HF RADIO MEASUREMENTS OF THE HIGH-ALTITUDE ACOUSTIC EFFECTS OF A GROUND- LEVEL EXPLOSION

1965 ◽  
Author(s):  
L. J. Griffiths ◽  
G. H. Barry ◽  
J. C. Taenzer
Keyword(s):  
High Altitude ◽  
Ground Level ◽  
Radio Measurements

HF radio measurements of high-altitude acoustic waves from a ground-level explosion

1966 ◽  
Vol 71 (17) ◽  
pp. 4173-4182 ◽  
Author(s):  
G. H. Barry ◽  
L. J. Griffiths ◽  
J. C. Taenzer
Keyword(s):  
High Altitude ◽  
Acoustic Waves ◽  
Ground Level ◽  
Radio Measurements

scholarly journals Simultaneous generalized and low-layer SCIDAR turbulence profiles at san pedro mártir observatory

2019 ◽  
Vol 490 (1) ◽  
pp. 1397-1405 ◽  
Author(s):  
R Avila ◽  
O Valdés-Hernández ◽  
L J Sánchez ◽  
I Cruz-González ◽  
J L Avilés ◽  
...  
Keyword(s):  
High Altitude ◽  
Wind Direction ◽  
Close Agreement ◽  
Baja California ◽  
Ground Level ◽  
Combined Effect ◽  
Moderate Altitude ◽  
San Pedro ◽  
Simultaneous Measurements

ABSTRACT We present optical turbulence profiles obtained with a Generalized SCIDAR (G-SCIDAR) and a low-layer SCIDAR (LOLAS) at the Observatorio Astronómico Nacional in San Pedro Mártir (OAN-SPM), Baja California, Mexico, during three observing campaigns in 2013, 2014, and 2015. The G-SCIDAR delivers profiles with moderate altitude-resolution (a few hundred metres) along the entire turbulent section of the atmosphere, while the LOLAS gives high altitude resolution (on the order of tens of metres) but only within the first few hundred metres. Simultaneous measurements were obtained on 2014 and allowed us to characterize in detail the combined effect of the local orography and wind direction on the turbulence distribution close to the ground. At the beginning of several nights, the LOLAS profiles show that turbulence peaks between 25 and 50 m above the ground, not at ground level as was expected. The G-SCIDAR profiles exhibit a peak within the first kilometre. In 55 per cent and 36 per cent of the nights stable layers are detected between 10 and 15 km and at 3 km, respectively. This distribution is consistent with the results obtained with a G-SCIDAR in 1997 and 2000 observing campaigns. Statistics computed with the 7891 profiles that have been measured at the OAN-SPM with a G-SCIDAR in 1997, 2000, 2014, and 2015 campaigns are presented. The seeing values calculated with each of those profiles have a median of 0.79, first and third quartiles of 0.51 and 1.08 arcsec, which are in close agreement with other long term seeing monitoring performed at the OAN-SPM.

scholarly journals The Bakerian lecture —Regularities and irregularities in the ionosphere—I

1937 ◽  
Vol 162 (911) ◽  
pp. 451-479 ◽  
Keyword(s):  
Specific Conductivity ◽  
Wave Length ◽  
Ground Level ◽  
Short Wave ◽  
The State ◽  
Total Conductivity ◽  
The Sun ◽  
Magnetic Studies ◽  
Short Wave Length ◽  
Radio Measurements

Our knowledge concerning the state of the atmosphere lying above about 80 km. in height has been derived from experiments on radio wave reflexion as well as from studies of terrestrial magnetism and of the aurora. The information derived from radio experiments is, fortunately, in the nature of a supplement to, rather than a duplicate of, information derivable in other ways. As one of the best examples in this connexion may be mentioned the question of electrical conductivity. Here the magnetic studies of Schuster and Chapman yield an estimate of the total conductivity for currents travelling horizontally, whereas the radio measurements give the state of ionization at different levels from which the specific conductivity at those levels may be estimated. One of the most striking things about the ionosphere is the marked solar control. Speaking generally it may be said that the ionization increases and decreases as the sun rises and sets. Again, speaking generally, we may say that the main part of the ionization is caused by solar-violet light. The rays from the sun meet the outer layers of the atmosphere first and the short wave-length radiation is absorbed there, causing ionization. It thus comes about that the study of the ionosphere becomes the study of an interesting part of the sun's spectrum which cannot be detected at ground level. It also becomes the study of certain atomic processes such as photo-ionization, recombination of ions and attachment of electrons to neutral molecules such as cannot be investigated at very low pressure in the laboratory, because of the influence of the walls of the vessel confining the gas.

