

Wind gets deflected due to the CF

About 5 - 10kts, faster the speed, bigger the deflection

21
Q

Land breeze

A

Opposite to sea breeze

22
Q

Katabatic wind

A

Typical at night, surface cools, gets denser and falls down the mountain

23
Q

Example of the katabatic effect

A

The Bora, effects the adratic sea

24
Q

Example of valley winds

A

High pressure in the north Western Europe to low pressure in the south
PGF goes through the alps causing a Venturi
Strong relatively cold and dry wind

25
Foehn wind
Stable, saturated air gets pushed up a mountain, cools, forms cap cloud, rains, dries, comes down the mountain as the DALR and is warmer
26
Examples of foehn wind
Alps | Chinook in the rockies
27
What happens in the med in winter
The low pressure over the med sea, drags the dry air from n Africa up This mixes with the cold air from the European land mass and can cause intense storms
28
Strong winds in the Southern Hemisphere
Roaring 40s Furious 50s Screaming 60s
29
Doldrums
Calm surface conditions due to surface convergence at the ITCZ
30
Harmattan
NE trade winds over w Africa Dry sands can impact visibility Strongest in jan due to the ITCZ moving downwards Reduces viz up to 3000ft Can extend to 10-15,000ft
31
Pampero
S America Cold polar air moves the flat land, increasing wind speed Strongest winds occur early summer