Antarctic ice shelves play a key role in regulating the rate of ice flow in tributary ice streams. Temporal variations in the associated ice-shelf buttressing stress are observed to impact ice flow in glaciers and ice streams. Ephemeral grounding induced by tides is an important mechanism for modulating the buttressing stress. Here, we develop an approach to inferring variations in 3-D surface displacements at an ice-shelf-stream system that explicitly accounts for ephemeral grounding. Using a temporally dense nine-month-long synthetic-aperture radar image acquisition campaign collected over Rutford Ice Stream, West Antarctica, by the 4-satellite COSMO-SkyMed constellation, we infer the ephemeral grounding zones and the spatiotemporal variation of the fortnightly ice-flow variability. We find ephemeral grounding zones along the western ice-shelf margin as well as a few prominent ephemeral grounding points in the central trunk and in the vicinity of the grounding zone. Our observations provide evidence for tide-modulated buttressing stress and the temporally asymmetric response of ice-shelf flow to tidal forcing. Long-term oceanic warming and ice-shelf thinning will cause the loss of ephemeral grounding and decrease in ice-shelf buttressing stress.

Knowledge of the ambient solar wind is important for accurate space-weather forecasting. A simple-but-effective method of forecasting near-Earth solar-wind conditions is “corotation”, wherein solar-wind structure is assumed to be fixed in the reference frame rotating with the Sun. Under this approximation, observations at a source spacecraft can be rotated to a target location, such as Earth. Forecast accuracy depends upon the rate of solar-wind evolution, longitudinal and latitudinal separation between the source and target, and latitudinal structure in the solar wind itself. The time-evolution rate and latitudinal structure of the solar wind are both strongly influenced by the solar cycle, though in opposing ways. A latitudinal offset is typically present, introducing an error to corotation forecasts. In this study, we use observations from the STEREO and near-Earth spacecraft to quantify the latitudinal error. Aliasing between the solar cycle and STEREO orbits means that individual contributions to the forecast error are difficult to isolate. However, by considering an 18-month interval near the end of solar minimum, we find that the latitudinal-offset contribution to corotation-forecast error cannot be directly detected for offsets <6º, but is increasingly important as offsets increase. This result can be used to improve solar-wind data assimilation, allowing representivity errors in solar-wind observations to be correctly specified. Furthermore, as the maximum latitudinal offset between L5 and Earth is ≈5º, corotation forecasts from a future L5 spacecraft should not be greatly affected by latitudinal offset.

Shore-oblique bathymetric features occur around the world and have been statistically correlated with enhanced shoreline retreat on sandy beaches. However, the physical mechanisms that explain a causal relationship are not well understood. In this study, radar remote sensing observations and results from a phase-resolved numerical model explore how complex morphology alters nearshore hydrodynamics. Observations at selected times during high-energy storm events as well as a suite of idealized simulations indicate that shore-oblique features induce strong spatial variations in the water surface elevation and wave breaking patterns. Re-emergent offshore flows and longshore current accelerations occur near the apex of the oblique nearshore features. The results suggest that complex bathymetric morphology exerts a powerful control on nearshore hydrodynamics and increases the potential for enhanced cross-shore and alongshore sediment transport, thus contributing to localized erosional zones.

Culverwell et al. (2023) described a new one-dimensional variational (1D-Var) retrieval approach for ionospheric GNSS radio occultation (GNSS-RO) measurements. The approach maps a one-dimensional ionospheric electron density profile, modeled with multiple ”Vary-Chap’ layers, to bending angle space. This paper improves the computational performance of the the 1D-Var retrieval using an improved background model and validates the approach by comparing with the COSMIC-2 profile retrievals, based on an Abel Transform inversion, and co-located (within 200 km) ionosonde observations using all suitable data from 2020. A three or four layer Vary-Chap in the 1D-Var retrieval shows improved performance compared to COSMIC-2 retrievals in terms of percentage error for the F2 peak parameters (NmF2 and hmF2). Furthermore, skill in retrieval (compared to COSMIC-2 profiles) throughout the bottomside (~90 km to 300 km) has been demonstrated. With a single Vary-Chap layer the performance is similar, but this improves by approximately 40% when using four-layers.

