Presentation on theme: "Dylan Jones University of Toronto"— Presentation transcript:
1 Dylan Jones University of Toronto Constraints on Free Tropospheric Ozone from the Tropospheric Emission Spectrometer (TES)Dylan Jones University of TorontoThomas Walker (University of Toronto)Mark Parrington (University of Edinburgh)Kevin Bowman, John Worden (JPL) Anne Thompson (Penn State)David Tarasick (Environment Canada) Ivanka Stajner (Noblis)Lee Murray (Harvard U.)
2 Tropospheric Emission Spectrometer (TES) Averaging kernels for retrieval at 30°N, 87°WhPahPahPa70-90 hPaOne of four instruments on the NASA Aura spacecraft (launched July 2004)Infrared Fourier transform spectrometer ( m)Nadir footprint = 8 km x 5 kmOrbit repeats every 16 days400 hPa700 hPaObjective: Assess the impact of assimilating TES data on surface ozone in GEM-MACH
3 Ozone Analysis for Aug 1-15th, 2006 Without assimilation (7 km)With TES assimilation (7 km)TES data were assimilated from 1 Jul. to 31 Aug into GEOS-Chem using a sequential Kalman filterAssimilation of TES data significantly increased ozone abundances across the extratropics
4 Ozone Analysis Over North America (at 5 km on 15 August 2006) Before assimilationAfter assimilationppb[Parrington et al., JGR, 2008]Assimilation of TES data increased O3 across North America by up to 40%Large increases in O3 in the eastern Pacific, in the vicinity of a stratospheric intrusion, and across Canada, linked to stratosphere-troposphere exchangeThe summertime O3 maximum over the southeast is more pronounced after assimilation
5 Modelled O3 Over North America along 40°N NOxO3 without TES assimO3 with TES assim[Parrington et al., JGR, 2008]The upper tropospheric ozone maximum is linked to NOx emissions from lightning, which were Tg N for North America (in August), a factor of 4 lower than recommended by Hudman et al. [JGR, 2007] based on comparisons of the model with aircraft data.
6 Comparison with IONS-06 Ozonesondes Over North America Mean (August 2006) O3 profile over North America (model sampled at the ozonesonde observation time and location)Mean ProfilesDifference relative to sondesSonde profileBefore assimAfter assim[Parrington et al., JGR, 2008]Significant improvement in fee tropospheric O3 ( hPa) after assimilation. The bias was reduced from a maximum of -35% to less than 5% (between hPa).
7 Comparison of TES analysis with assimilation of OMI and MLS GMAO OMI+MLS ozone assimilationGEOS-Chem ozone (7-8 km) for Aug. 2006Northern midlatitude in better agreement after assimilation of TES dataGEOS-Chem with TES assimilationGMAO – GEOS-Chem differencesGMAO – G-C with TESGMAO – G-C without TESOver Asia, the biased between GMAO ozone and GEOS-Chem decreased from 6.8 ppb to 1.4 ppb after TES assimilation[Worden et al., JGR, 2009]
8 Comparison of TES ozone analysis with assimilation of OMI and MLS Mean Ozone (Aug. 2006) Along 45°EGMAO OMI+MLS analysisTES assimilationWithout TES assimilationComparison of TES ozone analysis with assimilation of OMI and MLSThe O3 distribution in the TES analysis is more consistent with OMI+MLSThe Middle East ozone maximum is reduced in the TES assimilation, relative to the free running simulation[Worden et al., JGR, 2009]
9 Impact of TES Assimilation on Surface Ozone (Aug. 2006) Before assimilationAfter assimilationThe model overestimates surface ozone in the east and underestimates it in the westAssimilation increases surface O3 by as much as 9 ppb, with the largest increase in western North AmericaSurface O3 difference (assim - no assim)AQS and NAPS surface O3 dataTES-based estimates of background O3 are ppbBackground O3 at the surface before assimBackground O3 at the surface after assim[Parrington et al., GRL, 2009]
10 Evaluation with surface ozone measurements LocationMean bias before (ppb)Mean bias with TESKelowna, AB-1.814.52Bratt’s Lake, SK0.994.96Glacier NP, MT-5.610.65Pinnacles NM, CA-6.360.19Theodore Roosevelt NP, ND-8.39-4.49Table Mt., CA0.646.47Boulder, CO-3.90-0.37Dallas, TX5.148.74Egbert, ON1.634.90Narragansett, RI8.2111.26Coffeeville, MS11.7613.70Sumatra, FL16.0517.66Sites sensitive to background O3: TES assimilation reduced the biasSites sensitive to local O3 production: bias enhancedAssimilating TES data reduces the model bias in western North America at the sites most sensitive to background ozoneLarge residual bias at sites such as Egbert, Sumatra, and Table Mt. due to the coarse model resolution
11 Summary and Future Work Assimilation of TES data provides sufficient information to constrain the vertical structure of ozone in the free troposphereWe are interested in assimilating the TES data to assess their impact on the ozone simulation in GEM-MACH, with a focus on surface ozone forecasts in North America. (We will use MLS data to constrain stratospheric ozone.)Since the TES observational coverage is poor, an important issue to examine is the trade-off between vertical resolution and spatio-temporal coverage of free tropospheric ozone observationsWe are interested in comparing the impact of TES and OMI data on the surface ozone fields
12 Comparison of the new model with assimilated ozone v8 GEOS-Chem O3 Aug 2006, 5 kmO3 in v8 of GEOS-Chem with new lightning NOx source (and with biomass burning emissions based on GFED3)TES Assimilation Aug 2006, 5 kmIn the middle troposphere,relative to the TES assimilation, the mean bias between 20º-50ºN in the model decreased from about -7 ppb to 2 ppb with the new lightning NOx source
13 Chemical Data Assimilation Methodology Sequential sub-optimal Kalman filter:Observation Operator:Kalman Gain Matrix:Analysis Error Cov. Matrix:ModelGEOS-Chem model with detailed nonlinear tropospheric chemistryLinearized (LINOZ) O3 chemistry in the stratosphereModel transport driven by assimilated meteorological fields (GEOS-4) from the NASA GMAO (at a resolution of 2° x 2.5° or 4° x 5° )O3 and CO profile retrievals from TES are assimilated from 1 Jul Aug. 20066-hour analysis cycleAssumed initial forecast error of 50% for CO and O3Neglected horizontal correlations in forecast and observation error covariance matrices