Kilometre Scale Research Articles

Large scale seabed processes in a deep cool water carbonate ramp system: A case study of the Great Australian Bight

Among all the modern cool water carbonate margins in the world, the Great Australian Bight (GAB) presents several unique characteristics: a near complete absence of terrigenous input, highly energetic swell conditions producing vigorous off-shelf sedimentary transport to the upper continental slope, and overall high-sedimentation rates during the Pleistocene. All these conditions promoted biota and facies that are more typical of a highly productive carbonate margin. High-resolution bathymetric data collected from marine voyages between 2015 and 2017 revealed that the continental slopes of the central GAB are characterised by numerous channels and canyons as well as a large number of sedimentary mass-wasting features including kilometre scale submarine landslides and slumps. The morphometric and structural analysis of these seabed features across the continental slopes suggest that the three key controlling factors are: deep-rooted faults breaching the seabed, increasing slope gradient at the beginning of the lower continental slope, and channel wall erosion. Pulses of rapid sedimentary accumulation on the upper continental slopes, as well as differential uplift and subsidence combined with sea-level changes, appear to be the main trigger mechanisms for mass wasting.The GAB is the largest cool-water carbonate ramp system in the world. As such, the scale of sedimentary erosion and transport through channels and canyons caused by mass wasting identified in this work represents a major mechanism of carbon transfer to the deep oceans. Whilst high carbonate sedimentation during the Pleistocene in the GAB could be an important CO2 sink in the global ocean, high sedimentation on the outer shelf and continental slope could also increase mass wasting which could act as an effective mechanism for carbon transfer to the deep oceans. However, continental slopes in the Great Australian Bight have, until recently, remained poorly studied.

Quantification of groundwater storage heterogeneity in weathered/fractured basement rock aquifers using electrical resistivity tomography: Sensitivity and uncertainty associated with petrophysical modelling

Quantifying groundwater storage in weathered/fractured basement rock aquifers can be challenging owing to both their high degree of heterogeneity and their overall low storage capacity. Therefore, in these aquifers, the use of direct borehole hydraulic data is usually insufficient. Here we assessed the popular method of electrical resistivity tomography (ERT), combined with borehole data and including associated uncertainties, to resolve the spatial variability of groundwater storage properties at high resolution within a fractured mica schist aquifer in Ireland. Porosity distributions across both the saturated and unsaturated zones were calculated from two-dimensional (2D) ERT resistivities using two standard petrophysical models, Archie and Waxman & Smits (WS), the latter accounting for the influence of clay minerals on resistivity data. Our results demonstrated the importance of the hydrogeological conceptual constraints provided by ERT when parametrizing the 2D petrophysical models from borehole point data. They also confirmed the importance of accounting for clay minerals (the products of bedrock weathering processes) in the WS model, whereas predictions from Archie’s model produced unrealistically high porosity values of over an order of magnitude higher than the WS model. The WS model predicted porosities decreasing exponentially with depth, with values ranging from a few % in the shallowest, most-weathered part of the bedrock (upper 5 m on average) and deep fractured zones (to about 20 m deep), to <1% in the underlying fissured aquifer, and possibly down another order of magnitude in the deep massive bedrock. WS-derived porosities were in agreement with independent vertical water content profiles derived from magnetic resonance sounding (MRS), as well as point storativity values estimated from borehole hydraulic testing at the study site, with particularly good matches in the upper weathered/fractured bedrock and deeply weathered/fractured zones associated with regional faults. Detailed comparison suggested that WS provides an upper-bound estimate of groundwater storage in this environment. In the deep massive, un-weathered, and poorly fractured bedrock, however, discrepancies between groundwater storage estimate obtained from the three methods (ERT, MRS, and hydraulic) prevented reliable storage quantification, owing to the methods’ inherent technical limitations in such low porosity rocks. Our results demonstrated the suitability of resistivity tomography to quantify groundwater storage heterogeneity in weathered/fractured basement rock aquifers at high resolution and with reasonable overall uncertainty given the relative high uncertainties in petrophysical parameters at the kilometric scale. The results are promising for better characterization of groundwater storage variations in these hydrogeological systems, which are crucial to predict their response to climate variability and human exploitation.

