Publications

2026

• Semi-implicit modeling of plant–air convection in 3D vegetative canopies
  
  • Vernier Joseph
  • Amiot Baptiste
  • Edouard Sylvain
  • Dupont Eric
  • Ferrand Martin
  • Trotin Vincent
  • Combes Didier
  • Massin Patrick
  Agricultural and Forest Meteorology, Elsevier Masson, 2026, 388, pp.111293. Accurately estimating plant-air convective exchanges necessitates precise wind speed calculations and a reliable convective exchange coefficient model; but, both have not been fully investigated yet. While measuring heat flux, temperature, and wind speed within a vegetative canopy is highly intrusive and exhibits significant spatial variability, using Computational Fluid Dynamics (CFD) to simulate such complex geometries with diverse length scales presents its own challenges. In this work, wind speed and turbulence are simulated by the CFD solver code_saturne and plant-air convective exchanges are considered at the leaf-agglomerate scale instead of the leaf scale, which is too computationally costly, or the tree scale, which does not provide enough precision in terms of dynamic and thermal interactions. Plants' impacts on wind speed and turbulence are modeled with Katul's source and sink terms, and three new convective exchange coefficient models are derived: one reuses wall-laws from the fluid mechanics theory, another adapts an empirical formula from the porous medium theory, and the last corrects Thom's single leaf formula. They yield results comparable to those from literature formulas, demonstrating the correct dependencies on wind speed and leaf characteristic length scale. Additionally, they account for vegetative canopy parameters, such as leaf area density, and consider shear stress loss predicted by Katul's source and sink terms, whereas literature models do not. New parameter values for Katul's source and sink terms are chosen to better reproduce vertical as well as transverse experimental wind speed profiles. The proposed approach can then be applied across various domains, for example, in agrivoltaic configurations to better quantify tree energy and water exchanges beneath photovoltaic panels, or in agroforestry and hedgerow systems. (10.1016/j.agrformet.2026.111293)
  DOI : 10.1016/j.agrformet.2026.111293
• Integrated urban climate studies – first experiences and results from the interdisciplinary project inteGREEN
  
  • Kotthaus Simone
  • Haeffelin Martial
  • Bastin Sophie
  • Céspedes Jonnathan
  • Delarue Frederic
  • Drouin Marc-Antoine
  • Dupont Jean-Charles
  • Faber Misha
  • Fathalli Maroua
  • Faucheux Aurélien
  • Gros Valérie
  • Hersent Matthias
  • Lemonsu Aude
  • Leymarie Juliette
  • Luu Karène
  • Martinet Pauline
  • Nagel Tim
  • Ribaud Jean-Francois
  • Segura Barrero Ricard
  • van Hove Melania
  , 2026, pp.EGU26-11576. As extreme heat events are becoming more frequent and more intense in the context of climate change, it is a major objective to mitigate urban overheating through strategic urban planning and design. For example, the introduction and expansion of vegetation in urban settings is often considered a very promising means to reduce heat stress, and even more generally improve quality of life in cities as it is widely associated with better human health and well-being, flood risk management and biodiversity. However, also unwanted effects may occur, e.g. with respect to water demand, or social injustice. The specific design, placement, and management of greening solutions in the context of the complex urban environment highly determine the “success” of a given intervention.In practice, it is still challenging to implement solutions that fundamentally mitigate heat risk in urban settings while enhancing a city’s resilience. This is in part explained by the complexity and variability of natural and anthropogenic processes in the urban environment, but also by the insufficient integration of urban climate sciences at multiple levels – be it within the discipline itself (e.g. linking near-surface micro-climate conditions with synoptic-scale atmosphere dynamics) with other natural science disciplines (e.g. soil sciences, plant ecophysiology, …) with social and political sciences, ... or with those who are in fact responsible for implementing solutions on the ground (e.g. urban planners, architects, services of local authorities, etc). To ensure urban climate science will play a more active role in informing the rapid urban transitions that take place around the globe, all these components need to be connected more effectively through improved knowledge exchange and careful co-construction.To address this need, interdisciplinary initiatives are developing in many cities and regions. Here we present first experiences and results from the interdisciplinary project inteGREEN (funded through the French Priority Research programme for Sustainable Cities -- PEPR VDBI) and the recent ANR project H2C. inteGREEN is developing a more integrated view on the topic of vegetation in urban settings. Firstly, we describe how extreme heat hazards form in Paris and which influence can be attributed to the urban environment and the larger-scale weather circulations, respectively. Then we discuss how different types of vegetation can be used to reduce heat hazards under certain conditions (e.g. at night, during day). Finally, these ecosystem services are put into the larger context by e.g. incorporating considerations of soil and plant health in urban settings. We conclude with some experiences regarding the aspects of knowledge exchange and co-construction with diverse stakeholders in the Paris region. (10.5194/egusphere-egu26-11576)
  DOI : 10.5194/egusphere-egu26-11576
• Multi-pollutant contribution of wood heating to emissions, concentrations and population exposure during winter time down to the street levels
  
