In global climate models, CO2-driven warming causes strong and very widespread mean drying trends in climatic wetness indices like the Palmer Drought Severity Index, Aridity Index and Standardized Precipitation-Evapotranspiration Index. Yet, these same simulations also predict that runoff will not decline over most of Earth’s surface, that root-zone soil moisture and evaporative fraction will decline only regionally, and that vegetation will become broadly greener. Thus, actual drought impacts of warming in these models are far less broad and severe than implied by the drought indices. Here, I probe why this “index-impact gap” occurs, and whether it is a feature of reality as well as models. In particular, I show that the discrepancies are not just limited to simulations which assume a substantial direct CO2 effect on vegetation, but are also large in greenhouse-only simulations, implying that they occur for fundamental climatic reasons rather than via CO2-physiological pathways. I also review key observational evidence that the index-impact gap has also been large over the historical era and was very evident for the last glacial-to-interglacial warming, lending much additional credence to the model output.

A Helium Lidar system, which is being developed for measurements of metastable helium density in the thermosphere and exosphere, employs a CW 1083nm laser with power of 60W, a telescope array consisting of six 1m-diameter telescope and an area-array ICCD. To realize range-resolved remote sensing, the laser is located separately from the location of telescope with a distance of D and the laser beamed is leaned towards the Field-of-view (FOV) of the telescope array with an zenith angle of θ. The signal in a specific height is finally imaged onto a corresponding pixel of the ICCD. Before the retrieval of metastable helium density, the first procedure is to decide the relation between the pixels and corresponding heights. Based on the FOV of the telescope, the divergence angle of the laser beam, the geometry of the laser and telescope, and the size of the pixels, every pixel corresponds to a specific height range, as shown in Fig. 1. The darkest shade corresponds to one pixel of the ICCD. Therefore, the second procedure is to correct the height range overlap of the signal from adjacent pixels to decrease the smoothness of the signal profile caused by the height overlap of adjacent pixels. The signal received by the ICCD is simulated based on a metastable helium density model developed by Waldrop et. al. The results show that these two signal correcting procedures can improve the precision of each pixel’s signal by 5% in average.

A precise and accurate timescale is critical for calibrating major events in Earth history and testing their spatiotemporal relationships for putative causes. The Newark-Hartford astrochronostratigraphic polarity timescale (APTS) was developed in cyclical lacustrine continental deposits spanning 27 million years of Late Triassic and earliest Jurassic time using the theoretically constant 405 kyr eccentricity cycle linked to gravitational interactions with Jupiter-Venus as a tuning target and provides a major calibration for the early Mesozoic. While this cycle is both unimodal and the most metronomic of the major orbital cycles thought to pace Earth’s climate in numerical solutions, there has been no empirical confirmation of that behavior, given the potential chaotic behavior of the Solar System. An additional criticism of the Newark-Hartford APTS is that it is anchored only at its younger end by U-Pb zircon dates at 201.6 Ma. To test the validity of the dangling APTS and orbital periodicities, we recovered a diagnostic magnetic polarity sequence providing an unambiguous correlation to the APTS in the volcaniclastic-bearing Chinle Formation in drill core PFNP-1A from Petrified Forest National Park (Arizona, US). New U-Pb CA-TIMS detrital zircon dates from the core are indistinguishable from ages predicted by the APTS back to 215 Ma. The APTS is evidently continuous to a small fraction of a remarkably constant 405 kyr orbital eccentricity cycle, thus extending the empirical evidence well beyond theoretical solutions regarded as reliable back to only 50 Ma. The Newark-Hartford APTS becomes the longest directly calibrated polarity sequence and can be used to resolve various Earth history problems, for example, to differentiate provinciality from global temporal patterns in the ecological rise of early dinosaurs.

