wednesday april 27, 2011
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Wednesday April 27, 2011. ( Cyclones and Anticyclones; Complete Lab; Video - Twister) Period 2 Only. The Launch Pad Wednesday, 4/27/11. Explain the three controls of wind. Announcements. Please check your yearly average in this class. - PowerPoint PPT PresentationTRANSCRIPT
WednesdayApril 27, 2011
(Cyclones and Anticyclones; Complete Lab; Video -
Twister)Period 2 Only
The Launch PadWednesday, 4/27/11
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 DueLab – 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
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.
Idealized Global Circulation 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.
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 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.
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.
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
Complete LabAir Masses, the Middle-Latitude
Cyclone, and Weather Maps
VideoTwister