NP6.3 | Lagrangian transport and turbulence in the atmosphere and ocean
EDI
Lagrangian transport and turbulence in the atmosphere and ocean
Co-organized by AS5/OS4
Convener: Louis RivoireECSECS | Co-conveners: Silvia Bucci, Jezabel Curbelo, Yongxiang Huang, Tor Nordam, Ignacio Pisso, François G. Schmitt
Orals
| Mon, 15 Apr, 16:15–18:00 (CEST)
 
Room 0.94/95
Posters on site
| Attendance Tue, 16 Apr, 16:15–18:00 (CEST) | Display Tue, 16 Apr, 14:00–18:00
 
Hall X4
Orals |
Mon, 16:15
Tue, 16:15
This session will focus on studies in geophysical fluids including atmospheres and oceans (on Earth and elsewhere) that are approached from a Lagrangian perspective, together with topics associated with turbulence.

Lagrangian tools allow to predict the dispersion of pollutants and track their sources, capture unresolved physics, and reveal transport pathways and barriers between flow regimes that have different dynamical fates. As such, Lagrangian methods are used in a vast array of applications from turbulent scales to planetary scales in the atmosphere, oceans, and cryosphere.

Furthermore, turbulence is a major driver of nonlinear behavior and variability in geophysical fluids, influencing both passive and active scalars via changes in the velocity field and fluxes (air-sea exchanges). As such, turbulence is a key forcing in marine ecology: it modulates the contact rate between organisms and nutrients, re-suspension processes, the formation of blooms and thin layers, and even the adaptation of organisms to their environment.

We invite presentations on topics including – but not limited to – the following:
- Large-scale circulation studies (jets, gyres, overturning circulations) using direct Lagrangian modeling and/or age and chemical tracers;
- Exchanges between reservoirs and mixing studies (e.g. transport barriers in the stratosphere and in the ocean, stratosphere-troposphere exchange);
- Tracking long-range anthropogenic and natural influence (e.g. effects of recent volcanic eruptions and wildfire smoke plumes on the composition, chemistry, and dynamics of the atmosphere, transport of pollutants, dusts, aerosols, plastics, and fluid parcels in general, cirrus seeding by aviation, etc);
- Inverse modeling techniques for the assessment and constraint of emission sources;
- Turbulent flows, physical oceanography, biogeochemistry, marine ecology, marine sciences;
- Lagrangian Coherent Structures;
- Model and tool development, numerical and computational advances.

Session assets

Orals: Mon, 15 Apr | Room 0.94/95

Chairpersons: Silvia Bucci, Jezabel Curbelo, Ignacio Pisso
16:15–16:17
Ocean
16:17–16:27
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EGU24-6434
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NP6.3
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solicited
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On-site presentation
M. Josefina Olascoaga

Sargassum has historically been found in the subtropical North Atlantic gyre where it provides important habitat for diverse marine species. However, since 2011 with the development of the Great Atlantic Sargassum Belt in the equatorial Atlantic, abundance has greatly increased, resulting in shorelines mass stranding. These coastal inundations of Sargassum have major impacts on the ecology, economies, and health of affected areas.
Understanding the Sargassum raft's motion is required to be able to predict the areas that could be affected by Sargassum. The motion of the rafts is fundamentally unlike Lagrangian (i.e., infinitesimally small, neutrally buoyant) particle motion since they represent finite-size, buoyant objects subjected to the action of ocean currents, wind, and waves. In this talk, we will present a Maxey-Riley model for the motion of Sargassum rafts that takes their inertial nature into account as well as the elastic interactions within a raft and physiological changes affecting the structure of the rafts.  This will be accompanied by a discussion of results from field and laboratory experiments used to validate the model. Joint work with F. J. Beron-Vera and G. Bonner.

How to cite: Olascoaga, M. J.: A Maxey-Riley modeling framework for Sargassum raft drift, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6434, https://doi.org/10.5194/egusphere-egu24-6434, 2024.

16:27–16:37
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EGU24-13046
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NP6.3
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ECS
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On-site presentation
Siren Rühs, Erik van Sebille, Aimie Moulin, Emanuela Clementi, and Ton van den Bremer

Marine surface particle dispersal simulations are crucial for addressing societal issues such as plastic pollution, oil spills, biological connectivity, and recovery missions. However, the quality of these Lagrangian simulations depends on how well the underlying numerical model represents the prevalent ocean circulation features.

Here, we investigate how simulated surface particle dispersal changes, if the – often neglected or only approximated – impact of surface waves is included. Under the influence of surface waves, a particle not only moves with the Eulerian current velocity but also experiences a net drift in the direction of wave propagation, known as Stokes drift. Moreover, wave-current interactions result in wave-driven Eulerian currents. We use the output of a coupled ocean-wave model configuration for the Mediterranean Sea to answer the following questions: What is the relative impact of Stokes drift and wave-driven Eulerian currents? How well can the total wave impact be represented by the commonly used approximation consisting of the superposition of Eulerian currents and Stokes drift obtained from independenntly run ocean and wave models?

We find that Stokes drift as well as wave-driven Eulerian currents can have a non-negligible impact on surface particle dispersal. While both tend to act in opposing directions, they do not necessarily cancel each other out, due to different temporal and spatial variability. Our analyses suggest a seasonal dependency of the wave impact. For a major part of the Mediterranean Sea, ocean-wave coupling increases the simulated mean Lagrangian surface speed in winter through a dominant impact of Stokes drift and decreases it in summer through a dominant impact by wave-driven Eulerian currents. Yet, some regions also exhibit a dominance of either Stokes drift or wave-driven Eulerian current impact throughout the year. Consequently, applying the commonly used approximation is not always beneficial for surface particle simulations. The advantage or disadvantage of the approximation compared to neglecting any wave impact depends on the season, region, and Lagrangian measure of interest, and is difficult to estimate a priori. Hence, whenever possible, coupled ocean-wave models should be employed for surface particle dispersal simulations.

