Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2007. / Yeung, Pui-Kuen, Committee Member ; Lieuwen, Tim, Committee Member ; Menon, Suresh, Committee Chair ; Seitzman, Jerry, Committee Member ; Syed, Saadat, Committee Member.

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xxiv, 371 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 343-367).

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science. / Supervised by Edward N. Lorenz. / Includes bibliographical references (leaves 141-145). / by Lin Ho. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science / Bibliography: leaves 39-41. / by Giovanna Salustri. / M.S.

No description available.

Large eddy simulation is used to study the large-scale structures in a low subsonic mixing layer and their breakdown to small scales. For 3-D simulations, different finite-difference and pseudo-spectral schemes are tested. The (2, 4) MacCormack Scheme developed by Gottlieb and Turkel (1976) shows the best overall performance. It is very fast and supplies enough but not excessive artificial dissipation. Though slower than MacCormack scheme, the pseudo-spectral method has its advantage: high resolution of the high-wavenumber range when adequate de-aliasing scheme is used. When efficient fast Fourier transform routines are available, this method can be a very good alternative to the MacCormack scheme. Most of the simulations use a modified Smagorinsky-type model (Erlabacher et al. 1992). The effect of different models and model constants is also studied. It is found that the two subgrid-scale (SGS) models, the Smagorinsky model and the linear combination model (Bardina et al. 1983), show significant difference even at the low wavenumber range of the spectra. In the study of three-dimensional subsonic temporal mixing layers, it is found that the streamwise vortex tubes play an important role in the transition process. The vortex interaction of the streamwise vortex tubes and undulated spanwise vortex structures proves to be the dominant mechanism in the development of three-dimensionality and the subsequent generation of small-scale motions. In the absence of pairing of the spanwise vortex tubes, this vortex interaction causes uneven distribution of vorticity along the span of the spanwise vortex tubes and the breaking of the large structures. Following the breaking of the spanwise vortex tubes, the secondary streamwise vortex tubes become the dominant vortex structures. In the case involving pairing, it is found that the relative motion of the spanwise vortex tubes in the pre-pairing process creates much stronger strain rate field between the pairing vortex tubes than the case without pairing. The stronger strain rate field leads to the formation of streamwise vortex tubes with very high vorticity and low induced pressure. This also leads to much stronger vortex interaction between the spanwise and streamwise vortex tubes due to the increased strength of the streamwise vortex tubes. / Ph. D.

The atmospheric concentration of methane \((CH_4)\) - the most significant non-\(CO_2\) anthropogenic long-lived greenhouse gas - stabilized between 1999 and 2006 and then began to rise again. Explanations for this behavior differ but studies agree that more measurements and better modeling are needed to reliably explain the model-data discrepancies and predict future change. This dissertation focuses on measurements of \(CH_4\) and inverse modeling of atmospheric \(CH_4\) fluxes using field measurements at a variety of spatial scales. We first present a new fast-response instrument to measure the isotopic composition of \(CH_4\) in ambient air. The instrument was used to characterize mass fluxes and isofluxes (a isotopically-weighted mass flux) from a well-studied research fen in New Hampshire. Eddy-covariance and automatic chamber techniques produced consistent estimates of both the \(CH_4\) fluxes and their isotopic composition at sub-hourly resolution. We then characterize fluxes of \(CH_4\) from aircraft engines using measurements made with the same instrument during the Alternative Aviation Fuel Experiment (AAFEX), a study that aimed to determine the atmospheric impacts of alternative fuel use in the growing aviation industry. Emissions of \(CO_2\), \(CH_4\), and \(N_2O\) from different synthetic fuels were statistically indistinguishable from those of the widely used JP-8 jet fuel. We then present airborne observations of the long-lived greenhouse gas suite – \(CO_2\), \(CH_4\), \(N_2O\), and CO – during two aircraft campaigns, HIPPO and CalNex, made using a similar instrument built specifically for the NCAR HIAPER GV aircraft. These measurements are compared to data from other onboard sensors and show excellent agreement. We discuss the details of the end-to-end calibration procedures and the data quality-assurance and quality-control (QA/QC). Lastly, we quantify a top-down estimate of California’s \(CH_4\) emission inventory using the CalNex \(CH_4\) observations. Observed \(CH_4\) enhancements above background concentrations are simulated using a lagrangian transport model driven by validated meteorology. A priori source-specific emission inventories are optimized in a Bayesian inversion framework to show that California’s \(CH_4\) budget is 1.6 ± 0.34 times larger than the current estimate of California’s Air Resources Board (CARB), the body charged with enforcing the California Global Solutions Act and tracking emission changes over time. Findings highlight large underestimates of emissions from cattle and natural gas infrastructure. / Earth and Planetary Sciences

