The Eddy-Covariance Method - History, Status, and Prospects (Invited Presentation)

More than 60 years ago, the basics of the eddy-covariance method were proposed by Montgomery, Swinbank and Obukhov, with the first widely applicable sonic anemometers becoming available more than a decade later. For a long time, the method was only used by specialists like Dyer, Businger, and Kaimal, who developed the devices and correction methods, etc. For the last 20 years, the ecological community has had access to many commercial devices and has used the method to determine the carbon exchange within the FLUXNET programme. During this time, the focus was on the development of tools and instructions to enable even non-specialists to apply this not simple method. Three problems are still under discussion: the energy balance closure problem, the handling of non-turbulent situations, and the determination of the accuracy. The energy balance closure problem has a special difficulty because it is related to the terrain and not to the method itself. Nevertheless, papers have been published which discuss the problem as a sensor-specific issue, which would be much easier to handle. The development of sensors has become more and more a task carried out by engineers rather than scientists – not always to the benefit of the method. For the future, we should use the method to directly determine energy and matter fluxes in a turbulent atmosphere, while other methods must be used for non-turbulent conditions. Moreover, the energy balance closure problem is not unresolvable. In the future, it is important that specialists in atmospheric turbulence are also involved in work on the recommendations for the application of the method.