MET 112 Global Climate Change - Lecture 6QuestionsSlide 3Slide 4Water in the atmosphereSlide 6Slide 7CondensationClouds and radiationIndirect Effect due to aerosols (I)Indirect Effect due to aerosols (II)Clouds and day to day temperaturesSlide 13Low and High cloudsClouds and climateSlide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Changes in cloudsControls on ClimateSlide 26Slide 27Climate controls: Latitude/MountainsSlide 29Slide 30Slide 31Controls on Climate: OceansSlide 33Slide 34Slide 35Slide 36Controls on Climate: Pressure systemsSlide 38Slide 39Slide 40Slide 41Slide 42MET 112 Global Climate Change - Lecture 6Clouds and Global ClimateDr. Craig ClementsSan Jose State UniversityQuestionsQuestionsWhat role do clouds play on the Earth’s climate?What would happen to our climate if clouds were to increase/decrease?Hydrological CycleWater in the atmosphereWater in the atmosphereDefinitions:–Evaporation:–Condensation:–Precipitation:Process where a liquid changes into a gasProcess where a liquid changes into a gasAny liquid or solid water that Any liquid or solid water that falls from the atmosphere to falls from the atmosphere to the ground. (i.e. RAIN!)the ground. (i.e. RAIN!)Process where a gas changes into a liquidProcess where a gas changes into a liquidWater freely Water freely evaporating and evaporating and condensingcondensingSince more water Since more water molecules are molecules are evaporating than evaporating than condensing, then condensing, then net evaporation is net evaporation is occurring.occurring.Lid on:Lid on:Now, evaporation Now, evaporation and condensation and condensation are equal. The air are equal. The air above water is above water is now called now called ‘saturated’.‘saturated’.The humidity is The humidity is now 100%now 100%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 moleculesClouds and radiationClouds and radiationCloud - Climate InteractionsCloud - Climate InteractionsAlbedo 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.Indirect Effect due to aerosols (I)Certain aerosols may enhance cloud production and characterRecall how clouds form–Water vapor condenses to liquid water–This processes requires ‘cloud condensation nuclei’–Examples of cloud condensation nucleiDust, salt, smoke (all of which are natural aerosols)So, aerosols (with both natural and anthropogenic origin) –may serve as cloud condensation nuclei.Indirect Effect due to aerosols (II)More cloud condensation nuclei– would enhance cloud productionThe question then is how would clouds change–Current understanding is that This processes would increase cloud albedoThis processes would increase cloud albedo This idea of enhanced cloud formation by increases in aerosols is termed –The ‘indirect effect’ of aerosolsUnderstanding of these processes is currently incomplete.–But model results suggest more low clouds and thusTotal effect on Earth’s energy budget–Cooling–Radiative Forcing: negative–Cirrus cloud (high clouds) production possible, but still uncertain how important.Clouds and day to day Clouds and day to day temperaturestemperaturesImagine 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 cloudy, while on the second day (and evening) it is cloudy, while on the second day (and evening) it is clear. Based on this information alone:is clear. 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.Low and High cloudsLow and High cloudsConsider two types of clouds:Consider two types of clouds:1.1.Low levels clouds Low levels clouds 2.2.High levels cloudsHigh levels cloudsQ: 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 climateCloud 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 radiationFair/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 earthCirrus cloudsCirrocumulus cloudsAltocumulus cloudsStratocumulus cloudsCumulus clouds. Small cumulus clouds such as these are sometimes called fair weather cumulus, or cumulus humilisstratus cloudsExplain how the earth’s climate would change as a result of aircraft contrails.Changes in cloudsChanges in cloudsIncreases in low level clouds will:Increases in low level clouds will:–cool the surface (cooling outweighs warming)cool the surface (cooling outweighs 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)Controls on ClimateControls on ClimateSeasonal temperature and precipitation patterns Seasonal temperature and precipitation patterns are generally attributable to: are generally attributable to: LatitudeLatitudeMountains and highlandsMountains and highlandsLand and water locationLand and water locationPrevailing windsPrevailing windsPressure and wind systems Pressure and wind systems Ocean currentsOcean