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  • Other Sources  (2,155)
  • Meteorology and Climatology  (1,193)
  • Astrophysics  (962)
  • 2020-2024
  • 2015-2019  (2,155)
  • 1
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    Investigating Meteorological Conditions Associated with Valley Fever Outbreaks in Southwestern United States (2019)
    In:  Other Sources
    Details
    Publication Date: 2020-01-24
    Description: According to CDC, a sharp increase in reported Valley fever cases (Coccidioidomycosis) has been found between 2009 and 2012. Environmental conditions play an important role for Valley fever outbreaks. For example, dust storms can significantly increase the amount of the fungus Coccidioides in the air and associated strong winds can transport the fungus to other areas. In last years AGU session, we reported a preliminary study to investigate hydrometeorological conditions and their connection with dust storm activities in southwestern United States. We found wind is a major contributing factor for the seasonal variation of dust storm activities. Interannual variation of the regional hydrometeorological conditions are closely linked to the large-scale environment such as the Pacific Decadal Oscillation (PDO). Strong winds are linked with a number of weather events such cold front passages, thunderstorms that produce downbursts and strong winds, the Santa Ana winds, etc. In this presentation, we will report the results of our latest investigation on meteorological conditions associated with Valley fever outbreaks in southwestern United States, using NLDAS (North American Land Data Assimilation System), GPM (Global Precipitation Measurement), and MERRA-2 (Modern Era Retrospective-analysis for Research and Applications, Version 2) hourly datasets, from the NASA Goddard Earth Sciences (GES) Data and Information Services Center (DISC).
    Keywords: Meteorology and Climatology
    Type: GH44A-08 , GSFC-E-DAA-TN76501 , American Geophysical Union (AGU) Fall Meeting 2019; Dec 09, 2019 - Dec 13, 2019; San Francisco, CA; United States
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  • 2
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    What Caused the Record Floods of March 2019 Across the Middle East? (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-24
    Description: Atmospheric rivers (ARs) are responsible for some of the hydroclimatic extremes around the world. Their mechanisms and contribution to flooding in the Middle East are relatively poorly understood. This study shows that the record floods during March 2019 across the Middle East were caused by a powerful AR, originated from the North Atlantic Ocean. Iran, in particular, was substantially affected by the floods. The nearly 9000 km long AR propagated across North Africa and the Middle-East, and was fed by additional moisture from several other sources on its pathway. Simultaneous presence of a mid-latitude system and a subtropical jet facilitated the moisture supply. The AR, as passing over the Zagros Mountains, produced record rainfall induced by the orographic forcing.
    Keywords: Meteorology and Climatology
    Type: GSFC-E-DAA-TN76114
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  • 3
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    Pressure Balance and Intrabinary Shock Stability in Rotation-Powered State Redback and Transitional Millisecond Pulsar Binary Systems (2018)
    In:  CASI
    Details
    Publication Date: 2020-01-22
    Description: A number of low-mass millisecond pulsar (MSP) binaries in their rotation-powered state exhibit double-peaked X-ray orbital modulation centered at inferior pulsar conjunction. This state, which has been known to persist for years, has recently been interpreted as emission from a shock that enshrouds the pulsar. However, the pressure balance for such a configuration is a crucial unresolved issue. We consider two scenarios for pressure balance: a companion magnetosphere and stellar mass loss with gas dominance. It is found that the magnetospheric scenario requires several kilogauss poloidal fields for isobaric surfaces to enshroud the MSP, as well as for the magnetosphere to remain stable if there is significant mass loss. For the gas-dominated scenario, it is necessary that the companion wind loses angular momentum prolifically as an advection- or heating-dominated flow. Thermal bremsstrahlung cooling in the flow may be observable as a UV to soft X-ray component independent of orbital phase if the mass rate is high. We formulate the general requirements for shock stability against gravitational influences in the pulsar rotation-powered state for the gas-dominated scenario. We explore stabilizing mechanisms, principally irradiation feedback, which anticipates correlated shock emission and companion variability and predicts F(sub )/F(sub X) is approximately less than 14 for the ratio of pulsar magnetospheric -ray to total shock soft-to-hard X-ray fluxes. This stability criterion implies an unbroken extension of X-ray power-law emission to hundreds of keV for some systems. We explore observational discriminants between the gas-dominated and magnetospheric scenarios, motivating contemporaneous radio through -ray monitoring of these systems.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN67095 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 869; 2; 120
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  • 4
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    Global Assimilation of Loon Stratospheric Balloon Observations and Their Trajectories Relative to Tropical Waves (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-17