Physical habitat losses for Pacific salmonids in California’s Central Valley motivate stream restoration. Considerable river morphodynamics affect the sustainability of habitat enhancing interventions. In addition, the presence of large dams in many river catchments causes low sediment supply. This study revises existing stream restoration techniques for their ecologically efficient and physically stable embedding in a 36-km testbed river. Ecological efficiency is evaluated in terms of a commonly used hydraulic habitat suitability index. Physical stability results from 2D hydrodynamic modelling of bed shear stress during steady flows of different flood frequencies. We differentiate between terraforming, stabilizing and maintaining stream restoration techniques, which constitute three feature layers. The first layer, terraforming, includes artificial terrain modifications such as grading or backwater creation to generate new habitat. These features require stabilization, which is provided by the second feature layer. The stabilization (layer two) is achieved by bioengineering such as placement of streamwood, angular boulders and vegetation plantings. The third feature layer has the purpose to maintain newly created habitat, e.g., through artificial gravel injections. We illustrate the application of the three-layer-approach at one major restoration site of the lower Yuba River using a self-written Python package. Ecohydraulic 2D modeling was applied to designs with incremental layer additions to evaluate newly created spawning habitat and feature sustainability. This procedure represents a pertinent way for stream restoration planning, which avoids non-sustainable habitat enhancement features and implements ecologically as well as physically sustainable features only.

Allowing near-surface geophysics students to learn ground penetrating radar (GPR) data processing through hands-on exercises poses a challenge because of the high cost of professional GPR software. Free processing and visualization packages are scarce and often either require other commercial software such as Matab, which many students may not have on their own computers, or they are limited to specific operating systems. To allow students to process GPR data on their own computers, for example data collected as part of a class-based research project or online available data, the processing software needs to be (1) free, (2) platform independent, (3) easy to install and use, and should record the steps the students take to obtain their results in order to facilitate reproducibility and grading. GPRPy (https://github.com/NSGeophysics/GPRPy) is an open-source ground penetrating radar data processing and visualization software that has a graphical user interface and which is also scriptable. It is python-based, making it platform independent and independent of commercial programming environments. The graphical user interface allows for writing out humanly readable python scripts that can be run from the command line to automatize the data processing and visualization. GPRPy is hosted on the collaborative software development website GitHub, allowing educators and researchers to create and adapt their own versions to their needs.

The Shenhu hydrate reservoirs of northern South China Sea are speculated to form and accumulate under the free gas-rich environment, and accord with the flow-transportation-reaction process. During this process, the area has also experienced simultaneous alternations of the local geological structures and ambient environmental conditions. First-order reaction kinetics, which controls the hydrate reaction, is coupled with the seafloor sedimentation to quest the dynamic formation and aggregation mechanism of the Shenhu hydrate layers. Firstly, based on the indications from Peclet number, the hydrate reaction shall play more active roles during the natural sedimentation in this process. Secondly, when the average seafloor sedimentation rate and the initial seafloor were 5 cm/ka and 988 m, respectively, three moments (50 ka, 3 Ma, and 5 Ma) are chosen to investigate the evolution process of the hydrate reservoirs and exhibit the change of the local pressures, temperatures, dissolved methane and salt, phase saturations, stratum permeability, and pore capillary pressure. The results show that after 5 Ma the occurrence and distribution of hydrate-bearing sediments proceed to be nearly consistent with the current status. Finally, the effects of five factors, including methane flux, kinetic coefficient, initial fluid position, permeability and seafloor sedimentation rate which simultaneously control the accumulation together in this zone, are quantitatively discussed. It verifies that the reaction-sedimentation mechanism is applicable for researching the Shenhu hydrate system. Under this model it should have a small methane flux and relatively small reaction coefficient here.

