Why do some Martian dust storms, in some Mars years, expand to reach planet-encircling status, while the majority do not? In what ways do the largest regional events differ from those that become global? Comparisons of observations from these two categories of events may help answer these questions. The dust storm season of 2018, which included a global-scale dust event, was preceded by five successive dust storm seasons in which only regional-scale events were observed. The recent record thus presents an opportunity for making quantitative comparisons between regional-scale and global-scale dust events. Observations by the Mars Climate Sounder, on board the Mars Reconnaissance Orbiter spacecraft, provide unique 4D information on temperatures and aerosol loading of the Mars atmosphere, to altitudes of >80 km. Available MCS observations span the past eight Mars years. We have previously employed MCS observations to characterize the evolution in latitude, longitude, and altitude of atmospheric dust clouds during the initiation phase of the 2018 global event. Other atmospheric fields provide complementary information. For instance, observed changes with time in atmospheric ‘dynamical heating’ also help characterize the response of the Mars atmosphere to added dust loading. In this process, the atmosphere in regions far removed from the locations where dust is lifted may be warmed by adiabatic compression within the descending branches of Hadley-like meridional circulation cells. We will present and interpret MCS observations of these and other phenomena for selected large regional-scale dust events of Mars Years 29-33 (from 2009 through 2017), and draw comparisons with observations obtained during the 2018 global event. We will additionally explore the implications of the results within the context of current hypotheses for the triggering of the largest dust storms on sub-seasonal time scales.

A document by Nicholas Lutsko. Click on the document to view its contents.

There is no consensus on the physical mechanisms controlling the scale at which convective activity organizes near the Equator, where the Coriolis parameter is small. High resolution cloud-permitting simulations of non-rotating convection show the emergence of a dominant length scale, which has been referred to as convective self-aggregation. Furthermore, simulations in an elongated domain of size 12228km x 192km with a 3km horizontal resolution equilibrate to a wave-like pattern in the elongated direction, where the cluster size becomes independent of the domain size. These recent findings suggest that the size of convective aggregation may be regulated by physical mechanisms, rather than artifacts of the model configuration, and thus within the reach of physical understanding. We introduce a diagnostic framework relating the evolution of the length scale of convective aggregation to the net radiative heating, the surface enthalpy flux, and horizontal energy transport. We evaluate these length scale tendencies of convective aggregation in twenty high-resolution cloud-permitting simulations of radiative-convective equilibrium. While both radiative fluxes contribute to convective aggregation, the net longwave radiative flux operates at large scales (1000-5000 km) and stretches the size of moist and dry regions, while the net shortwave flux operates at smaller scales (500-2000 km) and shrinks it. The surface flux length scale tendency is dominated by convective gustiness, which acts to aggregate convective activity at smaller scales (500-3000 km). We further investigate the scale-by-scale radiative tendencies in a suite of nine mechanism denial experiments, in which different aspects of cloud radiation are homogenized or removed across the horizontal domain, and find that liquid and ice cloud radiation can individually aggregate convection. However, only ice cloud radiation can drive the convective cluster to scales exceeding 5000 km, because of the high optical thickness of ice, and the increase in coherence between water vapor and deep convection with horizontal scale. The framework presented here focuses on the length scale tendencies rather than a static aggregated state, which is a step towards diagnosing clustering feedbacks in the real world. Overall, our work underscores the need to observe and simulate surface fluxes, radiative and advective fluxes across the 1km-1000km range of scales to better understand the characteristics of turbulent moist convection.

Interferometric synthetic aperture radar (InSAR) measures surface deformation from repeated passes of satellites or aircraft and has become an important tool to study geophysical phenomena such as earthquakes. However, InSAR data analysis is challenging due to atmospheric water vapor that can mimic the effects of Earth deformation and thus lead to wrong interpretations. We present preliminary results on how to differentiate between tropospheric effects and surface deformation from earthquakes using a convolutional neural network. As earthquake training sets are sparse, our approach leverages transfer learning techniques for tropospheric patterns from areas where deformations are known to be mostly absent over short time periods, and classifies specific areas of interferograms to reflect regions that are dominated by deformation or tropospheric noise. The applicability of the training set to a new area may depend on the similarity of the two climates. Examples of tropospheric delays are shown from interferograms constructed from Sentinel-1 data over part of southern California with short temporal baselines, and examples of deformation are taken from interferograms generated using Okada models. Our classifier is tested on data from the 2018 Oaxaca earthquake in Mexico from Sentinel-1. This work is a step towards using neural networks for a fine-granular tile-based validation of interferograms and automatically removing unwanted effects from InSAR signals, as well as towards enhancing the agility of disaster response programs. The open source code is available in the PyInSAR package on GitHub under the MIT license. We acknowledge support from NASA AIST80NSSC17K0125 (PI Pankratius) and NSF ACI1442997 (PI Pankratius).