    Description: Project Loon has an overall goal of providing worldwide internet coverage using a network of long-duration super-pressure balloons. Beginning in 2013, Loon has launched over 1600 balloons from multiple tropical and middle latitude locations. These GPS tracked balloon trajectories provide lower stratospheric wind information over the oceans and remote land areas where traditional radiosonde soundings are sparse, thus providing unique coverage of lower stratospheric winds. To fully investigate these Loon winds we: 1) compare the Loon winds to winds produced by a global data assimilation system (DAS: NASA GEOS) and 2) assimilate the Loon winds into the same comprehensive DAS. During May through December 2016 Loon balloons were often able to remain near the equator by selectively adjusting the Loon altitude. Our results based on global wind analyses show that the expected mean poleward motion from the Brewer-Dobson circulation can be circumvented by vertically adjusting the Loon altitudes with the phasing with the meridional wind of equatorial Rossby waves, allowing the Loon balloons to remain in the tropics.
    Keywords: Meteorology and Climatology
    Type: GSFC-E-DAA-TN76448 , AGU Fall Meeting; Dec 09, 2019 - Dec 13, 2019; San Francisco, CA; United States
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  • 5
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    Increasing Impacts of Extreme Droughts on Vegetation Productivity Under Climate Change (2019)
    In:  Other Sources
    Details
    Publication Date: 2020-01-16
    Description: Terrestrial gross primary production (GPP) is the basis of vegetation growth and food production globally and plays a critical role in regulating atmospheric CO2 through its impact on ecosystem carbon balance. Even though higher CO2 concentrations in future decades can increase GPP, low soil water availability, heat stress and disturbances associated with droughts could reduce the benefits of such CO2 fertilization. Here we analysed outputs of 13 Earth system models to show an increasingly stronger impact on GPP by extreme droughts than by mild and moderate droughts over the twenty-first century. Due to a dramatic increase in the frequency of extreme droughts, the magnitude of globally averaged reductions in GPP associated with extreme droughts was projected to be nearly tripled by the last quarter of this century (2075-2099) relative to that of the historical period (1850-1999) under both high and intermediate GHG emission scenarios. By contrast, the magnitude of GPP reductions associated with mild and moderate droughts was not projected to increase substantially. Our analysis indicates a high risk of extreme droughts to the global carbon cycle with atmospheric warming; however, this risk can be potentially mitigated by positive anomalies of GPP associated with favourable environmental conditions.
    Keywords: Meteorology and Climatology
    Type: GSFC-E-DAA-TN76047 , Nature Climate Change (ISSN 1758-678X); 9; 948-953
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  • 6
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    Binary Black Hole Growth by Gas Accretion in Stellar Clusters (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-15
    Description: We show that binaries of stellar-mass black holes formed inside a young protoglobular cluster, can grow rapidly inside the clusters core by accretion of the intracluster gas, before the gas may be depleted from the core. A black hole with mass of the order of eight solar masses can grow to values of the order of thirty five solar masses in accordance with recent gravitational waves signals observed by LIGO. Due to the black hole mass increase, a binary may also harden. The growth of binary black holes in a dense protoglobular cluster through mass accretion indicates a potentially important formation and hardening channel.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN67184 , Astronomy & Astrophysics (ISSN 0004-6361) (e-ISSN 1432-0746); 621; L1
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  • 7
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    Tendency Bias Correction in Coupled and Uncoupled Global Climate Models with a Focus on Impacts over North America (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-15
    Description: We revisit the bias correction problem in current climate models, taking advantage of state-of-the-art atmospheric reanalysis data and new data assimilation tools that simplify the estimation of short-term (6 hourly) atmospheric tendency errors. The focus is on the extent to which correcting biases in atmospheric tendencies improves the models climatology, variability, and ultimately forecast skill at subseasonal and seasonal time scales. Results are presented for the NASA GMAO GEOS model in both uncoupled (atmosphere only) and coupled (atmosphereocean) modes. For the uncoupled model, the focus is on correcting a stunted North Pacific jet and a dry bias over the central United States during boreal summerlong-standing errors that are indeed common to many current AGCMs. The results show that the tendency bias correction (TBC) eliminates the jet bias and substantially increases the precipitation over the Great Plains. These changes are accompanied by much improved (increased) storm-track activity throughout the northern midlatitudes. For the coupled model, the atmospheric TBCs produce substantial improvements in the simulated mean climate and its variability, including a much reduced SST warm bias, more realistic ENSO-related SST variability and teleconnections, and much improved subtropical jets and related submonthly transient wave activity. Despite these improvements, the improvement in subseasonal and seasonal forecast skill over North America is only modest at best. The reasons for this, which are presumably relevant to any forecast system, involve the competing influences of predictability loss with time and the time it takes for climate drift to first have a significant impact on forecast skill.
