Relationship between global mean sea-level and global mean temperature in a climate simulation of the past millennium

The possibility of using global mean near-surface temperature, its rate of change or the global mean ocean heat-flux as predictors to statistically estimate the change of global mean sea-level is explored in the context of a long climate simulation of the past millennium with the climate model ECHO-G. Such relationships have recently been proposed to by-pass the difficulty of estimating future sea-level changes based on simulations with coarse-resolution climate models. It is found that, in this simulation, a simple linear relationship between mean temperature and the rate of change of sea level does not exist. A regression parameter linking both variables, and estimated in sliding 120-year windows, varies widely along the simulation and, in some periods, even attains negative values. The ocean heat-flux and the rate-of-change of mean temperature seem to better capture the rate-of-change of sea level due to thermal expansion.     

A Dynamic Model to Simulate Arsenic,Lead, and Mercury Contamination in the Terrestrial Environment During Extreme Floods of Rivers

Beside damages of infrastructure in industrial regions, extreme floods can cause contamination with particle‐bound pollutants, e. g., due to erosion of soils and sediments. In order to predict contamination with inorganic pollutants, the transport and fate of arsenic, lead, and mercury during a fictive flood event of River Vereinigte Mulde in the region of Bitterfeld (Germany) with 200 years recurrence time was modeled. The finite element model system Telemac2D, which is subdivided into a hydrodynamic (Telemac‐2D), a transport (Subief‐2D), and a water quality module (wq2subief) was applied. The transport and water quality model models were calibrated using results of sediment trap exposures in the floodplain of River Vereinigte Mulde. Model results exhibited that the spatial patterns of particle‐associated arsenic and lead concentrations significantly changed. Extended, mostly agriculturally used areas showed arsenic and lead concentrations between 150 and 200 mg kg^–1 and 250 and 300 mg kg^–1, respectively, while urban areas were to a great extent spared from high contamination with arsenic and lead. Concentrations of particle‐associated mercury showed a pattern distinct from those of arsenic and lead. Outside of small patches with concentrations up to 63 mg kg^–1, concentrations of particle‐associated mercury remained close to zero. Differences in the spatial patterns of the three pollutants regarded mainly arise from significantly different initial and boundary conditions. Sensitivity analyses of initial and boundary conditions revealed a high sensitivity of particle‐bound pollutant concentrations, whereas the sensitivities of concentrations of suspended sediments and soluble pollutants were mediocre to negligible.     

A Dynamic Model to Simulate Spills of Fuel and Diesel Oil in the Terrestrial Environment during Extreme Fluvial Floods

Extreme fluvial floods may cause severe contamination with fuel oil and diesel, originating from gasoline pipes and tanks in private households and industrial areas, respectively. Geo‐referenced oil spills in the region of Bitterfeld (Germany) after extreme flood events, such as in August 2002, were simulated using the two‐dimensional (2D) Finite Element model system Telemac2D, which is subdivided into a hydrodynamic (Telemac‐2D) and a transport module (Subief2D). Fuel oil settled via adhesion showed a thickness of less than 1.0 mm. Fuel oil concentrations on the flood wave amounted up to 80 g m^–3 in the vicinity of the point sources. At a distance of several hundred meters downstream of the point sources, the fuel oil concentrations were calculated to be zero. Settled areas were only partially contaminated with fuel oil. While one village experienced severe oil contamination, the town of Bitterfeld was almost unaffected by oil spills. It was demonstrated that the 2D transport model applied is capable of simulating fuel oil spills during extreme high waters in the terrestrial environment. Such simulations of fuel oil spills will feed into a GIS‐based decision support system of flood protection.     

