| 1. |
- Aemisegger, F., et al.
(författare)
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Deuterium excess as a proxy for continental moisture recycling and plant transpiration
- 2014
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 14:8, s. 4029-4054
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Tidskriftsartikel (refereegranskat)abstract
- Studying the evaporation process and its link to the atmospheric circulation is central for a better understanding of the feedbacks between the surface water components and the atmosphere. In this study, we use 5 months of deuterium excess (d) measurements at the hourly to daily timescale from a cavity ring-down laser spectrometer to characterise the evaporation source of low-level continental water vapour at the long-term hydrometeorological monitoring site Rietholzbach in northeastern Switzerland. To reconstruct the phase change history of the air masses in which we measure the d signature and to diagnose its area of surface evaporation we apply a Lagrangian moisture source diagnostic. With the help of a correlation analysis we investigate the strength of the relation between d measurements and the moisture source conditions. Temporal episodes with a duration of a few days of strong anticorrelation between d and relative humidity as well as temperature are identified. The role of plant transpiration, the large-scale advection of remotely evaporated moisture, the local boundary layer dynamics at the measurement site and recent precipitation at the site of evaporation are discussed as reasons for the existence of these modes of strong anticorrelation between d and moisture source conditions. We show that the importance of continental moisture recycling and the contribution of plant transpiration to the continental evaporation flux may be deduced from the d-relative humidity relation at the seasonal timescale as well as for individual events. The methodology and uncertainties associated with these estimates of the transpiration fraction of evapotranspiration are presented and the proposed novel framework is applied to individual events from our data set. Over the whole analysis period (August to December 2011) a transpiration fraction of the evapotranspiration flux over the continental part of the moisture source region of 62 % is found albeit with a large event-to-event variability (0 % to 89 %) for continental Europe. During days of strong local moisture recycling a higher overall transpiration fraction of 76 % (varying between 65 % and 86 %) is found. These estimates are affected by uncertainties in the assumptions involved in our method as well as by parameter uncertainties. An average uncertainty of 11 % results from the strong dependency of the transpiration estimates on the choice of the non-equilibrium fractionation factor. Other uncertainty sources like the influence of boundary layer dynamics are probably large but more difficult to quantify. Nevertheless, such Lagrangian estimates of the transpiration part of continental evaporation could potentially be useful for the verification of model estimates of this important land-atmosphere coupling parameter.
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| 2. |
- Scholder-Aemisegger, Franziska, et al.
(författare)
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Isotope meteorology of cold front passages: A case study combining observations and modeling
- 2015
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Ingår i: Geophysical Research Letters. - 1944-8007. ; 42:13, s. 5652-5660
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the role of below-cloud evaporation and evapotranspiration for the short-term variability of stable isotopes in near-surface water vapor and precipitation associated with central European cold fronts. To this end, a combination of observations with high temporal resolution and numerical sensitivity experiments with the isotope-enabled regional weather prediction model COSMOiso is used. The representation of the interaction between rain droplets and ambient vapor below the cloud is fundamental for adequately simulating precipitation isotopes ((p)) and total rainfall amount. Neglecting these effects leads to depletion biases of 20-40 in delta H-2(p) and 5-10% in delta O-18(p) and to an increase of 74% in rainfall amount. Isotope fractionation during soil evaporation is of primary importance for correctly simulating the variability of continental low-level vapor delta H-2(v) and delta O-18(v) and particularly of the secondary isotope parameter deuterium excess (d(v)).
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| 5. |
- Søgaard Jørgensen, Peter, et al.
(författare)
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Antibiotic and pesticide susceptibility and the Anthropocene operating space
- 2018
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Ingår i: Nature Sustainability. - : Springer Science and Business Media LLC. - 2398-9629. ; 1:11, s. 632-641
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Forskningsöversikt (refereegranskat)abstract
- Rising levels of antimicrobial and pesticide resistance increasingly undermine human health and systems for biomass production, and emphasize the sustainability challenge of preserving organisms susceptible to these biocides. In this Review, we introduce key concepts and examine dynamics of biocide susceptibility that must be governed to address this challenge. We focus on the impact of biocides on the capacity of susceptible organisms to prevent spread of resistance, and we then review how biocide use affects a broader suite of ecosystem services. Finally, we introduce and assess the state of what we term the Anthropocene operating space of biocide susceptibility, a framework for assessing the potential of antibiotic and pesticide resistance to undermine key functions of human society. Based on current trends in antibiotic, insecticide and herbicide resistance, we conclude that the states of all six assessed variables are beyond safe zones, with three variables surpassed regionally or globally.
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