Increasing agricultural demand for freshwater in the face of a changing climate requires improved irrigation management to maximize resource efficiency. Soil water deficits can significantly reduce plant growth and development, directly impacting crop quantity and quality. Dendrometers are a plant-based tool that have shown potential to improve irrigation management in high-value woody perennial crops (e.g. trees and vines). A dendrometer continuously measures small fluctuations in stem diameter; this has been directly correlated to water stress. While plant-based measures of water deficits are the best indication of water stress, current dendrometers are imprecise due to mechanical hysteresis and thermal expansion. The high-precision dendrometer created at the OPEnS Lab alleviates these key failure points using zero-thermal expansion carbon fiber, zero friction via a spring tensioning approach, and a linear magnetic encoder. The device achieves 0.5-micron resolution, and thermal fluctuations are less than 1 micron over diurnal swings of 25°C. The cost of the device varies with build quantity; parts are $200 - $450 each and assembly requires 6 to 12 hours per system. Dendrometers are currently being deployed with telemetry based on LoRa, which is under evaluation. Without solar charging and telemetry, the battery is sufficient for over two years of operation. Mass deployment of these automated dendrometers has the potential to provide a continuous record of water stress driven changes in stems, providing valuable decision support for irrigation management.

Mesozooplankton biomass plays a key parameter in the recruitment processes of fish and biogeochemical processes. Four decadal observations in the coastal Sea of Japan, the marginal sea of the North Pacific, indicate that wet weight-based mesozooplankton biomass is controlled by both environment-induced bottom-up and predatory-induced top-down processes. Interannual variations in mesozooplankton biomass using a generalized linear model approach showed a decrease in biomass during the 1980s, followed by a rapid increase in the early 1990s, and a gradual decrease in the 2010s. These interannual variations were the mirror image of the small pelagic planktivorous fish biomass. The difference in zooplankton biomass from the previous year was negatively correlated with the difference in small pelagic planktivorous fish biomass, which was supported by a Granger causality analysis. Therefore, the results of this study indicate that top-down control is one of the main causes of long-term variations of zooplankton biomass in the ocean.

Lower-viscosity fluids are commonly believed to be able to create more complex fractures in hydraulic fracturing, however, the mechanism remains stubbornly unclear. We use a new grain-scale model with accurate coupling of hydrodynamic forces to simulate the propagation of fluid-driven fracturing. The results clarify that fracturing fluid with a lower viscosity does not always create more complex fractures. The heterogeneity in the rock exerts the principal control on systematic evolution of fracture complexity. In homogeneous rock, low viscosity fluids result in low breakdown pressure, but viscosity exerts little influence on fracture complexity. However, in heterogeneous rock, lower viscosity can lead to more complex network of fracturing. A regime map shows the dependence of fracture complexity on the degree of rock heterogeneity where low viscosity fracturing fluid more readily permeates weak defects and creates complex fracture networks.

In this paper, we present the results obtained in the determination of the true North direction on Mars by using a gnomon on the InSight mission and compare the measurements with either the North determination from the Inertial Measurement Unit and Imaging analysis. The obtained measurement has been use to populate the SEIS orientation information in the archived SEIS data. Images taken during December 2018 and January 2019 allows to determine the gnomon shadow position and length over a target. By calculating the Sun local coordinates using planetary ephemeris VSOP87, the images are used to estimate the true North direction on the landing site. By using eight different images, we obtain the true North direction with an accuracy up to $2.5^{\circ}$, which is confirmed by the IMU and Imaging analysis. The true North direction is also confirmed by an image taken near local noon, when the sun crosses the meridian. The North determination precision is then discussed in view of the seismic determination of the back-azimuth.

