Numerical investigation of an oceanic resonant regime induced by hurricane winds

The oceanic mixed layer (OML) response to an idealized hurricane with different propagation speeds is investigated using a two-layer reduced gravity ocean model. First, the model performances are examined with respect to available observations relative to Hurricane Frances (2004). Then, 11 idealized simulations are performed with a Holland (Mon Weather Rev 108(8):1212–1218, 1980) symmetric wind profile as surface forcing with storm propagation speeds ranging from 2 to 12 m s⁻¹. By varying this parameter, the phasing between atmospheric and oceanic scales is modified. Consequently, it leads to different momentum exchanges between the hurricane and the OML and to various oceanic responses. The present study determines how OML momentum and heat budgets depend on this parameter. The kinetic energy flux due to surface wind stress is found to strongly depend on the propagation speed and on the cross-track distance from the hurricane center. A resonant regime between surface winds and near-inertial currents is clearly identified. This regime maximizes locally the energy flux into the OML. For fast-moving hurricanes (>6 m s⁻¹), the ratio of kinetic energy converted into turbulence depends only on the wind stress energy input. For slow-moving hurricanes (<6 m s⁻¹), the upwelling induced by current divergence enhances this conversion by shallowing the OML depth. Regarding the thermodynamic response, two regimes are identified with respect to the propagation speed. For slow-moving hurricanes, the upwelling combined with a sharp temperature gradient at the OML base formed in the leading part of the storm maximizes the oceanic heat loss. For fast propagation speeds, the resonance mechanism sets up the cold wake on the right side of the hurricane track. These results suggest that the propagation speed is a parameter as important as the surface wind speed to accurately describe the oceanic response to a moving hurricane.     

A map of the horizontal flows in the solar convection zone

The first map of the horizontal flows as a function of depth and heliocentric position in the solar convection zone is presented. The map is inferred from a least-squares smoothness-constrained inversion of velocities measured from ring diagrams of the solar p-mode oscillations. The data provide information in four longitude regions at a latitude just south of the solar equator. The presence of several features is suggested by the results:

Assessment of a 2016 mission concept: The search for trace gases in the atmosphere of Mars

The reported detection of methane in the atmosphere of Mars as well as its potentially large seasonal spatial variations challenge our understanding of both the sources and sinks of atmospheric trace gases. The presence of methane suggests ongoing exchange between the subsurface and the atmosphere of potentially biogenic trace gases, while the spatial and temporal variations cannot be accounted for with current knowledge of martian photochemistry. A Joint Instrument Definition Team (JIDT) was asked to assess concepts for a mission that might follow up on these discoveries within the framework of a series of joint missions being considered by ESA and NASA for possible future exploration of Mars. The following is based on the report of the JIDT to the space agencies (Zurek et al., 2009); a synopsis of the report was presented at the Workshop on Mars Methane held in Frascati, Italy, in November 2009. To summarize, the JIDT believed that a scientifically exciting and credible mission could be conducted within the evolving capabilities of the science/telecommunications orbiter being considered by ESA and NASA for possible launch in the 2016 opportunity for Mars.     

Sewer model development under minimum data requirements

Planning, design and operation of urban drainage systems is often based on hydraulic sewer modelling. Sewer models are also increasingly used to quantify pollution loads discharged to aquatic ecosystems (e.g. via combined sewer overflows), which ultimately allows an estimation of the ecological impact emanating from urban drainage systems. The establishment of such network models, however, requires detailed and accurate information about the sewer network structure and the connected surface area. This infrastructure data is often unavailable, confidential or available in ‘paper’ format only. The present paper outlines a novel approach to develop a hydraulic sewer model constrained by a minimum amount of data. The approach combines the application of a surface flow accumulation algorithm to a selectively manipulated Digital Elevation Model (DEM) with a routine for hydraulic network dimensioning to generate a close-to-reality sewer network ready to be implemented in a hydraulic modelling platform. The method is tested for three real-life catchments of which characteristics vary in scale, topography, state of development and network complexity. For all cases the generated network is implemented on the EPA-SWMM platform to allow hydrodynamic simulations. Model performance is assessed by (1) evaluating the spatial match of existing and generated network layout, (2) comparing the estimated hydraulic dimension with real-life infrastructure data and (3) benchmarking simulated runoff with measured data for a defined validation period. The analysis shows that the presented method is capable of reproducing the original network layout, network length and corresponding discharge rates based on little, freely available information. Further research potential is identified to improve the hydraulic dimensioning and the application to complex systems that include control structures. The presented approach is useful to estimate the scope of drainage networks including layout and design (e.g. for preliminary planning in emerging areas) to screen existing networks and to identify critical spots where more precise information is required.     

