This code uses a two-stream approximation to calculate snow spectral albedo and radiative fluxes at the interfaces of any number of snow layers with distinct properties.

• (1) Download the snicarAD_v3.m and snicarAD_v3_drv.m source files.
• (2) Download one of the following optics library packages from "Links to optics libraries": (a) snicar_v3_optics.tar.gz (637 MB), which includes all optics files EXCEPT those of algae; or (b) snicar_v3_optics_with_algae.tar.gz (7.1 GB), which includes everything in the above package AND algae. Please note that the algae library contains > 125,000 files.
• (3) Unpack the optics library into the directory of your choice, using: "tar xvfz "
• (4) In snicarAD_v3.m, set variable "dir_op_root" to the directory where you unpacked the optics library.
• (5) Run the template driver routine "snicarAD_v3_drv.m" and see basic output fields and a plot of spectral albedo.

Please see the header of snicarAD_v3.m for more information about input fields.

• Replacement of the tri-diagonal matrix two-stream solver with the Adding-Doubling solver (Dang et al.,2019)
• Solar zenith angle-dependent surface spectral irradiances
• Updated optical properties of light-absorbing constituents

• Snow algae (Cook et al.,2017)
• Non-spherical ice particles (He et al.,2017)
• CO2 ice (Hansen et al.,2005; Singh et al.,2016)
• Additional dust optical properties: (a) Saharan dust (Balkanski et al.,2007); (b) San Juan Mountains, Colorado (Skiles et al.,2017); (c) Greenland (Polashenski et al.,2015); (d) Martian dust (Wolff et al.2009,2010; Singh et al.,2016).
• Volcanic ash (Flanner et al.,2014)
• A larger size bin (5-50um radius) for dust and ash particles
• Multiple options for H2O ice refractive indices: (a) Warren et al.(1984); (b) Warren and Brandt (2008); (c) Merged Picard et al. (2016) / Warren and Brandt (2008).
• Several new options for surface spectral irradiance weighting
• Extension of the simulated spectrum down to 0.2um