No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 42-43). Also available via the Internet.

The dynamical nature of atmospheric disturbances in the Southern Hemisphere simulated by a two-level general circulation (GCM) model is studied. Time series of the dependent variables and diabatic heating components from 10 Southern Hemisphere winters (JJA) and summers (DJF) simulated by the Oregon State University two-level GCM are used. The time mean fields are presented and discussed. Variance and covariance analyses are performed to determine the geographical distribution, intensities and transport properties of high-frequency (periods between 2.5 and 10 days) and low-frequency (periods between 10 days and a season) transient eddies. These are discussed in terms of dynamical consistency with the time-mean circulation. It is found that the behavior of the high-frequency eddies at mid and high-latitudes is consistent with baroclinic instability theory, i.e., the eddies have properties similar to observed migratory weather disturbances. The low-frequency eddies appear to be quasi-stationary Rossby waves originating at middle latitudes. They seem to disperse energy in a manner consistent with arguments based on simple linear wave dynamics. During wintertime, the time mean flow directs eddies poleward where they grow by baroclinic processes. Also during wintertime, the slow phase velocity, fast group velocity and cyclic domain lead to quasi-resonant behavior on a hemispheric scale. / Graduation date: 1988

No description available.

A modified eddy correlation technique is applied to data obtained from a field experiment conducted in the Bight of Abaco during the Spring of 1990. The experiment yielded 3408 30 minute records of turbulent wind data sampled at 5 Hz. Wind stress estimates were successfully calculated for 3182 of these. The modification to the eddy correlation technique involved extending the cospectra to higher frequencies than were measured by the propeller anemometer to obtain a better estimate to the <i>uw</i> covariance. This resulted in a small increase to the <i>uw</i> covariance, and hence the drag coefficient. / Master of Science

Weak-wind flow in the nocturnal boundary is one of the most poorly understood problems in the field of meteorology. The understanding of weak-wind flows is essential for the improvement of regulatory dispersion models which are currently rendered invalid under weak-wind conditions and stable stratification. Recently there have been increased efforts directed towards improving the understanding nocturnal boundary layer dynamics. The results of these studies have shown that nocturnal boundary layer flows are often dominated by intermittent turbulence and motions occurring on horizontal scales ranging from hundreds of meters to several kilometers and on time scales of 1 minute to 1 hour. We refer to these scales as sub-meso. This connection has led to the hypothesis that intermittent turbulence generation may be the result of sub-meso motions that are subject to external forcing originating in the deeper boundary layer. However, these processes have proven difficult to measure as traditional sensor networks have failed to provide the vertical and horizontal coverage necessary to observe the driving forces on these scales. This study sought to close this knowledge gap using SOund Detection And Ranging (SODAR). SODAR is a ground based acoustic remote sensing technology that is capable of measuring wind and turbulence at multiple heights in the boundary layer. Data were collected with a pair of SODAR systems with sequentially increasing separation distance at the Oregon State University Botany and Plant Pathology lab during the summer of 2010. The data have indicated that motion occurring on time scales of 2 minutes to 32 minutes are isolated to the lowest 50 meters of the nocturnal boundary layer. Surface-layer measurements were collected using a pair of sonic anemometers placed at heights of 1.5 and 7 meters above ground level. Comparisons of surface-layer measurements and deeper boundary layer measurements have shown that when the surface layer stratification is stable, processes within the surface layer are not likely to be influenced by external forcing from aloft. In contrast external forcing from the deeper boundary layer may still have an influence on weak, nocturnal surface flows when the surface layer is weakly stratified as is shown for the case of low-level jets. / Graduation date: 2013

No description available.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 145-156).

<p> A study of metal enrichment of the intergalactic medium (IGM) using a series of smooth particle hydrodynamics (SPH) simulations is presented, employing models for metal cooling and the turbulent diffusion of metals and thermal energy. An adiabatic feedback mechanism was adopted where gas cooling was prevented on the timescale of supernova bubble expansion to generate galactic winds without explicit wind particles. The simulations produced a cosmic star formation history (SFH) that is broadly consistent with observations until z ~ 0.5, and a steady universal neutral hydrogen fraction (OHI) that compares reasonably well with observations. The evolution of the mass and metallicities in stars and various gas phases was investigated. At z=O, about 40% of the baryons are in the warm-hot intergalactic medium (WHIM), but most metals (80%-90%) are locked in stars. At higher redshifts the proportion of metals in the IGM is higher due to more efficient loss from galaxies. The results also indicate that IGM metals primarily reside in the WHIM throughout cosmic history, which differs from simulations with hydrodynamically decoupled explicit winds. The metallicity of the WHIM lies between 0.01 and 0.1 solar with a slight decrease at lower redshifts. The metallicity evolution of the gas inside galaxies is broadly consistent with observations, but the diffuse IGM is under-enriched at z ~ 2.5. Metals enhance cooling which allows WHIM gas to cool onto galaxies and increases star formation. Metal diffusion allows winds to mix prior to escape, decreasing the IGM metal content in favour of gas within galactic halos and star forming gas. Diffusion significantly increases the amount of gas with low metallicities and improves the density-metallicity relation. </p> <p> The galactic wind generation mechanism and the wind properties from our simulations were investigated. It was found that: 1. Galactic winds are most efficient for halos in the intermediate mass range 10^10Mo - 10^11 Mo . These winds dominate the metal ejection at all redshifts, although towards lower redshift the contributions from larger halos become relatively more important. At the low mass end gas is prevented from accreting onto halos and has very low metallicities. At the high mass end, the fraction of halo baryons escaped as winds declines along with the decline of stellar mass fraction in these halos. The decrease in wind ejection is likely because of the decreases in star formation activity, wind mass loading and wind escape efficiency as the halo mass increases. 2. The adiabatic feedback can generate winds with mass loading factors comparable to the ones used in explicit superwind models. The mass loading factor decreases towards lower redshift, implying that smaller halos have larger mass loading. 3. Metals located at lower density were generated at earlier epochs from small halos, suggesting that the wind traveling speed can affect the metal distribution in the IGM. </p> / Thesis / Doctor of Philosophy (PhD)

京都大学 / 新制・課程博士 / 博士(理学) / 甲第22984号 / 理博第4661号 / 新制||理||1669(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 藤 定義, 教授 佐々 真一, 教授 早川 尚男 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM