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Meteorological considerations of grapevine damage due to temperature variations: the 2019 late spring frost and summer heat wave events in Burgundy During 2019, the occurrence of two contrasting weather events, a cold snap and a heat wave, caused extensive damage to the vineyards of Northern Burgundy. The late spring cold snap, that occurred from May 5th to 7th, generated frost like conditions across the northern and north-western areas of the Côte-d'Or department. The weather stations of the Northern Auxois area, where the three observation and study sites are located, recorded minimum temperatures ranging between -1 and -2°C. On the 24th and the 25th of July vineyards were exposed, yet again, to an extreme temperature variation. A brief but unusually intense heat wave increased daily maximum temperatures up to 42°C in the department’s far north. Landforms such as plateaus were less exposed to the increase in temperatures due the limiting effect of higher elevations. This led to temperatures not exceeding 40°C above 300 m, elevation at which the vineyard sites of this study are located.Weather conditions that caused the early May frost event were related to a northern circulation present over Western Europe that persisted from the 28th of April to the 6th of May. The strong anticyclonic ridge stretching from Greenland to the Iberian Peninsula directed an air mass of arctic origin towards France. On July 24th and 25th, the presence of a surface high pressure system above Scandinavia, associated with a low-pressure center located near the Atlantic Ocean, generated an influx of a very hot air mass from the northern part of the African continent through France and neighbouring countries.The local impact of these two weather events was modulated by the topographical features specific to the study area: a limestone plateau strongly dissected by parallel valleys of S.E. / N.W. orientations. The three observation sites have similar soil characteristics and are located on south facing slopes. However, damage to vegetation was uneven across sites as well as within each site. These observations rise up the question of the influence of very fine-scale environmental conditions and the impact they might have on the different vegetative growth stages. Lastly, the variation in physiological response among grapevines and its effect on their sensitivity to the occurrence of different weather hazards is also to be considered.

In the space of the entire universe, the only conclusive evidence of life, is found on Earth. Although the ultimate source of all life is unknown, many investigators believe Earth, Mars, and Venus may have been seeded with life when these planets, and the sun, were forming in a galactic cluster of thousands of stars and protoplanets. Yet others hypothesize that while and after becoming established members of this solar system, these worlds became contaminated with life during the heavy bombardment phase when struck by millions of life-bearing meteors, asteroids, comets and oceans of ice. Because bolide impacts may eject tons of life-bearing debris into space, and as powerful solar winds may blow upper atmospheric organisms into space, these three planets may have repeatedly exchanged living organisms for billions of years. In support of these hypotheses is evidencesuggestiveof stromatolites, algae, and lichens on Mars, fungi on Mars and Venus, and formationsresemblingfossilized acritarchs and metazoans on Mars, and fossilized impressionsresemblingmicrobial organisms on the lunar surface, and dormant microbes recovered from the interior of a lunar camera. The evidence reviewed in this report supports the interplanetary transfer hypothesis and that Earth may be seeding this solar system with life.

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).

Depuis le début des années 2000, le « climato-pessimisme » est devenu un objet cinématographique de plus en plus prisé par les spectateurs, traduisant certaines angoisses de la société actuelle. Ainsi, les films catastrophe, dystopiques et post-apocalyptiques ne sont pas que de simples divertissements et manifestations de certains effets de mode, ils sont aussi le reflet des avancées scientifiques de leur temps. Dans cet article, 55 films ont été sélectionnés en fonction des différentes représentations du climat et des conditions météorologiques qu’ils proposent. Le climat est présenté et perçu très différemment d’un film à un autre. Bien que le changement climatique soit souvent devenu un contexte privilégié dans les scénarios des films récents, il n’est pas forcément mis en avant par rapport à d’autres menaces de grande ampleur auxquelles l’humanité pourrait faire face. Des conditions météo-climatiques hostiles confèrent en effet une ambiance adéquate qui s’ajoute aux multiples tourments subis par les protagonistes. L’analyse des phénomènes météo-climatiques fait ressortir certaines tentatives de se référer à des travaux et résultats scientifiques reconnus, si possible en lien avec des phénomènes aux impacts aussi spectaculaires que catastrophiques, et permet ainsi d’adresser des messages d’alerte et de mise en garde aux spectateurs. De nombreux films montrent aussi une certaine propension à plonger la Terre dans l’aridité. Au-delà de la pertinence scientifique plus ou moins valide d’une possible aridification selon le scénario concerné, l’esthétique des environnements désertiques (villes ensablées, tempêtes de poussière) est sans doute un effet délibérément recherché dans cette catégorie de films.

International audience; The objective of this study was to address the role of gully erosion on sediment delivery at the catchment scale by assessing the contribution of gullies to the total sediment yield at the outlet of the Kamech (Cape Bon, Tunisia), which is a small cultivated catchment in the Mediterranean environment. The methodology was based on the long-term analysis of the evolution of gully volume, and the total volume of sediment that reached the catchment outlet. The evolution of gully volume was assessed by field surveys and image analysis. The total volume of sediment was calculated using intensive field monitoring of the runoff and erosion in the reservoir at the catchment outlet. The contribution of gullies to the total flux of sediment that reached the catchment outlet was estimated to be less than 30%. This means that siltation of the reservoir was mainly due to erosion processes other than gully erosion, i.e., topsoil erosion processes such as rill and interrill erosion in cropland areas. This result was consistent with a previous independent estimation of the apportionment of gully and topsoil erosion sources conducted at the same site using the fingerprinting approach. Therefore, the study confirms that, even in a heavily eroded agricultural catchment area with a dense network of gullies, gully erosion nevertheless accounted for less than 30% of the total erosion balance. The results also showed that the cumulated gully length has decreased in the last fifty years, thus revealing the declining role of gullies. However, the decrease in gully activity could not be linked to an isolated factor. Complementary observations, such as the appearance of vegetation in the permanent gullies and the decrease in the percentage of active gullies, showed that the degree of hydro-sedimentary connectivity in the Kamech catchment has probably entered a decreasing phase. We also analysed the potential use of historical aerial images for studying gully erosion. We found that these images were useful for calculating accurate ortho-photography but failed to provide a DEM with the precision required to measure the historical volume of gullies.