 

How to cite: Rühs, S., van Sebille, E., Moulin, A., Clementi, E., and van den Bremer, T.: Non-negligible impact of Stokes drift and wave-driven Eulerian currents on simulated surface particle dispersal in the Mediterranean Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13046, https://doi.org/10.5194/egusphere-egu24-13046, 2024.

16:37–16:47
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EGU24-20185
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NP6.3
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On-site presentation
Guttorm Alendal, Prithvinath Madduri, Anna Oleynik, Helge Avlesen, and James R. Clark

We will report on two studies we have done related to Lagrangian transport of plastic particle in marine waters.

In the first study, we investigate the particle dynamics of tyre-wear microplastics that come from road traffic across two major bridges in Byfjorden, namely the Nordhordland Bridge and the Askøy Bridge. We employ a Lagrangian particle tracking framework, OpenDrift, with background horizontal velocities from Bergen Ocean Model (BOM), paired with a vertical sinking velocity obtained from Stokes law to track individual particle paths along the flow field until they reach the seafloor. The sinking velocity is picked from a distribution that is designed based on results from point source experiments, enabling us to cover the particle dynamics for a spectrum of sinking velocities. The basis of this study lies in using the variability in local currents, by conducting multiple experiments with distinct initial locations and release times to understand the similarities and differences in the footprint. In the particle simulation, the horizontal velocity experienced by individual particles depends on release time which is related to when in the tidal cycle the particle is released. We seek insights to discover potential aggregation zones and their corresponding gradients along the bottom of the fjord. We plan to shed light on ‘how particle dynamics change when we vary the sinking velocity’. These results could be applicable in identifying the mechanisms behind particle transport in fjords and can assist in designing sampling campaigns.

In the second, we assess the amount of transboundary plastic coming along the coast of western Norway, employing a nested modelling approach. We utilize emissions data of buoyant plastics from major European rivers (Meijer et al., 2021), as an input to our Lagrangian particle tracking model simulated using OpenDrift. The background currents are provided by the nested model which includes surface currents from three grids: A 4km model of the North Atlantic - Nordic4K (Lein et al., 2013), An 800m model covering Norway’s coastline - Norkyst800 (Albertsen et al., 2011), and 160m hydrodynamical model - NorFjords160 (Dalsøren et al., 2020). As particles transit through these nested grids, we precisely track the plastic pathways into the western Norwegian fjords around the city of Bergen. Employing this nested grid setup addresses problems with boundary conditions and mass balance. We present the estimates for the fraction of plastic moving into the fjord with focus on relative influence of wind and ocean currents on the transboundary movement of plastic. This study sheds light on processes responsible for near and far field transport, providing valuable insights for agencies working on trans-national pollution laws and implementing ocean clean-up strategies.

How to cite: Alendal, G., Madduri, P., Oleynik, A., Avlesen, H., and R. Clark, J.: Lagrangian modelling of plastic transport in marine waters. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20185, https://doi.org/10.5194/egusphere-egu24-20185, 2024.

16:47–16:57
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EGU24-4656
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NP6.3
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ECS
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On-site presentation
Rahel Vortmeyer-Kley, Bronwyn Cahill, Maximilian Berthold, and Ulrike Feudel

Describing and tracking three-dimensional flow structures in an ocean setting may explain elemental and biodiversity pattern. A possible tool can be finite time coherent sets. These sets are Lagrangian Coherent Structures characterized by minimal leakage and minimal exchange with their surrounding environment.

In oceanic settings, they can be understood as separated waterbodies or eddies playing an important role for transport and mixing processes.

Due to limited interaction with their surroundings, they even influence biological processes by providing competitive advantages for some species, for example, optimal temperature or nutrient conditions.

In a case study of three-dimensional finite time coherent sets in the Western Baltic Sea in May and July 2018, we show some different impacts on biological processes:

  • enhancement of phytoplankton growth in the set's surrounding,
  • transport of cold nutrient rich water from shallower to deeper regions, and
  • the formation of transient, moving dynamical niches with higher temperature inside the coherent set compared to its surrounding, prolonging the life of an existing phytoplankton bloom that is trapped during the formation of the coherent set.

Moreover, different dynamical patterns can be observed inside the finite time coherent sets during their travel and lifetime. Temporal stratification and mixing inside the coherent sets suppress or enhance growth temporally and locally.

In the coherent set’s surrounding, the formation of a “sticking” manifold supports the development of a local phytoplankton bloom in the upper water column.

Our case study in the Western Baltic Sea provides a first step towards understanding the impact of three-dimensional coherent sets on transport processes and phytoplankton growth in the Baltic Sea, as well as, the formation of dynamical pattern inside three-dimensional coherent sets.

How to cite: Vortmeyer-Kley, R., Cahill, B., Berthold, M., and Feudel, U.: Three-dimensional influencers in the Western Baltic Sea: finite time coherent sets and their role for biological processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4656, https://doi.org/10.5194/egusphere-egu24-4656, 2024.

16:57–17:07
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EGU24-3997
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NP6.3
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ECS
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On-site presentation
Tongya Liu and Ryan Abernathey

The methods used to identify coherent ocean eddies are either Eulerian or Lagrangian in nature, and nearly all existing eddy datasets are based on the Eulerian method. In this study, millions of Lagrangian particles are advected by satellite-derived surface geostrophic velocities over the period of 1993–2019. Using the method of Lagrangian-averaged vorticity deviation (LAVD), we present a global Lagrangian eddy dataset (GLED v1.0). This open-source dataset contains not only the general features (eddy center position, equivalent radius, rotation property, etc.) of eddies with lifetimes of 30, 90, and 180 days, but also the trajectories of particles trapped by coherent eddies over the lifetime. We present the statistical features of Lagrangian eddies and compare them with those of the most widely used sea surface height (SSH) eddies, focusing on generation sites, size, and propagation speed. A remarkable feature is that Lagrangian eddies are generally smaller than SSH eddies, with a radius ratio of about 0.5. Also, the validation using Argo floats indicates that coherent eddies from GLED v1.0 exist in the real ocean and have the ability to transport water parcels. Our eddy dataset provides an additional option for oceanographers to understand the interaction between coherent eddies and other physical or biochemical processes in the Earth system.

