Numerical Investigation of Tropospheric Halogen Release and Ozone Depletion in the Polar Spring

• Main Author: Cao, Le
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2014
• Subjects: Antarc*; Antarctic; Arctic; Sea ice
• Online Access: https://archiv.ub.uni-heidelberg.de/volltextserver/16801/; https://archiv.ub.uni-heidelberg.de/volltextserver/16801/1/DISST1.pdf; https://doi.org/10.11588/heidok.00016801; https://nbn-resolving.org/urn:nbn:de:bsz:16-heidok-168011

Ozone is one of the most important natural atmospheric constituents in both the stratosphere and the troposphere of the earth. Compared with the ozone in the stratosphere, which is mainly formed via the natural photolytic decomposition of oxygen molecules, the ozone in the troposphere originates from reactions involving volatile organic compounds (VOC) and nitrogen oxides (NOx). The near-surface mixing ratio of ozone varies with the regions. In pristine regions, such as the Arctic and the Antarctic, the natural mixing ratios of ozone in the troposphere range from 30 to 40 nmol/mol on average. About thirty years ago, a rapid destruction of the tropospheric ozone on a time scale of hours to days was observed in polar regions during spring time. Meanwhile, a negative correlation between halogen (e.g. Br and Cl) concentrations and ozone mixing ratios was found, which reveals the involvement of halogen species in the ozone depletion process. It has been presumed that halogen species participate in a variety of chemical reaction cycles, leading to ozone depletion. Moreover, the oxidation of inert halogen ions from aerosol particles, fresh sea ice or snow packs can also speed up the depletion of ozone in the troposphere by releasing Br2 and BrCl from the surfaces of these substrates. The tropospheric ozone depletion event has broad impacts on the atmospheric chemistry of the polar regions, such as changing the lifetimes of the hydrocarbons and the formation of the aerosol particles. Therefore, in this study, the modeling of tropospheric ozone depletion in polar spring is addressed. The first step is to identify an appropriate chemical reaction mechanism for capturing the temporal evolution of the chemical mixing ratios. Thus, a box model study is conducted, in which the transport of the air is not included and only chemical reactions are considered. Three chemical reaction schemes are investigated in the box model study: a bromine-only reaction scheme, which then is subsequently extended to include nitrogen and ...