1. Lesson 3! Albedo, Air and Water Currents

2. Today: Hand in Albedo Investigations In the News (10 mins)
Discussion on Albedo
Review Radiation
Intro to Conduction and Convection
Next Class: Convection Lab!

3. Albedo “Reflectiveness” of a surface Measured on a scale from 0 – 1,
Where α = 0 has no albedo, and α = 1 is pure reflection (high albedo)
Surfaces with a high albedo reflect more incoming solar radiation and therefore absorb less thermal energy
Snow, glaciers, and ice have high albedos

4. At Home Albedo Investigation! Review findings + Discuss/Explain
Snow , Ice, Clouds
Ashphalt, Rock
Forest / Vegetation
Oceans
Buildings, etc
Shiny vs Matte
What materials did you use to check differences in albedo? [Click for boxes]
How do these relate to the Earth’s climate system? [Click for names]
Clouds have albedo of 40-90%, (Think of being in a plane, rising above the dark, cloudy day to the sunny, bright clouds above)
Forests (5-10%), Grassland/Agriculture (20-25%), the face of the Earth has become lighter due to the conversion from forests to agricultural land.

5. What is a Negative Feedback Loop? What is a Positive Feedback Loop?
Feedback loops: the cause creates an effect that affects the original cause
Positive: the effect enhances the cause
Negative: the effect decreases the original cause (can produce stability in a system, the ability to self-regulate)

6. Changes in sea ice in the last few decades ← How does this figure → relate to feedback loops?
Images:
Since ice and snow strongly reflect the sunlight, reflection is significantly reduced if the area covered by ice and snow becomes smaller. The ground will be darker and take up more solar energy. On a warmer Earth the average snow cover will be lower.
If the sea becomes warmer, the ice is not only irradiated by the sun, but warmed up from all sides. Ice in warm water is melting faster than in air of the same temperature.
This loss of sea ice also means that the warming accelerates even more since more energy from the Sun is taken up by the dark oceans than by the bright ice. We call this effect a positive feedback.

7. Which of the following statements about albedo and its effect on global climate is true?
As the snow and polar icecaps grow, a decrease in albedo will result and more solar energy will be reflected from the ice.
As the snow and the polar icecaps melt, a decrease in albedo will result from the oceans reflecting more solar energy.
As snow and polar icecaps melt, a decrease in albedo will result in the oceans absorbing more solar energy.
As the snow and polar icecaps grow, an increase in albedo will result in the ice absorbing more radiation.
As the snow and polar icecaps melt, there will be no effect on albedo.
Correct answer is C.
Question #1

8. Energy Transfer Within the Climate System
The atmosphere and hydrosphere are the two essential parts of the climate system. Why?
They are both able to absorb and store thermal energy, so they act as heat sinks.
Through (Conduction) and Convection, this energy is transferred from regions that receive a lot of solar radiation to regions that receive less solar radiation.
In Earth’s energy transfer system, heat is always being transferred from hotter objects to colder objects
Image:

9. Recall Earth’s Energy Budget
Energy coming in in shortwave radiation. What do we do with the energy?
Energy Transfer System!

10. 3 Mechanisms of Heat Transfer in the Atmosphere
Radiation: the transfer of heat energy by electromagnetic waves. Think of feeling the sun on your face on a cold winter’s day (warm!). Sunlight warms your face without warming the air around it. We then emit infrared radiation which can be absorbed by the atmosphere.
Conduction: Conduction is the transfer of heat from one molecule to another within a substance. Air is an extremely poor conductor of heat. Therefore, conduction is only important in the atmosphere within the first several millimeters closest to the surface.
So how does the air transfer energy from one region to another?
3. Convection! Convection is the transfer of heat through the movement of a fluid, such as water or air stimulated by uneven heating of the earth. Temperature gradients create convection currents.
Radiation: Solar radiation mostly passes through the atmosphere and is absorbed by all objects, such as humans, trees, flowers, roads, etc. These objects will then warm up. Dark objects, such as asphalt roads, will absorb and warm faster than light colored objects, which reflect the radiation back to space (ALBEDO).. All substances emit radiation, but this emitted radiation will be at a longer wavelength that our eyes cannot see. This emitted radiation, called infrared radiation, can be absorbed by the atmosphere.

11. Radiation
Radiation is a method of heat transfer that does not require any medium.
It can take place in a vacuum.
In radiation, energy is transmitted in the form of waves.

12. Conduction!

13. Conduction
Conduction is the process by which heat is transmitted through a medium from one particle to another.
It is due to temperature differences.
Heat is conducted from a high temperature region to a lower temperature region.

14. Is air good conductor or insulator?
Think of holding a match close to a candle
Does the match get hot enough to burst into flame?
No! This shows that air is a very poor conductor
– it is a very good insulator.
All gases are
poor conductors.

