Benchmarking in a rotating annulus: a comparative experimental and numerical study of baroclinic wave dynamics

The differentially heated rotating annulus is a widely studied tabletop-size laboratory model of the general mid-latitude atmospheric circulation. The two most relevant factors of cyclogenesis, namely rotation and meridional temperature gradient are quite well captured in this simple arrangement. The radial temperature difference in the cylindrical tank and its rotation rate can be set so that the isothermal surfaces in the bulk tilt, leading to the formation of baroclinic waves. The signatures of these waves at the free water surface have been analyzed via infrared thermography in a wide range of rotation rates (keeping the radial temperature difference constant) and under different initial conditions. In parallel to the laboratory experiments, five groups of the MetStr\"om collaboration have conducted numerical simulations in the same parameter regime using different approaches and solvers, and applying different initial conditions and perturbations. The experimentally and numerically obtained baroclinic wave patterns have been evaluated and compared in terms of their dominant wave modes, spatio-temporal variance properties and drift rates. Thus certain ``benchmarks'' have been created that can later be used as test cases for atmospheric numerical model validation

a comparative experimental and numerical study of baroclinic wave dynamics

The differentially heated rotating annulus is a widely studied tabletop-size laboratory model of the general mid-latitude atmospheric circulation. The two most relevant factors of cyclogenesis, namely rotation and meridional temperature gradient are quite well captured in this simple arrangement. The radial temperature difference in the cylindrical tank and its rotation rate can be set so that the isothermal surfaces in the bulk tilt, leading to the formation of baroclinic waves. The signatures of these waves at the free water surface have been analyzed via infrared thermography in a wide range of rotation rates (keeping the radial temperature difference constant) and under different initial conditions. In parallel to the laboratory experiments, five groups of the MetStröm collaboration have conducted numerical simulations in the same parameter regime using different approaches and solvers, and applying different initial conditions and perturbations. The experimentally and numerically obtained baroclinic wave patterns have been evaluated and compared in terms of their dominant wave modes, spatio-temporal variance properties and drift rates. Thus certain “benchmarks” have been created that can later be used as test cases for atmospheric numerical model validation

Laser-Induced Breakdown Spectroscopy and X-ray Fluorescence Analysis of Bronze Objects from the Late Bronze Age Baley Settlement, Bulgaria

In the presented work, a total of 60 bronze artefacts from the prehistoric settlement of Baley, Bulgaria were analyzed by means of laser-induced breakdown spectroscopy (LIBS) and X-ray fluorescence spectroscopy (XRF). The archaeological finds were excavated from three levels, with a time span from the 15th century BC to the first half of the 11th century BC. The obtained analytical information was used for quantitative estimation of the amount of tin, lead and arsenic, which determine the mechanical properties of the alloy and the manufacturing technology. Based on the estimated quantities of these elements, a chemometric statistical analysis (principal component analysis—PCA) was performed to classify and divide the samples into separate groups according to the production dating. The data obtained in this study can be used for comparison with the elemental content in deposits from other settlements of this period

Crystallization and Preliminary X-ray Diffraction Analysis of the Rab Escort Protein-1 in Complex with Rab Geranylgeranyltransferase

Posttranslational prenylation of proteins is a widespread phenomenon and the majority of prenylated proteins are geranylgeranylated members of the Rab GTPase family. Geranylgeranylation is catalyzed by Rab geranylgeranyltransferase (RabGGTase) and is critical for the ability of Rab protein to mediate vesicular docking and fusion of various intracellular vesicles. RabGGTase consists of a catalytic small alpha, Greek/small beta, Greek heterodimer and an accessory protein termed Rab escort protein (REP-1) that delivers the newly prenylated Rab proteins to their target membrane. Mutations in the REP-1 gene in humans lead to an X-chromosome-linked defect known as choroideremia??a debilitating disease that inevitably culminates in complete blindness. Here we report in vitro assembly and purification of the stoichiometric ternary complex of RabGGTase with REP-1 stabilized by a hydrolysis-resistant phosphoisoprenoid analog??farnesyl phosphonyl(methyl)phoshonate. The complex formed crystals of extended plate morphology under low ionic-strength conditions. X-ray diffraction data were collected to 2.8 ? resolution at the ESRF. The crystals belong to the monoclinic space group P21, with unit-cell parameters a = 68.7, b = 197.7, c = 86.1 $$A, small beta, Greek = 113.4?. Preliminary structural analysis revealed the presence of one molecule in the asymmetric unit

Finite-volume models with implicit subgrid-scale parameterization for the differentially heated rotating annulus

The differentially heated rotating annulus is a classical experiment for the investigation of baroclinic flows and can be regarded as a strongly simplified laboratory model of the atmosphere in mid-latitudes. Data of this experiment, measured at the BTU Cottbus-Senftenberg, are used to validate two numerical finite-volume models (INCA and cylFloit) which differ basically in their grid structure. Both models employ an implicit parameterization of the subgrid-scale turbulence by the Adaptive Local Deconvolution Method (ALDM). One part of the laboratory procedure, which is commonly neglected in simulations, is the annulus spin-up. During this phase the annulus is accelerated from a state of rest to a desired angular velocity. We use a simple modelling approach of the spin-up to investigate whether it increases the agreement between experiment and simulation. The model validation compares the azimuthal mode numbers of the baroclinic waves and does a principal component analysis of time series of the temperature field. The Eady model of baroclinic instability provides a guideline for the qualitative understanding of the observations