The Heliospheric Imagers on board NASAs twin STEREO spacecraft show that coronal mass ejections (CMEs) can be visually complex structures. To explore this complexity, we created a web-based citizen science project in collaboration with the UK Science Museum, in which participants were shown pairs of differenced CME images, taken by the inner cameras of the Heliospheric Imagers (HI-1) on board the twin NASA STEREO spacecraft between 2008 and 2016. Participants were asked to decide which image in each pair appeared the most complicated. 4,028 volunteers conducted 246,692 comparisons of 20,190 image pairs, with each pair being classified by 12 independent users. A Bradley-Terry model was then applied to these data to rank the CMEs by their visual complexity. This complexity ranking revealed that the annual average visual complexity values follow the solar activity cycle, with a higher level of complexity being observed at the peak of the cycle, and the average complexity of CMEs observed by HI1-A was significantly higher than the complexity of CMEs observed by HI1-B. Visual complexity was found to be associated with CME size and brightness, but the differences between HI1-A and HI1-B images suggest that complexity may be influenced by the scale-sizes of structure in the CMEs. Whilst it might not be surprising that the complexity observed in these CME images follows the trend observed in sunspots and the solar cycle; these results demonstrate that there is a quantifiable change in the structure of CMEs seen in the inner heliosphere.

Reverse Time Migration (RTM) Surface Offset Gathers (SOGs) are demonstrated to deliver more superior residual dip information than ray-based approaches. It appears more powerful in complex geological settings, such as salt areas. Still, the computational cost of constructing RTM SOGs is a big challenge in applying it to 3D field data. To tackle this challenge, we propose a novel method using dips of local events as a guide for RTM gather interpolation. The residual-dip information of the SOGs is created by connecting local events from depth-domain to time-domain via ray tracing. The proposed method is validated by a synthetic experiment and a field example. It mitigates the computational cost by an order of magnitude while producing comparable results as fully computed RTM SOGs.

Harmful algal blooms (HABs), in particular those consisting of the cyanobacteria \textit{Microcystis}, are becoming increasingly more common across the globe. Despite the growing body of evidence that suggests vertical heterogeneity of \textit{Microcystis} can be a precursor to HAB formation, the abiotic drivers of vertical distribution of \textit{Microcystis} are poorly understood in the field environment. The prediction of subsurface cyanobacteria is also pertinent because subsurface concentrations are not easily recognizable to the public or lake system managers, creating an unnoticed safety hazard. High-frequency temporal and vertical data were collected from an Eulerian research station anchored in a stratified and eutrophic lake for five months. Data show that the magnitude of the subsurface \textit{Microcystis} concentration peak and the center of gravity of the deep cyanobacteria layer are statistically significantly mediated by the thermal structure of the lake. The peak subsurface cyanobacteria biovolume scales linearly with the thermocline depth and temperature, whereas the center of gravity of the subsurface cyanobacteria biovolume scales linearly with the mixed layer depth and temperature. Furthermore, our data suggest there is a seasonal evolution of the subsurface cyanobacteria center of gravity that could potentially indicate timing of HAB onset. Based on easily measured parameters associated with the vertical lake temperature profile and meteorological conditions, we provide evidence of predictable trends in subsurface cyanobacteria variables.

The SAMI3/ESF (Sami3 is also a model of the ionosphere/equatorial spread $F$) code is used to simulate the growth of equatorial plasma bubbles in the presence of a background wind field based on measured winds. The measured winds exhibit the well-known ‘midnight temperature maximum’ (MTM) pattern, in which an equatorward wind occurs simultaneously with a cessation in the zonal wind. The MTM is often preceded by strong equatorward winds (about 100 m/s). The circumstance where the MTM winds are symmetric across the equator is considered; here the meridional wind component in the southern hemisphere is the reverse of the northern meridional wind. The timing of the wind pattern relative to the imposition of a seed for the ESF instability is explored. We find that the simultaneous occurrence of a seed wave and a strong converging meridional wind pattern can produce post-midnight ESF. We further find that the seed wave and the sudden cessation of the zonal winds can also produce post-midnight ESF. The MENTAT (Magnetic mEridional NeuTrAl Thermospheric) code verifies the occurrence of converging meridional wind patterns such as those simulated here, based on ionosonde data. Results suggest that regional-scale wind measurements would aid in the prediction signal-disrupting ionospheric bubbles.

