The relevance of preferential flow in catchment scale simulations: Calibrating a 3D dual-permeability model using DREAM

The occurrence of preferential flow in the subsurface has often been shown in field experiments. However, preferential flow is rarely included in models simulating the hydrological response at the catchment scale. If it is considered, preferential flow parameters are typically determined at the plot scale and then transferred to larger-scale simulations. Here, we successfully used the optimization algorithm DiffeRential Evolution Adaptive Metropolis (DREAM) to calibrate a 3D physics-based dual-permeability model directly at the catchment scale. In order to keep computational costs of the optimization routine at a reasonable level, we limited the number of parameters to be calibrated to the ones that had been shown before to be most influential for the simulation of discharge. We also calibrated parameters of the matrix domain and the macropore domain with a fixed parameter ratio between soil layers instead of calibrating every layer separately. These ratios reflected observed depth profiles of soil hydraulic properties at our study site. The dual-permeability parameter sets identified during calibration were able to simulate observed discharge time series satisfactorily but did not outperform a calibrated single-domain reference model scenario. Saturated hydraulic conductivities of the macropore domain were calibrated such that they became very similar to matrix saturated hydraulic conductivities, thereby effectively removing the effect of macropores. This suggests that the incorporation of vertical preferential flow as represented by the dual-permeability approach was not relevant for reproducing the hydrometric response reasonably well in the studied catchment. We also tested the scale-invariance of the calibrated dual-permeability parameter sets by using the parameter sets performing best at catchment scale to simulate plot-scale bromide depth profiles obtained from tracer irrigation experiments. This parameter transfer proved to be not successful, indicating that soil hydraulic parameters are scale-variant, independent of the direction of parameter transfer.     

Multi-attribute machine learning analysis for weak BSR detection in the Pegasus Basin,Offshore New Zealand

Marine Geophysical Research - Much of our knowledge of gas hydrate in the Dongsha area of the South China Sea has been gained through intensive geophysical surveys and drilling. However, many...     

The use of local indicators of spatial association to improve LiDAR-derived predictions of potential amphibian breeding ponds

We examined whether spatially explicit information improved models that use LiDAR return signal intensity to discriminate in-pond habitat from terrestrial habitat at 24 amphibian breeding ponds. The addition of Local Indicators of Spatial Association (LISA) to LiDAR return intensity data significantly improved predictive models at all ponds, reduced residual error by as much as 74%, and appeared to improve models by reducing classification errors associated with types of in-pond vegetation. We conclude that LISA statistics can help maximize the information content that can be extracted from time resolved LiDAR return data in models that predict the occurrence of small, seasonal ponds.      

International legal options for the control of biofouling on international vessels

Shipping represents a threat as a vector for the transfer of non-indigenous marine species through the discharge of ballast water and biofouling of vessels’ external structures and internal piping. While considerable attention has been given to the management of ballast water, there currently exists no international legal instrument with which to control biofouling.A number of existing legal mechanisms may be applicable in the context of coastal States’ rights under international law. However, existing mechanisms are insufficient to regulate all aspects of the biofouling problem to ensure comprehensive management of the issue. There is, therefore, a need for the development of a comprehensive international agreement to address this gap. The issue of biofouling on international vessels has now been included on the work programme of the International Maritime Organisation (IMO). As a contribution to discussions on how to address this particular issue at an international level, this article provides an analysis of the options available through the IMO to address this issue.Having defined the specific “threat scenario” with regard to hull fouling, the article will consider: (i) the international legal framework that has been established to regulate the harmful impacts of international shipping; (ii) the range of practical measures that are available to manage biofouling on vessels; and (iii) international legal options available to States to address the threat of biofouling posed by international shipping.     

The effect of salinity on growth and weight loss of juvenile plaice (Pleuronectes platessa, L): An experimental test

Previous population estimates of the 0+ plaice (Pleuronectes platessa L.) in the Firth of Forth, east central Scotland, did not take account of the Forth estuary west of the Forth bridges. Previous work found plaice in the estuary grew as fast as, or faster than, the outer firth plaice. It was hypothesised that salinity may affect growth rates of early 0+ plaice. This hypothesis was tested in a laboratory experiment, by exposing juvenile plaice to three different, but naturally — experienced by the juveniles, salinities; 25, 30 and 35. Plaice fed a minimum ration did not grow in length. Mean weight decreased at all three salinities, however, the lowest weight loss was found at the lowest salinity (25) and the highest weight loss was found at the highest salinity (35). The minimum feeding ration was halted and plaice were then fed ad libitum. Consumption rates were not significantly different during the ad libitum feeding, while significant differences in mean weight change were found between the highest and lowest salinities.     

