1. A mass of moist, stable air gliding up and over these mountains condenses into lenticular clouds.
Fig. 5-CO, p.110

2. FIGURE 5.8 The primary ways clouds form: (a) surface heating and convection; (b) forced lifting along topographic barriers;(c) convergence of surface air; (d) forced lifting along weather fronts.
Fig. 5-8, p.118

3. From the 1st Law of Thermodynamics we can calculate how much an imaginary air parcel should cool as it is lifted through the atmosphere.
This cooling rate is called the adiabatic lapse rate.
Dry adiabatic lapse rate = about -10C/km
Moist adiabatic lapse rate = about -6C/km

4. Skew-T Diagram
FIGURE 5.2 The dry adiabatic rate. As long as the air parcel remains unsaturated, it expands and cools by approximately 10°C per 1000 m; the sinking parcel compresses and warms by the same amount (10°C per 1000 m).
Adiabatic lapse rates (dry and moist) are thermodynamic benchmarks that the atmosphere strives to attain, though it is only sometimes successful.
Dry adiabats plotted as broken red lines for ease of use (-10C/km)
Moist adiabats plotted as broken green lines for ease of use (about -6C/km)
Fig. 5-2, p.113

5. FIGURE 5.12 Orographic uplift, cloud development, and the formation of a rain shadow. Note how warm and dry the air becomes just from advecting over the mountain – cf. Boulder, CO. Say:
Unsaturated air cools/warms at 10C/1000m.
Saturated air cools at about 6C/1000m (it can never warm at this rate because the cloud would evaporate and so immediately become unsaturated).
Dew point temperature increases/decreases by about 2C/1000 m.
Fig. 5-12, p.120

6. 0 m
3000 m
30 C
18 C
-4 C/1000 m
Temp.
Alt.
-10 C/1000 m
FIGURE 5.3 A stable atmosphere. Compare the actual lapse rate to the adiabatic benchmark and make a decision:
An absolutely stable atmosphere exists when a rising air parcel is colder and heavier (i.e., more dense) than the environmental air surrounding it. If given the chance (i.e., released), the air parcel in both situations would return to its original position, the surface.
If environmental lapse rate is more positive than dry adiabatic lapse rate then the atmosphere is absolutely stable
Fig. 5-3, p.113

7. FIGURE 5.4 Cold surface air, on this morning, produces a stable atmosphere that inhibits vertical air motions and allows the fog and haze to linger close to the ground.
Fig. 5-4, p.114

8. 3000 m
Alt.
-10 C/1000 m
-11 C/1000 m
0 m
30 C
Temp.
FIGURE 5.5 An unstable atmosphere. An absolutely unstable atmosphere exists when a rising air parcel is warmer and lighter (i.e., less dense) than the air surrounding it. If given the chance (i.e., released), the lifted parcel in both (a) and (b) would continue to move away (accelerate) from its original position.
If environmental lapse rate is more negative than dry adiabatic lapse rate then the atmosphere is absolutely unstable.
Fig. 5-5, p.115

9. FIGURE 5.6 Unstable air. The warmth from the forest fire heats the air, causing instability near the surface. Warm, less-dense air (and smoke)bubbles upward, expanding and cooling as it rises. Eventually the rising air cools to its dew point, condensation begins, and a cumulus cloud forms.
Fig. 5-6, p.115

10. FIGURE 5.9 Cumulus clouds form as hot, invisible air bubbles detach themselves from the surface, then rise and cool to the condensation level. Below and within the cumulus clouds, the air is rising. Around the cloud, the air is sinking.
Note the positive lapse rate in the stratosphere: very stable therefore very difficult to mix tropospheric air up into stratosphere.
Anvil on some cumulonimbus.
Time scale of 1-2 years for vertical mixing so only long-lived pollutants can get into stratosphere
(CFC, O3 layer)
Fig. 5-9, p.118

11. FIGURE 5.11 Cumulus clouds developing into thunderstorms in a conditionally unstable atmosphere over the Great Plains. Notice that, in the distance, the cumulonimbus with the anvil top has reached the stable part of the atmosphere.
Fig. 5-11, p.119

12. FIGURE 5.13 The formation of lenticular clouds and many other orographic clouds.
Fig. 5-13, p.120

13. FIGURE 5. 14 Lenticular clouds (mountain wave clouds) forming over Mt
FIGURE 5.14 Lenticular clouds (mountain wave clouds) forming over Mt. Rainier, Washington.
Fig. 5-14, p.121

14. FIGURE 5.18 The distribution of ice and water in a cumulonimbus cloud.
Cloud droplets do not freeze at 0 C: they should, but they are so small the chances of finding a freezing nucleus to trigger the freezing inside the drop are extremely low.
Only when the droplet gets really cold (about -15 C to -20 C) are a few “forced” to freeze.
Only when they get to -40C do they completely freeze (glaciate).
As a result, a cloud, or regions within a cloud, can be dominated by water, mixed ice/water or ice, depending on temperature.
Fig. 5-18, p.123

