Influence of vertically and obliquely propagating gravity waves on the polar summer mesosphere

Science.gov (United States)

Thurairajah, B.; Siskind, D. E.; Bailey, S. M.

2017-12-01

Polar Mesospheric Clouds (PMCs) are sensitive to changes in temperature of the cold polar summer mesosphere, which in turn are modulated by gravity waves (GWs). In this study we investigate the link between PMCs and GWs that propagate both vertically (i.e. wave propagation is directly above the source region) and obliquely (lateral or non-vertical propagation upward but away from the source region). Several observational studies have analyzed the link between PMCs and vertically propagating GWs and have reported both positive and negative correlations. Moreover, while modelling studies have noted the possibility of oblique propagation of GWs from the low-latitude stratosphere to the high-latitude mesosphere, observational studies of the influence of these waves on the polar summer mesosphere are sparse. We present a comprehensive analysis of the influence of vertically and obliquely propagating GWs on the northern hemisphere (NH) polar summer mesosphere using data from 8 PMC seasons. Temperature data from the SOFIE experiment on the AIM satellite and SABER instrument on the TIMED satellite are used to derive GW parameters. SOFIE PMC data in terms of Ice Water Content (IWC) are used to quantify the changes in the polar summer mesosphere. At high latitudes, preliminary analysis of vertically propagating waves indicate a weak but positive correlation between GWs at 50 km and GWs at the PMC altitude of 84 km. Overall there is a negative correlation between GWs at 50 km and IWC and a positive correlation between GWs at 84 km and IWC. These results and the presence of a slanted structure (slanted from the low-latitude stratosphere to the high-latitude mesosphere) in GW momentum flux suggest the possibility of a significant influence of obliquely propagating GWs on the polar summer mesosphere

Simultaneous observations of noctilucent clouds and polar mesosphere summer echoes at Syowa Station, Antarctica

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Keisuke Hosokawa

2013-11-01

Full Text Available This paper reports simultaneous observations of visible noctilucent clouds (NLC and polar mesosphere summer echoes (PMSE at Syowa Station (69°01′S, 38°61′E in Antarctica. During a 1.5 h interval from 2000 to 2130 UT (2300 to 0030 LT on Feb. 11, 2009, visible NLC were observed south of Syowa Station. The oblique sounding HF radar of SuperDARN at Syowa Station simultaneously observed peculiar echoes in the closest two range gates. The echoes had a small Doppler velocity and a narrow spectral width, which are consistent with the characteristics of PMSE in the SuperDARN data. The simultaneous appearance of the visible NLC and peculiar near-range echoes observed by the HF radar suggests that the echoes were actually a signature of PMSE in the HF band. In addition, the data from the simultaneous measurements show that the spatial distributions of NLC and PMSE in the HF band were collocated with each other, which implies that oblique sounding HF radar is a useful tool for estimating the two-dimensional horizontal distribution of PMSE.

Star-Forming Clouds Feed, Churn, and Fall

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Kohler, Susanna

2017-12-01

Molecular clouds, the birthplaces of stars in galaxies throughout the universe, are complicated and dynamic environments. A new series of simulations has explored how these clouds form, grow, and collapse over their lifetimes.This composite image shows part of the Taurus Molecular Cloud. [ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey]Stellar BirthplacesMolecular clouds form out of the matter in between stars, evolving through constant interactions with their turbulent environments. These interactions taking the form of accretion flows and surface forces, while gravity, turbulence, and magnetic fields interplay are thought to drive the properties and evolution of the clouds.Our understanding of the details of this process, however, remains fuzzy. How does mass accretion affect these clouds as they evolve? What happens when nearby supernova explosions blast the outsides of the clouds? What makes the clouds churn, producing the motion within them that prevents them from collapsing? The answers to these questions can tellus about the gas distributed throughout galaxies, revealing information about the environments in which stars form.A still from the simulation results showing the broader population of molecular clouds that formed in the authors simulations, as well as zoom-in panels of three low-mass clouds tracked in high resolution. [Ibez-Meja et al. 2017]Models of TurbulenceIn a new study led by Juan Ibez-Meja (MPI Garching and Universities of Heidelberg and Cologne in Germany, and American Museum of Natural History), scientists have now explored these questions using a series of three-dimensional simulations of a population of molecular clouds forming and evolving in the turbulent interstellar medium.The simulations take into account a whole host of physics, including the effects of nearby supernova explosions, self-gravitation, magnetic fields, diffuse heating, and radiative cooling. After looking at the behavior of the broader population of

The role of sodium bicarbonate in the nucleation of noctilucent clouds

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J. M. C. Plane

2000-07-01

Full Text Available It is proposed that a component of meteoric smoke, sodium bicarbonate (NaHCO3, provides particularly effective condensation nuclei for noctilucent clouds. This assertion is based on three conditions being met. The first is that NaHCO3 is present at sufficient concentration (±104 cm-3 in the upper mesosphere between 80 and 90 km. It is demonstrated that there is strong evidence for this based on recent laboratory measurements coupled with atmospheric modelling. The second condition is that the thermodynamics of NaHCO3(H2On cluster formation allow spontaneous nucleation to occur under mesospheric conditions at temperatures below 140 K. The Gibbs free energy changes for forming clusters with n = 1 and 2 were computed from quantum calculations using hybrid density functional/Hartree-Fock (B3LYP theory and a large basis set with added polarization and diffuse functions. The results were then extrapolated to higher n using an established dependence of the free energy on cluster size and the free energy for the sublimation of H2O to bulk ice. A 1-dimensional model of sodium chemistry was then employed to show that spontaneous nucleation to form ice particles (n >100 should occur between 84 and 89 km in the high-latitude summer mesosphere. The third condition is that other metallic components of meteoric smoke are less effective condensation nuclei, so that the total number of potential nuclei is small relative to the amount of available H2O. Quantum calculations indicate that this is probably the case for major constituents such as Fe(OH2, FeO3 and MgCO3.Key words: Atmospheric composition and structure (aerosols and particles; cloud physics and chemistry; middle atmosphere · composition and chemistry

Retrieving mesospheric water vapour from observations of volume scattering radiances

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P. Vergados

2009-02-01

Full Text Available This study examines the possibility for a theoretical approach in the estimation of water vapour mixing ratios in the vicinity of polar mesospheric clouds (PMC using satellite observations of Volume Scattering Radiances (VSR obtained at the wavelength of 553 nm. The PMC scattering properties perturb the underlying molecular Rayleigh scattered solar radiance of the background atmosphere. As a result, the presence of PMC leads to an enhancement in the observed VSR at the altitude of the layer; the PMC VSRs are superimposed on the exponentially decreasing with height Rayleigh VSR, of the PMC-free atmosphere. The ratio between the observed and the Rayleigh VSR of the background atmosphere is used to simulate the environment in which the cloud layer is formed. In addition, a microphysical model of ice particle formation is employed to predict the PMC VSRs. The initial water vapour profile is perturbed until the modelled VSRs match the observed, at which point the corresponding temperature and water vapour profiles can be considered as a first approximation of those describing the atmosphere at the time of the observations. The role of temperature and water vapour in the cloud formation is examined by a number of sensitivity tests suggesting that the water vapour plays a dominant role in the cloud formation in agreement with experimental results. The estimated water vapour profiles are compared with independent observations to examine the model capability in the context of this study. The results obtained are in a good agreement at the peak of the PMC layer although the radiance rapidly decreases with height below the peak. This simplified scenario indicates that the technique employed can give a first approximation estimate of the water vapour mixing ratio, giving rise to the VSR observed in the presence of PMC.

Measurements of mesospheric ice aerosols using radars and rockets

Energy Technology Data Exchange (ETDEWEB)

Strelnikova, Irina; Li, Qiang; Strelnikov, Boris; Rapp, Markus [Leibniz Institute of Atmospheric Physics, Kuehlungsborn (Germany)

2010-07-01

Polar summer mesopause is the coldest region of Earth's atmosphere with temperatures as low as minus 130 C. In this extreme environment ice aerosol layers have appeared. Larger aerosols can be seen from the ground as clouds known as NLC (Noctilucent clouds). Ice aerosols from sub-visible range give rise to the phenomena known as Polar Mesosphere Sommer Echo (PMSE). For efficient scattering, electron number density must be structured at the radar half wavelength (Bragg condition). The general requirement to allow for the observation of structures at VHF and higher frequencies is that the dust size (and charge number) must be large enough to extend the convective-diffusive subrange of the energy spectrum of electrons (by reducing their diffusivity) to the wavelength which is shorter than the Bragg-scale of the probing radar. In this paper we present main results of ice particles measurements inside the PMSE layers obtained from in situ rocket soundings and newly developed radar techniques.

The polar mesosphere

International Nuclear Information System (INIS)

Morris, Ray; Murphy, Damian

2008-01-01

The mesosphere region, which lies at the edge of space, contains the coldest layer of the Earth's atmosphere, with summer temperatures as low as minus 130 °C. In this extreme environment ice aerosol layers have appeared since the dawn of industrialization—whose existence may arguably be linked to human influence—on yet another layer of the Earth's fragile atmosphere. Ground-based and space-based experiments conducted in the Arctic and Antarctic during the International Polar Year (IPY) aim to address limitations in our knowledge and to advance our understanding of thermal and dynamical processes at play in the polar mesosphere

Radar cross sections for mesospheric echoes at Jicamarca

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G. A. Lehmacher

2009-07-01

Full Text Available Radar cross sections (RCS of mesospheric layers at 50 MHz observed at Jicamarca, Peru, range from 10−18 to 10−16 m−1, three orders of magnitudes smaller than cross sections reported for polar mesospheric winter echoes during solar proton events and six orders of magnitude smaller than polar mesospheric summer echoes. Large RCS are found in thick layers around 70 km that also show wide radar spectra, which is interpreted as turbulent broadening. For typical atmospheric and ionospheric conditions, volume scattering RCS for stationary, homogeneous, isotropic turbulence at 3 m are also in the range 10−18 to 10−16 m−1, in reasonable agreement with measurements. Moreover, theory predicts maximum cross sections around 70 km, also in agreement with observations. Theoretical values are still a matter of order-of-magnitude estimation, since the Bragg scale of 3 m is near or inside the viscous subrange, where the form of the turbulence spectrum is not well known. In addition, steep electron density gradients can increase cross-sections significantly. For thin layers with large RCS and narrow spectra, isotropic turbulence theory fails and scattering or reflection from anisotropic irregularities may gain relevance.

Remote sensing of mesospheric electric fields using MF radars

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Meek, C. E.; Manson, A. H.; Martynenko, S. I.; Rozumenko, V. T.; Tyrnov, O. F.

2004-07-01

Large mesospheric electric fields can play an essential role in middle atmospheric electrodynamics (see, e.g., Goldberg, R. A., Middle Atmospheric Electrodynamics during MAP, Adv. Space Res. 10 (10) (1990) 209). The V/m electric fields of atmospheric origin can be the possible cause of large variations in the electron collision frequency at mesospheric altitudes, and this provides a unique opportunity to take measurements of electric fields in the lower ionosphere by using remote sensing instruments employing radiowave techniques. A technique has been proposed for making estimates of large mesospheric electric field intensities on the lower edge of the ionosphere by using MF radar data and the inherent effective electron collision frequency. To do this, data collected in Canada and Ukraine were utilized. The developed technique permits the changes in mesospheric electric field intensities to be derived from MF radar data in real time. The statistical analysis of data consistent with large mesospheric electric field intensities in the 60-67km region resulted in the following inferences. There are at least two mechanisms for the generation of large mesospheric electric fields in the mesosphere. The most likely mechanism, with a probability of 60-70%, is the summation of random fields from a large number of elementary small-scale mesospheric generators, which results in a one-parameter Rayleigh distribution of the total large mesospheric electric field intensity E with a mean value of approximately 0.7-0.9V/m in the 60-67km altitude region, or in the corresponding one-parameter exponential distribution of the intensity squared E2 of large mesospheric electric fields. The second mechanism of unknown nature, with 5-15% probability, gives rise to the sporadic appearance of large mesospheric electric field intensities E>2.5V/m with a mean of 4V/m. Statistically significant seasonal differences in the averaged large mesospheric electric field parameters have not been

The role of sodium bicarbonate in the nucleation of noctilucent clouds

Directory of Open Access Journals (Sweden)

J. M. C. Plane

Full Text Available It is proposed that a component of meteoric smoke, sodium bicarbonate (NaHCO₃, provides particularly effective condensation nuclei for noctilucent clouds. This assertion is based on three conditions being met. The first is that NaHCO₃ is present at sufficient concentration (±10⁴ cm^-3 in the upper mesosphere between 80 and 90 km. It is demonstrated that there is strong evidence for this based on recent laboratory measurements coupled with atmospheric modelling. The second condition is that the thermodynamics of NaHCO₃(H₂O_n cluster formation allow spontaneous nucleation to occur under mesospheric conditions at temperatures below 140 K. The Gibbs free energy changes for forming clusters with n = 1 and 2 were computed from quantum calculations using hybrid density functional/Hartree-Fock (B3LYP theory and a large basis set with added polarization and diffuse functions. The results were then extrapolated to higher n using an established dependence of the free energy on cluster size and the free energy for the sublimation of H₂O to bulk ice. A 1-dimensional model of sodium chemistry was then employed to show that spontaneous nucleation to form ice particles (n >100 should occur between 84 and 89 km in the high-latitude summer mesosphere. The third condition is that other metallic components of meteoric smoke are less effective condensation nuclei, so that the total number of potential nuclei is small relative to the amount of available H₂O. Quantum calculations indicate that this is probably the case for major constituents such as Fe(OH₂, FeO₃ and MgCO₃.

Key words: Atmospheric composition and structure (aerosols and particles; cloud physics and chemistry; middle atmosphere · composition and chemistry

Dusty Cloud Acceleration by Radiation Pressure in Rapidly Star-forming Galaxies

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Zhang, Dong; Davis, Shane W.; Jiang, Yan-Fei; Stone, James M.

2018-02-01

We perform two-dimensional and three-dimensional radiation hydrodynamic simulations to study cold clouds accelerated by radiation pressure on dust in the environment of rapidly star-forming galaxies dominated by infrared flux. We utilize the reduced speed of light approximation to solve the frequency-averaged, time-dependent radiative transfer equation. We find that radiation pressure is capable of accelerating the clouds to hundreds of kilometers per second while remaining dense and cold, consistent with observations. We compare these results to simulations where acceleration is provided by entrainment in a hot wind, where the momentum injection of the hot flow is comparable to the momentum in the radiation field. We find that the survival time of the cloud accelerated by the radiation field is significantly longer than that of a cloud entrained in a hot outflow. We show that the dynamics of the irradiated cloud depends on the initial optical depth, temperature of the cloud, and intensity of the flux. Additionally, gas pressure from the background may limit cloud acceleration if the density ratio between the cloud and background is ≲ {10}2. In general, a 10 pc-scale optically thin cloud forms a pancake structure elongated perpendicular to the direction of motion, while optically thick clouds form a filamentary structure elongated parallel to the direction of motion. The details of accelerated cloud morphology and geometry can also be affected by other factors, such as the cloud lengthscale, reduced speed of light approximation, spatial resolution, initial cloud structure, and dimensionality of the run, but these have relatively little affect on the cloud velocity or survival time.

The MaCWAVE program to study gravity wave influences on the polar mesosphere

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R. A. Goldberg

2006-07-01

Full Text Available MaCWAVE (Mountain and Convective Waves Ascending VErtically was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT. The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite measurements of thermal structures. The data have been used to define both the mean fields and the wave field structures and turbulence generation leading to forcing of the large-scale flow. In summer, launch sequences coupled with ground-based measurements at ARR addressed the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. These motions were measured with two 12-h rocket sequences, each involving one Terrier-Orion payload accompanied by a mix of MET rockets, all at ARR in Norway. The MET rockets were used to define the temperature and wind structure of the stratosphere and mesosphere. The Terrier-Orions were designed to measure small-scale plasma fluctuations and turbulence that might be induced by wave breaking in the mesosphere. For the summer series, three European MIDAS (Middle Atmosphere Dynamics and Structure rockets were also launched from ARR in coordination with the MaCWAVE payloads. These were designed to measure plasma and neutral turbulence within the MLT. The summer program exhibited a number of indications of significant departures of the mean wind and temperature structures from ``normal" polar summer conditions, including an unusually warm mesopause and a slowing of the formation of polar mesospheric summer echoes (PMSE and noctilucent clouds (NLC. This

The impact of galactic disc environment on star-forming clouds

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Nguyen, Ngan K.; Pettitt, Alex R.; Tasker, Elizabeth J.; Okamoto, Takashi

2018-03-01

We explore the effect of different galactic disc environments on the properties of star-forming clouds through variations in the background potential in a set of isolated galaxy simulations. Rising, falling, and flat rotation curves expected in halo-dominated, disc-dominated, and Milky Way-like galaxies were considered, with and without an additional two-arm spiral potential. The evolution of each disc displayed notable variations that are attributed to different regimes of stability, determined by shear and gravitational collapse. The properties of a typical cloud were largely unaffected by the changes in rotation curve, but the production of small and large cloud associations was strongly dependent on this environment. This suggests that while differing rotation curves can influence where clouds are initially formed, the average bulk properties are effectively independent of the global environment. The addition of a spiral perturbation made the greatest difference to cloud properties, successfully sweeping the gas into larger, seemingly unbound, extended structures and creating large arm-interarm contrasts.

Optical studies of noctilucent clouds in the extreme ultraviolet

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J. Hedin

2008-05-01

Full Text Available In order to better understand noctilucent clouds (NLC and their sensitivity to the variable environment of the polar mesosphere, more needs to be learned about the actual cloud particle population. Optical measurements are today the only means of obtaining information about the size of mesospheric ice particles. In order to efficiently access particle sizes, scattering experiments need to be performed in the Mie scattering regime, thus requiring wavelengths of the order of the particle size. Previous studies of NLC have been performed at wavelengths down to 355 nm from the ground and down to about 200 nm from rockets and satellites. However, from these measurements it is not possible to access the smaller particles in the mesospheric ice population. This current lack of knowledge is a major limitation when studying important questions about the nucleation and growth processes governing NLC and related particle phenomena in the mesosphere. We show that NLC measurements in the extreme ultraviolet, in particular using solar Lyman-α radiation at 121.57 nm, are an efficient way to further promote our understanding of NLC particle size distributions. This applies both to global measurements from satellites and to detailed in situ studies from sounding rockets. Here, we present examples from recent rocket-borne studies that demonstrate how ambiguities in the size retrieval at longer wavelengths can be removed by invoking Lyman-α. We discuss basic requirements and instrument concepts for future rocket-borne NLC missions. In order for Lyman-α radiation to reach NLC altitudes, high solar elevation and, hence, daytime conditions are needed. Considering the effects of Lyman-α on NLC in general, we argue that the traditional focus of rocket-borne NLC missions on twilight conditions has limited our ability to study the full complexity of the summer mesopause environment.

On the star-forming ability of Molecular Clouds

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Anathpindika, S.; Burkert, A.; Kuiper, R.

2018-02-01

The star-forming ability of a molecular cloud depends on the fraction of gas it can cycle into the dense-phase. Consequently, one of the crucial questions in reconciling star formation in clouds is to understand the factors that control this process. While it is widely accepted that the variation in ambient conditions can alter significantly the ability of a cloud to spawn stars, the observed variation in the star-formation rate in nearby clouds that experience similar ambient conditions, presents an interesting question. In this work, we attempted to reconcile this variation within the paradigm of colliding flows. To this end we develop self-gravitating, hydrodynamic realizations of identical flows, but allowed to collide off-centre. Typical observational diagnostics such as the gas-velocity dispersion, the fraction of dense-gas, the column density distribution (N-PDF), the distribution of gas mass as a function of K-band extinction and the strength of compressional/solenoidal modes in the post-collision cloud were deduced for different choices of the impact parameter of collision. We find that a strongly sheared cloud is terribly inefficient in cycling gas into the dense phase and that such a cloud can possibly reconcile the sluggish nature of star formation reported for some clouds. Within the paradigm of cloud formation via colliding flows this is possible in case of flows colliding with a relatively large impact parameter. We conclude that compressional modes - though probably essential - are insufficient to ensure a relatively higher star-formation efficiency in a cloud.

Smashing a Jet into a Cloud to Form Stars

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Kohler, Susanna

2017-12-01

What happens when the highly energetic jet from the center of an active galaxy rams into surrounding clouds of gas and dust? A new study explores whether this might be a way to form stars.The authors simulations at an intermediate (top) and final (bottom) stage show the compression in the gas cloud as a jet (red) enters from the left. Undisturbed cloud material is shown in blue, whereas green corresponds to cold, compressed gas actively forming stars. [Fragile et al. 2017]Impacts of FeedbackCorrelation between properties of supermassive black holes and their host galaxies suggest that there is some means of communication between them. For this reason, we suspect that feedback from an active galactic nucleus (AGN) in the form of jets, for instance controls the size of the galaxy by influencing star formation. But how does this process work?AGN feedback can be either negative or positive. In negative feedback, the gas necessary for forming stars is heated or dispersed by the jet, curbing or halting star formation. In positive feedback, jets propagate through the surrounding gas with energies high enough to create compression in the gas, but not so high that they heat it. The increased density can cause the gas to collapse, thereby triggering star formation.In a recent study, a team of scientists led by Chris Fragile (College of Charleston) modeled what happens when an enormous AGN jet slams into a dwarf-galaxy-sized, inactive cloud of gas. In particular, the team explored the possibility of star-forming positive feedback with the goal of reproducing recent observations of something called Minkowskis Object, a stellar nursery located at the endpoint of a radio jet emitted from the active galaxy NGC 541.The star formation rate in the simulated cloud increases dramatically as a result of the jets impact, reaching the rate currently observed for Minkowskis Objects within 20 million years. [Fragile et al. 2017]Triggering Stellar BirthFragile and collaborators used a

Active Dust Experiment in the Mesosphere

International Nuclear Information System (INIS)

Norberg, Carol; Pellinen-Wannberg, Asta

2008-01-01

The mesosphere stretches from an altitude of about 50 to 90 km above the Earth's surface. Meteors entering the Earth's atmosphere are believed to ablate and hence give rise to a thin layer of dust particles in the upper part of the Earth's mesosphere. It seems that the dust is most dense in a layer that lies between 80 and 90 km. The dust particles are thought to have sizes of a few to tens of nanometers. Efforts have been made to measure these particles using rockets and radar techniques with limited success. We propose to release dust into the mesosphere over northern Sweden at a height of about 90 km and observe the released dust using the EISCAT radar system. The dust will be launched from the Swedish Space Corporation Esrange Space Centre on a single-stage Improved-Orion rocket that will be launched so that its flight path will be in the radar field of view.

Effects of geomagnetic activity on the mesospheric electric fields

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A. M. Zadorozhny

1998-12-01

Full Text Available The results of three series of rocket measurements of mesospheric electric fields carried out under different geomagnetic conditions at polar and high middle latitudes are analysed. The measurements show a clear dependence of the vertical electric fields on geomagnetic activity at polar and high middle latitudes. The vertical electric fields in the lower mesosphere increase with the increase of geomagnetic indexes Kp and ∑Kp. The simultaneous increase of the vertical electric field strength and ion conductivity was observed in the mesosphere during geomagnetic disturbances. This striking phenomenon was displayed most clearly during the solar proton events of October, 1989 accompanied by very strong geomagnetic storm (Kp=8+. A possible mechanism of generation of the vertical electric fields in the mesosphere caused by gravitational sedimentation of charged aerosol particles is discussed. Simultaneous existence in the mesosphere of both the negative and positive multiply charged aerosol particles of different sizes is assumed for explanation of the observed V/m vertical electric fields and their behaviour under geomagnetically disturbed conditions.Keywords. Atmospheric composition and structure (aerosols and particles · Ionosphere (electric fields and currents · Meteorology and atmospheric dynamics (atmospheric electricity

Holographic estimate of the meson cloud contribution to nucleon axial form factor

Science.gov (United States)

Ramalho, G.

2018-04-01

We use light-front holography to estimate the valence quark and the meson cloud contributions to the nucleon axial form factor. The free couplings of the holographic model are determined by the empirical data and by the information extracted from lattice QCD. The holographic model provides a good description of the empirical data when we consider a meson cloud mixture of about 30% in the physical nucleon state. The estimate of the valence quark contribution to the nucleon axial form factor compares well with the lattice QCD data for small pion masses. Our estimate of the meson cloud contribution to the nucleon axial form factor has a slower falloff with the square momentum transfer compared to typical estimates from quark models with meson cloud dressing.

Effects of geomagnetic activity on the mesospheric electric fields

Directory of Open Access Journals (Sweden)

A. M. Zadorozhny

Full Text Available The results of three series of rocket measurements of mesospheric electric fields carried out under different geomagnetic conditions at polar and high middle latitudes are analysed. The measurements show a clear dependence of the vertical electric fields on geomagnetic activity at polar and high middle latitudes. The vertical electric fields in the lower mesosphere increase with the increase of geomagnetic indexes K_p and ∑K_p. The simultaneous increase of the vertical electric field strength and ion conductivity was observed in the mesosphere during geomagnetic disturbances. This striking phenomenon was displayed most clearly during the solar proton events of October, 1989 accompanied by very strong geomagnetic storm (K_p=8+. A possible mechanism of generation of the vertical electric fields in the mesosphere caused by gravitational sedimentation of charged aerosol particles is discussed. Simultaneous existence in the mesosphere of both the negative and positive multiply charged aerosol particles of different sizes is assumed for explanation of the observed V/m vertical electric fields and their behaviour under geomagnetically disturbed conditions.

Keywords. Atmospheric composition and structure (aerosols and particles · Ionosphere (electric fields and currents · Meteorology and atmospheric dynamics (atmospheric electricity

Revised Correlation between Odin/OSIRIS PMC Properties and Coincident TIMED/SABER Mesospheric Temperatures

Science.gov (United States)

Feofilov, A. G.; Petelina, S. V.; Kutepov, A. A.; Pesnell, W. D.; Goldberg, R. A.; Llewellyn, E. J.; Russell, J. M.

2006-01-01

The Optical Spectrograph and Infrared Imaging System (OSIRIS) instrument on board the Odin satellite detects Polar Mesospheric Clouds (PMCs) through the enhancement in the limb-scattered solar radiance. The Sounding of the Atmosphere using the Broadband Emission Radiometry (SABER) instrument on board the TIMED satellite is a limb scanning infrared radiometer that measures temperature and vertical profiles and energetic parameters for minor constituents in the mesosphere and lower thermosphere. The combination of OSIRIS and SABER data has been previously used to statistically derive thermal conditions for PMC existence [Petelina et al., 2005]. a, A.A. Kutepov, W.D. Pesnell, In this work, we employ the simultaneous common volume measurements of PMCs by OSIRIS and temperature profiles measured by SABER for the Northern Hemisphere summers of 2002-2005 and corrected in the polar region by accounting for the vibrational-vibrational energy exchange among the CO2 isotopes [Kutepov et al., 2006]. For each of 20 coincidences identified within plus or minus 1 degree latitude, plus or minus 2 degrees longitude and less than 1 hour time the frost point temperatures were calculated using the corresponding SABER temperature profile and water vapor densities of 1,3, and 10 ppmv. We found that the PMC presence and brightness correlated only with the temperature threshold that corresponds to the frost point. The absolute value of the temperature below the frost point, however, didn't play a significant role in the intensity of PMC signal for the majority of selected coincidences. The presence of several bright clouds at temperatures above the frost point is obviously related to the limitation of the limb geometry when some near- or far-field PMCs located at higher (and warmer) altitudes appear to be at lower altitudes.

Recent results from studies of electric discharges in the mesosphere

DEFF Research Database (Denmark)

Neubert, Torsten; Rycroft, M.; Farges, T.

2008-01-01

The paper reviews recent advances in studies of electric discharges in the stratosphere and mesosphere above thunderstorms, and their effects on the atmosphere. The primary focus is on the sprite discharge occurring in the mesosphere, which is the most commonly observed high altitude discharge...... to 1000 km distance, whereas elves and lightning have been shown significantly to affect ionization and heating of the lower ionosphere/mesosphere. Studies of the thunderstorm systems powering high altitude discharges show the important role of intracloud (IC) lightning in sprite generation as seen...

On the effective turbulence driving mode of molecular clouds formed in disc galaxies

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Jin, Keitaro; Salim, Diane M.; Federrath, Christoph; Tasker, Elizabeth J.; Habe, Asao; Kainulainen, Jouni T.

2017-07-01

We determine the physical properties and turbulence driving mode of molecular clouds formed in numerical simulations of a Milky Way-type disc galaxy with parsec-scale resolution. The clouds form through gravitational fragmentation of the gas, leading to average values for mass, radii and velocity dispersion in good agreement with observations of Milky Way clouds. The driving parameter (b) for the turbulence within each cloud is characterized by the ratio of the density contrast (σ _{ρ /ρ _0}) to the average Mach number (M) within the cloud, b=σ _{ρ /ρ _0}/M. As shown in previous works, b ˜ 1/3 indicates solenoidal (divergence-free) driving and b ˜ 1 indicates compressive (curl-free) driving. We find that the average b value of all the clouds formed in the simulations has a lower limit of b > 0.2. Importantly, we find that b has a broad distribution, covering values from purely solenoidal to purely compressive driving. Tracking the evolution of individual clouds reveals that the b value for each cloud does not vary significantly over their lifetime. Finally, we perform a resolution study with minimum cell sizes of 8, 4, 2 and 1 pc and find that the average b value increases with increasing resolution. Therefore, we conclude that our measured b values are strictly lower limits and that a resolution better than 1 pc is required for convergence. However, regardless of the resolution, we find that b varies by factors of a few in all cases, which means that the effective driving mode alters significantly from cloud to cloud.

Generating Free-Form Grid Truss Structures from 3D Scanned Point Clouds

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Hui Ding

2017-01-01

Full Text Available Reconstruction, according to physical shape, is a novel way to generate free-form grid truss structures. 3D scanning is an effective means of acquiring physical form information and it generates dense point clouds on surfaces of objects. However, generating grid truss structures from point clouds is still a challenge. Based on the advancing front technique (AFT which is widely used in Finite Element Method (FEM, a scheme for generating grid truss structures from 3D scanned point clouds is proposed in this paper. Based on the characteristics of point cloud data, the search box is adopted to reduce the search space in grid generating. A front advancing procedure suit for point clouds is established. Delaunay method and Laplacian method are used to improve the quality of the generated grids, and an adjustment strategy that locates grid nodes at appointed places is proposed. Several examples of generating grid truss structures from 3D scanned point clouds of seashells are carried out to verify the proposed scheme. Physical models of the grid truss structures generated in the examples are manufactured by 3D print, which solidifies the feasibility of the scheme.

Mars’ seasonal mesospheric transport seen through nitric oxide nightglow

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Milby, Zachariah; Stiepen, Arnaud; Jain, Sonal; Schneider, Nicholas M.; Deighan, Justin; Gonzalez-Galindo, Francisco; Gerard, Jean-Claude; Stevens, Michael H.; Bougher, Stephen W.; Evans, J. Scott; Stewart, A. Ian; Chaffin, Michael; Crismani, Matteo; McClintock, William E.; Clarke, John T.; Holsclaw, Greg; Montmessin, Franck; Lefevre, Franck; Forget, Francois; Lo, Daniel Y.; Hubert, Benoît; Jakosky, Bruce

2017-10-01

We analyze the ultraviolet nightglow in the atmosphere of Mars through nitric oxide (NO) δ and γ band emissions as observed by the Imaging UltraViolet Spectrograph (IUVS) instrument onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft when it is at apoapse and periapse.In the dayside thermosphere of Mars, solar extreme-ultraviolet radiation dissociates CO2 and N2 molecules. O(3P) and N(4S) atoms are carried from the dayside to the nightside by the day-night hemispheric transport process, where they descend through the nightside mesosphere and can radiatively recombine to form NO(C2Π). The excited molecules rapidly relax by emitting photons in the UV δ and γ bands. These emissions are indicators of the N and O atom fluxes from the dayside to Mars’ nightside and the descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015, 2017).Observations of these emissions are gathered from a large dataset spanning different seasonal conditions.We present discussion on the variability in the brightness and altitude of the emission with season, geographical position (longitude), and local time, along with possible interpretation by local and global changes in the mesosphere dynamics. We show the possible impact of atmospheric waves forcing longitudinal variability and data-to-model comparisons indicating a wave-3 structure in Mars’ nightside mesosphere. Quantitative comparison with calculations of the Laboratoire de Météorologie Dynamique-Mars Global Climate Model (LMD-MGCM) suggests the model reproduces both the global trend of NO nightglow emission and its seasonal variation. However, it also indicates large discrepancies, with the emission up to a factor 50 times fainter in the model, suggesting that the predicted transport is too efficient toward the night winter pole in the thermosphere by

3-Dimensional numerical simulations of the dynamics of the Venusian mesosphere and thermosphere

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Tingle, S.; Mueller-Wodarg, I. C.

2009-12-01

We present the first results from a new 3-dimensional numerical simulation of the steady state dynamics of the Venusian mesosphere and thermosphere (60-300 km). We have adapted the dynamical core of the Titan thermosphere global circulation model (GCM) [1] to a steady state background atmosphere. Our background atmosphere is derived from a hydrostatic combination of the VTS3 [2] and Venus International Reference Atmosphere (VIRA) [3] empirical models, which are otherwise discontinuous at their 100 km interface. We use 4th order polynomials to link the VTS3 and VIRA thermal profiles and employ hydrostatic balance to derive a consistent density profile. We also present comparisons of our background atmosphere to data from the ESA Venus Express Mission. The thermal structure of the Venusian mesosphere is relatively well documented; however, direct measurements of wind speeds are limited. Venus’ slow rotation results in a negligible Coriolis force. This suggests that the zonal circulation should arise from cyclostrophic balance; where the equatorward component of the centrifugal force balances poleward meridional pressure gradients [4]. The sparseness of direct and in-situ measurements has resulted in the application of cyclostrophic balance to measured thermal profiles to derive wind speeds [5] [6] [7] [8]. However, cyclostrophic balance is only strictly valid at mid latitudes (˜ ± 30-75°) and its applicability to the Venusian mesosphere has not been conclusively demonstrated. Our simulations, by solving the full Navier-Stokes momentum equation, will enable us assess the validity of cyclostrophic balance as a description of mesospheric dynamics. This work is part of an ongoing project to develop the first GCM to encompass the atmosphere from the cloud tops into the thermosphere. When complete, this model will enable self-consistent calculations of the dynamics, energy and composition of the atmosphere. It will thus provide a framework to address many of the

Spatial and Seasonal Variability of Temperature in CO2 Emission from Mars' Mesosphere

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Livengood, Timothy A.; Kostiuk, Theodor; Hewagama, Tilak; Kolasinski, John R.; Henning, Wade; Fast, Kelly Elizabeth; Sonnabend, Guido; Sornig, Manuela

2017-10-01

We have observed non-local thermodynamic equilibrium (non-LTE) emission of carbon dioxide that probes Mars’ mesosphere in 2001, 2003, 2007, 2012, 2014, and 2016. These measurements were conducted at 10.6 μm wavelength using the Goddard Space Flight Center Heterodyne Instrument for Planetary Winds and Composition (HIPWAC) from the NASA Infrared Telescope Facility (IRTF) at resolving power (1-33)×106. The Maxwellian broadening of the emission line can be measured at this resolution, providing a direct determination of temperature in the mesosphere. The nonLTE line appears as a narrow emission core within a broad absorption formed by tropospheric CO2, which provides temperature information reaching down to the martian surface, while the mesospheric line probes temperature at about 60-80 km altitude. We will report on the spatial distribution of temperature and emission line strength with local solar time on Mars, with latitude, as well as long-term variability including seasonal effects that modify the overall thermal structure of the atmosphere. These remote measurements complement results from orbital spacecraft through access to a broad range of local solar time on each occasion.This work has been supported by the NASA Planetary Astronomy and Solar Systems Observations Programs

A high-resolution study of mesospheric fine structure with the Jicamarca MST radar

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Sheth, R.; Kudeki, E.; Lehmacher, G.; Sarango, M.; Woodman, R.; Chau, J.; Guo, L.; Reyes, P.

2006-07-01

Correlation studies performed on data from recent mesospheric experiments conducted with the 50-MHz Jicamarca radar in May 2003 and July 2004 are reported. The study is based on signals detected from a combination of vertical and off-vertical beams. The nominal height resolution was 150 m and spectral estimates were obtained after ~1 min integration. Spectral widths and backscattered power generally show positive correlations at upper mesospheric heights in agreement with earlier findings (e.g., Fukao et al., 1980) that upper mesospheric echoes are dominated by isotropic Bragg scatter. In many instances in the upper mesosphere, a weakening of positive correlation away from layer centers (towards top and bottom boundaries) was observed with the aid of improved height resolution. This finding supports the idea that layer edges are dominated by anisotropic turbulence. The data also suggests that negative correlations observed at lower mesospheric heights are caused by scattering from anisotropic structures rather than reflections from sharp vertical gradients in electron density.

A high-resolution study of mesospheric fine structure with the Jicamarca MST radar

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R. Sheth

2006-07-01

Full Text Available Correlation studies performed on data from recent mesospheric experiments conducted with the 50-MHz Jicamarca radar in May 2003 and July 2004 are reported. The study is based on signals detected from a combination of vertical and off-vertical beams. The nominal height resolution was 150 m and spectral estimates were obtained after ~1 min integration. Spectral widths and backscattered power generally show positive correlations at upper mesospheric heights in agreement with earlier findings (e.g., Fukao et al., 1980 that upper mesospheric echoes are dominated by isotropic Bragg scatter. In many instances in the upper mesosphere, a weakening of positive correlation away from layer centers (towards top and bottom boundaries was observed with the aid of improved height resolution. This finding supports the idea that layer edges are dominated by anisotropic turbulence. The data also suggests that negative correlations observed at lower mesospheric heights are caused by scattering from anisotropic structures rather than reflections from sharp vertical gradients in electron density.

Mesospheric dynamics and chemistry from SME data

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Strobel, Darrell F.

1987-01-01

A fast Curtis matrix calculation of cooling rates due to the 15 micron band of CO2 is modified to parameterize the detailed calculations by Dickinson (1984) of infrared cooling by CO2 in the mesosphere and lower thermosphere. The calculations included separate NLTE treatment of the different 15 micron bands likely to be important for cooling. The goal was to compress the detailed properties of the different bands into a modified Curtis matrix, which represents one composite band with appropriate averaged radiative properties to allow for a simple and quick calculation of cooling rates given a temperature profile. Vertical constituent transport in the mesosphere was also studied.

Signatures of mesospheric particles in ionospheric data

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M. Friedrich

2009-02-01

Full Text Available The state of the ionosphere during the 2007 ECOMA/MASS campaign is described by in-situ observations by three sounding rockets launched from the Andøya Rocket Range and by ground based observations. The ground based measurements included the incoherent scatter radar EISCAT near Tromsø (both on UHF and VHF, as well as an MF radar, a meteor radar and an imaging riometer all located in the close vicinity of the rocket range. The pronounced electron density bite-outs seen by two of the rockets could not be detected from the ground, but the associated PMSE (Polar Mesospheric Summer Echoes provide indirect evidence of pronounced perturbations of mesospheric electron densities.

First Measurements of Polar Mesospheric Summer Echoes by a Tri-static Radar System

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La Hoz, C.

2015-12-01

Polar Mesospheric Summer Echoes (PMSE) have been observed for the first time by a tri-static radar system comprising the EISCAT VHF (224 MHz, 0.67 m Bragg wavelength) active radar in Tromso (Norway) and passive receiving stations in Kiruna, (Sweden) and Sodankyla (Finland). The antennas at the receiving stations, originally part of the EISCAT tri-static UHF radar system at 930 MHz, have been refitted with new feeder systems at the VHF frequency of the transmitter in Tromso. The refitted radar system opens new opportunities to study PMSE for its own sake and as a tracer of the dynamics of the polar mesosphere, a region that is difficult to investigate by other means. The measurements show that very frequently both remote receiving antennas detect coherent signals that are much greater than the regular incoherent scattering due to thermal electrons and coinciding in time and space with PMSE measured by the transmitter station in Tromso. This represents further evidence that PMSE is not aspect sensitive, as was already indicated by a less sensitive radar system in a bi-static configuration, and implying that the underlying atmospheric turbulence, at least at sub-meter scales, is isotropic in agreement with Kolmogorov's hypothesis. Measurements also show that the vertical rate of fall of persistent features of PMSE is the same as the vertical line of sight velocity inferred from the doppler shift of the PMSE signals. This equivalence forms the basis for using PMSE as a tracer of the dynamics of the background mesosphere. Thus, it is possible to measure the 3-dimensional velocity field in the PMSE layer over the intersection volume of the three antennas. Since the signals have large signal-to-noise ratios (up to 30 dB), the inferred velocities have high accuracies and good time resolutions. This affords the possibility to make estimates of momentum flux in the mesosphere deposited by overturning gravity waves. Gravity wave momentum flux is believed to be the engine of a

Observed Responses of Mesospheric Water Vapor to Solar Cycle and Dynamical Forcings

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Remsberg, Ellis; Damadeo, Robert; Natarajan, Murali; Bhatt, Praful

2018-04-01

This study focuses on responses of mesospheric water vapor (H2O) to the solar cycle flux at Lyman-α wavelength and to dynamical forcings according to the multivariate El-Nino/Southern Oscillation (ENSO) index. The zonal-averaged responses are for latitudes from 60°S to 60°N and pressure-altitudes from 0.01 to 1.0 hPa, as obtained from multiple linear regression analyses of time series of H2O from the Halogen Occultation Experiment for July 1992 to November 2005. The results compare very well with those from a separate simultaneous temporal and spatial (STS) method that also confirms that there are no significant sampling biases affecting both sets of results. Distributions of the seasonal amplitudes for temperature and H2O are in accord with the seasonal net circulation. In general, the responses of H2O to ENSO are anticorrelated with those of temperature. H2O responses to multivariate ENSO index are negative in the upper mesosphere and largest in the Northern Hemisphere; responses in the lower mesosphere are more symmetric with latitude. H2O responses to the Lyman-α flux (Lya) vary from strong negative values in the uppermost mesosphere to very weak, positive values in the tropical lowermost mesosphere. However, the effects of those H2O responses to the solar activity extend to the rest of the mesosphere via dynamical processes. Profiles of the responses to ENSO and Lya also agree reasonably with published results for H2O at the low latitudes from the Microwave Limb Sounder.

Mesospheric front observations by the OH airglow imager carried out at Ferraz Station on King George Island, Antarctic Peninsula, in 2011

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Giongo, Gabriel Augusto; Valentin Bageston, José; Prado Batista, Paulo; Wrasse, Cristiano Max; Dornelles Bittencourt, Gabriela; Paulino, Igo; Paes Leme, Neusa Maria; Fritts, David C.; Janches, Diego; Hocking, Wayne; Schuch, Nelson Jorge

2018-02-01

The main goals of this work are to characterize and investigate the potential wave sources of four mesospheric fronts identified in the hydroxyl near-infrared (OH-NIR) airglow images, obtained with an all-sky airglow imager installed at Comandante Ferraz Antarctic Station (EACF, as per its Portuguese acronym) located on King George Island in the Antarctic Peninsula. We identified and analyzed four mesospheric fronts in 2011 over King George Island. In addition, we investigate the atmospheric background environment between 80 and 100 km altitude and discuss the ducts and propagation conditions for these waves. For that, we used wind data obtained from a meteor radar operated at EACF and temperature data obtained from the TIMED/SABER satellite. The vertical wavenumber squared, m2, was calculated for each of the four waves. Even though no clearly defined duct (indicated by positive values of m2 sandwiched between layers above and below with m2 wind in the wave propagation direction (near to south) above the OH peak (88-92 km). The likely wave sources for these four cases were investigated by using meteorological satellite images and in two cases we could find that strong instabilities were potential sources, i.e., a cyclonic activity and a large convective cloud cell. In the other two cases it was not possible to associate troposphere sources as potential candidates for the generation of such wave fronts observed in the mesosphere and secondary wave sources were attributed to these cases.

Preface to special issue: Layered Phenomena in the Mesopause Region

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Chu, Xinzhao; Marsh, Daniel R.

2017-09-01

Historically, the Layered Phenomena in the Mesopause Region (LPMR) workshops have focused on studies of mesospheric clouds and their related science, including spectacular noctilucent clouds (NLCs), polar mesospheric clouds (PMCs), and polar mesospheric summer echoes (PMSEs). This is because, in the pre-technology era, these high-altitude ( 85 km) clouds revealed the existence of substance above the 'normal atmosphere' - our near-space environment is not empty! The occurrence and nature of these clouds have commanded the attention of atmospheric and space scientists for generations. Modern technologies developed in the last 50 years have enabled scientists to significantly advance our understanding of these layered phenomena. Satellite observations expanded these studies to global scales, while lidar and radar observations from the ground enabled fine-scale studies. The launch of the Aeronomy of Ice in the Mesosphere (AIM) satellite in 2007 brought mesospheric cloud research to a more mature level.

Effects of Major Sudden Stratospheric Warmings Identified in Midlatitude Mesospheric Rayleigh-Scatter Lidar Temperatures

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Sox, L.; Wickwar, V. B.; Fish, C. S.; Herron, J. P.

2014-12-01

Mesospheric temperature anomalies associated with Sudden Stratospheric Warmings (SSWs) have been observed extensively in the polar regions. However, observations of these anomalies at midlatitudes are sparse. The very dense 11-year data set, collected between 1993-2004, with the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory (ALO; 41.7°N, 111.8°W) at the Center for Atmospheric and Space Sciences (CASS) on the campus of Utah State University (USU), has been carefully examined for such anomalies. The temperatures derived from these data extend over the mesosphere, from 45 to 90 km. During this period extensive data were acquired during seven major SSW events. In this work we aim to determine the characteristics of the midlatitude mesospheric temperatures during these seven major SSWs. To do this, comparisons were made between the temperature profiles on individual nights before, during, and after the SSW events and the corresponding derived climatological temperature profiles (31-day by 11-year average) for those nights. A consistent disturbance pattern was observed in the mesospheric temperatures during these SSWs. A distinct shift from the nominal winter temperature pattern to a pattern more characteristic of summer temperatures was seen in the midlatitude mesosphere close to when the zonal winds in the polar stratosphere (at 10 hPa, 60° N) reversed from eastward to westward. This shift lasted for several days. This change in pattern included coolings in the upper mesosphere, comparable to those seen in the polar regions, and warmings in the lower mesosphere.

Analytic Closed-Form Solution of a Mixed Layer Model for Stratocumulus Clouds

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Akyurek, Bengu Ozge

Stratocumulus clouds play an important role in climate cooling and are hard to predict using global climate and weather forecast models. Thus, previous studies in the literature use observations and numerical simulation tools, such as large-eddy simulation (LES), to solve the governing equations for the evolution of stratocumulus clouds. In contrast to the previous works, this work provides an analytic closed-form solution to the cloud thickness evolution of stratocumulus clouds in a mixed-layer model framework. With a focus on application over coastal lands, the diurnal cycle of cloud thickness and whether or not clouds dissipate are of particular interest. An analytic solution enables the sensitivity analysis of implicitly interdependent variables and extrema analysis of cloud variables that are hard to achieve using numerical solutions. In this work, the sensitivity of inversion height, cloud-base height, and cloud thickness with respect to initial and boundary conditions, such as Bowen ratio, subsidence, surface temperature, and initial inversion height, are studied. A critical initial cloud thickness value that can be dissipated pre- and post-sunrise is provided. Furthermore, an extrema analysis is provided to obtain the minima and maxima of the inversion height and cloud thickness within 24 h. The proposed solution is validated against LES results under the same initial and boundary conditions. Then, the proposed analytic framework is extended to incorporate multiple vertical columns that are coupled by advection through wind flow. This enables a bridge between the micro-scale and the mesoscale relations. The effect of advection on cloud evolution is studied and a sensitivity analysis is provided.

Seasonal Transport in Mars' Mesosphere-Thermosphere revealed by Nitric Oxide nightglow

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Royer, E. M.; Stiepen, A.; Schneider, N. M.; Jain, S.; Milby, Z.; Deighan, J.; Gonzalez-Galindo, F.; Bougher, S. W.; Gerard, J. C. M. C.; Stevens, M. H.; Evans, J. S.; Stewart, I. F.; Chaffin, M.; McClintock, B.; Clarke, J. T.; Montmessin, F.; Holsclaw, G.; Lefèvre, F.; Forget, F.; Lo, D.; Hubert, B. A.; Jakosky, B. M.

2017-12-01

We analyze the ultraviolet nightglow in the atmosphere of Mars through the Nitric Oxide (NO) δ and γ band emissions observed by the Imaging Ultraviolet Spectrograph (IUVS, McClintock et al., 2015) when the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft is at apoapsis and periapsis. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation dissociates CO2 and N2 molecules. O(3P) and N(4S) atoms are carried by the day-to-night hemispheric transport. They descend in the nightside mesosphere, where they can radiatively recombine to form NO(C2Π). The excited molecules rapidly relax by emitting UV photons in the δ and γ bands. These emissions are thus indicators of the N and O atom fluxes transported from the dayside to Mars' nightside and the descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015, 2017). A large dataset of nightside disk images and vertical limb scans during southern winter, fall equinox and southern summer conditions have been accumulated since the beginning of the mission. We will present a discussion regarding the variability of the brightness and altitude of the emission with season, geographical position (longitude) and local time and possible interpretation for local and global changes in the mesosphere dynamics. We show the possible impact of atmospheric waves structuring the emission longitudinally and indicating a wave-3 structure in Mars' nightside mesosphere. Quantitative comparison with calculations from the LMD-MGCM (Laboratoire de Météorologie Dynamique-Mars Global Climate Model) show that the model globally reproduces the trends of the NO nightglow emission and its seasonal variation but also indicates large discrepancies (up to a factor 50 fainter in the model) suggesting that the predicted transport is too efficient toward the night winter pole

Properties of subvisible cirrus clouds formed by homogeneous freezing

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B. Kärcher

2002-01-01

Full Text Available Number concentrations and mean sizes of ice crystals and derived microphysical and optical properties of subvisible cirrus clouds (SVCs formed by homogeneous freezing of supercooled aerosols are investigated as a function of temperature and updraft speed of adiabatically ascending air parcels. The properties of such clouds are insensitive to variations of the aerosol number and size distribution. Based on criteria constraining the optical extinction, sedimentation time, and existence time of SVCs, longer-lived (>10min clouds, capable of exerting a measurable radiative or chemical impact, are generated within a narrow range of updraft speeds below 1-2cm s-1 at temperatures below about 215K, with concentrations of ice crystals not exceeding 0.1cm-3. The clouds do not reach an equilibrium state because the ice crystals sediment out of the formation layer typically before the supersaturation is removed. Two important conclusions emerge from this work. First, the above characteristics of SVCs may provide an explanation for why SVCs are more common in the cold tropical than in the warmer midlatitude tropopause region. Second, it seems likely that a limited number (-3 of effective heterogeneous freezing nuclei that nucleate ice below the homogeneous freezing threshold can control the formation and properties of SVCs, although homogeneous freezing nuclei are far more abundant.

On the origin of the mesospheric quasi-stationary planetary waves in the unusual Arctic winter 2015/2016

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Matthias, Vivien; Ern, Manfred

2018-04-01

The midwinter 2015/2016 was characterized by an unusually strong polar night jet (PNJ) and extraordinarily large stationary planetary wave (SPW) amplitudes in the subtropical mesosphere. The aim of this study is, therefore, to find the origin of these mesospheric SPWs in the midwinter 2015/2016 study period. The study duration is split into two periods: the first period runs from late December 2015 until early January 2016 (Period I), and the second period from early January until mid-January 2016 (Period II). While the SPW 1 dominates in the subtropical mesosphere in Period I, it is the SPW 2 that dominates in Period II. There are three possibilities explaining how SPWs can occur in the mesosphere: (1) they propagate upward from the stratosphere, (2) they are generated in situ by longitudinally variable gravity wave (GW) drag, or (3) they are generated in situ by barotropic and/or baroclinic instabilities. Using global satellite observations from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) the origin of the mesospheric SPWs is investigated for both time periods. We find that due to the strong PNJ the SPWs were not able to propagate upward into the mesosphere northward of 50° N but were deflected upward and equatorward into the subtropical mesosphere. We show that the SPWs observed in the subtropical mesosphere are the same SPWs as in the mid-latitudinal stratosphere. Simultaneously, we find evidence that the mesospheric SPWs in polar latitudes were generated in situ by longitudinally variable GW drag and that there is a mixture of in situ generation by longitudinally variable GW drag and by instabilities at mid-latitudes. Our results, based on observations, show that the abovementioned three mechanisms can act at the same time which confirms earlier model studies. Additionally, the possible contribution from, or impact of, unusually strong SPWs in the subtropical mesosphere to the disruption of

Climate impact of idealized winter polar mesospheric and stratospheric ozone losses as caused by energetic particle precipitation

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Meraner, Katharina; Schmidt, Hauke

2018-01-01

Energetic particles enter the polar atmosphere and enhance the production of nitrogen oxides and hydrogen oxides in the winter stratosphere and mesosphere. Both components are powerful ozone destroyers. Recently, it has been inferred from observations that the direct effect of energetic particle precipitation (EPP) causes significant long-term mesospheric ozone variability. Satellites observe a decrease in mesospheric ozone up to 34 % between EPP maximum and EPP minimum. Stratospheric ozone decreases due to the indirect effect of EPP by about 10-15 % observed by satellite instruments. Here, we analyze the climate impact of winter boreal idealized polar mesospheric and polar stratospheric ozone losses as caused by EPP in the coupled Max Planck Institute Earth System Model (MPI-ESM). Using radiative transfer modeling, we find that the radiative forcing of mesospheric ozone loss during polar night is small. Hence, climate effects of mesospheric ozone loss due to energetic particles seem unlikely. Stratospheric ozone loss due to energetic particles warms the winter polar stratosphere and subsequently weakens the polar vortex. However, those changes are small, and few statistically significant changes in surface climate are found.

Solar cycle variations in mesospheric carbon monoxide

Science.gov (United States)

Lee, Jae N.; Wu, Dong L.; Ruzmaikin, Alexander; Fontenla, Juan

2018-05-01

As an extension of Lee et al. (2013), solar cycle variation of carbon monoxide (CO) is analyzed with MLS observation, which covers more than thirteen years (2004-2017) including maximum of solar cycle 24. Being produced primarily by the carbon dioxide (CO2) photolysis in the lower thermosphere, the variations of the mesospheric CO concentration are largely driven by the solar cycle modulated ultraviolet (UV) variation. This solar signal extends down to the lower altitudes by the dynamical descent in the winter polar vortex, showing a time lag that is consistent with the average descent velocity. To characterize a global distribution of the solar impact, MLS CO is correlated with the SORCE measured total solar irradiance (TSI) and UV. As high as 0.8 in most of the polar mesosphere, the linear correlation coefficients between CO and UV/TSI are more robust than those found in the previous work. The photochemical contribution explains most (68%) of the total variance of CO while the dynamical contribution accounts for 21% of the total variance at upper mesosphere. The photochemistry driven CO anomaly signal is extended in the tropics by vertical mixing. The solar cycle signal in CO is further examined with the Whole Atmosphere Community Climate Model (WACCM) 3.5 simulation by implementing two different modeled Spectral Solar Irradiances (SSIs): SRPM 2012 and NRLSSI. The model simulations underestimate the mean CO amount and solar cycle variations of CO, by a factor of 3, compared to those obtained from MLS observation. Different inputs of the solar spectrum have small impacts on CO variation.

Climate impact of idealized winter polar mesospheric and stratospheric ozone losses as caused by energetic particle precipitation

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K. Meraner

2018-01-01

Full Text Available Energetic particles enter the polar atmosphere and enhance the production of nitrogen oxides and hydrogen oxides in the winter stratosphere and mesosphere. Both components are powerful ozone destroyers. Recently, it has been inferred from observations that the direct effect of energetic particle precipitation (EPP causes significant long-term mesospheric ozone variability. Satellites observe a decrease in mesospheric ozone up to 34 % between EPP maximum and EPP minimum. Stratospheric ozone decreases due to the indirect effect of EPP by about 10–15 % observed by satellite instruments. Here, we analyze the climate impact of winter boreal idealized polar mesospheric and polar stratospheric ozone losses as caused by EPP in the coupled Max Planck Institute Earth System Model (MPI-ESM. Using radiative transfer modeling, we find that the radiative forcing of mesospheric ozone loss during polar night is small. Hence, climate effects of mesospheric ozone loss due to energetic particles seem unlikely. Stratospheric ozone loss due to energetic particles warms the winter polar stratosphere and subsequently weakens the polar vortex. However, those changes are small, and few statistically significant changes in surface climate are found.

Energy balance constraints on gravity wave induced eddy diffusion in the mesosphere and lower thermosphere

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Strobel, D. F.; Apruzese, J. P.; Schoeberl, M. R.

1985-01-01

The constraints on turbulence improved by the mesospheric heat budget are reexamined, and the sufficiency of the theoretical evidence to support the hypothesis that the eddy Prandtl number is greater than one in the mesosphere is considered. The mesopause thermal structure is calculated with turbulent diffusion coefficients commonly used in chemical models and deduced from mean zonal wind deceleration. It is shown that extreme mesopause temperatures of less than 100 K are produced by the large net cooling. The results demonstrate the importance of the Prandtl number for mesospheric turbulence.

Statistical parameters of nonisothermal lower ionospheric plasma in the electrically active mesosphere

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Martynenko, S. I.; Rozumenko, V. T.; Tyrnov, O. F.; Manson, A. H.; Meek, C. E.

The large V/m electric fields inherent in the lower mesosphere play an essential role in lower ionospheric electrodynamics. They must be the cause of large variations in the electron temperature and the electron collision frequency and consequently of the transition of the ionospheric plasma in the lower part of the D region into a nonisothermal state. This study is based on the datasets on large mesospheric electric fields collected with the 2.2-MHz radar of the Institute of Space and Atmospheric Studies, University of Saskatchewan, Canada (52°N geographic latitude, 60.4°N geomagnetic latitude), and with the 2.3-MHz radar of the Kharkiv V. Karazin National University, Ukraine (49.6°N geographic latitude, 45.6°N geomagnetic latitude). The statistical analysis of these data is presented by [Meek, C.E., Manson, A.H., Martynenko, S.I., Rozumenko, V.T., Tyrnov, O.F. Remote sensing of mesospheric electric fields using MF radars. J. Atmos. Solar-Terr. Phys. 66, 881-890, 2004. 10.1016/j.jastp.2004.02.002]. The large mesospheric electric fields in the 60-67-km altitude range are experimentally established to follow a Rayleigh distribution in the 0 < E < 2.5 V/m interval. These data have permitted the resulting differential distributions of relative disturbances in the electron temperature, θ, and the effective electron collision frequency, η, to be determined. The most probable θ and η values are found to be in the 1.4-2.2 interval, and hence the nonstationary state of the lower part of the D region needs to be accounted for in studying processes coupling the electrically active mesosphere and the lower ionospheric plasma.

