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Wei, J.

Publications and source records attributed to Wei, J..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Online Visualization and Analysis of NASA Satellite-Based Global and Regional Precipitation Products Through Giovanni

Observational data are essential for Earth science research and applications. Traditional ground-based observations suffer from many limitations (e.g. costly deployment). As a result, data are often sparse and inconsistent, especially over vast oceans that cover nearly 71% of the Earth's surface, and for remote continents. Precipitation is one of the important physical parameters in the global hydrological cycle and other disciplines. Each year, severe floods and droughts happen in different parts of the world and cause significant damage to the economy, as well as human casualties (e.g. Hurricane Katrina, the Dust Bowl). Accurate and timely precipitation observations and predictions are important for research and applications. However, ground-based precipitation observations are quite limited, especially in remote and mountainous regions. Since the satellite era began, satellite-based precipitation products have gained popularity in Earth science research, applications, and education. Accessing satellite products can be a daunting task to many users, especially those who do not have prior experience or knowledge with satellite data. Recognizing this obstacle, the NASA Goddard Earth Sciences and Data and Information Services Center (GES DISC), home to data archives for the NASA-JAXA Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM), has developed data services including an online visualization and analysis tool, Giovanni (the Geospatial Interactive Online Visualization ANd aNalysis Infrastructure), enabling users at different levels to access, explore, and evaluate NASA satellite-based data products without downloading either data and software, or requiring coding. Currently, global and regional precipitation products from different satellite missions (TRMM, GPM) and projects (e.g. the Modern Era Retrospective-analysis for Research and Applications Version 2 (MERRA-2), and the North American Land Data Assimilation System (NLDAS)), ranging from half-hourly to monthly temporal resolution, are available in Giovanni. There are over 1900 variables in Giovanni, covering measurements in precipitation, hydrology, atmospheric dynamics, atmospheric chemistry, etc. In this poster presentation, we will provide a live demonstration of Giovanni and its latest development, including precipitation-related variables, and new basic features such as polar projections. The session will also provide a Q&A opportunity for attendees.

Giovanni↗
NASA NTRS2018

Challenges in Development of Online Visualization and Analysis Tools for Satellite Data

Over the years, various online visualization and analysis tools have been developed to facilitate satellite data access and help scientific users around the world to conduct research and develop applications (e.g., data product evaluation, what-if questions, etc.). For those who are new to satellite data products, using them can be a daunting task due to many obstacles in data processing such as data formats, complex data structures, special software packages, unfamiliar terminology, etc., especially when one is not sure whether a dataset is suitable for his/er research project. Even for experienced users, developing software for data processing and analysis can be a costly and time-consuming task. Online visualization tools can overcome many of these difficulties and allow users to focus on scientific questions. For example, Giovanni (the Geospatial Interactive Online Visualization and Analysis Infrastructure, https://giovanni.gsfc.nasa.gov), developed by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC), allows access over 1900 satellite and model variables in 82 measurement groups of 8 disciplines without downloading data and software. Main features include basic functions for data analysis and visualization, data provenance, output data in different formats (ASCII, NetCDF, GeoTIFF), and more. Over the years, ~1700 peer-reviewed publications in different disciplines have been benefited from Giovanni in research activities (e.g. initial investigation, what-if questions, product evaluation). Despite the success of online visualization and analysis tools, challenges and new opportunities still exist and more can be done with new requirements and technology. Examples are: a) how to increase the efficiency of dataset search by enhancing intuitive aspects; b) how to facilitate interdisciplinary research; c) how to provide data quality information; d) how to engage users to participate in data quality assessment; and more. NASA Earth Observing System Data and Information System (EOSDIS) satellite-based data products are processed at various levels ranging from Level 0 to Level 4. While most users use data products at higher levels (Level-3 and 4), products at lower levels are still important for case studies, algorithm development, ground validation, etc. In this presentation, we will use Giovanni as an example to present and discuss challenges and near-future opportunities for satellite data online visualization and analysis tools.