We perform a suite of laboratory friction experiments on saw-cut Westerly Granite surfaces and probe frictional state evolution in response to step changes in normal stress. The experiments are conducted with the objective of illuminating the origin of friction memory effects and the fundamental processes that yield friction rate and state dependence. In contrast to previous works, we measure directly the fault slip rate and account for changes in slip rate caused by normal stress perturbations. Further, we complement mechanical data acquisition by continuously probing the faults with ultrasonic pulses. We conduct the experiments at room temperature and humidity conditions in a servo controlled biaxial testing apparatus in the double direct shear configuration. The normal stress perturbations are carried out during steady shearing over a range of shear velocities, from 0.02 - 100 μm/s. We report observations of a transient shear stress and friction evolution with step increases and decreases in normal stress. Specifically, we show that shear stress evolves in a two-stage fashion – first linear-elastically, then inelastically in response to the normal stress step. We find that the excursions in slip rate resulting from the changes in normal stress must be accounted for in order to accurately predict fault strength evolution. The effects of induced changes in fault slip rate are also apparent in elastic wave properties. Ultrasonic wave amplitudes increase instantly in response to normal stress steps and then gradually decrease to a new steady state value, in part due to changes in fault slip rate. This decrease is strongly related to accelerated creep at the fault interface. We also demonstrate that steady state amplitudes are a reliable proxy for real contact area (RCA) at the fault interface. Previous descriptions of frictional state evolution during normal stress perturbations have not adequately accounted for large slip velocity excursions. Here, we do so by using the measured ultrasonic amplitudes as a proxy for frictional state during transient shear stress evolution. Our work improves understanding of induced seismicity and triggered earthquakes with particular focus on simulating static triggering and stress transfer phenomena using rate-and-state frictional formulations in earthquake rupture models.

In this talk, I will draw distinction between linear plasma waves and strong turbulent fluctuations and argue general characteristics of 3He rich solar energetic particle events favor the scenario that 3He ions are mostly energized via cyclotron resonance with proton cyclotron waves. These waves can be produced via magnetic reconnection at the ion diffusion scale and/or via cascade of turbulence energy from low to high frequencies. Both PIC and hybrid simulations can be used to verify these scenarios.

This study reports the presence of Australasian microtektites in a deep-sea core (U1452) retrieved during International Ocean Discovery Program (IODP) Expedition 354: Bengal Fan. These microtektites are found within a foraminifera-rich calcareous clay layer beneath the Brunhes–Matuyama (B–M) magnetostratigraphic boundary. Most of them are spherical and are less than one millimeter in diameter. Typical splash (dumbbell, teardrop, button etc.) and irregular-shaped forms were recovered. The most abundant microtektites are pale green in color, followed by opaque, pale brown, translucent and transparent varieties. They are characterized by various surficial attributes including pits, mounds, grooves and fractures. Geochemical analyses suggest that the major oxide compositions are very similar to Australasian microtektites, Australasites reported elsewhere and also to the average composition of upper crustal rocks. Transparent bottle green microtektites are relatively richer in MgO content and lower in silica to other microtektites found in U1452. Minor and trace elements show a wide range of distribution and individual samples show variation. Differences in minor and trace elements concentration are possibly due to the contamination from the impact ejecta. Other than microtektites, presence of possibly polymetallic exsolution texture, shocked minerals and unmelted and partly melted ejecta within the microtektite-bearing layer in the northern Indian Ocean provides further evidence that the Australasites and Australasian microtektites might have been formed by the impact of an extraterrestrial projectile at ~0.8 Ma, somewhere in Indochina.

We are using radio occultation (RO) measurements from Mars Global Surveyor to investigate the nighttime structure and dynamics in the lower atmosphere of Mars. High-resolution temperature profiles retrieved from the RO data contain unique information about nocturnal mixed layers (NMLs) – detached layers of neutral stability that form at night in response to radiative cooling by a water-ice cloud layer. Basic properties of the NMLs and constraints on their spatial distribution and seasonal evolution can be obtained through analysis of the RO profiles. We have examined more than 3000 RO profiles in a latitude band centered on the Phoenix landing site (234°E, 68°N), where nighttime water-ice clouds were observed by the LIDAR instrument (Whiteway et al., Science 325, 68-70, 2009). NMLs appear routinely in the western hemisphere in RO observations at 5 h local time from early summer of MY27. There is a close resemblance in both thickness (a few km) and altitude (about 4 km above the surface) to the cloud layer observed at the same local time by the Phoenix LIDAR in MY29. The NMLs confirm that radiative cooling by the Phoenix cloud is sufficient to trigger convective instability, as predicted by a Large Eddy Simulation (Spiga et al., Nat. Geosci. 10, 652-657, 2017). We have also analyzed more than 800 RO profiles from the northern tropics near summer solstice of MY28. Tropical NMLs are largely confined to regions of elevated terrain, where the daytime convective boundary layer is deep. At 4 h local time, the top of the NML is about 10 km below the peak of Olympus Mons. The spatial distribution of the NMLs appears to be influenced by diverse processes ranging from topographic circulations to planetary-scale thermal tides. In addition, we are using a Mars Global Circulation Model and Large Eddy Simulations to interpret the RO results. Goals of the modeling effort include: to identify the atmospheric processes that control the formation of nocturnal water ice clouds; to understand the spatial distribution of the clouds and their evolution with time of day and season; and to assess the impact of NMLs on the nighttime weather and water transport in the lowest scale height above the surface.

