Search

To perform spatial snow cover simulations for numerical avalanche forecasting, interpolation and downscaling of meteorological data are required, which introduce uncertainties. The repercussions of these uncertainties on modeled snow stability remain mostly unknown. We therefore assessed the contribution of meteorological input uncertainty to modeled snow stability by performing a global sensitivity analysis. We used the numerical snow cover model SNOWPACK to simulate two snow instability metrics, i.e., the skier stability index and the critical crack length, for a field site equipped with an automatic weather station providing the necessary input for the model. Simulations were performed for a winter season, which was marked by a prolonged dry period at the beginning of the season. During this period, the snow surface layers transformed into layers of faceted and depth hoar crystals, which were subsequently buried by snow. The early-season snow surface was likely the weak layer of many avalanches later in the season. Three different scenarios were investigated to better assess the influence of meteorological forcing on snow stability during (a) the weak layer formation period, (b) the slab formation period, and (c) the weak layer and slab formation period. For each scenario, 14 000 simulations were performed, by introducing quasi-random uncertainties to the meteorological input. Uncertainty ranges for meteorological forcing covered typical differences observed within a distance of 2 km or an elevation change of 200 m. Results showed that a weak layer formed in 99.7 % of the simulations, indicating that the weak layer formation was very robust due to the prolonged dry period. For scenario a, modeled grain size of the weak layer was mainly sensitive to precipitation, while the shear strength of the weak layer was sensitive to most input variables, especially air temperature. Once the weak layer existed (case b), precipitation was the most prominent driver for snow stability. The sensitivity analysis highlighted that for all scenarios, the two stability metrics were mostly sensitive to precipitation. Precipitation determined the load of the slab, which in turn influenced weak layer properties. For cases b and c, the two stability metrics showed contradicting behaviors. With increasing precipitation, i.e., deep snowpacks, the skier stability index decreased (became less stable). In contrast, the critical crack length increased with increasing precipitation (became more stable). With regard to spatial simulations of snow stability, the high sensitivity to precipitation suggests that accurate precipitation patterns are necessary to obtain realistic snow stability patterns.

The necessity of characterizing snow through objective, physically motivated parameters has led to new model formulations and new measurement techniques. Consequently, essential structural parameters such as density and specific surface area (for basic characterization) or mechanical parameters such as the critical crack length (for avalanche stability characterization) gradually replace the semiempirical indices acquired from traditional stratigraphy. These advances come along with new demands and potentials for validation. To this end, we conducted the RHOSSA field campaign, in reference to density (ρ) and specific surface area (SSA), at the Weissfluhjoch research site in the Swiss Alps to provide a multi-instrument, multi-resolution dataset of density, SSA and critical crack length over the complete winter season of 2015–2016. In this paper, we present the design of the campaign and a basic analysis of the measurements alongside predictions from the model SNOWPACK. To bridge between traditional and new methods, the campaign comprises traditional profiles, density cutter, IceCube, SnowMicroPen (SMP), micro-computed-tomography, propagation saw tests and compression tests. To bridge between different temporal resolutions, the traditional weekly to biweekly (every 2 weeks, used in this sense throughout the paper) snow pits were complemented by daily SMP measurements. From the latter, we derived a recalibration of the statistical retrieval of density and SSA for SMP version 4 that yields an unprecedented spatiotemporal picture of the seasonal evolution of density and SSA in a snowpack. Finally, we provide an intercomparison of measured and modeled estimates of density and SSA for four characteristic layers over the entire season to demonstrate the potential of high-temporal-resolution monitoring for snowpack model validation.