How to cite: Liu, T. and Abernathey, R.: A global Lagrangian eddy dataset based on satellite altimetry , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3997, https://doi.org/10.5194/egusphere-egu24-3997, 2024.

Turbulence
17:07–17:17
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EGU24-7549
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NP6.3
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ECS
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On-site presentation
Martin James, Francesco Viola, and Agnese Seminara

Odor transport in fluidic environments is a subject of great importance, holding implications for numerous scientific disciplines, including fluid dynamics, biological studies, and engineering disciplines. Odor tracking serves as the foundation for various natural processes, such as the navigation of marine organisms and the foraging behavior of insects. Turbulent fluctuations add another level of complexity to the problem of odor transport in fluidic environments. 

The odor emitted by swimmers is not only influenced by the environment but also by hydrodynamic fluctuations caused by their dynamics. This effect is evident in large swimmers, where the wakes caused by their swimming dynamics could potentially alter odor distribution. However, it is much less clear whether and how hydrodynamic interactions affect the odor distribution of mesoscale swimmers. 

In this work, we explore the coupling of chemical and mechanical signals from mesoscale swimmers (Reynolds number <= 50), immersed in a turbulent open channel flow. We use a model system comprising a collection of swimmers in an open channel flow to explore the propagation and interaction of these signals. Furthermore, we vary their Reynolds numbers and evaluate the consequential changes in odor distribution. We show that the velocity fluctuations due to the swimmers play a significant role in changing the range and distribution of odor signals by screening the intensity and fluctuations of odor distribution downstream. We found substantial differences in odor screening depending on whether the swimmers are 'pushers' or 'pullers', the latter being more effective in screening their odor from predators. Our findings provide valuable insights into the coupling of mechanical and chemical signals of mesoscale swimmers in turbulence with novel considerations regarding the evolutionary preferences of specific swimming modes. 

How to cite: James, M., Viola, F., and Seminara, A.: Impact of Swimmer Dynamics on Odor Transport by Mesoscale Swimmers in Turbulent Environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7549, https://doi.org/10.5194/egusphere-egu24-7549, 2024.

17:17–17:27
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EGU24-8754
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NP6.3
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Virtual presentation
Alexei Sentchev, Duc Thinh Nguyen, Duy Vinh Vu, and Stefano Berti

The study aims to assess turbulent dispersion processes in the coastal regions of northeastern Vietnam, in order to meet the major challenge of monitoring the fate of particulate materials in this part of the East Vietnam Sea, home to the most famous tourist sites and economic sites. The study area is strongly influenced by the freshwater discharge of the Red River, which creates a large river plume, greatly affecting coastal circulation and turbulent dispersion. The monsoon wind profoundly alters the dynamics of the river plume, pushing light surface water seaward over long distances, in summer, and toward the coast, in winter. Sea surveys were organized for the first time in this region in 2022 and 2023 to better characterize the processes controlling coastal flow variability and turbulent dispersion in the plume region and surrounding waters. Surface drifters, released in the  plume region, were tracked during short periods of time, lfrom one to a few days. Current velocity profiling and CTD profiling have been also done. Estimates of the relative dispersion based on surface drifter measurements have revealed that the dispersion regime is local, mainly ballistic and Richardson, induced by turbulent eddies whose size does not exceed a few km. Local wind variability, combined with variations in bathymetry, considerably affects the transport pathways of real drifters and modifies the dispersion regime. A coastal circulation model was used to better assess dispersion processes over the entire study area and for a wide range of variability in the main forcing terms. Virtual surface drifters were tracked in the model velocity field during the surveying periods. The results revealed that, on scale of several days, the transport of passive tracers is considerably affected by irregularities in current velocity fields associated with zones of current convergence and divergence. The results also demonstrated that merging observations with model outputs significantly improves the representation of small scale features of current variability, turbulent mixing, and horizontal stirring of tracers in the plume region.

How to cite: Sentchev, A., Nguyen, D. T., Vu, D. V., and Berti, S.: Assessment of turbulent dispersion in the Red River plume region, northeast Vietnam, based on Lagrangian observations and modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8754, https://doi.org/10.5194/egusphere-egu24-8754, 2024.

17:27–17:37
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EGU24-19490
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NP6.3
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ECS
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On-site presentation
Omer Babiker, Jørgen Aanes, Anqing Xuan, Lian Shen, and Simen A Ellingsen

Gas transfer between ocean and atmosphere is largely governed by the turbulence in the topmost centimetres beneath the free surface. It has been frequently observed that areas of strong positive divergence of the surface-tangential velocity field correspond to efficient surface renewal and consequently increased transfer of gas across the interface. Patches of strong positive surface divergence occur through intermittent upwelling events visible as ``boils'' on the surface.

It has been qualitatively observed that surface-attached ``bathtub'' vortices tend to appear at the edges of upwelling boils, as well as sharp valleys, sometimes referred to as ``scars”. Surface-attached vortices and scars leave imprints on the surface which are particularly simple to detect: the vortices are circular and live for a long time, while scars are sharp and elongated structures.

From direct numerical simulations, we show that a very high correlation exists between the time-dependent number of surface-attached vortices and the mean square of the surface divergence. We use a newly developed method whereby the surface-attached vortices are identified with high precision and accuracy from their surface imprint only.

We also looked at the turbulent structures just beneath the surface-attached vortices and the scars, noting how far under the surface these structures propagate and, thus, how far into the flow subsurface features can be read from patterns on the surface only.

The main application is in remote sensing, as these patterns on the surface can be easily detected using camera footage, for example. These patterns would give estimates of the subsurface quantities without the need for expensive measurement.

How to cite: Babiker, O., Aanes, J., Xuan, A., Shen, L., and Ellingsen, S. A.: What information can be gathered from patterns in turbulent free-surface flows?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19490, https://doi.org/10.5194/egusphere-egu24-19490, 2024.