The limited spatial scale of dispersal in soil arthropods revealed with whole-community haplotype-level metabarcoding.

Soil arthropod communities are highly diverse and critical for ecosystem functioning. However, our knowledge of spatial structure and the underlying processes of community assembly are scarce, hampered by limited empirical data on species diversity and turnover. We implement a high-throughput sequencing approach to generate comparative data for thousands of arthropods at three hierarchical levels: genetic, species and supra-specific lineages. A joint analysis of the spatial arrangement across these levels can reveal the predominant processes driving the variation in biological assemblages at the local scale. This multihierarchical approach was performed using haplotype-level COI metabarcoding of entire communities of mites, springtails and beetles from three Iberian mountain regions. Tens of thousands of specimens were extracted from deep and superficial soil layers and produced comparative phylogeographic data for >1,000 codistributed species and nearly 3,000 haplotypes. Local assemblage composition differed greatly between grasslands and forests and, within each habitat, showed strong spatial structure and high endemicity. Distance decay was high at all levels, even at the scale of a few kilometres or less. The local distance decay patterns were self-similar for the haplotypes and higher hierarchical entities, and this fractal structure was similar in all regions, suggesting that uniform processes of limited dispersal determine local-scale community assembly. Our results from whole-community metabarcoding provide insight into how dispersal limitations constrain mesofauna community structure within local spatial settings over evolutionary timescales. If generalized across wider areas, the high turnover and endemicity in the soil locally may indicate extremely high richness globally, challenging our current estimations of total arthropod diversity on Earth.

Geological and landscape particularities of Issafen-style chevron pattern in Tata region (Anti-Atlas, South Morocco)

The Tata region in southern Morocco is characterized by a great landscape diversity aesthetically outstanding and eloquent whose chevrons known as Issafen style (in reference to the name of a village in the region). The latter exhibits particular morpho-structural characters that illustrate the relationship between morphology and geological structure. They are shaped in the eastern short limb of a large syncline of north-south axial direction overturned to the west. The N-S slope of this eastern limb containing chevrons of hectometric to kilometric scale corresponds to a straightened limb with heterogeneous parasitic folds (training folds) that evolve laterally and vertically from the simple flexure to an open fold. It is sculpted by the processes of erosion giving rise to first-order and second-order chevrons, controlled both by the lithological nature of the geological formations and by the direction of the transverse joints especially with respect to the axis of the synclinal fold. The radius of curvature of chevrons evolves vertically by becoming more and more open downward, controlled by the variations of the dip of a large limb with folds and flexures. In this work, we will present the specific morpho-structural characters of the Issafen-style chevron pattern, presenting a tourist and scientific interest, by trying to make an analytical reading of this type of relief to explain its morphogenetic aspects by a simplified scientific mediation. In passing, we will remind their tourist assets and their importance in the development of the local territory.

Horizontal electric fields from flow of auroral O&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt;(&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;P) ions at sub-second temporal resolution

Abstract. Electric fields are a ubiquitous feature of the ionosphere and are intimately linked with aurora through particle precipitation and field-aligned currents. They exhibit order-of-magnitude changes on temporal and spatial scales of seconds and kilometres respectively which are not easy to measure; knowing their true magnitude and temporal variability is important for a theoretical understanding of auroral processes. We present a unique method to estimate ionospheric electric fields in the region close to (kilometre scale) a dynamic auroral arc by solving the continuity equation for the metastable O+(2P) ions, which emit as they move under the influence of electric fields during their 5 s lifetime. The main advantage of this optical method is the increase in temporal resolution over other methods such as ground-based radars. Simultaneous measurements of emission at 732.0 nm (from the O+(2P) ions) and prompt emissions at 673.0 nm (N2) and 777.4 nm (O), all at high spatial (100 m) and temporal (0.05 s) resolution, are used in the solution of the continuity equation, which gives the dynamic changes of the O+ ion population at all heights in a 3D volume close to the magnetic zenith. Perspective effects are taken into account by a new geometric method, which is based on an accurate estimate of the magnetic zenith position. The emissions resulting from the metastable ions are converted to brightness images by projecting them onto the plane of the ground, and the projected images are then compared with the measured images. The flow velocity of the ions is a free parameter in the solution of the continuity equation; the value that minimises the difference between the modelled and observed images is the extracted flow velocity at each time step. We demonstrate the method with an example event during the passage of a brightening arc feature, lasting about 10 s, in which the inferred electric fields vary between 20 and 120 mV m−1. These inferred electric fields are compared with SuperDARN measurements, which have an average value of 30 mV m−1. An excellent agreement is found in the magnitude and direction of the background electric field; an increase in magnitude during the brightening of the arc feature supports theories of small-scale auroral arc formation and electrodynamics.

