Variable infiltration capacity cold land process model updates

The Variable Infiltration Capacity (VIC) macroscale hydrologic model is distinguished from other Soil–Vegetation–Atmosphere Transfer schemes (SVATS) by its focus on runoff processes. These are represented via the variable infiltration curve, a parameterization of the effects of subgrid variability in soil moisture holding capacity, from which the model takes its name, and a representation of nonlinear baseflow. Recent upgrades to the model have improved its representation of cold land processes, and the effects of surface storage in lakes and wetlands. Specific improvements described in this paper include the following: (1) explicit representation of the canopy energy balance separate from the land surface when snow is intercepted in the canopy; (2) parameterization of the effects of spatial variability in soil freeze–thaw state and snow distribution on moisture and energy fluxes; and (3) effects of advection on snowmelt under conditions of partial snow cover. The effects of these model updates are demonstrated using data from the PILPS Phase 2(e) validation catchments within the Torne-Kalix River basin, Sweden.