Atmosphere
17:37–17:47
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EGU24-15051
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NP6.3
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On-site presentation
Michael Blaschek, Lucie Bakels, Marina Dütsch, and Andreas Stohl

Flexpart (FLEXible PARTicle dispersion model) is a numerical model that simulates the dispersion of gases and aerosols in the atmosphere. In order for Flexpart to be used, it must be installed and run on a (super)computer. However, this is associated with obstacles, as not all scientists have access to a supercomputer and there are often technical problems during installation or execution. In this project, we therefore want to develop a Flexpart Web Service (FLEXWEB) in which Flexpart can be run via a website. We will show first results and details on the implementation of a test project for a potential operational service. Flexpart will be containerized and the service will be run in a Kubernetes cluster (in “the” cloud or on premises) to calculate trajectories and make these results easily accessible to users. As soon as the simulation is complete, the output files will be made available for download and displayed graphically. In this way, we hope to simplify access to Flexpart for scientists worldwide.

How to cite: Blaschek, M., Bakels, L., Dütsch, M., and Stohl, A.: FLEXWEB - A flexible particle dispersion model web interface, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15051, https://doi.org/10.5194/egusphere-egu24-15051, 2024.

17:47–17:57
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EGU24-35
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NP6.3
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ECS
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On-site presentation
Henry Schoeller, Robin Chemnitz, Stephan Pfahl, Péter Koltai, and Maximilian Engel

Atmospheric Blocking - also known as Quasi-Stationary Atmospheric States (QSAS) - exert a major influence on mid-latitude atmospheric circulation and are known to be associated with extreme weather events. Previous work has highlighted the importance of the origin of air parcels that define the blocking region, especially with respect to non-adiabatic processes such as moisture transport and latent heating. So far, an objective method for clustering the individual Lagrangian trajectories passing through the QSAS into larger and - more importantly - spatially coherent air streams has not been established, which is the focus of our current work.

    Coherent sets are regions in the phase space of dynamical systems that keep their geometric integrity to a large extent during temporal evolution. We extract a low-dimensional representation of the Lagrangian data via diffusion maps and cluster the trajectories in this representation to estimate coherent sets. Our implementation adapts the existing methodology to the non-Euclidean geometry of Earth's atmosphere and its challenging scaling properties. Several example cases are investigated. 

    The results confirm the existence of spatially coherent feeder airstreams differing with respect to their dynamical properties and, more specifically, their latent heating contribution. Air streams experiencing a considerable amount of latent heating occur mainly during the maturing and maintanence phases of the QSAS and contribute to its stability. In our example cases, trajectories also exhibit an increase in density when passing through the blocking region during its maintanence phase, which is in line with the common understanding of QSAS as regions of high stability. 

How to cite: Schoeller, H., Chemnitz, R., Pfahl, S., Koltai, P., and Engel, M.: Lagrangian Coherence in Atmospheric Blocking, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-35, https://doi.org/10.5194/egusphere-egu24-35, 2024.

17:57–18:00

Posters on site: Tue, 16 Apr, 16:15–18:00 | Hall X4

Display time: Tue, 16 Apr 14:00–Tue, 16 Apr 18:00
Chairpersons: François G. Schmitt, Silvia Bucci, Tor Nordam
Ocean
X4.108
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EGU24-864
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NP6.3
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ECS
Comparing and contrasting tracer dispersion at mesoscale and submesoscale
(withdrawn)
Jim Thomas
X4.109
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EGU24-10533
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NP6.3
Mirna Batistić, Rade Garić, Marijana Hure, Nika Pasković, Laura Ursella, Vanessa Cardin, Giussepe Civitarese, Miroslav Gačić, and Stefano Miserocchi

The open southern Adriatic Sea with a maximum depth of 1242 m is one of the three sites of open deep-sea convection in the Mediterranean Sea. The effects of winter vertical mixing on zooplankton biomass were investigated in the open southern Adriatic Sea in February 2023. Samples were collected using Nansen nets (250 µm mesh size) in eight layers from 0 to 1200 m depth during day and night. The highest biomass values were sampled in the deeper layers below 300 m depth (twice as high as in the upper layers) both in the day and night samples. This could be related to vertical mixing in several pathways. This event was triggered by cold winter conditions and significant heat loss in the previous days, which together with the inflow of high salinity water from the eastern Mediterranean (38.96) caused strong vertical mixing down to 600 m depth. As a result of this event, relatively high chlorophyll-a concentrations (max. 0.33 mgm-3) were measured down to 600 m depth. Therefore, due to the vertical mixing, deeper layers received more food than usual from the surface, so that more food was available for deep-sea zooplankton organisms and they did not have to migrate upwards. The effect of vertical mixing in winter was also clearly visible in some zooplankton organisms that cannot effectively resist the vertical currents, so that they also contribute to the increase in biomass at depth. This is confirmed by the backscattering strength (Sv) data, which show that convective mixing resulted in a smeared Sv signal, indicating that the plankton was transported to deeper layers and no migration took place.

Future studies should consider the influence of open-sea convective events on vertical carbon export in the oligotrophic southern Adriatic.

 

How to cite: Batistić, M., Garić, R., Hure, M., Pasković, N., Ursella, L., Cardin, V., Civitarese, G., Gačić, M., and Miserocchi, S.: Vertical distribution of net zooplankton biomass at the time of winter vertical mixing in the open southern Adriatic Sea (Mediterranean Sea), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10533, https://doi.org/10.5194/egusphere-egu24-10533, 2024.

