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Monthly Forecasting at ECMWF

Monthly Forecasting at ECMWF. Fr é d é ric Vitart European Centre for Medium-Range Weather Forecasts. ECMWF: Weather and Climate Dynamical Forecasts. Seasonal Forecasts Month 2-7. Medium-Range Forecasts Day 1-10(15). Monthly Forecast Day 10-32. Product.

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Monthly Forecasting at ECMWF

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  1. Monthly Forecasting at ECMWF Frédéric Vitart European Centre for Medium-Range Weather Forecasts

  2. ECMWF: Weather and Climate Dynamical Forecasts Seasonal Forecasts Month 2-7 Medium-Range Forecasts Day 1-10(15) Monthly Forecast Day 10-32 Product Forecasting systems at ECMWF

  3. Index • Main sources of predictability on the monthly time-scale • Madden Julian Oscillation • Soil Moisture • Stratospheric Initial conditions • The ECMWF monthly forecast system • Description • Some examples of forecasts • Skill

  4. A particularly difficult time range: Is it an atmospheric initial condition problem as medium-range forecasting or is it a boundary condition problem as seasonal forecasting? Somesources of predictability : Sea surface temperatures Land surface conditions: snow-soil moisture The Madden Julian Oscillation Stratospheric variability Atmospheric dynamical processes (Rossby wave propagations, weather regimes…) Sea ice cover –thickness ? Bridging the gap between Climate and weather prediction

  5. Impact of soil moisture Koster et al, GRL 2011

  6. Stratospheric Sudden Warmings Chui and Kunz, 2009

  7. Stratospheric influence on the troposphere? Baldwin and Dunkerton, 2001

  8. Z1000 Response (Weak vortex-CTL) Stratospheric influence on the troposphere? D+1-D+10 D+11-D+20 From T. Jung et al 2005 D+21-D+30 D+31-D+40

  9. Synoptic Z500 Activity D+21-D+30 Stratospheric influence on the troposphere? From T. Jung et al 2005

  10. The Madden-Julian Oscillation (MJO) From Madden and Julian (1972)

  11. The Madden Julian Oscillation (MJO) MJO life cycle (From NASA) From http://www.bom.gov.au/bmrc/clf

  12. The Madden Julian Oscillation (MJO) • The MJO is a 40-50-day oscillation • The MJO is a near-global scale, quasi-periodic eastward moving disturbance in the surface pressure, tropospheric temperature and zonal winds over the equatorial belt. • The Madden-Julian Oscillation (MJO) is the dominant mode of variability in the tropics in time scales in excess of 1 week but less than 1 season. • The MJO has its peak activity during Northern winter and spring.

  13. The Madden Julian Oscillation (MJO) Why is the MJO so important? • Impact on the Indian and Australian summer monsoons (Yasunari 1979), Hendon and Liebman (1990) • Impact on ENSO. Westerly wind bursts produce equatorial trapped Kelvin waves, which have a significant impact on the onset and development of an El-Niňo event. Kessler and McPhaden (1995) • Impact on tropical storms (Maloney et al, 2000; Mo, 2000) • Impact on Northern Hemisphere weather

  14. Impact of the MJO on Extratropics Lin et al, MWR 2010 See also Simmons et al JAS 1983 Ting and Sardeshmukh JAS 1993

  15. MJO Prediction Combined EOF1 Combined EOF2 From Wheeler and Hendon, BMRC

  16. MJO FORECAST

  17. Impact on Europe Cassou (2008)

  18. MJO prediction Experiment’s setting: • 46 day forecasts at T255L62 coupled to HOPE • 15 members • Starting dates: 15 Nov/Dec/Jan/Feb/Mar/Apr 1989-2008 • Model Cycle 32R3 (operational cycle from 11/07 to 06/08)

  19. MJO Skill scores Bivariate RMS error Bivariate Correlation Ensemble mean/ reanalysis Ensemble mean/ reanalysis Ensemble Spread “Perfect Model” Climatology

