The 2016 Antarctic sea ice extent drop was a rapid decline that led to persistent low sea ice conditions. The drop followed a period of stability and even slight sea ice extent increase: this sudden change from extreme high values to an absolute minimum, which occurred in less than two years, is distinctive of this event, together with the lack of recovery that ensued.

Even though new record lows have been recently established, there is still a lot to uncover on the dynamics of the 2016 drop. While the event was triggered by atmospheric forcing, the potential preconditioning role of the ocean is unclear. To shed light on it, we perform sensitivity experiments with a fully-coupled regional climate model, which is re-initialized in January 2016 using different ocean and sea ice conditions but keeping boundary forcings in the atmosphere and ocean unchanged. We show that the state of the Southern Ocean in early 2016 does not determine whether the drop occurs or not, but indeed has an impact on its amplitude, regional characteristics and subsequent sea ice recovery.

This dramatic drop is unprecedented in our current observational record, but it is possible that other similar events have occurred before the beginning of the satellite era. We explore this possibility in a new spatial reconstruction of atmospheric and sea ice variables covering 1958-2023, built using a data assimilation method that combines station-based observations and results from large ensembles of simulations. Additionally, we force a sea ice-ocean model with the atmospheric reconstruction to estimate the oceanic variations. Our results indicate that a drop similar to the 2016 one occurred at the end of the 1970s. We then compare the spatial patterns and changes during the two events and investigate the links between the sea ice, ocean and atmosphere.

How to cite: Mezzina, B., Goosse, H., Huot, P.-V., Marchi, S., Van Lipzig, N., Dalaiden, Q., Francis, F., and Fogt, R.: What was the contribution of the ocean to the 2016 Antarctic sea ice extent drop and was this event unprecedented?, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-1143, https://doi.org/10.5194/ems2024-1143, 2024.

Atmospheric blocking describes a quasi-stationary weather pattern in midlatitudes which is characterised by a disruption of the westerly flow. Within the blocking anticyclone, large-scale subsidence of air effects dissipation of clouds whereas the precipitation rate increases around the block. The stationarity of the weather system increases the probability of extreme events as heatwaves, droughts or floods. Reanalyses show (multi)decadal variability of blocking frequency. This finding encourages the investigation of potential drivers of blocking, i.e. parameters in the climate system favouring or hampering the occurrence of blocking. One important driver is the variability of sea surface temperatures (SST) in the North Atlantic. In this study, we focus on a region in the south of Greenland and investigate the relationship between SST anomalies in that region and blocking in reanalyses and a subset of selected CMIP6 climate simulations. The region in the south of Greenland is known as the so-called “North Atlantic Warming Hole” because the SST trend is negative unlike in overwhelming parts of the ocean. The negative SST trend in the south of Greenland increases the temperature gradient to surrounding, warming areas resulting in a modification of the atmospheric circulation over the Atlantic and Europe and consequently in the frequency of blocking. Our results show a decreased blocking frequency over the North Atlantic in the case of a strong warming hole, i.e. in the case of a strong negative SST anomaly in the south of Greenland. The effect is strongest in winter. Over Europe, blocking frequency tends to be higher than on average. A comparison of reanalyses and CMIP6 simulations reveals that the climate models are neither able to simulate the SST trend in the North Atlantic properly nor the link between SST anomalies and blocking. Furthermore, different realisations of one model show different SST trends and different blocking patterns indicating an incomplete modelling of physical processes and feedbacks.

How to cite: Lohmann, R. and Ahrens, B.: How North Atlantic SST Anomalies Modify the Occurrence of Atmospheric Blocking, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-828, https://doi.org/10.5194/ems2024-828, 2024.

Many processes happen at the air-sea interface. Ocean-atmosphere exchange energy (heat, moisture and momentum), mass (precipitation, evaporation).

Ocean sea surface thermal structures affect the stability of the air-column and its properties through dynamical and thermodynamical processes within the marine atmospheric boundary layer (MABL). Such processes severely impact on sensitivity of surface fluxes, wind and cloud cover to fine scale variations of sea-surface temperature (SST). Moreover, nonlinearities in the fluxes of momentum, heat, freshwater and gases make the small scales important.

This study addresses the role of the ocean fine scales in north-west tropical Atlantic Ocean air-sea interactions, with the goal of evaluating the MABL statistical response to SST variability using cloud-resolving regional numerical simulations of the atmosphere and ocean. This is to quantify the physical process that can explain the modulation of low-level clouds and surface fluxes by SST variability.

Recent field campaign (EURECA and ATOMIC) have collected a wealth of data to study the link between circulation, clouds and air-sea coupling; deSzoeke et al. (2021) and Acquistapace et al. (2022) show that the increased MABL turbulence over warm SST is linked to enhanced low-level cloudiness because the MABL moisture is exported above the lifting condensation level (LCL). They do so in single case studies from in situ (ship) data.