Groundwater occurrence in crystalline basement complex is mainly due to the development of secondary porosity and permeability arising from the weathering and fracturing of the low porosity igneous and metamorphic basement rocks. In this study, geophysical survey involving seismic refraction and 2D electrical resistivity tomography (ERT) was conducted to assess the hydrogeological characteristics of the weathering profile of the crystalline basement rocks in Olomore, Abeokuta, southwestern Nigeria. The 2D ERT survey was conducted along five Traverses using dipole-dipole array with a minimum electrode spacing of 5.0 m in Traverses 1, 2, 3 and 5, and 10.0 m in Traverse 4, and a dipole separation factor of 1 – 4 in all the traverses; the observed apparent resistivity data were inverted using RES2DINV. The seismic refraction survey was conducted along the same traverses using 10 Hz electromagnetic geophones; the refraction data were processed using SeisImager with the first arrival travel times picked using Pickwin module and inverted using Plotrefa to obtain velocity model of the subsurface. A good correlation exists between the 2D ERT images and the seismic refraction velocity models. The effective depth of investigation for both ERT and seismic refraction is approximately 43.0 m in all the traverses except for ERT of Traverse 4 which 66.0 m depth of investigation. Four lithologic layers may be inferred with varying model resistivity and P-wave velocity range of 546-974 m/s, 1456-1877 m/s, 2042-2944 m/s, and 3041-6894 m/s respectively. Both ERT and seismic refraction images indicate that the regolith (collapsed zone and saprolite) is relatively thin (< 10.0 m) and may be unable to support adequate drawdown for good yield. But the weathered and fractured basement is sufficiently thick to support adequate drawdown for high groundwater storativity and yield; depth-to-bedrock is greater than 20.0 m in most part of the study area. The study shows that the combination of ERT and seismic refraction is effective for near-surface characterisation for hydrogeological investigations in crystalline basement complex.

Unmanned Aerial Vehicle (UAV) based Structure-from-Motion (SfM) techniques have renovated 3D topographic monitoring of earth surface, offering low-cost, rapid and reliable data acquisition and processing. Multi-temporal models of the river environment can be produced by autonomous operation in order to determine erosion, subsidence, landslide, soil transport and surface deformation in the riverbeds. Herein, the acquisition of repeated topographic surveys helps us to characterize the flow regime and to monitor the sediment dynamics. This study presents the hydromorphological changes of the meandering structures by using UAV-generated point clouds and Digital Surface Models (DSMs) produced by SfM at different times in the Büyük Menderes Basin located in the western part of Turkey. The processing of the data obtained with the flights were made in January and June 2018 at selected three meander locations with the highest visible changes according to the long-term satellite imageries. Especially, riverbank erosion along the river was determined by digitizing the edges and volumetric calculations of the eroded/deposited sediments derived from UAV-based measurements. In addition to the periodic volumetric differences of the meander structures, the differences in volumetric comparison methods for the same meander structures have been evaluated. Ultimately, the sediment profiles were extracted along the river banks at the selected part of the meanders and the amount of deposited sediments were determined to increase in a range between 1.5% and 3.3% of the total sediment. In conclusion, it is estimated that UAVs will be used instead of conventional photogrammetry aircraft in many future projects, considering the data production times and costs in large areas. Further, various digital cameras and sensors can be mounted on UAVs in order for examining the sediment effect on the health and productivity of plants in agricultural areas around the meanders.

