Experimental study of heat and momentum exchange between a forest lake and the atmosphere in winter

[摘要] The article presents the results of an experimental study of turbulent heat exchange between the surface of a frozen lake surrounded by forest and the atmospheric boundary layer. Heat and momentum fluxes were measured at three levels by an eddy covariance (EC) technique. Additionally, the heat fluxes were estimated by a surface energy balance method using a temperature profile measured in the snow cover and net longwave and shortwave radiation. The results of the measurements show that the eddy covariance fluxes correlate well with those obtained by the surface energy balance method, with a tendency of underestimation. The presence of wind-shear effects at treetop height demonstrated recently in a Large Eddy Simulation (LES) [3] was supported in our measurements by the fact that the momentum flux increased with height from the surface. The negative sensible heat flux increased with height most of the time. We suggest that this phenomenon may partially be caused by the high negative heat fluxes above the surface formed when warm advection occurs at altitudes of ∼100 m. During the warm advection events, Monin-Obukhov similarity theory (MOST) fails to reproduce the sharp increase of the negative heat flux at the surface layer. Beyond the warm advection events, the MOST calculations agree well with the EC fluxes, however, with some systematic underestimation bias.

[发布机构] A.M.Obukhov Institute of Atmospheric Physics RAS, Moscow, Russia^1;Lomonosov Moscow State University, Moscow, Russia^2;P.P.Shirshov Institute of Oceanology RAS, Moscow, Russia^3

[效力级别] 计算机科学

[关键词] Eddy covariance;Momentum exchange;Monin-Obukhov similarity theory;Sensible heat flux;Short-wave radiation;Temperature profiles;Turbulent heat exchange;Warm advection