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11.
Harold E. Brooks Aaron R. Anderson Kathrin Riemann Irina Ebbers Heather Flachs 《Atmospheric Research》2007,83(2-4):294-305
Annual cycles of convectively important atmospheric parameters have been computed for a variety of from the National Center for Atmospheric Research (NCAR)/National Centers for Environmental Prediction (NCEP) global reanalysis, using 7 years of reanalysis data. Regions in the central United States show stronger seasonality in combinations of thermodynamic parameters than found elsewhere in North America or Europe. As a result, there is a period of time in spring and early summer when climatological mean conditions are supportive of severe thunderstorms.The annual cycles help in understanding the large-scale processes that lead to the combination of atmospheric ingredients necessary for strong convection. This, in turn, lays groundwork for possible changes in distribution of the environments associated with possible global climate change. 相似文献
12.
Alessandro Fabbrizio Roland Stalder Kathrin Hametner Detlef Günther Katharina Marquardt 《Contributions to Mineralogy and Petrology》2013,166(2):639-653
We present new partition coefficients for various trace elements including Cl between olivine, pyroxenes, amphibole and coexisting chlorine-bearing aqueous fluid in a series of high-pressure experiments at 2 GPa between 900 and 1,300 °C in natural and synthetic systems. Diamond aggregates were added to the experimental capsule set-up in order to separate the fluid from the solid residue and enable in situ analysis of the quenched solute by LA–ICP–MS. The chlorine and fluorine contents in mantle minerals were measured by electron microprobe, and the nature of OH defects was investigated by infrared spectroscopy. Furthermore, a fluorine-rich olivine from one selected sample was investigated by TEM. Results reveal average Cl concentrations in olivine and pyroxenes around 20 ppm and up to 900 ppm F in olivine, making olivine an important repository of halogens in the mantle. Chlorine is always incompatible with Cl partition coefficients D Cl olivine/fluid varying between 10?5 and 10?3, whereas D Cl orthopyroxene/fluid and D Cl clinopyroxene/fluid are ~10?4 and D Cl amphibole/fluid is ~5 × 10?3. Furthermore, partitioning results for incompatible trace element show that compatibilities of trace elements are generally ordered as D amph/fluid ≈ D cpx/fluid > D opx/fluid > D ol/fluid but that D mineral/fluid for Li and P is very similar for all observed silicate phases. Infrared spectra of olivine synthesized in a F-free Ti-bearing system show absorption bands at 3,525 and ~3,570 cm?1. In F ± TiO2-bearing systems, additional absorption bands appear at ~3,535, ~3,595, 3,640 and 3,670 cm?1. Absorption bands at ~3,530 and ~3,570 cm?1, previously assigned to humite-like point defects, profit from low synthesis temperatures and the presence of F. The presence of planar defects could not be proved by TEM investigations, but dislocations in the olivine lattice were observed and are suggested to be an important site for halogen incorporation in olivine. 相似文献
13.
E. Kathrin Lang 《Planetary and Space Science》2011,59(8):722-732
Spectroscopic studies of the homogeneous and heterogeneous crystallization of supercooled ethane aerosol droplets performed under conditions representative of those in Titan's lower atmosphere are presented. Pure ethane aerosols and both internally- and externally-mixed ensembles of ethane/acetylene and ethane/carbon dioxide aerosols were generated in a bath gas cooling cell and their freezing dynamics monitored using infrared absorption spectroscopy. A detailed overview of the spectroscopic signatures of pure ethane and mixed ethane/acetylene and ethane/carbon dioxide aerosols and their phase-dependence is provided. The ice-nucleating efficiencies of acetylene and carbon dioxide aerosols were compared, as were the efficiencies of freezing via an immersion or contact freezing mechanism. The spectral data provided will be of significant use for remote sensing applications, while the nucleation studies have important consequences for models of Titan's ethane clouds. 相似文献
14.