Mesospheric signatures observed during 2010 minor stratospheric warming at King Sejong Station (62°S, 59°W)

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Eswaraiah, S.; Kim, Yong Ha; Hong, Junseok; Kim, Jeong-Han; Ratnam, M. Venkat; Chandran, A.; Rao, S. V. B.; Riggin, Dennis

2016-03-01

A minor stratospheric sudden warming (SSW) event was noticed in the southern hemisphere (SH) during September (day 259) 2010 along with two episodic warmings in early August (day 212) and late October (day 300) 2010. Among the three warming events, the signature of mesosphere response was detected only for the September event in the mesospheric wind dataset from both meteor radar and MF radar located at King Sejong Station (62°S, 59°W) and Rothera (68°S, 68°W), Antarctica, respectively. The zonal winds in the mesosphere reversed approximately a week before the September SSW event, as has been observed in the 2002 major SSW. Signatures of mesospheric cooling (MC) in association with stratospheric warmings are found in temperatures measured by the Microwave Limb Sounder (MLS). Simulations of specified dynamics version of Whole Atmosphere Community Climate Model (SD-WACCM) are able to reproduce these observed features. The mesospheric wind field was found to differ significantly from that of normal years probably due to enhanced planetary wave (PW) activity before the SSW. From the wavelet analysis of wind data of both stations, we find that strong 14-16 day PWs prevailed prior to the SSW and disappeared suddenly after the SSW in the mesosphere. Our study provides evidence that minor SSWs in SH can result in significant effects on the mesospheric dynamics as in the northern hemisphere.

Formation of Massive Molecular Cloud Cores by Cloud-cloud Collision

OpenAIRE

Inoue, Tsuyoshi; Fukui, Yasuo

2013-01-01

Recent observations of molecular clouds around rich massive star clusters including NGC3603, Westerlund 2, and M20 revealed that the formation of massive stars could be triggered by a cloud-cloud collision. By using three-dimensional, isothermal, magnetohydrodynamics simulations with the effect of self-gravity, we demonstrate that massive, gravitationally unstable, molecular cloud cores are formed behind the strong shock waves induced by the cloud-cloud collision. We find that the massive mol...

Simultaneous mesosphere-thermosphere-ionosphere parameter measurements over Gadanki (13.5°N, 79.2°E): First results

Science.gov (United States)

Taori, A.; Dashora, N.; Raghunath, K.; Russell, J. M., III; Mlynczak, Martin G.

2011-07-01

We report first simultaneous airglow, lidar, and total electron content measurements in the mesosphere-thermosphere-ionosphere system behavior from Gadanki (13.5°N, 79.2°E). The observed variability in mesospheric temperatures and 630 nm thermospheric emission intensity shows large variations from one night to another with clear upward propagating waves at mesospheric altitudes. The deduced mesospheric temperatures compare well with Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER)-derived temperatures, while the variability agrees well with lidar temperatures (on the night of simultaneous observations). The 630.0 nm thermospheric emission intensity and GPS-total electron content data exhibit occurrence of plasma depletions on the nights of 22-23 October and 22-23 May 2009, while no depletions are noted on the nearby nights of 23-24 October and 21-22 May 2009. These first simultaneous data reveal strong gravity-wave growth at upper mesospheric altitudes on the nights when plasma depletions were noted.

Mesospheric front observations by the OH airglow imager carried out at Ferraz Station on King George Island, Antarctic Peninsula, in 2011

Directory of Open Access Journals (Sweden)

G. A. Giongo

2018-02-01

Full Text Available The main goals of this work are to characterize and investigate the potential wave sources of four mesospheric fronts identified in the hydroxyl near-infrared (OH-NIR airglow images, obtained with an all-sky airglow imager installed at Comandante Ferraz Antarctic Station (EACF, as per its Portuguese acronym located on King George Island in the Antarctic Peninsula. We identified and analyzed four mesospheric fronts in 2011 over King George Island. In addition, we investigate the atmospheric background environment between 80 and 100 km altitude and discuss the ducts and propagation conditions for these waves. For that, we used wind data obtained from a meteor radar operated at EACF and temperature data obtained from the TIMED/SABER satellite. The vertical wavenumber squared, m2, was calculated for each of the four waves. Even though no clearly defined duct (indicated by positive values of m2 sandwiched between layers above and below with m2 < 0 was found in any of the events, favorable propagation conditions for horizontal propagation of the fronts were found in three cases. In the fourth case, the wave front did not find any duct support and it appeared to dissipate near the zenith, transferring energy and momentum to the medium and, consequently, accelerating the wind in the wave propagation direction (near to south above the OH peak (88–92 km. The likely wave sources for these four cases were investigated by using meteorological satellite images and in two cases we could find that strong instabilities were potential sources, i.e., a cyclonic activity and a large convective cloud cell. In the other two cases it was not possible to associate troposphere sources as potential candidates for the generation of such wave fronts observed in the mesosphere and secondary wave sources were attributed to these cases.

Statistics on the parameters of nonisothermal ionospheric plasma in large mesospheric electric fields

Science.gov (United States)

Martynenko, S.; Rozumenko, V.; Tyrnov, O.; Manson, A.; Meek, C.

The large V/m electric fields inherent in the mesosphere play an essential role in lower ionospheric electrodynamics. They must be the cause of large variations in the electron temperature and the electron collision frequency at D region altitudes, and consequently the ionospheric plasma in the lower part of the D region undergoes a transition into a nonisothermal state. This study is based on the databases on large mesospheric electric fields collected with the 2.2-MHz radar of the Institute of Space and Atmospheric Studies, University of Saskatchewan, Canada (52°N geographic latitude, 60.4°N geomagnetic latitude) and with the 2.3-MHz radar of the Kharkiv V. Karazin National University (49.6°N geographic latitude, 45.6°N geomagnetic latitude). The statistical analysis of these data is presented in Meek, C. E., A. H. Manson, S. I. Martynenko, V. T. Rozumenko, O. F. Tyrnov, Remote sensing of mesospheric electric fields using MF radars, Journal of Atmospheric and Solar-Terrestrial Physics, in press. The large mesospheric electric fields is experimentally established to follow a Rayleigh distribution in the interval 0 mesosphere and the lower ionospheric plasma.

Power spectra of mesospheric velocities in polar regions

Science.gov (United States)

Czechowsky, P.; Ruster, R.

1985-01-01

The mobile SOUSY radar was operated on Andoya in Northern Norway during the MAP/WINE campaign from November 1983 to February 1984 and for about two weeks in June 1984 to study the seasonal dependence of mesospheric structures and dynamics at polar latitudes. During the winter period, measurements were carried out on 57 days, primarily in coordination with the schedule of the rocket experiments. Echoes were detected in the troposphere and stratosphere up to 30 km and at mesospheric heights from about 50 to 90 km with a distinct maximum around noon. In summer, the radar system was operated continuously from 19th to the 28th of June 1984. Echoes occurred almost for 24 hours in the height range from 70 to 95 km showing no recognizable diurnal variation. Similar observations in polar latitudes were carried out for several years with the Poker Flat Radar in Alaska.

Recent progress in mesospheric gravity wave studies using nightglow imaging system

Energy Technology Data Exchange (ETDEWEB)

Taylor, Michael J.; Pendleton Junior, William R.; Pautet, Pierre-Dominique; Zhao, Yucheng; Olsen, Chris; Babu, Hema Karnam Surendra [Center for Atmospheric and Space Sciences, Utah State University, Logan, Utah (United States); Medeiros, Amauri F. [Universidade Federal de Campina Grande, Centro de Ciencias e Tecnologia, Unidade Academica de Fisica, Campina Grande, PB (Brazil); Takahashi, Hisao, E-mail: mtaylor@cc.usu.edu, E-mail: wpen@cc.usu.edu, E-mail: dominiquepautet@gmail.com, E-mail: yucheng@cc.usu.edu, E-mail: cmellob@gmail.com, E-mail: hema_sb@rediffmail.com, E-mail: afragoso@df.ufcg.edu.br, E-mail: hisaotak@laser.inpe.br [INPE, Sao Jose dos Campos, SP (Brazil)

2007-07-01

A variety of optical remote sensing techniques have now revealed a rich spectrum of wave activity in the upper atmosphere. Many of these perturbations, with periodicities ranging from {approx} 5 min to many hours and horizontal scales of a few tens of km to several thousands km, are due to freely propagating atmospheric gravity waves and forced tidal oscillations. Passive optical observations of the spatial and temporal characteristics of these waves in the mesosphere and lower thermosphere (MLT) region ( {approx} 80-100 km) are facilitated by several naturally occurring, vertically distinct nightglow layers. This paper describes the use of state-of-the-art ground-based CCD imaging techniques to detect these waves in intensity and temperature. All-sky (180 deg ) image measurements are used to illustrate the characteristics of small-scale, short period ( < 1 hour) waves and to investigate their seasonal propagation and momentum impact on the MLT region. These results are then contrasted with measurements of mesospheric temperature made using a new temperature mapping imaging system capable of determining induced temperature amplitudes of a large range of wave motions and investigating night-to-night and seasonal variability in mesospheric temperature. (author)

Equatorial enhancement of the nighttime OH mesospheric infrared airglow

International Nuclear Information System (INIS)

Baker, D J; Thurgood, B K; Harrison, W K; Mlynczak, M G; Russell, J M

2007-01-01

Global measurements of the hydroxyl mesospheric airglow over an extended period of time have been made possible by the NASA SABER infrared sensor aboard the TIMED satellite which has been functioning since December of 2001. The orbital mission has continued over a significant portion of a solar cycle. Experimental data from SABER for several years have exhibited equatorial enhancements of the nighttime mesospheric OH (Δv=2) airglow layer consistent with the high average diurnal solar flux. The brightening of the OH airglow typically means more H+O 3 is being reacted. At both the spring and autumn seasonal equinoxes when the equatorial solar UV irradiance mean is greatest, the peak volume emission rate (VER) of the nighttime Meinel infrared airglow typically appears to be both significantly brighter plus lower in altitude by several kilometres at low latitudes compared with midlatitude findings

Stratospheric warming influence on the mesosphere/lower thermosphere as seen by the extended CMAM

Directory of Open Access Journals (Sweden)

M. G. Shepherd

2014-06-01

Full Text Available The response of the upper mesosphere/lower thermosphere region to major sudden stratospheric warming (SSW is examined employing temperature, winds, NOX and CO constituents from the extended Canadian Middle Atmosphere Model (CMAM with continuous incremental nudging below 10 hPa (~ 30 km. The model results considered cover high latitudes (60–85° N from 10 to 150 km height for the December–March period of 2003/2004, 2005/2006 and 2008/2009, when some of the strongest SSWs in recent years were observed. NOX and CO are used as proxies for examining transport. Comparisons with ACE-FTS (Atmospheric Chemistry Experiment–Fourier Transform Spectrometer satellite observations show that the model represents well the dynamics of the upper mesosphere/lower thermosphere region, the coupling of the stratosphere–mesosphere, and the NOX and CO transport. New information is obtained on the upper mesosphere/lower thermosphere up to 150 km showing that the NOX volume mixing ratio in the 2003/2004 winter was very perturbed indicating transport from the lower atmosphere and intense mixing with large NOX influx from the thermosphere compared to 2006 and 2009. These results, together with those from other models and observations, clearly show the impact of stratospheric warmings on the thermosphere.

The seasonal variation of water vapor and ozone in the upper mesosphere - Implications for vertical transport and ozone photochemistry

Science.gov (United States)

Bevilacqua, Richard M.; Summers, Michael E.; Strobel, Darrell F.; Olivero, John J.; Allen, Mark

1990-01-01

This paper reviews the data base supplied by ground-based microwave measurements of water vapor in the mesosphere obtained in three separate experiments over an eight-year period. These measurements indicate that the seasonal variation of water vapor in the mesosphere is dominated by an annual component with low values in winter and high values in summer, suggesting that the seasonal variation of water vapor in the mesosphere (below 80 km) is controlled by advective rather than diffusive processes. Both the seasonal variation and the absolute magnitude of the water vapor mixing ratios obtained in microwave measurements were corroborated by measurements obtained in the Spacelab GRILLE and ATMOS experiments, and were found to be consistent with several recent mesospheric dynamics studies.

Space-borne observation of mesospheric bore by Visible and near Infrared Spectral Imager onboard the International Space Station

Science.gov (United States)

Hozumi, Y.; Saito, A.; Sakanoi, T.; Yamazaki, A.; Hosokawa, K.

2017-12-01

Mesospheric bores were observed by Visible and near Infrared Spectral Imager (VISI) of the ISS-IMAP mission (Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere mapping mission from the International Space Station) in O2 airglow at 762 nm wavelength. The mesospheric bore is moving front of sharp jump followed by undulations or turbulence in the mesopause region. Since previous studies of mesospheric bore were mainly based on ground-based airglow imaging that is limited in field-of-view and observing site, little is known about its horizontal extent and global behavior. Space-borne imaging by ISS-IMAP/VISI provides an opportunity to study the mesospheric bore with a wide field-of-view and global coverage. A mesospheric bore was captured by VISI in two consecutive paths on 9 July 2015 over the south of African continent (48ºS - 54ºS and 15ºE). The wave front aligned with south-north direction and propagated to west. The phase velocity and wave length of the following undulation were estimated to 100 m/s and 30 km, respectively. Those parameters are similar to those reported by previous studies. 30º anti-clockwise rotation of the wave front was recognized in 100 min. Another mesospheric bore was captured on 9 May 2013 over the south Atlantic ocean (35ºS - 43ºS and 24ºW - 1ºE) with more than 2,200 km horizontal extent of wave front. The wave front aligned with southeast-northwest direction. Because the following undulation is recognized in the southwest side of the wave front, it is estimated to propagate to northeast direction. The wave front was modulated with 1,000 km wave length. This modulation implies inhomogeneity of the phase velocity.

Molecular Hydrogen Images of Star Forming Regions in the Magellanic Clouds

Science.gov (United States)

Probst, Ronald G.; Barba, R.; Bolatto, A.; Chu, Y.; Points, S.; Rubio, M.; Smith, C.

2011-01-01

The Large and Small Magellanic Clouds exhibit a variety of star formation physics with multiple phase components in low metallicity, gas rich environments. The 10 K, 100 K, and 104 K regimes are well explored. We are imaging LMC and SMC star forming regions in 2.12 micron H2 emission which arises in the 1000 K transition zone of molecular clouds. This is an NOAO Survey program using the widefield IR camera NEWFIRM on the CTIO 4-m Blanco telescope during its limited southern deployment. The data set will have immediate morphological applications and will provide target selection for followup infrared spectroscopy. We will provide a public archive of fully calibrated images with no proprietary period. NOAO is operated by the Association of Universities for Research in Astronomy, under cooperative agreement with the National Science Foundation.

Radar observations of high-latitude lower-thermospheric and upper-mesospheric winds and their response to geomagnetic activity

International Nuclear Information System (INIS)

Johnson, R.M.

1987-01-01

Observations made by the Chatanika, Alaska, incoherent scatter radar during the summer months of 1976 to 1081 are analyzed to obtain high resolution lower-thermospheric neutral winds. Average winds and their tidal components are presented and compared to previous observational and model results. Upper-mesospheric neutral-wind observations obtained by the Poke Flat, Alaska Mesosphere-Stratosphere-Troposphere (MST) radar during the summer months of 1980 to 1982 are investigated statistically for evidence of variations due to geomagnetic activity. Observation of upper-mesospheric neutral winds made during two energetic Solar Proton Events (SPEs) by the Poker Flat, MST radar are presented. These results allow the low-altitude limits of magnetospheric coupling to the neutral atmosphere to be determined. Lower-thermospheric neutral winds are coupled to the ion convection driven by typical magnetospheric forcing above about 100 km. Coupling to lower atmospheric levels does not occur except during intervals of extreme disturbance of the magnetosphere-ionosphere-thermosphere system which are also accompanied by dramatically increased ionization in the high-latitude mesosphere, such as SPEs

Spherical solitons in Earth’S mesosphere plasma

International Nuclear Information System (INIS)

Annou, K.; Annou, R.

2016-01-01

Soliton formation in Earth’s mesosphere plasma is described. Nonlinear acoustic waves in plasmas with two-temperature ions and a variable dust charge where transverse perturbation is dealt with are studied in bounded spherical geometry. Using the perturbation method, a spherical Kadomtsev–Petviashvili equation that describes dust acoustic waves is derived. It is found that the parameters taken into account have significant effects on the properties of nonlinear waves in spherical geometry

A measurement of the turbulence-driven density distribution in a non-star-forming molecular cloud

Energy Technology Data Exchange (ETDEWEB)

Ginsburg, Adam; Darling, Jeremy [CASA, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Federrath, Christoph, E-mail: Adam.G.Ginsburg@gmail.com [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800 (Australia)

2013-12-10

Molecular clouds are supersonically turbulent. This turbulence governs the initial mass function and the star formation rate. In order to understand the details of star formation, it is therefore essential to understand the properties of turbulence, in particular the probability distribution of density in turbulent clouds. We present H{sub 2}CO volume density measurements of a non-star-forming cloud along the line of sight toward W49A. We use these measurements in conjunction with total mass estimates from {sup 13}CO to infer the shape of the density probability distribution function. This method is complementary to measurements of turbulence via the column density distribution and should be applicable to any molecular cloud with detected CO. We show that turbulence in this cloud is probably compressively driven, with a compressive-to-total Mach number ratio b=M{sub C}/M>0.4. We measure the standard deviation of the density distribution, constraining it to the range 1.5 < σ {sub s} < 1.9, assuming that the density is lognormally distributed. This measurement represents an essential input into star formation laws. The method of averaging over different excitation conditions to produce a model of emission from a turbulent cloud is generally applicable to optically thin line observations.

On the sizes and observable effects of dust particles in polar mesospheric winter echoes

Science.gov (United States)

Havnes, O.; Kassa, M.

2009-05-01

In the present paper, recent radar and heating experiments on the polar mesospheric winter echoes (PMWE) are analyzed with the radar overshoot model. The PMWE dust particles that influence the radar backscatter most likely have sizes around 3 nm. For dust to influence the electrons in the PMWE layers, it must be charged; therefore, we have discussed the charging of nanometer-sized particles and found that the photodetachment effect, where photons of energy less than the work function of the dust material can remove excess electrons, probably is dominant at sunlit conditions. For moderate and low electron densities, very few of the dust smaller than ˜3 nm will be charged. We suggest that the normal requirement that disturbed magnetospheric conditions with ionizing precipitation must be present to create observable PMWE is needed mainly to create sufficiently high electron densities to overcome the photodetachment effect and charge the PMWE dust particles. We have also suggested other possible effects of the photodetachment on the occurrence rate of the PMWE. We attribute the lack of PMWE-like radar scattering layers in the lower mesosphere during the summer not only to a lower level of turbulence than in winter but also to that dust particles are removed from these layers due to the upward wind draught in the summer mesospheric circulation system. It is likely that this last effect will completely shut off the PMWE-like radar layers in the lower parts of the mesosphere.

A YOUNG GIANT MOLECULAR CLOUD FORMED AT THE INTERFACE OF TWO COLLIDING SUPERSHELLS: OBSERVATIONS MEET SIMULATIONS

Energy Technology Data Exchange (ETDEWEB)

Dawson, J. R. [Department of Physics and Astronomy and MQ Research Centre in Astronomy, Astrophysics and Astrophotonics, Macquarie University, NSW 2109 (Australia); Ntormousi, E. [Service d' Astrophysique, CEA/DSM/IRFU Orme des Merisiers, Bat 709 Gif-sur-Yvette F-91191 (France); Fukui, Y.; Hayakawa, T. [Department of Physics and Astrophysics, Nagoya University, Chikusa-ku, Nagoya (Japan); Fierlinger, K., E-mail: joanne.dawson@mq.edu.au [University Observatory Munich, Scheinerstr. 1, D-81679 München (Germany)

2015-01-20

Dense, star-forming gas is believed to form at the stagnation points of large-scale interstellar medium flows, but observational examples of this process in action are rare. We here present a giant molecular cloud (GMC) sandwiched between two colliding Milky Way supershells, which we argue shows strong evidence of having formed from material accumulated at the collision zone. Combining {sup 12}CO, {sup 13}CO, and C{sup 18}O(J = 1-0) data with new high-resolution, three-dimensional hydrodynamical simulations of colliding supershells, we discuss the origin and nature of the GMC (G288.5+1.5), favoring a scenario in which the cloud was partially seeded by pre-existing denser material, but assembled into its current form by the action of the shells. This assembly includes the production of some new molecular gas. The GMC is well interpreted as non-self-gravitating, despite its high mass (M{sub H{sub 2}}∼1.7×10{sup 5} M{sub ⊙}), and is likely pressure confined by the colliding flows, implying that self-gravity was not a necessary ingredient for its formation. Much of the molecular gas is relatively diffuse, and the cloud as a whole shows little evidence of star formation activity, supporting a scenario in which it is young and recently formed. Drip-like formations along its lower edge may be explained by fluid dynamical instabilities in the cooled gas.

Molecular clouds toward three Spitzer bubbles S116, S117, and S118: Evidence for a cloud-cloud collision which formed the three H II regions and a 10 pc scale molecular cavity

Science.gov (United States)

Fukui, Yasuo; Ohama, Akio; Kohno, Mikito; Torii, Kazufumi; Fujita, Shinji; Hattori, Yusuke; Nishimura, Atsushi; Yamamoto, Hiroaki; Tachihara, Kengo

2018-05-01

We carried out a molecular-line study toward the three Spitzer bubbles S116, S117, and S118, which show active formation of high-mass stars. We found molecular gas consisting of two components with a velocity difference of ˜5 km s-1. One of them, the small cloud, has a typical velocity of -63 km s-1 and the other, the large cloud, has one of -58 km s-1. The large cloud has a nearly circular intensity depression, the size of which is similar to that of the small cloud. We present an interpretation that its cavity was created by a collision between the two clouds and that this collision compressed the gas into a dense layer elongating along the western rim of the small cloud. In this scenario, the O stars including those in the three Spitzer bubbles were formed in the interface layer compressed by the collision. Assuming that the relative motion of the clouds has a tilt of 45° to the line of sight, we estimate that the collision continued for the last 1 Myr at a relative velocity of ˜10 km s-1. In the S116-S117-S118 system the H II regions are located outside of the cavity. This morphology is ascribed to the density-bound distribution of the large cloud which caused the H II regions to expand more easily toward the outer part of the large cloud than towards the inside of the cavity. The present case proves that a cloud-cloud collision creates a cavity without the action of O-star feedback, and suggests that the collision-compressed layer is highly filamentary.

A High-velocity Cloud Impact Forming a Supershell in the Milky Way

Science.gov (United States)

Park, Geumsook; Koo, Bon-Chul; Kang, Ji-hyun; Gibson, Steven J.; Peek, J. E. G.; Douglas, Kevin A.; Korpela, Eric J.; Heiles, Carl E.

2016-08-01

Neutral atomic hydrogen (H I) gas in interstellar space is largely organized into filaments, loops, and shells, the most prominent of which are “supershells.” These gigantic structures, which require ≳ 3× {10}52 erg to form, are generally thought to be produced by either the explosion of multiple supernovae (SNe) in OB associations or, alternatively, by the impact of high-velocity clouds (HVCs) falling into the Galactic disk. Here, we report the detection of a kiloparsec (kpc)-size supershell in the outskirts of the Milky Way with the compact HVC 040 + 01-282 (hereafter, CHVC040) at its geometrical center using the “Inner-Galaxy Arecibo L-band Feed Array” H I 21 cm survey data. The morphological and physical properties of both objects suggest that CHVC040, which is either a fragment of a nearby disrupted galaxy or a cloud that originated from an intergalactic accreting flow, collided with the disk ˜5 Myr ago to form the supershell. Our results show that some compact HVCs can survive their trip through the Galactic halo and inject energy and momentum into the Milky Way disk.

The thermal and dynamical state of the atmosphere during polar mesosphere winter echoes

Directory of Open Access Journals (Sweden)

F.-J. Lübken

2006-01-01

Full Text Available In January 2005, a total of 18 rockets were launched from the Andøya Rocket Range in Northern Norway (69° N into strong VHF radar echoes called 'Polar Mesosphere Winter Echoes' (PMWE. The echoes were observed in the lower and middle mesosphere during large solar proton fluxes. In general, PMWE occur much more seldom compared to their summer counterparts PMSE (typical occurrence rates at 69° N are 1–3% vs. 80%, respectively. Our in-situ measurements by falling sphere, chaff, and instrumented payloads provide detailed information about the thermal and dynamical state of the atmosphere and therefore allow an unprecedented study of the background atmosphere during PMWE. There are a number of independent observations indicating that neutral air turbulence has caused PMWE. Ion density fluctuations show a turbulence spectrum within PMWE and no fluctuations outside. Temperature lapse rates close to the adiabatic gradient are observed in the vicinity of PMWE indicating persistent turbulent mixing. The spectral broadening of radar echoes is consistent with turbulent velocity fluctuations. Turbulence also explains the mean occurrence height of PMWE (~68–75 km: viscosity increases rapidly with altitude and destroys any small scale fluctuations in the upper mesosphere, whereas electron densities are usually too low in the lower mesosphere to cause significant backscatter. The seasonal variation of echoes in the lower mesosphere is in agreement with a turbulence climatology derived from earlier sounding rocket flights. We have performed model calculations to study the radar backscatter from plasma fluctuations caused by neutral air turbulence. We find that volume reflectivities observed during PMWE are in quantitative agreement with theory. Apart from turbulence the most crucial requirement for PMWE is a sufficiently large number of electrons, for example produced by solar proton events. We have studied the sensitivity of the radar echo strength on

The star-forming content of the W3 giant molecular cloud

Science.gov (United States)

Moore, T. J. T.; Bretherton, D. E.; Fujiyoshi, T.; Ridge, N. A.; Allsopp, J.; Hoare, M. G.; Lumsden, S. L.; Richer, J. S.

2007-08-01

We have surveyed a ˜0.9 square degree area of the W3 giant molecular cloud (GMC) and star-forming region in the 850-μm continuum, using the Submillimetre Common-User Bolometer Array on the James Clerk Maxwell Telescope. A complete sample of 316 dense clumps were detected with a mass range from around 13 to 2500 M⊙. Part of the W3 GMC is subject to an interaction with the H ii region and fast stellar winds generated by the nearby W4 OB association. We find that the fraction of total gas mass in dense, 850-μm traced structures is significantly altered by this interaction, being around 5-13 per cent in the undisturbed cloud but ˜25-37 per cent in the feedback-affected region. The mass distribution in the detected clump sample depends somewhat on assumptions of dust temperature and is not a simple, single power law but contains significant structure at intermediate masses. This structure is likely to be due to crowding of sources near or below the spatial resolution of the observations. There is little evidence of any difference between the index of the high-mass end of the clump mass function in the compressed region and in the unaffected cloud. The consequences of these results are discussed in terms of current models of triggered star formation.

UARS Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AL V001

Data.gov (United States)

National Aeronautics and Space Administration — The Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AL data product consists of daily, 4 degree increment latitude-ordered vertical profiles of...

UARS Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AT V001

Data.gov (United States)

National Aeronautics and Space Administration — The Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AT data product consists of daily, 65.536 second interval time-ordered vertical profiles of...

THE MASS-SIZE RELATION FROM CLOUDS TO CORES. II. SOLAR NEIGHBORHOOD CLOUDS

International Nuclear Information System (INIS)

Kauffmann, J.; Shetty, R.; Goodman, A. A.; Pillai, T.; Myers, P. C.

2010-01-01

We measure the mass and size of cloud fragments in several molecular clouds continuously over a wide range of spatial scales (0.05 ∼ 2 , is not well suited to describe the derived mass-size data. Solar neighborhood clouds not forming massive stars (∼ sun ; Pipe Nebula, Taurus, Perseus, and Ophiuchus) obey m(r) ≤ 870 M sun (r/pc) 1.33 . In contrast to this, clouds forming massive stars (Orion A, G10.15 - 0.34, G11.11 - 0.12) do exceed the aforementioned relation. Thus, this limiting mass-size relation may approximate a threshold for the formation of massive stars. Across all clouds, cluster-forming cloud fragments are found to be-at given radius-more massive than fragments devoid of clusters. The cluster-bearing fragments are found to roughly obey a mass-size law m ∝ r 1.27 (where the exponent is highly uncertain in any given cloud, but is certainly smaller than 1.5).

Turbulence characteristics in the tropical mesosphere as obtained by MST radar at Gadanki (13.5° N, 79.2° E

Directory of Open Access Journals (Sweden)

M. N. Sasi

2001-08-01

Full Text Available Turbulent kinetic energy dissipation rates (ε and eddy diffusion coefficients (Kz in the tropical mesosphere over Gadanki (13.5° N, 79.2° E, estimated from Doppler widths of MST radar echoes (vertical beam, observed over a 3-year period, show a seasonal variation with a dominant summer maximum. The observed seasonal variation of ε and Kz in the mesosphere is only partially consistent with that of gravity wave activity inferred from mesospheric winds and temperatures measured by rockets for a period of 9 years at Trivandrum (8.5° N, 77° E (which shows two equinox and one summer maxima lying close to Gadanki. The summer maximum of mesospheric ε and Kz values appears to be related to the enhanced gravity wave activity over the low-latitude Indian subcontinent during the southwest monsoon period (June – September. Both ε and Kz in the mesosphere over Gadanki show an increase with an increase in height during all seasons. The absolute values of observed ε and Kz in the mesosphere (above ~80 km does not show significant differences from those reported for high latitudes. Comparison of observed Kz values during the winter above Gadanki with those over Arecibo (18.5° N, 66° W shows that they are not significantly different from each other above the ~80 km altitude.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; tropical meteorology; wave and tides

Fast Molecular Cloud Destruction Requires Fast Cloud Formation

Energy Technology Data Exchange (ETDEWEB)

Mac Low, Mordecai-Mark [American Museum of Natural History, 79th Street at Central Park West, New York, NY 10024 (United States); Burkert, Andreas [Universitäts Sternwarte München, Ludwigs-Maximilian-Universität, D-81679 München (Germany); Ibáñez-Mejía, Juan C., E-mail: mordecai@amnh.org, E-mail: burkert@usm.lmu.de, E-mail: ibanez@ph1.uni-koeln.de [Max-Planck-Institut für Extraterrestrische Physik, D-85748 Garching bei München (Germany)

2017-09-20

A large fraction of the gas in the Galaxy is cold, dense, and molecular. If all this gas collapsed under the influence of gravity and formed stars in a local free-fall time, the star formation rate in the Galaxy would exceed that observed by more than an order of magnitude. Other star-forming galaxies behave similarly. Yet, observations and simulations both suggest that the molecular gas is indeed gravitationally collapsing, albeit hierarchically. Prompt stellar feedback offers a potential solution to the low observed star formation rate if it quickly disrupts star-forming clouds during gravitational collapse. However, this requires that molecular clouds must be short-lived objects, raising the question of how so much gas can be observed in the molecular phase. This can occur only if molecular clouds form as quickly as they are destroyed, maintaining a global equilibrium fraction of dense gas. We therefore examine cloud formation timescales. We first demonstrate that supernova and superbubble sweeping cannot produce dense gas at the rate required to match the cloud destruction rate. On the other hand, Toomre gravitational instability can reach the required production rate. We thus argue that, although dense, star-forming gas may last only around a single global free-fall time; the dense gas in star-forming galaxies can globally exist in a state of dynamic equilibrium between formation by gravitational instability and disruption by stellar feedback. At redshift z ≳ 2, the Toomre instability timescale decreases, resulting in a prediction of higher molecular gas fractions at early times, in agreement with the observations.

Temperature minima in the average thermal structure of the middle mesosphere (70 - 80 km) from analysis of 40- to 92-km SME global temperature profiles

Science.gov (United States)

Clancy, R. Todd; Rusch, David W.; Callan, Michael T.

1994-01-01

Global temperatures have been derived for the upper stratosphere and mesosphere from analysis of Solar Mesosphere Explorer (SME) limb radiance profiles. The SME temperature represent fixed local time observations at 1400 - 1500 LT, with partial zonal coverage of 3 - 5 longitudes per day over the 1982-1986 period. These new SME temperatures are compared to the COSPAR International Ionosphere Reference Atmosphere 86 (CIRA 86) climatology (Fleming et al., 1990) as well as stratospheric and mesospheric sounder (SAMS); Barnett and Corney, 1984), National Meteorological Center (NMC); (Gelman et al., 1986), and individual lidar and rocket observations. Significant areas of disagreement between the SME and CIRA 86 mesospheric temperatures are 10 K warmer SME temperatures at altitudes above 80 km. The 1981-1982 SAMS temperatures are in much closer agreement with the SME temperatures between 40 and 75 km. Although much of the SME-CIRA 86 disagreement probably stems from the poor vertical resolution of the observations comprising the CIRA 86 modelm, some portion of the differences may reflect 5- to 10-year temporal variations in mesospheric temperatures. The CIRA 86 climatology is based on 1973-1978 measurements. Relatively large (1 K/yr) 5- to 10-year trends in temperatures as functions of longitude, latitude, and altitude have been observed for both the upper stratosphere (Clancy and Rusch, 1989a) and mesosphere (Clancy and Rusch, 1989b; Hauchecorne et al., 1991). The SME temperatures also exhibit enhanced amplitudes for the semiannual oscillation (SAO) of upper mesospheric temperatures at low latitudes, which are not evident in the CIRA 86 climatology. The so-called mesospheric `temperature inversions' at wintertime midlatitudes, which have been observed by ground-based lidar (Hauschecorne et al., 1987) and rocket in situ measurements (Schmidlin, 1976), are shown to be a climatological aspect of the mesosphere, based on the SME observations.

Dominant winter-time mesospheric wave signatures over a low ...

Indian Academy of Sciences (India)

10.1016/j.jastp.2008.09.017. Taori A, Taylor M J and Franke S 2005 Terdiurnal wave signatures in the upper mesospheric tempera- ture and their association with the wind fields at low latitudes (20. °. N); J. Geophys. Res. 110 D09S06, doi: 10.1029/2004JD004564. Taori A and Taylor M J 2006 Characteristics of wave.

THE 'TRUE' COLUMN DENSITY DISTRIBUTION IN STAR-FORMING MOLECULAR CLOUDS

International Nuclear Information System (INIS)

Goodman, Alyssa A.; Pineda, Jaime E.; Schnee, Scott L.

2009-01-01

We use the COMPLETE Survey's observations of the Perseus star-forming region to assess and intercompare the three methods used for measuring column density in molecular clouds: near-infrared (NIR) extinction mapping; thermal emission mapping in the far-IR; and mapping the intensity of CO isotopologues. Overall, the structures shown by all three tracers are morphologically similar, but important differences exist among the tracers. We find that the dust-based measures (NIR extinction and thermal emission) give similar, log-normal, distributions for the full (∼20 pc scale) Perseus region, once careful calibration corrections are made. We also compare dust- and gas-based column density distributions for physically meaningful subregions of Perseus, and we find significant variations in the distributions for those (smaller, ∼few pc scale) regions. Even though we have used 12 CO data to estimate excitation temperatures, and we have corrected for opacity, the 13 CO maps seem unable to give column distributions that consistently resemble those from dust measures. We have edited out the effects of the shell around the B-star HD 278942 from the column density distribution comparisons. In that shell's interior and in the parts where it overlaps the molecular cloud, there appears to be a dearth of 13 CO, which is likely due either to 13 CO not yet having had time to form in this young structure and/or destruction of 13 CO in the molecular cloud by the HD 278942's wind and/or radiation. We conclude that the use of either dust or gas measures of column density without extreme attention to calibration (e.g., of thermal emission zero-levels) and artifacts (e.g., the shell) is more perilous than even experts might normally admit. And, the use of 13 CO data to trace total column density in detail, even after proper calibration, is unavoidably limited in utility due to threshold, depletion, and opacity effects. If one's main aim is to map column density (rather than temperature

Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes.

Science.gov (United States)

Zhou, Du; Yuan, Xi; Gao, Haoxiang; Wang, Ailing; Liu, Jun; El Fakir, Omer; Politis, Denis J; Wang, Liliang; Lin, Jianguo

2016-12-13

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques. This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

Turbulence characteristics in the tropical mesosphere as obtained by MST radar at Gadanki (13.5° N, 79.2° E

Directory of Open Access Journals (Sweden)

M. N. Sasi

Full Text Available Turbulent kinetic energy dissipation rates (ε and eddy diffusion coefficients (K_z in the tropical mesosphere over Gadanki (13.5° N, 79.2° E, estimated from Doppler widths of MST radar echoes (vertical beam, observed over a 3-year period, show a seasonal variation with a dominant summer maximum. The observed seasonal variation of ε and K_z in the mesosphere is only partially consistent with that of gravity wave activity inferred from mesospheric winds and temperatures measured by rockets for a period of 9 years at Trivandrum (8.5° N, 77° E (which shows two equinox and one summer maxima lying close to Gadanki. The summer maximum of mesospheric ε and K_z values appears to be related to the enhanced gravity wave activity over the low-latitude Indian subcontinent during the southwest monsoon period (June – September. Both ε and K_z in the mesosphere over Gadanki show an increase with an increase in height during all seasons. The absolute values of observed ε and K_z in the mesosphere (above ~80 km does not show significant differences from those reported for high latitudes. Comparison of observed K_z values during the winter above Gadanki with those over Arecibo (18.5° N, 66° W shows that they are not significantly different from each other above the ~80 km altitude.

Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; tropical meteorology; wave and tides

Observation of atomic oxygen O(1S) green-line emission in the summer polar upper mesosphere associated with high-energy (≥30 keV) electron precipitation during high-speed solar wind streams

Science.gov (United States)

Lee, Young-Sook; Kwak, Young-Sil; Kim, Kyung-Chan; Solheim, Brian; Lee, Regina; Lee, Jaejin

2017-01-01

The auroral green-line emission at 557.7 nm wavelength as arising from the atomic oxygen O(1S → 1D) transition typically peaks at an altitude of 100 km specifically in the nightside oval, induced by auroral electrons within an energy range of 100 eV-30 keV. Intense aurora is known as being suppressed by sunlight in summer daytime but usually occurs in low electrical background conductivity. However, in the present study in summer (July) sunlit condition, enhancements of O(1S) emission rates observed by using the Wind Imaging Interferometer/UARS were frequently observed at low altitudes below 90 km, where ice particles are created initially as subvisible and detected as polar mesosphere summer echoes, emerging to be an optical phenomenon of polar mesospheric clouds. The intense O(1S) emission occurring in summer exceeds those occurring in the daytime in other seasons both in occurrence and in intensity, frequently accompanied by occurrences of supersonic neutral velocity (300-1500 m s-1). In the mesosphere, ion motion is controlled by electric field and the momentum is transferred to neutrals. The intense O(1S) emission is well associated with high-energy electron precipitation as observed during an event of high-speed solar wind streams. Meanwhile, since the minimum occurrences of O(1S) emission and supersonic velocity are maintained even in the low precipitation flux, the mechanism responsible is not only related to high-energy electron precipitation but also presumably to the local conditions, including the composition of meteoric-charged ice particles and charge separation expected in extremely low temperatures (<150 K).

Ground-based Observations and Atmospheric Modelling of Energetic Electron Precipitation Effects on Antarctic Mesospheric Chemistry

Science.gov (United States)

Newnham, D.; Clilverd, M. A.; Horne, R. B.; Rodger, C. J.; Seppälä, A.; Verronen, P. T.; Andersson, M. E.; Marsh, D. R.; Hendrickx, K.; Megner, L. S.; Kovacs, T.; Feng, W.; Plane, J. M. C.

2016-12-01

The effect of energetic electron precipitation (EEP) on the seasonal and diurnal abundances of nitric oxide (NO) and ozone in the Antarctic middle atmosphere during March 2013 to July 2014 is investigated. Geomagnetic storm activity during this period, close to solar maximum, was driven primarily by impulsive coronal mass ejections. Near-continuous ground-based atmospheric measurements have been made by a passive millimetre-wave radiometer deployed at Halley station (75°37'S, 26°14'W, L = 4.6), Antarctica. This location is directly under the region of radiation-belt EEP, at the extremity of magnetospheric substorm-driven EEP, and deep within the polar vortex during Austral winter. Superposed epoch analyses of the ground based data, together with NO observations made by the Solar Occultation For Ice Experiment (SOFIE) onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite, show enhanced mesospheric NO following moderate geomagnetic storms (Dst ≤ -50 nT). Measurements by co-located 30 MHz riometers indicate simultaneous increases in ionisation at 75-90 km directly above Halley when Kp index ≥ 4. Direct NO production by EEP in the upper mesosphere, versus downward transport of NO from the lower thermosphere, is evaluated using a new version of the Whole Atmosphere Community Climate Model incorporating the full Sodankylä Ion Neutral Chemistry Model (WACCM SIC). Model ionization rates are derived from the Polar orbiting Operational Environmental Satellites (POES) second generation Space Environment Monitor (SEM 2) Medium Energy Proton and Electron Detector instrument (MEPED). The model data are compared with observations to quantify the impact of EEP on stratospheric and mesospheric odd nitrogen (NOx), odd hydrogen (HOx), and ozone.

Do minor sudden stratospheric warmings in the Southern Hemisphere (SH) impact coupling between stratosphere and mesosphere-lower thermosphere (MLT) like major warmings?

Science.gov (United States)

Eswaraiah, S.; Kim, Yong Ha; Liu, Huixin; Ratnam, M. Venkat; Lee, Jaewook

2017-08-01

We have investigated the coupling between the stratosphere and mesosphere-lower thermosphere (MLT) in the Southern Hemisphere (SH) during 2010 minor sudden stratospheric warmings (SSWs). Three episodic SSWs were noticed in 2010. Mesospheric zonal winds between 82 and 92 km obtained from King Sejong Station (62.22°S, 58.78°W) meteor radar showed the significant difference from usual trend. The zonal wind reversal in the mesosphere is noticed a week before the associated SSW similar to 2002 major SSW. The mesosphere wind reversal is also noticed in "Specified Dynamics" version of Whole Atmosphere Community Climate Model (SD-WACCM) and Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) simulations. The similar zonal wind weakening/reversal in the lower thermosphere between 100 and 140 km is simulated by GAIA. Further, we observed the mesospheric cooling in consistency with SSWs using Microwave Limb Sounder data. However, the GAIA simulations showed warming between 130 and 140 km after few days of SSW. Thus, the observation and model simulation indicate for the first time that the 2010 minor SSW also affects dynamics of the MLT region over SH in a manner similar to 2002 major SSW.[Figure not available: see fulltext.

Solar Energy Deposition Rates in the Mesosphere Derived from Airglow Measurements: Implications for the Ozone Model Deficit Problem

Science.gov (United States)

Mlynczak, Martin G.; Garcia, Rolando R.; Roble, Raymond G.; Hagan, Maura

2000-01-01

We derive rates of energy deposition in the mesosphere due to the absorption of solar ultraviolet radiation by ozone. The rates are derived directly from measurements of the 1.27-microns oxygen dayglow emission, independent of knowledge of the ozone abundance, the ozone absorption cross sections, and the ultraviolet solar irradiance in the ozone Hartley band. Fifty-six months of airglow data taken between 1982 and 1986 by the near-infrared spectrometer on the Solar-Mesosphere Explorer satellite are analyzed. The energy deposition rates exhibit altitude-dependent annual and semi-annual variations. We also find a positive correlation between temperatures and energy deposition rates near 90 km at low latitudes. This correlation is largely due to the semiannual oscillation in temperature and ozone and is consistent with model calculations. There is also a suggestion of possible tidal enhancement of this correlation based on recent theoretical and observational analyses. The airglow-derived rates of energy deposition are then compared with those computed by multidimensional numerical models. The observed and modeled deposition rates typically agree to within 20%. This agreement in energy deposition rates implies the same agreement exists between measured and modeled ozone volume mixing ratios in the mesosphere. Only in the upper mesosphere at midlatitudes during winter do we derive energy deposition rates (and hence ozone mixing ratios) consistently and significantly larger than the model calculations. This result is contrary to previous studies that have shown a large model deficit in the ozone abundance throughout the mesosphere. The climatology of solar energy deposition and heating presented in this paper is available to the community at the Middle Atmosphere Energy Budget Project web site at http://heat-budget.gats-inc.com.

MODELING THE ATOMIC-TO-MOLECULAR TRANSITION AND CHEMICAL DISTRIBUTIONS OF TURBULENT STAR-FORMING CLOUDS

Energy Technology Data Exchange (ETDEWEB)

Offner, Stella S. R. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Bisbas, Thomas G.; Viti, Serena [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6B (United Kingdom); Bell, Tom A., E-mail: stella.offner@yale.edu [Centro de Astrobiologia (CSIC-INTA), Carretera de Ajalvir, km 4, E-28850 Madrid (Spain)

2013-06-10

We use 3D-PDR, a three-dimensional astrochemistry code for modeling photodissociation regions (PDRs), to post-process hydrodynamic simulations of turbulent, star-forming clouds. We focus on the transition from atomic to molecular gas, with specific attention to the formation and distribution of H, C{sup +}, C, H{sub 2}, and CO. First, we demonstrate that the details of the cloud chemistry and our conclusions are insensitive to the simulation spatial resolution, to the resolution at the cloud edge, and to the ray angular resolution. We then investigate the effect of geometry and simulation parameters on chemical abundances and find weak dependence on cloud morphology as dictated by gravity and turbulent Mach number. For a uniform external radiation field, we find similar distributions to those derived using a one-dimensional PDR code. However, we demonstrate that a three-dimensional treatment is necessary for a spatially varying external field, and we caution against using one-dimensional treatments for non-symmetric problems. We compare our results with the work of Glover et al., who self-consistently followed the time evolution of molecule formation in hydrodynamic simulations using a reduced chemical network. In general, we find good agreement with this in situ approach for C and CO abundances. However, the temperature and H{sub 2} abundances are discrepant in the boundary regions (A{sub v} {<=} 5), which is due to the different number of rays used by the two approaches.

Solar activity influence on climatic variations of stratosphere and mesosphere in mid-latitudes

International Nuclear Information System (INIS)

Taubenheim, J.; Entzian, G.; Voncossart, G.

1989-01-01

The direct modulation of temperature of the mid-latitude mesosphere by the solar-cycle EUV variation, which leads to greater heat input at higher solar activity, is well established. Middle atmosphere temperature modulation by the solar cycle is independently confirmed by the variation of reflection heights of low frequency radio waves in the lower ionosphere, which are regularly monitored over about 30 years. As explained elsewhere in detail, these reflection heights depend on the geometric altitude of a certain isobaric surface (near 80 k), and on the solar ionizing Lyman-alpha radiation flux. Knowing the solar cycle variation of Lyman-alpha how much the measured reflection heights would be lowered with the transition from solar minimum to maximum can be calculated, if the vertical baric structure of the neutral atmosphere would remain unchanged. Any discrepancy between expected and observed height change must be explained by an uplifting of the isobaric level from solar minimum to maximum, caused by the temperature rise in the mesosphere. By integrating the solar cycle temperature changes over the height region of the middle atmosphere, and assuming that the lower boundary (tropopause) has no solar cycle variation, the magnitude of this uplifting can be estimated. It is given for the Lidar-derived and for the rocket-measured temperature variations. Comparison suggests that the real amplitude of the solar cycle temperature variation in the mesosphere is underestimated when using the rocket data, but probably overestimated with the Lidar data

Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station

Directory of Open Access Journals (Sweden)

D. Narayana Rao

Full Text Available Long-term VHF radar (53 MHz with 3° beam-width observations at Gadanki (13.5° N, 79.2° E, India, during the period from September 1995 to August 1999 are used to study monthly, seasonal and annual medians of vertical eddy diffusivity, K in the troposphere, lower stratosphere and mesosphere. First, the spectral width contribution due to non-turbulent effects has been removed for further analysis and the monthly, seasonal medians of K are calculated. The monthly median of K in the troposphere shows maximum and minimum in June-July and November-December, respectively. In general, large values of K are seen up to 10 km and then decrease with height. Larger values of K are observed during monsoon and post-monsoon than in winter and summer. In general, the maximum and minimum values of the annual median of K (in logarithmic values in the troposphere are found to be 0.25 and - 1.3 m² s^-1 respectively. In the mesosphere, the monthly median of K shows maximum and minimum during June-July and November-December, respectively, similar to the lower atmosphere. The value of K in the mesosphere becomes larger and it increases with height up to 75 km and again decreases above that height. The maximum values are seen during the summer, followed by equinoxes and a minimum during the winter. In general, the maximum and minimum values of K (in logarithmic values are found to be 0.7 and 0.3 m² s^-1, respectively, in the mesosphere. A comparison of Doppler spectral parameters in different beam directions shows anisotropy in both signal-to- noise ratio (SNR and spectral widths in the mesosphere, whereas it shows isotropy in SNR and anisotropy in the spectral widths in troposphere and lower stratosphere.

Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides

The Dominant Snow-forming Process in Warm and Cold Mixed-phase Orographic Clouds: Effects of Cloud Condensation Nuclei and Ice Nuclei

Science.gov (United States)

Fan, J.; Rosenfeld, D.; Leung, L. R.; DeMott, P. J.

2014-12-01

Mineral dust aerosols often observed over California in winter and spring from long-range transport can be efficient ice nuclei (IN) and enhance snow precipitation in mixed-phase orographic clouds. On the other hand, local pollution particles can serve as good CCN and suppress warm rain, but their impacts on cold rain processes are uncertain. The main snow-forming mechanism in warm and cold mixed-phase orographic clouds (refer to as WMOC and CMOC, respectively) could be very different, leading to different precipitation response to CCN and IN. We have conducted 1-km resolution model simulations using the Weather Research and Forecasting (WRF) model coupled with a spectral-bin cloud microphysical model for WMOC and CMOC cases from CalWater2011. We investigated the response of cloud microphysical processes and precipitation to CCN and IN with extremely low to extremely high concentrations using ice nucleation parameterizations that connect with dust and implemented based on observational evidences. We find that riming is the dominant process for producing snow in WMOC while deposition plays a more important role than riming in CMOC. Increasing IN leads to much more snow precipitation mainly due to an increase of deposition in CMOC and increased rimming in WMOC. Increasing CCN decreases precipitation in WMOC by efficiently suppressing warm rain, although snow is increased. In CMOC where cold rain dominates, increasing CCN significantly increases snow, leading to a net increase in precipitation. The sensitivity of supercooled liquid to CCN and IN has also been analyzed. The mechanism for the increased snow by CCN and caveats due to uncertainties in ice nucleation parameterizations will be discussed.

Secondary gravity waves from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere

Science.gov (United States)

Vadas, S.

2017-12-01

In this paper, we investigate the generation, propagation and effectsof secondary gravity waves (GWs) from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere in high-resolution GW-resolving models and in TEC/lidar/redline data. We show that secondary GWs generated from the dissipation of orographic GWs at McMurdo Station in Antarctica play a dominant role in the wave activity over McMurdo in the wintertime mesosphere. These secondary GWs are created in the stratosphere, and have been identified in models and data via their telltale "fishbone" appearance in z-t plots. We also show that secondary GWs from the dissipation of GWs excited by deep convectiongenerate concentric rings in the F-region ionosphere. These model results and data point to the importance of secondary GWs from momentumdeposition in the Earth's atmosphere and ionosphere.

Bite-outs and other depletions of mesospheric electrons

Science.gov (United States)

Friedrich, Martin; Rapp, Markus; Plane, John M.C.; Torkar, Klaus M.

2011-01-01

The ionised mesosphere is less understood than other parts of the ionosphere because of the challenges of making appropriate measurements in this complex region. We use rocket borne in situ measurements of absolute electron density by the Faraday rotation technique and accompanying DC-probe measurements to study the effect of particles on the D-region charge balance. Several examples of electron bite-outs, their actual depth as well as simultaneous observations of positive ions are presented. For a better understanding of the various dependencies we use the ratio β/αi (attachment rate over ion–ion recombination coefficient), derived from the electron and ion density profiles by applying a simplified ion-chemical scheme, and correlate this term with solar zenith angle and moon brightness. The probable causes are different for day and night; recent in situ measurements support existing hypotheses for daytime cases, but also reveal behaviour at night hitherto not reported in the literature. Within the large range of β/αi values obtained from the analysis of 28 high latitude night flights one finds that the intensity of scattered sunlight after sunset, and even moonlight, apparently can photodetach electrons from meteoric smoke particles (MSP) and molecular anions. The large range of values itself can best be explained by the variability of the MSPs and by occasionally occurring atomic oxygen impacting on the negative ion chemistry in the night-time mesosphere under disturbed conditions. PMID:27570472

Greening the Cloud

NARCIS (Netherlands)

van den Hoed, Robert; Hoekstra, Eric; Procaccianti, G.; Lago, P.; Grosso, Paola; Taal, Arie; Grosskop, Kay; van Bergen, Esther

The cloud has become an essential part of our daily lives. We use it to store our documents (Dropbox), to stream our music and lms (Spotify and Net ix) and without giving it any thought, we use it to work on documents in the cloud (Google Docs). The cloud forms a massive storage and processing

Formation of massive, dense cores by cloud-cloud collisions

Science.gov (United States)

Takahira, Ken; Shima, Kazuhiro; Habe, Asao; Tasker, Elizabeth J.

2018-05-01

We performed sub-parsec (˜ 0.014 pc) scale simulations of cloud-cloud collisions of two idealized turbulent molecular clouds (MCs) with different masses in the range of (0.76-2.67) × 104 M_{⊙} and with collision speeds of 5-30 km s-1. Those parameters are larger than in Takahira, Tasker, and Habe (2014, ApJ, 792, 63), in which study the colliding system showed a partial gaseous arc morphology that supports the NANTEN observations of objects indicated to be colliding MCs using numerical simulations. Gas clumps with density greater than 10-20 g cm-3 were identified as pre-stellar cores and tracked through the simulation to investigate the effects of the mass of colliding clouds and the collision speeds on the resulting core population. Our results demonstrate that the smaller cloud property is more important for the results of cloud-cloud collisions. The mass function of formed cores can be approximated by a power-law relation with an index γ = -1.6 in slower cloud-cloud collisions (v ˜ 5 km s-1), and is in good agreement with observation of MCs. A faster relative speed increases the number of cores formed in the early stage of collisions and shortens the gas accretion phase of cores in the shocked region, leading to the suppression of core growth. The bending point appears in the high-mass part of the core mass function and the bending point mass decreases with increase in collision speed for the same combination of colliding clouds. The higher-mass part of the core mass function than the bending point mass can be approximated by a power law with γ = -2-3 that is similar to the power index of the massive part of the observed stellar initial mass function. We discuss implications of our results for the massive-star formation in our Galaxy.

Properties of internal planetary-scale inertio gravity waves in the mesosphere

Directory of Open Access Journals (Sweden)

H. G. Mayr

2004-11-01

Full Text Available At high latitudes in the upper mesosphere, horizontal wind oscillations have been observed with periods around 10h. Waves with such a period are generated in our Numerical Spectral Model (NSM, and they are identified as planetary-scale inertio gravity waves (IGW. These IGWs have periods between 9 and 11h and appear above 60km in the zonal mean (m=0, as well as in m=1 to 4, propagating eastward and westward. Under the influence of the Coriolis force, the amplitudes of the waves propagating westward are larger at high latitudes than those propagating eastward. The waves grow in magnitude at least up to about 100km and have vertical wavelengths around 25km. Applying a running window of 15 days for spectral analysis, the amplitudes in the wind field are typically between 10 and 20m/s and can reach 30m/s in the westward propagating component for m=1 at the poles. In the temperature perturbations, the wave amplitudes above 100km are typically 5K and as large as 10K for m=0 at the poles. The IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in late winter and spring. Numerical experiments show that such waves are also generated without excitation of the migrating tides. The amplitudes and periods then are similar, indicating that the tides are not essential to generate the waves. However, the seasonal variations without tides are significantly different, which leads to the conclusion that non linear interactions between the semidiurnal tide and planetary waves must contribute to the excitation of the IGWs. Directly or indirectly through the planetary waves, the IGWs are apparently excited by the instabilities that arise in the zonal mean circulation. When the solar heating is turned off for m=0, both the PWs and IGWs essentially disappear. That the IGWs and PWs have common roots in their excitation mechanism is also indicated by the striking similarity of their seasonal variations in the

Some aspects of metallic ion chemistry and dynamics in the mesosphere and thermosphere

Science.gov (United States)

Mathews, J. D.

1987-01-01

The relationship between the formation of sporadic layers of metallic ion and the dumping of these ions into the upper mesosphere is discussed in terms of the tidal wind, classical (i.e., windshear) and other more complex, perhaps highly nonlinear layer formation mechanisms, and a possible circulation mechanism for these ions. Optical, incoherent scatter radar, rocket, and satellite derived evidence for various layer formation mechanisms and for the metallic ion circulation system is reviewed. The results of simple one dimensional numerical model calculations of sporadic E and intermediate layer formation are presented along with suggestions for more advanced models of intense or blanketing sporadic E. The flux of metallic ions dumped by the tidal wind system into the mesosphere is estimated and compared with estimates of total particle flux of meteoric origin. Possible effects of the metallic ion flux and of meteoric dust on D region ion chemistry are discussed.

Using Cloud Services for Library IT Infrastructure

OpenAIRE

Erik Mitchell

2010-01-01

Cloud computing comes in several different forms and this article documents how service, platform, and infrastructure forms of cloud computing have been used to serve library needs. Following an overview of these uses the article discusses the experience of one library in migrating IT infrastructure to a cloud environment and concludes with a model for assessing cloud computing.

Volatility of methylglyoxal cloud SOA formed through OH radical oxidation and droplet evaporation

Science.gov (United States)

Ortiz-Montalvo, Diana L.; Schwier, Allison N.; Lim, Yong B.; McNeill, V. Faye; Turpin, Barbara J.