The optical and VHF instrumentation on the FORTE satellite is used to document the combined phenomenology evolution of a lightning “megaflash” - mesoscale lightning that propagates laterally over exceptional distances. We identify a FORTE flash whose maximum extent was 82 km and inferred length over multiple distinct branches exceeded 100 km. This flash lasted 1.2 s and produced 250 optical and 591 RF events. We find that the channel development mapped by FORTE’s pixelated lightning imager (LLS) occurred at a typical speed of 2.6x10^5 m/s and was accompanied by sustained periods VHF emission that could individually exceed 100 ms in duration. The impulsive IC events generated by the flash indicate that this development occurred at altitudes between 3 and 8 km. Four +CG strokes were identified in the VHF waveform data that are responsible for two of the three highly-radiant LLS groups (the third radiant group came from a possible -CG while 2 of the +CGs were not as optically bright as the others). These strokes occurred at different locations throughout the flash footprint with the most distant strokes separated by approximately 50 km. These space-based observations match previous observations of megaflashes from space as well as ground-based measurements of slow negative leader development during “spider” lightning, suggesting that FORTE is sensing the same phenomena.

Polygonal Fault Systems (PFS) are an enigmatic class of small non-tectonic extensional faults. PFS are predominantly hosted in fine-grained sedimentary tiers and are prevalent along many continental margin basins. The genesis of PFS is widely debated and little is known about the timeframe for polygonal fault growth. We present the first measurements of throw rates for polygonal faults by measuring the vertical offset of seven age-calibrated horizons mapped using three-dimensional seismic reflection data from the Norwegian Sea. Individual polygonal faults exhibit a range of throw rate profiles through time, ranging from near linear to singly or multiply stepped. The stepped profiles have a range of short-term throw rates ranging from 0 to 18 m/Ma. Time-averaged throw rates of 180 polygonal faults over the entire 2.61-0 Ma interval are normally distributed and range between 1.4-10.9 m/Ma. We convert our PFS throw rates to displacement rates and compare these to published displacement rates for gravity driven and tectonic normal faults. We find that the displacement rates of polygonal faults mark the lower limit of a continuous spectrum of extensional fault displacement rates; they are up to two orders-of-magnitude slower than gravity-driven faults, and up to three orders-of-magnitude slower than the fastest growing tectonic faults. We attribute the ultra-slow kinematic behaviour to the non-tectonic nature of polygonal faults where throw accumulates primarily through dewatering of the largely fine-grained sediments comprising the host layers for the PFS, and differential volumetric strain between the fault footwalls and hangingwalls.

Terrestrial-aquatic interfaces such as salt marshes, mangroves, and similar wetlands provide an optimum natural environment for the sequestration and long-term storage of carbon (C) from the atmosphere, commonly known as coastal blue carbon. There are over 4 million acres of salt marsh in the US and over half of these are along the east coast of the US. Due to anthropogenic activities, this area presents the greatest nitrogen (N) pollution problem in coastal ecosystems in the U.S. as part of atmospheric N deposition, runoff, and riverine export. Ammonia (NH3) is the most abundant alkaline gas in the atmosphere. Agricultural intensification is the primary anthropogenic source of NH3 leading to a doubling of reactive nitrogen (Nr) entering the biosphere. Despite this, there are limited atmospheric measurements of NH3 concentrations in coastal areas along the east coast. The objective of this study is to advance our process-level understanding of NH3 air-surface exchange over a tidal salt marsh at the Saint Jones Reserve (DE), which is part of the National Estuarine Research Reserve System (NERRs). Continuous and high temporal resolution measurements of atmospheric NH3 concentrations were measured using a cavity ring-down spectrometer, reporting 30 min concentration averages. These high temporal resolution measurements allowed the estimation of the average diurnal cycle of NH3 fluxes using a new analytical methodology. Micrometeorological measurements were also measured using the eddy covariance system operated concurrently above the tidal marsh at the research site, which is part of the AmeriFlux network (US-StJ). This pilot study represents one of the few atmospheric measurements of NH3 over a tidal salt marsh in the eastern U.S. Such measurements are important to characterize the processes that influence the exchanges of NH3 between the atmosphere and the aquatic surface and provide baseline data to form more reliable parameterizations to simulate NH3 deposition and emissions in tidal salt marshes using surface-atmosphere transfer models.