Using numerical simulation of such region, we can extend the analysis of the entire EUREC4A region. We found that SST at the sub-mesoscale affects the air column stability and, therefore, the entrainment of dry and outer-MABL air. The main effects of such entrainment are visible in the dynamics of the mixed layer, both in terms of relative humidity (RH) response and in the vertical exchange of horizontal momentum. Changes in RH are reflected on surface fluxes and low-level clouds.

How to cite: Borgnino, M., Storer, A., Meroni, A., Desbiolles, F., and Pasquero, C.: The lower atmospheric response to SST sub-mesoscale variability: low level clouds and surface fluxes, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-597, https://doi.org/10.5194/ems2024-597, 2024.

How to cite: Paredes-Fortuny, L., Pastor, F., and Khodayar, S.: Physical drivers of marine heat waves intensification in the presence of atmospheric heat waves in the Mediterranean, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-859, https://doi.org/10.5194/ems2024-859, 2024.

The Northwest European shelf experienced unprecedented surface temperature anomalies in June 2023 (anomalies up to 5 °C locally, north of Ireland). The shelf average underwent its longest recorded category II marine heatwave (2.9°C anomaly for 16 days). With state-of-the-art observation and modelling capabilities, we completed an in-depth analysis of its origins, its feebacks on the weather and its likelihood of future recurrence. We showed the marine heatwave developed quickly due to strong atmospheric forcing (record high level of sunshine, weak winds, tropical air) and record weak wave activity under two weeks of anticyclonic weather regimes. Additionally, tidal activity (neap/spring tide) modulated the marine heatwave and contributed to its spatial heterogeneity. Once formed, this shallow marine heatwave fed back on the weather: over the sea it reduced cloud cover, helping to sustain the marine heatwave itself. Over land, it contributed to breaking June mean temperature records and to enhanced convective rainfall through stronger, warmer and moister sea breezes. This marine heatwave was intensified by the last 20-year warming trend in sea surface temperatures. Such sea surface temperatures are projected to become commonplace by the middle of the century under a high greenhouse gas emission scenario. This study was enabled by strong collaborations between observers and modellers of the ocean, waves and atmosphere. It highlights the necessity of long-term ocean observation for monitoring regional seas, complemented by regional reanalyses and climate projections. It also illustrates the usefulness of regional coupled systems for process understanding, short term weather forecasting and their potential for adding value to regional climate information.

How to cite: Berthou, S. and the Met Office, Plymouth Marine Lab, National Oceanography Centre, Scottish association for marine science (UK), Marine Institute (Ireland): Exceptional atmospheric conditions in June 2023 generated Northwest European marine heatwave which contributed to breaking land temperatures records, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-963, https://doi.org/10.5194/ems2024-963, 2024.

The AROBASE (AROme-BAsed coupled SystEm) project of CNRM aims to assemble a multi-coupled regional modelling platform of the physico-chemical atmosphere, the ocean (including sea ice and marine biogeochemistry), the waves and the continental surfaces (soil, vegetation, cities, snow, lakes and rivers), at kilometric scale.

In this context, a new high-resolution regional ocean configuration of the NEMO model has been developed. Named FRA36, it covers the maritime domain around mainland France with a resolution of ~2.5 km (ORCA 1/36° grid).
In order to prepare the future ocean-atmosphere coupled system, FRA36 is first used in a configuration forced by the operational analyses of the AROME-France atmospheric model, at a horizontal resolution of 1.3 km and a 3h temporal resolution. FRA36 uses the global Copernicus Marine Service operational oceanographic productions with data assimilation (GLO12 analyses product) for initialisation and boundary conditions.
We use this configuration to reproduce and analyse the summer 2022 succession of marine heatwave events around mainland France (English Channel, Bay of Biscay, North-Western Mediterranean Sea), using a continuous 3-month ocean simulation initialised the 1^st of June 2022.

First, the spatial and temporal evolution of the Sea Surface Temperature (SST) in this simulation is validated using satellite products. FRA36 reproduces well the succession of observed long-lasting warming periods, interspersed with sudden cold spells. Then, heat budgets in the ocean mixed layer are used to separate atmospheric (solar and non-solar fluxes) and oceanic (advection, mixing, entrainment) contributions to surface and sub-surface temperature variations. Following on from the Guinaldo et al. 2023 study, we here take advantage of the added value of having a 3D oceanic component, including explicit tides, and the atmospheric forcing at high spatio-temporal resolution from AROME-France, to characterise the respective atmospheric and oceanic contributions in the occurrences, maintenances and ends of this succession of high-stakes events.