The study and simulation of the Urban Heat Island (UHI) and Heat Index (HI) effects in the Houston-Galveston metropolitan area demand special attention, particularly in considering moist processes aloft. During the warm season, the afternoon sea breeze phenomenon in this coastal city acts as a natural air conditioner for city residents, facilitating the dispersion of pollutants, moisture, and heat. To delve into the intricate relationships among urbanization, clouds, and land-sea interaction, we conducted cloud- and urban-resolving simulations at a 900 m grid resolution. Results show that urbanization correlates with the presence of shallower cumulus clouds, cloud bases at higher altitudes, and increased cloud duration over the Galveston-Houston region compared to rural areas. These urban clouds benefit from the enhanced sensible heat and dynamic drag imparted by the urban landscape, thereby intensifying vertical mixing and moisture flux convergence. This dynamic interplay uplifts heat and moisture convergence, contributing to the enhancement of moist static energy that sustains the additional urban convection. Interestingly, our findings suggest that urbanization augments the mean HI while mitigating its afternoon high. An urban circulation dome emerges, overpowering the influence of land-sea circulations. Contrary to expectations, urbanization doesn’t seem to promote a stronger sea breeze that would favor moist and cooler air mass to the city. Instead, the influence of urbanization on cloud enhancement emerges as a crucial pathway responsible for reducing the afternoon HI values. Moreover, uncertainties in SSTs are closely linked to the sensitivities of land-sea circulations, which in turn modulate UHI and extreme heat indicators.

Serpentinization ubiquitously affects ultramafic rocks that interact with water, with strong implications for the origin of ancient microbial ecosystems, the chemical budget of the ocean, and the rheology of the oceanic crust. The increase in volume associated with this reaction, and its consequences for reaction progress, have been debated for over a century. Serpentine minerals are ~40% more voluminous than olivine, which suggests that fully serpentinized peridotite should have negative, or at least very low, porosity. Recent studies have proposed that self-propagating, reaction-driven fracturing can facilitate serpentinization reactions, but the nanoscale mechanisms by which fluid is transported through serpentinized fractures in order to react with fresh olivine surfaces remain poorly understood. To address this issue, we studied a sample of serpentinized harzburgite collected during ODP expedition 209 at site 1274, using Focused Ion Beam – Scanning Electron Microscopy (FIB-SEM)-assisted tomography. We specifically targeted the interface between the serpentinized peridotite and the unaltered primary mineralogy. The resultant images illustrate the presence of nanopores within the serpentine alteration products, primarily at the interface with the unreplaced minerals. Importantly, no pores were observed in the serpentine away from the grain boundaries with olivine, suggesting that these nanopores form during the initial stage of reaction, and then disappear with further reaction progress. We argue that the observed nanoporosity is an intrinsic feature of the serpentinization reaction, and that its transient presence during serpentinization is vital for facilitating reaction progress. We suggest that the transient nature of the pores arises from the opposing kinetics and thermodynamics of the replacement reaction. The former promotes the formation of voids that enhance the advective transport of fluids to the reaction front, while the latter drives the reduction of pore space by means of recrystallization of the serpentine aggregates and minimization of the interfacial energy.

A document by Zijing Wang. Click on the document to view its contents.

Geologic carbon storage is required for achieving negative CO2 emissions to deal with the climate crisis. The classical concept of CO2 storage consists in injecting CO2 in geological formations at depths greater than 800 m, where CO2 becomes a dense fluid, minimizing storage volume. Yet, CO2 has a density lower than the resident brine and tends to float, challenging the widespread deployment of geologic carbon storage. Here, we propose for the first time to store CO2 in supercritical reservoirs to reduce the buoyancy-driven leakage risk. Supercritical reservoirs are found at drilling-reachable depth in volcanic areas, where high pressure (p>21.8 MPa) and temperature (T>374 ºC) imply CO2 is denser than water. We estimate that a CO2 storage capacity in the range of 50-500 Mt yr-1 could be achieved for every 100 injection wells. Carbon storage in supercritical reservoirs is an appealing alternative to the traditional approach.