Bridge foundation scour is the most common cause for the failure of highway bridges. The assessment of local scouring mechanism around bridge piers provides information for decision-making regarding the pile footing design, predicting the safety of bridges under critical scoured conditions, and as a result, may help prevent unnecessary loses. Since scour in bridges is the water-induced erosion of soil particles around bridge foundations, the loss of lateral load capacity at bridge foundations may induce bridges to become highly vulnerable to failure when the effects of scour and floods are combined. In this study, high definition 3D models of the flood plain and the amount of current scour in bridge piles were acquired by Unmanned aerial vehicle (UAV) based measurements which provide a practical approach and bring high precision solutions considering traditional measurement systems. The present study evaluated the performance of bridges with reinforced concrete (RC) pile foundations under the effects of local scour and flood. Thus, a RC bridge constructed over Boğaçayı in Antalya, Turkey was selected as the case study. The vulnerability of the bridge was assessed under flood loading considering the predicted scour amount. The maximum flood loads according to different return periods (5, 20, 50, 100 and 500 years) and the corresponding maximum scour depths were determined by HEC-RAS software. As a result, the outputs were regarded as input parameters for the evaluation of lateral behavior of the bridge under consideration. The soil-pile foundation-structure interaction was implemented in the finite element models of pile groups. The multi-hazard performance of the bridge was evaluated under the maximum predicted scour depth and corresponding flood load. In conclusion, as the scour depth increased the fundamental periods, shear forces and the bending moments were observed to increase while the pile lateral load capacities diminished. Therefore, it was ascertained that the scour substantially deteriorated the performance of the bridge under multi-hazard environment.

Sand production is the process in which formation sand and gravel would migrate into the wellbore by the flow of reservoir fluids. This is a problem that endangers the safety of hydrate exploitation. The aim of this study is to understand sand production in during hydrate exploitation. A novel experimental apparatus was constructed to examine sand production in the hydrate-bearing sediments by applying the depressurization method. The maximum pressure of apparatus is 30 MPa, the temperature could be controlled from -253.15 to 313.15 K. The pore pressure, crustal stress, production pressure, gas flow rate, water production volume and subsidence rates could be measured. The vertical wellbore comprised liner 1 (ø32 mm × 135 mm, 3 mm holes, arrangement: 36°, holes row gap: 10 mm) and liner 3 (ø24 mm × 135 mm, 2.5 mm holes, arrangement: 36°, hole row gap: 10 mm) with a sand screen. Besides gas in from top, the sediment chamber (ø158 mm × 120 mm) had a middle mesh screen that allowed gas and water enter or vacuumize the chamber circumferentially around the sediments (ø158 mm × 100 mm). Sand production situation was recorded by HD camera through the visual window on the gas-solid-liquid separator. Hydrate production was divided into three periods: water, gas with water drops, and gas. We found fine sand production in the first period and sand grains production in the second. The sand production behaviours through the different gas production rates in two production method - depletion gas production curve and stable gas production curve were discussed. The grain sizes of sand production were increasing in the production period with hydrate saturation decreasing. The temperature related characteristics of the hydrate layers differed during different stages of hydrate production. The unique sputtering occurring owing to the decomposition of the hydrate might have provided the driving force for sand migration, and water gas bubbles or gaseous water drops from the decomposed hydrate might have enhanced sand carrying capacity. The subsidence of hydrate-bearing sediments was influenced by sand production, whereas the maintenance of crustal stress possibly influenced the rate and magnitude of subsidence. The stimulation at late production in low hydrate saturation might conduct the subsidence and sand production increased dramatically.

