Planning under deep uncertainty, when probabilistic characterizations of the future are unknown, is a major challenge in water resources management. Many planning frameworks advocate for “scenario-neutral” analyses in which alternative policies are evaluated over plausible future scenarios with no assessment of their likelihoods. Instead, these frameworks use sensitivity analysis to discover which uncertain factors have the greatest influence on performance. This knowledge can be used to design monitoring programs and adaptive policies that respond to changes in the critical uncertainties. However, scenario-neutral analyses make implicit assumptions about the range and independence of the uncertain factors that may not be consistent with the coupled human-hydrologic processes influencing the system. These assumptions could influence which factors are found to be most important and which policies most robust. Consequently, the assumptions of uniformity and independence could have decision-relevant implications. This study illustrates these implications using a multi-stakeholder planning problem within the Colorado River Basin, where hundreds of rights-holders vie for the river’s limited water under the law of prior appropriations. Variance-based sensitivity analyses are performed to assess users’ vulnerabilities to changing hydrologic conditions using four experimental designs: 1) scenario-neutral samples of hydrologic factors, centered on recent historical conditions, 2) scenarios informed by climate projections, 3) scenarios informed by paleo-hydrologic reconstructions, and 4) scenario-neutral samples of hydrologic factors spanning all previous experimental designs. Differences in sensitivities and user robustness rankings across the experiments illustrate the challenges of inferring the most consequential drivers of vulnerabilities to design effective monitoring programs and robust management policies.

Ground-based technological systems, such as power grids, can be affected by geomagnetically induced currents (GIC) during geomagnetic storms and magnetospheric substorms. This motivates the necessity to numerically simulate and, ultimately, forecast GIC. The prerequisite for the GIC modeling in the region of interest is the simulation of the ground geoelectric field (GEF) in the same region. The modeling of the GEF in its turn requires spatio-temporal specification of the source which generates the GEF, as well as an adequate regional model of the Earth’s electrical conductivity. In this paper we compare results of the GEF (and ground magnetic field) simulations using three different source models. Two models represent the source as a laterally varying sheet current flowing above the Earth. The first model is constructed using the results of a physics-based 3-D magnetohydrodynamic (MHD) simulation of near-Earth space, the second one uses ground-based magnetometers’ data and the Spherical Elementary Current Systems (SECS) method. The third model is based on a “plane wave” approximation which assumes that the source is locally laterally uniform. Fennoscandia is chosen as a study region and the simulations are performed for the 7-8 September 2017 geomagnetic storm. We conclude that ground magnetic field perturbations are reproduced more accurately using the source constructed via the SECS method compared to the source obtained on the basis of MHD simulation outputs. We also show that the difference between the GEF modeled using laterally nonuniform source and plane wave approximation is substantial in Fennoscandia.

The solar wind protons are accelerated to supersonic velocities within the distance of 10 solar radii from the Sun, as a consequence of a complex physical mechanism including particle kinetic effects as well as the field-particle energy and momentum exchange. We use a numerical kinetic model of the solar wind, accounting for Coulomb collisions (BiCoP), and model a solar wind accelerated only by the \emph{ambipolar} electrostatic filed ($E$) arising due to the difference in mass between electron and proton, and assuring quasi-neutrality and zero current. We study the effect $E$, which was found to be on the order of Dreicer electric field ($E_D$) \cite{Dreicer1959}, has on the resulting electron velocity distribution functions (VDF). The strahl electron radial evolution is represented by means of its \emph{pitch-angle width} (PAW), and the \emph{strahl parallel temperature} ($T_{s,\parallel}$). A continuous transition between collisional and weakly collisional regime results in broader PAW, compared to the single-exobase prediction imposed by the exospheric models. Collisions were found to scatter strahl electrons below 250 eV, which in turn has an effect on the measured $T_{s,\parallel}$. A slight increase was found in $T_{s,\parallel}$ with radial distance, and was stronger for the more collisional run. We estimate that the coronal electron temperature inferred from the observations of $T_{s,\parallel}$ in the solar wind, would be overestimated for between 8 and 15\%.

