title: Surface freezing of water.
abstract: Freezing, melting, evaporation and condensation of water are essential ingredients for climate and eventually life on Earth. In the present work, we show how surface freezing of supercooled water in an open container is conditioned and triggered-exclusively-by humidity in air. Additionally, a change of phase is demonstrated to be triggered on the water surface forming surface ice crystals prior to freezing of bulk. The symmetry of the surface crystal, as well as the freezing point, depend on humidity, presenting at least three different types of surface crystals. Humidity triggers surface freezing as soon as it overpasses a defined value for a given temperature, generating a plurality of nucleation nodes. An evidence of simultaneous nucleation of surface ice crystals is also provided.
authors.affiliation: Departamento de Teoría de la Señal, Universidad de Alcalá, EPS, N-II km 33,600, 28801 Alcalá de Henares, Spain ; Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Kiruna, Sweden.
authors.forename: J L
authors.initials: JL
authors.lastname: Pérez-Díaz
authors.affiliation: Saint George Tech Ltd., 71-75, Shelton Street, Coven Garden, London, WC2H 9JQ UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Álvarez-Valenzuela
authors.affiliation: MAG SOAR S.L., Av. de Europa, 82, 28341 Valdemoro, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Rodríguez-Celis