Genetic analysis of Boletus edulis suggests that intra-specific competition may reduce local genetic diversity as a woodland ages.

Ectomycorrhizal fungi are key players in terrestrial ecosystems yet their mating systems and population dynamics remain poorly understood. We investigated the fine-scale relatedness structure and genetic diversity of Boletus edulis, one of the world's most commercially important wild mushrooms. Microsatellite genotyping of fruiting bodies from 14 different sites around Bielefeld in Germany revealed little in the way of population structure over a geographic scale of several kilometres. However, on a more local scale we found evidence for elevated relatedness as well as inbreeding. We also observed a significant negative association between the genetic diversity of fruit and the age of the trees under which they were sampled. Taken together, our results suggest that as genets mature, they compete and potentially create conditions under which further spores struggle to become established. By implication, even though this species is widely picked, propagules remain common enough to create strong competition when new habitats become available.

A small‐tiled geographic mosaic of coevolution between Eurosta solidaginis and its natural enemies and host plant

AbstractWe identified a geographic mosaic of Eurosta solidaginis fly traits produced by coevolution of the stem gall‐forming fly with both its natural enemies and its host plants at small geographic scales in the presence of gene flow. These tritrophic interactions between the fly with its natural enemies and with its host‐plant Solidago altissima produced what has been termed a small‐tiled geographic mosaic of coevolution. Selection on gall diameter and length varies between prairie and forest habitats due to differences in host plants and natural‐enemy communities. At the prairie–forest ecotone where prairie and forest habitats are intermixed, we found that geographic selection mosaics on gall diameter and length varied on a scale of a few kilometers. Gall diameter variation among sites correlated with selection on gall diameters, indicating local adaptation. In contrast, gall lengths did not correlate with selection, indicating that gene flow may have prevented local adaptation of this trait. Eastern (forest) and western (prairie) subspecies of E. solidaginis have been proposed based on fly wing patterns, and these had intermediate forms in the ecotone indicating gene flow between these subspecies. Variation in wing patterns correlated with gall diameter, indicating that gene flow between prairie and forest fly populations may influence the distribution of gall traits. The ratio of forest to prairie vegetation increases with latitude, but there was no indication of latitudinal clines in gall or wing traits. Our results indicate that selection for differentiation in coevolved traits is strong enough to overcome gene flow in small tiles of habitat. The result is that ecological forces produce a dynamic mosaic of genetically differentiated locally adapted populations. It also indicates that prairie and forest host races of E. solidaginis form a mosaic hybrid zone in this region.

The Observed Seasonal Cycle of Submesoscale Processes in the Antarctic Marginal Ice Zone

AbstractSubmesoscale flows are energetic processes in the upper ocean that occur at scales of a few kilometers. These phenomena are important to climate because they can strongly impact vertical motions of heat, carbon, and biogeochemical properties between the surface and deep ocean. Their presence and magnitude are poorly understood in the Antarctic marginal ice zone (MIZ) and under sea ice due to a lack of observations. We present tagged southern elephant seal hydrographic data from the eastern Weddell Sea, over the austral late summer to spring in 2008, to assess the magnitude and seasonality of submesoscale processes in the Antarctic MIZ. We consider the linkages between sea ice cover, ocean stress variability, and mixed layer depth and how these influence the submesoscale fluxes. We find that there is a strong seasonal cycle in the magnitude of the equivalent heat flux from submesoscale flows (240 Wm−2), with peak activity occurring in midwinter. Periods of increased variability in sea ice cover, likely associated with leads, are also linked to restratification through submesoscale fluxes in midwinter. These findings have implications for understanding the magnitude and variability of upper ocean stratification and therefore highlights the importance of developing parameterizations for submesoscale processes in the Antarctic MIZ within global climate models.