How to cite: Beuvier, J., Lebeaupin Brossier, C., and Guinaldo, T.: Modelling the summer 2022 marine heatwave around France: disentangling atmospheric and oceanic contributions, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-270, https://doi.org/10.5194/ems2024-270, 2024.

Since the 1970s, the West Antarctic and the Antarctic Peninsula have experienced dramatic warming during austral spring. This study investigates the mechanism behind this phenomenon by analyzing observations and utilizing the Community Atmosphere Model version 4 (CAM4). Specifically, it focuses on how the tropical Pacific and Indian Ocean temperature anomaly mode (PIM) influences surface air temperature (SAT) anomalies across the West Antarctic during austral spring. The positive phase of the PIM is characterized by positive sea surface temperature anomalies (SSTAs) in the tropical central-eastern Pacific and western Indian Ocean, along with negative SSTAs in the Maritime Continent. This configuration leads to the generation of two branches of stationary Rossby wave trains originating from the tropical central Pacific and southeastern Indian Ocean. These waves propagate towards the West Antarctic, with an anticyclonic anomaly forming over the Amundsen Sea. The northerly winds transport warmer air to the Ross-Amundsen Seas, while southerly winds bring colder air to the Antarctic Peninsula-Weddell Sea region. This results in a dipole pattern of SAT anomalies over the West Antarctic. The dominance of SSTAs in the tropical central-eastern Pacific, particularly around the Maritime Continent, plays a crucial role in this process. Additionally, SSTAs in the western Indian Ocean, combined with those over the Maritime Continent, further contribute to the western pole of the SAT anomalies. Importantly, simulations incorporating prescribed PIM forcing accurately reproduce the observed dipolar SAT response across the West Antarctic, which highlights the necessity of considering the tropical Pacific and Indian Oceans as a unified system when studying Antarctic climate dynamics.

How to cite: Duan, A. and Zhang, P.: Connection between the Tropical Pacific and Indian Ocean and Temperature Anomaly across West Antarctic, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-108, https://doi.org/10.5194/ems2024-108, 2024.

On September 2-4, 2023, a heavy precipitation event (HPE) affecting numerous places of the Iberian Peninsula and Balearic Islands, provoked very high-socioeconomic impacts with several floods, damages to the basic and critical infrastructures and three fatalities in the Iberian central area. Previous to the event, the weather pattern over Europe was governed by two prominent ridges in the North Atlantic basin and the Mediterranean Sea, and a deep trough covering a large part of Western Europe. The combination of a deepening trough and the strengthening of two ridges, extending from the Azores to the British Isles and from Tunisia to the English Channel, induced the formation of a cut-off low over the western part of the Iberian Peninsula. At surface, a low was formed. Such setup in juxtaposition with very high Mediterranean and North Atlantic SSTs promoted vorticity advection and a high amount of moisture in low-levels.

In this study, the response to a warming climate that would affect this HPE at the end of the century is studied by applying the Pseudo-Global Warming Approach (PGWA). The SSP5-8.5 scenario of several climatic models from CMIP6 is used to obtain the climate change increment [FUTURE – PRESENT] needed to apply the PGWA. The increments are computed for all the prognostic variables and added to the IFS analysis to be used as initial/boundary conditions. The WRF-ARW model is used to simulate the event. A control simulation is performed using the IFS analysis as initial conditions without perturbation to compare it with the future-like climate simulation.

The results indicate notable changes in the surface low in a future-like climate, affecting to low-level moisture fluxes. The precipitation distribution is modified, with significant increments in the southern of the Iberian Peninsula and the Mediterranean coast. Although in the future-like climate simulation, the places of the socioeconomic impacts would change, the HPEs maintain very high levels of occurrence.

This study proves the PWGA utility in analyzing high-impact weather events enhancing our comprehension of how these events could change in a warming climate, thereby enhancing current early-warning systems.

How to cite: Calvo-Sancho, C., Montoro-Mendoza, A., González-Alemán, J. J., Díaz-Fernández, J., Bolgiani, P., López-Reyes, M., and Martín, M. L.: Assessing Heavy Precipitation Event Response to Global Warming Using the Pseudo-Global Warming Approach: Implications for Future High-Impact Weather Events in Southern Europe, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-534, https://doi.org/10.5194/ems2024-534, 2024.

