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.

The Baltic Sea is a shallow, stratified, brackish water sea with several subbasins. In this work, we analyzed CTD casts from HELCOM monitoring data of the Baltic Sea, data from FMI's glider missions in 2016 and 2017 and profiles from FMI's Argo floats. We used clustering and machine learning algorithms developed for time series analysis to classify vertical profiles. We endeavored to classify profiles into classes with similar shapes. Then, we defined whether it was possible to define the depth of the upper mixed layer and possible halocline depth in each of these classes. Our results show that time series classification algorithm can cluster vertical profiles of CTD temperature and salinity and classify them according to sea area and season.

Despite much field and laboratory research, the origin of calcification in coccolithophores remains indeterminate. While most experiments on living species are not applicable to extinct taxa, long-term morphologic changes in lineages under well constrained oceanographic conditions may help elucidate the primary forcing on coccolithophore evolution if examined in the context of fundamental requirements (e.g., nutrient availability) of the living cell. The Order Discoasterales (66–1.92 Ma) was among the most prolific (>600 species, 16 genera) with greatest abundance and diversity in warm oligotrophic waters. Their coccoliths tell a story of morphologic changes that affected also their constituent elements resulting in lightweight constructions that became increasingly cavernous as oligotrophy increased in the Paleocene ocean, leading to increase in surface/volume ratio in keeping with increase in cell size. This likely constitutes direct evidence that coccoliths were involved in regulating cell physiology, both by maintaining a sufficient surface for nutrient absorption when cell volume increases or when nutrient content in seawater decreases, and by determining sinking rates. The cavernous nature of coccoliths further suggest mixotrophic physiology. Calcification may thus have been the innovation permitting the migration of the ancestral coccolithophore from nutrient-rich coastal waters to the blue ocean.

Louisiana is undergoing rapid change from natural and anthropogenic forces, such as sea level rise, subsidence, and eutrophication. Sediment diversions on the lower Mississippi River are proposed as a large-scale restoration strategy to create new wetlands and sustain existing wetland areas in Barataria Basin, Louisiana. This will introduce a large volume of sediment and nutrient rich freshwater from the Mississippi River to the receiving basins. This will result in, at least, short term changes in light and nutrient dynamics and has potential to alter phytoplankton composition. In order to understand nitrogen dynamics in Barataria Basin due to large scale coastal restoration practices, the nitrogen budgets (including particulate and dissolved forms) were calculated from outputs of the Integrated Biophysical Model, which is based on the existing Delft3D model coupled with a water quality model (D-WAQ). Creating nitrogen budgets in estuarine systems allows for better understanding of the major sources, sinks, inputs and exports across the system, increasing understanding of the amount of nitrogen available to drive estuarine primary production. Quantification of nitrogen inputs, outputs and processes is essential because it is the limiting nutrient for most estuarine primary producers (e.g., phytoplankton and emergent macrophytes). Preliminary model results for the existing conditions suggest that the dissolved inorganic nitrogen in the estuarine waters is mainly derived from diffusional sediment fluxes and mineralization of particulate organic nitrogen. Most of the dissolved inorganic nitrogen was assimilated for phytoplankton growth. A relatively small portion of dissolved inorganic nitrogen was removed from the system through denitrification in the water column. More particulate organic nitrogen originated from emergent macrophytes than from phytoplankton primary production. These model results will help better understand how proposed sediment diversions on the lower Mississippi River may change the future ecological conditions of estuarine open water in coastal Louisiana.

