Impact of Seasonal Variations of Forest Structure on Eulerian Length Scale and Mixing Length

Turbulence within and immediately above a vegetation canopy is the driver of exchange processes within soil-plant-atmosphere system. Gaining better physical understanding of air motions in the roughness sublayer (RSL) and within the canopy itself, is a necessary first step towards a better understanding of mass and energy exchanges between atmosphere and vegetation. As a dynamical source and sink of momentum, heat, water vapor and gasses (Tóta et al., 2009), forest plays a crucial role in actual land-atmosphere-interaction. Turbulent transfer above and within the forest canopy is strongly influenced by forest architecture, its thermal characteristics and the significant drag of foliage (Fitzjarrald and Moore, 1995; Staebler and Fitzjarrald, 2005). Important feature of deciduous forest is seasonal variation of leaf area index (LAI) which has a significant impact on turbulent fluxes: a) between forest and atmosphere - through its influence on production and dissipation of turbulence and porosity of canopy top boundary; b) within-canopy - affecting soil and canopy energy balance and reducing momentum exchange. The objective of this study was to make deeper data ‘mining’ of large data sets of measured micrometeorological elements in order to document impact of seasonal variation of forest structure (through variation of LAI) on turbulent transfer between forest canopy and atmosphere (through variation of albedo and characteristic length scales, Eulerian length scale and mixing length)