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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Influence of African Easterly Wave Suppression on Atlantic Tropical Cyclone Activity in a Convection-Permitting Model

African easterly waves (AEWs) are strongly linked to Atlantic tropical cyclones (TCs) on the synoptic timescale by serving as seedling disturbances for TC genesis. However, it is unclear whether climatological TC frequency is limited by AEWs. We investigated the impact of suppressing AEWs using a 3-member ensemble of convection-permitting regional model simulations, in which AEWs were either retained or removed through the lateral boundary conditions. Suppressing AEWs did not substantially change seasonal TC number, but did influence TC intensity, genesis time and location. Suppressing AEWs produced stronger TCs, shifted peak TC genesis from September to August, and reduced (increased) TC genesis in the eastern Atlantic (Gulf of Mexico). Without AEWs, TCs generated under more favorable large-scale atmospheric conditions. Furthermore, these results indicate that AEWs may not be reliable predictors of basin-wide seasonal TC frequency. However, simulations provide evidence that AEWs could influence the large-scale environment that is important for TCs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Aerosol Indirect Effects on Water Vapor in the UTLS of Typhoon Saomai (2006)

The evolution of landfalling Typhoon Saomai (2006) is simulated using the Weather Research and Forecasting model with spectral bin microphysics scheme, showing tropical cyclone (TC) could vertically transport water vapor from troposphere to upper troposphere and lower stratosphere (UTLS). Three aerosol sensitivity experiments are conducted to explore the indirect effects of aerosol served as cloud condensation nuclei (CCN) on overshooting convection (OTC) and water vapor content in UTLS, namely MAR (maritime), MIX (semi‐continental) and CON (continental). Results revealed that CON simulation with high initial aerosol concentration showing invigorated convection at the periphery of the TC, which interfered with the reformation of TC eyewall, leading to TC weakening finally. In addition, CON simulated the least water content in UTLS through suppressing the number of convection overshooting the tropopause level. Most overshooting events take place during TC developing stage in the eyewall region before landfall. Higher levels of CCN concentration could lead to decreased number of OTC in TC, consistently reduced the water vapor content in UTLS. CON and MIX experiments simulated respectively 21.9% (16.2%) and 9.96% (1.5%) less OTC (water vapor content in UTLS) than MAR simulation. Further, water vapor content in UTLS is affected by the interaction of OTC and ice‐phase microphysics. The interesting point is that the CCN sensitivity experiments show that water vapor content in UTLS of a TC is sensitive to the CCN concentration in the boundary layer.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Investigation of the Sensitivity of Tropical Cyclogenesis to Aerosol Intervention

Abstract As risks from tropical cyclones (TCs) are fueled by climate change escalation, there is an urgent need for transformational solutions to complement traditional approaches. Seeding TCs using aerosols can be a promising method to reduce cyclone intensity, supported by theoretical understanding of the microphysical effects of aerosols on TC clouds. The ideal time to intervene effectively in TCs is likely during their initial stage, before TC wind speeds reach their peak. However, studies exploring potential aerosol effects on TC formation remain scarce. This study investigates how a TC embryo responds to the addition of aerosols of varying sizes using the Weather Research & Forecasting (WRF) model coupled with a spectral‐bin microphysics model. We found that aerosols of different sizes and concentrations distinctively affect the pre‐TC vortex's microstructure and dynamics. Fine and ultrafine aerosols enhance the latent heat of condensation, freezing, deposition, and riming, initially intensifying the vortex. However, this results in enhancement of the cold pool, thereby reducing inflow and surface fluxes, subsequently weakening the vortex. Coarse aerosols produce the opposite effect to that of fine and ultrafine aerosols. Coarse aerosols lead to a slower initial acceleration owing to enhanced warm rain. However, the resulting weaker cold pool is insufficient to effectively reduce the strength of the vortex at the later stage. This study provides critical insights into how aerosols of varying sizes and concentrations modulate the energy cascade and impact the evolution of a TC embryo, laying the groundwork for further research on TC risk management through aerosol intervention.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

