 |
| Titel |
Increase of total stratospheric NO2 in the tropics after 2001 |
| VerfasserIn |
M. Pastel, F. Goutail, J. P. Pommereau, A. Pazmino, G. Held |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027904
|
|
|
|
|
|
| Zusammenfassung |
| The tropical region is the main entry point of tropospheric chemical species lifted
by convection and transported into the stratosphere across the tropopause. It is
therefore the most sensitive region to dynamical and chemical changes. Long series of
NO2 columns have become available in the tropics from two SAOZ uv-visible
spectrometer stations, in Bauru (Brazil, 22Ë S, 49Ë W) since 1995 and in Reunion
Island (21Ë S, 55Ë E) in the Indian Ocean since 1993 with which the evolution of
the total NO2 has been investigated. Most significant modulation at both stations
is the seasonal cycle but of larger amplitude ~3.2*1015mol./cm2 in Bauru than
~2.4*1015mol./cm2 in Reunion because of the contribution tropospheric lightning and
biomass burning NOx in continental Brazil, absent over the oceanic Reunion station. As
shown by a multi-linear regression analysis, most important geophysical parameters
controlling the interannual variability are the Quasi-Biennial Oscillation (QBO) of
respectively -30% in Bauru and 20% in Reunion, followed by the El Niño-Southern
Oscillation (ENSO) of 17% and 11 % and the 11 year solar flux cycle of 11% at both
stations. After removing the signal from all statistically significant proxies, the
long-term evolution shows a total NO2increase by about ~0.2*10e15 mol./cm2
after 2001 at both stations, exceeding by far the trend expected from the known
N2O concentration increase of 2.5%/decade. The event is confirmed by the GOME
- SCIAMACHY NO2 total column series, but ignored by the SLIMCAT model
forced by ECMWF analyses. The partial NO2 column between 19-50 km derived
HALOE and SAGE II above the stations confirms the increase of NO2 after 2001 and
shows that it has occurred in the lower stratosphere. The coincidence of the NO2
enhancement with the drop of water vapour (~0.2 ppmv) reported by HALOE in the
lower stratosphere and the cooling of ~1K the tropopause, attributed by Randel
at al., (2006) to a reinforcement of the Brewer-Dobson circulation, suggests an
increase of the NOx concentration after 2001 following that of its N2O source, either
because of a faster B-D circulation or a more intense convective vertical transport. |
|
|
|
|
|
|