Global 3‐D solar‐type star‐disc dynamo systems: I. MHD modeling

We have carried out global three‐dimensional magnetohydrodynamic simulations of the star‐disc interaction region around a young solar‐type star. The magnetic field is generated and maintained by dynamos in the star as well as in the disc. The developing mass flows possess non‐periodic time‐variable azimuthal structure and are controlled by the nonaxisymmetric magnetic fields. Since the stellar field drives a strong stellar wind, accretion is anti‐correlated with the stellar field strength and disc matter is spiraling onto the star at low latitudes, both contrary to the generally assumed accretion picture. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

New constraints from the Hα line for the temperature of the transiting planet host star OGLE‐TR‐10

The spectroscopic analysis of systems with transiting planets gives strong constraints on planetary masses and radii as well as the chemical composition of the systems. The properties of the system OGLE‐TR‐10 are not well‐constrained, partly due to the discrepancy of previous measurements of the effective temperature of the host star. This work, which is fully independent from previous works in terms of data reduction and analysis, uses the Hα profile in order to get an additional constraint on the effective temperature. We take previously published UVES observations which have the highest available signal‐to‐noise ratio for OGLE‐TR‐10. A proper normalization to the relative continuum is done using intermediate data products of the reduction pipeline of the UVES spectrograph. The effective temperature then is determined by fitting synthetic Hα profiles to the observed spectrum. With a result of T_eff = 6020 ± 140 K, the Hα profile clearly favours one of the previous measurements. The Hα line is further consistent with dwarf‐like surface gravities as well as solar and super‐solar metallicities previously derived for OGLE‐TR‐10.The Hα line could not be used to its full potential, partly because of the varying shape of the UVES échelle orders after flat field correction. We suggest to improve this feature when constructing future spectrographs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Measurement of particle rotation in a saltation layer

Two computational methods to measure particle rotations from shadow images of sand particles saltating in a wind tunnel are presented. One method calculates the maximum of the cross‐correlations through multiple angular rotations of an imaged particle. The second method polar transforms both images and then calculates the correlation coefficient for multiple pixel displacements in the θ axis, corresponding to particle rotations. The results from both methods were analysed as a function of height above sand bed (3.7–33.4 mm) and particle size (0.32–0.93 mm equivalent mean diameter). Our results indicate little evidence that particle rotation speeds depend on either their size or height above the sand bed. Though similar results were obtained from both methods, there existed different advantages and disadvantages between the methods. Erroneous results likely arose from particles that were inadequately described by a 2‐D rotation axis, or from poorly imaged particles. At a wind tunnel speed of about 12 m/s, most particles rotated at around 300–400 rev/s. Negative rotations were also found, and their proportion was approximately 15% within the total range of ?450 to 850 rev/s. The ratio of displacement kinetic energy to rotation energy was compared across the various groups and had values between 15 and 40. The quotient showed little dependence on height, though decreased with increasing particle size. Wider applicability of the measurement methodology to study snow particle rotation is also discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Seasonal variation of the <Emphasis Type="Italic">M</Emphasis><Subscript>2</Subscript> tide

The seasonal cycle of the main lunar tidal constituent M ₂ is studied globally by an analysis of a high-resolution ocean circulation and tide model (STORMTIDE) simulation, of 19 years of satellite altimeter data, and of multiyear tide-gauge records. The barotropic seasonal tidal variability is dominant in coastal and polar regions with relative changes of the tidal amplitude of 5–10 %. A comparison with the observations shows that the ocean circulation and tide model captures the seasonal pattern of the M ₂ tide reasonably well. There are two main processes leading to the seasonal variability in the barotropic tide: First, seasonal changes in stratification on the continental shelf affect the vertical profile of eddy viscosity and, in turn, the vertical current profile. Second, the frictional effect between sea-ice and the surface ocean layer leads to seasonally varying tidal transport. We estimate from the model simulation that the M ₂ tidal energy dissipation at the sea surface varies seasonally in the Arctic (ocean regions north of 60°N) between 2 and 34 GW, whereas in the Southern Ocean, it varies between 0.5 and 2 GW. The M ₂ internal tide is mainly affected by stratification, and the induced modified phase speed of the internal waves leads to amplitude differences in the surface tide signal of 0.005–0.0150 m. The seasonal signals of the M ₂ surface tide are large compared to the accuracy demands of satellite altimetry and gravity observations and emphasize the importance to consider seasonal tidal variability in the correction processes of satellite data.