WNHS APES
THE ATMOSPHERE AS AN EARTH SYSTEM
(P. 500 – 505, 536 – 537)
Solar energy heats the atmosphere, helps create seasons, and causes air to circulate
CONVECTIVE CIRCULATION – Air at Earth’s surface is warmer and moister than air at high altitudes; warm air is
less dense so it rises and makes vertical currents; as it rises it expands and cools causing it to descend and
become denser
This drives WEATHER and CLIMATE:
Weather =specifies atmospheric conditions over short time periods and within small geographic areas
Climate =patterns of atmospheric conditions across large geographic regions over long periods of time
Circulation systems produce climate patterns
Hadley cells =convective cells near the equator
Surface air warms, rises, and expands causing heavy rainfall near the equator and giving rise to
tropical rainforests
Currents heading north and south are dry giving rise to deserts at 30 degrees
Ferrel cells and polar cells= lift air and create precipitation at 60 degrees latitude north and south
Conditions at the poles are dry
http://www.youtube.com/watch?v=DHrapzHPCSA
Global wind patterns
Atmospheric cells interact with Earth’s rotation to produce global wind patterns
As Earth rotates, equatorial regions spin faster
Coriolis effect =the apparent north-south deflection of air currents of the convective cells
http://www.youtube.com/watch?v=mcPs_OdQOYU
Northern Hemisphere –
Southern Hemisphere -
Doldrums= a region near the equator with few winds
Trade winds = between the equator and 30 degrees; Blow from east to west
Westerlies= from 30 to 60 degrees latitude; Blow from west to east
Air circulation drives ocean circulation
El Niño–Southern Oscillation (ENSO)

ENSO= a systematic shift in atmospheric pressure, sea surface temperature, and ocean circulation
in the tropical Pacific Ocean

Normal winds blow east to west, from high to low pressure This forms a large convective loop in
the atmosphere

Winds push water west, causing it to “pile up”  Nutrient-rich, cold water along Peru and Ecuador
rises from the deep

Decreased pressure in the eastern Pacific triggers El Niño  Warm water flows eastward,
suppressing upwellings
http://esminfo.prenhall.com/science/geoanimations/animations/26_NinoNina.html
http://www.youtube.com/watch?v=7FVZrw7bk1w
http://www.youtube.com/watch?feature=endscreen&v=ovDp1crqdOU&NR=1
http://www.youtube.com/watch?v=IvmeUStFvz8&feature=related
Effects of El Niño and La Niña

Coastal industries (e.g., Peru’s anchovy fisheries) are devastated  Worldwide, fishermen lost $8
billion in 1982–1983

Global weather patterns change  Rainstorms, floods, drought, fires

La Niña = the opposite of El Niño  Cold waters rise to the surface and extend westward

ENSO cycles are periodic but irregular (every 2–8 years)

Globally warming sea and air may be increasing the strength and frequency of these cycles