World GeographyWorld Geography

Weather and ClimateWeather and Climate

Factors that affect climateFactors that affect climate

• I. The Sun and Latitude:– Tilt of the earth as the planet revolves around

the Sun.• Determines which hemisphere receives the most

direct sunlight, which causes changing seasons.• Sun’s energy:

– ½ of the energy is absorbed in the atmosphere– Earth’s surface absorbs the other ½– Solar (from the Sun) energy is converted into heat and

measured according to temperature.

The Sun and Latitude cont.The Sun and Latitude cont.

• Greenhouse Effect: earth’s atmosphere traps heat energy.

• The greenhouse effect helps keep the planet warm, but recent evidence shows that the Earth has gotten noticeably warmer. What might cause this?

The Sun and Latitude cont.The Sun and Latitude cont.

II. “Atmospheric Pressure”II. “Atmospheric Pressure”

• The air around you is constantly pushing you, a force called atmospheric pressure, or air pressure.

• As you climb a mountain, there is less air pushing you down, thus the air gets thinner is harder to breath as humans.

Air pressure cont.Air pressure cont.

• At such high altitudes, air is too thin to breath, that is why plane’s are air sealed and pressurized.

• When you fly on a plane, your ears pop because of the changes in air and cabin pressure.

Air pressure cont.Air pressure cont.

- Low pressure area: when air is heated it expands, becomes less dense, and rises, creating a low- pressure area. As the air rises and cools, the water vapor it carries forms into clouds.

- Low pressure usually accompanies unstable weather conditions.

- Centers of low pressure are called cyclones.

• Cold air is dense and sinks towards Earth’s surface, creating centers of high pressure.

• High pressure systems usually bring more stable weather conditions.

Global Wind BeltsGlobal Wind Belts

Global wind belts cont.Global wind belts cont.

• Prevailing winds: winds that blow from the same direction most of the time.

• Sailors use the prevailing winds to guide trips.

• The zone of winds along the equator is calm, with no prevailing winds called the doldrums.

Global wind belts cont.Global wind belts cont.

• A front occurs when two air masses of vastly different temperatures collide.

III. Oceans and CurrentsIII. Oceans and Currents

• Oceans also affect climate.

• Location in respect to an ocean changes climate. Landlocked areas will be cooler than locations near oceans because of warm currents that carry heated waters.

““Weather Factors”Weather Factors”

• I. Precipitation: – The process with which water changes from

liquid to a gas is called evaporation.– The amount of water vapor in the air is called

humidity.– Condensation is the process with which water

vapor changes from gas to a liquid.

StormsStorms

• Hurricanes: the most powerful and destructive tropical cyclones.

• Typhoons: hurricanes in the Western Pacific Ocean areas (Asia).

• Tornadoes: twisting spirals of air in the middle- latitude areas.

• The U.S. has more tornadoes than any other country.

Climate and Vegetation PatternsClimate and Vegetation Patterns

• “Tropical Climates”– Tropical Humid Climates

• Example: Vietnam, Indonesia• Areas close to the equator• They never have truly cold weather.

– Because the warm air is always rising, this unstable air leads to almost daily thunderstorms and heavy rainfall.

– In some parts of the tropical humid climates all rainfall is concentrated into a wet season.

• Tropical wet and dry climates:– Just to the N and S of the tropical humid

climate.– Also called the tropical savanna climate.

• A savanna is an alternating pattern of wet and dry season.

• “Dry Climates”– Arid climates – stable sinking dry air all year.– Locations include: Mexico, Southern Africa,

and South America for example.– Soils tend to be thin and rocky.

• Semiarid climate:– Receive more moisture than Arid climates but

less than more humid areas.

– Humid subtropical climate:• Found on the eastern side of continents where

there are warm air ocean currents.• Usually contains forests.

• Deciduous forests – trees that lose their leaves during part of the year

• Coniferous forests – remain green all year.

• High latitude climates-– Subarctic climate – Canada, Greenland,

Northern Russia, parts of northern Europe.– Cold climate, but also supports vast

evergreen forests.

– Tundra climate – permanently frozen soil called permafrost.

• Ice Cap climate – found on Earth’s polar regions.