metr112 global climate change -- lecture 2 energy balance

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ETR112 Global Climate Change -- Lecture 2 Energy Balance Prof. Menglin Jin San Jose State University

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METR112 Global Climate Change -- Lecture 2 Energy Balance. Prof. Menglin Jin San 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. - PowerPoint PPT Presentation

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Page 1: METR112 Global Climate Change  -- Lecture 2   Energy Balance

METR112 Global Climate Change -- Lecture 2 Energy Balance

Prof. Menglin JinSan Jose State University

Page 2: METR112 Global Climate Change  -- Lecture 2   Energy Balance

Video Global Energy Balancehttp://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/energy%20balance/

a. Solar balance.mp4

b. Earth Energy balance .mp4

Page 3: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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?

Page 4: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 5: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 6: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 7: METR112 Global Climate Change  -- Lecture 2   Energy Balance

• 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:

Page 8: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 9: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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.

Page 10: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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:

Page 11: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 12: METR112 Global Climate Change  -- Lecture 2   Energy Balance

0.0 0.2 0.4+No Data

NASA MODIS-Observed Albedo For 14 - 29 September, 2001

Page 13: METR112 Global Climate Change  -- Lecture 2   Energy Balance

No Data

NASA MODIS Observed Albedo For 1 - 16 January, 2002

0.0 0.2 0.4+

Page 14: METR112 Global Climate Change  -- Lecture 2   Energy Balance

No Data

NASA MODS-Observed Albedo For 7 - 22 April, 2002

0.0 0.2 0.4+

Page 15: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 16: METR112 Global Climate Change  -- Lecture 2   Energy Balance

Energy of Earth

Page 17: METR112 Global Climate Change  -- Lecture 2   Energy Balance

http://earthguide.ucsd.edu/earthguide/diagrams/energybalance/index.html

Useful link on energy balance:

Page 18: METR112 Global Climate Change  -- Lecture 2   Energy Balance

Energy Balance video

http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/energy%20balance/

Earth’s Energy Budget.mp4

Page 19: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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.

Page 20: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 21: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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)

Page 22: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 23: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 24: METR112 Global Climate Change  -- Lecture 2   Energy Balance
Page 25: METR112 Global Climate Change  -- Lecture 2   Energy Balance

Just an example, could be higher or lower

Page 26: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

SurfaceAverage surface temperature = 15°C

Page 27: METR112 Global Climate Change  -- Lecture 2   Energy Balance

http://en.wikipedia.org/wiki/Solar_radiation#Climate_effect_of_solar_radiation

Page 28: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 29: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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?

Page 30: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 31: METR112 Global Climate Change  -- Lecture 2   Energy Balance

Radiation is the transfer of heat energy through space by electromagnetic radiation.

Page 32: METR112 Global Climate Change  -- Lecture 2   Energy Balance

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

Page 33: METR112 Global Climate Change  -- Lecture 2   Energy Balance

Fig. 2-2, p. 30

Page 34: METR112 Global Climate Change  -- Lecture 2   Energy Balance

Convection is the transfer of heat energy in a fluid.

Cumulus clouds indicates where upward convection currents are

Other example: In kitchen liquid boiling