15. Conduction & Climate Air is a really poor conductor of heat
Conduction happens close to the Earth’s surface (land and water)
(Think of the hot pavement on a summer evening – doesn’t heat the air)
Important in climate because:
Hot air rises ↑ (helps fuel convection currents)
Because air is such a poor energy conductor, large
vertical temperature gradients can exist near the
ground, particularly on clear and windless days. On
such days, the land surface may experience a great
deal of heating, as direct solar radiation is absorbed
and converted to infrared radiation (heat energy).
However, a series of thermometers mounted at
different heights above the ground would reveal that
air temperature falls off rapidly with height due to the
poor conductivity of air. (
(road image: elearning.stkc.go.th)
Conduction: particles must touch to transfer energy (in solids and liquids).
Because air is such a poor energy conductor, large vertical temperature gradients can exist near the ground, particularly on clear and windless days. On such days, the land surface may experience a great deal of heating, as direct solar radiation is absorbed and converted to infrared radiation (heat energy). However, a series of thermometers mounted at different heights above the ground would reveal that air temperature falls off rapidly with height due to the poor conductivity of air.

16. Convection!

17. Convection Hold your hand over and under the flame of a match.
What do you notice?
Why?
Hot air expands, becomes less dense and then rises.
Heat is convected upwards ↑

18. Convection in Liquids

19. Convection
The circulation of thermal energy in fluids (gases & liquids)
Cold air/water sinks = more dense
Warm air/water rises = less dense
Creating a current
Eg. Water: Pot of
water being heated
Eg. Air: Sea breeze
 Heat gained by the lowest layer of the atmosphere from radiation or conduction is most often transferred by convection.
Convective motions in the atmosphere are responsible for the redistribution of heat from the warm equatorial regions to higher latitudes and from the surface upward.
Example: water in a pot is heated over an open camp stove.
The water at the bottom of the pot heats up first. This causes it to expand. Since the warmed water has a lower density than the water around it, it rises up through the cooler, dense water. At the top of the pot, the water cools, increasing its density, which causes it to sink back down to the bottom. This up and down movement eventually heats all of the water. The continual cycling of the fluid is called a convection current.

20. Eg. Think of a sea breeze:
Sea breezes occur during the day time:
Sun-heated land heats the air, which then rises. Land heats faster than water (poor conductor) thus creating a temperature gradient
= Warm air rises, cold air from water takes its place = sea breeze
What do you think happens
during a land breeze?
(at night)
Image: green.wikia.com
Soil is a poor conductor of heat – surface heats up and releases heat, not much is transferred to lower levels (think of hot sand, cool beneath)
Compared to Oceans who absorb sun’s radiation and circulate thermal energy through convection currents down to deep depths – takes a lot more energy to heat the oceans
Thus, Convection current: The important concept is that heating (or cooling) of a column of air leads to horizontal differences in pressure, generating a pressure gradient force which causes the air to move and a circulation to develop. During the evening, the land cools faster than the water and the process is reversed. The net result is a land breeze, surface winds blow from the land out to sea.

21. Convection Currents
When the suns rays reaches the equator with greatest intensity, the air at the equator heats up and becomes less dense.
The colder air moves the dense air above it, forcing the worm air up in the atmosphere, this creates a area of low pressure below it.
When the warm air is high in the atmosphere, it spreads out towards the poles and cools down. And the cooler air sinks back to the earths surface, creating an area of high pressure
These cold and warm air creates a circular current called a convection current.

22. Heat Transfer as it Affects Climate
Convection: particles must circulate to transfer energy (in fluids - liquid or gas)

23. The sun heats the air near the earth's equator, which becomes less dense and rises upward. As it rises, it cools and becomes less dense than the air around it, spreading out and descending toward the equator again. These constantly moving cells of warm and cold air, known as Hadley Cells, drive the continual circulation of air at the earth's surface that we call wind. Atmospheric convection currents are also what keep clouds aloft.

24. Air Currents
Check out this site for background info

25. Ocean Currents

26. Ocean Currents What drives ocean currents?
Driven by differences in density, caused by salinity and temperature
the more saline the denser
the colder the denser

27. Changes in density based on Temperature & Salinity = Thermohaline Circulation
Image:

28. Get animations for ocean currents and for air currents

29. Regional Climate
The great lakes are also known for the strong moderating effect they have on the climate of the areas that surrounded these lakes. These huge water masses keep summer and winter temperature moderate, they also provide a lot of moisture.

30. Homework! Read & Answer “Check Your Learning” questions:
Text 8.3, 8.4, 8.6, 8.8
Develop some enthusiasm for our lab next class on Convection Currents!

31. How do ocean currents effect the heat transfer of the atmosphere?
The ocean and atmosphere are connected.
They work together to move heat and fresh water across the globe.
Wind-driven and ocean-current circulations move warm water toward the poles and colder water toward the equator.
The ocean can store much more heat than the land surfaces on the Earth. The majority of the thermal energy at the Earth’s surface is stored in the ocean.
Thus, the absorption and movement of energy on the Earth is related to the ocean-atmosphere system.
How do ocean currents effect the heat transfer of the atmosphere?