The key to reproducible data reduction and data processing in scientific research is the ability to faithfully record every step of the process in a reproducible format that is transparent and easy to communicate. This is not an easy task. Most of the time in experimental research that is not primarily computational in nature, it falls victim to the enormous effort required to design experiments well, run complex analytical procedures rigorously and efficiently, and interpret the results in the proper geologic, geochemical or biological context, with little time left to invest in documenting and constructing a reproducible data reduction workflow. While this is understandable, it introduces a high risk for error, makes it extremely difficult to share and discuss one’s approach or review others’, reproduce the calculations at a later point or even just revisit what was done conceptually. Part of the problem lies inherently with most data processing being difficult to document, part of black box process where the inner workings are inaccessible, or simply too divorced from the narrative of the scientific work it represents. One important obstacle that interferes frequently with attempts to remedy this situation in the stable isotope community is the lack of many basic computational and data access tools that enable the kinds of calculations and data processing isotope geochemists need to do on a day to day basis. Here, we introduce a new suite of software packages that provide efficient and transparent access to raw stable isotope ratio mass spectrometry (IRMS) data formats and enable reproducible data processing straight from raw analytical output through data reduction, quality control, visualization and data reporting that retains the necessary flexibility required for the enormous breadth of analytical goals in the stable isotope community. Presented tools will cover aspects of functionality provided by the isoreader (isoreader.kopflab.org), isoviewer (isoviewer.kopflab.org) and isoprocessor (isoprocessor.kopflab.org) software packages and are 100% open-source and freely available to everyone in the geochemical community and beyond.

The Mekong river is one of the most complex river systems in the world that is shared by six nations in Southeast Asia. The river still remains relatively undammed (most existing dams are in the tributaries and are small), and its hydrology today is dominated by large natural flow variations that support the highly productive agricultural and riverine ecological systems; however, this is changing due to the alterations in land use and construction of new dams both in the tributaries the mainstream. Understanding the changes in surface water dynamics is therefore crucial to provide realistic future predictions of changes in downstream floodplain and riverine ecology due to the construction of dams in the upstream. While the existing dams have caused little impact on mainstream flows, those under construction and planned are likely to cause severe and potentially permanent damage to downstream hydro-agro-ecological systems, and adversely impact the livelihood of millions. Here, using hydrodynamic model simulations (CaMa-Flood), we show that the effects of flow regulation on downstream river-floodplain dynamics are relatively predictable along the mainstream Mekong, but flow regulations could potentially disrupt the flood dynamics in the Tonle Sap River (TSR) and small distributaries in the Mekong Delta. Results suggest that TSR flow reversal could cease if the Mekong flood pulse is dampened by 50% and delayed by one-month. While flood occurrence in the vicinity of the Tonle Sap Lake and middle reach of the delta could increase due to enhanced low flow, it could decrease by up to five months in other areas due to dampened high flow, particularly during dry years. Further, areas flooded for less than five months and over six months are likely to be impacted significantly by flow regulations, but those flooded for 5-6 months could be impacted the least.

Azimuthal anisotropy quantified by teleseismic SKS, SKKS, PKS (“XKS”) and Local S wave splitting parameters is used to investigate mantle deformation and flow beneath the boundary of the North American and Caribbean plates and adjacent areas. A total of 2556 XKS and 299 pairs of local S wave splitting parameters were obtained at 23 stations. The observations can be divided into two groups based on the spatial distribution of the resulting fast polarization orientations. Those observed on the Caribbean Plate are mostly WNW-ESE which are mostly trench-parallel. In contrast, the fast orientations observed on the North American Plate are dominantly NNE-SSW which are approximately trench-orthogonal and are consistent with those previously observed in southern Mexico to the north of the area of the current study. At most of the stations at which XKS and local S wave splitting parameters are available, the splitting parameters from the two types of shear waves are comparable, suggesting that the observed azimuthal anisotropy is mostly from the mantle wedge above the slab. The observations especially those obtained at recently deployed stations in Guatemala provide new insights into the complicated mantle flow system associated with slab subduction and rollback, as well as lithospheric shearing along the southern boundary of the North American Plate.

