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Ozone Assimilation for Improved UV Index and AQHI Forecast at Environment Canada

This paper discusses the use of ozone assimilation to enhance the UV Index and Air Quality Health Index (AQHI) regional forecast at Environment Canada. It covers various components of the global system, such as stratospheric chemical modeling and measurements. The experiments and evaluation of the nesting approach are also discussed. The impact of this assimilation on UV Index and AQHI forecasts is evaluated.

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Ozone Assimilation for Improved UV Index and AQHI Forecast at Environment Canada

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  1. Ozone assimilation to improve UV-index and AQHI regional forecast at Environment CanadaJ. de Grandpré, Y. Rochon and R. Ménard Contributors: ARQI (C. McLinden, V. Fioletov, M. Moran, V. Bouchet) AQMAS (S. Gravel) , ARMA (G. Deblonde, L. Fillion), RPN (M. Charron, P. Vaillancourt), CMDA (G. Verner)

  2. Outline • Motivation • Global system components • Stratospheric chemical modelling • Chemical measurements • 3D-FGAT variational assimilation • Experiments and evaluation • Nesting approach • Impact on UV-index and AQHI forecasts

  3. Linearized Stratospheric chemistry (LINOZ)(McLinden et al., 2000) q : Ozone mixing ratio cO3 : Column ozone T : Temperature P-L : Photochemical tendency (O) : Climatological values No heterogeneous chemistry

  4. Sample ozone observation distributionTangent point orbit tracks for a 6 hour period (centered about 0 UTC) on 25 July 2008 584 20 partial column layers with ~5 layers in the troposphere ~3.2 km layers Day only Total column amounts Thinning: 1 degree separation Day only cloud free points 5502

  5. Global deterministic meteorological and chemical analysis and forecasting system 48 hr Forecast 48 hr Forecast 48 hr Forecast

  6. Evaluation • Control cycle: Meteorological assimilation + prognostic ozone (winter and summer cycles) • Ozone assimilation cycles: (Use of 6 hrs met analyses + 3D-Var ozone assimilation) • SBUV/2 • GOME-2 • Evaluation of ozone analyses and forecast against ozonesondes below 10 hPa

  7. Jan-Feb, 2009 O-A Ozone (%) SH No Assimilation SBUV/2 July 2008 EQ NH

  8. July, 2008 (WOUDC) LINOZ - WOUDC SBUV/2 - WOUDC SBUV/2 & GOME2 [Against OMI]

  9. GEM-MACH Upper Boundary Nesting • Pilot files (meteo and chem) : [GEM-Global] • GEM-MACH lid : [.1hPa  10 hPa] • GEM4-based version (Staggered Grid) Schematic of nesting (dark grey) and blending (light grey) zones used for UBN implementation. Recent GEM versions use Charney-Phillips vertical staggering with momentum levels dashed and thermodynamic levels solid lines. (Courtesy of R. McTaggart – Cowan)

  10. Benefits of the new system • Improvment of the AQHI forecast • Delivering of global ozone analyses • Improve radiative heating in the global NWP system • Use for temperature retrieval • Research application • UV-index Forecast

  11. Sample ozone observation distributionTangent point orbit tracks for a 6 hour period (centered about 0 UTC) on 25 July 2008 584 1748 165-300 km along track ~ 2.5 km in the vertical (NRT: 0.2 to 68 hPa) 20 usable partial column layers with ~5 ‘no-impact’ tropo. layers ~3.2 km layers Day only Total column amounts Thinning: 1 degree separation Day only cloud free points 5502

  12. Jan-Feb, 2009 Ozone Profiles (Pa) SH SH Ozonesondes No Assimilation (dashed) SBUV/2 assim (dashed) July 2008 EQ EQ NH NH

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