Influence of Climate Variability on Wheat Production in Portugal

Abstract

In this work we describe the temporal evolution of wheat production and yield in Portugal and the spatial context of this production in Alentejo region (Southern Portugal). Then we have identified the geographical extent of this area and related with wheat yield, using remote sensing data. For this purpose, we have used the normalized difference vegetation index (NDVI), retrieved between 1982 and 1999 from the AVHRR instrument. The year-to-year variations in Portuguese vegetation greenness were estimated and related to national wheat yield. A significant con-elation was found over Alentejo region and a validation using Corine2000 land cover map has confirmed the correspondence with arable land code pixels. Finally, we evaluate the relevance of the North Atlantic Oscillation (NAO) pattern in terms of wheat yield. A significant influence of the NAO, associated to spatial patterns of variation of different climatic fields, namely precipitation and radiation, on wheat yield in Alentejo region was found. The most significant monthly correlations were obtained for the two important stages in vegetative cycle, namely: February/March and April to June (NAO/Yield, Precipitation/Yield and Radiation/Yield).