The rainfall reduction in the 1970s, less marked in Central Africa than in West Africa, still had a major impact on the hydrological regimes of the region’s large rivers. The study of the hydropluviometric behavior of the Ubangi at Mobaye has the advantage of studying a basin excluding anthropogenic impact. Forest cover and population density have not changed since at least 1970. Statistical analysis of the breaks in the long rainfall time series from Ubangi at Mobaye (1935-2015) confirms a long period of drought from 1969 to 2006 corresponding to a reduction of -8% in rainfall. And the study of the corresponding hydrological series indicates a second downward break in 1981, few years after the rainfall increase. This period points an exceptional hydrological drought period until 2013, which is the first year with an increase of flows. The statistical study of the annual rainfall/flow series of the upstream basins over the period 1951-1995 (the Kotto at Kembé and Bria, the Mbomu at Bangassou and Zémio, the Uélé + Bili hydrographic system) highlights different hydrological behaviors related to the vegetation cover. The savanna basins show a continuous hydrological deficit marked by a runoff coefficient (CE) that fell to 5% only from the 1990s. On the other hand, the basins under forest show a runoff increase since 1990 marked by CE above 10%. Under savannah, the part of the flow infiltrating to recharge the aquifer would have decreased faster than under forest, which results in a runoff coefficient CE very significantly negatively correlated with the savanna area present in the studied watershed.

Many current research efforts undertake the solar flare classification task using the Space-weather HMI Active Region Patch (SHARP) parameters as the predictors. The SHARP parameters are scalar quantities based on spatial average or integration of physical quantities derived from the vector magnetic field, which loses information of the two-dimensional spatial distribution of the field and related quantities. In this paper, we construct two new sets of spatial features to expand the feature set used for the flare classification task. The first set uses the idea of topological data analysis to summarize the geometric information of the distributions of various SHARP parameters. The second set utilizes tools coming from spatial statistics to analyze the vertical magnetic field component Br and summarize its spatial variations and clustering patterns. All features are constructed within regions near the polarity inversion lines (PILs) and classification performances using the new features are compared against the SHARP parameters (also along PIL). We found that using the new features can improve the skill of the flare classification model and new features tend to have higher feature importance, especially the spatial statistics features. This potentially suggests that even using a single channel Br, instead of all SHARP parameters, one can still derive strongly predictive features for flare classification.

The coupling of CO2 emissions and tectonic activity in active plate margins is becoming increasingly prominent, as remote sensing techniques make this relationship readily observable on a global scale. However, direct observations of the processes that link emissions and seismicity are lacking. This study documents observations from the deep part of an ancient continental rift system, now exposed at the Earth’s surface. We demonstrate how volatiles and preexisting magma chamber structures affect the influx of new magma and how magma induced deformation plays a key role during the shift from initial plume related magmatism to rifting, by altering the rock rheology and facilitating strain localization. The outcrops are comprised of ultramafic cumulates, intersected by mafic dykes. The ultramafic cumulates consist of three units: the central series, upper layered series and the lower layered series, with the central series being the youngest and partly replacing the upper and lower layered series. The dykes intersecting the upper layered series are partially remolten and replaced by the influx of the central series cumulates. This is especially evident in mafic dykes in wherlitic cumulates of the upper layered series. Younger melts of the central series used the contact between the dykes and host wehrlite as a pathway. The heating caused partial melting of the mafic dyke, which acted as a lubricant during deformation. In addition to the lubrication effect of the melt, volatiles within the mafic dykes, including CO2 react with the mafic minerals within the host ultramafic rocks, leading to fracturing and brecciation, and locally followed by diffusion creep in the finer-grained material. PT-estimates indicate that this brecciation took place under lower crustal/upper mantle conditions. Hence, conditions of deformation can shift from low strain rate plastic creep to ultrafast localized seismic creep in a short time due to local structural and compositional inhomogeneities.

The effects of instrument noise on estimating the spectral attenuation rates of ocean waves in sea ice are explored using synthetic observations in which the true attenuation rates are known explicitly. The spectral shape of the energy added by noise, relative to the spectral shape of the true wave energy, is the critical aspect of the investigation. A negative bias in attenuation that grows in frequency is found across a range of realistic parameters. This negative bias decreases the observed attenuation rates at high frequencies, such that it can explain the rollover effect commonly reported in field studies of wave attenuation in sea ice. The published results from four field experiments are evaluated in terms of the noise bias, and a spurious rollover (or flattening) of attenuation is found in all cases. Remarkably, the wave heights are unaffected by the noise bias, because the noise bias occurs at frequencies that contain only a small fraction of the total energy.

