Chapter 6

Weather

Weather• An area’s short term (usually a day) atmospheric

condition• Differs from climate which is weather over a long

period of timeClimate• Determined by average temperature and

precipitation over a period of time (usually a year)• Climate then determines an areas biome

Atmosphere Layers• Troposphere is

where we live•Where weather happens

• Stratosphere contains the ozone layer•Block out harmful UV light from sun

Air CirculationCaused by 4 factors1. Uneven heating of the Earth’s

surface2. Evaporating water creating

convection cells3. Rotation of the Earth- spins faster at

the equator than at the poles causing prevailing winds

4. Seasons- caused by the tilt of the Earth

Unequal Heating of the Earth

Physical properties of atmosphere

• Warm air, less dense (rises)

• Cool air, more dense (sinks)

• Moist air, less dense (rises)

• Dry air, more dense (sinks)

Fig. 6.5

Convection Currents

Dry woodlands and shrublands (chaparral)

Temperate grassland

Temperate deciduous forest

Boreal forest (taiga), evergreen coniferousforest (e.g., montane coniferous forest)

Arctic tundra (polar grasslands)

Tropical savanna,thorn forest

Tropical scrub forest

Tropical deciduous forest

Tropical rain forest,tropical evergreen forest

Desert

Ice

Mountains(complex zonation)

Semidesert,arid grassland

Tropic ofCapricorn

Equator

Tropic ofCancer

Rotation of the Earth• Earth spins faster at the equator than at the poles• Causes prevailing winds

Earth’s Tilt Causes Seasons

Ocean Circulation

Ocean Currents and Climate• Ocean currents help to mix

nutrients and dissolved oxygen, as well as influence the climate of coastal regions

• Winds blowing westward push surface waters away from the coast and cold, nutrient rich water takes its place (upwelling)

• Upwelling leads to high productivity

El Nino

Every 3 to 7 years, the interaction of the Earth's atmosphere and ocean cause surface currents in the tropical Pacific Ocean to reverse direction.

Normal Conditions

El Nino Conditions

La Nina Conditions