Mean diurnal rainfall regimes over Eastern Africa (also referred to as the Greater Horn of Africa) are studied based on 3-hourly data from the TRMM 3B42 data set, averaged over a 17-year period (1998–2014). The consistency with long-term mean raingauge data, available for partly independent periods, varies from good (Sudan, Ethiopia, Eritrea and Somalia) to very good (Kenya, Tanzania and Uganda). Over sea (Indian Ocean and Red Sea), the diurnal rainfall distribution is quite uniform; however, a morning peak dominates and there is evidence of offshore phase propagation south of the equator. Over land, both rainfall frequency and rainfall amounts show a dominant afternoon maximum (1500–1800 East African Time, i.e. GMT + 3). However, many inland regions show a delayed rainfall maximum (evening, night-time or morning). The evening to night-time maximum found over some land areas is associated with a phase propagation from areas showing an afternoon peak. This occurs west of high ground areas (Sudan and parts of the Great Lakes region) and in belts parallel to the seashores (Eritrea, northeastern Ethiopia, Somalia and eastern Kenya). The latter provide indirect evidence that sea breeze effects can be detected at unexpectedly great distances from the coast (up to 300–400 km) in parts of Eastern Africa. A remarkable ring of early afternoon (1500) maxima is found around most lakes, although some east–west asymmetries occur. Over the lakes, a morning or late night maximum is mostly found. It is generally inversely related to the distance to the shorelines for the larger lakes, but over the mid-size lakes it is replaced by or competes with a late afternoon to evening maximum.

L'inondation par la mer (submersion marine) est le resultat d'une conjonction de facteurs : une faible pression atmospherique, un fort vent d'afflux (ces deux facteurs peuvent determiner une surcote ou « onde de tempete ») au moment d'une pleine mer de vive-eau. Le littoral francais de la Manche orientale a fait l'objet de travaux sur la caracterisation des submersions marines generatrices de dommages. A partir d'un inventaire de ces inondations entre 1949 et 2010, l'identification de parametres meteorologiques tels que le gradient de pression de nord-ouest et le passage du front froid permet de mieux apprehender la genese de la majorite des submersions. Cependant, quelques cas ne peuvent pas etre expliques par ces seuls parametres. Pour les comprendre, il est necessaire d'integrer un autre facteur a savoir les conditions meteo-marines prealables a l'inondation par la mer. En effet, de quelques jours a quelques semaines avant l'inondation, la plage peut s'adapter a des conditions hydrodynamiques un peu plus fortes en subissant un abaissement de son profil. Cet abaissement peut favoriser les franchissements et les dommages associes.La finalite de ce travail est de participer a l'amelioration du systeme d'alerte des inondations par la mer du secteur d'etude en utilisant des evenements extremes mais aussi non extremes pour mieux comprendre la variabilite des phenomenes.

This article proposes to use the Köppen classification to evidence climate change in Brazil. To do so, the average monthly temperature and precipitation data were computed for a set of 208 stations, representative of the climatic diversity of Brazil for the period from 1964 to 2015. The originality of our approach is not only to look at the shift between the averages of two references periods but also to observe how each year can be classified using Köppen’s classification; thus, we defined “annual climate types” (ACT) and established the frequency of ACTs for each station and each period of 26 years: 1964–1989 and 1990–2015. The statistical and cartographic treatment of this information makes it possible to define the limits of the climates of Brazil and look at its evolution showing the diversity of regional situations in Brazil. The results show that 35 stations (17%) changed from the average Köppen’s type, with significant regression of wet tropical types (Af and Am) and temperate types (C). On the other hand, the tropical (Aw), arid and semi-arid (B) types progress between the two periods showing significant modifications of the climatic limits in Brazil: extension of aridity in the northeast of Brazil and increasing extinction of tropical types upon temperate climates in the south of the country and upon rainy types in the south of the Amazon. These results are consistent with other studies and illustrate the potential for climate change and variability monitoring using a simple classification method.

