Snow albedo — key controlling factors Snow surface albedo varies with multiple environmental and physical parameters. Which set best captures the principal factors?

Introduction / Context:
Snow albedo controls Earth's surface energy balance in cold regions, shaping melt timing and hydrology. It is not a single number: it depends on wavelength, snow microstructure, illumination geometry, and even the optical thickness of the pack, among other factors like impurities (soot, dust) and liquid water content.

Given Data / Assumptions:

• Clean to moderately impure snow, wide range of sun angles.
• We focus on first-order dependencies.
• Semi-infinite vs. shallow packs considered qualitatively.

Concept / Approach:

Spectrally, snow is highly reflective in visible wavelengths and much less so in near-IR/SWIR. Larger grains increase path lengths and absorption, lowering albedo (especially in NIR). Low sun angles increase effective path length in the surface layers, often reducing apparent albedo. Thin snowpacks allow sub-surface/ground reflectance or absorption to influence the signal, modifying effective albedo relative to deep, optically thick snow.

Step-by-Step Solution:

Verification / Alternative check:

Remote-sensing retrievals of snow properties routinely invert NIR bands for grain size and use angular models (BRDF) to account for solar geometry, confirming these dependencies.

Why Other Options Are Wrong:

• Each listed factor is a known control; excluding any one would be incomplete.

Common Pitfalls:

• Ignoring impurity content, which can dominate in visible bands.
• Assuming a single “albedo value” without specifying band and geometry.

Final Answer:

All of these.