Arctic Bromine Chemistry
: The link to ozone depletion events; implemented into the Danish Eulerian Hemisphere Model

Student thesis: Master's Thesis


Ozone depletion events (ODEs), are longer or shorter periods with ozone mixing ratios below 20 ppb. ODEs are observed in the Arctic spring at several measuring sites. Research indicates that the ODEs are closely linked to Bromine Explosion Events (BEEs), also observed in the Arctic spring. The BEEs are anti-correlated with ODEs and hence a possibly responsible for ODEs. The full mechanism be-hind ODEs is not known. The occurrence of ODEs show a strong coexistence with Atmospheric Mercury Depletion Events AMDEs, indicating that the same atmosphere chemistry is responsible for both depletion events.Model studies have shown that the implementation of bromine chemistry linked to ozone chemistry, reduces the average mixing ratio of ozone in the Arctic. This is believed to be the first step towards future model simulation of both ODEs and AMDEs.The Danish Eulerian Hemisphere Model (DEHM) is a Fortran based3D chemical transport model, primarily used for assessment of air pollution transport.The work performed here has mainly been focussed towards the implementation of a full bromine chemistry scheme into DEHM, based on a model study by Yang et al. (2005). The presumption has been that implementation of a bromine chemistry scheme, would improve the capability of modeling/predicting the tropospheric ozone mixing ratios in the Arctic.In addition to the bromine scheme, the parametrization of production of aerosols was improved and heterogeneous chemistry on snow and cloud particles was also implemented. Furthermore a novel sea ice parametrization was investigated for the purpose of improving the release of bromine species to the Arctic. The Norwegian Arctic measuring station Zeppelin, has been of particular interest for model validation of time-series.A small improvement in the model performance of DEHM for ozone mixing ratios was observed with the expansion of the chemistry in DEHM. The future step will be to implement a chemistry scheme linking the bromine and the mercury scheme to each other, hopefully improving the simulation of mercury depositions in the Arctic.The main programming language used is Fortran77, smaller part of the code work is performed in MatLab. Graphs and plots are produced with Uniras, NCL graphics and MATLAB
Date of Award13 Apr 2013
Original languageEnglish
SupervisorJesper Heile Christensen (Supervisor), Ole John Nielsen (Supervisor) & Anne Lærke Sørensen (Supervisor)


  • Ozone depletion events
  • Atmospheric chemistry
  • numerical modeling
  • Danish Eulerian Hemiphere Model
  • DEHM
  • Troposphere chemistry

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