Mediterranean cyclones often exhibit phenomenological features typical of tropical (or sub-tropical) cyclones (e.g., a cloud free eye surrounded by spiraling rain bands around the center and a closed vortex associated with strong near-surface winds and heavy precipitation) causing extensive devastation over the coastal regions. More rarely (1-3 times per year) these cyclones undergo a tropical-like cyclone transition during their mature phase, exhibiting at some point during their evolution a deep warm core of diabatic origin and deep convection in proximity of the center. These cyclones are referred to as Medicanes (Mediterraean Hurricane). Generally, the term Medicane has been used for both cyclones with tropical-like characteristics, and for weaker warm seclusions present in the late stage of extra-tropical cyclones. The present work analyzes three Mediterranean cyclones (i.e., Helios, Juliette and Daniel) that occurred between February and September 2023. The analysis is mainly carried out using satellite passive microwave (PMW) measurements from different radiometers, which allow to monitor and to characterize the thermodynamic and microphysics characteristics during the cyclones’ life time, in particular the occurrence of a warm core and deep convection.  Moreover, the surface wind field is characterized by exploiting all the available scatterometers onboard LEO satellites (MetOp ASCAT and FY-3E WindRAD) highlighting the differences between the developing and the mature stage of the cyclones. Finally, a preliminary analysis about the role of dynamics and air-sea interaction processes favoring the tropical-like transition is also carried out.

The goal is to determine if the three considered cyclones exhibit tropical-like characteristics during their mature phase and can be considered as medicanes. The three cyclones show a very similar evolution during the initial phases, with stratospheric intrusion followed by the development of a warm anomaly in the low/mid-troposphere around the cyclone center, clearly driven by baroclinic processes. While for Helios, the PMW precipitation microphysics diagnostics show a near complete lack of deep convection near the cyclone center (within 100 km), during the final stage of the mature phase of Juliette and Daniel this feature is identified, indicating that diabatic heating plays a key role in the warm core development. This evolution is observed in nearly all the medicanes which have been studied, as they eventually develop a warm core driven by diabatic processes (e.g., Zorbas, Numa). Based on this analysis, it can be concluded that Helios is warm seclusion, while Juliette and Daniel can be classified as medicanes.

How to cite: D'Adderio, L. P., Sanò, P., Sebastianelli, S., Rysman, J.-F., Casella, D., Camplani, A., Miglietta, M. M., and Panegrossi, G.: The latest satellite-based advancements on the characterization of potential Mediterranean tropical-like cyclones, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-787, https://doi.org/10.5194/ems2024-787, 2024.

Windstorms associated with extratropical cyclones are destructive natural hazards. Processes governing the formation of near-surface winds are crucial for their societal impact but are not well understood and too small scale to be explicitly represented in numerical weather prediction models.

The explosive cyclone Alex made landfall in southern Britany in October 2020 causing extensive wind damage in Belle-Ile and further inland. We investigate the mechanisms allowing high momentum air to descend to the surface and the influence of wave driven air-sea interactions from the mesoscale O(100km) to the sub-mesoscale O(100m). For this purpose we run a series of stand-alone atmospheric simulations and coupled wave-atmosphere simulations using the Meso-NH and WAVEWATCH-III models incrementally decreasing the horizontal grid spacing by two from 1.6 km to 100 m. The high resolution allows explicit representation of shallow convection and of the most energetic turbulent eddies in the atmospheric boundary layer (Large Eddy Simulations). 

Online trajectory calculations allow for a Lagrangian air mass tracking in Meso-NH. In the 1.6 km simulations, these reveal the presence of 3 distinct airstreams responsible for the strongest winds. The evolution of state parameters along these trajectories helps match the airstreams to the classical conceptual model for extra tropical cyclones. Evidence hints to the presence of a rare sting jet associated with Alex’s extreme winds, along with the more common cold conveyor belt and dry intrusion. In the Large Eddy Simulations, the same Lagrangian approach shows how the high momentum air in the airstreams is brought down by coherent boundary-layer structures. The vertical momentum transport is further controlled by wave coupling, which influences the stability of the boundary layer and the surface drag. The impact of wave coupling and resolution on extreme winds is discussed for the different mesoscale airstreams.  The results show that the representation of both sub-mesoscale processes and air-sea interactions constrains the formation of near-surface winds under storm conditions.

How to cite: Brumer, S. E., Pantillon, F., and Pianezze, J.: The role of wave coupling from the mesoscale to the sub mesoscale in a sting jet windstorm, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-807, https://doi.org/10.5194/ems2024-807, 2024.

Abstract

In this work, we elucidate the dynamical core of the Atmosphere model Aeolus 2.0, characterized by intermediate complexity. This model is grounded in the pseudo-spectral moist-convective Thermal Rotating Shallow Water (mcTRSW) framework with minimal parametrization over the full sphere. The Dedalus algorithm, renowned for its handling of spin-weighted spherical harmonics, manages the pseudo-spectral problem-solving tasks. We introduce an improved version of moist convection and a novel approach to refine the estimation of sea surface evaporation flux and the columnar bulk of humidity, pivotal components of the bulk aerodynamic scheme. The proposed scheme incorporates factors such as zonal wind velocity, variations in lower troposphere (potential) temperature, and free convection to enhance accuracy.

