MET 112 Global Climate Change -
CLOUDS and CLIMATE
Prof. Menglin Jin
Department of Meteorology, San Jose State University
OutlineClouds FormationClouds Climatology
Clouds and the Radiation Budget
Clouds by Christina Rossetti
White sheep, white sheep,On a blue hill,
When the wind stopsYou all stand still
When the wind blowsYou walk away slow.
White sheep, white sheep,Where do you go?
A good repository of cloud photos in various categories can be found
at www.cloudappreciationsociety.org/gallery
QuestionsQuestions
What role do clouds play on the Earth’s climate?
What would happen to our climate if clouds were to increase/decrease?
Earth System Water Cycle
6 MET 112 Global Climate MET 112 Global Climate ChangeChange
Clouds are formed when air containing water vapor is cooled below a critical temperature called the dew point and the resulting moisture condenses into droplets on microscopic dust particles (condensation nuclei) in the atmosphere.
Clouds Formation
8 MET 112 Global Climate MET 112 Global Climate ChangeChange
Video
http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/clouds/
Clouds Formers –clouds and aerosols
CLOUDS: A visible mass of liquid water droplets suspended in the atmosphere above Earth's surface.
http://earthobservatory.nasa.gov/Library/glossary.php3
Clouds can form along warm and cold fronts, where air flows up the side of the mountain and cools
as it rises higher into the atmosphere, and when warm air blows over a colder surface,
such as a cool body of water.
Water in the atmosphereWater in the atmosphere
Definitions:
– Evaporation:
– Condensation:
– Precipitation:
Process where a liquid changes into a gasProcess where a liquid changes into a gas
Any liquid or solid water that Any liquid or solid water that falls from the atmosphere to the falls from the atmosphere to the ground. (i.e. RAIN!)ground. (i.e. RAIN!)
Process where a gas changes into a liquidProcess where a gas changes into a liquid
Water freely Water freely evaporating and evaporating and condensingcondensing
Since more water Since more water molecules are molecules are evaporating than evaporating than condensing, then net condensing, then net evaporation is evaporation is occurring.occurring.
CondensationCondensation
The process by which water vapor changes to a cloud droplet
Water vapor molecules may ‘stick’ to
condensation nuclei and grow (billions) to eventually form cloud droplet.
Examples of condensation nuclei include:a.a. DustDustb.b. SaltSaltc.c. SmokeSmoke
Condensation occurs primarily as temperature cools:-colder the molecules more likely they are to ‘stick’ to other molecules
Zonal Mean Cloud Effective Radius(M. D. King, S. Platnick et al. – NASA GSFC)
July 2006 (Collection 5)
Aqua
Clouds and radiationClouds and radiation
Cloud - Climate InteractionsCloud - Climate Interactions
Albedo effect - COOLINGAlbedo effect - COOLING Clouds reflect incoming solar radiation. Clouds reflect incoming solar radiation.
The cloud droplet size and total water content The cloud droplet size and total water content determine the overall reflectivity. determine the overall reflectivity.
Greenhouse effect - WARMINGGreenhouse effect - WARMING Clouds are good absorbers (and emitters) of long Clouds are good absorbers (and emitters) of long
wave (infrared) radiation.wave (infrared) radiation.
Clouds and day to day Clouds and day to day temperaturestemperatures
Imagine that you are going camping in the Sierras Imagine that you are going camping in the Sierras with your friends. On the first day (and evening) it with your friends. On the first day (and evening) it is clear, while on the second day (and evening) it is clear, while on the second day (and evening) it is cloud. Based on this information alone:is cloud. Based on this information alone:
Which day would be warmer?Which day would be warmer?
Which evening would be warmer?Which evening would be warmer?
Explain your answers.Explain your answers.
Which day would be warmer?
1. First day (clear)
2. Second day (cloudy)
3. Both the same
Which evening would be warmer?
1. First day (clear)
2. Second day (cloudy)
3. Both the same
Clouds types
Low and High cloudsLow and High clouds
Consider two types of clouds:Consider two types of clouds:
1.1. Low levels clouds Low levels clouds
2.2. High levels cloudsHigh levels clouds
Q: How is the Earth’s surface energy budget Q: How is the Earth’s surface energy budget different for low clouds compared to high different for low clouds compared to high clouds?clouds?
Clouds and climateClouds and climate
Cloud A: Low level, (dark, thick)Cloud A: Low level, (dark, thick)
Cloud B: High level, light Cloud B: High level, light (sub visible or thin)(sub visible or thin)
Excellent reflector of incoming radiation; good absorber/emitter of infrared radiation
Fair/poor reflector of incoming radiation; good/excellent absorber/emitter of
infrared radiation
So, clouds both warm and cool the earth. Overall, though, clouds act to cool the
earth
Changes in cloudsChanges in clouds
Increases in low level clouds will:Increases in low level clouds will:–
Increases in high level clouds will:Increases in high level clouds will:
Changes in cloudsChanges in clouds
Increases in low level clouds will:Increases in low level clouds will:– cool the surface (cooling outweighs cool the surface (cooling outweighs
warming)warming)
Increases in high level clouds will:Increases in high level clouds will:– warm the surface (warming outweighs warm the surface (warming outweighs
cooling)cooling)
Cirrus
Altocumulus (possibly cirrocumulus, depending on altitude of the clouds)
Stratocumulus
Broken stratocumulus
Nimbostratus
Cumulus humilis (commonly called 'fair weather cumulus')
Cumulus
Cumulus
Cumulus
Cumulus
Cumulonimbus
Stratus
Stratus
Cirrus
Clouds That Look Like Things
Explain how the earth’s climate would change as a result of aircraft contrails.
Class Participation
Concept MapConcept Map
Activity : Water Concept Map
Draw a concept map using the following terms. You may add additional terms if you wish.
Water vaporIceLiquid waterCondensationEvaporationGasHigh CloudLow CloudPrecipitationCondensation nucleiTemperatureWarmingCoolingAir
