1. Slide 1 Dust Modelling Workshop, 26 Feb08 Dust Modelling Workshop, Reading U., 26 February 2008 Modelling dust aerosols for the ECMWF IFS J.-J. Morcrette, A. Benedetti, L. Jones, J.W. Kaiser, O. Boucher 1, S. Kinne 2 ECMWF, Reading; 1 MetOffice, Exeter; 2 Max-Planck Institute, Hamburg As part of the GEMS project (Global Environmental Monitoring using Satellite and in-situ measurements) ECMWF is developing a version of its assimilation/forecast system including aerosols Here emphasis is put on the forward modelling of dust aerosols 3-bin representation: 0.03 – 0.55 – 0.9 – 20 mm (representing roughly 10, 20 and 70% of the mass of dust aerosols)

2. Slide 2 Dust Modelling Workshop, 26 Feb08 Dust production - 1 Based loosely on -Marticorena and Bergametti, 1995 -Ginoux et al., 2001 -Engelstaedter and Washington, 2007 Delineation of areas likely to be sources of dust aerosols by -Soil moisture in first model layer: sm1 -Fraction of bare soil within a model grid: fbs -Total albedo: a -UV-vis albedo ( < 0.7 m; from MODIS): auv -Wind at lowest model level (lml = 10m) v -Wind at lml but including gustiness: vg -Dust emission potential: dep

3. Slide 3 Dust Modelling Workshop, 26 Feb08 Dust production - 2 Delineation of areas likely to be sources of dust aerosols by: -Lifting threshold speed lts = f( sm1, bin mean particle radius) -Wind factor: v = v or vg v 3 = ( v – lts ) * v 2 Two possible formulations: if ( land.and. v > lts.and. fbs > 0.1) then if (a < 0.5.and. 0.08 < auv < 0.5 ) then flux= dep(i) * auv * v 3 endif if ( land.and. v > lts.and. fbs > 0.1) then if (sm1 < 0.2 sm1 sat ) then flux = C * dep(i) * (1-sm1) * v 3 endif Soil moisture-based Albedo-based

4. Slide 4 Dust Modelling Workshop, 26 Feb08 Tau 550 nm DU only original June 2003 original June 2007 Revised DEP June 2007 Revised DEP + gusts June 2007

5. Slide 5 Dust Modelling Workshop, 26 Feb08 Forward modelling of aerosols As part of the GEMS project, the IFS has been modified to include prognostic aerosols (sea-salt SS, dust DU, organic OM and black carbon BC, sulphate SU). Sources for SS and DU are linked to some of the model surface parameters (U10, soil moisture, UVis albedo, stdev orography, snow mask, gustiness). Sources for OM, BC and SU are taken from climatologies and/or inventories (GFEDm, GFED8d, SPEW, EDGAR databases). Aerosols are transported by advection, vertical diffusion and convection, and undergo their specific processes, i.e., sedimentation, dry deposition, wet deposition by large- scale and convective precipitation, and for OM and BC hygroscopic effects. The T L 159 L60 model has been simulating aerosols for the 2003-2004 GEMS-AER reference period (with climatological and 8day OM, BC and SU emissions). Comparisons with observational data (MODIS, CloudSat/CALIPSO, AERONET). Since 1 June 2007, the ECMWF operational model is used for experimental near-real time 72-hour aerosol forecasts, at T L 159 L91, and without any analysis. http://www.ecmwf.int/products/forecasts/d/inspect/catalog/research/gems/aer/optical_depth/

6. Slide 6 Dust Modelling Workshop, 26 Feb08 An experimental version of ECMWF IFS now produces in near-real time a 72- hour forecast (FC only, no analysis yet) of the total optical depth for an ensemble of aerosols (sea-salt, desert dust, organic matter, black carbon, and sulphate) Total optical depth 550 nm 20080108_00 + 39hr

7. Slide 7 Dust Modelling Workshop, 26 Feb08 natural = SS+DU anthropogenic = OM + BC + SU

8. Slide 8 Dust Modelling Workshop, 26 Feb08 Assessment Comparison with MODIS-derived aerosol optical depth at 550 nm Comparison with CALIPSO-derived cloud and aerosol masks Comparison with AERONET aerosol optical depth at various wavelengths

9. Slide 9 Dust Modelling Workshop, 26 Feb08 MODIS IFS MODIS July 2003 Sum 12hr-FCs July 2003

10. Slide 10 Dust Modelling Workshop, 26 Feb08 MODIS IFS MODIS Jan2004 Sum 12hr-FCs Jan2004

11. Slide 11 Dust Modelling Workshop, 26 Feb08 ECMWF model FC only at T L 159 L91 Modis Aqua MODIS Orbit

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13. Slide 13 Dust Modelling Workshop, 26 Feb08 ECMWF model FC only at T L 159 L91 Modis Aqua missing

14. Slide 14 Dust Modelling Workshop, 26 Feb08 ECMWF model FC only at T L 159 L91 Modis Aqua

15. Slide 15 Dust Modelling Workshop, 26 Feb08 ECMWF model FC only at T L 159 L91 Modis Aqua

16. Slide 16 Dust Modelling Workshop, 26 Feb08 July 2007 AERONET Model

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18. Slide 18 Dust Modelling Workshop, 26 Feb08 Comparison Analysis / Forecast Comparison A/F for DU aerosol type only Comparison A/F for each MODIS SW wavelength and all tropospheric aerosols

19. Slide 19 Dust Modelling Workshop, 26 Feb08 Forecast DU Analysis DU Comparison of monthly averaged optical depth of dust for July 2003: for a forecast only (left) and for the analysis system (right) Comparison Analysis / Forecast

20. Slide 20 Dust Modelling Workshop, 26 Feb08 LOA-AEROCOM_B 2000 LSCE-AEROCOM_B 2000 GOCART-AEROCOM_B 2000 ECMWF-GEMS_AER 2003 Watch the scales!

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