<p> The fire weather index (FWI), useful as a measure of forest fire danger, is calculated from precipitation and other weather variables. In the present environmental study, precipitation, fuel moisture codes, and fire behavior indices were available for a reference site and 4 higher elevation sites around Smithers, British Columbia. The objective of the study was to determine whether the use of local precipitation would lead to a different FWI than obtained from precipitation at the reference site.</p> <p> The features of the series of daily FWI values which needed to be taken into account were: peaks following dry periods, serial correlation, and heteroscedasticity. Two types of models were developed to characterize the record as a smooth component, for the upward and downward movements of the index, and a component of correlated error terms. The first type was a parametric Fourier series in a context of a generalized linear model (GLS) that allowed for serial correlation and heteroscedasticity. The second form was a smoothing cubic spline with a bootstrap procedure for estimation of standard errors and confidence bands. The question, of whether FWI on a particular day differed between a higher elevation station and the reference station, was addressed by adding a station effect to the GLS model and by graphical comparison of the smooth curves with confidence bands for the spline method.</p> <p> The Model-3 for the combined station effect is not able to capture the sharpness of the peak and found insignificant while cubic spline smoothing curves fitted to the bootstrap behave well to capture peaks and troughs in the index but it encounter some difficulties for few lower index values.</p> / Thesis / Master of Science (MSc)

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Hurricane Florence (2018) was unique due to its slow storm motion during landfall, causing convective rainbands to produce high amounts of precipitation along the coast of North Carolina. This study focuses on the relationship between precipitation asymmetries and atmospheric stability surrounding the tropical cyclone (TC) during the landfall period of a nearly-stationary TC. Previous research with idealized hurricane simulations suggests that atmospheric stability may vary surrounding a TC during landfall, with the atmosphere destabilizing offshore and stabilizing onshore. However, this finding has not been studied using a realistic approach. Due to Hurricane Florence's slow motion, the storm was situated at the land-ocean boundary for multiple days, providing an ideal opportunity to examine the role of atmospheric stability in modifying hurricane precipitation during landfall. This study uses the Advanced Research Weather Research and Forecasting (WRF-ARW) version 3.6.1 to produce high-resolution simulations to examine the variations in precipitation and atmospheric stability surrounding Hurricane Florence. Precipitation accumulation at different temporal scales was used to determine that asymmetries existed during the landfall period. Observed and model-simulated Convective Available Potential Energy (CAPE) were used to measure stability surrounding the TC. Simulated CAPE indicates that there was a significant difference between stability right- and left-of-track. In addition to a control simulation, two experimental simulations were conducted by modifying the land surface to vary the heat and moisture exchange coefficient (HS) and hold the surface roughness (Z0) constant. By isolating the HS to be more moist or dry, the altered low-level moisture was hypothesized to cause the precipitation and convection distributions to become more symmetrical or asymmetrical, respectively. The results from the experimental simulations showed that the altered land surface affects the relative humidity from the surface to 950 mb, which has an immediate impact on stability off-shore left-of-track. Overall, the precipitation and stability asymmetries were not significantly impacted by the altered near-surface moisture, indicating other physical factors contribute to the asymmetries. The results of this study provide insight into the role of atmospheric instability in generating asymmetrical precipitation distributions in landfalling TCs, which may be particularly important in slow-moving TCs like Hurricane Florence. / Master of Science / Landfalling tropical weather systems such as hurricanes can significantly impact coastal communities due to severe flooding and damaging winds. Hurricane Florence (2018) affected coastal and inland communities in North Carolina and South Carolina when the storm produced a significant amount of precipitation over the coastal region. During landfall, the center of Hurricane Florence moved slowly parallel to the coastline, which creates a suitable time frame to isolate and study the influence of landfall on precipitation asymmetries. Precipitation asymmetry occurs when more rainfall falls on one side of the hurricane; for example, heavier precipitation tends to occur on the right side of a hurricane during the landfall period. Hurricane rainbands that are responsible for producing heavy precipitation form in areas where there is higher moisture near the surface while lighter precipitation forms in areas where there is drier air near the surface. This study focuses on the relationship between land surface moisture and spatial variations of precipitation during the hurricane landfall period by studying observations and model simulations of Hurricane Florence. The model simulation of Hurricane Florence found that more precipitation fell on the right side of the storm, indicating that there was precipitation asymmetry. In order to understand how the precipitation asymmetries form, the model simulation of Hurricane Florence was modified to create two experiments. In the first experiment, the land surface was altered to have a moister land surface, which should cause the hurricane precipitation to be more symmetrical. In the second experiment, the land surface was altered to have a drier land surface, which should cause stronger precipitation asymmetry. However, the results did not match this expectation. Instead, both experiments simulated asymmetrical precipitation with more precipitation falling on the right side of each storm during the landfall period. These results suggest that the modified land surface moisture did not have a significant impact on the formation of precipitation asymmetries. Other factors are therefore suggested to have a more dominant influence on the development of precipitation. Overall, this work can support future studies by ruling out the impact of land surface moisture on a hurricane's precipitation formation during the landfall period.

