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  • 11
    Publication Date: 1957-12-01
    Print ISSN: 0003-021X
    Electronic ISSN: 1558-9331
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley
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  • 12
    Publication Date: 2019
    Description: Abstract Mass density variations can deviate from the expected behaviour caused by temperature due to changes in the composition. Such deviations can be especially significant during solar minimum conditions. Model‐data differences are typically resolved through temperature corrections while overlooking the role of errors in lower boundary composition. In this work, we use a data‐driven methodology to simultaneously estimate thermosphere composition and temperature contributions to model‐data differences. The methodology uses modal decomposition to extract high‐dimensional, reduced order basis functions for the covariance of the neutral thermospheric species and temperature. The extracted basis functions are combined with CHAMP and GRACE mass density measurements using a non‐linear least squares solver. We demonstrate the methodology using the Naval Research Laboratory's empirical MSIS (Mass Spectrometer and Incoherent Scatter) model to derive high‐dimensional basis functions. We characterize and quantify the contribution of temperature and lower boundary effects with oxygen and helium since the two species have a direct impact on drag and orbit prediction through gas‐surface interactions and mass density. We analyze the month of December in 2008, based on the work of Thayer et al. [2012], and estimate that lower boundary composition errors contribute approximately 50% of the model‐data differences.
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 13
    Publication Date: 2016-08-18
    Description: The presence of a near-record El Niño and a positive Pacific Meridional Mode provided an extraordinarily warm background state that fueled the 2015 eastern North Pacific hurricane season to near-record levels. We find that the western portion of the eastern North Pacific, referred to as the Western Development Region (WDR; 10°–20°N, 116°W–180°), set records for named storms, hurricane days and Accumulated Cyclone Energy in 2015. When analyzing large-scale environmental conditions, we show that record-warm sea surface temperatures, high mid-level relative humidity, high low-level relative vorticity, and record-low vertical wind shear were among the environmental forcing factors contributing to the observed tropical cyclone activity. We assess how intraseasonal atmospheric variability may have contributed to active and inactive periods observed during the 2015 hurricane season. We document that, historically, active seasons are associated with May-June El Niño conditions, potentially allowing for predictability of future active WDR seasons.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 14
    Publication Date: 2013-02-13
    Description: [1]  This paper describes initial results from a broad-scale study to assess decadal climate hindcast skills of the HadCM3, GFDL-CM2.1, NCAR-CCSM4, and MIROC5 global Earth System Models (ESMs) in experiments conducted under the Coupled Model Intercomparison Project 5. Analyses of decadal hindcast and simulation experiments using historical aerosol optical depthsshow statistically-significant decadal predictability skill of global-average and tropical sea-surface temperature (SST) anomalies during 1961 to 2010. The skill, however, varies by averaging region and decade. It was also found that volcanic eruptionsinfluence SSTs and are one of the sources of decadal SST hindcast skill. In the actual climate system, however, volcanic eruptions themselves are not predictable and, therefore, their effects on the climate system can only be predictd after eruptions. In the four ESMs utilized in this study, decadal hindcast skills of SST anomalies over ocean-basin size averaging regions generally improve due to model initialization with observed data.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 15
    Publication Date: 2011-10-19
    Description: New criteria for the identification of multiple tropopauses (MTs) in the tropics are proposed using COSMIC GPS RO data during 2006–2008 in the tropical belt (±30° latitude) and radiosonde data from 5 tropical stations during 1999 to 2008 in the ±15° latitude. In the present study, we emphasized that many times the WMO definition is not able to identify all the complex structures, such as MTs, and developed alternate criteria to delineate the MTs over the tropics effectively. The new criteria are based on the cold point tropopause (CPT) and its neighborhood points of inflection in the temperature profile rather than on lapse rate, which is used in the WMO definition. The method using the new criteria (called the cold point method) identifies MTs that occur below (referred to as Lower Tropopause, LT) and above (referred to as Second Tropopause, ST; and Third Tropopause, TT) the CPT. The percentage occurrences of MTs determined using the cold point method differ from those found using the WMO definition. The percentage occurrence of MTs within the tropics maximizes at the equator, reaching higher values in the northern hemisphere (NH) summer and lower values in the NH winter. Among the MTs, the percentage occurrence of the ST is the highest, followed by that of the LT. The percentage occurrence of MTs within the tropics also shows large longitudinal variability.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 16
    Publication Date: 2011-01-22
    Description: Extensive observations on various atmospheric parameters were carried out from Gadanki (13.48°N, 79.18°E), a tropical station in India, during the annular solar eclipse of 15 January 2010. In the present study, we report changes observed in temperature and ozone concentration in the lower stratosphere associated with the eclipse. Unusual enhancements in the temperature of 12.5 K and in ozone concentration of 5.5. mPa are observed around 21 km just after the eclipse. Plausible mechanisms for the observed eclipse effects are discussed using data of simultaneous vertical and horizontal winds collected through co-located MST radar observations. From the preliminary analysis, the temperature and ozone enhancements are attributed to large subsidence and horizontal advection, respectively.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 17
    Publication Date: 2011-05-05
    Description: Brominated diphenyl ethers (BDEs) are persistent environmental contaminants found in human blood, tissues, and milk. To assess the impact of the commercial BDE mixture DE-71 on the developing immune system in relation to hepatic and thyroid changes, adult (F0) rats were exposed to DE-71 by gavage at doses of 0, 0.5, 5, or 25 mg/kg body weight (bw)/d for 21 weeks. F0 rats were bred and exposure continued through gestation, lactation and postweaning. F1 pups were weaned and exposed to DE-71 by gavage from postnatal day (PND) 22 to 42. On PND 42, half of the F1 rats were assessed for toxicologic changes. The remaining F1 rats were challenged with the T-dependent antigen keyhole limpet hemocyanin (KLH) and immune function was assessed on PND 56. Dose-dependent increases in total BDE concentrations were detected in the liver and adipose of all F0 and F1 rats. In F0 rats, increased liver weight, hepatocellular hypertrophy, and decreased serum thyroxine (T4) were characteristic of DE-71 exposure. In F1 rats perinatal DE-71 exposure caused a nondose-dependent increase in body weight and dose-dependent increases in liver weight and hepatocellular hypertrophy. Serum T3 and T4 levels were decreased. In spleen from DE-71 exposed rats the area occupied by B cells declined while the area occupied by T cells increased; however, cellular and humoral immune responses to KLH challenge were not altered. Thus hepatic and thyroid changes in rats exposed perinatally to DE-71 were associated with altered splenic lymphocyte populations, an effect which has been linked to hypothyroidism. © 2011 Wiley Periodicals, Inc. Environ Toxicol, 2011.
