Modified snow algorithms in the Canadian land surface scheme: Model runs and sensitivity analysis at three boreal forest stands

Abstract Version 3.1 of the Canadian Land Surface Scheme (CLASS) contains a number of new algorithms of significance for snow simulations in the boreal forest. In particular, mixed precipitation is now modelled, the density of fresh snow varies with temperature and the maximum snowpack density varies with snow depth. A model for canopy interception and unloading of snow developed in the Canadian boreal forest has also been implemented. In this paper, nine‐month column runs of CLASS 3.1 are compared with CLASS 2.7, the current operational version. The model runs span the winter of 2002–03 at three boreal forest sites: a mature aspen stand, a mature jack pine stand and a mature black spruce stand, all located in central Saskatchewan. The focus is on the winter performance and the representation of snow. More accurate (lower) values of modelled snow density improve the modelled snowpack depth. The accuracy of the canopy interception algorithm could not be tested directly with respect to measured interception, but results suggest that the ability to unload intercepted snow is important for accurate estimates of sublimation loss, and that simulated snow water equivalent is sensitive to perceived canopy gap fraction, interception capacity, and unloading rate. Underestimation of the canopy gap fraction increases canopy interception and sublimation losses, and decreases snow water equivalent in the snowpack, and vice versa. Employing modified gap fraction values improved the modelled snow water equivalent at two of the sites. Modifications to the model are suggested to allow the total albedo to respond to changes in the modelled sub‐canopy albedo.

[1]  W. Allard.  Snow Hydrology: Summary Report of the Snow Investigations. Published by the North Pacific Division, Corps of Engineers, U.S. Army, Portland, Oregon, 1956. 437 pages, 70 pages of plates, maps and figs., 27 cm.* , 1957 .

[2]  A. H. Auer.  The Rain versus Snow Threshold Temperatures , 1974 .

[3]  Barry E. Goodison,et al.  Accuracy of Canadian Snow Gage Measurements , 1978 .

[4]  Michael H. Unsworth,et al.  The angular distribution and interception of diffuse solar radiation below overcast skies , 1980 .

[5]  J. Goudriaan,et al.  The bare bones of leaf-angle distribution in radiation models for canopy photosynthesis and energy exchange , 1988 .

[6]  I. Calder.  Evaporation in the Uplands , 1990 .

[7]  D. Verseghy,et al.  CLASS-A Canadian Land Surface Scheme for GCMs , 1993 .

[8]  D. Gluns,et al.  Snowfall interception on branches of three conifer species , 1991 .

[9]  S. Halldin,et al.  Evaporation of intercepted snow: Analysis of governing factors , 1994 .

[10]  John W. Pomeroy,et al.  Snowcover Accumulation, Relocation, and Management , 1995 .

[11]  J. Pomeroy,et al.  The Energy Balance of the Winter Boreal Landscape , 1996 .

[12]  S. T. Gower,et al.  Leaf area index of boreal forests: theory, techniques, and measurements , 1997 .

[13]  Peter D. Blanken,et al.  Energy balance and canopy conductance of a boreal aspen forest: Partitioning overstory and understory components , 1997 .

[14]  Dennis D. Baldocchi,et al.  Seasonal variation of energy and water vapor exchange rates above and below a boreal jack pine forest canopy , 1997 .

[15]  Alan K. Betts,et al.  Albedo over the boreal forest , 1997 .

[16]  John Moncrieff,et al.  Seasonal variation of carbon dioxide, water vapor, and energy exchanges of a boreal black spruce forest , 1997 .

[17]  S. Halldin,et al.  Snow interception evaporation. Review of measurementtechniques, processes, and models , 2001 .

[18]  John W. Pomeroy,et al.  Measurements and modelling of snow interception in the boreal forest , 1998 .

[19]  Robert A. Metcalfe,et al.  A statistical model of spatially distributed snowmelt rates in a boreal forest basin , 1998 .

[20]  R. Harding,et al.  Evaporation of intercepted snow: measurement and modelling , 1998 .

[21]  D. H. Gray,et al.  An evaluation of snow accumulation and ablation processes for land surface modelling , 1998 .

[22]  John W. Pomeroy,et al.  Coupled Modelling of Forest Snow Interception and Sublimation , 1998 .

