Characteristic features of the long atmospheric waves are discussed on the basis of spherical harmonic analysis of global weather charts for September 1957. At first, there is a discussion of the Trapezoidal and Simpson's numerical integration rules as applied to the computation of the Spherical harmonic coefficients. [...]

Spectral analysis (primarily in terms of spherical harmonics) is applied to the atmospheric dynamical equations in general, to truncated barotropic systems in particular and, in addition, to the global geopotential height field of the 500 mb surface for September 1957. [...]

A study was made in Alberta of the pattern of hailfall from four swath-giving storms, in order to determine whether or not, within the borders of the swath, there existed local hail-free regions. [...]

Measurements made by the AVHRR (Advanced Very High Resolution Radiometer) on board of five NOAA polar orbiting satellites were used to retrieve cloud optical depth (τ) and cloud droplet effective radius (r[sub eff]) for marine boundary layer clouds over the Pacific Ocean west of California and over the Southern Ocean near Tasmania. Retrievals were obtained for 21 days of data acquired between 1987 and 1995 from which over 300 subscenes ~ 256 km x 256 km in size were extracted. On this spatial scale cloud fields were found to have mean τ between 8 and 32 and mean r[sub eff] between 6 and 17 μm. The frequency distribution of τ is well approximated by a two parameter gamma distribution. The gamma distribution also provides a good fit to the observed r[sub eff] distribution if the distribution is symmetric or positively skewed but fails for negatively skewed or bi-modal distributions of r[sub eff] which were also observed. The retrievals show a relationship between τ and r[sub eff] which is consistent with a simple "reference" cloud model with reff ~ r[sup 1 / 5]. The proportionality constant depends on cloud droplet number concentration N and cloud subadiabaticity β through the parameter N[sub sat] = N/ [sq rt. Β]. Departures from the reference behaviour occur in scenes with spatially coherent N[sub sat] regimes, separated by a sharp boundary. AVHRR imagery is able to separate two N[sub sat] regimes if they differ by at least 30% in most cases. Satellite retrievals of τ and r[sub eff] were compared with in situ aircraft measurement near Tasmania. The retrievals overestimated r[sub eff] by 0.7 to 3.6 μm on different flights, in agreement with results from earlier comparison studies. The r[sub eff] overestimation was found to be an offset independent of τ. The reference cloud model and the N[sub sat] retrieval were tested on aircraft data and yield results consistent with direct in situ measurements of N and 8. Spectral and multifractal analyses of the spatial structure of cloud visible radiance, τ and r[sub eff] fields in 34 satellite scenes revealed scale breaks at 3 to 2 km in all analysed scenes in agreement with some earlier observations (Davis et al. (1996a)) but in contrast with other work (Lovejoy et al. (1993)). The nonstationarity H(1) and intermittency C(1) parameters were computed for the 34 scenes, stratified using the reference cloud model and according to mean τ and r[sub eff]. Similar values of H(1) and C(1) were found in all these categories. These measurements of the frequency distribution and spatial variability of τ, r[sub eff], liquid water path (Iwp), and N[sub sat] can be used to place constraints on mesoscale models of layer clouds.

<p> In the presence of a sufficient temperature gradient, snow evolves from an isotropic network of ice crystals to a transversely isotropic system of depth hoar chains. This morphology is often the weak layer responsible for full depth avalanches. Previous research primarily focused on quantifying the conditions necessary to produce depth hoar. Limited work has been performed to determine the underlying reason for the microstructural changes. Using entropy production rates derived from nonequilibrium thermodynamics, this research shows that depth hoar forms as a result of the snow progressing naturally toward thermal equilibrium. </p><p> Laboratory experiments were undertaken to examine the evolution of snow microstructure at the macro scale under nonequilibrium thermal conditions. Snow samples with similar initial microstructure were subjected to either a fixed temperature gradient or fixed heat input. The metamorphism for both sets of boundary conditions produced similar depth hoar chains with comparable increases in effective thermal conductivity. Examination of the Gibbs free energy and entropy production rates showed that all metamorphic changes were driven by the system evolving to facilitate equilibrium in the snow or the surroundings. This behavior was dictated by the second law of thermodynamics. </p><p> An existing numerical model was modified to examine depth hoar formation at the grain scale. Entropy production rate relations were developed for an open system of ice and water vapor. This analysis showed that heat conduction in the bonds had the highest specific entropy production rate, indicating they were the most inefficient part of the snow system. As the metamorphism advanced, the increase in bond size enhanced the conduction pathways through the snow, making the system more efficient at transferring heat. This spontaneous microstructural evolution moved the system and the surroundings toward equilibrium by reducing the local temperature gradients over the bonds and increasing the entropy production rate density. </p><p> The employment of nonequilibrium thermodynamics determined that the need to reach equilibrium was the underlying force that drives the evolution of snow microstructure. This research also expanded the relevance of nonequilibrium thermodynamics by applying it to a complicated, but well bounded, natural problem.</p>