In this study, by simulating the wave-particle interactions, we show that sub-relativistic/relativistic electron microbursts form the high-energy tail of pulsating aurora (PsA). Whistler-mode chorus waves that propagate along the magnetic field lines at high latitudes cause precipitation bursts of electrons with a wide energy range from a few keV (PsA) to several MeV (relativistic microbursts). The rising tone elements of chorus waves cause individual microbursts of sub-relativistic/relativistic electrons and the internal modulation of PsA with a frequency of a few Hz. The chorus bursts for a few seconds cause the microburst trains of sub-relativistic/relativistic electrons and the main pulsations of PsA. Our simulation studies demonstrate that both PsA and relativistic electron microbursts originate simultaneously from pitch angle scattering by chorus wave-particle interactions.

This paper represents the first national-level (United States) estimate of the economic impacts of vibriosis cases as exacerbated by climate change. Vibriosis is an illness contracted through foodborne and waterborne exposures to various Vibrio species (e.g., non-V. cholerae O1 and O139 serotypes) found in estuarine and marine environments, including within aquatic life such as shellfish and finfish. Objectives The objective of this study was to project climate-induced changes in vibriosis related to sea surface temperatures (SSTs) and associated economic impacts in the U.S. Methods Our analysis constructed three logistic regression models by Vibrio species, using vibriosis data sourced from the Cholera and Other Vibrio Illness Surveillance (COVIS) system and using historical SSTs. We relied on previous estimates of the cost-per-case of vibriosis to estimate future total annual medical costs, lost income from productivity loss, and mortality-related indirect costs throughout the U.S. We separately report results for V. parahaemolyticus, V. vulnificus, V. alginolyticus, and “V. spp” given the different associated health burden of each. Results By 2090, increases in SST are estimated to result in a 51 percent increase in cases annually relative to the baseline era (1995) under Representative Concentration Pathway (RCP) 4.5 and a 108 percent increase under RCP8.5. The cost of these illnesses is projected to reach over $5.2 billion annually under RCP4.5 and $7.3 billion annually under RCP8.5, relative to $2.2 billion in the baseline (2018 dollars), equivalent to 140 percent and 234 percent increases respectively. Discussion Vibriosis incidence is likely to increase in the U.S. under moderate and unmitigated climate change scenarios through increases in SST, resulting in a substantial burden of morbidity and mortality, and costing millions of dollars. These costs are mostly attributable to deaths, primarily from exposure to V. vulnificus. Evidence suggests that other factors, including sea surface salinity, may contribute to further increases in vibriosis cases in some regions of the U.S. and should be investigated.

A document by Yuanzhe Li. Click on the document to view its contents.

A new one-dimensional variational (1D-Var) retrieval method for ionospheric GNSS ra- dio occultation (GNSS-RO) measurements is described. The forward model implicit in the retrieval calculates the bending angles produced by a one-dimensional ionospheric electron density profile, modeled with multiple “Vary-Chap” layers. It is demonstrated that gradient based minimisation techniques can be applied to this retrieval problem. The use of ionospheric bending angles is discussed. This approach circumvents the need for Differential Code Bias (DCB) estimates when using the measurements. This new, general retrieval method is applicable to both standard GNSS-RO retrieval problems, and the truncated geometry of EUMETSAT’s Metop Second Generation (Metop-SG), which will provide GNSS-RO measurements up to about 600 km above the surface. The climatological a priori information used in the 1D-Var is effectively a starting point for the 1D-Var minimisation, rather than a strong constraint on the final solution. In this paper the approach has been tested with 143 COSMIC-1 measurements. We find that the method converges in 135 of the cases, but around 25 of those have high “cost at convergence” values. In the companion paper (Elvidge et al., 2023), a full statistical analysis of the method, using over 10,000 COSMIC-2 measurements, has been made.

