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Ulrich Lemmin

Cette personne a quitté l’EPFL

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Publications associées (66)

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A low-cost, autonomous mobile platform for limnological investigations, supported by high-resolution mesoscale airborne imagery

David Andrew Barry, Ulrich Lemmin, Anton Ivanov, Htet Kyi Wynn, Stepan Tulyakov, Abolfazl Irani Rahaghi, Ludovic Zulliger, Jean-Luc Liardon, Philippe Olivier Paccaud, Beat Marcel Geissmann

Two complementary measurement systems – built upon an autonomous floating craft and a tethered balloon – for lake research and monitoring are presented. The autonomous vehicle was assembled on a catamaran for stability, and is capable of handling a variety ...

2019

Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva

David Andrew Barry, Ulrich Lemmin, Abolfazl Irani Rahaghi

The dynamics of spatial heterogeneity of lake surface water temperature (LSWT) at subpixel satellite scale O(1 m) and its effect on the surface cooling estimation at typical satellite pixel areas O(1 km2) were investigated using an airborne platform. The m ...

2019

Parameterization of the logarithmic layer of double-averaged streamwise velocity profiles in gravel-bed river flows

Mário Jorge Rodrigues Pereira Da Franca, Ulrich Lemmin

The logarithmic layer of double-averaged (in time and space) streamwise velocity profiles obtained from field measurements made in the Swiss rivers, Venoge and Chamberonne is parameterized and discussed. Velocity measurements were made using a 3D Acoustic ...

2008

The Importance of Systematic Spatial Variability in the Surface Heat Flux of a Large Lake: A Multiannual Analysis for Lake Geneva

David Andrew Barry, Ulrich Lemmin, Andrea Cimatoribus, Abolfazl Irani Rahaghi

The spatiotemporal surface heat flux (SurHF) distribution over Lake Geneva, the largest lake in Western Europe, was estimated for a 7‐year period (2008–2014). Data sources included hourly maps of over‐the‐lake assimilated meteorological data from a validat ...

American Geophysical Union2019

Basin-scale gyres and mesoscale eddies in large lakes: A novel procedure for their detection and characterization, assessed in Lake Geneva

David Andrew Barry, Ulrich Lemmin, Frédéric Charles Soulignac, Seyed Mahmood Hamze Ziabari, Mehrshad Foroughan

In large lakes subject to the Coriolis force, basin-scale gyres and mesoscale eddies, i.e. rotating coherent water masses, play a key role in spreading biochemical materials and energy throughout the lake. In order to assess the spatial and temporal extent ...

2022

Gyre formation in open and deep lacustrine embayments: The example of Lake Geneva, Switzerland

David Andrew Barry, Alfred Johny Wüest, Ulrich Lemmin, Damien Bouffard, Amir Mehdi Razmi

Numerical simulations were carried out to investigate gyres within open lacustrine embayments subjected to parallel-to-shore currents. In such embayments, gyre formation occurs due to flow separation at the embayment’s upstream edge. High momentum fluid fr ...

Springer Verlag2017

Strong bottom currents in large, deep Lake Geneva generated by higher vertical-mode Poincaré waves

David Andrew Barry, Ulrich Lemmin, Rafael Sebastian Reiss

Although internal seiches are ubiquitous in large, deep lakes, little is known about the effect of higher vertical-mode seiches on deepwater dynamics. Here, by combining entire summer season current and temperature observations and 3D numerical modeling, w ...

Springer Science and Business Media LLC2024

Shear velocity estimates in rough-bed open-channel flow

Ulrich Lemmin, Fereshteh Bagherimiyab Hunkeler

Shear velocity u(*) is an important parameter in geophysical flows, in particular with respect to sediment transport dynamics. In this study, we investigate the feasibility of applying five standard methods [the logarithmic mean velocity profile, the Reyno ...

Wiley-Blackwell2013

Tracing Unconfined Nearfield Spreading of a River Plume Interflow in a Large Lake (Lake Geneva): Hydrodynamics, Suspended Particulate Matter, and Associated Fluxes

David Andrew Barry, Ulrich Lemmin, Htet Kyi Wynn, Frédéric Charles Soulignac, Violaine Florette Piton, Benjamin Daniel Graf

River inflows have a major influence on lake water quality due to their input of sediments, nutrients and contaminants. After leaving the river channel, river waters form a plume and interact with ambient lake waters. Strong hydrodynamic changes take place ...