    Keywords: Meteorology and Climatology
    Type: GSFC-E-DAA-TN64773 , Journal of Climate (ISSN 0894-8755) (e-ISSN 1520-0442); 32; 2; 639-661
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  • 8
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    NICER Observation of Unusual Burst Oscillations in 4U 1728-34 (2019)
    In:  Other Sources
    Details
    Publication Date: 2020-01-15
    Description: The Neutron Star Interior Composition Explorer has observed seven thermonuclear X-ray bursts from the lowmass X-ray binary neutron star 4U 1728-34 from the start of the missions operations until 2019 February. Three of these bursts show oscillations in their decaying tail, with frequencies that are within 1 Hz of the previously detected burst oscillations from this source. Two of these burst oscillations have unusual properties: they have large fractional root mean square (rms) amplitudes of 48% 9% and 46% 9%, and they are detected only at photon energies above 6 keV. By contrast, the third detected burst oscillation is compatible with previous observations of this source, with a fractional rms amplitude of 7.7% 1.5% rms in the 0.3 to 6.2 keV energy band. We discuss the implications of these large-amplitude burst oscillations, finding that they are difficult to explain with the current theoretical models for X-ray burst tail oscillations.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN75255 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 878; 2; 145
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  • 9
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    Expanding the Sample of Radio Minihalos in Galaxy Clusters (2019)
    In:  Other Sources
    Details
    Publication Date: 2020-01-15
    Description: Radio minihalos are diffuse synchrotron sources of unknown origin found in the cool cores of some galaxy clusters. We use GMRT and VLA data to expand the sample of minihalos by reporting three new minihalo detections (A2667, A907, and PSZ1 G139.61+24.20) and confirming minihalos in five clusters (MACS J0159.80849, MACS J0329.60211, RXC J2129.6+0005, AS 780, and A3444). With these new detections and confirmations, the sample now stands at 23, the largest sample to date. For consistency, we also reanalyze archival VLA 1.4 GHz observations of seven known minihalos. We revisit possible correlations between the nonthermal emission and the thermal properties of their cluster hosts. Consistent with our earlier findings from a smaller sample, we find no strong relation between the minihalo radio luminosity and the total cluster mass. Instead, we find a strong positive correlation between the minihalo radio power and X-ray bolometric luminosity of the cool core (r 〈 70 kpc). This supplements our earlier result that most, if not all, cool cores in massive clusters contain a minihalo. Comparison of radio and Chandra X-ray images indicates that the minihalo emission is typically confined by concentric sloshing cold fronts in the cores of most of our clusters, supporting the hypothesis that minihalos arise from electron reacceleration by turbulence caused by core gas sloshing. Taken together, our findings suggest that the origin of minihalos should be closely related to the properties of thermal plasma in cluster cool cores.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN75253 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 880; 2; 70
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  • 10
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    Prospects for Testing GR with Pulsar-Timing Gravitational-Wave Detection (2016)
    In:  Other Sources
    Details
    Publication Date: 2020-01-14
    Description: No abstract available
    Keywords: Astrophysics
    Type: JPL-CL-16-4572 , Gravitational Waves and Cosmology Conference; Oct 17, 2016 - Oct 21, 2016; Hamburg; Germany
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