Precipitation is any form of water that falls to the earths surface. This includes snow, rain, sleet, freezing rain, and hail. Precipitation is mostly generated in clouds. When water vapor droplets in clouds become so large that updrafts within the clouds can no longer support them, the water will fall to the earth under the force of gravity.
Influencing Factors
Physical factors that affect the type, occurrence, and amount of precipitation include geological location, air temperature, barometric pressure, and wind speed and direction.
Importance
Precipitation is needed to spread water to the surface of the earth. Without precipitation, all land would most likely be an desert. The amount and duration of precipitation events affect both water level and water quality within a body of water.
Precipitation supplies freshwater to lakes, rivers, and estuaries, which is an important source of dissolved oxygen and nutrients. Droughts lower the freshwater input to estuaries and the water levels of inland lakes. Lake levels influence water drainage and circulation patterns in freshwater estuaries.
Measurement
Precipitation is typically reported in millimeters or inches of the height of liquid precipitation. This amount is typically added over a certain period of time, such as inches per day. Precipitation also can be measured in other various ways. A tipping bucket rain gage uses a small cup that fills with precipitation. When the cup is full, it will tip and empty. A counter tracks how many times the cup tips, and after a certain time interval, this number is converted to a precipitation measurement. Heated tipping bucket rain gauges allow the measurement of snow and sleet.