The long-term climatology of high-frequency quasi-monochromatic gravity waves is presented using multi-year airglow images observed at Andes Lidar Observatory (ALO, 30.3ºS, 70.7ºW) in northern Chile. A large number of high-frequency gravity waves were retrieved from OH airglow images. The distribution of primary wave parameters including horizontal wavelength, vertical wavelength, intrinsic wave speed, and intrinsic wave period are obtained and are in the ranges of 20–30 km, 15–25 km, 50–100 ms-1, and 5–10 min, respectively. The waves tend to propagate against the local background winds and show clear seasonal variations. In austral winter (Ma–Aug), the observed wave occurrence frequency is higher and preferential wave propagation is equator-ward. In austral summer (Nov–Feb), the wave occurrence frequency is lower and the waves mostly propagate pole-ward. Critical-layer filtering plays an important role in determining the preferential propagation direction in certain months, especially for waves with a small observed phase speed (less than typical background winds). The wave occurrence and preferential propagation direction are shown to be related to the locations of convection activities nearby and their relative distance to ALO. However, other possible wave sources such as secondary wave generation and possible ducted propagation cannot be ruled out. The estimated momentum fluxes have typical values of a few to 10 m2s-2 and show seasonal variations with a clear anti-correlation with local background wind directions.

Unaweep Canyon (Uncompaghre Plateau, Colorado) represents an enigmatic landscape with a complex evolution. Interpretations for its origin have ranged from ancestral fluvial erosion in the late Cenozoic to glacial erosion in the Paleozoic, or some combination thereof, with significant implications for global climatic and large-scale tectonic reconstructions. To address the conflicting interpretations, we acquired a high-resolution seismic reflection profile to investigate the depth, structure, and sedimentary infill in the canyon. The dataset is further complemented with a high-resolution electrical resistivity survey. Integrated with other geophysical and geological data, the results unambiguously demonstrate an overdeepened Precambrian basement with pronounced transverse U-shape and corroborate the hypothesis of a pre-Quaternary glacial origin. Our data constitute the first detailed and high-resolution image of a buried pre-Quaternary glacial valley in North America, and thus have far-reaching implications for our understanding of global ice houses as well as the tectonic conditions enabling preservation of such systems.

Defining effective measures to reduce nitrate pollution in heterogeneous mesoscale catchments remains challenging if based on concentration measurements at the outlet only. One reason is our limited understanding of the sub-catchment contributions to nitrate export and their importance at different time scales. While upstream sub-catchments often disproportionally contribute to runoff generation and in turn to nutrient export, agricultural areas, which are typically found in downstream lowlands, are known to be a major source for nitrate pollution. To disentangle the interplay of these contrasting drivers of nitrate export, we analyzed seasonal long-term trends and event dynamics of nitrate concentrations, loads and the concentration-discharge relationship in three nested catchments within the Selke catchment (456 km²), Germany. The upstream sub-catchments (40.4 % of total catchment area, 34.5 % of N input) had short transit times and dynamic concentration-discharge relationships with elevated nitrate concentrations during wet seasons and events. Consequently, the upstream sub-catchments dominated nitrate export during high flow and disproportionally contributed to overall annual nitrate loads at the outlet (64 %). The downstream sub-catchment was characterized by higher N input, longer transit times and relatively constant nitrate concentrations between seasons, dominating nitrate export during low flow periods. Neglecting the disproportional role of upstream sub-catchments for temporally elevated nitrate concentrations and net annual loads can lead to an overestimation of the role of agricultural lowlands. Nonetheless, in agricultural lowlands, constantly high concentrations from nitrate legacies pose a long-term threat to water quality. This knowledge is crucial for an effective and site-specific water quality management.

Unlike English, in Chinese texts there is no natural separator-like space between words, which makes Chinese word segmentation a difficult information processing problem. At present, geological texts contain a large number of unregistered geological terms, and the existing rule-based methods, machine-learning and deep-learning algorithms still cannot solve the problem of word separation in geology, especially for the large number of unregistered words. In this paper, we explore a dual-corpus, deep learning model-based approach to geological text dictionaries and compare it with the general domain dictionary and single-corpus deep learning model dictionary methods. Our experiments show that the proposed method is significantly better than other methods in open testing, with a precision of 92.56%, recall of 91.44% and F1 of 92.00%. In this paper, the Chinese word segmentation of geological text can identify unregistered geological terms effectively and ensures the recognition rate of common words, which lays the foundation for natural language processing in the domain of geoscience.

