Introduction

MET 112 Global Climate Change -CLOUDS and CLIMATEProf. Menglin Susan Jin

Department of Meteorology, San Jos State University

OutlineClouds FormationClouds Climatology

Clouds and the Radiation BudgetClouds by Christina Rossetti

White sheep, white sheep,On a blue hill,When the wind stopsYou all stand stillWhen the wind blowsYou walk away slow.White sheep, white sheep,Where do you go?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. A Scientists view of Clouds CLOUDS: A visible mass of liquid water droplets suspended in the atmosphere above Earth's surface.

http://earthobservatory.nasa.gov/Library/glossary.php3A good repository of cloud photos in various categories can be foundat www.cloudappreciationsociety.org/gallery5 MET 112 Global Climate ChangeVideo: cloud formation in Tucsonhttp://www.youtube.com/watch?v=NiCSk1zxMEs Timelapse of Tucson cloud formations

5QuestionsWhat role do clouds play on the Earths climate?

What would happen to our climate if clouds were to increase/decrease?

How does clouds formation change with pollution?

6So today, after these very broad introductory comments, we will spend a short time looking at the nature of energy in the E-A system, then we will look at some very basic radiation concepts (here I dont want to get bogged down in complex detail, I just want to give you an overview of basic radiation concepts). However it is important that you have a basic understanding, because radiation is the primary energy source for driving atmospheric and ocean circulation and for all life on earth.

Finally today, well examine the mean annual global energy budget, concentrating especially on those significant climate leverage points.7 MET 112 Global Climate ChangeVideohttp://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/clouds/

DTS-5.mp4

Clouds-1.mp4 clouds and aerosols8 MET 112 Global Climate ChangeClouds Roles - Importance of CloudsClouds is part of hydrological cycle to move waterClouds is key in energyClouds absorb/reflect short wave radiation(clouds alebedo effect)Clouds emit longwave radiation back to spaceclouds absorb surface longwave radiation and keep the heat in the atmosphere to warm the surface(clouds greenhouse effect)

Earth System Water Cycle9

100% of the incoming energy from the sun is balanced by 100% percent total energy outgoing from the earth. incoming energy from the Sun = outgoing energy from the Earth. 101011 MET 112 Global Climate Change

since the Earth is much cooler than the Sun, its radiating energy is much weaker (long wavelength) infrared energy. energy radiation into the atmosphere as heat, rising from a hot road, creating shimmers on hot sunny days. The earth-atmosphere energy balance is achieved as the energy received from the Sun balances the energy lost by the Earth back into space. So, the Earth maintains a stable average temperature and therefore a stable climate. http://www.srh.noaa.gov/jetstream//atmos/energy.htm1111Clouds 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 FormationCLOUDS: A visible mass of liquid water droplets suspended in the atmosphere above Earth's surface.

http://earthobservatory.nasa.gov/Library/glossary.php3

1314 MET 112 Global Climate Change

Water freely evaporating and condensing

1415 MET 112 Global Climate Change

Water freely evaporating and condensing

Since more water molecules are evaporating than condensing, then net evaporation is occurring.15Clouds 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 atmosphereDefinitions:

Evaporation:

Condensation:

Precipitation:17Water in the atmosphereDefinitions:

Evaporation:

Condensation:

Precipitation:Process where a liquid changes into a gasAny liquid or solid water that falls from the atmosphere to the ground. (i.e. RAIN!)Process where a gas changes into a liquid18CondensationThe 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: Dust Salt Smoke Condensation occurs primarily as temperature cools:colder the molecules more likely they are to stick to other molecules19

21 MET 112 Global Climate ChangeAerosols Affect Cloud Droplet SizeCCN1.Aerosols serve as cloud condensation nuclie (CCN)CCN2. More aerosols, they will compete for water vapor to condense on, so smaller cloud dropletOcean caseLand case

Zonal Mean Cloud Effective Radius(M. D. King, S. Platnick et al. NASA GSFC)July 2006 (Collection 5)AquaWhy ocean has larger cloud droplets than land? 22Clouds and radiationCloud - Climate Interactions

Albedo effect - COOLINGClouds reflect incoming solar radiation. The cloud droplet size and total water content determine the overall reflectivity.

Greenhouse effect - WARMINGClouds are good absorbers (and emitters) of long wave (infrared) radiation.23Clouds and day to day temperaturesImagine that you are going camping in the Sierras with your friends. On the first day (and evening) it is clear, while on the second day (and evening) it is cloud. Based on this information alone:

Which day would be warmer?

Which evening would be warmer?

Explain your answers.

24Which day would be warmer?First day (clear)Second day (cloudy)Both the same25Which evening would be warmer?First day (clear)Second day (cloudy)Both the same26

Clouds types27Low and High cloudsConsider two types of clouds:

Low levels clouds High levels clouds

Q: How is the Earths surface energy budget different for low clouds compared to high clouds?

28Clouds and ClimateCloud A: Low level, (dark, thick)

Cloud B: High level, light (sub visible or thin)

29Clouds and climateCloud A: Low level, (dark, thick)

Cloud B: High level, light (sub visible or thin)

Excellent reflector of incoming radiation; good absorber/emitter of infrared radiationFair/poor reflector of incoming radiation; good/excellent absorber/emitter of infrared radiationSo, clouds both warm and cool the earth. Overall, though, clouds act to cool the earth30Changes in cloudsIncreases in low level clouds will:

Increases in high level clouds will:

31Changes in cloudsIncreases in low level clouds will:cool the surface (cooling outweighs warming)

Increases in high level clouds will:warm the surface (warming outweighs cooling)

32

Cirrus33

Altocumulus (possibly cirrocumulus, depending on altitude of the clouds)

34

Stratocumulus35

Broken stratocumulus36

Nimbostratus37

Cumulus humilis (commonly called 'fair weather cumulus')38

Cumulus

Cumulus

Cumulus

Cumulus

Cumulonimbus Stratus

Stratus

Cirrus

Clouds That Look Like Things

Explain how the earths climate would change as a result of aircraft contrails. 49

Class ParticipationConcept MapActivity : Water Concept MapDraw a concept map using the following terms. You may add additional terms if you wish.

Water vaporIceLiquid waterCondensationEvaporationGasHigh CloudLow CloudPrecipitationCondensation nucleiTemperatureWarmingCoolingAir