Development of a conceptual hydrogeological model for the evaluation of residence times of water in soil and groundwater: the state of Hesse case study, Germany

A regional conceptual hydrogeological model has been developed for evaluating residence times of both, percolate water in the unsaturated zone and groundwater in upper aquifers. The model is based on digitally geo-data bases available at the regional level and has been applied for the entire Federal State of Hesse (Germany) with a spatial resolution of 60?×?60?m. Residence times determined for unconsolidated rock areas typically ranged between 10 and 25?years, whereas residence times of <5?years were assessed for consolidated rock areas. With regard to the implementation of the EU Water Framework Directive, the determined residence times may help to assess the time periods between the introduction of well-targeted groundwater protection measures and their impact on groundwater and surface water quality, respectively.     

Crater morphology in sandstone targets: The MEMIN impact parameter study

Abstract– Hypervelocity (2.5–7.8 km s^?1) impact experiments into sandstone were carried out to investigate the influence of projectile velocity and mass, target pore space saturation, target‐projectile density contrast, and target layer orientation on crater size and shape. Crater size increases with increasing projectile velocity and mass as well as with increasing target pore space saturation. Craters in water‐saturated porous targets are generally shallower and larger in volume and in diameter than craters from equivalent impacts into dry porous sandstone. Morphometric analyses of the resultant craters, 5–40 cm in diameter, reveal features that are characteristic of all of our experimental craters regardless of impact conditions (I) a large central depression within a fragile, light‐colored central part, and (II) an outer spallation zone with areas of incipient spallation. Two different mechanical processes, grain fragmentation and intergranular tensile fracturing, are recorded within these crater morphologies. Zone (I) approximates the shape of the transient crater formed by material compression, displacement, comminution, and excavation flow, whereas (II) is the result of intergranular tensile fracturing and spallation. The transient crater dimensions are reconstructed by fitting quadric parabolas to crater profiles from digital elevation models. The dimensions of this transient and of the final crater show the same trends: both increase in volume with increasing impact energy, and with increasing water saturation of the target pore space. The relative size of the transient crater (in percent of the final crater volume) decreases with increasing projectile mass and velocity, signifying a greater contribution of spallation on the final crater size when projectile mass and velocity are increased.     

Web-based Data and Monitoring Platform for Complex Geotechnical Engineering Projects

Data management is the key of geotechnical risk management and disaster prevention providing right information at right time and right place. It supports regular construction cycles as well as handling of exceptional situations occurring probably during execution stages where the detailed knowledge of the actual state of construction is especially important. The web-based client–server software platform DoMaMoS was developed to cover all aspects in a new fashion. Main parts of the software are a graphical user interface, a SQL database and a controller application. Software development concerned user-friendly handling, geotechnical monitoring, security aspects, rapid access and adaptivity during a running project. Basic ideas and main features of the developed software are described and the practical application is shown.     

Radon-thoron monitoring in Tatun volcanic areas of northern Taiwan using LR-115 alpha track detector technique: Pre-calibration and installation

In the present study, experiments have been carried out to calibrate LR-115 alpha detector films in bare and cup-mode exposure for the measurement of radon and thoron concentrations in soil gas. Results showed non-uniformity in track formation on the films in bare-mode exposure. However, in cup-mode exposure the non-uniformity was reduced to a greater extent. The calibration factors obtained for radon in bare- and cup-mode exposures are 0.049 and 0.034 tr. cm^?2 per Bq m^?3 d, respectively. An attempt has been made to calibrate the radon-thoron discriminative cup with LR-115 films for simultaneous measurements of radon and thoron. This paper also presents the preliminary results of radonthoron monitoring in Tatun volcanic areas of northern Taiwan for the first time using radon-thoron discriminators with LR-115 films. The results show that the safe temperature to install the LR-115 films in volcanic areas is ≤ 65°C and thoron concentration in the study area is low.     

Alkali exchange equilibria between a silicate melt and coexisting magmatic volatile phase: an experimental study at 800°C and 100 MPa

Many experimental studies have been performed to evaluate the composition of coexisting silicate melts and magmatic volatile phases (MVP). However, few studies have attempted to define the relationship between melt chemistry and the acidity of a chloride-bearing fluid. Here we report data on melt composition as a function of the HCl concentration of coexisting brines. We performed 35 experimental runs with a NaCl-KCl-HCl-H₂O brine (70 wt% NaCl [equivalent])-silicate melt (starting composition of Qtz_0.38Ab_0.33Or_0.29, anhydrous) assemblage at 800°C and 100 MPa. We determined an apparent equilibrium constant