1. Air Pressure & Wind Patterns

2. What is air pressure?  Air pressure is the force of molecules pushing on an area.  Air pressure pushes in all direction  Why don’t you feel air pressure since its so heavy?  Air pressure pushes in ALL directions, so the force up is also equal to the force pushing down.

3. Air Pressure and altitude  Air pressure decreases as you move higher in the atmosphere, due to less air above you  Density also decreases air pressure.  Air at sea level is more dense than at high altitudes

4. Air Pressure  As altitude increases, air pressure decreases.  Air pressure also decreases as the amount of water vapor in the air goes up.  Warm air is less dense than cool air, so when temperatures are higher, the air pressure is usually lower.

5. Uneven heating causes air to move  Weather is the Earth’s atmosphere at a particular time.  Wind is air that moves horizontally or parallel to the ground.  Uneven heating of the surface causes PRESSURE DIFFERENCES, which create wind.  Wind always moves HIGH TO LOW PRESSURE!!!!!

7. What factor determines wind strength?  The difference in air pressure between two areas determines the strength of the wind.

8. Global winds  Can travel thousands of kilometers in steady patterns.  Caused by uneven heating of equator and north and south pole  Influence of Earth’s rotation of the wind is called the Coriolis effect.

9. Bands of calm air separate global wind belts

10. Calm Regions  Doldrums low pressure zone near the equator  Horse latitudes are high pressure zones 30 degrees north and south of the equator

11. Wind Belts  Trade winds blow from the EAST, moving from horse latitude to equator.  Westerlies blow from the WEST, moving from horse latitudes to the poles  Easterlies blow from the EAST moving from polar regions toward mid-latitudes.  Storms form when cold easterlies meet warm westerlies

12. Jet streams  Jet Streams flow in the upper troposphere from WEST to EAST.  Moves as fast as 124 miles/hour.  Jet streams are used to make weather predictions.

13. Local Winds  Warm air rises over land during the day  Warm air rises over the ocean at night.

14. Monsoons  Monsoons are winds that change direction with the seasons.  Caused by the different heating and cooling rates of land and sea.

15. Temperature affects water in the air.  EVAPORATION is the process which a liquid can change into a gas, this requires extra energy  Condensation is the process by which a gas changes into a liquid, occurs when moist air cools.

16. WATER CYCLE….  When air rises in the atmosphere it cools, condensing into ice crystals or water droplets.  When the droplets or ice crystals get heavy enough, they fall to the ground as precipitation.

17. Humidity & Relative Humidity  Humidity is the amount of water vapor in the air, caused by the lack of evaporation.  Saturation is a condition in which the rates of evaporation and condensation are equal.  Relative humidity compares the amount of water vapor in air with maximum amount of water vapor that can be present at that temperature.  Dew point is the temperature at which air with a given amount of water vapor will reach saturation. Higher the DP of air, the more water vapor.

19.  Clouds are made of CONDENSED water vapor

21. rm is approaching.

22. Cumulus Clouds  Cumulus Clouds Puffy white clouds with dark bases. Appear in fair weather. If they grow tall, they produce storms.

23. Stratus Clouds.  Stratus Clouds Smooth clouds, form with no air movement. Can produce steady, light precipitation.

24. Fog  FOG clouds that rest on the ground or a body of water. Forms when surface is colder than the air above it.

25. TYPES OF PRECIPITATION  Rain and Drizzle- Most common. Water droplets or ice crystals melting as they fall, usually in stratus clouds.  Freezing Rain - Rain that freezes when it hits the ground.  Sleet - Rain the freezes into ice pellets while falling in cold air.  Snow - Forms from ice crystals that merge in clouds  Hail - Forms when ice pellets move up and down in clouds, growing larger as they gain layers of ice.