Post on 20-Dec-2015
transcript
METR112 Global Climate Change -- Lecture 2 Energy Balance
Prof. Menglin JinSan Jose State University
Video Global Energy Balance
http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/energy%20balance/
a. Solar balance.mp4
b. Earth Energy balance .mp4
Video Global Energy Balance
What is the source of global energy?
What is the difference between icesheet and ocean in terms of their reflections on incoming solar radiation?
What are greenhouse gases? (CO2, H2O, N2, O2) in Atmosphere?
Video: Global Ice Albedo
http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/energy%20balance-albedo/
Ice Albedo.mp4
Global Ice Albedo.mp4
Arctic sea ice coverage, 1979 and 2003, all students need to read NASA http://www.learner.org/channel/courses/envsci/unit/text.php?unit=12&secNum=7
Albedo DefinitionThe ratio of the outgoing solar radiation reflected by an object to the incoming solar radiation incident upon it.
By Earth Observatory Glossary, NASAhttp://earthobservatory.nasa.gov/Library/glossary.php3?mode=all
IN OUTI I
α =IOUT
IIN IIN: Incoming solar radiation reaching the objectIout: Reflected solar radiaiton by the surface
• The Earth is not warming uniformly. • climate change is expected to affect the polar regions more severely:
-The Arctic is warming nearly twice as rapidly as the rest of the world; -winter temperatures in Alaska and western Canada have risen by
up to 3–4°C in the past 50 years, and - Arctic precipitation has increased by about 8 percent over the past century (mostly as rain)
Positive albedo feedback
Due to, partly:
Higher surface temperature
Less snow
Smaller albedo
More insolation in surface
By Reading NASA http://www.learner.org/channel/courses/envsci/unit/text.php?unit=12&secNum=7/ we can see:
Albedo of Earth
•The term albedo (Latin for white) is commonly used to or applied to the overall average reflection of an object.
•the albedo of the Earth is 0.39 (Kaufmann 1991 ) and this affects the equilibrium temperature of the Earth.
This is why albedo is important
Features of Albedo
•Dimensionless
•Range: 0 (dark) – 1 (bright)
The word is derived from Latin albedo "whiteness", in turn from albus "white".
•Albedo is determined by the structural and optical properties of the surface, such as shadow-casting, mutiple scattering, mutual shadowing, transmission, reflection, absorption and emission by surface elements, facet orientation distribution and facet density.
Answer: albedo plays the key role in surface energy balance as it decideshow much surface insolation is kept in Earth surface system
(1-α)Sd +LWd-εσTskin4 +SH+LE + G= 0
Why Is Surface Albedo Critical?
Surface Energy Budget:
Albedo= 0.0 indicates that the surface absorbs all solar radiation,
Albedo = 1.0 means that the surafce reflects all solar radiation
http://theothermy.blogspot.com/2007/12/albedo-and-cool-roofs.html
Conclusion from NASA MODIS Albedo
• Albedo varies across the global land surfaces. This is determined by land cover
• Albedo has clear seasonality
• Snow surafce has high albedo, forest has low albedo, desert has high albedo
http://earthguide.ucsd.edu/earthguide/diagrams/energybalance/index.html
Useful link on energy balance:
Energy Balance video
http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/energy%20balance/
Earth’s Energy Budget.mp4
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.
UnitsUnits
• Our class will use both English and Metric unit systems.• Most important:
– Distance (kilometres and miles) – Temperature (ºC and ºF)
• Conversions:
1.6 km = 1 mile; 1 km = 0.61 miles
(9/5 x ºC) + 32 = ºF
(ºF – 32) x 5/9 = ºC
Unit ReviewUnit Review
• What is the current temperature in ºC?
(current temp = 52F)• California is about 800 miles long (from
Oregon to Mexico). How many kilometers is that?
• If you were told that the average high temperature in Sydney Australia at this time of year is 26ºC, what temperature is that in ºF?
Class participation (2)
Three temperature scales:Three temperature scales:•KelvinKelvin•CelsiusCelsius•FahrenheitFahrenheit
•What does temperature What does temperature mean physically?mean physically?
•What does 0What does 0°° K mean? K mean?
°K= °C+273°K= °C+273
Temperaturethe degree of hotness or coldness of a body or environment (corresponding to its molecular activity)
Temperature is one of the principal parameters of thermodynamics. On the microscopic scale, temperature is defined as the average energy of microscopic motions of a single particle in the system per degree of freedom. On the macroscopic scale, temperature is the unique physical property that determines the direction of heat flow between two objects placed in thermal contact.
Cold temperature Warm temperature
Energy Balance
• Assume that the Earth’s surface is in thermodynamic equilibrium:
• Thermodynamic Equilibrium: – The flow of energy
away the surface equals the flow of energy toward the surface
Surface
Average surface temperature = 15°C
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.htm
Group Discussion
If you go camping with friends. The first day and night are clear and the 2nd day and night are cloudy.
• Which day is cold?
• Which night is cold?
• Why?
The Transfer Of Heat: 3 ways
The heat source for our planet is the
Energy from the sun is transferred through space and through the earth's atmosphere to the earth's surface.
Since this energy warms the earth's surface and atmosphere,
some of it is or becomes heat energy.
There are three ways heat is transferred into and through the atmosphere:
radiation conductionconvection
sun
The flow of heat by conduction occurs via collisions between atoms and molecules in the substance and the subsequent transfer of kinetic energy.
Take a look: http://www.nationmaster.com/encyclopedia/Image:Translational-motion.gif