Flashcards in Wind Deck (57)
What is Wind?
Air in motion over the earths surface
Wind Velocity is a ... quantity
What is a vector expressed as?
Magnitude and Direction
The wind magnitude is its speed in
Direction of wind refers to?
The direction FROM which the wind is blowing, expressed in degrees relative to North
Wind velocity is measured at
10 meters over open level terrain for 10 minutes
What is a gust?
Sudden increase in wind speed lasting a short time and dying suddenly
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
What is a veer?
Wind direction changes in clockwise manner
What is a back?
Wind direction changes in an anticlockwise manner
What is pressure gradient force?
Causes air to tend to flow from high to low pressure across isobars
What does the strength of pressure gradient depend on?
Spacing of isobars and is measured perpendicular to isobars
What is Coriolis effect?
Due to earths rotation, moving air is deflected to the left in the southern hemisphere
Where is Coriolis effect zero?
Where is Coriolis effect maximum?
What does the strength of Coriolis depend on?
- The stronger the wind, the stronger the deflection
- The relative strength of these forces governs wind direction
Buys Ballots Law
With your back to the wind the lower pressure system will be on your right (in the southern hemisphere)
The overall pattern of air circulation around the globe results from...
The distribution of pressure systems
Pressure systems are formed by...
Uneven heating of the earths surface
Why is there a large scale convection over the equator?
Air in contact with the earths surface at the equator is warmed and rises
What is the equatorial trough?
The rising air generates a low pressure system
What is the equatorial trough also called?
Inter-tropic convergence zone or the doldrums
At higher levels the air begins to move horizontally towards the ....
As the air cools....
What happens in the subtropical region?
It descends in the subtropical regions
Subsiding air forms a belt of high pressure known as...
What is the polar high?
Over the poles cold dense air results in a region of high pressure
What is the sub-polar low?
As converging air meets it is forced upwards, this forms a low pressure belt
What generates the world's major airstreams?
Movement of air near the surface from the high-pressure belts towards the low-pressure regions
In the southern hemisphere, Coriolis deflects moving air ...