Clouds and Moisture

Daily Web Guide

| Syllabus | Schedule | Weather Links | Email Kerry Magruder |

Reading Assignment	Browse through the Audubon Field Guide to the Weather and begin to familiarize yourself with the types of clouds. Figure out how you will make weather observations for your meteorological journal.
Reminders	Finish the Web Worksheet. Complete the Model of the Troposphere homework assignment. Turn both assignments in with your first journal.

Class notes:

Water facts

• The most wonderful chemical substance known...
  • Evaporative cooling
  • Temperature moderating (dry Oklahoma temps vary greatly)
  • Hydrogen bonding
• ...or not known. (Polywater)
• Sublimation: vapor to ice (snow)

The Water Planet

• Mars
• Moon
• Model Earth

Raindrops

• Totally clean air --> no weather!
• Measure drop diameter with dry cardboard
• Rain > 0.02 inch
  • Tall cumulonimbus clouds up to 10 miles high
• Drizzle < 0.02 inch
  • Layered stratus clouds 1 mile high, fall 1 hour
• Dew drops don't fall; they condense
• Freezing fog covers trees with ice

Hail

• Rain falls as sleet, freezing on the way down. Then recycled through the cloud by updrafts
• Each updraft adds a new icy layer; cut a hailstone in half and count the trip-layers
• 17.5 inch diameter hailstone, Coffeyville, Kansas, September 3 1979
• World's largest hailstone: ???

Why are clouds white?

• Why is the sky blue?
• What gives the sky a whitish hue?
• When is the sky reddish?
• "Red sky at night, sailor's delight; Red sky in morning, sailors take warning."

Cumulus clouds

• Accumulated, heaped up, puffy
• Formed by vertically rising air currents
• Fair weather afternoon cotton balls. Local heating, dissolve in evening, blue sky
• Thunderheads: cumulonimbus. "nimbus" = rain producing, tall. Thunderstorms and tornados. Along cold front, AFG p. 50

Stratus clouds

• Sheet-like, layered, spread out, blanket
• Fog if low enough, gray skies
• Air cooling without vertical movement.
• Produce drizzle, no rain or hail
• Nimbostratus produce rain (thick, dark)
• Altostratus. "alto" = medium altitude; 10,000 feet. rainy day ahead

High clouds; 20,000 feet

• Made of wind-stretched ice crystals
• Cirrus (feathery). Mare's tails a day before arrival of warm front
• Cirrostratus. Veils, Halos. "A ring around sun or moon means that rain will come real soon."

Mountains lift clouds

• Lenticular clouds (lens shaped), pressure waves
• Orographic rain; air cools with increased altitude as it is lifted over the mountains (AFG, p. 78)
• Rainshadow; Wet upwind, dry downwind