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Page 1© Crown copyright 2004 Seasonal forecasting activities at the Met Office Long-range Forecasting Group, Hadley Centre Presenter: Richard Graham ECMWF.

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Presentation on theme: "Page 1© Crown copyright 2004 Seasonal forecasting activities at the Met Office Long-range Forecasting Group, Hadley Centre Presenter: Richard Graham ECMWF."— Presentation transcript:

1 Page 1© Crown copyright 2004 Seasonal forecasting activities at the Met Office Long-range Forecasting Group, Hadley Centre Presenter: Richard Graham ECMWF Forecast Products Users Meeting, 15-17th June 2005

2 Page 2© Crown copyright 2004 Outline Brief summary 2004/5 Recent Met Office (GloSea) seasonal forecasts New website products Multi-model forecast combination/calibration

3 Page 3© Crown copyright 2004 Overview, 2004/5 Met Office GloSea model (version of HadCM3) main tool for seasonal prediction – used in conjunction with statistical methods now runs in parallel configuration with system2 in ECMWF Op. suite (multi-model) 15-member hindcasts 1987-present have been completed (12 starts/year) Met Office seasonal forecast website update - planned for July multi-model products (temperature and precipitation) probability for outer-quintile categories extensive upgrade of verification/validation information (research on multi-model combination/calibration) Use of ECMWF monthly system Met Office post-processed products supplied to various end users Talks: Bernd Becker and Stefan Meulemans - later today EU ENACT project completed 43-year global ocean re-analyses, different models and ODA methods analysis quality assessed through seasonal forecast impacts

4 Page 4© Crown copyright 2004 Recent forecasts: Nino3.4 SST anomaly, Dec04 – May05 Dec04Jan05 Feb05 Mar05Apr05 May05

5 Page 5© Crown copyright 2004 Recent forecasts: Outer-quintile temperature forecasts and verif DJF04/05 P(outer quintile) >40% IRI verification

6 Page 6© Crown copyright 2004 Skill assessment for outer quintiles – new website products

7 Page 7© Crown copyright 2004 Hindcast datasets used BACKRUNS (operational set) period: 1987-present (16 yrs, , used here) 15-member ensemble allows skill assessment for higher order (than tercile) categories DEMETER (research set) period: (43 yrs) 9-member ensemble

8 Page 8© Crown copyright 2004 BACKRUNS verification: temperature, ROC: selectable by region/initial date/lead time: tercilesouter-quintiles Example for Central America, JJA, 1-month lead ( )

9 Page 9© Crown copyright 2004 BACKRUNS verification: precipitation, ROC: selectable by region/initial date/lead time: tercilesouter-quintiles Example for Central America, JJA, 1-month lead ( )

10 Page 10© Crown copyright 2004 BACKRUNS: ROC skill maps Example for 2m temperature, JJA, 1m lead from GloSea hindcasts (16 yrs) local gridpoint ROC scores (area under the curve) Skill for outer-quintile extremes similar to that for outer terciles NB. But sample of events is smaller Event = temperature in upper tercile Event = temperature in upper quintile

11 Page 11© Crown copyright 2004 DEMETER: ROC skill maps Example for 2m temperature, JJA, 1m lead from GloSea DEMETER hindcasts (43 yrs) local gridpoint ROC scores (area under the curve) Event = temperature in upper tercileEvent = temperature in upper quintile

12 Page 12© Crown copyright 2004 BACKRUNS verification: precipitation, reliability: selectable by region/initial date/lead time: tercilesouter-quintiles Example for Central America, JJA, 1-month lead ( )

13 Page 13© Crown copyright 2004 European multi-model GloSea GloSea+ECMWF multi-model probability of well-above/below temperatures, Jun-Jul-Aug well above well below

14 Page 14© Crown copyright 2004 multi-model combination, calibration prediction of decile extremes

15 Page 15© Crown copyright 2004 Discriminant Analysis for multi-model combining/calibration Generalised squared distance; where, tcategory of interest (eg. upper quintile) x vector of predictor variables (elements = eg. t2m from different models) m t corresponding vector of mean predicted values (from hindcasts) when category t was observed (cross validated) S covariance matrix for different predictors (models) Predicted probability of category t given by… Take average of p t (x) over all ensemble members

