Download Driving Forces

Wind
Driving Forces
1. Pressure Gradient
•  Determines magnitude of wind speed and
wind direction
•  Stronger the pressure gradient, higher the
wind speed
•  Moves from an area of HIGH pressure to
LOW pressure
•  Example: vacuum sealed can…
•  Pressure gradient is the amount of pressure
between high and low pressure
Pressure Gradient
Low pressure/
High pressure gradient
Strong wind
High pressure, gentle
pressure gradient
Isobars
•  Isobars connect places
of equal pressure
•  The space between
bars indicates change
in pressure and
pressure gradient.
•  Isobars close together
means greater pressure
gradient (over
distance).
REFER TO YOUR
MAP
2. Coriolis Effect
•  The pull of the magnetic force of
the coriolis effect can change the
WIND DIRECTION only. It does
NOT affect the wind speed.
3. Friction at Earth’s Surface
•  *Friction slows surface
wind speed and diverts
direction of wind
•  Hills and mountains have
a major influence on wind
•  Wind speed increases with
height
•  Over ocean less friction
Ex. Airplane flying over mountainous
area will climb higher to reach
more stable air; avoid turbulence
Geostrophic Winds
Upper air winds
unaffected by
friction, faster
than surface wind
EX. Jet streams,
winds moving in
upper level at
120-240km/hr
(75-150 miles/hr
Jet streams form between cold and
warm air masses
RECAP QUESTIONS
•  1. Pressure Gradient
affects the ______ and
______ of wind.
•  2. Wind moves from an
area of _____ to _____
pressure.
•  3. Isobars close together
indicate what about the
pressure gradient?
•  4. The greater the
pressure gradient, than the
______ the wind speed.
•  5. The __________ of the
wind is effected by the
rotation of the earth.
Know as the
_____________.
•  6. The deflection of
wind is strongest at the
_______.
•  7. What influence do
hills and mountains
have on wind?
•  8. Wind speed ______
with height.
9.
•  10. Upper air winds
unaffected by friction
are called what?
Cyclones
•  Areas of LOW
pressure
•  In the N. Hemisphere
winds blow inward
and counter
clockwise
•  Associated with warm
humid conditions
Anticyclones
•  Areas of HIGH
pressure
•  Winds blow outward
and clockwise in
Northern
Hemisphere
Compare…
Cyclones and Anticyclones
•  RECAP QUESTIONS….
•  1. Cyclones are associated with areas of
_____ pressure.
•  2. Anticyclones in the Northern
Hemisphere wind moves in which
direction ?
•  3. T/F Cyclones wind direction is counter
clockwise in N. Hemi.
Middle-Latitude Cyclones
•  Middle-Latitude Cyclones are large centers
of low pressure that travel form west to east.
•  Last about 1-1/2 weeks and occur between
Florida and Alaska
Life cycle of middle-latitude cyclone
Mid-Latitude Cyclones often resemble a
“comma”
Pg 472
With Mid-Latitude Cyclones come storm
systems….thunderstorms, tornados and hurricanes
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cyc/
sat.rxml