The Role of Tropical Cyclone—Ocean Interactions in Future Changes in Hurricane Katrina

Tropical cyclone (TC) intensity and precipitation are projected to increase in the future. However, some projections are based on atmosphere‐only models in which sea surface temperatures are prescribed, whereas projections based on global atmosphere‐ocean coupled models can be subject to long‐term ocean biases. We investigated the role of TC‐ocean interactions in future changes in TC intensity and precipitation in Hurricane Katrina. We performed four‐member ensembles using convection‐permitting atmosphere‐only and atmosphere‐ocean regional models for the historical climate and four future climates. We found that although future TC intensity and precipitation increased regardless of ocean coupling, ocean coupling dampened the future minimum sea‐level pressure decrease by half and amplified future precipitation scaling. Compared to future changes in upper‐ocean temperature, changes in salinity contributed little to future changes in TC intensity. This study highlights the importance of considering TC‐ocean interactions to reduce uncertainty in the magnitude of future TC intensity and precipitation projections.

climate change↗
DOE OSTI2024

Ocean internal tides suppress tropical cyclones in the South China Sea

Abstract Tropical Cyclones (TCs) are devastating natural disasters. Analyzing four decades of global TC data, here we find that among all global TC-active basins, the South China Sea (SCS) stands out as particularly difficult ocean for TCs to intensify, despite favorable atmosphere and ocean conditions. Over the SCS, TC intensification rate and its probability for a rapid intensification (intensification by ≥ 15.4 m s −1 day −1 ) are only 1/2 and 1/3, respectively, of those for the rest of the world ocean. Originating from complex interplays between astronomic tides and the SCS topography, gigantic ocean internal tides interact with TC-generated oceanic near-inertial waves and induce a strong ocean cooling effect, suppressing the TC intensification. Inclusion of this interaction between internal tides and TC in operational weather prediction systems is expected to improve forecast of TC intensity in the SCS and in other regions where strong internal tides are present.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

TROPHY: A Topologically Robust Physics-Informed Tracking Framework for Tropical Cyclones

Tropical cyclones (TCs) are among the most destructive weather systems. Realistically and efficiently detecting and tracking TCs are critical for assessing their impacts and risks. In particular, the eye is a signature feature of a mature TC. Therefore, knowing the eyes’ locations and movements is crucial for both operational weather forecasts and climate risk assessments. Recently, a multilevel robustness framework has been introduced to study the critical points of time-varying vector fields. The framework quantifies the robustness (i.e., structural stability) of critical points across varying neighborhoods. By relating the multilevel robustness with critical point tracking, the framework has demonstrated its potential in cyclone tracking. An advantage is that it identifies cyclonic features using only 2D wind vector fields, which is encouraging as most tracking algorithms require multiple dynamic and thermodynamic variables at different altitudes. A disadvantage is that the framework does not scale well computationally for datasets containing a large number of cyclones. Herein this paper introduces a topologically robust physics-informed tracking framework (TROPHY) for TC tracking. The main idea is to integrate physical knowledge of TC to drastically improve the computational efficiency of multilevel robustness framework for large-scale climate datasets. First, during preprocessing, we propose a physics-informed feature selection strategy to filter 90% of critical points that are short-lived and have low stability, thus preserving good candidates for TC tracking. Second, during in-processing, we impose constraints during the multilevel robustness computation to focus only on physics-informed neighborhoods of TCs. We apply TROPHY to 30 years of 2D wind fields from reanalysis data in ERA5 and generate a number of TC tracks. In comparison with the observed tracks, we demonstrate that TROPHY can capture TC characteristics (e.g., frequency, intensity, duration, latitudes with maximum intensity, and genesis) that are comparable to and sometimes even better than a well-validated TC tracking algorithm that requires multiple dynamic and thermodynamic scalar fields.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Effect of sucrose on technetium and rhenium retention during vitrification of low-activity wastes