Spiny lobster sounds can be detectable over kilometres underwater

The detection ranges of broadband sounds produced by marine invertebrates are not known. To address this deficiency, a linear array of hydrophones was built in a shallow water area to experimentally investigate the propagation features of the sounds from various sizes of European spiny lobsters (Palinurus elephas), recorded between 0.5 and 100 m from the animals. The peak-to-peak source levels (SL, measured at one meter from the animals) varied significantly with body size, the largest spiny lobsters producing SL up to 167 dB re 1 µPa2. The sound propagation and its attenuation with the distance were quantified using the array. This permitted estimation of the detection ranges of spiny lobster sounds. Under the high ambient noise conditions recorded in this study, the sounds propagated between 5 and 410 m for the smallest and largest spiny lobsters, respectively. Considering lower ambient noise levels and different realistic propagation conditions, spiny lobster sounds can be detectable up to several kilometres away from the animals, with sounds from the largest individuals propagating over 3 km. Our results demonstrate that sounds produced by P. elephas can be utilized in passive acoustic programs to monitor and survey this vulnerable species at kilometre scale in coastal waters.

A synthetic 2-D-elastic full-waveform inversion study for the Ecuadorian margin—resolution capability of a dense onshore/offshore network

SUMMARY Subduction zones are the places on the Earth where the greatest earthquakes occur. It is now widely accepted that seismic asperities at the interface of subducting plates play a major role in whether a region of a subduction zone behaves seismically, creating strong earthquakes or exhibits aseismic slip. In the last decades, huge advances have been made to decipher the underlying processes; however, the physical parameters along the subduction zone interfaces are still not very well known due to a sparsity of high-resolution experiments and significant costs associated with amphibious seismic experiments. Therefore, synthetic tests are needed to investigate the potential of currently possible high density seismic deployments and to aid future experiment design. As standard local earthquake traveltime tomography in a subduction zone setting cannot resolve structures on a kilometre scale at depth, we explore the suitability of full-waveform inversion (FWI) to increase resolution by using amplitude and phase information in the recorded earthquake seismograms. We apply 2-D-elastic FWI to synthetic earthquake data, using vertical and horizontal receivers, and utilize a realistic model of the seismic velocities at the Ecuadorian margin. We add perturbations within the subducting plates of 4×4 km and 2×2 km in P- and S-wave velocities, respectively, such that potential crosstalk between the two models can be identified. Our results show that the location and amplitude of the perturbations can be reconstructed in high quality down to approximately 70 km depth. We find that the inversion of the S-wave velocity prior to the inversion of the P-wave velocity is necessary to guarantee a good reconstruction of both models; however, the spatial resolution of the S-wave model is superior to the P-wave model. We also show that frequencies up to 1 Hz are sufficient to achieve high resolution. Further tests demonstrate how results depend on the accuracy of the estimated source orientation. Resulting models do not suffer in quality as artefacts near the source positions compensate for the inaccuracy of source orientation. If sources are located within the subducted plate instead of beneath, resulting models are comparable and the convergence of the inversion scheme is sped up. The accuracy of the source position within the model compared to the true earthquake location is critical and implies that earthquake relocation during the inversion process is necessary, in a similar way as in local earthquake traveltime tomography.

