Understanding the impact of late season precipitation on the distribution of cotton yields provides insight into managing yield risks. This research combines Linear Moment Models with historical weather data to assess the impact of late season precipitation extremes on cotton production and revenue. The empirical analysis suggests that late season drought reduces both mean yield and variance. The shift in variance is coupled with an exchange of upside risk for downside risk implying that the variance reduction alone masks an important effect on producer’s risk. Revenue impacts suggest high revenue for irrigated acreage as compared to dryland acreage, and the late season drought impact on revenue shows that the use of irrigation causes increases in revenue as compared to dryland acreage.

Landfalling tropical cyclone (TC) induced precipitation poses a great risk to the rising coastal population globally. However, the impacts of tropical cyclone precipitation (TCP) are still difficult to predict due to rapid structural changes during landfall. This study applies a shape metric methodology to quantify the spatiotemporal evolution of TCP in the North Indian (NI), Western Pacific (WP), and North Atlantic (NA) basins. The International Best Track Archive for Climate Stewardship (IBTrACS) data and the Global Precipitation Mission (GPM)'s advanced Integrated Multisatellite Retrievals for GPM (IMERG) dataset is employed to study the 2014-2020 landfalling TCP at three analysis times: pre-landfall, landfall, and post-landfall. We examine three thresholds (2, 5, and 10 mm hr-1) and use six spatial metrics (area, closure, solidity, fragmentation, dispersion, and elongation) to quantify the shape of the precipitation pattern. To identify precipitation changes among the three analysis times and three basins, the Kruskal-Wallis test is applied. The three basins show important differences in size evolution. The greatest structural changes occur during post-landfall when the rainfall extent shrinks. The WP has the largest area of TCP and generates the highest maximum TCP of all basins. NA is the only basin where the precipitation area expands after landfall. NA also has the lowest closure for the three precipitation thresholds. NI precipitation has the lowest dispersion and maximum closure. Shape metrics such as closure and dispersion show a consistent inverse correlation. The maximum precipitation direction within the TCs is also examined in each basin. These results can inform guidelines that contribute to improved TCP forecasting and disaster mitigation strategies for vulnerable coastal populations globally. Future studies can apply shape metrics to the sub-basins in NI and WP to examine regional variability as there has been no such study in these basins. Future work can also investigate if the location of heavy rainfall within the TC structure affects flooding or other water hazards. / Master of Science / Landfalling tropical cyclones (TC) pose a significant threat to coastal populations worldwide, primarily due to the heavy rainfall. Predicting the rainfall during landfall is challenging as they undergo rapid changes. This study uses shape metrics to measure how this rainfall changes over time and space in three ocean basins: North Indian (NI), Western Pacific (WP), and North Atlantic (NA). The study uses a comprehensive collection of global TC best-track data i.e., International Best Track Archive for Climate Stewardship (IBTrACS). The rainfall measurement is derived from the satellite data i.e., the Global Precipitation Mission (GPM)'s advanced Integrated Multisatellite Retrievals for GPM (IMERG) to study landfalling rainfall between 2014 to 2020. Six spatial metrics (area, closure, solidity, fragmentation, dispersion, and elongation) were applied to quantify the shape and size of the precipitation pattern at three landfall times: pre-landfall, landfall, and post-landfall. The values of the shape metrics are compared between the ocean basins and landfall times using a statistical test. The results show that the most significant changes occur after landfall when the rainfall area decreases. WP has the largest area of rainfall and generates the highest maximum rainfall of all basins. NA is the only basin where the rainfall area expands after landfall. Shape metrics such as closure and dispersion share a consistent negative relationship. The maximum precipitation direction within the TCs is also examined in each basin. These results can contribute to improved tropical cyclone rainfall forecasting and disaster mitigation strategies for vulnerable coastal populations globally. Future studies can apply shape metrics to the sub-basins in NI and WP to examine regional variability as there has been no such study in these basins.