  • Lugon Lya
  • Kimmerlin Charles
  • Kim Youngseob
  • Pousset Pierre
  • Achille Jérémie
  • Joly Fabrice
  • Couvidat Florian
  • Collet Serge
  • Cuniasse Benjamin
  • Redaelli Matteo
  • Sartelet Karine
  Journal of Hazardous Materials, Elsevier, 2026, 506, pp.141603. This study quantifies the impact of residential wood heating on winter air quality in France, including street-level analysis in Paris. It applies a multi-scale model to simulate regulated and emerging pollutants, such as organic matter (OM), black carbon (BC), and ultrafine particles (UFP), associated with health risks. Wood-burning emissions in Île-de-France and Paris were estimated using detailed local surveys, a new classification of appliances and emission factors accounting for condensable compounds. Over France, emissions were quantified from the EMEP top-down emission inventory, with post-estimated condensables. Wood burning is a major contributor to particulate pollution: in France, it accounts for 39.9% of PM2.5, 72.4% of BC, and 76.7% of OM. In Paris, contributions are similar, except for BC (27.2% at street level), influenced by other sources, as road traffic. Contributions to UFP are lower, ranging from 7% in Parisian streets to 15.5% over France. Wood burning significantly contributes to outdoor population exposure in Paris (33% for PM2.5, 20% for BC, and 70% for OM), with heating emissions mostly from auxiliary and comfort use (98%). Two 2030 scenarios were evaluated: business-as-usual (BAU) and a national emission-reduction objective. Under BAU, PM2.5 emissions and concentrations decline by 32.6% and 13.4% over France, and by 18.1% and 14.2% in Paris. Concentration reductions are smaller than emission reductions because some PM2.5 components (e.g. inorganics) are unaffected by wood-burning controls. The national objective scenario achieves larger impacts, typically 50%-70% greater than BAU, reducing PM2.5 concentrations of about 22%-24% in urban and street environments. Environmental Implications Health risks of fine particles depend on their composition and size, with black carbon, organics, and ultrafine particles emerging as key indicators. Our results indicate that reducing residential wood heating is an effective policy lever to mitigate wintertime particulate pollution in urban areas. In Paris, a large share of emissions arises from auxiliary and comfort heating, suggesting that targeted measures addressing non-essential wood use could deliver substantial air-quality benefits. The transition to newer heating technologies should be carefully evaluated to ensure that improvements in mass-based air quality are not offset by increased ultrafine particle emissions, which are not covered by current regulations but may have important health implications. (10.1016/j.jhazmat.2026.141603)
  DOI : 10.1016/j.jhazmat.2026.141603
• Modeling secondary organic aerosols from β-caryophyllene: role of extremely low-volatile organic compounds on new particle formation and evaluation of the SOA composition
  
  • Shi Yijie
  • Couvidat Florian
  • Lannuque Victor
  • Sartelet Karine
  Environmental Science : Atmospheres, Royal Society of Chemistry, 2026. (10.1039/d5ea00133a)
  DOI : 10.1039/d5ea00133a
• Boundary-layer parameterization for assessing temperature and evaporation in floating photovoltaics at the utility-scale
  
  • Amiot Baptiste
  • Le Berre Rémi
  • Giroux-Julien Stéphanie
  • Ferrand Martin
  Renewable Energy, Elsevier, 2026, 258, pp.124901. A precursor model for parameterizing the effects of photovoltaic powerplants on the atmospheric boundary layer is developed using computational fluid dynamics. The method allows one to compute the surface roughness lengths, aerodynamical resistances of covered surfaces and convective heat transfer coefficients, adapted for any photovoltaic module layouts and wind directions. It has been applied for two setups: a wind tunnel system and a utility-scale floating photovoltaic installation. In these cases, the altitude-based velocity profiles was reproduced over the arrays; and we found that the turbulence generated by the photovoltaic/atmosphere interaction is greater for head-and tailwinds than sidewinds, therefore affecting the environment and the photovoltaic system. Constructing a digital twin of the floating array using large-scale meteorological fields and the parameters of the precursor model, the temperature of a monitored module was calculated and a spatial variation of 1.3 °C∕km and 5.8 °C∕km was estimated at the utility scale. Moreover, the waterbody evaporation was reduced by 40%-50% due to the photovoltaic panels blocking the vapour removal processes. This result decreased to 14%-20% when considering the flow spatial variations across the waterbody. Further research is necessary to adapt the parameterization to scenarios with low wind velocity. (10.1016/j.renene.2025.124901)
  DOI : 10.1016/j.renene.2025.124901
• A Soil–Plant–Atmosphere Continuum model coupled to CFD to simulate plant energy and water exchanges in heterogeneous microclimates
  
