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International audience; Spring frost has been recognized as the most harmful weather hazard for agriculture. One way to fight it back is using a wind machine - a 6-m diameter blowing fan atop a 10-m mast. It rotates on itself in approximately 4min30s and blows a slightly positive air using the strength of the nocturnal thermal inversion to mix cold air near the ground with warmer air above. Previous studies have focused on the protection area of the wind machine under different weather conditions or propeller designs. However, while weather conditions are undergone and field measurements are sparse, effects like the topography, the synergy between devices, or the addition of a burner are hard to catch and separate and are, therefore, not yet well understood. In this study, we present field measurements dedicated to the future calibration of a computational fluid dynamics model (PALM) involving an actuator disk to simulate a wind machine operating during radiative frost conditions. This numerical model will aim to understand better such tower's external effects, for which field measurements are challenging to implement. To characterize the jet of the propeller at the onset, vertical profiles were measured with a 3D sonic anemometer at high frequency (100Hz) 10 m away from the wind machine every meter between 3 and 15 m heights. Mass flow and momentum rates of about 500m3/s and 5000N were deduced for some different designs of wind machines. To characterize how the jet interacts with the ground regarding the distance from its source, 2D sonic anemometers were placed in a row in front of the wind machine. Results highlight three different zones where the jet behaved distinctively:- A dead zone, where the jet passed over the ground (0 to 30 m away from the WM);- An impact zone where the jet directly hit the ground with maximum velocity (40 to 60m away from the WM);- A spreading zone where the protection mixing was due to eddies spreading in the inter-rows and breaking into smaller eddies in contact with posts and vine plants (70m away from the WM and beyond). As the distance from the machine increased, the jet velocity decreased before vanishing.From these results about the onset condition and development of the jet, it will be possible to tune the rotating actuator disk to reproduce with PALM (an LES meteorological-oriented modeling system) an acceptable behavior of the flows (gust and weather interacting with the ground) despite several simplifications of the underlying physics. While calibrations are still ongoing, the first results are encouraging, whether it be on a wind machine in a free environment or with the reproduction of a radiative night situation. The primary analysis will focus on the animation of state variables to assist in analyzing statistical results on field measurements. As little knowledge is available about the combined use of a burner with a wind machine, several strategies for a burner location will be tested in order to initiate a research topic that the authors believe is currently unexplored.

This paper introduces a set of descriptors applied to weather regimes, that allow for a detailed monitoring of the location and intensity of their atmospheric centers of action (e.g. troughs and ridges) and the gradients between them, when applicable. Descriptors are designed to document the effect of climate variability and change in modulating the character of daily weather regimes, rather than merely their occurrence statistics.As a case study, the methodology is applied to Aotearoa New Zealand (ANZ), using ERA5 ensemble reanalysis data for the period 1979-2019. Here, we analyze teleconnections between the regimes and their descriptors, and large-scale climate variability. Results show a significant modulation of centers of action by the phase of the Southern Annular Mode, with a strong relationship identified with the latitude of atmospheric ridges. Significant associations with El Niño Southern Oscillation are also identified. Modes of large-scale variability have a stronger influence on the regimes’ intrinsic features than their occurrence. This demonstrates the usefulness of such descriptors, which help understand the relationship between mid-latitude transient perturbations and large-scale modes of climate variability.In future research, this methodological framework will be applied to analyze (i) low-frequency changes in weather regimes under climate change, in line with the southward shift of storm tracks, and (ii) regional-scale effects on the climate of ANZ, resulting from interaction with its topography.

International audience; Les modifications engendrées par le changement climatique affectent les climats régionaux et locaux, et ont une incidence directe sur les régions viticoles à échelle mondiale. Dans un contexte d'une hausse des températures et du fait de leurs conditions climatiques particulières, les espaces littoraux et insulaires pourraient devenir des espaces refuges pour la viticulture. Pourtant, ces espaces sont déjà soumis à des pressions importantes qui peuvent complexifier l'implantation des vignobles. Afin d'évaluer les potentialités de ces espaces, cette contribution présentera un modèle d'optimisation spatiale et multiobjectifs qui vise à identifier les zones les plus propices aux vignobles en fonction de différents scénarios préétablis.