A high proportion of non-crystalline (X-ray-amorphous) components has been found in all samples analyzed by CheMin on the Curiosity rover at Gale crater on Mars, and such X-ray-amorphous components probably occur at all sites that have been investigated thus far by landers and rovers. The amorphous material at Gale crater is rich in volatiles (S, Cl, and H2O), as indicated by other science payload elements (APXS, SAM). We demonstrate here that amorphization of S and Cl salts can be induced by energetic electrons and free radicals generated in a medium-strength electrostatic discharge (ESD) process during martian dust activities such as dust storms, dust devils, and grain saltation. Furthermore, we found that the amorphization is commonly accompanied by dehydration of the salts and oxidation of Cl, S, and Fe species. On the basis of experimentally observed rates of the above phase transformations and the mission-observed dust activities and wind speeds on Mars, we anticipate that similar phase transformations could occur on Mars within a time frame of years to hundreds of years. Considering the high frequency, long duration, and large areal coverage of Martian dust activities, our study suggests that the ESD induced by Martian dust activities may have contributed to some the S- and Cl-rich portion of X-ray amorphous materials observed in surface soils at Gale crater. Furthermore, dust activities in the Amazonian period may have generated and deposited a significant quantity

Asian monsoon rainfall impacts one third of the global population and predicting its variability and future change is of clear importance. However, the dynamics of even the climatological monsoon are not fully understood; seemingly unconnected behaviors and abrupt jumps in rainfall location occur in different regions through the year. Three independent subsystems have traditionally been considered: the East Asian, South Asian, and Western North Pacific monsoons. These are generally viewed as passive stationary-wave responses to insolation, but this picture cannot explain the abrupt jumps in rainfall location. Using model simulations, reanalysis and observations, we show that the complex behavior of all three subsystems in fact results from active propagation of the summertime ‘stationary’ wave. A continent-scale cyclone first expands northwestwards and then propagates eastwards via advective and evaporative feedbacks. We propose that the monsoon’s response to forcings may be understood by considering how this wave interacts with the background state.

Mesoscale organization of convection is typically not represented in global circulation models, and hence its influence on the global circulation is not accounted for. A parameterization aiming at representing the dynamical and physical effects of the circulation associated with organized convection, referred to as the multiscale coherent structure parameterization (MCSP), is implemented in the Energy Exascale Earth System Model version 1 (E3SMv1). Simulations are conducted to assess its impact on the simulated climate. Besides E3SMv1 simulations, we performed high-resolution (1 km) simulations using the Weather Research and Forecasting (WRF) Model to determine the temperature tendencies induced by mesoscale convective systems embedded in deep convection. We tuned the free parameters of the MCSP based on the WRF simulations. We found that the MCSP enhances Kevin wave spectra in E3SMv1, improves the representation of the Madden-Julian Oscillation, and reduces model precipitation biases over the tropical Pacific.

Reconstruction and prediction of the state of the near-Earth space environment is important for anomaly analysis, development of empirical models and understanding of physical processes. Accurate reanalysis or predictions that account for uncertainties in the associated model and the observations, can be obtained by means of data assimilation. The ensemble Kalman filter (EnKF) is one of the most promising filtering tools for non-linear and high dimensional systems in the context of terrestrial weather prediction. In this study, we adapt traditional ensemble based filtering methods to perform data assimilation in the radiation belts. We use a one-dimensional radial diffusion model with a standard Kalman filter (KF) to assess the convergence of the EnKF. Furthermore, with the split-operator technique, we develop two new three-dimensional EnKF approaches for electron phase space density that account for radial and local processes, and allow for reconstruction of the full 3D radiation belt space. The capabilities and properties of the proposed filter approximations are verified using Van Allen Probe and GOES data. Additionally, we validate the two 3D split-operator Ensemble Kalman filters against the 3D split-operator KF. We show how the use of the split-operator technique allows us to include more physical processes in our simulations and offers computationally efficient data assimilation tools that deliver accurate approximations to the optimal solution of the KF and are suitable for real-time forecasting. Future applications of the EnKF to direct assimilation of fluxes and non-linear estimation of electron lifetimes are discussed.

