A Model for the Spectral Albedo of Snow. I: Pure Snow

TLDR

The study presents a method to calculate snow spectral albedo across the solar spectrum, accounting for diffuse or direct radiation at any zenith angle. The model uses an adjustable effective grain size (and liquid‑equivalent depth for thin snow) and applies the delta‑Eddington approximation with Mie theory to capture anisotropic scattering, evaluating albedo from 0.3 to 5 µm as a function of grain size, zenith angle, snowpack thickness, and diffuse/direct solar incidence. The model reproduces the observed albedo decrease with snow aging by increasing grain size to 50–100 µm, demonstrating its ability to capture aging effects.

Abstract

Abstract We present a method for calculating the spectral albedo of snow which can be used at any wavelength in the solar spectrum and which accounts for diffusely or directly incident radiation at any zenith angle. For deep snow, the model contains only one adjustable parameter, an effective grain size, which is close to observed grain sizes. A second parameter, the liquid-equivalent depth, is required only for relatively thin snow. In order for the model to make realistic predictions, it must account for the extreme anisotropy of scattering by snow particles. This is done by using the “delta-Eddington” approximation for multiple scattering, together with Mie theory for single scattering. The spectral albedo from 0.3 to 5 μm wavelength is examined as a function of the effective grain size, the solar zenith angle, the snowpack thickness, and the ratio of diffuse to direct solar incidence. The decrease in albedo due to snow aging can be mimicked by reasonable increases in grain size (50–100 μm for new snow...