How does a dynamic surface roughness affect snowpack modeling?

The SNOWPACK model is a cryosphere model which incorporates several environmental model parameters, one of which being the aerodynamic roughness length (z(0)). The z(0) is considered a static parameter, however, research has shown that the z(0) of the surface is variable due to the changing nature of the snowpack surface throughout the winter season. This study highlights the sensitivity of the z(0) within the SNOWPACK model based on the outputs of sublimation, SWE, and sensible heat. The z(0) values were calculated in two ways, anemometrically (z(0-A)), using a wind profile, and geometrically (z(0-G)), measuring surface geometry. Calculated z(0-A) values were between 1.03 x 10(-6) to 0.12 m. The z(0-G) values were calculated from a terrestrial lidar scan using various resolution values of post-process resolutions. These resolutions of 0.01, 0.1, and 1 m resulted in z(0-G) values of 0.26, 0.08, and 0.01 m, respectively. Therefore, as the resolution coarsened, the z(0-G) values decreased. Lastly, these calculated z(0-G) values, a variable run, using weekly measured z(0-G) values, and 0.002 (SNOWPACK default), 0.02, and 0.2 m values were incorporated into the SNOWPACK model. When applied, cumulative sublimation, SWE, and sensible heat outputs varied by 131%, -71%, and -49%, when compared to the default z(0) value used within the model.