Detailed knowledge of fault geometry is important for accurate seismic hazard assessments. The Gulf of Aqaba, which corresponds to the southern termination of the 1200-km-long Dead Sea fault system, remains one of the least known parts of this plate boundary fault, in large part due to its location offshore. Classically, the Gulf of Aqaba has been described as a succession of three pull-apart basins. Here, building on a new multibeam bathymetric survey of the Gulf of Aqaba, we provide details about the geometry of the faults at the bottom of the gulf that controls its morphology. In particular, we identify a 50 km-long fault section that shows evidence of recent activation. We associate this fault section (Aragonese fault) with the section that ruptured during the 1995 magnitude Mw7.3 Nuweiba earthquake. In the southern part of the gulf, bathymetry emphasizes the strike-slip nature of the Arnona fault, while dip-slip motion seems to be accommodated mostly by faults located along the eastern edge of the gulf. Considering the simple linear geometry of the Arnona fault and the absence of any large earthquake for several centuries, despite an average slip-rate of ~5 mm/yr, this fault should be considered as a significant candidate for an earthquake rupture of magnitude 7 or above in the near future.

While about 17% of the adult population have significant hearing loss, we remain under-represented within academia outside of the field of Deaf Studies. One primary contributor to the leaky pipeline is lack of mentorship due to the difficulty of deaf and hard of hearing academics in recognizing one another. Hearing loss among non-signers is seldom obvious. Consequently, non-signing deaf and hard of hearing academics at predominantly hearing institutions often remain isolated without guidance on how to manage the myriad of communication challenges facing academics, such as teaching, leading group meetings, addressing questions at conferences, participating in discussions at professional meetings, and serving on grant proposal panels. Adequate solutions are often not available from our hearing health care providers nor from disability services offices, which are mandated and designed to serve undergraduate students. However, the success of all academics depends on mastering these different communication challenges. To fill the mentoring gap, we have started a blog by and for academics at all career stages with some degree of hearing loss called, “The Mind Hears”. This title derives from the Victor Hugo quote “What matters deafness of the ear when the mind hears, the one true deafness, the incurability deafness is that of the mind.” The goals of the blog are: To provide a forum for crowd-sourcing ways to minimize our challenges and share strategies for thriving in academia with hearing loss. To foster a network of deaf and hard of hearing academics who promote hearing inclusive strategies at universities. Through this blog we hope to reach deaf and hard of hearing academics all around the world, and thus reduce isolation in our community and build a community toolbox of resources and ideas. Hearing loss is variable and can affect us in many and different ways – but through this shared blog we hope to provide something of value to all of those who visit and contribute to our discussions.

Dunes dominate the bed of sandy rivers and they respond to flow by changing shape and size, modifying flow and sediment transport dynamics of rivers. Our understanding and ability to predict dune adaptation, particularly dune growth and decay, remains incomplete. Here we investigate dune growth from an initial flatbed in a laboratory setting by continuously mapping the 3D bed topography using a line laser scanner combined with a 3D camera. High-resolution profiles of flow velocity and sediment concentration providing both bedload and suspended sediment fluxes were obtained by deploying Acoustic Concentration and Velocity Profiler technology. Our analysis reveals that the magnitude of the dune slipface angle, which determines flow separation and controls turbulence production, adjusts to the imposed flow at time scales similar to the evolution of dune height and length. The initiation of a flow separation zone intensifies through scour, and results in acceleration of the dune growth. Gradients in sediment transport and the rate of dune growth are inherently linked to spatial variations in slipface angles. During dune growth, the slipface angle evolves differently than the ratio of dune height to length, which immediately reaches its equilibrium value after dune initiation.