Liu, Zhong↗
NASA NTRS2018

Investigating Hydrometeorological Conditions Associated with Increasing Dust Events in Southwestern United States

A recent study (Tong et al. 2017) shows a rapid intensification of dust storm activity over the southwestern United States in the past decades. For example, the frequency of windblown dust storms has increased 240 percent from 1990s to 2000s. Increasing dust storms can worsen air quality in the region. The study also finds that the intensification of dust events has a close connection with a fast-rising infectious disease (valley fever) caused by inhaling soil-dwelling fungi (Coccidioides immitis and C. posadasii) in the southwestern United States. Hydrometeorological conditions play an important role in dust storm activity, including winds, precipitation, soil moisture, atmospheric boundary stability, land surface types, etc. In this presentation, we describe our preliminary results of linking the dust trends to variations of hydrometeorological conditions at regional and global scales, using a number of Earth observations, including products from NLDAS (North American Land Data Assimilation System), TRMM (Tropical Rainfall Measuring Mission), and MERRA (Modern Era Retrospective-analysis for Research and Applications) datasets, from NASA Goddard Earth Sciences (GES) Data and Information Services Center (DISC). The GES DISC, one of the 12 NASA data centers, is home to multidisciplinary data archives such as precipitation, hydrology, atmospheric chemistry, atmospheric dynamics, etc. We demonstrate that multidisciplinary datasets and services at GES DISC can be used for interdisciplinary investigation to understand the interactions of Earth system components from an observational perspective.

satellite↗
NASA NTRS2018

GPM, TRMM, and Other Global Precipitation Products and Services at NASA GES DISC

Precipitation is a key environmental variable. For example, in agriculture, precipitation, temperature, water (soil moisture), solar radiation, NDVI, etc., are key variables.Rainfed agriculture – major farming practices that rely on rainfall for water.Rainfed agriculture: >95% of farmed land (sub-Saharan Africa); 90% (Latin America); 75% (Near East and North Africa); 65% (East Asia); 60% (South Asia).Droughts and floods can cause severe crop loss. The Goddard Earth Sciences (GES) Data and Information Services Center (DISC), one of 12 NASA data centers, is located in Greenbelt, Maryland, USA. The NASA GES DISC is a major data archive center for global precipitation, water & energy cycles, atmospheric composition, and climate variability.

Liu, Z.↗
NASA NTRS2018

OMI/TROPOMI Data Support from GES DISC

The NASA GES DISC has been the official archive center for data from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura mission since 2004. In recent years, the GES DISC has been evolving and improving its data management and services in order to promote its data to be easily discovered and accessed, as well as to facilitate data "interoperability". This presentation will summarize metrics collected of OMI data usage and GES DISC data services. In order to support the recently released Sentinel-5P/TROPOMI data from ESA at the NASA GES DISC, a new End User License Agreement (EULA) has been implemented for users accessing these data from the GES DISC.

Johnson, J.↗
NASA NTRS2017

Access NASA Satellite Global Precipitation Data Visualization on YouTube

Since the satellite era began, NASA has collected a large volume of Earth science observations for research and applications around the world. The collected and archived satellite data at 12 NASA data centers can also be used for STEM education and activities such as disaster events, climate change, etc. However, accessing satellite data can be a daunting task for non-professional users such as teachers and students because of unfamiliarity of terminology, disciplines, data formats, data structures, computing resources, processing software, programming languages, etc. Over the years, many efforts including tools, training classes, and tutorials have been developed to improve satellite data access for users, but barriers still exist for non-professionals. In this presentation, we will present our latest activity that uses a very popular online video sharing Web site, YouTube (https://www.youtube.com/), for accessing visualizations of our global precipitation datasets at the NASA Goddard Earth Sciences (GES) Data and Information Services Center (DISC). With YouTube, users can access and visualize a large volume of satellite data without the necessity to learn new software or download data. The dataset in this activity is a one-month animation for the GPM (Global Precipitation Measurement) Integrated Multi-satellite Retrievals for GPM (IMERG). IMERG provides precipitation on a near-global (60 deg. N-S) coverage at half-hourly time interval, providing more details on precipitation processes and development compared to the 3-hourly TRMM (Tropical Rainfall Measuring Mission) Multisatellite Precipitation Analysis (TMPA, 3B42) product. When the retro-processing of IMERG during the TRMM era is finished in 2018, the entire video will contain more than 330,000 files and will last ~3.6 hours. Future plans include development of flyover videos for orbital data for an entire satellite mission or project. All videos, including the one-month animation, will be uploaded and available at the GES DISC site on YouTube (https://www.youtube.com/user/NASAGESDISC).

