Simulation of Snow and Winter Albedo in the Canadian Land Surface Scheme: Preliminary Results for ESM-SnowMIP

The representation of snow processes in land surface schemes has come under much scrutiny in recent years due to the persistence in simulations of winter albedo biases, which are mostly positive, particularly in the boreal forest. A recent version (V3.6) of the Canadian Land Surface Scheme (CLASS) has shown a negative winter albedo bias in much of the boreal forest. An analysis of above-canopy albedo in relation to canopy snow cover revealed that the assigned albedo values for snow-covered canopy in CLASS were too small, that observed intercepted snow covered the canopy more quickly and usually unloaded more quickly than in CLASS simulations. A new interception-albedo parameterization (IAP) resulted in dramatic improvements in the simulated winter albedo at the site level, including sites associated with ESM-SnowMIP (Earth System Model - Snow Model Intercomparison Project). We present preliminary results from site-level simulations for ESM-SnowMIP using CLASS 3.6.2, which contains updated albedo values for snow-covered canopy, and we show the impact of our recent IAP developments. Tests of our IAP in global simulations forced with reanalysis data showed smaller improvements in the simulated albedo in boreal forests. Further investigation revealed that specified winter values of plant area index were smaller on average than at individual flux tower sites and smaller than suggested in recent studies. We examine the sensitivity of simulated albedo to plant area index in the land cover dataset.