// lecture 06 Flashcards
surface balance (Wm^-2)
- solar in: 160 Wm^-2, longwave in = 345, longwave out = 396, net longwave out = 51, evapoaration cooling = 88, thermal cooling = 20, residual in = 0.6 Wm^-2.
- in = 160 solar, out = 88 evaporation + 20 thermal + 51 IR,
- plus 0.6 Wm^-2 the earth is warming up.
atmosphere balance
- solar in: 80 W, longwave in = 396 W, longwave out = 584 W, net longwave out = 188 W, condensation heating = 88, thermal heating = 20 W.
- net radiation = 80 (solar) - 188 (longwave) = -108.
- net non-radiative = 88 (condensation) + 20 (thermals) = 108 W.
the atmosphere is mostly:
N2 (78%), O2 (21%), and Argon (1%), but none of these are greenhouse gases.
N2 and O2
are too simple and can’t absorb low-energy photons - Quantum Mechanics. Diatomic.
H2O, CO2, O3, and CH4
have more complicated structures and can vibrate and rotate in ways that can absorb and emit low-energy infrared photons. Polyatomic.
CO2 in vibration
absorbs and emits longwave radiation.
the complex minority constituents determine
the total greenhouse effect.
greenhouse gases absorb and emit
terrestrial (longwave, infrared) radiation and thereby warm the surface (because the temperature decreases with altitude).
- most important for total GHE, natural + anthropogenic.
- most important contributors to human=enhancement of the GHE - need to define a natural state, usually about 1750, which we can measure from bubbles in ice, etc.
most important GHGs overall:
water vapor (H2O), carbon dioxide (CO2), methane (CH4), and ozone (O3). these occur naturally, but CO2, CH4, and O3 are being changed by humans.
H2O vapor
is a function of earth’s surface temperature.
clouds absorb and emit
infrared at all wavelengths and reflect solar radiation pretty well too.
the most important GHG for the natural atmosphere is
H2O
the most important GHG for the human effect on global climate is
CO2.
