numerical modeling of flow processes over gravelly surfaces using structured grids and a numerical porosity treatment this article describes the development and validation of a method for representing the complex surface topography of gravel bed rivers in high resolution three dimensional computational fluid dynamic models this is based on a regular structured grid and the application of a porosity modification to the mass conservation equation in which fully blocked cells are assigned a porosity of zero fully unblocked cells are assigned a porosity of one and partly blocked cells are assigned a porosity of between 0 and 1 according to the percentage of the cell volume that is blocked the model retains an equilibrium wall function and an rng type two equation turbulence model the model is combined with a 0 002 m resolution digital elevation model of a flume based water worked gravel bed surface acquired using two media digital photogrammetry and with surface elevations that are precise to 0 001 m the model is validated by comparison with velocity data measured using a three component acoustic doppler velocimeter adv model validation demonstrates a significantly improved level of agreement than in previous studies notably in relation to shear at the bed although the resolution of model predictions was significantly higher than the adv measurements making model assessment in the presence of strong shear especially difficult a series of simulations to assess model sensitivity to bed topographic and roughness representation were undertaken these demonstrated inherent limitations in the prediction of 3 d flow fields in gravel bed rivers without high resolution topographic representation they also showed that model predictions of downstream flux were more sensitive to topographic smoothing that to changes in the roughness parameterization reflecting the importance of both mass conservation i e blockage and momentum conservation effects at the grain and bed form scale model predictions allowed visualization of the structure of form flow interactions at high resolution in particular the most protruding bed particles exerted a critical control on the turbulent kinetic energy maxima typically observed at about 20 of the flow depth above the bed

simulated headward erosion of bank gullies in the dry hot valley region of southwest china although the development and migration of gully headcuts can increase soil loss and accelerate landscape degradation considerably little attention has been paid to the spatiotemporal variations of the morphological characteristics of bank gully heads in the dry hot valley region of southwest china this study explored the in situ variations in soil loss rates and morphological characteristics in active bank gully heads testing the overland flow discharge with a range of 30 to 120 l min 1 in response to this flow actively migrating headcuts developed with retreat rates ranging from 2 6 to 7 9 mm h 1 all experimental runs resulted in a gradual increase in soil loss volume incision depth and retreat distance over time due to set flow rates for the gully beds and upstream areas of gully heads the soil erosion rates were greatest at the beginning of each run and progressively decreased during the scouring test non steady state soil erosion rates were observed in the headwall for the flow discharge levels examined for this study this was due to an abrupt slope collapse after long term scouring effects as degradation progressed similar trends emerged for temporal variations within the fractal dimensions of topographic surfaces in both the gully heads and upstream areas after the scouring was run for a period of 90 min asymptotic fractal dimensions of topographic surfaces were attained in the upstream areas and gully heads suggesting that steady state morphological characteristics had been realised it should be noted that headwall collapses are typically associated with a substantial increase in sediment yield where no other obvious change in morphological characteristics occurs in the headwall therefore even though a significant difference in the soil erosion rates and fractal dimensions of topographic surface values could be found between the bank gully heads and upstream areas the temporal variation in the morphological characteristics of bank gully heads was similar to those observed in upstream areas where ephemeral gullies developed c 2013 elsevier b v all rights reserved

electrical conductivity of the continental crust geophysical measurements indicate that the earth s continental lower crust has a high electrical conductivity for which no simple cause has been found explanation usually relies on either saline fluids saturating the pores or interconnected highly conducting minerals such as graphite fe ti oxides and sulphides providing conducting pathways attempts in the laboratory to clarify the problem have hitherto been unable to recreate conditions likely to be present at depth by controlling the confining pressure and pore fluid pressure applied to a rock saturated with saline fluids at temperatures between 270 c and 1000 c here we report conductivity data obtained using a cell designed to make such measurements on rocks saturated with saline fluids our results show that the conductivity of saturated samples of acidic rocks is explicable entirely in terms of conduction through the pore fluid whereas the conductivity of saturated basic rocks requires the presence of an additional conduction mechanism s we have used the experimental data to construct electrical conductivity depth profiles for the continental crust which when compared with profiles obtained from magnetotelluric observations demonstrate that a mid to lower crust composed of amphibolite saturated with 0 5 m nacl shows electrical conductivities sufficient to explain conductivity depth profiles for the continental crust inferred from geophysical measurements

on the existence of a geothermal anomaly in southern portugal abstract a geothermal anomaly for which the heat flow density hfd values are more than three times the normal average value for the earth has been reported to exist in hercynian structures in southern portugal in the area of the intersection of the messejana fault and the ferreira ficalho overthrust such high hfd values would imply that the thermal regime of the crust is different from that found in other hercynian regions to try to identify the geothermal anomaly in geoelectrical terms and to understand its origin and relation to the regional geological framework a magnetotelluric survey in the frequency range 0 031 128 hz was carried out in the area that includes the zone of high hfd values the results of the survey are discussed in conjunction with magnetic gravimetric and seismic information as well as synthetic calculations of temperature distributions within the crust it is concluded that the geothermal anomaly is probably a shallow feature and does not represent the regional thermal regime of the crust in southern portugal

electrical conductivity models for the continental crust based on laboratory measurements on high grade metamorphic rocks summary deep electrical conductivity soundings are increasingly being used as an additional source of information regarding the nature of the lower continental crust however a lack of relevant laboratory based conductivity measurements makes interpretation of such soundings difficult laboratory measurements have been made on saturated and unsaturated samples of possible lower crustal rock types subjected to confining pressures up to 0 4 gpa temperatures up to 300 c and with variable pore fluid pressure up to the confining pressure extrapolation of these results suggests that the surprisingly high conductivities deduced for depths of approximately 20 km in certain stable continental areas may result from a combination of basic rock type and high pore fluid pressures for whereas the conductivities measured in acid rock types can be explained in terms of conduction through the pore fluid alone the conductivities measured in basic rock types imply enhanced conduction presumably through the matrix or along grain boundaries the lower conductivities deduced from field experiments for the upper crust may be due to more acid rock types and or lower pore fluid pressures perhaps due to hydration reactions in areas where the high conductivity layer is coincident with a low velocity layer an explanation in terms of changing pore fluid pressure i e low to high with increasing depth seems more likely

ephemeral gully erosion in southern navarra spain abstract ephemeral gully erosion is a common type of water erosion in the loamy soils formed on the miocene marls of southern navarra a study has been conducted to describe the different types of ephemeral gullies and to determine their origin evolution and importance as sediment sources three main types were identified according to their origin classic ephemeral gullies formed within the same field where runoff starts drainage ephemeral gullies collecting the runoff from another upstream area and discontinuity ephemeral gullies due to some abrupt slope change in the landscape during 2 consecutive years of normal precipitation ephemeral gully erosion has caused significant soil losses locally over 2 66 kg m 2 yr 1 which is above tolerable levels in each year one short and intense rainfall event has been responsible for almost all soil losses from ephemeral gullies the main cause of gully formation is the lack of any proper waterway for conveying water excess conventional tillage practices provoked gully occurrence while the maintenance of stubble or vegetation cover completely prevented their formation although farmers refill gullies every year they reappear at the same position if no preventive measures are taken early winter has been the most critical period for gully formation when the soil is wetter and the surface cover is scarce but a strong summer thunderstorm also caused severe gully erosion in unprotected soils two simple topographic indices based on the area and the slope of the watersheds are useful to describe total soil losses

