1. Chapter 18:1 Clouds & Precip.
Precipitation - any form of water that falls from a cloud.
Water vapor makes up only 0-4 % of the volume of air.
3 phases or states of matter(s,l,g)
6 phase changes - (f&m, e&c, s&d)

2. Changing state requires that energy is transferred in the form of heat.
Latent Heat=“hidden heat” READ
Evaporation is a cooling process.
Energy must be absorbed…(pool, sweat, energy comes from skin)
Condensation energy must be released
violent storms - energy from warm tropical waters.

3. Humidity=amount of water vapor in air.
Saturated - air can NOT hold any more water vapor
Warm air can hold more water vapor than cold air.
Relative Humidity - ratio of the actual amount of water vapor to how much it can hold at that temperature.

4. How to change relative humidity…
1. Changed by adding or removing water vapor
2. Change the temperature.
Lowering air temperature causes an increase in relative humidity.
Raising air temperature causes a decrease in relative humidity.

5. Dew Point - temperature to which air must be cooled to reach saturation or condensation (fog, clouds).
2 instruments used to measure humidity
1. Hair Hygrometer – uses a hair!
2. Sling Psychrometer - 2 bulbs (one dry one wet)

6. High dew point temperatures indicate moist air.
Low dew point temperatures indicate dry air.
When the dew point is at or near the actual surface temperature expect humid, cloudy, or foggy conditions.

7. 18.2 CLOUDS
Saturation occurs when water vapor is added to air or air is cooled.
Compressed air warms.
Expanded air cools.
Adiabatic Temp. Changes—occur when air is compressed or expanded.

8. 4 Air Lifting Processes:
1. Orographic lifting = mountains
2. Frontal Wedging = at fronts the warm air rises over the cooler air.
3. Convergence = two air masses meet and the result is air rising.
4. Localized Lifting = warmer pockets of air over parking lots etc. rise

9. AIR STABILITY:
Stable air (similar temperature top & bottom) does not rise too much thus few or no clouds.
Unstable air (warmer temperatures at bottom compared to air at top) air rises thus clouds & possibly thunderstorms.
Radiosonde = weather balloon.
Temperature Inversions = read it! (flipped)

10. 18.3 Clouds are classified by form & height.
Cirrus - (curl of hair) - high, thin, wispy, made of ice. (front approaching)
Cumulus - (pile/heap) - cauliflower, puffy, smaller ones - fair weather, larger & darker - thunderstorms.
Stratus - (layered) - sheets, steady rain to overcast conditions.

11. Nimbus - rain clouds(dark gray)
HIGH - cirro - icy, smaller, thinner
MIDDLE - alto - medium sized
LOW - larger
Vertical Developed Clouds - low to high severe thunder/anvil/cumulonimbus

12. Unusual Clouds Lenticular=lens shaped over mountains
Heimholtz Waves=uh looks like waves
Contrails=exhaust of of jets
Mammatus=light bulb looking clouds
Anvil Head=cumulonimbus – vertically developed thunder clouds
Jomammatus=just kidding!

13. Fog-cloud with base near or at the surface.
Fog forms from either cooling or evaporation.
How precipitation forms? (read about it)
Pages
Types of precipitation - snow, sleet, hail, glaze or freezing rain, and rain

14. How All Clouds Form 1. Warmer air rises.
2. As it gets higher it cools down.
3. As it cools down it reaches its dew point (because cool air can’t hold as much water vapor).
4. Air at its dew point is saturated.
5. Saturated air condenses into water droplets (and they make up clouds).