X4.110
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EGU24-6839
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NP6.3
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ECS
Laura Gomez-Navarro, Erik van Sebille, Clement Ubelmann, Veronica Morales-Marquez, Ismael Hernandez-Carrasco, Joey Richardson, Duarte Soares, Pierre Daniel, Aurelie Albert, Jean-Marc Molines, Julien Le Sommer, and Laurent Brodeau

Understanding the oceanic surface dispersion has important applications in ocean pollution scenarios. Of the different ocean pollution events, some of which have the most impact both on the marine environment and, on society and economy are: marine plastics, oil spills and Sargassum inundation events. Understanding the ocean dynamics that affect their trajectories is vital to simulate their pathways, and thus know their sources and sinks. This can then be used to implement clean-up strategies and to better manage MPAs. It can also help reduce the impact of ocean pollution on the marine environment and some major economic sectors like tourism. High frequency motions have an important impact on the surface dynamics, but high temporal resolution data is necessary to study their effects. New datasets and methodologies have allowed to obtain better representations of high frequency motions. Here, we specifically focus on the high frequency motions due to tides (like for example internal waves), as well as inertial oscillations. We simulate surface trajectories of plastic, oil and Sargassum using the OceanParcels Lagrangian simulator. We focus on three regions in the Atlantic Ocean: Açores Islands, North Atlantic and Tropical Atlantic, respectively. For the plastic simulations we look at the effect of tides by using velocity outputs from a high-resolution model which is a twin simulation without and with tidal forcing. For the oil spills and Sargassum outputs we use a new surface currents product generated by combining velocity data from drifters, high-frequency winds and altimetry to reconstruct high-frequency surface currents. We find that considering high-frequency motions is key to correctly simulate their surface trajectories, but that further work is necessary to understand the ocean dynamics at the fine-scales that can drive the variability in these Lagrangian trajectories.

How to cite: Gomez-Navarro, L., van Sebille, E., Ubelmann, C., Morales-Marquez, V., Hernandez-Carrasco, I., Richardson, J., Soares, D., Daniel, P., Albert, A., Molines, J.-M., Le Sommer, J., and Brodeau, L.: Impact of high-frequency motions on oceanic surface dispersion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6839, https://doi.org/10.5194/egusphere-egu24-6839, 2024.

X4.111
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EGU24-12353
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NP6.3
Juan-Manuel Sayol, Isabel Vigo, David Garcia Garcia, and Cesar Bordehore

In this study we explore the most frequent trajectories of relevant demersal species in the western Mediterranean Sea. In particular, we focus on the Ibiza Channel, a region characterized by the interaction of water masses with distinct properties and by an intense fishing activity. Demersal species are suposed to be in planktonic stage, thus they behave, almost, as passive particles, being driven by the dominant ocean currents. The origin of selected demersal species, their preferred water mass properties, and their temporal variability are evaluated with a set of 2D and 3D backward Lagrangian simulations performed over a high-resolution ocean model. The model we use is the IBI-MFC, part of the Copernicus catalogue with a spatial resolution of 1/36º and 50 vertical layers. Moreover, the Lagrangian tracking is done with OceanParcels software.


With the above approach we get the most probable pathways, and associated water mass characteristics, of those demersal species of interest. Besides, a detailed evaluation of simulated trajectories provides interesting insights on the spatial and temporal changes in the origin of demersal species weeks before they reach the Ibiza Channel. These results are especially important to stablish new biodiversity hotspots that should be protected, e.g., as
eggs and larvae exportation areas.

How to cite: Sayol, J.-M., Vigo, I., Garcia Garcia, D., and Bordehore, C.: Lagrangian tracking of key demersal species in the western Mediterranean Sea: a high-resolution model approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12353, https://doi.org/10.5194/egusphere-egu24-12353, 2024.

X4.112
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EGU24-15796
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NP6.3
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ECS
|
|
Victor de Aguiar, Martina Idžanović, Johannes Röhrs, Malin Johansson, and Torbjørn Eltoft

Predicting trajectories of objects at the ocean’s surface, such as oil slicks or their utilization in search-and-rescue operations, relies heavily on underlying geophysical models. Uncertainties are inevitably present in the modeled ocean and atmospheric fields, and are inherited by the Lagrangian models, thus limiting drift forecasts up to a few days. Estimating and subsequently addressing the uncertainty of the background hydrodynamic model is critical for short-window response and preparedness. Uncertainty estimation in drift modeling has traditionally been performed by varying the magnitude of the so-called wind drift factor. Such an approach results essentially in a greater diffusion of the cloud of virtual particles as the geophysical dynamic system is fundamentally the same. This can be overcome by perturbing by hydrodynamic ensemble generation through e.g. initial condition and surface forcing perturbations.

To derive estimates of the uncertainties, we evaluate short-term (1-5 days) trajectory forecasts forced by the Barents-2.5 km operational ensemble prediction system (EPS) against observed trajectories of undrogued drifters deployed in Fram Strait and Barents Sea. Seventeen low-cost devices (OpenMetBuoy) were deployed in sea ice free conditions during two field campaigns in April and August 2022, respectively, with life spans varying between 10 days and 10 months. Using 48 time-lagged ensemble members, the uncertainty in drift predictions is quantified via error/spread ratio, two-dimensional (2D) rank histograms and reliability diagrams. The ability of the EPS to capture physical processes is verified through rotary auto- and cross-spectral analysis on 5-day segments.

Our results show that the EPS manages to capture the main rotary spectral features well, but it underestimates with up to two orders of magnitude the spectral energy density towards the higher frequencies (> 0.08 cycles per hour) for both regions. High coherence (> 0.7) between observed and modeled drifter velocities, obtained through rotary cross-spectral, was found for the Barents Sea region, decreasing to less than 0.4 for the simulations performed in the Fram Strait. Additionally, we did not find indications that the observed and modeled drifter velocities are coherent to each other relative to the wind forcing in the latter area. 

The error/spread and 2D rank histograms revealed that Barents-2.5 is underdispersive, with the Fram Strait simulations presenting higher deviation from the ideal uniform distribution and higher error/spread (2.5-5) in comparison to the Barents Sea case (1-2). Despite its lack of dispersion, the EPS is nonetheless reliable in the Barents Sea for cumulative traveled distances up to approximately 1 inertial cycle. In Fram Strait, the model over- (under-) estimates trajectory displacements for super- (sub-) inertial frequencies.

Three key outcomes are highlighted in this work: (1) Forcing simulations with wind observations marginally improves the energy spectral density, indicating that modeling improvements should focus on the ocean model; (2) Adding further ensemble members through time-lagging does not necessarily improve ensemble dispersion; (3) Ensemble underdispersion does not imply lack of reliability if the main driving forces (e.g. wind and tides) are well resolved by the model.