Observed snow stratigraphy and snow stability are of key importance for avalanche forecasting. Such observations are rare and snow cover models can improve the spatial and temporal resolution. To evaluate snow stability, failure initiation and crack propagation have to be considered. Recently, a new stability criterion relating to crack propagation, namely the critical crack length, was implemented into the snow cover model SNOWPACK. The critical crack length can also be measured in the field with a propagation saw test, which allows for an unambiguous comparison. To validate and improve the parameterization for the critical crack length, we used data from 3 years of field experiments performed close to two automatic weather stations above Davos, Switzerland. We monitored seven distinct weak layers and performed in total 157 propagation saw tests on a weekly basis. Comparing modeled to measured critical crack length showed some discrepancies stemming from model assumption. Hence, we replaced two variables of the original parameterization, namely the weak layer shear modulus and thickness, with a fit factor depending on weak layer density and grain size. With these adjustments, the normalized root-mean-square error between modeled and observed critical crack lengths decreased from 1.80 to 0.28. As the improved parameterization accounts for grain size, values of critical crack lengths for snow layers consisting of small grains, which in general are not weak layers, become larger. In turn, critical weak layers appear more prominently in the vertical profile of critical crack length simulated with SNOWPACK. Hence, minimal values in modeled critical crack length better match observed weak layers. The improved parameterization of critical crack length may be useful for both weak layer detection in simulated snow stratigraphy and also providing more realistic snow stability information – and hence may improve avalanche forecasting.

The aim of this clinical retrospective study was to analyse the prevalence of common disorders in 529 captive bearded dragons that were presented to three exotic animal clinics in Central Europe (Austria and Czech Republic) over a period of three years. A diagnosis was made on the basis of the presenting clinical signs and physical examination in 30.8% of the cases, whereas various additional diagnostic tests were performed in the other cases (69.2%). These included diagnostic imaging (radiography, ultrasound and computed tomography), examination of faecal samples for the presence of parasites, a blood-profile analysis, histological, as well as bacteriological and mycological examinations and necropsy. Gastrointestinal diseases (42.67%) like endoparasitism, constipation, sand ingestion, tympany and meteorism were the most common disorders. In 51.92% of the cases of constipation, endoparasites were present, whereas in 38.46% of the cases of constipation, metabolic bone diseases and imbalances in calcium and phosphorus levels were detected. Most of the analysed faecal samples (83.27%) were positive for the presence of endoparasites (48.7% pinworms, 25.39% coccidians and 16.06% flagellates). Dermatological problems (22.4%) contained skin tumours, which were observed in adult lizards (age range from three to eight years) and included spindle cell tumour on the eyelid, as well as spindle cell sarcoma, squamous cell carcinoma and melanoma on the trunk. Osteodystrophy, limb fractures and various types of necrosis on the limbs and tail were frequently observed musculoskeletal disorders (18.93%). Over half of all animals (57.14%) that underwent a blood test, showed a deviation in the calcium-phosphorus ratio, 63.98% showed hypocalcaemia and 26.71% hyperphosphataemia. Diseases of the urogenital system (9.47%) included renal diseases and dystocia. Neoplastic diseases besides skin tumours included two cases of leukaemia in 4-year-old bearded dragons, one of these with lymphoma in kidneys, lungs and liver and one ganglioneuroma in the body cavity of a bearded dragon of unknown age. Orthopaedic surgeries were most frequently performed to amputate the limbs or tail, whereas soft-tissue surgeries most often included the treatment of skin wounds and correction of cloacal prolapse, in addition to ovariectomy, salpingotomy or salpingectomy in female bearded dragons. Similar to the situation in Australia and the USA, infectious as well as non-infectious diseases are common in captive bearded dragons in Central Europe. Due to the high occurrence of endoparasitism, skin diseases and metabolic bone diseases in this present study, regular veterinary controls in bearded dragons including parasitological faecal examinations and optimisation of feeding and housing are necessary to improve the standard of health of bearded dragons kept as pet lizards in Europe.

