Publications by Ulrich Lemmin | EPFL Graph Search

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In the main river canyon of a deep peri-Alpine lake (Rhône River canyon in Lake Geneva, Switzerland), occasional turbidity currents have been observed and monitored using acoustic Doppler current profilers (ADCP) during summer. It has been hypothesized that floods at catchment basin scale and slides of sublacustrine deltaic deposits are the main cause of these turbidity currents. Here, using discharge and turbidity measurements in the Rhône River, 6 km upstream of Lake Geneva and observations from small sub

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 ...

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 ...

We propose a novel methodology – heat budget decomposition – to identify and quantify different deepwater-renewal processes during a very cold spell in 2012 in a large, deep lake (Lake Geneva, 309-m depth). Combined with field observations and numerical modeling, we find that 1D convective cooling only reached 200-m depth. Instead, cooling of the lake’s deepest layers was due to lateral advection of cold water, revealing the important role of 3D processes during winter deepwater renewal.

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 ...

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 ...

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 ...

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 ...

Lake delta morphology is determined by fluvial input, waves, lake currents, lake-level fluctuations and lake-basin topography. The current-dominated Versoix delta (Petit-Lac of Lake Geneva, Switzerland), has been studied in order to determine the role of wind-driven currents on transport and sedimentation of suspensions. Research included the study of sediment distribution in the lake basin, of currents due to wind forcing and modelling of lateral particle transport of suspended matter by lake currents.

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 ...

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 ...

We describe the development of a BVLOS (Beyond Visual Line-Of-Sight) model aircraft (UAV). The broad design requirements included: 1. BVLOS Legal authorization by the Swiss Federal Aviation authority 2. Suitable for land and water take-offs/landing 3. More than 60 minutes flight autonomy 4. Modularity of the imaging package 5. Real-time IR/RGB imagery Requirements 1 to 3 are driven by the goal of improving estimates of lake surface energy flux, since such fluxes have a major impact on long-term lake tempera

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 ...

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 ...

Hyperpycnal (negatively buoyant) river inflow into lakes and oceans often develops three-dimensional (3D) plunging flow patterns when laterally unconfined. To determine the 3D flow pattern characteristics, laboratory experiments of laterally unconfined plu ...

The dynamics of sediments entering lakes in river plumes is virtually unknown. This field study provides unprecedented evidence of the initiation and evolution of suspended sediment flocculation in the nearfield of the negatively-buoyant Rh & ocirc;ne Rive ...

A novel noise reduction method and corresponding technique are presented for improving turbulence measurements with acoustic Doppler velocimeters (ADVs) commonly used in field studies of coastal and nearshore regions, rivers, lakes, and estuaries. This bif ...

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 ...

We have developed and deployed a Web-based GIS data management framework, which facilitates an effective and highly structured search, retrieval and visualisation of multi-modal scientific data, as well as its subsequent dissemination in multiple and standardised forms beneficial for both the research partners involved in the project and the general public. In the context of the long term objectives of the Élémo project, the developed methodology may be utilised for automated and systematic collection of th

Theoretical studies on oceans and large lakes have shown that submesoscale instabilities in frontal zones tend to reduce horizontal density gradients and enhance vertical density gradients, thereby re-stratifying the Surface Mixed Layer (SML). Submesoscale ...

Ulrich Lemmin

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Sediment connectivity in Alpine basins: From isolated storms to turbidity currents in deep peri-Alpine lakes (examples from the Rhône basin and Lake Geneva, Switzerland)

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

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

A novel methodology to identify and quantify deepwater-renewal processes during winter cooling in a large, deep lake (Lake Geneva)

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

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

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

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

Sediment distribution on a current-dominated lake delta (Versoix delta, Lake Geneva, Switzerland)

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

A New Sensor Platform for Investigating Turbulence in Stratified Coastal Environments

A BVLOS UAV for Lake Surface Imagery

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

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

Unconfined Plunging of a Hyperpycnal River Plume Over a Sloping Bed and Its Lateral Spreading: Laboratory Experiments and Numerical Modeling

From Particles to Flocs: Revealing Where Flocculation Occurs in the Nearfield of a Negatively-Buoyant River Plume in a Large Lake (Lake Geneva)

Improved Turbulence Profiling with Field-Adapted Acoustic Doppler Velocimeters Using a Bifrequency Doppler Noise Suppression Method

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

Collaborative Web-GIS platform for systematic exploration of Lake Geneva

The role of submesoscale filaments in restratification of the surface mixed layer and dissolved oxygen variability in large Lake Geneva: field evidence complemented by Lagrangian particle-tracking