Evaluation of model simulations with satellite observed NO2 columns and

surface observations&

Some new results from OMI

N. Blond, LISA/KNMI

P. van Velthoven, H. Eskes, F. Boersma, R. van der A, P. Levelt, KNMI

M. van Roozendael, I. De Smedt, BIRA-IASB

EUMETNET-EEA, Copenhagen, 7-8 April 2005

Combining retrieval, modelling and assimilation to obtain NO2 tropospheric columns from SCIAMACHY/GOME

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

(TM)

Validation of (stratospheric) NO2 columns with ground-based observations

Good agreement in remote areasDeviations in industrialised (as expected)

Combined retrieval - modelling - assimilation approach

to GOME NO2

30 x 60 km2

Chimère model

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

Emissions (EMEP)

Motivation• Lack of NO2 profile observations for validating SCIAMACHY. Intermediate step: compare to a model Approach• Space-time co-location of Chimère output with individual

“cloud-free” SCIA pixels• Use averaging kernels from SCIAMACHY: Modelled column = SCIAMACHY kernel vector • model profile• 1 year of SCIAMACHY data - 2003Advantages• Comparison model-SCIAMACHY under exactly same conditions• Comparison independent of profile shape assumptions in retrieval

Motivation for comparison of Chimere with both ground-based and satellite obs

Comparison of Chimère to surface observations

Netherlands rural stations:Bias 0.1 ppb, RMS 7.2 ppb, Correlation 0.66

-- surface obs-- Chimère

SCIAMACHY vs. Chimère: yearly mean

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

SCIAMACHY vs. Chimère: 27 Feb 2004

SCIAMACHY vs. Chimère: 28 Mar 2004

Conclusions of evaluationSCIAMACHY-Chimère- surface obs

• Yearly mean: - very small bias SCIAMACHY - Chimère and Chimère - surface - Correlation coefficients ~0.7

• NO2 plumes similar

• Differences in details: - Seasonality (Chimère higher in winter) - Individual days - Detailed distribution

Planned KNMI web service:Surface - Chimère - satellite

New results from the Ozone Monitoring Instrument (OMI)

OMIOMI

MLSMLS

HIRDLSHIRDLS

TESTES

Launched: 15 July 2004 on EOS-AURA

OMI results: NO2

Courtesy: Pepijn Veefkind

13 x 24 km2 with daily global coverage

cloudcloud

OMI results: SO2 (Carn et al.)

Galeras and Tungurahuavolcanoes

La OroyaCu-smelter

Ilo Cu-smelter

Jan 2005G&T: 5300 td-1

Or: 500 td-1

Ilo: 1250 td-1

OMI results: formaldehyde

Internet addresses

Satellite productswww.gse-promote.orgwww.temis.nl

OMIwww.knmi.nl/omi eos-aura.gsfc.nasa.gov

Spare slides

NO2 column retrieval approach

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

Output• Detailed error estimates• Averaging kernels

SCIAMACHY vs. Chimère: 16 April 2004

SCIAMACHY vs. Chimère: 16 Sept 2004

Satellite instruments providing NO2 columns

GOME (April 1995, ERS-2, 40 x 320 km2) SCIAMACHY (February 2002, ENVISAT, 30 x 60 km2) OMI & TES (15 July 2004, EOS-AURA, 13 x 24 km2)

OMI measurement principle

13 km

(2 sec flight))2600 km

12 km/24 km (binned & co-added)

flight direction» 7 km/sec

viewing angle± 57 deg

2-dimensional CCD

wavelength ~ 780 pixels

swath~ 580 pixels

OMI properties UV and VIS backscatter spectrophotometer (270 - 500 nm)

Wide swath (2600 km) telescope yields daily global maps

Resolution of 13 x 24 km2 is best ever for air quality applications

Products: Ozone: total and tropospheric columns, profiles NO2 columns HCHO columns SO2 columns & Clouds (coverage, top pressure), Aerosols,

BrO, OClO, Surface UV Irradiance