geomorphometric assessment of spatial sediment connectivity in small alpine catchments abstract complex and rugged topography induces large variations in erosion and sediment delivery in the headwaters of alpine catchments an effective connection of hillslopes with the channel network results in highly efficient sediment transfer processes such as debris flows in contrast morphological conditions producing decoupling of hillslopes from channels e g glacial cirques may exclude large areas of the catchment from sediment delivery to its lower parts moreover an efficient connection between hillslopes and channel network does not always ensure an effective downstream transfer of sediment low slope channel reaches e g in hanging valleys cause sediment deposition which often results in changes of the sediment transport processes typically from debris flow to streamflow with low bedload and suspended load rates the availability of high resolution digital terrain models such as those derived from aerial lidar improves our capability to quantify the topographic controls on sediment connectivity a geomorphometric index based on the approach by borselli et al 2008 was developed and applied to assess spatial sediment connectivity in two small catchments of the italian alps featuring contrasting morphological characteristics the results of the geomorphometric analysis were checked against field evidences showing good performance and thus potential usefulness of the index

evidence for an extensive intrusive component of the deccan large igneous province in the narmada son lineament region india from three dimensional magnetotelluric studies abstract the crustal electrical structure beneath the western segment of narmada son lineament zone in central india has been imaged using magnetotelluric mt data set of 153 stations distributed over a grid 7 8 km site spacing three dimensional modeling of this data set brought out several major crustal conductors with different geometries at different depth levels in the crustal column the conductive features correlating with gravity high anomalies and high seismic velocity zones are interpreted to be mafic ultramafic bodies derived from mantle we infer that these bodies represent the intrusive component of the large igneous province lip of the deccan volcanic episode triggered by the passage of the indian continent over the reunion hot spot during the late cretaceous the disposition and the geometry of the subsurface magmatic bodies which must have served as magma chambers for outpouring of the deccan lavas suggest that they are closely related to the plumbing geometry of the lip of the deccan volcanic episode

runoff and soil moisture as driving factors in suspended sediment transport of a small mid mountain mediterranean catchment abstract soil moisture conditions play a key role in runoff and sediment load dynamics in river catchments of contrasting ecosystems however the highly marked seasonality of mediterranean climate affects hydrological processes and sediment transport strongly as evapotranspiration determines a succession of wet transition and dry periods throughout a hydrological year this study examines results of soil moisture water and sediment fluxes during five hydrological years in a representative small mid mountain mediterranean catchment it aims to assess the sediment load contribution and its variability at different temporal scales precipitation runoff and suspended sediment load were calculated at annual seasonal and event scales to assess inter and intra annual variability a database with 45 events was used to identify the main controlling factors over sediment load thought bivariate relationships and an analysis of soil moisture discharge and discharge suspended sediment concentration hysteresis at the annual scale lithology land use and soil conservation structures characteristic of the catchment caused low values of sediment yield although inter annual rates varied by up to three orders of magnitude 0 08 to 11 86 t km 2 y 1 seasonal analysis of accumulated sediment load showed that 80 was generated during the autumn and winter seasons at the event scale streamflow and soil moisture were the controlling factors for the largest sediment load contributions the highest frequency of clockwise discharge suspended sediment concentration hysteresis revealed that most of the sediment was generated from nearby sources although the largest sediment loads were contributed under wet antecedent conditions as depicted by the soil moisture discharge hysteresis assessment

quasi biennial oscillation effects in the semidiurnal tide of the antarctic lower thermosphere a continuous 37 year record of the geomagnetic field from argentine islands geomagnetic observatory at faraday research station 65 s 64 w antarctica has been analysed to reveal a 27 month periodicity in the amplitude of the semidiurnal sq variation in the h component significant at the 98 level this indicates the presence of a periodicity in the strength of the semidiurnal tide at dynamo region altitudes matching that of the quasi biennial oscillation qbo classically observed in the zonal stratospheric winds at equatorial latitudes it adds to similar observations olsen 1994 which demonstrated such an effect in the diurnal sq range at near equatorial latitudes but which showed no evidence for its presence at mid latitudes faraday research station is in a uniquely advantageous geophysical location for such geographically high latitude observations

electrical conductivity of fluid bearing quartzite under lower crustal conditions abstract the electrical conductivity of fluid bearing quartzite was determined as function of temperature and fluid fraction at 1 gpa in order to assess the origin of the high conductivity anomalies observed in the middle to lower crustal levels dihedral angles of quartz fluid quartz determined from recovered samples were below 60 suggesting that fluid forms an interconnected network through the quartz aggregate the electrical conductivity of quartzite increases with increasing temperature which can be approximately expressed by arrhenius equation the apparent activation enthalpy decreases from 0 70 to 0 25 ev with increasing fluid fraction in volume from 0 00043 to 0 32 the electrical conductivity of the fluid bearing quartzite increased with fluid fraction proportionally to a power law 0 56 0 71 within the temperature range of 900 1000 k the electrical conductivity of the aqueous fluid bearing quartzite with the maximum fluid fraction 0 32 was found to be about three orders of magnitude higher than that of dry quartzite at 1000 k however its electrical conductivity was definitely lower than the geophysically observed values of high conductivity anomalies even if the quartzite contained large fluid fractions 0 32 the present results suggest that fluid bearing quartzite is unable to account for the high conductivity anomalies in terms of fluid fraction a significant amount of other ionic species such as na cl and al in aqueous fluid in addition to silica phases dissolved in fluid is required to increase conductivity

human impacts on fluvial systems in the mediterranean region the long history of substantial human impacts on the landscape of the mediterranean region and their effects on fluvial systems is documented these effects have included impacts of deforestation and other land use changes agricultural terracing on a wide scale water transfers and irrigation schemes during the 20th century major changes were made directly to channels through channelisation construction of dams of various sizes and extraction of gravel and indirectly by reforestation these changes have caused a major phase of incision on some rivers runoff and soil erosion have been affected by types of crops and agricultural practices as well as by the varying extent of cultivation and grazing some recent agricultural practices involve wholescale relandscaping of the topography and alteration of surface properties of material the importance of analysing the connectivity within different land units and of the spatial position of human activity within a catchment is illustrated the analysis of connectivity is the key to understanding the variability of impact and the extent of propagation of effects

linking environmental regimes space and time interpretations of structural and functional connectivity connectivity as a concept has been increasingly part of discussions or explanations in hydrology geomorphology and ecology we address recent critiques of this approach by demonstrating how a refinement which distinguishes structural connectivity from functional connectivity can be used to explain patterns observed in very different environmental systems these systems are found in linkages between surface and subsurface flowpaths and the hyporheos in the river don a temperate river channel in yorkshire uk in surface and subsurface fluxes in agricultural land in the uk and in vegetation and surface conditions in a degrading environment at the sevilleta lter site in the semi arid southwest usa first we demonstrate long term geological and structural controls mediated by in channel processes second human organization of landscape elements is a significant control on runoff and erosion so that similar events can produce very different responses and vice versa third linkages between the removal of grass vegetation and runoff and erosion produce non linear and path dependent feedbacks which control the subsequent degradation of the landscape making the process difficult to reverse as a result of these studies we argue that even in cases where connectivity cannot be directly quantified at least at present this limitation does not prevent the concept from being a useful heuristic device for exploring responses of complex systems furthermore this result implies that an increasing need exists for disciplinary connectivity to investigate such systems

