Tuesday, August 7, 2012

Long-term and High-frequency Measurements of Nitrogen Oxides at GEOSummit Station, Greenland

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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