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Among severe weather events generated by deep convection, hail represents one of the most hazardous perils for agriculture, buildings, and properties. Moreover, in response to global warming, hailstorm frequency and severity are expected to increase in Europe. Therefore, a better understanding of hail hazards and risks is becoming increasingly crucial. However, major hurdles are posed by direct observations, by being heterogeneous, temporally limited, and scarce, as well as by numerical simulations, which generally lack sufficient detail to represent hailstorm dynamics properly. As a possible solution, hail likelihood can be indirectly assessed by combining multiple data sources, such as remote-sensing detections and ambient numerical predictors. The new high-resolution reanalysis SPHERA (High rEsolution ReAnalysis over Italy), developed at ARPAE, is considered to describe hail-favoring environments over Italy and nearby countries. SPHERA is dynamically downscaled from ERA5 and driven by the model COSMO at the convection-permitting resolution of 2.2 km. A set of predictors is selected and combined with Overshooting cloud Top (OT) satellite detections, constituting a reliable proxy for hail. OTs are automatically detected with a probabilistic algorithm (NASA) from geostationary Meteosat Second Generation SEVIRI infrared images. However, not all OTs are linked to hail. Hence, a filter based on their surrounding ambient conditions is developed to retain only OT occurrences with the potential for hailstorm formation. For this purpose, ESWD (European Severe Weather Database) crowdsourced hail reports are coupled with SPHERA proxies to characterize hailstorm environments. The analysis is performed over 2016-2020. Hence, the primary intent is to present the methodology rather than a comprehensive hail frequency characterization. More than a quarter of non-hailing OTs are removed, mainly over the Mediterranean sea and complex-topography areas. Maximum hail likelihood characterizes pre-Alpine regions and the northern Adriatic sea around 15 UTC in June-July, agreeing with previous European hail climatologies. The hit rate of ESWD reports with OTs exceeds 60%, i.e., ~20% more than the previous coupling of non-probabilistic OT detections with ERA-Interim over Europe. Different ambient characteristics are revealed by separating hit/miss reports for small/large hail events. Most hits present hailstones with diameters ≥3 cm, suggesting a better suitability of the method in case of severe hailstorms. Further, missed small-hail reports show peculiar environmental signatures characterized by lower instability, less wind shear, and colder atmospheric profiles. These results suggest a promising avenue to enhance hailstorm events identification. In addition, further extension of the analysis should shed more light on the climatology of hailstorms.

Hail is one of the most dangerous hazards for agriculture, infrastructures, and buildings of all severe-weather phenomena linked to deep moist convection. Due to global warming, the frequency and severity of hailstorms are expected to increase throughout Europe. It is, therefore, increasingly urgent to improve our understanding of hail hazard and risk. However, the intrinsic difficulties in systematically observing and simulating hail are still a major hurdle. While direct hail observations are heterogeneous, temporally-limited, and scarce, numerical simulations lack sufficient detail to represent the localized and rapidly-evolving hailstorm dynamics. A possible way to indirectly assess hail likelihood is through remote-sensing detections combined with numerical dynamical and thermodynamical characteristics of convective environments prone to hailstorm formation. Indeed, multiple data sources are necessary as, to date, more than a singular proxy is required to characterize hail. The new high-resolution reanalysis dataset SPHERA (High rEsolution ReAnalysis over Italy), developed at ARPAE, is considered for investigating hail-favoring environments over Italy and nearby countries. SPHERA is dynamically downscaled from ERA5, driven by the convection-permitting model COSMO (at 2.2 km grid spacing), providing meteorological data at hourly frequency. A set of parameters is extracted from SPHERA and combined with Overshooting cloud Top (OT) satellite detections, constituting a reliable proxy for hail. A probabilistic algorithm recently developed at NASA automatically detects OTs from geostationary Meteosat Second Generation SEVIRI infrared images. However, not all OTs are associated with hail formation in the storm. Hence, a filter is developed to retain only those occurrences linked to potential hailstorm formation based on the surrounding environmental conditions. To do so, ESWD (European Severe Weather Database) crowdsourced reports, representing the most reliable hail observational dataset in Europe, are coupled with SPHERA proxies to investigate convective environments nearby hailstorm events. The procedure is applied over five years (2016-2020). Hence, the primary purpose is to present the methodology rather than a sound hail frequency estimate. The resulting hailstorm characterization reveals a non-hailing OTs removal exceeding a quarter, mainly over the Mediterranean sea and complex-topography areas. The maximum hail likelihood is observed over pre-Alpine regions and the northern Adriatic sea around 15 UTC in June-July, in agreement with recent European hail climatologies. The validation against ESWD reports provides a hit rate exceeding 60%, roughly 20% more than the previous non-probabilistic OT detections coupling with ERA-Interim over Europe. Separating hit/miss reports and small/large hail reveals different characteristics of hail-prone environments. Most hit reports pertain to large hailstones (diameters ≥ 3 cm), suggesting an inclination of the method to perform better in cases of severe hail occurrences. Investigating the interrelations among SPHERA parameters quantifying the main mechanisms needed for hail formation (i.e., atmospheric instability, freezing level height, and storm organization), the leading role of thermal and thermodynamical factors over the kinetics of the storm emerges. These results suggest promising opportunities to enhance hail dynamics comprehension owing to the advancements in remote-sensing techniques and the development of convection-permitting numerical simulations. In addition, further extension of the analysis should shed more light on the climatology of hailstorms.