Este artigo se propõe a utilizar a classificação de Köppen para definir os tipos de climas anuais (TCA) para um conjunto de 208 estações representativas da diversidade climática do Brasil. Os dados médios mensais de temperatura e precipitação para o período 1961-2015 permitiram estabelecer a frequência dos TCA para cada estação. Os tratamentos estatísticos e cartográficos destas informações auxiliaram a esclarecer os limites climáticos do Brasil. Foram aplicados os conceitos de "núcleo forte", definidos como áreas onde os TCA são sempre ou quase sempre os mesmos, e "áreas de transição", locais onde há uma grande diversidade de TCA. Esta abordagem permite considerar um estudo detalhado das transições entre os tipos de climas tropicais (principalmente Aw, Am e Af), e ao sul, os subtropicais e temperados (Cwa e Cfa, principalmente) e discutir os limites climáticos. Cet article propose d'utiliser la classification de Köppen pour définir des « Types de Climats Annuels » (TCA) pour un ensemble de 208 stations, représentatives de la diversité climatique du Brésil. Les données moyennes mensuelles de températures et de précipitations pour la période 1961-2015 ont permis d'établir la fréquence des TCA pour chacune des stations. Le traitement statistique et cartographique de ces informations précise les limites des climats du Brésil : on applique ici les concepts de « noyaux forts », définis comme les régions où les TCA sont systématiquement ou majoritairement les mêmes, et « d'aires de transition », c'est-à-dire les régions où on trouve une grande diversité des TCA. Cette approche permet d'envisager une étude fine des transitions entre les types de climats tropicaux (essentiellement Aw, Am et Af) et ceux du sud, subtropicaux et tempérés (Cwa et Cfa notamment) et de discuter ces limites climatiques. This article proposes to use the Köppen classification to define "Annual Climate Types" (ACT) for a set of 208 stations, representative of the climatic diversity of Brazil. The average monthly temperature and precipitation data for the period 1961-2015 allow to establish the frequency of ACTs for each station. The statistical and cartographic treatment of this information makes it possible to define the limits of the climates of Brazil: here we apply the concepts of "strong nuclei", defined as the regions where the ACT are systematically or mostly the same, and "transition areas ", i.e. regions where there is a great diversity of ACT. This approach allows us to propose a detailed study of the transitions between the tropical climates types (mainly Aw, Am and Af) and those of the south, subtropical and temperate (Cwa and Cfa in particular) and discuss these climatic limits.

Este artigo se propoe a utilizar a classificacao de Koppen para definir os tipos de climas anuais (TCA) para um conjunto de 208 estacoes representativas da diversidade climatica do Brasil. Os dados medios mensais de temperatura e precipitacao para o periodo 1961-2015 permitiram estabelecer a frequencia dos TCA para cada estacao. Os tratamentos estatisticos e cartograficos destas informacoes auxiliaram a esclarecer os limites climaticos do Brasil. Foram aplicados os conceitos de "nucleo forte", definidos como areas onde os TCA sao sempre ou quase sempre os mesmos, e "areas de transicao", locais onde ha uma grande diversidade de TCA. Esta abordagem permite considerar um estudo detalhado das transicoes entre os tipos de climas tropicais (principalmente Aw, Am e Af), e ao sul, os subtropicais e temperados (Cwa e Cfa, principalmente) e discutir os limites climaticos.

International audience

International audience; Increased soil erosion, pressure on agricultural land, and climate change highlight the need for new management methods to mitigate soil loss. Management strategies should utilize comparable data sets of long‐term soil erosion monitoring across multiple environments. Adaptive soil erosion management in regions with intense precipitation requires an understanding of inter‐annual variability in sediment yield (SY) at regional scales. Here, a novel approach is proposed for analysing regional SY. We aimed to (i) investigate factors controlling inter‐ and intra‐annual SY, (ii) combine seasonality and time compression analyses to explore SY variability and (iii) discuss management implications for different Mediterranean environments. Continuous SY measurements totalling 104 years for eight small catchments were used to describe SY variability, which ranged from 0 to 271 t/ha/year and 0 to 116 t/ha/month. Maximum SY occurs in spring to summer for catchments with oceanic climates, while semi‐arid or dry summer climates experience SY minimums. We identified three time compression patterns at each time scale. Time compression was most intense for catchments with minimum SY in spring to summer. Low time compression was linked to very high soil loss, low run‐off and sediment production thresholds, and high connectivity. Reforestation, grassland and terracing changed SY magnitudes and time compression, but failed to reduce SY for large storm events. Periods with a high probability of high SY were identified using a combination of intra‐annual SY variability, seasonality analysis, and time compression analysis. Focusing management practices on monthly flow events, which account for the majority of SY, will optimise returns in Mediterranean catchments.

The paper presents the baseline climate of the Cotnari wine growing region, the climate under whose influence were set up the wine grape varieties, wine types and grapevine training systems of this vineyard. It is also presented the baseline climate suitability for wine grape growing and its spatial variation in the vineyard area. The study is based on the climate data for the 1961 to 1980 time period, previous to the beginning of the climate warming and, therefore, considered to be representative for the baseline climate time period. According to study results, the baseline climate of the Cotnari wine growing region was cool, with annual average temperatures by 8.5...,10.0°C, with a sum of the effective temperatures by 1081...,1382°C, with freezing phenomena at the beginning and towards the end of the growing season, and with very cool nights during the month of September (CI+2). Elements that generate the baseline climate suitability for wine grape growing were: high average temperatures for the month of July (19...21.1°C), long growing season up to 190 days, and high values for the global radiation, up to 93 kcal/cm2/April 1st - September 30th on the sunny slopes within the vineyard area. According to the multicriteria evaluation of the suitability for wine grape growing, 87.9% (1792 ha) of the vineyard surface was characterized by a baseline climate suitable for white quality wines and 11.9% (241.0 ha) by a baseline climate suitable for white table wines, sparkling wines and wines for distillates.

