As ozone precursors, nitrogen
oxides (NOx) which refer to nitric oxide (NO) and nitrogen dioxide
(NO2) play an essential role in tropospheric photochemistry. The catalytic
formation of tropospheric ozone (O3) is highly dependent on the
levels of NOx. Moreover, the long-range transport of reactive nitrogen
species from anthropogenic and wildfire emissions can affect tropospheric
composition and the O3 budget in remote regions, such as the Arctic.
GEOSummit Station, Greenland is located in the
remote Arctic at an elevation of 3200 m.a.s.l and thus allows for sampling in
the free troposphere away from local emissions, making it an ideal location for
measuring long-range transported emissions from North America and Europe.
Measurements of mixing ratios of NOx at the site by our group from June
2008 to June 2010 revealed a strong seasonal cycle. During late winter/early
spring there is an increase in NOx mixing ratios due to long-range
transport of pollution northwards. In summer the mixing ratios of NOx
decrease due to changing transport pathways and reach a minimum in early
winter. We are expanding on these earlier measurements by performing long-term
and high-frequency measurements of NO and NO2 from summer 2012 to
2016 at GEOSummit Station. The instrument is custom built for measurements of
NOx in remote regions with a precision better than 4 pptv and 6 pptv
(2-σ) for NO and NO2 respectively. Moreover, it can acquire NOx
mixing ratios every 6 minutes, which is very important for measuring
variability on a short time scale.
The new long-term dataset will contribute to a
better assessment of the NOx budget in the Arctic and improve our
understanding on the impact of long-range transported emissions on O3
levels within the region. The data will also contribute to the Arctic Observing Network (AON) and be made available for researchers to better understand Arctic
atmospheric chemistry, and to evaluate global chemical transport model simulations
for future climate predictions.
Note: Abstract for 2012 AGU fall meeting
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