2016-04-01

The volatility of secondary organic aerosol (SOA) formed through cloud processing (aqueous hydroxyl radical (radOH) oxidation and droplet evaporation) of methylglyoxal (MGly) was studied. Effective vapor pressure and effective enthalpy of vaporization (ΔHvap,eff) were determined using 1) droplets containing MGly and its oxidation products, 2) a Vibrating Orifice Aerosol Generator (VOAG) system, and 3) Temperature Programmed Desorption Aerosol-Chemical Ionization Mass Spectrometry (TPD Aerosol-CIMS). Simulated in-cloud MGly oxidation (for 10-30 min) produces an organic mixture of higher and lower volatility components with an overall effective vapor pressure of (4 ± 7) × 10-7 atm at pH 3. The effective vapor pressure decreases by a factor of 2 with addition of ammonium hydroxide (pH 7). The fraction of organic material remaining in the particle-phase after drying was smaller than for similar experiments with glycolaldehyde and glyoxal SOA. The ΔHvap,eff of pyruvic acid and oxalic acid + methylglyoxal in the mixture (from TPD Aerosol-CIMS) were smaller than the theoretical enthalpies of the pure compounds and smaller than that estimated for the entire precursor/product mix after droplet evaporation. After 10-30 min of aqueous oxidation (one cloud cycle) the majority of the MGly + radOH precursor/product mix (even neutralized) will volatilize during droplet evaporation; neutralization and at least 80 min of oxidation at 10-12 M radOH (or >12 h at 10-14 M) is needed before low volatility ammonium oxalate exceeds pyruvate.

Observation of mesospheric gravity waves at Comandante Ferraz Antarctica Station (62° S

Directory of Open Access Journals (Sweden)

P. B. Souza

2009-06-01

Full Text Available An airglow all-sky imager was operated at Comandante Ferraz Antarctica Station (62.1° S, 58.4° W, between April and October of 2007. Mesospheric gravity waves were observed using the OH airglow layer during 43 nights with good weather conditions. The waves presented horizontal wavelengths between 10 and 60 km and observed periods mainly distributed between 5 and 20 min. The observed phase speeds range between 5 m/s and 115 m/s; the majority of the wave velocities were between 10 and 60 m/s. The waves showed a preferential propagation direction towards the southwest in winter (May to July, while during spring (August to October there was an anisotropy with a preferential propagation direction towards the northwest. Unusual mesospheric fronts were also observed. The most probable wave source could be associated to orographic forcing, cold fronts or strong cyclonic activity in the Antarctica Peninsula.

Correlations of mesospheric winds with subtle motion of the Arctic polar vortex

Directory of Open Access Journals (Sweden)

Y. Bhattacharya

2010-01-01

Full Text Available This paper investigates the relationship between high latitude upper mesospheric winds and the state of the stratospheric polar vortex in the absence of major sudden stratospheric warmings. A ground based Michelson Interferometer stationed at Resolute Bay (74°43' N, 94°58' W in the Canadian High Arctic is used to measure mesopause region neutral winds using the hydroxyl (OH Meinel-band airglow emission (central altitude of ~85 km. These observed winds are compared to analysis winds in the upper stratosphere during November and December of 1995 and 1996; years characterized as cold, stable polar vortex periods. Correlation of mesopause wind speeds with those from the upper stratosphere is found to be significant for the 1996 season when the polar vortex is subtly displaced off its initial location by a strong Aleutian High. These mesopause winds are observed to lead stratospheric winds by approximately two days with increasing (decreasing mesospheric winds predictive of decreasing (increasing stratospheric winds. No statistically significant correlations are found for the 1995 season when there is no such displacement of the polar vortex.

Double seismic zone in downgoing slabs and the viscosity of the mesosphere

International Nuclear Information System (INIS)

Sleep, N.H.

1979-01-01

The seismic zone beneath several island arcs between about 100 and 200 km depth consists of an upper zone having down-dip compression and a lower zone having down-dip tension. Several numerical models of the Aleutina arc were computed to test the hypothesis that these double seismic zones are due to sagging of the slab under its own weight. This sagging occurs because the asthenosphere (between about 100 and 200 km) provides little support or resistance to the slab, which is supported from below by the more viscous mesosphere and from above by the lithosphere. The viscosity of the mesosphere was constrained to the interval between 0.25 x 10 22 and 0.5 x 10 22 P by noting that the slab would have mainly down-dip compression at higher viscosities and mainly down-dip tension at lower viscosities. The deviatoric stress in the slab and the fault plane between the slab and the island arc is about 200--300 bars (expressed as shear stress). The models were calibrated to the observed depth and gravity anomalies in the trench

Lost in Cloud

Science.gov (United States)

Maluf, David A.; Shetye, Sandeep D.; Chilukuri, Sri; Sturken, Ian

2012-01-01

Cloud computing can reduce cost significantly because businesses can share computing resources. In recent years Small and Medium Businesses (SMB) have used Cloud effectively for cost saving and for sharing IT expenses. With the success of SMBs, many perceive that the larger enterprises ought to move into Cloud environment as well. Government agency s stove-piped environments are being considered as candidates for potential use of Cloud either as an enterprise entity or pockets of small communities. Cloud Computing is the delivery of computing as a service rather than as a product, whereby shared resources, software, and information are provided to computers and other devices as a utility over a network. Underneath the offered services, there exists a modern infrastructure cost of which is often spread across its services or its investors. As NASA is considered as an Enterprise class organization, like other enterprises, a shift has been occurring in perceiving its IT services as candidates for Cloud services. This paper discusses market trends in cloud computing from an enterprise angle and then addresses the topic of Cloud Computing for NASA in two possible forms. First, in the form of a public Cloud to support it as an enterprise, as well as to share it with the commercial and public at large. Second, as a private Cloud wherein the infrastructure is operated solely for NASA, whether managed internally or by a third-party and hosted internally or externally. The paper addresses the strengths and weaknesses of both paradigms of public and private Clouds, in both internally and externally operated settings. The content of the paper is from a NASA perspective but is applicable to any large enterprise with thousands of employees and contractors.

GIANT MOLECULAR CLOUD FORMATION IN DISK GALAXIES: CHARACTERIZING SIMULATED VERSUS OBSERVED CLOUD CATALOGS

Energy Technology Data Exchange (ETDEWEB)

Benincasa, Samantha M.; Pudritz, Ralph E.; Wadsley, James [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Tasker, Elizabeth J. [Department of Physics, Faculty of Science, Hokkaido University, Kita-ku, Sapporo 060-0810 (Japan)

2013-10-10

We present the results of a study of simulated giant molecular clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 10{sup 4} M{sub ☉} and 10{sup 7} M{sub ☉}. We compare our simulated cloud population to two observational surveys: the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulated cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary—a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud-cloud gravitational encounters. We also find that the rate at which potentially star-forming gas accumulates within dense regions—wherein n{sub thresh} ≥ 10{sup 4} cm{sup –3}—is 3% per 10 Myr, in clouds of roughly 10{sup 6} M{sub ☉}. This suggests that star formation rates in observed clouds are related to the rates at which gas can be accumulated into dense subregions within GMCs via filamentary flows. The most internally well-resolved clouds are chosen for listing in a catalog of simulated GMCs—the first of its kind. The cataloged clouds are available as an extracted data set from the global simulation.

Role of orbital dynamics and cloud-cloud collisions in the formation of giant molecular clouds in global spiral structures

International Nuclear Information System (INIS)

Roberts, W.W. Jr.; Stewart, G.R.

1987-01-01

The role of orbit crowding and cloud-cloud collisions in the formation of GMCs and their organization in global spiral structure is investigated. Both N-body simulations of the cloud system and a detailed analysis of individual particle orbits are used to develop a conceptual understanding of how individual clouds participate in the collective density response. Detailed comparisons are made between a representative cloud-particle simulation in which the cloud particles collide inelastically with one another and give birth to and subsequently interact with young star associations and stripped down simulations in which the cloud particles are allowed to follow ballistic orbits in the absence of cloud-cloud collisions or any star formation processes. Orbit crowding is then related to the behavior of individual particle trajectories in the galactic potential field. The conceptual picture of how GMCs are formed in the clumpy ISMs of spiral galaxies is formulated, and the results are compared in detail with those published by other authors. 68 references

The ASSET intercomparison of stratosphere and lower mesosphere humidity analyses

Directory of Open Access Journals (Sweden)

H. E. Thornton

2009-02-01

Full Text Available This paper presents results from the first detailed intercomparison of stratosphere-lower mesosphere water vapour analyses; it builds on earlier results from the EU funded framework V "Assimilation of ENVISAT Data" (ASSET project. Stratospheric water vapour plays an important role in many key atmospheric processes and therefore an improved understanding of its daily variability is desirable. With the availability of high resolution, good quality Michelson Interferometer for Passive Atmospheric Sounding (MIPAS water vapour profiles, the ability of four different atmospheric models to assimilate these data is tested. MIPAS data have been assimilated over September 2003 into the models of the European Centre for Medium Range Weather Forecasts (ECMWF, the Belgian Institute for Space and Aeronomy (BIRA-IASB, the French Service d'Aéronomie (SA-IPSL and the UK Met Office. The resultant middle atmosphere humidity analyses are compared against independent satellite data from the Halogen Occultation Experiment (HALOE, the Polar Ozone and Aerosol Measurement (POAM III and the Stratospheric Aerosol and Gas Experiment (SAGE II. The MIPAS water vapour profiles are generally well assimilated in the ECMWF, BIRA-IASB and SA systems, producing stratosphere-mesosphere water vapour fields where the main features compare favourably with the independent observations. However, the models are less capable of assimilating the MIPAS data where water vapour values are locally extreme or in regions of strong humidity gradients, such as the southern hemisphere lower stratosphere polar vortex. Differences in the analyses can be attributed to the choice of humidity control variable, how the background error covariance matrix is generated, the model resolution and its complexity, the degree of quality control of the observations and the use of observations near the model boundaries. Due to the poor performance of the Met Office analyses the results are not included in

The ASSET intercomparison of stratosphere and lower mesosphere humidity analyses

Science.gov (United States)

Thornton, H. E.; Jackson, D. R.; Bekki, S.; Bormann, N.; Errera, Q.; Geer, A. J.; Lahoz, W. A.; Rharmili, S.

2009-02-01

This paper presents results from the first detailed intercomparison of stratosphere-lower mesosphere water vapour analyses; it builds on earlier results from the EU funded framework V "Assimilation of ENVISAT Data" (ASSET) project. Stratospheric water vapour plays an important role in many key atmospheric processes and therefore an improved understanding of its daily variability is desirable. With the availability of high resolution, good quality Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) water vapour profiles, the ability of four different atmospheric models to assimilate these data is tested. MIPAS data have been assimilated over September 2003 into the models of the European Centre for Medium Range Weather Forecasts (ECMWF), the Belgian Institute for Space and Aeronomy (BIRA-IASB), the French Service d'Aéronomie (SA-IPSL) and the UK Met Office. The resultant middle atmosphere humidity analyses are compared against independent satellite data from the Halogen Occultation Experiment (HALOE), the Polar Ozone and Aerosol Measurement (POAM III) and the Stratospheric Aerosol and Gas Experiment (SAGE II). The MIPAS water vapour profiles are generally well assimilated in the ECMWF, BIRA-IASB and SA systems, producing stratosphere-mesosphere water vapour fields where the main features compare favourably with the independent observations. However, the models are less capable of assimilating the MIPAS data where water vapour values are locally extreme or in regions of strong humidity gradients, such as the southern hemisphere lower stratosphere polar vortex. Differences in the analyses can be attributed to the choice of humidity control variable, how the background error covariance matrix is generated, the model resolution and its complexity, the degree of quality control of the observations and the use of observations near the model boundaries. Due to the poor performance of the Met Office analyses the results are not included in the intercomparison

Integration of a Zero-footprint Cloud-based Picture Archiving and Communication System with Customizable Forms for Radiology Research and Education.

Science.gov (United States)

Hostetter, Jason; Khanna, Nishanth; Mandell, Jacob C

2018-06-01

The purpose of this study was to integrate web-based forms with a zero-footprint cloud-based Picture Archiving and Communication Systems (PACS) to create a tool of potential benefit to radiology research and education. Web-based forms were created with a front-end and back-end architecture utilizing common programming languages including Vue.js, Node.js and MongoDB, and integrated into an existing zero-footprint cloud-based PACS. The web-based forms application can be accessed in any modern internet browser on desktop or mobile devices and allows the creation of customizable forms consisting of a variety of questions types. Each form can be linked to an individual DICOM examination or a collection of DICOM examinations. Several uses are demonstrated through a series of case studies, including implementation of a research platform for multi-reader multi-case (MRMC) studies and other imaging research, and creation of an online Objective Structure Clinical Examination (OSCE) and an educational case file. Copyright © 2018 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

Infrared polarimetry of dark clouds. Pt. 1. Magnetic field structure in Heiles Cloud 2

Energy Technology Data Exchange (ETDEWEB)

Tamura, Motohide; Nagata, Tetsuya; Sato, Shuji; Tanaka, Masuo

1987-01-15

The K-band polarization of 18 stars toward Heiles Cloud 2 in the Taurus dark cloud complex has been measured to investigate the structure of the magnetic field in this cloud. The observed polarization vectors are well aligned, with a mean position angle of approx. 50/sup 0/, which is perpendicular to the direction of the elongation of the cloud. This indicates that Heiles Cloud 2 has formed by contraction along the magnetic field, resulting in the flattened shape.

Lidar investigations on the optical and dynamical properties of cirrus clouds in the upper troposphere and lower stratosphere regions at a tropical station, Gadanki, India (13.5°N, 79.2°E)

Science.gov (United States)

Krishnakumar, Vasudevannair; Satyanarayana, Malladi; Radhakrishnan, Soman R.; Dhaman, Reji K.; Jayeshlal, Glory Selvan; Motty, Gopinathan Nair S.; Pillai, Vellara P. Mahadevan; Raghunath, Karnam; Ratnam, Madineni Venkat; Rao, Duggirala Ramakrishna; Sudhakar, Pindlodi

2014-01-01

High altitude cirrus clouds are composed mainly of ice crystals with a variety of sizes and shapes. They have a large influence on Earth's energy balance and global climate. Recent studies indicate that the formation, dissipation, life time, optical, and micro-physical properties are influenced by the dynamical conditions of the surrounding atmosphere like background aerosol, turbulence, etc. In this work, an attempt has been made to quantify some of these characteristics by using lidar and mesosphere-stratosphere-troposphere (MST) radar. Mie lidar and 53 MHz MST radar measurements made over 41 nights during the period 2009 to 2010 from the tropical station, Gadanki, India (13.5°N, 79.2°E). The optical and microphysical properties along with the structure and dynamics of the cirrus are presented as observed under different atmospheric conditions. The study reveals the manifestation of different forms of cirrus with a preferred altitude of formation in the 13 to 14 km altitude. There are considerable differences in the properties obtained among 2009 and 2010 showing significant anomalous behavior in 2010. The clouds observed during 2010 show relatively high asymmetry and large multiple scattering effects. The anomalies found during 2010 may be attributed to the turbulence noticed in the surrounding atmosphere. The results show a clear correlation between the crystal morphology in the clouds and the dynamical conditions of the prevailing atmosphere during the observational period.

Mesospheric Temperature Measurements over Scandinavia During the Gravity Wave Life Cycle Campaign (GW-LCYCLE)

Science.gov (United States)

Pautet, P. D.; Taylor, M.; Kaifler, B.

2016-12-01

The Gravity Wave Life Cycle (GW-LCYCLE) project took place in Northern Scandinavia during the winter 2015-16. This international program focused on investigating the generation and deep propagation of atmospheric gravity waves, especially the orographic waves generated over the Scandinavian mountain range. A series of instruments was operated at several ground-based locations and on-board the DLR HALO Gulfstream V and Falcon aircrafts. As part of this project, Utah State University (USU) deployed 3 Advanced Mesospheric Temperature Mappers (AMTM) at the ALOMAR facility, Norway (operational since December 2010), at the IRF institute in Kiruna, Sweden, and at the FMI institute in Sodankylä, Finland. Each of these instruments measures the OH (3,1) rotational temperature over a large region (200x160km) at 87km altitude. During the campaign, their total coverage extended across the Scandinavian Mountain Range, from the wind side in the west to 500 km to the east in the lee of the mountains, allowing the investigation of the occurrence and evolution of gravity waves (GWs) over this part of Scandinavia. Furthermore, the AMTM in Sodankylä operated in the container housing a DLR Rayleigh lidar. Both instruments ran simultaneously and autonomously from November 2015 to April 2016, providing an unprecedented complementary high-quality data set. This presentation will introduce preliminary results obtained during this campaign, in particular the evolution of the mesospheric temperature through the winter, the analysis of mountain waves occurrence and dynamics at mesospheric altitude, as well as the investigation of interesting individual GW cases.

Six years of mesospheric CO estimated from ground-based frequency-switched microwave radiometry at 57° N compared with satellite instruments

Directory of Open Access Journals (Sweden)

P. Forkman

2012-11-01

Full Text Available Measurements of mesospheric carbon monoxide, CO, provide important information about the dynamics in the mesosphere region since CO has a long lifetime at these altitudes. Ground-based measurements of mesospheric CO made at the Onsala Space Observatory, OSO, (57° N, 12° E are presented. The dataset covers the period 2002–2008 and is hence uniquely long for ground-based observations. The simple and stable 115 GHz frequency-switched radiometer, calibration method, retrieval procedure and error characterization are described. A comparison between our measurements and co-located CO measurements from the satellite sensors ACE-FTS on Scisat (v2.2, MLS on Aura (v3-3, MIPAS on Envisat (V3O_CO_12 + 13 and V4O_CO_200 and SMR on Odin (v225 and v021 is carried out. Our instrument, OSO, and the four satellite instruments show the same general variation of the vertical distribution of mesospheric CO in both the annual cycle and in shorter time period events, with high CO mixing ratios during winter and very low amounts during summer in the observed 55–100 km altitude range. During 2004–2008 the agreement of the OSO instrument and the satellite sensors ACE-FTS, MLS and MIPAS (200 is good in the altitude range 55–70 km. Above 70 km, OSO shows up to 25% higher CO column values compared to both ACE and MLS. For the time period 2002–2004, CO from MIPAS (12 + 13 is up to 50% lower than OSO between 55 and 70 km. Mesospheric CO from the two versions of SMR deviates up to ±65% when compared to OSO, but the analysis is based on only a few co-locations.

Six years of mesospheric CO estimated from ground-based frequency-switched microwave radiometry at 57° N compared with satellite instruments

Science.gov (United States)

Forkman, P.; Christensen, O. M.; Eriksson, P.; Urban, J.; Funke, B.

2012-11-01

Measurements of mesospheric carbon monoxide, CO, provide important information about the dynamics in the mesosphere region since CO has a long lifetime at these altitudes. Ground-based measurements of mesospheric CO made at the Onsala Space Observatory, OSO, (57° N, 12° E) are presented. The dataset covers the period 2002-2008 and is hence uniquely long for ground-based observations. The simple and stable 115 GHz frequency-switched radiometer, calibration method, retrieval procedure and error characterization are described. A comparison between our measurements and co-located CO measurements from the satellite sensors ACE-FTS on Scisat (v2.2), MLS on Aura (v3-3), MIPAS on Envisat (V3O_CO_12 + 13 and V4O_CO_200) and SMR on Odin (v225 and v021) is carried out. Our instrument, OSO, and the four satellite instruments show the same general variation of the vertical distribution of mesospheric CO in both the annual cycle and in shorter time period events, with high CO mixing ratios during winter and very low amounts during summer in the observed 55-100 km altitude range. During 2004-2008 the agreement of the OSO instrument and the satellite sensors ACE-FTS, MLS and MIPAS (200) is good in the altitude range 55-70 km. Above 70 km, OSO shows up to 25% higher CO column values compared to both ACE and MLS. For the time period 2002-2004, CO from MIPAS (12 + 13) is up to 50% lower than OSO between 55 and 70 km. Mesospheric CO from the two versions of SMR deviates up to ±65% when compared to OSO, but the analysis is based on only a few co-locations.

Silicon Chemistry in the Mesosphere and Lower Thermosphere

Science.gov (United States)

Plane, John M. C.; Gomez-Martin, Juan Carlos; Feng, Wuhu; Janches, Diego

2016-01-01

Silicon is one of the most abundant elements in cosmic dust, and meteoric ablation injects a significant amount of Si into the atmosphere above 80 km. In this study, a new model for silicon chemistry in the mesosphere lower thermosphere is described, based on recent laboratory kinetic studies of Si, SiO,SiO2, and S(exp +). Electronic structure calculations and statistical rate theory are used to show that the likely fate of SiO2 is a two-step hydration to silicic acid (Si(OH)4), which then polymerizes with metal oxides and hydroxides to form meteoric smoke particles. This chemistry is then incorporated into a whole atmosphere chemistry-climate model. The vertical profiles of Si+ and the Si(exp +)Fe(exp +) ratio are shown to be in good agreement with rocket-borne mass spectrometric measurements between 90 and 110 km. Si(exp +) has consistently been observed to be the major meteoric ion around 110 km; this implies that the relative injection rate of Si from meteoric ablation, compared to metals such as Fe and Mg, is significantly larger than expected based on the irrelative chondritic abundances. Finally, the global abundances of SiO and Si(OH)4 show clear evidence of the seasonal meteoric input function, which is much less pronounced in the case of other meteoric species.

Making and Breaking Clouds

Science.gov (United States)

Kohler, Susanna

2017-10-01

Molecular clouds which youre likely familiar with from stunning popular astronomy imagery lead complicated, tumultuous lives. A recent study has now found that these features must be rapidly built and destroyed.Star-Forming CollapseA Hubble view of a molecular cloud, roughly two light-years long, that has broken off of the Carina Nebula. [NASA/ESA, N. Smith (University of California, Berkeley)/The Hubble Heritage Team (STScI/AURA)]Molecular gas can be found throughout our galaxy in the form of eminently photogenic clouds (as featured throughout this post). Dense, cold molecular gas makes up more than 20% of the Milky Ways total gas mass, and gravitational instabilities within these clouds lead them to collapse under their own weight, resulting in the formation of our galaxys stars.How does this collapse occur? The simplest explanation is that the clouds simply collapse in free fall, with no source of support to counter their contraction. But if all the molecular gas we observe collapsed on free-fall timescales, star formation in our galaxy would churn a rate thats at least an order of magnitude higher than the observed 12 solar masses per year in the Milky Way.Destruction by FeedbackAstronomers have theorized that there may be some mechanism that supports these clouds against gravity, slowing their collapse. But both theoretical studies and observations of the clouds have ruled out most of these potential mechanisms, and mounting evidence supports the original interpretation that molecular clouds are simply gravitationally collapsing.A sub-mm image from ESOs APEX telescope of part of the Taurus molecular cloud, roughly ten light-years long, superimposed on a visible-light image of the region. [ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey 2. Acknowledgment: Davide De Martin]If this is indeed the case, then one explanation for our low observed star formation rate could be that molecular clouds are rapidly destroyed by feedback from the very stars

Response of the mesosphere-thermosphere-ionosphere system to global change - CAWSES-II contribution

Czech Academy of Sciences Publication Activity Database

Laštovička, Jan; Beig, G.; Marsh, R. D.

2014-01-01

Roč. 1, 11 November (2014), 21/ 1-21/ 19 ISSN 2197-4284 R&D Projects: GA ČR GAP209/10/1792; GA MŠk LD12070 Institutional support: RVO:68378289 Keywords : mesosphere * thermosphere * ionosphere * long-term trends * climatic change Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.progearthplanetsci.com/content/1/1/21

DISTRIBUTION AND ORIGIN OF HIGH-VELOCITY CLOUDS .3. CLOUDS, COMPLEXES AND POPULATIONS

NARCIS (Netherlands)

WAKKER, BP; VANWOERDEN, H

1991-01-01

We present the first complete catalogue of high-velocity clouds (HVCs), followed by a classification of these clouds into complexes and populations. The catalogue will form the basis for comparisons with theoretical models. The study described here yields the following conclusions: (1) Differential

Relationship between variability of the semidiurnal tide in the Northern Hemisphere mesosphere and quasi-stationary planetary waves throughout the global middle atmosphere

Directory of Open Access Journals (Sweden)

X. Xu

2009-11-01

Full Text Available To investigate possible couplings between planetary waves and the semidiurnal tide (SDT, this work examines the statistical correlations between the SDT amplitudes observed in the Northern Hemisphere (NH mesosphere and stationary planetary wave (SPW with wavenumber S=1 (SPW1 amplitudes throughout the global stratosphere and mesosphere. The latter are derived from the Aura-MLS temperature measurements. During NH summer-fall (July–October, the mesospheric SDT amplitudes observed at Svalbard (78° N and Eureka (80° N usually do not show persistent correlations with the SPW1 amplitudes in the opposite hemisphere. Although the SDT amplitudes observed at lower latitudes (~50–70° N, especially at Saskatoon (52° N, are often shown to be highly and positively correlated with the SPW1 amplitudes in high southern latitudes, these correlations cannot be sufficiently explained as evidence for a direct physical link between the Southern Hemisphere (SH winter-early spring SPW and NH summer-early fall mesospheric SDT. This is because the migrating tide's contribution is usually dominant in the mid-high latitude (~50–70° N NH mesosphere during the local late summer-early fall (July–September. The numerical correlation is dominated by similar low-frequency variability or trends between the amplitudes of the NH SDT and SH SPW1 during the respective equinoctial transitions. In contradistinction, during NH winter (November–February, the mesospheric SDT amplitudes at northern mid-high latitudes (~50–80° N are observed to be significantly and positively correlated with the SPW1 amplitudes in the same hemisphere in most cases. Because both the SPW and migrating SDT are large in the NH during the local winter, a non-linear interaction between SPW and migrating SDT probably occurs, thus providing a global non-migrating SDT. This is consistent with observations of SDT in Antarctica that are large in summer than in winter. It is suggested that

Aerosol-Forming Reactions of Glyoxal, Methylglyoxal and Amino Acids in Clouds

Science.gov (United States)

de Haan, D. O.; Smith, K. W.; Stroik, D. R.; Corrigan, A. L.; Lee, F. E.; Phan, J. T.; Conley, A. C.

2008-12-01

Glyoxal and methylglyoxal are two common aldehydes present in fog and cloud water. Amino acids are present in clouds at similar concentrations. Here we present bulk and aerosol mass spectroscopic data demonstrating that irreversible reactions between glyoxal and amino acids, triggered by droplet evaporation, produce N-derivatized imidazole compounds along with deeply colored Maillard reaction products. These reactions can occur in the dark and in the absence of oxidants. Reactions between methylglyoxal and amino acids produce analogous methylated products plus oligomers with masses up to m/z = 1000. These reactions, which go to completion on the 10-min-timescale of cloud processing, could be significant sources of secondary organic aerosol and humic-like substances (HULIS or brown carbon).

Radio continuum interferometry of dark clouds: A search for newly formed HII regions

International Nuclear Information System (INIS)

Gilmore, W.S.

1978-01-01

A search for compact HII regions embedded in dark clouds has been carried out in an effort to study local massive star formation. Approximately 20% of the total area of opaque dark cloud material in the sky with Av greater than or equal to 6 mag was surveyed with the NRAO three-element interferometer at 2695 MHz, and at least 5% more was surveyed with the NRAO 300-foot telescope at 4750 MHz. The regions surveyed include the dark cloud complexes in Perseus, Taurus, Orion, and Ophiuchus, as well as several smaller cloud complexes and individual clouds. No hidden compact HII regions embedded inside dark clouds were detected with certainty in the radio continuum. However, eleven HII regions with associated visible emission and eighteen other possible HII regions were detected. Five infrared sources thought to have the luminosities of early B stars were not detected in the radio continuum. These five sources showed high correlation with the presence of CO self-absorption, CO emission over a wide range of velocities, and type I OH masers, but an absence of coincident visible nebulosity and detectable radio continuum emission. Therefore, it is suggested that they represent an earlier evolutionary stage than those HII region detected in the radio continuum. This first evolutionary state marks the presence of ''pre-emergent'' (with respect to the molecular cloud) cocoon stars. HII regions in the second evolutionary state are marked by the presence of detectable radio continuum emission, i.e., they are stronger than 10 mJy at 2695 MHz. They have associated visible nebulosity, are relatively large, and appear to be located at the edges of molecular clouds. These are designated as ''emergent edge'' HII regions. The fact that many young HII regions are edge HII regions implies that massive stars are born near the edges of clouds, a phenomenon previously suggested by several other investigators

Polar mesosphere summer echoes (PMSE: Review of observations and current understanding

Directory of Open Access Journals (Sweden)

M. Rapp

2004-01-01

Full Text Available Polar mesosphere summer echoes (PMSE are very strong radar echoes primarily studied in the VHF wavelength range from altitudes close to the polar summer mesopause. Radar waves are scattered at irregularities in the radar refractive index which at mesopause altitudes is effectively determined by the electron number density. For efficient scatter, the electron number density must reveal structures at the radar half wavelength (Bragg condition for monostatic radars; ~3 m for typical VHF radars. The question how such small scale electron number density structures are created in the mesopause region has been a longstanding open scientific question for almost 30 years. This paper reviews experimental and theoretical milestones on the way to an advanced understanding of PMSE. Based on new experimental results from in situ observations with sounding rockets, ground based observations with radars and lidars, numerical simulations with microphysical models of the life cycle of mesospheric aerosol particles, and theoretical considerations regarding the diffusivity of electrons in the ice loaded complex plasma of the mesopause region, a consistent explanation for the generation of these radar echoes has been developed. The main idea is that mesospheric neutral air turbulence in combination with a significantly reduced electron diffusivity due to the presence of heavy charged ice aerosol particles (radii ~5–50 nm leads to the creation of structures at spatial scales significantly smaller than the inner scale of the neutral gas turbulent velocity field itself. Importantly, owing to their very low diffusivity, the plasma structures acquire a very long lifetime, i.e., 10 min to hours in the presence of particles with radii between 10 and 50 nm. This leads to a temporal decoupling of active neutral air turbulence and the existence of small scale plasma structures and PMSE and thus readily explains observations proving the absence of neutral air turbulence at

The Monoceros R2 Molecular Cloud

Science.gov (United States)

Carpenter, J. M.; Hodapp, K. W.

2008-12-01

The Monoceros R2 region was first recognized as a chain of reflection nebulae illuminated by A- and B-type stars. These nebulae are associated with a giant molecular cloud that is one of the closest massive star forming regions to the Sun. This chapter reviews the properties of the Mon R2 region, including the namesake reflection nebulae, the large scale molecula= r cloud, global star formation activity, and properties of prominent star forming regions in the cloud.

Thermosphere-ionosphere-mesosphere energetics and dynamics (TIMED). The TIMED mission and science program report of the science definition team. Volume 1: Executive summary

Science.gov (United States)

1991-01-01

A Science Definition Team was established in December 1990 by the Space Physics Division, NASA, to develop a satellite program to conduct research on the energetics, dynamics, and chemistry of the mesosphere and lower thermosphere/ionosphere. This two-volume publication describes the TIMED (Thermosphere-Ionosphere-Mesosphere, Energetics and Dynamics) mission and associated science program. The report outlines the scientific objectives of the mission, the program requirements, and the approach towards meeting these requirements.

Observation of a 27-day solar signature in noctilucent cloud altitude

Science.gov (United States)

Köhnke, Merlin C.; von Savigny, Christian; Robert, Charles E.

2018-05-01

Previous studies have identified solar 27-day signatures in several parameters in the Mesosphere/Lower thermosphere region, including temperature and Noctilucent cloud (NLC) occurrence frequency. In this study we report on a solar 27-day signature in NLC altitude with peak-to-peak variations of about 400 m. We use SCIAMACHY limb-scatter observations from 2002 to 2012 to detect NLCs. The superposed epoch analysis method is applied to extract solar 27-day signatures. A 27-day signature in NLC altitude can be identified in both hemispheres in the SCIAMACHY dataset, but the signature is more pronounced in the northern hemisphere. The solar signature in NLC altitude is found to be in phase with solar activity and temperature for latitudes ≳ 70 ° N. We provide a qualitative explanation for the positive correlation between solar activity and NLC altitude based on published model simulations.

Clustering, randomness, and regularity in cloud fields: 2. Cumulus cloud fields

Science.gov (United States)

Zhu, T.; Lee, J.; Weger, R. C.; Welch, R. M.

1992-12-01

During the last decade a major controversy has been brewing concerning the proper characterization of cumulus convection. The prevailing view has been that cumulus clouds form in clusters, in which cloud spacing is closer than that found for the overall cloud field and which maintains its identity over many cloud lifetimes. This "mutual protection hypothesis" of Randall and Huffman (1980) has been challenged by the "inhibition hypothesis" of Ramirez et al. (1990) which strongly suggests that the spatial distribution of cumuli must tend toward a regular distribution. A dilemma has resulted because observations have been reported to support both hypotheses. The present work reports a detailed analysis of cumulus cloud field spatial distributions based upon Landsat, Advanced Very High Resolution Radiometer, and Skylab data. Both nearest-neighbor and point-to-cloud cumulative distribution function statistics are investigated. The results show unequivocally that when both large and small clouds are included in the cloud field distribution, the cloud field always has a strong clustering signal. The strength of clustering is largest at cloud diameters of about 200-300 m, diminishing with increasing cloud diameter. In many cases, clusters of small clouds are found which are not closely associated with large clouds. As the small clouds are eliminated from consideration, the cloud field typically tends towards regularity. Thus it would appear that the "inhibition hypothesis" of Ramirez and Bras (1990) has been verified for the large clouds. However, these results are based upon the analysis of point processes. A more exact analysis also is made which takes into account the cloud size distributions. Since distinct clouds are by definition nonoverlapping, cloud size effects place a restriction upon the possible locations of clouds in the cloud field. The net effect of this analysis is that the large clouds appear to be randomly distributed, with only weak tendencies towards

A global climatology of the mesospheric sodium layer from GOMOS data during the 2002–2008 period

Directory of Open Access Journals (Sweden)

D. Fussen

2010-10-01

Full Text Available This paper presents a climatology of the mesospheric sodium layer built from the processing of 7 years of GOMOS data. With respect to preliminary results already published for the year 2003, a more careful analysis was applied to the averaging of occultations inside the climatological bins (10° in latitude-1 month. Also, the slant path absorption lines of the Na doublet around 589 nm shows evidence of partial saturation that was responsible for an underestimation of the Na concentration in our previous results. The sodium climatology has been validated with respect to the Fort Collins lidar measurements and, to a lesser extent, to the OSIRIS 2003–2004 data. Despite the important natural sodium variability, we have shown that the Na vertical column has a marked semi-annual oscillation at low latitudes that merges into an annual oscillation in the polar regions,a spatial distribution pattern that was unreported so far. The sodium layer seems to be clearly influenced by the mesospheric global circulation and the altitude of the layer shows clear signs of subsidence during polar winter. The climatology has been parameterized by time-latitude robust fits to allow for easy use. Taking into account the non-linearity of the transmittance due to partial saturation, an experimental approach is proposed to derive mesospheric temperatures from limb remote sounding measurements.

Solar Cycle Response and Long-Term Trends in the Mesospheric Metal Layers

Science.gov (United States)

Dawkins, E. C. M.; Plane, J. M. C.; Chipperfield, M.; Feng, W.; Marsh, D. R.; Hoffner, J.; Janches, D.

2016-01-01

The meteoric metal layers (Na, Fe, and K) which form as a result of the ablation of incoming meteors act as unique tracers for chemical and dynamical processes that occur within the upper mesosphere lower thermosphere region. In this work, we examine whether these metal layers are sensitive Fe indicators of decadal long-term changes within the upper atmosphere. Output from a whole-atmosphere climate model is used to assess the response of the Na, K, and Fe layers across a 50 year period (1955-2005). At short timescales, the K layer has previously been shown to exhibit a very different seasonal behavior compared to the other metals. Here we show that this unusual behavior is also exhibited at longer time scales (both the 11 year solar cycle and 50 year periods), where K displays a much more pronounced response to atmospheric temperature changes than either Na or Fe. The contrasting solar cycle behavior of the K and Na layers predicted by the model is confirmed using satellite and lidar observations for the period 2004-2013.

UARS Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AL V010 (UARIS3AL) at GES DISC

Data.gov (United States)

National Aeronautics and Space Administration — The Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AL data product consists of daily, 4 degree increment latitude-ordered vertical profiles of...

A parameterization of cloud droplet nucleation

International Nuclear Information System (INIS)

Ghan, S.J.; Chuang, C.; Penner, J.E.

1993-01-01

Droplet nucleation is a fundamental cloud process. The number of aerosols activated to form cloud droplets influences not only the number of aerosols scavenged by clouds but also the size of the cloud droplets. Cloud droplet size influences the cloud albedo and the conversion of cloud water to precipitation. Global aerosol models are presently being developed with the intention of coupling with global atmospheric circulation models to evaluate the influence of aerosols and aerosol-cloud interactions on climate. If these and other coupled models are to address issues of aerosol-cloud interactions, the droplet nucleation process must be adequately represented. Here we introduce a droplet nucleation parametrization that offers certain advantages over the popular Twomey (1959) parameterization

Green symbiotic cloud communications

CERN Document Server

Mustafa, H D; Desai, Uday B; Baveja, Brij Mohan

2017-01-01

This book intends to change the perception of modern day telecommunications. Communication systems, usually perceived as “dumb pipes”, carrying information / data from one point to another, are evolved into intelligently communicating smart systems. The book introduces a new field of cloud communications. The concept, theory, and architecture of this new field of cloud communications are discussed. The book lays down nine design postulates that form the basis of the development of a first of its kind cloud communication paradigm entitled Green Symbiotic Cloud Communications or GSCC. The proposed design postulates are formulated in a generic way to form the backbone for development of systems and technologies of the future. The book can be used to develop courses that serve as an essential part of graduate curriculum in computer science and electrical engineering. Such courses can be independent or part of high-level research courses. The book will also be of interest to a wide range of readers including b...

Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data

Directory of Open Access Journals (Sweden)

X. Xu

2009-09-01

Full Text Available The coupling processes in the middle atmosphere have been a subject of intense research activity because of their effects on atmospheric circulation, structure, variability, and the distribution of chemical constituents. In this study, the day-to-day variability of Aura-MLS (Microwave Limb Sounder temperature data are used to reveal the vertical and interhemispheric coupling processes in the stratosphere-mesosphere during four Northern Hemisphere winters (2004/2005–2007/2008. The UKMO (United Kingdom Meteorological Office assimilated data and mesospheric winds from MF (medium frequency radars are also applied to help highlight the coupling processes.

In this study, a clear vertical link can be seen between the stratosphere and mesosphere during winter months. The coolings and reversals of northward meridional winds in the polar winter mesosphere are often observed in relation to warming events (Sudden Stratospheric Warming, SSW for short and the associated changes in zonal winds in the polar winter stratosphere. An upper-mesospheric cooling usually precedes the beginning of the warming in the stratosphere by 1–2 days.

Inter-hemispheric coupling has been identified initially by a correlation analysis using the year-to-year monthly zonal mean temperature. Then the correlation analyses are performed based upon the daily zonal mean temperature. From the original time sequences, significant positive (negative correlations are generally found between zonal mean temperatures at the Antarctic summer mesopause and in the Arctic winter stratosphere (mesosphere during northern mid-winters, although these correlations are dominated by the low frequency variability (i.e. the seasonal trend. Using the short-term oscillations (less than 15 days, the statistical result, by looking for the largest magnitude of correlation within a range of time-lags (0 to 10 days; positive lags mean that the Antarctic summer mesopause is lagging, indicates

Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data

Directory of Open Access Journals (Sweden)

X. Xu

2009-09-01

Full Text Available The coupling processes in the middle atmosphere have been a subject of intense research activity because of their effects on atmospheric circulation, structure, variability, and the distribution of chemical constituents. In this study, the day-to-day variability of Aura-MLS (Microwave Limb Sounder temperature data are used to reveal the vertical and interhemispheric coupling processes in the stratosphere-mesosphere during four Northern Hemisphere winters (2004/2005–2007/2008. The UKMO (United Kingdom Meteorological Office assimilated data and mesospheric winds from MF (medium frequency radars are also applied to help highlight the coupling processes. In this study, a clear vertical link can be seen between the stratosphere and mesosphere during winter months. The coolings and reversals of northward meridional winds in the polar winter mesosphere are often observed in relation to warming events (Sudden Stratospheric Warming, SSW for short and the associated changes in zonal winds in the polar winter stratosphere. An upper-mesospheric cooling usually precedes the beginning of the warming in the stratosphere by 1–2 days. Inter-hemispheric coupling has been identified initially by a correlation analysis using the year-to-year monthly zonal mean temperature. Then the correlation analyses are performed based upon the daily zonal mean temperature. From the original time sequences, significant positive (negative correlations are generally found between zonal mean temperatures at the Antarctic summer mesopause and in the Arctic winter stratosphere (mesosphere during northern mid-winters, although these correlations are dominated by the low frequency variability (i.e. the seasonal trend. Using the short-term oscillations (less than 15 days, the statistical result, by looking for the largest magnitude of correlation within a range of time-lags (0 to 10 days; positive lags mean that the Antarctic summer mesopause is lagging, indicates that the temporal

UARS Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AT V010 (UARIS3AT) at GES DISC

Data.gov (United States)

National Aeronautics and Space Administration — The Improved Stratospheric and Mesospheric Sounder (ISAMS) Level 3AT data product consists of daily, 65.536 second interval time-ordered vertical profiles of...

Evidence of non-LTE Effects in Mesospheric Water Vapor from Spectrally-Resolved Emissions Observed by CIRRIS-1A

Science.gov (United States)

Zhou, D. K.; Mlynczak, M. G.; Lopez-Puertas, M.; Zaragoza, G.

1999-01-01

Evidence of non-LTE effects in mesospheric water vapor as determined by infrared spectral emission measurements taken from the space shuttle is reported. A cryogenic Michelson interferometer in the CIRRIS-1A shuttle payload yielded high quality, atmospheric infrared spectra. These measurements demonstrate the enhanced daytime emissions of H2O (020-010) which are the result of non-LTE processes and in agreement with non-LTE models. The radiance ratios of H2O (010 to 000) and (020 to 010) Q(1) transitions during daytime are compared with non-LTE model calculations to assess the vibration-to-vibration exchange rate between H2O and O2 in the mesosphere. An exchange rate of 1.2 x 10(exp -12)cc/s is derived.

Simultaneous observations of Polar Mesosphere Summer Echoes at two different latitudes in Antarctica

Directory of Open Access Journals (Sweden)

H. Nilsson

2008-11-01

Full Text Available Simultaneous observations of Polar Mesosphere Summer Echoes (PMSE at Wasa and Davis in Antarctica have been compared. Data with simultaneous observations were obtained for 16 days between 18 January and 5 February 2007. Wasa is at a higher geographic latitude than Davis, but at lower geomagnetic latitude. PMSE strength and occurrence frequency were significantly higher at Wasa. The variation of daily PMSE occurrence over the measurement period was in agreement with temperature and frost-point estimates from the Microwave Limb Sounder on the Aura spacecraft for both Wasa and Davis. The diurnal variation of PMSE strength and occurrence frequency as well as the shape of the altitude profiles of average PMSE strength and occurrence frequency were similar for the two sites. The deepest part of the evening minimum in PMSE occurrence frequency occurred for the same magnetic local time at the two sites rather than for the same local solar time. The study indicates that PMSE strength and occurrence increase between 68.6° and 73° geographic latitude, consistent with observed differences in mesospheric temperatures and water vapor content. The average altitude distribution of PMSE varies relatively little with latitude in the same hemisphere.

SABER (TIMED) and MLS (UARS) Temperature Observations of Mesospheric and Stratospheric QBO and Related Tidal Variations

Science.gov (United States)

Huang, Frank T.; Mayr, Hans G.; Reber, Carl A.; Russell, James; Mlynczak, Marty; Mengel, John

2006-01-01

More than three years of temperature observations from the SABER (TIMED) and MLS WARS) instruments are analyzed to study the annual and inter-annual variations extending from the stratosphere into the upper mesosphere. The SABER measurements provide data from a wide altitude range (15 to 95 km) for the years 2002 to 2004, while the MLS data were taken in the 16 to 55 km altitude range a decade earlier. Because of the sampling properties of SABER and MLS, the variations with local solar time must be accounted for when estimating the zonal mean variations. An algorithm is thus applied that delineates with Fourier analysis the year-long variations of the migrating tides and zonal mean component. The amplitude of the diurnal tide near the equator shows a strong semiannual periodicity with maxima near equinox, which vary from year to year to indicate the influence from the Quasi-biennial Oscillation (QBO) in the zonal circulation. The zonal mean QBO temperature variations are analyzed over a range of latitudes and altitudes, and the results are presented for latitudes from 48"s to 48"N. New results are obtained for the QBO, especially in the upper stratosphere and mesosphere, and at mid-latitudes. At Equatorial latitudes, the QBO amplitudes show local peaks, albeit small, that occur at different altitudes. From about 20 to 40 km, and within about 15" of the Equator, the amplitudes can approach 3S K for the stratospheric QBO or SQBO. For the mesospheric QBO or MQBO, we find peaks near 70 km, with temperature amplitudes reaching 3.5"K, and near 85 km, the amplitudes approach 2.5OK. Morphologically, the amplitude and phase variations derived from the SABER and MLS measurements are in qualitative agreement. The QBO amplitudes tend to peak at the Equator but then increase again pole-ward of about 15" to 20'. The phase progression with altitude varies more gradually at the Equator than at mid-latitudes. A comparison of the observations with results from the Numerical Spectral

Seasonal Variations of Mesospheric Gravity Waves Observed with an Airglow All-sky Camera at Mt. Bohyun, Korea (36° N

Directory of Open Access Journals (Sweden)

Yong Ha Kim

2010-09-01

Full Text Available We have carried out all-sky imaging of OH Meinel, O2 atmospheric and OI 557.7 nm airglow layers in the period from July of 2001 through September of 2005 at Mt. Bohyun, Korea (36.2° N, 128.9° E, Alt = 1,124 m. We analyzed the images observed during a total of 153 clear moonless nights and found 97 events of band-type waves. The characteristics of the observed waves (wavelengths, periods, and phase speeds are consistent with internal gravity waves. The wave occurrence shows an approximately semi-annual variation, with maxima near solstices and minima near equinoxes, which is consistent with other studies of airglow wave observations, but not with those of mesospheric radar/lidar observations. The observed waves tended to propagate westward during fall and winter, and eastward during spring and summer. Our ray tracing study of the observed waves shows that majority of the observed waves seemed to originate from mesospheric altitudes. The preferential directions and the apparent source altitudes can be explained if the observed waves are secondary waves generated from primary waves that have been selected by the filtering process and break up at the mesospheric altitudes.

Technical Note: VUV photodesorption rates from water ice in the 120–150 K temperature range – significance for Noctilucent Clouds

Directory of Open Access Journals (Sweden)

M. Yu. Kulikov

2011-02-01

Full Text Available Laboratory studies have been carried out with the aim to improve our understanding of physicochemical processes which take place at the water ice/air interface initiated by solar irradiation with a wavelength of 121.6 nm. It was intended to mimic the processes of ice particles characteristic of Noctilucent Clouds (NLCs. The experimental set-up used includes a high-vacuum chamber, a gas handling system, a cryostat with temperature controller, an FTIR spectrometer, a vacuum ultraviolet hydrogen lamp, and a microwave generator. We report the first results of measurements of the absolute photodesorption rate (loss of substance due to the escape of photoproducts into gas phase from thin (20–100 nm water ice samples kept in the temperature range of 120–150 K. The obtained results show that a flow of photoproducts into the gas phase is considerably lower than presumed in the recent study by Murray and Plane (2005. The experiments indicate that almost all photoproducts remain in the solid phase, and the principal chemical reaction between them is the recombination reaction H + OH → H₂O which is evidently very fast. This means that direct photolysis of mesospheric ice particles seems to have no significant impact on the gas phase chemistry of the upper mesosphere.

On polluted by admixtures plasma cloud state diagnostics

International Nuclear Information System (INIS)

Temko, S.W.; Temko, K.W.; Kuz'min, S.K.

1993-01-01

The state of bounded plasma is dependent on perturbations which are caused from changing of inner and outer thermodynamical parameters. The authors describe interactions in a plasma cloud by potential functions. Potential functions are mathematical models of real interactions of particles with each others and with ionized cloud surface. Potential functions define potential energy of corresponding interactions at ionized cloud. Potential functions are sums of far-action and near-action potentials. An ionized cloud is formed under action of inner, outer and surface forces nearly connected with each others. The result of the indicated forces joint action is geometrical form and dimensions of the weakly ionized plasma cloud. Geometrical form of the cloud and its dimensions are able to be changed. They consider only the small changing of small perturbations type. Surface geometrical form and dimensions of the cloud are not given a priori. They are to be obtained by self-consistent problem solving. The self-consistent problem is solved by space non-linear statistical thermodynamics proposed before by the authors. They use abstract potential theory, distribution theory, results by N.M. Krylov and N.N. Bogoljubov and known N.N. Bogoljubov methods of statistical physics. To choose potential functions, their numerical parameters, surface form and dimensions of the cloud, they use optimal experiment planning, likelihood method, Monte-Carlo, directed random search and computer experiment methods. To be likelihood function they used free energy of ionized cloud with admixtures. They refuse describing single particle behavior at small volume. They consider particles to be washed spots and describe particles by distributions. According to R. Feinman it is lawful. Bounded plasma state is described by vector-density of particles distribution. Term distribution is used in Sobolev-Schwartc sence. To precipitate admixtures is effective ultrasound coagulation

USGEO DMWG Cloud Computing Recommendations

Science.gov (United States)

de la Beaujardiere, J.; McInerney, M.; Frame, M. T.; Summers, C.

2017-12-01

The US Group on Earth Observations (USGEO) Data Management Working Group (DMWG) has been developing Cloud Computing Recommendations for Earth Observations. This inter-agency report is currently in draft form; DMWG hopes to have released the report as a public Request for Information (RFI) by the time of AGU. The recommendations are geared toward organizations that have already decided to use the Cloud for some of their activities (i.e., the focus is not on "why you should use the Cloud," but rather "If you plan to use the Cloud, consider these suggestions.") The report comprises Introductory Material, including Definitions, Potential Cloud Benefits, and Potential Cloud Disadvantages, followed by Recommendations in several areas: Assessing When to Use the Cloud, Transferring Data to the Cloud, Data and Metadata Contents, Developing Applications in the Cloud, Cost Minimization, Security Considerations, Monitoring and Metrics, Agency Support, and Earth Observations-specific recommendations. This talk will summarize the recommendations and invite comment on the RFI.

El Chichon and 'mystery cloud' aerosols between 30 and 55 km Global observations from the SME visible spectrometer

Science.gov (United States)

Clancy, R. T.

1986-01-01

Visible limb radiances measured by the Solar Mesosphere Explorer (SME) are used to obtain volume scattering ratios for aerosol loading in the 30-55 km altitude range of the stratosphere. Global maps of these ratios are presented for the period January 1982 to August 1984. Significant aerosol scattering from the 'mystery cloud' and El Chichon aerosol layers are found above 30 km. A timescale of approximately 2 months between the appearance of the aerosol at 30.5 km and at 37.5 km is consistent with vertical transport of aerosol or vapor by eddy diffusion above 30 km. An anticorrelation exists between aerosol scattering and stratospheric temperatures. Periods of lower stratospheric temperatures may account for the formation of aerosol between 40 and 55 km altitude.

YOUNG STELLAR OBJECTS IN THE LARGE MAGELLANIC CLOUD STAR-FORMING REGION N206

International Nuclear Information System (INIS)

Romita, Krista Alexandra; Meixner, M.; Sewilo, M.; Shiao, B.; Carlson, Lynn Redding; Whitney, B.; Babler, B.; Meade, M.; Indebetouw, R.; Hora, J. L.

2010-01-01

We present analysis of the energetic star-forming region Henize 206 (N206) located near the southern edge of the Large Magellanic Cloud (LMC) based on photometric data from the Spitzer Surveying the Agents of Galaxy Evolution (SAGE-LMC; IRAC 3.6, 4.5, 5.8, 8.0 μm and MIPS 24 μm), Infrared Survey Facility near-infrared survey (J, H, K s ), and the Magellanic Clouds Photometric Survey (MCPS UBVI) covering a wavelength range of 0.36-24 μm. Young stellar object (YSO) candidates are identified based upon their location in infrared color-magnitude space and classified by the shapes of their spectral energy distributions in comparison with a pre-computed grid of YSO models. We identify 116 YSO candidates: 102 are well characterized by the YSO models, predominately Stage I, and 14 may be multiple sources or young sources with transition disks. Careful examination of the individual sources and their surrounding environment allows us to identify a factor of ∼14.5 more YSO candidates than have already been identified. The total mass of these well-fit YSO candidates is ∼520 M sun . We calculate a current star formation rate of 0.27 x 10 -1 M sun yr -1 kpc -2 . The distribution of YSO candidates appears to follow shells of neutral material in the interstellar medium.

CLOUDS IN SUPER-EARTH ATMOSPHERES: CHEMICAL EQUILIBRIUM CALCULATIONS

Energy Technology Data Exchange (ETDEWEB)

Mbarek, Rostom; Kempton, Eliza M.-R., E-mail: mbarekro@grinnell.edu, E-mail: kemptone@grinnell.edu [Department of Physics, Grinnell College, Grinnell, IA 50112 (United States)

2016-08-20

Recent studies have unequivocally proven the existence of clouds in super-Earth atmospheres. Here we provide a theoretical context for the formation of super-Earth clouds by determining which condensates are likely to form under the assumption of chemical equilibrium. We study super-Earth atmospheres of diverse bulk composition, which are assumed to form by outgassing from a solid core of chondritic material, following Schaefer and Fegley. The super-Earth atmospheres that we study arise from planetary cores made up of individual types of chondritic meteorites. They range from highly reducing to oxidizing and have carbon to oxygen (C:O) ratios that are both sub-solar and super-solar, thereby spanning a range of atmospheric composition that is appropriate for low-mass exoplanets. Given the atomic makeup of these atmospheres, we minimize the global Gibbs free energy of formation for over 550 gases and condensates to obtain the molecular composition of the atmospheres over a temperature range of 350–3000 K. Clouds should form along the temperature–pressure boundaries where the condensed species appear in our calculation. We find that the composition of condensate clouds depends strongly on both the H:O and C:O ratios. For the super-Earth archetype GJ 1214b, KCl and ZnS are the primary cloud-forming condensates at solar composition, in agreement with previous work. However, for oxidizing atmospheres, K{sub 2}SO{sub 4} and ZnO condensates are favored instead, and for carbon-rich atmospheres with super-solar C:O ratios, graphite clouds appear. For even hotter planets, clouds form from a wide variety of rock-forming and metallic species.

Tropical behavior of mesospheric ozone as observed by SMM

Science.gov (United States)

Aikin, A. C.; Kendig, D. J.

1992-01-01

The seasonal behavior of low latitude mesospheric ozone, as observed by the SMM satellite solar occultation experiment, is detailed for the 1985-1989 period. Annual as well as semi-annual waves are observed in the 50-70 km altitude region. In the latitude range of +/- 30 deg the ozone phase and amplitude are functions of temperature and seasonal changes in solar flux. Temperature is the controlling factor for the equatorial region and seasonal changes in solar flux become more dominant at latitudes outside the equatorial zone (greater than +/- 15 deg). There is a hemispheric asymmetry in the ozone annual wave in the 20-30 deg region, with Northern Hemispheric ozone having a larger amplitude than Southern Hemispheric ozone.

Job Scheduling with Efficient Resource Monitoring in Cloud Datacenter

Directory of Open Access Journals (Sweden)

Shyamala Loganathan

2015-01-01

Full Text Available Cloud computing is an on-demand computing model, which uses virtualization technology to provide cloud resources to users in the form of virtual machines through internet. Being an adaptable technology, cloud computing is an excellent alternative for organizations for forming their own private cloud. Since the resources are limited in these private clouds maximizing the utilization of resources and giving the guaranteed service for the user are the ultimate goal. For that, efficient scheduling is needed. This research reports on an efficient data structure for resource management and resource scheduling technique in a private cloud environment and discusses a cloud model. The proposed scheduling algorithm considers the types of jobs and the resource availability in its scheduling decision. Finally, we conducted simulations using CloudSim and compared our algorithm with other existing methods, like V-MCT and priority scheduling algorithms.

Observations of the 10-micron natural laser emission from the mesospheres of Mars and Venus

Science.gov (United States)

Espenak, F.; Deming, D.; Jennings, D.; Kostiuk, T.; Mumma, M.; Zipoy, D.

1983-01-01

Observations of the total flux and center to limb dependence of the nonthermal emission occurring in the cores of the 9.4 and 10.4 micrometers CO2 bands on Mars are compared to a theoretical model based on this mechanism. The model successfully reproduces the observed center to limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations of Mars and Venus. The observed flux from Mars agrees closely with the prediction of the model; the flux observed from Venus is 74 percent of the flux predicted by the model. This emission is used to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T = 135 + or - 20 K. The frequency width of the emission is also analyzed to derive a temperature of 126 + or - 6 K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T = 204 + or - 10 K.

Observations of the 10 micrometer natural laser emission from the mesospheres of Mars and Venus

Science.gov (United States)

Deming, D.; Espenak, F.; Jennings, D.; Kostiuk, T.; Mumma, M. J.

1983-01-01

Observations of the total flux and center to limb dependence of the nonthermal emission occurring in the cores of the 9.4 and 10.4 micrometers CO2 bands on Mars are compared to a theoretical model based on this mechanism. The model successfully reproduces the observed center to limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations of Mars and Venus. The observed flux from Mars agrees closely with the prediction of the model; the flux observed from Venus is 74% of the flux predicted by the model. This emission is used to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T = 135 + or - 20 K. The frequency width of the emission is also analyzed to derive a temperature of 126 + or - 6 K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T = 204 + or - 10 K.

Observations of the 10 micrometer natural laser emission from the mesospheres of Mars and Venus

International Nuclear Information System (INIS)

Deming, D.; Espenak, F.; Jennings, D.; Kostiuk, T.; Mumma, M.J.

1983-06-01

Observations of the total flux and center to limb dependence of the nonthermal emission occurring in the cores of the 9.4 and 10.4 micrometers CO2 bands on Mars are compared to a theoretical model based on this mechanism. The model successfully reproduces the observed center to limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations of Mars and Venus. The observed flux from Mars agrees closely with the prediction of the model the flux observed from Venus is 74% of the flux predicted by the model. This emission is used to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T 135 + or - 20 K. The frequency width of the emission is also analyzed to derive a temperature of 126 + or - 6 K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T 204 + or - 10 K

Geomagnetic control of mesospheric nitric oxide concentration from simultaneous D and F region ionization measurements

International Nuclear Information System (INIS)

Pradhan, S.N.; Shirke, J.S.

1978-01-01

Investigations are made of D-region electron density profiles derived from 'partial reflection' measurements over a low latitude station (Ahmedabad) during a year of low solar activity. The index relating the electron density with the solar zenith angle is found to increase towards lower zenith angles suggesting both diurnal and seasonal variations in the Nitric oxide concentration. A close correlation is also found between the electron density at 80 km and the maximum ionization density in the F region above. This is interpreted as due to concomitant variation of a sizeable fraction of the Nitric oxide concentration in the mesosphere and lower thermosphere with the overhead F region ionization. A simplified global model is presented for the mesospheric Nitric oxide concentration based on the morphological features of F region and the relationship existing between the ionization levels in F and D regions. Many observed features of the D region ionization including the solar zenith angle dependence, latitudinal and geomagnetic anomaly and long term variability are explained on the basis of this model

CloudMC: a cloud computing application for Monte Carlo simulation.