  • Vernier Joseph
  • Edouard Sylvain
  • Amiot Baptiste
  • Ferrand Martin
  • Tuzet Andrée
  • Dupont Eric
  • Caruyer Céline
  • Iseghem Mike Van
  • Becker Axel
  • Combes Didier
  • Massin Patrick
  Agricultural and Forest Meteorology, Elsevier Masson, 2026, 376, pp.110906. Estimating plant growth conditions in agrivoltaic, agroforestry, or urban environments are applied examples exhibiting the need to consider the intricate relationships between spatially heterogeneous microclimate conditions (short-wave and long-wave radiation, wind, turbulence, and air temperature), plant and soil energy balances with air and water exchanges. To capture these connections, the Soil–Plant–Atmosphere Continuum model from A. Tuzet has been implemented in the computational fluid dynamics software code_saturne, which simulates spatially heterogeneous and time-varying fluid flows, along with short-wave and long-wave radiation. This coupling is compared to experimental measurements from two French sites of the Integrated Carbon Observatory System (ICOS). Our model achieves significant outcomes in assessing energy exchanges, maintaining a relative error of less than 20% compared to ICOS measurements. In addition to accurately reproducing variations of latent and sensible heat fluxes due to radiation, the coupling of the water balance and stomatal conductance models demonstrates its capability to predict the evolution of soil water content over several days. Finally, an extrapolative study of fictive environments with plants beneath obstacles reveals promising opportunities to understand how obstacle-induced shadows and wakes affect plant temperature. This leads the way for further research in agrivoltaic, agroforestry, or urban configurations with spatial scales from approximatively 10m² up to 1000m² and temporal scales ranging from single moments to several consecutive days. (10.1016/j.agrformet.2025.110906)
  DOI : 10.1016/j.agrformet.2025.110906
• Advanced modeling of gas chemistry and aerosol dynamics with SSH-aerosol v2.0
  
  • Sartelet Karine
  • Wang Zhizhao
  • Kim Youngseob
  • Lannuque Victor
  • Couvidat Florian
  Geoscientific Model Development, European Geosciences Union, 2026, 19 (1), pp.389-421. SSH-aerosol is developed to represent the evolution of primary and secondary pollutants in the atmosphere by processes linked to gas-phase chemistry, aerosol dynamics (coagulation, condensation/evaporation and nucleation) and intra-particle reactions. The representation of process complexity can be adjusted based on the user's choices. The model uses a sectional size distribution, and offers the capability to discretize chemical composition to account for the mixing state of particles. The algorithms are designed to represent the evolution of ultrafine particles: conservation of mass and number during numerical resolution, taking into account the Kelvin effect, the condensation dynamics of nonvolatile compounds, and nucleation. Different parameterizations are provided for nucleation: binary, ternary, heteromolecular and organic nucleation depending on the compounds involved. For gas-phase chemistry, schemes of different complexities can be handled: from simple schemes to model ozone, oxidants and inorganic chemistry (e.g. CB05, RACM2, Melchior2), to more complex schemes, e.g. from the Master Chemical Mechanism (MCM). The complexity of the schemes used for secondary organic aerosol (SOA) formation may also be adjusted: from schemes built from chamber data to near-explicit schemes from MCM. SOA schemes reduced using the GENOA algorithm are also provided for several precursors (toluene, a sesquiterpene and three monoterpenes), together with their evaluation against chamber or flow-tube experiments. A wall-loss module has also been added for easier comparisons to chamber experiments. Specific developments were made in version 2.0 to automatically link the chosen gas-phase mechanism to SOA formation by using the SMILES structure of organic compounds, allowing for the determination of their hydrophilic and hydrophobic properties and for the partitioning in both organic and aqueous phases. The gas/particle partitioning may also be represented with different complexities. For the organic phase, viscosity may be modelled, adapting the aerosol viscosity to its composition, and coupling organic and inorganic thermodynamics. The dynamic evolution of the partitioning may be computed explicitly or thermodynamic equilibrium may be assumed. Different options are also provided to simulate the chemistry of organic compounds inside the particles with different types of reactions: irreversible 1st order reactions, bulk oligomerization, hydratation of aldehydes and reactions of organic compounds with inorganic ions. The SSH-aerosol model may be installed with a docker for standalone use. It has also been coupled to several 3D models to represent gas and aerosol concentrations: from the local scale with computational fluid dynamic and street network models to the regional scale with chemistry-transport models. (10.5194/gmd-19-389-2026)
  DOI : 10.5194/gmd-19-389-2026
• Second-moment turbulent models for incompressible flows : some recent -and less recent- results
  
