Numerical modelling of snow and ice thicknesses in Lake Vanajavesi, Finland

Snow and ice thermodynamics was simulated applying a one-dimensional model for an individual ice season 2008–2009 and for the climatological normal period 1971–2000. Meteorological data were used as the model input. The novel model features were advanced treatment of superimposed ice and turbulent heat fluxes, coupling of snow and ice layers and snow modelled from precipitation. The simulated snow, snow–ice and ice thickness showed good agreement with observations for 2008–2009. Modelled ice climatology was also reasonable, with 0.5 cm d⁻¹ growth in December–March and 2 cm d⁻¹ melting in April. Tuned heat flux from water to ice was 0.5 W m⁻². The diurnal weather cycle gave significant impact on ice thickness in spring. Ice climatology was highly sensitive to snow conditions. Surface temperature showed strong dependency on thickness of thin ice (<0.5 m), supporting the feasibility of thermal remote sensing and showing the importance of lake ice in numerical weather prediction. The lake ice season responded strongly to air temperature: a level increase by 1 or 5°C decreased the mean length of the ice season by 13 or 78 d (from 152 d) and the thickness of ice by 6 or 22 cm (from 50 cm), respectively.