International audience

Spring frosts occurring after budburst constitute a significant risk for winegrowers and can lead to severe yield losses. Wind machines can contribute to protecting vineyards against these frost events. However, the efficiency of wind machine parks depends on the locations of wind machines concerning their performance and spatial variability of temperature during these frost events. This study aims to characterize wind machine performance and spatial variability of temperature, and propose a methodology for an a priori positioning wind machines on the vineyard of Quincy. To face this stake, the CUMA of Quincy vineyard came up with several partners in the SICTAG project (“Innovant System of Connected decision support and efficient real-time management of wind machine of the Centre Val de Loire”)., Les gelées printanières survenant après le débourrement des bourgeons sont particulièrement dévastatrices et conduisent pour les vignerons à une perte économique importante. Les tours antigel sont un des moyens existants permettant de lutter contre ces gelées. Cependant, l'efficacité d'un parc de tours dépend de leur positionnement, déterminé par les performances de la tour et de la variabilité spatiale de la température durant ces évènements gélifs. L'objectif de cette étude est de caractériser les performances des tours antigel et la variabilité de la température, permettant ainsi de proposer une méthodologie pour un positionnement a priori des tours antigel dans le vignoble de Quincy.

National audience; Les travaux présentés dans cet article répondent aux objectifs du premier volet du projet SICTAG. Celui-ci consiste à réaliser une étude de caractérisation du risque de gel à partir d'outils de modélisation et des données météorologiques existantes. Le but recherché est de comprendre la variabilité spatiale des températures à travers le terroir et de permettre in fine un positionnement optimal des tours et autres dispositifs antigel sur un terroir non couvert.

International audience

International audience; This paper presents a multi-agent approach for simulating the interactions between local climate, vine phenological cycle andwine production strategies. This approach is intended to provide a better understanding of agronomic itineraries adaptation to climatevariations. This approach is presented in the context of an implementation in Argentina, in the Mendoza area.; Cet article présente une approche de modélisation multi-agents visant à simuler les relations entre climat local, cycle phénologique de la vigne et stratégies de productions viticoles. Cette démarche se place dans la perspective de mieux comprendre les ajustements des itinéraires agronomiques aux variations du climat. L'ensemble de la démarche est exposé dans le contexte d'une application en Argentine, dans la région de Mendoza.

L’impact du changement climatique sur la viticulture nécessite d’élaborer des stratégies d’adaptation à l’échelle du vignoble. La variabilité climatique locale, notamment les effets sur la température, influence la croissance de la vigne et détermine les caractéristiques des vins. L’objectif, à travers l’analyse et la modélisation spatiale des températures, est de prendre en compte l’influence des facteurs environnementaux et topographiques sur les événements climatiques locaux. Cependant, cette méthode nécessite l’installation de réseau dense de data loggers enregistrant la température de l’air pour construire et valider les modèles statistiques climatiques locaux. L’imagerie thermique, issue de la télédétection, apparaît comme une donnée alternative afin de s’affranchir des réseaux de mesure. La température de l’air (Ta) peut être estimée à partir de données satellitaires dérivant la température de surface (LST) mesurée par MOderate-Resolution Imaging Spectroradiometer (MODIS) avec une résolution temporelle journalière et à 1 km de résolution spatiale. Une analyse comparée dans la vallée viticole de Waipara (Nouvelle-Zélande) durant la saison végétative 2017-2018 a mis en évidence de bonnes relations statistiques entre Ta et LST. Les analyses statistiques ont montré, pour les températures moyennes journalières, des résultats avec un RMSE moyen de 2,46°C et un coefficient R² > 0,7. A l’échelle diurne et nocturne, les températures minimales ont obtenu de meilleurs résultats, notamment avec le satellite Terra (RMSE ≈ 2,50°C et R2 ≈ 0,80), que les températures maximales (RMSE ≈ 4,90°C et R² ≈ 0,70).

