Have you ever just looked at clouds?  Why do we have clouds?  Why are there different shapes?  What can they tell us about the weather?

Understanding Clouds  Clouds form as warm air is forced upward  As the air is forced upward, it expands and cools

 Four mechanisms that can cause air to rise are orographic lifting, frontal wedging, convergence, and localized convective lifting. Orographic lifting occurs when mountains act as barriers to the flow of air, forcing the air to ascend.  Orographic Lifting What causes air to rise?  Frontal Wedging A front is the boundary between two adjoining air masses having contrasting characteristics.

What causes air to rise?

Convergence is when air flows together and rises.  Convergence Localized convective lifting occurs where unequal surface heating causes pockets of air to rise because of their buoyancy.  Localized Convective Lifting

What causes air to rise?

Understanding Clouds  As the air cools, the relative humidity reaches 100%

Humidity and Relative Humidity  Humidity is the amount of water vapor in the air  Relative humidity is a measure of the amount of water vapor that the air is holding, compared to the amount it can hold at a specific temperature

Humidity and Relative Humidity  When the air is holding as much moisture as it can, it’s said to be saturated

Can you explain this graph?

Water vapor begins to condense in tiny drops around nuclei. Nuclei are small particles of dust, salt, and smoke in the atmosphere

Cloud Types  Clouds are classified in two categories:  Shape, Height, and sometimes Rain Capacity

By Shape!  There are three main cloud types that are based on shape  Think you know any of them?  Stratus  Cumulus  Cirrus

Stratus Clouds  Stratus clouds form a smooth, even sheet  They usually form at low altitudes

Cumulus Clouds  These are masses of puffy, white clouds, often with flat bases  They form when air currents rise

Cumulus Clouds  They can be associated with both fair weather and Thunderstorms, based on their height.

Cirrus Clouds  Cirrus clouds are high, thin, white, feathery clouds containing ice crystals

Cirrus Clouds  Cirrus clouds are usually associated with fair weather, but they may indicate approaching storms

By Height  The prefix of cloud names can describe the height of cloud bases  Cirro: High clouds above 6000m

By Height  Alto: Middle elevation clouds between 2000 to 6000m  Strato: Low level clouds below 2000m

Rain Clouds  Nimbus clouds are dark clouds associated with precipitation

Rain Clouds  When a nimbus cloud is also a towering cumulus cloud, it’s called a cumulonimbus cloud

AltocumulusBlue-gray, blanket-likeRain or snow likelyMade of ice and water at middle heights CirrusWispy ice cloudsSeen in clear skiesMean good weather, but can mean a change in weather StratocumulusDark, heavy water- droplet clouds Rain or snow likelySeen at low or lower- middle heights CumulonimbusGiant thunderhead clouds Thunderstorms with heavy rain Hail, wind and lightening are on the way StratusFlat, low cloudsOvercast skiesLight rain, drizzle, or flurries likely CumulusFluffy, lower cloudsFair weatherClouds can grow. If growing late in day, indicates change in weather Name AppearanceConditions Facts

Ready for a quick review?  1. Clouds can form when the relative humidity reaches ____%  2. In order for clouds to form, water vapor begins to condense around ____of dust, salt, and smoke

 3. Clouds are classified by ____ and____ and sometimes rain capacity  4. Puffy, white clouds are called?  5. Mid elevation clouds between 2000 and 6000m

Let’s see how you did! Nuclei 3.Shape and height 4.Cumulus 5.Alto

Forms of Precipitation  Precipitation (pre-sip-uh- tay-shun) is any form of water that falls to the Earth's surface.

Types of Precipitation  The type of precipitation that falls to the ground depends upon the formation process and the temperatures of the environment between the cloud and the surface

Can you name the different types of precipitation?  Rain  Snow  Hail  Sleet  Freezing Rain

Rain  Rain develops when growing cloud droplets become too heavy to remain in the cloud and as a result, fall toward the surface as rain

 Rain can also begin as ice crystals that collect each other to form large snowflakes  As the falling snow passes through the freezing level into warmer air, the flakes melt

Rain from snow!

Snow  Snow is formed when ice crystals form from water vapor that is in the clouds directly above your heads!  This process is called sublimation

Hail  Hail is formed when updrafts carry raindrops upwards into extremely cold areas of the atmosphere

Hail  There the raindrops merge and freeze. When the frozen clumps get to heavy they fall to earth

Hail  Hail can vary in size, from the size of a small stone to that of a baseball! So be careful

Sleet  Sleet is frozen raindrops. Sleet begins as rain or snow and falls through a deep layer of cold air that contains temperatures below freezing that exist near the surface.

Sleet  Rain that falls through this extremely cold layer has time to freeze into small pieces of ice

Freezing Rain  Freezing rain is falling rain that cools below 0°C, but does not turn to ice in the air  The water is “supercooled”

When the drops hit anything they instantly turn to ice!

Humidity and Relative Humidity  Humidity is the amount of water vapor in the air  Relative humidity is a measure of the amount of water vapor that the air is holding, compared to the amount it can hold at a specific temperature

Humidity and Relative Humidity  When the air is holding as much moisture as it can, it’s said to be saturated

Can you explain this graph?

 In the cool of the morning, the air can’t hold as much moisture. We often have dew on a summer morning  Once the air has warmed, the relative humidity drops since the air can hold more moisture