A high-altitude balloon platform for determining exchange of carbon dioxide over agricultural landscapes

摘要

The exchange of carbon dioxide between the terrestrial biosphereand the atmosphere is a key process in the global carbon cycle. Givenemissions from fossil fuel combustion and the appropriation of net primaryproductivity by human activities, understanding the carbon dioxide exchangeof cropland agroecosystems is critical for evaluating future trajectories ofclimate change. In addition, human manipulation of agroecosystems has beenproposed as a technique of removing carbon dioxide from the atmosphere viapractices such as no-tillage and cover crops. We propose a novel method ofmeasuring the exchange of carbon dioxide over croplands using a high-altitudeballoon (HAB) platform. The HAB methodology measures two sequential verticalprofiles of carbon dioxide mixing ratio, and the surface exchange iscalculated using a fixed-mass column approach. This methodology is relativelyinexpensive, does not rely on any assumptions besides spatial homogeneity (nohorizontal advection) and provides data over a spatial scale betweenstationary flux towers and satellite-based inversion calculations. The HABmethodology was employed during the 2014 and 2015 growing seasons in centralIllinois, and the results are compared to satellite-based NDVI values and aflux tower located relatively near the launch site in Bondville, Illinois.These initial favorable results demonstrate the utility of the methodologyfor providing carbon dioxide exchange data over a large (10–100 km) spatialarea. One drawback is its relatively limited temporal coverage. Whilerecruiting citizen scientists to perform the launches could provide a moreextensive dataset, the HAB methodology is not appropriate for providingestimates of net annual carbon dioxide exchange. Instead, a HAB dataset couldprovide an important check for upscaling flux tower results and verifyingsatellite-derived exchange estimates.