Have you ever just looked Have you ever just looked at clouds?at clouds?
Why do we have Why do we have clouds?clouds?
Why are there Why are there different different shapes?shapes?
What can they What can they tell us about the tell us about the weather?weather?
Understanding CloudsUnderstanding Clouds
Clouds form as Clouds form as warmwarm air is air is forced upwardforced upward
As the air is As the air is forced upward, forced upward, it it expandsexpands and and coolscools
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?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?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
Understanding CloudsUnderstanding Clouds
As the air cools, As the air cools, the relative the relative humidity humidity reaches 100%reaches 100%
HumidityHumidity and and RelativeRelative Humidity Humidity
HumidityHumidity is the amount of is the amount of water vapor in the airwater vapor in the air
Relative humidityRelative humidity is a measure is a measure of the amount of water vapor of the amount of water vapor that the air is holding, that the air is holding, compared to the amount it can compared to the amount it can hold at a specific temperaturehold at a specific temperature
HumidityHumidity and and RelativeRelative Humidity Humidity
When the air is holding as When the air is holding as much moisture as it can, it’s much moisture as it can, it’s said to be said to be saturatedsaturated
Water vapor begins to condense Water vapor begins to condense in tiny drops around nuclei. in tiny drops around nuclei. Nuclei are small particles of Nuclei are small particles of dust, salt, and smoke in the dust, salt, and smoke in the
atmosphereatmosphere
Cloud TypesCloud Types Clouds are Clouds are
classified in classified in two two categories:categories:
ShapeShape, , HeightHeight, and , and sometimes sometimes RainRain CapacityCapacity
By Shape!By Shape! There are three main cloud There are three main cloud types that are based on shapetypes that are based on shape
Think you know any of them?Think you know any of them?
StratusStratus CumulusCumulus CirrusCirrus
Stratus CloudsStratus Clouds Stratus Stratus
clouds form clouds form a a smoothsmooth, , even sheeteven sheet
They usually They usually form at form at low low altitudesaltitudes
Cumulus CloudsCumulus Clouds These are These are
masses of masses of puffy, white puffy, white clouds, often clouds, often with flat baseswith flat bases
They form They form when air when air currents risecurrents rise
Cumulus CloudsCumulus Clouds They can be They can be
associated associated with both with both fair fair weather weather and and ThunderstormsThunderstorms, based on , based on their height.their height.
Cirrus CloudsCirrus Clouds Cirrus clouds Cirrus clouds
are high, thin, are high, thin, white, white, feathery feathery clouds clouds containing containing ice ice crystalscrystals
Cirrus CloudsCirrus Clouds Cirrus clouds Cirrus clouds
are usually are usually associated associated with fair with fair weather, but weather, but they may they may indicate indicate approaching approaching stormsstorms
By HeightBy Height The prefix of cloud names can The prefix of cloud names can
describe the height of cloud describe the height of cloud basesbases
Cirro:Cirro: High clouds above High clouds above 6000m6000m
By HeightBy Height
AltoAlto: Middle elevation clouds : Middle elevation clouds between between 2000 to 6000m2000 to 6000m
StratoStrato: Low level clouds below : Low level clouds below 2000m2000m
Rain CloudsRain Clouds NimbusNimbus
clouds are clouds are dark clouds dark clouds associated associated with with precipitationprecipitation
Rain CloudsRain Clouds When a nimbus When a nimbus
cloud is also a cloud is also a towering towering cumulus cloud, cumulus cloud, it’s called a it’s called a cumulonimbus cumulonimbus cloudcloud
Altocumulus Blue-gray, blanket-like Rain or snow likely Made of ice and water at middle heights
Cirrus Wispy ice clouds Seen in clear skies Mean good weather, but can mean a change in weather
Stratocumulus Dark, heavy water-droplet clouds
Rain or snow likely Seen at low or lower-middle heights
Cumulonimbus Giant thunderhead clouds
Thunderstorms with heavy rain
Hail, wind and lightening are on the way
Stratus Flat, low clouds Overcast skies Light rain, drizzle, or flurries likely
Cumulus Fluffy, lower clouds Fair weather Clouds can grow. If growing late in day, indicates change in weather
Name Appearance Conditions Facts
Ready for a quick review?Ready for a quick review?
