Upscaling fluxes from towers to regions, continents, and the globe: what have we learned?

Abstract:

The eddy covariance (EC) technique provides continuous measurements of ecosystem-level carbon, water, and energy exchange at various time scales. There are over 500 flux sites over the globe and they encompass a large range of ecosystem and climate types. Despite the growing number of EC flux sites, the flux measurements only represent the fluxes of the tower footprint. Various approaches have been used to upscale flux observations from towers to regions, continents, and the globe during the last several years. These approaches make use of satellite observations and meteorological reanalysis data that are both spatially and temporally continuous. The resulting gridded flux estimates have been used to examine the magnitude, distribution, and interannual variability of fluxes and to evaluate model simulations. This talk will focus on what we have learned from these upscaling efforts from the following aspects: (1) upscaling methods: progress and limitations; (2) representativeness of flux networks and influence on upscaled fluxes; (3) spatial patterns of the resulting gridded fluxes; (4) magnitude of upscaled fluxes; (5) temporal patterns of carbon and water fluxes; (6) interannual variability of fluxes and effects of disturbance and drought; (7) evaluating and informing ecosystem and earth system models; (8) uncertainty of upscaled fluxes; and (9) challenges and future opportunities. Examples will be drawn heavily from the studies that the presenter has led and/or been involved in.