1.  ADIABATIC HEATING/COOLING A. Adiabatic temperature changes occur when 1. Air is compressed as pressure increases a. Motion of air molecules increases b. Air will warm as descends due to compression 2. Air expands as pressure decreases a. Air will cool as rises due to expansion b. This is the most imp. process of cloud formation B. Adiabatic rates 1. Dry adiabatic rate a. Unsaturated air b. Rising air expands & cools at 1◦C /100m(10º/1000m) c. Descending air is compressed; warms at 1◦C/100 m

2. Can you explain why warm air cools as it rises?  Imagine a parcel of air rises after it is warmed.  Examine the relationship between pressure and the movement of air (speed and direction).

3. –Adiabatic Cooling  Decrease in temperature of an expanding gas –Adiabatic Heating  Heating of a gas as it undergoes compression

4. WINDWARD SIDE WET Air rises, expands, cools, condensation occurs, clouds form and it rains. LEEWARD SIDE DRY Air descends, is compressed, and heats up.

5. http://www.mrphome.net/mrp/rainsh adow.swf

6. http://www.mrphome.net/mrp/rainsh adow.swf

7.  As a parcel of dry air is moved upward, it expands and cools according to the dry adiabatic lapse rate. This graph compares the temperature of a rising and adiabatically cooling parcel of dry air with the average temperatures of the surrounding atmosphere when the temperature at the surface is 30 O C (86 O F).

8.  When the dew point temperature is reached in a rising parcel of air, the latent heat of vaporization is released as water vapor condenses. This release of heat warms the air, decreasing the density and accelerating the ascent. The new lapse rate from the release of latent heat is called the wet adiabatic lapse rate.

9. Determining Cloud Base What weather variables influence cloud base? Temperature Humidity Dew Point Air Pressure

10.  One atom of oxygen  Two atoms of hydrogen o + HH -- Water Chemical Properties