Modelling wintertime atmospheric chemistry from aircraft campaigns over the Western Atlantic Ocean

Atmospheric chemical transformations, which play a large role in controlling the formation of pollutants and climate forcers, have strong seasonal dependencies. In the warmer and more photochemically active summer months, strong oxidant formation leads to the rapid production of multiple secondary pollutants such as ozone and organic aerosol. In winter, primary pollutants react far more slowly and consequently spread over wider geographic areas downwind of sources.
The large majority of ambient measurements in polluted regions in the past years have focused on understanding emissions, transformation and transport under warm summertime conditions. However, the differences in chemistry and meteorology between summer and winter are significant and can cause important variations in the formation of pollutants, emissions patterns, and secondary aerosol formation, including their geographic distributions and export to remote regions.
In order to investigate these issues, NOAA (National Oceanic and Atmospheric Administration), NCAR (National Center for Atmospheric Research) and University of Washington (Seattle) conducted a field campaign in February-March 2015 using the NSF/NCAR C130 research aircraft, which flew several flights over the Northeastern United States and into the Western Atlantic Ocean.

Figure 1: The NSF/NCAR C130 research aircraft and particle composition data from the WINTER 2015 campaign (Guo et al., J. Geophys. Res., 2016).
This project aims to analyse the data from the WINTER 2015 campaign using highly detailed chemistry and transport modelling, focusing in particular on the chemical processes involving halogens, nitrogen oxides and ozone. The objective is to interpret the observations and understand the differences between winter and summer and the implications for the formation of pollutants in urban-influenced atmospheres.