Streamers are millimeter-diameter cold plasma discharges that can extend, branch, and interact with complex collective dynamics to form meter-scale systems. Such streamer systems can be expected to play an important role in lightning. Small-scale streamer systems may grow to provide sufficient ionization and intensification of field to support initiation of hot plasma channel development. Streamer systems developing ahead of the lightning channel may guide channel extension and help explain the observed step-wise extension process. Rapidly-developing streamer systems may also help explain recent observations of fast positive and negative breakdown. We present simulations of streamer system development based on approximate particle-like treatment of individual streamer behavior but including large-scale system dynamics including interaction, collision/connection, and secondary streamer initiation. Here we focus on the observable effects of such streamer system development, including electrostatic field change and electromagnetic wave emissions with frequencies up to 500 MHz. Preliminary results suggest high-frequency (HF) emissions due to streamer acceleration and interaction in isolated streamer systems are comparable in scale to observations of HF emission from lightning and develop before detectable static field change occurs, but these results depend on simulation parameters.

Heterogeneous snow accumulation in the mountains introduces uncertainty to water-supply forecasting in much of the world. Water managers’ awareness of the challenge may account for forecast errors in management decisions. We assess the impact of uncertainty in seasonal-water-supply forecasts on reservoir management using the western slope of the Sierra Nevada of California as a case study. We find that higher forecast uncertainty decreases the volume of water released from reservoirs between April and July, suggesting that water managers hedge against the possibility of lower-than-expected runoff. We modeled April-July water releases as a function of corresponding runoff forecasts, their reported uncertainty, and available storage capacity. An unbalanced (n=416) panel data model with fixed effects suggests that if uncertainty goes up by 10 units, water managers reduce releases by about 6 units, even holding the mean forecast constant. The forecast volume, its uncertainty, available storage capacity, and the interaction between forecasted volume and uncertainty were all statistically significant predictors (p < 0.005) of releases. Increased forecast uncertainty and increased available storage were significantly and inversely associated with April-July release volume, whereas forecast volume and the interaction between forecast uncertainty and forecast volume were significantly and positively associated with release volume. These results support the hypothesis that water managers behave as if they are risk-averse with respect to the possibility of less runoff than forecasted. Thus, reducing operational forecast uncertainty may result in more water being released, without the need for direct coordination with water managers.

The entire western US is in the midst of a megadrought. Combined with high temperatures, increasingly severe droughts are causing widespread forest mortality. In the Sierra Nevada, CA in particular, the Mediterranean climate exposes montane forests to water stress due to the summer drought. Normally, the slow melting of the winter snowpack helps to alleviate summer water stress, especially in riparian ecosystems that benefit from subsurface lateral inputs along a hillslope. However, the loss of the snowpack due to snow drought could potentially eliminate these buffering effects. This research aims to address the role of subsurface lateral redistribution in mediating vegetation responses to drought along a hillslope. We apply a spatially-distributed ecohydrologic model (RHESSys) to an experimental hillslope in a snow-dominated watershed in the Sierra Nevada, CA. We incorporate observed sap flow data from the experimental hillslope to estimate the relative differences in onset of water stress for upslope and riparian sites, which is used to constrain RHESSys drainage parameter uncertainty. Then, we run hypothetical multi-year drought experiments to investigate how climate variability translates to water stress on a hillslope. Our results challenge the common assumption that riparian forests are buffered against drought stress by subsurface lateral inputs. For all drought types, both upslope and riparian sites experience severe losses of net primary productivity (NPP), and on average upslope sites are more adversely affected (upslope loss of NPP = 50% vs. riparian = 35%). But even in a wet year, as temperatures rise and the snowpack disappears (i.e., warm snow drought), vegetation approaches a threshold response that destabilizes the riparian buffering effect. Our results show that for 12% of all scenarios, riparian NPP decreases more than upslope NPP, as a consequence of earlier snowmelt. Interactions between climate variability and ecophysiological uncertainty produce scenarios that exhibit the riparian threshold response. By recognizing the conditions that determine riparian sensitivity to drought, management actions can be proactive in preserving this important hydrological refugia.

