Transmission
Energy passes uninterrupted through the atmosphere or water
Energy Budget
a balance between shortwave energy received and longwave radiation lost
input (shortwave) – output (longwave)
Scattering is the:
physical interaction between incoming radiation and:
- Atmospheric gases
- dust
- cloud droplets
- water vapour
- pollutants
redirection without changing wavelength
Why is the sky blue?
- Violet and blue light: shorter wavelengths (scatter first)
- Red and yellow light: longest wavelength (travels the farthest)
- when light hits a gas molecule in our atmosphere, it is absorbed
- high frequency blues and violets get absorbed more
- the gas molecule then radiates the light in different directions (colour that was radiated is the same colour that was absorbed)
(Raleigh scattering)
Why is the sunset red?
- when the sun sets its further away from you
- the path to get to your eyes is longer, therefore the chance of the longwave red and yellow light hitting gas molecules is higher
- the light also travels through the lower atmosphere, which has a greater concentration of particles
- these particles reflect the light that hit them
Mie Scattering
The larger particles in the atmosphere (larger than the wavelengths of light) cause the sky to appear white
(haze, pollution)
in a very hazy/polluted area, all wavelengths of light are scattered evenly, making the human eye perceive it as white
Refraction
Bending of light resulting from a change in medium.
Insolation entering the atmosphere changes mediums. this causes a shift in speed and causes the light to bend (shift direction)
Albedo
(reflectivity of an object). the percentage of insolation that is reflected
Absorption
the assimilation of radiation by molecules of matter, converting the radiation from one form of energy to another
Clouds reflect ____
shortwave radiation
Clouds absorb _____
longwave radiation
Longwave radiation is absorbed in the atmosphere by:
carbon dioxide water vapour methane nitrous oxide chlorofluorocarbons (CFCs)
Cloud albedo forcing
Low, thick stratus clouds reflect about 90% of insolation
High-altitude, ice-crystal clouds reflect only about 50%
Cloud greenhouse forcing
Clouds, mainly high-altitude, ice-crystal clouds trap longwave radiation emitted from earth
Jet contrails create…
condensation trails that produce high cirrus clouds, which trap more radiation than it reflects.
Energy budget between the tropics
Energy surplus
Energy budget at the poles
Energy deficits
Daily Radiation Patterns
Maximum daily temperature lags by several hours (~3:00-4:00 pm)
Due to time it takes for energy to transfer (nonradiative & radiative)
Boundary layer
the lower atmosphere at the Earth’s surface where energy and moisture are continually exchanged
Microclimates (smaller than Boundary Layer Climates)
are local climate conditions over a relatively small area (i.e. parks, or parking lots)
Net radiation
the sum of all radiation gains and losses
- positive during the day
- negative during the night
Non-radiative ways to lose heat
3 WAYS
- Latent heat of evaporation
- Sensible heat
- Ground heating and cooling
**
Urban Heat Island
An urban micro-climate that is warmer on average than areas in the surrounding countryside due to interaction between solar radiation and various surface characteristics
heating is increased by modified urban surfaces:
(6) asphalt glass building geometry pollution human activity industry and transportation