Forecasting and early warning systems are important investments to protect lives, properties and livelihood. While early warning systems are frequently used to predict the magnitude, location and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services or financial loss. Complementing early warning systems with impact forecasts has a two‐fold advantage: it would provide decision makers with richer information to take informed decisions about emergency measures, and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multi‐hazard early warning systems. This review discusses the state‐of‐the‐art in impact forecasting for a wide range of natural hazards. We outline the added value of impact‐based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe. Plain language summary Forecasting and early warning systems are important investments to protect lives, properties and livelihood. While such systems are frequently used to predict the magnitude, location and timing of potentially damaging events, they rarely provide impact estimates, such as the expected physical damage, human consequences, disruption of services or financial loss. Extending hazard forecast systems to include impact estimates promises many benefits for the emergency phase, for instance, for organising evacuations. We review and compare the state‐of‐the‐art of impact forcasting across a wide range of natural hazards, and outline opportunities and key challenges for research and development of impact forecasting.

Accurate estimates of hail risk to exposed assets, such as crops, infrastructure, and vehicles, are required for both insurance pricing and preventive measures. Here we present an event catalog to describe the hail hazard in South Africa guided by 14 years of geostationary satellite observations of convective storms. Overshooting cloud tops have been detected, grouped, and tracked to describe the spatiotemporal extent of potential hail events. It is found that hail events concentrate mainly in the southeast of the country, along the Highveld, and around the eastern slopes. Events are most frequent from mid-November through February and peak in the afternoon, between 13:00 and 17:00 UTC. Multivariate stochastic modeling of event properties yields an event catalog spanning 25 000 years, aiming to estimate, in combination with vulnerability and exposure data, hail risk for return periods of 200 years.

From 10 to 12 June 2019, severe thunderstorms affected large parts of Germany. Hail larger than golf ball size caused considerable damage, especially in the Munich area where losses amount to EUR 1 billion. This event thus ranks among the ten most expensive hail events in Europe in the last 40 years. Atmospheric blocking in combination with a moist, unstably stratified air mass provided an excellent setting for the development of severe, hail‐producing thunderstorms across the country. image, German Research Foundation http://dx.doi.org/10.13039/501100001659

Globally relevant and locally devastating, hailstorms produce significant societal impacts; despite this, our understanding of hailstorms and our ability to predict them is still limited.

Over three weeks in May and June 2018, an exceptionally large number of thunderstorms hit vast parts of western and central Europe, causing precipitation of up to 80 mm and several flash floods. During this time, the large-scale atmospheric circulation, which was characterized by a blocking situation over northern Europe, influenced atmospheric conditions relevant for thunderstorm development. Initially, the southwesterly flow on the western flank of the blocking anticyclone induced the advection of warm, moist, and unstably stratified air masses. Due to a low-pressure gradient associated with the blocking anticyclone, these air masses were trapped in western and central Europe, remained almost stationary and prevented a significant air mass exchange. In addition, the low-pressure gradient led to weak flow conditions in the mid-troposphere and thus to low vertical wind shear that prevented thunderstorms from developing into severe organized systems. Most of the storms formed as local-scale, relatively slow-moving single cells. However, due to the related weak propagation speed, several thunderstorms were able to produce torrential heavy rain that affected local-scale areas and triggered several flash floods. Atmospheric blocking also increased the upper-level cut-off low frequency on its upstream regions, which was up to 10 times higher than the climatological mean. Together with filaments of positive potential vorticity (PV), the cut-offs served as trigger mechanisms for a majority of the thunderstorms. For the 22-day study period, we found that more than 50 % of lightning strikes can be linked to a nearby cut-off low or PV filament. The exceptional persistence of low stability combined with weak wind speed in the mid-troposphere over three weeks has not been observed during the past 30 years.

Over 3 weeks in May and June 2018, an exceptionally large number of thunderstorms hit vast parts of western and central Europe, causing precipitation accumulations of up to 80 mm within 1 h and several flash floods. This study examines the conditions and processes that made this particular thunderstorm episode exceptional, with a particular focus on the interaction of processes across scales. During the episode, a blocking situation persisted over northern Europe. Initially, the southwesterly flow on the western flank of the blocking anticyclone induced the advection of warm, moist, and unstably stratified air masses. Due to the low-pressure gradient associated with the blocking anticyclone, these air masses were trapped in western and central Europe, remained almost stationary, and prevented a significant air mass exchange. In addition, the weak geopotential height gradients led to predominantly weak flow conditions in the mid-troposphere and thus to low vertical wind shear that prevented thunderstorms from developing into severe organized systems. Due to a weak propagation speed in combination with high rain rates, several thunderstorms were able to accumulate enormous amounts of precipitation that affected local-scale areas and triggered several torrential flash floods. Atmospheric blocking also increased the upper-level cut-off low frequency on its upstream regions, which was up to 10 times higher than the climatological mean. Together with filaments of positive potential vorticity (PV), the cut-offs provided the mesoscale setting for the development of a large number of thunderstorms. During the 22 d study period, more than 50 % of lightning strikes can be linked to a nearby cut-off low or PV filament. The exceptionally persistent low stability over 3 weeks combined with a weak wind speed in the mid-troposphere has not been observed during the past 30 years., Weather and Climate Dynamics, 1 (2), ISSN:2698-4016, ISSN:2698-4008