The use of geophysical methods to characterize subsurface properties has significantly grown in the last decade. Although geophysics can bring relevant spatial and temporal information on subsurface processes, the quantitative interpretation and integration in models remain difficult. Indeed, standard deterministic solutions suffer from (excessive) smoothing and spatially variable resolution, whereas joint or coupled inversions remain difficult to apply in complex cases. Hermans et al. (2016) proved using cross-borehole ERT that physical properties distribution could be directly retrieved from data using Bayesian Evidential Learning (BEL). BEL uses a series of prior models to derive a direct relationship between data and forecast in a reduced dimension space. This can be challenging when the prediction becomes more complex with higher dimensions. In this contribution, we extend the work of Hermans et al. (2016) to a full 4D experiment (3D + time). We demonstrate that the shape and amplitude of the temperature plume can be retrieved, with uncertainty quantification, during a push-pull experiment using surface ERT. We analyze the robustness of the solution using a synthetic benchmark. The results indicate that the median of the posterior is very close to the true temperature distribution. The relative error increases at the edge of the temperature plume where the change of temperature is limited. This is related to the limited resolution of geophysics and the process of dimension reduction. We also investigate how discrete cosine transform can improve the dimension reduction process without altering the final prediction. Finally, we show that BEL is able to retrieve the spatio-temporal variability of the plume, while the smoothness constraint inversion fails to accurately image the corresponding contrast, largely underestimating the amplitude of the temperature change. BEL is therefore a well-suited framework for the interpretation of 4D geophysical data avoiding the drawbacks of standard deterministic solutions. Hermans, T., Oware, E., & Caers, J. (2016). Direct prediction of spatially and temporally varying physical properties from time-lapse electrical resistance data. Water Resources Research, 52, 7262-7283.

The gap between governmental policy and actions taken by local officials often exists and this gap could be even more severe when it is climate adaptation policy. On the other hand, most of existing studies tend to pay more attention to the structure and the performance of the model rather than the practical operation procedure. To minimize the gap and to evaluate the effectiveness of the adaptation policy, a cross-scale and cross-sector adaptation assessment model, Agriculture and Hydrology assessment model (AgriHydro), is proposed in this study. AgriHydro is established physically to embed top down policies and bottom up local actions and combine with the standard assessment framework, Climate Adaptation 6-Steps and Climate Risk Template, to support decision-making. For sub-models of the AgriHydro, the Aquacrop crop model and the system dynamic water distribution model were calibrated and integrated to form the feedback mechanism. The weather generator (WthGen) modular including climate change scenarios is also established and coupled into the AgriHydro to form a fully functional adaptation assessment tool. An actual application for analyzing the adaptation policy for water supply and crop yield in Taoyuan City of Taiwan is implemented due to the diversity and the complexity of Taoyuan City in land use and water system. The results reflect the possible trade-off of future risks between water resource and agriculture fields under different climate and social scenarios. Moreover, this study shows that the proposed model can provide the linkage to the standard assessment framework, which allows a consist understanding among users on risk and model output. This enables AgriHydro to become a practical and operational tool for decision making and ready for further application.

The Vector Electric Field Instrument (VEFI) aboard the CNOFS satellite recorded over 20 thousand 12-s-duration, 3-axis continuous VLF waveforms syncronously on 3 crossed antenna booms. Tbis provides an important data archive on Poynting flux and wave intensity, of relevance to wave-particle interactions in tbe low-latitude inner plasmasphere. We will provide a summary of all the observations, not limited to discrete whistlers associable with known lightning events (our focus in previous reports).

We analyze changes in vegetation greenness across the coastal, Andean, and Amazonian regions of continental Ecuador, 1982-2010. Using Normalized Difference Vegetation Index (NDVI) anomalies derived from the Advanced Very High-Resolution Radiometer (AVHRR) on monthly and annual bases, we identify: i) long-term changes in annual NDVI, ii) seasonal shifts in greenness patterns, and iii) spatial patterns of change in vegetation greenness. Results indicate overall significant greening, or NDVI increase, after the mid-1990s, with distinct seasonal and regional variations. In the Amazon changes occur between September and February, resulting in a prolonged growing season during the later period. Significant increases are witnessed in coastal regions between February and May, but with no change in growing season. Fluctuations in NDVI in the Andes mimic the coast in the western slopes and the Amazon in the eastern slopes but exclude major changes in NDVI. The research investigates the possible effects of precipitation and CO2, and contributes to the understanding of tropical vegetation change in a rapidly changing environment.