microscopic scale conductivity as explanation of magnetotelluric results from the alps of western switzerland summary recent mt soundings carried out in the penninic alps of valais have shown the presence of a very good outcropping conductor extremely high conductivity was attributed to the presence of graphite to verify this assumption the electrical properties of borehole black shales were measured under simulated physical conditions electrical frequency hydrostatic confining pressure internal fluid pressure temperature these measurements showed that under all physical conditions electrical frequency in the 0 005 200 hz interval hydrostatic confining pressure up to 39 mpa internal fluid pressure up to 23 mpa temperature up to 180 uc one of the samples studied was very conductive resistivity less than 2 vm under all physical conditions interestingly despite similar macroscopic aspect other samples from a nearby borehole were found to be only slightly conductive chemical mineralogical and petrographic investigations revealed that the enhanced electrical conductivity is mostly due to textural characteristics such as grain size and carbon film distribution at the grain boundaries rather than to chemical differences

observational evidence for temporary planetary wave forcing of the mlt during fall equinox we present direct observations of zonal wave numbers 1 and 2 planetary wave activity in the mesopause region derived from a longitudinal chain of high latitude northern hemisphere 51 66 n super dual auroral radar network radars over a 9 year period 2000 2008 the planetary wave activity observed shows a consistent increase around the fall equinox this is shown to be coincident with a minimum in the magnitude of the stratospheric winds and consequently a minimum in the stratospheric gravity wave filtering and the subsequent momentum deposition in the mesopause region despite this the observed meridional winds are shown to be perturbed poleward and mesopause temperatures rise temporarily suggesting that westward momentum deposition from planetary waves temporarily becomes the dominant forcing on the mesopause region each fall equinox

geomorphic considerations for erosion prediction current soil erosion prediction technology addresses processes of rainsplash overland flow sediment transport and rill erosion in small watersheds the effects of factors determining sediment yield from larger scale drainage basins in which sediment movement is controlled by the combined small scale processes and a complex set of channel and other basin scale sediment delivery processes such as soil creep bioturbation and accelerated erosion due to denudation of vegetation have been poorly evaluated general suggestions are provided for the development of erosion prediction technology at the geomorphic or drainage basin scale based on the separation of sediment yield data for channel and geomorphic processes from those of field scale soil loss an emerging technology must consider 1 the effects on sediment yield of climate geology and soils topography biotic interactions with other soil processes and land use practices 2 all processes of sediment delivery to a channel system and 3 the general tendency in most drainage basins for progressively greater sediment storage in the downstream direction

the sediment delivery problem abstract the linking of on site rates of erosion and soil loss within a drainage basin to the sediment yield at the basin outlet and improved knowledge and representation of the associated processes of sediment delivery represent a major research need within the field of erosion and sedimentation and also an important scale problem in drainage basin studies this paper reviews the limitations of the sediment delivery ratio concept by considering the problems of temporal and spatial lumping and its blackbox nature some recent advances in our understanding of the sediment delivery system and its modelling are described and the lack of detailed empirical investigations is highlighted the significance of recent concern for the role of sediments in the transport of nutrients and contaminants to sediment delivery studies is introduced and the need for further work in this field is emphasised

the value of google earth for erosion mapping abstract google earth ge has been used in several geomorphological contexts especially in the study of river networks glacial coastal landslides and desert landforms in some cases quantification is possible and landform process relations can be inferred ge has been little used in studies of contemporary soil erosion this brief case study illustrates the potential for quick free and accurate surveys that are particularly valuable as an aid to field work the main drawback of ge is the arbitrary timing of imagery in this case with only 3 years of complete coverage of the study area between 2001 and 2015

electrical resistivities of crustal fluids results of calculations on the electrical resistivities of crustal fluids as a function of temperature pressure and fluid composition indicate that crustal fluids can range in resistivity from approximately 1 m the dominant contribution to decreasing the resistivities of crustal fluids comes from increased concentrations of chloride and bicarbonate salts and increased temperature and density of the fluids calculations indicate that the sharpest decrease in fluid resistivity occurs at shallow depths 10 km and temperatures 300 c can not be readily explained as a product of variations in resistivities of crustal fluids these results indicate that a transition in mineralogy or pore shape geometry is more likely responsible for the observed decrease in electrical resistivity of the middle crust than a major change in fluid resistivity

electrical imaging of narmada son lineament zone central india from magnetotellurics the narmada son lineament nsl zone is the second most important tectonic feature after himalayas in the indian geology magnetotelluric mt studies were carried out in the nsl zone along a 130 km long nne ssw trending profile the area of investigation extends from edlabad 20 46 16 7 5 59 05 in the south to khandwa 21 53 51 7 6 18 05 i n the north the data shows in general the validity of a two dimensional 2d approach besides providing details on the shallow crustal section the 2d modeling results resolved four high conductive zones extending from the middle to deep crust spatially coinciding with the major structural features in the area namely the gavligarh tapti barwani sukta and narmada south faults the model for the shallow section has brought out a moderately resistive layer 30 150 m representing the exposed deccan trap layer overlying a conductive layer 10 30 m inferred to be the subtrappean gondwana sediments the latter resting on a high resistive basement upper crust the deccan trap thickness varies from around a few hundred meters to as much as 1 5 km along the traverse a subtrappean sedimentary basin like feature is delineated in the northern half of the traverse where a sudden thickening of subtrappean sediments amounting to as much as 2 km is noticed the high resistive upper crust is relatively thick towards the southern end and tends to become thinner towards the middle and northern part of the traverse the lower crustal segment is conductive over a major part of the profile considering the generally enhanced heat flow values in the nsl region coupled with characteristic gravity highs and enhanced seismic velocities coinciding with the mid to lower crustal conductors delineated from mt presence of zones of high density mafic bodies intrusives with fluids presumably associated with magmatic underplating of the crust in the zone of major tectonic faults in nsl region are inferred 2004 elsevier b v all rights reserved

catchment scale mapping of surface grain size in gravel bed rivers using airborne digital imagery 1 this study develops and assesses two methods for estimating median surface grain sizes using digital image processing from centimeter resolution airborne imagery digital images with ground resolutions of 3 cm and 10 cm were combined with field calibration measurements to establish predictive relationships for grain size as a function of both local image texture and local image semivariance independently acquired grain size data were then used to assess the algorithm performance results showed that for the 3 cm imagery both local image semivariance and texture are highly sensitive to median grain size with semivariance being a better predictor than image texture however in the case of 10 cm imagery sensitivity of image semivariance and texture to grain size was poor and this scale of imagery was found to be unsuitable for grain size estimation this study therefore demonstrates that local image properties in very high resolution digital imagery allow for automated grain size measurement using image processing and remote sensing methods

evidence from borehole samples for the role of accessory minerals in lower crustal conductivity the high electrical conductivity of the lower continental crust as inferred from geophysical measurements1 has defied a simple explanation both pore saturating brines2 and interconnected carbon films3 5 have been proposed as conducting pathways but their relative importance remains uncertain and may vary from place to place6 so far attempts to address this question in the laboratory have had to rely on samples of metamorphic rock collected from surface exposures7 10 although these rocks almost certainly originated in the lower crust chemical alteration during their transport to and residence at the surface is likely to have affected their conducting properties here we report conductivity data for pristine crustal rocks recovered from depths of up to 4 6 km in the ktb boreholes in southern germany our results show that the electrical conductivity of accessory phases such as fe ti oxides and sulphides can enhance or even surpass the high conductivity produced by saline fluids

