Water, The Atmosphere, and You

The Changing Forms of Water Water is the only substance on earth to naturally exist as a solid, liquid, and gas –Evaporation and condensation Latent Heat – energy that is absorbed or released during a phase change

Humidity and Dew Point Humidity – Percentage of water vapor in the air –Controlled by rates of condensation and evaporation –Saturated air = high humidity Dew Point – Temperature at which water will change from water vapor into tiny water droplets called dew (condensation) –Cooling process –Low pressure  high pressure –The higher the humidity the smaller the gap between air temperature and dew point

Why is dew forming on the outside of this ice cold glass of high quality H2O?

Clouds

Classification of Clouds Clouds are classified by their shape and their altitude. Three basic shapes –stratus clouds –cumulus clouds –cirrus clouds. Three altitude groups –low clouds (0-2,000 m) –middle clouds (2,000 to 6,000 m) –high clouds (above 6,000 m).

Stratus Clouds

Stratus clouds cover large areas of sky and often block out the sun Stratus means “sheet like” or “layered” Flat bottom clouds found at low altitudes Typically grey Two variations of stratus clouds are known as nimbostratus and altostratus. –Nimbostratus clouds can cause heavy precipitation –Altostratus clouds form at middle altitudes and are generally thinner than the low stratus clouds and produce very little precipitation.

Cumulus Clouds

low-level, puffy cloud with a top that resembles cotton balls and has a dark bottom –Cumulus means “piled” or “heaped.” –Most have a flat base If the base of cumulus clouds begins at middle altitudes, the clouds are called altocumulus clouds. Low clouds that are a combination of stratus and cumulus clouds are called stratocumulus clouds. Cumulonimbus – High, dark storm clouds that are often accompanied by rain, lightning, and thunder.

Cirrus Clouds

Feathery and thin cloud –Cirrus means “curly.” –Highest altitude of any cloud in the sky –Made of ice crystals –Very thin so light can easily pass through them Cirrocumulus clouds are rare, high-altitude, billowy clouds Cirrostratus clouds – Long, thin clouds that form a transparent veil across the sky. –A halo may appear around the sun or moon when either is viewed through a cirrostratus cloud.

Moon Halo through cirrostratus clouds

Sun Halo through cirrostratus clouds

Formation of Clouds Recipe for a cloud: –Water vapor –Condensation –Condensation nuclei