[ACC28-P08] Effect of snow impurities on albedo and radiative forcing observed during 9 winter seasons in Sapporo
Comparing the time series of the observed albedo and the model calculated value in each year of the analysis period, the calculated albedo variations due to the change in snow grain size and impurity concentration agreed well with the observations. The determination coefficient (R2) and the root mean square error (RMSE) in the whole period obtained from the albedo comparison between observation and calculation in the shortwave (SW) region were 0.856 and 0.043, respectively, confirming the high accuracy of PBSAM. Next, sensitivity experiments were conducted on albedo changes in the visible (VIS), near-infrared (NIR), and SW regions depending on the presence or absence of snow impurities which consist of black carbon (BC) and mineral dust. The albedo change due to snow impurities (BC + dust) in the whole period was -0.054 in the SW region. The contributions from BC and dust to the total SW albedo change were -0.046 and -0.008 by BC and dust, respectively. RF due to snow impurities in the whole period was +6.8 Wm-2, in which the contributions from BC and dust to the total RF were +5.5 Wm-2 and +1.3 Wm-2, respectively. Furthermore, RFs for the accumulation period and melting period were +2.6 Wm-2 and +20 Wm-2, respectively.
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