Observed spatiotemporal variability of boundary-layer turbulence over flat, heterogeneous terrain

In the spring of 2013, extensive measurements with multiple Doppler lidar systems were performed. The instruments were arranged in a triangle with edge lengths of about 3 km in a moderately flat, agriculturally used terrain in northwestern Germany. For 6 mostly cloud-free convective days, vertical velocity variance profiles were calculated. Weighted-averaged surface fluxes proved to be more appropriate than data from individual sites for scaling the variance profiles; but even then, the scatter of profiles was mostly larger than the statistical error. The scatter could not be explained by mean wind speed or stability, whereas time periods with significantly increased variance contained broader thermals. Periods with an elevated maximum of the variance profiles could also be related to broad thermals. Moreover, statistically significant spatial differences of variance were found. They were not influenced by the existing surface heterogeneity. Instead, thermals were preserved between two sites when the travel time was shorter than the large-eddy turnover time. At the same time, no thermals passed for more than 2 h at a third site that was located perpendicular to the mean wind direction in relation to the first two sites. Organized structures of turbulence with subsidence prevailing in the surroundings of thermals can thus partly explain significant spatial variance differences existing for several hours. Therefore, the representativeness of individual variance profiles derived from measurements at a single site cannot be assumed

Higher order quasi-Monte Carlo for Bayesian shape inversion

In this article, we consider a Bayesian approach towards data assimilation and uncertainty quantification in diffusion problems on random domains. We provide a rigorous analysis of parametric regularity of the posterior distribution given that the data exhibit only limited smoothness. Moreover, we present a dimension truncation analysis for the forward problem, which is formulated in terms of the domain mapping method. Having these novel results at hand, we shall consider as a practical example Electrical Impedance Tomography in the regime of constant conductivities. We are interested in computing moments, in particular expectation and variance, of the contour of an unknown inclusion, given perturbed surface measurements. By casting the forward problem into the framework of elliptic diffusion problems on random domains, we can directly apply the presented analysis. This straightforwardly yields parametric regularity results for the system response and for the posterior measure, facilitating the application of higher order quadrature methods for the approximation of moments of quantities of interest. As an example of such a quadrature method, we consider here recently developed higher order quasi-Monte Carlo methods. To solve the forward problem numerically, we employ a fast boundary integral solver. Numerical examples are provided to illustrate the presented approach and validate the theoretical findings

PHENOTYPIC RELATIONSHIP BETWEEN LINEAR TYPE TRAITS AND LONGEVITY OF SIMMENTAL COWS

U istraživanju fenotipske povezanosti između svojstava vanjštine i dugovječnosti korišteni su podaci Hrvatskog stočarskog centra o 4710 krava simentalske pasmine. Krave su izlučene u razdoblju između 1998. i 2007. godine te su imale podatke o ocjenama vanjštine. Dugovječnost je promatrana kroz dužinu proizvodnog vijeka koja je definirana kao broj dana od prvog telenja do datuma izlučenja. Grla su u proizvodnji bila prosječno 44,7 mjeseci odnosno 3,2 laktacije, dok je životni vijek iznosio u prosjeku 70,4 mjeseci. Između svojstava okvira i dugovječnosti simentalskih krava koeficijenti korelacije su se kretali u rasponu od 0,03 do 0,18, gdje je najniža statistički značajna (P<0,05) korelacija utvrđena između položaja zdjelice i dugovječnosti. Najviše je sa dugovječnošću bila povezana širina zdjelice (r=0,18, P<0,01). Vrlo niski koeficijenti korelacije utvrđeni su između svojstava vimena i dugovječnosti, a kretali su se u rasponu od 0,02 do 0,06. Pri tom su statistički visoko značajne (P<0,01) korelacije utvrđene između dugovječnosti i središnjeg suspenzornog ligamenta (0,05), dubine vimena (0,06) i debljine sisa (0,06). U odnosu na svojstva okvira i svojstva vimena, svojstva nogu bila su u slabijoj povezanosti sa dugovječnošću. Najjača i statistički visoko značajna (P<0,01) pozitivna korelacija s dugovječnošću utvrđena je za kut skočnog zgloba (0,05) te visinu papaka (0,08), dok su negativne i nesignifikantne korelacije utvrđene između dugovječnosti i izraženosti skočnog zgloba (-0,02) te putica (-0,01).The data of 4710 Simmental cows from the database of Croatian Livestock Centre were used for calculating the phenotypic correlations between linear type traits and longevity. Cows included in this research were culled from year 1998 to year 2007 and had scores for linear type traits. Longevity was defined as the number of days from first calving until culling. Average length of productive life was 44.7 months that is 3.2 lactations, and average length of true life was 70.4 months. Correlation coefficients between trunk conformation traits and longevity were in range of 0.03 to 0.18. The lowest correlation (P<0.05) was determined between rump side view and longevity, and the highest (P<0.01) between rump width and longevity. Very low correlation coefficients were determined between udder traits and longevity which were in range of 0.02 to 0.06. Statistically significant (P<0.01) correlations were obtained between longevity and suspensory ligament (0.05), udder depth (0.06) and teats thickness (0.06). By comparison with trunk conformation and udder traits, legs traits were in general in lower correlations with longevity. The highest statistically significant (P<0.01) positive correlations were determined between longevity and rear legs side view (0.05) that is longevity and heel depth (0.08). Negative and insignificant correlations were obtained between longevity and hock joint thickness (-0.02), i.e. between longevity and foot angle (-0.01)

