New features and enhancements in Community Land Model (CLM5) snow albedo
modeling: description, sensitivity, and evaluation
Abstract
We enhance the Community Land Model (CLM) snow albedo modeling by
implementing several new features with more realistic and physical
representations of snow-aerosol-radiation interactions. Specifically, we
incorporate the following model enhancements: (1) updating ice and
aerosol optical properties with more realistic and accurate datasets,
(2) adding multiple dust types, (3) adding multiple surface downward
solar spectra to account for different atmospheric conditions, (4)
incorporating a more accurate adding-doubling radiative transfer solver,
(5) adding nonspherical snow grain representation, (6) adding black
carbon-snow and dust-snow internal mixing representations, and (7)
adding a hyperspectral (480-band versus the default 5-band) modeling
capability. These model features/enhancements are included as new CLM
physics/namelist options, which allows for quantification of model
sensitivity to snow albedo processes and for multi-physics model
ensemble analyses for uncertainty assessment. The model updates will be
included in the next CLM version release. Sensitivity analyses reveal
stronger impacts of using the new adding-doubling solver, nonspherical
snow grains, and aerosol-snow internal mixing than the other new
features/enhancements. These enhanced snow albedo representations
improve the CLM simulated global snowpack evolution and land surface
conditions, with reduced biases in simulated snow surface albedo, snow
cover, snow water equivalent, snow depth, and surface temperature,
particularly over northern mid-latitude mountainous regions and polar
regions.