Jäckel, G.

Kunstmann, H.

Laux, P.

Tingem, M.

English

KITopen

1 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Onset of the rainy season and crop yield in Cameroon: Tools and perspectives for CameroonP. Laux1*, H. Kunstmann1, G. Jäckel1, T. R. Munang21 Institute for Meteorology and Climate Research (IMK-IFU), Garmisch-Partenkirchen, Germany2 Climate Change Adaptation Unit, Division of Environmental Policy Implementation (DEPI), United Nations Environment Programme (UNEP), Nairobi, Kenya2 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Rainfall = major limiting factor for agriculture in sub-Saharan Africa (SSA)Economies of SSA highly exposed to rainfall variabilityAgriculture accounts for 35% of the GDP, employs 70% of population> 95% of cropland managed under rainfed conditionsHigh rainfall variability on intra-annual, inter-annual and decadal scales (e.g. severe droughts in 1970s and 1980s)Crucial problem for rainfed agriculture (intra-annual): Decision about the optimal planting datePlanting as early as possible to avoid wasting of valuable growth timePlanting too early may lead to crop failures and high economic lossesMotivationGlobal climate change is expected to aggravate rainfall variability and water scarcity in 21. Century (IPCC, 2007)3 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Cameroon: Spatio-temporal rainfall variability0 50 100 150 200 250 300 35001020 YaoundéDOY01020 Batouri01020 Bamenda01020 Ngaoundéré01020 Garoua           Precipitation (mm)         GarouaNgaoundéréBatouriYaoundéBamenda1090 mm/a1514 mm/a2380 mm/a1500 mm/a1600 mm/a4 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Process-based crop modelling at 5 stations CropSystManagement• Planting date• Ploughing• FertilizationWeather• Temperature• Precipitation• Radiation• CO2Crop Yield (1979-2003)Soil properties5 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)CropSyst model (Stöckle et al., 2003)Multi-year, multi-crop process-based simulation model to study the effect of climate, soil, and management on productivity and environment of cropping systemsCalibration: Parametrisation of phenological (IRA, Cameroon) and crop-specific values (literature)ValidationDifference modeled and observed yields acceptable (< 10%)Represents inter-annual and spatial variability of observed crop yield6 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Coupled Planting Date - Crop Modelling            CropSystManagement• Planting date• Ploughing• FertilizationSoil propertiesWeather• Temperature• Precipitation• Radiation• CO2Crop Yield (1979-2003)AlgorithmOnset Rainy SeasonPlanting date for ech yearSoil properties7 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Algorithm Onset of the Rainy Season (ORS)Fuzzy logic-based ORS approach of Laux et al. (2008) for Volta Basin of West Africa, modified approach of Stern et al. (1981)3 membership functions:µ1: 2 parameters a1, a2Sufficient water at planting stageµ1Rainfall amount within 5-day-period [mm]a1a28 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)µ2b1b2Number of wet days within 5-day-period [days]Algorithm Onset of the Rainy Season (ORS)Fuzzy logic-based approach of Laux et al. (2008) for the Volta Basin of West Africa, modified approach of Stern et al. (1981)3 membership functions:µ2: 2 parameters b1, b2exclude single heavy showers as ORS 9 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Algorithm Onset of the Rainy Season (ORS)Fuzzy logic-based approach of Laux et al. (2008) for the Volta Basin of West Africa, modified approach of Stern et al. (1981)3 membership functions:µ3: 2 parameters c1, c2exclude total crop failureNumber of consecutive days after ORS, in which no dry spell > 6 days occurs [days]  c1c2µ310 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Algorithm Onset of the Rainy Season (ORS)Fuzzy logic-based approach of Laux et al. (2008) for the Volta Basin of West Africa, modified approach of Stern et al. (1981)Total membership grade:µTOT = µ1 · µ2 · µ3IF µTOT  > threshold k [0,...,1], THEN Onset Rainy SeasonORS approach with 7 parameters: k, a1, a2, b1, b2, c1, c2Parameters depend on region (weather, soil) and plant physiological aspects11 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Initialization parameter domain (7 parameters)Randomisation (500 realisations) of  the 7 parametersCalculation of the ORS dates (1979- 2003) using ORS approachSimulation Mean Crop Yield MCY (500 realisations) using CropSyst and ORS dates IterationsParameter domain of