Nocturnal low-level clouds over southern West Africa analysed using high-resolution simulations

We performed a high-resolution numerical simulation to study the development of extensive low-level clouds that frequently form over southern West Africa during the monsoon season. This study was made in preparation for a field campaign in 2016 within the Dynamics-aerosol-chemistry-cloud interactions in West Africa (DACCIWA) project and focuses on an area around the city of Savè in southern Benin. Nocturnal low-level clouds evolve a few hundred metres above the ground around the same level as a distinct low-level jet. Several processes are found to determine the spatio-temporal evolution of these clouds including (i) significant cooling of the nocturnal atmosphere caused by horizontal advection with the south-westerly monsoon flow during the first half of the night, (ii) vertical cold air advection due to gravity waves leading to clouds in the wave crests and (iii) enhanced convergence and upward motion upstream of existing clouds that trigger new clouds. The latter is caused by an upward shift of the low-level jet in cloudy areas leading to horizontal convergence in the lower part and to horizontal divergence in the upper part of the cloud layer. Although this single case study hardly allows for a generalisation of the processes found, the results added to the optimisation of the measurements strategy for the field campaign and the observations will be used to test the hypotheses for cloud formation resulting from this study

Bathymetry and Sediment Geochemistry of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut)

Arctic lakes can provide a long-term perspective on environmental change, including trends in long-range atmospheric transport and deposition of contaminants, inferred from studies of sediment cores. In this study, we conducted the first detailed bathymetric survey of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut), the world’s largest lake north of 74˚ latitude. With these data we were able to determine optimal locations for sediment coring and to collect and analyze profundal sediment cores. A bathymetric map of Lake Hazen was developed on the basis of 362 spot soundings obtained with GPS-coupled sounding equipment placed directly on the ice combined with additional soundings from a small boat. The deepest point in the lake (81˚49.5ʹ N; 70˚42.8ʹ W) was found to be 267 m deep. The lake volume was estimated to be 5.14 × 1010 m3, about 10% larger than previous estimates. Using estimates of the discharge of Lake Hazen from the Water Survey of Canada, we estimated the water retention time to be 89 years. Sediment cores were dated using 210Pb and 137Cs. Sedimentation rates at the deep point, estimated using the Constant Rate of Supply model for excess 210Pb, were relatively high (1260 g m-2yr-1) in the period 2005 – 1963 and lower (650 ± 100 g m-2yr-1) in horizons dated to 1950 – 1880. The majority of elements measured in sediment (24 of 29 consistently above detection limits), as well as organic carbon, showed less than 20% variation in concentrations in the top 10 cm (compacted depth), which represent deposition over approximately 140 years. Geochemical characteristics of the sediment suggest that erosional inputs from annual glacial melting are the major source of essentially all elements and that anthropogenic inputs from long-range transport of toxic metals such as mercury and lead are very low.Les lacs de l’Arctique peuvent fournir une perspective à long terme en matière de changement environnemental, notamment en ce qui a trait aux tendances relatives au transport atmosphérique et au dépôt de contaminants sur de longues périodes, tendances inférées à partir d’études de carottes de sédiments. Dans le cadre de la présente