magnetotelluric image of the crust and upper mantle in the backarc of the northwestern argentinean andes magnetotelluric data from the backarc of the central andes in nw argentinawere re examined by employing impedance tensor decomposition and 2 d inversion and modelling techniques the data in the period range of 50 15 000 s were collected on a profile of 220 km length reaching from the eastern cordillera across the santa barbara system to the andean foreland of the argentinean chaco after a dimensionality analysis data from most sites were treated as regional 2 d the exception was the eastern section of the profile where the magnetotelluric transfer functions for periods 1000 s reflect a 3 d earth application of two tensor decomposition schemes yielded a regional strike direction of n s which is the azimuth of the central andean mountain chains several 2 d models were obtained by pseudo and full 2 d occam inversion schemes special emphasis was placed on the inversion of phase data to reduce the influence of static shifts in the apparent resistivity data the smooth inversion models all show a good conductor at depth a final model was then calculated using a finite element forward algorithm the most prominent feature of the resulting model is a conductor which rises from depths of 180 km below the chaco region to 80 km beneath the santa barbara system and the eastern cordillera its interpretation as a rise of the electrical asthenosphere is supported by seismic attenuation studies magnetotelluric results surface heat flow distribution in the area and the electrical properties of crustal and mantle rocks suggest that the upper mantle is predominantly ductile beneath the eastern cordillera and the western santa barbara system this generally agrees with anelastic seismic attenuation models of the area and is useful in discriminating between models of q quality factor distribution

3d modelling of electrical anisotropy from electromagnetic array data hypothesis testing for different upper mantle conduction mechanisms abstract upper mantle electrical conductivities provide besides seismic velocities or thermal diffusivities another source of information on upper mantle structure and composition we present the results of a long period magnetotelluric dataset consisting of 64 sites covering an area of 300 km 400 km in central germany mapping electrical conductivities at the base of the lithosphere to seperate the effect of crustal and upper mantle structures we interprete the obtained dataset by 3d conductivity modelling we observe high conductivities and anisotropies at asthenospheric upper mantle depth with main bulk conductivities of 1 2 s m in west east and 4 1 0 3 s m in north south direction differing by about two orders of magnitude in comparing with results from laboratory measurements on electrical conductivites for various conduction mechanisms we are able to confine the conduction mechanisms possibly dominating at these depths with melt volume fractions of 1 only partial melt can be excluded as origin of the high upper mantle conductivities instead conductivity enhancement due to hydrogen diffusion along the olivine 1 0 0 axis is favoured as the dominant conduction mechanism at the base of the lithosphere

observations of a nonmigrating component of the semidiurnal tide over antarctica 1 data obtained from the mf radars situated at davis syowa and rothera in antarctica are used to detect a nonmigrating component of the semidiurnal tide in the mesosphere and lower thermosphere these radars are at similar latitudes and so share a common migrating tidal component by fitting semidiurnal tide vectors to each stations data and performing subtractions of these vectors for pairs of stations the migrating component can be removed and the difference between the nonmigrating components revealed non zero differences in the summer months december to march indicate the presence of a significant nonmigrating component modeling studies and observations at other sites suggest that it is most likely the westward propagating wavenumber 1 nonmigrating component that is contributing to the semidiurnal tide the data presented here are found to be consistent with this hypothesis a climatology of this nonmigrating component is presented and discussed comparisons with the global scale wave model suggest that latent heat release is not a significant forcing mechanism at these heights and latitudes

comment on electrical conductivity of albite quartz water and albite water nacl systems and its implication to the high conductivity anomalies in the continental crust by guo x yoshino t shimojuku a in their otherwise excellent study of the electrical conductivity of mineral systems including albite and aqueous fluids in the continental crust guo et al 2015 note that when archie s law archie 1942 is fitted to the data for bulk conductivity as a function of fluid fraction the exponent values are negative for all measurements made between 500 k and 900 k they note that the negative values indicate that the bulk conductivity decreases with increasing fluid fraction and that this is opposite to the accepted behaviour e g glover 2015 guo et al 2015 attempt to explain the behaviour by noting that the melting point of the ab qtz h2o system varies with increasing water content however there is an underlying problem with their use of the simple archie s law archie s law is given by the equation

evidence of electrical anisotropic structures in the lower crust and the upper mantle beneath the rhenish shield abstract we present the results of a long period electromagnetic investigation of the crust and upper mantle beneath the rhenish shield in western germany the magnetotelluric phase data reveal a frequency dependent regional strike that varies only smoothly across the array at short periods t 1000 s there is a consistent striking in we direction which provides strong evidence of an anisotropic structure in the upper mantle too geomagnetic data were also used whereas we reference the magnetic field components of all sites to an arbitrarily chosen field site that provides a direct view of the anomalous current flow we show that in case of a non one dimensional electrical substructure of the reference site all magnetic transfer functions of the other sites can be affected by lateral conductivity contrasts beneath the reference site a simple method to remove such effects is introduced applying this method the magnetic data show a distinct anomaly in the northwestern part of the area finally we present a 3d model of the conductivity structure beneath the rhenish shield which contains a superposition of two anisotropic structures in the lower crust 2000 s and the upper mantle 20 000 s respectively and a local anomaly in the upper crust 4000 s

effects of agricultural drainage systems on sediment connectivity in a small mediterranean lowland catchment abstract traditional drainage systems combining man made channels and subsurface tile drains have been used since roman times to control water excess in mediterranean lowland regions favouring adequate soil water regime for agriculture purposes however mechanization of agriculture abandonment or land use changes lead to a progressive deterioration of these drains in the last decades the effects of these structures on hydrological and sediment dynamics have been previously analyzed in a small mediterranean lowland catchment can revull mallorca spain 1 4 km2 by establishing an integrated sediment budget with a multi technique approach moreover the recent advances in morphometric techniques enable the completion of this analysis by the accurate identification of active areas i e sources pathway links and sinks and improve the understanding of de coupling mechanisms of water and sediment linkages in this study the borselli s index of connectivity ic cavalli et al 2013 s version derived from a lidar based high resolution dem 1 pt m 2 rmse

reconstruction of subgrid scale topographic variability and its effect upon the spatial structure of three dimensional river flow a new approach to describing the associated topography at different scales in computational fluid dynamic applications to gravel bed rivers was developed surveyed topographic data were interpolated using geostatistical methods into different spatial discretizations and grain size data were used with fractal methods to reconstruct the microtopography at scales finer than the measurement subgrid scale the combination of both scales of topography was then used to construct the spatial discretization of a three dimensional finite volume computational fluid dynamics cfd scheme where the topography was included using a mass flux scaling approach the method was applied and tested on a 15 m stretch of solfatara creek wyoming united states using spatially distributed elevation and grain size data model runs were undertaken for each topography using a steady state solution this paper evaluates the impact of the model spatial discretization and additional reconstructed variability upon the spatial structure of predicted three dimensional flow the paper shows how microtopography modifies the spatial structure of predicted flow at scales finer than measurement scale in terms of variability whereas the characteristic scale of predicted flow is determined by the cfd scale changes in microtopography modify the predicted mean velocity value by 3 6 for a mesh resolution of 5 cm whereas a change in the computational scale modifies model results by 60 the paper also points out how the spatial variability of predicted velocities is determined by the topographic complexity at different scales of the input topographic model