Sabine Rödelsperger Matthias Becker Carl Gerstenecker Gwendolyn Läufer Kathrin Schilling Dieter Steineck 《Journal of Geodynamics》2010,49(3-4):241-246
Within the project Exupéry, a hybrid deformation observation system is developed, which is part of a Volcano Fast Response System (VFRS). The VFRS shall be a mobile, robust, real-time, easy to use early warning system, which, in case of a volcanic crisis, will support the locale authorities in their decisions about hazard mitigation provisions, especially about the evacuation of people.The hybrid deformation observation system combines a ground-based Synthetic Aperture Radar named IBIS-L with a network of GPS receivers and will allow the continuous, weather independent determination of areal 3D displacements.In this paper we present the results of first tests with IBIS-L in an active quarry near Dieburg, Germany. A Digital Elevation Model (DEM) was determined with IBIS-L and compared with a DEM derived by terrestrial laser scanning and photogrammetry. The ability to determine accurate DEMs with IBIS-L is the basis for the combination of different observation techniques, as without a DEM the displacements observed with IBIS-L cannot be georeferenced.The standard deviation of the differences between the DEM by IBIS-L and the DEM by laser scanning and photogrammetry depends on the surface characteristics. We found a standard deviation of 0.8 m at a slope of rocks and debris, 2.0 m at mining terraces with low vegetation and 3.0 m in a vegetation covered area. 相似文献
15.
Kathrin Häb Nils H. Feige Lars S. Huettenberger Ariane Middel Hans Hagen 《Environmental Earth Sciences》2014,72(10):3781-3793
In urban microclimate research, ground-based thermography is used to gain insight into the spatial distribution of surface temperatures of various materials. Taking snapshots over a certain time span helps experts to observe the temporal thermo-radiative behavior of the monitored surface elements and therefore supports decisions on possible optimizations, e.g., improving the thermal comfort in a neighborhood. Appropriate visualization techniques facilitate decision-making and are thus crucial in the optimization process. In this study, we present a tool that eases the extraction of thermo-radiative features from multi-temporal thermographs taken from a monitored scene. Assisted by our tool, users can identify, choose, and register thermo-radiative features for each time step according to their individual research needs. The features’ temporal development is then visualized using a directed graph that encodes topological events as well as each feature’s size and summarizing statistics. To enhance this summary, a comprehensive animated sequence emphasizes the spatiotemporal behavior of the most significant thermo-radiative features. Salient developments are visually embedded and highlighted in the original infrared images, which are blended in an animation from time step to time step. Since we enable the user to interact with the data in a flexible way, noisy and low resolution image data sets can also be processed. 相似文献
16.
A case of offshore convective initiation by interacting land breezes near Darwin, Australia is investigated using convection-permitting model simulations, radar-derived precipitation observations, thermodynamic profiles from radiosonde soundings and surface measurements. These analyses elucidate the convergence of two land breezes in the Van Diemen Gulf, one originating from the Tiwi Islands and the other from mainland Australia; the convergence is sufficient to initiate a line of convection that forms parallel to the mainland coast in the early morning. While differing in small-scale features, the modeled system shows reasonably good agreement with the observed precipitation accumulations. However, using simulations with different initialization times and examining a second case, it is shown that the representation of the land-breeze system and subsequent convective initiation is very sensitive to the upstream wind and thermodynamic conditions, making correct simulation of these processes challenging. 相似文献
17.
Inter‐ and intra‐colonial genotypic diversity in hermatypic hydrozoans of the family Milleporidae 
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下载免费PDF全文 Genetic diversity is the basis for adaptation and therefore of primary scientific interest, especially in species that are threatened by anthropogenic challenges, e.g. climate change and/or pollution. Coral reefs are among the most threatened but also the most diverse ecosystems and have therefore been studied quite extensively. So far, most investigations have focused on scleractinian corals while the equally important reef builders, the hydrozoans, have been less considered. Here we provide the first study of genotypic variability as well as intra‐colonial genetic variability, the co‐occurrence of more than one genotype within a single colony, in Milleporidae based on microsatellites. We analysed two geographically distinct populations from the Millepora dichotoma complex, one from the Red Sea and one from the Great Barrier Reef. Additionally, a population of Millepora platyphylla was analysed from French Polynesia. We compared microsatellite multilocus genotypes and cytochrome c oxidase subunit I haplotypes for each of the three field sites to detect levels of genotypic diversity at the intra‐ and inter‐specific levels. Furthermore, we examined all species for the occurrence of intra‐colonial genetic variability, a recently described mechanism in scleractinian corals that might enhance the adaptive potential of sessile organisms. We found both species and all field sites to be genotypically variable. Twelve mitochondrial haplotypes and 27 multilocus microsatellite genotypes were identified. In addition, intra‐colonial genetic variability was detected in the M. dichotoma complex from the Great Barrier Reef as well as in M. platyphylla from French Polynesia. All of the intra‐colonial genetically variable colonies consisted of one main genotype and a second divergent genotype caused by somatic mutations (mosaicism). Our study proves that Milleporidae are genetically variable and that the phenomenon of intra‐colonial genetic variability also occurs in this important reef‐building family. 相似文献
18.