best 5% simulationsOptimal parameter domain for definition ORSΔ (MCY) < thresholdΔ (MCY) > thresholdORS parameter optimisation12 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)GarouaYaoundéBatouriNgaoundereBamendaResults of iteration process: station Yaoundé→ Mean attainable crop yield (1979-2003) increases per iteration→ Distribution narrows (CV decreases)13 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)ORS algorithm vs. traditional planting calendarProposed new method for planting dates would have allowed for:→ Increase in mean attainable crop yield: Yaoundé 15%, Garoua 50%→ Crop yield increases in anomalous dry yearsGarouaYaoundéBatouriNgaoundereBamenda14 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Impact of planting date adaptations and CC (2020s/2080s) Compared to traditional planting dates: → Increase of groundnut (maize) yields for Garoua and Batouri  → But: widened distribution for future crop yields: increase in variability!Distribution of mean crop yield at Garoua (2020s)15 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)SummaryCoupled Planting Date - Crop ModellingDeduction of optimal planting rules (planting dates)Significant increase of mean attainable crop yield, particularly at drier northern stations (Garoua, Batouri)Impact CC on future crop yield estimationsGroundnut yields are expected to increase in the 2020s and 2080s, Maize yields are expected to increase (decrease) in the 2020s (2080s)Using ORS approach reduces negative impacts of CC on maize yield(2080s), i.e. at northernmost stationsOUTLOOK: Coupled Planting Date - Crop Modelling for SSA using RCM output16 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Thank you for your attention17 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)18 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)“Challenge” for agricultural management in sub-Saharan AfricaScientifically sound information about the optimal planting date under present and future climate conditions and weak infrastructure19 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Direct CO2 effects + ΔP & ΔT + planting date adaptationsCompared to baseline 1961-1990: → Increase of groundnut yields for the 2020s and 2080s→ Increase (decrease) of maize yields for the 2020s (2080s)  → Aggravation of growing conditions for Bamenda20 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Climate change scenariosDifference (ratio) of the GCM statistics between modeled future climate and baseline climate Application of differences (ratios) on corresponding statistics of observed climate to form a new set of weather generator parameters21 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Impact of climate change on crop productivity1. Daily climate scenarios for 2020s and 2080s based on HadCM3 and GISS, and A2 and B2 scenario (8 scenarios for each station)Tmin, Tmax (Solar radiation)Precipitation2. Atmospheric CO2 conditions for baseline period 1961-1990, 2020s, and 2080s3. Crop yield simulations using future climate scenarios under baseline/future atmospheric CO2 conditions4. Crop yield simulations with/without adaptations of the planting date22 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Cameroon: Factors affecting rainfall variabilityHigh spatial and temporal rainfall variabilityClimate: semi-humid (South) to semi-arid (North)Intertropical Convergence Zone (ITCZ) South: bimodal (april/may & september/october)North: unimodal (august/september)TopographyGarouaYaoundéBatouriBamendaNgaoundéréElevation (m.a.s.l.)-26 - 250 251 - 500501 - 750751 - 1.0001.001 - 1.2501.251 - 1.5001.501 - 1.7501.751 - 2.0002.001 - 3.0003.001 - 4.02423 | P. Laux | Institute for Meteorology and Climate Research (IMK-IFU) | 26.03.09KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)Calibration/Validation CropSystParametrisation crop-specific values (maize, groundnut)Publications (e.g. Tingem et al., 2008)CropSyst user manualPhenological parametrisation (e.g. GDD)Institute of Agricultural Research (IRA) CameroonValidation: 5-year-period of observed yields: Difference between modeled and observed yields acceptableInterannual and spatial variability of crop yields Bild Validation

Onset of the rainy season and crop yield in sub-Saharan Africa - tools and perspectives for Cameroon

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Onset of the rainy season and crop yield in sub-Saharan Africa - tools and perspectives for Cameroon

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