This thesis examines the link between airborne flux estimates of CO$ sb2$, sensible heat, and water vapor, and surface parameters retrieved by remote sensing. Chapter 1 analyses the relationship between surface temperature and vegetation indices, obtained from the Advanced Very High Resolution Radiometer on board of NOAA-9 and -10 satellites, and fluxes of sensible heat, latent heat, and CO$ sb2$, estimated from aircraft. Linear relationships between CO$ sb2$ and the Normalized Difference Vegetation Index (NDVI) or the Simple Ratio vegetation index (SR) are found on a daily basis, but a highly nonlinear relationship appears for the seasonal variation. Latent Heat fluxes showed the poorest correlations with surface parameters. A seasonal linear relationship appeared between sensible heat and NDVI. Local extreme flux values due to the intermittency of boundary layer dynamics largely contribute to lower the correlations; such variations are the reason for the difficulties in relating fluxes obtained from single overpasses and over short distances to fixed points at the surface. This problem is further examined in Chapter 2, in which conditional sampling of airborne flux estimates is used to characterize the turbulent structures that are carrying flux, and their link to the surface. The analysis confirms that few extreme events may carry a significant fraction of the flux. Missing or hitting one of these structures may translate into very large oscillations on the flux estimate that are often not directly coupled to surface characteristics. A much clearer surface 'signature' emerges when measurements are taken within the surface layer, since the reorganization of turbulent structures that takes place with increasing height will result in a merging of the signature that came from different sources at the surface. This helps to explain some of the poor correlations obtained in Chapter 1 and reinforces the need for a better understanding of the distributions of these tu

Grid-type flight patterns at an altitude of 30 m were executed in the summer of 1991 by the Canadian Twin Otter flux research aircraft over a 15 km x 16.5 km agricultural area, as part of the San Joaquin Valley Air Quality Study/California Ozone Deposition Experiment (SJVAQS/CODE). Fast-response on board sensors for turbulence, temperature and gas concentrations permitted the spatial mapping of fluxes of momentum, sensible heat, moisture, CO$ sb2$ and ozone. Flux maps were produced in the form of GIS-interpolated 1 km averages, and in the discrete form of those coherent structures of the turbulent process, intermittent in time and space, which dominate the exchange of scalars between the ground and the atmosphere. The magnitude of surface-related mesoscale contributions to the flux was also quantified. Flux observations were compared against radiometrically observed surface temperatures and vegetation indices (NDVI), observed from aircraft and satellite (NOAA AVHRR), and surface characteristics from ground surveys. / Flux maps showed the expected correspondence between greenness, evapo(trans)ration (ET) and CO$ sb2$ exchange. Discrepancies between ozone flux maps and maps of greenness, ET or CO$ sb2$ were more pronounced than would be consistent with the hypothesis of stomatal control of ozone uptake. More insight into control mechanisms on ozone exchange is gained by an examination of the spatial coincidence between transporting structures for the various scalars (heat, moisture, CO$ sb2$ and ozone), through the Jaccard coefficient of co-location (J), which showed a lower value ($ rm0.3<J<0.6$) for coincidence in transfer between ozone and moisture than between moisture and CO$ sb2$ ($ rm0.5<J<0.8$). Analysis of J over the various land-use and crop-types in the test area, opens a door to a more differentiated understanding of the physical and physiological driving forces behind ozone uptake by soil and vegetation.