Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 155-167).

It has been demonstrated in past studies that drainage area (Ada) and mean annual precipitation depth (Pmean) are significant independent variables for predicting bankfull channel geometry. Bankfull width (Wbf), a particularly useful measure of bankfull channel geometry, is used in hydrology, fluvial geomorphology and stream ecology applications. Since precipitation depth does not generally have a normal distribution over a basin it is reasonable to question whether or not Pmean is the best measure of precipitation across a basin. That is, perhaps the median precipitation depth (P50) or the mean annual precipitation depth at the basin outlet (Poutlet) is more representative of precipitation in a basin. The objective of the study is to see if Pmean, P50, or Poutlet is a significantly better measure of precipitation in a watershed. Along with Ada, each of these precipitation measures was used to develop relationships for predicting Wbf for basins located across the continental U.S. Using several goodness-of-fit statistics i.e., coefficient of determination(R2), Standard error of estimates(SEE) and Akaike Information Criterion(∆AIC), the relationships were compared to determine which one had the greatest predictive strength. Estimates of Pmean, P50, and Poutlet were derived from a precipitation model developed by PRISM. Results from this study tentatively indicate that all three measures of precipitation depth yield models for predicting Wbf that have comparable goodness-of-fit statistics.

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The correlations between moon phases and precipitation maximums were investigated for selected stations in British Columbia in order to determine if they existed for: (a) individual stations; (b) grouped stations; (c) annual occurrences; (d) seasonal occurrences; and (e) geographic areas. The analysis consisted of a graphical presentation and a statistical test for randomness. Graphs of annual and seasonal moving totals for grouped and Individual stations were prepared. They were analyzed for peaks in the configuration of the graphs and for annual and seasonal components through the use of the X2p test. It is apparent from this study that there is a relationship between moon phases and precipitation maximums for grouped stations and individual stations in British Columbia. The evidence for the annual components of "lunar" precipitation for the individual stations shows, statistically, that the distributions are non-random and, graphically, that peaks are visible. Moreover, a shift of the peaks with latitude is discernible for the stations of British Columbia and it is suggested that this shift exists on a global scale. The evidence for the seasonal components of "lunar" precipitation for the individual stations is not as conclusive, either statistically or graphically. The seasonal graphs show peaks but the test for randomness yields inconsistent results. / Arts, Faculty of / Geography, Department of / Graduate

