Challenges for numerical weather prediction in the tropics: AMMA legacy

1. Challenges for numerical weather prediction in the tropics: AMMA legacy Aida Diongue NIANG ANACIM METEOROLOGY Senegal

2. Outline • Performance of NWP in the tropics and in Africa • Rainfall variability and impacts • AMMA programme and legacy • Implications for operational forecasting • Conclusion - Recommendations évaluation AERES 15-17 janvier 2008

3. Poor NWP model performance in Tropical Africa ECMWF Stable Equitable Error in Probability Space To monitor Precipitation forecast ECMWF the score measures the error in ‘probability space’ through use of the climatological cumulative distribution function Rodwell et al, 2010

4. Rainfall errros in NWP and climate models Similar errors in NWP and climate models: Misrepresentation of key processes (NWP & Climate models ): dry and moist convection, surface, radiation, turbulence, aerosols… NB: improvement of the model since From Met Office

5. Scores Evolution for Tropics: windfield • Wind RMS @72h is large ~5 m/s 850 hPa) and increases with altitude (~8 m/s 250 hPa) • Dispersion between models is ~1 to 2 m/s (850 to 250 hPa) • Progresses are slow! évaluation AERES 15-17 janvier 2008

6. Tropics: RMS errorsagainst TEMP observations throughforecast range • RMS error against TEMP observations increases fast with the forecast range at the same rate for all models évaluation AERES 15-17 janvier 2008

7. Model performance to predict AEWs in the WAM System at 3 longitudes • Very low score beyond 2 days • More skill for western Sahel • Impact on rainfall forecast évaluation AERES 15-17 janvier 2008 Private communication by Gareth Berry et al. 2008

8. RainfallVariability Over Sahel: Anomalies departuresfrom the mean (1905-2005) 20% 10% 0 17/07/1997 Water Vapor Channel -10% Monsoon onset -20% Niger à Malanville: 106 km²\ Jump of max rainfall [10E-10W] Sultan et al., 2003

9. Complexity of the West African Monsoon System Key features of the West African Monsoon Climate System during Boreal summer Heat Low SAL AEJ ITCZ Cold Tongue Chris Thorncroft

10. Global SST Teleconnections Remote effects of MJO Major River Basins Catchments Vegetation Soil Shallow Cells Pools Vegetation Soil Scale interactions Figure adaptedfrom Redelsperger et al , BAMS 2006 Global 10 km 4 Scale interactions Regional Monsoon Systems 10 km 3 AEWs Mesoscale Mesoscale Convective Systems Intraseasonal scale is a central scale for the understanding of Monsoon variability and its impacts: S2S 10 km 2 Deep Conv Cells Local 10 km 1 Hour Day Season Year Seasonal Cycle Interannual Variability Diurnal Cycle

11. Outline • Performance of NWP in the tropics and in Africa • Rainfall variability and impacts • AMMA programme and legacy • Implications for operational forecasting • Conclusion - Recommendations évaluation AERES 15-17 janvier 2008

12. Outline • Performance of NWP in the tropics and in Africa • Rainfall variability and impacts • AMMA programme and legacy • Conclusion - Recommendations évaluation AERES 15-17 janvier 2008

13. Decision makers Early warning systems, advices … WEATHERFORECASTING & CLIMAT PREDICTION Days Weeks Seaseson Interannual Climate Change Multidisciplinary approach Seamless Vision Redelperger et al. IMPACTS Water Ressources Land Surfaces Ocean Health West African Monsoon Agriculture Aerosols Chemestry

14. Observing strategy (original) ( Gourma Sal ( ( ( Dakar Niamey Ouaga Ouémé Meteor Déploiement SOP Réseau Radio-sondages ( 6 Avions de Recherche Bouées PIRATA Sites de Méso-Echelle Sites auxiliaires SOP Atalante Ocean-Atmosphere-Continental surface measuremens impacts  data (surveys, …) Multi-scale measurements (temporal & spatial) Multi-échelles dans le temps et dans l’espace 3 bateaux

15. AMMA LEGACY • Better understanding of the West African Monsoon Publications: ~ 600 reffered / 10 special issues : J. of GeophysicalResearch (2)/J. of AtmosphericPhysics & Chemistry/J. of Hydrology/Quarterly Journal & ASL (RMS)/Weather & Forecast & J. of Atmospheric Sciences (AMS) /Climate Dynamics • Capacity Building • PHD; ~ 160, 80 Aricans • ~ 40 researchunits for 20 different countries • Masters, Summer schools, workshop • Observations of the WAM: improvement of the operational observation network (soundings…), GPS, driftsondes, surface conditions, satellite, research observations (lidar, radar, aircraft…)  opportunity to evaluate NWP models and the impact of observations évaluation AERES 15-17 janvier 2008

