Recent changes and drivers of the atmospheric evaporative demand in the Canary Islands

Abstract. We analysed recent evolution and meteorological drivers of the atmospheric evaporative demand (AED) in the Canary Islands for the period 1961–2013. We employed long and high-quality time series of meteorological variables to analyse current AED changes in this region and found that AED has increased during the investigated period. Overall, the annual ET_o, which was estimated by means of the FAO-56 Penman–Monteith equation, increased significantly by 18.2 mm decade⁻¹ on average, with a stronger trend in summer (6.7 mm decade⁻¹). In this study we analysed the contribution of (i) the aerodynamic (related to the water vapour that a parcel of air can store) and (ii) radiative (related to the available energy to evaporate a quantity of water) components to the decadal variability and trends of ET_o. More than 90 % of the observed ET_o variability at the seasonal and annual scales can be associated with the variability in the aerodynamic component. The variable that recorded more significant changes in the Canary Islands was relative humidity, and among the different meteorological factors used to calculate ET_o, relative humidity was the main driver of the observed ET_o trends. The observed trend could have negative consequences in a number of water-depending sectors if it continues in the future.