Transcript Ch. 24.3 Winds - (www.ramsey.k12.nj.us).

Winds
Wind is the horizontal movement of air.
Air always moves from H  L pressure.
Temperature differences create pressure
differences.
Weather is based on the unequal heating of Earth’s surfaces. Some
surfaces heat up more than others. This warms up the air and
causes 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)
Regional Winds: Monsoon Winds
MOONSOON RAINS are
seasonal and experienced in
India & S.E. Asia (subtropical
locations)
Summer – Land is 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
Regional Wind Patterns: El Nino & La
Nina
Natural
short
range
change in
climate
due to
change in
wind
pattern
and
ocean
currents.
El Nino: Periodic warming of water in the
central & eastern Pacific Ocean (off coast of
Peru)
Normally this water is VERY COLD due to an upwelling from
the deep ocean.
• Warm water  warmer air  Less Pressure = trade
winds slacken or weaken
• Ocean currents in Pacific weaken or
reverse direction (b/c trade winds weaken)
Result: Abnormal weather (Rain on West
Coast; Milder Winter on East coast; more
Drought in Austrialia, and S.E Asia
When: Every 8 yrs (average)
Normal Years
Cold water off S.
America  High
pressure air = Trade
Winds blow AWAY from
S. America across
Pacific (Dry air in
Western Americas)
El Nino Years
Warmer water off S.
America  Less High
pressure air = Trade
Winds WEAKEN or
reverse
Changes what locations
get rain/snow/or draught
El Nino year
La Nina – cooler water
El Nino– Warmer water
La Nina = Opposite of El Nino
Year when the cold current off the
coast of S. America is “extra” cool.
Air off coast of S. America = High
Pressure
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 high speed wind at the top of the troposphere.
•Separates cold Canadian air from warm Gulf air.
•Steers weather.
• When jet stream dips south, NJ gets cold Canadian air.
• When jet streams moves north, NJ gets warm Gulf air.
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