interannual variations of the quasi 16 day oscillation in the polar summer mesospheric temperature nighttime measurements of the hydroxyl meinel 4 2 rotational band have been used to infer the mesospheric temperature over scandinavia from june to august during the years 1992 1995 while the nightly averaged temperatures show a statistically significant quasi 16 day oscillation in the 1992 and 1994 summer data none is observed during 1993 and 1995 when present the period amplitude and temporal behavior of this oscillation agree with both model predictions and previous wind measurements of the 1 3 rossby normal mode in the summer mesosphere thus this temperature oscillation appears to correspond to the thermal signature of the 16 day rossby mode its appearance in the summer mesosphere is shown to occur when the oscillating zonal flows in the upper stratosphere near the equator are in an eastward phase while it appears to be blocked during the westward phases this correspondence of the 16 day wave in the summer mesosphere with the eastward equatorial wind would favor the explanation that it is generated in the winter hemisphere and propagates vertically and toward the summer pole following the westerly mean winds

latitudinal variation of quasi biennial oscillation modulation of the semidiurnal tide in the lower thermosphere perturbations in the geomagnetic field at the earth s surface can result from variations in the neutral wind field in the lower thermosphere through dynamo action in the interfused ionospheric e region thus spectral analysis of the sq variations in ground based geomagnetic data extending continuously over many years and from several sites worldwide has been carried out to investigate the variation with latitude of quasi biennial oscillation qbo effects in the semidiurnal tide in the lower thermosphere this qbo modulation of the tide appears to be greatest around 60 latitude the phase of the oscillation is largely latitude independent and implies qbo modulation of the upward propagating semidiurnal tide close to its source region the semidiurnal tide appears to propagate upward more easily during the easterly phase of the tropical stratospheric qbo at 30 mbar than during the westerly phase

long term oscillations of the wind field in the tropical mesosphere and lower thermosphere from hawaii mf radar measurements 1 wind measurements in the mesosphere and lower thermosphere obtained with a medium frequency mf radar in hawaii 22 n 160 w spanning 16 years are employed to examine the intra annual and interannual variability of the mean and tidal motions at altitudes between 84 and 94 km intra annual periodicities range from 3 to 12 months with significant coherence in altitude and between the zonal and meridional components of each motion field interannual variations confirm the dominant periodicities identified previously at this site and elsewhere in particular the significant diurnal and less significant semidiurnal tidal responses at periods of 28 and 48 months amplitudes of these long period oscillations of the diurnal tide increase with altitude below 92 km and are larger than the amplitudes of the 12 month oscillations above 90 km phases of the 28 and 48 month oscillations show a downward progression with a slightly larger altitude variation in the meridional diurnal tide for the 28 month oscillation and a significantly larger altitude variation in the zonal diurnal tide for the 48 month oscillation the long and nearly continuous hawaii data set also enables characterization of the responses of the wind fields to the 11 year solar cycle both wind and tidal fields exhibit this periodicity but these responses display interesting and different relations to the phase of the solar cycle the 11 year oscillation of the meridional wind is nearly in phase with the solar cycle while the 11 year oscillation of the zonal wind is in approximate quadrature with the solar cycle the 11 year oscillations of the semidiurnal tidal amplitudes and the meridional diurnal amplitude are all in approximate quadrature with the solar cycle with the tidal amplitudes leading by 29 to 37 months while the 11 year oscillation of the zonal diurnal amplitude is somewhat nearer an antiphase than a quadrature relation to the solar cycle leading by 54 months

qbo effects on antarctic mesospheric winds and polar vortex dynamics 1 a dynamical link is demonstrated between the equatorial quasi biennial oscillation qbo and high latitude mesospheric zonal winds recorded by an imaging doppler interferometer idi at halley antarctica above 80 km eastward winds in winter an extension of the polar vortex into the mesosphere are strengthened under easterly 50 hpa qbo conditions this is similar to the holton tan effect in the stratosphere but working in opposition the weak winter time zonal winds are shown to differ by up to 2 6 m s dependent on qbo phase in spring zonal winds are most strongly correlated with the equatorial 25 hpa qbo and are significantly more westerly in november an extension of the qbo response in the stratosphere below it is suggested that qbo modulation of the vortex winds in the antarctic mesosphere is dependent on planetary wave activity from the antarctic in winter and arctic in spring

electric currents along earthquake faults and the magnetization of pseudotachylite veins pseudotachylites occur in the form of thin glassy veins quenched from frictional melts along the fault planes of major earthquakes they contain finely grained magnetite and often exhibit a high natural remanent magnetization nrm high nrm values imply strong local electric currents these currents must persist for some time while the pseudotachylite veins cool through the curie temperature of magnetite around 580 c there is no generally accepted theory explaining how such powerful persistent currents may be generated along the fault plane data presented here suggest the activation of electronic charge carriers which are present in igneous rocks in a dormant inactive form these charge carriers can be awakened by the application of stress they are electrons and defect electrons also known as positive holes or p holes for short while p holes are capable of spreading out of the stressed rock volume into adjacent p type conductive unstressed rocks electrons require a connection to the hot n type conductive lower crust however as long as the downward electron flow is not connected the circuit is not closed hence with the outflow of p holes impeded no current can be sustained this situation is comparable to that of a charged battery where one pole remains unconnected the friction melt that forms coseismically during rupture provides a conductive path downward which closes the circuit this allows a current to flow along the fault plane extrapolating from laboratory data every km 3 of stressed igneous rocks adjacent to the fault plane can deliver 10 3 10 5 a hence the current along the fault plane will not be limited by the number of charge carriers but more likely by the electronic conductivity of the cooling pseudotachylite vein the sheet current will produce a magnetic field whose vectors will lie in the fault plane and perpendicular to the flow direction 2006 elsevier b v all rights reserved

coupling between hillslopes and channels in upland fluvial systems implications for landscape sensitivity illustrated from the howgill fells northwest england abstract the sensitivity of upland fluvial systems depends on the magnitude and frequency of sediment and flood producing events modified by the internal coupling characteristics of the system this paper assesses the role of hillslope channel coupling for the sensitivity of upland geomorphic systems using evidence from a 30 year monitoring programme of geomorphic change in the carlingill valley howgill fells northwest england in the hillslope zone there is little sediment supply to the stream system locally slope failures occur in response to extreme events six such events in 30 years within the ca 6 km 2 carlingill valley in the footslope coupling zone basally induced gullies are major sediment sources to the stream sediment production events occur ca 30 times per year feeding sediment to basal debris cones stream floods which can entrain these sediments occur once every ca 2 5 years stream channel morphology is adjusted to this regime downstream of gullies channels are wide and braided elsewhere they are narrow and single thread as the gullies develop however this coupling weakens and the eroding slopes eventually stabilise by revegetation over the 30 year monitoring period there has been a progressive trend towards gully stabilisation and an associated reduction in channel instability massive destabilisation may occur in response to rare extreme flood events such an event return period 100 years occurred in neighbouring langdale and bowderdale valleys in june 1982 that event destabilised the system causing slope failures fan deposition and in some places a switch in channel style to wide braided channels since 1982 there has been a progressive recovery by slope stabilisation and single thread sinuous channels have become reestablished a different style of extreme event occurred in carlingill in october 1998 in response to the wettest week in the 30 year period a slope failure fed debris flows 400 m downslope almost coupling with the channel system future climatic change could render the system prone to destabilisation through either extreme flood events or through major slope failures

