albedo

• fraction of incident radiation reflected by a surface or body
• 0 (absorbs everything) to 1 (reflects everything)
• Bond albedo: over all wavelengths and directions (the one used in energy balance)
• geometric albedo: brightness at zero phase angle, relative to a flat, perfectly diffusing disk
• Bond albedos: Earth ≈ 0.30, Venus ≈ 0.76, Moon ≈ 0.11
• fresh snow ≈ 0.8, open ocean ≈ 0.06
• ice-albedo feedback: less ice → darker surface → more sunlight absorbed → more melting (positive feedback)
• role in a planet’s temperature: Stefan-Boltzmann law, zero-dimensional energy balance model