ABSTRACT
A one-dimensional thermodynamic sea ice model was constructed, in which different param-eterizations of the surface radiative fluxes were studied and compared. The effect of atmospheric stratification was taken into account in the calculation of the turbulent surface heat fluxes based on the Monin-Obukhov similarity theory. A two-layer parameterization of penetrating solar ra-diation attenuating through the sea ice was introduced. The ice model solves the full heat con-duction equation associated with heat fluxes and ice/snow mass moving boundaries. A conser-vative finite-difference numerical scheme of the heat conduction equation was derived using an integral interpolation method. This scheme was validated by numerical tests. The impact of nu-merical resolution on model predictions was studied. The ice model was coupled with a two-di-mensional hydrostatic mesoscale atmospheric boundary layer (ABL) model to study the effect of warm-air advection on ice thermodynamics and the air-ice coupling.
The model was applied to study the ice thermodynamic processes in the seasonal ice cover of the Bohai Sea and the Baltic Sea. The model results were compared with field measurements. The model simulated various surface fluxes well, in particular the turbulent fluxes. The model also well reproduces the diurnal variation of ice temperature and seasonal evolution of ice thickness.
Process study using the Baltic Air-Sea-Ice Study (BASIS) field data suggested that during an ice thermal equilibrium stage the modelled superimposed ice formation gives a good estimation of the snow-ice formation. The model initialization is important for a short-term simulation. A sub-surface melting in early spring due to solar radiation absorption was also simulated.
The heat transfer coefficient and temperature roughness length were studied based on the analy-sis of the turbulent surface fluxes measured during BASIS. There was good mutual agreement with the surface temperature and the turbulent fluxes estimated by the eddy-flux and the gradient methods and the ice model.
The numerical scheme of the ice model was verified against analytical solutions. During the freezing season, the effect of numerical resolution on model results is not significant. When the downward short-wave radiation become large, the absorption of this flux below the ice or snow surface changes the predictions of ice temperature and surface heat fluxes in a way depending on the model spatial resolution chosen. A two-layer scheme for handling penetrating solar radiation in ice is suitable for a fine-resolution model.
During advection of warm air over an initially cold snow/ice layer, the air-ice turbulent heat flux has a direction opposite to the prevailing upward heat flux from the ocean through the snow/ice. This results in a time-fetch and a time-depth dependent behaviour of the directionally-varying conductive heat flux in the snow/ice layer. From the point of view of ABL modelling, the inter-active coupling between the air and ice was most important when the wind was strong, while from the point of view of ice thermodynamic modelling the coupling was most important when the wind was light.

Key words: sea ice thermodynamics, air-ice interaction, surface heat balance, penetrating solar radiation, warm air advection, numerical model, numerical resolution, Bohai Sea, Baltic Sea.

More information is available at http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/cheng/
Bin@fimr.fi