Title: 3D CTM Study of Polar and Mid-Latitude Ozone Depletion and Climate Change
13D CTM Study of Polar and Mid-Latitude Ozone
Depletion and Climate Change
Wuhu Feng and Martyn Chipperfield School of Earth
and Environment,University of Leeds, U.K.
- Updated 3D CTM SLIMCAT (Recent improvements to
the model) - Polar Ozone Loss (2004/05 Arctic winter compared
with previous winters) - Mid-Latitudes Ozone change (Sensitivity
Experiments of BrO Chemistry) - Conclusions
Acknowledgments Supported by NERC and SCOUT-O3
projects
2SLIMCAT/TOMCAT 3D CTM
- Off-line chemical transport model Chipperfield,
JGR, 1999 - Extends to surface using hybrid ?-? levels
(SLIMCAT version). Variable horizontal/vertical
resolution. - Horizontal winds and temperatures from analyses
(e.g. UKMO, ECMWF (ERA-40 or operational)). - Vertical motion from diagnosed heating rates or
divergence. - Tropospheric physics convection, PBL mixing etc.
- Chemistry Full stratospheric chemistry scheme
(41 species, 160 reactions) with heterogeneous
chemistry on liquid/solid aerosols/PSCs and an
equilibrium denitrification scheme. - NAT-based denitrification scheme included.
- http//www.env.leeds.ac.
uk/slimcat
3Updated 3D CTM Arctic Ozone loss versus VPSC
New T42 run
Obs
New T15 run
Old T15 run
Chipperfield et al.(GRL, 2005)
- Linear relationship between ozone loss and PSC
volume - First successful CTM simulation of seasonal O3
column loss - and reproduces the past climate sensitivity of
Arctic ozone depletion on T.
4Record-Observed Arctic Ozone Loss in 04/05 Winter
Quirin Schiermeier (Nature,2005)
The Largest Arctic ozone losses observed in
2004/2005
5Cold Meteorological Conditions in 2004/2005
Arctic Winter
PSC Area
Minimum Temperature
- Large Area of PSC formation as result of very
low temperatures.
6Unusual polar vortex in 2004/2005 Arctic winter
Comparison of SLIMCAT runs for past 11 years
(ECMWF analyses)
493K
456K
- Largest Polar Vortex since late January in
2004/2005 Arctic winter.
7Large PSC Occurrence in 2004/2005 Arctic Winter
456K
493K
- Largest NAT PSC area from late January in 2004/5
- Largest Ice PSC area since late January in
2004/2005 Arctic winter.
8Comparison with O3 sonde data
10
Pressure
100
Ny-Alesund 79oN 12oE
- Model gives a good simulation of O3, except
overestimates the observations 300-100 hPa. - Large O3 depletion between 400-650K with the
largest ozone loss 450K.
1000
O3 (mPa)
700
Theta
550
500
450
400
350
300
O3 loss
O3 (vmr)
9Comparison with O3 sonde data
Passive O3
Chemical loss
- SLIMCAT reproduces the increase in December
ozone and also reproduces the large decline of
ozone mixing ratio from January to the mid-March.
10O3 Loss at 456K
Partial Column O3 Loss
Near-record large O3 loss in 2004/2005
Fast deactivation in March than 99/00
11CTM BrO problem
(Salawitch et al., GRL, 2005)
- Stratospheric bromine supplied by decomposition
of VSL (very short lived) - organics not considered in most global models
as well as tropospheric BrO - (Salawitch et al., GRL, 2005)
12BrO Experiment
- Multi-annual T15 run from 01/01/1977
- Forced by ECMWF analyses (ERA40Operational)
- Exp336 Basic SLIMCAT run with new Bry
- EXP337as EXP336 but with fixed halogen
- EXP338as EXP336 but without the extra bromine
species (about 6 pptv less Bry)
13Long-term Column Ozone Comparison (1978-2004)
- Model captures the observed year-to-year
variability - Low Tropical column O3, and too large O3 in the
mid and higher latitude
14Anomaly Mid-lat column ozone comparison
35N-60N
60S-35S
Fixed Halogen
Fixed Halogen
Basic Run
Basic Run
- Model reproduce the observed decrease of
mid-latitude column ozone, but large discrepancy
occurred in 1988 and 1993. - Large effect of BrO chemistry in the mid-latitude
ozone change
15Conclusions
- Updated New SLIMCAT CTM now gives a good
simulation of seasonal O3 column loss - Near-record Arctic ozone loss in 2004/2005 due
to much more chlorine activation occurring on the
largest surface areas of polar stratospheric
clouds (PSCs) inside the polar vortex at very low
temperatures, - However, less chlorine activation on PSCs in
March 2005 than 2000 slowed down further chemical
ozone loss in the late spring. - Stratospheric bromine supplied by decomposition
of VSL has been added in SLIMCAT and has
important effect on mid-latitude ozone trends.