caa a22 4500 528787519 20190509063409.0 cr unu---uuuuu 180924s2014 xx s 000 0 eng 10.3929/ethz-b-000100279 doi 10.5194/bg-11-2429-2014 doi (ETHRESEARCH)oai:www.research-collection.ethz.ch:20.500.11850/100279 Gap-filling strategies for annual VOC flux data sets [Elektronische Daten] [Ines Bamberger, Lukas; id_orcid 0000-0002-5569-0761 Hörtnagl, Mario Walser, Armin Hansel, Georg Wohlfahrt] Open access ethresearch Up to now the limited knowledge about the exchange of volatile organic compounds (VOCs) between the biosphere and the atmosphere is one of the factors which hinders more accurate climate predictions. Complete long-term flux data sets of several VOCs to quantify the annual exchange and validate recent VOC models are basically not available. In combination with long-term VOC flux measurements the application of gap-filling routines is inevitable in order to replace missing data and make an important step towards a better understanding of the VOC ecosystem-atmosphere exchange on longer timescales. We performed VOC flux measurements above a mountain meadow in Austria during two complete growing seasons (from snowmelt in spring to snow reestablishment in late autumn) and used this data set to test the performance of four different gap-filling routines, mean diurnal variation (MDV), mean gliding window (MGW), look-up tables (LUT) and linear interpolation (LIP), in terms of their ability to replace missing flux data in order to obtain reliable VOC sums. According to our findings the MDV routine was outstanding with regard to the minimization of the gap-filling error for both years and all quantified VOCs. The other gap-filling routines, which performed gap-filling on 24 h average values, introduced considerably larger uncertainties. The error which was introduced by the application of the different filling routines increased linearly with the number of data gaps. Although average VOC fluxes measured during the winter period (complete snow coverage) were close to zero, these were highly variable and the filling of the winter period resulted in considerably higher uncertainties compared to the application of gap-filling during the measurement period. The annual patterns of the overall cumulative fluxes for the quantified VOCs showed a completely different behaviour in 2009, which was an exceptional year due to the occurrence of a severe hailstorm, compared to 2011. Methanol was the compound which, at 381.5 mg C m−2 and 449.9 mg C m−2, contributed most to the cumulative VOC carbon emissions in 2009 and 2011, respectively. In contrast to methanol emissions, however, considerable amounts of monoterpenes (−327.3 mg C m−2) were deposited onto the mountain meadow during 2009 caused by a hailstorm. Other quantified VOCs had considerably lower influences on the annual patterns. Creative Commons Attribution 3.0 Unported http://creativecommons.org/licenses/by/3.0 ethresearch Bamberger Ines joint author Hörtnagl Lukas; id_orcid 0000-0002-5569-0761 joint author Walser Mario joint author Hansel Armin joint author Wohlfahrt Georg joint author Biogeosciences Göttingen : Copernicus 11 (8), pp. 2429-2442 http://hdl.handle.net/20.500.11850/100279 text/html WWW-Backlink auf das Repository (Open access) 1 Journal Article ethresearch ETHRESEARCH 856 40 http://hdl.handle.net/20.500.11850/100279 text/html WWW-Backlink auf das Repository (Open access) ETHRESEARCH 700 1- Bamberger Ines joint author ETHRESEARCH 700 1- Hörtnagl Lukas; id_orcid 0000-0002-5569-0761 joint author ETHRESEARCH 700 1- Walser Mario joint author ETHRESEARCH 700 1- Hansel Armin joint author ETHRESEARCH 700 1- Wohlfahrt Georg joint author ETHRESEARCH 773 0- Biogeosciences Göttingen : Copernicus 11 (8), pp. 2429-2442 SWISSBIB 528787519 BK010053 XK010053 XK010000 ETHRESEARCH ETHRESEARCH ETHRESEARCH Journal Article Open access