Bell RingerBell Ringer

What is dew point? What is dew point? How do you think this How do you think this relates to clouds?relates to clouds?

What do all of these words have What do all of these words have in common?in common?

Rain Hail

Sleet

Snow

Cirrus

Cumulus

Stratus

Fog

Hail

Glaze

Clouds and Clouds and PrecipitationPrecipitation

Cloud FormationCloud Formation

Clouds form Clouds form when when air is air is cooled to its cooled to its dew pointdew point as it as it risesrises

Video: How Clouds Form

Processes that lift AirProcesses that lift AirOrographic lifting •Elevated terrains, such as mountains act as a barrier to air flow•Air goes up mountain slopes•Causes a rain shadow effect

Frontal Wedging •Warm and cold air collide•Cooler, denser air acts as a barrier over which warmer dense air rises

Rising AirRising AirConvergence Convergence When air is the lower When air is the lower

atmosphere flows atmosphere flows together, lifting airtogether, lifting air

Localized Convective LiftingLocalized Convective LiftingUnequal heating of EarthUnequal heating of Earth’’s surface s surface may cause pockets of air to be may cause pockets of air to be warmed more than the warmed more than the surrounding airsurrounding air

The warm air is less dense and risesThe warm air is less dense and rises

CloudsCloudsClouds are Clouds are classified on classified on the basis of the basis of their form their form and height.and height.

Classified by FormClassified by FormCirrus Cirrus ((cirruscirrus = curl of hair) = curl of hair)

high, white, and thinhigh, white, and thinCumulus Cumulus ((cumuluscumulus = a pile) = a pile)

rounded individual cloud rounded individual cloud masses that have a flat masses that have a flat base and the appearance base and the appearance of rising domes or towersof rising domes or towers

Stratus Stratus ((stratusstratus = a layer) = a layer) best described as sheets best described as sheets or layers that cover much or layers that cover much or all of the skyor all of the sky

Classification of Classification of Clouds by Clouds by

HeightHeightHigh CloudsHigh Clouds Have bases above 6000 Have bases above 6000

metersmeters Cirrus: high, white and thinCirrus: high, white and thin Cirrostratus: flat layersCirrostratus: flat layers Cirrocumulus: fluffy massesCirrocumulus: fluffy masses

Middle Clouds (Alto)Middle Clouds (Alto) Have bases between 2000 Have bases between 2000

and 6000 metersand 6000 meters Altocumulus: rounded Altocumulus: rounded

masses that are larger and masses that are larger and denser than cirrocumulus denser than cirrocumulus cloudsclouds

Altostratus: uniform white Altostratus: uniform white to grayish sheet covering to grayish sheet covering the sky with the sun or the sky with the sun or moon visible as a bright spot moon visible as a bright spot

Low CloudsLow Clouds Have bases below 2000 metersHave bases below 2000 meters Stratus: uniform layer of Stratus: uniform layer of clouds that clouds that

covers much of the skycovers much of the sky Stratocumulus: scalloped bottom that Stratocumulus: scalloped bottom that

appears as long parallel rolls or broken appears as long parallel rolls or broken rounded patchesrounded patches

Nimbostratus: grayish clouds covering Nimbostratus: grayish clouds covering most of the sky often producing most of the sky often producing precipitationprecipitation

Cumulonimbus: cloud covering all three Cumulonimbus: cloud covering all three height producing thunderstormsheight producing thunderstorms

FogFog A cloud with A cloud with

its base at or its base at or very near the very near the ground.ground.

Formation of FogFormation of FogFormation by CoolingFormation by Cooling

thin layer of air in contact with thin layer of air in contact with the ground is cooled below its dew pointthe ground is cooled below its dew point

As the air cools, it becomes denser and As the air cools, it becomes denser and drains into low areas where thick fog drains into low areas where thick fog accumulation may occuraccumulation may occur

Formation by EvaporationFormation by Evaporation When cool air moves over warm When cool air moves over warm

water, enough moisture may evaporate water, enough moisture may evaporate from water surface to produce from water surface to produce saturationsaturation

As the rising water vapor meets the As the rising water vapor meets the cold air, it immediately condenses and cold air, it immediately condenses and rises with the air that is being warmed rises with the air that is being warmed from belowfrom below

How Does Precipitation How Does Precipitation Form?Form?

For For precipitation to precipitation to form, cloud form, cloud droplets must droplets must grow in volume grow in volume by roughly one by roughly one million times.million times.

Bergeron ProcessBergeron Process A A theory that relates the formation of theory that relates the formation of

precipitation to supercooled clouds, precipitation to supercooled clouds, freezing nuclei and the different freezing nuclei and the different saturation levels of ice and liquid saturation levels of ice and liquid waterwater

Supercooled: water in the liquid Supercooled: water in the liquid state below 0˚C (freezing)state below 0˚C (freezing)

Supersaturated: the condition of air Supersaturated: the condition of air that is more highly concentrated than that is more highly concentrated than is normally possible under given is normally possible under given temperature and pressure conditionstemperature and pressure conditions

Collision-Coalescence Collision-Coalescence ProcessProcess

Water drops collide Water drops collide and join together to and join together to form bigger dropsform bigger drops

Forms of Forms of PrecipitationPrecipitation The type of precipitation The type of precipitation

that reaches Earththat reaches Earth’’s s surface depends on the surface depends on the temperature profile in temperature profile in the lower few km of the the lower few km of the atmosphereatmosphere

RainRain: : drops of water that drops of water that fall from a cloud and have a fall from a cloud and have a diameter of at least 0.5 mmdiameter of at least 0.5 mm

SnowSnow: : light, fluffy,light, fluffy, six-six-sided ice crystalssided ice crystals

Forms of Forms of PrecipitationPrecipitation

SleetSleet: fall of small particles of : fall of small particles of clear to translucent iceclear to translucent ice

GlazeGlaze: when raindrops become : when raindrops become supercooled as they fall through supercooled as they fall through subfreezing air and turns to ice subfreezing air and turns to ice when they impact objectswhen they impact objects

HailHail: form of solid precipitation : form of solid precipitation which consists of balls of which consists of balls of irregular lumps of ice produced irregular lumps of ice produced in cumulonimbus cloudsin cumulonimbus clouds

Exit TicketExit Ticket

1) How are clouds classified?1) How are clouds classified? 2) List and describe the three main types of 2) List and describe the three main types of

clouds.clouds. 3) Explain what determines the type of 3) Explain what determines the type of

precipitation that reaches Earth’s surface.precipitation that reaches Earth’s surface.