challenges for numerical weather prediction in the tropics: amma legacy aida diongue niang anacim...
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Challenges for numerical weather prediction in the
tropics: AMMA legacy
Aida Diongue NIANGANACIM
METEOROLOGYSenegal
évaluation AERES 15-17 janvier 2008 2
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
ECMWF
Rodwell et al, 2010
Stable Equitable Error in Probability Space To monitor Precipitation forecastthe 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 15-17 janvier 2008 From Jean-Philippe lafore, Meteo-France and CNRS
Scores Evolution for Tropics: wind field
•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 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 15-17 janvier 2008 7Private communication by Gareth Berry et al. 2008
at 3 longitudes
• Very low score beyond 2 days•More skill for western Sahel •Impact on rainfall forecast
-10%
-20%
Niger à Malanville: 106 km²\
20%10%
0
Rainfall Variability Over Sahel:
Anomalies departures from the mean (1905-2005)
17/07/1997Water 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 SSTTeleconnectionsRemote effects of MJO
Mesoscale Convective Systems
Deep ConvCells
Monsoon Systems
Global
Mesoscale
Regional
Local
YearSeasonDayHour
104 km
103km
102km
101km
Diurnal Diurnal CycleCycle
Seasonal Seasonal CycleCycle
Interannual Interannual VariabilityVariability
Shallow Cells
Major River Basins
Catchments
Vegetation Soil
Pools VegetationSoil
Scale interactionsScale interactions
Intraseasonal Intraseasonal scale is a central scale is a central scale for the scale for the understanding of understanding of Monsoon Monsoon variability and its variability and its impacts: impacts: S2SS2S
Scale interactionsScale interactions Figure adapted from Redelsperger et al , BAMS 2006
AEWs
évaluation AERES 15-17 janvier 2008 11
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 15-17 janvier 2008 12
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
IMPACTSIMPACTS
Water Ressources
Health
Agriculture
Multidisciplinary approach
WEATHERFORECASTING & CLIMAT PREDICTION
Days Weeks Seaseson Interannual Climate Change
Decision makers
Early warning systems, advices … Early warning systems, advices …
Seamless Vision Redelperger et al.
Multi-échelles dans le temps et dans l’espace
NiameNiame
yy
DakarDakarOuagaOuaga
GourmGourmaa
OuéOuémémé
SalSal
Sites de Méso-Sites de Méso-EchelleEchelle
6 Avions de Recherche
Déploiement SOP
Sites auxiliaires SOP
Bouées PIRATABouées PIRATA
Réseau Radio-Réseau Radio-sondagessondages
Atalante
Meteor
Ocean-Atmosphere-Continental surface measuremens
impacts data (surveys, …)
Multi-scale measurements (temporal & spatial)
3 bateaux
Observing strategy (original)
évaluation AERES 15-17 janvier 2008 15
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 correctionPreAMMA: with a 2005 networkNOAMMA: 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 15-17 janvier 2008
Assimilation of AMSUB over land
Karbou et al, 2009a, b
TCWV diurnal cycle at TOMB
• 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
• 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 15-17 janvier 2008 19
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) 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
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
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
http://isv.sedoo.fr
évaluation AERES 15-17 janvier 2008 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 .