9: Energy Balance
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Define Earth’s Energy Balance
The earth-atmosphere energy balance is the balance between incoming energy from the Sun and outgoing energy from the Earth. Energy released from the Sun is emitted as shortwave light and ultraviolet energy. When it reaches the Earth, some is reflected back to space by clouds, some is absorbed by the atmosphere, and some is absorbed at the Earth’s surface.
Define Planetary Albedo
The fraction of the incoming solar energy scattered by Earth back to space
Earth’s Energy Balance Calculation (Shortwave) 100 Units
8 Scattered by air 17 Reflected by clouds 6 Reflected by surface = 31 Total lost to space (69 Total gain of Shortwave)) 19 absorbed by ozone water vapor & dust 4 absorbed by clouds 46 absorbed by surface
Earth’s Energy Balance Calculation (Longwave) 100 Units
15 total Emit by surface 6 absorbed by GHGs (9 Lost to space) 20 Emit by clouds to space 40 Emit by H2O, CO2 & O3 Total loss of Longwave = 69
Earth’s Energy Balance Calculation (Land)
46 SW absorbed 15 LW emitted = Surplus of 31 units Need to transfer to atmosphere (sensible & latent heat)
Earth’s Energy Balance Calculation (Atmosphere)
23 SW & 6 LW units = 29 absorbed 60 units emitted Deficit of 31 units Need to transfer to land (latent & sensible heat)
Sensible Heat 1) Define
1) The thermal energy whose transfer to or from a substance results in a change of temperature. (heat you can feel) Flux of energy which heats the atmosphere above the surface
Latent Heat 1) Define 2) Give Two Examples 3) Why is it the most efficient mechanism for heat transfer?
1) Transfer of heat resulting in a change of phase, but no change in temperature 2) Water vapor a) condensation in troposphere b) evaporation at the surface 3) Due to large ocean mass of Earth
Latent or Sensible Heat 1) Water Melting 2) Water Boiling 3) Water Freezing 4) Steam cooling or warming
1) Sensible heat 2) Latent heat 3) Neither 4) Neither
1) Which is higher, latent or sensible heat? 2) Why?
1) Latent heat will always be higher 2) Due to Earth large ocean mass & so water is constantly evaporating
Which will be dominated by latent heat or sensible heat? 1) Saturated Soil 2) Dry Soil 3) Vegetated Surface
1) Latent heat 2) Sensible heat 3) Latent heat due to transpiration, drives thermals & convection over the land
Energy Balance - Net All-Wave Radiation 1) Define 2) Formula 3) Surface Energy Balance formula What Denotes 4) Q* 5) Qh 6) Qle 7) Qg
1) Balance between incoming & outgoing long & short wave radiation 2) Q* = (SW low - SW high) + (LW low - LW high) 3) Q* = Qh + Qle + Qg 4) Net radiation 5) Sensible heat 6) Latent heat 7) Ground heat flux
Ground Heat Flux 1) Depends on 2) In comparison with latent & sensible is it large or small
1) Thermal conductivity of the soil 2) Generally very small
Define Austral Summer
Summer in the Southern Hemisphere; November-February
Define Austral Winter
Winter in the Southern Hemisphere; June-September
Energy Balance During the austral summer, where is the peak radiation?
Southern hemisphere
Energy Balance During the austral winter, where is the peak radiation?
Northern hemisphere
Net Radiation (Positive) 1) Where? 2) What colour/s depicts it?
1) At equator 40 N to 40 S (always positive) 2) Yellow to red
Net Radiation (Negative) 1) Where? 2) What does it mean if you are negative 3) What colour/s depicts it?
1) At the poles 2) Means you are losing more energy than you are gaining 3) Blue/green
The oceans & atmosphere transfer heat & moisture from the equator to the poles Why is it positive at the equator yet negative at the pole?
less and less energy from the sun, due to earth being a sphere, -same ray of light heating the poles is heating a bigger area than the ray of light heating equator, energy is more diffuse, so as we move down, we have a positive balance at the equator and a negative balance at the poles
Where is the 1) Low incidence angle 2) High incidence angle
1) 40* N 2) At the equator
Why do we get a Net Energy 1) Gain 2) Neutral 3) Loss
1) Solar input higher than infrared output 2) At the equator 3) Solar input lower than infrared output
Global Atmospheric Circulation When do Jet Streams occur?
When cells meet (Ferrel, Hadley, Polar), these are regions where you have a lot of air coming together
Global Atmospheric Circulation Name the three cells & Where are they located
Ferrel Cell 60 N & S Hadley Cell 30 N & S Polar Cell 60 - 70 N & S