NOAA/National Ocean Service’s (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) provides users with real-time currents at more than sixty stations, currents predictions at thousands of historic and active stations, and operational currents nowcast and near-term forecast information in navigable estuaries, harbors, rivers, and coastal regions of the United States as an integral part of its safe navigation mission. CO-OPS performs at least one current survey each year to update currents predictions in regions of particular interest to stakeholders. NOS’ Operational Forecast Systems (OFS) operate and maintain fully 3-D hydrodynamic models that provide regional nowcast and forecast (48-60 hours) guidance for water levels, currents, salinity, and temperature. By combining the information available from real-time observations, current surveys, historic current predictions, and OFS output, both the tidal current predictions and the OFS forecast products can be improved. Tidal current predictions are traditionally generated based on analysis of at least one month of six-minute observation data obtained from a physically deployed current meter using harmonic least squares techniques to resolve tidal constituents. By using longer time series and traditional techniques combined with additional statistical methods, a more accurate representation of the tidal flow and a more exact match to the shape of the tidal current curve is obtained. By applying these methods to long-term OFS output at locations where long-term physical observations also exist, tidal current predictions based on model data within the model domain can be verified. Once verified, the number of available “virtual stations” exponentially increases the repository of tidal current predictions. Users can choose any location of interest and receive tidal current predictions that can be incorporated into integrated, user-friendly navigation products and tools. We will evaluate this technique in the lower Chesapeake Bay using output from the Chesapeake Bay Operational Forecast System (CBOFS) and real-time currents data.

Recent geological observations imply that slow slip events (SSEs) occur in fault zones with a finite thickness of ~100s of meters. The bulk matrix of the fault zone deforms viscously, while pervasive frictional surfaces are distributed in the viscous matrix. In this theoretical study, we investigate the rupture behaviors of a frictional-viscous-mixing fault model and explore its potential to generate a single SSE. To simultaneously consider both the 10s-kilometer-scale rupture propagations and the 100s-meter-scale “frictional-viscous” features in the same model, we treat a fault zone as a zero-thickness “surface” embedded in an elastic medium. The “frictional-viscous” characteristics are parameterized into a constitutive relation, or “friction law”, where fault strength is partitioned into a frictional and a viscous component. For simplicity, the frictional strength is set to be slip weakening, while the viscous strength increases linearly as the bulk shear rate (slip rate) increases. We explore the rupture behaviors of the above model both analytically and numerically. We find that: 1. Final slip is proportional to the static stress drop and slipping area length, as in fast earthquakes. Peak slip rate increases with dynamic frictional stress drop, while a high viscous coefficient can significantly reduce slip rate, leading to slow slip behaviors. 2. Rupture propagation speed is mainly controlled by the radiation damping factor and viscous coefficient and can be significantly reduced compared to typical fast earthquakes when the viscous coefficient is high. 3. The slip rate decay time increases with the viscous coefficient and slipping area length, which eventually predicts M~T^3 scaling. When frictional stress drop is ~1MPa and the viscous coefficient is smaller than the radiation damping factor μ/(2β), the above models predict the fast slip behavior of regular fast earthquakes. Our model predicts slow slip behaviors in a wide range of parameter space when stress drop is low and viscous coefficient is high. In particular, a frictional strength drop of ~10 kPa and viscous coefficient of 10^4-10^5 μ/(2β) can simultaneously explain many independent characteristic rupture parameters of SSEs. Our model can be further tested with future geophysical, geological, and experimental data.

My laboratory is developing an accelerometer. However, if you do not install the dedicated software, you can not browse the data. In addition, since it is necessary to go to the site on a semi-annual basis and collect data due to capacity problems, the current operation is burdened. In order to solve these problems, we devised WebGL that enables high-speed drawing when processing a large amount of data such as Big Data, and a Web application that uses server that can transmit, save, and download acquired data. In this application, an accelerometer and a raspberry pie are connected, and the raspberry pie receives data obtained from the accelerometer and sends the data to a server installed in a laboratory by SCP file transfer at regular intervals. These data specify the location and date from the client side through the Internet browser, download the data using the download function of the browser, read this data on the application and draw the waveform. The data obtained from the accelerometer in the development to date is converted into a CSV file and transferred to the server. These data can be downloaded and displayed on the web application. For the google map displayed on the right side of the screen, it is to make the application more useful by registering the location where the accelerometer was set in the future.