Cities are the most sensitive and vulnerable places to climate variability and change and weather-related extreme events given high population density, with the aggravating factor that urban climate also suffers modifications due to the widespread replacement of the natural surface altering the local thermal conditions. The Aburrá Valley is a narrow valley located at the tropical Andes in northern South America with urban areas between 1300 and 2000 m.a.s.l, a population of approximate 3.9 million people, and a comfortable climate relative to standard indoor conditions. In this work, we examine observed weather patterns in the local scale and the urban canopy layer (UCL) using data from weather stations at sites with different surface features regarding vegetation/non-impervious fractions and urban structure (Sky View Factor SVF). UCL data is available from two data sources, the first one from a field campaign using all-in-one weather sensors at the valley´s bottom, and the second one from a low-cost sensor network with robust temperature and humidity data as part of a local citizen science project with measurements in a diverse altitude range. Results suggest that at the local scale there exist different climate mean conditions due to altitude, with significant weather variability depending on radiation levels and rainfall occurrence, but at the same time, the urban effects are evident since the lowest altitude stations do not necessarily register the highest temperatures depending on the local characteristics. UCL measurements show that, while the altitude defines a background state, there are notable differences between places mainly influenced by insolation changes due to vegetation around and above sensors. Currently, the local population does not perceive thermal stress as a risk factor because it is not difficult to find places with appropriate thermal conditions when thermal discomfort arises. However, this research is relevant considering the projected local surface temperature increase due to climate change and the inexistence of baseline studies assessing the thermal comfort in outdoors to support local adaptation actions. The results of this study are useful for urban planning and building design to improve thermal conditions, especially in open spaces.

This paper analyses magnetosphere-ionosphere (MI) coupling from a perspective that is independent of inertial reference frame, explicitly acknowledging the role of the principle of relativity in MI coupling. For the first time in the context of MI coupling, we discuss the literature on the low-velocity limit of the theory of special relativity applied to electrodynamics. In many MI coupling theories, a particular low-velocity limit applies, known as the “magnetic limit”. Two important consequences of the magnetic limit are: 1) Maxwell’s equations cannot contain a displacement current and be consistent with the magnetic limit and 2) the magnetic field is not modified by currents created by charge densities in motion, thus charge density is approximately zero. We show how reference frame-independent descriptions of MI coupling require that ion-neutral relative velocities and ion-neutral collisions are key drivers of the physics. Electric fields, on the other hand, depend on reference frame, and can be zero in an appropriate frame. Currents are independent of reference frame and will flow when the electric field is close to zero. Starting with the same momentum equations that are typically used to derive Ohm’s law, we derive an equation that relates the perpendicular current to collisions between ions and neutrals, and electrons and neutrals, without reference to electric fields. Ignoring the relative motion between ions and neutrals will result in errors exceeding 100% for estimates of high latitude Joule heating during significant geomagnetic storms when ion-neutral velocity differences are largest near the initiation of large-scale ion convection.

Overlapping areas between Protected Areas and Indigenous peoples’ territories are important spaces for articulating cross-scale governing institutions and augmenting socioecological adaptability in developing countries. However, cooperation hinges on conflicts resolution between local (Indigenous peoples’ authorities) and national institutions (Protected Areas’ federal managers), official recognition of ancestral rights to Indigenous peoples, and the investment of social and financial capital for protecting important natural resources in synchrony with local communities. For this, is necessary to improve our understanding of the impacts of cross-scale interaction on natural resources’ conservation. In this research, we study these interactions on the Orinoco River watershed, one of the most important areas for the conservation of biodiversity in South America. Overlaps between Protected Areas and Indigenous peoples’ territories in this watershed account for 9% of its surface area. To test the effect of different political setups on conservation, we employed conservation indicators that use spatially-defined biophysical attributes. First, we explored differences between governing units (non-overlapping Protected Areas or PA, non-overlapping Indigenous peoples’ territories or IT, and overlapping areas or OV), then, we analyzed different overlapping categories (Partial, Near, None, and Full), finally, we analyzed how the recognition of ancestral rights impacts local governance by comparing Indigenous territories with rights and without rights. We found that conservation measurements were higher where any type of overlap took place, which suggests that the interaction between local and national institutions has a positive effect on the protection of important ecosystem services, furthermore, the proxies used to measure ecosystem services values indicate that areas contiguous to OV (Near overlapping category) have greater benefit than commonly expected. Our results were inconclusive regarding the effect of public recognition to local authorities on the local governance; however, this study contributes to the body of evidence about the contribution of these communities to the conservation of strategic ecosystems. This research highlights the importance of collaborative work for the conservation of natural resources, furthermore, it could support future investments of public funds on the creation and strengthening of cross-scale alliances and coalitions for the conservation and management of strategic ecosystems in the Orinoco River watershed.