In geotechnical engineering, numerical analysis of pile capacity is often performed in such a way that piles are modeled using only the geometry of their final position in the ground and simply loaded to failure. In these analyses, the stress changes caused by the pile installation are neglected, irrespective of the installation method. For displacement piles, which are either pushed or hammered into the ground, such an approach is a very crude simplification. To model the entire installation process of displacement piles a number of additional nonlinear effects need to be considered. As the soil adjacent to the pile is displaced significantly, small deformation theory is no longer applicable and a large deformation finite element formulation is required. In addition, the continuously changing interface between the pile and the soil has to be considered. Recently, large deformation frictional contact has been used to model the pile installation and cone penetration processes. However, one significant limitation of the analysis was the use of linear elements, which have proven to be less accurate than higher order elements for nonlinear materials such as soils.
This paper presents a large deformation frictional contact formulation which can be coupled consistently with quadratic solid elements. The formulation uses the so-called mortar-type discretisation of the contact surfaces. The performance of this contact discretisation technique is demonstrated by accurately predicting the stress transfer between the pile and the soil surfaces. 相似文献
19.
Martin Piringer Sylvain Joffre Alexander Baklanov Andreas Christen Marco Deserti Koen De Ridder Stefan Emeis Patrice Mestayer Maria Tombrou Douglas Middleton Kathrin Baumann-Stanzer Aggeliki Dandou Ari Karppinen Jerzy Burzynski 《Boundary-Layer Meteorology》2007,124(1):3-24
The specific problems of determining and simulating the surface energy balance (SEB) and the mixing height (MH) over urban
areas are examined. The SEB and MH are critical components of algorithms and numerical models for the urban boundary layer,
though the constituent parts of the SEB and the MH are not routinely measured by national weather services. Parameterisations
are thus needed in applications. In this investigation, several recently developed algorithms and models for estimating the
SEB and MH were applied to new datasets and assessed. Results are discussed in terms of the need for spatial resolution and
the parameters needed to describe the urban atmosphere. Limitations of models are identified and recommendations for further
development and observations are given. Having identified gaps in knowledge, key findings from new urban experiments and numerical
modelling for the SEB and MH are given. The diurnal cycle for the SEB is significantly different from rural conditions—urban
heat storage is needed in urban parameterisations. The urban MH is increased over the rural MH, as shown by several numerical
schemes and careful sodar analyses. This work has been carried out within the COST-715 Action “Meteorology applied to urban
air pollution problems (1998–2004). COST 715 reached a consensus proposing representatively sited measurements of meteorological
parameters and turbulent fluxes above roof-tops, and recognised that such data are needed to improve numerical models of the
urban surface processes. 相似文献
20.
Kathrin Abraham Sophie Opfergelt François Fripiat Anne-Julie Cavagna Jeroen T.M. de Jong Stephen F. Foley Luc André Damien Cardinal 《Geostandards and Geoanalytical Research》2008,32(2):193-202
We report silicon isotopic determinations for USGS rock reference materials BHVO-1 and BHVO-2 using a Nu Plasma multi-collector (MC)-ICP-MS, upgraded with a new adjustable entrance slit, to obtain medium resolution, as well as a stronger primary pump and newly designed sampler and skimmer cones ("B" cones). These settings, combined with the use of collector slits, allowed a resolution to be reached that was sufficient to overcome the 14 N16 O and 14 N2 interferences overlying the 30 Si and the 28 Si peaks, respectively, in an earlier set-up. This enabled accurate measurement of both δ30 Si and δ29 Si. The δ value is expressed in per mil variation relative to the NBS 28 quartz reference material. Based on data acquired from numerous sessions spread over a period of six months, we propose a recommended average δ30 Si of −0.33 ± 0.05‰ and −0.29 ± 0.11‰ (2se) for BHVO-1 and BHVO-2, respectively. Our BHVO grand mean silicon isotope composition (δ30 Si =−0.31 ± 0.06‰) is significantly more negative than the only published value for BHVO-2, but is in very good agreement with the recently established average value of ocean island basalts (OIB), confirming the conclusion that the OIB reservoir has a distinct isotopic composition from the solar reservoir as sampled by chondrites. 相似文献