Quantitative precipitation estimation (QPE) remains a key area of uncertainty in hydrological modeling, particularly in small, urban watersheds which respond rapidly to precipitation and can experience significant spatial variability in rainfall fields. Few studies have compared QPE methods in small, urban watersheds, and studies which have examined this topic only compared model results on an event basis using a small number of storms. This study sought to compare the efficacy of multiple QPE methods when simulating discharge in a small, urban watershed on a continuous basis using an operational hydrologic model and QPE forcings. The Research Distributed Hydrologic Model (RDHM) was used to model a basin in Roanoke, Virginia, USA forced with QPEs from four methods: mean field bias (MFB) correction of radar data, kriging of rain gauge data, uncorrected radar data, and a basin-uniform estimate from a single gauge inside the watershed. Based on comparisons between simulated and observed discharge at the basin outlet for a 6-month period in 2018, simulations forced with the uncorrected radar QPE had the highest accuracy, as measured by root mean square error (RMSE) and peak flow relative error, despite systematic underprediction of the mean areal precipitation (MAP). Simulations forced with MFB corrected radar data consistently and significantly overpredicted discharge but had the highest accuracy in predicting the timing of peak flows. / Master of Science / Estimating the amount of rain that fell during a precipitation event remains a key source of error when predicting how much stormwater runoff will be produced, particularly in small, urban watersheds which respond rapidly to precipitation and can experience significant spatial variability in rainfall distribution. Rainfall estimation in small, urban watersheds has received relatively little attention, and studies which have examined this topic have generally only examined a small number of discrete storm events. This study sought to compare the efficacy of multiple precipitation estimation methods when simulating discharge in a small, urban watershed on a continuous basis using an operational hydrologic model and precipitation inputs. The Research Distributed Hydrologic Model (RDHM), commonly used by the National Weather Service, was used to model a basin in Roanoke, Virginia, USA forced with rainfall estimates from four methods: mean field bias (MFB) correction of radar data, kriging of rain gauge data, uncorrected radar data, and a basin-uniform estimate from a single gauge inside the watershed. Based on comparisons between simulated and observed discharge at the basin outlet for a 6-month period in 2018, simulations forced with the uncorrected radar QPE had the highest accuracy, as measured by several performance statistics, despite systematic underprediction of actual precipitation. Simulations forced with MFB corrected radar data consistently and significantly overpredicted discharge but had the highest accuracy in predicting the timing of peak flows.

Indiana University-Purdue University Indianapolis (IUPUI) / Paleoclimate records from North and South America were used to develop a holistic understanding of global paleo-hydroclimatic drivers across a range of boundary conditions. Here, geophysical analysis of lacustrine sediment stratigraphy at Lago de Tota, Boyaca, Colombia provided evidence for significant lake-level fluctuations through the late Quaternary and produced a record that potentially spans the last 60 ka. Seismic data revealed a series of off-lap and on-lap sequences in the upper ~20 m of sediments that indicated large amplitude changes in lake-level, driven by variability in the mean latitude of the Intertropical Convergence Zone as controlled by insolation- and ocean circulation-driven hemispheric temperature gradients during glacial/stadial and interglacial/interstadial events. In North America, late Holocene flood recurrence in the Midwest and Holocene changes in the mean latitude of the polar front jet stream were investigated through multi-proxy examinations of sediment cores collected from swale lakes in northern Kentucky and southern Indiana, and a glacially formed kettle lake in northern Indiana. These results showed that the midlatitude jet stream was displaced to the south during the late Holocene, which increased the amount of Midwestern precipitation sourced from the northern Pacific and Arctic, especially during prolonged cool conditions. During these cool periods, when atmospheric flow was meridional and a greater amount of precipitation was delivered from the northerly sources, Ohio River flooding increased. During warm conditions, when clockwise mean-state atmospheric circulation advected southerly moisture from the Gulf of Mexico into the Midwest, flooding on the Ohio River decreased. At present, streamflow in the Midwest is demonstrated here to be generally increasing, despite atmospheric conditions typically associated with reduced streamflow in the paleo-record, due in part to increasing precipitation and modern land-use dynamics. Together, these studies demonstrate the sensitivity and vulnerability of local-scale hydrological processes to synoptic climate change.