Indeed, we demonstrate how the model enables the simulation of various atmospheric phenomena such as the Madden-Julian Oscillation and localized extreme heatwaves. For example, Aeolus 2.0 has facilitated the proposal of a novel theory for the genesis and dynamics of the MJO (Rostami et al., 2022). According to this theory, an eastward-propagating MJO-like structure can be generated in a self-sustained and self-propelled manner due to the nonlinear relaxation (adjustment) of a large-scale positive buoyancy anomaly, a depressed anomaly, or a combination of these. This occurs when the anomaly reaches a critical threshold in the presence of moist convection at the Equator. This MJO-like episode possesses a convectively coupled 'hybrid structure' consisting of a 'quasi-equatorial modon' with an enhanced vortex pair and a convectively coupled baroclinic Kelvin wave (BKW), exhibiting a greater phase speed than that of a dipolar structure on an intraseasonal time scale.

Additionally, we demonstrate the model's capability to simulate extreme localized heatwaves in mid-latitudes (Rostami et al., 2024). This study examines the influence of large-scale localized temperature anomalies in mid-latitude regions on condensation patterns and corresponding circulation in various environments. Depending on the perturbation’s characteristics, they can induce atmospheric instability, leading to precipitation systems such as rain bands and distinctive cloud patterns. The study also demonstrates the initiation of an anticyclonic high-pressure rotation in the upper troposphere due to heating on lower troposphere, resulting in an anisotropic northeast-southwest tilted circulation of heat flux.

Relevant references:

• Rostami, M., Stefan P., Fallah B., Aeolus 2.0: Unveiling Novel Bulk Aerodynamics and Moist Convection in a Thermal Rotating Shallow Water Dynamical Core, Journal of Advances in Modeling Earth Systems (JAMES), 2024, (Under Revision).

• Rostami, M., Severino, L., Petri, S., & Hariri, S., Dynamics of localized extreme heatwaves in the mid-latitude atmosphere: A conceptual examination. Atmospheric Science Letters, 2023, e1188, doi: 10.1002/asl.1188, https://doi.org/10.1002/asl.1188.

• Rostami, M., Zhao, B. & Petri, S., On the genesis and dynamics of Madden–Julian oscillation-like structure formed by equatorial adjustment of localized heating. Quarterly Journal of the Royal Meteorological Society, 2022, 148 (749), 3788– 3813, doi:10.1002/qj.4388, https://doi.org/10.1002/qj.4388.

How to cite: Rostami, M., Petri, S., and Fallah, B.: Aeolus 2.0: Novel Bulk Aerodynamics and Moist Convection Schemes in an mcTRSW Dynamical Core to Capture Dynamics of Extreme Events, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-6, https://doi.org/10.5194/ems2024-6, 2024.

As part of the BIOCLEVER project and of the IPSODES project of the Progetto Nazionale di Ricerche in Antartide (PNRA), the sigma-coordinate ocean circulation model Parthenope University Southern Ocean Model (PARSOM) is coupled with a Lagrangian particle tracking algorithm to perform forward and backward mode simulations in the summer season to determine the possible path of the different stages of Pleuragramma antarctica sampled at 22 stations located between Terranova Bay and Whale Bay in the Ross Sea (RS). The RS is the second largest source of Antarctic Bottom Water (AABW) that supplies the lower limb of the global overturning circulation and ventilates the abyssal ocean. Dense Shelf Waters, precursor of the AABW, form on the RS continental shelf in winter by cooling and brine releasing during sea ice formation processes. The local circulation is influenced by the Ross Gyre, which regulates the proximity of the relatively warm waters of the Antarctic Circumpolar Current to the continental shelf. PARSOM the includes the whole Southern Ocean with a latitudinal extension ranging from 30° S to 80° S, so that no spurious lateral boundaries affect the RS internal response. The bathymetry is derived from the GEBCO dataset, the momentum flux and total heat fluxes (i.e. the sum of the latent and sensible heat and long wave radiation fluxes) are provided by the ECMWF ERA5 reanalysis and the initialization and relaxation to climatology are based on the World Ocean Atlas 2009 dataset.

PARSOM simulates the dynamics of the RG, and the results show a significant weakening during the summer of 2015. We investigate the relationships with local wind-driven and large-scale circulation. It was found that, in 2015, the northern branch of the RG, which interacts with the ACC, showed intensification, leading to a reduction in both the intensity and the eastward extension of the gyre itself.

How to cite: Colella, A., de Ruggiero, P., Pierini, S., Falco, P., La Mesa, M., and Zambianchi, E.: Lagrangian tracking of Pleuragramma antarctica in the Ross Sea using a circulation model of the Southern Ocean (PARSOM), EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-936, https://doi.org/10.5194/ems2024-936, 2024.