Time-related information of pre-eruptive magmatic processes is locked in the chemical profile of compositionally zoned minerals and can be retrieved by means of elemental diffusion chronometry. However, only the timescale of the outermost rim is commonly resolved, limiting our knowledge of timescales to those directly preceding the eruption. A major obstacle is the need to accurately constrain temperatures at which diffusion occurred. This is particular difficult for multiple zoned minerals where the different compositional boundaries indicate multiple physicochemical changes of melt environments during the lifetime of a crystal. Here, we argue that elemental diffusion chronostratigraphy can be fully resolved for crystals that have spent their lifetime in hot storage. Under this condition, crystals will be kept at the temperature of the eruptible magma(s), and diffusion timescales approximate the storage of the crystal in question in different melt environments. We further argue that hot storage conditions are typical of open-conduit systems in steady-state and are driven by the regular supply of fresh hot magmas determining the constant presence of eruptible magma. Fe-Mg interdiffusion in pyroxenes from Stromboli and Popocatepetl volcanoes are used as examples to reconstruct the time-dependent elemental diffusion chronostratigraphy of single crystals and discuss magma dynamics implications. Uncertainties introduced by temperature estimates and other input data, including experimentally derived values for the activation energy E and the pre-exponential factor D0, have large effects on the accuracy of modelled timescales, which need to be correctly evaluated and mitigated. Elemental diffusion chronostratigraphy is an extremely powerful tool to obtain time-related temporal information on the dynamics and histories of volcanic plumbing systems, which can lead to an in-depth knowledge of the magmatic system far beyond late-stage pre-eruptive processes. Combined with monitoring data and other petrological, geological and geophysical constraints at active volcanoes, they can greatly enhance our capability to inform volcanic hazard assessments.

The combined gravitational pulls from the moon and the sun result in periodical tidal stresses at rates potentially exceeding the tectonic ones. Yet, tidal triggering of earthquakes in critically stressed faults is still under debate and controversial results have been obtained, depending upon specific physical properties and geological settings. Although no universal triggering pattern between earthquakes and tides has been observed in oceanic environments, previous research implies relation between increased seismicity rates and low tides at particular sites at fast-spreading ridges in the Pacific. We present a dataset of 4719 microearthquakes (-1.4≤ML≤4.0) recorded by an Ocean Bottom Seismometer (OBS) network at the slow-spreading equatorial Mid-Atlantic Ridge from March 2016 to February 2017. We use a single-station template matching technique to focus on a small volume, spreading within a ~5km radius from the station. The origin time of the events and their epicentral location is sufficiently determined for a robust comparison with the ocean tides. Our analysis suggests a significant correlation between seismic potential and tidal forces, with the majority of events occurring during or towards low tides, i.e., during maximized extensional stress and maximized extensional stress rate. The tidal dependence of magnitude distribution is also investigated. Although the b-values are generally lower at low tides, the differences are not sufficiently large to achieve statistical significance. However, seismic bursts (enhanced activity rate clusters), occurring at rates above the reference seismicity, are exclusively initiated at extensional stress rates. Coulomb stress modelling implies that slip is promoted during low tides at low-angle normal faults. Local morphology, seismicity distribution and focal mechanisms suggest the existence of high angle faults at shallower depths. Coulomb modelling suggests slip on these faults should not be triggered at low tides unless another factor is considered. One possibility is the presence of a shallow magma chamber. Such a chamber has also been suggested by previous seismic imaging results. Overall, the result yields new insight into magmatic – tectonic cycles and seismicity triggering at mid-ocean ridges.

