Mrs. Harsh6th Grade Science

2/9/2010

Air Rises at the Equator & Sinks at the PolesDifferences in air pressure are generally

cause by unequal heating of the earth.Area at equator receives more direct

sunlight, causing warm, less dense air to rise to create an area of low pressure.

Warm air flows toward poles.At the poles the air cools & sinks.As cold air sinks, pressure increases.The cold air then flows toward equator. P.

459Winds that blow from 30 degrees latitude

almost to the equator are called trade winds.

Pressure Belts are Found Every 30 degrees

Pressure belt: bands of high pressure & low pressure found about every 30 degrees of latitude.Air travels in many large circular patterns called convection cells, which are separated by pressure belts.

The Coriolis EffectNot only affects ocean currents, but also the path of winds as well.

Winds traveling north curve east and winds traveling south curve to the west.

Global vs. Local WindsGlobal Local

Combination of convection cells & Coriolis effect produces patterns of air circulation called Global Winds.

Generally move short distances and can blow from any direction.

Mountains or shorelines can produce temperature difference that cause local winds.

Land heats faster than water. Air above land becomes

warmer than above the ocean.Warm air rises, cold air from

ocean replaces it.At night land cools faster, wind

blows toward the ocean. P. 462

Jet StreamsNarrow belts of high-speed winds that blow

in the upper troposphere and lower stratosphere.

Unlike global winds, jet streams do not follow regular paths around the earth.

Jet streams affect the movement of storms, thus meteorologists can track a storm if they know the location of a jet stream.

Review:How does air temperature over landmasses

and adjacent bodies of water change between day and night.During the day, the air is cooler over water.

At night, the air is cooler over land.