Subduction megathrust heterogeneity characterized from 3D seismic data

Megathrust roughness and structural complexity are thought to be controls on earthquake slip at subduction zones because they result in heterogeneity in shear strength and resolved stress. However, because active megathrust faults are difficult to observe, the causes and scales of complexity are largely unknown. Here we measured the in situ properties of the megathrust of the Middle America subduction zone in a three-dimensional seismic reflection volume to determine how fault properties vary. We quantify spatial variability in the megathrust roughness, overburden and rock physical properties. Heterogeneity in the megathrust roughness exists at length scales of a few kilometres because the megathrust is dissected by active lower-plate normal faults, which offset the megathrust and renewed fault roughness. Spatial variations in the rock physical properties at the plate interface are characterized by correlation length scales of hundreds of metres. Frontal prism taper, historical seismicity and the variation in earthquake stress drop values local to the megathrust are all affected by the heterogeneity at these length scales. Both geometric and rheological complexities may therefore control the mechanical behaviour of the subduction plate interface, which includes earthquake rupture characteristics. Geometric and rheological complexities may control the mechanical behaviour of megathrusts, according to an analysis of the heterogeneity in roughness and rock properties of the Middle America megathrust from 3D seismic reflection data.

Marine Aquaculture Impacts on Marine Biota in Oligotrophic Environments of the Mediterranean Sea – A Review

The potential impacts of marine aquaculture are reviewed, focussing both on small-scale local effects near the farm environment and a broad spatial scale of many kilometres that impacts a number of different ecosystem components. Local changes in productivity, biodiversity and behavioural changes of wild fauna affected by nearby farm habitats were examined. Global aquaculture trends of growth perspectives as related to seafood supply, impacts on wild stock and biodiversity depletion, genetic changes in wild fish populations due to the escapement of cultured fish, capture-based aquaculture and its potential impacts on marine habitats were discussed. Adopting integrated principles in planning aquaculture development and respecting the assimilative capacity of a potential farming zone may reduce negative consequences of the aquaculture industry on the marine ecosystem.

Across-Fault Velocity Gradients and Slip Behavior of the San Andreas Fault Near Parkfield.

A long‐lasting question in earthquake physics is why slip on faults occurs as creep or dynamic rupture. We compute passive measurements of the seismic P wave velocity gradient across the San Andreas Fault near Parkfield, where this transition of slip mode occurs at a scale of a few kilometers. Unbiased measurements are obtained through the application of a new Bayesian local earthquake tomographic code that avoids the imposition of any user‐defined, initial velocity‐contrast across the fault, or any damping scheme that may cause biased amplitude in retrieved seismic velocities. We observe that across‐fault velocity gradients correlate with the slip behavior of the fault. The P wave velocity contrast decays from 20% in the fault section that experience dynamic rupture to 4% in the creeping section, suggesting that rapid change of material properties and attitude to sustain supra‐hydrostatic fluid pressure are conditions for development of dynamic rupture. Low Vp and high Vp/Vs suggest that fault rheology at shallow depth is conversely controlled by low frictional strength material.

A multi-sensor approach to retrieve emissivity angular dependence over desert regions

Land surface emissivity is a directional quantity and most natural surfaces are anisotropic emitters. Experimental studies show that for homogeneous surfaces like bare soils, the emissivity decreases with view angle. Translation of the directionality of emissivity as obtained from experiments or models to satellite spatial scales of kilometers or more is challenging given the natural heterogeneity of the land surface at those scales. We propose a multi-sensor approach to retrieve TIR emissivity angular dependence from satellite observations. The method is based on simultaneous radiance measurements over stable and homogeneous targets, performed by multiple remote sensing platforms in low-earth orbit (MODIS/VIIRS) and geostationary orbits (SEVIRI) with different viewing configurations. In the case of homogeneous scenes, we assume that differences in observed brightness temperatures are exclusively due to differences in the atmospheric optical path and in surface emissivity within each view angle, as surface temperature is the same for both sensors. We then use radiative transfer simulations to derive the emissivity changes between the sensors due to the viewing position. It is shown that emissivity values decrease with view angle for all thermal infrared channels considered, with the highest variations for channel centered at 8.7 μm, followed by 10.8 and 12.0 μm, respectively. The MODIS MYD21 product agrees with the multi-sensor approach for the 8.7 μm channel but shows negligible dependence on view angle for 10.8 and 12.0 μm bands. Results suggest that the emissivity calibration curve used in the MYD21 algorithm restricts the retrieval of the full angular variation of emissivity at these channels. A sensitivity analysis shows that the proposed multi-sensor method is robust, with reduced impact of the uncertainty of the atmospheric correction on the retrieval. The impact of emissivity angular dependence on retrieved LST may be as high as 3.0 and 1.0 K, respectively, for the GSW and the TES algorithms for angles up to 65°.