Over the past 60+ years, an enormous amount of exploration geophysics survey data has been collected around the globe, the majority of which is high-quality 2D and 3D seismic data acquired by the petroleum energy industry. Much of this ‘legacy’ data still has significant commercial value today and in the future, for hydrocarbon exploration, gas storage (methane, helium, hydrogen…), groundwater, minerals, CO2 sequestration, geothermal, and other purposes. However, there is likely a subset of this exploration data that is of little further commercial value, but may be of immense value to academic, government and industry researchers, for example. This may include very long 2D seismic lines recorded in frontier exploration areas which turned out to be non-prospective; for example along convergent margin subduction zones or major continental tectonic fault zones, which are absent of major sedimentary basins. Shared access to this subset of legacy data would provide an extremely useful opportunity and resource for academic researchers and others, much as shared earthquake data via the IRIS network has revolutionized our understanding of earthquakes, faults and tectonics. There are several challenges that would need to be overcome before such legacy data can be shared widely among the broader geophysical community. Much of this legacy data is archived on old magnetic tape media that is now physically degrading, making it difficult to recover the data. The data would need to be collected, recovered, QC’ed, archived with associated metadata, and stored on modern digital data storage systems like the IRIS DMC, newer cloud-based systems like OSDU, or other options. The data archival, maintenance and support for a shared data distribution system would require a sustainable business model and funding from all of the data stakeholders, including government agencies like NSF, academic universities, and industry users. Data use agreements would need to be structured to ensure that data is used for non-commercial purposes as appropriate, data users respect various legal terms and conditions, and data is not shared freely among individual recipients without the approval of the host data center.

The Bureau of Reclamation serves water to 31 million people and 20 percent of irrigators in the western United States. Reclamation generates large amounts of data and information describing reservoir operations, hydropower generation, environmental compliance, invasive mussels, infrastructure, and other aspects of Reclamation’s mission activities. Much of these data are currently accessed on a program-specific basis via legacy information management & technology (IMT) systems, often without modern features such as machine-readable data formats and web-services. The Department of the Interior’s Open Water Data Initiative addresses these issues, and Reclamation is striving to improve its data-publishing efforts, making its data more easily found, accessed, and applied to support public and private sector activities. This presentation provides an overview of two IMT systems that Reclamation has developed under OWDI: the Reclamation Water Information System (RWIS, water.usbr.gov) and the Reclamation Information Sharing Environment (RISE). RWIS was developed first as a pilot, demonstrating how multiple programs’ water data could be combined into a modernized data-publishing system. It provides free access to reservoir and water time series data from Reclamation’s five regions, includes map and query interfaces for data discovery and access, and web-services for automated retrieval. Based on the success of the RWIS pilot, Reclamation has more recently focused on developing RISE, which will envelop RWIS and feature a much larger collection of Reclamation data, including water quality as it pertains to Reclamation water management activities, invasive mussels, hydropower, and infrastructure, and more. RISE will also serve a mix of data types, going beyond RWIS’ scope of time series data to also include geospatial and documents data. This presentation summarizes RISE development approach, architecture and previews the upcoming release in Winter 2019.

Spatial and temporal distributions of Clear-Air Turbulence (CAT) in the Northern Hemisphere were investigated using 41 years (1979 – 2019) of the European Centre for Medium-range Weather Forecast Reanalysis version 5 (ERA5) data. We used two groups of CAT diagnostics to determine occurrence frequencies: 1) commonly used empirical turbulence indices (TI1, TI2, and TI3) and their components [vertical wind shear (VWS), deformation, divergence, and divergence tendency], and 2) theoretical instability indicators Richardson number (Ri), potential vorticity (PV), and Brunt-Vӓisӓlӓ frequency. The empirical indices showed high frequencies of MOG-level CAT potential over the East Asian, Eastern Pacific, and Northwest Atlantic regions in winter. Over East Asia, the entrance region of the strong upper-level jets, showed the highest frequencies in TI1, TI2, and TI3 mainly due to strong VWS. The Eastern Pacific and Northwestern Atlantic areas near the exit region of the jet had relatively high frequencies of these and also Ri. PV frequency was high on the southern side of the jet primarily due to negative relative vorticity. Long-term increasing trends of MOG-level CAT potential also appeared in those three regions mainly due to the warming in lower latitudes. The most significant increasing trend was found over East Asia, due to the strengthening of the East Asian jet and VWS due to the strong meridional temperature gradients in the mid-troposphere induced by warming in the tropics and cooling in eastern Eurasia. These trends over East Asia are expected to be of importance to efficient aviation operations across the northwestern Pacific Ocean.

