Simplifying Sirius: sensitivity analysis and development of a meta-model for wheat yield prediction

A sensitivity analysis and analysis of the structure of the Sirius wheat mo del has resulted in the development of a simpler meta-model, which produced very similar yield predictions to Sirius of potential and water-limited yi elds at two locations in the UK, Rothamsted and Edinburgh. This greatly inc reases the understanding of the nature and consequences of the relationship s implicit within Sirius. The analysis showed that the response of wheat cr ops to climate could be explained using a few simple relationships. The met a-model aggregates the three main Sirius components, the calculation of lea f area index, the soil water balance model and the evapotranspiration calcu lations. into simpler equations. This results in a requirement for calibrat ion of fewer model parameters and means that weather variables can be provi ded on a monthly rather than a daily lime-step, because the meta-model can use cumulative values of weather variables. Consequently the meta-model is a valuable tool for regional impact assessments when detailed input data ar e usually not available. Because the meta-model was developed from the anal ysis of Sirius, rather than from statistical fitting of yield to weather da ta, it should perform well for other locations in Great Britain and with di fferent management scenarios. (C) 2001 Elsevier Science B,V. All rights res erved.