Coupled modeling of water, vapor and heat in unsaturated soils – Field applications and numerical studies

Steenpaß, Christian

Book/Dissertation / PhD Thesis

FZJ-2013-05769

Coupled modeling of water, vapor and heat in unsaturated soils – Field applications and numerical studies

Steenpaß, C. (Corresponding author)FZJ*

2013
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-854-9

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich . Reihe Energie & Umwelt / Energy & Environment 167, X, 123 S. (2013) = Dissertation, RWTH Aachen, 2013

Please use a persistent id in citations: http://hdl.handle.net/2128/14697

Abstract: The present work is part of the Sonderforschungsbereich TransregioCollaborative Research Center 32 (SFB/TR32). This interdisciplinary research projectfocuses on interaction of energy, water, and carbon between the domains of soil,vegetation, and lower atmosphere and resulting patterns of state variables. Soilsurface water content and temperature patterns provide the lower boundary foratmospheric and the upper boundary for hydrologic problems, making the soil surfacean important interface between both domains. Because of the strong non-linearity ofsoil hydraulic properties (SHP), measureable soil water content and, directly linked byevaporation, temperature patterns develop even at relatively small scales of a fewdecimeters. This link between temperature and water content and the resultingformation of measureable patterns within soils makes consideration of coupled heatand water fluxes inevitable when trying to simulate or predict underlying processes.The present work was conducted in the first research period of SFB TR 32 and focuswas on near surface fluxes and patterns in bare soils. Within this context, the presentthesis consists of three key objectives:First, the influence of neglecting thermal effects on instantaneous fluxes suchas diurnal evaporation and on state variables such as surface temperature and watercontent is studied. Over a period of five days, evaporation, water content andtemperature were calculated using a coupled and an uncoupled modeling approach.Measured meteorological data were taken as upper boundary condition. Both modelswere run assuming wet and dry initial conditions. Results show that with wet initialconditions, differences between coupled and uncoupled approach are negligible. In adry soil, differences in actual evaporation rate in both model approaches resulted inrelatively large differences in modeled soil surface temperatures (SST). In the upperpart of the soil, influence of thermal and isothermal vapor flux components has asignificant effect on the total net water flux (as entirety of liquid water and vapor).Furthermore, the enhancement factor (Cass et al. 1984) used to compensate

Keyword(s): Dissertation

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