FluxNet

FluxNet is a global network of micrometeorological tower sites that use eddy covariance methods to measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere. Fluxnet is a global 'network of regional networks' that serves to provide an infrastructure to compile, archive and distribute data for the scientific community. It works to ensure that different flux networks are calibrated to facilitate comparison between sites, and it provides a forum for the distribution of knowledge and data between scientists. FluxNet is a global network of micrometeorological tower sites that use eddy covariance methods to measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere. Fluxnet is a global 'network of regional networks' that serves to provide an infrastructure to compile, archive and distribute data for the scientific community. It works to ensure that different flux networks are calibrated to facilitate comparison between sites, and it provides a forum for the distribution of knowledge and data between scientists. As of April 2014, there are over 683 tower sites in continuous long-term operation. Researchers also collect data on site vegetation, soil, trace gas fluxes, hydrology, and meteorological characteristics at the tower sites. According to the Fluxnet website, the goals of the project are as follows: Scientists have been measuring water vapor and carbon dioxide exchange between the Earth's surface and the atmosphere since the late 1950s. The relatively undeveloped computing capabilities and solid state measurement capabilities made it almost impossible to be able to get accurate measurements. Early scientists such as John Monteith used the 'flux gradient' method to make semi-accurate assessments of the fluxes in a variety of natural settings. The work of scientists such as Monteith realized that the Flux Gradient method was not nearly as accurate as it needed to be when used to measure trace gas exchange in tall forests. Eventually, they realized that the downfall of their models was caused by 'large scale transport in the roughness sublayer'. The reason for these data inaccuracies was hypothesized to arise from Monin-Obukhov scaling theory. As digital technology advanced throughout the 1970s and 80s, so did advances in the sensors and digital hardware necessary to provide the means to make advanced measurements of fluxes with what became known as the eddy covariance technique. With this method as well as further advances in digital data storage, it became possible for curious scientists to make these eddy flux measurements for long periods of time and consequently get a sense of annual carbon dioxide and water vapor changes in the biosphere. As these techniques became more widespread in the scientific community, more research groups took the initiative to establish further measurement sites. Eventually, enough sites were established to allow research of fluxes over wide areas of land with the help of multiple investigators. An example of such a study is the 'Boreal Ecosystem-Atmosphere Study'. With the success of such projects, participating scientists began to explore the idea of creating a global network of sensor sites that could be used to integrate their data and provide access for the members of the academic community and general public. At a meeting in La Thuile, Italy during 1995, contributing scientists began to discuss the feasibility of such a network. With the successful conclusion of this meeting, there was an increase in the rate of sensor site installation and the growth of regional networks. Eventually, the Euroflux network took hold in 1996 and was soon followed by the AmeriFlux network in 1997. When NASA saw the enthusiasm from the scientific community for these two networks as well as the possibility to integrate trace gas data from the ground with data from the Earth Observatory Satellite, it finally funded the Fluxnet project as a whole in 1998. In 2002, Fluxnet was added to the NOAA Observing System Architecture (NOSA). Future FluxNet sites are planned according to a desirable accuracy in the acquired data. With the current model used to determine flux between the surface and the atmosphere, it is desirable to situate the tower in an area with uniform vegetative cover and minimal disturbances in the terrain. Deviations in terrain or plant cover would prevent a constant gas flux along the height of the tower. Another very important part of the sensor array is the tower on which it rests. The sensor tower must fit within a certain design criteria dependent on: