Seasonality of reactive nitrogen oxides (NO_y) at Neumayer Station, Antarctica

Abstract

NO, NOy (total reactive nitrogen oxides), gaseous HNO3, and particulate nitrate (p‐NO3−) were measured at Neumayer Station from February 1999 to January 2000. In addition, during February 1999, the NOy component species peroxyacetyl nitrate (PAN) and methyl, ethyl, i‐propyl, and n‐propyl nitrates were determined. We found a mean NOy mixing ratio of 46 ± 29 pptv, with significantly higher values between February and end of May (58 ± 35 pptv). Between February and November, the (HNO3 + p‐NO3−)/NOy ratio was extremely low (around 0.22) and in contrast to NOy the seasonality of p‐NO3− and HNO3 showed a distinct maximum in November and December, leading to a (HNO3 + p‐NO3−)/NOy ratio of 0.66. Trajectory analyses and radioisotope measurements (7Be, 10Be, 210Pb, and 222Rn) indicated that the upper troposphere or stratosphere was the main source region of the observed NOy with a negligible contribution of ground‐level sources at northward continents. Frequent maxima of NOy mixing ratios up to 100 pptv are generally associated with air mass transport from the free troposphere of continental Antarctica, while air masses with the lowest NOy mixing ratios were typically advected from the marine boundary layer.

The impact of the chemical production of methyl nitrate from the NO + CH<sub>3</sub>O<sub>2</sub> reaction on the global distributions of alkyl nitrates, nitrogen oxides and tropospheric ozone: a global modelling study

“…In the study of Neu et al (2008) mixing ratios of between 35-40 ppt of CH 3 ONO 2 occurred in the LT for latitudes below 60 • S as a result of prescribing emissions in the SH, which are too high when compared to these measurements (see Tables 1a and b), similar to HIGHBR. Furthermore, the observed variability in CH 3 ONO 2 at Neumayer did not show any correlation with the origin of air masses; this provides further evidence of the importance of some type of local source term such as a chemical production term investigated here (Weller et al, 2002).…”

“…Measurements on the Antarctic around 70-75 • S have revealed surprisingly high resident mixing ratios of between 2-14 ppt CH 3 ONO 2 , indicating a possible link to NO x emissions from snow (e.g. Weller et al, 2002;Wang et al, 2007). Compared to other alkyl nitrates, CH 3 ONO 2 is the most abundant at these southerly latitudes (Jones et al, 2011).…”

“…For these comparisons, three-hourly model output is averaged into daily means in order to partially account for the impact of any diurnal cycle on resident mixing ratios due to photolytic destruction. The measurement data derived at these sites have been published in Roberts et al (1998), Walagu et al (1992), Weller et al (2002) and Jones et al (2011), respectively, although time-resolved measurements are not provided for Chebogue Point and therefore are not shown. The comparison clearly shows that HIGHBR results in an excess of CH 3 ONO 2 , with mixing ratios approximately an order of magnitude too high for the NH sites shown and a factor of two too high for Antarctica.…”

“…It is located on an ice shelf ∼ 10 km away from the northeastern Weddell Sea, and is considered to be representative of a location with pristine air transported either over the snow pack on Antarctica or from over the surrounding ocean and sea ice. Here we use the measurement values published by Weller et al (2002), who analysed air from flasks by gas chromatography to determine mixing ratios of alkyl nitrates.…”

Characterising terrestrial influences on Antarctic air masses using Radon-222 measurements at King George Island

“…Weller et al, 2002;Maenhaut et al, 1979). Briefly exploring these two possibilities, if seasonality in the continental signature reaching the troposphere (assuming a seasonally constant radon source function) was the sole factor, less than half (∼ 45 %) as much boundary layer air would need to be lofted/convected to the troposphere in winter than in summer.…”