The American Geophysical Union (AGU) is committed to inspiring and educating present and future generations of diverse, innovative, and creative Earth and space scientists. To meet our commitment, AGU provides career and educational resources, webinars, mentoring, and support for students and professionals at each level of development to reduce barriers to achievement and to promote professional advancement. AGU is also working with other organizations and educational institutions to collaborate on projects benefiting the greater geoscience community. The presentation will include an overview of current Pathfinder efforts, collaborative efforts, and an appeal for additional partnerships.

We have measured the salt content changes of soil samples in laboratory experiments to simulate the salt and water migration that may cause duricrust formation on Mars. Although the cold, dry surface of modern Mars lacks abundant, liquid water, salts may stabilize scant liquid water as thin films through freezing point depression, allowing them to migrate along temperature and water concentration gradients driven by evaporation at the surface, and to transport salts where they precipitate and cement loose soil grains into crusts. Our work also demonstrates that spectral data complements salt content changes we measured, by showing changes in the hydration states inferred in the 1950 nm water band. We simulated salt and water migration, required in salt crust formation, in Mars analog regolith, through desiccating wet loess doped with either MgCl2, MgSO4, or CaSO4 at a temperature range of -196 °C to 150 °C. Our experiments allowed exploring temperature and depth dependencies on water and salt behaviors in 2 cm tall cylindrical soil sample tubes. The 1000 nm to 2400 nm spectral slope and the area of the 1950 nm water band correlate with salt concentration. MgSO4 exhibits the greatest migration, CaSO4 hydrates with weak migration, and MgCl2 migrates with moderate hydration. Spectral analysis may be useful in estimating salt and water migration, and in turn, aiding in interpreting hydrological and climatic history of the regolith of Mars.

We constrain the orientation of the horizontal stress field from borehole image data in a transect across the Hikurangi Subduction Margin. This region experiences NW-SE convergence leading to recurrent slow slip events. The direction of the horizontal maximum stress is E-W at an active thrust fault near the subduction margin trench. This trend changes to NNW-SSE in the Tuaheni Basin in the offshore accretionary wedge, and to NE-SW in the onshore forearc. Multiple, tectonic and geological processes, either individually or in concert, may explain this variability. A general offshore-onshore stress rotation may reflect a change from dominantly compressional tectonics at the deformation front, to a strike-slip and/or extensional stress regime closer to the Taupo Volcanic Zone. In addition, the offshore stress may be affected by topography and/or stress rotation around subducting seamounts, and/or temporal stress changes during the slow slip cycle.

Evolving preferential dissolution channels are common features formed during reactive fluid flow in carbonate rocks. Understanding these is of particular importance in applications involving subsurface engineered reservoirs but predicting their progression is currently challenging and poorly understood. Here, we propose a new approach to predict both the spatial distribution and extent of dissolution using a combination of experimental work, X-ray microtomography (μCT) and machine learning. We have conducted experiments, under reservoir conditions of temperature and pressure, involving pre- and post-flooding μCT characterisations, and coupled the outputs with a neural network to predict locations where carbonate was most likely to be dissolved. Our simulations demonstrate that our new solution can identify the key geometrical features that are important during dissolution, and can accurately predict the location and spread of dissolution. An important benefit of this approach is that it can accurately predict dissolution channels through forward prediction, while it does not require further chemical parameters, using instead common and accessible variables.

Surface latent heat flux (LHF) has been deemed as the determinant driver of the stratocumulus-to-cumulus transition (SCT). The distinct signature of the LHF in driving the SCT, however, has not been found in observations. This motivates us to ask: how determinant the LHF is to SCT? To answer it, we conduct large-eddy simulations in a Lagrangian setup in which the sea-surface temperature increases over time to mimic a low-level cold air advection. To isolate the role of LHF, we conduct a mechanism-denial experiment in which the LHF adjustment is turned off to evaluate the response of SCT. The simulations confirm the indispensable roles of LHF in sustaining (although not initiating) the boundary layer decoupling (first stage of SCT) and driving the cloud regime transition (second stage of SCT). Specifically, we found that decoupling can happen without the need for LHF to increase as long as the capping inversion is weak enough to ensure high entrainment efficiency. The decoupled state, however, cannot sustain without the help of LHF adjustment, leading to the recoupling of the boundary layer. In the coupled boundary layer, the stratocumulus sheet thins over time due to the lack of moisture supply, eventually leading to a cloud-free boundary layer. Interestingly, the stratocumulus sheet sustains longer without LHF adjustment. The mechanisms underlying the findings are explained from the perspectives of cloud-layer budgets of energy (first stage) and liquid water path (second stage). Lastly, we develop a new model diagnostic that offers a physically robust conceptualization of boundary layer decoupling.

