Estimating the energy balance over forests including advection and horizontal flux divergence

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One of the unsolved problems of measuring surface fluxes is the difference between available energy (sum of net radiation and heat flux due to storage changes) and the turbulent fluxes of latent heat and sensible heat when measured independently in the field. This results in the so-called lack of energy balance closure or closure problem. Concerning the estimation of sensible heat and latent heat it is suspected that neglected advection processes are a main contributor to this lack. Also, there is evidence that there may be a link between the energy budget imbalance and other scalar fluxes like CO2 fluxes. This will be crucial for the estimation of correct CO2 sinks of forests and of the biosphere in general typically based on eddy covariance measurements. In the frame of this project the influence of advection on energy balance closure will be examined. Two unique long-term datasets of intensive measurement campaigns at different forest sites (Tharandt, Germany; Renon, Italy) will be used to assess better understanding of the role of advection on the energy balance. Vertical and horizontal advection as well as horizontal flux divergence will be investigated. The influence of storage, of heterogeneity and of topography on advective fluxes will be addressed to identify possible reasons for imbalances observed at the two sites and elsewhere.