Thesis (Ph. D.)--University of Chicago, Dept. of the Geophysical Sciences, June 2000. / Includes bibliographical references. Also available on the Internet.

The advent of satellite limb scatter measurements has allowed the stratosphere to be studied at a scope unparalleled by previous observational techniques, affording the opportunity to study structures on both small spacial and temporal scales. Utilizing these measurements to their fullest has fueled the development of radiative transfer models to simulate the measurements, but also inversion techniques to retrieve atmospheric parameters. The limb scatter instrument OSIRIS, onboard the Odin satellite, is currently used in conjunction with the SASKTRAN radiative transfer model and multiplicative algebraic reconstruction technique to retrieve stratospheric aerosol extinction. In this work, the aerosol information content of limb scatter measurements is explored and an improved version of the aerosol retrieval is developed through the simultaneous retrieval of a second aerosol parameter, the Angstrom coefficient, which is related to particle size. The sensitivity of limb scatter measurements to aerosol is investigated through forward modelling of OSIRIS measurements as a function of wavelength, satellite geometry and particle size. Information content of the measurements is investigated to determine the feasibility of retrieving various aerosol size parameters and a simple linear inversion technique is tested. Results from this study are used to develop a non-linear inversion technique with minimal sensitivity to the required assumptions. Incorporation of longer wavelength data into the retrieval allows for the determination of the wavelength dependence of the scattered signal, which when combined with a lognormal particle size distribution of constant mode width allows for the retrieval of aerosol number density and mode radius. Conversion of these parameters to extinction and the Angstrom coefficient provides retrieved quantities with minimal dependence on the assumed size distribution. Application of this technique to the OSIRIS data set shows improved extinction results through both internal comparisons of the data and when compared with other results from SAGE II, III and CALIPSO satellite measurements. Although the retrieved Angstrom coefficient shows some bias due to the required assumptions, comparisons with the SAGE II data set show considerable improvement over the apriori estimate.

Thesis (Ph. D.)--York University, 1999. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 166-174). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL:http://gateway.proquest.com/openurl?url_ver=Z39.88-2004 & res_dat=xri:pqdiss & rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation & rft_dat=xri:pqdiss:NQ39262.

No description available.

No description available.

The polar vortex is a large scale cyclone located in the middle atmosphere near to the planet’s geographic poles. These vortices form during the hemispheric winter and break down in the spring of the following year. They may also break down in mid winter, causing a sudden stratospheric warming event (SSW). The vortex is thought to be preconditioned leading up to these warming events, resulting in the breakdown of the vortex. Integral diagnostics are used to investigate the stripping of air from the vortex as part of this preconditioning. Contour diagnostics of mass and circulation are calculated using ERA-40 reanalysis data for the stratosphere. The edge of the vortex is easily identifiable in these diagnostics as a high gradient of Ertel’s potential vorticity (PV), and the warming events are also clearly visible. From these the amount of air removed from the vortex is determined from the balance equation of the mass integral. These terms show that there are significant amounts of air removed from the vortex, with several stripping events identifiable in them through the winter, especially in those during which a major sudden warming event occurred. These stripping events can be seen in corresponding PV maps, where tongues of PV can be seen to be stripped from the vortex and mixed into the surrounding surf zone of turbulent air. From the integral diagnostics a Lagrangian measure of the meridional circulation in the stratosphere is also calculated. In the final part of the thesis a shallow water model is used to investigate a quantitative link between forcing and the amount of stripping of the vortex. It is found that when the forcing is large enough there is significant stripping of mass from the vortex. This does not lead to SSWs in all cases, and the total amount of stripping is not found to be proportional to the maximum amplitude of the forcing.