Burn severity influences various biophysical and biogeochemical processes, and it is projected to increase in the coming decades across high-latitude ecosystems. However, the impact of burn severity on thermokarst (e.g., land subsidence after ground ice melting) is not well understood. We used time-series image analysis to assess the effects of burn severity and ground ice content on thermokarst processes in the Noatak National Preserve, northwestern Alaska. To extend the temporal depth for illustrating fire-thermokarst linkages, we evaluated eight existing fire indices derived from visible and near-infrared (380-1100 nm) spectral bands and developed burn severity maps of historical fires using Landsat MSS sensors (operation between 1972-1992). Our results reveal that tundra fire is a significant factor in creating thermokarst landforms (p<0.01), and that the magnitude of thermokarst varies with burn severity levels and ground ice content (p<0.05). An abrupt increase in thermokarst occurred one year after fire but the rate of thermokarst decreased after three years. The area of thermokarst three years after fire was highest in high-severity burns (385 ± 47 m2 thermokarst area/ha burned area), followed by moderate- (255 ± 32 m2/ha) and low-severity (201 ± 42 m2/ha) burns. Ground ice content interacted with burn severity to affect thermokarst; the area of thermokarst was twice as large in landscapes with high ground ice (356 ± 67 m2/ha) as in landscapes of low ground ice (167 ± 39 m2/ha) three years after fire. Among the eight fire indices, the Global Environmental Monitoring Index (GEMI) demonstrates the strongest correlation with field-based estimates (R2 = 0.8). Burn-severity maps reconstructed with GEMI reveal that over a 40-year study period, thermokarst expansion occurred more rapidly in high-severe burns than in low-severity or unburned areas. Our results suggest that the projected increase in burn severity may result in abrupt and long-lasting permafrost degradation in tundra ecosystems with potential consequences on Arctic carbon stocks.

The use of stable isotopic tracer methods is becoming a popular approach for in situ evapotranspiration (ET) partitioning studies at the ecosystem scale. Ecosystem evapotranspiration is usually partitioned based on different isotopic composition among the aggregated ET flux (δET) and its two components: physical evaporation process (δE) and biological transpiration process (δT). Uncertainties in calculating these three isotopic compositions, especially δET, are usually not negligible and could propagated to large uncertainty in the ET partitioning outcomes. In this study, we present a new ET partitioning approach utilizing dual isotope-based evapotranspiration partitioning based on d-excess (d-excess = δ2H - 8 × δ18O) . A field deployable laser absorption spectrometer was used for in situ measurements of isotopic composition (δ2H and δ18O) of atmospheric water vapor at different heights within the turbulently mixing ecosystem boundary layer for tallgrass prairie. This study incorporated a new refinement to the Craig-Gordon model to describe δE. During non-growing season, estimates of δET—based on Keeling plot and flux-gradient approaches—were compared against δE values derived by the Craig-Gordon model, under the assumption of no transpiration and thus the equality between δET and δE. During the growing season, coupled with isotopic sampling in plant and soils, we partitioned ET into transpiration and evaporation. This refined dual isotope-based approach of ET partitioning shows promise in reducing the uncertainties of the fractional contributions of evaporation and transpiration, thus enhance our understanding on the mechanisms underlying plant water use efficiency and the role of vegetation ecophysiological processes in eco-hydrologic processes under the changing environment.

Current General Circulation Models (GCMs) are struggling to capture the observed diurnal cycle of precipitation. One major problem is that GCMs usually have difficulties to simulate nocturnal deep convections. Nocturnal deep convections are usually decoupled with the land surface and are controlled by other factors aloft, which have not been fully understood. The Plains Elevated Convection at Night (PECAN) is a multi-institutional collaborated field experiment conducted at the central Great Plains during summertime (1 June to 15 July) 2015 on the purpose of improving the understanding and simulation of the processes that initial and maintain deep convections at night. During the 45-day PECAN period there are 31 intensive operational periods (IOP) of nighttime deep convections, each last for one night. The unique part of PECAN experiment is the use of 6 fixed and 4 mobile PECAN Integrated Sounding Arrays (PISA) to take detailed measurements for each IOP. These detailed measurements of thermodynamics, wind and water vapor profiles in high temporal resolution (typically 90-min) allow the observation of the evolution of boundary layer and propagating features. We will report results from the analysis of these PISAs using a constrained variational analysis method to understand the large-scale environment that control the nighttime deep convections at the central Great Plains.