[23]  S. Linder,et al.  Effects of soil warming during spring on photosynthetic recovery in boreal Norway spruce stands , 1999 .

[24]  T. Terajima,et al.  Energy balance above a boreal coniferous forest: a difference in turbulent fluxes between snow‐covered and snow‐free canopies , 1999 .

[25]  Bart Nijssen,et al.  A simplified approach for predicting shortwave radiation transfer through boreal forest canopies , 1999 .

[26]  Jean-François Mahfouf,et al.  The representation of soil moisture freezing and its impact on the stable boundary layer , 1999 .

[27]  T. Terajima,et al.  The effect of canopy-snow on the energy balance above a coniferous forest , 1999 .

[28]  John W. Pomeroy,et al.  Turbulent fluxes during blowing snow: field tests of model sublimation predictions , 1999 .

[29]  Ming-ko Woo,et al.  Simulation of snowmelt in a subarctic spruce woodland: 2. Open woodland model , 2000 .

[30]  N. Kouwen,et al.  Towards closing the vertical water balance in Canadian atmospheric models: Coupling of the land surface scheme class with the distributed hydrological model watflood , 2000 .

[31]  Sune Linder,et al.  Botany: Constraints to growth of boreal forests , 2000, Nature.

[32]  M. Woo,et al.  Simulation of snowmelt in a subarctic spruce woodland: 1. Tree model , 2000 .

[33]  D. Verseghy,et al.  Parametrization of peatland hydraulic properties for the Canadian land surface scheme , 2000, Data, Models and Analysis.

[34]  Wenjun Chen,et al.  Increased carbon sequestration by a boreal deciduous forest in years with a warm spring , 2000 .

[35]  S. Gryning,et al.  Progress in understanding of land surface/atmosphere exchanges at high latitudes , 2001 .

[36]  T. A. Black,et al.  The seasonal water and energy exchange above and within a boreal aspen forest , 2001 .

[37]  R. Dickinson,et al.  The Representation of Snow in Land Surface Schemes: Results from PILPS 2(d) , 2001 .

[38]  John W. Pomeroy,et al.  Prediction of seasonal snow accumulation in cold climate forests , 2002 .

[39]  T. A. Black,et al.  Comparing the carbon budgets of boreal and temperate deciduous forest stands , 2002 .

[40]  T. A. Black,et al.  Effects of seasonal and interannual climate variability on net ecosystem productivity of boreal deciduous and conifer forests , 2002 .

[41]  E. Soulis,et al.  Implications during transitional periods of improvements to the snow processes in the land surface scheme ‐ hydrological model WATCLASS , 2002 .

[42]  V. Arora.  MODELING VEGETATION AS A DYNAMIC COMPONENT IN SOIL‐VEGETATION‐ATMOSPHERE TRANSFER SCHEMES AND HYDROLOGICAL MODELS , 2002 .

[43]  Teemu Kokkonen,et al.  Snow processes in a forest clearing and in a coniferous forest , 2002 .

[44]  Dennis P. Lettenmaier,et al.  Measurement of snow interception and canopy effects on snow accumulation and melt in a mountainous maritime climate, Oregon, United States , 2002 .

[45]  Angela Lundberg,et al.  Estimating winter evaporation in boreal forests with operational snow course data , 2003 .

[46]  T. Griffisa,et al.  Ecophysiological controls on the carbon balances of three southern boreal forests , 2003 .

[47]  Alan G. Barr,et al.  Year‐round observations of the energy and water vapour fluxes above a boreal black spruce forest , 2003 .

[48]  S. Halldin,et al.  Snow accumulation in forests from ground and remote‐sensing data , 2004 .

[49]  T. Black,et al.  Inter-annual variability in the leaf area index of a boreal aspen-hazelnut forest in relation to net ecosystem production , 2004 .

[50]  Natascha Kljun,et al.  Seasonal variation and partitioning of ecosystem respiration in a southern boreal aspen forest , 2004 .

[51]  Chris Derksen,et al.  Characterizing local scale snow cover using point measurements during the winter season , 2006 .

[52]  D. Verseghy,et al.  Class—A Canadian land surface scheme for GCMS. I. Soil model , 2007 .