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Ulrich Lemmin

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Related publications (67)

Insights into the dynamics of the deep hypolimnion of Lake Geneva as revealed by long-term temperature, oxygen, and current measurements

In order to identify or shed light on dominant long-term processes of the deep hypolimnion of Lake Geneva (309 m depth), time series of temperature and horizontal currents and profiles of temperature and oxygen, taken for over a decade in the deepest part ...

American Society of Limnology and Oceanography2020

Wintertime Coastal Upwelling in Lake Geneva: An Efficient Transport Process for Deepwater Renewal in a Large, Deep Lake

Ulrich Lemmin, David Andrew Barry, Rafael Sebastian Reiss, Andrea Cimatoribus

Combining field measurements, 3‐D numerical modeling, and Lagrangian particle tracking, we investigated wind‐driven, Ekman‐type coastal upwelling during the weakly stratified winter period 2017/2018 in Lake Geneva, Western Europe's largest lake (max. depth ...

2020

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

Ulrich Lemmin, David Andrew Barry, Anton Ivanov, Htet Kyi Wynn, Jérôme Béguin, Ludovic Zulliger, Nawaaz Sidharth Gujja Shaik, Jean-Luc Liardon, Philippe Olivier Paccaud, Beat Marcel Geissmann, Abolfazl Irani Rahaghi, Pascal Klaus, Stepan Tulyakov

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

Ulrich Lemmin, David Andrew Barry, 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

Achieving high-resolution thermal imagery in low-contrast lake surface waters by aerial remote sensing and image registration

Ulrich Lemmin, Daniel Sage, David Andrew Barry, Abolfazl Irani Rahaghi

A two-platform measurement system for realizing airborne thermography of the Lake Surface Water Temperature (LSWT) with ~0.8 m pixel resolution (sub-pixel satellite scale) is presented. It consists of a tethered Balloon Launched Imaging and Monitoring Plat ...

2019

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

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

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

Tracking Lagrangian transport in Lake Geneva: A 3D numerical modeling investigation

Ulrich Lemmin, David Andrew Barry, Andrea Cimatoribus

Lake Geneva, the largest freshwater lake in Western Europe, is subject to important environmental pressures from its densely populated shores and watershed. To maintain and improve water quality in this lake, as well as in other enclosed or semi‐enclosed b ...

American Society of Limnology and Oceanography2019

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

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

Ulrich Lemmin, Damien Bouffard, David Andrew Barry, 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

Nonlinear dynamics of the near-shore boundary layer of a large lake (Lake Geneva)

Ulrich Lemmin, Damien Bouffard, David Andrew Barry, Andrea Cimatoribus

We examine near-shore and pelagic current variability in Lake Geneva, a large and deep lake in western Europe, using observations from several measurement locations and a three-dimensional numerical model for the period 2014-2016. Linear internal seiche mo ...

2018

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

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

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

Detection and reconstruction of large-scale coherent flow structures in gravel-bed rivers

Ulrich Lemmin, Mário Jorge Rodrigues Pereira Da Franca

Large-scale flow structures (LSFS) in the streamwise direction are important features of gravel-bed river flows, because they may contribute to sediment transport and gas exchange. In the present study, these structures are detected using Huang's empirical ...

Wiley-Blackwell2015

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

Leman-Baikal: Remote sensing of lakes using an ultralight plane

Ulrich Lemmin, Bertrand Merminod, Natacha Tofield-Pasche, Damien Bouffard, Yosef Akhtman, Dragos Constantin, Martin Rehak, Vincent Maurice Nouchi, Galina Shinkareva

The Leman-Baikal project constitutes an international Swiss-Russian collaborative research initiative in the field of physical limnology. The three-year framework involves the development and deployment of a novel multispectral and hyperspectral remote sen ...

2014

Direct effects of dominant winds on residence and travel times in the wide and open lacustrine embayment: Vidy Bay (Lake Geneva, Switzerland)

Ulrich Lemmin, Florence Bonvin, David Andrew Barry, Tamar Kohn, Roham Bakhtyar, Amir Mehdi Razmi

Numerical simulations were carried out to determine the residence (or flushing) time of water in Vidy Bay (north shore of Lake Geneva) for different meteorological conditions. A hydrodynamic model (Delft3DFLOW) was applied to simulate the flow field in the ...

Springer Verlag2014

Deployment of a dynamic penetrometer from manned submersibles for fine-scale geomorphology studies

Ulrich Lemmin, David Andrew Barry, Nicolas Le Dantec

Dynamic penetrometers reveal information about seafloor strength, stratification, stability, and sediment remobilization. However, positioning is often limited to a range of meters making it difficult to target small-scale geomorphologic features. Deployme ...

Association for the Sciences of Limnology and Oceanography (ASLO)2013

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

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

Kelvin waves in Lake Geneva

Ulrich Lemmin, Damien Bouffard

The passage of Kelvin waves in Lake Geneva after strong wind events was experimentally investigated in 1987 and 2002 using thermistor chains, current meters and Acoustic Doppler Current Profilers (ADCP) probing the whole water column, including the bottom ...

Elsevier Sci Ltd2013

Fine sediment dynamics in unsteady open-channel flow studied with acoustic and optical systems

Ulrich Lemmin, Fereshteh Bagherimiyab Hunkeler

In order to simulate fine sediment dynamics over an armored bed in a tidal river, unsteady accelerating, then steady open-channel flow over a movable (but not moving) coarse gravel bed (D-50=5.5 mm) was studied. A layer of fine sediment (D-50=120 mu m) was ...

Elsevier2012

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