The ice sheet-ocean modeling community is making large strides toward developing coupled models capable of examining the interactions and feedbacks between ice shelves and ocean along the Antarctic margin. We present preliminary results and address some of the challenges that have arisen during the development of a coupled ice sheet-ocean model. The ice sheet model is icepack, a shallow-shelf finite element model written in Python. The ocean model is the Regional Ocean Modelling System (ROMS), a terrain-following vertical (sigma) coordinate model that has been modified to interface with a moving ice shelf. These two models are coupled in an online configuration using the Framework for Ice Sheet Ocean Coupling (FISOC). The use of a model with sigma coordinates for the ocean component introduces a simplification and a complication to modeling a moving ice draft. The sigma coordinate system retains the same number of vertical layers at any depth, eliminating the need to convert grid cells between ice and water, when using a fixed grounding line configuration. However, as the ice shelf draft evolves in time, topographic configurations develop that induce pressure gradient errors in ROMS. We quantify these errors in an idealized set-up with an artificially changing ice draft following the ISOMIP+ geometry. We compare results between an ice draft that is smoothed to meet standard ROMS smoothing criteria (rx0, rx1) and a non-smoothed ice draft. Finally, we present a simple parameterization in a buffer zone near the grounding line that uses interpolated melt rates from the ocean model, allowing us to maintain a steep ice topography in the ice model without inducing pressure gradient errors in the short water column in the ocean model. This model configuration will be applied to Pine Island Glacier and used to examine present and possible future states of the ice sheet-ocean system.

Propagation of electromagnetic (EM) waves from radar and communication devices at sea can be significantly affected by the low-altitude atmospheric refractive conditions. Characterizing the spatial and temporal variability of refractivity is thus crucial to many important Navy and civilian applications. Surface layer models based on Monin-Obukhov Similarity Theory (MOST), such as the Navy Atmospheric Vertical Surface Layer Model (NAVSLaM), can be used to estimate the vertical refractive structure of the evaporation duct (ED) from measured or forecasted environmental parameters, assuming a horizontally-homogeneous stratified atmosphere. As air and sea surface temperature are two critical inputs to NAVSLaM, the rapid variation in sea surface temperature (SST) and air-sea temperature difference in the Gulf Stream region provides a relatively controlled environment for investigating the utility of NAVSLaM under inhomogeneous ducting conditions. In this paper, EM propagation in the ED over the Gulf Stream is investigated using measured data from the Coupled Air-Sea Processes and Electromagnetic-ducting Research (CASPER) East Coast experiment conducted off the coast of Duck, NC, during October-November of 2015. Measurements of the one-way propagation loss between a transmitter and receiving array as a function of the range were performed during ship crossings of the Gulf Stream. Concurrent and co-located meteorological and oceanographic measurements were also collected within the marine atmospheric boundary layer (MABL), including air temperature, SST, relative humidity, air pressure and wind speed to be used as inputs to NAVSLaM. The environmental conditions in the region of the Gulf Stream are used to model the low-altitude refractivity profiles as a function of height and range, which are input into the Advanced Propagation Model (APM) for predicting the EM propagation. Of particular focus is the effect of the rapid change in SST across the boundary between the warmer Gulf Stream and the colder surrounding ocean. EM measurements are compared with the simulated propagation loss based on the range-dependent refractivity profile predicted from NAVSLaM, as well as a best-fit Paulus-Jeske ED model. Both stable and unstable conditions encountered during the CASPER East experiment are investigated.