On 19 October 2014, Mars experienced a very close encounter with Comet C/2013 A1 Siding Spring. Using data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express (MEX), we assess the interaction of the Martian ionosphere with the comet’s atmosphere and possibly magnetic tail during the orbit of their closest approach. The topside ionospheric electron density profile is evaluated from the peak density of the ionosphere to the local plasma around Mars Express. We find unusual, complex and rapid variability in the ionospheric profile along the MEX orbit, not seen even after the impact of large coronal mass ejections. Before closest approach, large electron density reductions predominate, which could be caused either by comet water-damping, or comet magnetic field interactions. After closest approach, a substantial electron density rise predominates. Moreover, several extra topside layers are visible along the whole orbit at different altitudes, which could be related to different processes as we discuss.

Open, interdisciplinary science inevitably relies heavily on standards. Standards are those often unseen agreements that we take for granted when systems and processes are working fine. Yet standards work is perpetual, laborious, and sometimes contentious, especially for standards to work across diverse disciplines. Standards development, maintenance, and implementation is a complex, ongoing socio-technical process. NASA has developed a progressively open science policy and strategy that calls for the establishment of a data standards process reaching across the five diverse divisions of the Science Mission Directorate. This is a delicate exercise. We, therefore, seek to apply a holistic yet pragmatic approach to developing and maintaining a standards process. We adopt an ecological philosophy that focuses on the interactions within the data ecosystem and how standards facilitate those interactions. We couple high-level analysis with on the ground experimentation. We began by 1) mapping information ecosystem components (e.g. data centers, missions, services, protocols, users), 2) establishing how the components interact (e.g. sharing (meta)data, funding, personnel exchange), and 3) modelling system dynamics (e.g. creation of products from multiple data centers, redundant processes, shared services). The goal is to apply understanding of the ecosystem to real world applications (e.g. planning a new mission, implementing new policy requirements, improving process efficiency, etc.). We have also conducted studies of historical standardization efforts, documenting lessons learned and cautionary tales. We then contrast this more abstract work with real examples. We reviewed and assessed multiple existing standards development processes both within and external to NASA. We now work to implement an initial test process which can be further optimized. We seek to define a consistent approach for assigning persistent identifiers for research objects, especially for the purposes of citation. The experience from this relatively ‘simple’ test case adds a pragmatic perspective on how researchers and engineers actually work. This presentation will review the details of this methodology and our initial findings.

Spontaneous aggregation of deep convection is a common feature of idealized numerical simulations of the tropical atmosphere in Radiative-Convective Equilibrium (RCE). However, at coarse grid resolution where deep convection is not fully resolved, the occurrence of this phenomenon is extremely sensitive to subgrid-scale processes. This study focuses on the role played by mixing and entrainment, either provided by the turbulence model or the implicit numerical dissipation. We have analyzed the results of two different models, WRF and SAM, and we have compared different configurations by varying the turbulence models, the numerical schemes and the horizontal spatial resolution. At coarse grid resolution (3 km), removing turbulent mixing prevents the occurrence of Convective Self-Aggregation (CSA) in low numerical diffusion models, while delaying it in high numerical diffusion models. When the horizontal grid resolution is refined to 1 km (thus reducing the implicit numerical dissipation), CSA is achieved only by increasing the explicit turbulent mixing. In this case, CSA was found to occur even with a small amount of shallow clouds. Therefore, this study suggests that the sensitivity of CSA to horizontal grid resolution is not primarily due to the corresponding decrease in shallow clouds. Instead, it is found that turbulent mixing and dissipation at small scales regulate the amplitude of humidity perturbations introduced by convection in the free troposphere: the greater the dissipation at small scales, the greater the size and the strength of humidity perturbations in the free troposphere that can destabilize the RCE state.

The Greenland Ice Sheet discharges ice to the ocean through hundreds of outlet glaciers. Recent acceleration of Greenland outlet glaciers has been linked to both oceanic and atmospheric drivers. Here, we leverage temporally dense observations, regional climate model output, and newly developed time series analysis tools to assess the most important forcings causing ice flow variability at one of the largest Greenland outlet glaciers, Helheim Glacier, from 2009 to 2017. We find that ice speed correlates most strongly with catchment-integrated runoff at seasonal to interannual scales, while multi-annual flow variability correlates most strongly with multi-annual terminus variability. The multiple relevant time scales and the influence of subglacial topography on Helheim Glacier’s dynamics highlight different regimes that can inform modeling and forecasting of its future. Notably, our results suggest that the recent terminus history observed at Helheim is a response to, rather than the cause of, upstream changes.

