Edge-to-Stem Variability in Wet-Canopy Evaporation From an Urban Tree Row

Evaporation from wet-canopy (\(E_\mathrm{C}\)) and stem (\(E_\mathrm{S}\)) surfaces during rainfall represents a significant portion of municipal-to-global scale hydrologic cycles. For urban ecosystems, \(E_\mathrm{C}\) and \(E_\mathrm{S}\) dynamics play valuable roles in stormwater management. Despite this, canopy-interception loss studies typically ignore crown-scale variability in \(E_\mathrm{C}\) and assume (with few indirect data) that \(E_\mathrm{S}\) is generally \({<}2\%\) of total wet-canopy evaporation. We test these common assumptions for the first time with a spatially-distributed network of in-canopy meteorological monitoring and 45 surface temperature sensors in an urban Pinus elliottii tree row to estimate \(E_\mathrm{C}\) and \(E_\mathrm{S}\) under the assumption that crown surfaces behave as “wet bulbs”. From December 2015 through July 2016, 33 saturated crown periods (195 h of 5-min observations) were isolated from storms for determination of 5-min evaporation rates ranging from negligible to 0.67 \(\hbox {mm h}^{-1}\). Mean \(E_\mathrm{S}\) (0.10 \(\hbox {mm h}^{-1}\)) was significantly lower (\(p < 0.01\)) than mean \(E_\mathrm{C}\) (0.16 \(\hbox {mm h}^{-1}\)). But, \(E_\mathrm{S}\) values often equalled \(E_\mathrm{C}\) and, when scaled to trunk area using terrestrial lidar, accounted for 8–13% (inter-quartile range) of total wet-crown evaporation (\(E_\mathrm{S}+E_\mathrm{C}\) scaled to surface area). \(E_\mathrm{S}\) contributions to total wet-crown evaporation maximized at 33%, showing a general underestimate (by 2–17 times) of this quantity in the literature. Moreover, results suggest wet-crown evaporation from urban tree rows can be adequately estimated by simply assuming saturated tree surfaces behave as wet bulbs, avoiding problematic assumptions associated with other physically-based methods.     

Coherent structure dynamics and sediment particle motion around a cylindrical pier in developing scour holes

Recent investigations on the dynamics of the turbulent horseshoe vortex system (THV) around cylindrical piers have shown that the rich coherent dynamics of the vortical structures is dominated by low-frequency bimodal fluctuations of the velocity field. In spite of these advances, many questions remain regarding the changes of the flow and sediment transport dynamics as scour progresses. In this investigation we carry out laboratory experiments to register the development of the scour hole around a cylindrical pier in a fine-sand bed (d ₅₀ = 0.36 mm). We use the bathymetry measured in the experiment to simulate the flow field employing the detached-eddy simulation approach (DES), which has shown to resolve most of the turbulent stresses around surface-mounted obstacles. From these simulations we compare the dynamics of the THV to the flat-bed case, and analyze the effects on particle transport and sediment flux using the Lagrangian particle model of Escauriaza and Sotiropoulos (2011b) to study the impact of the changes of the flow on the sediment dynamics.     

The Rio Narcea gold belt intrusions: geology, petrology, geochemistry and timing

This paper discusses the petrographical, mineralogical and geochemical characteristics of the intrusive rocks located along the Rio Narcea Gold Belt, and the timing of formation of the El Valle-Boinás deposit. Rocks in the belt range from quartz-monzodiorites through quartz-monzogranites to monzogranites. The former are made up of pyroxene (clino and ortho), amphibole (magnesiohornblende), biotite, zoned plagioclase (An35-70), and to a lesser degree quartz and K-feldspar. The monzogranites consist of biotite, zoned plagioclase (An30-60), quartz and K-feldspar. All igneous rocks are characterized by the presence of ilmenite and the lack or scarce presence of magnetite indicating their formation under reducing conditions. The granitoids are calc-alkaline I type, potassium-rich and highly reducent with more ferrous than ferric iron. Their characteristics are like the plutons associated with gold and copper (zinc) skarns, but their characteristics reflect more reducent formation conditions, increasing their capacity to form gold skarns.The Boinas granitoid emplacement occurred at about 303±6 Ma and generated calcic and magnesic skarns at the contact with limestone and dolostones of the Láncara Formation. Skarns and granitoids were first altered to amphibole and sericite, respectively, and mineralized at 302±9 Ma. The intrusion of subvolcanic porphyritic dikes produced a second period of alteration at 285±4 Ma, characterized by carbonatization and sericitization of the monzogranites and chloritization and serpentinization of the skarns. The later intrusion of diabasic dikes at 255±6 Ma produced limited carbonatization, silicification and sericitization and hypogene oxidation of the previous stages. Supergene oxidation then occurred at the top of the ore and along fractures and breccias.     