precipitation↗
NASA NTRS2017

Accessing Suomi NPP OMPS Products through the GES DISC Online Data Services

This presentation will provide an overview of the OMPS products available at the GES DISC archive, as well as demonstrate the various data services provided by the GES DISC. Since the TOMS, SBUV, and EOS Aura (OMI, MLS, HIRDLS) data products are also available from the GES DISC archive, these can be easily accessed and compared with the OMPS data.

OMPS↗
DOE OSTI2017

A magnetic topological semimetal Sr 1-y Mn 1-z Sb2 (y, z < 0.10)

Weyl (WSMs) evolve from Dirac semimetals in the presence of broken time-reversal symmetry (TRS) or space-inversion symmetry. The WSM phases in TaAs-class materials and photonic crystals are due to the loss of space-inversion symmetry. For TRS-breaking WSMs, despite numerous theoretical and experimental efforts, few examples have been reported. Here in this paper, we report a new type of magnetic semimetal Sr 1-y Mn 1-z Sb 2 (y, z < 0.1) with nearly massless relativistic fermion behaviour (m* = 0.04 - 0.05m 0 , where m 0 is the free-electron mass). This material exhibits a ferromagnetic order for 304 K < T < 565 K, but a canted antiferromagnetic order with a ferromagnetic component for T < 304 K. The combination of relativistic fermion behaviour and ferromagnetism in Sr 1-y Mn 1-z Sb2 offers a rare opportunity to investigate the interplay between relativistic fermions and spontaneous TRS breaking.

36 MATERIALS SCIENCE↗
DOE OSTI2016

π Berry phase and Zeeman splitting of Weyl semimetal TaP

Here, the recent breakthrough in the discovery of Weyl fermions in monopnictide semimetals provides opportunities to explore the exotic properties of relativistic fermions in condensed matter. The chiral anomaly-induced negative magnetoresistance and π Berry phase are two fundamental transport properties associated with the topological characteristics of Weyl semimetals. Since monopnictide semimetals are multiple-band systems, resolving clear Berry phase for each Fermi pocket remains a challenge. Here we report the determination of Berry phases of multiple Fermi pockets of Weyl semimetal TaP through high field quantum transport measurements. We show our TaP single crystal has the signatures of a Weyl state, including light effective quasiparticle masses, ultrahigh carrier mobility, as well as negative longitudinal magnetoresistance. Furthermore, we have generalized the Lifshitz-Kosevich formula for multiple-band Shubnikov-de Haas (SdH) oscillations and extracted the Berry phases of π for multiple Fermi pockets in TaP through the direct fits of the modified LK formula to the SdH oscillations. In high fields, we also probed signatures of Zeeman splitting, from which the Landé g-factor is extracted.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Edge multi-energy soft x-ray diagnostic in Experimental Advanced Superconducting Tokamak