A 10-yr geostationary (GEO) overshooting cloud-top (OT) detection database using Multifunction Transport Satellite (MTSAT) Japanese Advanced Meteorological Imager (JAMI) observations has been developed over the Australian region. GEO satellite imagers collect spatially and temporally detailed observations of deep convection, providing insight into the development and evolution of hazardous storms, particularly where surface observations of hazardous storms and deep convection are sparse and ground-based radar or lightning sensor networks are limited. Hazardous storms often produce one or more OTs that indicate the location of strong updrafts where weather hazards are typically concentrated, which can cause substantial impacts on the ground such as hail, damaging winds, tornadoes, and lightning and to aviation such as turbulence and in-flight icing. The 10-yr OT database produced using an automated OT detection algorithm is demonstrated for analysis of storm frequency, diurnally, spatially, and seasonally relative to known features such as the Australian monsoon, expected regions of hazardous storms along the southeastern coastal regions of southern Queensland and New South Wales, and the preferential extratropical cyclone track along the Indian Ocean and southern Australian coast. A filter based on atmospheric instability, deep-layer wind shear, and freezing level was used to identify OTs that could have produced hail. The filtered OT database is used to generate a hail frequency estimate that identifies a region extending from north of Brisbane to Sydney and the Goldfields–Esperance region of eastern Western Australia as the most hail-prone regions.

At the end of July 2013, a series of severe thunderstorms associated with heavy rainfall, severe wind gusts, and large hail affected parts of Germany. On 28 July 2013, two supercells formed almost simultaneously in southern Germany, from which only the more southerly cell produced hailstones up to 10 cm in diameter on a hailswath approximately 120 km long and 15–20 km wide. For the insurance industry, this event with losses of more than EUR 1 billion was one of the most expensive natural disasters that has ever occurred in Germany. This paper investigates the creation, temporal evolution, and effects of the most severe supercell that day by considering and merging radar and satellite data, eyewitness reports, insurance loss data, and numerical model studies. Observations of hail at ground level fit very well with a cold–ring-shaped structure in the cloud top brightness temperature observed by a geostationary satellite imager. Various simulations conducted with the convection-permitting COnsortium for Small-scale MOdeling (COSMO) revealed that the track of the hailstorm could be reproduced only when convection was triggered artificially by two warm bubbles that produced single cells that were precursors of the supercell. The model results suggested that the supercell developed near a pre-existing single cell through low-level flow convergence in an environment with moderate CAPE, but substantial wind shear and storm-relative helicity, both of which persisted for several hours in the area in which the supercell moved.

This article presents a hail frequency estimation based on the detection of cold overshooting cloud tops (OTs) from the Meteosat Second Generation (MSG) operational weather satellites, in combination with a hail-specific filter derived from the ERA-INTERIM reanalysis. This filter has been designed based on the atmospheric properties in the vicinity of hail reports registered in the European Severe Weather Database (ESWD). These include Convective Available Potential Energy (CAPE), 0–6-km bulk wind shear and freezing level height, evaluated at the nearest time step and interpolated from the reanalysis grid to the location of the hail report. Regions highly exposed to hail events include Northern Italy, followed by South-Eastern Austria and Eastern Spain. Pronounced hail frequency is also found in large parts of Eastern Europe, around the Alps, the Czech Republic, Southern Germany, Southern and Eastern France, and in the Iberic and Apennine mountain ranges.

Hagel verursacht regelmäßig immense Schäden. Daher ist es wichtig, Hagelrisiken besser abschätzen zu können.

Severe thunderstorms associated with large hail are among the most important perils in several European regions. Due to the local-scale extent of hail-affected areas and a lack of appropriate observing systems in most regions, hailstorms are not captured accurately and comprehensively, which makes statistical analysis of their frequency or climatology more difficult. Various studies have been conducted so far to describe and analyze the frequency of hailstorms or related impacts. These studies, however, refer to a wide range of spatial scales and consider different time periods, investigation methods, or hailstone diameters. This article will give a comprehensive overview and review of the present state of knowledge on hail hazard and hail frequency over recent decades up to centuries across Europe and is intended as a reference for future studies. We attempted to summarize and synthesize the various prevailing studies with the objective to identify regions that are most prone to hail hazard. Another focus is put on mechanisms that may explain spatial variability and inhomogeneities in hail frequency observed across various spatial scales.