Grapevines are highly sensitive to environmental conditions, with variability in weather and climate (particularly temperature) having a significant influence on wine quality, quantity and style. Improved knowledge of spatial and temporal variations in climate and their impact on grapevine response allows better decision-making to help maintain a sustainable wine industry in the context of medium to long term climate change. This paper describes recent research into the application of mesoscale weather and climate models that aims to improve our understanding of climate variability at high spatial (1 km and less) and temporal (hourly) resolution within vineyard regions of varying terrain complexity. The Weather Research and Forecasting (WRF) model has been used to simulate the weather and climate in the complex terrain of the Marlborough region of New Zealand. The performance of the WRF model in reproducing the temperature variability across vineyard regions is assessed through comparison with automatic weather stations. Coupling the atmospheric model with bioclimatic indices and phenological models (e.g. Huglin, cool nights, Grapevine Flowering Véraison model) also provides useful insights into grapevine response to spatial variability of climate during the growing season, as well as assessment of spatial variability in the optimal climate conditions for specific grape varieties.

Night-time clear and calm weather conditions cause a highly contrasting fine-scale spatial temperature distribution, locally depending on topographic features, type of soil and land cover. The combination of meteorological and geographical features with plant phenology points out the strong sensitivity of spring phenology to the occurrence of late frosts. Spring frosts can have serious impacts on plant growth and can penalize economic sectors depending on fruit and wine production. Therefore, spring is the most monitored season. Strong frosts occurred in France in late April 2016, causing local and long-lasting (several consecutive hours) temperature records below -5°C in some lowland places. The same features occurred in spring 2017 and 2019. The study of the combined meteorological and topoclimatic features causing the spring frosts of 2016 in France was carried out in the lower and middle Loire Valley. This part of the Loire valley is one of the studied wine regions of the European project LIFE-ADVICLIM (ADaptation of VIticulture to CLIMate change: High resolution observations of adaptation scenarii). In this study, the following points are developed: the climate conditions in the geographical context of the lower and middle Loire Basin; the synoptic scale meteorology associated with late frosts and the peculiarity of spring frost compared to winter frost. The cold event of 27 April 2016 between Nantes and Orléans is analysed using a methodology that takes into account geography at fine scales. A comparative study is carried out between two nearby weather stations, representative of different local-scale geographical contexts: Romorantin, located on a valley floor with a sandy soil, and Lye, located on an open hilltop. The results show how the nested space-time scales must be taken into account to explain the contrasting temperature distribution: the synoptic scale allows frost risk triggering, while at local scale their effective impacts on the studied site to be highlighted, in terms of intensity and duration of the frost event., Dès que la situation météorologique est propice à l’établissement d’un temps clair et calme, des contrastes thermiques importants apparaissent de nuit au gré de facteurs locaux comme la topographie et la nature des sols. Si l’on croise ces composantes atmosphériques et géographiques avec la phénologie de la vigne, le printemps s’avère être une période particulièrement surveillée en raison de l’occurrence possible de gelées pouvant hypothéquer le développement du végétal et, par conséquent, pénaliser la production de raisins impactant les filières maraîchères et viticoles. Ce fut notamment le cas en France et dans certains pays voisins fin avril 2016, avec localement des gelées sous abri fortes (inférieures à -5°C) et durables (plusieurs heures consécutives). Le phénomène s’est également produit en 2017 et 2019. Pour illustrer les combinaisons de situations météorologiques et de phénomènes topoclimatiques à risques gélifs chez la vigne, l’étude de cas porte sur la basse et moyenne vallée de la Loire, région viticole française objet du programme européen LIFE-ADVICLIM (ADaptation of VIticulture to CLIMate change : High resolution observations of adaptation scenarii). Après avoir présenté le cadre climatique général du secteur d’étude, le contexte météorologique d’échelle synoptique et la particularité des gelées tardives par rapport à celles de pleine saison hivernale, l’article analyse la géographie à échelle fine de l’événement gélif du 27 avril 2016 entre Nantes et Orléans. Un zoom sur deux stations voisines représentatives de contextes géographiques différents (Romorantin à la topographie en creux sur sol sableux et Lye sur une colline dégagée) permet ensuite de montrer comment les jeux d’échelles spatio-temporelles mènent à une répartition thermique tout en contrastes, entre l’échelle synoptique (pour définir un potentiel de gelée tardive) et locale (pour en voir l’expression effective sur le terrain, en intensité comme en durée).