<p> A survey of observations and analyses of the Mars year (MY) 25 planet-encircling dust storm (PDS) on Mars is presented. The environmental causes and dynamical mechanisms responsible for PDS initiation, expansion, decay, and interannual frequency are not fully understood. PDS seasonal occurrence suggests the presence of climatic and environmental components, yet interannual variability suggests that initiation and expansion mechanisms are not solely seasonal in character. The objectives of this research were to better understand the dynamical processes and circulation components responsible for MY 25 PDS initiation and evolution and to analyze why a PDS developed in MY 25 and not in MY 24 or 26.</p><p> Negative anomalies in temperature data with &sim;3-sol periodicity indicate the presence of baroclinic eddies. After comparing these eddies with dust storms observed in satellite imagery, the author hypothesized that six eastward-traveling transient baroclinic eddies triggered the MY 25 precursor storms due to the enhanced dust lifting associated with their low-level wind and stress fields. They were followed by a seventh eddy that contributed to dust storm expansion. All seven eddy cold anomalies were less than &ndash;4.5 K. It is possible that the sustained series of high-amplitude eddies in MY 25 were a factor in PDS onset and expansion.</p>

<p> Northeastern and mid-Atlantic United States are understudied from the perspective of hurricane vulnerability. In an attempt to fill this gap in research, this dissertation attempted to assess the hurricane vulnerability of the northeastern and mid-Atlantic United States through the construction of a Composite Hurricane Vulnerability Index (CHVI) for 184 counties extending from Maine to Virginia. The CHVI was computed by incorporating indicators of human vulnerability and physical exposure. Human vulnerability was derived from demographic, social and economic characteristics whereas physical exposure was based on attributes of the natural and built up environments. The spatial distribution of the CHVI and its component indices were examined and analyzed to meet the research goals, which were a) to develop indices of human vulnerability, physical exposure and composite hurricane vulnerability for all counties; b) to assess vulnerability distribution in terms of population size, metropolitan status (metropolitan versus non metropolitan counties) and location (coastal versus inland counties); c) to identify the specific underlying causes of vulnerability; d) to identify the significant clusters and outliers of high vulnerability; and e) to examine overlaps between high human vulnerability and high physical exposure in the region.</p><p> Results indicated high overall vulnerability for counties that were metropolitan and / or coastal. Vulnerability was high at both ends of the population continuum. Coastal areas had high natural exposure whereas metropolitan areas had high built exposure. In large metropolitan counties, human vulnerability was influenced most strongly by economic vulnerability. In non-metropolitan and small metropolitan counties, vulnerability was an outcome of a combination of demographic, social and economic factors. Vulnerability clusters and intersections pointed towards high vulnerability in the major cities along the northeastern megalopolis, in the Hampton Roads section of Virginia and in parts of Delmarva Peninsula. </p><p> Research findings have important implications for disaster management. Evidence of relationship of population size, metropolitan status and location with vulnerability levels provides a new perspective to vulnerability assessment. Identification of high vulnerability counties can lead to effective resource allocation and emergency management and mitigation plans. Detection of dominant underlying causes of vulnerability can help develop targeted strategies for vulnerability reduction.</p>

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