Lecture 4
Spring 2005
Atmospheric circulation transfers energy and mass on a great
scale- energy balance, weather patterns and sea currents.
How are winds named?
Learning Objectives
1.
Define air
pressure and describe how it is measured.
·
Motion, size and number of air molecules
create air pressure
·
Air pressure is a product of the density and
temperature of air an mass
·
Barometer- instrument the measures air
pressure
2.
Define wind and how it is measured
·
Wind- horizontal
movement of air across earth’s surface
·
Wind- produced by
differences in air pressure
·
Properties- speed and
direction
·
Anemometer- measures
wind speed
·
Wind Vane- measures
wind direction
How wind is created, role
of air pressure
See how wind works:
http://www.usatoday.com/weather/wwind0.htm
3.
Explain the four driving forces within the atmosphere
(determine speed & direction)
a.
Gravity- equally
compresses air world-wide
b.
Pressure
Gradient Force-drives air from high (dense) to low (less dense)pressure
areas.
·
Related to differences in heating (cold, dense
vs hot, lighter air)
·
Dense air at poles pushing towards equator
·
Isobar- an isoline of constant pressure values
·
Spacing between isobars indicates intensity of
pressure difference (gradient)
·
High pressure area- air descends, pushing air
out across the surface- towards lower pressure areas
c.
Coriolis
Force- deflective force due to earth’s rotation. Deflects anything that flies or flows across
the surface (earth’s rotational speed at equator = 1,041 mph)
d.
Friction
Force- drag on wind as it moves across the surface (up to 1,600 feet)
4.
Describe the primary high- and low-pressure
areas and principal winds. (Table 6.2 on
page 155.)
Know and be able to explain Table 6-2 Four Hemispheric
Pressure Areas (page 155.) Which are
thermal (why) and which are dynamic (why.)
ITCZ- Intertropical Convergence Zone- zone of circulation
(convergence of winds) along the equator.
This zone moves during the year with changes in air temperatures (driven
by the seasons) (Moist, warm air) See Figure 6.13 on page 158. Understand- warm air can hold more moisture
than cold air.
Trade Winds- Winds converging on the equatorial
low-pressure trough
5.
Describe upper-air circulation and its support
role for surface systems- mapped as constant isobaric surfaces (Figure 6.16,
page 161)
Ridge- altitude
variation for high pressure
Trough- altitude
variation for low pressure
6.
Jet Streams-
concentrated, upper-level band of wind- supports local surface
7.
Explain several types of local winds:
land-sea
breezes- (Figure 6.19) (page 164-165)
mountain-valley
breezes- Figure 6.20 (page -166)
katabatic
winds- gravity drainage winds
regional
monsoons- annual cycle of returning summer precipitation
1.
Discern the basic pattern of the Earth's major
surface and deep ocean currents.
Upwelling current- surface waters are swept away from
coast, causing cool-nutrient rich waters to rise from great depths (Pacific
coasts)
Driving forces of ocean currents:
·
Wind
·
Coriolis
Effect
·
Water
density differences (temperature and salinity)
·
Topography
·
Tides
Basic pattern of Earth’s major surface and deep ocean currents
(Gulf Stream, western intensification and Upwelling current)
Complete circuit takes 1,000 years
You read the book!!! Now see the movie!!!!
http://sealevel.jpl.nasa.gov/gallery/tiffs/videos/global-conveyor.mov
Air pressure
Coriolis Effect
Primary circulation/Secondary circulation/Tertiary circulation
Meridian flows
Zonal flows
Isobar
Trade winds
Jet Stream
Gulf Stream (Coriolis Effect, winds and western intensification)
Upwelling current