Continuous event-based rainfall samples were collected at three sites throughout the Pensacola airshed from 2005 - 2011. Samples were analyzed for total mercury (Hg), a suite of trace metals (TMs), and major ions in order to understand how thunderstorms affected their wet deposition and concentrations in rainfall, estimate the contributions from regional coal combustion and other anthropogenic sources to Hg and TMs in rainfall along the Gulf Coast, and investigate the possible influence that a local 950 megawatt coal-fired power plant had on rainfall chemistry in the Pensacola airshed. Mercury was measured with a Tekran 2600 using a method that was a variation of the standard method used by the US Environmental Protection Agency (EPA) to measure total Hg in water which allowed for the analysis of TMs from the same bottle without having to worry about contamination from reagents during sample preparation. Trace metals were measured used an Agilent 7500cs quadrupole inductively coupled plasma mass spectrometer (ICP-MS) while utilizing an octopole reaction cell (ORC) which allowed for the detection of key coal-combustion tracers like arsenic (As) and selenium (Se). Our findings show that summertime rainfall Hg concentrations are higher compared to other months despite higher rainfall amounts. In contrast, other measured pollutant TMs and ions did not show a consistent seasonal pattern. By incorporating Automated Surface Observing System data from nearby Pensacola International Airport and WSR-88D radar data from Eglin Air Force Base, we were able to classify the storm type (thunderstorms or non-thunderstorms) and analyze altitudes of hydrometeor formation for individual rain events. This showed that mid-altitude and high-altitude composite reflectivity radar values were higher for both thunderstorm and non-thunderstorm ”warm season” (May - Sept) rain events compared to ”cool season” (Oct - Apr) events including cool season thunderstorms. Thus, warm season events can scavenge more soluble reactive gaseous Hg from the free troposphere. Two separate multiple linear regression analyses were conducted on log-transformed data using interaction and non-interaction terms to understand the relationship between precipitation depth, season, and storm-type on sample concentrations. The regressions without interaction terms showed that the washout coefficients for more volatile TMs like Hg and Se were less pronounced compared to other pollution-type elements and that their concentrations were therefore less diluted for a given increase in precipitation depth, but otherwise displayed similar coefficients for season and storm-type. The regression model with interaction terms revealed a more interesting dynamic where thunderstorms caused enhanced Hg concentrations in rainfall regardless of season or precipitation depth while showing a more volume-dependent relationship with TM concentrations as concentrations increased with increasing rainfall amounts relative to non-thunderstorm events. This suggests a vacuum cleaner effect such that for increasing storm strength, non-Hg aerosol TMs in the boundary layer are further entrained into a storm cell. With this understanding, a positive matrix factorization (PMF) analysis was conducted using the EPA PMF 5.0 software to estimate the contribution of different sources to Hg deposition. Our results suggest that approximately 84% (72 - 89%; 95% CI) of Hg in rainfall along the northern Gulf of Mexico is due to long-range transport from distant sources while a negligible amount (0 - 21%; 95% CI) comes from regional coal combustion. However, we found that anthropogenic sources like regional coal combustion and ore smelting were significant contributors to rainfall concentrations of other pollution-type TMs like copper, zinc, As, Se, and non-sea salt SO42-. Using modeled wind profiles via the HYSPLIT trajectory model, we assessed whether plumes from a local coal-fired power plant (”Plant Crist”) could be detected in the rainfall chemistry of rain events occurring downwind of the plant. We limit this analysis to cool season rain events between June 2007 (when the model began) and December 2011 (when the study ended) because modeled wind profiles showed better agreement with observations during this time period compared to the warm season. We also limit this analysis to cool season events since the spatial distribution of rainfall throughout the area is more even during this time which makes sample comparisons between sites easier since Hg/TM concentrations are affected by precipitation depth. Furthermore, we focus on Hg and other pollution-type TMs and major ions such as As, Se, and non-sea salt SO42- in this analysis as they serve as tracers of coal combustion. For our ”unpaired-site” analysis, we analyzed, for each individual site, the rainfall chemistry in a given sample as a function of the proportion of rain events associated with that sample that occurred downwind of Plant Crist. Using this method, we were not able to find evidence that the plant had a significant influence on Hg/TM concentrations or Hg/TM:Al enrichment ratios in rainfall. Similarly, for our ”paired-site” analysis, we consider the differences in rainfall chemistry between two sites - an upwind and downwind site pair - that were impacted by the same rain event where the downwind site was exposed to plumes from Plant Crist while the upwind site was not. As with the unpaired-site analysis, we did not find significant differences in the rainfall chemistry between upwind-downwind site pairs with regards to sample concentrations or enrichment ratios. A multiple linear regression analysis was then conducted using interaction terms to understand the relationship between the operation of a wet flue-gas desulfurization system (which began operation at the plant during the middle of the study), the relative exposure a rainfall sample had to the plumes coming from the plant, and the log-transformed precipitation depth on log-transformed sample concentrations. Besides for As, the first regression analysis did not find coefficient values of any statistical significance for any of the variables that would indicate that the scrubber affected the rainfall chemistry at the two urban sites nearest to the plant. The calculations for As gave mixed results as the coefficients for the non-interaction terms suggested that the scrubber and the plumes emanating from Plant Crist affected the concentration of As in rainfall while the interaction terms suggested that they did not. We perform another multiple linear regression analysis, but remove the complicating effects of precipitation depth on Hg/TM concentrations and instead analyze the effects that the scrubber and the plumes coming from the plant might have had on Hg/TM:Al ratios. Again, these results were inconclusive as the regression coefficients suggested that the scrubber helped reduce Hg and TM emissions from the plant while also suggesting that samples with more exposure to the plant’s plumes had lower enrichment ratios. We propose that we were unable to detect a chemical signal from Plant Crist in our rain samples due to a few possible reasons including quick scavenging of TMs from the plume at the onset of a rain event before reaching our sites, the reliance on radar data to determine start and stop times for rain events at the sites as opposed to on-site measurements, and relatively low spatiotemporal resolution for the wind trajectory model. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2018. / July 16, 2018. / Coal combustion, Mercury, Source-apportionment, Thunderstorms, Trace metals, Trajectory analyis / Includes bibliographical references. / William M. Landing, Professor Directing Dissertation; Thomas E. Miller, University Representative; Christopher D. Holmes, Committee Member; Henry E. Fuelberg, Committee Member; Vincent J. M. Salters, Committee Member.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Oceanography." Includes bibliographical references (p. 116-133).