Science.gov (United States)

Miras, H; Jiménez, R; Miras, C; Gomà, C

2013-04-21

This work presents CloudMC, a cloud computing application-developed in Windows Azure®, the platform of the Microsoft® cloud-for the parallelization of Monte Carlo simulations in a dynamic virtual cluster. CloudMC is a web application designed to be independent of the Monte Carlo code in which the simulations are based-the simulations just need to be of the form: input files → executable → output files. To study the performance of CloudMC in Windows Azure®, Monte Carlo simulations with penelope were performed on different instance (virtual machine) sizes, and for different number of instances. The instance size was found to have no effect on the simulation runtime. It was also found that the decrease in time with the number of instances followed Amdahl's law, with a slight deviation due to the increase in the fraction of non-parallelizable time with increasing number of instances. A simulation that would have required 30 h of CPU on a single instance was completed in 48.6 min when executed on 64 instances in parallel (speedup of 37 ×). Furthermore, the use of cloud computing for parallel computing offers some advantages over conventional clusters: high accessibility, scalability and pay per usage. Therefore, it is strongly believed that cloud computing will play an important role in making Monte Carlo dose calculation a reality in future clinical practice.

MIPAS observations of longitudinal oscillations in the mesosphere and the lower thermosphere: climatology of odd-parity daily frequency modes

Directory of Open Access Journals (Sweden)

M. García-Comas

2016-09-01

Full Text Available MIPAS global Sun-synchronous observations are almost fixed in local time. Subtraction of the descending and ascending node measurements at each longitude only includes the longitudinal oscillations with odd daily frequencies nodd from the Sun's perspective at 10:00. Contributions from the background atmosphere, daily-invariant zonal oscillations and tidal modes with even-parity daily frequencies vanish. We have determined longitudinal oscillations in MIPAS temperature with nodd and wavenumber k = 0–4 from the stratosphere to 150 km from April 2007 to March 2012. To our knowledge, this is the first time zonal oscillations in temperature have been derived pole to pole in this altitude range from a single instrument. The major findings are the detection of (1 migrating tides at northern and southern high latitudes; (2 significant k = 1 activity at extratropical and high latitudes, particularly in the Southern Hemisphere; (3 k = 3 and k = 4 eastward-propagating waves that penetrate the lower thermosphere with a significantly larger vertical wavelength than in the mesosphere; and (4 a migrating tide quasi-biennial oscillation in the stratosphere, mesosphere and lower thermosphere. MIPAS global measurements of longitudinal oscillations are useful for testing tide modeling in the mesosphere and lower thermosphere region and as a lower boundary for models extending higher up in the atmosphere.

Polar mesosphere winter echoes during MaCWAVE

Directory of Open Access Journals (Sweden)

S. Kirkwood

2006-07-01

Full Text Available During the MaCWAVE winter campaign in January 2003, layers of enhanced echo power known as PMWE (Polar Mesosphere Winter Echoes were detected by the ESRAD 52 MHz radar on several occasions. The cause of these echoes is unclear and here we use observations by meteorological and sounding rockets and by lidar to test whether neutral turbulence or aerosol layers might be responsible. PMWE were detected within 30 min of meteorological rocket soundings (falling spheres on 5 separate days. The observations from the meteorological rockets show that, in most cases, conditions likely to be associated with neutral atmospheric turbulence are not observed at the heights of the PMWE. Observations by instrumented sounding rockets confirm low levels of turbulence and indicate considerable small-scale structure in charge density profiles. Comparison of falling sphere and lidar data, on the other hand, show that any contribution of aerosol scatter to the lidar signal at PMWE heights is less than the detection threshold of about 10%.

CHPS IN CLOUD COMPUTING ENVIRONMENT

OpenAIRE

K.L.Giridas; A.Shajin Nargunam

2012-01-01

Workflow have been utilized to characterize a various form of applications concerning high processing and storage space demands. So, to make the cloud computing environment more eco-friendly,our research project was aiming in reducing E-waste accumulated by computers. In a hybrid cloud, the user has flexibility offered by public cloud resources that can be combined to the private resources pool as required. Our previous work described the process of combining the low range and mid range proce...

A stationary phase solution for mountain waves with application to mesospheric mountain waves generated by Auckland Island

Science.gov (United States)

Broutman, Dave; Eckermann, Stephen D.; Knight, Harold; Ma, Jun

2017-01-01

A relatively general stationary phase solution is derived for mountain waves from localized topography. It applies to hydrostatic, nonhydrostatic, or anelastic dispersion relations, to arbitrary localized topography, and to arbitrary smooth vertically varying background temperature and vector wind profiles. A simple method is introduced to compute the ray Jacobian that quantifies the effects of horizontal geometrical spreading in the stationary phase solution. The stationary phase solution is applied to mesospheric mountain waves generated by Auckland Island during the Deep Propagating Gravity Wave Experiment. The results are compared to a Fourier solution. The emphasis is on interpretations involving horizontal geometrical spreading. The results show larger horizontal geometrical spreading for nonhydrostatic waves than for hydrostatic waves in the region directly above the island; the dominant effect of horizontal geometrical spreading in the lower ˜30 km of the atmosphere, compared to the effects of refraction and background density variation; and the enhanced geometrical spreading due to directional wind in the approach to a critical layer in the mesosphere.

Vliv Cloud Computingu na Supply Chain Management

OpenAIRE

Karkošková, Soňa

2013-01-01

Master thesis "Impact of Cloud Computing on Supply Chain Management" analyses the provisioning of IT resources in the form of cloud computing services and their impact on supply chain management environment. Attention is focused particularly on providing SaaS model of public applications delivery. The Cloud SCM implementation offers many advantages especially for small and medium sized companies. In this thesis I analysed the specifics of the deployment of Cloud SCM in highly unstable market ...

SPH simulations of star/planet formation triggered by cloud-cloud collisions

OpenAIRE

Kitsionas, Spyridon; Whitworth, Anthony Peter; Klessen, Ralf S.

2007-01-01

We present results of hydrodynamic simulations of star formation triggered by cloud-cloud collisions. During the early stages of star formation, low-mass objects form by gravitational instabilities in protostellar discs. A number of these low-mass objects are in the sub-stellar mass range, including a few objects of planetary mass. The disc instabilities that lead to the formation of low-mass objects in our simulations are the product of disc-disc interactions and/or interactions between the ...

High-mass star formation possibly triggered by cloud-cloud collision in the H II region RCW 34

Science.gov (United States)

Hayashi, Katsuhiro; Sano, Hidetoshi; Enokiya, Rei; Torii, Kazufumi; Hattori, Yusuke; Kohno, Mikito; Fujita, Shinji; Nishimura, Atsushi; Ohama, Akio; Yamamoto, Hiroaki; Tachihara, Kengo; Hasegawa, Yutaka; Kimura, Kimihiro; Ogawa, Hideo; Fukui, Yasuo

2018-05-01

We report on the possibility that the high-mass star located in the H II region RCW 34 was formed by a triggering induced by a collision of molecular clouds. Molecular gas distributions of the 12CO and 13CO J = 2-1 and 12CO J = 3-2 lines in the direction of RCW 34 were measured using the NANTEN2 and ASTE telescopes. We found two clouds with velocity ranges of 0-10 km s-1 and 10-14 km s-1. Whereas the former cloud is as massive as ˜1.4 × 104 M⊙ and has a morphology similar to the ring-like structure observed in the infrared wavelengths, the latter cloud, with a mass of ˜600 M⊙, which has not been recognized by previous observations, is distributed to just cover the bubble enclosed by the other cloud. The high-mass star with a spectral type of O8.5V is located near the boundary of the two clouds. The line intensity ratio of 12CO J = 3-2/J = 2-1 yields high values (≳1.0), suggesting that these clouds are associated with the massive star. We also confirm that the obtained position-velocity diagram shows a similar distribution to that derived by a numerical simulation of the supersonic collision of two clouds. Using the relative velocity between the two clouds (˜5 km s-1), the collisional time scale is estimated to be ˜0.2 Myr with the assumption of a distance of 2.5 kpc. These results suggest that the high-mass star in RCW 34 was formed rapidly within a time scale of ˜0.2 Myr via a triggering of a cloud-cloud collision.

A cloud/particle model of the interstellar medium - Galactic spiral structure

Science.gov (United States)

Levinson, F. H.; Roberts, W. W., Jr.

1981-01-01

A cloud/particle model for gas flow in galaxies is developed that incorporates cloud-cloud collisions and supernovae as dominant local processes. Cloud-cloud collisions are the main means of dissipation. To counter this dissipation and maintain local dispersion, supernova explosions in the medium administer radial snowplow pushes to all nearby clouds. The causal link between these processes is that cloud-cloud collisions will form stars and that these stars will rapidly become supernovae. The cloud/particle model is tested and used to investigate the gas dynamics and spiral structures in galaxies where these assumptions may be reasonable. Particular attention is given to whether large-scale galactic shock waves, which are thought to underlie the regular well-delineated spiral structure in some galaxies, form and persist in a cloud-supernova dominated interstellar medium; this question is answered in the affirmative.

MOLECULAR CLOUD EVOLUTION. III. ACCRETION VERSUS STELLAR FEEDBACK

International Nuclear Information System (INIS)

Vazquez-Semadeni, Enrique; ColIn, Pedro; Gomez, Gilberto C.; Ballesteros-Paredes, Javier; Watson, Alan W.

2010-01-01

We numerically investigate the effect of feedback from the ionization heating from massive stars on the evolution of giant molecular clouds (GMCs) and their star formation efficiency (SFE), which we treat as an instantaneous, time-dependent quantity. We follow the GMCs' evolution from their formation to advanced star-forming stages. After an initial period of contraction, the collapsing clouds begin forming stars, whose feedback evaporates part of the clouds' mass, opposing the continuing accretion from the infalling gas. Our results are as follows: (1) in the presence of feedback, the clouds attain levels of the SFE that are consistent at all times with observational determinations for regions of comparable star formation rates. (2) However, the dense gas mass is larger in general in the presence of feedback, while the total mass (dense gas + stars) is nearly insensitive to the presence of feedback, suggesting that it is determined mainly by the accretion, while the feedback inhibits mainly the conversion of dense gas to stars, because it acts directly to reheat and disperse the gas that is directly on its way to forming stars. (3) The factor by which the SFE is reduced upon the inclusion of feedback is a decreasing function of the cloud's mass, for clouds of size ∼10 pc. This naturally explains the larger observed SFEs of massive-star-forming regions. (4) The clouds may attain a pseudo-virialized state, with a value of the virial mass very similar to the actual cloud mass. However, this state differs from true virialization in that the clouds, rather than being equilibrium entities, are the centers of a larger-scale collapse, in which accretion replenishes the mass consumed by star formation. (5) The higher-density regions within the clouds are in a similar situation, accreting gas infalling from the less-dense, more extended regions of the clouds. (6) The density probability density functions of the regions containing the clouds in general exhibit a shape

FEASIBILITY COMPARISON OF AIRBORNE LASER SCANNING DATA AND 3D-POINT CLOUDS FORMED FROM UNMANNED AERIAL VEHICLE (UAV-BASED IMAGERY USED FOR 3D PROJECTING

Directory of Open Access Journals (Sweden)

I. I. Rilskiy

2017-01-01

Full Text Available New, innovative methods of aerial surveys have changed the approaches to information provision of projecting dramatically for the last 15 years. Nowadays there are at least two methods that claim to be the most efficient way for collecting geospatial data intended for projecting – the airborne laser scanning (LIDAR data and photogrammetrically processed unmanned aerial vehicle (UAV-based aerial imagery, forming 3D point clouds. But these materials are not identical to each other neither in precision, nor in completeness.Airborne laser scanning (LIDAR is normally being performed using manned aircrafts. LIDAR data are very precise, they allow us to achieve data about relief even overgrown with vegetation, or to collect laser reflections from wires, metal constructions and poles. UAV surveys are normally being performed using frame digital cameras (lightweight, full-frame, or mid-size. These cameras form images that are being processed using 3D photogrammetric software in automatic mode that allows one to generate 3D point cloud, which is used for building digital elevation models, surfaces, orthomosaics, etc.All these materials are traditionally being used for making maps and GIS data. LIDAR data have been popular in design work. Also there have been some attempts to use for the same purpose 3D-point clouds, formed by photogrammetric software from images acquired from UAVs.After comparison of the datasets from these two different types of surveying (surveys were made simultaneously on the same territory, it became possible to define some specific, typical for LIDAR or imagery-based 3D data. It can be mentioned that imagery-based 3D data (3D point clouds, formed in automatic mode using photogrammetry, are much worse than LIDAR data – both in terms of precision and completeness.The article highlights these differences and makes attempts at explaining the origin of these differences. 

CloudMC: a cloud computing application for Monte Carlo simulation

International Nuclear Information System (INIS)

Miras, H; Jiménez, R; Miras, C; Gomà, C

2013-01-01

This work presents CloudMC, a cloud computing application—developed in Windows Azure®, the platform of the Microsoft® cloud—for the parallelization of Monte Carlo simulations in a dynamic virtual cluster. CloudMC is a web application designed to be independent of the Monte Carlo code in which the simulations are based—the simulations just need to be of the form: input files → executable → output files. To study the performance of CloudMC in Windows Azure®, Monte Carlo simulations with penelope were performed on different instance (virtual machine) sizes, and for different number of instances. The instance size was found to have no effect on the simulation runtime. It was also found that the decrease in time with the number of instances followed Amdahl's law, with a slight deviation due to the increase in the fraction of non-parallelizable time with increasing number of instances. A simulation that would have required 30 h of CPU on a single instance was completed in 48.6 min when executed on 64 instances in parallel (speedup of 37 ×). Furthermore, the use of cloud computing for parallel computing offers some advantages over conventional clusters: high accessibility, scalability and pay per usage. Therefore, it is strongly believed that cloud computing will play an important role in making Monte Carlo dose calculation a reality in future clinical practice. (note)

Measurements of the structure and circulation of the stratosphere and mesosphere, 1970

Science.gov (United States)

Smith, W. S.; Theon, J. S.; Wright, D. U., Jr.; Casey, J. F.; Horvath, J. J.

1972-01-01

Complete data from a total of 26 meteorological rocket soundings of the stratosphere and mesosphere conducted from Barrow, Alaska; Churchill, Canada; and Wallops Island, Va., are presented. These data consist of temperature, pressure, density, and wind profiles from 16 acoustic grenade soundings that cover the 30- to 90-km altitude range, and temperature, pressure, and density profiles from 10 pitot probe soundings that cover the 25- to 120-km altitude range. Errors for each of the 16 grenade soundings are also included. No analysis of the meteorological significance of the data is attempted.

Formation of giant cloud complexes by the Parker-Jeans instability

International Nuclear Information System (INIS)

Elmegreen, B.G.

1982-01-01

The Parker-Jeans instability is considered as a possible mechanism for forming the giant cloud complexes observed near OB associations. We use a previously derived dispersion relation to evaluate the masses and growth times of the dominant modes in this instability. The results show that massive clouds (Mroughly-equal10 6 M/sub sun/) can form quickly (roughly-equal12 million yr) in the high density environments (5 cm -3 ) associated with spiral density wave shocks. For densities larger than about 3 cm -3 , these clouds form primarily as a result of the self-graviational forces in the interstellar medium. Lower mass clouds (Mroughly-equal10 5 M/sub sun/) can form in lower density environments as a result of the pure Parker instability. The masses of the clouds that form when the density exceeds about 3 cm -3 are insensitive to the magnetic field strength, cosmic ray pressure, and ambient density (even in compressed media.). These masses are essentially the Jeans mass in a magnetic interstellar medium. The occurrence of a characteristic mass may explain the similarity of the local OB associations. The role of the Parker-Jeans instability as part of a complete theory of cloud formation is summarized

Retrieval of nitric oxide in the mesosphere and lower thermosphere from SCIAMACHY limb spectra

Directory of Open Access Journals (Sweden)

S. Bender

2013-09-01

Full Text Available We use the ultra-violet (UV spectra in the range 230–300 nm from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY to retrieve the nitric oxide (NO number densities from atmospheric emissions in the gamma-bands in the mesosphere and lower thermosphere. Using 3-D ray tracing, a 2-D retrieval grid, and regularisation with respect to altitude and latitude, we retrieve a whole semi-orbit simultaneously for the altitude range from 60 to 160 km. We present details of the retrieval algorithm, first results, and initial comparisons to data from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS. Our results agree on average well with MIPAS data and are in line with previously published measurements from other instruments. For the time of available measurements in 2008–2011, we achieve a vertical resolution of 5–10 km in the altitude range 70–140 km and a horizontal resolution of about 9° from 60° S–60° N. With this we have independent measurements of the NO densities in the mesosphere and lower thermosphere with approximately global coverage. This data can be further used to validate climate models or as input for them.

Cloud Formation, Sea-Air-Land Interaction, Mozambique, Africa

Science.gov (United States)

1991-01-01

This rare depiction of the physical interactions of air land and sea in cloud formation was seen over Mozambique (12.0S, 40.5E). Moist low air, heated as it moves over land, rises and forms clouds. Even the coastal islands have enough heat to initiate the process. Once begun, the circulation is dynamic and the descending motion suppresses cloud formation on either side of the cloud stream. As clouds move inland, they rise to follow the land upslope.

AN ANALYSIS OF THE DEUTERIUM FRACTIONATION OF STAR-FORMING CORES IN THE PERSEUS MOLECULAR CLOUD

Energy Technology Data Exchange (ETDEWEB)

Friesen, R. K. [National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903 (United States); Kirk, H. M. [Origins Institute, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1 (Canada); Shirley, Y. L., E-mail: friesen@di.utoronto.ca [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)

2013-03-01

We have performed a pointed survey of N{sub 2}D{sup +} 2-1 and N{sub 2}D{sup +} 3-2 emission toward 64 N{sub 2}H{sup +}-bright starless and protostellar cores in the Perseus molecular cloud using the Arizona Radio Observatory Submillimeter Telescope and Kitt Peak 12 m telescope. We find a mean deuterium fractionation in N{sub 2}H{sup +}, R{sub D} = N(N{sub 2}D{sup +})/N(N{sub 2}H{sup +}), of 0.08, with a maximum R{sub D} = 0.2. In detected sources, we find no significant difference in the deuterium fractionation between starless and protostellar cores, nor between cores in clustered or isolated environments. We compare the deuterium fraction in N{sub 2}H{sup +} with parameters linked to advanced core evolution. We only find significant correlations between the deuterium fraction and increased H{sub 2} column density, as well as with increased central core density, for all cores. Toward protostellar sources, we additionally find a significant anticorrelation between R{sub D} and bolometric temperature. We show that the Perseus cores are characterized by low CO depletion values relative to previous studies of star-forming cores, similar to recent results in the Ophiuchus molecular cloud. We suggest that the low average CO depletion is the dominant mechanism that constrains the average deuterium fractionation in the Perseus cores to small values. While current equilibrium and dynamic chemical models are able to reproduce the range of deuterium fractionation values we find in Perseus, reproducing the scatter across the cores requires variation in parameters such as the ionization fraction or the ortho-to-para-H{sub 2} ratio across the cloud, or a range in core evolution timescales.

CLOUD TECHNOLOGY AS A WAY OF UKRAINIAN EDUCATION DEVELOPMENT

OpenAIRE

T. Zaytseva; T. Arkhipova

2014-01-01

This article is devoted to defining the forms and the required components cloud technology usage during studying of subject teachers. In order to improve the learning process it’s necessary to use such powerful technology as ‘cloud computing’. They support traditional forms of education and also are a new step in the development of education. Cloud technologies are-effective, efficient and flexible way to satisfy the needs of students during getting of new knowledge. Nowadays a characteris...

THE EVOLUTION OF GAS CLOUDS FALLING IN THE MAGNETIZED GALACTIC HALO: HIGH-VELOCITY CLOUDS (HVCs) ORIGINATED IN THE GALACTIC FOUNTAIN

International Nuclear Information System (INIS)

Kwak, Kyujin; Shelton, Robin L.; Raley, Elizabeth A.

2009-01-01

In the Galactic fountain scenario, supernovae and/or stellar winds propel material into the Galactic halo. As the material cools, it condenses into clouds. By using FLASH three-dimensional magnetohydrodynamic simulations, we model and study the dynamical evolution of these gas clouds after they form and begin to fall toward the Galactic plane. In our simulations, we assume that the gas clouds form at a height of z = 5 kpc above the Galactic midplane, then begin to fall from rest. We investigate how the cloud's evolution, dynamics, and interaction with the interstellar medium (ISM) are affected by the initial mass of the cloud. We find that clouds with sufficiently large initial densities (n ≥ 0.1 H atoms cm -3 ) accelerate sufficiently and maintain sufficiently large column densities as to be observed and identified as high-velocity clouds (HVCs) even if the ISM is weakly magnetized (1.3 μG). However, the ISM can provide noticeable resistance to the motion of a low-density cloud (n ≤ 0.01 H atoms cm -3 ) thus making it more probable that a low-density cloud will attain the speed of an intermediate-velocity cloud rather than the speed of an HVC. We also investigate the effects of various possible magnetic field configurations. As expected, the ISM's resistance is greatest when the magnetic field is strong and perpendicular to the motion of the cloud. The trajectory of the cloud is guided by the magnetic field lines in cases where the magnetic field is oriented diagonal to the Galactic plane. The model cloud simulations show that the interactions between the cloud and the ISM can be understood via analogy to the shock tube problem which involves shock and rarefaction waves. We also discuss accelerated ambient gas, streamers of material ablated from the clouds, and the cloud's evolution from a sphere-shaped to a disk- or cigar-shaped object.

In-cloud processes of methacrolein under simulated conditions – Part 3: Hygroscopic and volatility properties of the formed secondary organic aerosol

Directory of Open Access Journals (Sweden)

A. Monod

2009-07-01

Full Text Available The hygroscopic and volatility properties of secondary organic aerosol (SOA produced from the nebulization of solutions after aqueous phase photooxidation of methacrolein was experimentally studied in a laboratory, using a Volatility-Hygroscopicity Tandem DMA (VHTDMA. The obtained SOA were 80% 100°C-volatile after 5 h of reaction and only 20% 100°C-volatile after 22 h of reaction. The Hygroscopic Growth Factor (HGF of the SOA produced from the nebulization of solutions after aqueous-phase photooxidation of methacrolein is 1.34–1.43, which is significantly higher than the HGF of SOA formed by gas-phase photooxidation of terpenes, usually found almost hydrophobic. These hygroscopic properties were confirmed for SOA formed by the nebulization of the same solutions where NaCl was added. The hygroscopic properties of the cloud droplet residuals decrease with the reaction time, in parallel with the formation of more refractory compounds. This decrease was mainly attributed to the 250°C-refractive fraction (presumably representative of the highest molecular weight compounds, which evolved from moderately hygroscopic (HGF of 1.52 to less hygroscopic (HGF of 1.36. Oligomerization is suggested as a process responsible for the decrease of both volatility and hygroscopicity with time. The NaCl seeded experiments enabled us to show that 19±4 mg L⁻¹ of SOA was produced after 9.5 h of reaction and 41±9 mg L⁻¹ after 22 h of in-cloud reaction. Because more and more SOA is formed as the reaction time increases, our results show that the reaction products formed during the aqueous-phase OH-oxidation of methacrolein may play a major role in the properties of residual particles upon the droplet's evaporation. Therefore, the specific physical properties of SOA produced during cloud processes should be taken into account for a global estimation of SOA and their atmospheric impacts.

Measurements of the structure and circulation of the stratosphere and mesosphere, 1971-2

Science.gov (United States)

Smith, W. S.; Theon, J. S.; Wright, D. U., Jr.; Ramsdale, D. J.; Horvath, J. J.

1974-01-01

Complete data from a total of 43 meteorological rocket soundings of the stratosphere and mesosphere conducted from Barrow, Alaska; Churchill, Canada; Wallops Island Va.; and Kourou, French Guiana are presented. These data consist of temperature, pressure, density, and wind profiles from 35 acoustic grenade soundings that cover the 30 to 90 km altitude range, and temperature, pressure, and density profiles from 8 pitot probe soundings that cover the 25 to 120 km altitude range. Errors for each of the 35 acoustic grenade soundings are also included.

Processing Terrain Point Cloud Data

KAUST Repository

DeVore, Ronald; Petrova, Guergana; Hielsberg, Matthew; Owens, Luke; Clack, Billy; Sood, Alok

2013-01-01

Terrain point cloud data are typically acquired through some form of Light Detection And Ranging sensing. They form a rich resource that is important in a variety of applications including navigation, line of sight, and terrain visualization

Global Software Development with Cloud Platforms

Science.gov (United States)

Yara, Pavan; Ramachandran, Ramaseshan; Balasubramanian, Gayathri; Muthuswamy, Karthik; Chandrasekar, Divya

Offshore and outsourced distributed software development models and processes are facing challenges, previously unknown, with respect to computing capacity, bandwidth, storage, security, complexity, reliability, and business uncertainty. Clouds promise to address these challenges by adopting recent advances in virtualization, parallel and distributed systems, utility computing, and software services. In this paper, we envision a cloud-based platform that addresses some of these core problems. We outline a generic cloud architecture, its design and our first implementation results for three cloud forms - a compute cloud, a storage cloud and a cloud-based software service- in the context of global distributed software development (GSD). Our ”compute cloud” provides computational services such as continuous code integration and a compile server farm, ”storage cloud” offers storage (block or file-based) services with an on-line virtual storage service, whereas the on-line virtual labs represent a useful cloud service. We note some of the use cases for clouds in GSD, the lessons learned with our prototypes and identify challenges that must be conquered before realizing the full business benefits. We believe that in the future, software practitioners will focus more on these cloud computing platforms and see clouds as a means to supporting a ecosystem of clients, developers and other key stakeholders.

New insights for mesospheric OH: multi-quantum vibrational relaxation as a driver for non-local thermodynamic equilibrium

Directory of Open Access Journals (Sweden)

K. S. Kalogerakis

2018-01-01

Full Text Available The question of whether mesospheric OH(v rotational population distributions are in equilibrium with the local kinetic temperature has been debated over several decades. Despite several indications for the existence of non-equilibrium effects, the general consensus has been that emissions originating from low rotational levels are thermalized. Sky spectra simultaneously observing several vibrational levels demonstrated reproducible trends in the extracted OH(v rotational temperatures as a function of vibrational excitation. Laboratory experiments provided information on rotational energy transfer and direct evidence for fast multi-quantum OH(high-v vibrational relaxation by O atoms. We examine the relationship of the new relaxation pathways with the behavior exhibited by OH(v rotational population distributions. Rapid OH(high-v + O multi-quantum vibrational relaxation connects high and low vibrational levels and enhances the hot tail of the OH(low-v rotational distributions. The effective rotational temperatures of mesospheric OH(v are found to deviate from local thermodynamic equilibrium for all observed vibrational levels. Dedicated to Tom G. Slanger in celebration of his 5 decades of research in aeronomy.

Satellite observations and modeling of transport in the upper troposphere through the lower mesosphere during the 2006 major stratospheric sudden warming

Directory of Open Access Journals (Sweden)

W. H. Daffer

2009-07-01

Full Text Available An unusually strong and prolonged stratospheric sudden warming (SSW in January 2006 was the first major SSW for which globally distributed long-lived trace gas data are available covering the upper troposphere through the lower mesosphere. We use Aura Microwave Limb Sounder (MLS, Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS data, the SLIMCAT Chemistry Transport Model (CTM, and assimilated meteorological analyses to provide a comprehensive picture of transport during this event. The upper tropospheric ridge that triggered the SSW was associated with an elevated tropopause and layering in trace gas profiles in conjunction with stratospheric and tropospheric intrusions. Anomalous poleward transport (with corresponding quasi-isentropic troposphere-to-stratosphere exchange at the lowest levels studied in the region over the ridge extended well into the lower stratosphere. In the middle and upper stratosphere, the breakdown of the polar vortex transport barrier was seen in a signature of rapid, widespread mixing in trace gases, including CO, H₂O, CH₄ and N₂O. The vortex broke down slightly later and more slowly in the lower than in the middle stratosphere. In the middle and lower stratosphere, small remnants with trace gas values characteristic of the pre-SSW vortex lingered through the weak and slow recovery of the vortex. The upper stratospheric vortex quickly reformed, and, as enhanced diabatic descent set in, CO descended into this strong vortex, echoing the fall vortex development. Trace gas evolution in the SLIMCAT CTM agrees well with that in the satellite trace gas data from the upper troposphere through the middle stratosphere. In the upper stratosphere and lower mesosphere, the SLIMCAT simulation does not capture the strong descent of mesospheric CO and H₂O values into the reformed vortex; this poor CTM performance in the upper stratosphere and lower mesosphere results

Statistical analysis of mesospheric gravity waves over King Sejong Station, Antarctica (62.2°S, 58.8°W)

Science.gov (United States)

Kam, Hosik; Jee, Geonhwa; Kim, Yong; Ham, Young-bae; Song, In-Sun

2017-03-01

We have investigated the characteristics of mesospheric short period (King Sejong Station (KSS) (62.22°S, 58.78°W) during a period of 2008-2015. By applying 2-dimensional FFT to time differenced images, we derived horizontal wavelengths, phase speeds, and propagating directions (188 and 173 quasi-monochromatic waves from OH and OI airglow images, respectively). The majority of the observed waves propagated predominantly westward, implying that eastward waves were filtered out by strong eastward stratospheric winds. In order to obtain the intrinsic properties of the observed waves, we utilized winds simultaneously measured by KSS Meteor Radar and temperatures from Aura Microwave Limb Sounder (MLS). More than half the waves propagated horizontally, as waves were in Doppler duct or evanescent in the vertical direction. This might be due to strong eastward background wind field in the mesosphere over KSS. For freely propagating waves, the vertical wavelengths were in the interquartile range of 9-33 km with a median value of 15 km. The vertical wavelengths are shorter than those observed at Halley station (76°S, 27°W) where the majority of the observed waves were freely propagating. The difference in the wave propagating characteristics between KSS and Halley station suggests that gravity waves may affect mesospheric dynamics in this part of the Antarctic Peninsula more strongly than over the Antarctic continent. Furthermore, strong wind shear over KSS played an important role in changing the vertical wavenumbers as the waves propagated upward between two airglow layers (87 and 96 km).

Cloud Infrastructure & Applications - CloudIA

Science.gov (United States)

Sulistio, Anthony; Reich, Christoph; Doelitzscher, Frank

The idea behind Cloud Computing is to deliver Infrastructure-as-a-Services and Software-as-a-Service over the Internet on an easy pay-per-use business model. To harness the potentials of Cloud Computing for e-Learning and research purposes, and to small- and medium-sized enterprises, the Hochschule Furtwangen University establishes a new project, called Cloud Infrastructure & Applications (CloudIA). The CloudIA project is a market-oriented cloud infrastructure that leverages different virtualization technologies, by supporting Service-Level Agreements for various service offerings. This paper describes the CloudIA project in details and mentions our early experiences in building a private cloud using an existing infrastructure.

The Community Cloud Atlas - Building an Informed Cloud Watching Community

Science.gov (United States)

Guy, N.; Rowe, A.

2014-12-01

The sky is dynamic, from long lasting cloud systems to ethereal, fleeting formations. After years of observing the sky and growing our personal collections of cloud photos, we decided to take to social media to share pictures, as well as build and educate a community of cloud enthusiasts. We began a Facebook page, the Community Cloud Atlas, described as "...the place to show off your pictures of the sky, identify clouds, and to discuss how specific cloud types form and what they can tell you about current and future weather." Our main goal has been to encourage others to share their pictures, while we describe the scenes from a meteorological perspective and reach out to the general public to facilitate a deeper understanding of the sky. Nearly 16 months later, we have over 1400 "likes," spanning 45 countries with ages ranging from 13 to over 65. We have a consistent stream of submissions; so many that we decided to start a corresponding blog to better organize the photos, provide more detailed explanations, and reach a bigger audience. Feedback from users has been positive in support of not only sharing cloud pictures, but also to "learn the science as well as admiring" the clouds. As one community member stated, "This is not 'just' a place to share some lovely pictures." We have attempted to blend our social media presence with providing an educational resource, and we are encouraged by the response we have received. Our Atlas has been informally implemented into classrooms, ranging from a 6th grade science class to Meteorology courses at universities. NOVA's recent Cloud Lab also made use of our Atlas as a supply of categorized pictures. Our ongoing goal is to not only continue to increase understanding and appreciation of the sky among the public, but to provide an increasingly useful tool for educators. We continue to explore different social media options to interact with the public and provide easier content submission, as well as software options for

Method of approximating the effects of blast mitigation materials on particulate-containing clouds formed by explosions

International Nuclear Information System (INIS)

Dyckes, G.W.

1983-09-01

A numerical model was developed for predicting the effect of blast mitigation materials on the rise and entrainment rate of explosively driven buoyant clouds containing radiotoxic particles. Model predictions for clouds from unmitigated explosions agree with published observations. More experimental data are needed to assess the validity of predictions for clouds from mitigated explosions

Heterogeneous Data Storage Management with Deduplication in Cloud Computing

OpenAIRE

Yan, Zheng; Zhang, Lifang; Ding, Wenxiu; Zheng, Qinghua

2017-01-01

Cloud storage as one of the most important services of cloud computing helps cloud users break the bottleneck of restricted resources and expand their storage without upgrading their devices. In order to guarantee the security and privacy of cloud users, data are always outsourced in an encrypted form. However, encrypted data could incur much waste of cloud storage and complicate data sharing among authorized users. We are still facing challenges on encrypted data storage and management with ...

The Ethics of Cloud Computing.

Science.gov (United States)

de Bruin, Boudewijn; Floridi, Luciano

2017-02-01

Cloud computing is rapidly gaining traction in business. It offers businesses online services on demand (such as Gmail, iCloud and Salesforce) and allows them to cut costs on hardware and IT support. This is the first paper in business ethics dealing with this new technology. It analyzes the informational duties of hosting companies that own and operate cloud computing datacentres (e.g., Amazon). It considers the cloud services providers leasing 'space in the cloud' from hosting companies (e.g., Dropbox, Salesforce). And it examines the business and private 'clouders' using these services. The first part of the paper argues that hosting companies, services providers and clouders have mutual informational (epistemic) obligations to provide and seek information about relevant issues such as consumer privacy, reliability of services, data mining and data ownership. The concept of interlucency is developed as an epistemic virtue governing ethically effective communication. The second part considers potential forms of government restrictions on or proscriptions against the development and use of cloud computing technology. Referring to the concept of technology neutrality, it argues that interference with hosting companies and cloud services providers is hardly ever necessary or justified. It is argued, too, however, that businesses using cloud services (e.g., banks, law firms, hospitals etc. storing client data in the cloud) will have to follow rather more stringent regulations.

Evidence of long-term change in zonal wind in the tropical lower mesosphere: Observations and model simulations

Czech Academy of Sciences Publication Activity Database

Ratnam, M. V.; Kumar, G. K.; Rao, N. V.; Murthy, B. V. K.; Laštovička, Jan; Qian, L.

2013-01-01

Roč. 40, č. 2 (2013), s. 397-401 ISSN 0094-8276 R&D Projects: GA ČR GAP209/10/1792 Institutional support: RVO:68378289 Keywords : mesosphere * zonal wind * long-term trends * TIME-GCM * climate change Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 4.456, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/grl.50158/abstract

CLOUD TECHNOLOGY AS A WAY OF UKRAINIAN EDUCATION DEVELOPMENT

Directory of Open Access Journals (Sweden)

T. Zaytseva

2014-06-01

Full Text Available This article is devoted to defining the forms and the required components cloud technology usage during studying of subject teachers. In order to improve the learning process it’s necessary to use such powerful technology as ‘cloud computing’. They support traditional forms of education and also are a new step in the development of education. Cloud technologies are-effective, efficient and flexible way to satisfy the needs of students during getting of new knowledge. Nowadays a characteristic feature of our time is rapid growing of using cloud technology. That is why we are spectators of implementation of cloud technologies and services in the system of higher and secondary education, too. A common information space in education using mostly cloud technologies that provide Microsoft and Google is creating now. Google Apps for Education containing free tools that allows teachers and students to communicate, teach and learn more effectively and efficiently. Significant advantage of using cloud services is providing application development and storage of large amounts of data on servers in distributed information processing centers via the Internet. That is why cloud technology is a powerful tool to activate students' self-guidance work. Surely, growing demand for professionals who knows the technology of cloud computing will increase slowly.

Observational evidence for the aerosol impact on ice cloud properties regulated by cloud/aerosol types

Science.gov (United States)

Zhao, B.; Gu, Y.; Liou, K. N.; Jiang, J. H.; Li, Q.; Liu, X.; Huang, L.; Wang, Y.; Su, H.

2017-12-01

The interactions between aerosols and ice clouds (consisting only of ice) represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. The observational evidence for the aerosol impact on ice cloud properties has been quite limited and showed conflicting results, partly because previous observational studies did not consider the distinct features of different ice cloud and aerosol types. Using 9-year satellite observations, we find that, for ice clouds generated from deep convection, cloud thickness, cloud optical thickness (COT), and ice cloud fraction increase and decrease with small-to-moderate and high aerosol loadings, respectively. For in-situ formed ice clouds, however, the preceding cloud properties increase monotonically and more sharply with aerosol loadings. The case is more complicated for ice crystal effective radius (Rei). For both convection-generated and in-situ ice clouds, the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters, but the sensitivities of Rei to aerosols under the same water vapor amount differ remarkably between the two ice cloud types. As a result, overall Rei slightly increases with aerosol loading for convection-generated ice clouds, but decreases for in-situ ice clouds. When aerosols are decomposed into different types, an increase in the loading of smoke aerosols generally leads to a decrease in COT of convection-generated ice clouds, while the reverse is true for dust and anthropogenic pollution. In contrast, an increase in the loading of any aerosol type can significantly enhance COT of in-situ ice clouds. The modulation of the aerosol impacts by cloud/aerosol types is demonstrated and reproduced by simulations using the Weather Research and Forecasting (WRF) model. Adequate and accurate representations of the impact of different cloud/aerosol types in climate models are crucial for reducing the

Latitudinal Dependence of the Energy Input into the Mesosphere by High Energy Electrons

Science.gov (United States)

Wagner, C. U.; Nikutowski, B.; Ranta, H.

1984-01-01

Night-time ionspheric absorption measurements give the possibility to study the precipitation of high energy electrons into the mesosphere during and after magnetospheric storms. The uniform Finnish riometer network was used together with measurements from Kuhlungsborn and Collm (GDR) to investigate the night-time absorption as a function of latitude (L=6.5 to 2.5) and storm-time for seven storms. The common trends visible in all these events are summarized in a schematic average picture, showing the distribution of increased ionospheric absorption as a function of latitude (L value) and storm-time.

pCloud: A Cloud-based Power Market Simulation Environment

Energy Technology Data Exchange (ETDEWEB)

Rudkevich, Aleksandr; Goldis, Evgeniy

2012-12-02

This research conducted by the Newton Energy Group, LLC (NEG) is dedicated to the development of pCloud: a Cloud-based Power Market Simulation Environment. pCloud is offering power industry stakeholders the capability to model electricity markets and is organized around the Software as a Service (SaaS) concept -- a software application delivery model in which software is centrally hosted and provided to many users via the internet. During the Phase I of this project NEG developed a prototype design for pCloud as a SaaS-based commercial service offering, system architecture supporting that design, ensured feasibility of key architecture's elements, formed technological partnerships and negotiated commercial agreements with partners, conducted market research and other related activities and secured funding for continue development of pCloud between the end of Phase I and beginning of Phase II, if awarded. Based on the results of Phase I activities, NEG has established that the development of a cloud-based power market simulation environment within the Windows Azure platform is technologically feasible, can be accomplished within the budget and timeframe available through the Phase II SBIR award with additional external funding. NEG believes that pCloud has the potential to become a game-changing technology for the modeling and analysis of electricity markets. This potential is due to the following critical advantages of pCloud over its competition: - Standardized access to advanced and proven power market simulators offered by third parties. - Automated parallelization of simulations and dynamic provisioning of computing resources on the cloud. This combination of automation and scalability dramatically reduces turn-around time while offering the capability to increase the number of analyzed scenarios by a factor of 10, 100 or even 1000. - Access to ready-to-use data and to cloud-based resources leading to a reduction in software, hardware, and IT costs

Cloud-point extraction and spectrophotometric determination of ...

African Journals Online (AJOL)

Aneco-friendly, simple and very sensitive method was developed for preconcentration and determination of clonazepam (CLO) in pharmaceutical dosage forms using cloud point extraction (CPE) technique. The method is based on cloud point extraction of product from oxidative coupling between reduced CLO and ...

Precipitation-generated oscillations in open cellular cloud fields.

Science.gov (United States)

Feingold, Graham; Koren, Ilan; Wang, Hailong; Xue, Huiwen; Brewer, Wm Alan

2010-08-12

Cloud fields adopt many different patterns that can have a profound effect on the amount of sunlight reflected back to space, with important implications for the Earth's climate. These cloud patterns can be observed in satellite images of the Earth and often exhibit distinct cell-like structures associated with organized convection at scales of tens of kilometres. Recent evidence has shown that atmospheric aerosol particles-through their influence on precipitation formation-help to determine whether cloud fields take on closed (more reflective) or open (less reflective) cellular patterns. The physical mechanisms controlling the formation and evolution of these cells, however, are still poorly understood, limiting our ability to simulate realistically the effects of clouds on global reflectance. Here we use satellite imagery and numerical models to show how precipitating clouds produce an open cellular cloud pattern that oscillates between different, weakly stable states. The oscillations are a result of precipitation causing downward motion and outflow from clouds that were previously positively buoyant. The evaporating precipitation drives air down to the Earth's surface, where it diverges and collides with the outflows of neighbouring precipitating cells. These colliding outflows form surface convergence zones and new cloud formation. In turn, the newly formed clouds produce precipitation and new colliding outflow patterns that are displaced from the previous ones. As successive cycles of this kind unfold, convergence zones alternate with divergence zones and new cloud patterns emerge to replace old ones. The result is an oscillating, self-organized system with a characteristic cell size and precipitation frequency.

A Condensation–coalescence Cloud Model for Exoplanetary Atmospheres: Formulation and Test Applications to Terrestrial and Jovian Clouds

Energy Technology Data Exchange (ETDEWEB)

Ohno, Kazumasa; Okuzumi, Satoshi [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan)

2017-02-01

A number of transiting exoplanets have featureless transmission spectra that might suggest the presence of clouds at high altitudes. A realistic cloud model is necessary to understand the atmospheric conditions under which such high-altitude clouds can form. In this study, we present a new cloud model that takes into account the microphysics of both condensation and coalescence. Our model provides the vertical profiles of the size and density of cloud and rain particles in an updraft for a given set of physical parameters, including the updraft velocity and the number density of cloud condensation nuclei (CCNs). We test our model by comparing with observations of trade-wind cumuli on Earth and ammonia ice clouds in Jupiter. For trade-wind cumuli, the model including both condensation and coalescence gives predictions that are consistent with observations, while the model including only condensation overestimates the mass density of cloud droplets by up to an order of magnitude. For Jovian ammonia clouds, the condensation–coalescence model simultaneously reproduces the effective particle radius, cloud optical thickness, and cloud geometric thickness inferred from Voyager observations if the updraft velocity and CCN number density are taken to be consistent with the results of moist convection simulations and Galileo probe measurements, respectively. These results suggest that the coalescence of condensate particles is important not only in terrestrial water clouds but also in Jovian ice clouds. Our model will be useful to understand how the dynamics, compositions, and nucleation processes in exoplanetary atmospheres affect the vertical extent and optical thickness of exoplanetary clouds via cloud microphysics.

A Condensation–coalescence Cloud Model for Exoplanetary Atmospheres: Formulation and Test Applications to Terrestrial and Jovian Clouds

International Nuclear Information System (INIS)

Ohno, Kazumasa; Okuzumi, Satoshi

2017-01-01

A number of transiting exoplanets have featureless transmission spectra that might suggest the presence of clouds at high altitudes. A realistic cloud model is necessary to understand the atmospheric conditions under which such high-altitude clouds can form. In this study, we present a new cloud model that takes into account the microphysics of both condensation and coalescence. Our model provides the vertical profiles of the size and density of cloud and rain particles in an updraft for a given set of physical parameters, including the updraft velocity and the number density of cloud condensation nuclei (CCNs). We test our model by comparing with observations of trade-wind cumuli on Earth and ammonia ice clouds in Jupiter. For trade-wind cumuli, the model including both condensation and coalescence gives predictions that are consistent with observations, while the model including only condensation overestimates the mass density of cloud droplets by up to an order of magnitude. For Jovian ammonia clouds, the condensation–coalescence model simultaneously reproduces the effective particle radius, cloud optical thickness, and cloud geometric thickness inferred from Voyager observations if the updraft velocity and CCN number density are taken to be consistent with the results of moist convection simulations and Galileo probe measurements, respectively. These results suggest that the coalescence of condensate particles is important not only in terrestrial water clouds but also in Jovian ice clouds. Our model will be useful to understand how the dynamics, compositions, and nucleation processes in exoplanetary atmospheres affect the vertical extent and optical thickness of exoplanetary clouds via cloud microphysics.

Development of a Survivable Cloud Multi-Robot Framework for Heterogeneous Environments

Directory of Open Access Journals (Sweden)

Isaac Osunmakinde

2014-10-01

Full Text Available Cloud robotics is a paradigm that allows for robots to offload computationally intensive and data storage requirements into the cloud by providing a secure and customizable environment. The challenge for cloud robotics is the inherent problem of cloud disconnection. A major assumption made in the development of the current cloud robotics frameworks is that the connection between the cloud and the robot is always available. However, for multi-robots working in heterogeneous environments, the connection between the cloud and the robots cannot always be guaranteed. This work serves to assist with the challenge of disconnection in cloud robotics by proposing a survivable cloud multi-robotics (SCMR framework for heterogeneous environments. The SCMR framework leverages the combination of a virtual ad hoc network formed by robot-to-robot communication and a physical cloud infrastructure formed by robot-to-cloud communications. The quality of service (QoS on the SCMR framework was tested and validated by determining the optimal energy utilization and time of response (ToR on drivability analysis with and without cloud connection. The design trade-off, including the result, is between the computation energy for the robot execution and the offloading energy for the cloud execution.

RCW 36 in the Vela Molecular Ridge: Evidence for high-mass star-cluster formation triggered by cloud-cloud collision

Science.gov (United States)

Sano, Hidetoshi; Enokiya, Rei; Hayashi, Katsuhiro; Yamagishi, Mitsuyoshi; Saeki, Shun; Okawa, Kazuki; Tsuge, Kisetsu; Tsutsumi, Daichi; Kohno, Mikito; Hattori, Yusuke; Yoshiike, Satoshi; Fujita, Shinji; Nishimura, Atsushi; Ohama, Akio; Tachihara, Kengo; Torii, Kazufumi; Hasegawa, Yutaka; Kimura, Kimihiro; Ogawa, Hideo; Wong, Graeme F.; Braiding, Catherine; Rowell, Gavin; Burton, Michael G.; Fukui, Yasuo

2018-05-01

A collision between two molecular clouds is one possible candidate for high-mass star formation. The H II region RCW 36, located in the Vela molecular ridge, contains a young star cluster (˜ 1 Myr old) and two O-type stars. We present new CO observations of RCW 36 made with NANTEN2, Mopra, and ASTE using 12CO(J = 1-0, 2-1, 3-2) and 13CO(J = 2-1) emission lines. We have discovered two molecular clouds lying at the velocities VLSR ˜ 5.5 and 9 km s-1. Both clouds are likely to be physically associated with the star cluster, as verified by the good spatial correspondence among the two clouds, infrared filaments, and the star cluster. We also found a high intensity ratio of ˜ 0.6-1.2 for CO J = 3-2/1-0 toward both clouds, indicating that the gas temperature has been increased due to heating by the O-type stars. We propose that the O-type stars in RCW 36 were formed by a collision between the two clouds, with a relative velocity separation of 5 km s-1. The complementary spatial distributions and the velocity separation of the two clouds are in good agreement with observational signatures expected for O-type star formation triggered by a cloud-cloud collision. We also found a displacement between the complementary spatial distributions of the two clouds, which we estimate to be 0.3 pc assuming the collision angle to be 45° relative to the line-of-sight. We estimate the collision timescale to be ˜ 105 yr. It is probable that the cluster age found by Ellerbroek et al. (2013b, A&A, 558, A102) is dominated by the low-mass members which were not formed under the triggering by cloud-cloud collision, and that the O-type stars in the center of the cluster are explained by the collisional triggering independently from the low-mass star formation.

Application of cloud services in education

Directory of Open Access Journals (Sweden)

G. Kiryakova

2017-09-01

Full Text Available Educational institutions in information society rely heavily on information and communication technologies. They allow them to follow innovative pedagogical paradigms and approaches and implement modern forms of training that are tailored to the needs and characteristics of the new generation of learners. More and more educational institutions are turning to the use of cloud services, because they are extremely effective alternative for providing the high quality resources and services to all participants in the learning process at an affordable price. The main objective of this study is to present the most popular cloud services – cloud-based office suites and cloud storage services, focusing on their use in education.

Security model for VM in cloud

Science.gov (United States)

Kanaparti, Venkataramana; Naveen K., R.; Rajani, S.; Padmvathamma, M.; Anitha, C.

2013-03-01

Cloud computing is a new approach emerged to meet ever-increasing demand for computing resources and to reduce operational costs and Capital Expenditure for IT services. As this new way of computation allows data and applications to be stored away from own corporate server, it brings more issues in security such as virtualization security, distributed computing, application security, identity management, access control and authentication. Even though Virtualization forms the basis for cloud computing it poses many threats in securing cloud. As most of Security threats lies at Virtualization layer in cloud we proposed this new Security Model for Virtual Machine in Cloud (SMVC) in which every process is authenticated by Trusted-Agent (TA) in Hypervisor as well as in VM. Our proposed model is designed to with-stand attacks by unauthorized process that pose threat to applications related to Data Mining, OLAP systems, Image processing which requires huge resources in cloud deployed on one or more VM's.

Aerosol-cloud feedbacks in a turbulent environment: Laboratory measurements representative of conditions in boundary layer clouds

Science.gov (United States)

Cantrell, W. H.; Chandrakar, K. K.; Karki, S.; Kinney, G.; Shaw, R.

2017-12-01

Many of the climate impacts of boundary layer clouds are modulated by aerosol particles. As two examples, their interactions with incoming solar and upwelling terrestrial radiation and their propensity for precipitation are both governed by the population of aerosol particles upon which the cloud droplets formed. In turn, clouds are the primary removal mechanism for aerosol particles smaller than a few micrometers and larger than a few nanometers. Aspects of these interconnected phenomena are known in exquisite detail (e.g. Köhler theory), but other parts have not been as amenable to study in the laboratory (e.g. scavenging of aerosol particles by cloud droplets). As a complicating factor, boundary layer clouds are ubiquitously turbulent, which introduces fluctuations in the water vapor concentration and temperature, which govern the saturation ratio which mediates aerosol-cloud interactions. We have performed laboratory measurements of aerosol-cloud coupling and feedbacks, using Michigan Tech's Pi Chamber (Chang et al., 2016). In conditions representative of boundary layer clouds, our data suggest that the lifetime of most interstitial particles in the accumulation mode is governed by cloud activation - particles are removed from the Pi Chamber when they activate and settle out of the chamber as cloud droplets. As cloud droplets are removed, these interstitial particles activate until the initially polluted cloud cleans itself and all particulates are removed from the chamber. At that point, the cloud collapses. Our data also indicate that smaller particles, Dp defined through the use of the Dämkohler number, the ratio of the characteristic turbulence timescale to the cloud's microphysical response time. Chang, K., et al., 2016. A laboratory facility to study gas-aerosol-cloud interactions in a turbulent environment: The Π Chamber. Bull. Amer. Meteor. Soc., doi:10.1175/BAMS-D-15-00203.1

On the existence of tropical anvil clouds

Science.gov (United States)

Seeley, J.; Jeevanjee, N.; Langhans, W.; Romps, D.

2017-12-01

In the deep tropics, extensive anvil clouds produce a peak in cloud cover below the tropopause. The dominant paradigm for cloud cover attributes this anvil peak to a layer of enhanced mass convergence in the clear-sky upper-troposphere, which is presumed to force frequent detrainment of convective anvils. However, cloud cover also depends on the lifetime of cloudy air after it detrains, which raises the possibility that anvil clouds may be the signature of slow cloud decay rather than enhanced detrainment. Here we measure the cloud decay timescale in cloud-resolving simulations, and find that cloudy updrafts that detrain in the upper troposphere take much longer to dissipate than their shallower counterparts. We show that cloud lifetimes are long in the upper troposphere because the saturation specific humidity becomes orders of magnitude smaller than the typical condensed water loading of cloudy updrafts. This causes evaporative cloud decay to act extremely slowly, thereby prolonging cloud lifetimes in the upper troposphere. As a consequence, extensive anvil clouds still occur in a convecting atmosphere that is forced to have no preferential clear-sky convergence layer. On the other hand, when cloud lifetimes are fixed at a characteristic lower-tropospheric value, extensive anvil clouds do not form. Our results support a revised understanding of tropical anvil clouds, which attributes their existence to the microphysics of slow cloud decay rather than a peak in clear-sky convergence.

Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

OpenAIRE

Y. Liu; W. Wu; M. P. Jensen; T. Toto

2011-01-01

This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surfaced-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fractio...

Mesospheric Na Variability and Dependence on Geomagnetic and Solar Activity over Arecibo

Science.gov (United States)

Jain, K.; Raizada, S.; Brum, C. G. M.

2017-12-01

The Sodium (Na) resonance lidars located at the Arecibo Observatory offer an excellent opportunity to study the mesosphere/lower thermosphere(MLT) region. Different metals like Fe, Mg, Na, K, Ca and their ions are deposited in the 80 - 120 km altitude range due to the ablation of meteors caused by frictional heating during their entry into the Earth's atmosphere. We present an investigation of the neutral mesospheric Na atom layers over Arecibo. Data on the Na concentrations was collected using a resonance lidar tuned to the of Na wavelength at 589 nm. This wavelength is achieved with a dye-laser pumped by the second harmonic (532 nm) generated from a state-of-the-art commercial Nd:YAG laser. The backscattered signal is received on a 0.8 m (diameter) Cassegrain telescope. The study is based on this data acquired from 1998-2017 and its relation to variations in geomagnetic and solar conditions. We also investigate seasonal and long term trends in the data. The nightly-averaged altitude profiles were modeled as Gaussian curves. From this modeled data we obtain parameters such as the peak, abundance, centroid and width of the main Na layer. Preliminary results show that the Na abundance is more sensitive to changes in geomagnetic and solar variations as compared to the width and centroid height. The seasonal variation exhibits higher peak densities during the local summer and has a secondary maximum during the winter [as shown in the attached figure]. Our analysis demonstrates a decrease in the peak and the abundance of Na atoms with the increase of solar and geomagnetic activity.

The sensitivities of in cloud and cloud top phase distributions to primary ice formation in ICON-LEM

Science.gov (United States)

Beydoun, H.; Karrer, M.; Tonttila, J.; Hoose, C.

2017-12-01

Mixed phase clouds remain a leading source of uncertainty in our attempt to quantify cloud-climate and aerosol-cloud climate interactions. Nevertheless, recent advances in parametrizing the primary ice formation process, high resolution cloud modelling, and retrievals of cloud phase distributions from satellite data offer an excellent opportunity to conduct closure studies on the sensitivity of the cloud phase to microphysical and dynamical processes. Particularly, the reliability of satellite data to resolve the phase at the top of the cloud provides a promising benchmark to compare model output to. We run large eddy simulations with the new ICOsahedral Non-hydrostatic atmosphere model (ICON) to place bounds on the sensitivity of in cloud and cloud top phase to the primary ice formation process. State of the art primary ice formation parametrizations in the form of the cumulative ice active site density ns are implemented in idealized deep convective cloud simulations. We exploit the ability of ICON-LEM to switch between a two moment microphysics scheme and the newly developed Predicted Particle Properties (P3) scheme by running our simulations in both configurations for comparison. To quantify the sensitivity of cloud phase to primary ice formation, cloud ice content is evaluated against order of magnitude changes in ns at variable convective strengths. Furthermore, we assess differences between in cloud and cloud top phase distributions as well as the potential impact of updraft velocity on the suppression of the Wegener-Bergeron-Findeisen process. The study aims to evaluate our practical understanding of primary ice formation in the context of predicting the structure and evolution of mixed phase clouds.

Large, cold, and unusual molecular cloud in Monoceros

International Nuclear Information System (INIS)

Maddalena, R.J.; Thaddeus, P.; and Columbia University)

1985-01-01

Observations of the J = 1 → 0 rotational transition of CO near the galactic plane in Monoceros (lroughly-equal216 0 ) reveal a molecular cloud with unusually low peak CO temperatures (T/sub R/ -1 ) typical of much warmer clouds. At the assumed distance of 3 kpc, the cloud is large (250 x 100 pc), has a mass of 7-11 x 10 5 M/sub sun/, and is well removed from the galactic midplane (130 pc). Except for a possible H II region, all the signs of star formation usually shown by clouds of comparable mass are missing. The cloud, unlike cloud complexes of similar size, is a single, continuous object that apparently has not been torn apart by star formation. Clouds with such properties are rare in the Galaxy; only one or two similar objects have been found. We discuss the possibility that the cloud is young and not yet forming stars but will evolve into a typical cloud complex once star formation begins

Submm-Wave Radiometry for Cloud/Humidity/Precipitation Sciences

Science.gov (United States)

Wu, Dong L.

2011-01-01

Although active sensors can provide cloud profiles at good vertical resolution, clouds are often coupled with dynamics to form fast and organized structures. Lack of understanding of these organized systems leads to great challenge for numerical models. The deficiency is partly reflected, for example, in poorly modeled intraseasonal variations (e.g., MJD). Remote sensing clouds in the middle and upper troposphere has been challenging from space. Vis/IR sensors are sensitive to the topmost cloud layers whereas low-frequency MW techniques are sensitivity to liquid and precipitation at the bottom of cloud layers. The middle-level clouds, mostly in the ice phase, require a sensor that has moderate penetration and sensitivity to cloud scattering, in order to measure cloud water content. Sensors at submm wavelengths provide promising sensitivity and coverage with the spatial resolution needed to measure cloud water content floating in the upper air. In addition, submm-wave sensors are able to provide better measurements of upper-tropospheric humidity than traditional microwave instruments.