Using a machine learning technique called echo state network (ESN), we have developed an emulator to model the physics-based global magnetohydrodynamic (MHD) simulation results of REPPU (REProduce Plasma Universe) code. The inputs are the solar wind time series with date and time, and the outputs are the time series of the ionospheric auroral current system in the form of two-dimensional (2D) patterns of field-aligned current, potential, and conductivity. We mediated a principal component analysis for a dimensionality reduction of the 2D map time series. In this study, we report the latest upgraded Surrogate Model for REPPU Auroral Ionosphere version 2 (SMRAI2) with significantly improved resolutions in time and space (5 min in time, ~1 degrees in latitude, and 4.5 degrees in longitude), where the dipole tilt angle is also newly added as one of the input parameters to reproduce the seasonal dependence. The fundamental dependencies of the steady-state potential and field-aligned current patterns on the interplanetary magnetic field (IMF) directions are consistent with those obtained from empirical models. Further, we show that the ESN-based emulator can output the AE index so that we can evaluate the performance of the dynamically changing results, comparing with the observed AE index. Since the ESN-based emulator runs a million times faster than the REPPU simulation, it is promising that we can utilize the emulator for the real-time space weather forecast of the auroral current system as well as to obtain large-number ensembles to achieve future data assimilation-based forecast.

A method is presented for retrieving temperature and composition from 150-350 km in Earth’s thermosphere using total number density measurements made via EUV solar occultations by the PROBA2/LYRA instrument. Systematic and random uncertainties are calculated and found to be less than 5% for the temperature measurements and 5-20% for the composition measurements. Regression coefficients relating both temperature and the [O]/[N2] abundance ratio with EUV irradiance at 150, 275 and 350 km are reported. Additionally, it is shown that the altitude where [O] equals [N2] decreases with increasing solar EUV irradiance, an effect attributed to thermal expansion. Temperatures from 2010 to 2017 are compared with estimates from the MSIS empirical model and show good agreement at the dawn terminator but LYRA is markedly cooler at the dusk terminator, with the MSIS-LYRA temperature difference increasing with solar activity. Anthropogenic cooling can explain this discrepancy at periods of lower solar activity, but the divergence of temperature with increasing solar activity remains unexplained. LYRA measurements of the exospheric sensitivity to EUV irradiance are compared with contemporaneous measurements made at Mars, showing that the exospheric temperature at Mars is approximately half as sensitive to EUV variability as that of Earth.

Generation Z (Gen-Z) is composed of those born in the late 1990’s or after. The first cohorts of Gen-Z students gradually started to enter colleges after 2013. Gen-Z students are very different than millennials in almost all aspects. They are more likely to reject the traditional and conventional teaching methods that lack active learning components. A shift towards modern and interactive student-centered methods is being implemented by a new generation of instructors to better serve Gen-Z needs. However, this transition from passive lecture-based instruction to active learning methods is hindered by a gap that we call “the missing step”. This missing step in the transition phase refers to training and preparing future faculty to adopt research-based instructional strategies. My fellow aspiring professors and I were mostly educated via old-school methods. Without proper training on STEM teaching, we were likely to approach our teaching by modeling what we saw. If granted the opportunity to teach engineering in a faculty role, we would have come into it lacking teaching theory and instructional strategies rooted in engineering education. If a new instructor is not familiar with subjects such as “active learning”, “backward design”, “evidence-based instructional strategies”, “flipped classroom”, and “Bloom’s revised taxonomy”, or is not acquainted with importance of modern classroom assessment techniques, rubrics, and motivation strategies, the result will be an unfillable gap between the instructor and the Gen-Z students. I was in the first cohort of Ph.D. students who completed the College of Engineering’s graduate teaching fellowship program at the University of Nebraska-Lincoln. This one-year, well-structured, peer-observation program gave me invaluable knowledge about teaching following the research, helped me in designing a course in Canvas system, taught me how to write my teaching philosophy properly, and prepared me to achieve the CIRTL associate status. Starting such a program in every school for interested graduate students can make a significant difference. I will present my perspectives on the program and its impact.

This study exploits the high-density zonal sampling at the turnaround latitude of the High Resolution Dynamics Limb Sounder (HIRDLS) in the Southern Hemisphere to investigate the missing drag in chemistry-climate models near 60 S. Gravity wave (GW) properties including amplitude, zonal wavenumber, vertical wavelength, and momentum flux are estimated with a wavelet analysis method based on the S-transform. Monthly means of GW properties compare well with estimates from previous studies. We further investigate the contribution to GW momentum flux above orographic and nonorographic regions and find that while fluxes are much larger locally over orographic regions, the contribution to the zonal mean is roughly 3 times smaller than the contribution over nonorographic regions. We also investigate the relationship with the zonal wind and find that GW momentum flux is highly correlated with the near surface winds over orographic regions. In addition to momentum flux, we also provide estimates of the zonal drag and use these estimates to evaluate the current GW parameterizations and resolved wave forcing in models participating in phase 1 of the Chemistry-Climate Model Initiative (CCMI-1). The HIRDLS zonal drag estimates suggest that the CCMI-1 models have insufficient zonal drag, especially in June, July, and August, and that the majority of the missing drag is over nonorographic regions. Our discussion includes implications for the Brewer-Dobson Circulation and ozone hole.

