Seasonal weather forecast for crop yield modeling in Europe is one of the applications of weather risk management, tte variability of weather at different time scales, such as daily, monthly, seasonal and beyond, is one of the factors that determine the growth of field-grown crops, tte key weather parameters for crop prediction are rainfall, temperature and solar radiation, secondary parameters being humidity and wind speed. Crop predictions require forecasts of these variables several weeks or even months ahead to enable informed management decisions, ttere is an increasing demand for climate predictions at different time scales in Europe, because they have valuable benefit for decision-making in the management of European Union agricultural production. Examples of this are monthly forecasts for emergency plans to reduce the impact of warm or cold spells, seasonal forecasts to cope with the remote effects caused by El Niño or La Niña events, inter-annual forecasts as a contribution for the management of food crisis and multi-decadal predictions to design plans to mitigate and adapt to climate change.
In the framework of the EU-funded DEMETER (Development of a European Multimodel Ensemble System for Seasonal to Inter-annual Prediction) project, led by the European Centre for Medium-Range Weather Forecasts (ECMWF, UK), ensembles of global coupled climate models have shown some skill for seasonal climate prediction (Palmer et al., 2004). Meteorological outputs of the seasonal prediction system were used in a crop yield model to assess the performance and usefulness of such a system for crop yield forecasting (Cantelaube and Terres, 2005). An innovative method for supplying seasonal forecast information to crop simulation models was developed. It consisted in running a crop model from each individual downscaled member output of climate models. An ensemble of crop yields was obtained and a probability distribution function (PDF) was derived. Preliminary results of wheat yield simulations in Europe using downscaled DEMETER seasonal weather forecasts suggest that reliable crop yield predictions can be obtained using an ensemble multi-model approach. When compared to the operational system, for the same level of accuracy, earlier crop forecasts are obtained with the DEMETER system. Furthermore, PDFs of wheat yield provide information on both the yield anomaly and the uncertainty of the forecast. Based on the spread of the PDF, the user can directly quantify the benefits and risk of taking weather-sensitive decisions.
ttis project officially ended in September 2003, but the data and results generated are being used by a steadily increasing section of the scientific community (Doblas-Reyes et. al. 2006). tte use of ensembles of seasonal weather forecasts brings additional information for the crop yield forecasts and therefore has valuable benefit for decision-making in the management of European Union agricultural production. Skilful seasonal weather forecasts and related seasonal crop yield forecasts could generate an economical benefit for the CAP.
Seasonal forecasting in Europe is still more at the research level than at practical level. Obstacles for operational application, like mismatch between farmers' needs and the scale and relevance of available forecasts or insufficient understanding by farmers and their advisors will probably remain in near future. Agrometeorologi-cal community in Europe is challenged to help to close this gap in future.
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