Geomagnetic control of polar mesosphere summer echoes

Directory of Open Access Journals (Sweden)

J. Bremer

2000-02-01

Full Text Available Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N, 16.0°E from 1994 until 1997 polar mesosphere summer echoes (PMSE have been investigated in dependence on geomagnetic K indices derived at the Auroral Observatory Tromsø (69.66°N, 18.94°E. During night-time and morning hours a significant correlation between the signal-to-noise ratio (SNR of the radar results and the geomagnetic K indices could be detected with a maximum correlation near midnight. The correlation becomes markedly smaller in the afternoon and early evening hours with a minimum near 17 UT. This diurnal variation is in reasonable agreement with riometer absorption at Ivalo (68.55°N, 27.28°E and can be explained by the diurnal variation of ionization due to precipitating high energetic particles. Therefore, a part of the diurnal PMSE variation is caused by this particle precipitation. The variability of the solar EUV variation, however, has no significant influence on the PMSE during the observation period.Keywords: Ionosphere (auroral ionosphere - Magnetospheric physics (energetic particles, precipitating - Radio science (remote sensing

Arctic Strato-Mesospheric Temperature and Wind Variations

Science.gov (United States)

Schmidlin, F. J.; Goldberg, R. A.

2004-01-01

Upper stratosphere and mesosphere rocket measurements are actively used to investigate interaction between the neutral, electrical, and chemical atmospheres and between lower and upper layers of these regions. Satellite temperature measurements from HALOE and from inflatable falling spheres complement each other and allow illustrations of the annual cycle to 85 km altitude. Falling sphere wind and temperature measurements reveal variability that differs as a function of altitude, location, and time. We discuss the state of the Arctic atmosphere during the summer 2002 (Andoya, Norway) and winter 2003 (ESRANGE, Sweden) campaigns of MaCWAVE. Balloon-borne profiles to 30 km altitude and sphere profiles between 50 and 90 km show unique small-scale structure. Nonetheless, there are practical implications that additional measurements are very much needed to complete the full vertical profile picture. Our discussion concentrates on the distribution of temperature and wind and their variability. However, reliable measurements from other high latitude NASA programs over a number of years are available to help properly calculate mean values and the distribution of the individual measurements. Since the available rocket data in the Arctic's upper atmosphere are sparse the results we present are basically a snapshot of atmospheric structure.

Studies on cloud stability of apricot nectar

NARCIS (Netherlands)

Siliha, H.A.I.

1985-01-01

Cloud loss behaviour in pasteurized apricot nectar was found to be different from that of other fruit juices. The cloud particles settled slowly on standing and a gel formed. On standing for a longer period the gel contracts and a clear supernatant layer which can be considered partly as

Kennicutt-Schmidt Relation Variety and Star-forming Cloud Fraction

Energy Technology Data Exchange (ETDEWEB)

Morokuma-Matsui, Kana [Chile Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka-shi, Tokyo 181-8588 (Japan); Muraoka, Kazuyuki, E-mail: kana.matsui@nao.ac.jp [Department of Physical Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan)

2017-03-10

The observationally derived Kennicutt-Schmidt (KS) relation slopes differ from study to study, ranging from sublinear to superlinear. We investigate the KS-relation variety (slope and normalization) as a function of integrated intensity ratio, R {sub 31} = CO( J = 3–2)/CO( J = 1–0) using spatially resolved CO( J = 1–0), CO( J = 3–2), H i, H α, and 24 μ m data of three nearby spiral galaxies (NGC 3627, NGC 5055, and M83). We find that (1) the slopes for each subsample with a fixed R {sub 31} are shallower, but the slope for all data sets combined becomes steeper, (2) normalizations for high R {sub 31} subsamples tend to be high, (3) R {sub 31} correlates with star formation efficiency, therefore the KS relation depends on the distribution in R {sub 31}–Σ{sub gas} space of the samples: no Σ{sub gas} dependence of R {sub 31} results in a linear slope of the KS relation, whereas a positive correlation between Σ{sub gas} and R {sub 31} results in a superlinear slope of the KS relation, and (4) R {sub 31}–Σ{sub gas} distributions are different from galaxy to galaxy and within a galaxy: galaxies with prominent galactic structure tend to have large R {sub 31} and Σ{sub gas}. Our results suggest that the formation efficiency of a star-forming cloud from molecular gas is different among galaxies as well as within a galaxy, and it is one of the key factors inducing the variety in galactic KS relation.

Comparison of convective clouds observed by spaceborne W-band radar and simulated by cloud-resolving atmospheric models

Science.gov (United States)

Dodson, Jason B.

Deep convective clouds (DCCs) play an important role in regulating global climate through vertical mass flux, vertical water transport, and radiation. For general circulation models (GCMs) to simulate the global climate realistically, they must simulate DCCs realistically. GCMs have traditionally used cumulus parameterizations (CPs). Much recent research has shown that multiple persistent unrealistic behaviors in GCMs are related to limitations of CPs. Two alternatives to CPs exist: the global cloud-resolving model (GCRM), and the multiscale modeling framework (MMF). Both can directly simulate the coarser features of DCCs because of their multi-kilometer horizontal resolutions, and can simulate large-scale meteorological processes more realistically than GCMs. However, the question of realistic behavior of simulated DCCs remains. How closely do simulated DCCs resemble observed DCCs? In this study I examine the behavior of DCCs in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and Superparameterized Community Atmospheric Model (SP-CAM), the latter with both single-moment and double-moment microphysics. I place particular emphasis on the relationship between cloud vertical structure and convective environment. I also emphasize the transition between shallow clouds and mature DCCs. The spatial domains used are the tropical oceans and the contiguous United States (CONUS), the latter of which produces frequent vigorous convection during the summer. CloudSat is used to observe DCCs, and A-Train and reanalysis data are used to represent the large-scale environment in which the clouds form. The CloudSat cloud mask and radar reflectivity profiles for CONUS cumuliform clouds (defined as clouds with a base within the planetary boundary layer) during boreal summer are first averaged and compared. Both NICAM and SP-CAM greatly underestimate the vertical growth of cumuliform clouds. Then they are sorted by three large-scale environmental variables: total preciptable

Providing Availability, Performance, and Scalability By Using Cloud Database

OpenAIRE

Prof. Dr. Alaa Hussein Al-Hamami; RafalAdeeb Al-Khashab

2014-01-01

With the development of the internet, new technical and concepts have attention to all users of the internet especially in the development of information technology, such as concept is cloud. Cloud computing includes different components, of which cloud database has become an important one. A cloud database is a distributed database that delivers computing as a service or in form of virtual machine image instead of a product via the internet; its advantage is that database can...

SUPERGIANT SHELLS AND MOLECULAR CLOUD FORMATION IN THE LARGE MAGELLANIC CLOUD

Energy Technology Data Exchange (ETDEWEB)

Dawson, J. R.; Dickey, John M. [School of Mathematics and Physics, University of Tasmania, Sandy Bay Campus, Churchill Avenue, Sandy Bay, TAS 7005 (Australia); McClure-Griffiths, N. M. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Marsfield NSW 2122 (Australia); Wong, T. [Astronomy Department, University of Illinois, Urbana, IL 61801 (United States); Hughes, A. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany); Fukui, Y. [Department of Physics and Astrophysics, Nagoya University, Chikusa-ku, Nagoya (Japan); Kawamura, A., E-mail: joanne.dawson@utas.edu.au [National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan)

2013-01-20

We investigate the influence of large-scale stellar feedback on the formation of molecular clouds in the Large Magellanic Cloud (LMC). Examining the relationship between H I and {sup 12}CO(J = 1-0) in supergiant shells (SGSs), we find that the molecular fraction in the total volume occupied by SGSs is not enhanced with respect to the rest of the LMC disk. However, the majority of objects ({approx}70% by mass) are more molecular than their local surroundings, implying that the presence of a supergiant shell does on average have a positive effect on the molecular gas fraction. Averaged over the full SGS sample, our results suggest that {approx}12%-25% of the molecular mass in supergiant shell systems was formed as a direct result of the stellar feedback that created the shells. This corresponds to {approx}4%-11% of the total molecular mass of the galaxy. These figures are an approximate lower limit to the total contribution of stellar feedback to molecular cloud formation in the LMC, and constitute one of the first quantitative measurements of feedback-triggered molecular cloud formation in a galactic system.

"Cloud" assemblies: quantum dots form electrostatically bound dynamic nebulae around large gold nanoparticles.

Science.gov (United States)

Lilly, G Daniel; Lee, Jaebeom; Kotov, Nicholas A

2010-10-14

Dynamic self-assembled structures of nanoparticles can be produced using predominantly electrostatic interactions. Such assemblies were made from large, positively charged Au metal nanoparticles surrounded by an electrostatically bound cloud of smaller, negatively charged CdSe/ZnS or CdTe quantum dots. At low concentrations they are topologically similar to double electric layers of ions and corona-like assemblies linked by polymer chains. They can also be compared to the topological arrangement of some planetary systems in space. The great advantages of the cloud assemblies are (1) their highly dynamic nature compared to more rigid covalently bound assemblies, (2) simplicity of preparation, and (3) exceptional versatility in components and resulting optical properties. Photoluminescence intensity enhancement originating from quantum resonance between excitons and plasmons was observed for CdSe/ZnS quantum dots, although CdTe dots displayed emission quenching. To evaluate more attentively their dynamic behavior, emission data were collected for the cloud-assemblies with different ratios of the components and ionic strengths of the media. The emission of the system passes through a maximum for 80 QDs ∶ 1 Au NP as determined by the structure of the assemblies and light absorption conditions. Ionic strength dependence of luminescence intensity contradicts the predictions based on the Gouy-Chapman theory and osmotic pressure at high ionic strengths due to formation of larger chaotic colloidally stable assemblies. "Cloud" assemblies made from different nanoscale components can be used both for elucidation of most fundamental aspects of nanoparticle interactions, as well as for practical purposes in sensing and biology.

Sensitivity of Middle Atmospheric Temperature and Circulation in the UIUC Mesosphere-Stratosphere-Troposphere GCM to the Treatment of Subgrid-Scale Gravity-Wave Breaking

Science.gov (United States)

Yang, Fanglin; Schlesinger, Michael E.; Andranova, Natasha; Zubov, Vladimir A.; Rozanov, Eugene V.; Callis, Lin B.

2003-01-01

The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean- flow forcing due to breaking gravity waves was investigated using the University of Illinois at Urbana-Champaign 40-layer Mesosphere-Stratosphere-Troposphere General Circulation Model (MST-GCM). Three GCM experiments were performed. The gravity-wave forcing was represented first by Rayleigh friction, and then by the Alexander and Dunkerton (AD) parameterization with weak and strong breaking effects of gravity waves. In all experiments, the Palmer et al. parameterization was included to treat the breaking of topographic gravity waves in the troposphere and lower stratosphere. Overall, the experiment with the strong breaking effect simulates best the middle atmospheric temperature and circulation. With Rayleigh friction and the weak breaking effect, a large warm bias of up to 60 C was found in the summer upper mesosphere and lower thermosphere. This warm bias was linked to the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. With the strong breaking effect, the GCM was able to simulate this reversal, and essentially eliminated the warm bias. This improvement was the result of a much stronger meridional transport circulation that possesses a strong vertical ascending branch in the summer upper mesosphere, and hence large adiabatic cooling. Budget analysis indicates that 'in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are small. To obtain a transport circulation in the mesosphere of the UIUC MST-GCM that is strong enough to produce the observed cold summer mesopause, gravity-wave forcing larger than 100 m/s/day in magnitude is required near the summer mesopause. In

Mesospheric Water Vapor Retrieved from SABER/TIMED Measurements

Science.gov (United States)

Feofilov, Arte, G.; Yankovsky, Valentine A.; Marshall, Benjamin T.; Russell, J. M., III; Pesnell, W. D.; Kutepov, Alexander A.; Goldberg, Richard A.; Gordley, Larry L.; Petelina, Svetlama; Mauilova, Rada O.;

On the electric breakdown field of the mesosphere and the influence of electron detachment

DEFF Research Database (Denmark)

Neubert, Torsten; Chanrion, Olivier Arnaud

2013-01-01

It has been suggested recently that electron associative detachment from negative atomic oxygen ions provides an additional source of free electrons in electric discharges of the mesosphere, the sprites, and gigantic jets. Here we study attachment under some simplifying assumptions and show...... that the threshold field decreases with time and can reach values well below the conventional threshold field. The concept of a fixed threshold field therefore itself breaks down. We find that the growth rate decreases with decreasing electric field and that long exposure time of electric fields therefore is needed...

Cloud Macroscopic Organization: Order Emerging from Randomness

Science.gov (United States)

Yuan, Tianle

2011-01-01

Clouds play a central role in many aspects of the climate system and their forms and shapes are remarkably diverse. Appropriate representation of clouds in climate models is a major challenge because cloud processes span at least eight orders of magnitude in spatial scales. Here we show that there exists order in cloud size distribution of low-level clouds, and that it follows a power-law distribution with exponent gamma close to 2. gamma is insensitive to yearly variations in environmental conditions, but has regional variations and land-ocean contrasts. More importantly, we demonstrate this self-organizing behavior of clouds emerges naturally from a complex network model with simple, physical organizing principles: random clumping and merging. We also demonstrate symmetry between clear and cloudy skies in terms of macroscopic organization because of similar fundamental underlying organizing principles. The order in the apparently complex cloud-clear field thus has its root in random local interactions. Studying cloud organization with complex network models is an attractive new approach that has wide applications in climate science. We also propose a concept of cloud statistic mechanics approach. This approach is fully complementary to deterministic models, and the two approaches provide a powerful framework to meet the challenge of representing clouds in our climate models when working in tandem.

Molecular clouds in Orion and Monoceros

International Nuclear Information System (INIS)

Maddalena, R.J.

1986-01-01

About one-eighth of a well-sampled 850 deg 2 region of Orion and Monoceros, extending from the Taurus dark cloud complex to the CMa OB 1 association, shows emission at the frequency of the J = 1 → 0 transition of CO coming from either local clouds (d 8 from the galactic plane or from more distant objects located within a few degrees of the plane and well outside the solar circle. Local giant molecular clouds associated with Orion A and B have enhanced temperatures and densities near their western edges possibly due to compression of molecular gas by a high pressure region created by the cumulative effects of ∼10 supernovae that occurred in the Orion OB association. Another giant molecular cloud found to be associated with Mon R2 may be related to the Orion clouds. Two filamentary clouds (one possible 200 pc long but only 3-10 pc wide) were found that may represent a new class of object; magnetic fields probably play a role in confining these filaments. An expanding ring of clouds concentric with the H II region S 264 and its ionizing 08 star λ Ori was also investigated, and a possible evolutionary sequence for the ring is given in detail: the clouds probably constitute fragments of the original cloud from which λ Ori formed, the gas pressure of the H II region and the rocket effect having disrupted the cloud and accelerated the fragments to their present velocities

Cloud-Top Entrainment in Stratocumulus Clouds

Science.gov (United States)

Mellado, Juan Pedro

2017-01-01

Cloud entrainment, the mixing between cloudy and clear air at the boundary of clouds, constitutes one paradigm for the relevance of small scales in the Earth system: By regulating cloud lifetimes, meter- and submeter-scale processes at cloud boundaries can influence planetary-scale properties. Understanding cloud entrainment is difficult given the complexity and diversity of the associated phenomena, which include turbulence entrainment within a stratified medium, convective instabilities driven by radiative and evaporative cooling, shear instabilities, and cloud microphysics. Obtaining accurate data at the required small scales is also challenging, for both simulations and measurements. During the past few decades, however, high-resolution simulations and measurements have greatly advanced our understanding of the main mechanisms controlling cloud entrainment. This article reviews some of these advances, focusing on stratocumulus clouds, and indicates remaining challenges.

Cloud type comparisons of AIRS, CloudSat, and CALIPSO cloud height and amount

Directory of Open Access Journals (Sweden)

B. H. Kahn

2008-03-01

Full Text Available The precision of the two-layer cloud height fields derived from the Atmospheric Infrared Sounder (AIRS is explored and quantified for a five-day set of observations. Coincident profiles of vertical cloud structure by CloudSat, a 94 GHz profiling radar, and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO, are compared to AIRS for a wide range of cloud types. Bias and variability in cloud height differences are shown to have dependence on cloud type, height, and amount, as well as whether CloudSat or CALIPSO is used as the comparison standard. The CloudSat-AIRS biases and variability range from −4.3 to 0.5±1.2–3.6 km for all cloud types. Likewise, the CALIPSO-AIRS biases range from 0.6–3.0±1.2–3.6 km (−5.8 to −0.2±0.5–2.7 km for clouds ≥7 km (<7 km. The upper layer of AIRS has the greatest sensitivity to Altocumulus, Altostratus, Cirrus, Cumulonimbus, and Nimbostratus, whereas the lower layer has the greatest sensitivity to Cumulus and Stratocumulus. Although the bias and variability generally decrease with increasing cloud amount, the ability of AIRS to constrain cloud occurrence, height, and amount is demonstrated across all cloud types for many geophysical conditions. In particular, skill is demonstrated for thin Cirrus, as well as some Cumulus and Stratocumulus, cloud types infrared sounders typically struggle to quantify. Furthermore, some improvements in the AIRS Version 5 operational retrieval algorithm are demonstrated. However, limitations in AIRS cloud retrievals are also revealed, including the existence of spurious Cirrus near the tropopause and low cloud layers within Cumulonimbus and Nimbostratus clouds. Likely causes of spurious clouds are identified and the potential for further improvement is discussed.

The tropical Atlantic surface wind divergence belt and its effect on clouds

OpenAIRE

Y. Tubul; I. Koren; O. Altaratz

2015-01-01

A well-defined surface wind divergence (SWD) belt with distinct cloud properties forms over the equatorial Atlantic during the boreal summer months. This belt separates the deep convective clouds of the intertropical convergence zone (ITCZ) from the shallow marine stratocumulus cloud decks forming over the cold-water subtropical region of the southern Hadley cell. Using the QuikSCAT-SeaWinds and Aqua-MODIS instruments, we examined the large-scale spatiotemporal ...

High performance computing network for cloud environment using simulators

OpenAIRE

Singh, N. Ajith; Hemalatha, M.

2012-01-01

Cloud computing is the next generation computing. Adopting the cloud computing is like signing up new form of a website. The GUI which controls the cloud computing make is directly control the hardware resource and your application. The difficulty part in cloud computing is to deploy in real environment. Its' difficult to know the exact cost and it's requirement until and unless we buy the service not only that whether it will support the existing application which is available on traditional...

A comparison of shock-cloud and wind-cloud interactions: effect of increased cloud density contrast on cloud evolution

Science.gov (United States)

Goldsmith, K. J. A.; Pittard, J. M.

2018-05-01

The similarities, or otherwise, of a shock or wind interacting with a cloud of density contrast χ = 10 were explored in a previous paper. Here, we investigate such interactions with clouds of higher density contrast. We compare the adiabatic hydrodynamic interaction of a Mach 10 shock with a spherical cloud of χ = 103 with that of a cloud embedded in a wind with identical parameters to the post-shock flow. We find that initially there are only minor morphological differences between the shock-cloud and wind-cloud interactions, compared to when χ = 10. However, once the transmitted shock exits the cloud, the development of a turbulent wake and fragmentation of the cloud differs between the two simulations. On increasing the wind Mach number, we note the development of a thin, smooth tail of cloud material, which is then disrupted by the fragmentation of the cloud core and subsequent `mass-loading' of the flow. We find that the normalized cloud mixing time (tmix) is shorter at higher χ. However, a strong Mach number dependence on tmix and the normalized cloud drag time, t_{drag}^' }, is not observed. Mach-number-dependent values of tmix and t_{drag}^' } from comparable shock-cloud interactions converge towards the Mach-number-independent time-scales of the wind-cloud simulations. We find that high χ clouds can be accelerated up to 80-90 per cent of the wind velocity and travel large distances before being significantly mixed. However, complete mixing is not achieved in our simulations and at late times the flow remains perturbed.

Cloud Computing, Tieto Cloud Server Model

OpenAIRE

Suikkanen, Saara

2013-01-01

The purpose of this study is to find out what is cloud computing. To be able to make wise decisions when moving to cloud or considering it, companies need to understand what cloud is consists of. Which model suits best to they company, what should be taken into account before moving to cloud, what is the cloud broker role and also SWOT analysis of cloud? To be able to answer customer requirements and business demands, IT companies should develop and produce new service models. IT house T...

The Lifetimes and Evolution of Molecular Cloud Cores

Science.gov (United States)

Vázquez-Semadeni, Enrique; Kim, Jongsoo; Shadmehri, Mohsen; Ballesteros-Paredes, Javier

2005-01-01

We discuss the lifetimes and evolution of clumps and cores formed as turbulent density fluctuations in nearly isothermal molecular clouds. In order to maintain a broad perspective, we consider both the magnetic and nonmagnetic cases. In the latter, we argue that clumps are unlikely to reach a hydrostatic state if molecular clouds can in general be described as single-phase media with an effective polytropic exponent γecriticality of their ``parent clouds'' (the numerical boxes). In subcritical boxes, magnetostatic clumps do not form. A minority of moderately gravitationally bound clumps form, which however are dispersed by the turbulence in ~1.3 Myr, suggesting that these few longer lived cores can marginally be ``captured'' by AD to increase their mass-to-flux ratio and eventually collapse, although on timescales not significantly longer than the dynamical ones. In supercritical boxes, some cores manage to become locally supercritical and collapse in typical timescales of 2 tfc (~1 Myr). In the most supercritical simulation, a few longer lived cores are observed, which last for up to ~3 Myr, but these end up re-expanding rather than collapsing, because they are sub-Jeans in spite of being supercritical. Fewer clumps and cores form in these simulations than in their nonmagnetic counterpart. Our results suggest the following: (1) not all cores observed in molecular clouds will necessarily form stars and that a class of ``failed cores'' should exist, which will eventually redisperse and which may be related to the observed starless cores; (2) cores may be out-of-equilibrium, transient structures, rather than quasi-magnetostatic configurations; (3) the magnetic field may help reduce the star formation efficiency by reducing the probability of core formation, rather than by significantly delaying the collapse of individual cores, even in magnetically supercritical clouds.

Services Recommendation System based on Heterogeneous Network Analysis in Cloud Computing

OpenAIRE

Junping Dong; Qingyu Xiong; Junhao Wen; Peng Li

2014-01-01

Resources are provided mainly in the form of services in cloud computing. In the distribute environment of cloud computing, how to find the needed services efficiently and accurately is the most urgent problem in cloud computing. In cloud computing, services are the intermediary of cloud platform, services are connected by lots of service providers and requesters and construct the complex heterogeneous network. The traditional recommendation systems only consider the functional and non-functi...

76 FR 13984 - Cloud Computing Forum & Workshop III

Science.gov (United States)

2011-03-15

..., Reference Architecture and Taxonomy, Target USG Agency Business Use Cases and SAJACC were formed. The... Technology Roadmap; a series of high-value target U.S. Government Agency Cloud Computing Business Use Cases; a first version of a neutral cloud computing reference architecture and taxonomy; the NIST Standards...

Use of cloud computing in biomedicine.

Science.gov (United States)

Sobeslav, Vladimir; Maresova, Petra; Krejcar, Ondrej; Franca, Tanos C C; Kuca, Kamil

2016-12-01

Nowadays, biomedicine is characterised by a growing need for processing of large amounts of data in real time. This leads to new requirements for information and communication technologies (ICT). Cloud computing offers a solution to these requirements and provides many advantages, such as cost savings, elasticity and scalability of using ICT. The aim of this paper is to explore the concept of cloud computing and the related use of this concept in the area of biomedicine. Authors offer a comprehensive analysis of the implementation of the cloud computing approach in biomedical research, decomposed into infrastructure, platform and service layer, and a recommendation for processing large amounts of data in biomedicine. Firstly, the paper describes the appropriate forms and technological solutions of cloud computing. Secondly, the high-end computing paradigm of cloud computing aspects is analysed. Finally, the potential and current use of applications in scientific research of this technology in biomedicine is discussed.

Survey for Sensor-Cloud System from Business Process Outsourcing Perspective

OpenAIRE

Kim, JeongYeon

2015-01-01

Cloud computing is a new IT trend to meet the new business requirements such as business agility and operational efficiency with business process outsourcing (BPO). Sensor-Cloud infrastructure is the extended form of cloud computing to manage the sensors which are scattered throughout the network. Several benefits of adopting cloud computing including cost saving, high scalability, and business risk reductions also can be applied to sensor data collection. As a first investment for new techno...

The tropical Atlantic surface wind divergence belt and its effect on clouds

OpenAIRE

Y. Tubul; I. Koren; O. Altaratz

2015-01-01

A well-defined surface wind divergence (SWD) belt with distinct cloud properties forms over the equatorial Atlantic during the boreal summer months. This belt separates the deep convective clouds of the Intertropical Convergence Zone (ITCZ) from the shallow marine stratocumulus cloud decks forming over the cold-water subtropical region of the southern branch of the Hadley cell in the Atlantic. Using the QuikSCAT-SeaWinds and Aqua-MODIS instruments, we examined the large-scal...

+Cloud: An Agent-Based Cloud Computing Platform

OpenAIRE

González, Roberto; Hernández de la Iglesia, Daniel; de la Prieta Pintado, Fernando; Gil González, Ana Belén

2017-01-01

Cloud computing is revolutionizing the services provided through the Internet, and is continually adapting itself in order to maintain the quality of its services. This study presents the platform +Cloud, which proposes a cloud environment for storing information and files by following the cloud paradigm. This study also presents Warehouse 3.0, a cloud-based application that has been developed to validate the services provided by +Cloud.

MOLECULAR CLOUDS IN THE TRIFID NEBULA M20: POSSIBLE EVIDENCE FOR A CLOUD-CLOUD COLLISION IN TRIGGERING THE FORMATION OF THE FIRST GENERATION STARS

International Nuclear Information System (INIS)

Torii, K.; Enokiya, R.; Sano, H.; Yoshiike, S.; Hanaoka, N.; Ohama, A.; Furukawa, N.; Dawson, J. R.; Moribe, N.; Oishi, K.; Nakashima, Y.; Okuda, T.; Yamamoto, H.; Kawamura, A.; Mizuno, N.; Onishi, T.; Fukui, Y.; Maezawa, H.; Mizuno, A.

2011-01-01

A large-scale study of the molecular clouds toward the Trifid Nebula, M20, has been made in the J = 2-1 and J = 1-0 transitions of 12 CO and 13 CO. M20 is ionized predominantly by an O7.5 star HD164492. The study has revealed that there are two molecular components at separate velocities peaked toward the center of M20 and that their temperatures-30-50 K as derived by a large velocity gradient analysis-are significantly higher than the 10 K of their surroundings. We identify the two clouds as the parent clouds of the first generation stars in M20. The mass of each cloud is estimated to be ∼10 3 M sun and their separation velocity is ∼8 km s -1 over ∼1-2 pc. We find that the total mass of stars and molecular gas in M20 is less than ∼3.2 x 10 3 M sun , which is too small by an order of magnitude to gravitationally bind the system. We argue that the formation of the first generation stars, including the main ionizing O7.5 star, was triggered by the collision between the two clouds in a short timescale of ∼1 Myr, a second example alongside Westerlund 2, where a super-star cluster may have been formed due to cloud-cloud collision triggering.

Size-density relations in dark clouds: Non-LTE effects

International Nuclear Information System (INIS)

Maloney, P.

1986-01-01

One of the major goals of molecular astronomy has been to understand the physics and dynamics of dense interstellar clouds. Because the interpretation of observations of giant molecular clouds is complicated by their very complex structure and the dynamical effects of star formation, a number of studies have concentrated on dark clouds. Leung, Kutner and Mead (1982) (hereafter LKM) and Myers (1983), in studies of CO and NH 3 emission, concluded that dark clouds exhibit significant correlations between linewidth and cloud radius of the form delta v varies as R(0.5) and between mean density and radius of the form n varies as R(-1), as originally suggested by Larson (1981). This result suggests that these objects are in virial equilibrium. However, the mean densities inferred from the CO data of LKM are based on an local thermodynamic equilibrium (LTE) analysis of their 13CO data. At the very low mean densities inferred by LKM for the larger clouds in their samples, the assumption of LTE becomes very questionable. As most of the range in R in the density-size correlation comes from the clouds observed in CO, it seems worthwhile to examine how non-LTE effects will influence the derived densities. Microturbulent models of inhomogeneous clouds of varying central concentration with the linewidth-size and mean density-size relations found by Myers show sub-thermal excitation of the 13CO line in the larger clouds, with the result that LTE analysis considerbly underestimates the actual column density. A more general approach which doesn't require detailed modeling of the clouds is to consider whether the observed T/sub R/*(13CO)/T/sub R/*(12CO) ratios in the clouds studied by LKM are in the range where the LTE-derived optical depths be seriously in error due to sub-thermal excitation of the 13CO molecule

Design and Implementation of a Cloud Computing Adoption Decision Tool: Generating a Cloud Road

Science.gov (United States)

Bildosola, Iñaki; Río-Belver, Rosa; Cilleruelo, Ernesto; Garechana, Gaizka

2015-01-01

Migrating to cloud computing is one of the current enterprise challenges. This technology provides a new paradigm based on “on-demand payment” for information and communication technologies. In this sense, the small and medium enterprise is supposed to be the most interested, since initial investments are avoided and the technology allows gradual implementation. However, even if the characteristics and capacities have been widely discussed, entry into the cloud is still lacking in terms of practical, real frameworks. This paper aims at filling this gap, presenting a real tool already implemented and tested, which can be used as a cloud computing adoption decision tool. This tool uses diagnosis based on specific questions to gather the required information and subsequently provide the user with valuable information to deploy the business within the cloud, specifically in the form of Software as a Service (SaaS) solutions. This information allows the decision makers to generate their particular Cloud Road. A pilot study has been carried out with enterprises at a local level with a two-fold objective: to ascertain the degree of knowledge on cloud computing and to identify the most interesting business areas and their related tools for this technology. As expected, the results show high interest and low knowledge on this subject and the tool presented aims to readdress this mismatch, insofar as possible. PMID:26230400

Design and Implementation of a Cloud Computing Adoption Decision Tool: Generating a Cloud Road.

Directory of Open Access Journals (Sweden)

Iñaki Bildosola

Full Text Available Migrating to cloud computing is one of the current enterprise challenges. This technology provides a new paradigm based on "on-demand payment" for information and communication technologies. In this sense, the small and medium enterprise is supposed to be the most interested, since initial investments are avoided and the technology allows gradual implementation. However, even if the characteristics and capacities have been widely discussed, entry into the cloud is still lacking in terms of practical, real frameworks. This paper aims at filling this gap, presenting a real tool already implemented and tested, which can be used as a cloud computing adoption decision tool. This tool uses diagnosis based on specific questions to gather the required information and subsequently provide the user with valuable information to deploy the business within the cloud, specifically in the form of Software as a Service (SaaS solutions. This information allows the decision makers to generate their particular Cloud Road. A pilot study has been carried out with enterprises at a local level with a two-fold objective: to ascertain the degree of knowledge on cloud computing and to identify the most interesting business areas and their related tools for this technology. As expected, the results show high interest and low knowledge on this subject and the tool presented aims to readdress this mismatch, insofar as possible.

Design and Implementation of a Cloud Computing Adoption Decision Tool: Generating a Cloud Road.

Science.gov (United States)

Bildosola, Iñaki; Río-Belver, Rosa; Cilleruelo, Ernesto; Garechana, Gaizka

2015-01-01

Migrating to cloud computing is one of the current enterprise challenges. This technology provides a new paradigm based on "on-demand payment" for information and communication technologies. In this sense, the small and medium enterprise is supposed to be the most interested, since initial investments are avoided and the technology allows gradual implementation. However, even if the characteristics and capacities have been widely discussed, entry into the cloud is still lacking in terms of practical, real frameworks. This paper aims at filling this gap, presenting a real tool already implemented and tested, which can be used as a cloud computing adoption decision tool. This tool uses diagnosis based on specific questions to gather the required information and subsequently provide the user with valuable information to deploy the business within the cloud, specifically in the form of Software as a Service (SaaS) solutions. This information allows the decision makers to generate their particular Cloud Road. A pilot study has been carried out with enterprises at a local level with a two-fold objective: to ascertain the degree of knowledge on cloud computing and to identify the most interesting business areas and their related tools for this technology. As expected, the results show high interest and low knowledge on this subject and the tool presented aims to readdress this mismatch, insofar as possible.

Precipitation formation from orographic cloud seeding.

Science.gov (United States)

French, Jeffrey R; Friedrich, Katja; Tessendorf, Sarah A; Rauber, Robert M; Geerts, Bart; Rasmussen, Roy M; Xue, Lulin; Kunkel, Melvin L; Blestrud, Derek R

2018-02-06

Throughout the western United States and other semiarid mountainous regions across the globe, water supplies are fed primarily through the melting of snowpack. Growing populations place higher demands on water, while warmer winters and earlier springs reduce its supply. Water managers are tantalized by the prospect of cloud seeding as a way to increase winter snowfall, thereby shifting the balance between water supply and demand. Little direct scientific evidence exists that confirms even the basic physical hypothesis upon which cloud seeding relies. The intent of glaciogenic seeding of orographic clouds is to introduce aerosol into a cloud to alter the natural development of cloud particles and enhance wintertime precipitation in a targeted region. The hypothesized chain of events begins with the introduction of silver iodide aerosol into cloud regions containing supercooled liquid water, leading to the nucleation of ice crystals, followed by ice particle growth to sizes sufficiently large such that snow falls to the ground. Despite numerous experiments spanning several decades, no direct observations of this process exist. Here, measurements from radars and aircraft-mounted cloud physics probes are presented that together show the initiation, growth, and fallout to the mountain surface of ice crystals resulting from glaciogenic seeding. These data, by themselves, do not address the question of cloud seeding efficacy, but rather form a critical set of observations necessary for such investigations. These observations are unambiguous and provide details of the physical chain of events following the introduction of glaciogenic cloud seeding aerosol into supercooled liquid orographic clouds.

Silicon Photonics Cloud (SiCloud)

DEFF Research Database (Denmark)

DeVore, P. T. S.; Jiang, Y.; Lynch, M.

2015-01-01

Silicon Photonics Cloud (SiCloud.org) is the first silicon photonics interactive web tool. Here we report new features of this tool including mode propagation parameters and mode distribution galleries for user specified waveguide dimensions and wavelengths.......Silicon Photonics Cloud (SiCloud.org) is the first silicon photonics interactive web tool. Here we report new features of this tool including mode propagation parameters and mode distribution galleries for user specified waveguide dimensions and wavelengths....

Technical note: Evaluation of the simultaneous measurements of mesospheric OH, HO2, and O3 under a photochemical equilibrium assumption - a statistical approach

Science.gov (United States)

Kulikov, Mikhail Y.; Nechaev, Anton A.; Belikovich, Mikhail V.; Ermakova, Tatiana S.; Feigin, Alexander M.

2018-05-01

This Technical Note presents a statistical approach to evaluating simultaneous measurements of several atmospheric components under the assumption of photochemical equilibrium. We consider simultaneous measurements of OH, HO2, and O3 at the altitudes of the mesosphere as a specific example and their daytime photochemical equilibrium as an evaluating relationship. A simplified algebraic equation relating local concentrations of these components in the 50-100 km altitude range has been derived. The parameters of the equation are temperature, neutral density, local zenith angle, and the rates of eight reactions. We have performed a one-year simulation of the mesosphere and lower thermosphere using a 3-D chemical-transport model. The simulation shows that the discrepancy between the calculated evolution of the components and the equilibrium value given by the equation does not exceed 3-4 % in the full range of altitudes independent of season or latitude. We have developed a statistical Bayesian evaluation technique for simultaneous measurements of OH, HO2, and O3 based on the equilibrium equation taking into account the measurement error. The first results of the application of the technique to MLS/Aura data (Microwave Limb Sounder) are presented in this Technical Note. It has been found that the satellite data of the HO2 distribution regularly demonstrate lower altitudes of this component's mesospheric maximum. This has also been confirmed by model HO2 distributions and comparison with offline retrieval of HO2 from the daily zonal means MLS radiance.

submitter Unexpectedly acidic nanoparticles formed in dimethylamine–ammonia–sulfuric-acid nucleation experiments at CLOUD

CERN Document Server

Lawler, Michael J; Kim, Jaeseok; Ahlm, Lars; Tröstl, Jasmin; Praplan, Arnaud P; Schobesberger, Siegfried; Kürten, Andreas; Kirkby, Jasper; Bianchi, Federico; Duplissy, Jonathan; Hansel, Armin; Jokinen, Tuija; Keskinen, Helmi; Lehtipalo, Katrianne; Leiminger, Markus; Petäjä, Tuukka; Rissanen, Matti; Rondo, Linda; Simon, Mario; Sipilä, Mikko; Williamson, Christina; Wimmer, Daniela; Riipinen, Ilona; Virtanen, Annele; Smith, James N

2016-01-01

New particle formation driven by acid–base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10–30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models, which predict a higher dimethylaminium fraction when NH3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : ...

Bigdata Driven Cloud Security: A Survey

Science.gov (United States)

Raja, K.; Hanifa, Sabibullah Mohamed

2017-08-01

Cloud Computing (CC) is a fast-growing technology to perform massive-scale and complex computing. It eliminates the need to maintain expensive computing hardware, dedicated space, and software. Recently, it has been observed that massive growth in the scale of data or big data generated through cloud computing. CC consists of a front-end, includes the users’ computers and software required to access the cloud network, and back-end consists of various computers, servers and database systems that create the cloud. In SaaS (Software as-a-Service - end users to utilize outsourced software), PaaS (Platform as-a-Service-platform is provided) and IaaS (Infrastructure as-a-Service-physical environment is outsourced), and DaaS (Database as-a-Service-data can be housed within a cloud), where leading / traditional cloud ecosystem delivers the cloud services become a powerful and popular architecture. Many challenges and issues are in security or threats, most vital barrier for cloud computing environment. The main barrier to the adoption of CC in health care relates to Data security. When placing and transmitting data using public networks, cyber attacks in any form are anticipated in CC. Hence, cloud service users need to understand the risk of data breaches and adoption of service delivery model during deployment. This survey deeply covers the CC security issues (covering Data Security in Health care) so as to researchers can develop the robust security application models using Big Data (BD) on CC (can be created / deployed easily). Since, BD evaluation is driven by fast-growing cloud-based applications developed using virtualized technologies. In this purview, MapReduce [12] is a good example of big data processing in a cloud environment, and a model for Cloud providers.

Kinetic Requirements for the Measurement of Mesospheric Water Vapor at 6.8 (microns) under Non-LTE Conditions

Science.gov (United States)

Zhou, Daniel K.; Mlynczak, Martin G.; Lopez-Puertas, Manuel; Russell, James M., III

1999-01-01

We present accuracy requirements for specific kinetic parameters used to calculate the populations and vibrational temperatures of the H2O(010) and H2O(020) states in the terrestrial mesosphere. The requirements are based on rigorous simulations of the retrieval of mesospheric water vapor profiles from measurements of water vapor infrared emission made by limb scanning instruments on orbiting satellites. Major improvements in the rate constants that describe vibration-to- vibration exchange between the H2O(010) and 02(1) states are required in addition to improved specification of the rate of quenching Of O2(1) by atomic oxygen (0). It is also necessary to more accurately determine the yield of vibrationally excited O2(l) resulting from ozone photolysis. A contemporary measurement of the rate of quenching of H2O(010) by N2 and O2 is also desirable. These rates are either highly uncertain or have never before been measured at atmospheric temperatures. The suggested improvements are necessary for the interpretation of water vapor emission measurements at 6.8 microns to be made from a new spaceflight experiment in less than 2 years. The approach to retrieving water vapor under non-LTE conditions is also presented.

Error analysis for mesospheric temperature profiling by absorptive occultation sensors

Directory of Open Access Journals (Sweden)

M. J. Rieder

Full Text Available An error analysis for mesospheric profiles retrieved from absorptive occultation data has been performed, starting with realistic error assumptions as would apply to intensity data collected by available high-precision UV photodiode sensors. Propagation of statistical errors was investigated through the complete retrieval chain from measured intensity profiles to atmospheric density, pressure, and temperature profiles. We assumed unbiased errors as the occultation method is essentially self-calibrating and straight-line propagation of occulted signals as we focus on heights of 50–100 km, where refractive bending of the sensed radiation is negligible. Throughout the analysis the errors were characterized at each retrieval step by their mean profile, their covariance matrix and their probability density function (pdf. This furnishes, compared to a variance-only estimation, a much improved insight into the error propagation mechanism. We applied the procedure to a baseline analysis of the performance of a recently proposed solar UV occultation sensor (SMAS – Sun Monitor and Atmospheric Sounder and provide, using a reasonable exponential atmospheric model as background, results on error standard deviations and error correlation functions of density, pressure, and temperature profiles. Two different sensor photodiode assumptions are discussed, respectively, diamond diodes (DD with 0.03% and silicon diodes (SD with 0.1% (unattenuated intensity measurement noise at 10 Hz sampling rate. A factor-of-2 margin was applied to these noise values in order to roughly account for unmodeled cross section uncertainties. Within the entire height domain (50–100 km we find temperature to be retrieved to better than 0.3 K (DD / 1 K (SD accuracy, respectively, at 2 km height resolution. The results indicate that absorptive occultations acquired by a SMAS-type sensor could provide mesospheric profiles of fundamental variables such as temperature with

Error analysis for mesospheric temperature profiling by absorptive occultation sensors

Directory of Open Access Journals (Sweden)

M. J. Rieder

2001-01-01

Full Text Available An error analysis for mesospheric profiles retrieved from absorptive occultation data has been performed, starting with realistic error assumptions as would apply to intensity data collected by available high-precision UV photodiode sensors. Propagation of statistical errors was investigated through the complete retrieval chain from measured intensity profiles to atmospheric density, pressure, and temperature profiles. We assumed unbiased errors as the occultation method is essentially self-calibrating and straight-line propagation of occulted signals as we focus on heights of 50–100 km, where refractive bending of the sensed radiation is negligible. Throughout the analysis the errors were characterized at each retrieval step by their mean profile, their covariance matrix and their probability density function (pdf. This furnishes, compared to a variance-only estimation, a much improved insight into the error propagation mechanism. We applied the procedure to a baseline analysis of the performance of a recently proposed solar UV occultation sensor (SMAS – Sun Monitor and Atmospheric Sounder and provide, using a reasonable exponential atmospheric model as background, results on error standard deviations and error correlation functions of density, pressure, and temperature profiles. Two different sensor photodiode assumptions are discussed, respectively, diamond diodes (DD with 0.03% and silicon diodes (SD with 0.1% (unattenuated intensity measurement noise at 10 Hz sampling rate. A factor-of-2 margin was applied to these noise values in order to roughly account for unmodeled cross section uncertainties. Within the entire height domain (50–100 km we find temperature to be retrieved to better than 0.3 K (DD / 1 K (SD accuracy, respectively, at 2 km height resolution. The results indicate that absorptive occultations acquired by a SMAS-type sensor could provide mesospheric profiles of fundamental variables such as temperature with

Cloud Processed CCN Suppress Stratus Cloud Drizzle

Science.gov (United States)

Hudson, J. G.; Noble, S. R., Jr.

2017-12-01

Conversion of sulfur dioxide to sulfate within cloud droplets increases the sizes and decreases the critical supersaturation, Sc, of cloud residual particles that had nucleated the droplets. Since other particles remain at the same sizes and Sc a size and Sc gap is often observed. Hudson et al. (2015) showed higher cloud droplet concentrations (Nc) in stratus clouds associated with bimodal high-resolution CCN spectra from the DRI CCN spectrometer compared to clouds associated with unimodal CCN spectra (not cloud processed). Here we show that CCN spectral shape (bimodal or unimodal) affects all aspects of stratus cloud microphysics and drizzle. Panel A shows mean differential cloud droplet spectra that have been divided according to traditional slopes, k, of the 131 measured CCN spectra in the Marine Stratus/Stratocumulus Experiment (MASE) off the Central California coast. K is generally high within the supersaturation, S, range of stratus clouds (< 0.5%). Because cloud processing decreases Sc of some particles, it reduces k. Panel A shows higher concentrations of small cloud droplets apparently grown on lower k CCN than clouds grown on higher k CCN. At small droplet sizes the concentrations follow the k order of the legend, black, red, green, blue (lowest to highest k). Above 13 µm diameter the lines cross and the hierarchy reverses so that blue (highest k) has the highest concentrations followed by green, red and black (lowest k). This reversed hierarchy continues into the drizzle size range (panel B) where the most drizzle drops, Nd, are in clouds grown on the least cloud-processed CCN (blue), while clouds grown on the most processed CCN (black) have the lowest Nd. Suppression of stratus cloud drizzle by cloud processing is an additional 2nd indirect aerosol effect (IAE) that along with the enhancement of 1st IAE by higher Nc (panel A) are above and beyond original IAE. However, further similar analysis is needed in other cloud regimes to determine if MASE was

Cloud Computing as Network Environment in Students Work

OpenAIRE

Piotrowski, Dominik Mirosław

2013-01-01

The purpose of the article was to show the need for literacy education from a variety of services available in the cloud computing as a specialist information field of activity. Teaching at university in the field of cloud computing related to the management of information could provide tangible benefits in the form of useful learning outcomes. This allows students and future information professionals to begin enjoying the benefits of cloud computing SaaS model at work, thereby freeing up of...

Rayleigh lidar observation of tropical mesospheric inversion layer: a comparison between dynamics and chemistry

Directory of Open Access Journals (Sweden)

Ramesh K.

2018-01-01

Full Text Available The Rayleigh lidar at National Atmospheric Research Laboratory, Gadanki (13.5°N, 79.2°E, India operates at 532 nm green laser with ~600 mJ/pulse since 2007. The vertical temperature profiles are derived above ~30 km by assuming the atmosphere is in hydrostatic equilibrium and obeys ideal gas law. A large mesospheric inversion layer (MIL is observed at ~77.4-84.6 km on the night of 22 March 2007 over Gadanki. Although dynamics and chemistry play vital role, both the mechanisms are compared for the occurrence of the MIL in the present study.

Rayleigh lidar observation of tropical mesospheric inversion layer: a comparison between dynamics and chemistry

Science.gov (United States)

Ramesh, K.; Sridharan, S.; Raghunath, K.

2018-04-01

The Rayleigh lidar at National Atmospheric Research Laboratory, Gadanki (13.5°N, 79.2°E), India operates at 532 nm green laser with 600 mJ/pulse since 2007. The vertical temperature profiles are derived above 30 km by assuming the atmosphere is in hydrostatic equilibrium and obeys ideal gas law. A large mesospheric inversion layer (MIL) is observed at 77.4-84.6 km on the night of 22 March 2007 over Gadanki. Although dynamics and chemistry play vital role, both the mechanisms are compared for the occurrence of the MIL in the present study.

The thermodynamics of molecular cloud fragmentation : Star formation under non-Milky Way conditions

NARCIS (Netherlands)

Hocuk, S.; Spaans, M.

Context. Properties of candidate stars, forming out of molecular clouds, depend on the ambient conditions of the parent cloud. We present a series of 2D and 3D simulations of fragmentation of molecular clouds in starburst regions, as well as of clouds under conditions in dwarf galaxies, leading to

Cloud vertical profiles derived from CALIPSO and CloudSat and a comparison with MODIS derived clouds

Science.gov (United States)

Kato, S.; Sun-Mack, S.; Miller, W. F.; Rose, F. G.; Minnis, P.; Wielicki, B. A.; Winker, D. M.; Stephens, G. L.; Charlock, T. P.; Collins, W. D.; Loeb, N. G.; Stackhouse, P. W.; Xu, K.

2008-05-01

CALIPSO and CloudSat from the a-train provide detailed information of vertical distribution of clouds and aerosols. The vertical distribution of cloud occurrence is derived from one month of CALIPSO and CloudSat data as a part of the effort of merging CALIPSO, CloudSat and MODIS with CERES data. This newly derived cloud profile is compared with the distribution of cloud top height derived from MODIS on Aqua from cloud algorithms used in the CERES project. The cloud base from MODIS is also estimated using an empirical formula based on the cloud top height and optical thickness, which is used in CERES processes. While MODIS detects mid and low level clouds over the Arctic in April fairly well when they are the topmost cloud layer, it underestimates high- level clouds. In addition, because the CERES-MODIS cloud algorithm is not able to detect multi-layer clouds and the empirical formula significantly underestimates the depth of high clouds, the occurrence of mid and low-level clouds is underestimated. This comparison does not consider sensitivity difference to thin clouds but we will impose an optical thickness threshold to CALIPSO derived clouds for a further comparison. The effect of such differences in the cloud profile to flux computations will also be discussed. In addition, the effect of cloud cover to the top-of-atmosphere flux over the Arctic using CERES SSF and FLASHFLUX products will be discussed.

Size-density relations in dark clouds: Non-LTE effects

Science.gov (United States)

Maloney, P.

1986-01-01

One of the major goals of molecular astronomy has been to understand the physics and dynamics of dense interstellar clouds. Because the interpretation of observations of giant molecular clouds is complicated by their very complex structure and the dynamical effects of star formation, a number of studies have concentrated on dark clouds. Leung, Kutner and Mead (1982) (hereafter LKM) and Myers (1983), in studies of CO and NH3 emission, concluded that dark clouds exhibit significant correlations between linewidth and cloud radius of the form delta v varies as R(0.5) and between mean density and radius of the form n varies as R(-1), as originally suggested by Larson (1981). This result suggests that these objects are in virial equilibrium. However, the mean densities inferred from the CO data of LKM are based on an local thermodynamic equilibrium (LTE) analysis of their 13CO data. At the very low mean densities inferred by LKM for the larger clouds in their samples, the assumption of LTE becomes very questionable. As most of the range in R in the density-size correlation comes from the clouds observed in CO, it seems worthwhile to examine how non-LTE effects will influence the derived densities. One way to assess the validity of LTE-derived densities is to construct cloud models and then to interpret them in the same way as the observed data. Microturbulent models of inhomogeneous clouds of varying central concentration with the linewidth-size and mean density-size relations found by Myers show sub-thermal excitation of the 13CO line in the larger clouds, with the result that LTE analysis considerbly underestimates the actual column density. A more general approach which doesn't require detailed modeling of the clouds is to consider whether the observed T sub R*(13CO)/T sub R*(12CO) ratios in the clouds studied by LKM are in the range where the LTE-derived optical depths (and hence column densities) can be seriously in error due to sub-thermal excitation of the 13CO

First in situ measurement of the vertical distribution of ice volume in a mesospheric ice cloud during the ECOMA/MASS rocket-campaign

Directory of Open Access Journals (Sweden)

M. Rapp

2009-02-01

Full Text Available We present in situ observations of mesospheric ice particles with a new particle detector which combines a classical Faraday cup with the active photoionization of particles and subsequent detection of photoelectrons. Our observations of charged particles and free electrons within a decaying PMSE-layer reveal that the presence of charged particles is a necessary but not sufficient condition for the presence of PMSE. That is, additional requirements like a sufficiently large electron density – which we here estimate to be on the order of ~100 cm−3 – and the presence of small scale structures (commonly assumed to be caused by turbulence need to be satisfied. Our photoelectron measurements reveal a very strong horizontal structuring of the investigated ice layer, i.e., a very broad layer (82–88 km seen on the upleg is replaced by a narrow layer from 84.5–86 km only 50 km apart on the downleg of the rocket flight. Importantly, the qualitative structure of these photoelectron profiles is in remarkable qualitative agreement with photometer measurements on the same rocket thus demonstrating the reliability of this new technique. We then show that the photoelectron currents are a unique function of the ice particle volume density (and hence ice mass within an uncertainty of only 15% and we derive corresponding altitude profiles of ice volume densities. Derived values are in the range ~2–8×10−14 cm3/cm3 (corresponding to mass densities of ~20–80 ng/m3, and water vapor mixing ratios of 3–12 ppm and are the first such estimates with the unique spatial resolution of an in situ measurement.

Radiation-hydrodynamics of HII regions and molecular clouds

International Nuclear Information System (INIS)

Sandford, M.T. II; Whitaker, R.W.; Klein, R.I.

1981-01-01

Two-dimensional calculations of ionization-shock fronts surrounding neutral cloud clumps reveal that a radiation-driven implosion of the clump can occur. The implosion of a cloud clump results in the formation of density enhancements that may eventually form low mass stars. The smaller globules produced may become Herbig-Haro objects, or maser sources

Cloud phase identification of Arctic boundary-layer clouds from airborne spectral reflection measurements: test of three approaches

Directory of Open Access Journals (Sweden)

A. Ehrlich

2008-12-01

Full Text Available Arctic boundary-layer clouds were investigated with remote sensing and in situ instruments during the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR campaign in March and April 2007. The clouds formed in a cold air outbreak over the open Greenland Sea. Beside the predominant mixed-phase clouds pure liquid water and ice clouds were observed. Utilizing measurements of solar radiation reflected by the clouds three methods to retrieve the thermodynamic phase of the cloud are introduced and compared. Two ice indices I_S and I_P were obtained by analyzing the spectral pattern of the cloud top reflectance in the near infrared (1500–1800 nm wavelength spectral range which is characterized by ice and water absorption. While I_S analyzes the spectral slope of the reflectance in this wavelength range, I_S utilizes a principle component analysis (PCA of the spectral reflectance. A third ice index I_A is based on the different side scattering of spherical liquid water particles and nonspherical ice crystals which was recorded in simultaneous measurements of spectral cloud albedo and reflectance.

Radiative transfer simulations show that I_S, I_P and I_A range between 5 to 80, 0 to 8 and 1 to 1.25 respectively with lowest values indicating pure liquid water clouds and highest values pure ice clouds. The spectral slope ice index I_S and the PCA ice index I_P are found to be strongly sensitive to the effective diameter of the ice crystals present in the cloud. Therefore, the identification of mixed-phase clouds requires a priori knowledge of the ice crystal dimension. The reflectance-albedo ice index I_A is mainly dominated by the uppermost cloud layer (τ<1.5. Therefore, typical boundary-layer mixed-phase clouds with a liquid cloud top layer will

Primordial Molecular Cloud Material in Metal-Rich Carbonaceous Chondrites

Science.gov (United States)

Taylor, G. J.

2016-03-01

The menagerie of objects that make up our Solar System reflects the composition of the huge molecular cloud in which the Sun formed, a late addition of short-lived isotopes from an exploding supernova or stellar winds from a neighboring massive star, heating and/or alteration by water in growing planetesimals that modified and segregated the primordial components, and mixing throughout the Solar System. Outer Solar System objects, such as comets, have always been cold, hence minimizing the changes experienced by more processed objects. They are thought to preserve information about the molecular cloud. Elishevah Van Kooten (Natural History Museum of Denmark and the University of Copenhagen) and co-authors in Denmark and at the University of Hawai'i, measured the isotopic compositions of magnesium and chromium in metal-rich carbonaceous chondrites. They found that the meteorites preserve an isotopic signature of primordial molecular cloud materials, providing a potentially detailed record of the molecular cloud's composition and of materials that formed in the outer Solar System.

Layered phenomena in the mesopause region

Science.gov (United States)

Plane, J. M. C.; Bailey, S. M.; Baumgarten, G.; Rapp, M.

2015-05-01

This special issue of the Journal of Atmospheric and Solar-Terrestrial Physics comprises a collection of papers which were mostly presented at the 11th Layered Phenomena in the Mesopause Region (LPMR) Workshop, held at the University of Leeds between 29th July 2013 and 1st August 2013. The topics covered at the workshop included atmospheric dynamics, mesospheric ice clouds, meteoric metal layers, meteoric smoke particles, and airglow layers. There was also a session on the potential of planned sub-orbital spacecraft for making measurements in the mesosphere and lower thermosphere (MLT).

Ionization profile of beta radiation from radioactive cloud

International Nuclear Information System (INIS)

Vujovic, M.; Vojvodic, V.

1978-01-01

A method for calculation of the ionization profile induced by beta radiation from a radioactive cloud is given. The procedure can be applied for high altitudes of the could (H 75 km) as well as for lower ones, when the thickness of the cloud must be taken into account. The final result is given in the analytical form. (author)

Long-term behavior of the concentration of the minor constituents in the mesosphere – a model study

Directory of Open Access Journals (Sweden)

M. Grygalashvyly

2009-04-01

Full Text Available We investigate the influence the rising concentrations of methane, nitrous oxide and carbon dioxide which have occurred since the pre-industrial era, have had on the chemistry of the mesosphere. For this investigation we use our global 3-D-model COMMA-IAP which was designed for the exploration of the MLT-region and in particular the extended mesopause region. Assumptions and approximations for the trends in the Lyman-α flux (needed for the water vapor dissociation rate, methane and the water vapor mixing ratio at the hygropause are necessary to accomplish this study. To approximate the solar Lyman-α flux back to the pre-industrial time, we derived a quadratic fit using the sunspot number record which extends back to 1749 and is the only solar proxy available for the Lyman-α flux prior to 1947. We assume that methane increases with a constant growth rate from the pre-industrial era to the present. An unsolved problem for the model calculations consists of how the water vapor mixing ratio at the hygropause should be specified during this period. We assume that the hygropause was dryer during pre-industrial times than the present. As a consequence of methane oxidation, the model simulation indicates that the middle atmosphere has become more humid as a result of the rising methane concentration, but with some dependence on height and with a small time delay of few years. The solar influence on the water vapor mixing ratio is insignificant below about 80 km in summer high latitudes, but becomes increasingly more important above this altitude. The enhanced water vapor concentration increases the hydrogen radical concentration and reduces the mesospheric ozone. A second region of stronger ozone decrease is located in the vicinity of the stratopause. Increases in CO₂ concentration enhance slightly the concentration of CO in the mesosphere. However, its influence upon the chemistry is small and its main effect is connected with a cooling

The effect of breaking gravity waves on the dynamics and chemistry of the mesosphere and lower thermosphere (invited review)

Science.gov (United States)

Garcia, R. R.

1986-01-01

The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.

Making limb and nadir measurements comparable: A common volume study of PMC brightness observed by Odin OSIRIS and AIM CIPS

Science.gov (United States)

Benze, Susanne; Gumbel, Jörg; Randall, Cora E.; Karlsson, Bodil; Hultgren, Kristoffer; Lumpe, Jerry D.; Baumgarten, Gerd

2018-01-01

Combining limb and nadir satellite observations of Polar Mesospheric Clouds (PMCs) has long been recognized as problematic due to differences in observation geometry, scattering conditions, and retrieval approaches. This study offers a method of comparing PMC brightness observations from the nadir-viewing Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument and the limb-viewing Odin Optical Spectrograph and InfraRed Imaging System (OSIRIS). OSIRIS and CIPS measurements are made comparable by defining a common volume for overlapping OSIRIS and CIPS observations for two northern hemisphere (NH) PMC seasons: NH08 and NH09. We define a scattering intensity quantity that is suitable for either nadir or limb observations and for different scattering conditions. A known CIPS bias is applied, differences in instrument sensitivity are analyzed and taken into account, and effects of cloud inhomogeneity and common volume definition on the comparison are discussed. Not accounting for instrument sensitivity differences or inhomogeneities in the PMC field, the mean relative difference in cloud brightness (CIPS - OSIRIS) is -102 ± 55%. The differences are largest for coincidences with very inhomogeneous clouds that are dominated by pixels that CIPS reports as non-cloud points. Removing these coincidences, the mean relative difference in cloud brightness reduces to -6 ± 14%. The correlation coefficient between the CIPS and OSIRIS measurements of PMC brightness variations in space and time is remarkably high, at 0.94. Overall, the comparison shows excellent agreement despite different retrieval approaches and observation geometries.