The complete set of ASCA X-ray observations of non-magnetic cataclysmic variables

We present the complete set of 34 ASCA observations of non-magnetic cataclysmic variables. Timing analysis reveals large X-ray flux variations in dwarf novae in outburst (Z Cam, SS Cyg and SU UMa) and orbital modulation in high inclination systems (including OY Car, HT Cas, U Gem, T Leo). We also found episodes of unusually low accretion rate during quiescence (VW Hyi and SS Cyg). Spectral analysis reveals broad temperature distributions in individual systems, with emission weighted to lower temperatures in dwarf novae in outburst. Absorption in excess of interstellar values is required in dwarf novae in outburst, but not in quiescence. We also find evidence for subsolar abundances and X-ray reflection in the brightest systems.
LS Peg, V426 Oph and EI UMa have X-ray spectra that are distinct from the rest of the sample and all three exhibit candidate X-ray periodicities. We argue that they should be reclassified as intermediate polars.
In the case of V345 Pav we found that the X-ray source had been previously misidentified.     

Thermokarst sediments and sedimentary structures, Tuktoyaktuk Coastlands, western Arctic Canada

Abrupt climate warming during glacial–interglacial transitions promotes regional thermokarst activity in areas of ice-rich permafrost. The ensuing thaw-related processes of melt-out, soft-sediment deformation and resedimentation may produce widespread thermokarst sediments and sedimentary structures. Examples of the most distinctive thermokarst sediments and sedimentary structures from the Tuktoyaktuk Coastlands, western Arctic Canada, comprise: (1) soft-sediment deformation structures (thermokarst involutions) in a palaeoactive layer; (2) ice-wedge casts and composite-wedge casts; (3) peaty to sandy diamicton deposited mainly by debris flows in retrogressive thaw slumps; and (4) a basal unit of diamicton and/or impure sand in some thermokarst-basin sequences, deposited by progradation of resedimented materials in thermokarst lakes. Many of the thermokarst sediments and sedimentary structures in the Tuktoyaktuk Coastlands formed as a result of rapid climate warming during the last glacial–interglacial transition, although some continue to form at present due to local (non-climatic) factors.Identification of thermokarst sediments and sedimentary structures in the geological record requires evidence for the thaw of excess ice. Direct evidence for the former occurrence of excess ice includes: (1) ice-wedge casts; (2) composite-wedge casts; (3) lenticular platy microstructures in frost-susceptible sediment; (4) certain near-surface brecciation of frost-susceptible bedrock; and (5) ramparted depressions attributed to the decay of frost mounds. Indirect evidence for former excess ice results where thaw consolidation initiates soft-sediment deformation or gelifluction.     

Thermodynamics of mixing in diopside–jadeite,CaMgSi<Subscript>2</Subscript>O<Subscript>6</Subscript>–NaAlSi<Subscript>2</Subscript>O<Subscript>6</Subscript>, solid solution from static lattice energy calculations

Static lattice energy calculations (SLEC), based on empirical interatomic potentials, have been performed for a set of 800 different structures in a 2 × 2 × 4 supercell of C2/c diopside with compositions between diopside and jadeite, and with different states of order of the exchangeable Na/Ca and Mg/Al cations. Excess static energies of these structures have been cluster expanded in a basis set of 37 pair-interaction parameters. These parameters have been used to constrain Monte Carlo simulations of temperature-dependent properties in the range of 273–2,023 K and to calculate a temperature–composition phase diagram. The simulations predict the order–disorder transition in omphacite at 1,150 ± 20°C in good agreement with the experimental data of Carpenter (Mineral Petrol 78:433–440, 1981). The stronger ordering of Mg/Al within the M1 site than of Ca/Na in the M2 site is attributed to the shorter M1–M1 nearest-neighbor distance, and, consequently, the stronger ordering force. The comparison of the simulated relationship between the order parameters corresponding to M1 and M2 sites with the X-ray refinement data on natural omphacites (Boffa Ballaran et al. in Am Mineral 83:419–433, 1998) suggests that the cation ordering becomes kinetically ineffective at about 600°C.     

FAUST observations of ultraviolet sources in the directions of NGC 4038–39 and 6752

Analysis of ultraviolet (UV) observations with the FAUST shuttle-borne telescope toward the Antennae and NGC 6752 celestial regions resulted in the detection of 46 and 221 candidate sources respectively, for a signal-to-noise ratio of 8. We discuss the source detection process and the identification of UV sources with optical counterparts. Using correlations with existing catalogues, we present reliable identifications for approximately 60 per cent of the sources. We find that most identified objects are B, A and F stars. The remaining identified objects are galaxies, a white dwarf in a binary system, and two K-type stars. Nearly all of the remaining unidentified objects have assigned optical counterparts but, lacking additional information, we give these only as best estimates. With help from new diagnostic diagrams, we suggest that these unclassified objects are main-sequence (or giant) stars within the local spiral arm or halo; or other hot evolved objects within the local spiral arm. We discuss the nature of the objects found and compare our results with those predicted from spectral and Galactic models.