Precipitation Chapter 16 Section 5 Pages Chapter 16 Section 5 Pages

Precipitation Water evaporates into the air from every water surface on Earth and living things. Returns to Earth as a form of precipitation- any form of water that falls from clouds and reaches Earth’s surface.

Precipitation Comes from Clouds. –Not all clouds produce precipitation. Water Droplets grow by colliding and combining with other cloud droplets until they are heavy enough to fall.

How Precipitation Forms

Rain Most common form of precipitation. Must be.5mm in diameter. –Smaller= mist or drizzle. Fall from nimbostratus clouds.

Sleet Rain drops fall through a layer of air below 0°C (freezing point of water) and freeze into solid particles of ice (pellets). Smaller than.5mm in diameter.

Water vapor in a cloud is converted directly into ice crystals (snowflakes). Have an endless number of shapes and patterns. All with six sides or branches. Join together to form larger clumps. Snow

Freezing Rain Rain drops fall through the air and freeze when they touch a cold surface. Thick layers are heavy and can cause tree branches to break, power lines to fall. Makes sidewalks and roads slippery and dangerous.

Hail Larger than 5mm in diameter. Forms inside cumulonimbus cloud. (thunderstorm cloud) Causes damage to crops, buildings, and vehicles.

Hail Starts as an ice pellet inside a cold region of a cloud. Strong updrafts in the cloud cause the ice pellet to go up and down, adding a layer of ice each trip. Becomes heavy enough to fall.

Measuring Precipitation Rain gauge- an open ended can or tube that collects rainfall. –Has a funnel at the top to increase the accuracy of the measurement. Snow fall- measured with a ruler or snow is melted and the depth is measured.

Controlling Precipitation Drought- long periods of low precipitation. –Can damage crops. Which causes higher food prices. –Can cause widespread hunger or famine.

Controlling Precipitation Cloud seeding- a method to produce rain during a drought. Dropping Frozen CO 2 (Dry Ice) into clouds. –Causes water to start condensing on ice crystals and to grow. Dropping Silver Iodide Crystals –Acts as artificial condensation nuclei –Can be used to clear fog from an airport.