Tectonics of an extinct ridge-transform intersection,Drake Passage (Antarctica)

New swath bathymetric, multichannel seismic and magnetic data reveal the complexity of the intersection between the extinct West Scotia Ridge (WSR) and the Shackleton Fracture Zone (SFZ), a first-order NW-SE trending high-relief ridge cutting across the Drake Passage. The SFZ is composed of shallow, ridge segments and depressions, largely parallel to the fracture zone with an `en echelon' pattern in plan view. These features are bounded by tectonic lineaments, interpreted as faults. The axial valley of the spreading center intersects the fracture zone in a complex area of deformation, where N120° E lineaments and E–W faults anastomose on both sides of the intersection. The fracture zone developed within an extensional regime, which facilitated the formation of oceanic transverse ridges parallel to the fracture zone and depressions attributed to pull-apart basins, bounded by normal and strike-slip faults.On the multichannel seismic (MCS) profiles, the igneous crust is well stratified, with numerous discontinuous high-amplitude reflectors and many irregular diffractions at the top, and a thicker layer below. The latter has sparse and weak reflectors, although it locally contains strong, dipping reflections. A bright, slightly undulating reflector observed below the spreading center axial valley at about 0.75 s (twt) depth in the igneous crust is interpreted as an indication of the relict axial magma chamber. Deep, high-amplitude subhorizontal and slightly dipping reflections are observed between 1.8 and 3.2 s (twt) below sea floor, but are preferentially located at about 2.8–3.0 s (twt) depth. Where these reflections are more continuous they may represent the Mohorovicic seismic discontinuity. More locally, short (2–3 km long), very high-amplitude reflections observed at 3.6 and 4.3 s (twt) depth below sea floor are attributed to an interlayered upper mantle transition zone. The MCS profiles also show a pattern of regularly spaced, steep-inclined reflectors, which cut across layers 2 and 3 of the oceanic crust. These reflectors are attributed to deformation under a transpressional regime that developed along the SFZ, shortly after spreading ceased at the WSR. Magnetic anomalies 5 to 5 E may be confidently identified on the flanks of the WSR. Our spreading model assumes slow rates (ca. 10–20 mm/yr), with slight asymmetries favoring the southeastern flank between 5C and 5, and the northwestern flank between 5 and extinction. The spreading rate asymmetry means that accretion was slower during formation of the steeper, shallower, southeastern flank than of the northwestern flank.     

Structure of the South Powell Ridge (NE Antarctic Peninsula): new clues for changing tectonic regimes near the Scotia/Antarctica Plate boundary

The structure of the South Powell Ridge (SPR), separating the Late Cenozoic ocean-floored Powell Basin and the Mesozoic Weddell Sea domain, is revealed by multichannel seismic data. The SPR appears as a basement high, bounded northward by transtensional faults and by normal and major reverse faults to the south. These margin features seem to be linked to the Powell Basin southern strike-slip margin and to the Jane Arc paleotrench, respectively. We suggest the ridge evolved from the Antarctic Peninsula passive margin to become the deformational front of the Scotia/Antarctica Plate boundary, later being welded to the Antarctic Plate. Received: 18 August 1997 / Revision received: 4 May 1998     

Physiography and deposition on a distal deep-sea system: The Valencia Fan (Northwestern Mediterranean)

The Valencia Fan developed as the distal fill of a deep-sea valley, detached from the continental slope and the main sedimentary source. A survey of side-scan sonar, Sea Beam and reflection seismics shows that the sediment is largely fed through the Valencia Valley. The upper fan comprises large channels with low-relief levees, and the middle fan has sinuous distributary channels. Depositional bedforms predominate on the valley floor and levees, and erosional bedforms are common in the valley walls. A change to slope on the fan apex and the presence of volcanoes on the upper fan are the main factors influencing fan-growth pattern.     

Tectonics of the triple junction at the southern end of the Shackleton Fracture Zone (Antarctic Peninsula)

The southern end of the Shackleton Fracture Zone is subducted below the South Shetland forearc, while the basal detachment of the forearc continues eastward of the Shackleton ridge as a thrust fault. The western boundary between the Antarctic/Scotia plates is located at the eastern margin of the Shackleton ridge, where an elongated depositional basin and a morphological trough delineates the contact. The boundary of the Antarctic/Scotia plates and the South Shetland forearc form a triple junction at the intersection of the Shackleton Fracture Zone with the trench, between these two plates, and an independent South Shetland block.     

Styles of compressional neotectonics in the eastern Alboran Sea

The preliminary interpretation of new high-resolution seismic reflection profiles from the eastern Alboran Sea indicates strong geological similarities between this region and southeastern Spain. The principal neotectonic elements, which result from roughly north-south compression, are defined by northeast-southwest oriented wrenches separated by intervening north-south and west-northwest-east-southeast strike-slip faults. Variations in direction of principal stress axes have permitted faulting to alternate between these two systems, and for reverse faulting to occur within some wrench zones during periods when there was a component of compression perpendicular to them.     

On the swimming strategies to escape a rip current: a mathematical approach

Rip currents represent significant hazards to swimmers all around the world. The danger arises when a misinformed swimmer uses an inadequate strategy to escape the rip, such as fighting the current directly. This can lead to fatigue, panic, and in some cases drowning. There exists a range of strategies put forward by experts (both lifeguards and scientists) to escape rip currents. However, these recommendations are based on a limited number of scientific studies and there is still much discrepancy surrounding the best strategy to escape a rip. Thus, here we present a simple, physics-based theoretical model aimed at assessing different escape strategies in terms of their associated ‘energetic cost’ (in work and power) for any given rip current and swimmer’s proficiency level. Many combinations of swimmers and rips are considered, including both idealised and a realistic rip current. Our quantitative results back the common knowledge that swimming against the rip (which is strongly discouraged by lifeguards) is almost universally the worst possible strategy, especially when compared against strategies favoured by experts, such as floating with the current before attempting to swim back to the shore. For a realistic rip, our results suggest that swimming directly against the rip can require several times more power from the swimmer than other strategies advised by lifeguards, thus lending further scientific support to experts’ recommendations. This study may help promote education around the dangers posed by rip currents and how best to address them.