Analysis of a simulation with prognostic ozone in ARPEGE-Climat Jean-François Royer, Hubert Teysseidre, Hervé Douville, Sophie Tyteca Meteo-France, CNRM, Toulouse Importance of ozone Overview the ARPEGE-Climat ozone parameterization Presentation of the forced simulation Mean seasonal cycle Interannual variability Reproduction of the ozone hole Conclusions and perspectives

Importance of ozone Absorption of UV and IR radiation Complex tropospheric and stratospheric chemistry Long term trends observed in total ozone Stratospheric ozone depletion over the South Pole (ozone hole) since the 1970s Many studies have shown evidence of the impact of anthropic perturbations on atmospheric chemistry (CFCs, NOx, CH4, CO …) Stratospheric trends due to the inverse greenhouse effect Impact of stratospheric cooling on ozone photochemistry and ozone catalytic destruction by chlorine compounds WMO/UNEP Scientific Assessment of Ozone Depletion (1998, 2002)

Purpose of the presentation To document the capacity the ARPEGE-Climat GCM, that includes a ozone as a prognostic variable with a simple parameterization of its photochemistry, to reproduce the main characteristics of ozone distribution To evaluate its capacity at simulating its observed long term evolution in response to SST, greenhouse gas forcing, and changing composition of the atmosphere To identify the impact and signature of anthropic perturbations on the evolution of the ozone layer

Description of the simulations ARPEGE-Climat version 3 Dynamics and resolution: Semi-lagrangian version with ozone transport T63 linear grid (128x64 points) 45 levels in the vertical Physical parameterizations State-of-the-art GCM physics (convective and large-scale precipitation, interactive clouds, turbulence, land surface processes ISBA) ECMWF (Fouquart, Morcrette) radiation scheme (every 3 hours) with major greenhouse gases (CO2, CH4, N20, O3, CFC-11 and CFC-12) Sulfate Aerosols: direct and indirect effects (Boucher and Lohman parameterization implemented by Hu RM et al 2002) prognostic computation of ozone concentration

The forced simulation Aerosols concentrations (J Penner) The sea surface temperatures (SSTs) are specified according to the observed monthly means (Reynolds analyses) over the period Ozone transport and simplified photochemistry Derived from the 2D zonal model MOBIDIC –(MOdel of BI-DImensional Chemistry) 50 year simulation starting in 1950 Observed GHGs: CO2 CH4 N2O CFC11 CFC12+(others)

Climate statistics MOBIDICStratosphericchemistry Observed SSTs (monthly-mean) Sea-ice ISBA Land surface CO2 CH4 N2O CFCs Zonal Averages (10 years) ARPEGE-Climat AGCM Cl Zonal-mean coefficients for O 3 parameterization Aerosols

The 2D photochemical model MOBIDIC [Cariolle, CNRM, 1984 ; Teyssèdre, UPS, 1994] 2 dimensions (latitude, pressure) thermodynamical forcings from ARPEGE-Climat (T, v *, w *, K yy, K yz, K zz ) stratospheric chemistry : 56 species, 175 reactions studies of atmospheric impact (supersonic aircraft) for ozone linear parametrisation : chemical equilibrium => (P-L) ; r O 3 ; T ;  +/- 10% perturbation => new equilibrium :  (P-L) /  r O 3 ;  (P-L) /  T ;  (P-L) /  

linearised ozone chemistry [Cariolle and Déqué, JGR, 1986]  r O 3 /  t = (P-L) + (r O 3 - r O 3 )  (P-L) /  r O 3 + (T – T)  (P-L) /  T + (  –  )  (P-L) /   - K het (Cl y (year) ) 2 r O 3 from 3D GCMfrom 2D photochemical model ( , p) (P-L) : ozone production-loss termr O 3 : ozone mixing ratio T : temperature  : ozone column above gridpoint K het : heterogeneous chemistryCl y (year) : total chlorine for given year

(P-L)

r O 3  (P-L) /  r O 3

T  (P-L) /  T

  (P-L) /  

K het (T  195 K under sunlight conditions)

Validation of the results Comparison of the climate of the 60s and 90s Maps of the differences between 20-year mean simulated distributions for two different periods – – Total ozone column (DU= Dobson Units ~ mm O3 at STP) Ozone concentration (volume mixing ratio in ppmv) Validation of the ozone distribution –Comparison with UGAMP 5-year ozone climatology Monthly, 2.5° x 2.5°, 47 levels (Li and Shine, 1995) Available at BADC

Ozone column (DU) UGAMPARPEGE-Climat Septembre March

ARPEGE-ClimatMarch Difference from mean: colour scale 20-year mean : isolines

Ozone over NH

ARPEGE-Climat Difference from mean: colour scale 20-year mean : isolines September

SP September

Seasonal evolution of the O3 column (DU) UGAMPARPEGE-Climat

Ozone Difference from mean: colour scale 20-year mean : isolines

Vertical distribution of O3 concentration (ppmv) UGAMPARPEGE-Climat Annual mean

Seasonal evolution at 10 hPa

hPa surface ozone Ozone columntemperature Montly anomalies with respect to global average

Monthly anomaly with respect to average for ozone column (DU) over South Pole (80-90°S)

Conclusions The ozone transport and simple parameterization of its sources and sinks is able to reproduce the geographical and seasonal distribution patterns of total ozone column The vertical distribution of ozone in the stratosphere is simulated realistically In response to the increase of CFCs the model simulates a reduction of ozone in the upper stratosphere due to its increased destruction by released chlorine This leads to a cooling in the upper stratosphere due to the reduction of UV absorption However due to the tropospheric response the total ozone column increases slightly, which is not in agreement with observations

Conclusions (2) The heterogeneous chemistry parameterization is able to reproduce the destruction of ozone by PSCs in the South Polar vortex at the begining of Austral spring Though the structure of the simulated ozone hole is realistic its intensity is too weak Need to revise and adjust the destruction coefficient for heterogeneous chemistry to improve the efficiency of the parameterization in future C20C simulations