Schwere Hagelstürme in Deutschland und Europa: Schwere Hagelstürme können innerhalb von nur wenigen Minuten erhebliche Schäden in Milliardenhöhe an Gebäuden, landwirtschaftlichen Kulturen oder Fahrzeugen verursachen. Hagel entsteht in Gewitterwolken aus der Interaktion verschiedener Prozesse auf unterschiedlichen Raum- und Zeitskalen. Diese reichen von wolkenmikrophysikalischen Vorgängen im Nanometerbereich über die Entstehung von Gewitterwolken im Bereich von einigen Kilometern bis hin zu geeigneten Großwetterlagen, die sich über rund 1000 km erstrecken. Die räumliche Ausdehnung der Hagelzüge und folglich auch die Schadenflächen sind dagegen sehr stark begrenzt. Aus diesem Grund liegen nur sehr wenige zuverlässige, qualitativ hochwertige Hagelbeobachtungen über längere Zeiträume vor. Um die lokale Hagelhäufigkeit, die beispielsweise für die Quantifizierung des Hagelrisikos von Versicherungen benötigt wird, zu bestimmen, werden Hagelsignale meist indirekt aus Datensätzen verschiedener Fernerkundungssysteme (z.B. Radare, Satelliten) abgeleitet. Diesbezügliche Untersuchungen zeigen eine sehr hohe räumliche Variabilität der Hagelereignisse, die sowohl von der großräumigen Klimatologie als auch von lokalen topografischen Eigenschaften bestimmt ist. Basierend auf verschiedenen, für die Entstehung von Hagel relevanten meteorologischen Größen aus Beobachtungs- oder Modelldaten zeigen alle Studien, dass die Wahrscheinlichkeit von Hagelstürmen über Deutschland und Mitteleuropa in den vergangenen Jahren vor allem durch die Zunahme der Konvektionsenergie in der Atmosphäre angestiegen ist und in der Zukunft wohl weiter ansteigen wird. Severe Hailstorms in Germany and Europe: Within only a few minutes, severe hailstorms can cause significant damage running into billions to buildings, agricultural crops or vehicles. Hail forms inside of thunderstorm clouds due to the interaction of different processes on different spatial and temporal scales. These range from cloud microphysics on the nanometer scale to the formation of storm clouds on the kilometer scale to large-scale weather conditions that extend to around 1000 kilometers. The spatial extent of the hailstreaks and, consequently, also the damage patterns are spatially very limited. For this reason, there is a significant lack of reliable, high-quality observational hail data over longer periods. In order to determine the local hail frequency, which is needed, for example, by the insurance industry to quantify the hail risk, hail signals are usually determined indirectly using datasets from remote sensing instruments such as radars or satellites. Related examinations reveal a very high spatial variability of the hail events, which is determined by both the large-scale climatology and local-scale topographic characteristics. Based on various meteorological parameters relevant to the formation of hailstorms gained from observations or model data, studies show that the probability of hailstorms over Germany and central Europe has increased over recent years, above all due to the increase in convective energy in the atmosphere, and likely will continue to increase over future decades.

Hailstorms represent one of the major sources of damage and insurance loss to residential, commercial, and agricultural assets in several parts of Central Europe. However, there is little knowledge of hail risk across Europe beyond local historical damage reports due to the relative rarity of severe hail events and the lack of uniform detection methods. Here we present a new stochastic catalog of hailstorms for Europe. It is based on satellite observations of overshooting cloud tops (OT) that indicate very strong convective updrafts and hail reports from the European Severe Weather Database (ESWD). Historic hail events are defined based on OT detections from satellite infrared brightness temperatures between 2004 and 2011 for the warm seasons (April–September). The satellite-based historical event properties are complemented by hailstone observations from ESWD to stochastically simulate more than 1 million individual events with an event footprint resolution of 10 km. The final hail event catalog presented in this paper is the first one with a spatial event distribution that is based on a single homogeneous observation source over Europe. Areas of high hail probability or hail risk are found over Central and Southern Europe, including mountainous regions such as the Alps or the Pyrenees. Another region of relatively high hail risk is present over central Eastern Europe.

The analyses specific threshold of lightning discharges density and thunderstorms days for different type of landscape and level of altitudes were determinate. For Central Europe from 9° W to 20° E and from 42° to 56° N (11° x 14° sectors) for April–September period from 2001 to 2014 were investigated. For Europe for the altitude range from 10 m below sea level (bsl) to 200 m above sea level (asl) the highest lightning discharge density is associated with the forest, shrub and wet, urban areas. For the altitude range 200–1000 m asl the highest lightning discharges density is associated with water (river, lakes), urban and forest areas. For the altitude range level from 1000 m asl to 2000 m asl the highest lightning discharges density is associated with the water, forest and grass types. A dense forest on the track of the flow of a moist air mass can promote the rise of air and the formation of convective clouds and lightning strokes. The effect of rives, channels and large lakes on moisture and development of thunderstorm clouds may account for impact on cloud-to-ground (CG) lightning activity. For three flat 3° x 5° areas with similar meteorological and synoptic conditions, increased CG lightning activity is possible if there is a difference in altitude between different types of landscapes. The altitude difference further contributes to the development of convective clouds producing lightning.