electrical conductivity of albite quartz water and albite water nacl systems and its implication to the high conductivity anomalies in the continental crust abstract the electrical conductivities of albite water albite quartz water and albite water nacl systems have been measured in terms of impedance spectroscopy at 1 gpa and 400 1000 k the relationship between electrical conductivity and temperature in the albite quartz water system cannot be expressed by the arrhenian formula whereas that in the brine bearing system follow the arrhenian law showing small temperature dependence the electrical conductivity of the albite quartz water samples decreased with decreasing temperature from 1000 to 800 k then increased rapidly upon further cooling from 800 to around 550 k the bulk conductivities of the albite quartz water system are consistent with variation of the total concentration of the dissolved electric charge carriers of h oh na alo 2 and hsio 3 in aqueous fluid with temperature based on the thermal dynamic calibration there is a small negative dependence of bulk conductivity on aqueous fluid fraction electrical conductivity of the albite water nacl samples is higher than that of the albite quartz water samples which shows the following features 1 small dependence of conductivity on the temperature 2 increase of electrical conductivity with the fluid fraction and the salinity our results suggest that the high conductivity anomalies of 10 1 s m typically observed in the continental crust can be explained by the presence of albite and quartz with fluid fraction as low as 0 014 at temperatures lower than 650 k in the case that the geotherm is higher than 650 k the observed value of 10 1 s m can be explained by the brine bearing albite with a fluid fraction of 1 vol if the salinity is similar to the seawater

accuracy of topographic index models at identifying ephemeral gully trajectories on agricultural fields abstract topographic index ti models have been widely used to predict trajectories and initiation points of ephemeral gullies egs in agricultural landscapes prediction of egs strongly relies on the selected value of critical ti threshold and the accuracy depends on topographic features agricultural management and datasets of observed egs this study statistically evaluated the predictions by ti models in two paired watersheds in central kansas that had different levels of structural disturbances due to implemented conservation practices four ti models with sole dependency on topographic factors of slope contributing area and planform curvature were used in this study the observed egs were obtained by field reconnaissance and through the process of hydrological reconditioning of digital elevation models dems the kernel density estimation analysis was used to evaluate ti distribution within a 10 m buffer of the observed eg trajectories the eg occurrence within catchments was analyzed using kappa statistics of the error matrix approach while the lengths of predicted egs were compared with the observed dataset using the nash sutcliffe efficiency nse statistics the ti frequency analysis produced bi modal distribution of topographic indexes with the pixels within the eg trajectory having a higher peak the graphs of kappa and nse versus critical ti threshold showed similar profile for all four ti models and both watersheds with the maximum value representing the best comparison with the observed data the compound topographic index cti model presented the overall best accuracy with nse of 0 55 and kappa of 0 32 the statistics for the disturbed watershed showed higher best critical ti threshold values than for the undisturbed watershed structural conservation practices implemented in the disturbed watershed reduced ephemeral channels in headwater catchments thus producing less variability in catchments with egs the variation in critical thresholds for all ti models suggested that ti models tend to predict eg occurrence and length over a range of thresholds rather than find a single best value

super dual auroral radar network observations of meteor echoes radar echoes from ranges less than 500 km are routinely observed by the super dual auroral radar network superdarn on most days many of these echoes have properties which are markedly different from what one would expect from e or f region irregularities we show that these unusual short range hf echoes are due to scattering off meteor trails this explains why among other things the doppler shift from the short range echoes taken from the superdarn saskatoon antenna are consistent with the mesospheric winds observed by the saskatoon mf radar this means that the superdarn radars can be used to study neutral winds at meteor heights a result which is especially interesting since it opens up the capability for a global coverage of mesospheric winds using the worldwide distribution of superdarn radars

quasi biennial oscillation influence on long period planetary waves in the antarctic upper mesosphere 1 long period planetary wave data derived from meteor wind observations recorded over a 12 year period with the superdarn radar at halley antarctica are presented and compared with the phase of the quasi biennial oscillation qbo throughout the equatorial stratosphere enhanced planetary wave activity in the antarctic upper mesosphere is found during the summer months when the qbo in the equatorial upper stratosphere is westerly and during the late winter when the qbo in the upper stratosphere is easterly these quasi biennial enhancements in planetary wave activity coincide with a reduction in strength by up to 30 of the late winter eastward winds in the antarctic upper mesosphere in addition when the qbo is in the correct phase for enhanced planetary wave activity in the upper mesosphere above halley planetary wave activity measured in the upper mesosphere of the high latitude northern hemisphere is reduced and vice versa these results clearly indicate significant interhemispheric propagation of planetary waves from the winter to summer hemispheres observational evidence that the stratospheric qbo induces a strong enough qbo in the equatorial upper mesosphere to act as a gate to the interhemispheric propagation of these long period waves is discussed in light of these results

first results from the meteor radar at south pole a large 12 hour oscillation with zonal wavenumber one the first mesopause region ca 92 5 km wind measurements from the meteor radar at amundsen scott station at south pole are described measurements are made along four orthogonal azimuth directions approximately 2 from the geographic south pole a large 20 ms 1 oscillation in the northward wind is observed with 12 hour period and zonal wavenumber one a similar wave was observed during august 1 13 1992 at south pole by hernandez et al 1993 using optical methods the predominant semidiurnal tide in the atmosphere is migrating with the apparent motion of the sun with s 2 the s 1 oscillation is interpreted here to result from the nonlinear interaction between the migrating semidiurnal tide and a stationary wave with s 1 the present mechanism represents an alternative to the gravity wave driven pseudotide theory put forth by walterscheid et al 1986 to explain the occurrence of unexpectedly large semidiurnal tidal oscillations at high latitudes

quasi biennial modulation of the southern hemisphere stratospheric polar vortex observations reveal that the wintertime southern hemisphere stratospheric polar vortex is modulated by the phase of the equatorial quasi biennial oscillation qbo the high latitude southern stratosphere is shown to be slightly colder throughout the winter and the final warming occurs later when the qbo is in its west phase during may october the modulation of winds by the qbo is confined to midlatitudes at the edge of the polar vortex the difference between west and east phase composites of zonal mean wind during november at the time of the final warming in the southern hemisphere exceeded 14 ms 1 this difference is very similar to that in january in the northern hemisphere while northern hemisphere qbo effects are optimized using equatorial winds near 40 hpa southern hemisphere effects are best seen using 25 hpa winds

