What Causes Weather?

We should have discovered that land and water do not heat up at

the same rate. If things went correctly, we should know that

land heats up & cools down faster than water. Therefore, the

sun will heat up land quicker than oceans.

That means that the hot air over land rises and cool air from over the ocean will blow in to take its

place.

This uneven heating of the Earth causes hot air to rise and cold air to sink, leading to movement of

air in the atmosphere.

atmosphere

• A blanket of air surrounding the Earth

• made up of gases, water, dust, & other small particles

• It is divided into layers, based on temperature

• troposphere, stratosphere, mesosphere, thermosphere

Troposphere

• Bottom layer of the atmosphere

• most of Earth’s weather occurs here

• 8 miles thick (13 km)• Supersonic aircraft fly

in this layer

Stratosphere

• 2nd layer of the atmosphere

• contains the ozone layer

• some aircraft fly in this layer

• 21 miles (50 km)

Mesosphere

• Third layer of the atmosphere

• coldest layer• this is the layer where

meteors burn up• 50 miles (80 km)

Thermosphere

• The top layer of the atmosphere

• very high temperatures• gradually merges into

space• 196 miles (320 km)

Air pressure

• Gravity pulls on air

• lower in the atmosphere means greater air pressure

• cold air is heavier than warm air

• when cold air sinks it forces up warm air

Wind

• Movement of air• air is constantly

moving • 3 reasons• gravity, temperature,

Earth’s rotation• moves from high to

low or cold to warm

Local Wind

• A wind that results from a local difference in temperature

• wind blowing in from the sea over a beach during the day

• wind blowing from land to water at night

Prevailing winds

• Global winds• always blow in the

same direction• caused by uneven

heating of the Earth’s surface and rotation

• creates many circles of air

• moves in curved paths

????????

• What two factors cause prevailing winds?

• In what layer of the atmosphere does most weather occur?

• In what layer is the ozone layer?

• What drives all weather on the Earth?

• Why is the climate warmer near the equator?