A complete portrait of a cell requires a detailed description of its molecular topography: proteins must be linked to particular organelles. Immunocytochemical electron microscopy can reveal locations of proteins with nanometer resolution but is limited by the quality of fixation, the paucity of antibodies and the inaccessibility of antigens. Here we describe correlative fluorescence electron microscopy for the nanoscopic localization of proteins in electron micrographs. We tagged proteins with the fluorescent proteins Citrine or tdEos and expressed them in Caenorhabditis elegans, fixed the worms and embedded them in plastic. We imaged the tagged proteins from ultrathin sections using stimulated emission depletion (STED) microscopy or photoactivated localization microscopy (PALM). Fluorescence correlated with organelles imaged in electron micrographs from the same sections. We used these methods to localize histones, a mitochondrial protein and a presynaptic dense projection protein in electron micrographs.

Neurotransmitter release is achieved through the fusion of synaptic vesicles with the neuronal plasma membrane (exocytosis). Vesicles are then retrieved from the plasma membrane (endocytosis). It was hypothesized more than 3 decades ago that endosomes participate in vesicle recycling, constituting a slow endocytosis pathway required especially after prolonged stimulation. This recycling model predicts that newly endocytosed vesicles fuse with an endosome, which sorts (organizes) the molecules and buds exocytosis-competent vesicles. We analyzed here the endosome function using hippocampal neurons, isolated nerve terminals (synaptosomes), and PC12 cells by stimulated emission depletion microscopy, photooxidation EM, and several conventional microscopy assays. Surprisingly, we found that endosomal sorting is a rapid pathway, which appeared to be involved in the recycling of the initial vesicles to be released on stimulation, the readily releasable pool. In agreement with the endosomal model, the vesicle composition changed after endocytosis, with the newly formed vesicles being enriched in plasma membrane proteins. Vesicle proteins were organized in clusters both in the plasma membrane (on exocytosis) and in the endosome. In the latter compartment, they segregated from plasma membrane components in a process that is likely important for sorting/budding of newly developed vesicles from the endosome.

The representation of the quasi-biennial oscillation (QBO) is investigated in the ERA-40 reanalysis. In the lower stratosphere, where there are a reasonable number of observations, the representation of the QBO is equally good throughout the record. However, strong differences between the first and the second half of the zonal wind data set are found in the upper stratosphere, with a typical offset of –10 m/s in the equatorial zonal wind in the earlier part versus the later part of the ERA-40 record. At the same time, the strength of the QBO is similar. The 7-year running means of zonal wind, wind shear and temperature reveal interesting structures with major changes occuring in the beginning and the middle of the 1980s. Possible explanations are discussed. The identified change of the reanalysed wind profiles over time in ERA-40 demands for a careful use of equatorial upper stratospheric winds from the reanalysis e.g.~for model validation purposes.

Because of the diffraction resolution barrier, optical microscopes have so far failed in visualizing the mitochondrial cristae, that is, the folds of the inner membrane of this 200 to 400 nm diameter sized tubular organelle. Realizing a approximately 30 nm isotropic subdiffraction resolution in isoSTED fluorescence nanoscopy, we have visualized these essential structures in the mitochondria of intact cells. We find a pronounced heterogeneity in the cristae arrangements even within individual mitochondrial tubules.

We demonstrate the first realization of immuno-Raman microspectroscopy, a novel methodology in immunohistochemistry. The in situ detection of antigens in tissue specimens is achieved by surface-enhanced Raman scattering (SERS) from aromatic Raman labels covalently linked to the corresponding antibody. As an example of applications of this new Raman technique, we present the localization of prostate-specific antigen (PSA) in epithelial tissue from patients with prostate carcinoma (PCA). Copyright © 2006 John Wiley & Sons, Ltd.

As pointed out by the forth assessment report of the Intergovernmental Panel on Climate Change, IPCC-AR4 (Meehl et al., 2007), the contribution of the two major ice sheets, Antarctica and Greenland, to global sea level rise, is a subject of key importance for the scientific community. By the end of the next century, a 3–5 °C warming is expected in Greenland. Similar temperatures in this region were reached during the last interglacial (LIG) period, 130–115 ka BP, due to a change in orbital configuration rather than to an anthropogenic forcing. Ice core evidence suggests that the Greenland ice sheet (GIS) survived this warm period, but great uncertainties remain about the total Greenland ice reduction during the LIG. Here we perform long-term simulations of the GIS using an improved ice sheet model. Both the methodologies chosen to reconstruct palaeoclimate and to calibrate the model are strongly based on proxy data. We suggest a relatively low contribution to LIG sea level rise from Greenland melting, ranging from 0.7 to 1.5 m of sea level equivalent, contrasting with previous studies. Our results suggest an important contribution of the Antarctic ice sheet to the LIG highstand.

Changing climate conditions on Greenland influence the snow accumulation rate and surface mass balance (SMB) on the ice sheet and, ultimately, its shape. This can in turn affect local climate via orography and albedo variations and, potentially, remote areas via changes in ocean circulation triggered by melt water or calving from the ice sheet. Examining these interactions in the IPSL global model requires improving the representation of snow at the ice sheet surface. In this paper, we present a new snow scheme implemented in LMDZ, the atmospheric component of the IPSL coupled model. We analyse surface climate and SMB on the Greenland ice sheet under insolation and oceanic boundary conditions for modern, but also for two different past climates, the last glacial inception (115 kyr BP) and the Eemian (126 kyr BP). While being limited by the low resolution of the general circulation model (GCM), present-day SMB is on the same order of magnitude as recent regional model findings. It is affected by a moist bias of the GCM in Western Greenland and a dry bias in the north-east. Under Eemian conditions, the SMB decreases largely, and melting affects areas in which the ice sheet surface is today at high altitude, including recent ice core drilling sites as NEEM. In contrast, glacial inception conditions lead to a higher mass balance overall due to the reduced melting in the colder summer climate. Compared to the widely applied positive degree-day (PDD) parameterization of SMB, our direct modelling results suggest a weaker sensitivity of SMB to changing climatic forcing. For the Eemian climate, our model simulations using interannually varying monthly mean forcings for the ocean surface temperature and sea ice cover lead to significantly higher SMB in southern Greenland compared to simulations forced with climatological monthly means.

