Holger Bremer, M. von Koenig, A. Kleinboehl, H. Kuellmann,
K. Kuenzi, K. Bramstedt, J. P. Burrows, K.-U. Eichmann, and M. Weber
Institute of Environmental Physics, University of Bremen, Bremen, Germany
A. P. H. Goede
Space Research Organization of the Netherlands, Utrecht,
The Netherlands
Abstract
In the winter 1999/2000 the Airborne SUbmillimeter Radiometer ASUR
participated in the THESEO 2000/SOLVE project onboard the NASA
research aircraft DC-8. During three deployments in early December
1999, late January, and early March 2000 the ASUR instrument took
various measurements of ozone and key species related to
stratospheric ozone chemistry.
After the sunlight reached the vortex region in January 2000 peak
values of about 1.8 ppb ClO were measured by ASUR. There was nearly
no ozone destruction observed during the period between mid-December
1999 and late January 2000. As expected from ASUR observation of high
chlorine activation and continuously low temperatures until
mid-March, significant ozone depletion was observed between late
January and mid-March 2000. In order to determine ozone loss it is
important to separate dynamical and chemical effects. Since N2O is
a good tracer due to its chemical stability in the lower stratosphere
for determining ozone changes due to descent of air, ozone loss can
be estimated from simultaneous measurements of ozone and N2O by
ASUR. Between mid-December 1999 and mid-March 2000 a chemical ozone
loss of about 30% (eq. 1.1 ppm) in the altitude range between 19.0
and 22.2 km and of about 40% (eq. 1.15 ppm) between 16.0 and 18.1
km was observed. The airmasses subsided 2.1-3.2 km in the lower
stratosphere due to diabatic descent in the period from mid-December
1999 to mid-March 2000 as derived from ASUR N2O measurements.
Vortex-averaged ASUR measurements of ozone are systematical greater
than results from GOME (Global Ozone Monitoring Experiment) which has
a similar vertical resolution than ASUR. This, however, has little
impact on the determination of delta ozone and chemical loss
estimates.