 |
| Titel |
High temporal resolution Br2, BrCl and BrO observations in coastal Antarctica |
| VerfasserIn |
Z. Buys, N. Brough, L. G. Huey, D. J. Tanner, R. Glasow, A. E. Jones |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 3 ; Nr. 13, no. 3 (2013-02-01), S.1329-1343 |
| Datensatznummer |
250017632
|
| Publikation (Nr.) |
 copernicus.org/acp-13-1329-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| There are few observations of speciated inorganic bromine in polar regions
against which to test current theory. Here we report the first high temporal
resolution measurements of Br2, BrCl and BrO in coastal Antarctica,
made at Halley during spring 2007 using a Chemical Ionisation Mass
Spectrometer (CIMS). We find indications for an artefact in daytime BrCl
measurements arising from conversion of HOBr, similar to that already
identified for observations of Br2 made using a similar CIMS method.
Using the MISTRA model, we estimate that the artefact represents a
conversion of HOBr to Br2 of the order of several tens of percent,
while that for HOBr to BrCl is less but non-negligible. If the artefact is
indeed due to HOBr conversion, then nighttime observations were unaffected.
It also appears that all daytime BrO observations were artefact-free. Mixing
ratios of BrO, Br2 and BrCl ranged from instrumental detection limits
to 13 pptv (daytime), 45 pptv (nighttime), and 6 pptv (nighttime),
respectively. We see considerable variability in the Br2 and BrCl
observations over the measurement period which is strongly linked to the
prevailing meteorology, and thus air mass origin. Higher mixing ratios of
these species were generally observed when air had passed over the sea-ice
zone prior to arrival at Halley, than from over the continent. Variation in
the diurnal structure of BrO is linked to previous model work where
differences in the photolysis spectra of Br2 and O3 is suggested
to lead to a BrO maximum at sunrise and sunset, rather than a noon-time
maxima. This suite of Antarctic data provides the first analogue to similar
measurements made in the Arctic, and of note is that our maximum measured
BrCl (nighttime) is less than half of the maximum measured during a similar
period (spring-time) in the Arctic (also nighttime). This difference in
maximum measured BrCl may also be the cause of a difference in the
Br2 : BrCl ratio between the Arctic and Antarctic. An unusual event of
trans-continental air mass transport appears to have been responsible for
severe surface ozone depletion observed at Halley over a 2-day period. The
halogen source region appears to be the Bellingshausen Sea, to the west of
the Antarctic Peninsula, with the air mass having spent 3 1/2 days
in complete darkness crossing the continent prior to arrival at Halley. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|