Clouds form when rising air cools and the moisture in it condenses to form water droplets
As the air cools the amount of water vapor needed for saturation decreases and the relative humidity increases.
Relative humidity reaches 100% the air is saturated
Then water vapor begins to condense in tiny droplets around small particles (dust & salt)
Millions of droplets form clouds
Classified by shapes & height
The shape and high vary on the temp, pressure, and water vapor in the atmosphere.
Some extend high and others are low and flat
Dense clouds bring rain or snow
Thin clouds appear on sunny days
Three Main Types:
– low-level blankets of cloud. The name "stratus" means "layers" in Latin, although you in fact rarely see the layers in stratus clouds. Instead they appear as a grey, shapeless sheet of cloud extending in all directions across the sky. They are usually only about 1 km thick, but can be as much as 1000 km wide. Stratus clouds build up when a layer of warm, moist air rises slowly over a mass of colder air. These clouds are often dark and gloomy, and are associated with rain and drizzle. Stratus clouds can sometimes rest on the ground or sea instead of up in the air, and they are then called ‘fog’.
Three Main Types
– fluffy, cumulus clouds are named after the word "heap". These are the most familiar clouds and look like heaps of cotton wool or large cauliflower’s. Cumulus clouds are found at a height of about 500 metres and are composed of tiny water droplets. They form when sunshine warms pockets of moist air and causes them to rise quickly. As they get higher, the pocket of air billows out and forms the familiar fluffy shape as the moist air cools and condenses into water droplets. These clouds are usually seen in fine weather, when the sky is blue.
Three Main Types
– high-level, wispy clouds. The name originates from the Latin word meaning "curl of hair". These feathery clouds form very high up in the sky (at altitudes between 5 km and 14 km) where it is very cold. They are therefore made up of tiny ice crystals rather than water droplets. Cirrus clouds occur in warm air which is being slowly lifted over a large area by an approaching cold front, and they are therefore often the signal of bad weather.
All the forms of water that fall from the air to the Earth's surface are called precipitation. Whether the precipitation is snow, rain, sleet or hail depends on the temperature of the air that the water falls through. If the air is above freezing, the precipitation will most likely be rain. If the air is below freezing, the precipitation will most likely be snow. When air temperature is only a few degrees above freezing, precipitation may fall as sleet.
Hail is most commonly formed within the cumulonimbus clouds of thunderstorms. Large updrafts of air can throw rain droplets high up into the tops of the cloud. The temperature is well below freezing, and the droplets freeze. The droplets then fall and can become caught in further updrafts, adding a second coating of ice to make the hailstones larger. This cycle continues until the hailstones are too heavy to be lifted again. They then falls as hail. The stronger the updrafts in the cloud, the longer the hail develops, and the larger the hailstones are when they falls.