Subsidence, Mixing and Denitrification of Arctic Polar Vortex Air Measured During POLARIS
Abstract. A new technique is presented to determine the degree of denitrification that occured during the 1996/97 Arctic winter, based on balloon and aircraft borne measurements of NO,, N2O and CH4. The NO, / N20 relation can undergo significant change due to isentropic mixing of subsided vortex air...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.582.3268 http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/16853/1/99-0261.pdf |
| Summary: | Abstract. A new technique is presented to determine the degree of denitrification that occured during the 1996/97 Arctic winter, based on balloon and aircraft borne measurements of NO,, N2O and CH4. The NO, / N20 relation can undergo significant change due to isentropic mixing of subsided vortex air masses with extra-vortex air due to the high non-linearity of the relation. In this study high-altitude balloon measurements are used to define the properties of air masses that later descend in the polar vortex to altitudes sampled by the ER-2 aircraft (i.e. 20km) and mix isentropically with mid-latitude air. Observed correlations of CH4 and N20 obtained are used to quantify the degree of subsidence and mixing for individual air masses. Based on these results the expected mixing ratio of NO, resulting from subsidence and mixing, defined here as NO,**, is calculated and compared with the measured mixing ratio of NO,. NO, and NO,** agree well during most parts of the flights. A slight deficit of NO, vs. NO,* * is found only for a limited region during the ER-2 flight on April 26,1997. This deficit is interpreted as indication for weak denitrification (-2-3 ppbv) in that air mass. The small degree of denitrification is con-sistent with the temperature history of the sampled air, which hardly encountered temperatures below the frostpoint during the Arctic winter 1996/97. Much larger degrees of denitrification would have been inferred if mixing effects had been ignored, which is the traditional approach to diagnose denitrification. Our analysis demonstrates the importance of using other correla-tions of conserved species to be able to accurately interpret changes in the NO, / N2O relation with respect to denitrification. |
|---|