•          Precipitation is any form of water that falls from clouds and reaches Earth's surface.

–        Cloud droplets or ice crystals must grow heavy enough to fall through the air.

–        Droplets grow by colliding and combining with other cloud droplets.

–        When heavy enough, they fall out of the cloud as raindrops.

•          Common types of precipitation include:

–        Rain

•          Most common type of precipitation

•          Rain = 0.5 mm in diameter

•          Smaller drops are called drizzle or mist

•          Common types of precipitation include:

–        Sleet

•          Ice particles smaller than 0.5 mm in diameter

•          Forms when raindrops fall through a layer of freezing air and turn into solid ice particles.

•          Common types of precipitation include:

–        Freezing Rain

•          Forms when raindrops freeze on a cold surface.

•          Thick layers of ice may form, causing damage to tree branches and power lines.

•          Common types of precipitation include:

–        Hail (Hailstones)

•          Pellets of ice larger than 5 mm

•          Forms only inside cumulonimbus clouds during a thunderstorm.

–        Strong updrafts in the cloud carry the hailstone up and down through the cold region many times, adding a new layer of ice.

–        It eventually falls when it becomes too heavy for the updraft.

•          Common types of precipitation include:

–        Snow

•          Forms when water vapor in a cloud is converted directly into ice crystals

•          Each snowflake has six sides.

•          Measuring Precipitation:

–        Meteorologists measure rainfall with a rain gauge.

•          Rain gauge = open-ended can or tube that collects rainfall.

•          Rain is measured by dipping a ruler into the water or by reading a marked scale.

•          Snowfall is measured by using a ruler or by melting collected snow and measuring the depth of water it produces.

–        On average, 10 cm of snow = 1 cm of rain

•          Drought

–        Drought is a long period of low precipitation.

–        Cause crops to fail which producing widespread hunger, or famine.

–        Prevention?

•          Cloud seeding = dropping tiny crystals of dry ice and silver iodide from airplanes.

•          Water vapor can condense on the particles of silver iodide, forming rain or snow.

•          The dry ice cools the droplets so they can condense without particles.