becomes saturated before the top does. There are different conditions of stability for parcels of air at different elevations. Example: = Dry adiabatic rate Altitude 4000' 3000' 2000' 1000' 0' Temperature (°F.) Lapse rate Dry adiabatic rate 0 ft. - 50°F. 50°F. 1000 " - 42°F. 44.5°F. 2000 " - 45°F. 39°F. 3000 " - 41°F. 33.5°F. 4000 " - 38°F. 28°F. From surface to 1000' the air is unstable because the air particle is warmer than its surroundings. From 1000' to 2000' the air is stable (because the air particle is colder than its surroundings (inversion)). From 2000' to 4000' the air is conditionally stable because the particle is between the dry and wet adiabatic rates. Evaporation and Condensation Evaporation is going on almost all of the time. Condensation, on the other hand, is not a constant thing, but is more intense and more perceptible. Impurities in water tends to reduce evaporation. There is a loss of heat when water molecules evaporate from a water surface (latent heat of evaporation), the amount of which varies with the temp., but is not a straight line function. Example: 600 cal./gm. is lost at 0°C, but only 540? cal./gm. is lost at 100°C. Wind increases evaporation by: 1) advection - lateral movement of air (this occurs along coastlines where continental air is carried over the water) 2) turbulence - vertical movement of air. Turbulence is far more significant in this process.