Predictability of the African Drought. Part III: Evaluation of NCAR/CSM and UK Metoffice/PRECIS models

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2 Predictability of the African Drought. Part III: Evaluation of NCAR/CSM and UK Metoffice/PRECIS models Dr. Andre KAMGA Foamouhoue ICTP/ African Drought Conference- June 2008

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4 Motivation Economic and social development in Africa rely quite significantly on rainfall ( eg. GDP loss in Mozambique due to the severity of tropical cyclones related floods in 2000, 10 Billions CFA aid for 2008 to the Agriculture community following very late start of the 2007 summer monsoon in Senegal) It is therefore crucial for Africa s sustainable development to capitalize on substantial investments made by the international community to monitor and predict weather phenomena and particularly rainfall

5 Objectives Highlight strengths and weaknesses of climate models over parts of Africa Suggest approach to handle these deficiencies when using models for forecasting and projections Discuss future research agenda for climate model development/interpretation over region.

6 2006 Some evidences of climate variability Rainfall anomalies for Niger (average of 59 stations between 1961 and 2006) Figure 1 : Anomalies moyennes annuelles de la pluviométrie (en mm) période ,0 150,0 100,0 50,0 0,0-50,0-100,0-150,0-200, Années Anomalies

7 Tmax anomalies Figure 2: Anomalies moyennes annuelles de la température maximale ( C) période ,50 1,00 0,50 0,00-0,50-1,00-1,50 Années

8 Tmin Anomalies Figure 3: Anomalies moyennes annuelles de la température minimale( C ) période ,50 1,00 0,50 0,00-0,50-1,00-1,50-2,00 Années

9 MOIS DE AVRIL 34,0 33,5 33,0 32,5 32,0 31,5 31,0 30,5 30, ANNEES MOIS DE JUILLET 31,5 31,0 30,5 30,0 29,5 29,0 28,5 28,0 27,5 27,0 26, Monthly Tmax for April and July for Libreville-Gabon ANNEES

10 Record Tmin mostly observed during the 80s and 90s Records des temperatures minimales depuis la creation des stations Stations/Localités Tillaberi Niamey Konni Zinder Tahoua Maradi Diffa Mainé Soroa Gouré N Guigmi Magaria Agadez Bilma 10,5 10,4 9,6 7,9 7, ,8 4,5 2,6 2 0,9 2,4- janv-98 janv-82 janv-81 déc-80 déc-80 déc-80 janv-83 déc-80 janv-93 janv-93 janv-82 févr-01 janv-95

11 Record Tmax mostly during the 90s Records des temperatures maximales depuis la création des stations au niger Zinder Dosso Maradi Tahoua Niamey Aero B. Konni Agade z Mainé Soroa Diffa Tillabery Magaria Bilma N'Guigmi 44,6 44,7 45,2 45,6 45,6 45, ,4 46,5 46,8 46,8 47,1 47,2 23/04/ /04/ /02/ /04/ /04/ /04/ /05/ /04/ /06/ /04/ /06/ /05/ /05/1998

12 Number of very hot days/365: More hot days since the 80s. 0,14 0,12 0,1 0,08 0,06 0,04 0, N'Guigmi Niamey Aéro Tillabéry

13 Number of extreme rain events > 60 mm Diffa Magaria Mainé Soroa

14 Changes on discharge annual cycle River Niger in Niamey ( number 3 in Africa) Le fleuve Niger à Niamey - débits journaliers débit (m3/s) / / / / / /

15 Rainfall, malaria and meningitis in Niger J F_M A_M_J J_A_S O_N_D Taux d'attaque m oyen du Paludism e pour Hbts Cum ul m oyen trim estriel de pluie (mm) Taux d'attaque m oyen de la M e n in g ite p our Hbts S1 S5 S9 S13 S17 S21 S25 S29 S33 S37 S41 S45 S49 TA_Trim pluvio_cumul 35 cum ul Pluie hebdom adaire m o y en ( m m ) TA_Hebdo pluvio_cumul

16 Expected global impacts (IPCC reports)

17 Verification of Climate projections Global Model ( NCAR/CSM) Regional Model ( HADRM3 or PRECIS)

18 NCAR/CSM v1.3 described by Blackmon et al.(2001) JJA sahelian observed precip anom(left) and CSM simulated anom(rigth). Base period

19 Same as previously but fortemperature anomalies. Quite frequent warm years since early 80s in the obs and mid 80s in CSM.

20 JJA observed (above) and simulated (below) precip rates ( mm/day)

21 Observed minus simulated precip rates. More rainfall in the CSM over the much of Sahel and the Highlands (Guinean highlands, Jos plateau,and Cameroon mountains, Ethiopian Highlands and its extension probably up to the Drakensberg in South Africa).

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23 PRECIS under predicts extreme temperatures.

24 NCAR/CSM cooling up to 6 K

25 Comparaison PRECIS NCEP Analyses Zonal wind at 200hPa et 600hPa Simulated AEJ and TEJ stronger than observed

26 Annual cycle of temperature Observations( blue); simulations (red). Nov-Mars( Model warming); April-Oct ( Model cooling) Tmax in March instead of April in the Obs R=0.58 R=0.68

27 Annual cycle of Temperature Simulation and observations quite similar R=0.97

28 Systematic Cool bias in the NCAR/CSM

29 Precipitation climatology May and June

30 Same as above but for August and September

31 Annual cycle of precipitation. Early onset, peak and withdrawal on the moonson precipitation well captured R=0.89 R=0.68

32 Annual cycle for Coastal cities R=0.97 R=0.77

33 Less rain in the CSM over Sahel With early onset. Substantial underforecasting over the gulf of Guinea.

34 Annual cycle on a Hovmöller diagram latitude temps

35 Moonsson circulation Stronger in the Model 10

36 Simulated AEJ below Its normal latitude Position. «explain under prediction of rainfall over Sahel?»

37 Simulated TEJ core less intense

38 Warming trend. Observations may be even warmer if the cool bias observed in past climate persists. With bias corrections CSM Temp projections over Africa become closer to other IPCC models. Normal-above normal precip trend more likely if the dry biasis corrected

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40 Interannual variability over Sahel R= R=0.76

41 Gulf of Guinea R=0.77 R=0.87

42 IPCC Models verification for better estimation of uncertainties in scenarios over Africa It is necessary to maintain (CMIP) and strengthen a comprehensive verification of IPCC models over all Africa. Such an experiment may help to better interpret models outputs and significantly improve estimation and communication of projections and related uncertainties for impacts and adaptation in Africa.

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