Sucrose (C 12 H 22 O 11 ) has been used in low-activity waste (LAW) melter feeds containing large fractions of nitrates, nitrites, or both because it facilitates foam suppression and denitration. This study focused on the effect of sucrose in LAW feeds on technetium (Tc) and rhenium (Re) retention. The amount of sucrose added in feeds was varied to differentiate the carbon-to-nitrogen mole ratio (C/N ratio). The results show that larger sucrose addition (higher C/N ratio) enhances Tc and Re retention. Reducing conditions induced by sucrose decomposition and early chemical reactions between sucrose and NaNO 3 /NaNO 2 are expected to increase Tc and Re retention. However, high sucrose addition decreased sulfur (S) retention slightly because sodium sulfate decomposes in reducing conditions at lower temperature. This early sulfate decomposition can affect Tc and Re retention partly because these species can be soluble in sulfate phases. This correlation indicates that the decrease of sulfate phases in the glass by early decomposition can reduce the solubility of Tc and Re in the sulfate phases, which may increase Tc and Re retention in the glass. In addition, continuous gas evolution and vigorous foaming at the foaming temperature range of 700–900°C may influence Tc and Re retention process interrupting retention or facilitating volatilization.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Deep Learning Experiments for Tropical Cyclone Intensity Forecasts

Reducing tropical cyclone (TC) intensity forecast errors is a challenging task that has interested the operational forecasting and research community for decades. To address this, we developed a deep learning (DL)-based multilayer perceptron (MLP) TC intensity prediction model. The model was trained using the global Statistical Hurricane Intensity Prediction Scheme (SHIPS) predictors to forecast the change in TC maximum wind speed for the Atlantic basin. In the first experiment, a 24-h forecast period was considered. To overcome sample size limitations, we adopted a leave one year out (LOYO) testing scheme, where a model is trained using data from all years except one and then evaluated on the year that is left out. When tested on 2010–18 operational data using the LOYO scheme, the MLP outperformed other statistical–dynamical models by 9%–20%. Additional independent tests in 2019 and 2020 were conducted to simulate real-time operational forecasts, where the MLP model again outperformed the statistical–dynamical models by 5%–22% and achieved comparable results as HWFI. The MLP model also correctly predicted more rapid intensification events than all the four operational TC intensity models compared. In the second experiment, we developed a lightweight MLP for 6-h intensity predictions. When coupled with a synthetic TC track model, the lightweight MLP generated realistic TC intensity distribution in the Atlantic basin. Therefore, the MLP-based approach has the potential to improve operational TC intensity forecasts, and will also be a viable option for generating synthetic TCs for climate studies.

58 GEOSCIENCES↗
NASA NTRS2003

Assessing Impacts of Global Warming on Tropical Cyclone Tracks

A new approach is proposed to assess the possible impacts of the global climate change on tropical cyclone (TC) tracks in the western North Pacific (WNP) basin. The idea is based on the premise that the future change of TC track characteristics is primarily determined by changes in large-scale environmental steering flows. It is demonstrated that the main characteristics of the current climatology of TC tracks can be derived from the climatological mean velocity field of TC motion by using a trajectory model. The climatological mean velocity of TC motion, which is composed of the large-scale steering and beta drift, is determined on each grid of the basin. The mean beta drift is estimated from the best track data, and the mean large-scale steering flow is computed from the NCEP/NCAR reanalysis for the current climate state. The derived mean beta drift agrees well with the results of previous observational and numerical studies in terms of its direction and magnitude. The outputs of experiments A2 and B2 of the Geophysical Fluid Dynamics Laboratory (GFDL) R30 climate model suggest that the subtropical high will be persistently weak over the western part of the WNP or shift eastward during July-September in response to the future climate change. By assuming that the mean beta drift in the future climate state is unchanged, the change in the general circulation by 2059 will decrease the TC activities in the WNP, but favor a northward shift of typical TC tracks. As a result, the storm activities in the South China Sea will decrease by about 12%, while the Japan region will experience an increase of TCs by 12-15%. During the period of 2000-2029, the tropical storms that affect the China region will increase by 5-6%, but return to the current level during 2030-2059. It is also suggested that, during the period of 2030-2059 tropical storms will more frequently affect Japan and the middle latitude region of China given that the formation locations remain the same as in the current climate state.