    Print ISSN: 1520-4081
    Electronic ISSN: 1522-7278
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Wiley
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  • 18
    Publication Date: 2014-03-26
    Description: Primary explosives, unlike secondary explosives, show a very rapid transition from combustion (or deflagration) to detonation and are considerably sensitive to small stimuli, such as impact, friction, electrostatic discharge, and heat. Primary explosives generate either a large amount of heat or a shockwave, which makes the transfer of the detonation to a less sensitive propellant or secondary explosive possible. 1 Primary explosives are key components in detonators and primers, which are the initiating elements to many military items such as small, medium, and large caliber munitions, mortars, artillery, warheads, etc. The two most common military primary explosives are lead azide and lead styphnate. Lead based compounds such as these have well-established hazards to health and the environment. To overcome these concerns, in common U.S. Army detonators and primers lead azide was replaced with DBX-1 [copper(I) nitrotetrazolate], recently developed by Pacific Scientific Energetic Materials Company and the U.S. Naval Surface Warfare Center at Indian Head. Further, in order to minimize the dangers to personnel and equipment associated with synthesizing and handling primary explosives, a dedicated, remote-operated facility for the synthesis and testing of primary explosives has been developed.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 19
    Publication Date: 2011-08-16
    Description: A UHF/VHF beacon receiver located in Helwan, Egypt, frequently observes structures in ΔTEC/Δt measurements (where TEC is total electron count), where the F region (300 km) intercept of the radio rays crosses the steep topographic gradients associated with the Anatolian Plateau. There are three classes of structures: bumps, ripples and waves. A bump is defines as a single spatial ΔTEC/Δt peak with a peak-to-trough amplitude of at least 0.01 TECU/s (1 TEC unit (TECU) = 1016 electrons/m2) that is at least 1° wide in F region latitude. A ripple is a bump with smaller structures on either side of the central bump. Finally, waves have amplitudes ≥0.01 TECU/s with several roughly equal peaks. These features were observed repeatedly in a number passes from 31 August to 30 November 2008. Over half of passes had either a bump (34.6%), a ripple (18.2%) or a wave (6.3%). Most of these structures occur near areas with large orographic gradients. The prevailing surface wind blows across the mountains when bumps and ripples are observed. These correlations suggest that the local ionosphere is affected by the ground topography, most likely through the orographic lifting and the associated gravity waves.
    Print ISSN: 0048-6604
    Electronic ISSN: 1944-799X
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 20
    Publication Date: 2012-09-20
    Description: Wave, current, acoustic backscatter and suspended sediment concentration measurements (both single-point and vertical profiles estimated by conversion of acoustic backscatter data) are used to investigate wave-current-cohesive sediment interaction on the muddy Atchafalaya inner shelf. During an energetic storm, we propose that bed state follows a cycle of dilation due to fluidization, erosion, deposition with fluid mud formation and consolidation. A one-dimensional-vertical cohesive sediment transport model is calibrated using current and concentration profiles to estimate the physical parameters that could not be measured directly, e.g., bottom stresses. Estimated bed position and computed bottom stresses suggest that the critical erosion threshold is in the range of 0.3 Pa to 0.5 Pa. The study site is impacted by a sediment-laden fresh water plume coming from the Atchafalaya River mouth. Bed density evolution during the storm is estimated from vertical sediment exchange between the water column and the bed excluding the duration of passage of a sediment-carrying water front. The values are in the range of 1,030 kg/m3 to 1,200 kg/m3 and indicate that the bed density increases during the erosion phase and decreases during deposition. At the end of the storm, it shows a steady increasing trend during hindered settling and exceeds the space-filling value during consolidation. Both the critical erosion shear stress and bed density values are consistent with the results of laboratory tests on samples from the experimental site.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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