Publication Date:
2020-10-16
Description:
The sources and sinks of stratospheric reactive nitrogen (NOy) in the Antarctic are
known only qualitatively, because of the very few measurements of NOy available in this
region. As a result, the effects of stratospheric NOy short- and long-term changes on the
stratospheric concentration of ozone, water vapor, and other climate-forcing agents are
still uncertain. To better understand the annual cycle of polar stratospheric NOy, we
estimate its concentration in the Antarctic stratosphere during part of 1993 and throughout
1995. These estimates are obtained at seven potential temperature levels, extending from
18 to 30 km of altitude, and are associated with ground-based measurements of another
tracer, N2O, in order to produce NOy-N2O correlation curves that can provide insights
on nitrogen sources and sinks. To estimate NOy mixing ratios, we use ground-based and
satellite measurements of major NOy constituents, connected by using air parcel trajectories
and supplemented by model calculations of minor contributing species for which no
suitable measurements exist. All the available NOy-N2O correlation points are averaged
over three representative seasonal time periods in 1993 and six periods in 1995. Results
show very similar correlation curves during the late summer and the fall of 1995, and again
during the early spring 1993 compared with the early and late winter of 1995, although
there are large seasonal changes due to transport and to condensation of NOy onto polar
stratospheric clouds. We calculate a loss from the latter process of N = (6.3 ± 2.6) 107 kg of stratospheric nitrogen in the southern polar vortex during 1995.We also compare
our correlation curves with those obtained in the Antarctic stratosphere during the
Atmospheric Trace Molecule Spectroscopy mission ATMOS/ATLAS-3 in November
1994, finding important similarities but also critical differences that suggest that extravortex
air is generally not an adequate representation of prewinter inner vortex
conditions. Calculations of NOy winter removal in the Antarctic stratosphere which have
used extra-vortex measurements as a surrogate for prewinter conditions may thus have
underestimated true NOy removal. Our prewinter NOy estimates in the vortex core
match values obtained by atmospheric models that incorporate upper atmospheric
sources of NOy, supporting the belief that such sources have a significant effect on polar
stratospheric NOy.
Description:
Published
Description:
4428
Description:
5A. Ricerche polari e paleoclima
Description:
JCR Journal
Keywords:
polar NOy
;
NOy-N2O correlations
;
denitrification
;
01.01. Atmosphere
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