How to cite: de Aguiar, V., Idžanović, M., Röhrs, J., Johansson, M., and Eltoft, T.: Time-lagged Ensemble Model Verification for Short-term Prediction of Drifter Trajectories , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15796, https://doi.org/10.5194/egusphere-egu24-15796, 2024.

X4.113
|
EGU24-20175
|
NP6.3
|
ECS
Sara Cloux González, Enrico Ser-Giacomi, Crístobal López, and Emilio Hernández-García

Marine litter, particularly plastic pollution, has become a pressing environmental concern, requiring extensive knowledge of its distribution and effects [Chassignet et al., 2021; Wayman et al., 2021]. Therefore, it is important to consider the intricate interaction between ocean dynamics and the dispersion of marine debris, addressing the different scale processes that influence its distribution, accumulation and fate [Van Sebille et al., 2020]. Coastal areas, characterized by complex hydrodynamics, have a unique balance between atmospheric energy inputs and coastal and seabed dissipation, resulting in distinct dynamic features of the open ocean.


We develop Lagrangian tools aimed to obtain information on 3D motions based on surface observations, combining data from satellite observations, model simulations, and future oceanographic campaigns. Climatologies of these Lagrangian indicators, together with their implications for vertical motions, will be presented.


References


E. P. Chassignet, X. Xu, and O. Zavala-Romero, “Tracking marine litter with a global ocean model: where does it go? where does it come from?”  Frontiers in Marine Science, vol. 8, p. 667591, 2021.


C. Wayman and H. Niemann, “The fate of plastic in the ocean environment – a minireview,” Environmental Science: Processes & Impacts, vol. 23, no. 2, pp. 198–212, 2021.


E. Van Sebille et al., “The physical oceanography of the transport of floating marine debris,” p. 2, 2020.

How to cite: Cloux González, S., Ser-Giacomi, E., López, C., and Hernández-García, E.: Unraveling vertical dynamics: Estimating oceanic transport in marine debris dispersal using circulation structures and Lagrangian tools., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20175, https://doi.org/10.5194/egusphere-egu24-20175, 2024.

X4.114
|
EGU24-10330
|
NP6.3
Ana M. Mancho

In this presentation, I will describe a maritime oil spill case that affected the Eastern Mediterranean and several Middle Eastern countries' shorelines in early 2021 [1]. The sequence of events was successfully reconstructed, supported by remote sensing images and Lagrangian Coherent Structures. The comparison of the performance of various datasets found connections between Lagrangian Coherent Structures and Uncertainty Quantification [2].

Acknowledgments

Support from PIE project Ref. 202250E001 funded by CSIC, from grant PID2021-123348OB-I00 funded by MCIN/ AEI /10.13039/501100011033/ and by FEDER A way for making Europe.

References

[1] G. García-Sánchez, A. M. Mancho, A. G. Ramos, J. Coca, S. Wiggins. Structured pathways in the turbulence organizing recent oil spill events in the Eastern Mediterranean.   Scientific Reports 12, 3662 (2022).

[2] G. Garcia-Sanchez, A.M. Mancho, M. Agaoglou, S. Wiggins. New links between invariant dynamical structures and uncertainty quantification. Physica D 453, 133826 (2023).

How to cite: Mancho, A. M.: Quantifying Uncertainty in Lagrangian Transport for Assessing Environmental Problems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10330, https://doi.org/10.5194/egusphere-egu24-10330, 2024.

X4.115
|
EGU24-12049
|
NP6.3
|
ECS
Dimitrios Antivachis, Kristofer Döös, Lars Axell, Lars Arneborg, and Inga Monika Koszalka

Algal blooms are common in the Baltic Sea during the summer, where they pose a significant threat to coastal services and industries. Lagrangian Coherent Structures (LCS) have been shown to play an important role in driving the mixing and transport of water masses and tracers in other ocean basins, such as the Mediterranean Sea (Antivachis et al. 2023), and are thus expected to have a strong effect on transport processes and the development and spread of algal blooms in the Baltic Sea.

In this work, we use trajectory-derived Largangian diagnostics to investigate the distribution and variability of LCS in the Baltic Sea, using a series of 10-day trajectory experiments during summer 2022. Finite Size Lyapunov Exponent (FSLE), Trajectory Rotation Angle (TRA) and related metrics are
used to assess the impact of LCS on horizontal mixing and dispersion processes in the basin. The potential influence of LCS on the spread and impact of algal blooms by opening/closing off transport pathways and exposing/shielding coastal regions is investigated by relating the spatiotemporal distribution of LCS to surface cyanobacteria concentrations obtained from satellite observations. The LCS regime in the Baltic Sea is compared to the ones observed in the Mediterranean in the author’s previous work (Antivachis et al. 2023). This is the first study to map the LCSs of the Baltic Sea and investigate their impact on algal blooms in that basin.

This work is part of the ongoing ALGOTL project, funded by the Swedish research council for sustainable development (FORMAS), aiming to develop a Lagrangian modelling and forecasting framework for algae growth and dispersion for assessing the risk posed by algal blooms. Particle advection is carried out using velocity fields from the Swedish Hydrological and Meteorological Institute (SMHI) NEMO-Nordic configuration (Hordoir et al. 2019) and the TRACMASS Lagrangian trajectory code (Aldama-Campino et al. 2020).

References

Dimitrios Antivachis, Vassilios Vervatis, and Sarantis Sofianos. Lagrangian coherent structures in the mediterranean sea: Seasonality and basin regimes. Progress in Oceanography, 215:103051, 2023. https://doi.org/10.1016/j.pocean.2023.103051

Hordoir, R., Axell, L., Höglund, A., Dieterich, C., Fransner, F., Gröger, M., Liu, Y., Pemberton, P., Schimanke, S., Andersson, H., Ljungemyr, P., Nygren, P., Falahat, S., Nord, A., Jönsson, A., Lake, I., Döös, K., Hieronymus, M., Dietze, H., Löptien, U., Kuznetsov, I., Westerlund, A., Tuomi, L., and Haapala, J.: Nemo-Nordic 1.0: a NEMO-based ocean model for the Baltic and North seas – research and operational applications, Geosci. Model Dev., 12, 363–386, https://doi.org/10.5194/gmd-12-363-2019, 2019. 

