Climatology and Atmospheric Radiation
Climatology and atmospheric radiation covers the energy balance, radiation laws, general circulation, and major climate modes. Expect questions that connect a radiation calculation to the greenhouse effect or a circulation cell to observed climate.
Core rules
- Planck's law gives spectral radiance; Wien's law gives λmax ≈ 2898/T (μm, K); Stefan-Boltzmann gives E = εσT⁴.
- The solar constant is about 1361 W m⁻². A planet's effective temperature uses absorbed solar energy spread over four times the cross-sectional area: Te = [S(1-a)/(4σ)]^1/4.
- Earth's albedo is about 0.30; the effective temperature is about 255 K, while the surface averages about 288 K. The 33 K difference is the greenhouse effect, not a violation of energy balance.
- General circulation: Hadley cells (tropics), Ferrel cells (midlatitudes), polar cells; the Asian monsoon and ENSO are leading regional modes.
Worked example
With S = 1361 W m⁻² and a = 0.30, absorbed flux is 1361 × 0.70 = 952.7 W m⁻²; divided by 4 gives 238.2 W m⁻². Then Te = (238.2/5.67×10⁻⁸)^1/4 = (4.20×10⁹)^1/4 ≈ 255 K. If you forget the factor of 4, you get about 360 K, which is the classic error.
Traps
Using surface albedo instead of planetary albedo; omitting emissivity; mixing Wien and Stefan-Boltzmann; failing to convert °C to K; and attributing ENSO to a single local process rather than coupled ocean-atmosphere dynamics.