At Anglo American Platinum's Precious Metal Refinery, rhodium separates from a base metal-rich solution by precipitation. Hexachlororhodate (III) ions and cationic protonated diethylenetriamine ions exchange to form diethylenetriammonium hexachlororhodate (III) crystals, a rhodium metal precursor. The objective of this work is to determine nucleation and growth kinetics of diethylenetriammonium hexachlororhodate (III) salt. Two reactor configurations, namely a transient continuous stirred tank reactor (CSTR) and a t-mixer plug flow reactor (PFR), were used to determine nucleation and growth rates. The objective of the configurations was to eliminate kinetic biases that may be caused by mixing at the mesoscale. Transient saturation in the CSTR ranged up to 43, and in the PFR saturation was varied between 2 and 64. Precipitation kinetic parameters were estimated through data fitting concentration and volume average crystal size profiles to a mass and population balance model. Temperature dependence of kinetic parameters was found to be universal between reactor configurations. Both growth through interfacial attachment and agglomeration, as defined in this work, were exothermic processes with activation energies of -192.9kJ/mol and -656.1kJ/mol respectively. Nucleation was found to be an endothermic process with an activation energy of 50.9kJ/mol in accord with the observed heat of crystallisation. No evidence of heterogeneous primary nucleation in the form of crystals adhering to the side walls of the reactor or the agitator blades was observed. The experiments were not explicitly designed to distinguish between primary and secondary nucleation mechanisms, therefore excluding one over the other is not justified. However, considering the presence of nucleated crystals in each system combined with the good model fit using a nucleation rate expression typically associated with secondary nucleation, it is likely that the dominating nucleation mechanism is secondary in nature. In the PFR configuration, nucleation and growth occur at a faster rate compared to the CSTR under the experimental conditions in this work. This observation is inferred from the fitted temperature independent kinetic parameters and is linked to a much higher mixing intensity achieved in the PFR relative to the CSTR. Flow conditions, described by the Reynolds number, can limit conversion in the PFR configuration by a mixing limitation at the micro- or mesoscale. Micro- and mesoscale mixing were represented by a characteristic length scale that was empirically related to temperature for the microscale and fluid velocity for the mesoscale. Under conditions where the Reynolds number is below the point where conversion is independent of the Reynolds number, either micromixing or mesomixing can become a rate limitation. At a sufficiently high Reynolds number neither micromixing nor mesomixing limits conversion and the system equilibrium becomes the limitation. In the CSTR, the system equilibrium limited reaction conversion as the micro- and mesoscale mixing zones were sufficiently small relative to the reactor volume. Parameters related to mixing were found to differ between the configurations, which was caused by different flow patterns within each configuration. Scanning electron microscopy (SEM) photographs suggest that crystals in the PFR configuration collide both in the radial and axial direction, giving rise to a feathery flat and elongated agglomerated crystal cluster. In contrast, the crystals in the CSTR configuration collide in a chaotic but consistent pattern, giving rise to a desert rose-like agglomerated crystal cluster. The derived model used to describe agglomeration is based on the agglomeration principles proposed by Von Smoluchowski coupled with Fick's law of diffusion and gives a good representation of crystal size. The PFR growth rate supersaturation exponent was 1.13, suggesting a Burton-Cabrera-Frank type growth model, and is indicative of crystal growth from screw dislocations that is limited either through mass transfer to the crystal surface, or surface integration. Thus, in this instance, the rate of aqueous hexachlororhodate (III) conversion to crystal would be responsive to mixing conditions on the micro- or mesoscale, as was experimentally found in the PFR configuration. In comparison, the CSTR growth rate supersaturation exponent was 2.31 and is more in line with polynuclear growth that appears to be limited by interfacial attachment kinetics, as the system equilibrates in the bulk. Lastly, a key finding of this work is the ability to manipulate the crystal morphology by changing reactor configuration. By creating elongated flat crystal structures in the PFR configuration as opposed to a desert rose crystal structure in the CSTR, it may be possible to reduce impurities within the crystal by entraining less mother liquor.

<p> The macroscopic mechanical behaviour of alloys is intimately related to their structure at the atomic level. The influence of small (<0.1μ) ordered coherent particles (𝛄') on the mechanical properties of Ni-Al alloys has been studied. The maximum strength of polycrystals occurs at 0.45 volume fraction 𝛄' and grain boundary embrittlement occurs at higher volume fractions. It was shown that long range order in the particles affects strength by increasing the anti-phase boundary energy. In monocrystals the deformation behaviour is strongly influenced by the amount of particles present. </p> <p> By growing very large particles of 𝛄' (~1.0μ) dislocation-particle interactions have been studied. Stacking faults have been observed in the particles whose bounding dislocation Burgers vectors were determined. By suitable heat treatment still larger 𝛄' particles (~10µ) were formed which had incoherent interfaces. The dislocation networks at the interfaces were analysed. </p> / Thesis / Doctor of Philosophy (PhD)

