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  • Met Office dust forecastingUsing the Met Office Unified ModelDavid Walters: Manager Global Atmospheric Model Development, Met Office.(with M.E. Brooks, B. Ingleby, B. Johnson, J. Mulcahy, Y. Pradhan)

  • Dust forecasting with the MetUM

  • Met Office Unified Model(MetUM)A 'seamless' model used across all time and space scales.

  • Met Office Unified ModelAtmospheric model componentsDynamics:Regular lat/lon grid.Non-hydrostatic dynamics with a deep atmosphere.Semi-implicit time integration with 3D semi-Lagrangian advection.Atmospheric tracer advectionPhysics:Spectral band radiationDiagnostic or prognostic cloudMixed-phase ppnMass flux convectionBoundary layerGravity wave schemesJULES land-surface modelAerosols/chemistry:CLASSIC: SO4, Soot, Biomass smoke, OCFF, xNO3, seasalt, dustUnited Kingdom Chemistry Aerosol (UKCA) community model

  • Dust in the MetUMWoodward (2001,2011)Dry Ut* prescribed for each binSoil moisture contribution to Ut* from top soil layerFriction velocity scheme using explicit U* over bare soil only:

    Kawamura (1951)Iverson and White (1982)Fecan et al. (1999)Horizontal flux calculated for 9 size divisions

  • Dust in the MetUMCrisis Area Model implementationMrel, sand/silt/clay & soil properties from HWSDNachtergaele et al (2008)Gillette (1979)

  • Dust in the MetUMMapping from horizontal to vertical fluxUsing 6 size divisions:Dynamically diagnosed from horizontal flux distribution:

    orPrescribed following a fixed size distribution:

    Currently used in climate researchCurrently used in limited area NWP

  • Dust in the MetUMMapping from horizontal to vertical fluxUsing 2 size divisions:

    Uses prescribed size distribution only

    Currently used in global NWP

  • Dust in the MetUMDetails of the prescribed size distributionsContinuous function used:

  • Dust in the MetUMDetails of the prescribed size distributionsDiscretised forms (6 and 2 bins):

  • Dust in the MetUMOnce dust is lifted:

    Transported by SL advection and Interacts with radiation scheme via direct aerosol effect

    Removed via dry/wet depositionBalkanski et al. (2007)Can use climatological dust in radiation instead

  • Operational dust modelsSouthern Asia Model 12km 70L (80km lid) 4D-Var DA 6 bin dust scheme since 2008 No dust DA No dust in LBCsNorth Africa Model 12km 70L (80km lid) 3D-Var DA 6 bin dust scheme since 2011 No dust DA No dust in LBCsGlobal Model N512 (~25km) 70L (80km lid) 4D-Var DA 2 bin dust scheme since 2011 No dust DA Radiation uses climatology

  • Dust model validation

  • Dust forecast validation

  • Dust Aerosol Optical Thickness (AOT) compared to AERONET

    Dust forecast validation

  • Dust forecast performance


  • Dust forecast validation

    Equitable Threat Score (ETS): fraction of observed events that were correctly predicted, reduced by the numbers you would expect by chance.0 no skill1 - perfectEquitable Threat Score (ETS):Demanding score for small scale features as correct prediction means: exactly right place right time (3 hour window)

  • Other validation methodsSubjective verification (including from theatre)

    Verification of visibility against SYNOP/METAR

    Model inter-comparisonObservational campaigns

  • Global Model validationPre-operational testing (April 2011)

    Met Office research news article on global dust forecasting:

  • Global Model resultsPre-operational testing Skill scores over SAM region: beats the SAM for low severity events capturing inflow into domain misses high severity events high res models still required?

    Model went operational in July 2011 Provide forecasts to SDS-WAS through MACC-II project from December 2011

  • Future developments

  • Dust model developmentsValidation show dust from areas with seasonal vegetation is important: link dust emissions to radiative bare soil fractionDust DA currently being developed (to use SEVERI and MODIS AOD products)Emissions sensitive to soil properties, soil moisture etc: further improvements required in these areasContinuing to develop satellite products currently provided to WMO SDS-WAS Feedback on these products appreciated

  • SummaryPlease take home the following pointsMet Office dust forecasts operational since 2008Model validation shows reasonable performance and has identified areas of potential improvementDust in 25km global NWP since summer 2011Global model data to SDS-WAS from December 2011

  • Questions

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