Snow remote sensing concepts: identify the correct statements regarding albedo, spectral albedo for semi-infinite snow, water equivalent height, and homogeneity of a snow pack.

Introduction / Context:
Snow radiometry is central to hydrology, cryosphere studies, and climate monitoring. Terms like albedo, spectral albedo (for semi-infinite layers), snow water equivalent (SWE), and snow pack homogeneity appear frequently in remote sensing and surveying exams.

Given Data / Assumptions:

• Albedo is defined with respect to upwelling and downwelling radiative fluxes.
• Spectral albedo considers wavelength dependence and often assumes optically thick (semi-infinite) snow to avoid substrate effects.
• Water equivalent height is the water column height after complete melting of snow.
• A homogeneous snow pack shows minimal vertical variation in mean grain size.

Concept / Approach:
Snow's high albedo in visible wavelengths, its spectral behavior, and SWE conversion underpin streamflow forecasts and energy-balance modeling. Grain size evolution and layering alter scattering and absorption, hence the need to specify homogeneity when interpreting reflectance.

Step-by-Step Solution:
Albedo: ratio up-flux / down-flux just above the surface.Spectral albedo: computed per wavelength, typically for semi-infinite snow to neglect background.SWE: physically, water height obtained from melting a unit area column of snow.Homogeneous pack: average grain size does not vary significantly with depth.All statements are correct; therefore select 'All of these'.

Verification / Alternative check:
Snow hydrology references define albedo and SWE in these exact terms and treat semi-infinite assumptions for spectral albedo computations.

Why Other Options Are Wrong:

• Any single statement alone omits the others, all of which are accurate.

Common Pitfalls:

• Confusing broadband albedo with spectral albedo.
• Misinterpreting SWE as mass rather than equivalent water column height.

Final Answer:
All of these