SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Intercomparison of SCIAMACHY NOIntercomparison of SCIAMACHY NO22, ,

the Chimthe Chimèère air-quality model and re air-quality model and surface observationssurface observations

Nadège Blond,LISA, Paris, France

Henk Eskes, Folkert Boersma, Ronald van der AKNMI, Netherlands

Michel van Roozendael, Isabelle De SmedtBIRA-IASB, Belgium

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Slant column retrieval approach (BIRA-IASB)

DOAS slant column:• "raw" L1, v 4.02 L1, v 5.01 L1• Non-linear least-squares inversion (Marquardt-Levenberg) • Wavelength window 426.3 - 451.3 • NO2 243K (Bogumil), O3 (Bogumil), O2-O2, H2O• 2nd order polynomial• Undersampling cross section• Ring (Vountas)• Offset correction based on measurement over Indian Ocean

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Combined retrieval - modelling - assimilation approach to SCIA NO2

Careful treatment needed for:• Clouds• Surface albedo• Profile shape• Aerosol

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Slant to vertical column retrieval approach (KNMI)

Air-mass factor calculation:• Temperature correction (NO2 cross section)• TM3 / TM4 (tropospheric) CTM • Assimilation of slant columns -> stratospheric "background"• Fresco cloud fraction and cloud top pressure• TOMS / GOME combined albedo map (Herman, Koelemeijer)• DAK RTM height-dependent AMF lookup table• Tropospheric AMF based on TM profile shape, clouds

Product:• Detailed error estimates• Averaging kernels

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Validation results (ACVE-2), stratosphereJ. C. Lambert

NO2 products:• SCIA processor• IUP• SAO• BIRA-IASB• Heidelberg

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Combined retrieval - modelling - assimilation approach

to GOME NO2

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Chimère model

Developed in FranceR. Vautard, H. Schmidt, L. Menut, M. Beekman, N. Blond, ... )Operational air-quality forecasts: http://www.prevair.org/

Model ingredients:• MELCHIOR chemistry (82 species, 333 reactions) • EMEP emissions• ECMWF meteorological analyses• 15 vertical layers, surface - 200 hPa• Boundary conditions from MOZART monthly-mean climatology

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Emissions

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Intercomparisons Chimère, SCIA and surface observations

Motivation:• Lack of profile observations of NO2 for validation purposes: use model as intermediate for indirect validation study

Approach:• Space-time collocation of Chimère fields to individual SCIA pixels• Application of averaging kernels: Simulated SCIA-equiv column = kernel vector • model NO2 profile• One year of SCIA data, 2003; Cloud free (cloud radiance < 50%)

Advantages:• Compare model-SCIA under exactly same conditions (e.g. cloud free)• Comparison independent of profile shape assumptions in the retrieval

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Chimère and surface observations (RIVM, NL)

- surface observation

- Chimère

Netherlands:(rural stations)Bias 0.1 ppbRMS 7.2 ppbCorrel. 0.66

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

SCIAMACHY vs. Chimère: yearly mean

Yearly-mean bias = 0.2 1015 molec cm-2, RMS 2.9, correl.coeff. 0.73Cloud-free pixels

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

SCIAMACHY vs. Chimère: 27 Feb 2004

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

SCIAMACHY vs. Chimère: 28 Mar 2004

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

SCIAMACHY vs. Chimère: 16 April 2004

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

SCIAMACHY vs. Chimère: 16 Sep 2004

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Synergy: Surface - Chimère - SCIAMACHY

SCIAMACHY Validation Workshop Bremen, 6-8 Dec 2004

Conclusions NO2 comparisons

SCIAMACHY - Chimère - surface • Yearly mean: - very small bias SCIA - Chimère and Chimère - surface - Correlation coefficients 0.7 typically• SCIA and Chimère resolution comparable• Extended NO2 plumes compare well• Details show differences: - Seasonality (winter Chimère higher) - Individual days - Distribution - Amount of detail