Weather

Wind

May 21, 2008

Wind

• A wind is the horizontal movement of air from an area of high pressure to an area of low pressure.

• All winds are caused by differences in air pressure.

• What causes most differences in air pressure?– Unequal heating of the atmosphere

Measuring Wind• Winds are described by their direction and

speed.• The name of a wind tells you where the

wind is coming from. For example, a sound wind blows from the south toward the north. A north wind blows to the south.

• Speed is measured with an anemometer.• An anemometer has cups mounted on

spokes that spin on an axle. The force of the wind turns the axle. A speedometer attached to the axle shows the wind speed.

Wind-Chill Factor

• Wind-chill factor is increased cooling caused by wind.

• Felt due to the wind blowing over skin removes body heat.– What type(s) of heat transfer takes place?

• Conduction and convection

Local Winds

• Local winds are winds that blow over short distances.

• Local winds are caused by __________.– Difference in pressure caused by ________– Unequal heating of Earth’s surface within a

small area.

Sea Breeze

• During the day land heats up faster than water.

• This causes lower pressure over land

• Wind moves air from over the water (high pressure) to over the land (low pressure)

Land Breeze

• At night the situation reverses.

• Land cools more quickly than water creating a high pressure

• Air flows from over land to over water

Monsoons

• Sea and land breezes over a large region that change direction with the seasons are called monsoons.

Global Winds

• Global winds are effected by the combination of two causes:– Global

convection currents

– Coriolis effect

Closure

• What is wind?

• What causes wind?

• How is wind measured?

• Describe how a sea/land breeze is formed.

• What is the difference between a sea/land breeze and a monsoon?

• What are global winds and how are they formed?

Homework

• Wind – Assignment

• Weather Quiz Friday

• Weather Test Tuesday