1. Clouds can form when the 1. Clouds can form when the relative humidity reaches ____relative humidity reaches ____%%
2. In order for clouds to form, 2. In order for clouds to form, water vapor begins to water vapor begins to condense around ____of dust, condense around ____of dust, salt, and smokesalt, and smoke
3. Clouds are classified by ____ 3. Clouds are classified by ____ and____ and sometimes rain and____ and sometimes rain capacitycapacity
4. Puffy, white clouds are called?4. Puffy, white clouds are called? 5. Mid elevation clouds between 5. Mid elevation clouds between
2000 and 6000m2000 and 6000m
Let’s see how you did!Let’s see how you did!
1.1. 100100
2.2. NucleiNuclei
3.3. Shape and heightShape and height
4.4. CumulusCumulus
5.5. AltoAlto
Forms of Forms of PrecipitationPrecipitationPrecipitation (pre-sip-uh-Precipitation (pre-sip-uh-tay-shun) is any form of tay-shun) is any form of water that falls to the water that falls to the Earth's surfaceEarth's surface. .
Types of PrecipitationTypes of Precipitation
The type of precipitation that The type of precipitation that falls to the ground depends falls to the ground depends upon the formation process upon the formation process and the temperatures of the and the temperatures of the environment between the environment between the cloud and the surfacecloud and the surface
Can you name the Can you name the different types of different types of
precipitation?precipitation? RainRain SnowSnow HailHail SleetSleet
Freezing RainFreezing Rain
RainRain Rain develops when Rain develops when growing cloud droplets growing cloud droplets become too heavy to become too heavy to
remain in the cloud and remain in the cloud and as a result, fall toward the as a result, fall toward the
surface as rainsurface as rain
Rain can also Rain can also begin as ice begin as ice crystals that crystals that collect each collect each other to form other to form large large snowflakessnowflakes
As the falling As the falling snow passes snow passes through the through the freezing level freezing level into warmer into warmer air, the flakes air, the flakes melt melt
SnowSnow
Snow is formed when ice Snow is formed when ice crystals form from water crystals form from water vapor that is in the clouds vapor that is in the clouds directly above your heads!directly above your heads!
This process is called This process is called sublimationsublimation
HailHail Hail is formed Hail is formed
when updrafts when updrafts carry raindrops carry raindrops upwards into upwards into extremely cold extremely cold areas of the areas of the atmosphereatmosphere
HailHail There the There the
raindrops raindrops merge and merge and freeze. When freeze. When the frozen the frozen clumps get to clumps get to heavy they fall heavy they fall to earthto earth
HailHail Hail can vary Hail can vary
in size, from in size, from the size of a the size of a small stone to small stone to that of a that of a baseball! baseball! So So be carefulbe careful
SleetSleet Sleet is frozen raindrops. Sleet is frozen raindrops.
Sleet begins as rain or snow Sleet begins as rain or snow and falls through a deep and falls through a deep layer of cold air that layer of cold air that contains temperatures contains temperatures below freezing that exist below freezing that exist near the surfacenear the surface..
SleetSleet Rain that falls Rain that falls
through this through this extremely extremely cold layer has cold layer has time to freeze time to freeze into small into small pieces of icepieces of ice
Freezing RainFreezing Rain Freezing rain is falling rain that Freezing rain is falling rain that
cools below 0°C, but does not cools below 0°C, but does not turn to ice in the air turn to ice in the air
The water is “The water is “supercooledsupercooled””
When the drops hit anything When the drops hit anything they instantly turn to ice!they instantly turn to ice!
HumidityHumidity and and RelativeRelative Humidity Humidity
HumidityHumidity is the amount of is the amount of water vapor in the airwater vapor in the air
Relative humidityRelative humidity is a measure is a measure of the amount of water vapor of the amount of water vapor that the air is holding, that the air is holding, compared to the amount it can compared to the amount it can hold at a specific temperaturehold at a specific temperature
HumidityHumidity and and RelativeRelative Humidity Humidity
When the air is holding as When the air is holding as much moisture as it can, it’s much moisture as it can, it’s said to be said to be saturatedsaturated
In the cool of the morning, the In the cool of the morning, the air can’t hold as much air can’t hold as much moisture. We often have moisture. We often have dew dew on a summer morningon a summer morning
Once the air has warmed, the Once the air has warmed, the relative humidity drops since relative humidity drops since the air can hold more moisturethe air can hold more moisture