Do Now

1. Do Now • 1. What Factors influence air temperature? • 2. What factors influence air pressure? • 3. How does air move in and around a low pressure system? • 4. What happens to air as it rises?

2. Dew Point and Relative Humidity

3. Dew Point • The temperature at which the air can no longer hold all of its water vapor, and some of the water vapor must condense into liquid water. • The dew point is always lower than or equal to the air temperature.

4. If the air temperature cools to the dew point, or if the dew point rises to equal the air temperature, then dew, fog or clouds begin to form. • If the dew point temperature equals the air temperature, the relative humidity is 100%. • Relative Humidity is a comparison of the actual amount of water in the atmosphere to the amount of moisture it can hold.

5. As air temperature increases the air’s ability to hold moisture increases. • In order for a cloud to form there must be condensation nuclei present and the air must be saturated(100% relative humidity). • http://www.youtube.com/watch?v=z6B3YMzPu2c&safe=active

8. Rising Moist Air = Cloud As air rises it expands and cools.

9. Why do we sweat? Evaporation is a cooling process. When the air is dry(low relative humidity) evaporation happens quickly When the air is moist(high relative humidity) evaporation happens slowly

11. Dry Bulb 22°C Wet Bulb 16°C

12. Dry Bulb 22°C Wet Bulb 16°C

13. Dry Bulb 4°C Wet Bulb -1°C

14. Dry Bulb 4°C Wet Bulb -1°C

15. Forms of Precipitation • Rain • Snow • Sleet • Freezing Rain • Hail • Condensation- Dew, Frost, Clouds

16. Condensation = Clouds

17. Fog

18. Wet Snow

19. Freezing Rain

21. Mechanisms That Cause Precipitation • Fronts • Lows • Convection Within An Airmass • Geographic Barriers

22. Earth’s Surface is Heated. Warm Air Rises and expands causing it to cool.

26. Mechanisms That Cause Precipitation • Fronts • Lows • Convection Within An Airmass • Geographic Barriers • http://www.youtube.com/watch?v=3dZKUMtT0v0&safe=active

28. Air Masses • Air masses are described by their place of origin. • Where an air mass originates determines the properties of the air mass. • Air masses are described by temperature and moisture content.

30. Fronts • Cold Front • Warm Front • Occluded Front • Stationary Front

31. Cold Front • A continental polar airmass moves into a maritime tropical airmass. • The denser continental polar air mass moves under the maritime tropical airmass forcing it to rise. • As the maritime tropical air rises it cools allowing clouds and precipitation to form.

32. cP mT X Earth’s Surface Cold Front

33. Where is the zone of precipitation? What types of clouds form along a cold front?

37. Warm Front • A maritme tropical airmass moves into a continental polar airmass. • The less dense maritme tropical airmass rides up and over the continental polar airmass. • As the maritime tropical air rises it cools allowing clouds and precipitation to form.

38. mT cP X Earth’s Surface Warm Front

45. Occluded Front • An occluded front forms is association with a low pressure system when a maritime tropical air mass gets caught between two continental polar air masses. • The less dense maritime tropical air mass is forced to rise between the two continental polar air masses. • As the maritime tropical air rises it cools allowing clouds and precipitation to form.

46. mT cP cP Earth’s Surface X Occluded Front

47. Rotation is faster for the cold front