Cet article propose d'utiliser la classification de Köppen pour définir des « Types de Climats Annuels » (TCA) pour un ensemble de 208 stations, représentatives de la diversité climatique du Brésil. Les données moyennes mensuelles de températures et de précipitations pour la période 1961-2015 ont permis d'établir la fréquence des TCA pour chacune des stations. Le traitement statistique et cartographique de ces informations précise les limites des climats du Brésil : on applique ici les concepts de « noyaux forts », définis comme les régions où les TCA sont systématiquement ou majoritairement les mêmes, et « d'aires de transition », c'est-à-dire les régions où on trouve une grande diversité des TCA. Cette approche permet d'envisager une étude fine des transitions entre les types de climats tropicaux (essentiellement Aw, Am et Af) et ceux du sud, subtropicaux et tempérés (Cwa et Cfa notamment) et de discuter ces limites climatiques. This article proposes to use the Köppen classification to define « Annual Climate Types » (ACT) for a set of 208 stations, representative of the climatic diversity of Brazil. The average monthly temperature and precipitation data for the period 1961-2015 allow to established the frequency of ACTs for each station. The statistical and cartographic treatment of this information makes it possible to define the limits of the climates of Brazil: here we apply the concepts of « strong nuclei », defined as the regions where the ACT are systematically or mostly the same, and « transition areas », i.e. regions where there is a great diversity of ACT. This approach allows us to propose a detailed study of the transitions between the tropical climates types (mainly Aw, Am and Af) and those of the south, subtropical and temperate (Cwa and Cfa in particular) and discuss these climatic limits.

This work proposes an alternative method to answer the issue of quasi-exhaustive mapping of erosion features on kilometre square areas by remote sensing. This study presents a method to produce decimetric Digital Elevation Models (DEMs) with kite aerial photography and an algorithm to map gully erosion from these DEMs. Kite aerial photography is robust and cheap in comparison to Unmanned Aerial Vehicles (UAVs). The use of such a simple apparatus is made possible if the flight angle of the kite is steady. Experimentation and modelling show that this goal can be reached with these two predetermined conditions: the right kite must be used in the right wind and the line must be light and thin. In our study, we used a 10 m2 framed delta kite in 4–5 Beaufort winds using a Dyneema® line of 1 mm in diameter and 0.5 g/m in weigth for image acquisition on the day of experiment. Within two successive flights, 752 images were acquired. The photogrammetric software used was Micmac, an open-source software written and maintained by the French national institute of geographic and forest information (IGN). It allowed to obtain DEM covering 3.18 km2. Geographical reference was given by 8 ground points and 469 independent points were surveyed for validation. Estimated mean error on altitudes was 0.07 m and standard deviation of this error 0.22 m, for a 0.11 m ground sampling distance. In order to illustrate the potential of such detailed DEMs at the watershed scale, a simple gully detection algorithm was briefly described and implemented. As with several others, the method does not refer to the relationship between slope and drainage area but uses local convolution of the DEM. Considering a smoothed DEM as a proxy of the geomorphological process of gullies healing, proposed gully detection algorithm relies on substracting smoothed DEM from the original DEM. The depth of each feature is then estimated and only the bulkier elements are kept as potential gullies. Despite our algorithm detecting undesired artefacts – most of them being man-made structures such as houses and roads – all gully heads and all channels are detected. Therefore results show the benefits of the production and use of decimetric DEMs on an entire kilometre square watershed with kite-borne imagery.

National audience

oral presentation+proceedings

International audience

International audience

Le contexte actuel de changement climatique global soulève de nombreuses questions quant à l’évolution des climats aux échelles régionales et locales. La littérature scientifique, de plus en plus riche à ce sujet, mérite d’être approfondie. La méthode des « Types de Climats Annuels » (TCA) a été utilisée, selon la classification climatique de Köppen, afin d’analyser la variabilité spatio-temporelle du climat en France. À l’échelle régionale, les fréquences d’apparition des TCA ont été étudiées pour 110 stations, pour la période 1951-2010 et pour les deux sous-périodes 1951-1980 et 1981-2010. Les résultats font ressortir : (1) l’influence de la latitude, de la continentalité et du relief sur la répartition spatiale des TCA sur l’ensemble de la période (1951-2010); (2) l’augmentation des fréquences d’apparition des « nouveaux TCA » à été chaud (typesCsaetCfa) à partir des années 1980, notamment dans le Sud de la France. Ces nouveaux TCA soulignent à leur tour certains contrastes régionaux.

Global warming is causing earlier phenological dates for vines and changes in the quality of wines all around the world. To understand how vines are liable to react to future climate evolution, the climate of viticultural areas needs to be known as accurately as possible. In this article, temporal evolution and spatial variability of temperature in the wine producing area of the Loire Valley were analysed with a multi-scalar approach. First, the regional evolution of temperature and bioclimatic indices were studied over the past 60 years in the wine-producing area of the Loire Valley and showed a general warming at all locations in the regional weather station network (Meteo-France). Secondly, temperature data from weather stations located within the vineyards between Angers and Saumur were studied for the year 2010 and underlined spatial variability of temperature between the different plots according to the different topoclimates. Finally, particular attention was paid to the Coteaux du Layon vineyards (sweet wine producing appellation) where 21 temperature data loggers were set up in the vine rows to study climate at local scale. The study showed, in particular, that the spatial variability of temperature and bioclimatic indices in these vineyards was greater than those observed at larger scales. Copyright © 2012 Royal Meteorological Society