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Microscale numerical simulations and field measurements of the climate during a spring frost event in a vineyard equipped with anti-freeze towers. Spring frosts are especially devastating for vine crops. One method used to protect vineyard is to resort to wind machines. However, some weaknesses currently still remain on the effect of the machine on its environment and the implementation and servitude of its operation according to frost local forecast. In order to face this concern, the agricultural cooperative of Quincy has associated with partners to develop the SICTAG Project. The aim of this project is to initiate an approach to automatize the management of the wind machines farm. Wireless sensors networks will be implemented in the vineyard and numerical simulations (WRF and OpenFOAM) will be run to characterize and assess the wind machine’s operation, alone or in synergy, and to design predictive models of frost occurrence at local micro scale. The point here is to control the individual operation of the wind machines to field measurements to protect the plot against the frost, in an efficient way and at reduced energy costs., Les gelées printanières sont particulièrement dévastatrices pour les exploitations viticoles. Un des moyens de protéger les vignobles est le recours aux tours antigel. Toutefois, des lacunes persistent aujourd'hui sur l'action de la tour sur son environnement et sur l'implantation et l'asservissement de leur fonctionnement en fonction de la prévision locale du risque gélif. Pour faire face à cet enjeu, la CUMA des vignobles de Quincy (France) s'est associée à différents partenaires dans le cadre du projet SICTAG. Ce projet a pour objectif d'initier une démarche visant l'automatisation de la gestion d'un parc de tours antigel. Des réseaux de capteurs seront implantés dans le vignoble et des simulations numériques (WRF et OpenFOAM) seront réalisées pour caractériser le fonctionnement des tours et pour concevoir des modèles prédictifs du risque gélif à la micro-échelle du terroir. Il s'agit ici d'asservir le fonctionnement individuel des tours à des mesures de terrain pour prémunir la parcelle contre le risque de gel, et ceci de manière efficiente et à moindre coût énergétique.

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International audience; Viticulture is a complex and dynamic system, where climate is a key environmental component of plant suitability and productivity. From field to farm level, climate also plays a prominent role in ongoing practices, shaping winegrowers' decision making and adaptive management. With a changing climate, the wine sector faces many environmental and socio-economic challenges, to which winegrowers are required to adapt. Given the perennial nature of grape growing, there is a need to develop strategies that deal with both short- and long-term climate changes, while likewise accounting for contextual vulnerability. The content of this article aims to provide an overview of climate-driven scales, outlining the spatial complexity and temporal dynamics in viticulture. In addressing these aspects, this literature review offers a framework of scale and cross-scale interactions for policymakers and stakeholders to use when considering responses to attenuate climate change and to reduce its impacts on grape and wine production. The article concludes by discussing the local and context-dependent nature of viticulture in a changing global climate, by emphasizing that the question of scale is fundamental to assessing expected impacts, understanding uncertainty and framing sustainable policies and responses over space and in time.

Understanding climate variability in a winegrowing region is fundamental to understanding how its vineyards can adapt to climate change. For Uruguay, studying the vulnerability and adaptive responses of vineyards to climate change and climate variability is relevant due to its winegrowing region's economic importance and cultural heritage. Winegrowers and technical advisors were interviewed to evaluate their perceptions of climate change, vulnerability of their vineyards and how to adapt them. The main results showed that winegrowers had a clear perception of annual climate variability. The respondents highlighted the extreme climate events that had occurred over the previous few years and 71% of them believed that they had increased in frequency. Despite the perception of increase in climate variability in the region, they did not associate it with climate change. Overall, 43% of respondents agreed that changes in certain viticulture practices in recent years could have been due to climate change, especially those related to the preventive use of pesticides. The respondents identified climate risks that resulted in "bad" years for yield and quality (increase in extreme events (e.g., storms, hail), decrease in "cold" units in winter (i.e., temperatures0 °C), increase in "hot" hours (i.e.,35 °C), increase in precipitation during the growing season and ripening period) as well as their impacts on vineyards. An adaptation matrix was developed from the viticulture practices that the winegrowers used in response to climate variability. Medium- and long-term adaptive responses to climate change can be based on the knowledge of winegrowers and their advisors.

