1. Clouds

2. How do clouds form? Water vapor that has evaporated or transpirated into the air and as they rise they begin to cool As the water vapor cools it attaches itself to microscopic particles, such as dust, dirt and sea salt and a cloud is created

3. Types of clouds There are three types of cloud: High Clouds Found high in the troposphere, above 18,000 feet composed primarily of ice crystals usually present a bright white, or mostly white appearance except near sunrise or sunset Mid-level clouds Found in the middle of the troposphere, between 6,500 to 18,000 feet composed of ice crystals and water droplets Low clouds Found below 6,500 feet in the troposphere mostly composed of water droplets, however, when temperatures are cold enough, these clouds may also contain ice particles and snow.

4. High Clouds Cirrus (cirrus - curl or tuft of hair) Whiter than any other cloud in the sky These clouds have a hair-like, wispy appearance that look like tufts of hair Cirrocumulus (cirrus - curl or tuft of hair; cumulus - heap or pile) Made of lots of small white clouds - called cloudlets that are grouped together Composed almost entirely from ice crystals, The little cloudlets are regularly spaced, often arranged as ripples in the sky. They are relatively rare Cirrostratus (cirrus - lock or tuft of hair; stratus - flattened or spread out) a semi-transparent, whitish cloud that has a smooth appearance, like a veil totally or partly covering the sky, and generally producing a halo appearance. Can span thousands of miles across the sky

5. Mid-Level Clouds Altostratus clouds (altum - height; stratus - flattened or spread out) are gray or blue-gray in color usually cover the entire sky. often form ahead of storms that will produce continuous precipitation Altocumulus clouds (altum - height; cumulus - heap or pile) appear as gray, puffy masses, sometimes rolled out in parallel waves or bands. They usually appear on a warm, humid summer morning often means thunderstorms may occur by late afternoon.

6. Low Level Clouds Cumulus (cumulus - heap or pile) Detached, dense clouds that are cauliflower in shape Normally spotted in fair weather, but if they get too big they can produce showers Bright white on the top from the sun, but dark on the bottom Stratus (stratus - flattened or spread out) generally gray cloud layer Very low to the ground and can sometimes look like fog if thick enough, the cloud will drizzle, ice, or snow

7. Low Level Clouds (continued) Cumulonimbus (cumulus - heap; nimbus - rainy cloud) heavy and dense cloud in the form of a mountain or huge tower. The upper portion of the cloud is usually smoothed and almost always flattened in the shape of an anvil. Commonly known as thunderclouds Produces precipitation, like rain but can create extreme weather such as heavy downpours, hail storms, lightning and tornados Stratocumulus (stratus - flattened; cumulus - heap) clumps or patches of cloud varying in color from bright white to dark grey can be present in all types of weather conditions, from dry weather to light rain and snow

9. Types of Cloud Video

10. How Does Air Rise? 4 Ways that cause air to rise: 1) Mountain lift – air that rises because it is going over a mountain 2) Frontal lift – air that rises at a front 3) Convergence – air that is forced to rise because it is converging 4) Convection – air that rises because it is less dense that its surroundings

11. Mountain Lift Air moves upward when wind forces it toward a sloping terrain such as a mountain As the air rises, it expands and cools and clouds are formed Precipitation forms on windward side of mountain (the side the wind is hitting) A Rain shadow (little precipitation) forms on leeward side of mountain.

12. Windward SideLeeward Side

13. Rain Shadow A rain shadow is an area of less precipitation and clouds on the downwind side of a mountain (the anti-cloud!)

14. Rain Shadow

15. Frontal Lifting Fronts occur when two large air masses of different temperatures meet Four Types of Fronts 1) Cold Front 2)Warm Front 3)Stationary Front 4)Occluded Front

16. Cold Front A cold front occurs when a more dense air mass (cold air) pushes under a less dense air mass (warm air)

17. Clouds forming at a Cold Front A cold front creates Cirrus, cirrostratus (from thunderstorm anvils), sometimes Altocumulus and Cumulonimbus clouds Precipitation created is showers of rain or snow and often thunderstorms

18. Warm Front A warm front occurs when a less dense air mass (warm air) rides up over a more dense air mass (cold air)

19. Clouds forming at a Warm Front Cirrus, Cirrostratus (possibly cirrocumulus), Altostratus clouds can be formed Precipitation that is created is a steady rain or drizzle and snow, freezing rain or sleet may occur on the cold side of front

20. Stationary Front Forms when warm and cold air meet and neither air mass has the force to move the other. They remain stationary, or “standing still.”

21. Clouds forming at a Stationary Front Clouds associated with stationary fronts are usually stratus, altostratus, and cirrostratus clouds Precipitation is usually light to moderate, and steady rain or snow and can stay around for days, causing prolonged periods of dreary, gloomy weather.

22. Occluded Front Forms when a warm air mass gets caught between two cold air masses. The warm air mass rises as the cool air masses push and meet in the middle.

23. Clouds forming at a Occluded Front Since the warm air mass is being pushed up from the cold air masses on both sides, cumulonimbus clouds are formed. These clouds bring lots of precipitation.

24. Convergence Occurs when surface winds converge (come toward each other) Often occurs at low pressure troughs (the big L on a weather map or at the boundaries of two large air masses) Air rises as the surface winds come together cooling the air and forming clouds All of the different cloud types are formed by convergence, especially altocumulus, altostratus, stratocumulus and stratus clouds.

25. Convection Occurs when air molecules rise when they are warmed and become less dense than their surroundings Convection forms clouds because as the warm air rises it cools and condenses Often forms cumulus clouds or sometimes cumulonimbus