Ch 24.3 Winds
Weather is the horizontal movement of air.
Air always moves from H  L pressure.
Temperature differences create pressure
differences.
Local Winds: Sea & Land Breezes
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm?chapter_no=vis
ualization
Local Breezes – over short distances
Ex.: Land
Sea breezes
breezes– –happen
happenduring
at night
thebecause
day because
LANDLAND
COOLS
Heats
Up FASTER
DOWN
FASTER
THAN
THAN
WATER
WATER.
(water takes a long time to heat up
and cool down).
Air is mostly heated by I.R. re-radiated off of surfaces.
Warmer surfaces  Warmer air  Less dense (more expanded) Low Pressure
Cooler surfaces Cooler air  Denser  High Pressure
Wind moves from H  L pressure
Local Breezes – over short distances
Ex.: Land breezes – happen at night because LAND COOLS
DOWN FASTER THAN WATER.
Air is mostly heated by I.R. re-radiated off of surfaces.
Warmer surfaces  Warmer air  Less dense (more expanded) Low
Pressure
Cooler surfaces Cooler air  Denser  High Pressure
Wind moves from H  L pressure
Warm air
•More Kinetic
Energy
•Less Dense
•Low Pressure
•Rises (less dense)
•Room for moisture
Cold air
•Less Kinetic Energy
•Denser
•High Pressure
•Sinks(denser)
•Dry (less room for
moisture)
Seasonal Winds: Monsoon Winds
MOONSOON RAINS are
seasonal and experienced in
India & S.E. Asia (subtropical
locations)
Summer – Land in warmer
(Low Pressure) than Water
(High Pressure). Air moves
from water to land carrying
moisture --- RAIN.
It can rain 37 ft of rain in a few
months.
Remember … Land heats up
faster than water.
Winter – Land is cooler than
water. Air moves from land to
water – this is a DRY SEASON
Global Winds
GLOBAL WINDS – DUE TO
DIFF. IN PRESSURE
Warm air rises at the equator
and cold dense air sinks at the
poles. In general wind want to
move from Poles  Equator,
but E’s rotation CURVES the
path of wind.
CORIOLIS EFFECT – DUE
TO EARTH’S ROTATION,
CURVES THE PATH OF THE
WIND.
WARM AIR RISES – LOW PRESSURE
COOL AIR SINKS – HIGH PRESSURE
Wind & Surface Currents
deflect TO THE RIGHT in the
N. Hemi; TO THE LEFT in
the S. Hemi.
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1905/es1905page01.cfm?chapter_no=visualization
http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp29/animations/ch29/global_wind_circulation.swf
Global Winds: Warm Low Pressure Air (carrying
moisture) Rises @ Equator and Sinks @ 30 N & S
(dry, sinking, high pressure air)
http://www.coolschool.ca/lor/GEO12/unit9/U09L03.htm
Global Winds: There are 3 major convection cells of
rising and sinking air for each hemisphere.
Due to Coriolis: Air
deflects to the Right
in the N. Hemi. And
to the Left in the S.
Hemi.
Remember: start
at the BASE of the
arrow.
http://www.ukdivers.net/meteorology/coriolis.htm
Winds Aloft (high in Troposphere)
JET STREAM –
•Rivers of wind high in the atmosphere - above about 20,000
feet (Tropopause: Boundary of Tropo. & Stratosphere)
•Also help determine the locations of areas of high and low air
pressure at the Earth's surface.
•Steers Weather.
•Jet stream dips south … we get cold Canadian air
•Jet stream slides north … warm Gulf air rides up.
Jet Stream:
http://www.wunderground.com/US/Region/US/pxJetStream.html
http://www.pbs.org/wgbh/nova/vanished/jet
str_giving.html
Current Jet Stream Animations:
http://www.wunderground.com/global/Regi
on/EU/pxJetStream.html