A significant stress drop characterizes sometimes earthquakes induced by injection or extraction of fluids in rocks. Moreover, long-term fluid operations in underground reservoirs can impact a seismogenic reaction of the rocks per a unit volume of the involved fluid. The seismogenic index is a quantitative characteristic of such a reaction. We derive a relationship between the seismogenic index and the stress drop. We propose a simple and rather general phenomenological model of the stress drop of induced events in various faulting regimes. Our results suggest that high stress drops of some earthquakes induced by long-term underground fluid operations may be controlled by drops of cohesion of more cohesive faults getting seismically activated due to gradually increasing with time differential stresses. On the one hand, this effect can result in an increase of seismogenic index with production time. On the other hand, a production-caused depleting of the pore pressure can also cause a systematic increase of the stress drop. This provides an additional contribution to the growth of seismogenic index with production time at such reservoirs.

Climate models have long-standing difficulties simulating the South Pacific Convergence Zone (SPCZ) and its variability. For example, the default Zhang-McFarlane (ZM) convection scheme in the Community Atmosphere Model version 5 (CAM5) produces too much light precipitation and too little heavy precipitation in the SPCZ, with this bias toward light precipitation even more pronounced in the SPCZ than in the tropics as a whole. Here, we show that implementing a recently developed convection scheme in the CAM5 yields significant improvements in the simulated SPCZ during austral summer and discuss the reasons behind these improvements. In addition to intensifying both mean rainfall and its variability in the SPCZ, the new scheme produces a larger heavy rainfall fraction that is more consistent with observations and state-of-the-art reanalyses. This shift toward heavier, more variable rainfall increases both the magnitude and altitude of diabatic heating associated with convective precipitation, intensifying lower tropospheric convergence and increasing the influence of convection on the upper-level circulation. Increased diabatic production of potential vorticity in the upper troposphere intensifies the distortion effect exerted by convection on transient Rossby waves that pass through the SPCZ. Weaker distortion effects in simulations using the ZM scheme allow waves to propagate continuously through the region rather than dissipating locally, further reducing updrafts and weakening convection in the SPCZ. Our results outline a dynamical framework for evaluating model representations of tropical–extratropical interactions within the SPCZ and clarify why convective parameterizations that produce ‘top-heavy’ profiles of deep convective heating better represent the SPCZ and its variability.

We present a characterization of transient-large-amplitude (TLA) geomagnetic disturbances that occurred at six stations of the Magnetometer Array for Cusp and Cleft Studies throughout 2015. TLA events are defined as one or more short-timescale (< 60 seconds) dB/dt signature with magnitude > 6 nT/s. A semi-automated dB/dt search algorithm was developed to identify TLA events in ground magnetometer data and used to identify 40 TLA dB/dt events. We demonstrate the existence of large-amplitude dB/dt with timescale less than 10 seconds in nine of the events. The association of these events to sudden commencements is relatively weak, rather the events are more likely to occur in relation to substorm onsets. However, 15% of TLA events show no direct association to geomagnetic storms, substorms or nighttime magnetic impulse events.

• Two fresh anomalies observed in the eastern subpolar North Atlantic upper ocean during 1992-2017 share similar spatial characteristics. • Salt budget analysis shows the 2012-2016 fresh anomaly in the upper 200 m occurs due to transport of anomalous salinity by mean currents. • In contrast, the fresh anomaly in the 1990s is due to anomalous circulation of the mean salinity field.