Wu, Li-Guang↗
NASA NTRS1997

Local homogeneity of cell cycle length in developing mouse cortex

We have measured the amount of variation in the length of the cell cycle for cells in the pseudostratified ventricular epithelium (PVE) of the developing cortex of mice on embryonic day 14. Our measurements were made in three cortical regions (i.e., the neocortex, archicortex, and periarchicortex) using three different methods: the cumulative labeling method (CLM), the percent labeled mitoses (PLM) method, and a comparison of the time needed for the PLM to ascend from 0 to 100% with the time needed for the PLM to descend from 100 to 0%. These 3 different techniques provide different perspectives on the cytokinetic parameters. Theoretically, CLM gives an estimate for a maximum value of the total length of the cell cycle (TC), whereas PLM gives an estimate of a minimum value of TC. The difference between these two estimates indicates that the range for TC is +/-1% of the mean TC for periarchicortex, +/-7% for neocortex, and +/-8% for archicortex. This was confirmed by a lengthening of the PLM descent time in comparison with its ascent time. The sharpness of the transitions and the flatness of the plateau of the PLM curves indicate that 99% of the proliferating cells are within this narrow estimated range for TC; hence, only approximately 1% deviate outside of a relatively restricted range from the average TC of the population. In the context of the possible existence within the cortical PVE of two populations with markedly dissimilar cell cycle kinetics from the mean, one such population must comprise approximately 99% of the total population, and the other, if it exists, is only approximately 1% of the total. This seems to be true for all three cortical regions. The narrow range of TC indicates a homogeneity in the cell cycle length for proliferating cells in three different cortical regions, despite the fact that progenitor cells of different lineages may be present. It further predicts the existence of almost synchronous interkinetic nuclear movements of the proliferating cells in the ventricular zone during early development of the cerebral cortex.

Non-NASA Center↗
NASA NTRS2006

Techniques for Connecting Superconducting Thin Films

Several improved techniques for connecting superconducting thin films on substrates have been developed. The techniques afford some versatility for tailoring the electronic and mechanical characteristics of junctions between superconductors in experimental electronic devices. The techniques are particularly useful for making superconducting or alternatively normally conductive junctions (e.g., Josephson junctions) between patterned superconducting thin films in order to exploit electron quantum-tunneling effects. The techniques are applicable to both low-Tc and high-Tc superconductors (where Tc represents the superconducting- transition temperature of a given material), offering different advantages for each. Most low-Tc superconductors are metallic, and heretofore, connections among them have been made by spot welding. Most high-Tc superconductors are nonmetallic and cannot be spot welded. These techniques offer alternatives to spot welding of most low-Tc superconductors and additional solutions to problems of connecting most high-Tc superconductors.

Mester, John↗
NASA NTRS2014

Effects of Dopant on Depoling Temperature in Modified BiScO3 - PbTiO3

In recent years there has been a renewed interest for high temperature piezoelectrics for both terrestrial and aerospace applications. These applications are limited in part by the operating temperature, which is usually taken as one half of the Curie temperature (Tc), and is 200C for one of the most widely used commercial piezoelectrics, Pb(Zr,Ti)O3 (PZT). In an effort to increase Tc, subsequent research into high temperature Bi(BB)O3 PbTiO3 piezoelectrics led to the discovery of the morphotropic phase boundary (MPB) in the high-Tc BiScO3 PbTiO3 (BS-PT) system with a Tc of 460C and a d33 of 460 pmV. The Tc marks the ferroelectric to paraelectric phase transformation and while, in general, a phase transformation leads to thermal depoling in piezoelectrics with low or moderate Tcs, for high Tc piezoelectrics thermally assisted dipole rotation can lead to randomization of domains at temperatures below Tc. It becomes necessary to determine the depoling temperature (Td) which dictates the actual working temperature range. By doping for Sc and Ti the Td can be shifted while maintaining similar electromechanical properties as a function of temperature. The effect of this B-site doping on depoling temperature has been explored through the characterization of microstructure and weakhigh field measurements.