Environmental concerns and greenhouse gas emissions are driving policymakers and scientists to focus on improving waterborne transport efficiency. Accurate knowledge of the sea state and weather conditions is crucial for enhancing maritime transport efficiency and developing innovative technologies that could facilitate better management of ships and their subsystems during offshore and coastal operations. In this regard, the University of Naples Parthenope joins the National Centre for Sustainable Mobility (CNMOST) providing weather and sea state observations and forecast with two main aims: to develop a digital twin model of ship and marine environment and to provide informations to autonomous navigation system and vehicles. The digital twin activities will be useful to replicate the behavior of the ship in its operating environment, enabling understanding of how the ship will react in different situations, such as varying or even extreme environmental conditions. This technology allows ship managers to test onboard performance and conditions, preempt breakdowns and malfunctions, and make informed decisions regarding crew management and maintenance activities under different scenarios. On the other hand, marine and atmospheric observations and forecast will be used in support of the creation of an autonomous navigation system to enhance navigation safety and situational awareness, improve passenger comfort, and optimize the ship's route, thereby reducing fuel consumption and emission. To achieve these goals, the need for a dedicated test area to validate these innovative technologies is crucial. In this context, the existing monitoring network of the Gulf of Naples of the University Parthenope, widely used for the study of sea coastal processes of the region, has been further extended with new devices. The network comprises advanced meteo-oceanographic technologies e.g., a coastal high-frequency radar system, a strategic weather stations network, an unmanned marine glider for high-resolution physical and biological data collection, tidegauges, hydrophones, wavebuoy and multi-parameter probe for comprehensive data gathering.  Furthermore, a state-of-the-art high resolution regional ocean model (ROMS) and atmospheric forecasting chain (WRF) have been implemented to provide sea/weather real-time data and predictions (meteo.uniparthenope.it). Both products represent strategic information for advanced decision support systems and improved situational awareness for ship management and autonomous marine vehicles, providing insights into the external disturbances that affect the ship dynamic with consequences on fuel consumption, safety, and comfort. By employing this comprehensive network, the crucial data needed to optimize maritime operations and minimize its environmental impact are collected.

Acknowledgments
This work was supported by the European Union – NextGenerationEU. Piano Nazionale di Ripresa e Resilienza, Missione 4 Componente 2 Investimento 1.4 “Potenziamento strutture di ricerca e creazione di "campioni nazionali di R&S" su alcune Key Enabling Technologies”.  Code CN00000023 – Title: “Sustainable Mobility Center (Centro Nazionale per la Mobilità Sostenibile – CNMS)”, Spoke 3 Waterways, WP 3 Toward Autonomous Navigation.

How to cite: Cotroneo, Y., de Ruggiero, P., Gifuni, L., Montella, R., Di Luccio, D., De Vita, C. G., Zambianchi, E., Fusco, G., Buonocore, B., Pierini, S., and Budillon, G.: Weather and sea state observations and modeling in the Gulf of Naples in support of sustainable maritime mobility, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-970, https://doi.org/10.5194/ems2024-970, 2024.

The high-resolution Campania Regional Ocean Model (CROM), coupled with an online Lagrangian particle tracking algorithm (TRACE), is used to investigate the horizontal and vertical behaviour of different (in terms of size and density) plastic polymer types during February and August 2016 in the Gulf of Naples, a coastal marine area of the southern Tyrrhenian Sea, heavily affected by anthropic stress due to the presence of numerous tourist attractions, high population density, and intense maritime commercial activity. The choice of a winter (February 2016) and a summer month (August 2016) in our simulations aims to understand how seasonality, and thus the different hydrological features of the marine environment, affect the 3D transport of plastic particles since variation of the seawater density also plays a critical role in the particle settling dynamics. The transport of passive particles is evaluated based on the three-dimensional Eulerian velocity fields provided by the ocean model. The virtual particles are released in several hot spot areas in the Gulf of Naples where most of the marine debris is supposed to come from: the Sarno River mouth, the harbour of Naples, and the coastal area of Bagnoli. A sensitivity analysis on the vertical sinking for negatively buoyant particles is carried out. The sinking behaviour is determined by the settling velocity, which depends on the physical properties of the individual litter item as well as on the hydrodynamical features of the marine environment. Different numerical experiments are carried out to evaluate the effect of marine dynamics on three-dimensional transport.

How to cite: Gifuni, L., de Ruggiero, P., Cianelli, D., Pierini, S., and Zambianchi, E.: Three-dimensional Lagrangian microplastic transport simulations in the Gulf of Naples (Southern Tyrrhenian Sea), EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-830, https://doi.org/10.5194/ems2024-830, 2024.

Climate change is evident in many aspects, among them there is the response of the sea to the progressive increase of the atmospheric temperature, the changes in the inland precipitation regimes and the surface wind field pattern. In this frame, the Mediterranean area is a hot spot, where atmosphere and sea interact with a high degree of coupling, and there is deep interest for its evolution.