<p> Water vapor, clouds and aerosols are three major components in the atmosphere that largely influence the Earth's climate and weather systems. However, there is still a lack of understanding on the distribution and interaction of these components. Large uncertainties still remain in estimating the magnitude and direction of the aerosol indirect effect on cloud radiative forcing, which potentially can either double or cancel out all anthropogenic greenhouse gas effect. In particular, a small variation in water vapor mixing ratio and cloud distribution in the upper troposphere and lower stratosphere (UT/LS) can generate large impacts on the Earth's surface temperature. Yet the understanding of water vapor and clouds in the UT/LS is still limited due to difficulties in observations. To improve our understanding of these components, observations are needed from the microscale (~100 m) to the global scale. The first part of my PhD work is to provide quality-controlled, high resolution (~200 m), in situ water vapor observations using an open-path, aircraft-based laser hygrometer. The laboratory calibrations of the laser hygrometer were conducted using complementary experimental systems. The second part is to compare the NASA AIRS/AMSU-A water vapor and temperature retrievals with aircraft-based observations from the surface to the UT/LS at 87&deg;N-67&deg;S in order to understand the accuracy and uncertainties in remote sensing measurements. The third part of my research analyzes the spatial characteristics and formation condition of ice supersaturation (ISS), the birthplace of cirrus clouds, and shows that water vapor horizontal heterogeneities play a key role in determining the spatial distribution of ISS. The fourth part is to understand the formation and evolution of ice crystal regions (ICRs) in a quasi-Lagrangian view. Finally, to help estimate the hemispheric differences in ice nucleation, the ISS distribution and ICR evolution are compared between the two hemispheres. Overall, these analyses provided a microphysical scale yet global perspective of the formation of ISS and cirrus clouds. Ultimately, these efforts will help to improve the understanding of human activities' influences on clouds, water vapor and relative humidity in the UT/LS and provide more accurate representations of these components in future climate prediction.</p>

<p> A PM_2.5 monitoring network was established around Lake Tahoe during fall 2011, which, in conjunction with measurements at prescribed burns and smoke dispersion modeling based on the Fire Emission Production Simulator and the Hybrid Single Particle Lagrangian Integrated Trajectory (FEPS-HYSPLIT) Model, served to evaluate the prescribed burning impacts on air quality. Emissions from pile and understory prescribed burns were characterized using a mobile air monitoring system. In field PM_2.5 emission factors showed ranges consistent with laboratory combustion of wet and dry fuels. Measurements in the smoke plume showed progression from flaming to smoldering phase consistent with FEPS and PM_2.5 emission factors generally increased with decreasing combustion efficiency. Model predicted smoke contributions are consistent with elevated ambient PM_2.5 concentrations in three case studies, and high meteorological model resolution (2km &times; 2 km) seems to produce accurate smoke arriving times. In other cases, the model performance is difficult to evaluate due to low predicted smoke contributions relative to the typical ambient PM_2.5 level. Synergistic assessment of modeling and measurement can be used to determine basin air quality impact. The findings from this study will help land management agencies better understand the implications of managing fire at the wildland-urban interface.</p>

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Previous research has shown that there is considerable enhancement of tropospheric ozone over the African continent. The role of biomass burning as a source of ozone precursor gases and the atmospheric circulation, in particular the anticyclonic gyres over southern Africa, are known to be important in the accumulation of ozone over the subcontinent. In addition, the injection of ozone-rich air from the stratosphere is known to account for the occurrence of ozone peaks in the upper troposphere. This thesis is aimed at investigating the occurrence of high ozone events, defined as 2::100 ppbv, over Africa. Their variability in time (seasonal distribution) and space (latitudinal distribution) is quantified for the upper tropospheric region (~l 0 - 12 km) from 35°N to approximately 35°S . The data used are part of the MOZAIC (Measurement of OZone and wAter vapour by Airbus In-service airCraft) database. Ozone, water vapour. and temperature are measured at cruise altitude by these in-service aircraft, and this study explores data gathered on flights between Europe and Africa over the period January 1996 to December 1998. Complementary data from the European Centre for Medium Range Weather Forecasts (ECMWF) and satellite images are used to investigate case studies for selected flights in order to determine the origin of ozone episodes. Backward trajectory modeling is used to determine the source of air masses possibly related to ozone episodes. Correspondence with high potential vorticity and low water vapour content are used as