References: -Air Command Weather Manual Ch 5, 11, -FTGU pages 129-132 : References: -Air Command Weather Manual Ch 5, 11, -FTGU pages 129-132 40 Minutes 5.07 Wind BC Online Ground School: Meteorology
Slide 2 : Review from 5.06
Poll – 3 questions
Slide 3 : MTPs:
Terminology and background
Low level and Surface Winds
Diurnal Effects
http://www.youtube.com/watch?v=b43lAoovqd8
Slide 4 : Wind
the horizontal movement of air
created by pressure differences in the horizontal
Slide 5 : Pressure Gradient
the rate of change of pressure over a given distance
measured at right angles to the isobars
close together = steeper gradient and stronger winds
further apart = shallower gradient and weaker winds
Slide 6 : Pressure Gradient
Slide 7 : Veering
Wind changes direction clockwise
Wind veers and increases during the day
Wind veers and increases with increase in altitude Backing
Wind changes direction counter-clockwise
Wind backs and decreases at night
Wind backs and decreases with descent in altitude
Slide 8 : Example:
Winds start the day at 300o and by 1400 the winds are 340o and by night they are 310o
Slide 9 : Coriolis Force:
Earth turns below atmosphere
In N Hemisphere deflected to the right
To left in S Hemisphere
http://www.youtube.com/watch?v=_36MiCUS1ro
Slide 10 : Questions:
Wind is:
The horizontal movement of air created by pressure differences (horizontal)
Pressure Gradient is:
The rate of change of pressure measured over a given distance, measured at right angles to the isobars
Backing is:
Change in direction anti-clockwise
Describe Coriolis Force
Rotation of earth causes air to be deflected to the right in the N Hem. Until parallel with the isobars
Slide 11 : Surface friction
Friction between surface and atmosphere slows movement of air, this in turn slows Coriolis force
Only up to a few thousand feet (except in mountainous regions)
Slide 12 : Gusts
a brief rapid increase of wind speed.
may be associated with a rapid change in wind direction
Causes may be related to mechanical turbulence and unequal heating
Slide 13 : What is surface friction and what are it’s effects?
Friction between surface and atmosphere
Slows movement of air and therefore Coriolis force
Air tends to move across isobars at slight angles
Gusty conditions may be caused by
Mechanical turbulence
Uneven heating of the earth
Slide 14 : If isobaric pattern and pressure gradient are identical
During day…
At night…
Slide 15 : Land and Sea Breezes
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Slide 18 : Memory Tool
Ana goes up and throws the Kat down.
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Slide 21 : When do sea breezes occur?
During the day – high pressure over water, low over land.
What causes a Katabatic wind?
At night, air in contact with slope cools, becomes more dense, and flows down hill.
What is it called when vapour changes to liquid?
Condensation
Slide 22 : Effects of a Hurricane