Evaluation of wind-induced dust-PM emission from unpaved roads varying in silt content by experimental results

Increasing pressures on land uses lead to dust emission and atmospheric pollution. The U.S. Environmental Protection Agency (EPA) published the document Compilation of Air Pollutant Emission Factors (AP-42), which provides tools to estimate dust emissions from surfaces of unpaved roads. However, unpaved roads are subjected to dust emission by wind, regardless of vehicles traveling, and overall these could be a substantial contribution to mass transfer and pollution. This study integrates experiments in a boundary-later wind tunnel of dust fluxes and numerical model that was developed for PM dispersion in the atmosphere. We tested the dust emission in response to changes in the silt content in the soil. Reference soils were used to simulate dust fluxes under various wind velocities. The results of the wind-induced dust were used for comparison with the calculated emission coefficients by the AP-42. The empirical parameters of dust fluxes by wind were used in the atmospheric PM dispersion model at a spatial scale of several kilometers from the source area. The results show the dependence of dust emission on the silt content, which is the major factor in AP-42, as well as the wind velocity. The AP-42 equations do not accurately predict PM fluxes by wind. Coupling of the AP-42 equations and natural wind erosion is necessary to estimate the total dust emission from unpaved roads. This study can contribute to the establishment of a database for assessments of environmental pollution.

Short-Range Numerical Weather Prediction of Extreme Precipitation Events Using Enhanced Surface Data Assimilation

A limited-area kilometre scale numerical weather prediction system is applied to evaluate the effect of refined surface data assimilation on short-range heavy precipitation forecasts. The refinements include a spatially dependent background error representation, use of a flow-dependent data assimilation technique, and use of data from a satellite-based scatterometer instrument. The effect of the enhancements on short-term prediction of intense precipitation events is confirmed through a number of case studies. Verification scores and subjective evaluation of one particular case points at a clear impact of the enhanced surface data assimilation on short-range heavy precipitation forecasts and suggest that it also tends to slightly improve them. Although this is not strictly statistically demonstrated, it is consistent with the expectation that a better surface state should improve rainfall forecasts.

Effectiveness of Swiss protected areas in maintaining populations of rare vascular plants

Biodiversity is currently experiencing an accelerated decline in terms of species and populations, mainly because of habitat loss. The designation of protected areas has therefore become essential for biodiversity conservation. However, compelling evidence for the long-term effectiveness of protected areas in maintaining species diversity is still scarce, especially for plant species, as analyses are often hampered by the limited availability of informative datasets from different time periods. Here we analysed the effectiveness of Swiss protected areas in maintaining vascular plant species typical for two habitat types, namely wetlands and dry grasslands. Furthermore, we tested whether the effect of protected areas on species persistence varies between low (<1000 m a.s.l.) and high elevations (≥1000 m a.s.l.). Data included several thousand historical occurrences, which were re-surveyed after 2002 at the scale of square kilometres. For each re-surveyed species, we identified the square kilometres where it had disappeared and those where it still occurred. We found that the amount of protected area within the square kilometres had a positive effect on the persistence of plant species in the studied habitat types. The effect, however, primarily occurred at low elevations, and even in square kilometres with the largest amount of protected area species declines were still observed. While protected areas at higher elevations are often embedded in a less intensively used matrix, which provides small habitat patches for threatened species, protected areas at lower elevations are often islands within an inhospitable, intensively managed matrix. This explains why protected areas at higher elevations are less important for the persistence of species within square kilometres studied here. Moreover, wetlands and dry grasslands have suffered from changes in land use or heavy exploitation during the past centuries, especially at lower elevations, with ongoing losses of species and populations occurring even within protected areas. Protected areas thus decelerate the landscape-scale loss of species but (apparently) do not fully stop it.

