Here is a summary of the article:

## Snowpack Optical Properties

The article discusses how the Community Land Model (CLM) calculates the optical properties of the snowpack, which are used to determine the snowpack's reflectivity and radiative effects.

Key points:

1. Ice optical properties are derived offline and stored in lookup tables for online retrieval in CLM. These properties are calculated using Mie theory and then weighted into the 5 spectral bands used by CLM.

2. The broadband mass-extinction cross section and single-scatter albedo are calculated by weighting the fine-resolution Mie properties by the incident solar flux and the diffuse albedo of an optically thick snowpack.

3. The lookup tables contain optical properties for a range of ice grain effective radii (30-1500 μm).

4. Optical properties are also provided for snowpack impurities like black carbon and dust, which can significantly affect the snowpack's optical properties.

5. Tables are provided listing the single-scatter albedo, mass-extinction values, and asymmetry parameters for the ice and impurities in the 5 CLM spectral bands.

The article describes the detailed calculations and data underlying the representation of snowpack optical properties in the CLM land surface model.