This paper is concerned with the detection of fronts in satellite images. We focus on some specific textured patterns of clouds that are visible on Meteosat Second Generation (MSG) images and generated at the so-called “sea breeze front”. This is the limit of the penetration of the sea breeze inland. The sea breeze circulation is a phenomenon that arises when land and sea surface temperatures reveal strong variations. This generates a landward wind that creates a cloud-free area starting from the coast line and ending at the sea breeze front. With the new geostationary meteorological sensors like MSG, this band of cloud-free area can clearly be seen. The automatic analysis of the sea breeze front with such image sensors (instead of using local measurements) is then of great importance. It has the precious advantage to extract huge amount of data and to get rid of the use of local sensors. Unfortunately, from an image processing point of view, this front appears as the limit of a very textured area. It is sometimes disturbed by clouds located in higher layers of the atmosphere. Due to this complexity, conventional detection methods issued from computer vision are not adapted. In this paper we propose an approach that automatically detects fronts in images and we apply this framework to the sea breeze fronts. The methodology is based on the well-known active contour method (or “snake”) issued from the computer vision community. The specific textures involved as well as the transparency phenomena are dealt with some properties of the wavelet decomposition of the images. This decomposition enables to compute several criteria related to the presence or not of a front that are combined using the Dempster–Shafer theory. The validation of our approach is done on synthetic and real data. It is important to outline that the presented theoretical framework is not only devoted to the detection of the sea breeze front but can also be used to detect any others textured patterns.

International audience; At finer scales, raindrops are the sources of the onset of soil erosion. Understanding the effects of raindrops at the decimeter scale is useful for soil erosion prediction, understanding erosion principles, and deriving erosion control management practices. The objective of this study was to develop and rest a physically based model to predict the effect of raindrop erosion on soil microtopography and identify the parameters that can be experimentally measured. The model has three parameters: (i) detachment rate mu similar to (9.0 +/- 4.0) x 10(-2) kg m(-2) mm(-1), (ii) average projection distance lambda similar to 0.15 +/- 0.05 m, and (iii) a dimensionless anisotropy coefficient delta similar to 3 +/- 1, which expresses the slope dependency of lambda and mu. Variation in soil height caused by raindrop erosion followed a diffusion-type equation with a source term. Under uniform conditions of soil and rainfall, the model simplifies into a basic diffusion equation. Under the homogeneous bare soil condition, soil surface roughness is predicted by an exponential decay model. Under nonuniform conditions, when sparse perennial vegetation protects the soil locally from raindrop impact (a common surface feature in semiarid areas), the model predicts that small mounds of 2 to 30 cm in height can develop underneath the cover. On a horizontal surface, the mound height asymptotically tends to a limit. On sloping areas, however, mounds are predicted to develop faster, higher, and to be asymmetric. Under both flat and sloping terrain, model predictions were found consistent with published data and models, with the noticeable improvement that the model parameters can be measured by laboratory experiments.

An accurate knowledge of the weather patterns causing winter rainfall over the Scorff watershed in western Brittany (W. France) was developed prior to studies of the impact of the climate factor on land use management, and of the hydrological reponses to rain-producing weather patterns. These two studies are carried out in the context of the climate change. The identification of rainy air-circulation types was realized using the objective computational version of the 29-type Hess and Brezowsky Grosswetterlagen system of classifying European synoptic regimes, for the cold season (November-March) of the 1958–2005 period at the reference weather station of Lorient, and 13 other stations located in western and southern Brittany, including a more detailed study for the wet 2000–2001 cold season for three reference stations of the Scorff watershed (Lorient, Plouay and Plouray). The precipitation proportion (including the days with rainfall ≥20 mm) was calculated by major air-circulation type (GWT: see Appendix A) and by individual air-circulation subtype (GWL: see Appendix A) for the studied time-period. The most frequently occurrence of rainy days associated with westerly and southerly GWL confirmed well-known observations in western Europe and so justify the use of the Hess-Brezowsky classification in other areas outside Central Europe. The southern or south-western exposure of the watershed with a hilly inland area enhanced the heavy rainfall generated by the SW and S circulation types, and increased the difference between the rainfall amounts of coastal and inland stations during the wettest days.

"Based on two case studies conducted at local sites in Northern Thailand and Lao PDR, the objectives of this paper are (i) to assess whether conditions for the establishment of PES at the watershed level exist in the uplands of mainland SE Asia and (ii) to examine and discuss limitations that are likely to impinge on direct transfer of the PES concept as well as the institutional adaptations and support that are required for the successful implementation of PES markets in this regional context. The study???s main findings are that: (i) acceptance of PES principles and constraints are directly related to stakeholders??? perception of their land rights irrespective of their actual rights; (ii) willingness to pay (WTP) is very low among local stakeholders, making any PES market unlikely to emerge without external support; (iii) the classical scheme for watershed services hardly applies in its original form because environmental service (ES) providers and buyers are generally the same people; (iv) where potential ES buyers feel that ES providers are better-off or wealthier than them, they do not have any WTP for ES; (v) good governance, including a strong liaising at various levels between people and the authorities is a strong prerequisite for the successful establishment of PES markets, even without direct government funding."