If a weak snow layer below a cohesive slab is present in the snow cover, unstable snow conditions can prevail for days or even weeks. We monitored the temporal evolution of a weak layer of faceted crystals as well as the overlaying slab layers at the location of an automatic weather station in the Steintälli field site above Davos (Eastern Swiss Alps). We focussed on the crack propagation propensity and performed propagation saw tests (PSTs) on 7 sampling days during a 2-month period from early January to early March 2015. Based on video images taken during the tests we determined the mechanical properties of the slab and the weak layer and compared them to the results derived from concurrently performed measurements of penetration resistance using the snow micro-penetrometer (SMP). The critical cut length, observed in PSTs, increased overall during the measurement period. The increase was not steady and the lowest values of critical cut length were observed around the middle of the measurement period. The relevant mechanical properties, the slab effective elastic modulus and the weak layer specific fracture, overall increased as well. However, the changes with time differed, suggesting that the critical cut length cannot be assessed by simply monitoring a single mechanical property such as slab load, slab modulus or weak layer specific fracture energy. Instead, crack propagation propensity is the result of a complex interplay between the mechanical properties of the slab and the weak layer. We then compared our field observations to newly developed metrics of snow instability related to either failure initiation or crack propagation propensity. The metrics were either derived from the SMP signal or calculated from simulated snow stratigraphy (SNOWPACK). They partially reproduced the observed temporal evolution of critical cut length and instability test scores. Whereas our unique dataset of quantitative measures of snow instability provides new insights into the complex slab-weak layer interaction, it also showed some deficiencies of the modelled metrics of instability – calling for an improved representation of the mechanical properties.

libRadtran is a widely used software package for radiative transfer calculations. It allows one to compute (polarized) radiances, irradiance, and actinic fluxes in the solar and thermal spectral regions. libRadtran has been used for various applications, including remote sensing of clouds, aerosols and trace gases in the Earth's atmosphere, climate studies, e.g., for the calculation of radiative forcing due to different atmospheric components, for UV forecasting, the calculation of photolysis frequencies, and for remote sensing of other planets in our solar system. The package has been described in Mayer and Kylling (2005). Since then several new features have been included, for example polarization, Raman scattering, a new molecular gas absorption parameterization, and several new parameterizations of cloud and aerosol optical properties. Furthermore, a graphical user interface is now available, which greatly simplifies the usage of the model, especially for new users. This paper gives an overview of libRadtran version 2.0.1 with a focus on new features. Applications including these new features are provided as examples of use. A complete description of libRadtran and all its input options is given in the user manual included in the libRadtran software package, which is freely available at http://www.libradtran.org.

Industrially produced N-fertilizer is essential to the production of cereals that supports current and projected human populations. We constructed a top-down global N budget for maize, rice, and wheat for a 50-year period (1961 to 2010). Cereals harvested a total of 1551 Tg of N, of which 48% was supplied through fertilizer-N and 4% came from net soil depletion. An estimated 48% (737 Tg) of crop N, equal to 29, 38, and 25 kg ha(-1) yr(-1) for maize, rice, and wheat, respectively, is contributed by sources other than fertilizer- or soil-N. Non-symbiotic N2 fixation appears to be the major source of this N, which is 370 Tg or 24% of total N in the crop, corresponding to 13, 22, and 13 kg ha(-1) yr(-1) for maize, rice, and wheat, respectively. Manure (217 Tg or 14%) and atmospheric deposition (96 Tg or 6%) are the other sources of N. Crop residues and seed contribute marginally. Our scaling-down approach to estimate the contribution of non-symbiotic N2 fixation is robust because it focuses on global quantities of N in sources and sinks that are easier to estimate, in contrast to estimating N losses per se, because losses are highly soil-, climate-, and crop-specific.

Industrially produced N-fertilizer is essential to the production of cereals that supports current and projected human populations. We constructed a top-down global N budget for maize, rice, and wheat for a 50-year period (1961 to 2010). Cereals harvested a total of 1551 Tg of N, of which 48% was supplied through fertilizer-N and 4% came from net soil depletion. An estimated 48% (737 Tg) of crop N, equal to 29, 38, and 25 kg ha(-1) yr(-1) for maize, rice, and wheat, respectively, is contributed by sources other than fertilizer- or soil-N. Non-symbiotic N2 fixation appears to be the major source of this N, which is 370 Tg or 24% of total N in the crop, corresponding to 13, 22, and 13 kg ha(-1) yr(-1) for maize, rice, and wheat, respectively. Manure (217 Tg or 14%) and atmospheric deposition (96 Tg or 6%) are the other sources of N. Crop residues and seed contribute marginally. Our scaling-down approach to estimate the contribution of non-symbiotic N2 fixation is robust because it focuses on global quantities of N in sources and sinks that are easier to estimate, in contrast to estimating N losses per se, because losses are highly soil-, climate-, and crop-specific.

