11:15 AM - 11:30 AM
[ACC27-09] Effect of snow impurities on the radiation budget and snow melting observed at Sapporo during 10 winter seasons
Comparing the time series of the observed broadband albedos with the theoretically calculated values, the calculated albedo variations due to the change in snow grain size and impurity concentration agreed well with the observations in each year of the analysis period. The determination coefficient (R2) and the root mean square error (RMSE) for the whole period obtained from the albedo comparison in the shortwave (SW) spectral region were 0.847 and 0.046, respectively, confirming the high accuracy of PBSAM. Next, sensitivity experiments were conducted on the albedo changes in the visible (VIS), near-infrared (NIR), and SW regions depending on the presence and absence of snow impurities. The albedo change and RF due to snow impurities (BC + mineral dust) in the whole period were -0.053 and +6.7 Wm-2, respectively for the SW region. In addition, we estimated total snowmelt amount from the surface energy balance calculation and measured energy flux between the bottom of the snowpack and the underlying ground. The total estimated amount of snow melt for the whole period was 398 mm w. e..The contributions from surface melting and melting at the ground were 76% and 24%, respectively. The melting energy due to snow impurity-induced albedo reduction is equivalent to 28% of total amount of snow melting, which is larger than the melting at the ground and is not negligible. Furthermore, the contributions from BC and dust to this value are 21% and 7%, respectively.
Aoki, T., K. Kuchiki, M. Niwano, Y. Kodama, M. Hosaka and T. Tanaka (2011), Physically based snow albedo model for calculating broadband albedos and the solar heating profile in snowpack for general circulation models. J. Geophys. Res., 116, D11114, doi:10.1029/2010JD015507.