2022

Improving surface heat flux estimation for a large lake through model optimization and two-point calibration: The case of Lake Geneva

David Andrew Barry, Ulrich Lemmin, Damien Bouffard, Abolfazl Irani Rahaghi, Andrea Cimatoribus

Net Surface Heat Flux (SurHF) was estimated from 2008 to 2014 for Lake Geneva (Switzerland/France), using long‐term temperature depth profiles at two locations, hourly maps of reanalysis meteorological data from a numerical weather model and lake surface w ...

Association for the Sciences of Limnology and Oceanography (ASLO)2018

Ripple formation and sediment-suspension events in unsteady depth-varying open-channel flow

Ulrich Lemmin, Fereshteh Bagherimiyab Hunkeler

The development of ripples and its effects on suspended sediment during unsteady flow was studied experimentally to understand and quantify the processes during floods. Quasi-instantaneous profiles of velocity and sediment concentration were taken simultan ...

Crc Press-Taylor & Francis Group2014

Large-scale coherent flow structures in rough-bed open-channel flow observed in fluctuations of three-dimensional velocity, skin friction and bed pressure

Ulrich Lemmin, Fereshteh Bagherimiyab Hunkeler

The dynamics of large-scale coherent structures (LSCS) are investigated in a rough-bed flow over the whole water column and longitudinal and transverse turbulent fluxes of momentum are compared. The relation between LSCS and fluctuations of skin friction a ...

Taylor & Francis Ltd2018

Effects of natural surfactants on the spatial variability of surface water temperature under intermittent light winds on Lake Geneva

David Andrew Barry, Ulrich Lemmin, Mehrshad Foroughan

The spatial variability of lake surface water temperature (LSWT) between smooth and rough surface areas and its potential association with the natural surfactant distribution in the surface microlayer were investigated for the first time in a lake. In spri ...

2022

Moyens de réduction de bruit des mesures acoustiques de la turbulence - Means of noise reduction in acoustic turbulence measurements

Ulrich Lemmin, Koen Blanckaert

2006

Wind‐Induced Hypolimnetic Upwelling Between the Multi‐Depth Basins of Lake Geneva During Winter: An Overlooked Deepwater Renewal Mechanism?

David Andrew Barry, Ulrich Lemmin, Rafael Sebastian Reiss

Combining field observations, 3D hydrodynamic modeling, and particle tracking, we investigated wind-induced interbasin exchange between the Petit Lac (PL) (depth 75 m) and Grand Lac (GL) (depth 309 m) basins of Lake Geneva in early winter. Following a stro ...

2022

Detecting submesoscale cold filaments in a basin-scale gyre in large, deep Lake Geneva (Switzerland/France)

David Andrew Barry, Ulrich Lemmin, Amir Mehdi Razmi, Seyed Mahmood Hamze Ziabari

Submesoscale filaments are a well-documented feature of oceanic flow fields. Based on the analysis of high-resolution 3D numerical simulations, field observations and remote sensing imagery, this study, carried out in Lake Geneva, Western Europe's largest ...

2022

Field Observations Reveal How Plunging Mixing and Sediment Resuspension Affect the Pathway of a Dense River Inflow Into a Deep Stratified Lake

David Andrew Barry, Ulrich Lemmin

The pathway of dense river inflows into lakes, which affects the lake water quality, is not accurately predicted by existing models. The pathway of a dense riverine inflow in a lake with a submerged canyon is analyzed based on measurements during a 4-month ...

Amer Geophysical Union2024

A New Sensor Platform for Investigating Turbulence in Stratified Coastal Environments

Ulrich Lemmin, Damien Bouffard

Characterizing and quantifying vertical exchange processes is essential for understanding physical and biological dynamics in stratified lakes and oceans. Unfortunately, the role of mixing is still poorly understood because of the challenges of conducting ...

American Meteorological Society2013

Hydro-sedimentary processes of a plunging hyperpycnal river plume revealed by synchronized remote imagery and gridded current measurements

David Andrew Barry, Ulrich Lemmin, Koen Blanckaert

The present knowledge of plunging hyperpycnal river plumes is mainly based on two-dimensional (confined) laboratory experiments. Several hypotheses on three-dimensional (unconfined) flow processes have been made, but not tested in situ. In this field study ...

American Geophysical Union2024

Chimney‐Like Intense Pelagic Upwelling in the Center of Basin‐Scale Cyclonic Gyres in Large Lake Geneva

David Andrew Barry, Ulrich Lemmin, Rafael Sebastian Reiss, Seyed Mahmood Hamze Ziabari, Mehrshad Foroughan

Basin-scale quasi-geostrophic gyres are common features of large lakes subject to Coriolis force. Cyclonic gyres are often characterized by dome-shaped thermoclines that form due to pelagic upwelling that takes place in their center. At present, the dynami ...

2023