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

évaluation AERES janvier Outline 1.Performance of NWP in the tropics and in Africa 2.Rainfall variability and impacts 3. AMMA programme and legacy 4.Implications for operational forecasting 5.Conclusion - Recommendations

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

Rainfall errros in NWP and climate models 4 From Met Office 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

évaluation AERES janvier 2008 From Jean-Philippe lafore, Meteo-France and CNRS Scores Evolution for Tropics: wind field Wind 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 janvier Tropics: RMS errors against TEMP observations through forecast range RMS error against TEMP observations increases fast with the forecast range at the same rate for all models

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

-10% -20% Niger à Malanville: 10 6 km²\ 20% 10% 0 Rainfall Variability Over Sahel: Anomalies departures from the mean ( ) 17/07/1997 Water Vapor Channel Monsoon onset [10E-10W] Sultan et al., 2003 Jump of max rainfall

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

Global SST Teleconnections Remote effects of MJO Mesoscale Convective Systems Deep Conv Cells Monsoon Systems Global Mesoscale Regional Local YearSeasonDay Hour 10 4 km 10 3 km 10 2 km 10 1 km DiurnalCycle SeasonalCycleInterannualVariability Shallow Cells Major River Basins Catchments Vegetation Soil Pools Vegetation Soil Scale interactions Intraseasonal scale is a central scale for the understanding of Monsoon variability and its impacts: S2S Scale interactions Scale interactions Figure adapted from Redelsperger et al, BAMS 2006 AEWs

évaluation AERES janvier Outline 1.Performance of NWP in the tropics and in Africa 2.Rainfall variability and impacts 3. AMMA programme and legacy 4.Implications for operational forecasting 5.Conclusion - Recommendations

évaluation AERES janvier Outline 1.Performance of NWP in the tropics and in Africa 2.Rainfall variability and impacts 3. AMMA programme and legacy 4.Conclusion - Recommendations

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

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

évaluation AERES janvier AMMA LEGACY –Better understanding of the West African Monsoon Publications: ~ 600 reffered / 10 special issues : J. of Geophysical Research (2)/J. of Atmospheric Physics & Chemistry/J. of Hydrology/Quarterly Journal & ASL (RMS)/Weather & Forecast & J. of Atmospheric Sciences (AMS) /Climate Dynamics –Capacity Building –PHD; ~ 160, 80 Aricans – ~ 40 research units 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

AMMA: Impact of using the AMMA radiosonde dataset New radiosonde stations Enhanced time sampling Bias correction for RH developed at ECMWF (Agusti-Panareda et al) Data impact studies With various datasets, 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

Similar results obtained at ECMWF Monthly averaged RR better with bias correction Faccani et al, 2009 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 AMMA: Impact of using the AMMA radiosonde dataset (2)

évaluation AERES janvier 2008 Assimilation of AMSUB over land Karbou et al, 2009a, b TCWV diurnal cycle at TOMB 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 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 TCWV (EXP-CTL)

évaluation AERES janvier Outline 1.Performance of NWP in the tropics and in Africa 2.Rainfall variability and impacts 3. AMMA programme and legacy 4.Implications for operational forecasting 5.Conclusion - Recommendations

20 Forecast during 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) 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

Forecasters’ Handbook project Leaded 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 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

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

Project Collaboration between Senegal Weather Service and CNRM/MOANA: researchers and forecasters A real-time website, simple but easily and rapidly evolving, according to the encountered needs and ideas Use of websites providing complementary information (broader context) – e.g. MJO: Wheeler’s website + NCEP Regular reports (~2/week) and discussions between Toulouse and Dakar. Use of the products in operation al forecasting Paper in preparation for BAMS

évaluation AERES janvier 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.