How are Clouds Born?

1. How are Clouds Born?

2. What type of air is the least dense? • Warm air is less dense than cold air. • Moist air is less dense than dry air. • The least dense air of all would be air that is __________ and __________

3. What type of air is the least dense? • Warm air is less dense than cold air. • Moist air is less dense than dry air. • The least dense air of all would be air that is warm and moist.

4. How does density affect air movement? • Cold, dry air is more dense and will ____. • Warm, moist air is less dense and will ____

5. How does density affect air movement? • Cold, dry air is more dense and will sink. • Warm, moist air is less dense and will rise.

6. What about temperature? • As we rise up through the troposphere temperature will _______. • Therefore a column of warm moist air rising will get colder as it gains altitude. • This column of air will also expand due to the fact that air molecules at higher altitudes are more spread apart (less influence by gravity). • Depending on the Relative Humidity of the air it could eventually cool until it reaches _________ Temperature.

7. What about temperature? • As we rise up through the troposphere temperature will decrease. • Therefore a column of warm moist air rising will get colder as it gains altitude. • This column of air will also expand due to the fact that air molecules at higher altitudes are more spread apart (less influence by gravity). • Depending on the Relative Humidity of the air it could eventually cool until it reaches dewpoint Temperature.

8. Do the Dew!! • At dewpoint the air is ________ and can no longer hold more water vapor. • If ________ ________ are present, tiny water droplets will condense on them to form a cloud. • Once the water droplets grow in size and mass, they can drop to the earth as precipitation.

9. Do the Dew!! • At dewpoint the air is saturated and can no longer hold more water vapor. • If condensation nuclei are present, tiny water droplets will condense on them to form a cloud. • Once the water droplets grow in size and mass, they can drop to the earth as precipitation.

10. And that’s how clouds are born!

11. Do Now • What is the Dew Point Temperature if the air temperature is 8 ˚ and the Relative Humidity is 51%? • Answer: -2 ˚

12. Do Now • What is the Relative Humidity if The dry bulb is 16 ˚ and the dew point is 4 ˚? • Answer: 45%

13. Do Now • What is the Relative humidity of the following air mass? Dry Bulb=26˚; Dew Point=11 ˚? • Answer: 39%

14. Do Now • What is the Relative humidity of the following air mass? Dry Bulb=26˚; Dew Point=18 ˚? • Answer: 64%

15. Do Now • What is the Relative humidity of the following air mass? Dry Bulb=26˚; Dew Point=25 ˚? • Answer: 92%

16. Do Now • What happens to relative humidity as the difference between air temperature and dew point temperature gets smaller? • Answer: Relative Humidity increases.

17. Do Now • What happens to the difference between air temperature and dew point temperature as air descends? (Use the cloud base altitude chart) • Answer: It increases.

18. Do Now • Is a descending air mass becoming more or less humid? • Answer: Less Humid.

19. Orographic Effect

20. Orographic Effect • A mountain can force air to rise. • As the air rises it cools and expands. • When the air reaches dew point temperature clouds form ( if condensation nuclei are present). • As the air moves past the mountain it will sink and become dry due to an increase in temperature.

21. Orographic Effect • The moist side of the mountain is called the windward side, and will have a lot of precipitation throughout the year. • The dry side of the mountain is called the leeward side and will often be the site of deserts.