Global warming has implications for thermal stress for grapevines during ripening, so that wine producers need to adapt their viticultural practices to ensure optimum physiological response to environmental conditions in order to maintain wine quality. The aim of this paper is to assess the ability of the Weather Research and Forecasting (WRF) model to accurately represent atmospheric processes at high resolution (500 m) during two events during the grapevine ripening period in the Stellenbosch Wine of Origin district of South Africa. Two case studies were selected to identify areas of potentially high daytime heat stress when grapevine photosynthesis and grape composition were expected to be affected. The results of high-resolution atmospheric model simulations were compared to observations obtained from an automatic weather station (AWS) network in the vineyard region. Statistical analysis was performed to assess the ability of the WRF model to reproduce spatial and temporal variations of meteorological parameters at 500-m resolution. The model represented the spatial and temporal variation of meteorological variables very well, with an average model air temperature bias of 0.1 °C, while that for relative humidity was −5.0 % and that for wind speed 0.6 m s−1. Variation in model performance varied between AWS and with time of day, as WRF was not always able to accurately represent effects of nocturnal cooling within the complex terrain. Variations in performance between the two case studies resulted from effects of atmospheric boundary layer processes in complex terrain under the influence of the different synoptic conditions prevailing during the two periods.

International audience

International audience; Context and purpose of the study - Global climate change affects regional climates and hold implications for wine growing regions worldwide (Jones, 2007 and 2015; Van Leeuwen and Darriet, 2016). The prospect of 21st century climate change consequently is one of the major challenges facing the wine industry (Keller, 2010). They vary from short-term impacts on wine quality and style, to long-term issues such as varietal suitability and the economic sustainability of traditional wine growing regions (Schultz and Jones 2010 ; Quénol 2014). Within the context of a global changing climate, most studies that addressfuture impacts andpotential adaptation strategies are largely based on modelling technologies. However, veryfew studies model the complex interaction between environmental features, plant behaviourand farming activities at local scales. In viticulture, this level of assessment is of particularimportance, as it is the scale where adaptation matters the most. Within this context, it seems appropriate to develop a modelling approach, able to simulate the impact of environmental conditions and constraints on vine behaviour and the dynamics of viticultural activities.Material and methods -Our modeling approach, named SEVE (Simulating Environmental impacts on Viticultural Ecosystems), has been designed to describe viticultural practices with responsive agents constrained by exogenous variables (biophysical, socio-economic and regulatory constraints). Based on multi-agent paradigm, SEVE has two principle objectives, first, to simulate grapevine phenology and grape ripening according to climate variability and secondly, to simulate viticultural practices and adaptation strategies under environmental, economic and socio-technical constraints.Each activity is represented by an autonomous agent able to react and adapt its reaction to the variability of environmental constraints. The reaction chain results from a combination of natural and anthropogenic stresses integrated at different scale level (from plot to vineyard).Results- Simulation results underline that small scale variability is strongly linked with vine phenology stages and ripeness potential.Over the next century, winegrowers will likely be confronted by increasing temperatures and changing rainfall patterns that will have important impacts on agronomic itineraries and adaptation strategies.Through different experiment in european vineyards in the context of ADVICLIM project (http://www.adviclim.eu/), SEVE model provide prospective simulation of potential adaptation strategies from short-term (e.g. in harvest management practices) to long-term adjustment, such as in varietal selection. In response to increasing temperatures and changing rainfall patterns, they vary therefore in nature and effectiveness, where longterm measures in the choice in grapevine variety and the use of irrigation seem to bethe most effective.

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