Actuator↗
DOE OSTI2020

Materials Data on TlZn2Tc by Materials Project

TcZn2Tl crystallizes in the cubic F-43m space group. The structure is three-dimensional. Tc is bonded in a distorted body-centered cubic geometry to ten Zn and four equivalent Tl atoms. There are four shorter (2.81 Å) and six longer (3.24 Å) Tc–Zn bond lengths. All Tc–Tl bond lengths are 2.81 Å. There are two inequivalent Zn sites. In the first Zn site, Zn is bonded in a 8-coordinate geometry to six equivalent Tc, four equivalent Zn, and four equivalent Tl atoms. All Zn–Zn bond lengths are 2.81 Å. All Zn–Tl bond lengths are 2.81 Å. In the second Zn site, Zn is bonded in a 8-coordinate geometry to four equivalent Tc and four equivalent Zn atoms. Tl is bonded in a distorted body-centered cubic geometry to four equivalent Tc and four equivalent Zn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Rh by Materials Project

Tc3Rh is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Tc1- sites. In the first Tc1- site, Tc1- is bonded to eight equivalent Tc1- and four equivalent Rh3+ atoms to form distorted TcTc8Rh4 cuboctahedra that share corners with four equivalent RhTc12 cuboctahedra, corners with fourteen equivalent TcTc8Rh4 cuboctahedra, edges with six equivalent RhTc12 cuboctahedra, edges with twelve equivalent TcTc8Rh4 cuboctahedra, faces with four equivalent RhTc12 cuboctahedra, and faces with sixteen TcTc8Rh4 cuboctahedra. There are six shorter (2.67 Å) and two longer (2.86 Å) Tc–Tc bond lengths. There are two shorter (2.74 Å) and two longer (2.76 Å) Tc–Rh bond lengths. In the second Tc1- site, Tc1- is bonded to eight equivalent Tc1- and four equivalent Rh3+ atoms to form distorted TcTc8Rh4 cuboctahedra that share corners with four equivalent RhTc12 cuboctahedra, corners with fourteen TcTc8Rh4 cuboctahedra, edges with six equivalent RhTc12 cuboctahedra, edges with twelve equivalent TcTc8Rh4 cuboctahedra, faces with four equivalent RhTc12 cuboctahedra, and faces with sixteen TcTc8Rh4 cuboctahedra. There are six shorter (2.67 Å) and two longer (2.86 Å) Tc–Tc bond lengths. There are two shorter (2.74 Å) and two longer (2.76 Å) Tc–Rh bond lengths. Rh3+ is bonded to twelve Tc1- atoms to form RhTc12 cuboctahedra that share corners with six equivalent RhTc12 cuboctahedra, corners with twelve TcTc8Rh4 cuboctahedra, edges with eighteen TcTc8Rh4 cuboctahedra, faces with eight equivalent RhTc12 cuboctahedra, and faces with twelve TcTc8Rh4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tc3Os by Materials Project

Tc3Os is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Tc+2.33- is bonded to eight equivalent Tc+2.33- and four equivalent Os7+ atoms to form distorted TcTc8Os4 cuboctahedra that share corners with four equivalent OsTc12 cuboctahedra, corners with fourteen equivalent TcTc8Os4 cuboctahedra, edges with six equivalent OsTc12 cuboctahedra, edges with twelve equivalent TcTc8Os4 cuboctahedra, faces with four equivalent OsTc12 cuboctahedra, and faces with sixteen equivalent TcTc8Os4 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.71–2.77 Å. There are two shorter (2.71 Å) and two longer (2.77 Å) Tc–Os bond lengths. Os7+ is bonded to twelve equivalent Tc+2.33- atoms to form OsTc12 cuboctahedra that share corners with six equivalent OsTc12 cuboctahedra, corners with twelve equivalent TcTc8Os4 cuboctahedra, edges with eighteen equivalent TcTc8Os4 cuboctahedra, faces with eight equivalent OsTc12 cuboctahedra, and faces with twelve equivalent TcTc8Os4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoTc3 by Materials Project