Forecasting relativistic electron fluxes at geostationary Earth orbit (GEO) has been a long term goal of the scientific community, and significant advances have been made in the past, but the relation to the interior of the radiation belts, that is, to lower $L-$shells is still not clear. In this work we have identified 60 relativistic electron enhancement events at GEO to study the radial response of outer belt fluxes and the correlation between the fluxes at GEO and those at lower $L-$shells. The enhancement events occurred between 1 October 2012 and 31 December 2017 and were identified using GOES 15 $>$2 MeV fluxes at GEO, which we have used to characterize the radial response of the radiation belt, by comparing to fluxes measured by the Van Allen probes ECT-REPT between $2.55.0$, and generally similar for $L>4.5$. Post enhancement maximum fluxes show a remarkable correlation for all $L > 4.0$ although the magnitude of the pre-existing fluxes on the outer belt plays a significant role and makes the ratio of pre-to-post enhancement fluxes less predictable in the region $4.0

Tsunamis in the Mediterranean Sea have been increasingly investigated in the last decades due to past destructive events. We present a novel approach for evaluating tsunami-induced coastal inundation, based on a generalization of Green’s law and a chain of intermediate and small-scale numerical simulations. At the intermediate level, simulations with a linear solver are made to identify the coastal distribution of a novel parameter, namely α, condensing all nearshore wave transformations other than shoaling. α represents a proxy for coastal susceptibility to the tsunami impact. Small-scale modelling of coastal flooding performed in the southern Italy on a freely available DTM at the Esaro river estuary (Calabria) yields inundation levels that compare well with those obtained via intermediate-scale modelling, with a saving in computational time of about 41%. This demonstrates the helpfulness of α to “scale” the offshore wave input and reduce the computational effort to evaluate flooding at regional scale.

Spatially-explicit knowledge of the origins of water resources for ecosystems and rivers is challenging when using tracer data alone. We use simulations from a spatially-distributed model calibrated by extensive ecohydrological datasets in a small, energy-limited catchment, where hillslope-riparian dynamics are broadly representative of humid boreal headwater catchments that are experiencing rapid environmental transition. We hypothesize that in addition to wetness status, landscape heterogeneity modulates the water pathways that sustain ecosystem function and streamflows. Simulations show that catchment storage inversely controls streamwater ages year-round, but only during the drier seasons for transpiration and soil evaporation. The ages of these evaporative outputs depend much less on wetness status in the oft-saturated riparian soils than on the freely-draining hillslopes that subsidize them. This work highlights the need to consider local dynamics and time-changing lateral heterogeneities when interpreting the ages, and thus the vulnerability, of water resources feeding streams and ecosystems in landscapes.

Pulsating auroras (PsAs) are considered to be caused by energetic (~10 keV) electron precipitations. Additionally, soft electron precipitations (~1 keV) have often been observed in PsAs. These soft electron precipitations enhance the electron density in the ionospheric F region. However, to date, the relationship between PsAs and soft electron precipitation has not been well understood. In this study, using the data taken by the European incoherent scatter radar and the auroral all-sky imager at Tromso;, we conducted two case studies to investigate, in detail, the relationship between the electron density height profile and the type of aurora. Additionally, we conducted statistical studies for 14 events to elucidate how often F region electron density enhancement occurs with a PsA. We consequently found that 76% of electron density height profiles showed a local peak in the F region, with electron temperature enhancements. It was also found that 89% of the F region peak altitudes were above the peak altitude of the ionization rate produced by electrons of characteristic energy below 100 eV. The occurrence rate of these profiles in the hourly magnetic local time (MLT) exceeded 80% in the 22–3 MLT sectors. We suggest that the electron density enhancement in the F region would have been caused by electrostatic electron cyclotron harmonic waves in the magnetosphere. Another candidate would have been polar patches that had traveled from the dayside ionosphere.

• Poor estimates of the sinking speed of marine aggregates stem primarily high variance in aggregate excess density. • Self-similarity of aggregation facilitates efficiently modelling of aggregate size and excess density, and hence sinking speed. • This provides a mechanistic description of how planktonic communities impact the size and density-resolved export flux of organic matter.