Turbulent flow in a meander bend of a lowland river: field measurements and preliminary results

River hydrodynamicsBed roughness and flow resistanc

Modelling of flexible aquatic plants from silicone syntactic foams

In experiments with vegetated flows, natural plants are often represented by artificial surrogates, which eliminate effects of plants physiology to easy fit the experimental set-ups. Using surrogates of flexible aquatic plants, the buoyancy and rigidity are supposed to match those in tissues of the natural plants. This paper introduces a new technique for manufacturing composite surrogates from silicon syntactic foams and reports on laboratory tests, which illustrate that such surrogates respond to flow similarly to the natural plants. Practical applications are illustrated by examples from recent field-based experiments

Hydraulic conditions over bed forms control the benthic fauna distribution in a lowland river (Spree River, Germany).

River engineeringRiver habitat management and restoratio

Numerical study of the statistical characteristics of the mixing processes in rivers

A detailed analysis of statistical characteristics of the vertical mixing process in a horizontally homogeneous and stationary river flow is given. Stochastic models of Langevin type and random displacement models are developed to calculate the statistical characteristics of the vertical mixing. For validation, Langevin type models and random displacement models conventionally applied in this field are compared. All the methods show a good qualitative agreement. However the random diplacement model with constant coefficients is shown to perform with considerable deviations

Changes in three-dimensional flow structure at a river confluence with changes in momentum ratio

River hydrodynamicsTurbulent open channel flow and transport phenomen

Interactions between diurnal winds and floodplain mosaics control the insect boundary layer in a river corridor

Insect flight along river corridors is a fundamental process that facilitates sustainable succession and diversity of aquatic and terrestrial insect communities in highly dynamic fluvial environments. This study examines variations in the thickness of the insect boundary layer (i.e., the pre-surface atmosphere layer in which air velocity does not exceed the sustained speed of flying insects) caused by interactions between diurnal winds and the heterogenous habitat mosaics in the floodplain of a braided river. Based on advective–diffusive theory, we develop and test a semi-empirical model that relates vertical flux of flying insects to vertical profiles of diurnal winds. Our model suggests that, in the logarithmic layer of wind, the density of insect fluxes decreases exponentially with the altitude due to the strong physical forcing. Inside the insect boundary layer, the insect fluxes can increase with the altitude while the winds speed remains nearly constant. We suggest a hypothesis that there is a close correspondence between the height of discontinuity points in the insect profiles (e.g. points with abrupt changes of the insect flux) and the displacement heights of the wind profiles (e.g. points above which the wind profile is logarithmic). Vertical profiles were sampled during three time-intervals at three different habitat locations in the river corridor: a bare gravel bar, a gravel bar with shrubs, and an island with trees and shrubs. Insects and wind speed were sampled and measured simultaneously over each location at 1.5-m intervals up to approximately 17 m elevation. The results support our working hypothesis on close correspondence between discontinuity and displacement points. The thickness of the insect boundary layer matches the height of the discontinuity points and was about 5 m above the bare gravel bar and the gravel bar with shrubs. Above the island, the structure of the insect boundary layer was more complex and consisted of two discontinuity points, one at the mean height of the trees’ crowns (ca. 15 m), and a second, internal boundary layer at the top of the shrubs (ca. 5 m). Our findings improve the understanding of how vegetation can influence longitudinal and lateral dispersal patterns of flying insects in river corridors and floodplain systems. It also highlights the importance of preserving terrestrial habitat diversity in river floodplains as an important driver of both biotic and abiotic (i.e., morphology and airscape) heterogeneit

Montreal Protocol's impact on the ozone layer and climate

It is now recognized and confirmed that the ozone layer shields the biosphere from dangerous solar UV radiation and is also important for the global atmosphere and climate. The observed massive ozone depletion forced the introduction of limitations on the production of halogen-containing ozone-depleting substances (hODS) by the Montreal Protocol and its Amendments (MPA). Further research was aimed at analyzing the role played by the Montreal Protocol to increase public awareness of its necessity. In this study, we evaluate the benefits of the Montreal Protocol on climate and ozone evolution using the Earth system model (ESM) SOCOLv4.0 which includes dynamic ocean, sea ice, interactive ozone, and stratospheric aerosol modules. Here, we analyze the results of the numerical experiments performed with and without limitations on the ozone-depleting substances emissions. In the experiments, we have used CMIP6 SSP2-4.5 and SSP5-8.5 scenarios for future forcing behavior. We confirm previous results relative to catastrophic ozone layer depletion in the case without MPA limitations. The climate effects of MPA consist of additional global mean warming by up to 2.5 K in 2100 caused by the direct radiative effect of the hODS. We also obtained dramatic changes in several essential climate variables such as regional surface air temperature, sea-ice cover, and precipitation fields. Our research updates and complements previous modeling studies on the quantification of MPA benefits for the terrestrial atmosphere and climate.</p