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Met Office & RADAGAST Sean Milton, Glenn Greed & Malcolm Brooks

Met Office & RADAGAST Sean Milton, Glenn Greed & Malcolm Brooks Global Model Development & Diagnostics. 4 July 2006. Outline Global Model – evaluation vs ARM, Niamey data Dec 2005- March 2006. Cloud free days 8 th March dust storm Saharan CAMM – Evaluating the Dust Parametrization.

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Met Office & RADAGAST Sean Milton, Glenn Greed & Malcolm Brooks

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  1. Met Office & RADAGAST Sean Milton, Glenn Greed & Malcolm Brooks Global Model Development & Diagnostics 4 July 2006

  2. Outline • Global Model – evaluation vs ARM, Niamey data Dec 2005- March 2006. • Cloud free days • 8th March dust storm • Saharan CAMM – Evaluating the Dust Parametrization

  3. Surface SW fluxes - Cloud Free days • Systematic • underestimate • SW ~ 50Wm-2 • Poor Surf. Albedo • Overestimate • SW ~ 50Wm-2 • Lack of Aerosol?

  4. GERB (ARG) Model Model - GERB Reflected SW TOA– Clear sky sampling May 2003-May 2006 R.Allan ESSC

  5. Surface LW Fluxes – Cloud Free days • Systematic lag in • modelled LW - • 3hr radiation • timestep. • Overestimate • LW at night • Overestimate • LW throughout diurnal cycle

  6. Surf. Radiation Balance – Cloud Free Days Net radiation errors of 100-150Wm-2

  7. Dust Case Study: Mar 8-9th 2006

  8. Observed Surf. Radiation Balance – ARM, Niamey Atmospheric Radiative Heating SW -40 LW +130

  9. Surface SW fluxes – 6-10 March 2006

  10. Surface LW fluxes : 6-10 March

  11. Observed Surf. Radiation Balance – ARM, Niamey

  12. Saharan Regional Model (~20km)

  13. Dust Case Study: Mar 8th 2006 (N216 Global tests) Original Dust Parameters Revised Dust Parameters

  14. Latest dust parametrization settings in CAMM

  15. Dust in Saharan Regional Model • We have a test case with detailed obs at Niamey. 4th-9th Mar 2006 • AODs now available in the CAM for validation of uplift dust scheme tuning. • Full radiative impacts feedback is now included as • we have a better ballpark for dust, rather than no SW at the surface. • Distribution of dust remains similar while concentrations are now • approx 100x less. This is only a 1st guess for tuning. Much more evaluation is required. • This new version will be supporting DODO2.

  16. Summary • Cloud free days – model has +100-150 Wm-2 error in net surface radiation. • Lack of aerosol (dust & biomass) • Poor specification of surface albedo • Major Dust event 8th March – net surface radiation errors of +300 Wm-2 • Modified dust parametrization in Saharan CAMM tuned to 8th March Dust case– much better agreement with observed AOT – available for DODO2. • Future • Further evaluation of dust parametrizaton (DODO2) • Diurnal cycle? • W.African Monsoon period.

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