Transcript 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)
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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
ECHAM4.5 at the SAWS
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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 leadtime)
First objective multi-model forecast
Old subjective consensus forecast
The current long-range forecast multi-model ensemble system of
the South African Weather Service
Ensemble 1
Ensemble 2
Ensemble 3
Ensemble 4
(ECHAM4.5 at
SAWS)
(CCAM at UP)
(CCM3.6 at IRI)
(CFS at CPC)
5 members
24 members
40 members
12 members
Combining algorithm:
1. CPT downscaling
2. Equal weights
Multi-model ensemble
New forecasting system
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UEA CRU data (0.5° resolution)
– Precipitation
– Minimum temperatures
– Maximum temperatures
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MOS using 850 hPa geopotential
height fields
– Domain: 10N-50S; 0-70E
Production date: from July 2008
DJF rainfall simulation skill
DJF 1999/2000 precip & max
temp PROBABILITY forecasts
Precip
Max T
A typical example of the format of the forecasts
Rainfall forecast issued in December
DMC and VACS
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DMC
– SAWS to compile draft document on
modernizing the SARCOF process
– DMC has been receiving MM forecasts
from SAWS since August 2008
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MM work to be linked with VACS
– Workshop in 2009 (will introduce product)
ENSO forecast
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CCA (antecedent
SST)
ECHAM4.5-MOM3
(from Dave DeWitt)
CFS (NCEP)
The planned long-range forecast multi-model ensemble system
of the South African Weather Service
Ensemble 1
Ensemble 2
Ensemble 3
Ensemble 4
(ECHAM4.5 at
SAWS)
(CCAM at UP)
(CCM3.6 at IRI)
(CFS at CPC)
5 members
24 members
40 members
12 members
Combining algorithm:
1. CPT downscaling
2. Equal weights
Ensemble 5+6 (+7)
(GloSea4 at UKMO
and
Multi-model ensemble
(& verification statistics)
CPTEC/COLA at
INPE
(ECMWF?))