Clouds

The Recipe Clouds need three things to form –Moisture –Cooling air to it’s Dew Point (condensation) –Condensation Nuclei (dust, smoke)

How do we get to the Dew Point The easiest way to bring an air masses temperature to it’s dew point is to move air to a higher altitude Moist Air As the moist air rises it’s temperature decreases and the water vapour begins to condense Warm Cool

The drier air is the farther it has to climb to reach it’s dew point At higher altitudes the temperatures are much colder and below freezing Dry AirMoist Air

Moist air has more water vapour and will become saturated at a warmer temperature As a result clouds will form at lower altitudes out of water droplets Moist Air

When the Dew point is below freezing this means that when the water vapour condense it will actually freeze into ice crystals This usually happens at very high altitudes in dry conditions Moist Air

Cloud types Clouds can be classified in three different ways –Shape –Altitude –Is there precipitation?

Cumulus –Puffy Stratus –Shapeless –fog Cirrus –Dry conditions –Ice crystals Cloud Shape

Cloud Height Up to 2000 m –Just use cloud shape name 2000 – 6000 m –Use prefix “alto” with the shape 6000 m and above –Use prefix “cirro-” or suffix “-cirrus” with cloud shape –Example – altostratus or cirrostratus

Precipitation –Use prefix “nimbo-” or suffix “nimbus” with the shape –Example - cumulonimbus

Precipitation The average drop is just 0.02 mm across in a cloud (too small to fall) By the time it hits the ground the average drop is 2 mm across So how does it grow?

Growing by Coalesce As the raindrop falls in the cloud it collides with other drops and begins to grow Wind will continue to circulate the drop until it becomes to heavy and falls to the ground as precipitation