Lecture 3: Energy and the Atmopshere Flashcards
What causes the discrepancy between the actual average temperature of the earth and the radiative equilibrium temperature?
Greenhouse gases in the atmosphere interfere with radiation and traps heat inside, causing the earth’s temperature to be 33 K hotter than expected.
How many distinct layers of the atmosphere are there?
Four
What is the troposphere?
The troposphere is the most important layer for heat transfer within the atmosphere (also where weather takes place).
What are the main compositions of the atmosphere?
Various gases (N2, O2, CO2, water vapour…), clouds, dust, microplastics
What is scattering (in terms of radiation)?
Solar radiation entering the atmosphere and colliding with air, dust, or cloud particles, deflecting the light in all directions (shorter wavelengths are more effectively scattered hence a blue sky).
What is reflection (in terms of radiation)?
Solar energy entering the atmosphere and colliding with particles –> reflecting back to where they came from rather than scattering in all directions
What is albedo?
The reflectance of a surface/how much given energy source will be reflected back (instead of absorbed).
Often measured in % of the entire energy source.
What does a low albedo mean?
Less energy reflected (more energy absorbed). Ex: darker surfaces such as an ocean
What does a high albedo mean?
More energy reflected (less energy absorbed). Ex: lighter energy absorbed such as glaciers or fresh snow
What is absorption (in terms of radiation)?
The process by which kinetic energy in the form of EM radiation is absorbed by colder substances in the atmosphere/terrestrial surface.
What are selective absorbers?
Objects which are better at absorbing some wavelengths than others.
How do selective absorbers in the atmosphere work?
Many atmospheric gases are transparent to short waves but will absorb longwave radiation. This means shortwave radiation (from the sun) can enter the atmosphere but longwave radiation (IR) is trapped inside (greenhouse effect)
Where does the energy absorbed by selective absorbers in the atmosphere go?
It is mainly re-emitted into space but some is also re-emitted back towards the planet surface (why the planet can sustain a higher temperature than what should be possible based only on solar energy input).
How does conduction affect the global energy budget?
Energy moved directly from molecules of the ground to molecules in the air which directly touch the ground.
How does convection affect the global energy budget?
Energy moved through warming air in the atmosphere: air is warmed from the ground (conduction) and then the hot air rises (convection).
