Modeling reactive atmospheric chemistry in the Arctic region

Shaddy AHMED

Most models used to predict Arctic scale or global ozone, largely ignore or include simplified descriptions of halogen chemistry. example, the current distributed version of the regional Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem, https://ruc.noaa.gov/wrf/wrf-chem/) does not include a description of halogen chemistry. WRF-Chem is frequently used to study Arctic atmospheric chemistry (e.g. Thomas et al., 2013 ; Thomas et al., 2017 ; Marelle et al., 2017). Inaccurate predictions of boundary layer ozone severely limits our ability to predict Arctic atmospheric chemistry. In addition, we currently do not know how atmospheric chemistry is influenced by the chemical recycling on ice and snow surfaces, which are rapidly changing in a warming Arctic.

This PhD will focus on 1D and 3D regional modeling of halogen chemistry in the arctic, with a focus on improving predictions of boundary layer ozone. This will include identifying the most likely initiating steps for halogen activation, improving the description of heterogeneous halogen recycling in models, and quantifying impacts using well defined model case studies. Work aims to answer the following science questions :
– What are the emissions source regions that contribute to halogen activation and result in ozone depletion events ?
– What combinations of bromine and chlorine emissions/recycling on surfaces (sea-ice, snow, aerosols) and atmospheric dynamics result in sustained bromine activation events and ozone depletion ?
– What combination of emissions/surface recycling of halogens is needed in a 3D regional model to capture the nature of bromine activation events and their impacts on ozone in the Arctic ?

Supervisors : J. THOMAS (CHIANTI) and A. DOMMERGUE (CHIANTI)