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MET 112 Global Climate Change - Lecture 3. Clouds and global climate Dr. Eugene Cordero San Jose State University. Outline Water in the earth system Clouds and the radiation budget Seasons and energy balance Atmospheric circulation Climate Game. Questions.
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MET 112 Global Climate Change - Lecture 3 Clouds and global climate Dr. Eugene Cordero San Jose State University Outline • Water in the earth system • Clouds and the radiation budget • Seasons and energy balance • Atmospheric circulation • Climate Game MET 112 Global Climate Change
Questions • What role do clouds play on the Earth’s climate? • What would happen to our climate if clouds were to increase/decrease? MET 112 Global Climate Change
Water in the atmosphere • Definitions: • Evaporation: • Condensation: • Precipitation: Process where a liquid changes into a gas Process where a gas changes into a liquid Any liquid or solid water that falls from the atmosphere to the ground. (i.e. RAIN!) MET 112 Global Climate Change
Water freely evaporating and condensing Since more water molecules are evaporating than condensing, then net evaporation is occurring. MET 112 Global Climate Change
Lid on: The humidity is now 100% MET 112 Global Climate Change
Lid on: Now, evaporation and condensation are equal. The air above water is now called ‘saturated’. The humidity is now 100% MET 112 Global Climate Change
Condensation • 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: • Dust • Salt • Smoke • Condensation occurs primarily as temperature cools: • colder the molecules more likely they are to ‘stick’ to • other molecules MET 112 Global Climate Change
http://www.ssec.wisc.edu/data/comp/cmoll/cmoll.html MET 112 Global Climate Change
Clouds and radiation Cloud - Climate Interactions Albedo effect - COOLING • Clouds reflect incoming solar radiation. • The cloud droplet size and total water content determine the overall reflectivity. Greenhouse effect - WARMING • Clouds are good absorbers (and emitters) of long wave (infrared) radiation. MET 112 Global Climate Change
Clouds and day to day temperatures Imagine that you are going camping in the Sierras with your friends. On the first day (and evening) it is cloudy, while on the second day (and evening) it is clear. Based on this information alone: Which day would be warmer? Which evening would be warmer? Explain your answers. MET 112 Global Climate Change
0 of 70 Which day would be warmer? • First day (clear) • Second day (cloudy) • Both the same MET 112 Global Climate Change
0 of 70 Which evening would be warmer? • First day (clear) • Second day (cloudy) • Both the same MET 112 Global Climate Change
Low and High clouds Consider two types of clouds: • Low levels clouds • High levels clouds Q: How is the Earth’s surface energy budget different for low clouds compared to high clouds? MET 112 Global Climate Change
Clouds and climate Cloud A: Low level, (dark, thick) Cloud B: High level, light (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 MET 112 Global Climate Change
Changes in clouds • Increases in low level clouds will: • Increases in high level clouds will: MET 112 Global Climate Change
Changes in clouds • Increases in low level clouds will: • cool the surface (cooling outweighs warming) • Increases in high level clouds will: • warm the surface (warming outweighs cooling) MET 112 Global Climate Change
Explain how the earth’s climate would change as a result of aircarft contrails.
Questions • What percentage of the sun’s radiation is • absorbed by the Earth’s surface? • absorbed by the atmosphere • reflected out to space? • What percentage of the energy received by the earth’s surface comes directly from greenhouse gas emissions? • If the sun’s radiation was to increase by 10%, how would the following energy units change (increase, decrease or stay the same) • Energy gained by the Earth’s surface. • Energy lost by the Earth’s surface. • Energy emitted by greenhouse gases. • Energy lost to space. MET 112 Global Climate Change
0 of 70 What percentage of the Sun’s radiation is absorbed by the Earth’s surface? • 19% • 51% • 70% • 117% MET 112 Global Climate Change
0 of 70 What percentage of the Sun’s radiation is absorbed by the Earth’s atmosphere? • 19% • 51% • 70% • 117% MET 112 Global Climate Change
0 of 70 What percentage of the sun’s radiation is reflected out to space? • 19% • 30% • 64% • 70% • 111% MET 112 Global Climate Change
0 of 70 What percentage of the energy gained by the earth’s surface comes directly from greenhouse gas emissions? • 30% • 43% • 51% • 65% • 70% MET 112 Global Climate Change
0 of 70 If the Sun’s radiation was to increase by 10%, how would the energy gained by the earth’s surface change? • Increase • Decrease • Stay the same MET 112 Global Climate Change
0 of 70 If the Sun’s radiation was to increase by 10%, how would the energy emitted by greenhouse gases change? • Increase • Decrease • Stay the same MET 112 Global Climate Change
0 of 70 If the Sun’s radiation was to increase by 10% the energy • Entering the top of the atmosphere would exceed the energy leaving • Entering the top of the atmosphere would be less than leaving • Entering and leaving would be the same MET 112 Global Climate Change
Definitions • Insolation – • Solstice – • Equinox – Incoming solar radiation day of the year when the sun shines directly over 23.5°S or 23.5°N days of the year when the sun shines directly over the equator MET 112 Global Climate Change
Sun angle MET 112 Global Climate Change
Sun angle (2) MET 112 Global Climate Change
What influences incoming solar energy? • The Sun’s angle of incidence: • Lower sun angle, • Higher sun angle, • Length of time the Sun shines each day: • Summer season, • Winter season, less incoming energy more incoming energy more sun hours less sun hours MET 112 Global Climate Change
Why do we have seasons? MET 112 Global Climate Change
What month do you think this graph represents? a) December b) March c) June d) September MET 112 Global Climate Change
0 of 70 What month do you think this graph represents? • December • March • June • September MET 112 Global Climate Change
Review questions • On June 21st, at what latitude is the sun directly overhead at noon? • On September 22nd, at what latitude is the sun directly overhead at noon? • How many hours of daylight are present at the South Pole on February 20th? • Where would you expect to have longer days; 45 ° N on June 21st or 50°S on Dec 21st? MET 112 Global Climate Change
0 of 70 On June 21st, at what latitude is the sun directly overhead at noon? • Equator (0) • 23.5°N • 23.5°S • 90°N (north pole) • 90°S (south pole) MET 112 Global Climate Change
0 of 70 How many hours of daylight are present at the South Pole on February 20th? • 0 hours • 6 hours • 12 hours • 18 hours • 24 hours MET 112 Global Climate Change