An aerial netting study of insects migrating at high altitude over England

2004 ◽  
Vol 94 (2) ◽  
pp. 123-136 ◽  
Author(s):  
J.W. Chapman ◽  
D.R. Reynolds ◽  
A.D. Smith ◽  
E.T. Smith ◽  
I.P. Woiwod
Keyword(s):  
Global Warming ◽  
High Altitude ◽  
North Sea ◽  
Ground Level ◽  
Diel Periodicity ◽  
Tethered Balloon ◽  
Extensive Survey ◽  
Economic Significance ◽  
Large Populations ◽  
The Uk

AbstractDay and night sampling of windborne arthropods at a height of 200 m above ground was undertaken at Cardington, Bedfordshire, UK, during July 1999, 2000 and 2002, using a net supported by a tethered balloon. The results from this study are compared with those from the classic aerial sampling programmes carried out by Hardy, Freeman and colleagues over the UK and North Sea in the 1930s. In the present study, aerial netting was undertaken at night as well as daytime, and so the diel periodicity of migration could be investigated, and comparisons made with the results from Lewis and Taylor’s extensive survey of flight periodicity near ground level. In some taxa with day-time emigration, quite large populations could continue in high-altitude flight after dark, perhaps to a previously underrated extent, and this would greatly increase their potential migratory range. Any trend towards increases in night temperatures, associated with global warming, would facilitate movements of this type in the UK. Observations on the windborne migration of a variety of species, particularly those of economic significance or of radar-detectable size, are briefly discussed.

scholarly journals Comparisons of spectrally resolved nightglow emission locally simulated with space and ground level observations

2020 ◽  
Vol 10 ◽  
pp. 21 ◽  
Author(s):  
Christophe Bellisario ◽  
Pierre Simoneau ◽  
Philippe Keckhut ◽  
Alain Hauchecorne
Keyword(s):  
High Altitude ◽  
Large Scale ◽  
Molecular Diffusion ◽  
Ground Level ◽  
Atmospheric Tides ◽  
Emission Rates ◽  
Spectral Radiation ◽  
Volume Emission ◽  
Spectrally Resolved ◽  
The Impact

A mesospheric model of the airglow emission is developed to recover the night variations observed at ground level. The model is based on a 1D vertical photochemical model, including the photodissociation and heating processes. The spectral radiation is calculated at high altitude and propagated through the atmosphere to the ground. We also include short scale vertical dynamic such as turbulences and the molecular diffusion. Simulations reveal realistic emissions when compared with space observations. In addition, we estimate the impact of changes associated with parameterized atmospheric tides. The comparison with observations is performed over high altitude and ground level. We confront the model outputs at high altitude with satellite observations (SABER and GOMOS) and the simulations propagated at ground level are compared to local measurements campaigns performed in France and India. Biases between observed and simulated radiances and volume emission rates are suspected to be due to the impact of gravity waves or the large scale dynamic.

scholarly journals Cloud-Enabled High-Altitude Platform Systems: Challenges and Opportunities

2021 ◽  
Vol 2 ◽  
Author(s):  
Khaleel Mershad ◽  
Hayssam Dahrouj ◽  
Hadi Sarieddeen ◽  
Basem Shihada ◽  
Tareq Al-Naffouri ◽  
...  
Keyword(s):  
High Altitude ◽  
Ad Hoc ◽  
Ground Level ◽  
High Energy ◽  
Cloud Services ◽  
Base Stations ◽  
High Altitude Platform ◽  
Wide Range ◽  
Challenges And Opportunities ◽  
Hoc Networks

Augmenting ground-level communications with flying networks, such as the high-altitude platform system (HAPS), is among the major innovative initiatives of the next generation of wireless systems (6G). Given HAPS quasi-static positioning at the stratosphere, HAPS-to-ground and HAPS-to-air connectivity frameworks are expected to be prolific in terms of data acquisition and computing, especially given the mild weather and quasi-constant wind speed characteristics of the stratospheric layer. This paper explores the opportunities stemming from the realization of cloud-enabled HAPS in the context of telecommunications applications and services. The paper first advocates for the potential physical advantages of deploying HAPS as flying data-centers, also known as super-macro base stations. The paper then describes various cloud services that can be offered from the HAPS and the merits that can be achieved by this integration, such as enhancing the quality, speed, and range of the offered services. The proposed services span a wide range of fields, including satellites, Internet of Things (IoT), ad hoc networks (such as sensor; vehicular; and aerial networks), gaming, and social networks. For each service, the paper illustrates the methods that would be used by cloud providers to offload the service data to the HAPS and enable the cloud customers to consume the service. The paper further sheds light on the challenges that need to be addressed for realizing practical cloud-enabled HAPS, mainly, those related to high energy, processing power, quality of service (QoS), and security considerations. Finally, the paper discusses some open issues on the topic, namely, HAPS mobility and message routing, HAPS security via blockchain and machine learning, artificial intelligence-based resource allocation in cloud-enabled HAPS, and integration with vertical heterogeneous networks.

scholarly journals A Refined Calibration Procedure of Two-Channel Sun Photometers to Measure Atmospheric Precipitable Water at Various Antarctic Sites

2008 ◽  
Vol 25 (2) ◽  
pp. 213-229 ◽  
Author(s):  
Claudio Tomasi ◽  
Boyan Petkov ◽  
Elena Benedetti ◽  
Luca Valenziano ◽  
Angelo Lupi ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Altitude ◽  
Sea Level ◽  
Precipitable Water ◽  
Ground Level ◽  
Calibration Procedure ◽  
Square Root ◽  
Aging Effects ◽  
Calibration Curves ◽  
The Antarctic

