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)

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.

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.

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.

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)

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.

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.

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

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)

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.

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

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!

Fog-cloud with base near or at the surface. Fog forms from either cooling or

evaporation. How precipitation forms? (read about it) Pages 520-521 Types of precipitation - snow, sleet, hail,

glaze or freezing rain, and rain

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).