title: Contrasting suspended covers reveal the impact of an artificial monolayer on heat transfer processes at the interfacial boundary layer.
abstract: The highly variable performance of artificial monolayers in reducing evaporation from water storages has been attributed to wind speed and wave turbulence. Other factors operating at the interfacial boundary layer have seldom been considered. In this paper, two physical shade covers differing in porosity and reflectivity were suspended over 10 m diameter water tanks to attenuate wind and wave turbulence. The monolayer octadecanol was applied to one of the covered tanks, and micrometeorological conditions above and below the covers were monitored to characterise diurnal variation in the energy balance. A high downward (air-to-water) convective heat flux developed under the black cover during the day, whereas diurnal variation in the heat flux under the more reflective, wind-permeable white cover was much less. Hourly air and water temperature profiles under the covers over 3 days when forced convection was minimal (low wind speed) were selected for analysis. Monolayer application reduced temperature gain in surface water under a downward convective heat flux, and conversely reduced temperature loss under an upward convective heat flux. This 'dual property' may explain why repeat application of an artificial monolayer to retard evaporative loss (reducing latent heat loss) does not inevitably increase water temperature.
authors.affiliation: National Centre for Engineering in Agriculture, University of Southern Queensland, Toowoomba, Queensland 4350, Australia E-mail: Pam.Pittaway@usq.edu.au.
authors.forename: P
authors.initials: P
authors.lastname: Pittaway
authors.affiliation: Escuela Técnica Superior de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Martínez-Alvarez
authors.affiliation: National Centre for Engineering in Agriculture, University of Southern Queensland, Toowoomba, Queensland 4350, Australia E-mail: Pam.Pittaway@usq.edu.au.
authors.forename: N
authors.initials: N
authors.lastname: Hancock
mesh_terms: D018481:Convection; D005233:Fatty Alcohols; D006358:Hot Temperature; D008834:Microclimate; D016062:Porosity; D013499:Surface Properties; D014835:Volatilization; D014867:Water; D014881:Water Supply; D014919:Wind
chemical_list: D005233:Fatty Alcohols; D014867:Water