Predicting the climate for the future and how it will impact ice sheet evolution requires coupling ice sheet models with climate models. However, before we attempt to develop a realistic coupled setup, we propose, in this study, to first analyse the impact of a model simulated climate on an ice sheet. We undertake this exercise for a set of regional and global climate models. Modelled near surface air temperature and precipitation are provided as upper boundary conditions to the GRISLI (GRenoble Ice Shelf and Land Ice model) hybrid ice sheet model (ISM) in its Greenland configuration. After 20 kyrs of simulation, the resulting ice sheets highlight the differences between the climate models. While modelled ice sheet sizes are generally comparable to the observed one, there are considerable deviations among the ice sheets on regional scales. These deviations can be explained by biases in temperature and precipitation near the coast. This is especially true in the case of global models. But the deviations between the climate models are also due to the differences in the atmospheric general circulation. To account for these differences in the context of coupling ice sheet models with climate models, we conclude that appropriate downscaling methods will be needed. In some cases, systematic corrections of the climatic variables at the interface may be required to obtain realistic results for the Greenland ice sheet (GIS).

In the context of global warming, the contribution of the two major ice sheets, Antarctica and Greenland, to global sea level rise is a subject of key importance for the scientific community (4th assessment report of the Intergovernmental Panel on climate change, IPCC-AR4, Meehl et al., 2007). By the end of the next century, a 3–5 °C warm up is expected in Greenland. Similar temperatures in this region were reached during the last interglacial (LIG) period due to a change in orbital configuration rather than to anthropogenic forcing. Ice core evidence suggests that the Greenland Ice Sheet (GIS) has survived this warm period but great uncertainties remain about the total Greenland ice reduction during the LIG and its sea level rise contribution. In order to improve our confidence in future state projections, we first intend to reconstruct the past states of the GIS using ice sheet modelling, and confront the simulations with paleo data. The chosen methodoly of paleoclimate reconstruction is strongly based on proxy data. Proxy data are also used to constrain the ice sheet model during the calibration phase. Our estimates of Greenland melting contribution to sea level rise during the LIG period range from 0.65 to 1.5 m of sea level equivalent.

The prediction of future climate and ice sheet evolution requires coupling of ice sheet and climate models. Before proceeding to a coupled setup, we propose to analyze the impact of model simulated climate on an ice sheet. Here, we undertake this exercise for a set of regional and global climate models. Modelled near surface air temperature and precipitation are provided as upper boundary condition to the GRISLI (GRenoble Ice Shelf and Land Ice model) hybrid ice sheet model (ISM) in its Greenland configuration. After 20 kyr of simulation, the resulting ice sheets highlight the differences between the climate models. While modelled ice sheet sizes are generally comparable to the observed ones, there are considerable deviations among the ice sheets on regional scales. These can be explained by difficulties in modelling local temperature and precipitation near the coast. This is especially true in the case of global models. But the deviations of each climate model are also due to the differences in the atmospheric general circulation. In the context of coupling ice sheet and climate models, we conclude that appropriate downscaling methods will be needed and systematic corrections of the climatic variables at the interface may be required in some cases to obtain realistic results for the Greenland ice sheet (GIS).

International audience; Samples of precipitation and atmospheric water vapor were collected together with shallow firn/ice cores as part of the new deep drilling project in northwest Greenland: the NEEM project. These samples were analyzed for their isotope composition to understand the processes affecting the climatic signal archived in the water stable isotope records from the NEEM deep ice core. The dominant moisture source for the snow deposited at the NEEM‐site may be originating as far south as 35°N from the western part of the Atlantic Ocean. The surface atmospheric water vapor appears in isotopic equilibrium with the snow surface indicating a large water exchange between the atmosphere and snowpack. The interannual variability of NEEM shallow firn/ice cores stable isotope data covering the last ∼40 years shows an unexpectedly weak NAO signal. Regional to global atmospheric models simulate a dominant summer precipitation in the NEEM area, suggesting that the intermittency of modern winter precipitation is responsible for the lack of a strong NAO imprint. The interannual variability of NEEM isotope data however shows a strong correlation with interannual variations of Baffin Bay sea ice cover, a relationship consistent with air mass trajectories. NEEM deep ice core isotopic records may therefore provide detailed information on past Baffin Bay sea ice extent. NEEM stable water isotope content increasing trend points to a local warming trend of ∼3.0°C over the last 40 years.

