Stefanie Falk

Polar boundary layer bromine explosion and ozone depletion events in the chemistry–climate model EMAC v2.52: implementation and evaluation of AirSnow algorithm

Publication date Mar 28 2018 Geosci. Model Dev.

Abstract Ozone depletion events (ODE) in the polar boundary layer are observed frequently in spring. ODE serve as source of tropospheric BrO at high latitudes. A treatment of bromine release and recycling on sea ice and snow covered surfaces has been implemented in global chemistry-climate model EMAC based on scheme of Toyota et al. (2011). Many aspects of bromine enhancement and associated ODE are reproduced in both polar regions. Further bromine release mechanisms can now be tested in a global model.

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Brominated VSLS and their influence on ozone under a changing climate

Publication date Sep 25 2017 Atmospheric Chemistry and Physics

Abstract Brominated very short-lived source gases (VSLS) contribute significantly to the tropospheric and stratospheric bromine loading. We find an increase of future ocean-atmosphere flux of brominated VSLS of 8–10 % compared to present day. A decrease in the tropospheric mixing ratios of VSLS and an increase in the lower stratosphere are attributed to changes in atmospheric chemistry and transport. Bromine impact on stratospheric ozone at the end of the 21st century is reduced compared to present day.

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• Falk, Stefanie & Søvde, Ole Amund (2019). Update and evaluation of the ozone dry deposition in Oslo CTM3 v1.0. Geoscientific Model Development.  ISSN 1991-959X.  12(11), s 4705- 4728 . doi: https://doi.org/10.5194/gmd-12-4705-2019 Vis sammendrag

  High concentrations of ozone in ambient air are hazardous not only to humans but to the ecosystem in general. The impact of ozone damage on vegetation and agricultural plants in combination with advancing climate change may affect food security in the future. While the future scenarios in themselves are uncertain, there are limiting factors constraining the accuracy of surface ozone modeling also at present: the distribution and amount of ozone precursors and ozone-depleting substances, the stratosphere–troposphere exchange, as well as scavenging processes. Removal of any substance through gravitational settling or by uptake by plants and soil is referred to as dry deposition. The process of dry deposition is important for predicting surface ozone concentrations and understanding the observed amount and increase of tropospheric background ozone. The conceptual dry deposition velocities are calculated following a resistance-analogous approach, wherein aerodynamic, quasi-laminar, and canopy resistance are key components, but these are hard to measure explicitly. We present an update of the dry deposition scheme implemented in Oslo CTM3. We change from a purely empirical dry deposition parameterization to a more process-based one which takes the state of the atmosphere and vegetation into account. We examine the sensitivity of the scheme to various parameters, e.g., the stomatal conductance-based description of the canopy resistance and the choice of ozone surface resistance, and evaluate the resulting modeled ozone dry deposition with respect to observations and multi-model studies. Individual dry deposition velocities are now available for each land surface type and agree generally well with observations. We also estimate the impact on the modeled ozone concentrations at the surface. We show that the global annual total ozone dry deposition decreases with respect to the previous model version (−37 %), leading to an increase in surface ozone of more than 100 % in some regions. While high sensitivity to changes in dry deposition to vegetation is found in the tropics and the Northern Hemisphere, the largest impact on global scales is associated with the choice of prescribed ozone surface resistance over the ocean and deserts.

• Byre, Hanne Eline; Falk, Stefanie; Stordal, Frode & Berntsen, Terje Koren (2019). An Investigation of Source Regions Contributing to the Deposition of Reactive Nitrogen in Arctic and Boreal Areas. Vis sammendrag

  Long range atmospheric transport is an important source of reactive nitrogen (Nr) to Boreal and Artic ecosystems. The combined effect of climate change and deposition of reactive nitrogen which is an important nutriant for these systems, have the potential to change the carbon storage in high latitude reservoirs. Furthermore a change in vegetation, will lead to changes in the exchange of energy and humidity between the land surface and the atmosphere. We have conducted several model studies to investigate and quantify the importance and contribution of distinguished source regions to Nr deposition in polar and sub-polar regions in the northern hemisphere. Using a global chemistry transport model, we will assess the following questions: To what extent are emissions from agriculture in South-Asia affecting NOx deposition in the Arctic? What would happen if we shut down the automotive sector in Germany, do we see a reduction in the amount of NOx deposited in Norway?

• Falk, Stefanie; Stordal, Frode & Vollsnes, Ane Victoria (2019). Ozon und seine Auswirkungen auf die Vegetation in Nordskandinavien. Vis sammendrag

  Ozon ist eines der wichtigsten Spurengasen in der Atmosphäre. Während es uns in Form der Ozonschicht in der Stratosphäre vor schädlicher, kurzwelliger Strahlung schützt, zählt es in der planetaren Grenzschicht zu den überaus schädlichen Reizgasen. Eine Aufnahme einer Dosis von 50 ppm über die Dauer von 30 min gilt für den Menschen als tödlich. Pflanzen nehmen Ozon durch ihre Stoma auf, wo dieses zur Zerstörung von Zellen beiträgt, die der Photosynthese dienen, und letztlich Wachstum und Ertrag reduziert. Die empfindlichen Ökosysteme im Norden Skandinaviens erfahren bereits durch den Klimawandel einen erhöhten Stress. Sollte das Polarmeer dauerhaft eisfrei werden, so würde sich der Schiffsverkehr und damit die Menge der Ozonvorläufersubstanzen drastisch erhöhen. Insbesondere während des Polarsommers ist eine nächtliche Reparatur der entstandenen Ozonschäden gehindert. Wir präsentieren hier einen Überblick über die schädlichen Auswirkungen von Ozon auf Vegetation und erste Studien zu der Entwicklung von Ozonkonzentrationen in Nordskandinavien. Dabei greifen wir sowohl auf Langzeitmessungen als auch Modellsimulationen zurück.

• Stordal, Frode; Berntsen, Terje Koren; Büker, Patrick; Falk, Stefanie; Rydsaa, Johanne Hope; Gillies, David & Vollsnes, Ane Victoria (2018). Ozone and climate stresses on sub-ARctic tundra vegetation: Modelling of stomatal fluxes in midnight sun.
• Vollsnes, Ane Victoria; Eriksen, Aud Berglen; Büker, Patrick; Kauserud, Håvard; Falk, Stefanie & Stordal, Frode (2018). Ozone stress on sub-Arctic tundra vegetation: ozone exposure experiments with daylength manipulation..
• Vollsnes, Ane Victoria; Eriksen, Aud Berglen; Falk, Stefanie; Berntsen, Terje Koren; Kauserud, Håvard; Emberson, Lisa D. & Stordal, Frode (2018). Project The double punch: ozone and climate stresses on vegetation.
• Vollsnes, Ane Victoria; Eriksen, Aud Berglen; Falk, Stefanie; Bryn, Anders; Viken, Jeanette & Stordal, Frode (2018). Ozonforurensning. Klima, vegetasjon og matproduksjon.