electrical conductivity of icelandic deep geothermal reservoirs up to supercritical conditions insight from laboratory experiments electrical resistivity is extensively used in geothermal systems to accurately determine the existing conditions of the reservoirs at depth up to this point technical challenges related to pore fluid confinement made difficult to measure electrical conductivity at temperatures and pressures representative of very deep geothermal reservoirs in this study we are overcoming these limitations thanks to a new electrical resistivity cell designed to fit into a high temperature gas medium apparatus this allows us to perform resistivity measurement at temperatures up to 700 c and at effective pressures up to 100 mpa i e a confining pressure of 130 mpa and an equilibrium pore pressure of 30 mpa using cm scale plugs rock samples originate from five boreholes located in the icelandic geothermal fields of reykjanes rn 17b hyaloclastite rn 19 rn 30 dolerites and hengill nj 17 basalt and nj 17b hyaloclastite these samples were selected for their high degree of hydrothermal alteration in the epidote and amphibole facies i e temperature of 250 c and 400 c respectively and their wide range of porosities from 3 to 20 to determine the effects of surface mineral and electrolytic conductions on bulk electrical conduction experiments were performed under dry and saturated conditions using three different fluid salinities at temperatures ranging from 25 to 350 c electrical conductivity in all our experiments increases as a result of both increasing surface and electrolytic conduction then under supercritical conditions i e temperature from 374 c to 600 c electrical conductivity strongly decreases due to the evolution of water density and dielectric constant that affect both surface and electrolyte conduction at higher temperatures 500 c 700 c the rock conductivities lie within the range of dry rock electrical conductivity values suggesting that mineral conduction controls the bulk conductivity with ferromagnesian minerals acting as principal contributors of mineral conduction amphibole rich samples show an irreversible increase in conductivity at temperature above 500 c 600 c which can be attributed to amphibole dehydration comparison of these laboratory data to magnetotelluric soundings and downhole temperatures obtained beneath several geothermal areas indicate a good agreement between laboratory and large scale surveys our results provide a general trend that helps interpreting electrical conductivity surveys in the icelandic crust

quasi biennial modulation of the semidiurnal tide in the upper mesosphere above halley antarctica we present an analysis of a long term archive of horizontal wind data derived from meteor wind observations from a superdarn radar at halley antarctica 76s 27w systematic differences between the 12 hour component in the meridional wind and the climatological mean are observed showing evidence of a quasi biennial modulation of the high latitude semidiurnal tide in the upper mesosphere the amplitude of the observed tides is enhanced when the equatorial stratospheric quasibiennial oscillation above 10 hpa is westerly this enhancement is greatest in the summertime tidal amplitudes when the zonal wavenumber one s 1 nonmigrating component dominates the semidiurnal wind field and is coincident with an enhancement of the summertime planetary wave activity in the upper mesosphere these observations strongly support the hypothesis that the s 1 component of the semidiurnal tide observed at high latitudes is due to a non linear interaction between the migrating s 2 semidiurnal tide and quasi stationary s 1 planetary waves

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

gully erosion impacts factors and control gully erosion attracts increasing attention from scientists as reflected by two recent international meetings poesen and valentin eds catena 50 2 4 87 564 li et al 2004 gully erosion under global change sichuan science technology press chengu china 354 pp this growing interest is associated with the increasing concern over off site impacts caused by soil erosion at larger spatial scales than the cultivated plots the objective of this paper is to review recent studies on impacts factors and control of gully erosion and update the review on dgully erosion and environmental change importance and research needst poesen et al 2003 catena 50 2 4 91 134 for the farmers the development of gullies leads to a loss of crop yields and available land as well as an increase of workload i e labour necessary to cultivate the land gullies can also change the mosaic patterns between fallow and cultivated fields enhancing hillslope erosion in a feedback loop in addition gullies tend to enhance drainage and accelerate aridification processes in the semi arid zones fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion in this respect tracers such as carbon nitrogen the nuclear bomb derived radionuclide 137 cs magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment recent studies conducted in australia china ethiopia and usa showed that the major part of the sediment in reservoirs might have come from gully erosion gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess european belt chinese loess plateau north america and sandy soils sahelian zone north east thailand or in soils prone to piping and tunnelling such as dispersive soils most of the time the gullying processes are triggered by

nonlinear interactions in the upper atmosphere the s 1 and s 3 nonmigrating semidiurnal tides 1 a semidiurnal oscillation with zonal wave number s 1 has been observed over the south pole and longitudinal variations of the semidiurnal tide at northern midlatitudes have been ascribed to the presence of nonmigrating tides a three dimensional nonlinear spectral model is used herein to study nonlinear wave wave interaction as a possible mechanism for the generation of nonmigrating tides in the mesosphere and lower thermosphere in particular the s 1 and s 3 nonmigrating semidiurnal tides are studied as a by product of the nonlinear interaction between the semidiurnal s 2 migrating tide and a stationary s 1 planetary wave in the lower and middle atmosphere this process is found to yield significant amplitudes 10 30 m s 1 of the nonmigrating semidiurnal components with s 1 and s 3 in the upper atmosphere comparisons with monthly nonmigrating tidal amplitudes and phases at 95 km derived from high resolution doppler imager and wind imaging interferometer wind measurements from uars show good agreement with the model simulations the effect of the dissipating nonmigrating tides on the zonal mean circulation is found to reinforce that of the migrating component contributing 10 20 m s 1 to the zonal wind field and 5 10 m s 1 to the mean meridional wind field several other wave components are generated through nonlinear interactions including 6 hour tides with zonal wave numbers s 0 1 4 and a semidiurnal oscillation with s 6 these wave components have amplitudes in the range 6 30 m s 1 in the 110 150 km height regime the combination of all nonmigrating tides together with the migrating component suggests significant longitudinal variations in the semidiurnal tide in the e region which may be important for studies of the quiet time generation of ionospheric electric fields by the dynamo mechanism

sediment connectivity a framework for understanding sediment transfer at multiple scales a major challenge for geomorphologists is to scale up small magnitude processes to produce landscape form yet existing approaches have been found to be severely limited new ways to scale erosion and transfer of sediment are thus needed this paper evaluates the concept of sediment connectivity as a framework for understanding processes involved in sediment transfer across multiple scales we propose that the concept of sediment connectivity can be used to explain the connected transfer of sediment from a source to a sink in a catchment and movement of sediment between different zones within a catchment over hillslopes between hillslopes and channels and within channels using fluvial systems as an example we explore four scenarios of sediment connectivity which represent end members of behaviour from fully linked to fully unlinked hydrological and sediment connectivity sediment travel distance when combined with an entrainment parameter reflecting the frequency magnitude response of the system maps onto these end members providing a coherent conceptual model for the upscaling of erosion predictions this conceptual model could be readily expanded to other process domains to provide a more comprehensive underpinning of landscape evolution models thus further research on the controls and dynamics of travel distances under different modes of transport is fundamental copyright 2014 john wiley sons ltd

long term observations of the wind field in the antarctic and arctic mesosphere and lower thermosphere at conjugate latitudes 1 mean winds semidiurnal and diurnal tides and trends and long period oscillations spanning a solar cycle from early 1999 through june 2010 measured by medium frequency mf radars at conjugate antarctic and arctic latitudes syowa antarctica 69 s 39 6 e and andenes norway 69 3 n 16 e are described and compared zonal mean winds are stronger and more uniform from year to year over the antarctic with a stronger eastward winter jet spanning the range of altitudes presented 70 to 96 km the summer westward jet is also stronger and maximizes at higher altitudes over the antarctic than over the arctic the eastward winter jet over the arctic while generally weaker exhibits a localized maximum in late winter at 2 to 3 year intervals meridional mean winds likewise achieve somewhat stronger maxima at higher altitudes over the antarctic than over the arctic semidiurnal tide amplitudes are typically somewhat larger over the antarctic and similar in the two components with maxima at 85 km or above and narrow responses that tend to cluster from february to may and september to november over the antarctic and from december to february and june to september over the arctic zonal diurnal tide amplitudes are quite similar between the sites with maxima extending from 70 to 90 km and slightly stronger over the antarctic meridional diurnal amplitudes display more significant growth with altitude achieve stronger maxima at the highest altitudes presented and typically exhibit a single and narrow maximum during december to february over the antarctic and double maxima from may to september over the arctic also discussed are trends and long period oscillations over a solar cycle observed in these mean and tidal wind fields

