 Air Pressure: the amount that air presses or pushes on anything  You usually do not notice air pressure, but you do notice its effects Air Pressure and Wind

 As you travel higher above the earth, the air pressure changes  Higher=Less Pressure

 Temperature also changes the higher you travel.  The Earth’s surface heats the air.  Farther From Earth = Cooler Temperature Temperature: 34ºF Temperature: 54ºF Temperature: 76ºF

 As the air near the surface of the earth becomes warmer, the air particles move farther apart.  The air become lighter and rises  This is when a low-pressure area forms Low Air Pressure

 Cole air s heavier than warm air.  It’s air particles are packed closer together and push down harder.  This is when a high-pressure area forms. High Air Pressure

 Air moves from a place with high pressure to a place with low pressure.  Air moving is called wind.  When the cooler air from a high-pressure area sinks toward the earth, it causes wind.  That’s why you will feel a cool breeze…even on a warm, summer day. Wind

 Barometer Measuring Air Pressure

 Wind Vane Measuring Wind Direction

 Anemometer Measuring Wind Speed

 What causes wind? Let’s Review! Wind is caused by air moving from a high-pressure area to a low-pressure area.

 How is air pressure measured? Air pressure is measured by a barometer.

 How do scientists measure wind direction? Scientists measure wind direction with a wind vane.

 How do scientists measure wind speed? Scientists measure wind speed with an anemometer.