title: Measuring eddy covariance fluxes of ozone with a slow-response analyser.
abstract: Ozone (O3) fluxes above a temperate mountain grassland were measured by means of the eddy covariance (EC) method using a slow-response O3analyser. The resultant flux loss was corrected for by a series of transfer functions which model the various sources of high- and, in particular, low-pass filtering. The resulting correction factors varied on average between 1.7 and 3.5 during night and day time, respectively. A cospectral analysis confirmed the accuracy of this approach. O3fluxes were characterised by a comparatively large random uncertainty, which during daytime typically amounted to 60 %. EC O3fluxes were compared against O3flux measurements made concurrently with the flux-gradient (FG) method. The two methods generally agreed well, except for a period between sun rise and early afternoon, when the FG method was suspected of being affected by the presence of photochemical sources/sinks. O3flux magnitudes and deposition velocities determined with the EC method compared nicely with the available literature from grassland studies. We conclude that our understanding of the causes and consequences of various sources of flux loss (associated with any EC system) has sufficiently matured so that also less-than-ideal instrumentation may be used in EC flux applications, albeit at the cost of relatively large empirical corrections.
authors.affiliation: Institut für Ökologie, Universität Innsbruck, Sternwartestr. 15, 6020 Innsbruck, AUSTRIA.
authors.forename: Georg
authors.initials: G
authors.lastname: Wohlfahrt
authors.affiliation: Institut für Ökologie, Universität Innsbruck, Sternwartestr. 15, 6020 Innsbruck, AUSTRIA.
authors.forename: Lukas
authors.initials: L
authors.lastname: Hörtnagl
authors.affiliation: Institut für Ökologie, Universität Innsbruck, Sternwartestr. 15, 6020 Innsbruck, AUSTRIA.
authors.forename: Albin
authors.initials: A
authors.lastname: Hammerle
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck, AUSTRIA.
authors.forename: Martin
authors.initials: M
authors.lastname: Graus
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck, AUSTRIA.
authors.forename: Armin
authors.initials: A
authors.lastname: Hansel
keywords: cospectra; flux-gradient method; frequency response corrections; grassland; random uncertainty; transfer function