15. FIGURE 5.15 Relative sizes of raindrops, cloud droplets, and condensation nuclei.
Growing from CCN to cloud droplet by condensation is quite fast – a few minutes.
But, growing from a cloud drop to a rain drop by continued condensation ( a million-fold increase in volume) would take days – it just doesn’t happen in nature.
There must be another way to grow into a raindrop that does not involve condensation.
Fig. 5-15, p.121

16. Nobody really understands where these come from.
FIGURE 5.16 Collision and coalescence. (a) In a warm cloud composed only of small cloud droplets of uniform size, the droplets are less likely to collide as they all fall very slowly at about the same speed. Those droplets that do collide, frequently do not coalesce because of the strong surface tension that holds together each tiny droplet. (b) In a cloud composed of different size droplets, larger droplets fall faster than smaller droplets. Although some tiny droplets are swept aside, some collect on the larger droplet’s forward edge, while others (captured in the wake of the larger droplet) coalesce on the droplet’s backside.
Cloud drops:
Are nearly all the same diameter.
Experience a very viscous atmosphere – similar to what a human would experience in a pool of molasses.
As a result, they all fall at about the same velocity, and they go only where the air moves them and nowhere else. So how do rain drops grow?
Fig. 5-16, p.122

17. FIGURE 5.17 A cloud droplet rising then falling through a warm cumulus cloud can grow by collision and coalescence and emerge from the cloud as a large raindrop.
Note: You need vertical development in a cloud for precipitation to form.
Fig. 5-17, p.123

18. Which of the three drops drawn here represents the real shape of a falling raindrop?

19. FIGURE 5.23 The streaks of falling precipitation that evaporate before reaching the ground are called virga.
Fig. 5-23, p.128

20. FIGURE 5.19 In a saturated environment, the water droplet and the ice crystal are in equilibrium, as the number of molecules leaving the surface of each droplet and ice crystal equals the number returning. The greater number of vapor molecules above the liquid indicates, however, that the saturation vapor pressure over water is greater than it is over ice.
In other words, liquid droplets are more “volatile” than solid ice crystals.
Fig. 5-19, p.124

21. FIGURE 5. 20 The ice-crystal process
FIGURE 5.20 The ice-crystal process. The greater number of water vapor molecules around the liquid droplets causes water molecules to diffuse from the liquid drops toward the ice crystals. The ice crystals absorb the water vapor and grow larger, while the water droplets grow smaller.
Fig. 5-20, p.125

22. Fig. 5-21, p.125 FIGURE 5.21 Ice particles in clouds.
Photomicrograph of a rimed snowflake – accretion at work, Eventually this could grow into a graupel pellet.
Fig. 5-21, p.125

23. FIGURE 5.24 The dangling white streamers of ice crystals beneath these cirrus clouds are known as fallstreaks. The bending of the streaks is due to the changing wind speed with height.
Fig. 5-24, p.129

24. FIGURE 5.25 Computer color enhanced image of dendrite snowflakes.
Much better photographs are available at
Fig. 5-25, p.130

25. FIGURE 5.26 Sleet forms when a partially melted snowflake or a cold raindrop freezes into a pellet of ice before reaching the ground.
Fig. 5-26, p.131

26. FIGURE 5.27 An accumulation of rime forms on tree branches as supercooled fog droplets freeze on contact in the below-freezing air.
Fig. 5-27, p.131

27. FIGURE 5.28 A heavy coating of freezing rain during this ice storm caused tree limbs to break and power lines to sag.
Fig. 5-28, p.131

28. FIGURE 5. 29 The accumulation of small hail after a thunderstorm
FIGURE 5.29 The accumulation of small hail after a thunderstorm. The hail formed as super cooled cloud droplets collected on ice particles called graupel inside a cumulonimbus cloud.
Fig. 5-29, p.133

29. FIGURE 5.30 This giant hailstone — the largest ever reported in the United States with a diameter of 17.8 cm (7 in.) — fell on Aurora, Nebraska, during June, 2003.
Fig. 5-30, p.133

30. FIGURE 5.31Hailstones begin as embryos (usually ice particles) that remain suspended in the cloud by violent updrafts. When the updrafts are tilted, the ice particles are swept horizontally through the cloud, producing the optimal trajectory for hailstone growth. Along their path, the ice particles collide with supercooled liquid droplets, which freeze on contact. The ice particles eventually grow large enough and heavy enough to fall toward the ground as hailstones.
Fig. 5-31, p.133

31. FIGURE 5.32 Components of the standard rain gauge.
Fig. 5-32, p.134

32. FIGURE 5. 33 The tipping bucket rain gauge
FIGURE 5.33 The tipping bucket rain gauge. Each time the bucket fills with one-hundredth of an inch of rain, it tips, sending an electric signal to the remote recorder.
Fig. 5-33, p.135

33. NEXRAD WSR-88D
FIGURE 5.34 (a) Doppler radar display showing precipitation intensity over Oklahoma for April 24, The numbers under the letters DBZ represent the logarithmic scale for measuring the size and volume of precipitation particles.
Fig. 5-34a, p.136

34. FIGURE 5.34 (b) Doppler radar display showing1-hour rainfall amounts over Oklahoma for April 24, 1999.
Fig. 5-34b, p.136