Depuis une vingtaine d’années, la côte de Saint-Trojan, au sud-ouest de l’île d’Oléron, s’érode à un rythme très soutenu. Différentes stratégies sont à l’étude pour maintenir le site en l’état. La dune et les plages de sable fin font en effet office de vitrine publicitaire pour l’économie touristique. La question de leur préservation est devenue un enjeu majeur pour la population locale. Ce n’est pas une préoccupation uniquement environnementale, mais aussi économique et sociale. Le phénomène a déjà été largement décrit, notamment par les aménageurs locaux. Mais l’érosion marine n’intervient pas de manière continue et s’exerce presqu’uniquement lors de conditions paroxysmales, pendant les tempêtes. Nous proposons ici une nouvelle méthode (qualitative et probabiliste) d’évaluation de la vulnérabilité aux tempêtes de la frange littorale. Il s’agit d’employer un modèle de comportement. Ce modèle fait d’abord l’inventaire des conditions météo-marines qui conduisent à l’érosion et tente ensuite de prévoir leur survenue. La méthode de prédiction passe par une représentation graphique de la contrainte qu’exercent les principaux agents marins. Le modèle est validé a posteriori (avec des mesures archivées) mais aussi a priori en tant qu’outil de prédiction. Bien qu’il soit efficace pour prédire les phases d’érosion, il doit encore être amélioré sur certains points. A terme, il est envisagé que cet outil puisse servir de veille climatique dans le cadre d’une amélioration de l’actuel dispositif de gestion.

L’objectif est de contribuer au développement des connaissances sur le climat à échelle fine des vignobles uruguayens. La variabilité de la température est étudiée en relation avec les circulations atmosphériques locales dans la région viticole côtière de Montevideo et Canelones, la plus importante du pays, au sud de l’Uruguay. Des capteurs de température ont été installés dans des vignobles, répartis principalement en fonction de la topographie et de la distance à l’estuaire du Río de la Plata. Cette étude porte sur trois saisons végétatives (septembre à mars, pour 2012, 2013 et 2014), sur les données observées de température obtenues par neuf capteurs ainsi que des données climatiques complémentaires d’humidité relative et de vent (vitesse et direction) issues de deux stations météorologiques automatiques, situées à 0,8 et 14,8 km du Río de la Plata. L’étude des données climatiques horaires de vent a permis d’identifier la fréquence de brise de mer sur la région viticole pendant la période de maturation du raisin. La chute des températures a atteint plus de 4°C entre 10 h et 14 h (Heure Locale) sur toutes les parcelles exposées au Sud lors du jour le plus chaud de l’été 2012. De moindre ampleur et de plus courte durée, cette baisse des températures a été enregistrée jusqu’à 30 km à l’intérieur du vignoble. Dans des conditions thermiques extrêmes au cœur de la période de maturation des raisins, l’impact de la brise sur les températures de la région viticole peut réduire le stress thermique pour l’activité photosynthétique et ainsi, être bénéfique au développement des composantes primaires et secondaires dans les raisins.

A severe cold wave hits a large part of Europe between late January and mid-February 2012 and caused damages in the vineyard of Moldavia in Northeastern Romania. During the cold wave, the daily minimum temperature fell near −30 °C at some weather stations in Moldavia, but the hilly terrain caused strong temperature differences at small scales: up to 10 °C in a few kilometres. Three main cold spells with very low minimum temperatures were identified in association with the succession of three circulation types (according to the Hess-Brezowsky classification): Fennoscandian high anticyclonic (HFA, January 29–February 4), Central European ridge (BM, February 5–7) and northeast anticyclonic NEA (NEA, February 8–11). A multi-scale agroclimatic analysis in the vineyard of Cotnari (Moldavia, Romania) was carried out in the particular meteorological context of the early 2012 European cold wave. The results especially pointed out the local-scale (topoclimatic) effects on the high spatial variability of temperature and consequently a contrasting spatial distribution of damage on grape vine. The analysis of data recorded from temperature loggers installed in several test sites in the vineyard of Cotnari, depending on its topographical features, and of the observations of frost damage on grape vines (on vine buds, vine canes and even vine arms and trunks) pointed out a significant correlation between the topographic position and the grape vine variety.

L’enquete sur le climat a la fin du Moyen Âge, pendant ce que les historiens appellent le « petit âge glaciaire » (PAG) est demeuree jusqu’ici presqu’inexistante pour l’ouest de la France par manque de donnees exploitables. Le present article essaie de combler ce deficit en utilisant la « Chronique » du notaire lavallois Guillaume Le Doyen. Ce texte en vers de pietre qualite relate les evenements locaux entre 1481 et 1537 et, comme souvent a l’epoque, il retient quantite de notations meteorologiques qui peuvent permettre d’etudier le climat de l’Ouest pendant presque 60 ans. Une fois etabli le degre de fiabilite des notations et en considerant que Le Doyen nous livre avant tout le climat vecu, l’etude devient possible. L’hiver est bien repere comme le printemps et l'ete. L’etude de la variabilite aboutit a constater a cette epoque une remission dans le petit âge glaciaire, les periodes froides n’etant pas dominantes. L’etude se termine par l’examen des inondations a Laval auxquelles l’auteur est evidemment sensible. La chronique permet une approche du climat tempere de l’Ouest, sensiblement nuance par rapport a ce qui est observe a Paris, mais il faudrait pouvoir etendre l’enquete a d’autres sources pour confirmer cela.

This paper presents a new methodology for the calculation of a digital elevation model (DEM) and the corresponding orthophotography at very high resolution (20 cm for the DEM, 10 cm for the orthophotography) on a large surface (more than 3 km2). Image acquisition was done with an off-the-shelf camera (Sony NEX-5N) attached to a delta kite. Developing the most accessible methodology being one of the goals of this study, the overall cost of the apparatus is limited to less than 1500 euros. This method has been developed to form an alternative with acquisitions from small Unmanned Aerial Vehicles (UAV). In particular, kite as payload carrier is seen as being complementary to lightweight multicopters, which are increasingly used for remote sensing applications [1, 2]. Kite is of a strong interest when the use of radio-controlled and motorized systems is hampered by local regulation and/or when too strong winds keep these lightweight devices on ground.