The formation of grain boundary precipitates of the high temperature β phase from the supersaturated ɤ phase has been examined in Ag-5.64 wt.% aluminum alloys at 688°C . Large grained samples were used and the boundary misorientations were determined by X-ray diffraction. At low angle boundaries only primary sideplates formed while above a misorientation of 17° lenticular precipitates were dominant. Precipitate growth was studied on individual grain boundaries using a statistical technique. The lengthening and thickening rates were independent of the grain boundary misorientation indicating that grain boundary diffusion was not significant under these conditions. The precipitates grew with constant shape, with both the length and thickness increasing parabolically with time. By approximating the shape of the precipitate to that of an oblate spheroid growing with constant shape, an equivalent diffusion coefficient was calculated. The value obtained was in good agreement with measurements obtained from diffusion couples. The nature of the quenched β phase was also examined using optical and electron microscopy. The βphase transformed rapidly on cooling, forming a massive [symbol omitted] product or an acicular martensite at higher quenching rates. The structures were very similar to those reported for the Cu-Ga and Cu-Al systems. Many grain boundary precipitates showed unequal growth into the two matrix grains. Measurements of the matrix habit plane suggested that a possible orientation relationship existed between the precipitate and that grain into which no development occurred. In this case the precipitate nucleated in one grain but grew into the opposite grain. Precipitates which developed equally into both grains exhibited no apparent habit relationship with either grain. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Extreme precipitation in Illinois contributes to impacts across diverse landscapes, posing threats to agriculture in rural areas and infrastructure in urban centers. Previous studies have reported an increase in the frequency of heavy precipitation in the region and projected its amplification under climate change. However, these findings are often characterized by inconsistent and/or inappropriate approaches for estimating historical trends and their significance and often lack process-based understanding regarding future changes in extreme event climatology. This study aims to obtain robust regional extreme precipitation trends and relate those trends to large-scale circulation and humidity. The climatology and trends of daily extreme precipitation are established by applying a peaks-over-threshold approach to the newly developed NOAA NCEI nClimGrid-D dataset which includes daily precipitation totals at 5-km resolution. For trend estimation, we use Theil-Sen estimation with three approaches designed to emphasize correction of inflation in the significance of the estimated trends: (1) a “naïve” approach in which we simply consider the direct output of the Theil-Sen method and assess significance using a traditional Mann-Kendall test, (2) an approach based on a modified Mann-Kendall test to account for serial autocorrelation in the assessment of significance, and (3) an approach that also controls for the false discovery rate associated with a large number of tests by considering field significance. To relate these trends to large scale drivers, a multivariate self-organizing map is constructed based on standardized 500 mb geopotential height and 850 mb specific humidity obtained from the ECMWF ERA-5 reanalysis dataset. We use a Monte Carlo experiment to identify weather types most associated with extreme precipitation in the area. Temporal and spatial characteristics of the identified weather types are then analyzed to better understanding their role in changes in the frequency of extreme precipitation events across the region. As expected, the results indicate a stark contrast between the naive and more complex approaches for significance testing, where controlling for autocorrelation and test multiplicity reduces the spatial extent of significant trends across all extreme precipitation thresholds. Extreme precipitation in Illinois is found to be associated with a small number of specific weather types characterized by distinct patterns of geopotential height and humidity. Furthermore, the weather types most frequently associated with extreme precipitation are increasing in frequency, suggesting that changes in atmospheric circulation related to moisture transport and convergence are a major contributor to changes in extreme precipitation in Illinois.

A stalagmite was collected in the Salón de la Permencia of the Majaguas Cave, that is a part of the Majaguas-Cantera Cave System in Cuba. The use of this stalagmite as a natural climate archive is advantageous not only because stalagmites can record continuous episodes of growth that are thousands of years in duration but also because they are easily and reliably dated, using U/Th dating methods. With this method, the stalagmite was reliably dated to 100 ka and was still active when removed from the cave for analysis. The stable isotopes of oxygen and carbon from this stalagmite from Western Cuba presents information of significant influencing factors on Caribbean precipitation records, and past climatic events during the Pleistocene. Due to the lack of high- resolution records for Western Cuba, this study verifies and adds to our knowledge of past climate variability for the Cuban region and the Caribbean as a whole. The δ18O data in MCS-01 shows a pattern that is very similar to the D-O and Heinrich events clearly recorded in the NGRIP ice core, especially at ~82ka and between 78-70ka. This study provides a continuous precipitation record for the area during the Pleistocene, allowing a greater understanding of the climate drivers that have had an impact on past precipitation patterns in this region.

The purpose of this study was to evaluate the influence of horizontal moisture fluxes from Atmospheric Rivers (ARs) on extreme precipitation (EP) events in the continental United States (CONUS). Climatological results for both EP, objectively defined using a peaks-over-threshold and block maxima approach, and ARs were processed and analyzed for co-occurrence. EP analyses produced a positive linear trend in magnitude, determined through the block maxima approach, in the Central US and a positive linear trend in frequency, determined by the peaks-over-threshold approach, predominantly for the Northern half of the CONUS. AR results show over 70 AR days throughout the country, and a linear trend of 10 less days per decade in the Central US. Results of the co-occurrence analysis suggest an increasing trend of about one instance of co-occurrence per decade throughout much of the Eastern Coast, Midwest and Pacific Northwest, with a corresponding negative linear trend of about one instance of co-occurrence per decade for much of the Southwest US to Louisiana. Throughout the world, the study of EP, and the careful analysis of its behavior, and possible amplification sources such as ARs, at the national and regional scale is imperative to obtain a comprehensive understanding of hydrometeorological impacts.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Bibliography: leaf 86. / M.S.