Environmental Research Aircraft: an innovative methodology to monitor productivity of agro-Mediterranean ecosystems.

In the light of the Kyoto protocol, worldwide efforts are under way aimed at identifying the spatial and temporal distribution of sources and sinks of atmospheric CO2. The estimate of the sink/source strength of vegetated surfaces is now possible with reasonable accuracy and the techniques are well established, while difficulties exist into up scaling these figures at the regional and then the global scale. To bridge the gap, current modelling efforts need to be validated by flux measurements at a wider scale with respect to towers. Instrumented small aeroplanes are the state-of-art to provide reliable data sets for these purposes. Sky Arrow ERA (Environmental Research Aircraft) is an aircraft recently developed in Italy, which can operate under different configurations to measure surface fluxes of mass, momentum and energy, as well as georeferenced vertical atmospheric profiles of gas concentrations, turbulence and wind. The 3D components of wind along with the concentrations of carbon dioxide and water vapour are sampled at high frequency. The component of true displacement of the aircraft, measured by an inertial-GPS system mounted on board, is then subtracted to allow for calculation of the actual fluxes by means of the conventional eddy correlation technique. Data are stored in the computer mounted on board of the aircraft and are then post-processed using a software package specifically developed for this purpose. A detailed description of the technique is provided, along with a comparison with ground based flux data.