ИСТИНА

Adequate estimation of gas emission from the northern territories requires calculation of balances of heat, moisture, and gases at the surface of water bodies on the sub-grid scale of climate models. Lakes are an important ”liquid land” surface type. Having a lower albedo and larger heat capacity than solid land, lakes absorb more solar radiation and store more heat, and often have different surface temperature than the surrounding landscape. Lake surfaces are aerodynamically much smoother than vegetated land surfaces, thus enhancing variations of fluxes of momentum, heat, moisture and gases between the land and the atmosphere. Existent estimations of lake-atmosphere fluxes are often based on experimental studies in the ocean and lakes where the wind sheltering and mesoscale turbulence effects are not significant. Quantification the momentum, heat, and mass exchange between the atmosphere and the underlying surface is a central problem of the atmospheric boundary-layer (ABL) research. Parameterization of air-sea/land fluxes is of obvious relevance for the modelling of coupled atmosphere-ocean/land system, including climate modelling, weather forecasting, environmental impact studies, and many other applications. Traditionally, the flux-gradient and flux-variance relationships in the surface layer are described by Monin-Obukhov similarity theory (Monin and Obukhov 1954), which assumes horizontal homogeneity of the underlying surface, including surface fluxes, aerodynamic and thermal roughness (Garratt 1994; Kaimal and Finnigan 1994; Wyngaard 2010). This assumption is reasonable in many instances, and allows focusing on 1-D processes, but it is nominally violated in the inhomogeneous forest zone where horizontal gradients are steep (Panin, Bernhofer 2008). Statistical properties of turbulence in the atmospheric surface layer have been extensively studied over homogeneous surfaces. However, detailed description of disturbances in the flow, generated over transition zones between surfaces with different roughness remains an important subject of theoretical and experimental studies (Garratt 1990, 1994, Coceal and Belcher 2005, Detto et al, 2008). This task is complicated by the absence of energy balance closure formulation -is a fundamental and pervasive problem in micrometeorology (e.g., Foken, 2008; Panin and Bernhofer 2008; Leuning et al. 2012 and references therein). This paper presents the results of experimental studies of the turbulent structure of the surface layer in winter. Experiments were conducted over a small lake (close to White Sea Biological Station (WSBS) of Moscow State University) surrounded by forest.. The purpose of this study is evaluation of turbulent transport in the system “lake water– near-surface air – surrounding forest”. In order to distinguish the influence of the inhomogeneous landscape on the turbulent exchange in the atmosphere-surface system, excluding the effects of the thermal regime of the lake, the experiment was carried out in winter time over an ice-covered lake surface. In the first case (2015) we used an array of acoustic anemometers mounted at different distances from the lake. Measurements were taken at two heights in the center of the lake. In the second case (2017) 6-meter mast with instruments was installed in the center of the lake. There were 3 levels of ultrasonic three-component anemometers (2m, 4m and 6m) and two levels of standard meteorological measurement (3m and 5m). Temperature profile in the atmosphere was recorded with 50m step by microwave profiler MTP-5. Turbulent fluxes were calculated with Eddy-Covariance and gradient methods. This work was supported by the Russian Scientific Foundation under grant 17-17-01210.