Radiation Flashcards
Why does temperature rise in the stratosphere?
Ozone absorption of insolation
Why does temperature rise in the thermosphere?
Intense solar radiation excites molecules
What happens to incoming solar radiation? There are three possible fates.
- Scattering: by particles in atmosphere. Wavelength is unchanged
- Reflection: by clouds particles, and surfaces back to space as shortwaves
- Absorption: by gases and dust in the atmosphere and at the surface causes warming
So what is scattering exactly?
Some short waves are scattered by particles in the atmosphere. No effect on temperature.
If there was no atmosphere to produce scattering what would happen to the sky?
The sky would be dark, like the moon.
Why does the sky appear blue on a sunny day?
The shortest visible waves (blue and violet) are scattered more by oxygen and nitrogen in atmosphere
Why is the sunset/ sunrise yellow, red, and orange?
Oblique angle at sunrise/sunset = LONG distance travel. All blues scatter out, only “longer” red waves are visible at surface
What is the albedo?
Albedo = percent of insolation (short waves) reflected by a surface
What kind of surfaces reflect best and have the highest albedos?
Fresh snow, light roof, water bodies
What is absorbed radiation and what can it be converted to
Absorbed radiation (that part that is NOT reflected) is emitted as longwave (terrestrial) radiation that can be converted to heat
What do cooler surfaces emit?
Cooler surfaces emit long-wave radiation
What happens to long-waves in the atmosphere?
Long-waves are trapped in the ATM by greenhouse gases
So basically absorbed waves mean = ____?
Heat
Reflect waves = _____?
No heat (and maybe even cooling)
What is the Snow-Temperature Feedback Effect?
snow/ice reflects radiation back to space
What does snow and ice cause temperatures to be?
Even colder then before (positive feedback, cooling causes more cooling)
What would happen if snow/ ice was melted?
melting snow/ice would decrease albedo and make temperatures rise in that location (positive feedback, heating causes more heating)
what are some ways that humans change earth’s albedo?
Asphalt, tar, building materials that absorb rather than reflect
What is the average radiation of dense urban areas?
average 20-30% reflection
What do low albedo surfaces do?
Low albedo surfaces absorb NRG and emit long-wave radiation that can be trapped and warm the lower atmosphere
Does deforestation raise or lower albedo?
Usually raises albedo, thus can cause cooling
What is the bottom line on earth’s NRG budget?
At the Global Scale, system is in BALANCE
100 units come in—100 units go out
Is NRG distribution the same in every place on the earth?
NRG Distribution varies from place to place and through time. “Overheated tropics, underheated poles”
What does this uneven distribution of energy do?
Drives atmosphere-Ocean Circulation!
