Chemistry and Transport in the Lower Stratosphere

1
Chemistry and Transport in the Lower
Stratosphere Wuhu Feng1, Martyn Chipperfield1,
Howard Roscoe2 1. Institute for Atmospheric
Science, School of the Environment, University of
Leeds, U.K 2. British Antarctic Survey, Madingley
Road, Cambridge, U.K. fengwh_at_env.leeds.ac.uk
2. SLIMCAT 3D CTM 3D off-line chemical
transport model. ?-? vertical coordinate.
Detailed stratospheric chemical scheme. Model
simulation from 1989, then seasonal runs for the
selected winter spring. (resolution 2.8o x 2.8o x
24 levels )
1. Introduction Chemical transport models (CTMs)
are powerful tools to study the processes
controlling the observed polar ozone depletion in
the lower stratosphere (LS). Here we show how the
SLIMCAT 3D CTM has been improved and now produces
good simulations both in the Antarctic and Arctic
regions for recent years. Some sensitivity
experiments (i.e. initialization, model
horizontal resolution, chemical processes and
radiation scheme) are also shown to investigate
their effect on the calculation of chemistry and
transport in the LS in the Arctic polar
winter/spring.
3. Antarctic Ozone Loss
4 Arctic Ozone Loss
Fig. 1. Daily minimum TOMS total O3 between 50oS
and 90oS compared with SLIMCAT output from May 2
to Nov. 30.
Fig. 2. Comparison of O3 sonde data at 450K at
Neumayer (71oS, 352oE) for 2000 and 2002 with
SLIMCAT.
Fig. 7. Comparison of O3 sonde observations (
marks) at Ny-Alesund (79oN,12oE) with SLIMCAT for
selected Arctic winters 1999/2000 (left),
2002/03 (middle) and 2003/04 (right). Also shown
are some sensitivity tests.
Fig. 4. Diagnosed chemical O3 loss rate
(ppbv/day) due to two main catalytic cycles
ClOClO (left) and ClOBrO (right)
Fig. 3. Variation of Cly species averaged
southward of 60oS at 450K for 2000 and 2002.
Fig. 9. Comparison of MKIV data with SLIMCAT runs
with/without heterogeneous reaction.
Fig. 8. Comparison between aircraft data (ER-2
and M55 flights) and SLIMCAT.
Fig. 5. Evolution of the log-normalised
equivalent length (EL) as a function of
equivalent latitude on 450K.
Fig. 6. Log-normalised EL mapped onto 380 K and
521 for Sep. 26 in 2000 and 2002.
Fig 11. Polar ClOx and HCl at 493K for recent
10 Arctic winters
Fig 10. Minimum T northward of 50oN at 456K and
575K
Fig. 12. Polar O3 loss (65o-90oN) for 10 years.

• SLIMCAT successfully reproduces the evolution
  of observed O3 both in the Antarctic and Arctic
  Recent improvements to boundary conditions, model
  resolution, chemical and radiation processes in
  the model lead to better tracer transport and
  polar ozone loss
• Two separated, strong mixing regions are
  consistent with split O3 hole in SH in 2002. Less
  late chlorine activation and strong descent in
  this winter.
• Very early chlorine activation occurred in
  2002/03 Arctic winter.

Acknowledgements. Emily Schuckbrugh for
equivalent length code Gert König-Langlo and P.
von der Gathen for O3 sonde data B. Sen, G.
Toon, J. F. Blavier for MKIV data C.R. Webster,
C.M. Volk, A. Ulanovsky, F. Ravegnani, J. Host,
E.C. Richard for ER2 and M55 aircraft data NASA
for TOMS data and BADC for ECMWF analyses. This
work was supported by U.K. NERC, EU TOPOZ III and
QUILT projects.
References Feng W, et al, JAS, (in press) Feng
W, et al, ACP, (submitted).