Abstract
Abstract. Local-scale advection of energy from warm snow-free surfaces to cold snow-covered surfaces is an important component of the energy balance during snow-cover depletion. Unfortunately, this process is difficult to quantify in one-dimensional snowmelt models. This paper proposes a simple sensible and latent heat advection model for snowmelt situations that can be readily coupled to one-dimensional energy balance snowmelt models. An existing advection parameterization was coupled to a conceptual frozen soil infiltration surface water retention model to estimate the areal average sensible and latent heat advection contributions to snowmelt. The proposed model compared well with observations of latent and sensible heat advection, providing confidence in the process parameterizations and the assumptions applied. Snow-covered area observations from unmanned aerial vehicle imagery were used to update and evaluate the scaling properties of snow patch area distribution and lengths. Model dynamics and snowmelt implications were explored within an idealized modelling experiment, by coupling to a one-dimensional energy balance snowmelt model. Dry, snow-free surfaces were associated with advection of dry air that compensated for positive sensible heat advection fluxes and so limited the net influence of advection on snowmelt. Latent and sensible heat advection fluxes both contributed positive fluxes to snow when snow-free surfaces were wet and enhanced net advection contributions to snowmelt. The increased net advection fluxes from wet surfaces typically develop towards the end of snowmelt and offset decreases in the one-dimensional areal average melt energy that declines with snow-covered area. The new model can be readily incorporated into existing one-dimensional snowmelt hydrology and land surface scheme models and will foster improvements in snowmelt understanding and predictions.
Highlights
Sensible and latent turbulent heat fluxes contributing to snowmelt are complicated during snow-covered area (SCA) depletion by the lateral redistribution of energy from snowfree surfaces to snow
The scaling parameters necessary to describe the spatial heterogeneity of snow and snow-free patches were re-evaluated with unmanned aerial vehicle (UAV) data
Coupling of the simple advection model with snow-cover geometry scaling laws, SCA depletion, frozen soil infiltration and a surface detention fractional water area parameterization resulted in a model that meets the objective of a formulation that can account for latent heat advection (LEA) and heat advection (HA) to snow as an areal average contribution
Summary
Sensible and latent turbulent heat fluxes contributing to snowmelt are complicated during snow-covered area (SCA) depletion by the lateral redistribution of energy from snowfree surfaces to snow. The differences in surface energetics between snowcovered and snow-free areas lead to a heterogeneous distribution of surface temperature and near-surface water vapour. These horizontal gradients drive a lateral exchange of heat (sensible heat advection) and water vapour (latent heat advection when considering the induced condensation or sublimation) over the leading edge of a snow patch.
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