Mantle convection is driven by the transport of heat from a planetary interior. This heat may come from the internal energy of the mantle or may come from the core beneath and in general there will be contributions from both. Past investigations of mixed-mode heating have revealed unusual behavior that confounds our intuition based on boundary layer theory applied to end-member cases. In particular, increased internal heating can cause a decrease in convective velocity despite an increase in surface heat flow. We investigate this behavior using numerical experiments and develop a scaling for velocity in the mixed-heating case. We identify a planform transition that impacts both heat flux and convective velocities. More significantly, we demonstrate that increased internal heating leads not only to a decrease in internal velocities but also a decrease in the velocity of the upper thermal boundary layer (a model analog of the Earth’s lithosphere). This behavior is connected to boundary layer interactions and is independent of any partic- ular rheological assumptions. In simulations with a temperature-dependent viscosity and a finite yield stress, increased internal heating does not cause an absolute decrease in surface velocity but does cause a decrease in sur- face velocity relative to the purely bottom or internally heated cases as well as a transition to rigid-lid behavior at high heating rates. The differences between a mixed system and end-member cases have implications for under- standing the connection between plate tectonics and mantle convection and for planetary thermal history modeling.

Preparedness is important for reducing potential losses from various disasters. There are limited studies that investigated the concrete reasons for not adopting a specific preparedness action. This paper fills such a gap using representative national survey data from China. Seven disaster preparedness actions, namely “preparing food and water at home,” “pay attention to disaster-related information,” “making emergency plans,” “being aware of nearest shelters,” “being aware of building code,” “participating in exercise or drills” and “being a volunteer for emergencies” are used as the measure of preparedness behaviors. Overall, the public has adopted more material-related preparedness actions, equipped with fewer awareness activities, and had the least community participation-related preparedness behaviors. The primary reasons for not adopting these actions are “not aware,” “don’t know where to buy or where to reach,” and “the action is not useful, there is no necessary,” while “costly,” “need special knowledge,” “don’t have time,” “need collaboration with others,” “energy-consuming” and “not my responsibility” are the less chose reasons. Besides, trust in government, relocation due to disasters, living in urban areas, and a higher degree of socioeconomic status are positively correlated with higher probabilities of adopting all the seven preparedness activities. These findings highlight the importance of community outreach from emergency management professionals to increase the public’s awareness of preparing for potential disasters. It is necessary to let the general public know the existence of these preparedness actions, and these actions can reduce losses.

AbstractAmong the photosynthetic powerhouses of aquatic ecosystems, microalgae are now the most promising source of sustainable and bioactive compounds with massive potential in the functional food category. Unicellular cell plants differing the synthesis of various substances, including proteins, lipids, carbohydrates and pigmented substances, which are important to their living and contribute to the workout of human health. Carotenoids and polyunsaturated fatty acids (PUFAs) present in a wealth of compounds have been the most attractive compounds due to their antioxidative and anti-inflammatory properties, which may be beneficial in alleviating oxidative stress and chronic inflammation. Spirulina and chlorella are two of the most consumable microalgae. They have been developed commercially as nutraceuticals because they offer a useful nutrient profile that includes essential amino acids, vitamins, and minerals needed to maintain human health. Because of its diverse bioactivity, microalgae can be used to create functional foods that target particular health issues like metabolic disorders and cardiovascular diseases. Because microalgae can be grown on non-arable land with little freshwater requirements, they do not compete with traditional agriculture, which further justifies their integration into the food industry. Furthermore, the heterotrophic cultivation of microalgae techniques that depend on sources of organic carbon for growth offers a chance to raise the yield of bioactive compounds and possibly lower production costs. This strategy aligns with the biorefinery concept, which maximizes resource utilization and economic viability by using microalgae as a biotechnological platform to produce high-value nutraceuticals and biofuels simultaneously. Only a few microalgal compounds have been successfully commercialized, and most studies on them are still preclinical. However, continued research and technological developments in the processing and cultivation of microalgae are opening the door to a broader range of uses in functional foods.