Many human activities rely on accurate knowledge of the sea surface dynamics. This is especially true during storm events, when wave-current interactions might represent a leading order process of the upper ocean. In this study, we assess and analyse the impact of including three wave-dependent processes in the ocean momentum equation of the Met Office North West European Shelf (NWS) ocean-wave forecasting system on the accuracy of the simulated surface circulation. The analysis is conducted using ocean currents and Stokes drift data produced by different implementations of the coupled forecasting systems to simulate the trajectories of surface (iSphere) and 15 m drogued (SVP) drifters affected by four storms selected from winter 2016. Ocean and wave simulations differ only in the degree of coupling and the skills of the Lagrangian simulations are evaluated by comparing model results against the observed drifter tracks. Results show that, during extreme events, ocean-wave coupling improves the accuracy of the surface dynamics by 4%. Improvements are larger for ocean currents on the shelf (8%) than in the open ocean (4%): this is thought to be due to the synergy between strong tidal currents and more mature decaying waves. We found that the Coriolis-Stokes forcing is the dominant wave-current interaction for both type of drifters; for iSpheres the secondary wave effect is the wave-modulated water-side stress while for SVPs the wave-dependent sea surface roughness is more important. Our results indicate that coupled ocean-wave systems may play a key role for improving the accuracy of particle transport simulations.

Observations of fold growth in fold-thrust belt settings show that brittle deformation can be localized or distributed. Localized shear is associated with frictional slip on primary faults, while distributed brittle deformation is recognized in the folding of the bulk medium. The interplay of these processes is clearly seen in fault-bend folds, which are folds cored by a fault with an abrupt change in dip (e.g., a ramp-décollement system). While the kinematics of fault-bend folding were described decades ago, the dynamics of these structures remain poorly understood, especially the evolution of fault slip and off-fault deformation over different periods of the earthquake cycle. In order to investigate the dynamics of fault-bend folding, we develop a numerical modeling framework that combines a long-term elasto-plastic model of folding in a layered medium with a rate-state frictional model of fault strength evolution in order to simulate geologically and mechanically consistent earthquake sequences. In our simulations, slip on the ramp-décollement fault and inelastic fold deformation are mechanically coupled processes that build geologic structure. As a result, we observe that folding of the crust does not occur steadily in time but is modulated by earthquake cycle stresses. We suggest combining seismological and geodetic observations with geological fault models to uncover how elastic and inelastic crustal deformation generate fault-bend folds. We find that distinguishing between the elastic and inelastic response of the crust to fault slip is possible only in the postseismic period following large earthquakes, indicating that for most fault systems this information currently remains inaccessible.

Strong strain and pore pressure changes are observed after three Mw 4.5+ local and one Mw 7.2 regional earthquakes during 2010‒2017 in borehole strainmeters near Anza, California. The strain change emerges immediately after the earthquakes and lasts 40‒100 days with amplitudes up to 1e−7, larger than the coseismic strain offsets. The pore pressure exhibits change immediately after the earthquakes at some boreholes and with a delay of 4‒10 days at the others. A joint analysis of the observed postseismic strain and pore pressure change suggests that the postseismic strains could be explained by combined effects of poroelastic deformation due to earthquake-induced pore pressure change and elastic deformation due to an earthquake-triggered aseismic slip on a nearby fault. Our study indicates that, in addition to possible aseismic fault slips triggered by an earthquake, pore pressure changes after the earthquake could be even more important in producing postseismic deformation.