Abstract Two-channel sun photometers can be easily employed at Antarctic sites, where harsh environmental conditions prevail, to carry out measurements of precipitable water W. In the very dry air conditions observed in the Antarctic atmosphere, water vapor does not produce strong absorption features along the sun path. Therefore, these instruments need to be calibrated using analytical forms different from the square root regime, which can be determined by simulating the output voltages measured at Antarctic sites, for the spectral near-IR curves of extraterrestrial solar irradiance, instrumental responsivity parameters, and atmospheric transmittance, relative to various measurement periods. For this purpose, average models of the Antarctic atmosphere from the ground level up to the 30-km altitude were considered for different solar zenith angles and relative humidity conditions. The ratios between the output voltages simulated in the band and window channels were plotted as a function of total water vapor content Cw, for each site and each period, to define the best-fit calibration curves, which were subsequently normalized to the field measurements to take into account the aging effects on the filter transmission characteristics. Each of the five calibration curves was found to present a slope coefficient decreasing gradually with Cw from values higher than 0.8 to about 0.6. Using these curves, measurements of W were obtained, which differ appreciably at both sea level and high-altitude sites from those given by the square root calibration curves, avoiding large overestimation errors of 10%–40% at the high-altitude sites and underestimation errors of 5%–15% at the sea level site.

Performance during Positive Pressure Breathing after Rapid Decompression Up to 72000 Feet

1997 ◽  
Vol 39 (1) ◽  
pp. 102-110 ◽  
Author(s):  
Ann Elise Lindeis ◽  
W. D. Fraser ◽  
Barry Fowler
Keyword(s):  
High Altitude ◽  
Ground Level ◽  
Positive Pressure ◽  
Blood Oxygen ◽  
Low Oxygen ◽  
Blood Oxygen Saturation ◽  
Pressure Oxygen ◽  
Rapid Decompression ◽  
High Pressure Oxygen ◽  
The Right

Positive pressure breathing (PPB) is a survival system that delivers high-pressure oxygen and body counterpressure in the event of cockpit depressurization at high altitude, but the ability of aircrew to perform an emergency "get-me-down" maneuver with this system is unknown. To address this question, a serial choice reaction time (RT) task was administered to six participants, who were sustained with PPB after rapid decompression to 60000 feet (18 288 m) or 72 000 feet (21946 m) in a hypobaric chamber (Experiment 1). Hypoxia was monitored by blood oxygen saturation (SaO2). Experiment 2 assessed the effects of PPB alone on performance. In Experiment 3, performance was measured while the rate of decrease of Sao2 observed in Experiment 1 was replicated with low oxygen mixtures at ground level. During the first 60 s at 72 000 feet, RT increased by 79 ms because of a shift of the whole distribution to the right. PPB at ground level did not increase RT. Decreasing Sao2 at ground level increased RT, but only after a delay. We conclude that inattention to the task, PPB alone, or, surprisingly, hypoxia cannot explain the majority of the impairment observed in Experiment 1. Rather, PPB and low pressure at high altitude interacted to exacerbate lacrimation, thereby degrading vision. Implications for the design of get-me-down maneuvers are discussed.

scholarly journals Desert crossing strategies of migrant songbirds vary between and within species

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Frédéric Jiguet ◽  
Malcolm Burgess ◽  
Kasper Thorup ◽  
Greg Conway ◽  
José Luis Arroyo Matos ◽  
...  
Keyword(s):  
Light Intensity ◽  
High Altitude ◽  
General Rule ◽  
Ground Level ◽  
Temperature Data ◽  
Above Ground Level ◽  
Ecological Barriers ◽  
Common Strategy ◽  
Migration Strategies ◽  
Migratory Songbird

AbstractEach year, billions of songbirds cross large ecological barriers during their migration. Understanding how they perform this incredible task is crucial to predict how global change may threaten the safety of such journeys. Earlier studies based on radar suggested that most songbirds cross deserts in intermittent flights at high altitude, stopping in the desert during the day, while recent tracking with light loggers suggested diurnal prolongation of nocturnal flights and common non-stop flights for some species. We analyzed light intensity and temperature data obtained from geolocation loggers deployed on 130 individuals of ten migratory songbird species, and show that a large variety of strategies for crossing deserts exists between, but also sometimes within species. Diurnal stopover in the desert is a common strategy in autumn, while most species prolonged some nocturnal flights into the day. Non-stop flights over the desert occurred more frequently in spring than in autumn, and more frequently in foliage gleaners. Temperature recordings suggest that songbirds crossed deserts with flight bouts performed at various altitudes according to species and season, along a gradient ranging from low above ground in autumn to probably >2000 m above ground level, and possibly at higher altitude in spring. High-altitude flights are therefore not the general rule for crossing deserts in migrant songbirds. We conclude that a diversity of migration strategies exists for desert crossing among songbirds, with variations between but also within species.

Sign in / Sign up

Export Citation Format

Share Document