Simulation models for the evolution of cloud systems. I. Introduction and preliminary simulations

International Nuclear Information System (INIS)

Pumphrey, W.A.; Scalo, J.M.

1983-01-01

The evolution of systems of interactings gas clouds is investigated, with application to protogalaxies in galaxy clusters, proto--globular clusters in galacies, and protostellar fragments in interstellar clouds. The evolution of these systems can be parameterized in terms of three dimensionless quantities: the number of clouds, the volume filling factor of clouds, and the fraction of the mass of the system in clouds. We discuss the range of parameter space in which direct cloud collisions, tidal encounters, interactions of clouds with ambient gas, cloud collapse, cloud orbital motion due to the gravitational acceleration of the rest of the system, and cumulative long-range gravitational scatterings are important. All of these processes except for long-range gravitational scattering and probably tidal encounters are competitive for the systems of interest. The evolution of the mass spectrum and velocity distribution of clouds in self-gravitating clouds should be dominated by direct collisions for high-mass clouds and by drag, accretion, or ablation for small-mass clouds. We tentatively identify the critical mass at which the collision time scale equals the collapse time scale with the low-mass turnovers observed in the mass spectrum of stars in open clusters, and predict that rich galaxy clusters should exhibit variations in the faint end of the luminosity function if these clusters form by fragmentation. If collisions perturb the attempted collapse of clouds, the low-mass ''stars'' should form before high-mass stars

The Needs of Virtual Machines Implementation in Private Cloud Computing Environment

Directory of Open Access Journals (Sweden)

Edy Kristianto

2015-12-01

Full Text Available The Internet of Things (IOT becomes the purpose of the development of information and communication technology. Cloud computing has a very important role in supporting the IOT, because cloud computing allows to provide services in the form of infrastructure (IaaS, platform (PaaS, and Software (SaaS for its users. One of the fundamental services is infrastructure as a service (IaaS. This study analyzed the requirement that there must be based on a framework of NIST to realize infrastructure as a service in the form of a virtual machine to be built in a cloud computing environment.

Mesospheric sodium over Gadanki during Geminid meteor shower 2007

Science.gov (United States)

Lokanadham, B.; Rakesh Chandra, N.; Bhaskara Rao, S. Vijaya; Raghunath, K.; Yellaiah, G.

Resonance LIDAR system at Gadanki has been used for observing the mesospheric sodium during the night of 12-13 Dec 2007 when the peak activity of Geminid meteor shower occurred. Geminid meteor shower is observed along with the co-located MST radar in the altitude range 80-110 km. Sodium density profiles have been obtained with a vertical resolution of 300 m and a temporal resolution of 120 s with sodium resonance scattering LIDAR system. The sodium layers were found to exist in the altitude range 90-100 km. The enhanced Geminid meteor rates were recorded with the co-located MST radar in the same altitude range. The sodium concentration in the atmospheric altitude of ~93 km is estimated to be 2000 per cc where the meteoric concentration of Geminid is maximum and reduced to around 800 on the non activity of Geminid. These observations showed that the sodium levels in the E-region are found to be increasing during meteor shower nights at least by a factor of two.

Subsonic islands within a high-mass star-forming infrared dark cloud

Science.gov (United States)

Sokolov, Vlas; Wang, Ke; Pineda, Jaime E.; Caselli, Paola; Henshaw, Jonathan D.; Barnes, Ashley T.; Tan, Jonathan C.; Fontani, Francesco; Jiménez-Serra, Izaskun; Zhang, Qizhou

2018-03-01

High-mass star forming regions are typically thought to be dominated by supersonic motions. We present combined Very Large Array and Green Bank Telescope (VLA+GBT) observations of NH3 (1,1) and (2,2) in the infrared dark cloud (IRDC) G035.39-00.33, tracing cold and dense gas down to scales of 0.07 pc. We find that, in contrast to previous, similar studies of IRDCs, more than a third of the fitted ammonia spectra show subsonic non-thermal motions (mean line width of 0.71 km s-1), and sonic Mach number distribution peaks around ℳ = 1. As possible observational and instrumental biases would only broaden the line profiles, our results provide strong upper limits to the actual value of ℳ, further strengthening our findings of narrow line widths. This finding calls for a re-evaluation of the role of turbulent dissipation and subsonic regions in massive-star and cluster formation. Based on our findings in G035.39, we further speculate that the coarser spectral resolution used in the previous VLA NH3 studies may have inhibited the detection of subsonic turbulence in IRDCs. The reduced turbulent support suggests that dynamically important magnetic fields of the 1 mG order would be required to support against possible gravitational collapse. Our results offer valuable input into the theories and simulations that aim to recreate the initial conditions of high-mass star and cluster formation.

Cloud-particle galactic gas dynamics and star formation

International Nuclear Information System (INIS)

Roberts, W.W. Jr.

1983-01-01

Galactic gas dynamics, spiral structure, and star formation are discussed in the context of N-body computational studies based on a cloud-particle model of the interstellar medium. On the small scale, the interstellar medium appears to be cloud-dominated and supernova-perturbed. The cloud-particle model simulates cloud-cloud collisions, the formation of stellar associations, and supernova explosions as dominant local processes. On the large scale in response to a spiral galactic gravitational field, global density waves and galactic shocks develop with large-scale characteristics similar to those found in continuum gas dynamical studies. Both the system of gas clouds and the system of young stellar associations forming from the clouds share in the global spiral structure. However, with the attributes of neither assuming a continuum of gas (as in continuum gas dynamical studies) nor requiring a prescribed equation of state such as the isothermal condition so often employed, the cloud-particle picture retains much of the detail lost in earlier work: namely, the small-scale features and structures so important in understanding the local, turbulent state of the interstellar medium as well as the degree of raggedness often observed superposed on global spiral structure. (Auth.)

The Spitzer survey of interstellar clouds in the gould belt. VI. The Auriga-California molecular cloud observed with IRAC and MIPS

International Nuclear Information System (INIS)

Broekhoven-Fiene, Hannah; Matthews, Brenda C.; Harvey, Paul M.; Gutermuth, Robert A.; Huard, Tracy L.; Miller, Jennifer F.; Tothill, Nicholas F. H.; Nutter, David; Bourke, Tyler L.; DiFrancesco, James; Jørgensen, Jes K.; Allen, Lori E.; Chapman, Nicholas L.; Dunham, Michael M.; Merín, Bruno; Terebey, Susan; Peterson, Dawn E.

2014-01-01

We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70, and 160 μm observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 deg 2 with IRAC and 10.47 deg 2 with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors, and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkHα 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the relative fraction of YSOs in earlier (Class I and F) and later (Class II) classes compared to other clouds. We perform simple SED modeling of the YSOs with disks to compare the mid-IR properties to disks in other clouds and identify 14 classical transition disk candidates. Although the AMC is similar in mass, size, and distance to the OMC, it is forming about 15-20 times fewer stars.

The Spitzer survey of interstellar clouds in the gould belt. VI. The Auriga-California molecular cloud observed with IRAC and MIPS

Energy Technology Data Exchange (ETDEWEB)

Broekhoven-Fiene, Hannah; Matthews, Brenda C. [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8W 3P6 (Canada); Harvey, Paul M. [Astronomy Department, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States); Gutermuth, Robert A. [Department of Astronomy, University of Massachusetts, Amherst, MA (United States); Huard, Tracy L.; Miller, Jennifer F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Tothill, Nicholas F. H. [School of Computing, Engineering and Mathematics, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751 (Australia); Nutter, David [School of Physics and Astronomy, Cardiff University, Queen' s Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Bourke, Tyler L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); DiFrancesco, James [National Research Council Herzberg Astronomy and Astrophysics, Victoria, BC, V9E 2E7 (Canada); Jørgensen, Jes K. [Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-DK-2100 Copenhagen Ø. (Denmark); Allen, Lori E. [National Optical Astronomy Observatories, Tucson, AZ (United States); Chapman, Nicholas L. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Dunham, Michael M. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Merín, Bruno [Herschel Science Centre, ESAC-ESA, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain); Terebey, Susan [Department of Physics and Astronomy PS315, 5151 State University Drive, California State University at Los Angeles, Los Angeles, CA 90032 (United States); Peterson, Dawn E. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); and others

2014-05-01

We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70, and 160 μm observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 deg{sup 2} with IRAC and 10.47 deg{sup 2} with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors, and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkHα 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the relative fraction of YSOs in earlier (Class I and F) and later (Class II) classes compared to other clouds. We perform simple SED modeling of the YSOs with disks to compare the mid-IR properties to disks in other clouds and identify 14 classical transition disk candidates. Although the AMC is similar in mass, size, and distance to the OMC, it is forming about 15-20 times fewer stars.

An Intense Traveling Airglow Front in the Upper Mesosphere-Lower Thermosphere with Characteristic of a Turbulent Bore Observed over Alice Springs, Australia

Science.gov (United States)

Walterscheid, R. L.; Hecht, J. H.; Hickey, M. P.; Gelinas, L. J.; Vincent, R. A.; Reid, I. M.; Woithe, J.

2010-12-01

The Aerospace Corporation’s Nightglow Imager observed a large step-function change in airglow in the form of a traveling front in the OH and O2 airglow emissions over Alice Springs Australia on February 2, 2003. The front exhibited a stepwise increase of nearly a factor two in the OH brightness and a stepwise decrease in the O2 brightness. The change in brightness in each layer was associated with a strong leading disturbance followed by a train of weak barely visible waves. The OH airglow brightness behind the front was the brightness night for 02 at Alice Springs that we have measured in seven years of observations. The OH brightness was among the five brightest. The event was associated with a strong phase-locked two-day wave (TDW).We have analyzed the stability conditions for the upper mesosphere and lower thermosphere and found that the airglow layers were found in a region of strong ducting. The thermal structure was obtained from combining data from the SABER instrument on the TIMED satellite and the NRLMSISE-00 model. The wind profile was obtained by combining the HWM07 model and MF radar winds from Buckland Park Australia. We found that the TDW-disturbed profile was significantly more effective in supporting a high degree of ducting than a profile based only on HWM07 winds. Dramatic wall events have been interpreted as manifestations of undular bores (e.g., Smith et al. [2003]). Undular bores are nonlinear high Froude number events that must generate an ever increasing train of waves to carry the excess energy away from the bore front. Only a very weak wave train behind the initial disturbance was seen for the Alice Springs event. The form of the amplitude ordering was not typical of a nonlinear wave train. Therefore a bore interpretation requires another means of energy dissipation, namely turbulent dissipation. We suggest that a reasonable interpretation of the observed event is a turbulent bore. We are unaware of any previous event having

Electron Cloud Build Up and Instability in the CLIC Damping Rings

CERN Document Server

Rumolo, G; Papaphilippou, Y

2008-01-01

Electron cloud can be formed in the CLIC positron damping ring and cause intolerable tune shift and beam instability. Build up simulations with the Faktor2 code, developed at CERN, have been done to predict the cloud formation in the arcs and wigglers of the damping rings. HEADTAIL simulations have been used to study the effect of this electron cloud on the beam and assess the thresholds above which the electron cloud instability would set in.

The African Research Cloud - A Friendly Entry Point to Research Computing

OpenAIRE

Walt, Anelda Van der; Pretorius, Boeta

2016-01-01

The slides were presented at the first African Research Cloud Workshop in Pretoria, South Africa on 27 - 28 October 2016 [1].The slides formed part of an introduction for a session about using cloud infrastructure, and specifically the African Research Cloud, for training purposes.The session was co-facilitated with Dr Bradley Frank and Dr Michelle Cluver.[1] "African Research Cloud Workshop." The Institute for Data Intensive Astronomy (IDIA). IDIA, n.d. Web. 3 Nov. 2016.  

Dynamic electronic institutions in agent oriented cloud robotic systems.

Science.gov (United States)

Nagrath, Vineet; Morel, Olivier; Malik, Aamir; Saad, Naufal; Meriaudeau, Fabrice

2015-01-01

The dot-com bubble bursted in the year 2000 followed by a swift movement towards resource virtualization and cloud computing business model. Cloud computing emerged not as new form of computing or network technology but a mere remoulding of existing technologies to suit a new business model. Cloud robotics is understood as adaptation of cloud computing ideas for robotic applications. Current efforts in cloud robotics stress upon developing robots that utilize computing and service infrastructure of the cloud, without debating on the underlying business model. HTM5 is an OMG's MDA based Meta-model for agent oriented development of cloud robotic systems. The trade-view of HTM5 promotes peer-to-peer trade amongst software agents. HTM5 agents represent various cloud entities and implement their business logic on cloud interactions. Trade in a peer-to-peer cloud robotic system is based on relationships and contracts amongst several agent subsets. Electronic Institutions are associations of heterogeneous intelligent agents which interact with each other following predefined norms. In Dynamic Electronic Institutions, the process of formation, reformation and dissolution of institutions is automated leading to run time adaptations in groups of agents. DEIs in agent oriented cloud robotic ecosystems bring order and group intellect. This article presents DEI implementations through HTM5 methodology.

Stratocumulus Cloud Top Radiative Cooling and Cloud Base Updraft Speeds

Science.gov (United States)

Kazil, J.; Feingold, G.; Balsells, J.; Klinger, C.

2017-12-01

Cloud top radiative cooling is a primary driver of turbulence in the stratocumulus-topped marine boundary. A functional relationship between cloud top cooling and cloud base updraft speeds may therefore exist. A correlation of cloud top radiative cooling and cloud base updraft speeds has been recently identified empirically, providing a basis for satellite retrieval of cloud base updraft speeds. Such retrievals may enable analysis of aerosol-cloud interactions using satellite observations: Updraft speeds at cloud base co-determine supersaturation and therefore the activation of cloud condensation nuclei, which in turn co-determine cloud properties and precipitation formation. We use large eddy simulation and an off-line radiative transfer model to explore the relationship between cloud-top radiative cooling and cloud base updraft speeds in a marine stratocumulus cloud over the course of the diurnal cycle. We find that during daytime, at low cloud water path (CWP correlated, in agreement with the reported empirical relationship. During the night, in the absence of short-wave heating, CWP builds up (CWP > 50 g m-2) and long-wave emissions from cloud top saturate, while cloud base heating increases. In combination, cloud top cooling and cloud base updrafts become weakly anti-correlated. A functional relationship between cloud top cooling and cloud base updraft speed can hence be expected for stratocumulus clouds with a sufficiently low CWP and sub-saturated long-wave emissions, in particular during daytime. At higher CWPs, in particular at night, the relationship breaks down due to saturation of long-wave emissions from cloud top.

Response of noctilucent cloud brightness to daily solar variations

Science.gov (United States)

Dalin, P.; Pertsev, N.; Perminov, V.; Dubietis, A.; Zadorozhny, A.; Zalcik, M.; McEachran, I.; McEwan, T.; Černis, K.; Grønne, J.; Taustrup, T.; Hansen, O.; Andersen, H.; Melnikov, D.; Manevich, A.; Romejko, V.; Lifatova, D.

2018-04-01

For the first time, long-term data sets of ground-based observations of noctilucent clouds (NLC) around the globe have been analyzed in order to investigate a response of NLC to solar UV irradiance variability on a day-to-day scale. NLC brightness has been considered versus variations of solar Lyman-alpha flux. We have found that day-to-day solar variability, whose effect is generally masked in the natural NLC variability, has a statistically significant effect when considering large statistics for more than ten years. Average increase in day-to-day solar Lyman-α flux results in average decrease in day-to-day NLC brightness that can be explained by robust physical mechanisms taking place in the summer mesosphere. Average time lags between variations of Lyman-α flux and NLC brightness are short (0-3 days), suggesting a dominant role of direct solar heating and of the dynamical mechanism compared to photodissociation of water vapor by solar Lyman-α flux. All found regularities are consistent between various ground-based NLC data sets collected at different locations around the globe and for various time intervals. Signatures of a 27-day periodicity seem to be present in the NLC brightness for individual summertime intervals; however, this oscillation cannot be unambiguously retrieved due to inevitable periods of tropospheric cloudiness.

Charging of mesospheric aerosol particles: the role of photodetachment and photoionization from meteoric smoke and ice particles

Directory of Open Access Journals (Sweden)

M. Rapp

2009-06-01

Full Text Available Time constants for photodetachment, photoemission, and electron capture are considered for two classes of mesospheric aerosol particles, i.e., meteor smoke particles (MSPs and pure water ice particles. Assuming that MSPs consist of metal oxides like Fe2O3 or SiO, we find that during daytime conditions photodetachment by solar photons is up to 4 orders of magnitude faster than electron attachment such that MSPs cannot be negatively charged in the presence of sunlight. Rather, even photoemission can compete with electron capture unless the electron density becomes very large (>>1000 cm−3 such that MSPs should either be positively charged or neutral in the case of large electron densities. For pure water ice particles, however, both photodetachment and photoemission are negligible due to the wavelength characteristics of its absorption cross section and because the flux of solar photons has already dropped significantly at such short wavelengths. This means that water ice particles should normally be negatively charged. Hence, our results can readily explain the repeated observation of the coexistence of positive and negative aerosol particles in the polar summer mesopause, i.e., small MSPs should be positively charged and ice particles should be negatively charged. These results have further important implications for our understanding of the nucleation of mesospheric ice particles as well as for the interpretation of incoherent scatter radar observations of MSPs.

El Niño-Southern Oscillation effect on quasi-biennial oscillations of temperature diurnal tides in the mesosphere and lower thermosphere

Science.gov (United States)

Sun, Yang-Yi; Liu, Huixin; Miyoshi, Yasunobu; Liu, Libo; Chang, Loren C.

2018-05-01

In this study, we evaluate the El Niño-Southern Oscillation (ENSO) signals in the two dominant temperature diurnal tides, diurnal westward wavenumber 1 (DW1) and diurnal eastward wavenumber 3 (DE3) on the quasi-biennial oscillation (QBO) scale (18-34 months) from 50 to 100 km altitudes. The tides are derived from the 21-year (January 1996-February 2017) Ground-to-Topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) temperature simulations and 15-year (February 2002-February 2017) Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature observations. The results show that ENSO warm phases shorten the period ( 2 years) of the QBO in DW1 amplitude near the equator and DE3 amplitude at low latitudes of the Northern Hemisphere. In contrast, the QBO period lengthens ( 2.5 years) during the ENSO neutral and cold phases. Correlation analysis shows the long-lasting effect of ENSO on the tidal QBO in the mesosphere and lower thermosphere.[Figure not available: see fulltext.

Cloud networking understanding cloud-based data center networks

CERN Document Server

Lee, Gary

2014-01-01

Cloud Networking: Understanding Cloud-Based Data Center Networks explains the evolution of established networking technologies into distributed, cloud-based networks. Starting with an overview of cloud technologies, the book explains how cloud data center networks leverage distributed systems for network virtualization, storage networking, and software-defined networking. The author offers insider perspective to key components that make a cloud network possible such as switch fabric technology and data center networking standards. The final chapters look ahead to developments in architectures

Research on Key Technologies of Cloud Computing

Science.gov (United States)

Zhang, Shufen; Yan, Hongcan; Chen, Xuebin

With the development of multi-core processors, virtualization, distributed storage, broadband Internet and automatic management, a new type of computing mode named cloud computing is produced. It distributes computation task on the resource pool which consists of massive computers, so the application systems can obtain the computing power, the storage space and software service according to its demand. It can concentrate all the computing resources and manage them automatically by the software without intervene. This makes application offers not to annoy for tedious details and more absorbed in his business. It will be advantageous to innovation and reduce cost. It's the ultimate goal of cloud computing to provide calculation, services and applications as a public facility for the public, So that people can use the computer resources just like using water, electricity, gas and telephone. Currently, the understanding of cloud computing is developing and changing constantly, cloud computing still has no unanimous definition. This paper describes three main service forms of cloud computing: SAAS, PAAS, IAAS, compared the definition of cloud computing which is given by Google, Amazon, IBM and other companies, summarized the basic characteristics of cloud computing, and emphasized on the key technologies such as data storage, data management, virtualization and programming model.

A global analysis of the ozone deficit in the upper stratosphere and lower mesosphere

Science.gov (United States)

Eluszkiewicz, Janusz; Allen, Mark

1993-01-01

The global measurements of temperature, ozone, water vapor, and nitrogen dioxide acquired by the Limb Infrared Monitor of the Stratosphere (LIMS), supplemented by a precomputed distribution of chlorine monoxide, are used to test the balance between odd oxygen production and loss in the upper stratosphere and lower mesosphere. An efficient photochemical equilibrium model, whose validity is ascertained by comparison with the results from a fully time-dependent one-dimensional model at selected latitudes, is used in the calculations. The computed ozone abundances are systematically lower than observations for May 1-7, 1979, which suggests, contrary to the conclusions of other recent studies, a real problem in model simulations of stratospheric ozone.

Processing Terrain Point Cloud Data

KAUST Repository

DeVore, Ronald

2013-01-10

Terrain point cloud data are typically acquired through some form of Light Detection And Ranging sensing. They form a rich resource that is important in a variety of applications including navigation, line of sight, and terrain visualization. Processing terrain data has not received the attention of other forms of surface reconstruction or of image processing. The goal of terrain data processing is to convert the point cloud into a succinct representation system that is amenable to the various application demands. The present paper presents a platform for terrain processing built on the following principles: (i) measuring distortion in the Hausdorff metric, which we argue is a good match for the application demands, (ii) a multiscale representation based on tree approximation using local polynomial fitting. The basic elements held in the nodes of the tree can be efficiently encoded, transmitted, visualized, and utilized for the various target applications. Several challenges emerge because of the variable resolution of the data, missing data, occlusions, and noise. Techniques for identifying and handling these challenges are developed. © 2013 Society for Industrial and Applied Mathematics.

Protostellar formation in rotating interstellar clouds. I. Numerical methods and tests

International Nuclear Information System (INIS)

Boss, A.P.

1980-01-01

The details of how dense interstellar clouds collapse to form protostars are obscured from observation by the very clouds in which the condensation takes place, leaving an observational gap between the clouds and pre--main-sequence (PMS) stars. There is also a gap of roughly four orders of magnitude between the specific spin angular momentum of such clouds and that of PMS stars. Thus in order to fully understand the sequence of events in stellar formation, we must construct theoretical models of the collapse and fragmentation of rotating interstellar clouds into single or multiple protostellar systems

First in situ measurement of the vertical distribution of ice volume in a mesospheric ice cloud during the ECOMA/MASS rocket-campaign

Energy Technology Data Exchange (ETDEWEB)

Rapp, M.; Strelnikova, I.; Strelnikov, B. [Leibniz-Institute of Atmospheric Physics, Kuehlungsborn (DE)] (and others)

2009-07-01

We present in situ observations of mesospheric ice particles with a new particle detector which combines a classical Faraday cup with the active photoionization of particles and subsequent detection of photoelectrons. Our observations of charged particles and free electrons within a decaying PMSE-layer reveal that the presence of charged particles is a necessary but not sufficient condition for the presence of PMSE. That is, additional requirements like a sufficiently large electron density - which we here estimate to be on the order of {proportional_to}100 cm{sup -3} - and the presence of small scale structures (commonly assumed to be caused by turbulence) need to be satisfied. Our photoelectron measurements reveal a very strong horizontal structuring of the investigated ice layer, i.e., a very broad layer (82-88 km) seen on the upleg is replaced by a narrow layer from 84.5-86 km only 50 km apart on the downleg of the rocket flight. Importantly, the qualitative structure of these photoelectron profiles is in remarkable qualitative agreement with photometer measurements on the same rocket thus demonstrating the reliability of this new technique. We then show that the photoelectron currents are a unique function of the ice particle volume density (and hence ice mass) within an uncertainty of only 15% and we derive corresponding altitude profiles of ice volume densities. Derived values are in the range {proportional_to}2-8 x 10{sup -14} cm{sup 3}/cm{sup 3} (corresponding to mass densities of {proportional_to}20-80 ng/m{sup 3}, and water vapor mixing ratios of 3-12 ppm) and are the first such estimates with the unique spatial resolution of an in situ measurement. (orig.)

First in situ measurement of the vertical distribution of ice volume in a mesospheric ice cloud during the ECOMA/MASS rocket-campaign

Directory of Open Access Journals (Sweden)

M. Rapp

2009-02-01

Full Text Available We present in situ observations of mesospheric ice particles with a new particle detector which combines a classical Faraday cup with the active photoionization of particles and subsequent detection of photoelectrons. Our observations of charged particles and free electrons within a decaying PMSE-layer reveal that the presence of charged particles is a necessary but not sufficient condition for the presence of PMSE. That is, additional requirements like a sufficiently large electron density – which we here estimate to be on the order of ~100 cm⁻³ – and the presence of small scale structures (commonly assumed to be caused by turbulence need to be satisfied. Our photoelectron measurements reveal a very strong horizontal structuring of the investigated ice layer, i.e., a very broad layer (82–88 km seen on the upleg is replaced by a narrow layer from 84.5–86 km only 50 km apart on the downleg of the rocket flight. Importantly, the qualitative structure of these photoelectron profiles is in remarkable qualitative agreement with photometer measurements on the same rocket thus demonstrating the reliability of this new technique. We then show that the photoelectron currents are a unique function of the ice particle volume density (and hence ice mass within an uncertainty of only 15% and we derive corresponding altitude profiles of ice volume densities. Derived values are in the range ~2–8×10⁻¹⁴ cm³/cm³ (corresponding to mass densities of ~20–80 ng/m³, and water vapor mixing ratios of 3–12 ppm and are the first such estimates with the unique spatial resolution of an in situ measurement.

Study of glow discharge positive column with cloud of disperse particles

International Nuclear Information System (INIS)

Polyakov, D.N.; Shumova, V.V.; Vasilyak, L.M.; Fortov, V.E.

2011-01-01

The study aims to describe plasma parameters changes induced by clouds of disperse micron size particles. Dust clouds were formed in the positive column of glow discharge in air at pressure 0.1-0.6 torr and current 0.1-3 mA. The simultaneous registration of discharge voltage and dust cloud parameters was carried out. Experimental results were simulated using diffusion model. The dust cloud is shown to smooth the radial electron concentration profile, increase electric field strength and electron temperature and stabilize the discharge. The cloud is demonstrated to be a trap for positive ions without increase of discharge current. -- Highlights: → 25% increase of longitudinal electric field strength in discharge with dust cloud. → The smoothing effect of dust cloud on radial electron and ion concentration profiles. → Dust cloud as a trap for positive ions without increase of discharge current. → Increase of electron temperature in discharge with dust cloud. → Increase of discharge stability in presence of dust cloud.

Sedimentation Efficiency of Condensation Clouds in Substellar Atmospheres

Science.gov (United States)

Gao, Peter; Marley, Mark S.; Ackerman, Andrew S.

2018-03-01

Condensation clouds in substellar atmospheres have been widely inferred from spectra and photometric variability. Up until now, their horizontally averaged vertical distribution and mean particle size have been largely characterized using models, one of which is the eddy diffusion–sedimentation model from Ackerman and Marley that relies on a sedimentation efficiency parameter, f sed, to determine the vertical extent of clouds in the atmosphere. However, the physical processes controlling the vertical structure of clouds in substellar atmospheres are not well understood. In this work, we derive trends in f sed across a large range of eddy diffusivities (K zz ), gravities, material properties, and cloud formation pathways by fitting cloud distributions calculated by a more detailed cloud microphysics model. We find that f sed is dependent on K zz , but not gravity, when K zz is held constant. f sed is most sensitive to the nucleation rate of cloud particles, as determined by material properties like surface energy and molecular weight. High surface energy materials form fewer, larger cloud particles, leading to large f sed (>1), and vice versa for materials with low surface energy. For cloud formation via heterogeneous nucleation, f sed is sensitive to the condensation nuclei flux and radius, connecting cloud formation in substellar atmospheres to the objects’ formation environments and other atmospheric aerosols. These insights could lead to improved cloud models that help us better understand substellar atmospheres. For example, we demonstrate that f sed could increase with increasing cloud base depth in an atmosphere, shedding light on the nature of the brown dwarf L/T transition.

Electrical discharge occurring between a negatively charged particle cloud and a grounded sphere electrode

International Nuclear Information System (INIS)

Higashiyama, Y; Migita, S; Toki, K; Sugimoto, T

2008-01-01

Electrostatic discharge occurring between a space-charge cloud and a grounded object was investigated using a large-scale charged particle cloud formed by using three set of cloud generators consisting of a blower and corona charger. The ejecting velocity of the particles affects the formation of the charged cloud. At the lower velocity, the charged cloud spread due to electrostatic repulsion force, while at the higher velocity cloud forms an elongated conical shape. To cause electrostatic discharge between the cloud and a grounded object, a grounded sphere electrode with 100 mm in diameter was set at the inside or outside of the cloud. The brush-like discharge channels reached the maximum length of 0.55 m. The discharge current has a waveform with single or multi-peak, a current peak of several amperes, the maximum charge quantity of 2 μC, and the duration of several microseconds. The relationship between the charge quantity and the current peak or the duration in each discharge was examined. The discharge between the cloud and the electrode placed at the outside of the cloud has relatively longer channels and multi-peak current with the longer duration, while that at the inside of the cloud has the lower charge quantity with single peak.

A survey of IoT cloud platforms

Directory of Open Access Journals (Sweden)

Partha Pratim Ray

2016-12-01

Full Text Available Internet of Things (IoT envisages overall merging of several “things” while utilizing internet as the backbone of the communication system to establish a smart interaction between people and surrounding objects. Cloud, being the crucial component of IoT, provides valuable application specific services in many application domains. A number of IoT cloud providers are currently emerging into the market to leverage suitable and specific IoT based services. In spite of huge possible involvement of these IoT clouds, no standard cum comparative analytical study has been found across the literature databases. This article surveys popular IoT cloud platforms in light of solving several service domains such as application development, device management, system management, heterogeneity management, data management, tools for analysis, deployment, monitoring, visualization, and research. A comparison is presented for overall dissemination of IoT clouds according to their applicability. Further, few challenges are also described that the researchers should take on in near future. Ultimately, the goal of this article is to provide detailed knowledge about the existing IoT cloud service providers and their pros and cons in concrete form.

On the Need of Network coding for Mobile Clouds

DEFF Research Database (Denmark)

Fitzek, Frank; Heide, Janus; Pedersen, Morten Videbæk

for mobile clouds. The paper will list the benefits of network coding for mobile clouds as well as introduce both concepts in a tutorial way. The results used throughout this paper are collaborative work of different research institutes, but mainly taken from the mobile device group at Aalborg University.......This paper advocates the need of network coding for mobile clouds. Mobile clouds as well as network coding are describing two novel concepts. The concept of mobile clouds describes the potential of mobile devices to communicate with each other and form a cooperative cluster in which new services...... and potentials are created. Network coding on the other side enables the mobile cloud to communicate in a very efficient and secure way in terms of energy and bandwidth usage. Even though network coding can be applied in a variety of communication networks, it has some inherent features that makes it suitable...

Formation of giant molecular clouds in global spiral structures: the role of orbital dynamics and cloud-cloud collisions

International Nuclear Information System (INIS)

Roberts, W.W. Jr.; Stewart, G.R.

1987-01-01

The different roles played by orbital dynamics and dissipative cloud-cloud collisions in the formation of giant molecular clouds (GMCs) in a global spiral structure are investigated. The interstellar medium (ISM) is simulated by a system of particles, representing clouds, which orbit in a spiral-perturbed, galactic gravitational field. The overall magnitude and width of the global cloud density distribution in spiral arms is very similar in the collisional and collisionless simulations. The results suggest that the assumed number density and size distribution of clouds and the details of individual cloud-cloud collisions have relatively little effect on these features. Dissipative cloud-cloud collisions play an important steadying role for the cloud system's global spiral structure. Dissipative cloud-cloud collisions also damp the relative velocity dispersion of clouds in massive associations and thereby aid in the effective assembling of GMC-like complexes

Mesospheric temperatures estimated from the meteor radar observations at Mohe, China

Science.gov (United States)

Liu, Libo; Liu, Huixin; Chen, Yiding; Le, Huijun

2017-04-01

In this work, we report the estimation of mesospheric temperatures at 90 km height from the observations of the VHF all-sky meteor radar operated at Mohe (53.5 °N, 122.3° E), China, since August 2011. The kinetic temperature profiles retrieved from the observations of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) satellite are processed to provide the temperature (TSABER) and temperature gradient (dT/dh) at 90 km height. Based on the SABER temperature profile data an empirical dT/dh model is developed for the Mohe latitude. First, we derive the temperatures from the meteor decay times (Tmeteor) and the Mohe dT/dh model gives prior information of temperature gradients. Secondly, the full-width of half maximum (FWHM) of the meteor height profiles is calculated and further used to deduce the temperatures (TFWHM) based on the strong linear relationship between FWHM and TSABER. The temperatures at 90 km deduced from the decay times (Tmeteor) and from the meteor height distributions (TFWHM) at Mohe are validated/calibrated with TSABER. The temperatures present a considerable annual variation, being maximum in winter and minimum in summer. Harmonic analyses reveal that the temperatures have an annual variation consistent with TSABER. Our work suggests that the FWHM has a good performance in routine estimation of the temperatures. It should be pointed out that the slope of FWHM and TSABER is 10.1 at Mohe, which is different from that of 15.71 at King Sejong (62.2° S, 58.8° E) station. Acknowledgments The TIMED/SABER kinetic temperature (version 2.0) data are provided by the SABER team through http://saber.gats-inc.com/. The temperatures from the NRLMSISE-00 model are calculated using Aerospace Blockset toolbox of MATLAB (2016a). This research was supported by National Natural Science Foundation of China (41231065, 41321003). We acknowledge the use of meteor radar

Evaluation of Passive Multilayer Cloud Detection Using Preliminary CloudSat and CALIPSO Cloud Profiles

Science.gov (United States)

Minnis, P.; Sun-Mack, S.; Chang, F.; Huang, J.; Nguyen, L.; Ayers, J. K.; Spangenberg, D. A.; Yi, Y.; Trepte, C. R.

2006-12-01

During the last few years, several algorithms have been developed to detect and retrieve multilayered clouds using passive satellite data. Assessing these techniques has been difficult due to the need for active sensors such as cloud radars and lidars that can "see" through different layers of clouds. Such sensors have been available only at a few surface sites and on aircraft during field programs. With the launch of the CALIPSO and CloudSat satellites on April 28, 2006, it is now possible to observe multilayered systems all over the globe using collocated cloud radar and lidar data. As part of the A- Train, these new active sensors are also matched in time ad space with passive measurements from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer - EOS (AMSR-E). The Clouds and the Earth's Radiant Energy System (CERES) has been developing and testing algorithms to detect ice-over-water overlapping cloud systems and to retrieve the cloud liquid path (LWP) and ice water path (IWP) for those systems. One technique uses a combination of the CERES cloud retrieval algorithm applied to MODIS data and a microwave retrieval method applied to AMSR-E data. The combination of a CO2-slicing cloud retireval technique with the CERES algorithms applied to MODIS data (Chang et al., 2005) is used to detect and analyze such overlapped systems that contain thin ice clouds. A third technique uses brightness temperature differences and the CERES algorithms to detect similar overlapped methods. This paper uses preliminary CloudSat and CALIPSO data to begin a global scale assessment of these different methods. The long-term goals are to assess and refine the algorithms to aid the development of an optimal combination of the techniques to better monitor ice 9and liquid water clouds in overlapped conditions.

Molecular gas in the H II-region complex RCW 166: Possible evidence for an early phase of cloud-cloud collision prior to the bubble formation

Science.gov (United States)

Ohama, Akio; Kohno, Mikito; Fujita, Shinji; Tsutsumi, Daichi; Hattori, Yusuke; Torii, Kazufumi; Nishimura, Atsushi; Sano, Hidetoshi; Yamamoto, Hiroaki; Tachihara, Kengo; Fukui, Yasuo

2018-05-01

Young H II regions are an important site for the study of O star formation based on distributions of ionized and molecular gas. We reveal that two molecular clouds at ˜48 km s-1 and ˜53 km s-1 are associated with the H II regions G018.149-00.283 in RCW 166 by using the JCMT CO High-Resolution Survey (COHRS) of the 12CO(J = 3-2) emission. G018.149-00.283 comprises a bright ring at 8 μm and an extended H II region inside the ring. The ˜48 km s-1 cloud delineates the ring, and the ˜53 km s-1 cloud is located within the ring, indicating a complementary distribution between the two molecular components. We propose a hypothesis that high-mass stars within G018.149-00.283 were formed by triggering during cloud-cloud collision at a projected velocity separation of ˜5 km s-1. We argue that G018.149-00.283 is in an early evolutionary stage, ˜0.1 Myr after the collision according to the scheme detailed by Habe and Ohta (1992, PASJ, 44, 203), which will be followed by a bubble formation stage like RCW 120. We also suggest that nearby H II regions N21 and N22 are candidates for bubbles possibly formed by cloud-cloud collision. Inoue and Fukui (2013, ApJ, 774, L31) showed that the interface gas becomes highly turbulent and realizes a high-mass accretion rate of 10-3-10-4 M⊙ yr-1 by magnetohydrodynamical numerical simulations, which offers an explanation of the O-star formation. The fairly high frequency of cloud-cloud collision in RCW 166 is probably due to the high cloud density in this part of the Scutum arm.

Colliding clouds and star formation in NGC 1333

International Nuclear Information System (INIS)

Loren, R.B.

1976-01-01

Ongoing star formation in the NGC 1333 molecular cloud is found to be the result of a cloud-cloud collision. Two velocity components at 6.3 and 8.3 km s -1 are observable in the CO and 13 CO spectra, with strong self-abosorption occurring only in the 8.3 km s -1 component. The cloud-cloud collision provides compression and heating of the back side of the 8.3 km s -1 cloud, while cool, unshocked gas on the front side of this cloud results in the observed self-absorption. With the 6.3 km s -1 cloud on the far side of the collision interface, no self-absorption occurs at this velocity. One result of the collision is the coalescence of the two velocity components into a single, intermediate velocity component observed at 7.5 km s -1 . Associated with this postcollision gas is a chain of newly formed stars which illuminates and heats the nebulosity of NGC 1333.At one end of this chain of stars is a region of enhanced CO line broadening, indicating a nonhomologous gravitational collapse of this portion of the cloud. The infrared stars closest to the part of the cloud which is collapsing are completely obscured at visual wavelengths, and several are associated with Herbig-Haro (HH) objects. With increasing displacement from the region of collapse, the stars become more visible, are probably older, and the CO self-absorption decreases at these positions in the cloud.The observed region in which the cloud-cloud collision is occurring is located at the intersection of an expanding neutral hydrogen shell and lower-velocity background H I

Planetary wave-gravity wave interactions during mesospheric inversion layer events

Science.gov (United States)

Ramesh, K.; Sridharan, S.; Raghunath, K.; Vijaya Bhaskara Rao, S.; Bhavani Kumar, Y.

2013-07-01

lidar temperature observations over Gadanki (13.5°N, 79.2°E) show a few mesospheric inversion layer (MIL) events during 20-25 January 2007. The zonal mean removed SABER temperature shows warm anomalies around 50°E and 275°E indicating the presence of planetary wave of zonal wave number 2. The MIL amplitudes in SABER temperature averaged for 10°N-15°N and 70°E-90°E show a clear 2 day wave modulation during 20-28 January 2007. Prior to 20 January 2007, a strong 2day wave (zonal wave number 2) is observed in the height region of 80-90 km and it gets largely suppressed during 20-26 January 2007 as the condition for vertical propagation is not favorable, though it prevails at lower heights. The 10 day mean zonal wind over Tirunelveli (8.7°N, 77.8°E) shows deceleration of eastward winds indicating the westward drag due to wave dissipation. The nightly mean MF radar observed zonal winds show the presence of alternating eastward and westward winds during the period of 20-26 January 2007. The two dimensional spectrum of Rayleigh lidar temperature observations available for the nights of 20, 22, and 24 January 2007 shows the presence of gravity wave activity with periods 18 min, 38 min, 38 min, and vertical wavelengths 6.4 km, 4.0 km, 6.4 km respectively. From the dispersion relation of gravity waves, it is inferred that these waves are internal gravity waves rather than inertia gravity waves with the horizontal phase speeds of ~40 m/s, ~37 m/s, and ~50 m/s respectively. Assuming the gravity waves are eastward propagating waves, they get absorbed only in the eastward local wind fields of the planetary wave thereby causing turbulence and eddy diffusion which can be inferred from the estimation of large drag force due to the breaking of gravity wave leading to the formation of large amplitude inversion events in alternate nights. The present study shows that, the mesospheric temperature inversion is caused mainly due to the gravity wave breaking and the inversion

Cloud Computing Fundamentals

Science.gov (United States)

Furht, Borko

In the introductory chapter we define the concept of cloud computing and cloud services, and we introduce layers and types of cloud computing. We discuss the differences between cloud computing and cloud services. New technologies that enabled cloud computing are presented next. We also discuss cloud computing features, standards, and security issues. We introduce the key cloud computing platforms, their vendors, and their offerings. We discuss cloud computing challenges and the future of cloud computing.

Electric field measuring and display system. [for cloud formations

Science.gov (United States)

Wojtasinski, R. J.; Lovall, D. D. (Inventor)

1974-01-01

An apparatus is described for monitoring the electric fields of cloud formations within a particular area. It utilizes capacitor plates that are alternately shielded from the clouds for generating an alternating signal corresponding to the intensity of the electric field of the clouds. A synchronizing signal is produced for controlling sampling of the alternating signal. Such samplings are fed through a filter and converted by an analogue to digital converter into digital form and subsequently fed to a transmitter for transmission to the control station for recording.

Alone on a wide wide sea. The origin of SECCO 1, an isolated star-forming gas cloud in the Virgo cluster*†‡

Science.gov (United States)

Bellazzini, M.; Armillotta, L.; Perina, S.; Magrini, L.; Cresci, G.; Beccari, G.; Battaglia, G.; Fraternali, F.; de Zeeuw, P. T.; Martin, N. F.; Calura, F.; Ibata, R.; Coccato, L.; Testa, V.; Correnti, M.

2018-06-01

SECCO 1 is an extremely dark, low-mass (M⋆ ≃ 105 M⊙), star-forming stellar system lying in the low-velocity cloud (LVC) substructure of the Virgo cluster of galaxies, and hosting several H II regions. Here, we review our knowledge of this remarkable system, and present the results of (a) additional analysis of our panoramic spectroscopic observations with MUSE, (b) the combined analysis of Hubble Space Telescope and MUSE data, and (c) new narrow-band observations obtained with OSIRIS@GTC to search for additional H II regions in the surroundings of the system. We provide new evidence supporting an age as young as ≲ 4 Myr for the stars that are currently ionizing the gas in SECCO 1. We identify only one new promising candidate H II region possibly associated with SECCO 1, thus confirming the extreme isolation of the system. We also identify three additional candidate pressure-supported dark clouds in Virgo among the targets of the SECCO survey. Various possible hypotheses for the nature and origin of SECCO 1 are considered and discussed, also with the help of dedicated hydrodynamical simulations showing that a hydrogen cloud with the characteristics of SECCO 1 can likely survive for ≳ 1 Gyr while travelling within the LVC Intra Cluster Medium.

Relationships among cloud occurrence frequency, overlap, and effective thickness derived from CALIPSO and CloudSat merged cloud vertical profiles

Science.gov (United States)

Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.

2010-01-01

A cloud frequency of occurrence matrix is generated using merged cloud vertical profiles derived from the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and cloud profiling radar. The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical profiles can be related by a cloud overlap matrix when the correlation length of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches random overlap with increasing distance separating cloud layers and that the probability of deviating from random overlap decreases exponentially with distance. One month of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat data (July 2006) support these assumptions, although the correlation length sometimes increases with separation distance when the cloud top height is large. The data also show that the correlation length depends on cloud top hight and the maximum occurs when the cloud top height is 8 to 10 km. The cloud correlation length is equivalent to the decorrelation distance introduced by Hogan and Illingworth (2000) when cloud fractions of both layers in a two-cloud layer system are the same. The simple relationships derived in this study can be used to estimate the top-of-atmosphere irradiance difference caused by cloud fraction, uppermost cloud top, and cloud thickness vertical profile differences.

From clouds to stars

International Nuclear Information System (INIS)

Elmegreen, B.G.

1982-01-01

At the present time, the theory of star formation must be limited to what we know about the lowest density gas, or about the pre-main sequence stars themselves. We would like to understand two basic processes: 1) how star-forming clouds are created from the ambient interstellar gas in the first place, and 2) how small parts of these clouds condense to form individual stars. We are interested also in knowing what pre-main sequence stars are like, and how they can interact with their environment. These topics are reviewed in what follows. In this series of lectures, what we know about the formation of stars is tentatively described. The lectures begin with a description of the interstellar medium, and then they proceed along the same direction that a young star would follow during its creation, namely from clouds through the collapse phase and onto the proto-stellar phase. The evolution of viscous disks and two models for the formation of the solar system are described in the last lectures. The longest lectures, and the topics that are covered in most detail, are not necessarily the ones for which we have the most information. Physically intuitive explanations for the various processes are emphasized, rather then mathematical explanations. In some cases, the mathematical aspects are developed as well, but only when the equations can be used to give important numerical values for comparison with the observations

Earthquake forewarning — A multidisciplinary challenge from the ground up to space

Science.gov (United States)

Freund, Friedemann

2013-08-01

Most destructive earthquakes nucleate at between 5-7 km and about 35-40 km depth. Before earthquakes, rocks are subjected to increasing stress. Not every stress increase leads to rupture. To understand pre-earthquake phenomena we note that igneous and high-grade metamorphic rocks contain defects which, upon stressing, release defect electrons in the oxygen anion sublattice, known as positive holes. These charge carriers are highly mobile, able to flow out of stressed rocks into surrounding unstressed rocks. They form electric currents, which emit electromagnetic radiation, sometimes in pulses, sometimes sustained. The arrival of positive holes at the ground-air interface can lead to air ionization, often exclusively positive. Ionized air rising upward can lead to cloud condensation. The upward flow of positive ions can lead to instabilities in the mesosphere, to mesospheric lightning, to changes in the Total Electron Content (TEC) at the lower edge of the ionosphere, and electric field turbulences. Advances in deciphering the earthquake process can only be achieved in a broadly multidisciplinary spirit.

In-flight calibration of mesospheric rocket plasma probes

International Nuclear Information System (INIS)

Havnes, Ove; Hartquist, Thomas W.; Kassa, Meseret; Morfill, Gregor E.

2011-01-01

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.

In-flight calibration of mesospheric rocket plasma probes

Energy Technology Data Exchange (ETDEWEB)

Havnes, Ove [Institute for Physics and Technology, University of Tromsoe, N-9037 Tromsoe (Norway); University Studies Svalbard (UNIS), N-9170 Longyearbyen, Svalbard (Norway); Hartquist, Thomas W. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Kassa, Meseret [Institute for Physics and Technology, University of Tromsoe, N-9037 Tromsoe (Norway); Morfill, Gregor E. [Max-Planck-Institute fuer extraterrestrische Physik, D-85741Garching (Germany)

2011-07-15

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.

In-flight calibration of mesospheric rocket plasma probes.

Science.gov (United States)

Havnes, Ove; Hartquist, Thomas W; Kassa, Meseret; Morfill, Gregor E

2011-07-01

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.

Enterprise content management in the cloud

Directory of Open Access Journals (Sweden)

Jaroslava Klegová

2013-01-01

Full Text Available At present the attention of many organizations concentrates to the Enterprise Content Management system (ECM. Unstructured content grows exponentially, and Enterprise Content Management system helps to capture, store, manage, integrate and deliver all forms of content across the company. Today, decision makers have possibility to move ECM systems to the cloud and take advantages of cloud computing. Cloud solution can provide a crucial competitive advantage. For example, it can reduce fixed IT department cost and ensure faster ECM implementation.To achieve the maximum level of benefits from implementation of ECM in the cloud it is important to understand all possibilities and actions during the implementation. In this paper, the general model of the ECM implementation in the cloud is proposed and described. The risk may relate to all aspects of the implementation, such as cost, schedule or quality. This is the reason why the introduced model places emphasize on risk. The aim of the article is to identify risks of the ECM implementation in the cloud and quantify the impact of risk. The article is focused on the Monte Carlo method. Monte Carlo method is a technique that uses random numbers and probability to solve problems. Based on interviews with an IT managers there is created an example of possible scenarios and the risk is evaluated using the Monte Carlo method.

Identifying the impact of G-quadruplexes on Affymetrix 3' arrays using cloud computing.

Science.gov (United States)

Memon, Farhat N; Owen, Anne M; Sanchez-Graillet, Olivia; Upton, Graham J G; Harrison, Andrew P

2010-01-15

A tetramer quadruplex structure is formed by four parallel strands of DNA/ RNA containing runs of guanine. These quadruplexes are able to form because guanine can Hoogsteen hydrogen bond to other guanines, and a tetrad of guanines can form a stable arrangement. Recently we have discovered that probes on Affymetrix GeneChips that contain runs of guanine do not measure gene expression reliably. We associate this finding with the likelihood that quadruplexes are forming on the surface of GeneChips. In order to cope with the rapidly expanding size of GeneChip array datasets in the public domain, we are exploring the use of cloud computing to replicate our experiments on 3' arrays to look at the effect of the location of G-spots (runs of guanines). Cloud computing is a recently introduced high-performance solution that takes advantage of the computational infrastructure of large organisations such as Amazon and Google. We expect that cloud computing will become widely adopted because it enables bioinformaticians to avoid capital expenditure on expensive computing resources and to only pay a cloud computing provider for what is used. Moreover, as well as financial efficiency, cloud computing is an ecologically-friendly technology, it enables efficient data-sharing and we expect it to be faster for development purposes. Here we propose the advantageous use of cloud computing to perform a large data-mining analysis of public domain 3' arrays.

Ubiquity and impact of thin mid-level clouds in the tropics.

Science.gov (United States)

Bourgeois, Quentin; Ekman, Annica M L; Igel, Matthew R; Krejci, Radovan

2016-08-17

Clouds are crucial for Earth's climate and radiation budget. Great attention has been paid to low, high and vertically thick tropospheric clouds such as stratus, cirrus and deep convective clouds. However, much less is known about tropospheric mid-level clouds as these clouds are challenging to observe in situ and difficult to detect by remote sensing techniques. Here we use Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite observations to show that thin mid-level clouds (TMLCs) are ubiquitous in the tropics. Supported by high-resolution regional model simulations, we find that TMLCs are formed by detrainment from convective clouds near the zero-degree isotherm. Calculations using a radiative transfer model indicate that tropical TMLCs have a cooling effect on climate that could be as large in magnitude as the warming effect of cirrus. We conclude that more effort has to be made to understand TMLCs, as their influence on cloud feedbacks, heat and moisture transport, and climate sensitivity could be substantial.

Private Cloud Communities for Faculty and Students

Directory of Open Access Journals (Sweden)

Daniel R. Tomal

2015-09-01

Full Text Available Massive open online courses (MOOCs and public and private cloud communities continue to flourish in the field of higher education. However, MOOCs have received criticism in recent years and offer little benefit to students already enrolled at an institution. This article advocates for the collaborative creation and use of institutional, program or student-specific private cloud communities developed as a way to promote academic identity, information dissemination, social discourse, and to form a bridge between faculty, administration and students. Concrete steps to build a private cloud are described. Placing a greater emphasis on meeting the needs of enrolled students versus engaging the masses in a MOOC for “edutainment” purposes is recommended.

The simulation of molecular clouds formation in the Milky Way

Science.gov (United States)

Khoperskov, S. A.; Vasiliev, E. O.; Sobolev, A. M.; Khoperskov, A. V.

2013-01-01

Using 3D hydrodynamic calculations we simulate formation of molecular clouds in the Galaxy. The simulations take into account molecular hydrogen chemical kinetics, cooling and heating processes. Comprehensive gravitational potential accounts for contributions from the stellar bulge, two- and four-armed spiral structure, stellar disc, dark halo and takes into account self-gravitation of the gaseous component. Gas clouds in our model form in the spiral arms due to shear and wiggle instabilities and turn into molecular clouds after t ≳ 100 Myr. At the times t ˜ 100-300 Myr the clouds form hierarchical structures and agglomerations with the sizes of 100 pc and greater. We analyse physical properties of the simulated clouds and find that synthetic statistical distributions like mass spectrum, `mass-size' relation and velocity dispersion are close to those observed in the Galaxy. The synthetic l-v (galactic longitude-radial velocity) diagram of the simulated molecular gas distribution resembles observed one and displays a structure with appearance similar to molecular ring of the Galaxy. Existence of this structure in our modelling can be explained by superposition of emission from the galactic bar and the spiral arms at ˜3-4 kpc.

Star Forming Dense Cloud Cores in the TeV -ray SNR RX J1713.7-3946

Energy Technology Data Exchange (ETDEWEB)

Sano, H.; Sato, J.; Yamamoto, H.; Hayakawa, T.; Torii, K.; Moribe, N.; Kawamura, A.; Okuda, T.; Mizuno, N.; Onishi, T.; Maezawa, H.; Inoue, T.; Inutsuka, S.; Tanaka, T.; Mizuno, A.; Ogawa, H.; Stutzki, J.; Bertoldi, F.; Anderl, S.; Bronfman, L.; Koo, B.C.

2010-10-27

RX J1713.7-3946 is one of the TeV {gamma}-ray supernova remnants (SNRs) emitting synchrotron X rays. The SNR is associated with molecular gas located at {approx}1 kpc. We made new molecular observations toward the dense cloud cores, peaks A, C and D, in the SNR in the {sup 12}CO(J=2-1) and {sup 13}CO(J=2-1) transitions at angular resolution of 90 degrees. The most intense core in {sup 13}CO, peak C, was also mapped in the {sup 12}CO(J=4-3) transition at angular resolution of 38 degrees. Peak C shows strong signs of active star formation including bipolar outflow and a far-infrared protostellar source and has a steep gradient with a r{sup -2.2 {+-} 0.4} variation in the average density within radius r. Peak C and the other dense cloud cores are rim-brightened in synchrotron X rays, suggesting that the dense cloud cores are embedded within or on the outer boundary of the SNR shell. This confirms the earlier suggestion that the X rays are physically associated with the molecular gas (Fukui et al. 2003). We present a scenario where the densest molecular core, peak C, survived against the blast wave and is now embedded within the SNR. Numerical simulations of the shock-cloud interaction indicate that a dense clump can indeed survive shock erosion, since shock propagation speed is stalled in the dense clump. Additionally, the shock-cloud interaction induces turbulence and magnetic field amplification around the dense clump that may facilitate particle acceleration in the lower-density inter-clump space leading to the enhanced synchrotron X rays around dense cores.

Light in Condensed Matter in the Upper Atmosphere as the Origin of Homochirality: Circularly Polarized Light from Rydberg Matter

Science.gov (United States)

Holmlid, Leif

2009-08-01

Clouds of the condensed excited Rydberg matter (RM) exist in the atmospheres of comets and planetary bodies (most easily observed at Mercury and the Moon), where they surround the entire bodies. Vast such clouds are recently proposed to exist in the upper atmosphere of Earth (giving rise to the enormous features called noctilucent clouds, polar mesospheric clouds, and polar mesospheric summer radar echoes). It has been shown in experiments with RM that linearly polarized visible light scattered from an RM layer is transformed to circularly polarized light with a probability of approximately 50%. The circular Rydberg electrons in the magnetic field in the RM may be chiral scatterers. The magnetic and anisotropic RM medium acts as a circular polarizer probably by delaying one of the perpendicular components of the light wave. The delay process involved is called Rabi-flopping and gives delays of the order of femtoseconds. This strong effect thus gives intense circularly polarized visible and UV light within RM clouds. Amino acids and other chiral molecules will experience a strong interaction with this light field in the upper atmospheres of planets. The interaction will vary with the stereogenic conformation of the molecules and in all probability promote the survival of one enantiomer. Here, this strong effect is proposed to be the origin of homochirality. The formation of amino acids in the RM clouds is probably facilitated by the catalytic effect of RM.

Light in condensed matter in the upper atmosphere as the origin of homochirality: circularly polarized light from Rydberg matter.

Science.gov (United States)

Holmlid, Leif

2009-01-01

Clouds of the condensed excited Rydberg matter (RM) exist in the atmospheres of comets and planetary bodies (most easily observed at Mercury and the Moon), where they surround the entire bodies. Vast such clouds are recently proposed to exist in the upper atmosphere of Earth (giving rise to the enormous features called noctilucent clouds, polar mesospheric clouds, and polar mesospheric summer radar echoes). It has been shown in experiments with RM that linearly polarized visible light scattered from an RM layer is transformed to circularly polarized light with a probability of approximately 50%. The circular Rydberg electrons in the magnetic field in the RM may be chiral scatterers. The magnetic and anisotropic RM medium acts as a circular polarizer probably by delaying one of the perpendicular components of the light wave. The delay process involved is called Rabi-flopping and gives delays of the order of femtoseconds. This strong effect thus gives intense circularly polarized visible and UV light within RM clouds. Amino acids and other chiral molecules will experience a strong interaction with this light field in the upper atmospheres of planets. The interaction will vary with the stereogenic conformation of the molecules and in all probability promote the survival of one enantiomer. Here, this strong effect is proposed to be the origin of homochirality. The formation of amino acids in the RM clouds is probably facilitated by the catalytic effect of RM.

How to build a cloud chamber?

International Nuclear Information System (INIS)

Mariaud, C.

2012-01-01

The cloud chamber had its heyday in the first half of last century and allowed the discovery of new particles such as the anti-electron, the muon and the neutral and the charged kaon. The bubble chamber replaced it in the mid fifties. This article recalls the principle of the cloud chamber and shows, in a detailed way, how to proceed to build one with on-the-shelf materials. This design is based on the use of isopropanol whose liquefaction through the form of droplets materializes the track of the particle and on the use of combined Peltier cells (instead of CO 2 snow) to cool the chamber. This cloud chamber has been successfully used in schools to observe particles mainly electrons, alphas and muons generated by cosmic rays. (A.C.)

An Examination of the Nature of Global MODIS Cloud Regimes

Science.gov (United States)

Oreopoulos, Lazaros; Cho, Nayeong; Lee, Dongmin; Kato, Seiji; Huffman, George J.