An intense tropical cyclone, Typhoon Jebi, landed the central part of Japan in September 2018 and caused severe damages due to strong winds. Typhoon Jebi obtained the lifetime minimum central pressure of 915 hPa and took a track very similar to past disastrous typhoons: Typhoon Nancy (1961) and Muroto Typhoon (1934). In Osaka City, the 1st, 2nd, and 3rd highest record of instantaneous wind speeds are 60.0 m/s in September 1934, 50.6 m/s in September 1961, and 47.4 m/s in September 2018, respectively, suggesting that a typhoon has been the most threatening windstorm in the area. Buildings and structures in urban areas are known to affect significantly the magnitude of wind gustiness. Because of the growing urbanization globally, quantification of turbulent winds in densely-built, urban districts is important to understand the underlying risks of wind damages. We investigate the influences of densely built urban environments on the occurrence of wind gusts in urban districts of Osaka and Kyoto City during the landfall of Typhoon Jebi by merging mesoscale meteorological and building-resolving large-eddy simulations (LES). By explicitly representing realistic buildings and structures in LES, this study examines complex/complicated characteristics of winds within the densely built urban environment. With the successful reproduction of the track and intensity of the typhoon in meteorological simulations, the simulated winds at the boundary-layer top of the LES model are used to quantify the wind gusts in the urban district. The maximum wind gust in the analysis area of Osaka is around 60-70 m/s, which is comparable to the wind speed at the height of about 300 m. Such wind gusts are generated by instantaneous downward momentum transfer in areas of a cluster of buildings with variable heights. Instantaneous wind gusts are further examined in terms of building density and are found to be strongest when the building packing density is moderate. The results suggest that the risks of wind damages would be maximized in urban districts where the building height is inhomogeneous and the packing density is moderate.

Global river models are crucial for simulating and forecasting floods, especially in regions lacking dedicated flood forecasting systems. Reservoir operations significantly affect flow simulations, impacting forecast accuracy. In this study, we improved a storage-outflow-type global reservoir operation scheme of the global river hydrodynamics model CaMa-Flood, which calculates reservoir outflow based on reservoir storage. First, a non-linear storage-outflow function using convex and concave curves was implemented to enhance flood control and reduce the number of required parameters. Second, a gradual transition in the storage-outflow function was proposed to avoid simulated outflow instability. Third, the outflow during the water-use phase was recalibrated to reflect water availability in dry periods, rather than using annual mean discharge. A case study involving 85 dams in Mainland Southeast Asia was conducted to evaluate the efficacy of the three key modifications by comparing the proposed reservoir operation scheme against three degraded schemes. Using a linear storage-outflow function caused 43% of the 61 reservoirs with a flood control capacity greater than 100 million cubic meters (MCM) to overutilize their flood control capacity during the non-flood water-excess phase. The proposed non-linear function reduced the number of such reservoirs to 27%. In addition, the gradual transition of the storage-outflow function eliminated unrealistic outflow oscillation. Furthermore, parameter estimation for water-use outflow based on reservoir water-use capacity and dry period river discharge enabled better utilization of reservoir capacity during dry seasons. Overall, the proposed reservoir operation scheme holds promise for enhancing the accuracy of global flood simulation within global river models.

A fundamental quantity in tropical dynamics is the ‘convective mass flux’, which measures the upwards mass flux in tropical convection. Changes in convective mass flux under warming are an important, and uncertain, aspect of climate change. Here we build off recent work linking changes in mass flux to the clear-sky energy budget to show that convective mass fluxes decrease along isotherms at around 3-5 % K-1 under warming. We show that this constraint holds throughout the free-troposphere and across a hierarchy of models; from idealized radiative-convective equilibrium simulations to CMIP6 models. This decrease in convective mass flux with warming is driven by a stabilization of the lapse rate and can be captured with a simple analytical model. We also revisit previous work by Held and Soden (2006), who proposed a scaling for changes in the convective mass flux at cloud-base with warming. We show that the Held and Soden scaling does not capture inter-model spread in cloud-base mass flux changes under warming in cloud-resolving models. Altogether, this work provides a quantitative constraint on changes in convective mass flux throughout the troposphere which can be derived from first principles, and which is verified across a hierarchy of models.