Abstract
Many applications related to Earth observation such as monitoring water resources and vegetation to climate change impact analysis, have undergone fast developments in the last few years due to the advancements of methods, models, and the increased availability of data. These applications are characterized through a set of requirements in terms of data needs (Verstraete et al. 2015). Requirements for the robust monitoring of geophysical variables are expressed in terms of six criteria: uncertainty, horizontal resolution, vertical resolution, observing cycle, timeliness, and stability (where appropriate) (OSCAR 2021a) and they apply to a wide range of applications such as hydrology, agricultural meteorology, climate, nowcasting and atmospheric processes.