Part I: The energy-atmosphere system
What controls strength of sun waves?
Distance of the sun. earths revolution around sun and its tilt, atmosphere filtering effect.
Solar constant of 1400 w/m once sun rays get to earth
Everywhere has 12 hours of day and 12 hours of night
When sun sees both poles at same time
Sub solar point at equator
Happens twice in a year. Fall and spring
Equal amount of light hitting north and south. North=south
Sub solar point is the condition of the earth where sun is directly over head.
90 degrees over on horizon.
Axis line is 23.5* north of light
24 hour darkness in North
Sub solar point 23.5* south of equator
Sub solar point Is 23.5* north of equator
24 hour darkness in South
Geometric positions are important because they control position of sub solar point and therefore angle
of indication. Angle of incidence is important because energy from sun is diluted in low angle positions
and less diluted in high angle positions.
Tilt of the axis causes seasons. Seasons are effective way of distributing energy. If no tilt than we would
have hotter equator and colder poles.
Sun degree is 26* during Winter, 50* during Spring, fall and 73* during Summer solstice.
Time of day/year (Check slides for graph)
What Controls Angle of Incidence?
Latitude, time of day, time of year
Solar Energy to Earth and the Seasons How does solar radiation flow through Earth’s atmosphere?
1. Nature and forms of radiation
Wavelength is a measure of solar radiation.
- Long wave and short wave
2. Laws governing energy flows
Energy is in equilibrium. Moves from surplus to deficit
Rate of energy movement is proportional to energy gradient. Energy moves through colder things faster
Energy cannot be created or destroyed (conservation of energy)
I= t+a+ α
3. Laws Describing Radiation from surfaces
The Electromagnetic Spectrum
Long waves are in lower half. Short waves are top half. Both can be broken down into components.
Short wave is the light that we can see.
1) Inverse relationship between temperature of an object and wavelength it emits
Weins’ Law: (Delta)max = b/T
b is constant and T is surface temperature. b = 2898, T = temp [K]… kelvin
Explains horizontal difference in graph
2) Flow of radiant energy from a surface is directly related to the surface energy to the fourth
power. Increase temperature of the surface a little bit, you increase the temperature of
radiation by a lot.
The wavelength of maximum intensity radiation grows longer as the absolute temperature of the
radiating body decreases.
Stefan-Boltzman law: M = σT
Explains vertical difference in graph
4. Budgets of radiation and energy
Earth’s atmosphere transmits, absorbs and reflects the suns energy (t+a+α)
Atmosphere is an “energy filter”
With filter 1400 w/m square radiation but around 500 is transmitted.
If no filter than all is transmitted
Filter causes radiation to be transmitted, absorbed or reflected. The ground does the same thing.
Depends on ground properties. Ex. Snow has better reflective properties than asphalt.
Atmosphere also varies. About 10000km deep, 97% within ground and 30km above.
21% oxygen 1% argon, Carbon Dioxide, Water vapour
Green house gasses (absorb long waves). Increase the absorption of energy and warms atmosphere.
Photosynthesis – respiration
Vary in concentration
If there is an increase in ‘a’, than temperature is going to rise.
How does “atmospheric filter” vary with time?
Clouds can cause absorption of 5-20% and reflection of 35-60%. So only 45-10% reaches the ground.
Filter is not a constant thing, but is more dynamic.
- reduces by absorbing and reflecting energy
- It also transforms absorbed short wave energy into long wave energy. If reflected it stays short
- It also scatters energy. Direct and diffuse.
- ‘Alpha’ is reflected energy that stays short wave. Diffuse if it reflects off something in
atmosphere and doesn’t reach the ground.
- ‘t’ is Direct energy that makes it through atmosphere to ground.
- ‘a’ is energy that is absorbed and reemitted as long wave. Greenhouse gasses are good at
absorbing the long wave energy. GG101 Lecture part 1_3: Radiation and Energy Balances
Albedo (α): Ratio of the amount of radiation reflected by a body to the amount incident upon it.
Varies according to colour of surface. Bright surfaces are good reflectors such as snow.
Transmission varies. Over opaque surface is low but on water surface it can be up to 50%. If good
reflector than you’re a bad absorber. Inverse relationship.
Incoming is downward directed arrow. Outgoing is upward directed arrow.
Net all-wave radiation (radiation balance) – Q* = (S˅ – S˄) + (L˅ – L˄)
Q* = S* + L* = 100 units S is short wave, L is long wave.
Energy balance: Q* = Qe+Qh+Qg
Qe - This part of the energy balance changes the phase of water. Latent heat flux. Latent heat causes
Latent heat is the heat released or absorbed by a chemical substance or a thermodynamic system
during a change of state that occurs without a change in temperature, meaning a phase transition such
as the melting of ice or the boiling of water.
Latent heat flux: the flux of heat from the Earth's surface to the atmosphere that is associated with
evaporation or transpiration of water at the surface and subsequent condensation of water vapour in
Qh - Goes to heat the air above the ground. Sensible heat flux. Molecular conduction – Energy
transferred from particle to particle. Molecular convection – Movement of the heated particles or
molecules. Heat that goes to warming up the air.
Qg – goes vertically downward to heat the ground below the surface. Ground heat flux. Conduction and
occasionally convection with moving water.
Phase Changes of Water
Release latent heat.
Absorb latent heat: Takes energy out of something like taking money from a bank.
Sublimation is solid to vapour. That is why sublimation is evaporation and melting added.
Day-time & Night-time Fluxes
During night time there is only long wave. During day time you must incorporate short and long.
Evaporation is pointed upwards because its making energy away from balance.
Day: Energy is directed away from surface. During day there is +deltaQ. Flux convergence when +deltaQ
Night: More energy going away from ground than into ground. Reverse form day. Energy is going back.
During night there is -deltaQ. Flux divergence when -deltaQ
To have evaporation you need energy and water. So does not work in deserts.
At a farm Qe term is dominant because energy is being put into evaporation. Partitioning of Solar Radiation
Q* = 48 + (-16)
Different ground surfaces heat up air above it differently. Part 1_4: Global Temperatures
Profile of the Atmosphere
Temperature changes throughout the atmosphere
Heterosphere – outer atmosphere
- From 80km and above: same as thermosphere
- Layer of gasses. Sorted by molecular weight of gas molecules
Homosphere – inner atmosphere
- Surface to 80km
- Gasses evenly blended
Less pressure as you go up the atmosphere – molecules are farther apart as you go up.
- Starts at 1000 millibars and goes to zero as it goes higher.
- 1000-175 Millibars in troposphere, 175-0.78 in stratosphere, 0.78- 0.0