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Advanced Ensemble Generation Techniques for Sub-Seasonal Prediction

This project aims to explore the impact of forecast strategies, initialization techniques, and coupled perturbations on sub-seasonal forecasts. It includes studying stochastic parameterizations and model uncertainties to improve prediction skill. The proposed stochastic physics experiment under the WWRP/S2S project will analyze the effect of stochastic forcing on forecast timescales. Key topics include forecast configuration strategies and benchmarking spread-error relationships in S2S systems. Collaboration with centers like ECMWF, NCEP, BoM, and JMA will facilitate investigating coupled perturbations and developing advanced techniques for a data-driven forecast approach.

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Advanced Ensemble Generation Techniques for Sub-Seasonal Prediction

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  1. Ensemble generation sub-project Y. Takaya, A. Kumar S2S SG meeting ,1-2 April 2019, ECMWF, Reading, UK

  2. Actions (TBD) presented at SG meeting on 21 Sep. 2018 • Discuss possible coordinated experiment with PDEF • Coupled initialization/perturbations (There is a few systems. Under development at NCEP (CFSv3), ECMWF, JMA…) • Set up of wiki page • Questionnaire about the ensemble generation technique; • Studythe influence of forecast configuration strategiesBurst mode/LAF mode: a preliminary investigation presented at S2D conf. Ens size impact could be studied using real-time forecasts in S2S database. • Benchmark the spread-error relationshipNeed other metrics to deal with non-stationary variability? • Explore the impacts of coupled initial perturbations Under development at a few centers (ECMWF, NCEP, BoM, JMA). Basically to be done at individual centers, summarize the activity with the questionnaire; • Investigate the impact of stochastic parameterizations Discussion with PDEF/WGNE was initiated. (Next slide).

  3. Investigate the impact of stochastic parameterizations WGNE-33/PDEF joint meeting (Oct 9-13, Tokyo) • The Stochastic physics project was discussed at WGNE/PDEF meeting (Judith Berner, Caroline Reynols)Report available at:http://wgne.meteoinfo.ru/wp-content/uploads/2018/11/WGNE33-report.pdfA proposed S2S stochastic physics experiment was also discussed. In this experiment, S2S forecasts would be performed and made available with and without stochastic forcing (particularly SPPT) to examine the impact of stochastic forcing on sub-seasonal to seasonal forecast timescales. This project is proposed under the WWRP/S2S project.

  4. Study the influence of forecast configuration strategies (1) Takaya presentation at International Conferences on Subseasonal to Decadal Prediction, 17-21 September 2018, NCAR, Boulder, CO, USA

  5. Study the influence of forecast configuration strategies (2) Takaya presentation at International Conferences on Subseasonal to Decadal Prediction, 17-21 September 2018, NCAR, Boulder, CO, USA

  6. Study the influence of forecast configuration strategies (3) Takaya presentation at International Conferences on Subseasonal to Decadal Prediction, 17-21 September 2018, NCAR, Boulder, CO, USA

  7. Study the influence of forecast configuration strategies (4) Takaya presentation at International Conferences on Subseasonal to Decadal Prediction, 17-21 September 2018, NCAR, Boulder, CO, USA

  8. Explore the impacts of coupled initial perturbations • Under development at a few centers (ECMWF, NCEP, BoM, JMA). Basically to be done at individual centers, summarize the activity with the questionnaire. • CSIRO: O’Kane et al. 2018Coupled Data Assimilation and Ensemble Initialization with Application to Multiyear ENSO Prediction • ECMWF: ECMWF is developing the weakly CDA. • JMA: My colleagues and I at MRI are working on the CDA and coupled Bred Vector. • Review of the current status of CDA is documented (Penny et al. 2017 BAMS, Ocean’Obs white paper)https://journals.ametsoc.org/doi/10.1175/BAMS-D-17-0036.1

  9. Benchmark the spread-error relationship • To be done, this year…

  10. Backups

  11. Stochastic sub-seasonal to seasonal prediction project: S22S – A proposal • Joint WWRP/WCRP S2S/PDEF/WGNE project targeted as the quantifying the benefits of stochastic parameterization on the S2S timescale • One-time research dataset to complement S2S operational database • Forecasts with and without Stochastically Perturbed Parameterization Scheme SPPT (operational complement) - this schemes is widely used and relatively easy to implement • Quantify impact of SPPT on mean bias, probabilistic skill and process-based verification

  12. S2S Phase 2 ensemble sub-project (science questions) • Relative merits of initial-perturbation strategies for the sub-seasonal timescale (ens. size, burst/LAF, etc.); • Ocean and coupled initial perturbations for potential skill improvements in certain regimes (e.g. MJO, tropical cyclone); • Over-confident predictions due to the discrepancy between the observed and forecast spread resulting from both random and systematic errors; • Understanding and representing model uncertainty (e.g., stochastic physics) for the sub-seasonal timescale; • Forecasting the uncertainty in flow-dependent/non-stationary subseasonal forecasts, spread-skill measure. (c.f. Rodwell et al. 2018 BAMS).

  13. S2S Phase 2 ensemble sub-project (possible topics) • Studythe influence of forecast configuration strategies, including initialization strategies used in the current generation of S2S prediction systems (burst and lagged ensemble) on the forecast spread; • Benchmark the spread-error relationship in the current generation of S2S prediction systems; • Explore the impacts of coupled initial perturbations on the sub-seasonal prediction, and develop techniques of coupled initial perturbations; • Investigate the impact of stochastic parameterizations for the sub-seasonal prediction.

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