  20. Impact on Precipitation anomalies (Summer)

  21. Impact on Tropical Cyclone Density (Summer) Vitart, GRL 2009

  22. Impact on the Extratropics- Z500 anomalies

  23. Impact on weather regimes in hindcasts Phase3+10 days Phase6+10 days NAO+ Atlantic ridge Scandinavian blocking NAO-

  24. T850 anomalies – NDJFM 1989-2008 Phase 3 + 10 days Phase 6 + 10 days ERA MODEL Degree C

  25. Probabilistic skill scores – NDJFMA 1989-2008 Reliability Diagram Probability of 2-m temperature in the upper tercile Day 19-25 Europe N. Extratropics 0.04 0.03 -0.06 -0.09 NO MJO in IC MJO in IC

  26. The ECMWF monthly forecasting system • A 51-member ensemble is integrated for 32 days twice a week (Mondays and Thursdays at 00Z) • Atmospheric component: IFS with the latest operational cycle and with a T639L62 resolution till day 10 and T319L62 after day 10. • Persisted SST anomalies till day 10 and ocean-atmosphere coupling from day 10 till day 32. • Oceanic component: HOPE (from Max Plank Institute) with a zonal resolution of 1.4 degrees and 29 vertical levels • Coupling: OASIS (CERFACS). Coupling every 3 hours.

  27. The ECMWF VarEPS-monthly forecasting system EPS Integration at T639 Initial condition Heat flux, Wind stress, P-E Day 32 Day 10 Coupled forecast at TL319 Ocean only integration

  28. The ECMWF monthly forecasting system • Atmospheric initial conditions: ECMWF operationalanalysis • Oceanic initial conditions: “Accelerated” ocean analysis • Perturbations: • Atmosphere: Singular vectors + stochastic physics • Ocean: Wind stress perturbations during the data assimilation • Background statistics: 5-member ensemble integrated at the same day and same month as the real-time time forecast over the past 20 years (a total of 100 member ensemble). Initial conditions: ERA Interim. Produced once a week.

  29. The ECMWF monthly forecasting system Anomalies (temperature, precipitation..) -

  30. The ECMWF monthly forecasting system Probabilities (temperature, precipitation..) -

  31. The ECMWF monthly forecasting system

  32. The ECMWF monthly forecasting system Experimental product: Tropical cyclone activity

  33. MJO Forecasts

  34. Precip anomalies : 26 July 2010 – 01 August 2010

  35. Skill of the ECMWF Monthly Forecasting System ROC score: 2-meter temperature in the upper tercile Day 5-11 Day 12-18 Day 19-25 Day 26-32

  36. Skill of the ECMWF Monthly Forecasting System 2-meter temperature in upper tercile - Day 12-18 ROC score Reliability diagram Persistence of day 5-11 Day 12-18 Monthly forecast day 12-18 Day 19-25 Persistence of day 5-18 Monthly forecast day 19-32

  37. OLR anomalies - Forecast range: day 15

  38. MJO skill scores

  39. Impact of the MJO on the N. Extratropics 2002 MOFC hindcasts 2012 MOFC hindcasts ERA Interim

  40. NAO skill scores – Day 19-25

  41. Performance of the monthly Forecasts 2-metre temperature ROC area over Northern Extratropics Day 12-18 Day 26-32 Day 19-25

  42. Conclusion • SSTs, Soil moisture, stratospheric initial conditions and MJO are source of predictability at the intra-seasonal time scale. In particular the MJO has a significant impact on the forecast skill scores beyond day 20. • The monthly forecasting system produces forecasts for days 12-18 that are generally better than climatology and persistence of day 5-11. Beyond day 20, the monthly forecast is marginally skilful. For some applications and some regions, these forecasts could however be of some interest. • There has been a clear improvement in the monthly forecast skill scores over the past 10 years. This improvement is likely to be related to improved prediction in the Tropics and most especially improved MJO prediction.

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