It has been shown by Schlesinger and Mintz (1979) that the UCLA general circulation model (GCM) is able to simulate the observed negative correlation between the total amount of ozone in a vertical atmospheric column (the total ozone) and the eastward-propagating synoptic disturbances in the troposphere, with the total ozone maxima and minima located respectively at the troughs and ridges of the tropospheric waves. The goal of the present study was to understand how the GCM simulated this observed relationship. Our analysis shows that the transient-eddy total ozone disturbances were an omnipresent feature of the GCM January simulation in the northern hemisphere midlatitudes, just as they are in nature. It is also found that the transient-eddy total ozone disturbances in the northern hemisphere midlatitudes were closely related to the transient-eddy geopotential heights there throughout the entirety of the simulation. Furthermore, the correlations between these two quantities are negative up to the 72 mb level and attain their largest negative values at the 300 mb level. The analysis also shows that the transient-eddy disturbances in the stratosphere are out of phase with their counterparts in the troposphere, in accord with what would be expected from Dines compensation. In the GCM simulation there is a well-defined positive correlation between the total ozone and the ozone content in each of the model layers in the upper troposphere and lower and middle stratosphere. It is found that although layers 5-8 (19.3-150 mb) contain the largest percentage of the total ozone, it is predominantly layers 6-9 (37.3 -300 mb) that make the largest contribution to the temporal variations of total ozone. In accordance with the observations, a strong negative correlation is found between the simulated total ozone and the height of the simulated tropopause. However, changing the height of the tropopause cannot in itself change the total ozone, but rather only its partitioning between the stratosphere and the troposphere. Our analysis clearly shows that it is the ozone convergence and divergence in an atmospheric column, not the photochemical ozone production and destruction, which are responsible for the synoptic increases and decreases of total ozone. / Graduation date: 1988

This thesis provides highlights of the atmospheric research conducted during the program of studies 2003-07. The theme is variability of the winds at mesospheric heights (60-100 km) due to Planetary Waves (PW, 2-30 days) over middle and high latitudes. Considerable energy and momentum are transported by atmospheric waves, and their global characteristics are required to understand many phenomena and explain coupling processes within the atmosphere. The vertical propagation of PW from the upper troposphere to the mesosphere is investigated by applying the Morlet wavelet and wave number analysis to the MetO (United Kingdom Meteorological Office) stratospheric assimilated fields, TOMS total (column) ozone, and Medium Frequency (MFR) and Meteor Wind (MWR) radar measurements. The results show that large-scale eastward propagating PW dominate at tropopause and low stratospheric heights, while westward PW become comparable or even stronger in the upper stratosphere and above during months other than summer. There are also strong seasonal dependences of the PW activity in each of the stratospheric and mesospheric regions, which are attributed, at least partially, to the influence of the background wind on PW propagation. Longitudinal variations in PW activity are explained by longitudinal variations in these winds.<p>During summer (westward zonal winds) PW activity is reduced in the stratosphere and only relatively fast westward propagating PW, such as quasi 2-day wave (Q2DW), are able to reach mesospheric heights from below. The results obtained using 14 years of MFR data at Saskatoon provide a unique climatology (70-100 km) of this wave: in addition to summer activity the Q2DW is also present at low mesospheric heights in winter, especially when the eastward winds are weak; there are significant interannual variations in Q2DW activity in both seasons. Strong latitudinal and longitudinal differences in Q2DW occurrence and amplitude are shown from the comparisons of wind data at several stations.<p>During winter, when zonal winds are eastward, the PW coupling between stratosphere and mesosphere is stronger than during other seasons. Detailed data analysis has been performed for the Arctic winter of 2004/05, for which the stratospheric state is described using conventional zonal mean parameters as well as the newer Q-diagnostic. Spectral analyses for this winter show relatively weak PW activity at stratospheric and mesospheric heights and strong latitudinal and longitudinal differences of mean winds and PW characteristics consistent with the form and location of the polar vortex. <p>In addition to the vertical coupling it has also been shown that weaker horizontal inter-hemispheric coupling occurs during equinoctial months, when eastward winds dominate globally. It is demonstrated that with favorable conditions, planetary waves with 10, 16 and 25 day periods penetrate to the opposite hemisphere.

