Chemical regimes over Europe – long term , seasonal and day to day

variability

Matthias Beekmann

LISA University Paris 7 and 12, CNRS

Créteil, France

Thanks to Robert Vautard for discussions and MM5 data

Definitions

VOC sensitive regime:

• VOC emission reductions more favorable for ozone reduction

• Near intense anthropogenic emission sources

• Low VOC / NOx emission ratio

• Weak actinic flux

• Radical chain terminationNO2 + OH -> ….RCOO2 + NO2 -> …. RO2 + NO -> ….

NOx sensitive regime :

• NOx emission reductions more favorable for ozone reduction

• Rurales areas

• High VOC / NOx emission ratio

• Strong actinic flux

• Radical chain terminationHO2 + HO2 -> ….RO2 + HO2 -> ….

INTRODUCTION Environmental conditions

Chemical cycles

PLAN

Many older studies, but no comprehensive work addressing: • Differences in chemical regimes with respect to target

• Interannual, seasonal variability

• Day to day variability, which forcings ?

• Long term variability (decades)

• Dependency to model configuration

Developed by: IPSL, LISA /CNRS, INERIS [http://euler.lmd.polytechnique.fr/chimere]

Model domain : 10°W-23°E, 35°-58°N

Horizontal resolution : 0.5° x 0.5°

Vertical resolution: 8 layers in hybrid pressure coordinates

Pk=akptop + bkpsurf; ptop=500 mbar

Chemical mechanism: reduced MELCHIOR ( 44 species, 120 reactions)

here use of gas phase only

Meteorology: MM5 driven by NCEP Reanalysis or Forecast

Emissions: EMEP NOx,VOC, CO, SO2, 10 SNAP sectors; res. 50x50 km

Biogenic emissions of isoprene, pinene and NO

Boundary conditions: LMD-Z/INCA , MOZART , GOCART (PM)

CHIMERE CHEMISTRY-TRANSPORT MODEL

ResultsReference simulation

• Daily O3 maximum

• Surface = 0 – 50 m

• Average over • May – August• 2001

2002 2003

Results (2)Emission scenarii

Chemical Regime = NOx -30 % minus

VOC -30% emission scenario

Chemical Regime Emissions

Industrial NOx emissions 1010 mol. cm-2 s-1

=> Strong dependence of chem. regime on emission strength, modulated by meteorology

• Daily O3 max. => basic pollution indicator

• Daily OX max.OX = O3 + NO2

=> normalises out O3 titration by NO

• AOT60

hours max [O3 – 60 ppb, 0] => climatological health index

• AOT90

hours max [O3 – 90 ppb, 0]=> pollution peak indicator

• SUMO 35 days max [daily max O3

8h – 35 ppb, 0] => climatological health index

Chemical regimes for different targets

Chemical regimes for different targets

maximum daily OX concentration May – August 2001- 2003 average

Chemical regimes for different targets

SUMO35 May – August 2001 – 2003 integration/ average

Chemical regimes for different targets

AOT60 May – August 2001 – 2003 integration/ average

Chemical regimes for different targets

AOT90 May – August 2001 – 2003 integration/ average

Chemical regimes for different targetsConclusions

General structure keeps unchanged irrespective of target :

• NW EU VOC sensitive

• SE EU NOx sensitive• • North Italy NOx sensitive with exceptions

• Shipping track VOC sensitive

Are these model results robust ?

• Model has been evaluated with ozone measurements over Western Europe=> Small bias, RMSE ~ 20% , R ~ 80% over WE

• But no garantee, that sensitivity of PO3 to EVOC and ENOx is correct

• Ideal solution: Monte Carlo simulations => give global uncertainty

• Here sensitivity tests

* EVOC + 40 %

* other chemical mecanism: extended Melchior (~80 compounds, 320 reactions) instead of reduced one (40 compounds, ~120 reactions, operator approach)

* look at model layer 2 (50 – 200 m) instead of layer 1 (0-50m) => regions with complex vertical structure

Robustness test O3max

Many structures absent

Robustness test AOT90

Interannual variability O3max

Seasonal variability O3max

The heatwave caseAugust 2003

O3max AOT90

O3max and AOT90 : NOx sensitive regime more extended

Day to day variability of chemical regimesO3max

• Integration over the strongly VOC sensitive region in NW – Europe

• From May to August 2001

Day to day variability of chemical regimesO3max

Chemical regime is always VOC sensitive over North-Western Europe

No dependency on ozone levels

How can day to day variability be explained ?

Day to day variability of chemical regimesO3max

Dependence on emission accumulation (NOy)

Dependence on classical chemical regime tracersO3 / NOz ratio

O3 / NOz ratio

Chemical regime for 1980 – 2020 emissions

• Is the chemical regime expected to change for future emission scenarii ?

• Did it change in the past ?

=> Use EMEP 1980 , 1990, 2010 and 2020 expert emissions in addition to 2002 one’s

=> No change in boundary conditions , trends not clear

Chemical regime for 1980 – 2020 emissionsO3max

1980 1990

2010 2020

Chemical regime for 1980 – 2020 emissionsAOT90

Year

1980

Year 2020

Conclusions • Chemical regime is (in CHIMERE European CTM)

VOC sensitive over North Western Europe, NOx sensitive over Mediterranean region and Eastern Europe

• This is robust with respect to :* target

* model uncertainty* interannual, seasonal, day to day variability

• Northern Italy : NOx sensitive, with exceptions (Milan area, …. exceptions not so robust)

• Shipping emissions : VOC sensitive, but complex vertical structure

• 1980 to 2020 emission changes drive system to more NOx sensitive in NW EU, in North Italy