temperature profiles in the earth of importance to deep electrical conductivity models deep in the earth the electrical conductivity of geological material is extremely dependent on temperature the knowledge of temperature is thus essential for any interpretation of magnetotelluric data in projecting lithospheric structural models the measured values of the terrestrial heat flow radiogenic heat production and thermal conductivity of rocks allow the extrapolation of surface observations to a greater depth and the calculation of the temperature field within the lithosphere various methods of deep temperature calculations are presented and discussed characteristic geotherms are proposed for major tectonic provinces of europe and it is shown that the existing temperatures on the crust upper mantle boundary may vary in a broad interval of 350 1 000 c the present work is completed with a survey of the temperature dependence of electrical conductivity for selected crustal and upper mantle rocks within the interval 200 1 000 c it is shown how the knowledge of the temperature field can be used in the evaluation of the deep electrical conductivity pattern by converting the conductivity versus temperature data into the conductivity versus depth data

measurements of rill and gully erosion in sicily this article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at sparacia experimental area and two ephemeral gullies egs located in the tremamargi basin sicily italy at first the available literature data together with the measurements carried out in this investigation were used to show that the eg length is a key parameter for the estimation of the eroded volume then the comparison among the pairs length and volume corresponding to measured rills egs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type rill eg and gully while a different scale factor has to be used for each erosion process finally a single relationship applicable to all channelized erosion processes was deduced applying the dimensional analysis and the self similarity theory copyright 2011 john wiley sons ltd

modeling river bed morphology roughness and surface sedimentology using high resolution terrestrial laser scanning 1 recent advances in technology have revolutionized the acquisition of topographic data offering new perspectives on the structure and morphology of the earth s surface these developments have had a profound impact on the practice of river science creating a step change in the dimensionality resolution and precision of fluvial terrain models the emergence of hyperscale survey methods including structure from motion photogrammetry and terrestrial laser scanning tls now presents the opportunity to acquire 3 d point cloud data that capture grain scale detail over reach scale extents translating these data into geomorphologically relevant products is however not straightforward unlike traditional survey methods tls acquires observations rapidly and automatically but unselectively this results in considerable noise associated with backscatter from vegetation and other artifacts moreover the large data volumes are difficult to visualize require very high capacity storage and are not incorporated readily into gis and simulation models in this paper we analyze the geomorphological integrity of multiscale terrain models rendered from a tls survey of the braided river feshie scotland these raster terrain models are generated using a new computationally efficient geospatial toolkit the topographic point cloud analysis toolkit topcat this performs an intelligent decimation of point cloud data into a set of 2 5 d terrain models that retain information on the high frequency subgrid topography as the moments of the locally detrended elevation distribution the results quantify the degree of terrain generalization inherent in conventional fluvial dems and illustrate how subgrid topographic statistics can be used to map the spatial pattern of particle size grain roughness and sedimentary facies at the reach scale

short term variation of the s 1 nonmigrating semidiurnal tide during the 2002 stratospheric sudden warming 1 in this study the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm is used to examine short term changes in the global structure of the migrating and s 1 nonmigrating semidiurnal tides in a model run approximating the 2002 southern hemisphere stratospheric sudden warming the time gcm is found to resolve an s 1 nonmigrating semidiurnal tide with latitudinal structure similar to that of prior studies and with global structure in the mlt region strongly correlated with southern hemisphere planetary wave 1 pw1 wave events prior to equinox comparison with a control run with no planetary wave activity eliassen palm flux and correlation analysis of the s 1 semidiurnal tide structure suggest that the wave propagates from the source region in the winter hemisphere stratosphere into both the summer and winter lower thermospheres the amplitudes of the migrating semidiurnal tide in the southern hemisphere are anticorrelated with the nonmigrating tide suggesting significant energy loss due to nonmigrating tidal generation a result not previously seen the amplitude of the s 1 nonmigrating semidiurnal tide from time gcm is also compared with data from the south pole meteor radar system while the observations show bursts of nonmigrating tidal activity correlated to pw1 activity of comparable amplitudes to the model results these events do not always appear at the same times as those in the model this suggests that while the processes generating the nonmigrating tide in time gcm are realistic the time gcm run itself displays differences in time evolution compared to the observations during this time

field petrophysical and carbon isotope studies on the lapland granulite belt implications for deep continental crust the palaeoproterozoic lapland granulite belt is a seismically reflective and electrically conductive sequence of deep crustal 6 9 kbar rocks in the northern fennoscandian shield it is composed of garnet sillimanite gneisses khondalites and pyroxene granulites enderbites which in certain thrust sheets form about 500 m thick interlayers the structure was formed by the intrusion of intermediate to basic magmas into turbiditic sedimentary rocks under granulite facies metamorphism accompanied by shearing of the deep crust about 1 93 1 90 gyr ago gal granulites were upthrust 1 90 1 87 ga and the belt was divided by crustal scale duplexing into four structural units whose layered structure was preserved the thrust structures are recognized by the repetition of lithological ensembles and by discordant structural patterns well distinguishable in airborne magnetic and electromagnetic data thrusting gave rise to clockwise pressure temperature evolution of the belt however some basic rocks possibly record an isobaric cooling path the low bulk resistivity of the belt 200 1000 m is caused by interconnected graphite and subordinate sulphides in shear zones on the basis of carbon isotope ratios this graphite is derived mostly from sedimentary organic carbon the seismic reflectivity of the belt may be caused by velocity and density differences between pyroxene granulites and khondalites as well as by shear zones

a new perspective on the longitudinal variability of the semidiurnal tide the longitudinal variability of the semidiurnal tide in the antarctic upper mesosphere is investigated by comparison of observations from two radars at approximately opposite sides of antarctica under the assumption that the tide is composed of an s 2 migrating and s 1 westward propagating non migrating component only the relative phases of the components are shown to vary with season such that the waves are typically in constructive interference during the winter summer months at longitudes around 0 degrees e 180 degrees e we show that this has profound effects on the seasonal behaviour of the semidiurnal tide around 78 degrees s dependent on the longitude and that no single station observations at this latitude can be considered representative of a zonal mean the superposition of these two waves is used to interpret differences in previously published ground based climatologies of the tide citation hibbins r e o j marsh a j mcdonald and m j jarvis 2010 a new perspective on the longitudinal variability of the semidiurnal tide geophys res lett 37 l14804 doi 10 1029 2010gl044015

electrical conductivity measurement of granulite under mid to lower crustal pressure temperature conditions summary we have developed a technique to measure electrical conductivity of crustal rocks with relatively low conductivity and complicated mineral components in order to compare with results given by magneto telluric mt measurements a granulite from hidaka metamorphic belt hmb in hokkaido japan at high temperature and pressure conditions was obtained the granulite sample was ground and sintered under the conditions similar to those of mid to lower crust we have observed smooth and reversible change of conductivity with temperature up to about 900 k at 1 gpa the results were consistent with the electrical conductivity structures suggested by the mt data analysis considering pore fluid conduction mechanism or the role of accessory minerals in the rock the mechanisms of electrical conductivity paths in dry or basic rocks should be reconsidered