The goal of this study is twofold. First, we aim at developing a simple model as an interpretative framework for the water vapor isotopic variations in the tropical troposphere over the ocean. We use large-eddy simulations to justify the underlying assumptions of this simple model, to constrain its input parameters and to evaluate its results. Second, we aim at interpreting the depletion of the water vapor isotopic composition in the lower and mid-troposphere as precipitation increases, which is a salient feature in tropical oceanic observations. This feature constitutes a stringent test on the relevance of our interpretative framework. Previous studies, based on observations or on models with parameterized convection, have highlighted the roles of deep convective and meso-scale downdrafts, rain evaporation, rain-vapor diffusive exchanges and mixing processes. The interpretative framework that we develop is a two-column model representing the net ascent in clouds and the net descent in the environment. We show that the mechanisms for depleting the troposphere when precipitation rate increases all stem from the higher tropospheric relative humidity. First, when the relative humidity is larger, less snow sublimates before melting and a smaller fraction of rain evaporates. Both effects lead to more depleted rain evaporation and eventually more depleted water vapor. This mechanism dominates in regimes of large-scale ascent. Second, the entrainment of dry air into clouds reduces the vertical isotopic gradient and limits the depletion of tropospheric water vapor. This mechanism dominates in regimes of large-scale descent.

Lakes are often defined by seasonal cycles. The seasonal timing, or phenology, of many lake processes, such as primary productivity, are changing in response to human activities. However, long-term records exist for few lakes, and extrapolating patterns observed in these lakes to entire landscapes is exceedingly difficult using the limited number of in situ observations that are available. Limited landscape level observations means we do not know how common shifts in lake phenology are at macroscales. Here, we use a new remote sensing dataset, LimnoSat-US, to analyze U.S. summer lake color phenology between 1984 and 2020 across more than 26,000 lakes. Our results show that summer lake color seasonality can be generalized into five distinct phenology groups that follow well-known patterns of phytoplankton succession. The frequency with which lakes transition from one phenology group to another is tied to lake and landscape level characteristics. Lakes with high discharge and low variation in their seasonal extent are generally more stable while lakes in areas with high interannual variations in climate and catchment population density show less stability. Our research reveals previously unexamined spatiotemporal patterns in lake seasonality and demonstrates the utility of LimnoSat-US, which, with over 22 million remote sensing observations of lakes, creates novel opportunities to systematically examine changing lotic ecosystems at a national scale.

Alfred Wegener Institute’s (AWI) IceBird program is a series of airborne campaigns carried out in winter and summer using a fixed-wing Basler BT-67 research aircraft to measure Arctic sea ice and to monitor its change. In 2017, the primary scientific instrument configuration including an airborne laser scanner (ALS) for surface topography and freeboard measurements and a tethered electromagnetic induction sounding instrument (EM-Bird) for total (snow+ice) thickness measurements was complemented with an ultrawideband frequency-modulated continuous-wave microwave radar to measure snow thickness. With the unique instrumentation onboard the IceBird campaigns, we are able to observe the respective thicknesses of the snow and sea-ice layers in high resolution along survey tracks on regional scale. Here, we describe the IceBird program concept and focus on the winter campaigns that take advantage of the full instrument configuration. We present recent data of high-resolution, collocated, airborne sea-ice and snow thickness and freeboard measurements based on over 3000 km of profiles collected in the western Arctic Ocean in April 2017 and 2019. The individual parameters are important for describing and monitoring the state of the Arctic sea ice and validating retrievals from satellite data, but combined they offer further possibilities to characterize sea ice. By assuming isostatic equilibrium, we are able to derive up-to-date estimates for sea-ice bulk density for first-year and multi-year ice, including deformed ice. As an outlook, we derive a parametrization of sea-ice bulk density based on sea-ice freeboard for further applications, such as evaluating the freeboard-to-thickness conversion for satellite altimetry.

