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Flashcards in Wind Deck (57)
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1

What is Wind?

Air in motion over the earths surface

2

Wind Velocity is a ... quantity

Vector

3

What is a vector expressed as?

Magnitude and Direction

4

The wind magnitude is its speed in

Knots

5

Direction of wind refers to?

The direction FROM which the wind is blowing, expressed in degrees relative to North

6

Wind velocity is measured at

10 meters over open level terrain for 10 minutes

7

What is a gust?

Sudden increase in wind speed lasting a short time and dying suddenly

8

What is a squall?

Sudden increase in wind speed by at least 16kts or more, lasting at least one minute and reaching top speeds of 22kts

9

What is a veer?

Wind direction changes in clockwise manner

10

What is a back?

Wind direction changes in an anticlockwise manner

11

What is pressure gradient force?

Causes air to tend to flow from high to low pressure across isobars

12

What does the strength of pressure gradient depend on?

Spacing of isobars and is measured perpendicular to isobars

13

What is Coriolis effect?

Due to earths rotation, moving air is deflected to the left in the southern hemisphere

14

Where is Coriolis effect zero?

Equator

15

Where is Coriolis effect maximum?

Poles

16

What does the strength of Coriolis depend on?

Wind Speed
- The stronger the wind, the stronger the deflection
- The relative strength of these forces governs wind direction

17

Buys Ballots Law

With your back to the wind the lower pressure system will be on your right (in the southern hemisphere)

18

The overall pattern of air circulation around the globe results from...

The distribution of pressure systems

19

Pressure systems are formed by...

Uneven heating of the earths surface

20

Why is there a large scale convection over the equator?

Air in contact with the earths surface at the equator is warmed and rises

21

What is the equatorial trough?

The rising air generates a low pressure system

22

What is the equatorial trough also called?

Inter-tropic convergence zone or the doldrums

23

At higher levels the air begins to move horizontally towards the ....

Poles

24

As the air cools....
What happens in the subtropical region?

It descends in the subtropical regions

25

Subsiding air forms a belt of high pressure known as...

Subtropical ridge

26

What is the polar high?

Over the poles cold dense air results in a region of high pressure

27

What is the sub-polar low?

As converging air meets it is forced upwards, this forms a low pressure belt

28

What generates the world's major airstreams?

Movement of air near the surface from the high-pressure belts towards the low-pressure regions

29

In the southern hemisphere, Coriolis deflects moving air ...

Left

30

Why do we experience seasons?

Due to the tilt of the Earths axis