1. © Crown copyright Met Office Met Office dust forecasting Using the Met Office Unified Model™ David Walters: Manager Global Atmospheric Model Development, Met Office. (with M.E. Brooks, B. Ingleby, B. Johnson, J. Mulcahy, Y. Pradhan)

2. © Crown copyright Met Office Dust forecasting with the MetUM

3. © Crown copyright Met Office Met Office Unified Model™ (MetUM) A 'seamless' model used across all time and space scales. MetUM framework includes: OPS, VAR, VER …

4. © Crown copyright Met Office Met Office Unified Model™ Atmospheric model components Dynamics: Regular lat/lon grid. Non-hydrostatic dynamics with a deep atmosphere. Semi-implicit time integration with 3D semi-Lagrangian advection. Atmospheric tracer advection Physics: Spectral band radiation Diagnostic or prognostic cloud Mixed-phase ppn Mass flux convection Boundary layer Gravity wave schemes JULES land-surface model Aerosols/chemistry: CLASSIC: SO 4, Soot, Biomass smoke, OCFF, xNO 3, seasalt, dust United Kingdom Chemistry Aerosol (UKCA) community model

5. © Crown copyright Met Office Dust in the MetUM Woodward (2001,2011) Horizontal flux: Dry U t * prescribed for each bin Soil moisture contribution to U t * from top soil layer Friction velocity scheme using explicit U* over bare soil only: Kawamura (1951) 100031610031.6103.161.00.3160.1 Upper lim (  m) 31610031.6103.161.00.3160.10.0316 Lower lim (  m) 987654321Size division Saltation only Horizontal and vertical flux Iverson and White (1982) Fecan et al. (1999) Horizontal flux calculated for 9 size divisions

6. © Crown copyright Met Office Dust in the MetUM Crisis Area Model implementation M rel, sand/silt/clay & soil properties from HWSD Nachtergaele et al (2008) e.g. grid-box clay fraction Vertical flux: Gillette (1979)

7. © Crown copyright Met Office Dust in the MetUM Mapping from horizontal to vertical flux Using 6 size divisions: Dynamically diagnosed from horizontal flux distribution: or Prescribed following a fixed size distribution: Currently used in climate research Currently used in limited area NWP

8. © Crown copyright Met Office Dust in the MetUM Mapping from horizontal to vertical flux Using 2 size divisions: Uses prescribed size distribution only 100031610031.6103.161.00.3160.1 Upper lim (  m) 31610031.6103.161.00.3160.10.0316 Lower lim (  m) 987654321Size division Horizontal saltation flux 102 Upper lim (  m) 20.1 Lower lim (  m) 21Size division Vertical flux Currently used in global NWP

9. © Crown copyright Met Office Dust in the MetUM Details of the prescribed size distributions Continuous function used:

10. © Crown copyright Met Office Dust in the MetUM Details of the prescribed size distributions Discretised forms (6 and 2 bins):

11. © Crown copyright Met Office Dust in the MetUM Once dust is lifted: Transported by SL advection and Interacts with radiation scheme via direct aerosol effect Removed via dry/wet deposition Balkanski et al. (2007) Can use climatological dust in radiation instead

12. © Crown copyright Met Office Operational dust models Southern Asia Model 12km 70L (80km lid) 4D-Var DA 6 bin dust scheme since 2008 No dust DA No dust in LBCs North Africa Model 12km 70L (80km lid) 3D-Var DA 6 bin dust scheme since 2011 No dust DA No dust in LBCs Global Model N512 (~25km) 70L (80km lid) 4D-Var DA 2 bin dust scheme since 2011 No dust DA Radiation uses climatology

13. © Crown copyright Met Office Dust model validation

14. © Crown copyright Met Office Dust forecast validation

15. © Crown copyright Met Office Dust Aerosol Optical Thickness (AOT) compared to AERONET Dust forecast validation

16. © Crown copyright Met Office ← → DUST ← → DUST ← … DUST Dust forecast performance

17. © Crown copyright Met Office Equitable Threat Score (ETS): fraction of observed events that were correctly predicted, reduced by the numbers you would expect by chance. 0 – no skill 1 - perfect Equitable Threat Score (ETS): Demanding score for small scale features as correct prediction means: exactly right place right time (3 hour window) Dust forecast validation

18. © Crown copyright Met Office Other validation methods Subjective verification (including from theatre) Verification of visibility against SYNOP/METAR Model inter-comparison Observational campaigns

19. © Crown copyright Met Office Global Model validation Pre-operational testing (April 2011) Met Office research news article on global dust forecasting: http://www.metoffice.gov.uk/research/news/dust-forecasting

20. © Crown copyright Met Office Global Model results Pre-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

21. © Crown copyright Met Office Future developments

22. © Crown copyright Met Office Dust model developments Validation show dust from areas with seasonal vegetation is important: link dust emissions to “radiative bare soil fraction” Dust DA currently being developed (to use SEVERI and MODIS AOD products) Emissions sensitive to soil properties, soil moisture etc: further improvements required in these areas Continuing to develop satellite products currently provided to WMO SDS-WAS Feedback on these products appreciated

23. © Crown copyright Met Office Please take home the following points Met Office dust forecasts operational since 2008 Model validation shows reasonable performance and has identified areas of potential improvement Dust in 25km global NWP since summer 2011 Global model data to SDS-WAS from December 2011 Summary

24. © Crown copyright Met Office Questions