Aldama-Campino, Aitor, Döös, Kristofer, Kjellsson, Joakim, & Jönsson, Bror. (2020, December 17). TRACMASS: Formal release of version 7.0 (Version v7.0-beta). Zenodo. http://doi.org/10.5281/zenodo.4337926

How to cite: Antivachis, D., Döös, K., Axell, L., Arneborg, L., and Koszalka, I. M.: Lagrangian Coherent Structure regimes in the Baltic Sea and impact on algal blooms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12049, https://doi.org/10.5194/egusphere-egu24-12049, 2024.

X4.116
|
EGU24-14231
|
NP6.3
|
ECS
|
Rahul Deogharia, Hitesh Gupta, and Sourav Sil

The Bay of Bengal (BoB) annually experiences four phases of Coastally Trapped Kelvin Waves (CTKWs), namely, the first upwelling (January–March), first downwelling (April–June), second upwelling (July–September), and second downwelling (October–December). The upwelling and downwelling CTKWs are associated with propagating patches of negative and positive Sea-Surface Height Anomaly (SSHA) respectively. The second downwelling CTKW is the strongest and travel farthest . Given that the CTKWs are known to be confined near the coast, their behavior can also be effectively understood using the hyperbolic Lagrangian Coherent Structures (hLCSs) approach, wherein such structures act as barriers to material advection. The hLCSs are a set of material surfaces with pointwise maximal (minimal) repulsion and are referred to a repelling (attracting) hLCSs. 

In this study, we have computed the repelling hLCSs from the climatological (1993–2020) geostrophic currents derived from Archiving, Validation and Interpretation of Oceanographic (AVISO) altimetry data. These hLCSs were found to show close correspondence with the climatological SSHA signatures of the different phases of the CTKWs in the BoB. An even better correspondence was seen between these repelling hLCSs and the gradient of climatological SSHA fields. Moreover, these repelling hLCS were found to be located almost at a distance of Rossby Radius of Deformation (Rd) away from the coast. 

The hLCSs associated with the CTKWs have major implications on the advection patterns of passive tracer fields such as sea surface temperature, sea surface salinity, and chlorophyll-a. Since, these hLCSs act as material barriers, they were found to separate water masses with different thermodynamic and biological properties on either side of the hLCs. This can potentially result in distinct coastal circulations and biological productivity near the coast.

How to cite: Deogharia, R., Gupta, H., and Sil, S.: A Lagrangian Perspective of Coastally Trapped Kelvin Waves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14231, https://doi.org/10.5194/egusphere-egu24-14231, 2024.

Turbulence
X4.117
|
EGU24-7728
|
NP6.3
Mapping the transport of floating macroalgae in sea surface on the basis of high-resolution UAV images
(withdrawn)
Qianguo Xing, Jinghu Li, Jing Ding, Yingcheng Lu, Xiangyang Zheng, and Yingzhuo Hou
X4.118
|
EGU24-13515
|
NP6.3
|
ECS
Oceanic turbulence observations from autonomous profiling floats
(withdrawn)
Anneke ten Doeschate, Jean-Phillipe Juteau, Fabian Wolk, and Rolf Lueck
X4.119
|
EGU24-17084
|
NP6.3
|
ECS
|
|
Kévin Robache, François G. Schmitt, and Yongxiang Huang

The oceans interact and exchange CO2 with the atmosphere through different processes that form the biological and physical pumps. The atmospheric and oceanic partial pressures of CO2 are therefore chemical tracers impacted by numerous forcing processes, including turbulence. Turbulence thus has an impact on the fluctuations of pCO2 and on their difference, the sign of which determines the direction of the air-sea flux of CO2.

Here, we used a published database (Sutton et al., 2019) to study the scaling properties of sea temperature, sea salinity, atmospheric and oceanic pCO2 and their difference ∆pCO2 time series recorded at 38 locations every 3 hours. Fourier spectral analysis revealed scaling for ranges between 3 days and 3 months approximately. The statistics of spectral slopes over this scaling range has been considered. Then, empirical mode decomposition and Hilbert spectral analysis were used to study the intermittency properties of the time series of 3 buoys having a large enough data points. For all three locations the intermittent multifractal properties of pCO2 were considered. Some main parameters were extracted assuming a lognormal multifractal model.

How to cite: Robache, K., Schmitt, F. G., and Huang, Y.: Scaling and intermittent properties of atmospheric and oceanic turbulent pCO2 time series and their difference, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17084, https://doi.org/10.5194/egusphere-egu24-17084, 2024.

Atmosphere
X4.120
|
EGU24-20942
|
NP6.3
Ignacio Pisso, Stephen Platt, Norbert Schmidbauer, Sabine Eckhardt, Nikolaos Evangeliou, Erik Marthinsen, Rona Thompson, and Massimo Cassiani

Following the sabotage of the Nord Stream 1 and 2 subsea pipelines on 26 September 2022, natural gas leaks resulted in unprecedented emissions of methane that were detected by several ICOS stations. As the plume traveled North, the detections occurred mainly in Scandinavia. NILU’s initial modeling activities provided a preliminary estimate of 155 KtonCH4 for the leaks that was made public as a press release. A recent collaborative effortorganized by the United Nations Environment Programme’s International Methane Emissions Observatory (UNEP’s IMEO) provided new model-based pipeline rupture outflow rates. In combination with updated ICOS CH4 time series we updated the estimated release values produced. We discuss the uncertainties associated with the atmospheric modelling for this updated analysis with emphasis on the Lagrangian transport aspects of the problem and the associated uncertainties.

How to cite: Pisso, I., Platt, S., Schmidbauer, N., Eckhardt, S., Evangeliou, N., Marthinsen, E., Thompson, R., and Cassiani, M.: Nordstream pipelines CH4 leak estimates and transport uncertainty using ICOS data and the FLEXPART Lagrangian particle dispersion model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20942, https://doi.org/10.5194/egusphere-egu24-20942, 2024.

