1. Moisture and Clouds Current Weather Humidity Clouds
Adiabatic Processes
Return Exam 1
For Next Class: Read Chapter 5 (pp )

2. Yes, it does snow in North Carolina! February 2009 Bethel, NC
100” mean annual snowfall at
highest elevations and >24” from
big storms at middle elevations
January 1977
Matney, NC
Johnson, Southern Snow

3. Humidity
What is humidity and what are the different ways to measure humidity in the atmosphere?

4. Water Vapor in the Atmosphere
Humidity: any one of many ways of describing the amount of water vapor in the air
Varies with the season, from one day to the next, within a single day, and from one place to another
© AMS

5. Water Vapor in the Atmosphere
Relative Humidity
Compares the actual amount of water vapor in the air with the amount of water vapor that would be present if that same air were saturated
Expressed as a percentage
When air is saturated,
relative humidity is 100%
Varies inversely with
temperature
© AMS

6. Relative Humidity
Figure 7.8

7. Water Vapor in the Atmosphere
Vapor Pressure
Pressure produced by the gas molecules composing air depends on
mass of the molecules
kinetic molecular activity
© AMS

8. Water Vapor in the Atmosphere
Saturated Air
Raising the air temperature increases saturation vapor pressure
Lowering the air temperature reduces saturation vapor pressure
© AMS

9. Saturation Vapor Pressure
Figure 7.12

10. Specific humidity: grams of water vapor per kilogram of air (g/kg)
Absolute humidity: grams of water vapor per cubic meter of air (g/m3)
Source: Wikipedia

11. Maximum Specific Humidity
Figure 7.13

12. Humidity Patterns
Figure 7.11

13. Precipitable Water
Depth of water that would be produced if all the water vapor in a vertical column of air were condensed into liquid water
© AMS

14. Dewpoint
The dewpoint is the temperature at which dew forms and is a measure of atmospheric moisture. It is the temperature to which air must be cooled at constant pressure and water content to reach saturation.
Source: Wikipedia

15. Wet Bulb Temperature
The wet-bulb temperature is the temperature a parcel of air would have if it were cooled to saturation (100% relative humidity) by the evaporation of water into it, with the latent heat being supplied by the parcel.
Critical temperature for snowmaking at ski resorts
Source: Wikipedia

16. Cloud Types and Identification
Clouds that produce precipitation are called nimbostratus and cumulonimbus.
Figure 7.22

17. Adiabatic Processes
Figure 7.17

18. Adiabatic Cooling
Figure 7.17

19. Adiabatic Heating
Figure 7.17

20. Atmospheric Lifting Mechanisms
Figure 8.6

21. Orographic Precipitation
Figure 8.9

22. Orographic Patterns
Figure 8.10

23. NC Precipitation
Where is the wettest place in North Carolina? Driest?

24. Asheville Lake Toxaway
Driest Weather Station inches (annual average)
Lake Toxaway
Wettest Weather Station inches (annual avg.)
EPA-NIEHS Climate Change Workshop, June 17, 2011

25. Average Annual Precipitation