  • Bennoura-Bouchiba Nadjib
  • Ferrand Martin
  • Hérard Jean-Marc
  , 2026.
• Specifications for second-order turbulence-moment models in incompressible flows
  
  • Bennoura-Bouchiba Nadjib
  • Ferrand Martin
  • Hérard Jean-Marc
  ESAIM: Proceedings and Surveys, EDP Sciences, 2026.
• Plastic pollution in Leeward, Moorea and Cook islands (South Pacific): A baseline study
  
  • Galgani François
  • Roque d'Orbcastel Emmanuelle
  • Bouvier Thierry
  • Claro Francoise
  • Herman Mii
  • Penno Troy
  • Dupont Eric
  Marine Pollution Bulletin, Elsevier, 2026, 222, pp.118759. Plastic pollution is increasingly affecting the South Pacific, including remote islands and coastal regions of Small Island Developing States (SIDS), yet data remain sparse in many areas. This baseline study presents original data on beach macrolitter and microplastics in surface waters and sediments across six islands of French Polynesia (Moorea, Bora Bora, Tahaa) and the Cook Islands (Aitutaki, Rarotonga), collected during a cruise in 2024. Beach surveys revealed high plastic contamination on most sites, with macroplastics (size >2.5 cm) densities ranging from 18 to 58 items/100 m, exceeding European threshold values (e.g. 22 items/100 m) on majority of sampled beaches. Single-use plastics and plastic fragments dominated litter, with local sources such as tourism and coastal activities clearly identifiable. Surface microplastics (315 μm–5 mm) were found at low densities, ranging from 0 to 4668 particles/km2, confirming relatively low contamination in surface waters. Only 17 particles were detected from 8 manta net tows. Sediment and beach microplastic analysis yielded very limited results, with microplastics found at only two sites (Huahine and Rarotonga), dominated by fragments and colored fibers. These results suggest localized contamination linked to urbanization and tourism rather than widespread oceanic inputs. Despite methodological limitations due to the cruise format, this study contributes rare data from undersampled regions, supporting long-term monitoring efforts and informing future policy and mitigation actions. The results underline the need to improve regional waste management, which will be beneficial for local societies largely based on tourism (10.1016/j.marpolbul.2025.118759)
  DOI : 10.1016/j.marpolbul.2025.118759
• Multidimensional simulations of incompressible turbulent flows using a Godunov-type scheme for second-order moment equations
  
  • Bennoura-Bouchiba Nadjib
  • Ferrand Martin
  • Hérard Jean-Marc
  , 2026. Turbulence modelling for incompressible flows remains challenging when strong anisotropy and intercom- ponent energy transfer are essential, as in thermal-hydraulics or atmospheric boundary layers. To address the limitations of eddy-viscosity closures, we consider the second-order turbulence-moment equations that transport the full Reynolds-stress tensor, with intercomponent energy redistribution modelled by the clas- sical Rotta return-to-isotropy closure. A key difficulty in numerical simulations of such equations lies in maintaining the realisability of the Reynolds-stress tensor—symmetry and positive semi-definiteness—at the discrete level to avoid loss of hyperbolicity and numerical breakdown. We introduce a global two-step algorithm for multidimensional incompressible Reynolds-averaged Navier–Stokes equations: (i) an explicit Godunov-type convective predictor for stable, accurate transport of Reynolds stresses; and (ii) an implicit correction step applied to the mean velocity to enforce incompressibility and account for pressure, while the Reynolds stresses are updated using a dedicated diffusion–source operator. A key innovation is a semi- implicit, realisability-preserving strategy embedded in both the convection step and the integration of the Rotta source term, guaranteeing positive semi-definiteness in every cell and substep. Validation includes tests of the Rotta model using ordinary differential equations, where the Reynolds stress trajectories remain within the Lumley triangle, and full simulations of a plane mixing layer. Results capture turbulence onset, self-similar growth, and Reynolds stress evolution, with good agreement to experimental data even on coarse meshes.