16 Page 16© Crown copyright 2004 Area with BS > 95% significant for 2m temp outer quintiles DEMETER ( ) Black: Raw Ensemble GloSea. Red: Raw Ensemble Multi-model Blue: Discriminant GloSea. Green: Discriminant Multi-model. All seasons 0,1,2,3 months lead

17 Page 17© Crown copyright 2004 Area with ROC skill > 95% significant 2m temp DEMETER ( ) Black: Raw Ensemble GloSea. Red: Raw Ensemble Multi-model Blue: Discriminant GloSea. Green: Discriminant Multi-model. All seasons 0,1,2,3 months lead

18 Page 18© Crown copyright 2004 European multi-model GloSeaGloSea calibrated probability of well-above/below temperatures, Jun-Jul-Aug well above well below

19 Page 19© Crown copyright 2004 ROC significance for calibrated forecasts of outer deciles: temperature, Europe, JAS ( ) >95% significance GloSea GloSea+ system2+ Meteo- France Multi-model

20 Page 20© Crown copyright 2004 ROC significance for calibrated forecasts of outer deciles: temperature, Europe, AMJ ( ) >95% significance GloSea GloSea+ system2+ Meteo- France Multi-model

21 Page 21© Crown copyright 2004 Summary + key plans New website products – July 05 Multi-model Outer-quintiles probabilities Expanded verification information Next year Calibrated products Higher order extremes (deciles) Need to resolve trade off between reliability and resolution EU ENSEMBLES project Investigate multi-annual/decadal skill Compare ensemble initialisation strategies Next generation GloSea Investigate/prepare new Hadley Centre climate model (HadGEM1) for use in seasonal prediction

22 Page 22© Crown copyright 2004 ENSEMBLES project: Met Office seasonal/multi-annual/decadal runs Model DePreSys (HadCM3) Current oper. range decadal assimilation method GloSea (HadCM3) Seasonal (6months) Conventional (OI type) calibrated anomalies 9-ensemble experiments pert. ODA pert. phys. lagged avge pert. phys. lagged avge Hindcasts period: GloSea: ->7m:1 st /15 th May/Nov 1 st June/Dec ->14m:1 st May/June/Nov/Dec -> 10y:1 st May 1964, 1994 DePreSys: -> 10y:1 st May/Nov (all years)

23 Page 23© Crown copyright 2004 Questions & Answers

24 Page 24© Crown copyright 2004 Seasonal forecasting activities at the Met Office Long-range Forecasting Group, Hadley Centre Presenter: Richard Graham ECMWF Forecast Products Users Meeting, 15-17th June 2005

25 Page 25© Crown copyright 2004 Outer quintile temperature forecasts and verif FMA 05 P(outer quintile) >40% IRI verification

26 Page 26© Crown copyright 2004 Seasonal forecasting system : GloSea Enhanced version of the Hadley Centre Climate model HadCM3 Six month real-time 41 member ocean atmosphere global forecast ensemble 5 ocean analyses from perturbed wind stresses Ocean analyses further perturbed with instantaneous SST perturbations hindcast (BACKRUN) period, 1987-present ( used here) Ocean Analysis - 5 member ensemble Real - Time Forecast 41 member ensemble Retrospective Forecasts - 15 member ensemble Atmosphere NWP/re- analyses 15 member

27 Page 27© Crown copyright 2004 BACKRUNS verification: temperature, reliability: selectable by region/initial date/lead time: tercilesouter-quintiles Example for Central America, JJA, 1-month lead ( )

28 Page 28© Crown copyright 2004 Discriminant Analysis -used to calibrate dynamical forecasts and combine ensembles from multi-model -Multi-variate: different predictors (models) considered together, relative skill taken into account Pdfs for above, middle and below terciles, given value of a predictor (illustration) Calculated using historical data and hindcasts


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