 |
| Titel |
On the emissions and transport of bromoform: sensitivity to model resolution and emission location |
| VerfasserIn |
M. R. Russo, M. J. Ashfold, N. R. P. Harris, J. A. Pyle |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 24 ; Nr. 15, no. 24 (2015-12-21), S.14031-14040 |
| Datensatznummer |
250120237
|
| Publikation (Nr.) |
 copernicus.org/acp-15-14031-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Bromoform (CHBr3) is a short-lived species with an important but poorly
quantified ocean source. It can be transported to the Tropical Tropopause
Layer (TTL), in part by rapid, deep convective lifting, from where it can
influence the global stratospheric ozone budget. In a modelling study, we
investigate the importance of the regional distribution of the emissions and
of model resolution for the transport of bromoform to the TTL. We use two
idealized CHBr3 emission fields (one coastal, one uniformly distributed
across the oceans) implemented in high- and coarse-resolution (HR and CR)
versions of the same global model and focus on February as the period of
peak convection in the West Pacific. Using outgoing long-wave radiation and
precipitation as metrics, the HR version of the model is found to represent
convection better. In the more realistic HR model version, the coastal
emission scenario leads to 15–20 % more CHBr3 in the global TTL, and
up to three times more CHBr3 in the TTL over the Maritime Continent,
than when uniform emissions of the same tropical magnitude are employed.
Using the uniform emission scenario in both model versions, the distribution
of CHBr3 at 15.7 km (approximately the level of zero net radiative
heating) is qualitatively consistent with the differing geographic
distributions of convection. However, averaged over the whole tropics, the
amount of CHBr3 in the TTL in the two model versions is similar. Using
the coastal scenario, in which emissions are particularly high in the
Maritime Continent because of its long coastlines, the mixing ratio of
CHBr3 in the TTL is enhanced over the Maritime Continent in both model
versions. The enhancement is larger, and the peak in CHBr3 mixing ratio
occurs at a higher altitude, in the HR model version. Our regional-scale
results indicate that using aircraft measurements and coarse global models
to infer CHBr3 emissions will be very difficult, particularly if (as is
possible) emissions are distributed heterogeneously and in regions of strong
convective activity. In contrast, the global-scale agreement between our CR
and HR calculations suggests model resolution is less vital for studies
focused on the transport of bromine into the global stratosphere. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|