Sea breezes were investigated during the maturation period of wine grapes in the South-Western Cape under particular synoptic wind conditions (onshore for Table Bay and offshore for False Bay). Observations from an automatic weather station network located in the Stellenbosch wine-producing area as well as the Regional Atmospheric Modelling System (RAMS, non-hydrostatic, parallel, version 4.3) were used. Results showed that two sea breezes developed, one from Table Bay late in the morning, and the other from False Bay later in the afternoon. The coastal low strengthened and deflected the sea breeze from Table Bay towards the south and south-east of the study area, while the offshore large-scale circulation hindered the development of the sea breeze in the opposite direction over False Bay and delayed its movement towards land. The decrease in temperature resulting from the onset of the sea breeze from the Atlantic early in the afternoon could be significant for viticulture, reducing the duration and intensity of high temperature stress on grapevine functioning at the coolest locations.

La variabilité climatique, notamment pluviométrique, a été étudiée dans le Nord-Ouest de l’Argentine durant la période 1951-2000. À une variabilité interannuelle d’autant plus forte que l’on se rapproche du piémont andin semi-aride et semi-aride (Mendoza, San Juán), s’ajoutent des oscillations de plus longue durée, en particulier une succession d’années anormalement arrosées à partir des années 1970. L’étude comparée de la période la plus arrosée (1971-1990) et de la période précédente, plus sèche (1951-1970), montre que l’augmentation des précipitations a été très variable d’une station à une autre, et l’analyse sur l’ensemble du vingtième siècle ne montre pas de lien significatif avec l’oscillation australe. Cependant, l’apparition plus fréquente de types de climats annuels plus humides, en particulier pour certaines stations situées en limite du domaine marqué par l’aridité (Santiago del estero), soulève le problème des conséquences économiques, humaines et environnementales d’un retour éventuel à une période moins arrosée.

Les circulations de brise de mer favorisent l’apparition de types de temps relativement frais et humides mais le plus souvent ensoleilles sur les espaces cotiers par rapport aux regions interieures. Une methode d’identification des fronts de brise par teledetection a ete appliquee a l’Europe de l’Ouest et au nord-est du Bresil, afin d’en calculer la frequence d’apparition et la distance preferentielle de penetration dans les terres aux heures chaudes de la journee. Le suivi des fronts de brise a ete effectue durant la saison chaude en Europe occidentale (mai a septembre 2000) et la moins arrosee dans le Nord-Est du Bresil (septembre a decembre 2000). La distance de penetration des fronts de brise varie en fonction de l’exposition de la cote aux vents dominants, en Europe comme au Bresil. Cependant, la succession de situations meteorologiques variees impose des configurations diverses d’un mois a l’autre en Europe de l’Ouest, tandis de la regularite des alizes fait ressortir une plus grande permanence, dans l’espace et dans le temps, de la localisation des fronts de brise au nord-est du Bresil.

Summary Predicting the rate at which rain infiltrates on steep slopes is very uncertain. There is no consistent information in the literature. We have therefore related infiltrability to slope gradient under field conditions by experimenting on a gravelly loamy soil occupying the upper half of a cultivated convex hill in northern Thailand. Fifteen 1 m × 1 m plots with slope gradients ranging from 16 to 63% were established, and simulated rain was allowed to fall on them at controlled rates and for fixed times. We obtained the following results. The surface fell 0.4–7.2 mm due to compaction and soil loss. The proportions of crust (0–40%) and embedded gravel (10–60%), the runoff coefficient (0.05–0.78 mm mm−1), the mean sediment concentrations (0–5.6 g l−1), and soil detachment (10–313 g m−2) were more pronounced on the gentle slopes than on the steep ones. The steady final infiltration rate (1–107 mm hour−1) increased sharply with increasing slope gradient. Microaggregates tended to behave like sand and become tightly packed on gentle slopes (packing crust). These results suggest that the vertical component of kinetic energy, which is greater on gentle slopes, has a dominant role. Nevertheless, the differences in compaction and in sediment concentration could not be ascribed to the vertical component of kinetic energy alone. On steep slopes the horizontal component of the kinetic energy is transformed into shear stress, hampering the development of crusts so that water can still infiltrate. On steeper slopes, the water film was thinner, thereby limiting the role of splash. We conclude that the relationship between slope gradient and infiltrability depends on the nature of the soil and must be examined in the light of surface crusting processes.

Le travail présente la notion de limite appliquée à des objets morpho-climatiques littoraux. D'un point de vue spatial, la notion de limite a une pertinence juridique (elle sert à définir le Domaine Public Maritime) mais il est délicat de lui trouver une existence concrète sur le terrain, tant elle est mobile et prend le plus souvent la forme d'un gradient. Son caractère de non discontinuité est accentué par le fait que ses caractéristiques théoriques ne coïncident pas avec sa position physique. On peut prouver, sur une plage macro-tidale, que le niveau hydrologique de référence est 1) parfaitement calculable, 2) jamais observé, ni par le stationnement de l'eau, ni par le centre géométrique du profil de plage. On peut également prouver que le climat littoral, particulièrement sur une côte à dunes (en Afrique du Sud), différencie plus le littoral de l'intérieur immédiat que de la mer ouverte. Ces exemples montrent que la notion de limite, dans ce type de contexte scientifique, n'est pas un concept satisfaisant. On peut très bien analyser le fonctionnement morpho-climatique d'un littoral sans l'invoquer. Un exemple est développé en Nouvelle Zélande sur un littoral répondant et aux tsunamis et aux périodes de relaxations.