A multi-energy soft x-ray (ME-SXR) diagnostic has been built for electron temperature profile in the edge plasma region in Experimental Advanced Superconducting Tokamak (EAST) after two rounds of campaigns. Originally, five preamplifiers were mounted inside the EAST vacuum vessel chamber attached to five vertically stacked compact diode arrays. A custom mechanical structure was designed to protect the detectors and electronics under constraints of the tangential field of view for plasma edge and the allocation of space. In the next experiment, the mechanical structure was redesigned with a barrel structure to absolutely isolate it from the vacuum vessel. Multiple shielding structures were mounted at the pinhole head to protect the metal foils from lithium coating. The pre-amplifiers were moved to the outside of the vacuum chamber to avoid introducing interference. Twisted copper cooling tube was embedded into the back-shell near the diode to limit the temperature of the preamplifiers and diode arrays during vacuum vessel baking when the temperature reached 150 °C. Electron temperature profiles were reconstructed from ME-SXR measurements using neural networks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Tuning the carrier concentration to improve the thermoelectric performance of CuInTe{sub 2} compound

The electronic and transport properties of CuInTe{sub 2} chalcopyrite are investigated using density functional calculations combined with Boltzmann theory. The band gap predicted from hybrid functional is 0.92 eV, which agrees well with experimental data and leads to relatively larger Seebeck coefficient compared with those of narrow-gap thermoelectric materials. By fine tuning the carrier concentration, the electrical conductivity and power factor of the system can be significantly optimized. Together with the inherent low thermal conductivity, the ZT values of CuInTe{sub 2} compound can be enhanced to as high as 1.72 at 850 K, which is obviously larger than those measured experimentally and suggests there is still room to improve the thermoelectric performance of this chalcopyrite compound.

36 MATERIALS SCIENCE↗
NASA NTRS2014

Giovanni-4: The Next Generation

This talk discusses the new aspects of Giovanni-4. Covered in the talk are new features in Giovanni-4, including shape fileservices, seasonal analysis services, the Omnibus Portal, navigation among variables, and comparison services.

analysis↗
DOE OSTI2014

Enhanced thermoelectric performance of a quintuple layer of Bi{sub 2}Te{sub 3}

The electronic structure of a quintuple layer (QL) of Bi{sub 2}Te{sub 3} is calculated using the first-principles pseudopotential method. It is found that the band gap of an isolated QL is considerably larger than that of bulk Bi{sub 2}Te{sub 3}. The electronic transport of the QL is, then, evaluated using the semiclassical Boltzmann theory within the relaxation time approximation. By fitting the energy surface from first-principles calculations, a suitable Morse potential is constructed and used to predicate the lattice thermal conductivity via equilibrium molecular dynamics simulations. By optimizing the carrier concentration of the system, the ZT of Bi{sub 2}Te{sub 3} QL can be enhanced to a relatively high value. Moreover, the ZT value exhibits strong temperature dependence and can reach as high as 2.0 at 800 K. This value can be further increased to 2.2 by the substitution of Bi atoms with Sb atoms, giving nominal formula of (Bi{sub 0.25}Sb{sub 0.75}){sub 2}Te{sub 3}. The significantly enhanced ZT value makes QL a very appealing candidate for thermoelectric applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Temperature dependence of the magnetostriction in polycrystalline PrFe{sub 1.9} and TbFe{sub 2} alloys: Experiment and theory

A remarkable magnetostriction λ{sub 111} as large as 6700 ppm was found at 70 K in PrFe{sub 1.9} alloy. This value is even larger than the theoretical maximum of 5600 ppm estimated by the Steven's equivalent operator method. The temperature dependence of λ{sub 111} for PrFe{sub 1.9} and TbFe{sub 2} alloys follows well with the single-ion theory rule, which yields giant estimated λ{sub 111} values of about 8000 and 4200 ppm for PrFe{sub 1.9} and TbFe{sub 2} alloys, respectively, at 0 K. The easy magnetization direction of PrFe{sub 1.9} changes from [111] to [100] as temperature decreases, which leads to the abnormal decrease of the magnetostriction λ. The rare earth sublattice moment increases sharply in PrFe{sub 1.9} alloy with decreasing temperature, resulting in the remarkably largest estimated value of λ{sub 111} at 0 K according to the single-ion theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