A seamless numerical model of coupled multiphase flow and inertial mechanics in fractured porous media is proposed. The model develops an automatic time step size control method to efficiently and accurately capture transitions between flow with small deformation, quasi-static slip, and dynamic rupture with seismic wave propagation. The model utilizes a mixed and embedded approach that represents fractures explicitly. The mixed discretization combines an extended finite element method (XFEM) with a projection embedded discrete fracture and matrix (pEDFM) finite volume method. Mechanical inertia is approximated implicitly using a stable Newmark scheme, and fracture contact constraints for stick-slip conditions are enforced by a Lagrange Multiplier approach that is stabilized by Polynomial Pressure Projection (PPP). The temporal adaption method combines discretization error, Coulomb friction, and slip rate considerations to capture pre-seismic triggering, co-seismic spontaneous rupture, and arrest. The model is applied to simulate multiple cycles of induced seismic rupture under various multiphase fluid production and injection scenarios. This is enabled by time step size control to automatically span transitions across seven orders of magnitude in timescales.

Western boundary currents (WBCs) have intensified and become more eddying in recent decades due to the spin-up of the ocean gyres, resulting in warmer open ocean temperatures. However, relatively little is known of how WBC intensification will affect temperatures in adjacent continental shelf waters where societal impact is greatest. We use the well-observed East Australian Current (EAC) to investigate WBC warming impacts on shelf waters and show that temperature increases are non-uniform in shelf waters along the latitudinal extent of the EAC. Shelf waters poleward of 32°S, are warming more than twice as fast as those equatorward of 32°S. We show that non-uniform shelf temperature trends are driven by an increase in lateral heat advection poleward of the WBC separation, along Australia’s most populous coastline. The large scale nature of the process indicates that this is applicable to WBCs broadly, with far-reaching biological implications.

Beaches are highly variable environments and respond to changes in wave forcing, themselves modulated by climate variability. Here, we analyse three high-quality beach profile datasets to robustly investigate, for the first time, the link between shoreline change, wave forcing and climate variability along the Atlantic coast of Europe. Winter wave conditions are strongly associated with North Atlantic Oscillation (NAO) and Western Europe Pressure Anomaly (WEPA), with WEPA explaining 50–80% of the winter wave power variability. Shoreline variability during winter is also strongly linked to NAO and WEPA, with WEPA explaining 25% of the winter shoreline variability. Winter wave conditions and associated shoreline variability are both unrelated to El Nino Southern Oscillation (ENSO). In addition to the atmospherically-forced beach morphological response, shoreline change also depends strongly on the antecedent conditions as evidenced by significant correlations between summer/winter shoreline response and the shoreline position at the start of each season.

According to the 2020 FEMA Fact Sheet (FEMA, 2020), Puerto Rico and Virgin Islands are located in a high risk region for earthquake damage. In the last year (05-jul-2019 to 05-jul 2020) the Puerto Rico Seismic Network (PRSN) recorded 136 earthquakes with magnitudes greater than 4.0 and two events had magnitudes greater than or equal to 6.0. The last update of the seismic hazard maps for Puerto Rico and the US Virgin Islands was performed in 2003. According to Mueller et al. (2010), the Bunce fault, the Muertos Trough and related fault structures were not included in the hazard map. The Great Southern Puerto Rico fault, was considered largely quiescent, but Piety et al. (2008) through paleoseismic studies, evidenced activity in this one. Otherwise, offshore faults in southern Puerto Rico were not considered, because their rates of activity were poorly known and assumed to be most likely small. However, starting in December 2019 the Southwestern Puerto Rico (SWPR) Seismic Sequence has been active and continues to be active in these southern offshore faults. According to the StEER technical report (Miranda et al., 2020), the events that occurred between December 2019 and January 2020 caused damage to approximately 10,000 structures and more than 8,000 people were displaced. Based on these facts, and considering that previously unknown tectonic fault structures have been revealed by the SWPR Seismic Sequence (Lopez et al., 2020b), a reevaluation of the seismic threat to Puerto Rico is required. This should include the seismic activity that, according to the PRSN catalog, consists of more than 50,000 events since 2002 to date. This new seismic hazard evaluation will include multiple earthquakes with magnitudes greater than M 5 which were not part of the catalog in 2001. The purpose of this study is generating a new Ground Motion Prediction Equation (GMPE) that incorporates the current seismicity for the region, which unlike the local model used in Mueller et al. (2010) the data will be used directly to obtain the ground motion relationships (Motazedian et al., 2005). This new data now permits to obtain a GMPE from a regression analysis. In the first stage of the research, the aim is generating a preliminary GMPE based on crustal seismicity (events less than 25 km deep) which represents more than 60% of the total registered earthquakes in the PRSN catalog.