larger chemical ozone loss in 2004/2005 arctic winter/spring

Larger Chemical Ozone Loss in 2004/2005 Arctic Winter/Spring

Wuhu Feng and Martyn ChipperfieldSchool of Earth and Environment, University of Leeds

Acknowledgments

R. Salawitch, P. von der Gathen, H. Kuhlman et al

• Temperatures• Modelled fields of ClOx, NOy, H2O etc.• Modelled O3 loss• Comparison with previous years• Comparison with ASUR data

Temperatures 04/05 v 99/00

Minimum Temperature – Cold winters since 95/96

SLIMCAT/TOMCAT 3D CTM• Off-line 3D chemical transport model

• Extends to surface using hybrid - levels (SLIMCAT version).

• Horizontal winds and temperatures from ECMWF analyses.

• Vertical motion from diagnosed heating rates.

• Chemistry: ‘Full’ stratospheric chemistry scheme (41 species, 160 reactions) with heterogeneous chemistry on liquid/solid aerosols/PSCs and an equilibrium (NAT rock) denitrification scheme.

• Near real time run: 2.8o x 2.8o x 24 levels (0-60 km)

• Web page with results:

http://www.env.leeds.ac.uk/slimcat

What has changed in model to improve polar O3?

A lot! Key points for polar O3 are probably:

• Updated kinetics (JPL 2002) + faster JCl2O2 (Burkholder et al extended to 450 nm).

• NAT-based denitrification scheme.• Minimum aerosol (H2SO4) loading.

• Better vertical transport (more Cly in lower stratosphere) and no lower boundary near tropopause.

• ECMWF analyses (ERA40 + operational).

• Source gas scenarios: + 100pptv short-lived organic Cl, + shift in long-lived organic loading to shorter lived species.

SLIMCAT 3D CTM – Arctic winters since 1994/95

SLIMCAT 3D CTM – Modelled dehydration

O3 at Ny Alesund

SLIMCAT ClOx and NOy at Ny Alesund

SLIMCAT v ASUR Data

31/1/2005 5/2/2005

HCl HCl

ClO

N2O

ClO

N2O

Recent results (3/3/2000)

Conclusions

• (Updated) SLIMCAT model does a good job in simulation of polar ozone + related species for 2004/05 Arctic winter.

• ‘Largest modelled Arctic ozone loss so far’ for this time of year.

• Strongest modelled chlorine activation and much more descent than previous years

• Model captures the dehydration as measured on January 26 at (~67N, 27E)