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© Crown copyright 2007
Monthly-Seasonal forecastingAlberto ArribasMonthly to Decadal group, Met Office Hadley Centre
Geneva, December 2011
Our strategy for monthly-seasonal forecasting
- Unified monthly-seasonal system, fully integrated with model development process
- Using latest available model version (from NWP to monthly-seasonal)
- Focus on understanding physical mechanisms: Aim is to improve the model faster to increase forecast skill faster
Paper documenting the system when launched in 2009:
The GloSea4 Ensemble Prediction System for Seasonal Forecasting.
Arribas et al, 2011
Mon. Wea. Rev., 139, 1891–1910.
GloSea4 (Global Seasonal Forecasting system version 4)
Link with model development means frequent model upgrades and hindcast run in real-time
(as forecast)
Consequence: shorter hindcast
Hindcastsize Update
frequency
GloSea4 history
Summer 2009:GloSea4 starts
• GA 1.0• N96L38 Orca(1)L42• Hindcast: 1989-2002
November 2010:Model upgrade
• GA 2.0• N96L85 Orca(1)L75• Sea-ice initialisation• Hindcast: 1996-2009
March 2011:Daily forecast
• Daily initialisation• Monthly system
Arribas etal, 2011
GloSea4 plans
November 2011:Model upgrade • GA 3.0
• N96L85 Orca(1)L75
Summer 2012:Model upgrade
• GA 4.0• N216L85 Orca(0.25)L75
• ~ 50km (mid-lat)
Current operational system
Model version: HadGEM3 GA2.0
Resolution: N96L85 O(1)L75 (~120 km, ~ 1 dg)
Simulations length: 7 months
Model uncertainties represented by: • SKEB2 stochastic physics
Initial conditions uncertainties represented by:• Lagged ensemble
Initialisation
Forecast (daily):Atmosphere & land surf: NWP analysisOcean & sea-ice: Seasonal ODA (Optimal
Interpolation)
14-year Hindcast (1996-2009):Atmosphere & land surf: ERA-interim Ocean & sea-ice: Seasonal ODA reanalysisFixed start dates of 1st, 9th, 17th, 25th of each month
Ensemble: lagged approach
Seasonal Forecast:2 members run each day. Forecast updated every week: 42 members (last 3 weeks)Bias corrected using hindcast (~168 members)
Hindcast (for monthly-seasonal):14 year hindcast run in real time, 3 members per year and start date completed every week (i.e. 42 members/week)
Monthly Forecast:2 members each day. Forecast updated daily: 28 members (last 7 days)Bias corrected using hindcast (~168 members)
20/06/2011
20/06/2011
How the system runs, an example
Atmos & land surf: NWP anal
Ocean/sea-ice: Seasonal ODA
Atmos & land surf: ERA-i
Ocean: Seasonal ODA reanalysis
25/07/1996 (m1)
25/07/1997 (m1)
25/07/1998 (m1)
25/07/1999 (m1)
25/07/2000 (m1)
25/07/2001 (m1)
Monday
21/06/2011
21/06/2011
25/07/2002 (m1)
25/07/2003 (m1)
25/07/2004 (m1)
25/07/2005 (m1)
25/07/2006 (m1)
25/07/2007 (m1)
Tuesday
26/06/2011
26/06/2011
25/07/2004 (m3)
25/07/2005 (m3)
25/07/2006 (m3)
25/07/2007 (m3)
25/07/2008 (m3)
25/07/2009 (m3)
Sunday
Each week: 14x 7-month forecasts, 14x 2-month forecasts (for monthly forecast) and 42x 7-month hindcasts (1996-2009)
20/06/2011
20/06/2011
21/06/2011
21/06/2011
26/06/2011
26/06/2011
An international system ...
KMA (Rep. of Korea) • Joint seasonal forecast system• Shared workload and computing costs:
possibility to extend hindcast and increase resolution
NCMRWF (India) – implementing GloSea for research
Our approach to data sharing
Happy to make NON real-time forecasts (at least 1-month old) and hindcast freely available for research
• Africa: ~ 6 centres currently analysing data from GloSea4 hindcasts
• China Meteorological Agency (hindcast)• Japan (hindcast and non real-time fcst)• UK Universities (hcst and non real-time fcst)• etc
Real time data ...
Real time forecast and hindcast data (same set of seasonal forecasting standard products) supplied to:
• WMO Lead Centre
• EUROSIP
ENSO and ENSO
teleconnections
Nino 3.4 SST
From
May
From
Nov
ACC RMSE / SpreadNino 3.4 SST
ENSO Telecon. (precip)
Observations L85 - GloSea4
JJA
DJF
An example of a recently improved physical
mechanism:
ENSO – Europe teleconnection
Importance of vertical resolution: ENSO teleconn.
January-February anomalies, NCEP 1950-2000
Toniazzo and Scaife 2006
Obs Moderate el Nino Obs Stong el Nino
L38 model – moderate Nino L38 model – stong Nino
January-February anomalies, NCEP 1950-2000
Toniazzo and Scaife 2006
Moderate el Nino Stong el Nino
L85 model – moderate Nino L85 model – stong Nino
Importance of vertical resolution: Stratospheric model
Future improvements: higher resolution
ENSO teleconnections with Indian monsoonO
bs
L38
L85
N216
N96
Future developments: Benefits of higher spatial resolution
Obs
This error is common to many climate modelsIt affects remote regionsN216 has better ENSO pattern and teleconnections
Sarah Ineson, Dave Rowell
Benefits of higher resolution: Improved Atlantic Blocking
Gulf Stream Bias
Wly wind bias
=> Blocking Deficit
No Gulf Stream Bias
No Wly wind bias
=> Good Blocking
New Model
Scaife et al., Geophys. Res. Lett., submitted.
Blocking Frequency
1 degree ocean
0.25 degree ocean
MJO
Other recent improvements:
Arctic sea-ice
Forecasting Arctic Sea-ice
observations
Hindcast Forecast
2011 Arctic Sea-ice forecast
Products from the
GloSea4 system
• We are a WMO Global Producing Centre• Member of EUROSIP• Contributor to WMO Lead Centre
• Products: hurricanes, water management, etc
• Main customer for monthly-seasonal is UK Government
Public forecast for 2011Released 26th May 2011Near- to above-normal activity predicted
Observed to dateNovember
forecastSeason total
Tropical storms 16 2 18
ACE index 111 5 116
Main forecast product for government
ENSO prediction from April-Sep (EUROSIP)
Apr May Jun
Jul Aug Sep
Inputs into forecast
Euro-SIP Output
Ensemble mean PMSL Anomalies: November
GloSea4 ECMWF MeteoFranceFrance
Inputs into forecast
GPC output
PMSL anom
Pretoria Montreal
Toulouse
Tokyo
Seoul
MelbourneWashington
CPTEC
Exeter
Beijing
ECMWF
Moscow
Inputs into forecast
Government product: Fig. 1
Government product: Fig. 2
Government product: Fig. 3