Greenhouse Effect & Global Warming Flashcards
Where does our energy come from? Write down as many sources as possible.
The majority of energy comes directly or indirectly from the sun.
For example:
1. Solar power comes
from the sun.
2. Biomass uses photosynthesis
to convert sunlight into sugars.
3. Wind is caused by the sun heating
the planet and causing movement of air.
4. Wind subsequently generates waves as it passes over the oceans (Wave power).
5. Rainfall comes from solar evaporation which supplies hydroelectric power.
6. The energy in fossil fuels, ultimately comes from the sun.
Are there any exceptions to where energy typically comes from? What are they?
Yes, these are:
1. Nuclear power (heat generated by radioactive decay of matter) mass of atoms is converted into energy by Einstein’s equation.
2. Geothermal (do not confuse with GSHPs as Heat pumps are collect heat from just under the surface so are still indirectly supplied by the sun). Geothermal is drilled much deeper into the ground or a natural phenomenon where heat comes from the core of the planet (accretion) and by nuclear reactions. It is the gravitational potential energy from the formation of the planet (space dust) was trapped as heat in the earth’s core.
3. Tidal - gravitational and potential energy from the moon & sun
How much solar electromagnetic radiation is reflected back into space vs what reaches the atmosphere?
50% goes back into space
True or false: Hot air is more dense than cool air.
False - less dense
How much energy does the world consume in a year?
595 exajoules = 595 x 10^18 J
Why does not all energy from the sun (that enters the earth’s atmosphere) not reach the surface? What 4 main optical processes are involved?
The earth has to maintain an energy balance:
Energy in = energy out
Processes involved include:
1. Radiation
2. Absorption
3. Scattering
4. Emission
What is direct and indirect radiation?
Direct Radiation - light does not interact with the atmosphere (direct from the Sun and will cast a shadow) e.g. intense sunlight
Indirect radiation - light that is scattered in the atmosphere (does not cast a shadow) e.g. overcast
What is absorption?
Light energy is taken in by the molecules in the atmosphere. The energy is transferred to electrons within the molecules usually resulting in the generation of heat and possibly re-emission.
What makes photovoltaics unique in terms of absorption?
Most materials when they absorb light generate heat but not always. For photovoltaic materials they generate electricity rather than heat.
What is scattering?
Any process that can alter the direction that light is travelling e.g. reflection and refraction.
What is emission?
Electromagnetic radiation radiates from all objects. The amount and wavelength of the radiation emitted by an object depends upon its temperature. e.g. The sun is very hot so emits a lot of UV, visible light & infrared.
What parameters are involves in absorption & scattering and how does this link to the greenhouse effect?
Parameters:
1. Refractive index
2. Reflectance
3. Transmission
4. Absorbance
These all vary as a function of wavelength. The variation in these properties at different wavelengths is what causes the greenhouse effect.
Name the 3 types of scattering in order of particle size.
- Rayleigh scattering
- Mie scattering
- Geometric scattering
What is Rayleigh scattering?
This is the smallest in terms of particles compared to wavelength of light (wavelength to the power of -4)
e.g. Refractive index n fluctuations in atmospheric gases.
These shorter wavelengths are more scattered than longer wavelengths and are seen more in the daytime.
In the sky, is blue or red the longer/less scattered wavelength?
Red - which is why it appears when the sun is close to the horizon as it has to pass through a longer physical distance through the atmosphere to reach our eyes.
What equations describe the scattering processes reflection and refraction at an interface between 2 materials?
Fresnel’s equation
What equations are used to describe absorbance?
Beer Lambert Law
