Analysis of the relationship between yield in cereals and remotely sensed fAPAR in the framework of monitoring drought impacts in Europe

Abstract

Abstract. This study analyses the relationship between satellite-measured fAPAR (Fraction of Absorbed Photosynthetically Active Radiation), which are continuously monitored by the European Drought Observatory (EDO) of the EU’s Copernicus Emergency Management Service, and crop yield data for cereals, which are collected by Eurostat. Different features of the relationship between annual yield and multiple time series of fAPAR, collected during different periods of the year, were investigated. Two key outcomes of the analysis were the identification of the period from March to October as that when the highest positive correlation between fAPAR and yield is detected in Europe on average, and February to May as the period when most of the negative correlation are observed. While both periods align well with the commonly assumed dynamic of the growing season, spatial differences are also observed across Europe. On the one hand, the Mediterranean regions report the highest correlation values (r > 0.8) and the longest continuous periods with positive statistically significant results (up to 7 months), covering most of the growing season. On the other hand, the central European region is characterized by the most limited positive correlation values, with only 2 months or less showing statistically significant results. While marked differences on the overall capability to capture the full dynamic of yield are observed across Europe, fAPAR anomalies seem capable to distinguish between drought and no/drought years in most of the cases if negative yield anomalies are used as a proxy variable for drought impacts.