Tc3Co is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Tc+0.67- is bonded to eight equivalent Tc+0.67- and four equivalent Co2+ atoms to form TcCo4Tc8 cuboctahedra that share corners with four equivalent CoTc12 cuboctahedra, corners with fourteen equivalent TcCo4Tc8 cuboctahedra, edges with six equivalent CoTc12 cuboctahedra, edges with twelve equivalent TcCo4Tc8 cuboctahedra, faces with four equivalent CoTc12 cuboctahedra, and faces with sixteen equivalent TcCo4Tc8 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.66–2.70 Å. There are two shorter (2.65 Å) and two longer (2.69 Å) Tc–Co bond lengths. Co2+ is bonded to twelve equivalent Tc+0.67- atoms to form CoTc12 cuboctahedra that share corners with six equivalent CoTc12 cuboctahedra, corners with twelve equivalent TcCo4Tc8 cuboctahedra, edges with eighteen equivalent TcCo4Tc8 cuboctahedra, faces with eight equivalent CoTc12 cuboctahedra, and faces with twelve equivalent TcCo4Tc8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiTc3 by Materials Project

Tc3Si is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Tc+1.33- is bonded to eight equivalent Tc+1.33- and four equivalent Si4+ atoms to form TcSi4Tc8 cuboctahedra that share corners with four equivalent SiTc12 cuboctahedra, corners with fourteen equivalent TcSi4Tc8 cuboctahedra, edges with six equivalent SiTc12 cuboctahedra, edges with twelve equivalent TcSi4Tc8 cuboctahedra, faces with four equivalent SiTc12 cuboctahedra, and faces with sixteen equivalent TcSi4Tc8 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.64–2.78 Å. There are two shorter (2.68 Å) and two longer (2.71 Å) Tc–Si bond lengths. Si4+ is bonded to twelve equivalent Tc+1.33- atoms to form SiTc12 cuboctahedra that share corners with six equivalent SiTc12 cuboctahedra, corners with twelve equivalent TcSi4Tc8 cuboctahedra, edges with eighteen equivalent TcSi4Tc8 cuboctahedra, faces with eight equivalent SiTc12 cuboctahedra, and faces with twelve equivalent TcSi4Tc8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ReTc3 by Materials Project

ReTc3 is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Re7+ is bonded to twelve equivalent Tc+2.33- atoms to form ReTc12 cuboctahedra that share corners with six equivalent ReTc12 cuboctahedra, corners with twelve equivalent TcRe4Tc8 cuboctahedra, edges with eighteen equivalent TcRe4Tc8 cuboctahedra, faces with eight equivalent ReTc12 cuboctahedra, and faces with twelve equivalent TcRe4Tc8 cuboctahedra. There are six shorter (2.73 Å) and six longer (2.76 Å) Re–Tc bond lengths. Tc+2.33- is bonded to four equivalent Re7+ and eight equivalent Tc+2.33- atoms to form TcRe4Tc8 cuboctahedra that share corners with four equivalent ReTc12 cuboctahedra, corners with fourteen equivalent TcRe4Tc8 cuboctahedra, edges with six equivalent ReTc12 cuboctahedra, edges with twelve equivalent TcRe4Tc8 cuboctahedra, faces with four equivalent ReTc12 cuboctahedra, and faces with sixteen equivalent TcRe4Tc8 cuboctahedra. There are a spread of Tc–Tc bond distances ranging from 2.74–2.78 Å.

36 MATERIALS SCIENCE↗