2014-01-01

We introduce global cloud regimes (previously also referred to as "weather states") derived from cloud retrievals that use measurements by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Aqua and Terra satellites. The regimes are obtained by applying clustering analysis on joint histograms of retrieved cloud top pressure and cloud optical thickness. By employing a compositing approach on data sets from satellites and other sources, we examine regime structural and thermodynamical characteristics. We establish that the MODIS cloud regimes tend to form in distinct dynamical and thermodynamical environments and have diverse profiles of cloud fraction and water content. When compositing radiative fluxes from the Clouds and the Earth's Radiant Energy System instrument and surface precipitation from the Global Precipitation Climatology Project, we find that regimes with a radiative warming effect on the atmosphere also produce the largest implied latent heat. Taken as a whole, the results of the study corroborate the usefulness of the cloud regime concept, reaffirm the fundamental nature of the regimes as appropriate building blocks for cloud system classification, clarify their association with standard cloud types, and underscore their distinct radiative and hydrological signatures.

Considerations about Cloud Services: Learning

Directory of Open Access Journals (Sweden)

Riccardo Cognini

2013-05-01

Full Text Available Cloud services are ubiquitous: for small to large companies the phenomenon of cloud service is nowadays a standard business practice. This paper would compile an analysis over a possible implementation of a cloud system, treating especially the legal aspect of this theme. In the Italian market has a large number of issues arise form cloud computing. First of all, this paper investigates the legal issues associated to cloud computing, specific contractual scheme that is able to define rights a duties both of user (private and/or public body and cloud provider. On one side there is all the EU legislative production related to privacy over electronic communication and, furthermore, the Privacy Directive is under a revision process to be more adaptable to new challenges of decentralized data treatment, but concretely there are no any structured and well defined legal instruments. Objectives: we present a possible solution to address the uncertainty of this area, starting from the EU legislative production with the help of the specific Italian scenario that could offer an operative solution. Indeed the Italian legal system is particularly adaptable to changing technologies and it could use as better as possible to adapt the already existing legal tools to this new technological era. Prior work: after an introduction to the state of the art, we show the main issues and their critical points that must be solved. Approach: observation of the state of the art to propose a new approach to find the suitable disciple

FILAMENTARY STRUCTURE OF STAR-FORMING COMPLEXES

International Nuclear Information System (INIS)

Myers, Philip C.

2009-01-01

The nearest young stellar groups are associated with 'hubs' of column density exceeding 10 22 cm -2 , according to recent observations. These hubs radiate multiple 'filaments' of parsec length, having lower column density and fewer stars. Systems with many filaments tend to have parallel filaments with similar spacing. Such 'hub-filament structure' is associated with all of the nine young stellar groups within 300 pc, forming low-mass stars. Similar properties are seen in infrared dark clouds forming more massive stars. In a new model, an initial clump in a uniform medium is compressed into a self-gravitating, modulated layer. The outer layer resembles the modulated equilibrium of Schmid-Burgk with nearly parallel filaments. The filaments converge onto the compressed clump, which collapses to form stars with high efficiency. The initial medium and condensations have densities similar to those in nearby star-forming clouds and clumps. The predicted structures resemble observed hub-filament systems in their size, shape, and column density, and in the appearance of their filaments. These results suggest that HFS associated with young stellar groups may arise from compression of clumpy gas in molecular clouds.

Cloud occurrences and cloud radiative effects (CREs) from CERES-CALIPSO-CloudSat-MODIS (CCCM) and CloudSat radar-lidar (RL) products

Science.gov (United States)

Ham, Seung-Hee; Kato, Seiji; Rose, Fred G.; Winker, David; L'Ecuyer, Tristan; Mace, Gerald G.; Painemal, David; Sun-Mack, Sunny; Chen, Yan; Miller, Walter F.

2017-08-01

Two kinds of cloud products obtained from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat, and Moderate Resolution Imaging Spectroradiometer (MODIS) are compared and analyzed in this study: Clouds and the Earth's Radiant Energy System (CERES)-CALIPSO-CloudSat-MODIS (CCCM) product and CloudSat radar-lidar products such as GEOPROF-LIDAR and FLXHR-LIDAR. Compared to GEOPROF-LIDAR, low-level (40°). The difference occurs when hydrometeors are detected by CALIPSO lidar but are undetected by CloudSat radar. In the comparison of cloud radiative effects (CREs), global mean differences between CCCM and FLXHR-LIDAR are mostly smaller than 5 W m-2, while noticeable regional differences are found. For example, CCCM shortwave (SW) and longwave (LW) CREs are larger than FXLHR-LIDAR along the west coasts of Africa and America because the GEOPROF-LIDAR algorithm misses shallow marine boundary layer clouds. In addition, FLXHR-LIDAR SW CREs are larger than the CCCM counterpart over tropical oceans away from the west coasts of America. Over midlatitude storm-track regions, CCCM SW and LW CREs are larger than the FLXHR-LIDAR counterpart.

Aerosol processing in stratiform clouds in ECHAM6-HAM

Science.gov (United States)

Neubauer, David; Lohmann, Ulrike; Hoose, Corinna

2013-04-01

Aerosol processing in stratiform clouds by uptake into cloud particles, collision-coalescence, chemical processing inside the cloud particles and release back into the atmosphere has important effects on aerosol concentration, size distribution, chemical composition and mixing state. Aerosol particles can act as cloud condensation nuclei. Cloud droplets can take up further aerosol particles by collisions. Atmospheric gases may also be transferred into the cloud droplets and undergo chemical reactions, e.g. the production of atmospheric sulphate. Aerosol particles are also processed in ice crystals. They may be taken up by homogeneous freezing of cloud droplets below -38° C or by heterogeneous freezing above -38° C. This includes immersion freezing of already immersed aerosol particles in the droplets and contact freezing of particles colliding with a droplet. Many clouds do not form precipitation and also much of the precipitation evaporates before it reaches the ground. The water soluble part of the aerosol particles concentrates in the hydrometeors and together with the insoluble part forms a single, mixed, larger particle, which is released. We have implemented aerosol processing into the current version of the general circulation model ECHAM6 (Stevens et al., 2013) coupled to the aerosol module HAM (Stier et al., 2005). ECHAM6-HAM solves prognostic equations for the cloud droplet number and ice crystal number concentrations. In the standard version of HAM, seven modes are used to describe the total aerosol. The modes are divided into soluble/mixed and insoluble modes and the number concentrations and masses of different chemical components (sulphate, black carbon, organic carbon, sea salt and mineral dust) are prognostic variables. We extended this by an explicit representation of aerosol particles in cloud droplets and ice crystals in stratiform clouds similar to Hoose et al. (2008a,b). Aerosol particles in cloud droplets are represented by 5 tracers for the

Protostellar formation in rotation interstellar clouds. III. Nonaxisymmetric collapse

International Nuclear Information System (INIS)

Boss, A.P.

1980-01-01

A full three spatial-dimension gravitational hydrodynamics code has been used to follow the collapse of isothermal rotating clouds subjected to various nonaxialy symmetric perturbations (NAP). An initially axially symmetric cloud collapsed to form a ring which then fragmented into a binary protostellar system. A low thermal energy cloud with a large bar-shaped NAP collapsed and fragmented directly into a binary; higher thermal energy clouds damp out such NAPs while higher rotational rotational energy clouds produce binaries with wider separations. Fragmentation into single and binary systems has been seen. The tidal effects of other nearby protostellar clouds are shown to have an important effect upon the collapse and should not be neglected. The three-dimensional calculations indicate that isothermal interstellar clouds may fragment (with or without passing through a transitory ring phase) into protostellar objects while still in the isothermal regime. The fragments obtained have masses and specific spin angular momenta roughly a 10th that of the original cloud. Interstellar clouds and their fragments may pass through successive collapse phases with fragmentation and reduction of spin angular momentum (by conversion to orbital angular momentum and preferential accretion of low angular momentum matter) terminating in the formation of pre--main-sequence stars with the observed pre--main-sequence rotation rates

Formation of massive clouds and dwarf galaxies during tidal encounters

Science.gov (United States)

Kaufman, Michele; Elmegreen, Bruce G.; Thomasson, Magnus; Elmegreen, Debra M.

1993-01-01

Gerola et al. (1983) propose that isolated dwarf galaxies can form during galaxy interactions. As evidence of this process, Mirabel et al. (1991) find 10(exp 9) solar mass clouds and star formation complexes at the outer ends of the tidal arms in the Antennae and Superantennae galaxies. We describe observations of HI clouds with mass greater than 10(exp 8) solar mass in the interacting galaxy pair IC 2163/NGC 2207. This pair is important because we believe it represents an early stage in the formation of giant clouds during an encounter. We use a gravitational instability model to explain why the observed clouds are so massive and discuss a two-dimensional N-body simulation of an encounter that produces giant clouds.

Photoionization-regulated star formation and the structure of molecular clouds

Science.gov (United States)

Mckee, Christopher F.

1989-01-01

A model for the rate of low-mass star formation in Galactic molecular clouds and for the influence of this star formation on the structure and evolution of the clouds is presented. The rate of energy injection by newly formed stars is estimated, and the effect of this energy injection on the size of the cloud is determined. It is shown that the observed rate of star formation appears adequate to support the observed clouds against gravitational collapse. The rate of photoionization-regulated star formation is estimated and it is shown to be in agreement with estimates of the observed rate of star formation if the observed molecular cloud parameters are used. The mean cloud extinction and the Galactic star formation rate per unit mass of molecular gas are predicted theoretically from the condition that photionization-regulated star formation be in equilibrium. A simple model for the evolution of isolated molecular clouds is developed.

Cold H I clouds near the supernova remnant W44

International Nuclear Information System (INIS)

Sato, F.

1986-01-01

The cold H I clouds near the supernova remnant W44 are investigated by the use of the Maryland-Green Bank Survey (Westerhout 1973). Several clouds with a mean diameter of about 20 pc are distributed in the region. They do not seem to make a shell around W44, contrary to the suggestion by Knapp and Kerr (1974) based on the low-resolution data at coarse grids. Some of them form a chain, about 100 pc in length, extending approximately along the galactic equator. It resembles the cold H I cloud near W3 and W4. The major constituent of the clouds is probably the hydrogen molecule, and the total mass of the entire complex amounts to 25,000 81,000 solar masses. The estimated Jeans mass indicates that they will contract to dense molecular clouds. Therefore, it may safely be concluded that the cold H1 cloud complex near W44 is a giant molecular cloud at an early evolutionary stage. 14 references

QUANTITATIVELY ASSESSING THE ROLE OF CLOUDS IN THE TRANSMISSION SPECTRUM OF GJ 1214b

Energy Technology Data Exchange (ETDEWEB)

Morley, Caroline V.; Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Kempton, Eliza M.-R. [Department of Physics, Grinnell College, Grinnell, IA 50112 (United States); Marley, Mark S.; Zahnle, Kevin [NASA Ames Research Center, 245-3, Moffett Field, CA 94035 (United States); Vissher, Channon, E-mail: cmorley@ucolick.org [Southwest Research Institute, Boulder, CO 80302 (United States)

2013-09-20

Recent observations of the super-Earth GJ 1214b show that it has a relatively featureless transmission spectrum. One suggestion is that these observations indicate that the planet's atmosphere is vertically compact, perhaps due to a water-rich composition that yields a large mean molecular weight. Another suggestion is that the atmosphere is hydrogen/helium-rich with clouds that obscure predicted absorption features. Previous models that incorporate clouds have included their effect without a strong physical motivation for their existence. Here, we present model atmospheres of GJ 1214b that include physically motivated clouds of two types. We model the clouds that are present in chemical equilibrium, as has been suggested to occur on brown dwarfs, which include KCl and ZnS for this planet. We also include clouds that form as a result of photochemistry, forming a hydrocarbon haze layer. We use a photochemical kinetics model to understand the vertical distribution and available mass of haze-forming molecules. We model both solar and enhanced-metallicity cloudy models and determine the cloud properties necessary to match observations. In enhanced-metallicity atmospheres, we find that the equilibrium clouds can match the observations of GJ 1214b if they are lofted high into the atmosphere and have a low sedimentation efficiency (f{sub sed} = 0.1). We find that models with a variety of hydrocarbon haze properties can match the observations. Particle sizes from 0.01 to 0.25 μm can match the transmission spectrum with haze-forming efficiencies as low as 1%-5%.

How chemistry influences cloud structure, star formation, and the IMF

NARCIS (Netherlands)

Hocuk, S.; Cazaux, S.; Spaans, M.; Caselli, P.

2016-01-01

In the earliest phases of star-forming clouds, stable molecular species, such as CO, are important coolants in the gas phase. Depletion of these molecules on dust surfaces affects the thermal balance of molecular clouds and with that their whole evolution. For the first time, we study the effect of

STAR FORMATION LAWS: THE EFFECTS OF GAS CLOUD SAMPLING

International Nuclear Information System (INIS)

Calzetti, D.; Liu, G.; Koda, J.

2012-01-01

Recent observational results indicate that the functional shape of the spatially resolved star formation-molecular gas density relation depends on the spatial scale considered. These results may indicate a fundamental role of sampling effects on scales that are typically only a few times larger than those of the largest molecular clouds. To investigate the impact of this effect, we construct simple models for the distribution of molecular clouds in a typical star-forming spiral galaxy and, assuming a power-law relation between star formation rate (SFR) and cloud mass, explore a range of input parameters. We confirm that the slope and the scatter of the simulated SFR-molecular gas surface density relation depend on the size of the sub-galactic region considered, due to stochastic sampling of the molecular cloud mass function, and the effect is larger for steeper relations between SFR and molecular gas. There is a general trend for all slope values to tend to ∼unity for region sizes larger than 1-2 kpc, irrespective of the input SFR-cloud relation. The region size of 1-2 kpc corresponds to the area where the cloud mass function becomes fully sampled. We quantify the effects of selection biases in data tracing the SFR, either as thresholds (i.e., clouds smaller than a given mass value do not form stars) or as backgrounds (e.g., diffuse emission unrelated to current star formation is counted toward the SFR). Apparently discordant observational results are brought into agreement via this simple model, and the comparison of our simulations with data for a few galaxies supports a steep (>1) power-law index between SFR and molecular gas.

Relation of Cloud Occurrence Frequency, Overlap, and Effective Thickness Derived from CALIPSO and CloudSat Merged Cloud Vertical Profiles

Science.gov (United States)

Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.

2009-01-01

A cloud frequency of occurrence matrix is generated using merged cloud vertical profile derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR). The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical pro les can be related by a set of equations when the correlation distance of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches the random overlap with increasing distance separating cloud layers and that the probability of deviating from the random overlap decreases exponentially with distance. One month of CALIPSO and CloudSat data support these assumptions. However, the correlation distance sometimes becomes large, which might be an indication of precipitation. The cloud correlation distance is equivalent to the de-correlation distance introduced by Hogan and Illingworth [2000] when cloud fractions of both layers in a two-cloud layer system are the same.

Magnetohydrodynamic Simulations of the Formation of Molecular Clouds toward the Stellar Cluster Westerlund 2: Interaction of a Jet with a Clumpy Interstellar Medium

International Nuclear Information System (INIS)

Asahina, Yuta; Kawashima, Tomohisa; Furukawa, Naoko; Enokiya, Rei; Yamamoto, Hiroaki; Fukui, Yasuo; Matsumoto, Ryoji

2017-01-01

The formation mechanism of CO clouds observed with the NANTEN2 and Mopra telescopes toward the stellar cluster Westerlund 2 is studied by 3D magnetohydrodynamic simulations, taking into account the interstellar cooling. These molecular clouds show a peculiar shape composed of an arc-shaped cloud on one side of the TeV γ -ray source HESS J1023-575 and a linear distribution of clouds (jet clouds) on the other side. We propose that these clouds are formed by the interaction of a jet with clumps of interstellar neutral hydrogen (H i). By studying the dependence of the shape of dense cold clouds formed by shock compression and cooling on the filling factor of H i clumps, we found that the density distribution of H i clumps determines the shape of molecular clouds formed by the jet–cloud interaction: arc clouds are formed when the filling factor is large. On the other hand, when the filling factor is small, molecular clouds align with the jet. The jet propagates faster in models with small filling factors.

Magnetohydrodynamic Simulations of the Formation of Molecular Clouds toward the Stellar Cluster Westerlund 2: Interaction of a Jet with a Clumpy Interstellar Medium

Energy Technology Data Exchange (ETDEWEB)

Asahina, Yuta; Kawashima, Tomohisa [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan); Furukawa, Naoko; Enokiya, Rei; Yamamoto, Hiroaki; Fukui, Yasuo [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan); Matsumoto, Ryoji, E-mail: asahina@cfca.jp [Department of Physics, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

2017-02-20

The formation mechanism of CO clouds observed with the NANTEN2 and Mopra telescopes toward the stellar cluster Westerlund 2 is studied by 3D magnetohydrodynamic simulations, taking into account the interstellar cooling. These molecular clouds show a peculiar shape composed of an arc-shaped cloud on one side of the TeV γ -ray source HESS J1023-575 and a linear distribution of clouds (jet clouds) on the other side. We propose that these clouds are formed by the interaction of a jet with clumps of interstellar neutral hydrogen (H i). By studying the dependence of the shape of dense cold clouds formed by shock compression and cooling on the filling factor of H i clumps, we found that the density distribution of H i clumps determines the shape of molecular clouds formed by the jet–cloud interaction: arc clouds are formed when the filling factor is large. On the other hand, when the filling factor is small, molecular clouds align with the jet. The jet propagates faster in models with small filling factors.

Temperature responses to the 11 year solar cycle in the mesosphere from the 31 year (1979-2010) extended Canadian Middle Atmosphere Model simulations and a comparison with the 14 year (2002-2015) TIMED/SABER observations

Science.gov (United States)

Gan, Quan; Du, Jian; Fomichev, Victor I.; Ward, William E.; Beagley, Stephen R.; Zhang, Shaodong; Yue, Jia

2017-04-01

A recent 31 year simulation (1979-2010) by extended Canadian Middle Atmosphere Model (eCMAM30) and the 14 year (2002-2015) observation by the Thermosphere Ionosphere Mesosphere and Dynamics/Sounding of the Atmosphere using Broadband Emssion Radiometry (TIMED/SABER) are utilized to investigate the temperature response to the 11 year solar cycle on the mesosphere. Overall, the zonal mean responses tend to increase with height, and the amplitudes are on the order of 1-2 K/100 solar flux unit (1 sfu = 10-22 W m-2 Hz-1) below 80 km and 2-4 K/100 sfu in the mesopause region (80-100 km) from the eCMAM30, comparatively weaker than those from the SABER except in the midlatitude lower mesosphere. A pretty good consistence takes place at around 75-80 km with a response of 1.5 K/100 sfu within 10°S/N. Also, a symmetric pattern of the responses about the equator agrees reasonably well between the two. It is noteworthy that the eCMAM30 displays an alternate structure with the upper stratospheric cooling and the lower mesospheric warming at midlatitudes of the winter hemisphere, in favor of the long-term Rayleigh lidar observation reported by the previous studies. Through diagnosing multiple dynamical parameters, it is manifested that this localized feature is induced by the anomalous residual circulation as a consequence of the wave-mean flow interaction during the solar maximum year.

Evaluation of Decision Trees for Cloud Detection from AVHRR Data

Science.gov (United States)

Shiffman, Smadar; Nemani, Ramakrishna

2005-01-01

Automated cloud detection and tracking is an important step in assessing changes in radiation budgets associated with global climate change via remote sensing. Data products based on satellite imagery are available to the scientific community for studying trends in the Earth's atmosphere. The data products include pixel-based cloud masks that assign cloud-cover classifications to pixels. Many cloud-mask algorithms have the form of decision trees. The decision trees employ sequential tests that scientists designed based on empirical astrophysics studies and simulations. Limitations of existing cloud masks restrict our ability to accurately track changes in cloud patterns over time. In a previous study we compared automatically learned decision trees to cloud masks included in Advanced Very High Resolution Radiometer (AVHRR) data products from the year 2000. In this paper we report the replication of the study for five-year data, and for a gold standard based on surface observations performed by scientists at weather stations in the British Islands. For our sample data, the accuracy of automatically learned decision trees was greater than the accuracy of the cloud masks p < 0.001.

Charging of mesospheric aerosol particles: the role of photodetachment and photoionization from meteoric smoke and ice particles

Directory of Open Access Journals (Sweden)

M. Rapp

2009-06-01

Full Text Available Time constants for photodetachment, photoemission, and electron capture are considered for two classes of mesospheric aerosol particles, i.e., meteor smoke particles (MSPs and pure water ice particles. Assuming that MSPs consist of metal oxides like Fe₂O₃ or SiO, we find that during daytime conditions photodetachment by solar photons is up to 4 orders of magnitude faster than electron attachment such that MSPs cannot be negatively charged in the presence of sunlight. Rather, even photoemission can compete with electron capture unless the electron density becomes very large (>>1000 cm⁻³ such that MSPs should either be positively charged or neutral in the case of large electron densities. For pure water ice particles, however, both photodetachment and photoemission are negligible due to the wavelength characteristics of its absorption cross section and because the flux of solar photons has already dropped significantly at such short wavelengths. This means that water ice particles should normally be negatively charged. Hence, our results can readily explain the repeated observation of the coexistence of positive and negative aerosol particles in the polar summer mesopause, i.e., small MSPs should be positively charged and ice particles should be negatively charged. These results have further important implications for our understanding of the nucleation of mesospheric ice particles as well as for the interpretation of incoherent scatter radar observations of MSPs.

Contrasting Cloud Composition Between Coupled and Decoupled Marine Boundary Layer Clouds

Science.gov (United States)

WANG, Z.; Mora, M.; Dadashazar, H.; MacDonald, A.; Crosbie, E.; Bates, K. H.; Coggon, M. M.; Craven, J. S.; Xian, P.; Campbell, J. R.; AzadiAghdam, M.; Woods, R. K.; Jonsson, H.; Flagan, R. C.; Seinfeld, J.; Sorooshian, A.

2016-12-01

Marine stratocumulus clouds often become decoupled from the vertical layer immediately above the ocean surface. This study contrasts cloud chemical composition between coupled and decoupled marine stratocumulus clouds. Cloud water and droplet residual particle composition were measured in clouds off the California coast during three airborne experiments in July-August of separate years (E-PEACE 2011, NiCE 2013, BOAS 2015). Decoupled clouds exhibited significantly lower overall mass concentrations in both cloud water and droplet residual particles, consistent with reduced cloud droplet number concentration and sub-cloud aerosol (Dp > 100 nm) number concentration, owing to detachment from surface sources. Non-refractory sub-micrometer aerosol measurements show that coupled clouds exhibit higher sulfate mass fractions in droplet residual particles, owing to more abundant precursor emissions from the ocean and ships. Consequently, decoupled clouds exhibited higher mass fractions of organics, nitrate, and ammonium in droplet residual particles, owing to effects of long-range transport from more distant sources. Total cloud water mass concentration in coupled clouds was dominated by sodium and chloride, and their mass fractions and concentrations exceeded those in decoupled clouds. Conversely, with the exception of sea salt constituents (e.g., Cl, Na, Mg, K), cloud water mass fractions of all species examined were higher in decoupled clouds relative to coupled clouds. These results suggest that an important variable is the extent to which clouds are coupled to the surface layer when interpreting microphysical data relevant to clouds and aerosol particles.

INFERENCE OF INHOMOGENEOUS CLOUDS IN AN EXOPLANET ATMOSPHERE

Energy Technology Data Exchange (ETDEWEB)

Demory, Brice-Olivier; De Wit, Julien; Lewis, Nikole; Zsom, Andras; Seager, Sara [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Fortney, Jonathan [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Knutson, Heather; Desert, Jean-Michel [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Heng, Kevin [Center for Space and Habitability, University of Bern, Sidlerstrasse 5, CH-3012, Bern (Switzerland); Madhusudhan, Nikku [Department of Physics and Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Gillon, Michael [Institut d' Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août, 17, Bat. B5C, B-4000 Liège 1 (Belgium); Barclay, Thomas [NASA Ames Research Center, M/S 244-30, Moffett Field, CA 94035 (United States); Parmentier, Vivien [Laboratoire J.-L. Lagrange, UMR 7293, Université de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d' Azur B.P. 4229, F-06304 Nice Cedex 4 (France); Cowan, Nicolas B., E-mail: demory@mit.edu [Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, F165, Evanston, IL 60208 (United States)

2013-10-20

We present new visible and infrared observations of the hot Jupiter Kepler-7b to determine its atmospheric properties. Our analysis allows us to (1) refine Kepler-7b's relatively large geometric albedo of Ag = 0.35 ± 0.02, (2) place upper limits on Kepler-7b thermal emission that remains undetected in both Spitzer bandpasses and (3) report a westward shift in the Kepler optical phase curve. We argue that Kepler-7b's visible flux cannot be due to thermal emission or Rayleigh scattering from H{sub 2} molecules. We therefore conclude that high altitude, optically reflective clouds located west from the substellar point are present in its atmosphere. We find that a silicate-based cloud composition is a possible candidate. Kepler-7b exhibits several properties that may make it particularly amenable to cloud formation in its upper atmosphere. These include a hot deep atmosphere that avoids a cloud cold trap, very low surface gravity to suppress cloud sedimentation, and a planetary equilibrium temperature in a range that allows for silicate clouds to potentially form in the visible atmosphere probed by Kepler. Our analysis does not only present evidence of optically thick clouds on Kepler-7b but also yields the first map of clouds in an exoplanet atmosphere.

Context-aware distributed cloud computing using CloudScheduler

Science.gov (United States)

Seuster, R.; Leavett-Brown, CR; Casteels, K.; Driemel, C.; Paterson, M.; Ring, D.; Sobie, RJ; Taylor, RP; Weldon, J.

2017-10-01

The distributed cloud using the CloudScheduler VM provisioning service is one of the longest running systems for HEP workloads. It has run millions of jobs for ATLAS and Belle II over the past few years using private and commercial clouds around the world. Our goal is to scale the distributed cloud to the 10,000-core level, with the ability to run any type of application (low I/O, high I/O and high memory) on any cloud. To achieve this goal, we have been implementing changes that utilize context-aware computing designs that are currently employed in the mobile communication industry. Context-awareness makes use of real-time and archived data to respond to user or system requirements. In our distributed cloud, we have many opportunistic clouds with no local HEP services, software or storage repositories. A context-aware design significantly improves the reliability and performance of our system by locating the nearest location of the required services. We describe how we are collecting and managing contextual information from our workload management systems, the clouds, the virtual machines and our services. This information is used not only to monitor the system but also to carry out automated corrective actions. We are incrementally adding new alerting and response services to our distributed cloud. This will enable us to scale the number of clouds and virtual machines. Further, a context-aware design will enable us to run analysis or high I/O application on opportunistic clouds. We envisage an open-source HTTP data federation (for example, the DynaFed system at CERN) as a service that would provide us access to existing storage elements used by the HEP experiments.

AceCloud: Molecular Dynamics Simulations in the Cloud.

Science.gov (United States)

Harvey, M J; De Fabritiis, G

2015-05-26

We present AceCloud, an on-demand service for molecular dynamics simulations. AceCloud is designed to facilitate the secure execution of large ensembles of simulations on an external cloud computing service (currently Amazon Web Services). The AceCloud client, integrated into the ACEMD molecular dynamics package, provides an easy-to-use interface that abstracts all aspects of interaction with the cloud services. This gives the user the experience that all simulations are running on their local machine, minimizing the learning curve typically associated with the transition to using high performance computing services.

VMware private cloud computing with vCloud director

CERN Document Server

Gallagher, Simon

2013-01-01

It's All About Delivering Service with vCloud Director Empowered by virtualization, companies are not just moving into the cloud, they're moving into private clouds for greater security, flexibility, and cost savings. However, this move involves more than just infrastructure. It also represents a different business model and a new way to provide services. In this detailed book, VMware vExpert Simon Gallagher makes sense of private cloud computing for IT administrators. From basic cloud theory and strategies for adoption to practical implementation, he covers all the issues. You'll lea

Scavenging of particulate elemental carbon into stratus cloud

Energy Technology Data Exchange (ETDEWEB)

Kaneyasu, Naoki; Maeda, Takahisa [National Inst. for Resources and Environment, Tsukuba (Japan)

1995-12-31

The role of atmospheric aerosols on the alternation of cloud radiative properties has widely been recognized since 1977 when Tomey and his coworkers have numerically demonstrated the effect of increased cloud condensation nuclei (CCN). At the same time, cloud processes are one of the most important factor in controlling the residence time of atmospheric aerosols through the wet removal process. The redistribution of the size and the composition of pre-cloud aerosols is also the important role of cloud process on the nature of atmospheric aerosols. In order to study these cloud-aerosol interaction phenomena, the incorporation of aerosols into cloud droplets is the first mechanism to be investigated. Among the several mechanisms for the incorporation of aerosols into cloud droplets, nucleation scavenging, is the potentially important process in the view of cloud-aerosol interactions. This critical supersaturation for a given radius of a particle can be theoretically calculated only for pure species, e.g., NaCl. However, a significant portion of the atmospheric aerosols is in the form of internal mixture of multiple components, such as SO{sub 4}{sup 2-}, NO{sub 3}{sup -}, NH{sub 4}{sup +} and particulate elemental carbon. The knowledge acquired by field measurements is therefore essential on this subject. The present study focuses on the scavenging of major components of urban atmospheric aerosols, in particular the incorporation of particulate elemental carbon into stratus cloud. Particulate elemental carbon is the strongest light absorbing species in visible region, and has potential to change the optical property of cloud. On the basis of the measurements conducted at a mountain located in the suburb of Tokyo Metropolitan area, Japan, some insights on the scavenging of particulate elemental carbon into cloud droplet will be presented

Scavenging of particulate elemental carbon into stratus cloud

Energy Technology Data Exchange (ETDEWEB)

Kaneyasu, Naoki; Maeda, Takahisa [National Inst. for Resources and Environment, Tsukuba (Japan)

1996-12-31

The role of atmospheric aerosols on the alternation of cloud radiative properties has widely been recognized since 1977 when Tomey and his coworkers have numerically demonstrated the effect of increased cloud condensation nuclei (CCN). At the same time, cloud processes are one of the most important factor in controlling the residence time of atmospheric aerosols through the wet removal process. The redistribution of the size and the composition of pre-cloud aerosols is also the important role of cloud process on the nature of atmospheric aerosols. In order to study these cloud-aerosol interaction phenomena, the incorporation of aerosols into cloud droplets is the first mechanism to be investigated. Among the several mechanisms for the incorporation of aerosols into cloud droplets, nucleation scavenging, is the potentially important process in the view of cloud-aerosol interactions. This critical supersaturation for a given radius of a particle can be theoretically calculated only for pure species, e.g., NaCl. However, a significant portion of the atmospheric aerosols is in the form of internal mixture of multiple components, such as SO{sub 4}{sup 2-}, NO{sub 3}{sup -}, NH{sub 4}{sup +} and particulate elemental carbon. The knowledge acquired by field measurements is therefore essential on this subject. The present study focuses on the scavenging of major components of urban atmospheric aerosols, in particular the incorporation of particulate elemental carbon into stratus cloud. Particulate elemental carbon is the strongest light absorbing species in visible region, and has potential to change the optical property of cloud. On the basis of the measurements conducted at a mountain located in the suburb of Tokyo Metropolitan area, Japan, some insights on the scavenging of particulate elemental carbon into cloud droplet will be presented

Department of Defense Use of Commercial Cloud Computing Capabilities and Services

Science.gov (United States)

2015-11-01

models (Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service ( SaaS )), and four deployment models (Public...NIST defines three main models for cloud computing: IaaS, PaaS, and SaaS . These models help differentiate the implementation responsibilities that fall...and SaaS . 3. Public, Private, Community, and Hybrid Clouds Cloud services come in different forms, depending on the customer’s specific needs

Climatology and trends of mesospheric (58-90) temperatures based upon 1982-1986 SME limb scattering profiles

Science.gov (United States)

Clancy, R. Todd; Rusch, David W.

1989-01-01

Atmospheric temperature profiles for the altitude range 58-90 km were calculated using data on global UV limb radiances from the SME satellite. The major elements of this climatology include a high vertical resolution (about 4 km) and the coverage of the 70-90 km altitude region. The analysis of this extensive data set provides a global definition of mesospheric-lower thermospheric temperature trends over the 1982-1986 period. The observations suggest a pattern of 1-2 K/year decreases in temperatures at 80-90-km altitudes accompanied by 0.5-1.5 K/year increases in temperatures at 65-80-km altitudes.

Carbon monoxide in clouds at low metallicity in the dwarf irregular galaxy WLM.

Science.gov (United States)

Elmegreen, Bruce G; Rubio, Monica; Hunter, Deidre A; Verdugo, Celia; Brinks, Elias; Schruba, Andreas

2013-03-28

Carbon monoxide (CO) is the primary tracer for interstellar clouds where stars form, but it has never been detected in galaxies in which the oxygen abundance relative to hydrogen is less than 20 per cent of that of the Sun, even though such 'low-metallicity' galaxies often form stars. This raises the question of whether stars can form in dense gas without molecules, cooling to the required near-zero temperatures by atomic transitions and dust radiation rather than by molecular line emission; and it highlights uncertainties about star formation in the early Universe, when the metallicity was generally low. Here we report the detection of CO in two regions of a local dwarf irregular galaxy, WLM, where the metallicity is 13 per cent of the solar value. We use new submillimetre observations and archival far-infrared observations to estimate the cloud masses, which are both slightly greater than 100,000 solar masses. The clouds have produced stars at a rate per molecule equal to 10 per cent of that in the local Orion nebula cloud. The CO fraction of the molecular gas is also low, about 3 per cent of the Milky Way value. These results suggest that in small galaxies both star-forming cores and CO molecules become increasingly rare in molecular hydrogen clouds as the metallicity decreases.

Magnetic seismology of interstellar gas clouds: Unveiling a hidden dimension.

Science.gov (United States)

Tritsis, Aris; Tassis, Konstantinos

2018-05-11

Stars and planets are formed inside dense interstellar molecular clouds by processes imprinted on the three-dimensional (3D) morphology of the clouds. Determining the 3D structure of interstellar clouds remains challenging because of projection effects and difficulties measuring the extent of the clouds along the line of sight. We report the detection of normal vibrational modes in the isolated interstellar cloud Musca, allowing determination of the 3D physical dimensions of the cloud. We found that Musca is vibrating globally, with the characteristic modes of a sheet viewed edge on, not the characteristics of a filament as previously supposed. We reconstructed the physical properties of Musca through 3D magnetohydrodynamic simulations, reproducing the observed normal modes and confirming a sheetlike morphology. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Resolving the mesospheric nighttime 4.3 µm emission puzzle: comparison of the CO2(ν3) and OH(ν) emission models

Science.gov (United States)

Panka, Peter A.; Kutepov, Alexander A.; Kalogerakis, Konstantinos S.; Janches, Diego; Russell, James M.; Rezac, Ladislav; Feofilov, Artem G.; Mlynczak, Martin G.; Yiğit, Erdal

2017-08-01

In the 1970s, the mechanism of vibrational energy transfer from chemically produced OH(ν) in the nighttime mesosphere to the CO2(ν3) vibration, OH(ν) ⇒ N2(ν) ⇒ CO2(ν3), was proposed. In later studies it was shown that this "direct" mechanism for simulated nighttime 4.3 µm emissions of the mesosphere is not sufficient to explain space observations. In order to better simulate these observations, an additional enhancement is needed that would be equivalent to the production of 2.8-3 N2(1) molecules instead of one N2(1) molecule in each quenching reaction of OH(ν) + N2(0). Recently a new "indirect" channel of the OH(ν) energy transfer to N2(ν) vibrations, OH(ν) ⇒ O(1D) ⇒ N2(ν), was suggested and then confirmed in a laboratory experiment, where its rate for OH(ν = 9) + O(3P) was measured. We studied in detail the impact of the "direct" and "indirect" mechanisms on CO2(ν3) and OH(ν) vibrational level populations and emissions. We also compared our calculations with (a) the SABER/TIMED nighttime 4.3 µm CO2 and OH 1.6 and 2.0 µm limb radiances of the mesosphere-lower thermosphere (MLT) and (b) with ground- and space-based observations of OH(ν) densities in the nighttime mesosphere. We found that the new "indirect" channel provides a strong enhancement of the 4.3 µm CO2 emission, which is comparable to that obtained with the "direct" mechanism alone but assuming an efficiency that is 3 times higher. The model based on the "indirect" channel also produces OH(ν) density distributions which are in good agreement with both SABER limb OH emission observations and ground and space measurements. This is, however, not true for the model which relies on the "direct" mechanism alone. This discrepancy is caused by the lack of an efficient redistribution of the OH(ν) energy from higher vibrational levels emitting at 2.0 µm to lower levels emitting at 1.6 µm. In contrast, the new  indirect  mechanism efficiently removes at least five quanta in each

Giant molecular cloud collisions as triggers of star formation. VI. Collision-induced turbulence

Science.gov (United States)

Wu, Benjamin; Tan, Jonathan C.; Nakamura, Fumitaka; Christie, Duncan; Li, Qi

2018-05-01

We investigate collisions between giant molecular clouds (GMCs) as potential generators of their internal turbulence. Using magnetohydrodynamic (MHD) simulations of self-gravitating, magnetized, turbulent GMCs, we compare kinematic and dynamic properties of dense gas structures formed when such clouds collide compared to those that form in non-colliding clouds as self-gravity overwhelms decaying turbulence. We explore the nature of turbulence in these structures via distribution functions of density, velocity dispersions, virial parameters, and momentum injection. We find that the dense clumps formed from GMC collisions have higher effective Mach number, greater overall velocity dispersions, sustain near-virial equilibrium states for longer times, and are the conduit for the injection of turbulent momentum into high density gas at high rates.

The Spitzer Survey of Interstellar Clouds in the Gould Belt. VI. The Auriga-California Molecular Cloud Observed with IRAC and MIPS

Science.gov (United States)

Broekhoven-Fiene, Hannah; Matthews, Brenda C.; Harvey, Paul M.; Gutermuth, Robert A.; Huard, Tracy L.; Tothill, Nicholas F. H.; Nutter, David; Bourke, Tyler L.; DiFrancesco, James; Jorgensen, Jes K.;

THE MAGELLANIC INTER-CLOUD PROJECT (MAGIC). I. EVIDENCE FOR INTERMEDIATE-AGE STELLAR POPULATIONS IN BETWEEN THE MAGELLANIC CLOUDS

Energy Technology Data Exchange (ETDEWEB)

Noeel, N. E. D.; Read, J. I. [ETH Zuerich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland); Conn, B. C.; Rix, H.-W. [Max Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany); Carrera, R. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38200, La Laguna, Tenerife (Spain); Dolphin, A., E-mail: noelia@phys.ethz.ch [Raytheon Company, P.O. Box 11337, Tucson, AZ 85734-1337 (United States)

2013-05-10

The origin of the gas in between the Magellanic Clouds (MCs)-known as the ''Magellanic Bridge'' (MB)-is puzzling. Numerical simulations suggest that the MB formed from tidally stripped gas and stars in a recent interaction between the MCs. However, the apparent lack of stripped intermediate- or old-age stars associated with the MB is at odds with this picture. In this paper, we present the first results from the MAGellanic Inter-Cloud program (MAGIC) aimed at probing the stellar populations in the inter-Cloud region. We present observations of the stellar populations in two large fields located in between the Large and Small Magellanic Clouds (LMC/SMC), secured using the WFI camera on the 2.2 m telescope in La Silla. Using a synthetic color-magnitude diagram technique, we present the first quantitative evidence for the presence of intermediate-age and old stars in the inter-Cloud region. The intermediate-age stars-which make up {approx}28% of all stars in the region-are not present in fields at a similar distance from the SMC in a direction pointing away from the LMC. This provides potential evidence that these intermediate-age stars could have been tidally stripped from the SMC. However, spectroscopic studies will be needed to confirm or rule out the tidal origin for the inter-Cloud gas and stars.

Transport of mesospheric H2O during and after the stratospheric sudden warming of January 2010: observation and simulation

Directory of Open Access Journals (Sweden)

A. K. Smith

2012-06-01

Full Text Available The transportable ground based microwave radiometer MIAWARA-C monitored the upper stratospheric and lower mesospheric (USLM water vapor distribution over Sodankylä, Finland (67.4° N, 26.6° E from January to June 2010. At the end of January, approximately 2 weeks after MIAWARA-C's start of operation in Finland, a stratospheric sudden warming (SSW disturbed the circulation of the middle atmosphere. Shortly after the onset of the SSW water vapor rapidly increased at pressures between 1 and 0.01 hPa. Backward trajectory calculations show that this strong increase is due to the breakdown of the polar vortex and meridional advection of subtropical air to the Arctic USLM region. In addition, mesospheric upwelling in the course of the SSW led to an increase in observed water vapor between 0.1 and 0.03 hPa. After the SSW MIAWARA-C observed a decrease in mesospheric water vapor volume mixing ratio (VMR due to the subsidence of H2O poor air masses in the polar region. Backward trajectory analysis and the zonal mean water vapor distribution from the Microwave Limb Sounder on the Aura satellite (Aura/MLS indicate the occurrence of two regimes of circulation from 50° N to the North Pole: (1 regime of enhanced meridional mixing throughout February and (2 regime of an eastward circulation in the USLM region reestablished between early March and the equinox. The polar descent rate determined from MIAWARA-C's 5.2 parts per million volume (ppmv isopleth is 350 ± 40 m d−1 in the pressure range 0.6 to 0.06 hPa between early February and early March. For the same time interval the descent rate in the same pressure range was determined using Transformed Eulerian Mean (TEM wind fields simulated by means of the Whole Atmosphere Community Climate Model with Specified Dynamics (SD-WACCM. The average value of the SD-WACCM TEM vertical wind is 325 m d−1 while the along trajectory vertical displacement is 335 m d−1. The similar descent rates found indicate good

Creating cloud-free Landsat ETM+ data sets in tropical landscapes: cloud and cloud-shadow removal

Science.gov (United States)

Sebastián Martinuzzi; William A. Gould; Olga M. Ramos Gonzalez

2007-01-01

Clouds and cloud shadows are common features of visible and infrared remotelysensed images collected from many parts of the world, particularly in humid and tropical regions. We have developed a simple and semiautomated method to mask clouds and shadows in Landsat ETM+ imagery, and have developed a recent cloud-free composite of multitemporal images for Puerto Rico and...

Privacy Penetration Testing: How to Establish Trust in Your Cloud Provider

DEFF Research Database (Denmark)

Probst, Christian W.; Sasse, M. Angela; Pieters, Wolter

2012-01-01

In the age of cloud computing, IT infrastructure becomes virtualised and takes the form of services. This virtualisation results in an increasing de-perimeterisation, where the location of data and computation is irrelevant from a user’s point of view. This irrelevance means that private...... and institutional users no longer have a concept of where their data is stored, and whether they can trust in cloud providers to protect their data. In this chapter, we investigate methods for increasing customers’ trust into cloud providers, and suggest a public penetration-testing agency as an essential component...... in a trustworthy cloud infrastructure....

Interstellar clouds and the formation of stars

Energy Technology Data Exchange (ETDEWEB)

Alfven, H; Carlqvist, P [Kungliga Tekniska Hoegskolan, Stockholm (Sweden). Institutionen foer Plasmafysik

1978-05-01

Part I gives a survey of the drastic revision of cosmic plasma physics which is precipitated by the exploration of the magnetosphere through in situ measurements. The 'pseudo-plasma formalism', which until now has almost completely dominated theoretical astrophysics, must be replaced by an experimentally based approach involving the introduction of a number of neglected plasma phenomena, such as electric double layers, critical velocity, and pinch effect. The general belief that star light is the main ionizer is shown to be doubtful; hydromagnetic conversion of gravitational and kinetic energy may often be much more important. In Part II the revised plasma physics is applied to dark clouds and star formation. Magnetic fields do not necessarily counteract the contraction of a cloud; they may just as well 'pinch' the cloud. Magnetic compression may be the main mechanism for forming interstellar clouds and keeping them together. Part III treats the formation of stars in a dusty cosmic plasma cloud. Star formation is due to an instability, but it is very unlikely that it has anything to do with the Jeans instability. A reasonable mechanism is that the sedimentation of 'dust' (including solid bodies of different size) is triggering off a gravitationally assisted accretion. A 'stellesimal' accretion analogous to the planetesimal accretion leads to the formation of a star surrounded by a very low density hollow in the cloud. Matter falling in from the cloud towards the star is the raw material for the formation of planets and satellites.

Joint Hybrid Backhaul and Access Links Design in Cloud-Radio Access Networks

KAUST Repository

Dhifallah, Oussama Najeeb; Dahrouj, Hayssam; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

2015-01-01

The cloud-radio access network (CRAN) is expected to be the core network architecture for next generation mobile radio systems. In this paper, we consider the downlink of a CRAN formed of one central processor (the cloud) and several base station

Electron-microscope study of cloud and fog nuclei

Energy Technology Data Exchange (ETDEWEB)

Ogiwara, S; Okita, T

1952-01-01

Droplets of clouds on a mountain and of fog in an urban area were captured and the form, nature and size of their nuclei were studied by means of an electron-microscope and by a chamber of constant humidity. These nuclei have similar form and nature to the hygroscopic particles in haze and to the artificially produced combustion particles. No sea-salt nuclei were found in our observations, therefore, sea-spray appears to be an insignificant source of condensation nuclei. It was found that both the cloud and the fog nuclei originated in combustion products which were the mixture of hygroscopic and non-hygroscopic substances, and that the greater part of the nuclei did not contain pure sulfuric acid.

The challenge of networked enterprises for cloud computing interoperability

OpenAIRE

Mezgár, István; Rauschecker, Ursula

2014-01-01

Manufacturing enterprises have to organize themselves into effective system architectures forming different types of Networked Enterprises (NE) to match fast changing market demands. Cloud Computing (CC) is an important up to date computing concept for NE, as it offers significant financial and technical advantages beside high-level collaboration possibilities. As cloud computing is a new concept the solutions for handling interoperability, portability, security, privacy and standardization c...

Photogrammetric Analysis of Rotor Clouds Observed during T-REX

Science.gov (United States)

Romatschke, U.; Grubišić, V.

2017-12-01

Stereo photogrammetric analysis is a rarely utilized but highly valuable tool for studying smaller, highly ephemeral clouds. In this study, we make use of data that was collected during the Terrain-induced Rotor Experiment (T-REX), which took place in Owens Valley, eastern California, in the spring of 2006. The data set consists of matched digital stereo photographs obtained at high temporal (on the order of seconds) and spatial resolution (limited by the pixel size of the cameras). Using computer vision techniques we have been able to develop algorithms for camera calibration, automatic feature matching, and ultimately reconstruction of 3D cloud scenes. Applying these techniques to images from different T-REX IOPs we capture the motion of clouds in several distinct mountain wave scenarios ranging from short lived lee wave clouds on an otherwise clear sky day to rotor clouds formed in an extreme turbulence environment with strong winds and high cloud coverage. Tracking the clouds in 3D space and time allows us to quantify phenomena such as vertical and horizontal movement of clouds, turbulent motion at the upstream edge of rotor clouds, the structure of the lifting condensation level, extreme wind shear, and the life cycle of clouds in lee waves. When placed into context with the existing literature that originated from the T-REX field campaign, our results complement and expand our understanding of the complex dynamics observed in a variety of different lee wave settings.

Zen of cloud learning cloud computing by examples on Microsoft Azure

CERN Document Server

Bai, Haishi

2014-01-01

Zen of Cloud: Learning Cloud Computing by Examples on Microsoft Azure provides comprehensive coverage of the essential theories behind cloud computing and the Windows Azure cloud platform. Sharing the author's insights gained while working at Microsoft's headquarters, it presents nearly 70 end-to-end examples with step-by-step guidance on implementing typical cloud-based scenarios.The book is organized into four sections: cloud service fundamentals, cloud solutions, devices and cloud, and system integration and project management. Each chapter contains detailed exercises that provide readers w

Cloud based emergency health care information service in India.

Science.gov (United States)

Karthikeyan, N; Sukanesh, R

2012-12-01

A hospital is a health care organization providing patient treatment by expert physicians, surgeons and equipments. A report from a health care accreditation group says that miscommunication between patients and health care providers is the reason for the gap in providing emergency medical care to people in need. In developing countries, illiteracy is the major key root for deaths resulting from uncertain diseases constituting a serious public health problem. Mentally affected, differently abled and unconscious patients can't communicate about their medical history to the medical practitioners. Also, Medical practitioners can't edit or view DICOM images instantly. Our aim is to provide palm vein pattern recognition based medical record retrieval system, using cloud computing for the above mentioned people. Distributed computing technology is coming in the new forms as Grid computing and Cloud computing. These new forms are assured to bring Information Technology (IT) as a service. In this paper, we have described how these new forms of distributed computing will be helpful for modern health care industries. Cloud Computing is germinating its benefit to industrial sectors especially in medical scenarios. In Cloud Computing, IT-related capabilities and resources are provided as services, via the distributed computing on-demand. This paper is concerned with sprouting software as a service (SaaS) by means of Cloud computing with an aim to bring emergency health care sector in an umbrella with physical secured patient records. In framing the emergency healthcare treatment, the crucial thing considered necessary to decide about patients is their previous health conduct records. Thus a ubiquitous access to appropriate records is essential. Palm vein pattern recognition promises a secured patient record access. Likewise our paper reveals an efficient means to view, edit or transfer the DICOM images instantly which was a challenging task for medical practitioners in the

THE PHYSICAL CONDITIONS IN A PRE-SUPER STAR CLUSTER MOLECULAR CLOUD IN THE ANTENNAE GALAXIES

International Nuclear Information System (INIS)

Johnson, K. E.; Indebetouw, R.; Evans, A. S.; Leroy, A. K.; Brogan, C. L.; Hibbard, J.; Sheth, K.; Whitmore, B. C.

2015-01-01

We present an analysis of the physical conditions in an extreme molecular cloud in the Antennae merging galaxies. This cloud has properties consistant with those required to form a globular cluster. We have obtained ALMA CO and 870 μm observations of the Antennae galaxy system with ∼0.″5 resolution. This cloud stands out in the data with a radius of ≲24 pc and mass of >5 × 10 6 M ⊙ . The cloud appears capable of forming a globular cluster, but the lack of associated thermal radio emission indicates that star formation has not yet altered the environment. The lack of thermal radio emission places the cloud in an early stage of evolution, which we expect to be short-lived (≲1 Myr) and thus rare. Given its mass and kinetic energy, for the cloud to be confined (as its appearance strongly suggests) it must be subject to an external pressure of P/k B ≳ 10 8 K cm −3 –10,000 times higher than typical interstellar pressure. This would support theories that high pressures are required to form globular clusters and may explain why extreme environments like the Antennae are preferred environments for generating such objects. Given the cloud temperature of ∼25 K, the internal pressure must be dominated by non-thermal processes, most likely turbulence. We expect the molecular cloud to collapse and begin star formation in ≲1 Myr

TURBULENCE DECAY AND CLOUD CORE RELAXATION IN MOLECULAR CLOUDS

International Nuclear Information System (INIS)

Gao, Yang; Law, Chung K.; Xu, Haitao

2015-01-01

The turbulent motion within molecular clouds is a key factor controlling star formation. Turbulence supports molecular cloud cores from evolving to gravitational collapse and hence sets a lower bound on the size of molecular cloud cores in which star formation can occur. On the other hand, without a continuous external energy source maintaining the turbulence, such as in molecular clouds, the turbulence decays with an energy dissipation time comparable to the dynamic timescale of clouds, which could change the size limits obtained from Jean's criterion by assuming constant turbulence intensities. Here we adopt scaling relations of physical variables in decaying turbulence to analyze its specific effects on the formation of stars. We find that the decay of turbulence provides an additional approach for Jeans' criterion to be achieved, after which gravitational infall governs the motion of the cloud core. This epoch of turbulence decay is defined as cloud core relaxation. The existence of cloud core relaxation provides a more complete understanding of the effect of the competition between turbulence and gravity on the dynamics of molecular cloud cores and star formation

COMPARATIVE STUDY OF CLOUD COMPUTING AND MOBILE CLOUD COMPUTING

OpenAIRE

Nidhi Rajak*, Diwakar Shukla

2018-01-01

Present era is of Information and Communication Technology (ICT) and there are number of researches are going on Cloud Computing and Mobile Cloud Computing such security issues, data management, load balancing and so on. Cloud computing provides the services to the end user over Internet and the primary objectives of this computing are resource sharing and pooling among the end users. Mobile Cloud Computing is a combination of Cloud Computing and Mobile Computing. Here, data is stored in...

Review of Cloud Computing and existing Frameworks for Cloud adoption

OpenAIRE

Chang, Victor; Walters, Robert John; Wills, Gary

2014-01-01

This paper presents a selected review for Cloud Computing and explains the benefits and risks of adopting Cloud Computing in a business environment. Although all the risks identified may be associated with two major Cloud adoption challenges, a framework is required to support organisations as they begin to use Cloud and minimise risks of Cloud adoption. Eleven Cloud Computing frameworks are investigated and a comparison of their strengths and limitations is made; the result of the comparison...

Prototyping manufacturing in the cloud

Science.gov (United States)

Ciortea, E. M.

2017-08-01

This paper attempts a theoretical approach to cloud systems with impacts on production systems. I call systems as cloud computing because form a relatively new concept in the field of informatics, representing an overall distributed computing services, applications, access to information and data storage without the user to know the physical location and configuration of systems. The advantages of this approach are especially computing speed and storage capacity without investment in additional configurations, synchronizing user data, data processing using web applications. The disadvantage is that it wants to identify a solution for data security, leading to mistrust users. The case study is applied to a module of the system of production, because the system is complex.

ON THE STAR FORMATION RATES IN MOLECULAR CLOUDS

International Nuclear Information System (INIS)

Lada, Charles J.; Lombardi, Marco; Alves, Joao F.

2010-01-01

In this paper, we investigate the level of star formation activity within nearby molecular clouds. We employ a uniform set of infrared extinction maps to provide accurate assessments of cloud mass and structure and compare these with inventories of young stellar objects within the clouds. We present evidence indicating that both the yield and rate of star formation can vary considerably in local clouds, independent of their mass and size. We find that the surface density structure of such clouds appears to be important in controlling both these factors. In particular, we find that the star formation rate (SFR) in molecular clouds is linearly proportional to the cloud mass (M 0.8 ) above an extinction threshold of A K ∼ 0.8 mag, corresponding to a gas surface density threshold of Σ gas ∼ 116 M sun pc 2 . We argue that this surface density threshold corresponds to a gas volume density threshold which we estimate to be n(H 2 ) ∼ 10 4 cm -3 . Specifically, we find SFR (M sun yr -1 ) = 4.6 ± 2.6 x 10 -8 M 0.8 (M sun ) for the clouds in our sample. This relation between the rate of star formation and the amount of dense gas in molecular clouds appears to be in excellent agreement with previous observations of both galactic and extragalactic star-forming activity. It is likely the underlying physical relationship or empirical law that most directly connects star formation activity with interstellar gas over many spatial scales within and between individual galaxies. These results suggest that the key to obtaining a predictive understanding of the SFRs in molecular clouds and galaxies is to understand those physical factors which give rise to the dense components of these clouds.

Decentralized Group Sparse Beamforming for Multi-Cloud Radio Access Networks

KAUST Repository

Dhifallah, Oussama Najeeb

2015-12-06

Recent studies on cloud-radio access networks (CRANs) assume the availability of a single processor (cloud) capable of managing the entire network performance; inter-cloud interference is treated as background noise. This paper considers the more practical scenario of the downlink of a CRAN formed by multiple clouds, where each cloud is connected to a cluster of multiple-antenna base stations (BSs) via high-capacity wireline backhaul links. The network is composed of several disjoint BSs\\' clusters, each serving a pre-known set of single-antenna users. To account for both inter- cloud and intra-cloud interference, the paper considers the problem of minimizing the total network power consumption subject to quality of service constraints, by jointly determining the set of active BSs connected to each cloud and the beamforming vectors of every user across the network. The paper solves the problem using Lagrangian duality theory through a dual decomposition approach, which decouples the problem into multiple and independent subproblems, the solution of which depends on the dual optimization problem. The solution then proceeds in updating the dual variables and the active set of BSs at each cloud iteratively. The proposed approach leads to a distributed implementation across the multiple clouds through a reasonable exchange of information between adjacent clouds. The paper further proposes a centralized solution to the problem. Simulation results suggest that the proposed algorithms significantly outperform the conventional per-cloud update solution, especially at high signal-to-interference-plus- noise ratio (SINR) target.

THE BOLOCAM GALACTIC PLANE SURVEY. III. CHARACTERIZING PHYSICAL PROPERTIES OF MASSIVE STAR-FORMING REGIONS IN THE GEMINI OB1 MOLECULAR CLOUD

International Nuclear Information System (INIS)

Dunham, Miranda K.; Evans, Neal J.; Harvey, Paul; Merello, Manuel; Rosolowsky, Erik; Cyganowski, Claudia J.; Aguirre, James; Bally, John; Battersby, Cara; Ginsburg, Adam; Glenn, Jason; Stringfellow, Guy S.; Bradley, Eric Todd; Dowell, Darren; Drosback, Meredith; Schlingman, Wayne; Shirley, Yancy L.; Walawender, Josh; Williams, Jonathan P.

2010-01-01

We present the 1.1 mm Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1 molecular cloud complex, and targeted NH 3 observations of the BGPS sources. When paired with molecular spectroscopy of a dense gas tracer, millimeter observations yield physical properties such as masses, radii, mean densities, kinetic temperatures, and line widths. We detect 34 distinct BGPS sources above 5σ = 0.37 Jy beam -1 with corresponding 5σ detections in the NH 3 (1,1) transition. Eight of the objects show water maser emission (20%). We find a mean millimeter source FWHM of 1.12 pc and a mean gas kinetic temperature of 20 K for the sample of 34 BGPS sources with detections in the NH 3 (1,1) line. The observed NH 3 line widths are dominated by non-thermal motions, typically found to be a few times the thermal sound speed expected for the derived kinetic temperature. We calculate the mass for each source from the millimeter flux assuming the sources are isothermal and find a mean isothermal mass within a 120'' aperture of 230 ± 180 M sun . We find a total mass of 8400 M sun for all BGPS sources in the Gemini OB1 molecular cloud, representing 6.5% of the cloud mass. By comparing the millimeter isothermal mass to the virial mass calculated from the NH 3 line widths within a radius equal to the millimeter source size, we find a mean virial parameter (M vir /M iso ) of 1.0 ± 0.9 for the sample. We find mean values for the distributions of column densities of 1.0 x 10 22 cm -2 for H 2 , and 3.0 x 10 14 cm -2 for NH 3 , giving a mean NH 3 abundance of 3.0 x 10 -8 relative to H 2 . We find volume-averaged densities on the order of 10 3 -10 4 cm -3 . The sizes and densities suggest that in the Gem OB1 region the BGPS is detecting the clumps from which stellar clusters form, rather than smaller, higher density cores where single stars or small multiple systems form.