Abstract The term Anthropocene initially emerged from the Earth System science community in the early 2000s, denoting a concept that the Holocene Epoch has terminated as a consequence of human activities. First associated with the onset of the Industrial Revolution, it was then more closely linked with the Great Acceleration in industrialization and globalization from the 1950s that fundamentally modified physical, chemical, and biological signals in geological archives. Since 2009, the Anthropocene has been evaluated by the Anthropocene Working Group, tasked with examining it for potential inclusion in the Geological Time Scale. Such inclusion requires a precisely defined chronostratigraphic and geochronological unit with a globally synchronous base and inception, with the mid‐twentieth century being geologically optimal. This reflects an Earth System state in which human activities have become predominant drivers of modifications to the stratigraphic record, making it clearly distinct from the Holocene. However, more recently, the term Anthropocene has also become used for different conceptual interpretations in diverse scholarly fields, including the environmental and social sciences and humanities. These are often flexibly interpreted, commonly without reference to the geological record, and diachronous in time; they often extend much further back in time than the mid‐twentieth century. These broader conceptualizations encompass wide ranges and levels of human impacts and interactions with the environment. Here, we clarify what the Anthropocene is in geological terms and compare the proposed geological (chronostratigraphic) definition with some of these broader interpretations and applications of the term “Anthropocene,” showing both their overlaps and differences.

The title compound, C20H10F12N4O4S2, is an organic diaryl disulfide compound with trifluoroacetamide substituents at the ortho-positions of each benzene ring. There are two molecules (labeled A and B) in the asymmetric unit. The F atoms of three of the –CF3 groups exhibit rotational disorder over two positions each. The S—S bond distances are 2.0914 (7) and 2.0827 (6) Å for molecules A and B, respectively. The dihedral angle between the S—S—C and S—C—C planes is 103.05 (15)° for molecule A and 104.09 (15)° for molecule B. The three-dimensional supramolecular architecture of the crystal is sustained by numerous N—H...O, N—H...S and C—H...O interactions.

The title compound, [Fe(C44H28N4)(C4H6N2)2]·2C4H6N2, is a six-coordinate FeII–porphyrinate complex with the metal located on a center of inversion and coordinated by two axial 1-methylimidazole ligands; the complex crystallizes as a 1-methylimidazole disolvate. The 1-methylimidazole group bonded to the FeII atom [occupancy ratio 0.789 (4):0.211 (4)] and the unbound 1-methylimidazole molecule [0.519 (4):0.481 (4)] were disordered. The average Fe—N(porphyrinate) bond length is 1.998 (3) Å and the axial Fe—N(imidazole) bond length is 1.9970 (12) Å. In the crystal, molecules are linked into a three-molecule aggregate by two weak C—H...N interactions.

The title compound, [Fe(C64H64N8O4)Cl], is a five-coordinate square-pyramidal porphyrin complex with a chloride ion in the axial position, being coordinated from the protected side of the porphyrin; the FeIII atom is displaced by 0.474 (5) Å from the 24-atom mean plane of the porphyrin core towards the chloride. The porphyrin moiety is a `picket-fence' 5,10,15,20-tetrakis[2-(2,2-dimethylpropanamido)phenyl]porphyrinate (por) group. The Fe—Cl bond length is 2.221 (2) Å and the Fe—N(por) bond lengths are in the range 2.043 (5)–2.063 (5) Å. The supramolecular architecture of the crystal is sustained by C—H...O interactions between the pyrrolic and phenyl H atoms of one molecule and the carbonyl O atoms of the 2,2-dimethylpropanamido groups of adjacent molecules. The methyl groups of three of the four tert-butyl substituents exhibited rotational disorder over two positions. The investigated crystal was twinned by a twofold rotation about the (001) axis with a refined twin ratio of 0.4086 (16).

