A two-dimensional numerical mesoscale model, which ic1udes radiative and turbulent transfers, has been constructed to study the formation, development and dissipation of coastal stratus cloud under an inversion. In the model, the delta-Eddington and emissivity approximations are used for the solar and thermal radiative transfers, respectively. K-theory parameterization is adopted for the turbulent transfer. Ground surface temperature and moisture are predicted using the methods of Deardorff (1977, 1978). This model is applied to a domain which extends 180 km into sea and 240 km inland horizontally and about 2 km from the earth1s surface vertically. A bare, flat soil surface is assumed. As a prelude to the study of the stratus cloud, sea breeze circulations with and without a temperature inversion have been investigated. The model without an inversion yields speeds of the sea breeze front which are close to the values that have been observed under insolation and other meteorological conditions similar to those used in the model. The presence of an inversion causes the depth of sea breeze circulation to be shallower and its inland penetration during the evening hours to be weaker compared to the case without inversion; however, the basic structure of the sea breeze circulation is unaffected by the inversion. The model has been used to study the growth, development and dissipation of stratus cloud under an inversion in the west coast region of the United States. The effects of large scale motions on these processes have also been examined. Cloud parameters such as the times of initial formation and of dissipation inland, the maximum distance of inland penetration, the maximum liquid water path and the cloud-top height are affected in the presence of such large scale motions; for example, both the maximum liquid water path and the cloud-top height are appreciably enhanced - by about a factor of two - when large scale westerly winds (U[subscript g]=5mfs, V[subscript g]=0) are present compared to the case when U[subscript g]=V[subscript g]=0. The cloud parameters predicted by the model are in close correspondence with existing observations in southern California. It is found that the sea breeze circulation is not appreciably affected by the presence of moderate amounts of stratus cloud. While advection plays a dominant role in the horizontal development of the stratus cloud inland, radiative processes (cooling and heating) are observed to govern the vertical growth and dissipation of the cloud layer. Vertical growth is influenced by the rate of radiative cooling at cloud-top. Because of the combined effects of solar and surface heating, the stratus inland is observed to dissipate more rapidly during the morning hours than the cloud over the ocean where surface heating is minimal. / Graduation date: 1984

A procedure for model-assisted climate impact assessment is developed. The approach combines data from observations and atmospheric general circulation models (GCNs), and provides the basis for a potentially valuable means of using information derived from GCMs for climate impact assessments on local scales. The first component of this procedure is an extension of the 'climate inverse' method of Kim al. (1984). Daily mesoscale temperature and precipitation values are stochastically specifed on the basis of observational data representing the average over an area corresponding to a GCN grid element. Synthetic local data sets generated in this manner resemble the corresponding observations with respect to various spatial and temporal statistical measures. A method for extrapolation to grid-scale 'scenarios' of a changed climate on the basis of control and experimental integrations of a GCM, in conjunction with observational data, is also presented. The statistical characteristics of daily time series from each of these data sources are portrayed in terms of the parameters of a multivariate time-domain stochastic model. Significant differences between the model data sets are applied to the corresponding parameters derived from the observations, and synthetic data Bets representing the inferred changed climate are generated using Monte-Carlo simulations. The use of the procedure is illustrated in a case study. The potential climatic impacts of a doubling of atmospheric carbon dioxide concentrations on three important North American grain cropping regions is investigated using two 'physiological' crop models. Although the specific results must be interpreted with caution, they are moderately optimistic and demonstrate possible means by which agricultural production may adapt to climatic changes. / Graduation date: 1987

Graduation date: 1984

The nonlinear response of an ocean system subjected to random excitations can exhibit very complex dynamic behaviors including jump phenomena and coexistence of attractors. In this study, the stochastic system response behavior of a simple (Duffing) oscillator under narrow-band random excitations is first examined in the subharmonic resonance region. A semi-analytical procedure based on the nonlinear response characteristics of the corresponding deterministic system is developed to derive the response transition probabilities within individual attraction domains and among finite attraction domains under the assumptions of stationarity and Markov process. Overall response amplitude probability distributions are obtained by applying the Bayes formula to the two different types of response transition probability distributions. To validate the prediction capability of the semi-analytical method, numerical simulation of the responses of the Duffing system are generated and statistical characteristics of the response behavior are compared with prediction results. It is shown that the semi-analytical procedure provides more accurate predictions than other approximate methods available in the literature. A parametric study on the effects of variations in excitation intensity and degree of narrow-bandedness is conducted. Results confirmed that the nonlinear response characteristics including jump phenomenon and co-existence of attraction domains are preserved under narrow-band random excitations. The semi-analytical prediction method developed above is then applied to analyze the stochastic response behavior of a nonlinear mooring system subjected to random ocean waves. For modeling of the structural system, a nonlinear�� structure, nonlinearly-damped (NSND) model is employed and a reverse multiple�� input/single-output technique is applied to identify the system coefficients. To verify the accuracy and capability of the semi-analytical method in predicting the complex behaviors of the nonlinear mooring system, analytical predictions are compared with experimental results and numerical simulations. System response amplitude probability distributions predicted by the semi-analytical procedure are shown to be in good agreement with experimental and simulation results. / Graduation date: 2001