The air maximum temperature in Brittany was correlated for 6 sunny days of the year 1997 with the geographical coordinates usually used in climatological studies : altitude, latitude and distance from the coast. Then the infrared data from the NOAA satellite was compared to the air temperature data recorded at the available weather stations. Statistical tests show a significant correlation between the air temperature data and the data recorded with the AVHRR radiometer. A statistical method of interpolation was used with a multiple regression and taken into account all the used coordinates and parameters. The results allow to show maps of the interpolated daily air maximum temperature in Brittany with a resolution of 1 km. The results show for 2 cases out 3 a difference of less than 1°C between the interpoled temperature and the recorded temperature., La température maximale de l'air en Bretagne pour 6 journées ensoleillées de 1997 a été corrélée aux paramètres traditionnellement retenus en climatologie : altitude, latitude, distance à la côte. Les données infrarouge du satellite NOAA sont ensuite confrontées aux mêmes données de température. Les tests montrent la bonne corrélation qui existe entre les valeurs mesurées sous abri et celles mesurées par le radiomètre AVHRR. Finalement une méthode d'interpolation par régression multiple est proposée tenant compte de l'ensemble des paramètres et permettant une cartographie des températures de l'air à un kilomètre de résolution spatiale : dans 2 cas sur 3 la méthode donne une erreur inférieure à un degré., Dubreuil Vincent, Montgobert Marion, Planchon Olivier. Une méthode d'interpolation des températures de l'air en Bretagne : combinaison des paramètres géographiques et des mesures infrarouge NOAA - AVHRR. In: Hommes et Terres du Nord, 2002/1. Les échelles fines en climatologie, sous la direction de Gérard Beltrando. pp. 26-39.

The micro-topography of a groundnut plot in Senegal has been recorded over a full cultivation cycle, using an automated device able to measure 16.2 m2 at every 5 cm with an accuracy of 1 mm. Tillage is horse drawn, perpendicular to the general slope, and generates oriented microreliefs. Surface Storage Capacity (SSC) was calculated on both raw and slope-detrended surfaces. Additionally, various boundary conditions (BC) were used: no-wall; three-wall (up, left and right); or mirror (the Digital Elevation Model (DEM) surrounded by eight alternately reversed images of itself). SSC is more affected by these variants than by the variations of microrelief itself. Whatever the calculation method, SSC (as well as random roughness), follows a decreasing exponential with cumulated rainfall, but the coefficients of the exponential differ widely to each other. This suggests that SSC values could be of little use when they are obtained on various slopes, arbitrarily detrended or not, and calculated with arbitrary BC. We suggest a simple geometric model to characterise the way microrelief empties as the slope increases. The model has two calibrated depth-ratio parameters, one in each direction. It gives a more coherent framework for calculation and use of SSC. The model was applied to one of the DEMs of the data set, sampled after the first rain following hoeing. With the mirror-BC and detrended slope, SSC was 3.6 mm. Microrelief was found to behave in the same proportions, when tilted, than a tetrahedral container 94 times wider than deeper in the tillage direction and 11 times perpendicularly. This model represents the volume of surface water that cannot flow in any direction. With three-wall-BC, SSC was 6.7 mm, 1.4 mm remaining on the plot whatever the slope angle, and 5.3 mm behaving the same as a container 69 times wider than deeper. A possible use of this model is illustrated with an attempt to upscale the sampled plot to the watershed to which it belongs.

International audience

International audience; Water erosion of cultivated soils is a threat to the sustainability of agriculture, especially in Mediterranean areas. For a long time, Mediterranean farmers have thus adopted some soil conservation practices. Actual ditch networks, which are generally associated with terraces, result from historical successive farmer settlements and are one of these soil conservation practices. By intercepting surface run-off, ditches decrease slope length and prevent soil erosion on downstream plots. However, since water erosion hazard and ditch network geometries are highly variable in vineyards landscape and since ditch building and maintaining are costly, the objective of this study was to identify and map the resulting efficiency of ditch networks in preventing soil erosion. For a given area, a ditch network efficiency is defined here as the balance between the network density, i.e. network cumulated length for a given area unit, and the erosion sensitivity over an area which measures the performance of the ditch network in limiting soil erosion. The erosion efficiency of ditch networks was thus identified using both i) computer generated ditch networks with various spatial configurations and ii) the stream power index as an erosion sensitivity indicator, computed from a DTM in which each ditch network was burned. The stream power index of the actual networks were compared with a set of generated networks whose density and topology were selected to maximize the performance in preventing soil erosion thanks to the use of a self-developed optimized stochastic network generator. For four 1 km2 hillslopes, we showed that the performances of actual networks to prevent soil erosion was among the best that were obtained by simulated networks with even greater densities. Furthermore, we showed that the stream power index values that accounted for the actual ditch networks to prevent soil erosion hazard was both minimal and weakly variable in the whole study area (30 km2 ) at hillslope scale, whatever the other erosion factors, namely topography and landuse. This suggested that densities and topologies of actual ditch networks in the catchment have been optimized by farmers through individual acts along the last centuries in order to limit the soil erosion hazard. This also confirms there is very little room to propose new ditch network spatial configurations that better prevent vineyards soil erosion.