Rainfall estimation from in situ soil moisture observations at several sites in Europe: an evaluation of the SM2RAIN algorithm - Brocca, Luca; Massari, Christian; Ciabatta, Luca; Moramarco, Tommaso; Penna, Daniele; Zuecco, Giulia; Pianezzola, Luisa; Borga, Marco; Matgen, Patrick; Martínez-Fernández, José