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Constraints on Free Tropospheric Ozone from the Tropospheric Emission Spectrometer (TES) Dylan Jones University of Toronto Thomas Walker (University of.

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Presentation on theme: "Constraints on Free Tropospheric Ozone from the Tropospheric Emission Spectrometer (TES) Dylan Jones University of Toronto Thomas Walker (University of."— Presentation transcript:

1 Constraints on Free Tropospheric Ozone from the Tropospheric Emission Spectrometer (TES) Dylan Jones University of Toronto Thomas 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 One of four instruments on the NASA Aura spacecraft (launched July 2004) Infrared Fourier transform spectrometer (  m) Nadir footprint = 8 km x 5 km Orbit repeats every 16 days Tropospheric Emission Spectrometer (TES) 700 hPa 400 hPa hPa Objective: Assess the impact of assimilating TES data on surface ozone in GEM-MACH hPa hPa hPa Averaging kernels for retrieval at 30°N, 87°W

3 Ozone Analysis for Aug 1-15th, 2006 TES data were assimilated from 1 Jul. to 31 Aug into GEOS-Chem using a sequential Kalman filter Assimilation of TES data significantly increased ozone abundances across the extratropics Without assimilation (7 km) With TES assimilation (7 km)

4 Ozone Analysis Over North America (at 5 km on 15 August 2006) ppb Before assimilation After assimilation Assimilation of TES data increased O 3 across North America by up to 40% Large increases in O 3 in the eastern Pacific, in the vicinity of a stratospheric intrusion, and across Canada, linked to stratosphere-troposphere exchange The summertime O 3 maximum over the southeast is more pronounced after assimilation [Parrington et al., JGR, 2008]

5 Modelled O 3 Over North America along 40°N NOx O 3 without TES assim O 3 with TES assim 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. [Parrington et al., JGR, 2008]

6 Comparison with IONS-06 Ozonesondes Over North America Significant improvement in fee tropospheric O 3 ( hPa) after assimilation. The bias was reduced from a maximum of -35% to less than 5% (between hPa). Sonde profile Before assim After assim Mean (August 2006) O 3 profile over North America (model sampled at the ozonesonde observation time and location) Mean ProfilesDifference relative to sondes [Parrington et al., JGR, 2008]

7 Comparison of TES analysis with assimilation of OMI and MLS Northern midlatitude in better agreement after assimilation of TES data GMAO OMI+MLS ozone assimilation GEOS-Chem with TES assimilation GMAO – GEOS-Chem differences GEOS-Chem ozone (7-8 km) for Aug Over 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] GMAO – G-C with TES GMAO – G-C without TES

8 Comparison of TES ozone analysis with assimilation of OMI and MLS GMAO OMI+MLS analysis TES assimilation Without TES assimilation Mean Ozone (Aug. 2006) Along 45°E [Worden et al., JGR, 2009] The O 3 distribution in the TES analysis is more consistent with OMI+MLS The Middle East ozone maximum is reduced in the TES assimilation, relative to the free running simulation

9 Impact of TES Assimilation on Surface Ozone (Aug. 2006) The model overestimates surface ozone in the east and underestimates it in the west Assimilation increases surface O 3 by as much as 9 ppb, with the largest increase in western North America [Parrington et al., GRL, 2009] TES-based estimates of background O 3 are ppb Before assimilationAfter assimilation Surface O3 difference (assim - no assim) AQS and NAPS surface O3 data Background O3 at the surface after assimBackground O3 at the surface before assim

10 LocationMean bias before (ppb) Mean bias with TES Kelowna, AB Bratt’s Lake, SK Glacier NP, MT Pinnacles NM, CA Theodore Roosevelt NP, ND Table Mt., CA Boulder, CO Dallas, TX Egbert, ON Narragansett, RI Coffeeville, MS Sumatra, FL Evaluation with surface ozone measurements Assimilating TES data reduces the model bias in western North America at the sites most sensitive to background ozone Large residual bias at sites such as Egbert, Sumatra, and Table Mt. due to the coarse model resolution Sites sensitive to background O 3 : TES assimilation reduced the bias Sites sensitive to local O 3 production: bias enhanced

11 Summary and Future Work Assimilation of TES data provides sufficient information to constrain the vertical structure of ozone in the free troposphere We 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 observations o We are interested in comparing the impact of TES and OMI data on the surface ozone fields

12 TES Assimilation Aug 2006, 5 km Comparison of the new model with assimilated ozone v8 GEOS-Chem O 3 Aug 2006, 5 km In 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 O 3 in v8 of GEOS-Chem with new lightning NOx source (and with biomass burning emissions based on GFED3)

13 Chemical Data Assimilation Methodology Sequential sub-optimal Kalman filter: Model Kalman Gain Matrix: Analysis Error Cov. Matrix: GEOS-Chem model with detailed nonlinear tropospheric chemistry Linearized (LINOZ) O 3 chemistry in the stratosphere Model transport driven by assimilated meteorological fields (GEOS-4) from the NASA GMAO (at a resolution of 2° x 2.5° or 4° x 5° ) O 3 and CO profile retrievals from TES are assimilated from 1 Jul Aug hour analysis cycle Assumed initial forecast error of 50% for CO and O 3 Neglected horizontal correlations in forecast and observation error covariance matrices Observation Operator:

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