The clustered distribution of shallow slow earthquakes in the Nankai Trough has been attributed to different factors such as seamount subduction, pore fluid pressure, fluid migration, and sediment input. However, there is still a lack of comprehensive understanding of how these factors interact to generate slow earthquakes. We examined the seismic reflection profiles crossing four subducted seamounts off Muroto to understand how it deforms the accretionary wedge. Along-trough reflection profiles within the accretionary wedge were also used to infer the lithology of the underthrusted sediments. The seamounts are at different stages of subduction and their associated underplated sediments were identified. Comparison with sandbox models indicate that the underplated sediments are likely comprised of fluid-rich trench fill sediments. A negative polarity decollement and transparent underthrust is observed off Muroto. The transparent underthrust is interpreted as mudstone, while stratified underthrust sediments in other regions is interpreted as turbidites. By comparing with numerical simulations, we propose the following deformational history off Muroto: (1) subduction of the first seamount resulted in underplating of a large volume of fluid-rich trench fill sediments, (2) the underplated sediments are undergoing horizontal compression from subsequent subduction of the three seamounts resulting in high pore pressure consistent with previously reported low velocity zones, and (3) the horizontal compression may also result in fluid expulsion and these fluids migrate updip and get trapped because the mudstones serve as an impermeable cap. This mechanism accounts the aforementioned factors associated with slow earthquakes and likely controls the clustered distribution off Muroto.

The fine particulate matter (PM2.5) in Chinese megacities has declined significantly after the implementation of strict mitigation strategies since 2013. However, the concentration of wintertime nitrate in PM2.5 (p-NO3-) has only changed slightly and became the dominant inorganic component despite considerable precursor emission reductions. Discerning chemical mechanisms leading to nitrate growth during haze events is critical to implementing effective pollution mitigation policies. The oxygen isotope anomaly of nitrate (Δ17O(NO3-)) is a powerful means to distinguish nitrate formation mechanisms. Nevertheless, the observed high Δ17O(NO3-) values were significantly underestimated by chemical transport models during extreme haze events (PM2.5 > 225 μg m-3) in Beijing, indicating an incomplete understanding of nitrate chemistry. To reconcile this model-observation discrepancy, we compiled reported Δ17O(NO3-) data in Beijing haze along with relevant observational parameters (e.g., hydroxyl (OH) reactivity, peroxyl radical concentrations), then tested assumptions on Δ17O of key precursors (e.g., OH and nitrogen dioxide (NO2)), recalculated Δ17O(NO3-) and compared them with observations. Our results indicate that considering heterogeneous dinitrogen pentoxide reactions on chlorine-containing aerosols (N2O5 + Cl- chemistry) with a nitryl chloride (ClNO2) yield of ~ 0.75 can explain the observed high Δ17O(NO3-) during extreme haze events. According to the Δ17O(NO3-) data, on average this heterogeneous N2O5 + Cl- chemistry can explain ~ 60% of nighttime nitrate production and make daytime and nocturnal pathways equally important in winter Beijing haze (PM2.5 >75 μg m-3). Our results highlight the critical role of reactive chlorine chemistry in air pollution/chemistry in inland cities.

Between 5 and 25% of the total momentum transferred between the atmosphere and ocean is transmitted via the growth of long surface gravity waves called ‘swell’. In this paper, we use large eddy simulations to show that swell-transmitted momentum excites near-inertial waves and drives turbulent mixing that deepens a rotating, stratified, turbulent ocean surface boundary layer. We find that swell-transmitted currents are less effective at producing turbulence and mixing the boundary layer than currents driven by an effective surface stress. Overall, however, the differences between swell-driven and surface-stress-driven boundary layers are relatively minor. In consequence, our results corroborate assumptions made in Earth system models that neglect the vertical structure of swell-transmitted momentum fluxes and instead parameterize all air-sea momentum transfer processes with an effective surface stress.

To achieve the 1.5°C target of the Paris agreement, rapid, sustained, and deep emission reductions are required, which often includes negative emissions through land-based mitigation. However, the effects of future land-use change on climate are often not considered when quantifying the climate-induced impacts on human heat stress and labour capacity. By conducting simulations with three fully-coupled Earth System Models, we project the effects of land-use change on heat stress and outdoor labour capacity for two contrasting future land-use scenarios under high-ambition mitigation. Achieving a sustainable land-use scenario with increasing global forest cover instead of an inequality scenario with decreasing forest cover in the Global South causes a global cooling ranging between 0.09°C and 0.35°C across the Earth System Models. However, the effects on human heat stress are less strong, especially over the regions of intense land-use change such as the tropics, where biogeophysical effects on near-surface relative humidity and wind speed counteract the cooling effect under warm extremes. The corresponding influence on outdoor labour capacity is small and inconsistent across the three Earth System Models. These results clearly highlight the importance of land-use change scenarios for achieving global temperature targets while questioning the adaptation potential for reduction in heat stress.