henk eskes, no2 workshop knmi, 10 sep 2007 a combined retrieval, modelling and assimilation approach...
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Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
A combined retrieval, modelling and assimilation approach to estimate tropospheric NO2 from OMI measurements
Ruud Dirksen, Folkert Boersma1, Henk Eskes, Ronald van der A, Pepijn Veefkind, Pieternel Levelt,Ellen Brinksma, Eric Bucsela2, Ed Celarier2, Jim Gleason2
KNMI, the Netherlands1 Harvard, USA2 NASA, USA
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Eleven years of NO2 data
GOME, 1996 - 2003SCIAMACHY, 2003 - presentKNMI - IASB retrieval
OMI, 2004 - presentKNMI - NASA retrieval
Images and detailed data products, including averaging kernels and error estimates,available on the TEMIS and PROMOTE web siteswww.temis.nlwww.gse-promote.org
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
OMI instrument overview
• Nadir viewing imaging spectrometer• Wide swath (2600km) & high spatial resolution
(13x24/48 km2) => Daily global coverage• 2D-CCD detectors: instantaneous recording of FOV and
spectrum• Spectral range 270-500nm (0.4 – 0.6nm resolution)• Data products:
O3 column & profile, NO2, aerosols, clouds, SO2, BrO, OClO, HCHO
• EOS-AURA platform, launched 15 July 2004• Sun-synchronous orbit, equator overpass time 13:40
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
There are two OMI products: 1. Operational product (NASA-KNMI)
2. Near-real time product (KNMI-NASA)
• To provide users with near-real time air pollution monitoring environmental agencies, air quality forecasters EU GEMS project:
- NRT comparison OMI with regional AQ models over Europe
• To generate a long-term consistent dataset fromGOME, SCIAMACHY, OMI, GOME-2
Near real time OMI data publicly available since October 2006 via www.temis.nlBoersma et al. Atmos.Chem.Phys. 7, 2103, 2007
OMI near-real time product: Purpose
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
NO2 retrieval developed at KNMI
Combinedretrieval-modelling-assimilation-approach
Boersma et al. JGR, D04311, 2004
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
NO2 retrieval: error contributions
Typical 30-50% error for individual pixelsBoersma et al. JGR 2004
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Ingredient 1: Daily chemical forecast with OMI NO2 assimilation
Large uncertainty on slant columns with estimated high tropospheric column
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Ingredient 2: Near-real time OMI tropospheric NO2 retrieval
NASA/KNMI DOAS algorithm
Processing time < 2 mins
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Reprocessing status
L1b reprocessing of entire mission completed L2 reprocessing will commence within a few weeks DOMINO reprocessing follows immediately after
completion of L2 reprocessing (~2 months)
Changes No de-striping (optional - after the retrieval) HDF-EOS5 output format to be consistent with other OMI
products
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Reprocessing changes
Better handling of flagging in L2 algorithm (filtering of e.g. saturated pixels) less spurious pixels
Annual mean solar irradiance spectrum => reduction of stripes, improved S/N
Better dark current correction => reduction of stripes. Stripe at least factor 3 smaller
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Reprocessing changes
v3 (2007 reprocessing)v2
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Reprocessing changes
v3 with stripe filteringv3 (2007 reprocessing)
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
GOME NO2 intercomparison
IPCC contextVan Noije et al., ACP 2006
NO2 products:• Univ. Bremen (A. Richter)• Harvard, Dalhousie (R. Martin)• IASB / KNMI
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
GOME NO2 intercomparison
IUP Bremen Dalhousie KNMI/BIRA
Ns425 – 455 nm 425-450 nm 426.3 – 451.3 nm
Ns,stRef. sector scaled to SLIMCAT strat.
Ref. Sector Data-assimilation in TM4
Cloud fraction (albedo)
FRESCO 0.2 cloud fraction; only cloud selection, no further correction
GOMECAT (Kuruso) FRESCO (0.8)
Cloud pressure Not used GOMECAT FRESCO
Albedo GOME (Koelemeijer) GOME(Koelemeijer) TOMS/GOME (1x1)
Profile shape MOZART-2 run for 1997, monthly averages on 2.8 x 2.8 °
GEOS-CHEM TM4 (3x2)
Temperature correction
No ? Yes, ECMWF T-profiles
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Validation with surface measurements
Schaub et al., ACP 6, 2006
Cloud free
Cloudy
Daniel Schaub, EMPA
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
SCIAMACHY vs. Chimère: yearly mean 2003
Blond et al., JGR 112, 2007
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
KNMI OMI near-real time NO2, 13-16 Oct 2005
SundaySaturday
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Chimere model @ OMI overpass time, 13-16 Oct 2005
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Tropospheric NO2 by OMI, May 2006
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Recent results: Greek forest fires August 2007
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
MediterraneanApr 2006 May 2006
Sep 2006 Oct 2006
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
OMI - SCIAMACHY, May & July 2006
Differences due to diurnal variation in emission
Boersma et al. submitted to JGR
Boersma et al., submitted to JGR
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Dandelions, OMI L2 and OMI NRT
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Dandelions, OMI L2 and OMI NRT
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
GOME / SCIA / OMI experience• retrieval improvements should focus on cloud/aerosol
treatment, surface albedo, stratospheric background, profile shape
• Comparison algorithms: KNMI-NASA-IUP-BIRA-Dal-UHei
2007 reprocessing major improvement
SCIA + OMI : morning vs afternoon
Comparison with regional-scale models to exploit resolution
Future: Use of NRT-OMI (GOME-2) for air-quality applications
ConclusionsConclusions
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
1. Find window with smallest variation in initial columns
2. Compute mean column vs. across track viewing angle
3. FFT analysis to smooth
Stripe correction
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
SCIAMACHY - OMI, October 2004
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
SCIAMACHY, October 2004
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
OMI, October 2004
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
SCIAMACHY - OMI, October 2004
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Trend over China
GOME, 1997 SCIA, 2004
R.J. van der A et al., JGR 111, 2006
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Van der A et al., 2006
Trend in NO2 column over China
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Van der A et al., 2006
Trend NO2 concentration worldwide
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Seasonal dependence, GOME en SCIAMACHY
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Seasonal dependence, TM4 model
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
Source attribution
Henk Eskes, NO2 workshop KNMI, 10 Sep 2007
OMI - SCIAMACHY, average
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