Water in the Atmosphere Power point brought to you by your science teacher: Mr. Foley Power point brought to you by your science teacher: Mr. Foley Also brought to you by water: it’ll quench your thirst!

The Water Cycle The movement of water between the atmosphere and Earth’s surface is the water cycle.

Evaporation Evaporation is the process by which water molecules in water escape into the air as water vapor. Water vapor is also added by living things…even you!

Humidity  Humidity is the measure of amount of water vapor in the air.  The percentage (%) of water vapor in the air compared to maximum amount the air could hold is called relative humidity.  At 10º Celsius, 1 cubic meter of air can hold a max of 8 grams of H 2 o

Psychrometer  A tool used to measure relative humidity.

Clouds Clouds of all kinds form when water vapor in the air becomes liquid water or ice crystals. Condensation is the process by which molecules of water vapor in the air become liquid water. The temperature at which condensation begins is called the dew point.

Clouds continue… In order for water vapor to condense it needs a surface to attach to such as tiny particles of dust, salt, or soil in our air. This is how the clouds form in the middle of our atmosphere yo! Sometimes the water condenses on things we see around us and makes dew…if cold enough it turns to frost. The warm air near the ground rises and expands upward. As this happens it cools off becoming less dense. When the air is cooled to its dew point, and if particles are around in the air, then clouds can form! Wicked cool.

Rain shadow…what?!  When the wind hits the windward side of a mountain, that air is pushed up the mountain causing it to cool to form clouds, which then cry upon us and give life below.  But wait, the other side of the mountain range, the leeward side, gets jipped! The leeward side gets little moisture complemented with dry winds and a desert climate.  The leeward side has warm dry winds called Chinooks.

Rain shadow: p.s. the camel is a relative of Mr. Stark.

Types of Clouds

Cumulus (kyoo myuh lus)  “cumulus” means “heap” or “mass”  Form at 2km above ground up to 18km.  Generally are a sign of fair weather.  The tall towering flat top cumulus clouds produce showers and thunderstorms. They are called cumulonimbus clouds. Nimbus meaning “rain.”

Cumulus pictures

altocumulus Alto = “high” 2 – 6 km above the ground.

cumulus

Stratus Clouds Stratus clouds form flat layers. Strato = “spread out” Stratus clouds usually cover most of the sky.

Altostratus

Stratus/Nimbostratus

Cirrus (seer us)  Cirrus clouds are wispy and feathery.  Form only at high levels above 6km where temps are really low.  Cirrus clouds are made of ice crystals.

cirrocumulus: indicate a storm is on its way.

cirrus