Planetary radiative property: What is the ratio of total solar radiant energy returned by a body to the total radiant energy incident upon it called?

Introduction / Context:
Radiative terms are often confused in remote sensing and climatology. The question targets the specific planetary-scale quantity used to gauge how bright or dark a body is to incoming solar radiation, integrating over all viewing directions and wavelengths in a defined band.

Given Data / Assumptions:

• Energy considered is solar (shortwave) incident on a planetary body.
• Returned energy includes reflected and scattered portions.
• Directional and spectral averaging is implied in the standard definition.

Concept / Approach:
Albedo is the hemispherical-directional ratio of reflected to incident solar energy, often broadband (0.3–3 μm). It can be defined as Bond albedo (global, all angles) or spherical/planetary albedo. Reflectance is usually a surface-level, narrowband, and geometry-specific property; reflectance factor normalizes reflectance to a Lambertian standard.

Step-by-Step Solution:
Identify the required ratio: returned (reflected) / incident solar energy.Map terminology: this integrated ratio is albedo.Distinguish from reflectance and reflectance factor, which are geometry/band specific.Select “albedo” as the correct term.

Verification / Alternative check:
Earth’s mean Bond albedo ≈ 0.30; fresh snow can have albedo > 0.8, deserts ~0.3–0.5, oceans ~0.06–0.1—values widely cited in climate studies.

Why Other Options Are Wrong:
Reflectance: Often directional and narrowband.Reflectance factor: A normalized reflectance quantity relative to a Lambertian surface.Emissivity: Property for thermal emission, not reflected solar energy.None of these: Incorrect because “albedo” precisely fits.

Common Pitfalls:
Using “reflectance” when the integrated planetary quantity “albedo” is intended; mixing shortwave (albedo) with longwave (emissivity) concepts.

Final Answer:
albedo.