5,811 research outputs found
Modelling fine scale route choice of upstream migrating fish as they approach an instream structure
This study used pattern-oriented modelling (POM) to investigate the space use and behavioural response of upstream migrating European river lamprey (Lampetra fluviatilis) to the two-dimensional hydrodynamic conditions created by an instream structure (triangular profile gauging weir). Passive Integrated Transponder (PIT) and acoustic telemetry were used to map the spatial-temporal distribution patterns of lamprey as they migrated upstream. Acoustic Doppler velocimetry and computer modelling were used to quantify the hydrodynamic environment. In adherence with the POM methodology, multiple movement models, incorporating increasingly complex environmental feedback mechanisms and behavioural rules were created and systematically assessed to identify which factors might reproduce the observed patterns. The best model was a spatially explicit Eulerian-Lagrangian Individual Based Model (IBM) that included two simple behaviours: 1) tortuous non-directed swimming when in low flow velocity (< 0.1 m sâ1) and 2) persistent directed (against the flow) swimming in moderate to high flow velocity (â„ 0.1 m sâ1). The POM indicated that flow heterogeneity was an important influence of lamprey space use and that simple behavioural rules (i.e. two separate movement behaviours in response to flow velocity) were sufficient to reproduce the main movement pattern observed: avoidance of flow recirculating regions near the banks. The combination of field telemetry, hydrodynamic modelling and POM provided a useful framework for systematically identifying the key factors (hydrodynamic and behavioural) that governed the space use of the target species and would likely work well for investigating similar relationships in other aquatic species
Investigating summer thermal stratification in Lake Ontario
Summer thermal stratification in Lake Ontario is simulated using the 3D
hydrodynamic model Environmental Fluid Dynamics Code (EFDC). Summer temperature
differences establish strong vertical density gradients (thermocline) between the epilimnion
and hypolimnion. Capturing the stratification and thermocline formation has been a
challenge in modeling Great Lakes. Deviating from EFDC's original Mellor-Yamada (1982)
vertical mixing scheme, we have implemented an unidimensional vertical model that uses
different eddy diffusivity formulations above and below the thermocline (Vincon-Leite,
1991; Vincon-Leite et al., 2014). The model is forced with the hourly meteorological data
from weather stations around the lake, flow data for Niagara and St. Lawrence rivers; and
lake bathymetry is interpolated on a 2-km grid. The model has 20 vertical layers following
sigma vertical coordinates. Sensitivity of the model to vertical layers' spacing is thoroughly
investigated. The model has been calibrated for appropriate solar radiation coefficients and
horizontal mixing coefficients. Overall the new implemented diffusivity algorithm shows
some successes in capturing the thermal stratification with RMSE values between 2-3°C.
Calibration of vertical mixing coefficients is under investigation to capture the improved
thermal stratification
Mammalian Brain As a Network of Networks
Acknowledgements AZ, SG and AL acknowledge support from the Russian Science Foundation (16-12-00077). Authors thank T. Kuznetsova for Fig. 6.Peer reviewedPublisher PD
Maine Cooperative Fish and Wildlife Research Unit and Department of Wildlife, Fisheries, and Conservation Biology 2018 Report to Cooperators
The Maine Cooperative Fish and Wildlife Research Unit and the University of Maine Department of Wildlife, Fisheries, and Conservation Biology summarized the past yearâs research, accomplishments, and activities in this annual report
An acoustic view of ocean mixing
Knowledge of the parameter K (turbulent diffusivity/"mixing intensity") is a key to understand transport processes of matter and energy in the ocean. Especially the almost vertical component of K across the ocean stratification
(diapycnal diffusivity) is vital for research on biogeochemical cycles or greenhouse gas budgets.
Recent boost in precision of water velocity data that can be obtained from vessel-mounted acoustic instruments (vmADCP) allows identifying ocean regions of elevated diapycnal diffusivity during research cruises - in high horizontal resolution and without extra ship time needed.
This contribution relates acoustic data from two cruises
in the Tropical North East Atlantic Oxygen Minimum Zone
to simultaneous field observations of diapycnal diffusivity:
pointwise measurements by a microstructure profiler
as well as one integrative value from a large scale Tracer Release Experiment
Numerical modeling of thermal bar and stratification pattern in Lake Ontario using the EFDC model
Thermal bar is an important phenomenon in large, temperate lakes like Lake
Ontario. Spring thermal bar formation reduces horizontal mixing, which in turn, inhibits the
exchange of nutrients. Evolution of the spring thermal bar through Lake Ontario is
simulated using the 3D hydrodynamic model Environmental Fluid Dynamics Code (EFDC).
The model is forced with the hourly meteorological data from weather stations around the
lake, flow data for Niagara and St. Lawrence rivers, and lake bathymetry. The simulation is
performed from April to July, 2011; on a 2-km grid. The numerical model has been
calibrated by specifying: appropriate initial temperature and solar radiation attenuation
coefficients. The existing evaporation algorithm in EFDC is updated to modified mass
transfer approach to ensure correct simulation of evaporation rate and latent heatflux.
Reasonable values for mixing coefficients are specified based on sensitivity analyses. The
model simulates overall surface temperature profiles well (RMSEs between 1-2°C). The
vertical temperature profiles during the lake mixed phase are captured well (RMSEs <
0.5°C), indicating that the model sufficiently replicates the thermal bar evolution process. An
update of vertical mixing coefficients is under investigation to improve the summer thermal
stratification pattern. Keywords: Hydrodynamics, Thermal BAR, Lake Ontario, GIS
Recommended from our members
Designing Sustainable Landscapes: Project Overview
Project overview [updated 3/17/2017] -- This 50-page document is intended to serve as a general description of the DSL project, including an overview of our approach to meeting the project goals and objectives. This is the one document to rule them all and THE document to read to get a pretty good picture of the DSL project and our LCAD model and the various data products produced. This document is fairly detailed, but makes references to other more detailed documents (see below) that provide the technical details of our modeling approach. It is highly recommended that you read this document before attempting to read any of the other technical documents, as this document provides the overall framework of the project and establishes the context for the more specific technical documents
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