When wind blows over the ocean, short wind-waves (of wavelength smaller than 10 meters) are generated, rapidly reaching an equilibrium with the overlying turbulence (at heights lower than 10 meters). Understanding this equilibrium is key to many applications since it determines (i) air-sea fluxes of heat, momentum and gas, essential for numerical models, (ii) energy loss from wind to waves, which regulates how swell is generated and how energy is transferred to the ocean mixed layer and (iii) the ocean surface roughness, visible from remote sensing measurements. Here we review phenomenological models describing this equilibrium: those couple a TKE and wave action budget through several wave-growth processes, including airflow separation events induced by breaking waves. Even though those models aim at reproducing measurements of air-sea fluxes and wave growth, some of the observed variability is still unexplained. Hence, after reviewing several state-of-the-art phe-nomenological models, we discuss recent numerical experiments to give hints about future improvements. We suggest three main directions, which should be addressed both through dedicated experiments and theory: (i) a better quantification of the variability of wind-wave growth and of the role played by the modulation of short and breaking wind-waves by long wind-waves, (ii) an improved understanding of the imprint of wind-waves on turbulent coherent structures and (iii) a quantification of the interscale interactions for a realistic wind-waves sea, where several wind-and-waves coupling processes coexist at multiple time and space scales.

A new characteristic parameter max or peak displacement Pd. The comparison results show that for magnitude between 4.0-7.3, Sdτ has better correlation with magnitude and higher estimate accuracy than either τpmax or Pd. Hypocentral distance is not required when using Sdτ, but it can be used to further improve the accuracy of magnitude estimate. These results confirm that Sdτ can significantly improve the accuracy and timeliness of continuous magnitude estimation in an EEW system.

Conventional tide gauges are usually housed along the coast. Satellite altimetry works well in the open ocean but poorly near the coast due to issues such as signal contamination by land returns. These limitations lead to an observational gap in the coastal ocean. Using data collected by a GPS installed on top of an anchored spar-buoy in Tampa Bay, we retrieved water levels through a combination of precise positioning and interferometric reflectometry. Individual water level retrievals agree with a nearby acoustic tide gauge at ~16 cm level. Amplitude and phase of the major tidal constituents are well recovered by the GPS spar-buoy measurements. Over a 2-year period, agreement of daily mean sea levels measured by the GPS spar-buoy and a nearby acoustic tide gauge is 3.1 cm. When sea level data measured by the GPS spar-buoy are included in the coastal ocean circulation model, low-frequency error propagated from the open boundary is reduced.

Acidic fluid flow in geologic formations leads to mineral dissolution and, under certain circumstances, to localized dissolution forming a dendritic pattern, known as wormhole. Such patterns of conduits and caves are often observed in karstic aquifer and deliberately engineered in oil and gas well stimulation with acid injection. Experimental studies suggest that various parameters such as fluid velocity or material heterogeneity control the wormhole formation. While many numerical and experimental studies found the acid flow velocity to play a controlling role, most models need to randomly seed material heterogeneities to induce wormholes. Here we show that a phase-field approach, which diffuses a sharp interface in a continuous manner, is capable of simulating wormhole without random seeds by accounting for the energy expenditure in the dissolution topology. We verified the model against the sharp interface counterpart in one-dimensional simulations. We then performed the two-dimensional simulations to qualitatively validate wormhole formation and growth patterns against acid injection experiments on carbonate rocks under radial flow conditions. The simulation results indicate that the injected acid is rapidly consumed near the acid entry point at low injection rates while the live acid becomes available at the tip of the dissolved cavity under high rates and thus wormhole starts to grow resulting in much faster acid breakthrough.