Error in hydraulic head and gradient time-series measurements: a quantitative appraisal

Abstract. Hydraulic head and gradient measurements underpin practically all investigations in hydrogeology. There is sufficient information in the literature to suggest that head measurement errors can impede the reliable detection of flow directions and significantly increase the uncertainty of groundwater flow rate calculations. Yet educational textbooks contain limited content regarding measurement techniques, and studies rarely report on measurement errors. The objective of our study is to review currently accepted standard operating procedures in hydrological research and to determine the smallest head gradients that can be resolved. To this aim, we first systematically investigate the systematic and random measurement errors involved in collecting time-series information on hydraulic head at a given location: (1) geospatial position, (2) point of head, (3) depth to water, and (4) water level time series. Then, by propagating the random errors, we find that with current standard practice, horizontal head gradients &lt;10-4 are resolvable at distances ⪆170 m. Further, it takes extraordinary effort to measure hydraulic head gradients &lt;10-3 over distances &lt;10 m. In reality, accuracy will be worse than our theoretical estimates because of the many possible systematic errors. Regional flow on a scale of kilometres or more can be inferred with current best-practice methods, but processes such as vertical flow within an aquifer cannot be determined until more accurate and precise measurement methods are developed. Finally, we offer a concise set of recommendations for water level, hydraulic head and gradient time-series measurements. We anticipate that our work contributes to progressing the quality of head time-series data in the hydrogeological sciences and provides a starting point for the development of universal measurement protocols for water level data collection.

Surface-Atmosphere Coupling Scale, the Fate of Water, and Ecophysiological Function in a Brazilian Forest.

Tropical South America plays a central role in global climate. Bowen ratio teleconnects to circulation and precipitation processes far afield, and the global CO2 growth rate is strongly influenced by carbon cycle processes in South America. However, quantification of basin‐wide seasonality of flux partitioning between latent and sensible heat, the response to anomalies around climatic norms, and understanding of the processes and mechanisms that control the carbon cycle remains elusive. Here, we investigate simulated surface‐atmosphere interaction at a single site in Brazil, using models with different representations of precipitation and cloud processes, as well as differences in scale of coupling between the surface and atmosphere. We find that the model with parameterized clouds/precipitation has a tendency toward unrealistic perpetual light precipitation, while models with explicit treatment of clouds produce more intense and less frequent rain. Models that couple the surface to the atmosphere on the scale of kilometers, as opposed to tens or hundreds of kilometers, produce even more realistic distributions of rainfall. Rainfall intensity has direct consequences for the “fate of water,” or the pathway that a hydrometeor follows once it interacts with the surface. We find that the model with explicit treatment of cloud processes, coupled to the surface at small scales, is the most realistic when compared to observations. These results have implications for simulations of global climate, as the use of models with explicit (as opposed to parameterized) cloud representations becomes more widespread.

Capacity Planning of LoRa Networks With Joint Noise-Limited and Interference-Limited Coverage Considerations

LoRa networks are emerging low power wide area networks (LP-WAN) that are configured as star-of-star networks. Within each underlying star network, potentially thousands of LoRa end-devices utilize the patented chirp spread spectrum-based LoRa modulation to communicate directly with a LoRa gateway over long distances at the scale of kilometers. Typically, each LoRa gateway supports six quasi-orthogonal logical star networks that correspond to the available LoRa modulation spreading factors. The aggregate capacity of a LoRa gateway is evaluated as the number of end-devices that could be supported within the corresponding cell area by all six available spreading factor networks while fulfilling some QoS coverage requirement. Successful coverage of LoRa signals could be mainly attributed to noise-limited and interference-limited considerations. In the LoRa literature, these two factors have been treated in an isolated manner, where independent SNR and SIR thresholds have been set to signify coverage. However, in reality, the SNR threshold for successful coverage depicts a decreasing function of the SIR experienced by the end-device of interest. In this paper, the capacity of LoRa networks is evaluated with joint noise and interference considerations. The presented framework for capacity evaluation has the advantage that it derives the cumulative capacity distribution that could be supported from the cell-edge towards the cell-center of an individual LoRa gateway. It is then demonstrated that the capacity distribution curves could be employed in the LoRa network planning of an example IoT home security application.