Starting with the Mean Field Method (MFM) and Boundary Element Method (BEM), we investigate a mathematical model based on these two methods for studying particle-coarsening process in alloys. With MFM, second-phase particles are considered to be merged into bulk matrix, which greatly simplifies computation. However, the Mean-Field model itself is limited to a system with extremely small volume fractions of second phase. By combining BEM with MFM, this mathematical model shows the influence of second phase in particle-coarsening process. Our primary work demonstrates the robustness and capability of this model. This model is however limited to particle coarsening that is far away from grain boundaries. In this dissertation, we successfully extend the model to particle coarsening near grain boundaries. A major improvement made to the previous mathematical model is based on solute atoms conservation and diffusion theory. The capability and validity of the novel model is demonstrated by a binary alloy system. The simulation results are shown to quantitatively reproduce the essential features of particle coarsening near grain boundaries in certain alloys: a) precipitation Free Zones (PFZs) form near grain boundaries, b) the width of PFZs is proportional to square root of time, c) particles at the edge of PFZs are larger than those inside the grain. This novel model is shown to be well suited in describing particle coarsening near grain boundaries. On the other hand, it proves the credibility of the theories built in our mathematical model, i.e., the formation of PFZs near grain boundaries is caused by diffusion of solute atoms. / Thesis / Master of Applied Science (MASc)

Precipitation polymerization is a unique method that produces narrow-disperse, uniform polymer particles with clean surfaces. In this research, internally structured poly(divinylbenzene-co-chloromethylstyrene) polymer microspheres were prepared by thermal imprinting precipitation polymerization. The influence of thermal profiles and the monomer/crosslinker feed ratio on the resulting core-shell microspheres were explored by optical and transmission electron microscopy, and potential route to extend this technique to other polymer system was discussed. Further surface functionalization of this type of particles was demonstrated by substitution of chlorine with cysteine, a good and hydrophilic nucleophile. Narrow-disperse, hydrophilic particles may in future serve as components of synthetic extracellular matrices used in exploring cell-matrix interactions in a 3D context. / Thesis / Master of Science (MSc)

<p> Statistical analyses between the relationship of tree-ring widths with variations in climate were used to examine the limiting climatic factors upon the growth rate of Picea mariana along the treeline and in hopes of reconstructing past climate. Tree-ring widths were used as a proxy measure of growth rates to establish the relationship of annual variances in temperature and precipitation on the growth rate of trees. Twelve tree cores were sampled from separate trees along the treeline northeast of Yellowknife, Northwest Territories. The trees, (with cores spanning 40 -160 years per tree), were compared to monthly and seasonal variations of both temperature and precipitations. A stepwise regression model was used to examine the climate-growth response. No climatic variables were found to illicit a general response pattern. The growth rate of trees along the treeline, northeast of Yellowknife do not appear to be dependent upon variations in the regional climate. Therefore, no climatic reconstructions were possible.</p> / Thesis / Bachelor of Arts (BA)

<p> International Nickel Company's 1250 ft. stack located in Sudbury, Ontario emits an estimated 3,000 tons of sulphur oxide daily. The purpose of this study is to investigate the use of stable sulphur isotopes as a means of tracing the movement of these sulphur oxide emissions. Sulphur isotope analysis were done for lakewater, rainwater and sediment samples taken from the Sudbury-Timagami district and also for particulate and gas samples taken from the 600 ft. level of the International Nickel Company's 1250 ft. stack. </p> <p> The s s^34 values of lake surface samples showed a decrease related directly to the increase of the logarithm of the distance from Sudbury. The maximum s s^34 value for the lakewater samples was + 8.49 p.p.t. at a distance of 7 miles from Sudbury. The minimum s s^34 value for lakewater samples was+2.97 p.p.t. at a distance of 55 miles from Sudbury. </p> <p> The rainwater s s^34 values vary from + 4.85 p.p.t. recorded for a station 5 miles north of Sudbury to + 2.07 p.p.t. for a station 60 miles east north east of Sudbury. </p> <p> The increase in s s^34 values in the lakewater relative to rainwater strongly suggest that the oxidation of so2(g) to s4^2- is occurring in the lakes in the Sudbury-Timagami district. </p> / Thesis / Bachelor of Arts (BA)