Future climate scenarios for the Mediterranean are already available form a rich set of regional climate simulation, both for atmosphere and the sea. Anyway, stakeholders require information on future climate having a spatial resolution higher than that characterizing the regional scale. Furthermore, many local process of interaction between atmosphere, hydrosphere and sea, especially along the coasts and in shallow waters, have a poor representation in the available model outputs. Attempting to fill in the gap, downscaling is applied to regional climate and basin scale simulations.

In this work, we present a methodology to generate ensembles of high resolution downscaled sea state to the local scale, for the three main climate scenarios, namely RCP2.6, RCP4.5 and RCP 8.5. Using boundary conditions from EURO-CORDEX, MED-CORDEX ensembles, hydrological projections derived from inland precipitation scenarios, runs of a shallow water numerical model (SHYFEM) have been conducted to explore time windows for each decade in the future up to the end of the XXI century.

Starting from preliminary sensitive tests on the response of small spatial domains to the forcing and boundary conditions, we conclude that the effort to run very high resolution models, up to 10 m of horizontal resolution for a full and continuous secular time range, is not an efficient approach.

Instead, the quick response of the coastal system to the boundary and the forcing allows to generate a large set of local area sensitivity studies, with computational resources and times that are worth to be considered useful besides efficient.

This approach explores decadal time windows of many future scenarios with the spatial resolution required by a large spectrum of stakeholders who require details on future temperature, salinity and level along the coasts, in the lagoons and in the open sea facing the coastal areas.

In addition to the methodology, we present a summary of the results of its application to the northern Adriatic Sea, including the northeastern most lagoon. Furthermore, we show how those results become inputs for case studies on climate change impacts at the local scale and they support the definition of risk minimization actions, as requested by climate adaptation plans.

This work has been conducted with the contribution from the EU co-financing and the Interreg Euro-MED Programme, in the frame of MedSeaRise Project, exploiting the results of the Interreg IT-HR AdriaClim project.

How to cite: Giaiotti, D., Minigher, A., Gianesini, E., and Pittis, M.: A novel approach to generate very high resolution climate scenario for coastal areas, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-984, https://doi.org/10.5194/ems2024-984, 2024.

Coastal floods are one of the main natural hazards which often lead to disasters worldwide including in Sweden. In the Baltic Sea, extreme sea levels (ESL) are driven by different processes such as seiches, pre-conditioning of the Baltic Sea (filling) and storm surges. Predicting those along with accurate uncertainties range is essential for marine coastal management and planning to better mitigate potential impacts. It is well known that Climate Change is currently changing coastal conditions globally and around Sweden. In this context, this study aims to characterize the atmospheric drivers of ESL along the coastline of Sweden and predict return levels of extreme sea heights. Machine Learning tools like Random Forest are then used to predict storm tide time series, characterising extreme sea levels, based on atmospheric drivers such as wind and surface pressure. The model is firstly trained with ERA5 reanalysis and tide gauge observations. It is then used to predict storm tides from 1850 to 2100 using input variables from CMIP6 models as EC-Earth. Predictions are then compared with observation values in a statistical way over the co-occurring time period. Results show that storm tides are driven by different atmospheric characteristics (i.e. wind direction, wind speed and surface pressure) at each station but that stations located close to each other can be grouped accordingly. For instance, strong westerly winds greatly contribute to storm tides on the west coast of Sweden while southernly winds are driving storm tides on the northern Swedish Baltic coast. Our main results include investigating trends in extreme values of storm tides. Based on the EC-Earth historical and ssp245 climate model, a decrease in storm tide of 1 to 4 mm/decade is to be expected along the east coast of Sweden while no trend seems to be noticeable on the west coast of Sweden. 

How to cite: Dubois, K., Nilsson, E., and Rutgerssoon, A.: Exploring sea level projections and their return levels around the Baltic Sea with a focus on uncertainties, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-714, https://doi.org/10.5194/ems2024-714, 2024.