Turbulence and star formation in molecular clouds

International Nuclear Information System (INIS)

Larson, R.B.

1981-01-01

Data for many molecular clouds and condensations show that the internal velocity dispersion of each region is well correlated with its size and mass, and these correlations are approximately of power-law form. The dependence of velocity dispersion on region size is similar to the Kolmogoroff law for subsonic turbulence, suggesting that the observed motions are all part of a common hierarchy of interstellar turbulent motions. The regions studied are mostly gravitationally bound and in approximate virial equilibrium. However, they cannot have formed by simple gravitational collapse, and it appears likely that molecular clouds and their substructures have been created at least partly by processes of supersonic hydrodynamics. The hierarchy of subcondensations may terminate with objects so small that their internal motions are no longer supersonic; this predicts a minimum protostellar mass of the order of a few tenths of a solar mass. Massive 'protostellar' clumps always have supersonic internal motions and will therefore develop complex internal structures, probably leading to the formation of many pre-stellar condensation nuclei that grow by accretion to produce the final stellar mass spectrum. Molecular clouds must be transient structures, and are probably dispersed after not much more than 10 7 yr. (author)

FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN): Molecular clouds toward W 33; possible evidence for a cloud-cloud collision triggering O star formation

Science.gov (United States)

Kohno, Mikito; Torii, Kazufumi; Tachihara, Kengo; Umemoto, Tomofumi; Minamidani, Tetsuhiro; Nishimura, Atsushi; Fujita, Shinji; Matsuo, Mitsuhiro; Yamagishi, Mitsuyoshi; Tsuda, Yuya; Kuriki, Mika; Kuno, Nario; Ohama, Akio; Hattori, Yusuke; Sano, Hidetoshi; Yamamoto, Hiroaki; Fukui, Yasuo

2018-05-01

We observed molecular clouds in the W 33 high-mass star-forming region associated with compact and extended H II regions using the NANTEN2 telescope as well as the Nobeyama 45 m telescope in the J = 1-0 transitions of 12CO, 13CO, and C18O as part of the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN) legacy survey. We detected three velocity components at 35 km s-1, 45 km s-1, and 58 km s-1. The 35 km s-1 and 58 km s-1 clouds are likely to be physically associated with W 33 because of the enhanced 12CO J = 3-2 to J = 1-0 intensity ratio as R_3-2/1-0} > 1.0 due to the ultraviolet irradiation by OB stars, and morphological correspondence between the distributions of molecular gas and the infrared and radio continuum emissions excited by high-mass stars. The two clouds show complementary distributions around W 33. The velocity separation is too large to be gravitationally bound, and yet not explained by expanding motion by stellar feedback. Therefore, we discuss whether a cloud-cloud collision scenario likely explains the high-mass star formation in W 33.

Cloud CCN feedback

International Nuclear Information System (INIS)

Hudson, J.G.

1992-01-01

Cloud microphysics affects cloud albedo precipitation efficiency and the extent of cloud feedback in response to global warming. Compared to other cloud parameters, microphysics is unique in its large range of variability and the fact that much of the variability is anthropogenic. Probably the most important determinant of cloud microphysics is the spectra of cloud condensation nuclei (CCN) which display considerable variability and have a large anthropogenic component. When analyzed in combination three field observation projects display the interrelationship between CCN and cloud microphysics. CCN were measured with the Desert Research Institute (DRI) instantaneous CCN spectrometer. Cloud microphysical measurements were obtained with the National Center for Atmospheric Research Lockheed Electra. Since CCN and cloud microphysics each affect the other a positive feedback mechanism can result

The dependence of stellar properties on initial cloud density

Science.gov (United States)

Jones, Michael O.; Bate, Matthew R.

2018-05-01

We investigate the dependence of stellar properties on the initial mean density of the molecular cloud in which stellar clusters form using radiation hydrodynamical simulations that resolve the opacity limit for fragmentation. We have simulated the formation of three star clusters from the gravitational collapse of molecular clouds whose densities vary by a factor of a hundred. As with previous calculations including radiative feedback, we find that the dependence of the characteristic stellar mass, Mc, on the initial mean density of the cloud, ρ, is weaker than the dependence of the thermal Jeans mass. However, unlike previous calculations, which found no statistically significant variation in the median mass with density, we find a weak dependence approximately of the form Mc∝ρ-1/5. The distributions of properties of multiple systems do not vary significantly between the calculations. We compare our results to the result of observational surveys of star-forming regions, and suggest that the similarities between the properties of our lowest density calculation and the nearby Taurus-Auriga region indicate that the apparent excess of solar-type stars observed may be due to the region's low density.

Interstellar clouds and the formation of stars

International Nuclear Information System (INIS)

Alfen, H.; Carlqvist, P.

1977-12-01

The 'pseudo-plasma formalism' which up to now has almost completely dominated theoretical astrophysics must be replaced by an experimentally based approach, involving the introduction of a number of neglected plasma phenomena, such as electric double layers, critical velocity, and pinch effect. The general belief that star light is the main ionizer is shown to be doubtful; hydromagnetic conversion of gravitational and kinetic energy may often be much more important. The revised plasma physics is applied to dark clouds and star formation. Magnetic fields do not necessarily counteract the contraction of a cloud, they may just as well 'pinch' the cloud. Magnetic compression may be the main mechanism for forming interstellar clouds and keeping them together. Star formation is due to an instability, but it is very unlikely that it has anything to do with the Jeans instablility. A reasonable mechanism is that the sedimentation of 'dust' (including solid bodies of different size) is triggering off a gravitationally assisted accretion. The study of the evolution of a dark cloud leads to a scenario of planet formation which is reconcilable with the results obtained from studies based on solar system data. This means that the new approach to cosmical plasma physics discussed logically leads to a consistent picture of the evolution of dark clouds and the formation of solar systems

Simulations of large winds and wind shears induced by gravity wave breaking in the mesosphere and lower thermosphere (MLT) region

OpenAIRE

X. Liu; X. Liu; J. Xu; H.-L. Liu; J. Yue; W. Yuan

2014-01-01

Using a fully nonlinear two-dimensional (2-D) numerical model, we simulated gravity waves (GWs) breaking and their contributions to the formation of large winds and wind shears in the mesosphere and lower thermosphere (MLT). An eddy diffusion coefficient is used in the 2-D numerical model to parameterize realistic turbulent mixing. Our study shows that the momentum deposited by breaking GWs accelerates the mean wind. The resultant large background wind increases the GW's app...

Laboratory simulations show diabatic heating drives cumulus-cloud evolution and entrainment

Science.gov (United States)

Narasimha, Roddam; Diwan, Sourabh Suhas; Duvvuri, Subrahmanyam; Sreenivas, K. R.; Bhat, G. S.

2011-01-01

Clouds are the largest source of uncertainty in climate science, and remain a weak link in modeling tropical circulation. A major challenge is to establish connections between particulate microphysics and macroscale turbulent dynamics in cumulus clouds. Here we address the issue from the latter standpoint. First we show how to create bench-scale flows that reproduce a variety of cumulus-cloud forms (including two genera and three species), and track complete cloud life cycles—e.g., from a “cauliflower” congestus to a dissipating fractus. The flow model used is a transient plume with volumetric diabatic heating scaled dynamically to simulate latent-heat release from phase changes in clouds. Laser-based diagnostics of steady plumes reveal Riehl–Malkus type protected cores. They also show that, unlike the constancy implied by early self-similar plume models, the diabatic heating raises the Taylor entrainment coefficient just above cloud base, depressing it at higher levels. This behavior is consistent with cloud-dilution rates found in recent numerical simulations of steady deep convection, and with aircraft-based observations of homogeneous mixing in clouds. In-cloud diabatic heating thus emerges as the key driver in cloud development, and could well provide a major link between microphysics and cloud-scale dynamics. PMID:21918112

One-step solution fabrication of magnetic chains consisting of jingle-bell-shaped cobalt mesospheres

Science.gov (United States)

Liang, Fang; Guo, Lin; Zhong, QunPeng; Wen, Xiaogang; Yang, Shihe; Zheng, Wangzhi; Chen, Chinping; Zhang, Nina; Chu, Weiguo

2006-09-01

Using a one-step solution phase approach, the authors have synthesized uniform jingle bell-shaped cobalt mesopheres (550-750nm) and assembled the mesospheres into long magnetic chains (20-30μm). All of the cobalt spheres are hollow with ˜40nm thick shells but each contains an ˜200nm diameter solid ball. The nano- to mesoscale structures were realized via reaction of CoCl2•6H2O and N2H4•H2O in the presence of polyvinylpyrrolidone (PVP) in an ethylene glycol solution. Magnetic measurements show a coercivity of about 75Oe with a remnance of 9.6emu /g at 300K. We propose a possible mechanism for the formation of the nanoto mesoscale structures.

Cloud Governance

DEFF Research Database (Denmark)

Berthing, Hans Henrik

Denne præsentation beskriver fordele og værdier ved anvendelse af Cloud Computing. Endvidere inddrager resultater fra en række internationale analyser fra ISACA om Cloud Computing.......Denne præsentation beskriver fordele og værdier ved anvendelse af Cloud Computing. Endvidere inddrager resultater fra en række internationale analyser fra ISACA om Cloud Computing....

The Relationship Between Infrared Dark Cloud and Stellar Properties

Science.gov (United States)

Calahan, Jenny; Hora, Joseph L.

2018-01-01

Massive stars are known to form within infrared dark clouds (IRDCs), but many details about how molecular clouds collapse and form stars remain poorly understood.We determine the relationship between the dark cloud mass and the population of young stellar objects (YSOs) associated with the cloud to shed light on the physical processes occurring within these star forming regions. We chose to use a sample of IRDCs and YSOs within the Cygnus-X region, a close-by giant star formation complex that has every stage of star formation represented. Using observations from IRAC, MIPS, PACS, and SPIRE on Spitzer and Herschel we identified a sample of 30,903 YSOs and 167 IRDCs. We derived the class of each YSO as well as the mass of YSO and IRDCs from the flux information. Using these parameters, as well as their locations in the cloud, we were sorted IRDC fragments into larger filaments and associate a set of YSOs with each IRDC. By measuring and comparing parameters such as YSO total mass, number of YSOs, Class 0, Class I, and Class II populations, distance from host filament, and filament mass we tested for correlations between the YSO and IRDC parameters. Using this treasure trove of information, we find that Class 0 and I objects are located more closely to their host IRDC than their Class II counterparts. We also find that high-density IRDCs are better environments for star formation than low-density IRDCs. However, we find no correlation between the total mass of the IRDC and the largest YSO mass in the IRDC, suggesting that IRDCs of any mass can have massive YSOs associated with them.The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

Ionizing feedback from massive stars in massive clusters - III. Disruption of partially unbound clouds

Science.gov (United States)

Dale, J. E.; Ercolano, B.; Bonnell, I. A.

2013-03-01

We extend our previous smoothed particle hydrodynamics parameter study of the effects of photoionization from O-stars on star-forming clouds to include initially unbound clouds. We generate a set of model clouds in the mass range 104-106 M⊙ with initial virial ratios Ekin/Epot = 2.3, allow them to form stars and study the impact of the photoionizing radiation produced by the massive stars. We find that, on the 3 Myr time-scale before supernovae are expected to begin detonating, the fraction of mass expelled by ionizing feedback is a very strong function of the cloud escape velocities. High-mass clouds are largely unaffected dynamically, while low-mass clouds have large fractions of their gas reserves expelled on this time-scale. However, the fractions of stellar mass unbound are modest and significant portions of the unbound stars are so only because the clouds themselves are initially partially unbound. We find that ionization is much more able to create well-cleared bubbles in the unbound clouds, owing to their intrinsic expansion, but that the presence of such bubbles does not necessarily indicate that a given cloud has been strongly influenced by feedback. We also find, in common with the bound clouds from our earlier work, that many of the systems simulated here are highly porous to photons and supernova ejecta, and that most of them will likely survive their first supernova explosions.

Web-scale data management for the cloud

CERN Document Server

Lehner, Wolfgang

2013-01-01

The efficient management of a consistent and integrated database is a central task in modern IT and highly relevant for science and industry. Hardly any critical enterprise solution comes without any functionality for managing data in its different forms. Web-Scale Data Management for the Cloud addresses fundamental challenges posed by the need and desire to provide database functionality in the context of the Database as a Service (DBaaS) paradigm for database outsourcing. This book also discusses the motivation of the new paradigm of cloud computing, and its impact to data outsourcing and se

Vertical distribution of the particle phase in tropical deep convective clouds as derived from cloud-side reflected solar radiation measurements

Directory of Open Access Journals (Sweden)

E. Jäkel

2017-07-01

Full Text Available Vertical profiles of cloud particle phase in tropical deep convective clouds (DCCs were investigated using airborne solar spectral radiation data collected by the German High Altitude and Long Range Research Aircraft (HALO during the ACRIDICON-CHUVA campaign, which was conducted over the Brazilian rainforest in September 2014. A phase discrimination retrieval based on imaging spectroradiometer measurements of DCC side spectral reflectivity was applied to clouds formed in different aerosol conditions. From the retrieval results the height of the mixed-phase layer of the DCCs was determined. The retrieved profiles were compared with in situ measurements and satellite observations. It was found that the depth and vertical position of the mixed-phase layer can vary up to 900 m for one single cloud scene. This variability is attributed to the different stages of cloud development in a scene. Clouds of mature or decaying stage are affected by falling ice particles resulting in lower levels of fully glaciated cloud layers compared to growing clouds. Comparing polluted and moderate aerosol conditions revealed a shift of the lower boundary of the mixed-phase layer from 5.6 ± 0.2 km (269 K; moderate to 6.2 ± 0.3 km (267 K; polluted, and of the upper boundary from 6.8 ± 0.2 km (263 K; moderate to 7.4 ± 0.4 km (259 K; polluted, as would be expected from theory.

Constraining Aerosol-Cloud-Precipitation Interactions of Orographic Mixed-Phase Clouds with Trajectory Budgets

Science.gov (United States)

Glassmeier, F.; Lohmann, U.

2016-12-01

Orographic precipitation is prone to strong aerosol-cloud-precipitation interactions because the time for precipitation development is limited to the ascending section of mountain flow. At the same time, cloud microphysical development is constraint by the strong dynamical forcing of the orography. In this contribution, we discuss how changes in the amount and composition of droplet- and ice-forming aerosols influence precipitation in idealized simulations of stratiform orographic mixed-phase clouds. We find that aerosol perturbations trigger compensating responses of different precipitation formation pathways. The effect of aerosols is thus buffered. We explain this buffering by the requirement to fulfill aerosol-independent dynamical constraints. For our simulations, we use the regional atmospheric model COSMO-ART-M7 in a 2D setup with a bell-shaped mountain. The model is coupled to a 2-moment warm and cold cloud microphysics scheme. Activation and freezing rates are parameterized based on prescribed aerosol fields that are varied in number, size and composition. Our analysis is based on the budget of droplet water along trajectories of cloud parcels. The budget equates condensation as source term with precipitation formation from autoconversion, accretion, riming and the Wegener-Bergeron-Findeisen process as sink terms. Condensation, and consequently precipitation formation, is determined by dynamics and largely independent of the aerosol conditions. An aerosol-induced change in the number of droplets or crystals perturbs the droplet budget by affecting precipitation formation processes. We observe that this perturbation triggers adjustments in liquid and ice water content that re-equilibrate the budget. As an example, an increase in crystal number triggers a stronger glaciation of the cloud and redistributes precipitation formation from collision-coalescence to riming and from riming to vapor deposition. We theoretically confirm the dominant effect of water

Young star clusters in nearby molecular clouds

Science.gov (United States)

Getman, K. V.; Kuhn, M. A.; Feigelson, E. D.; Broos, P. S.; Bate, M. R.; Garmire, G. P.

2018-06-01

The SFiNCs (Star Formation in Nearby Clouds) project is an X-ray/infrared study of the young stellar populations in 22 star-forming regions with distances ≲ 1 kpc designed to extend our earlier MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) survey of more distant clusters. Our central goal is to give empirical constraints on cluster formation mechanisms. Using parametric mixture models applied homogeneously to the catalogue of SFiNCs young stars, we identify 52 SFiNCs clusters and 19 unclustered stellar structures. The procedure gives cluster properties including location, population, morphology, association with molecular clouds, absorption, age (AgeJX), and infrared spectral energy distribution (SED) slope. Absorption, SED slope, and AgeJX are age indicators. SFiNCs clusters are examined individually, and collectively with MYStIX clusters, to give the following results. (1) SFiNCs is dominated by smaller, younger, and more heavily obscured clusters than MYStIX. (2) SFiNCs cloud-associated clusters have the high ellipticities aligned with their host molecular filaments indicating morphology inherited from their parental clouds. (3) The effect of cluster expansion is evident from the radius-age, radius-absorption, and radius-SED correlations. Core radii increase dramatically from ˜0.08 to ˜0.9 pc over the age range 1-3.5 Myr. Inferred gas removal time-scales are longer than 1 Myr. (4) Rich, spatially distributed stellar populations are present in SFiNCs clouds representing early generations of star formation. An appendix compares the performance of the mixture models and non-parametric minimum spanning tree to identify clusters. This work is a foundation for future SFiNCs/MYStIX studies including disc longevity, age gradients, and dynamical modelling.

Comparisons of Satellite-Deduced Overlapping Cloud Properties and CALIPSO CloudSat Data

Science.gov (United States)

Chang, Fu-Lung; Minnis, Patrick; Lin, Bing; Sun-Mack, Sunny

2010-01-01

Introduction to the overlapped cloud properties derived from polar-orbiting (MODIS) and geostationary (GOES-12, -13, Meteosat-8, -9, etc.) meteorological satellites, which are produced at the NASA Langley Research Center (LaRC) cloud research & development team (NASA lead scientist: Dr. Patrick Minnis). Comparison of the LaRC CERES MODIS Edition-3 overlapped cloud properties to the CALIPSO and the CloudSat active sensing data. High clouds and overlapped clouds occur frequently as deduced by CALIPSO (44 & 25%), CloudSat (25 & 4%), and MODIS (37 & 6%). Large fractions of optically-thin cirrus and overlapped clouds are deduced from CALIPSO, but much smaller fractions are from CloudSat and MODIS. For overlapped clouds, the averaged upper-layer CTHs are about 12.8 (CALIPSO), 10.9 (CloudSat) and 10 km (MODIS), and the averaged lower-layer CTHs are about 3.6 (CALIPSO), 3.2 (CloudSat) and 3.9 km (MODIS). Based on comparisons of upper and lower-layer cloud properties as deduced from the MODIS, CALIPSO and CloudSat data, more enhanced passive satellite methods for retrieving thin cirrus and overlapped cloud properties are needed and are under development.

Securing the Cloud Cloud Computer Security Techniques and Tactics

CERN Document Server

Winkler, Vic (JR)

2011-01-01

As companies turn to cloud computing technology to streamline and save money, security is a fundamental concern. Loss of certain control and lack of trust make this transition difficult unless you know how to handle it. Securing the Cloud discusses making the move to the cloud while securing your peice of it! The cloud offers felxibility, adaptability, scalability, and in the case of security-resilience. This book details the strengths and weaknesses of securing your company's information with different cloud approaches. Attacks can focus on your infrastructure, communications network, data, o

Versatile element for free-space dividing and redirecting neutral-atom clouds

International Nuclear Information System (INIS)

Arakelyan, I. V.; Chattrapiban, N.; Mitra, S.; Hill, W. T. III

2007-01-01

We introduce a tunnel lock that can be exploited to divide, delay, and alter the direction of traveling clouds of cold atoms. This versatile free-space element is implemented by crossing two atom tunnels formed by low-intensity, blue-detuned dark-hollow (Bessel mode) laser beams. We show that clouds of cold Rb atoms initially moving within one tunnel can be transferred to the other without heating by gating the intensities of the two tunnels--a tunnel lock--with an efficiency limited by the overlap volume. The element also can be used to divide a single cloud into smaller clouds, each having a distinct momentum

A Comparison of MODIS/VIIRS Cloud Masks over Ice-Bearing River: On Achieving Consistent Cloud Masking and Improved River Ice Mapping

Directory of Open Access Journals (Sweden)

Simon Kraatz

2017-03-01

Full Text Available The capability of frequently and accurately monitoring ice on rivers is important, since it may be possible to timely identify ice accumulations corresponding to ice jams. Ice jams are dam-like structures formed from arrested ice floes, and may cause rapid flooding. To inform on this potential hazard, the CREST River Ice Observing System (CRIOS produces ice cover maps based on MODIS and VIIRS overpass data at several locations, including the Susquehanna River. CRIOS uses the respective platform’s automatically produced cloud masks to discriminate ice/snow covered grid cells from clouds. However, since cloud masks are produced using each instrument’s data, and owing to differences in detector performance, it is quite possible that identical algorithms applied to even nearly identical instruments may produce substantially different cloud masks. Besides detector performance, cloud identification can be biased due to local (e.g., land cover, viewing geometry, and transient conditions (snow and ice. Snow/cloud confusions and large view angles can result in substantial overestimates of clouds and ice. This impacts algorithms, such as CRIOS, since false cloud cover precludes the determination of whether an otherwise reasonably cloud free grid consists of water or ice. Especially for applications aiming to frequently classify or monitor a location it is important to evaluate cloud masking, including false cloud detections. We present an assessment of three cloud masks via the parameter of effective revisit time. A 100 km stretch of up to 1.6 km wide river was examined with daily data sampled at 500 m resolution, examined over 317 days during winter. Results show that there are substantial differences between each of the cloud mask products, especially while the river bears ice. A contrast-based cloud screening approach was found to provide improved and consistent cloud and ice identification within the reach (95%–99% correlations, and 3%–7% mean

Stable Low Cloud Phase II: Nocturnal Event Study

Science.gov (United States)

Bauman, William H., III; Barrett, Joe, III

2007-01-01

This report describes the work done by the Applied Meteorology Unit (AMU) in developing a database of nights that experienced rapid (formation in a stable atmosphere, resulting in ceilings at the Shuttle Landing Facility (TTS) that violated Space Shuttle Flight Rules (FR). This work is the second phase of a similar AMU task that examined the same phenomena during the day. In the first phase of this work, the meteorological conditions favoring the rapid formation of low ceilings include the presence of any inversion below 8000 ft, high relative humidity (RH) beneath the inversion and a clockwise turning of the winds from the surface to the middle troposphere (-15000 ft). The AMU compared and contrasted the atmospheric and thermodynamic conditions between nights with rapid low ceiling formation and nights with low ceilings resulting from other mechanisms. The AMU found that there was little to discern between the rapidly-forming ceiling nights and other low ceiling nights at TTS. When a rapid development occurred, the average RH below the inversions was 87% while non-events had an average RH of 79%. One key parameter appeared to be the vertical wind profile in the Cape Canaveral, FL radiosonde (XMR) sounding. Eighty-three percent of the rapid development events had veering winds with height from the surface to the middle troposphere (-15,000 ft) while 61% of the non-events had veering winds with height. Veering winds indicate a warm-advection regime, which supports large-scale rising motion and ultimately cloud formation in a moist environment. However, only six of the nights (out of 86 events examined) with low cloud ceilings had an occurrence of rapidly developing ceilings. Since only 7% rapid development events were observed in this dataset, it is likely that rapid low cloud development is not a common occurrence during the night, or at least not as common as during the day. In the AMU work on the daytime rapid low cloud development (Case and Wheeler 2005), nearly

ECONOMIC DENIAL OF SUSTAINABILITY (EDOS ATTACK ON CLOUD – A SURVEY

Directory of Open Access Journals (Sweden)

A. Somasundaram

2016-12-01

Full Text Available Cloud computing is a promising technology aims to provide reliable, customized and quality of service computation environments for cloud users in terms of Software as a Service-SaaS , Plat- form as a Service-PaaS and Infrastructure as Service-IaaS, which is provided on the pay per use basis. Cloud computing enables services to be deployed and accessed globally on demand with little maintenance by providing QoS as per service level agreement (SLA of customer. However, due to elasticity of resources, cloud systems are facing severe security problems. One of the most serious threats to cloud computing is EDoS (economic Distributed Denial of Service aims to consume the cloud resource by attacker and impose financial burden to the legitimate user, where integrity, availability and confidentiality of the cloud services are never compromised but affects the accountability which leads to inaccurate billing. Since the billing models of cloud services may not be mature enough to properly account for an EDoS attack. These paper surveys, the different techniques that generate, detect and mitigate the EDoS Attack on Cloud.

Broadening of cloud droplet spectra through turbulent entrainment and eddy hopping

Science.gov (United States)

Abade, Gustavo; Grabowski, Wojciech; Pawlowska, Hanna

2017-11-01

This work discusses the effect of cloud turbulence and turbulent entrainment on the evolution of the cloud droplet-size spectrum. We simulate an ensemble of idealized turbulent cloud parcels that are subject to entrainment events, modeled as a random Poisson process. Entrainment events, subsequent turbulent mixing inside the parcel, supersaturation fluctuations, and the resulting stochastic droplet growth by condensation are simulated using a Monte Carlo scheme. Quantities characterizing the turbulence intensity, entrainment rate and the mean fraction of environmental air entrained in an event are specified as external parameters. Cloud microphysics is described by applying Lagrangian particles, the so-called superdroplets. They are either unactivated cloud condensation nuclei (CCN) or cloud droplets that form from activated CCN. The model accounts for the transport of environmental CCN into the cloud by the entraining eddies at the cloud edge. Turbulent mixing of the entrained dry air with cloudy air is described using a linear model. We show that turbulence plays an important role in aiding entrained CCN to activate, providing a source of small cloud droplets and thus broadening the droplet size distribution. Further simulation results will be reported at the meeting.

Modeling and Security in Cloud Ecosystems

Directory of Open Access Journals (Sweden)

Eduardo B. Fernandez

2016-04-01

Full Text Available Clouds do not work in isolation but interact with other clouds and with a variety of systems either developed by the same provider or by external entities with the purpose to interact with them; forming then an ecosystem. A software ecosystem is a collection of software systems that have been developed to coexist and evolve together. The stakeholders of such a system need a variety of models to give them a perspective of the possibilities of the system, to evaluate specific quality attributes, and to extend the system. A powerful representation when building or using software ecosystems is the use of architectural models, which describe the structural aspects of such a system. These models have value for security and compliance, are useful to build new systems, can be used to define service contracts, find where quality factors can be monitored, and to plan further expansion. We have described a cloud ecosystem in the form of a pattern diagram where its components are patterns and reference architectures. A pattern is an encapsulated solution to a recurrent problem. We have recently expanded these models to cover fog systems and containers. Fog Computing is a highly-virtualized platform that provides compute, storage, and networking services between end devices and Cloud Computing Data Centers; a Software Container provides an execution environment for applications sharing a host operating system, binaries, and libraries with other containers. We intend to use this architecture to answer a variety of questions about the security of this system as well as a reference to design interacting combinations of heterogeneous components. We defined a metamodel to relate security concepts which is being expanded.

Cloud management and security

CERN Document Server

Abbadi, Imad M

2014-01-01

Written by an expert with over 15 years' experience in the field, this book establishes the foundations of Cloud computing, building an in-depth and diverse understanding of the technologies behind Cloud computing. In this book, the author begins with an introduction to Cloud computing, presenting fundamental concepts such as analyzing Cloud definitions, Cloud evolution, Cloud services, Cloud deployment types and highlighting the main challenges. Following on from the introduction, the book is divided into three parts: Cloud management, Cloud security, and practical examples. Part one presents the main components constituting the Cloud and federated Cloud infrastructure(e.g., interactions and deployment), discusses management platforms (resources and services), identifies and analyzes the main properties of the Cloud infrastructure, and presents Cloud automated management services: virtual and application resource management services. Part two analyzes the problem of establishing trustworthy Cloud, discuss...

Data provenance assurance in the cloud using blockchain

Science.gov (United States)

Shetty, Sachin; Red, Val; Kamhoua, Charles; Kwiat, Kevin; Njilla, Laurent

2017-05-01

Ever increasing adoption of cloud technology scales up the activities like creation, exchange, and alteration of cloud data objects, which create challenges to track malicious activities and security violations. Addressing this issue requires implementation of data provenance framework so that each data object in the federated cloud environment can be tracked and recorded but cannot be modified. The blockchain technology gives a promising decentralized platform to build tamper-proof systems. Its incorruptible distributed ledger/blockchain complements the need of maintaining cloud data provenance. In this paper, we present a cloud based data provenance framework using block chain which traces data record operations and generates provenance data. We anchor provenance data records into block chain transactions, which provide validation on provenance data and preserve user privacy at the same time. Once the provenance data is uploaded to the global block chain network, it is extremely challenging to tamper the provenance data. Besides, the provenance data uses hashed user identifiers prior to uploading so the blockchain nodes cannot link the operations to a particular user. The framework ensures that the privacy is preserved. We implemented the architecture on ownCloud, uploaded records to blockchain network, stored records in a provenance database and developed a prototype in form of a web service.

Cloud Manufacturing Service Paradigm for Group Manufacturing Companies

Directory of Open Access Journals (Sweden)

Jingtao Zhou

2014-07-01

Full Text Available The continuous refinement of specialization requires that the group manufacturing company must be constantly focused on how to concentrate its core resources in special sphere to form its core competitive advantage. However, the resources in enterprise group are usually distributed in different subsidiary companies, which means they cannot be fully used, constraining the competition and development of the enterprise. Conducted as a response to a need for cloud manufacturing studies, systematic and detailed studies on cloud manufacturing schema for group companies are carried out in this paper. A new hybrid private clouds paradigm is proposed to meet the requirements of aggregation and centralized use of heterogeneous resources and business units distributed in different subsidiary companies. After the introduction of the cloud manufacturing paradigm for enterprise group and its architecture, this paper presents a derivation from the abstraction of paradigm and framework to the application of a practical evaluative working mechanism. In short, the paradigm establishes an effective working mechanism to translate collaborative business process composed by the activities into cloud manufacturing process composed by services so as to create a foundation resulting in mature traditional project monitoring and scheduling technologies being able to be used in cloud manufacturing project management.

Cloud computing patterns fundamentals to design, build, and manage cloud applications

CERN Document Server

Fehling, Christoph; Retter, Ralph; Schupeck, Walter; Arbitter, Peter

2014-01-01

The current work provides CIOs, software architects, project managers, developers, and cloud strategy initiatives with a set of architectural patterns that offer nuggets of advice on how to achieve common cloud computing-related goals. The cloud computing patterns capture knowledge and experience in an abstract format that is independent of concrete vendor products. Readers are provided with a toolbox to structure cloud computing strategies and design cloud application architectures. By using this book cloud-native applications can be implemented and best suited cloud vendors and tooling for i

Spectral shifting strongly constrains molecular cloud disruption by radiation pressure on dust

Science.gov (United States)

Reissl, Stefan; Klessen, Ralf S.; Mac Low, Mordecai-Mark; Pellegrini, Eric W.

2018-03-01

Aim. We aim to test the hypothesis that radiation pressure from young star clusters acting on dust is the dominant feedback agent disrupting the largest star-forming molecular clouds and thus regulating the star-formation process. Methods: We performed multi-frequency, 3D, radiative transfer calculations including both scattering and absorption and re-emission to longer wavelengths for model clouds with masses of 104-107 M⊙, containing embedded clusters with star formation efficiencies of 0.009-91%, and varying maximum grain sizes up to 200 μm. We calculated the ratio between radiative and gravitational forces to determine whether radiation pressure can disrupt clouds. Results: We find that radiation pressure acting on dust almost never disrupts star-forming clouds. Ultraviolet and optical photons from young stars to which the cloud is optically thick do not scatter much. Instead, they quickly get absorbed and re-emitted by the dust at thermal wavelengths. As the cloud is typically optically thin to far-infrared radiation, it promptly escapes, depositing little momentum in the cloud. The resulting spectrum is more narrowly peaked than the corresponding Planck function, and exhibits an extended tail at longer wavelengths. As the opacity drops significantly across the sub-mm and mm wavelength regime, the resulting radiative force is even smaller than for the corresponding single-temperature blackbody. We find that the force from radiation pressure falls below the strength of gravitational attraction by an order of magnitude or more for either Milky Way or moderate starbust conditions. Only for unrealistically large maximum grain sizes, and star formation efficiencies far exceeding 50% do we find that the strength of radiation pressure can exceed gravity. Conclusions: We conclude that radiation pressure acting on dust does not disrupt star-forming molecular clouds in any Local Group galaxies. Radiation pressure thus appears unlikely to regulate the star

Military clouds: utilization of cloud computing systems at the battlefield

Science.gov (United States)

Süleyman, Sarıkürk; Volkan, Karaca; İbrahim, Kocaman; Ahmet, Şirzai

2012-05-01

Cloud computing is known as a novel information technology (IT) concept, which involves facilitated and rapid access to networks, servers, data saving media, applications and services via Internet with minimum hardware requirements. Use of information systems and technologies at the battlefield is not new. Information superiority is a force multiplier and is crucial to mission success. Recent advances in information systems and technologies provide new means to decision makers and users in order to gain information superiority. These developments in information technologies lead to a new term, which is known as network centric capability. Similar to network centric capable systems, cloud computing systems are operational today. In the near future extensive use of military clouds at the battlefield is predicted. Integrating cloud computing logic to network centric applications will increase the flexibility, cost-effectiveness, efficiency and accessibility of network-centric capabilities. In this paper, cloud computing and network centric capability concepts are defined. Some commercial cloud computing products and applications are mentioned. Network centric capable applications are covered. Cloud computing supported battlefield applications are analyzed. The effects of cloud computing systems on network centric capability and on the information domain in future warfare are discussed. Battlefield opportunities and novelties which might be introduced to network centric capability by cloud computing systems are researched. The role of military clouds in future warfare is proposed in this paper. It was concluded that military clouds will be indispensible components of the future battlefield. Military clouds have the potential of improving network centric capabilities, increasing situational awareness at the battlefield and facilitating the settlement of information superiority.

Clustering, randomness, and regularity in cloud fields. 4: Stratocumulus cloud fields

Science.gov (United States)

Lee, J.; Chou, J.; Weger, R. C.; Welch, R. M.

1994-01-01

To complete the analysis of the spatial distribution of boundary layer cloudiness, the present study focuses on nine stratocumulus Landsat scenes. The results indicate many similarities between stratocumulus and cumulus spatial distributions. Most notably, at full spatial resolution all scenes exhibit a decidedly clustered distribution. The strength of the clustering signal decreases with increasing cloud size; the clusters themselves consist of a few clouds (less than 10), occupy a small percentage of the cloud field area (less than 5%), contain between 20% and 60% of the cloud field population, and are randomly located within the scene. In contrast, stratocumulus in almost every respect are more strongly clustered than are cumulus cloud fields. For instance, stratocumulus clusters contain more clouds per cluster, occupy a larger percentage of the total area, and have a larger percentage of clouds participating in clusters than the corresponding cumulus examples. To investigate clustering at intermediate spatial scales, the local dimensionality statistic is introduced. Results obtained from this statistic provide the first direct evidence for regularity among large (more than 900 m in diameter) clouds in stratocumulus and cumulus cloud fields, in support of the inhibition hypothesis of Ramirez and Bras (1990). Also, the size compensated point-to-cloud cumulative distribution function statistic is found to be necessary to obtain a consistent description of stratocumulus cloud distributions. A hypothesis regarding the underlying physical mechanisms responsible for cloud clustering is presented. It is suggested that cloud clusters often arise from 4 to 10 triggering events localized within regions less than 2 km in diameter and randomly distributed within the cloud field. As the size of the cloud surpasses the scale of the triggering region, the clustering signal weakens and the larger cloud locations become more random.

Clustering, randomness, and regularity in cloud fields. 4. Stratocumulus cloud fields

Science.gov (United States)

Lee, J.; Chou, J.; Weger, R. C.; Welch, R. M.

1994-07-01

To complete the analysis of the spatial distribution of boundary layer cloudiness, the present study focuses on nine stratocumulus Landsat scenes. The results indicate many similarities between stratocumulus and cumulus spatial distributions. Most notably, at full spatial resolution all scenes exhibit a decidedly clustered distribution. The strength of the clustering signal decreases with increasing cloud size; the clusters themselves consist of a few clouds (less than 10), occupy a small percentage of the cloud field area (less than 5%), contain between 20% and 60% of the cloud field population, and are randomly located within the scene. In contrast, stratocumulus in almost every respect are more strongly clustered than are cumulus cloud fields. For instance, stratocumulus clusters contain more clouds per cluster, occupy a larger percentage of the total area, and have a larger percentage of clouds participating in clusters than the corresponding cumulus examples. To investigate clustering at intermediate spatial scales, the local dimensionality statistic is introduced. Results obtained from this statistic provide the first direct evidence for regularity among large (>900 m in diameter) clouds in stratocumulus and cumulus cloud fields, in support of the inhibition hypothesis of Ramirez and Bras (1990). Also, the size compensated point-to-cloud cumulative distribution function statistic is found to be necessary to obtain a consistent description of stratocumulus cloud distributions. A hypothesis regarding the underlying physical mechanisms responsible for cloud clustering is presented. It is suggested that cloud clusters often arise from 4 to 10 triggering events localized within regions less than 2 km in diameter and randomly distributed within the cloud field. As the size of the cloud surpasses the scale of the triggering region, the clustering signal weakens and the larger cloud locations become more random.

Cloud blueprints for integrating and managing cloud federations

NARCIS (Netherlands)

Papazoglou, M.; Heisel, M.

2012-01-01

Contemporary cloud technologies face insurmountable obstacles. They follow a pull-based, producer-centric trajectory to development where cloud consumers have to ‘squeeze and bolt’ applications onto cloud APIs. They also introduce a monolithic SaaS/PaaS/IaaS stack where a one-size-fits-all mentality

Galaxy CloudMan: delivering cloud compute clusters.

Science.gov (United States)

Afgan, Enis; Baker, Dannon; Coraor, Nate; Chapman, Brad; Nekrutenko, Anton; Taylor, James

2010-12-21

Widespread adoption of high-throughput sequencing has greatly increased the scale and sophistication of computational infrastructure needed to perform genomic research. An alternative to building and maintaining local infrastructure is "cloud computing", which, in principle, offers on demand access to flexible computational infrastructure. However, cloud computing resources are not yet suitable for immediate "as is" use by experimental biologists. We present a cloud resource management system that makes it possible for individual researchers to compose and control an arbitrarily sized compute cluster on Amazon's EC2 cloud infrastructure without any informatics requirements. Within this system, an entire suite of biological tools packaged by the NERC Bio-Linux team (http://nebc.nerc.ac.uk/tools/bio-linux) is available for immediate consumption. The provided solution makes it possible, using only a web browser, to create a completely configured compute cluster ready to perform analysis in less than five minutes. Moreover, we provide an automated method for building custom deployments of cloud resources. This approach promotes reproducibility of results and, if desired, allows individuals and labs to add or customize an otherwise available cloud system to better meet their needs. The expected knowledge and associated effort with deploying a compute cluster in the Amazon EC2 cloud is not trivial. The solution presented in this paper eliminates these barriers, making it possible for researchers to deploy exactly the amount of computing power they need, combined with a wealth of existing analysis software, to handle the ongoing data deluge.

Cloud blueprint : A model-driven approach to configuring federated clouds

NARCIS (Netherlands)

Papazoglou, M.; Abello, A.; Bellatreche, L.; Benatallah, B.

2012-01-01

Current cloud solutions are fraught with problems. They introduce a monolithic cloud stack that imposes vendor lock-in and donot permit developers to mix and match services freely from diverse cloud service tiers and configure them dynamically to address application needs. Cloud blueprinting is a

Structure, shape, and evolution of radiatively accelerated QSO emission-line clouds

International Nuclear Information System (INIS)

Blumenthal, G.R.; Mathews, W.G.

1979-01-01

The possibility that the broad emission-line regions of QSOs and active galactic nuclei are formed by a multitude of small clouds which are radiatively accelerated is discussed. Although this model is by no means certain at present, it has four virtues: (1) Observed emission-line widths can be produced with observationally allowed electron densities, UV luminosities, and ionization levels. (2) The acceleration force is coherent in each cloud are found. (3) Reasonable line profiles can result for all emission lines. (4) Photoionization of hydrogen accounts for both heating and acceleration of the emission-line gas. A self-consistent model is developed for the structure, shape, and evolution of radiatively accelerated clouds. The shape varies with cloud mass, and two distinct types of clouds. Fully ionized clouds of very low mass approach a nearly spherical shape. However, all clouds having masses greater than some critical mass adopt a ''pancake'' shape. The condition for constant cloud mass in the cloud frame is shown to be equivalent to the equation of motion of a cloud in the rest frame of the QSO. The emission-line profiles can be sensitive to radial variations in the properties of the intercloud medium, and those properties that correspond to observed profiles are discussed. Finally, the covering factor of a system of pancake clouds is estimated along with the total number of clouds required--approximately 10 14 clouds in each QSO

Thin Cloud Detection Method by Linear Combination Model of Cloud Image

Science.gov (United States)

Liu, L.; Li, J.; Wang, Y.; Xiao, Y.; Zhang, W.; Zhang, S.

2018-04-01

The existing cloud detection methods in photogrammetry often extract the image features from remote sensing images directly, and then use them to classify images into cloud or other things. But when the cloud is thin and small, these methods will be inaccurate. In this paper, a linear combination model of cloud images is proposed, by using this model, the underlying surface information of remote sensing images can be removed. So the cloud detection result can become more accurate. Firstly, the automatic cloud detection program in this paper uses the linear combination model to split the cloud information and surface information in the transparent cloud images, then uses different image features to recognize the cloud parts. In consideration of the computational efficiency, AdaBoost Classifier was introduced to combine the different features to establish a cloud classifier. AdaBoost Classifier can select the most effective features from many normal features, so the calculation time is largely reduced. Finally, we selected a cloud detection method based on tree structure and a multiple feature detection method using SVM classifier to compare with the proposed method, the experimental data shows that the proposed cloud detection program in this paper has high accuracy and fast calculation speed.

Meteorological observations in support of a hill cap cloud experiment

Energy Technology Data Exchange (ETDEWEB)

Nielsen, Morten

1998-06-01

Humid air flows form a hill cap cloud over the Agana mountain ridge in the north-east of Tenerife. The HILLCLOUD project utilised this cloud formation to investigate the chemical and physical properties of cloud aerosols by land based observations. The project was part of the second Aerosol characterisation Experiment (ACE-2) of the International Global Atmospheric chemistry project (IGAC). The present report describes meteorological observations in support of the hill cap cloud experiment. Time-series of wind speed, wind direction, temperature and humidity were collected at ground-based meteorological stations during a period starting one year in advance of the main campaign. A series of radiosonde detecting the upstream stability and wind profile were launched during the main campaign. (au) 5 tabs., 32 ills., 6 refs.

Near InfraRed Imaging Spectrograph (NIRIS) for ground-based mesospheric OH(6-2) and O2(0-1) intensity and temperature measurements

Science.gov (United States)

Singh, Ravindra P.; Pallamraju, Duggirala

2017-08-01

This paper describes the development of a new Near InfraRed Imaging Spectrograph (NIRIS) which is capable of simultaneous measurements of OH(6-2) Meinel and O2(0-1) atmospheric band nightglow emission intensities. In this spectrographic technique, rotational line ratios are obtained to derive temperatures corresponding to the emission altitudes of 87 and 94 km. NIRIS has been commissioned for continuous operation from optical aeronomy observatory, Gurushikhar, Mount Abu (24.6°N, 72.8°E) since January 2013. NIRIS uses a diffraction grating of 1200 lines mm^{-1} and 1024× 1024 pixels thermoelectrically cooled CCD camera and has a large field-of-view (FOV) of 80° along the slit orientation. The data analysis methodology adopted for the derivation of mesospheric temperatures is also described in detail. The observed NIRIS temperatures show good correspondence with satellite (SABER) derived temperatures and exhibit both tidal and gravity waves (GW) like features. From the time taken for phase propagation in the emission intensities between these two altitudes, vertical phase speed of gravity waves, cz, is calculated and along with the coherent GW time period `τ ', the vertical wavelength, λ z, is obtained. Using large FOV observations from NIRIS, the meridional wavelengths, λ y, are also calculated. We have used one year of data to study the possible cause(s) for the occurrences of mesospheric temperature inversions (MTIs). From the statistics obtained for 234 nights, it appears that in situ chemical heating is mainly responsible for the observed MTIs than the vertical propagation of the waves. Thus, this paper describes a novel near infrared imaging spectrograph, its working principle, data analysis method for deriving OH and O2 emission intensities and the corresponding rotational temperatures at these altitudes, derivation of gravity wave parameters (τ , cz, λ z, and λ y), and results on the statistical study of MTIs that exist in the earth's mesospheric

Characterization of the cloud conditions at Ny-Ålesund using sensor synergy and representativeness of the observed clouds across Arctic sites

Science.gov (United States)

Nomokonova, Tatiana; Ebell, Kerstin; Löhnert, Ulrich; Maturilli, Marion

2017-04-01

Clouds are one of the crucial components of the hydrological and energy cycles and thus affecting the global climate. Their special importance in Arctic regions is defined by cloud's influence on the radiation budget. Arctic clouds usually occur at low altitudes and often contain highly concentrated tiny liquid drops. During winter, spring, and autumn periods such clouds tend to conserve the long-wave radiation in the atmosphere and, thus, produce warming of the Arctic climate. In summer though clouds efficiently scatter the solar radiation back to space and, therefore, induce a cooling effect. An accurate characterization of the net effect of clouds on the Arctic climate requires long-term and precise observations. However, only a few measurement sites exist which perform continuous, vertically resolved observations of clouds in the Arctic, e.g. in Alaska, Canada, and Greenland. These sites typically make use of a combination of different ground-based remote sensing instruments, e.g. cloud radar, ceilometer and microwave radiometer in order to characterize clouds. Within the Transregional Collaborative Research Center (TR 172) "Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3" comprehensive observations of the atmospheric column are performed at the German-French Research Station AWIPEV at Ny-Ålesund, Svalbard. Ny-Ålesund is located in the warmest part of the Arctic where climate is significantly influenced by adiabatic heating from the warm ocean. Thus, measurements at Ny-Ålesund will complement our understanding of cloud formation and development in the Arctic. This particular study is devoted to the characterization of the cloud macro- and microphysical properties at Ny-Ålesund and of the atmospheric conditions, under which these clouds form and develop. To this end, the information of the various instrumentation at the AWIPEV observatory is synergistically analysed: information about the thermodynamic

Spiral structure and star formation. II. Stellar lifetimes and cloud kinematics

International Nuclear Information System (INIS)

Hausman, M.A.; Roberts, W.W. Jr.

1984-01-01

We present further results of our model, introduced in Paper I, of star formation and star-gas interactions in the cloud-dominated ISMs of spiral density wave galaxies. The global density distribution and velocity field of the gas clouds are virtually independent of stellar parameters and even of mean free path for the wide range of values studied, but local density variations are found which superficially resemble cloud complexes. Increasing the average life span of ''spiral tracer'' stellar associations beyond about 20 Myr washes out the spiral pattern which younger associations show. Allowing clouds to form several successive associations (sequential star formation) slightly increases the frequency of interarm, young-star spurs and substantially increases the average star formation rate. The mean velocity field of clouds shows tipped oval streamlines, similar to both continuum gas dynamical models and stellar-kinematic models of spiral density waves. These streamlines are almost ballistic orbits except close to the spiral arms. Newly formed stellar associations leave the spiral density peak with initial tangential velocitie shigher than ''postshock'' values and do not fall back into the ''preshock'' region. By varying our stellar parametes within physically reasonable limits, we may reproduce spiral galaxies with a wide range of morphological appearaces

Evaluating the Influence of the Client Behavior in Cloud Computing.

Science.gov (United States)

Souza Pardo, Mário Henrique; Centurion, Adriana Molina; Franco Eustáquio, Paulo Sérgio; Carlucci Santana, Regina Helena; Bruschi, Sarita Mazzini; Santana, Marcos José

2016-01-01

This paper proposes a novel approach for the implementation of simulation scenarios, providing a client entity for cloud computing systems. The client entity allows the creation of scenarios in which the client behavior has an influence on the simulation, making the results more realistic. The proposed client entity is based on several characteristics that affect the performance of a cloud computing system, including different modes of submission and their behavior when the waiting time between requests (think time) is considered. The proposed characterization of the client enables the sending of either individual requests or group of Web services to scenarios where the workload takes the form of bursts. The client entity is included in the CloudSim, a framework for modelling and simulation of cloud computing. Experimental results show the influence of the client behavior on the performance of the services executed in a cloud computing system.

Sahara Dust Cloud

Science.gov (United States)

2005-01-01

[figure removed for brevity, see original site] Dust Particles Click on the image for Quicktime movie from 7/15-7/24 A continent-sized cloud of hot air and dust originating from the Sahara Desert crossed the Atlantic Ocean and headed towards Florida and the Caribbean. A Saharan Air Layer, or SAL, forms when dry air and dust rise from Africa's west coast and ride the trade winds above the Atlantic Ocean. These dust clouds are not uncommon, especially during the months of July and August. They start when weather patterns called tropical waves pick up dust from the desert in North Africa, carry it a couple of miles into the atmosphere and drift westward. In a sequence of images created by data acquired by the Earth-orbiting Atmospheric Infrared Sounder ranging from July 15 through July 24, we see the distribution of the cloud in the atmosphere as it swirls off of Africa and heads across the ocean to the west. Using the unique silicate spectral signatures of dust in the thermal infrared, AIRS can detect the presence of dust in the atmosphere day or night. This detection works best if there are no clouds present on top of the dust; when clouds are present, they can interfere with the signal, making it much harder to detect dust as in the case of July 24, 2005. In the Quicktime movie, the scale at the bottom of the images shows +1 for dust definitely detected, and ranges down to -1 for no dust detected. The plots are averaged over a number of AIRS observations falling within grid boxes, and so it is possible to obtain fractional numbers. [figure removed for brevity, see original site] Total Water Vapor in the Atmosphere Around the Dust Cloud Click on the image for Quicktime movie The dust cloud is contained within a dry adiabatic layer which originates over the Sahara Desert. This Saharan Air Layer (SAL) advances Westward over the Atlantic Ocean, overriding the cool, moist air nearer the surface. This burst of very dry air is visible in the AIRS retrieved total water

Essentials of cloud computing

CERN Document Server

Chandrasekaran, K

2014-01-01

ForewordPrefaceComputing ParadigmsLearning ObjectivesPreambleHigh-Performance ComputingParallel ComputingDistributed ComputingCluster ComputingGrid ComputingCloud ComputingBiocomputingMobile ComputingQuantum ComputingOptical ComputingNanocomputingNetwork ComputingSummaryReview PointsReview QuestionsFurther ReadingCloud Computing FundamentalsLearning ObjectivesPreambleMotivation for Cloud ComputingThe Need for Cloud ComputingDefining Cloud ComputingNIST Definition of Cloud ComputingCloud Computing Is a ServiceCloud Computing Is a Platform5-4-3 Principles of Cloud computingFive Essential Charact

Lidar measurements of mesospheric temperature inversion at a low latitude

Energy Technology Data Exchange (ETDEWEB)

Siva Kumar, V.; Bhavani Kumar, Y.; Raghunath, K.; Rao, P.B. [National MST Radar Facility, Tirupati (India); Krishnaiah, M. [Sri Venkateswara Univ., Tirupati (India). Dept. of Physics; Mizutani, K.; Aoki, T.; Yasui, M.; Itabe, T. [Communication Research Lab., Tokyo (Japan)

2001-08-01

The Rayleigh lidar data collected on 119 nights from March 1998 to February 2000 were used to study the statistical characteristics of the low latitude mesospheric temperature inversion observed over Gadanki (13.5 N, 79.2 E), India. The occurrence frequency of the inversion showed semiannual variation with maxima in the equinoxes and minima in the summer and winter, which was quite different from that reported for the mid-latitudes. The peak of the inversion layer was found to be confined to the height range of 73 to 79 km with the maximum occurrence centered around 76 km, with a weak seasonal dependence that fits well to an annual cycle with a maximum in June and a minimum in December. The magnitude of the temperature deviation associated with the inversion was found to be as high as 32 K, with the most probable value occurring at about 20 K. Its seasonal dependence seems to follow an annual cycle with a maximum in April and a minimum in October. The observed characteristics of the inversion layer are compared with that of the mid-latitudes and discussed in light of the current understanding of the source mechanisms. (orig.)

ANGULAR MOMENTUM IN GIANT MOLECULAR CLOUDS. I. THE MILKY WAY

International Nuclear Information System (INIS)

Imara, Nia; Blitz, Leo

2011-01-01

We present a detailed analysis comparing the velocity fields in molecular clouds and the atomic gas that surrounds them in order to address the origin of the gradients. To that end, we present first-moment intensity-weighted velocity maps of the molecular clouds and surrounding atomic gas. The maps are made from high-resolution 13 CO observations and 21 cm observations from the Leiden/Argentine/Bonn Galactic H I Survey. We find that (1) the atomic gas associated with each molecular cloud has a substantial velocity gradient-ranging from 0.02 to 0.07 km s -1 pc -1 -whether or not the molecular cloud itself has a substantial linear gradient. (2) If the gradients in the molecular and atomic gas were due to rotation, this would imply that the molecular clouds have less specific angular momentum than the surrounding H I by a factor of 1-6. (3) Most importantly, the velocity gradient position angles in the molecular and atomic gas are generally widely separated-by as much as 130 deg. in the case of the Rosette molecular cloud. This result argues against the hypothesis that molecular clouds formed by simple top-down collapse from atomic gas.

A semi-empirical model for mesospheric and stratospheric NOy produced by energetic particle precipitation

Directory of Open Access Journals (Sweden)

B. Funke

2016-07-01

Full Text Available The MIPAS Fourier transform spectrometer on board Envisat has measured global distributions of the six principal reactive nitrogen (NOy compounds (HNO3, NO2, NO, N2O5, ClONO2, and HNO4 during 2002–2012. These observations were used previously to detect regular polar winter descent of reactive nitrogen produced by energetic particle precipitation (EPP down to the lower stratosphere, often called the EPP indirect effect. It has further been shown that the observed fraction of NOy produced by EPP (EPP-NOy has a nearly linear relationship with the geomagnetic Ap index when taking into account the time lag introduced by transport. Here we exploit these results in a semi-empirical model for computation of EPP-modulated NOy densities and wintertime downward fluxes through stratospheric and mesospheric pressure levels. Since the Ap dependence of EPP-NOy is distorted during episodes of strong descent in Arctic winters associated with elevated stratopause events, a specific parameterization has been developed for these episodes. This model accurately reproduces the observations from MIPAS and is also consistent with estimates from other satellite instruments. Since stratospheric EPP-NOy depositions lead to changes in stratospheric ozone with possible implications for climate, the model presented here can be utilized in climate simulations without the need to incorporate many thermospheric and upper mesospheric processes. By employing historical geomagnetic indices, the model also allows for reconstruction of the EPP indirect effect since 1850. We found secular variations of solar cycle-averaged stratospheric EPP-NOy depositions on the order of 1 GM. In particular, we model a reduction of the EPP-NOy deposition rate during the last 3 decades, related to the coincident decline of geomagnetic activity that corresponds to 1.8 % of the NOy production rate by N2O oxidation. As the decline of the geomagnetic activity level is expected to continue in the

The influence of surface roughness on cloud cavitation flow around hydrofoils

Science.gov (United States)

Hao, Jiafeng; Zhang, Mindi; Huang, Xu

2018-02-01

The aim of this study is to investigate experimentally the effect of surface roughness on cloud cavitation around Clark-Y hydrofoils. High-speed video and particle image velocimetry (PIV) were used to obtain cavitation patterns images (Prog. Aerosp. Sci. 37: 551-581, 2001), as well as velocity and vorticity fields. Results are presented for cloud cavitating conditions around a Clark-Y hydrofoil fixed at angle of attack of α =8{°} for moderate Reynolds number of Re=5.6 × 105. The results show that roughness had a great influence on the pattern, velocity and vorticity distribution of cloud cavitation. For cavitating flow around a smooth hydrofoil (A) and a rough hydrofoil (B), cloud cavitation occurred in the form of finger-like cavities and attached subulate cavities, respectively. The period of cloud cavitation around hydrofoil A was shorter than for hydrofoil B. Surface roughness had a great influence on the process of cloud cavitation. The development of cloud cavitation around hydrofoil A consisted of two stages: (1) Attached cavities developed along the surface to the trailing edge; (2) A reentrant jet developed, resulting in shedding and collapse of cluster bubbles or vortex structure. Meanwhile, its development for hydrofoil B included three stages: (1) Attached cavities developed along the surface to the trailing edge, with accumulation and rotation of bubbles at the trailing edge of the hydrofoil affecting the flow field; (2) Development of a reentrant jet resulted in the first shedding of cavities. Interaction and movement of flows from the pressure side and suction side brought liquid water from the pressure side to the suction side of the hydrofoil, finally forming a reentrant jet. The jet kept moving along the surface to the leading edge of the hydrofoil, resulting in large-scale shedding of cloud bubbles. Several vortices appeared and dissipated during the process; (3) Cavities grew and shed again.

CLOUD PARAMETERIZATIONS, CLOUD PHYSICS, AND THEIR CONNECTIONS: AN OVERVIEW

International Nuclear Information System (INIS)

LIU, Y.; DAUM, P.H.; CHAI, S.K.; LIU, F.

2002-01-01

This paper consists of three parts. The first part is concerned with the parameterization of cloud microphysics in climate models. We demonstrate the crucial importance of spectral dispersion of the cloud droplet size distribution in determining radiative properties of clouds (e.g., effective radius), and underline the necessity of specifying spectral dispersion in the parameterization of cloud microphysics. It is argued that the inclusion of spectral dispersion makes the issue of cloud parameterization essentially equivalent to that of the droplet size distribution function, bringing cloud parameterization to the forefront of cloud physics. The second part is concerned with theoretical investigations into the spectral shape of droplet size distributions in cloud physics. After briefly reviewing the mainstream theories (including entrainment and mixing theories, and stochastic theories), we discuss their deficiencies and the need for a paradigm shift from reductionist approaches to systems approaches. A systems theory that has recently been formulated by utilizing ideas from statistical physics and information theory is discussed, along with the major results derived from it. It is shown that the systems formalism not only easily explains many puzzles that have been frustrating the mainstream theories, but also reveals such new phenomena as scale-dependence of cloud droplet size distributions. The third part is concerned with the potential applications of the systems theory to the specification of spectral dispersion in terms of predictable variables and scale-dependence under different fluctuating environments