Mapping basin scale variable source areas from multitemporal remotely sensed observations of soil moisture behavior

Soil moisture is an important and highly variable component of the hydrologic cycle. Active microwave remote sensing offers the potential for frequent observation of soil moisture at basin and regional scales. Notwithstanding recent advances, the goal of obtaining accurate and reliable measurements or maps of soil moisture from these instruments remains elusive. The main difficulties for active sensors such as synthetic aperture radar (SAR) are the combined effects of soil moisture, surface roughness, and vegetation on the backscattered signal. We show that it is possible to separate soil moisture information from the other physical factors that dominate the radar backscattering, such as topography and land cover, through a principal component analysis of a time series of eight European Remote Sensing (ERS) SAR images. The soil moisture patterns observed in one of the principal components are consistent with the rainfall-runoff dynamics of a catchment and reflect the variable source areas occuring in the vicinity of the river network.3235–3244Pubblicat

Wave interaction with a sea dike using a VOF finite-volume method

This paper represents a solver for numerical simulation of breaking waves, developed at Ghent University using an implicit cellstaggered VOF finite volume approach. The mathematical model is based on unsteady incompressible Navier-Stokes (NS) equations with a free surface. A flux-difference splitting approach with the MUSCL type (or the ENO scheme) and a central-difference scheme are applied for evaluation of the inviscid and viscous fluxes, respectively. A projection method is involved for coupling of the pressure and the velocity. A free surface is tracked with the VOF method, in which the approximate dynamic boundary conditions are implemented. In addition, second- and fourth-order artificial damping terms are introduced to the velocity normal to the cell face. A Sommerfeld radiation condition is implemented at the open boundary to dissipate the energy of outgoing waves. Moreover, cut-cell techniques are utilized for treatment of an arbitrary geometry. The solver can capture many physical phenomena during the interaction of waves with a dike, when a wave run-up and overtopping over an impermeable sea dike are performed in a numerical wave tank

Optimal pattern of interacting wave power devices

The contribution of Wave Energy Converters (WECs) to the renewable energy supply is continuously rising. To produce a considerable amount of electricity, wave power devices or WECs need to be placed in a farm.In a farm WECs interact and the amount of produced electricity is affected to a certain extent, depending on the lay-out of the farm. In order to find the optimal lay-out WECs are studied in a numerical mild-slope type model, generally used for wave propagation in coastal applications. The existing model is adapted by simulating the energy extraction of a WEC through sponge layers.The adjusted model can be used to study the optimal lay-out and electricity production of a farm

Resource utilization and trophic position of nematodes and harpacticoid copepods in and adjacent to Zostera noltii beds

This study examines the resource use and trophic position of nematodes and harpacticoid copepods at the genus/species level in an estuarine food web in Zostera noltii beds and in adjacent bare sediments using the natural abundance of stable carbon and nitrogen isotopes. Microphytobenthos and/or epiphytes are among the main resources of most taxa, but seagrass detritus and sediment particulate organic matter contribute as well to meiobenthos nutrition, which are also available in deeper sediment layers and in unvegetated patches close to seagrass beds. A predominant dependence on chemoautotrophic bacteria was demonstrated for the nematode genus Terschellingia and the copepod family Cletodidae. A predatory feeding mode is illustrated for Paracomesoma and other Comesomatidae, which were previously considered first-level consumers (deposit feeders) according to their buccal morphology. The considerable variation found in both resource use and trophic level among nematode genera from the same feeding type, and even among congeneric nematode species, shows that the interpretation of nematode feeding ecology based purely on mouth morphology should be avoided