Synaptic vesicles recycle repeatedly in order to maintain synaptic transmission. We have previously proposed that upon exocytosis the vesicle components persist as clusters, which would be endocytosed as whole units. It has also been proposed that the vesicle components diffuse into the plasma membrane and are then randomly gathered into new vesicles. We found here that while strong stimulation (releasing the entire recycling pool) causes the diffusion of the vesicle marker synaptotagmin out of synaptic boutons, moderate stimulation (releasing approximately 19% of all vesicles) is followed by no measurable diffusion. In agreement with this observation, synaptotagmin molecules labeled with different fluorescently tagged antibodies did not appear to mix upon vesicle recycling, when investigated by subdiffraction resolution stimulated emission depletion (STED) microscopy. Finally, as protein diffusion from vesicles has been mainly observed using molecules tagged with pH-sensitive green fluorescent protein (pHluorin), we have also investigated the membrane patterning of several native and pHluorin-tagged proteins. While the native proteins had a clustered distribution, the GFP-tagged ones were diffused in the plasma membrane. We conclude that synaptic vesicle components intermix little, at least under moderate stimulation, possibly because of the formation of clusters in the plasma membrane. We suggest that several pHluorin-tagged vesicle proteins are less well integrated in clusters.

[1] The quasi-biennial oscillation (QBO) of stratospheric zonal winds induces a secondary meridional circulation (SMC) consisting of QBO variations in meridional and vertical winds. In this work, we investigate how these instantaneous meridional circulation anomalies add over time to variations of stratospheric transport. To that end, we compute backward parcel trajectories on the basis of the output of a chemistry-climate model (CCM). At the equator, the trajectories show the strongest vertical parcel displacement over a seasonal timescale when the QBO progresses toward easterly phase in the middle stratosphere. During the solstitial seasons a large number of parcels come from the summer hemisphere, causing in addition a QBO variation in the spread of the total ascent among equatorial parcels. A QBO effect on meridional transport is diagnosed from PV gradients during summer in the easterly phase of the QBO, which suggests a variation of the tropical-subtropical barrier strength. Analyses of the parcel trajectories and CCM trace gas distributions confirm this finding. We suggest that this variation is due to the combined effects of QBO and annual variation in meridional advection and in wave-induced eddy transport.

The quasi-biennial oscillation (QBO) of stratospheric zonal winds induces a secondary meridional circulation (SMC) consisting of QBO variations in meridional and vertical winds. In this work, we investigate how these instantaneous meridional circulation anomalies add over time to variations of stratospheric transport. To that end, we compute backward parcel trajectories on the basis of the output of a chemistry-climate model (CCM). At the equator, the trajectories show the strongest vertical parcel displacement over a seasonal timescale when the QBO progresses toward easterly phase in the middle stratosphere. During the solstitial seasons a large number of parcels come from the summer hemisphere, causing in addition a QBO variation in the spread of the total ascent among equatorial parcels. A QBO effect on meridional transport is diagnosed from PV gradients during summer in the easterly phase of the QBO, which suggests a variation of the tropical-subtropical barrier strength. Analyses of the parcel trajectories and CCM trace gas distributions confirm this finding. We suggest that this variation is due to the combined effects of QBO and annual variation in meridional advection and in wave-induced eddy transport.

The influence of various atmospheres and quenching rates during the melt-spinning process, the influence of pre-annealing in air, and surface treatments (mechanical polishing, laser beam irradiation) on surface crystallization of (Co,Ni)B glasses have been studied systematically by means of X-ray diffraction fraction and quantitative optical and electron microscopy. Higher cooling rates during the melt-spinning process lead to a decrease in the number of nucleation sites and/or postcritical nuclei. Remelting of a thin surface layer by laser beam irradiation eleminates quenched-in nuclei at the surfaces of Ni66B34 and Ni64B36 metallic glasses totally. Casting NiB and CoNiB metallic glasses in an oxygen atmosphere changes the surface composition of the ribbon because of selective oxidation of boron, thus influencing crystallization kinetics and morphology of the crystallizing phases; in CoB glasses, on the other hand, no significant influence of oxidation on crystallization behaviour has been observed. Pre-annealing in air (210 °C/48 h) after elimination of quenched-in nuclei in Ni64B36 metallic glass promotes the formation of Ni2B crystals with a strong [001]-texture.

Owing to its sensitivity and noninvasiveness, far-field fluo-rescence microscopy would be almost ideal for biologicalimaging if the resolution of its established variants were notlimitedbydiffractiontoDr l=ð2n sinaÞ,withldenotingthewavelength of light, n the index of refraction, and a theaperture angle of the objective lens.