étude, nous avons effectué le premier levé bathymétrique détaillé du lac Hazen (parc national Quttinirpaaq, île d’Ellesmere, Nunavut), le plus grand lac de la planète situé au nord de 74˚ de latitude. Grâce aux données prélevées, nous avons réussi à déterminer les meilleurs emplacements pour le prélèvement de carottes de sédiments de même que pour la collecte et l’analyse de carottes de sédiments profonds. Une carte bathymétrique du lac Hazen a été dressée en fonction de 362 sondages obtenus au moyen de matériel d’appareils phoniques dotés de GPS placés directement sur la glace et supplémentés par des sondages recueillis à partir d’un petit bateau. Le point le plus profond du lac (81˚49,5ʹ N; 70˚42,8ʹ O) a été trouvé à 267 m de profondeur. Le volume du lac a été évalué à 5,14 × 1010 m3, soit 10 % de plus que les évaluations précédentes. À l’aide d’estimations du déversement du lac Hazen obtenues auprès de la Division des relevés hydrologiques du Canada, nous avons évalué que la durée de rétention de l’eau était de 89 ans. La datation des carottes de sédiments a été faite à l’aide de 210Pb et de 137Cs. Les taux de sédimentation au point profond, estimés en s’appuyant sur le modèle CRS (Constant Rate of Supply) pour l’excédent 210Pb, étaient relativement élevés (1260 g m-2an-1) pour la période allant de 2005 à 1963, et moins élevés (650 ± 100 g m-2an-1) pour la période de 1950 à 1880. La majorité des éléments mesurés dans les sédiments (24 sur 29 étaient uniformément au-dessus des seuils de détection) ainsi que dans le carbone organique ont produit une variation de concentrations de moins de 20 % dans les 10 cm supérieurs (profondeur compactée), ce qui représente des dépôts s’échelonnant sur environ 140 ans. Les caractéristiques géochimiques des sédiments laissent présumer que les matières d’érosion découlant de la fonte glaciaire annuelle constituent la source principale de sensiblement tous les éléments, et que les matières anthropiques provenant du transport à grande distance de métaux toxiques, tels que le mercure et le plomb, sont très faibles

Why Do Only Some Galaxy Clusters Have Cool Cores?

Flux-limited X-ray samples indicate that about half of rich galaxy clusters have cool cores. Why do only some clusters have cool cores while others do not? In this paper, cosmological N-body + Eulerian hydrodynamic simulations, including radiative cooling and heating, are used to address this question as we examine the formation and evolution of cool core (CC) and non-cool core (NCC) clusters. These adaptive mesh refinement simulations produce both CC and NCC clusters in the same volume. They have a peak resolution of 15.6 h^{-1} kpc within a (256 h^{-1} Mpc)^3 box. Our simulations suggest that there are important evolutionary differences between CC clusters and their NCC counterparts. Many of the numerical CC clusters accreted mass more slowly over time and grew enhanced cool cores via hierarchical mergers; when late major mergers occurred, the CC's survived the collisions. By contrast, NCC clusters experienced major mergers early in their evolution that destroyed embryonic cool cores and produced conditions that prevented CC re-formation. As a result, our simulations predict observationally testable distinctions in the properties of CC and NCC beyond the core regions in clusters. In particular, we find differences between CC versus NCC clusters in the shapes of X-ray surface brightness profiles, between the temperatures and hardness ratios beyond the cores, between the distribution of masses, and between their supercluster environs. It also appears that CC clusters are no closer to hydrostatic equilibrium than NCC clusters, an issue important for precision cosmology measurements.Comment: 17 emulateapj pages, 17 figures, replaced with version accepted to Ap