Causes for the differences in precipitation morphology observed and investigation. / Master of Science

This thesis describes testing of an electrostatic precipitator that has a portion of the main precipitator flow drawn through a porous (fabric) collecting surface. Tests investigated effects of flow through the collecting surface (side flow) on precipitator turbulence and particulate removal efficiency. Particulate removal tests were conducted at both ambient temperature and boiler slipstream conditions. Side flow was shown to reduce turbulence in the boundary layers of the collecting plates, but to have no significant effect on turbulence in the main gas stream (beyond the boundary layer). Side flow was shown to create a more uniform horizontal velocity profile within the precipitator. Side flow was shown to have little effect on the reentrainment of single particles, but appears to reduce reentrainment of an established dust layer. Reentrainment was shown to be an important concern primarily for particles greater than three micrometers in diameter. This research strongly indicated the advisability of using two stage electrostatic precipitation for the collection of particles less than three micrometers in size. / Master of Science

The atmospheric effect of greenhouse gas emissions is posing an increasing threat to the stability of the global climate. Like many developing nations, the western Africa nation of Nigeria faces risks from climate change, with potential effects on the environment upon which Nigerians rely and on broader social constructs, including the national economy. Nigeria's diverse topography, which stretches from dry northern regions of the sub-Sahara to lush southern rainforests along the Gulf of Guinea, accentuates susceptibility to a variety of climate-related hazards, including warming, irregular rainfall patterns, and extreme weather occurrences. Driven by the influence of tropical climates on the global climate system and the importance of climate variability and change specifically within Nigeria, this study of the Nigerian hydroclimate explicitly characterizes historical variability and change through analysis of in-situ daily climate data. Daily maximum and minimum air temperature and total precipitation data from 1982 through 2011 were obtained from the Nigeria Meteorological Service for 20 locations across the country. Given the limited temporal extent of the data, two popular satellite-derived precipitation products were tested for usability as supplements to the in-situ data. Each of the satellite-derived products depicts rainfall with an unrealistically high frequency and with a temporal trend that is opposite reality. Only in-situ data were analyzed further, beginning with a methodology to define the climatological wet and dry seasons across the country. The critical wet season across Nigeria was found to last between 120 days (north) and 200 days (south), beginning April/May and ending September/October, with wetness migrating from nearer the southern coastline northward through the country during the Northern Hemisphere summer, before retreating south again. As with seasonality, the spatial distribution of precipitation amount and frequency relates to distance northward from the southern coast. Wet season precipitation approaches 2500 mm from an average of more than 115 wet days along the coast, to only about 350 mm and 35 days across far northern Nigeria. Conversely, the dry season produces 300 mm from 30 wet days across the south, and only 80 mm from less than 10 days across the north. The wet season in Nigeria accounts for greater than 90% of annual precipitation and number of wet days. Nigeria experienced a warming and wetting of the climate during the 30-year study period, during both the wet and dry seasons. However, a change in the equitable distribution of precipitation across wet days (i.e., daily intensity) is not greatly evident, as it is for many other regions of the world. Thus, the likely benefit of greater precipitation does not appear to be mitigated by the risks associated with an increase in the frequency of high-intensity rainfall events. But tempering the positive precipitation signal is the likely detrimental effect of warming. Inter-annual variability in the wetness of the critical wet season is evident in the synoptic atmospheric expression of the inter-tropical convergence zone/discontinuity, but also in sea surface temperatures within the Gulf of Guinea. Historically, sea surface temperatures are considerably higher during the wettest wet season years compared to the driest years, possibly indicating a short-distance teleconnection that may offer seasonal predictability. / Master of Science / Nigeria is experiencing the consequences of global climate change caused by gases that trap heat in the atmosphere. Nigeria is endowed with a diverse terrain, with green rainy parts in the south and arid regions in the north. In Nigeria, the economy and the environment are both being impacted by climate change. Decades of climatic data from various regions of the nation were examined in this research. We discovered that Nigeria is generally becoming wetter and warmer. Most of the yearly precipitation falls during the rainy season, which runs from April to October. There hasn't been much of an increase in extremely heavy rain, though, because the intensity of the rainfall hasn't increased significantly. However, higher temperatures can lead to issues. The amount of rain that falls in Nigeria is also influenced by sea surface temperature in the Gulf of Guinea. This study sheds light on how Nigeria's weather is changing due to climate change, which may have negative effects on both people and the environment.