16. AMMA: Impact of using the AMMA radiosonde dataset • New radiosonde stations • Enhanced time sampling • Bias correction for RHdeveloped at ECMWF (Agusti-Panareda et al) • Data impact studies Withvariousdatasets, With and without RH bias correction Number of soundings provided on GTS in 2006 and 2005 Period: 15 July- 15 September, 0 and 12 UTC

17. Similar results obtained at ECMWF Monthly averaged RR better with bias correction AMMA: Impact of using the AMMA radiosonde dataset (2) AMMABC: AMMA + RH bias correction PreAMMA: with a 2005 network NOAMMA: No Radiosonde data CPC: Observations • Positive impact of the assimilation of AMMA dataset • Very poor performances of NOAMMA • Best performance of AMMABC Faccani et al, 2009

18. Assimilation of AMSUB over land • Developments @ Météo-France • to assimilate surface sensitive satellite humidity channels over land (Karbou et al., 2006) • To improve the hydrological cycle over the Tropics, in particular over the AMMA region (Karbou et al., 2009a/b, Impact on TCWV Average over the period 1 Aug-14 Sep’06 TCWV diurnal cycle at TOMB TCWV (EXP-CTL) • Positive impact of the assimilation of AMSU over land • Large impact over Tropics in Monsoon regions • especially over Africa and in region with a poor data coverage • Improvement of the diurnal cycle Karbou et al, 2009a, b évaluation AERES 15-17 janvier 2008

19. Outline • Performance of NWP in the tropics and in Africa • Rainfall variability and impacts • AMMA programme and legacy • Implications for operational forecasting • Conclusion - Recommendations évaluation AERES 15-17 janvier 2008

20. Forecastduring the AMMA-SOP 2006 • An unique experiment at ACMAD(Support WM0, AMMA, Europe (FP6), MF, Médias-France) • Operational forecast during 4 months (JJAS) in 2006 • 2 briefings/day to guide the field experiment • 15 forecasters from 12 West African countries • Tools and methods • Synergie Forecasting System (MF) • 4 Stations at ACMAD fed with NWP products + Observations with the RETIM link • AOC-Web site (Medias, MF)http://aoc.amma-international.org/ • VSAT internet link at ACMAD • Reports, quicklooks, NWP products (ECMWF, UKMET, MF, NCEP, Morocco), diagnostics, research models… • MCS tracking: RDT from SAF-Nowcasting • Development of a forecasting method WASA/F • 2 weeks training for forecasters • Major learning • NWP skill is poor especially for convection • But NWP is very useful for the large scale mass and circulation • Need of observations, adequate NWP products and diagnostics • Need to combine several NWPs • Diversity of methods across West African Forecasters • Need to have a forecasters handbook

21. Forecasters’ Handbook projectLeaded by Parker (University of Leeds) and colleagues • Collaborative programme with the aims of documenting existing good practice in forecasting, and accelerating the translation of new research results into operational forecasting practice. • The document is close to completion and is expected to be published in 2015. • The main challenge: to bridge the scientific gap between the theoretical and operational side • Various new tools for forecasters, including new conventions for plotting of synthetic charts (the West African Synthetic Analysis/Forecast, or WASA/WASF system) and new diagnostics with various case studies. • THORPEX support , specifically by supporting two workshops, at the International Centre for Theoretical Physics (ICTP) in 2009, and in Dakar in March 2013

22. WASA- WASF (West African Synthetic Analysis /Forecast) WASA du 06/08/06 06TU

23. http://isv.sedoo.fr Project • Collaboration betweenSenegalWeather Service and CNRM/MOANA: researchers and forecasters • A real-time website, simple but easily and rapidlyevolving, according to the encounteredneeds and ideas • Use of websitesprovidingcomplementary information (broadercontext) • e.g. MJO: Wheeler’swebsite + NCEP • Regular reports (~2/week) and discussions between Toulouse and Dakar. • Use of the products in operation al forecasting Paper in preparation for BAMS

24. Summary and Recommendations • NWP skill over Tropics and especially over Africa is still poor as compared with extra-tropics • Due to the lack of observations and to the importance of the role played by the physics (dry and moist convection, surface, radiation, turbulence, aerosols…) • Nevertheless large scale thermodynamical and dynamical structures that force convection are better depicted and are very useful for forecasting weather • AMMA allowed to demonstrate the positive impact and the key importance of improving the operational observation networks • Major progresses have been performed in recent years especially in the assimilation area (microwave data) • Efforts to be made by countries to maintain orenhance observing systems • Nevertheless the forecast skill of the water cycle and of precipitation progresses very slowly • Lessons learned during the forecasting exercise and some research results being put in the West African Forecasting guide • New Metrics and better diagnostics adapted to Tropics (and Africa) in the framework of MISVA but need for more particularly for Ensemble prediction • Recommendations: Seamlessness means also that any place in the world get advantage of improvement and availability of weather products to predict particularly for HIW prediction by first easing access to NWP products . évaluation AERES 15-17 janvier 2008