This thesis provides highlights of the atmospheric research conducted during the program of studies 2003-07. The theme is variability of the winds at mesospheric heights (60-100 km) due to Planetary Waves (PW, 2-30 days) over middle and high latitudes. Considerable energy and momentum are transported by atmospheric waves, and their global characteristics are required to understand many phenomena and explain coupling processes within the atmosphere. The vertical propagation of PW from the upper troposphere to the mesosphere is investigated by applying the Morlet wavelet and wave number analysis to the MetO (United Kingdom Meteorological Office) stratospheric assimilated fields, TOMS total (column) ozone, and Medium Frequency (MFR) and Meteor Wind (MWR) radar measurements. The results show that large-scale eastward propagating PW dominate at tropopause and low stratospheric heights, while westward PW become comparable or even stronger in the upper stratosphere and above during months other than summer. There are also strong seasonal dependences of the PW activity in each of the stratospheric and mesospheric regions, which are attributed, at least partially, to the influence of the background wind on PW propagation. Longitudinal variations in PW activity are explained by longitudinal variations in these winds.<p>During summer (westward zonal winds) PW activity is reduced in the stratosphere and only relatively fast westward propagating PW, such as quasi 2-day wave (Q2DW), are able to reach mesospheric heights from below. The results obtained using 14 years of MFR data at Saskatoon provide a unique climatology (70-100 km) of this wave: in addition to summer activity the Q2DW is also present at low mesospheric heights in winter, especially when the eastward winds are weak; there are significant interannual variations in Q2DW activity in both seasons. Strong latitudinal and longitudinal differences in Q2DW occurrence and amplitude are shown from the comparisons of wind data at several stations.<p>During winter, when zonal winds are eastward, the PW coupling between stratosphere and mesosphere is stronger than during other seasons. Detailed data analysis has been performed for the Arctic winter of 2004/05, for which the stratospheric state is described using conventional zonal mean parameters as well as the newer Q-diagnostic. Spectral analyses for this winter show relatively weak PW activity at stratospheric and mesospheric heights and strong latitudinal and longitudinal differences of mean winds and PW characteristics consistent with the form and location of the polar vortex. <p>In addition to the vertical coupling it has also been shown that weaker horizontal inter-hemispheric coupling occurs during equinoctial months, when eastward winds dominate globally. It is demonstrated that with favorable conditions, planetary waves with 10, 16 and 25 day periods penetrate to the opposite hemisphere.

Interactions between societal, natural, and infrastructure systems can be beneficial or harmful to society. Society benefits from natural systems by being provided with the basic necessities of life (air, water, and food). However, events such as stratospheric ozone depletion demonstrate that society ultimately can be harmed by societal impacts on natural systems. Domain knowledge is developed from observation of natural, societal, and infrastructure systems. Domain knowledge is contained within scientific knowledge and engineering knowledge. Scientific knowledge is gained through structured observation and rigorous analysis of natural and societal systems. Engineering knowledge is partially developed from scientific knowledge and is used to manipulate natural and societal systems. Technology is the application of engineering knowledge. In the past two centuries scientific and engineering knowledge have produced technologies that affect the interaction between societal and natural systems. Although scientists and engineers are in positions to advise on policies to address problems involving societal/natural system interactions, their contributions are not always fully utilized. This research examines feedback mechanisms that describe societal, natural, and infrastructure system interaction to develop an improved understanding of the dynamic interactions between society, natural systems, infrastructure systems, scientific and engineering knowledge, technology, and public policy. These interactions are investing through and opposing case study analysis performed using computer simulation modeling. The stratospheric ozone depletion study represents a case in which domain experts successfully influenced public policy. The U.S. civilian nuclear power study represents a case in which domain experts were less successful in influencing public policy. The system dynamics methodology is used to construct these two highly integrated models of societal-natural system interaction. Individual model sectors, based on existing theory, describe natural/infrastructure systems, knowledge and technology development, societal risk perception, and public policy. The work reveals that the influence of scientists and engineers in the public policy is due in part to their ability to shift dominance between causal feedback mechanisms that seek to minimize societal risk from natural systems and feedback mechanisms that seek to minimize the economic risk of increased regulations. The ability to alter feedback mechanism dominance is not solely dependent upon scientists and engineers ability to develop knowledge but to a larger extent depends on their ability to interact with policy makers and society when describing issues involving natural and infrastructure systems.