CLOUD FORMATION Like fog, clouds form when air cools to its ________________________. Clouds can form at ____________________________ in the troposphere. At temperatures above freezing, clouds are made of __________________________. Below freezing, clouds are usually mixtures of snow crystals and ____________________ water. Name: ______________________________

Types of Clouds There are 4 main types of clouds: Clouds are classified both by their ________________ (or altitude) and their ______________. Cloud heights are measured as distance above the _______________, not above sea level.

Stratus and strato- describe clouds that form in ___________________. When air movement is mainly _________________________, clouds form in layers. Above 7000 meters, they are called ________________________. At altitudes over meters, they are called __________________________. Stratus clouds are layered, _________clouds.

When air movement is mainly vertical, clouds grow upward in great puffs, these are cumuliform clouds. Above 7000 meters, they are called cirrocumulus. Between 2000 and 7000 meters, cumuliform clouds are called altocumulus.

The names of the most common clouds are formed from one or more of the same five words or word parts: - stratus/strato- means layered - cumulus/cumulo- means clouds that grow upward - cirrus/cirro- describe high, feathery ice clouds - alto- describes clouds located between 2000 and 7000 meters - Nimbus/nimbo- refer to dark rain clouds.

CLOUD FORMATION The shape of a cloud shows how the air moves through it. Cumulus clouds form when rising air currents are lighter than the surrounding air, so they float. As air above warm ground areas heats up, the air becomes less dense and rises. As it rises, it cools. If the air cools to its dew point, a cumulus cloud forms. The atmospheric level at which condensation occurs is called the lower condensation level.

The adiabatic lapse rate is the rate at which air cools as it rises. Unsaturated air cools at a rate of about 10 o C for every kilometer it rises. The cooling is caused ONLY by the expanding air as it rises. This rate is called the dry-adiabatic lapse rate.

The moist-adiabatic lapse rate is the rate at which saturated air cools as it rises. This rate varies from about 5 o C - 9 o C per kilometer. The moist-adiabatic lapse rate is less than the dry-adiabatic lapse rate because when water vapor condenses, it releases heat. This release of heat is a very important factor in the formation of clouds and storms.

The heat released during condensation can fuel the growth of huge cumulonimbus clouds. In fact, knowing the condensation level is important for forecasting the weather. For example, by knowing the height at which clouds will form and how high they will grow, meteorologists can predict the severity of a resulting storm.