Effect of the Representative Source Area for Eddy Covariance Measuraments on Energy Balance Closure for Maize Fields in the Po Valley, Italy

Abstract

This paper has as main objective to show the effect of the representative source area for eddy covariance measurements (called footprint) on energy balance closure. Energy balance closure was evaluated by a statistical regression of turbulent energy fluxes (sensible and latent heat) against available energy (net radiation and soil ground heat flux). The footprint was calculated using an approximate analytical model based on a combination of Lagrangian stochastic dispersion model and dimensional analysis. The data were measured by two eddy covariance towers located on maize fields in Landriano (PV) and Livraga (LO) at the Po Valley, Italy. The main results obtained using only the flux data which have a source area included into the cultivated field shows that there is a slight improvement on the energy balance closure. The stability conditions of the atmosphere plays a fundamental role on the slope of the linear regression and on footprint size, in particular way, it is shown when the energy balance closure is analysed for different sectors of the field in function of the wind directions.