The solvated title compound, [Fe(C44H28N4)(C4H6N2)(C7H7NO)]·CH2Cl2, is a porphyrin complex containing an octahedrally coordinated FeII atom with 1-methylimidazole [Fe—N = 2.0651 (17) Å] and o-nitrosotoluene ligands at the axial positions. The o-nitrosotoluene ligand is N-bound to iron(II) [Fe—N = 1.8406 (18)Å and Fe—N—O = 122.54 (14)°]. The axial N—Fe—N linkage is almost linear, with a bond angle of 177.15 (7)°. One phenyl group of the porphyrin ligand is disordered over two orientations in a 0.710 (3):0.290 (3) ratio. The dichloromethane solvent molecule was severely disordered and its contribution to the scattering was removed with the SQUEEZE routine [van der Sluis & Spek (1990). Acta Cryst. A46, 194–201].

The title compound, [Fe(C44H28N4)(C6HF4O)], is a porphyrin complex with iron(III) in fivefold coordination with a tetrafluorophenolate group as the axial ligand. The Fe atom and the phenolate ligand are disordered across the porphyrin ring with the two phenolates appearing to be roughly related by a center of symmetry. The occupancies of the two phenolate groups refined to 0.788 (3) for the major component and 0.212 (3) for the minor component. The structure shows extraordinary Fe displacements of 0.488 (4) (major) and 0.673 (4) Å (minor) from the 24-atom mean plane of the porphyrin. The Fe—Np distances range from 2.063 (4) to 2.187 (6) Å and the Fe—O distances are 1.903 (5) Å for major component and 1.87 (2) Å for minor component. The four phenyl groups attached to the porphyrin ring form dihedral angles of 63.4 (4), 49.6 (4), 62.4 (4), and 63.3 (4)° (in increasing numerical order) with the three nearest C atoms of the porphyrin ring. The major and minor component phenolate groups form dihedral angles of 24.9 (4)° and 24.8 (4)°, respectively, with the four porphyrin N atoms. The Fe...Fe distance between the two iron(III) atoms of adjacent porphyrin molecules is 6.677 (3) Å. No close intermolecular interaction was observed. The crystal studied was twinned by inversion, with a major–minor component ratio of 0.53 (3):0.47 (3).

The title compound, [Fe(C6HF4O)(C48H36N4O4)]·C6H12, represents a five-coordinate iron(III) porphyrin complex in a square-pyramidal geometry with a tetrafluorophenolate anion as the axial ligand. The FeIII atom is displaced by 0.364 (2) Å from the 24-atom mean plane of the porphyrinate ring towards the tetrafluoro phenolate anion. The average Fe—N distance is 2.053 (2) Å and the Fe—O distance is 1.883 (2) Å. A porphyrin aryl H atom points in the general direction of the phenoxide ring. The mean plane separation between the 24-atom porphyrin planes of two adjacent porphyrin rings is ∼3.7 Å, and the lateral shift is ∼3.5 Å resu, ting in an Fe...Fe separation of 5.6167 (14) Å.

The title compound, [OsCl(NO)(C48H36N4)]·4C4H8O, is a six-coordinate osmium(II) porphyrin complex with nitrosyl (NO) and chloride (Cl) ligands trans to each other in an octahedral geometry. The metal complex lies on a fourfold rotation axis that passes through the Os, N, O and Cl atoms. The NO and Cl ligands are disordered in an 0.511 (12):0.486 (12) ratio.

The title dinitrosyl iron diphosphane complex, [Fe(NO)2(C18H12Cl3P)2] or Fe(NO)2L2 [L = P(C6H4-p-Cl)3] belongs to the family of metal dinitrosyl compounds with the general formula Fe(NO)2(L)x, referred to collectively as dinitrosyl iron compounds (DNICs). The iron atom is tetrahedrally coordinated by two phosphane ligands and two NO groups with Fe—N—O bond angles of 178.76 (15) and 177.67 (14)°.