 |
| Titel |
Eight Years of Stratospheric BrO and NO2 Profiles from SCIAMACHY Compared to ECHAM5/MESSy2 Atmospheric Chemistry (EMAC) Simulations |
| VerfasserIn |
Steffen Dörner, Sven Kühl, Janis Pukite, Patrick Jöckel, Marcel Dorf, Thomas Wagner |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052395
|
|
|
|
|
|
| Zusammenfassung |
| Since 2002 the Scanning Imaging Absorption Spectrometer for Atmospheric Chromatography
(SCIAMACHY) on the Environmental Satellite (ENVISAT) measures solar radiation
that is transmitted, backscattered and reflected from the atmosphere. From these
measurements stratospheric profiles of various trace gases can be retrieved. In this study,
the data set of the MPI Chemistry Mainz for vertical profiles of NO2, BrO and
OClO is compared to the ECHAM5/MESSy2 atmospheric chemistry (EMAC)
simulations for the lower to middle stratosphere (15 km to 35 km). This comparison
is performed systematically on the global scale for the years between 2002 and
2009.
In order to collocate both data sets in time and space, the EMAC results have been
sampled on-line (i.e., during the model run-time) along all possible orbits of the satellite
measurements. Therefore, error sources like differences caused by the influence of the diurnal
cycle are minimised. For the comparison we follow two different approaches: First, vertical
profiles of NO2 and BrO are averaged temporally and zonally to focus on the general global
distribution. Second, the global distribution patterns in five-day averaged maps are compared
for individual altitudes. While the first approach allows to quantify the systematic
differences, the zonally and vertically resolved comparison reveals the impact of
stratospheric transport processes on a smaller time scale by emphasising the longitudinal
variation.
For both comparisons a generally good agreement is found for absolute values and
distribution patterns. Differences within 20 % for NO2 with systematically larger number
densities for the EMAC simulations and 30 % for BrO with generally larger number densities
for the satellite measurements are found. NO2 and BrO for the polar regions and NO2
for the tropics show larger deviations of up to 40 %. Considering the longitudinal
variation, also different shapes of the distributions are revealed for certain regions and
seasons.
While some of these differences may be explained by simplifications performed in the
retrieval, the simulation of the stratospheric meteorology appears to be another reason for
deviations. To investigate this point in more detail, stratospheric temperatures and potential
vorticity from the EMAC simulations are compared to operational analyses data
provided by the ECMWF. In general, a good agreement of both quantities is found.
This is partially due to the weak nudging of the EMAC simulations towards the
ECMWF analyses in the troposphere. However, large differences may develop for the
polar vortex region especially during warm polar winter seasons in the northern
hemisphere.
With our quantitative comparison of all three data sets problems in both SCIAMACHY
measurements and EMAC simulations could be identified using also the information from
balloon borne measurements. On the one hand the comparisons indicate an underestimation
of NO2 for tropics and a general overestimation of BrO by the satellite measurements. On the
other hand possible problems with the simulation of the polar vortex meteorology and an
overestimation of NO2 number densities for the high latitudes by EMAC may be concluded. |
|
|
|
|
|
|