This dissertation addresses three topics on applied microeconomics. First, we investigate issues of market power and tax incidence in the U.S. brewing industry. Since alcohol consumption can be addictive, we derive a structural econometric model of addiction from a dynamic oligopoly game. This model identifies the degree of market power in a dynamic setting and allows us to test the hypothesis that federal tax incidence differs from state excise tax. Results indicate that beer producers have a modest market power and an increase in federal excise tax is more effective to reduce consumption than state excise taxes. Second, we estimate the effect of sulfur dioxide (S0���) emissions regulations on the productivity growth and opportunity cost of 261 phase I generating units. The Clean Air Act Amendment (CAAA) of 1990 required units to reduce emissions to 2.5 pounds per mmBTU fuel input in the phase I period (1995-99). We calculate Luenberger productivity indicators using directional technology distance function for 209 units in 1990-1999. There is more potential to reduce pure technical inefficiency since it is the main source of inefficiency in phase I period. Productivity declined, hut it i not significantly different from the productivity growth of pre-phase I. So environmental policy is successful to reduce SO��� emission without sacrificing productivity growth. Opportunity cost declined, but the opportunity cost of scrubber and "other" strategy increase. Third, we estimate the regulatory effect on strategy choice of 257 phase I units using multinomial logit model. We assume behavioral cost is a function of shadow input prices, output, SO��� emissions and regulatory variables. Results suggest regulation significantly affect choices. Units located in high-sulfur coal states are more likely to choose scrubber, allowance or "other" strategy through shadow capital price effect. Allowance trade and sales restriction negatively affect allowance, scrubber or fuel switch strategy. Non-private units are more likely to choose allowance strategy while private units are likely to choose less uncertain scrubber and fuel switch. Units subject to stringent local regulation are more likely to choose "other" strategy and scrubber and units with substitution/compensation boilers are more likely to choose allowance and "other" strategies. / Graduation date: 2003

Graduation date: 1998

Graduation date: 1997

This thesis presents an examination of the nearshore wave bottom boundary layer under conditions of significant sediment response. Using both field observations and simple models, the response of the bottom boundary layer to random waves is shown to have a complex behavior. First, the linearized wave bottom boundary layer governing equation is solved with a transformation of the cross-shore velocity to a distorted spatial domain, resulting in an analytic expression for the temporal and vertical structure of the cross-shore velocity under an arbitrary wave field. Model predictions of the bed shear velocity are in good agreement with laboratory measurements. The model is limited by assuming zero velocity at a fixed bed and that turbulence generation is solely due to bottom shear. Next, a comprehensive set of near bed cross-shore velocity, sediment suspension, and bed elevation observations, collected in 2 m water depth on the North Carolina coast, are presented. The observations show a cross-shore velocity structure which decays with increasing proximity to the bed as predicted by simple theory. Bottom shears based on rms amplitude decay and time-averaged phase shifts are lower than model predictions and may be indicative of more rapid mixing of momentum than assumed in the above model. Also, frequency-dependent estimates of the phase and amplitude vertical structure show a nonlinear response of the wave bottom boundary layer over the incident band. Through most flow phases, estimates of turbulent kinetic energy increase linearly from the bed, however under large wave crests, enhanced turbulence levels are observed and are well correlated to active sediment suspension events. Estimates of dissipation rates are significantly less than those observed in an actively breaking surf zone wave, and significantly greater than those observed in ocean boundary layers, and continental shelf current boundary layers. Finally, an Oregon coast field experiment showed an intermittent high frequency velocity variance structure which was correlated to suspended sediment events. A linear shear instability analysis determined that during the period of flow reversal there exists a potential for generating turbulence due to shear instabilities of the vertical structure of cross-shore velocity. / Graduation date: 1997

Design phase decisions based on diagnosability lead to lower system costs and, in turn, higher quality products by means of reducing maintenance time and increasing system reliability. A case for diagnosability is presented. Functions of diagnosability are expounded upon including life cycle costs, statistical analysis, and design criterion to emphasize the necessity of diagnosability analysis early in the design phase. A diagnosability prediction metric is developed for system modeling of component failure rates and unjustified removals. The metric emphasizes ambiguity of system component indications as well as system structure. The metric is evaluated using historical data from the bleed air control system (BACS) on the Boeing 737-300. Seven design changes are suggested based on improving system diagnosability by changing component functions, modifying indications, and adding or changing sensors. The resulting designs are compared via Boeing's life cycle cost mechanism, DEPCOST model, based on cost improvements. It is shown that system improvements based on this prediction technique will increase the quality of a product since increased diagnosability decreases life cycle costs. / Graduation date: 1996

Graduation date: 1996