WIND (8.10A)
What causes wind (and just about everything else with this unit)?
 The UNEVEN HEATING of the Earth causes differences in AIR PRESSURE
 The Sun’s energy is more concentrated at the EQUATOR and spread out over the
POLES.
 Warm air is LESS dense and has LOW pressure – which means it rises.
 Cold air is MORE dense and has HIGH pressure – which means it sinks.
 When WARM air rises, COLD air will move in and replace it.
 Air pressure moves in a pattern from HIGH to LOW This pattern is called
CONVECTION.
 The density changes caused by TEMPERATURE changes create convection cells
 Where these cells meet, prevailing winds and jet streams form
 Prevailing Winds
o Polar Easterlies – Blow EAST to WEST toward the EQUATOR.
o Westerlies – MID latitudes blow WEST to EAST toward the POLES
o Easterlies (TRADE Winds) – Blow EAST to WEST toward the EQUATOR.
o Think EASTERLIES toward the EQUATOR
Coriolis Effect
 As the Earth rotates, the winds BEND around the Earth.
 In the NORTHERN Hemisphere, winds bend to the RIGHT
 In the SOUTHERN Hemisphere, winds bend to the LEFT.
OCEAN CURRENTS
 WARM Currents flow AWAY from the EQUATOR.
 COLD Currents flow TOWARD the EQUATOR.
What influences currents ?
o Sun, Wind, Gravity, Coriolis effect
Surface Currents
 Make up 10% of the oceans’ water, up to 400m.
 Surface ocean currents are cause by the surface WIND patterns.
Deep Water Currents
 Make up 90 % of the ocean’s water
El Nino
 Abnormally WARM surface ocean temperatures off the coast of SOUTH America
 Causes UNUSUAL weather patterns across the globe.
 Causing rain where it doesn’t usually occur and drought where it usually rains
La Nina
 Abnormally COOL surface ocean temperatures off the coast of SOUTH America
 Causes UNUSUAL weather patterns across the globe.
Oceans Effect on Climate
 WATER holds more heat than the AIR and LAND
 Cold currents will cause coastlines to be COOLER, warm currents will cause
coastlines to be WARMER.
AIR MASSES (8.10B)
Humidity
 The AMOUNT OF WATER VAPOR IN THE AIR
 PSYCHROMETER– measures the humidity
 HUMIDITY affects the DENSITY of the air
 COLD air is heavier than WARM air (this is the most important thing to
remember!!!!!!!)
What is an air mass?
 A body of air that has the same PRESSURE and HUMIDITY throughout
How do air masses form?
 If a large body of AIR sits over an area for a long period of time, it will ADAPT TO
THE TEMPERATURE, PRESSURE, AND HUMIDITY CHARACTERISITCS of the
land or water beneath it
Location, location, location
 Air masses over the EQUATOR will have HIGH temperatures.
 Air masses over POLAR REGIONS will have LOW temperatures.
 Air masses over WATER (maritime) will have HIGH humidity (moisture content).
 Air masses over LAND (continental) will have LOW humidity (moisture content).
Labeling Air Masses
 Air masses that form over water are called MARITIME.
 Air masses that form over land are called CONTINENTAL.
Classifications of Air Masses
Abbreviation
mT –
cT –
mP –
cP –
cA –
Classification
maritime tropical
continental tropical
maritime polar
continental polar
continental arctic

How do air masses move?
 CONVECTION!!!!!
 Warm air RISES, and cold air MOVES IN to REPLACE it.
 A CIRCULAR pattern is formed.
 Causes AIR and WATER currents to form.
Characteristics
warm, moist air
– warm, dry air
cold, moist air
cold, dry air
super cold, dry air