The slot region between the radiation belts in the magnetosphere is considered to be stable and safe for satellite missions, but strong disturbances during space weather events can cause an enhancement of the electron radiation environment in this area. This paper provides an analysis of the dynamics of electron flux in 1998-2007 with specific attention to slot filling events and preceded geomagnetic activity. Flux of energetic electrons, with energies E>0.63 MeV, E>1.5 MeV, and E>3 MeV, was obtained from detectors on board the HEO-3 satellite in highly elliptical orbit. To evaluate geomagnetic conditions, associated with enhancement of electron flux, all the ‘slot filling events’ were studied together with geomagnetic activity provided by Dst and Kp global indices as well as with thehourly range indices of geomagnetic variations at mid-latitude. These geomagnetic indices were used for assessment of a threshold and frequency of occurrence of slot filling events. Regression analysis has been used to find a relationship between the maximum filling of the slot region due to space weather event and preceding geomagnetic activity level. Influence of the cumulative time of periods of enhanced geomagnetic activity to the variation of the electron flux in the slot region has been analysed. Suitability of different indices of geomagnetic activity for estimation of rate of occurrence of slot filling events and for assessment of electron flux in the slot region is discussed.

A drought is a slowly developing natural phenomenon that can occur in all climatic zones and can be defined as a temporary but significant decrease in water availability. Over the past three decades, the cost of droughts in Europe has amounted to over 100 billion euros and it is expected to considerably increase as future droughts are projected to be more severe and long-lasting. Although drought monitoring and management are largely studied in the literature, they often fail at yielding precise information on critical events occurrence and associated impacts such as reduction of electricity production or crop failures. This is due to the difficulty of capturing the complexity of drought dynamics, which evolve over diverse temporal (and spatial) scales, including short-term meteorological droughts, medium-term agricultural droughts, and long-term hydrological droughts, as well as the non-physical aspects related to droughts (water management, irrigation, etc.). In this work, we contribute a Machine Learning based framework named FRIDA (FRamework for Index-based Drought Analysis) for the identification of impact-based, site-specific drought indexes. FRIDA is a fully automated data-driven approach that relies on advanced feature extraction algorithms to identify relevant drought drivers from a pool of candidate hydro-meteorological variables. Selected predictors are combined into an index representing a surrogate of the drought conditions in the considered area, including either observed or simulated water deficits or remotely sensed information about the state of the crops. FRIDA is portable across different contexts for supporting the formulation of basin-specific indexes to better inform drought management strategies. Several real-world examples will be used to provide a synthesis of recent applications of FRIDA in case studies featuring diverse hydroclimatic conditions and variable levels of data availability.

The 3D S-wave velocity of shallow structure, especially the Quaternary sediments at 0-1 km near the surface, is an important issue of concern in urban planning and construction for the requirements of seismic hazard assessment and disaster mitigation. Due to the facility and less dependence on the site environment, noise-based technique is an ideal way to acquire the fine structure of urban sedimentary basin. Based on the dense array composed of more than 900 stations deployed in Tongzhou at a local scale of 20 × 40 km2, we proved the lateral variation of the phase velocity of multi-mode surface waves can be estimated directly with adequate accuracy by beamforming seismic noise with moving subarray, without tomography. Rayleigh wave phase velocity maps, at frequencies between 0.3 and 2.5 Hz for the fundamental mode as well as 0.8 and 3.0 Hz for the first overtone, are obtained. The 3D S-wave velocity model at 0-1 km depth with lateral resolution of 1 km is then established by inverting phase velocity maps of two modes. The thickness of the sediments is delineated by the impedance interface given by microtremor H/V (horizontal-to-vertical) spectral ratio. The model is in good agreement with tectonic unit. The sedimentary thickness of Daxing high and two sags located around Gantang and Xiadian are respectively 100-400 m and 400-600 m, which correlates well with the isosurface of S-wave velocity at 1 km/s. The model also presents some evidence on the extension of Daxing fault along NE direction.