X4.121
|
EGU24-2652
|
NP6.3
|
ECS
Lucie Bakels, Daria Tatsii, Anne Tipka, Marina Dütsch, Michael Blaschek, Silvia Bucci, Andreas Plach, Martin Vojta, Petra Seibert, Ignacio Pisso, Sabine Eckhardt, Massimo Cassiani, Christine Groot Zwaaftink, Marie Mulder, and Andreas Stohl

Numerical methods and advanced simulation codes play a crucial role in helping us understand complex atmospheric processes. As technology progresses, it's important to develop sophisticated code for accurate and efficient simulations. In this update to FLEXPART, a Lagrangian model used in numerous studies for the past 30 years, we've made significant improvements. This version of FLEXPART shows improvements in accuracy and computational efficiency. By using native ECMWF coordinates, we reduced conservation errors by about 8-10% for semi-conserved quantities like potential vorticity. The shape of aerosol particles are now properly accounted for, greatly improving the accuracy of the deposition of non-spherical particles (e.g. microplastic fibers). Additionally, the incorporation of OpenMP parallelisation makes the model better suited for handling large input data and extended simulation periods. We've also introduced new methods for the input and output of particles in FLEXPART. Users can now run FLEXPART with their own particle input data, making it more adaptable for specific research scenarios.

How to cite: Bakels, L., Tatsii, D., Tipka, A., Dütsch, M., Blaschek, M., Bucci, S., Plach, A., Vojta, M., Seibert, P., Pisso, I., Eckhardt, S., Cassiani, M., Groot Zwaaftink, C., Mulder, M., and Stohl, A.: FLEXPART-11: Advancements in a Lagrangian Atmospheric Model for Enhanced Accuracy, Efficiency, and Flexibility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2652, https://doi.org/10.5194/egusphere-egu24-2652, 2024.

X4.122
|
EGU24-14799
|
NP6.3
Stephan Henne, Pirmin Kaufmann, Lukas Emmenegger, and Dominik Brunner

Over the last years, the numerical weather prediction (NWP) and climate model ICON has become the operational forecasting tool for several national weather services and research groups. Operational analysis or re-analysis fields from NWP models are often used as input for offline-coupled atmospheric chemistry and transport models. Among the latter, Lagrangian Particle Dispersion Models (LPDMs) allow computationally efficient simulations, especially for point sources such as hazardous releases and for receptor-oriented studies such as determining the sensitivity of a concentration observation to upstream surface fluxes (i.e., estimating concentration footprints). One frequently used LPDM is the FLEXible PARTticle (FLEXPART) model, which is available for inputs from different global and regional NWPs (e.g., ECMWF-IFS, WRF, COSMO). Although these versions differ in the applied horizontal and vertical coordinate systems, they have in common that they interpolate gridded NWP output from a rectangular grid to particle positions. In contrast, ICON solves its state variables on a triangular grid. To make best use of ICON output, a direct interpolation from its native grid to particle positions is required. However, compared to a rectangular grid, where interpolation can be done in a straightforward fashion applying bi-linear or bi-cubic interpolation, interpolation from a triangular grid requires additional considerations concerning the choice of interpolation stencil and weight calculations.

Starting from FLEXPART for COSMO, which shares the same vertical grid system with ICON, we revised and generalized how FLEXPART interpolates from grid input to particle positions. Four different direct interpolation methods were implemented: next neighbor (containing triangle), inverse distance weight, barycentric interpolation, and radial basis function interpolation. The resulting FLEXPART version is runs efficiently with outputs from both COSMO and ICON. Next to the direct implementation, we also evaluated an indirect coupling in which ICON output is first interpolated onto a COSMO-like, staggered grid and then used as input for FLEXPART-COSMO.

Both direct and indirect FLEXPART-ICON approaches were thoroughly evaluated by comparison of individual plume simulations resulting from point sources. As a reference simulation, the same point sources were simulated with the Aerosols and Reactive Trace gases (ART) extension of the ICON model. We discuss differences in the performance between the direct and indirect approach and between the interpolation methods. Computational costs for the different approaches are evaluated and trade-offs between model performance and computational efficiency are discussed. 

How to cite: Henne, S., Kaufmann, P., Emmenegger, L., and Brunner, D.: Offline-Coupling of the Lagrangian Particle Dispersion Model FLEXPART to ICON, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14799, https://doi.org/10.5194/egusphere-egu24-14799, 2024.

X4.123
|
EGU24-15769
|
NP6.3
Knut-Frode Dagestad, Johannes Rohrs, Martina Idzanovic, Edel Rikardsen, and Gaute Hope

Predicting the drift of objects and substances in the ocean is relevant for several important applications, such as assisting search and rescue and oil cleanup operations, and for understanding and analysing the drift and distribution of plastics or fish eggs and larvae in the ocean.

The largest uncertainty of such simulations is normally due to currents obtained from ocean models, in particular for the short-term applications such as oil spill accidents and search and rescue operations. Assimilation of observations help make the ocean models more precise, but unfortunately only a limited amount of observations with high spatial resolution are available.

Trajectory models compensate for the imprecise forcing data by adding horizontal diffusivity, providing a spatial spread to encompass the most likely drift. However, a more realistic spread can be obtained by running an ensemble ocean model, where current fields are perturbed in a more physically sound way.

In this study, we are analysing a set of ocean surface drifters released in the Fram Strait and Barents Sea, within the domain of an 24 member ensemble setup of ROMS with 2.5km pixel size, run operationally by MET Norway.

We explore and demonstrate methods to combine the ensemble current fields to improve the predictability of the drifter trajectories. Also, we demonstrate a method for further improvement of future predictability for situations where a recent part of the drift trajectory is known, e.g. for an object with GPS tracking that has lost connection.

How to cite: Dagestad, K.-F., Rohrs, J., Idzanovic, M., Rikardsen, E., and Hope, G.: Using Ensemble Ocean Currents for Drift Predictions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15769, https://doi.org/10.5194/egusphere-egu24-15769, 2024.