In the afternoon of July 22, 2023, a very intense thunderstorm developed over the central Po Valley. It  quickly cross the Adriatic sea traveling from the center of the Po Valley to the Croatian coast, moving in the direction northwest-southeast. The thunderstorm speed ranged between 50 and 80km/h, with a downdraft exceeding 100 km/h, wind gust up to 120 km/h, which led to the formation of intense hailstorms with hail larger than 8 cm. The pressure difference between the front and central regions of storm,  reaced  6 hPa, with peaks up to 10 hPa. As the supercell moved towards the coast, the combined effects of the downdraft and the pressure variation, along with the storm's speed, likely triggered a meteotsunami. Both amateur evidences and instrumental observations showed the propagation of a  wave along the Adriatic coast, from North to South, with an amplitude of about 40 cm and a period of approximately 20 minutes. This phenomenon was observed from Ravenna (where the stormcell moves from land to sea) to Ancona, San Benedetto del Tronto, and Ortona with a propagation speed comparable with the storm  speed thus, in good agreement with a possible Proudman resonance. Physical analysis and numerical simulations of the atmosphere and ocean were performed  using numerical models: WRF (Weather Research and Forecasting System), ICON (Icosahedral Numerical Model), and ROMS (Regional Oceanographic Modeling System), coupled with SWAN (Simulating Waves in Nearshore) at 1 km horizontal resolution. The atmospheric results accurately reproduced  the storm's structure and evolution. The coupled ROMS and SWAN model was performed to assess the individual impacts of the downdraft, the vertical component of the downdraft, the pressure surge, and the overall storm surge. This work presents the outcomes and key factors contributing to the generation and amplification of this phenomenon.

How to cite: Memmola, F., Vilibic, I., Coluccelli, A., Brocchini, M., Corvaro, S., Penna, P., Falco, P., Ricchi, A., and Ferretti, R.: On the generation of a meteotsunami, the case study of supercell storm, over Adriatic Sea, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-799, https://doi.org/10.5194/ems2024-799, 2024.

We explore instances of unusual long-wave activity of meteorological origin along the coastal waters of north-west Europe during the summer of 2022. These events include meteorological tsunamis, i.e. waves in the tsunami frequency band originated by sharp atmospheric pressure variations and amplified by multiple resonant effects, and wind-generated infragravity waves which can trigger local seiches in enclosed basins and harbours

Anomalous "tidal surges" were observed on 18 June 2022 in Wales, followed by similar occurrences in Ireland, France, and Spain. Additionally, several anomalous long-wave events were reported in south England and Wales on the morning of 19 July 2022. Our investigation involved analysing surface and high-altitude air pressure fields, as well as sea level oscillations for both days.

We determine that the events on 18 June were a series of meteorological tsunamis, spreading across several western European countries and initiated by localised pressure disturbances originating within a low-pressure system over the North Atlantic Ocean. A local examination of the southern coast of Ireland suggests that Proudman resonance played a key role in amplifying the meteotsunami as it travelled eastward in the afternoon of 18 June. Similarly, our analysis of the events on 19 July indicates that the tidal surge observed in the UK and anomalous signals recorded in Ireland and France were likely instances of seiching triggered by infragravity waves. We conducted numerical simulations of the 18 June event using Volna-OP2, which solves the non-linear shallow water equations employing a finite volume discretisation technique. We also examined the influence of atmospheric wave velocity on the amplification of sea surface elevation.

How to cite: Renzi, E., Bergin, C., Kokina, T., Pelaez-Zapata, D. S., Giles, D., and Dias, F.: Recent meteorological tsunamis and other anomalous tidal surge events in western Europe, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-184, https://doi.org/10.5194/ems2024-184, 2024.

Using global ocean vertical temperature anomaly data, we identified that a significant response of the sea temperature anomaly (STA) to the solar radio flux (SRF) exists. We found that the STA exhibited a significant correlation with Asian summer and winter precipitation, among which the response from the Qinghai–Tibet Plateau (the QTP) was particularly noticeable. Based on NCEP/NCAR reanalysis data, the latent heat flux (LHF) anomaly, which plays a key role in winter precipitation in China, especially over the QTP, showed a significant response to the SRF in the Pacific. The results demonstrated the bottom-up mechanism of impact of solar activity (SA) on the plateau snow through sea–air interaction. Meanwhile, a top-down mechanism was also present. When the SRF was high, the stratospheric temperature in the low and mid-latitudes increased and the temperature gradient pointed to the pole to strengthen the westerly wind in the mid-latitudes. The EP flux showed that atmospheric long waves in the high altitudes propagated downward from the stratosphere to the troposphere. A westerly (easterly) wind anomaly occurred in the south (north) of the QTP at 500 hPa and the snowfall rate over the QTP tended to increase. When the SRF was low, the situation was the opposite, and the snowfall rate tended to decrease. The model results confirmed that when total solar irradiance (TSI) became stronger (weaker), both of the solar radiation fluxes at the top of the atmosphere and the surface temperature over the QTP increased (decreased), the vertical updraft intensified (weakened), and the snowfall rate tended to increase (decrease) accordingly. These conclusions are helpful to deepen the understanding of SA’s influence on the snow cover over the QTP. 

Keywords: solar activity; snow cover; Qinghai–Tibet Plateau; bottom-up mechanism; top-down mechanism; model simulation

How to cite: Yan, S. and Zhou, Y.: Response of Global Sea Temperature to Solar Radio Flux and Its Influence on Precipitation, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-980, https://doi.org/10.5194/ems2024-980, 2024.