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Multi-model operational seasonal forecasts for SADC

Multi-model operational seasonal forecasts for SADC. Willem A. Landman Asmerom Beraki Cobus Olivier Francois Engelbrecht. Conformal-Cubic Atmospheric Model (CCAM). Runs performed on a computer cluster at the University of Pretoria Climatological ensemble runs - 12hr LAF (5 members)

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Multi-model operational seasonal forecasts for SADC

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  1. Multi-model operational seasonal forecasts for SADC Willem A. Landman Asmerom Beraki Cobus Olivier Francois Engelbrecht

  2. Conformal-Cubic Atmospheric Model (CCAM) • Runs performed on a computer cluster at the University of Pretoria • Climatological ensemble runs - 12hr LAF (5 members) • Atmospheric initial conditions for climatological runs obtained from NCEP reanalysis data • Climatological simulations performed for the period: 1979-2003. Lower boundary forcing from AMIP SST and sea-ice

  3. ECHAM4.5 at the SAWS • All runs performed on NEC SX-8 • Climatological (6 members) and operational ensemble runs - 24hr LAF • Atmospheric initial conditions from ECMWF (1979 to 1996) analysis • Climatological dataset (1979-2003) constructed using AMIP physics; model constrained by lower boundary conditions generated from a high resolution AMIP2 dataset for SST and sea-ice • Operational set-up: persisted and forecast SSTs obtained from a high resolution observed SST (optimum interpolation v-2) and IRI (mean) respectively (6 members each) • 12-member ensemble operational runs on 18th of each month for 6 consecutive months (i.e., 0-5 months lead-time)

  4. First objective multi-model forecast Old subjective consensus forecast

  5. The current long-range forecast multi-model ensemble system of the South African Weather Service Ensemble 1 (ECHAM4.5 at SAWS) 12 members Ensemble 2 (CCAM at UP) 5 members Ensemble 3 (CCM3.6 at IRI) 24 members Ensemble 4 (CFS at CPC) 40members Combining algorithm: 1. CPT downscaling 2. Equal weights Multi-model ensemble

  6. New forecasting system • UEA CRU data (0.5° resolution) • Precipitation • Minimum temperatures • Maximum temperatures • MOS using 850 hPa geopotential height fields • Domain: 10N-50S; 0-70E Production date: from July 2008

  7. DJF rainfall simulation skill

  8. DJF 1999/2000 precip & max temp PROBABILITY forecasts Precip Max T A typical example of the format of the forecasts

  9. Rainfall forecast issued in December

  10. DMC and VACS • DMC • SAWS to compile draft document on modernizing the SARCOF process • DMC has been receiving MM forecasts from SAWS since August 2008 • MM work to be linked with VACS • Workshop in 2009 (will introduce product)

  11. ENSO forecast • CCA (antecedent SST) • ECHAM4.5-MOM3 (from Dave DeWitt) • CFS (NCEP)

  12. The planned long-range forecast multi-model ensemble system of the South African Weather Service Ensemble 1 (ECHAM4.5 at SAWS) 12 members Ensemble 2 (CCAM at UP) 5 members Ensemble 4 (CFS at CPC) 40members Ensemble 3 (CCM3.6 at IRI) 24 members Combining algorithm: 1. CPT downscaling 2. Equal weights Ensemble 5+6 (+7) (GloSea4 at UKMO and CPTEC/COLA at INPE (ECMWF?)) Multi-model ensemble (& verification statistics)

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