Part 2 Flashcards
If the earth did not rotate, where would surface wind flow from the subtropical ridge?
North and south
What is the deflection of moving air called
Coriolis effect
Which direction does the air flow from the subtropical ridge to the equatorial trough
South easterly flow
How is the behaviour of the wind determined at any moment
Combination of the Coriolis effect and the pressure gradient force
What is gradient flow?
The flow exactly follows the isobars (tangential to the isobars)
When is surface wind speed lowest
Between midnight and dawn
Why is surface wind speed lowest at night
Absence of surface heating allows the air to remain in contact with the surface where friction slows it down
What is geostrophic flow
Gradient flow when the isobars are straight - there is an exact balance between the two forces and the wind swings neither right or left. The wind blowing at a constant speed along straight isobars
What is the meaning of the wind backing
The wind has changed in such a way that an observer has to turn to his left to continue facing the wind
What is the meaning of the wind veering
The wind has changed direction in such a way that an observer has to turn to his right to continue facing it
What are the surface wind changes over the gradient wind over land
Surface wind speed drops by two thirds and direction veers by 30 degrees
Change in speed and direction of the surface wind speed over the sea
Speed drops by one third and direction veers by 10 degrees
What is a wind squall
The wind speed changing by at least 16 knots to reach 22 knots or more and must be sustained for more than one minute
What is a wind gust?
A rapid increase in wind strength followed by a lull or slackening back to the average speed
Vertical wind shear definition
Aircraft passage through the windshear has a vertical component such as during a climb or descent
