ABSTRACT
In nature, water can take solid or liquid form under many situations in the atmosphere and on the surface of the earth. Precipitation is a special category or subset of the conditions under which water exists. Specifically, water particles, in either liquid or solid form, to be defined as precipitation that must both 1) fall from the atmosphere and 2) reach the ground. This definition would then include rain, drizzle, snow, sleet, and freezing rain and exclude other forms of water in the atmosphere such as clouds, fog, dew, rime, or frost in that it must fall from the atmosphere. It also eliminates forms such as virga since precipitation must reach the ground.[1]
BEGINNINGS OF THE PROCESS
What determines the type of precipitation? The vertical temperature and moisture profiles of the atmosphere are important factors. If ice crystals encounter warm and cold layers of air on the way to the ground, then the form of precipitation could change. Vertical motions of the air are also factors since they will affect the path of the water particles on the way to the ground. No matter what the type of precipitation we see at the ground, the process usually begins in clouds. Tiny droplets join to form much bigger drops, which, begin to fall earthward. At lower temperatures, clouds may consist of ice crystals that form from the freezing of water droplets or sublimate directly from water vapor into solid ice crystals. The crystals begin to collide and aggregate to form snowflakes that start to fall toward the earth. The process, however, is just beginning. The temperature and moisture structure of the atmosphere determines which form of precipitation is observed at the ground.