The quasi-biennial oscillation (QBO) of zonal wind is a prominent mode of variability in the tropical stratosphere. It affects not only the meridional circulation and temperature over a wide latitude range but also the transport and chemistry of trace gases such as ozone. Compared to a QBO less circulation, the long-term climatological means of these quantities are also different. These climatological net effects of the QBO can be studied in general circulation models that extend into the middle atmosphere and have a chemistry and transport component, so-called Chemistry Climate Models (CCMs). In this work we show that the CCM MAECHAM4-CHEM can reproduce the observed QBO variations in temperature and ozone mole fractions when nudged towards observed winds. In particular, it is shown that the QBO signal in transport of nitrogen oxides NOx plays an important role in reproducing the observed ozone QBO, which features a phase reversal slightly below the level of maximum of the ozone mole fraction in the tropics. We then compare two 20-year experiments with the MAECHAM4-CHEM model that differ by including or not including the QBO. The mean wind fields differ between the two model runs, especially during summer and fall seasons in both hemispheres. The differences in the wind field lead to differences in the meridional circulation, by the same mechanism that causes the QBO's secondary meridional circulation, and thereby affect mean temperatures and the mean transport of tracers. In the tropics, the net effect on ozone is mostly due to net differences in upwelling and, higher up, the associated temperature change. We show that a net surplus of up to 15% in NOx in the tropics above 10 hPa in the experiment that includes the QBO does not lead to significantly different volume mixing ratios of ozone. We also note a slight increase in the southern vortex strength as well as earlier vortex formation in northern winter. Polar temperatures differ accordingly. Differences in the strength of the Brewer-Dobson circulation and in further trace gas concentrations are analysed. Our findings underline the importance of a representation of the QBO in CCMs.

Tackling biological problems often involves the imaging and localization of cellular structures on the nanometer scale. Although optical super-resolution below 100 nm can be readily attained with stimulated emission depletion (STED) and photoswitching microscopy methods, attaining an axial resolution

The representation of the quasi-biennial oscillation (QBO) is investigated in the ERA-40 reanalysis. In the lower stratosphere, where there are a reasonable number of observations, the representation of the QBO is equally good throughout the record. However, strong differences between the first and the second half of the zonal wind data set are found in the upper stratosphere, with a typical offset of –10 m/s in the equatorial zonal wind in the earlier part versus the later part of the ERA-40 record. At the same time, the strength of the QBO is similar. The 7-year running means of zonal wind, wind shear and temperature reveal interesting structures with major changes occuring in the beginning and the middle of the 1980s. Possible explanations are discussed. The identified change of the reanalysed wind profiles over time in ERA-40 demands for a careful use of equatorial upper stratospheric winds from the reanalysis e.g.~for model validation purposes.

8 pages, 9 figures, 4 tables., We present a quantitative investigation by linear Raman spectroscopy of a methane/air premixed flame from a commercial burner. Rotational temperatures and absolute densities of the major species, N2, O2, CH4, CO2, and H2O have been measured in a grid of points across the flame section. Axial and radial profiles of temperature and densities are reported, and mass balances along the flame axis are discussed. We show the capabilities of this technique for combustion studies by using currently available standard detectors and spectrometers., This work has been supported by the Spanish Ministerio de Educación y Ciencia, research project FIS2004-2576.

Crystallization of melt-spun NiB metallic glasses in the concentration range from 30 to 36 at.% B has been investigated systematically by means of optical and electron microscopy. In all NiB glasses nucleation occurs preferentially at the free surface of the ribbon. The strong {001} fibre texture of the Ni2B phase (C16 structure) might result from nickel enrichment at the surface, since the Ni2B structure contains nickel layers parallel to the (001) plane. Histograms of the crystal diameter distribution reveal quenched-in nuclei with a scatter in growth rates of about 10% rather than heterogeneous nucleation with transient rates. For the polymorphic crystallization Ni66B34 → Ni2B growth rates in the [110] as well as in the [001] direction have been found to be controlled by an Arrhenius-type equation. For the growth into the ribbon in [001] direction a pre-exponential factor u0 = 6 × 1011 m s−1 and an activation energy Q = 263 kJ mol−1 have been estimated; growth in the plane is slower by a factor of about 4. NiB glasses with lower or higher boron contents exhibit eutectic crystallization reactions with slightly slower growth rates. In a number of glasses with boron contents below 34 at.% crystallization of the metastable boride Ni7B3 (hexagonal: a = 0.696 nm; c = 0.438 nm) has been observed.

Die Zersetzung von Wustitschichten – gebildet im Wasserdampf auf niedrig-legierten Stahlen (13 CrMo 44, 10 CrMo 9 10) bei T > 600°C – wurde untersucht. Der Mechanismus der Zersetzungsreaktionen wurde anhand von Gefuge- und Phasenanalysen an schnell abgekuhlten Proben und Proben, die einer konstanten Temperaturbehandlung bei T < 600°C ausgesetzt waren, ermittelt. Der Wustitzerfall in die stabilen Phasen Magnetit und α-Eisen bei T < 600°C erzeugt ein charakteristisches Zersetzungsgefuge, das die eindeutige Identifizierung von ursprunglich vorhanden gewesenem Wustit auch nach dessen vollstandiger Ruckumwandlung ermoglicht. Wustite in oxide layers on low-alloy steels in water vapour. II. Decomposition of wustite The decomposition of wustite in oxide layers on low-alloy steels formed in water steam at T > 600°C was investigated. The mechanism of the decomposition reaction was analysed by studying the microstructure and phase composition of differently quenched wustite samples and of samples which had been treated at a constant temperature below 600°C. The decomposition of wustite into the stable phases magnetite and α-iron lead to a characteristic decomposition microstructure which makes the identification of originally present wustite clearly possible, even after the complete transformation of this wustite into the stable phases.