Friday
April 29, 2011
(Cyclones and Anticyclones;
Complete Lab; Video Twister)
Period 8 Only
The Launch Pad
Friday, 4/29/11
Explain the
three
controls of
wind.
Announcements
Please check your yearly
average in this class.
If you are below 70 for the
year, please come and see
me ASAP!
There are only two more
grades remaining!
Assignments For This Six-Weeks
Date Issued
Date Due
Lab – Air Masses, the Mid-Latitude
Cyclones, and Weather Maps
4/20
4/25
Cyclones and Anticyclones
A cyclone is a center of low
pressure where the pressure
decreases even more toward
the center.
The winds associated with a
cyclone in the Northern
Hemisphere circle inward
(called a convergence) with a
counterclockwise rotation.
In the Southern Hemisphere,
cyclone winds circle inward
(convergence) with a
clockwise rotation.
Cyclones and Anticyclones
A cyclone is associated
with rising air, and
often bring clouds and
precipitation.
An anticyclone is a
center of high
pressure, with the
pressure increasing
toward the center.
Cyclones and Anticyclones
Cyclones and Anticyclones
Winds associated with an
anticyclone In the Northern
Hemisphere swirl outward (a
divergence) in a clockwise
direction.
Winds associated with an
anticyclone In the Southern
Hemisphere swirl outward (a
divergence) in a
counterclockwise direction.
Anticyclones are associated
with subsiding air and usually
bring “fair” weather.
Cyclonic and Anticyclonic Winds in the
Northern Hemisphere
Figure 18.11
Airflow Associated with Surface Cyclones
and Anticyclones
Figure 18.13
The underlying cause of Earth’s wind is unequal
surface heating by the Sun.
On the rotating Earth, there are three pairs of
atmospheric cells that redistribute heat.
The center of this zone of subsiding air is the
subtropical high pressure zone, which encircles the
globe near 30 degrees latitude, north and south.
Idealized Global Circulation
At the surface, airflow is outward from the
subtropical high.
Air traveling equatorward from the subtropical high
produces the trade winds.
Air traveling poleward from the subtropical high
produces the westerly winds (westerlies
As the upper-level flow from the
equatorial low reaches 20-30 degrees
latitude, north or south, it sinks back
toward the surface. This produces hot,
arid conditions.
Near the equator, the rising air is
associated with the pressure zone
known as the equatorial low pressure
zone, a region marked by abundant
precipitation.
As the westerlies move poleward, they
encounter the cool easterlies in the region of
the subpolar low pressure zone.
The interaction of these warm and cool
winds prodcuces the stormy belt known as
the polar front.
The source region for the variable polar
easterlies is the polar high pressure zone.
Here, cold polar air is subsiding and
spreading equatorward.
Complete Lab
Air Masses, the
Middle-Latitude
Cyclone, and Weather
Maps
Video
Twister