stratospheric tracers and are indicative of stratospheric-tropospheric injection. Marked seasonal and latitudinal differences in the frequency and nature of ozone episodes are noted between the northern and southern latitudes. The seasonal variation of ozone episodes is more prominent in the extratropics than in the tropics. The highest frequencies are observed in the Northern Hemisphere to the north of 200N in spring and summer, and in the Southern Hemisphere to the south of 30°8 in winter and spring . Between these latitudes the distribution of peaks is sparse. An exception is observed during the austral spring when a relatively high number of peaks south of the equator is evident. The spring frequency peak is common to both hemispheres and is likely to result from a biomass burning influence, and stratospheric ozone injection into the troposphere during this season. Ozone peaks north of 15°N are greater in magnitude (up to 350 ppbv) than those in the tropics and in the Southern Hemisphere, where peaks do not exceed 200 ppbv. The horizontal extent of the ozone events ranged from a few tens of kilometers to over 1000 km in the boreal spring, although they seldom exceeded 100 km in the tropics. Two case studies were examined in detail. In the first case study, ozone peaks up to 180 ppbv were observed at approximately 12° S in the summer. They ranged between 3.5 and 21 km in horizontal extent and were accompanied by increased relative humidity and evidence of uplift. They were attributed to localized biomass burning and subsequent convective uplift to the upper troposphere. The possibility of enhancement due to convective uplift and lightning production was discussed. The second case study, in which an ozone peak of 287 ppbv was observed at approximately 31°S in springtime, had a horizontal extent of 840 km and was accompanied by low relative humidity values and high potential vorticity, indicative of air of stratospheric origin. / Thesis (M.Sc.)-University of Natal, Durban, 2002.

As the demand for global renewable energy grows, so does the demand for more efficient energy conversion machines and better wind resource assessment. The need to convert as much energy as possible with little cost remains the biggest challenge. In the wind energy sector, the quantity of the resource “wind” is not hard to locate, as with current ground and space based remote sensing technologies, and climate reanalysis techniques, the mapping of average wind speeds across the globe is achievable. The difficulty lies in identifying the “quality” of the wind resource. “Quality” is the measure of the time variant properties of the wind, and time scale here does not represent seasonal, monthly, or the daily variability, but rather the changes within hours, minutes, seconds, and sub‐second periods. Wind possesses a highly unpredictable, and non‐universal character, which is referred to as turbulence. These intermittencies in the wind speed create variable mechanical loads on the structure of wind turbines leading to fatigue, and ultimately failure. Identifying site specific qualities of the wind resource is very crucial in the design and selection process of the wind turbine. Physical theories explaining wind turbulence phenomena over flat terrain have been critiqued and tested by observations, and in general, have achieved reasonable success in explaining surface layer wind dynamics that can be applied universally. This universality, and the extrapolation of flat terrain theories to complex terrain applications, breaks down most of the time due to the newly recognized spatial and temporal spectrum of interaction modes, mechanically and thermodynamically, with the surrounding complex terrain. In terrain as found in New Zealand, most of the wind farm development is carried out over complex terrain, with ridge top and mountainous installations. In this study, an experimental campaign was carried out over a coastal ridge top, proposed for wind farming, to investigate mean and turbulent wind flow features significant for wind turbine selection and placement across the ridge. The steep sloped faces of the ridge, high wind speeds and its proximity to the sea made this location ideal for a benchmark investigation site. Ultra‐sonic ii anemometers, a sodar (sound detection and ranging) wind profiler, and high resolution LES (large eddy simulation) numerical modelling were all utilized separately and in an interconnected way to provide a comprehensive analysis of the wind dynamics over the ridge top. The three principal components of the investigation were: the effect of the upstream topography and the thermal circulation associated with the proximity to the sea on the observed and modelled wind shear vertical profile; the role that the near upwind terrain plays in shaping the turbulence energy spectrum and influencing the predicted spectrum, ultimately affecting isotropy in the flow field and turbulence length scales; turbulence advection from far topography, and the role that far upwind terrain plays in altering the wind turbulence in a measurement area or at a single point. Results showed that the thermal wind circulations and upstream steep topography could dictate the wind shear profile, and consequently have a large impact on wind turbine height selection and placement. The sodar proved to be a very useful tool in identifying vertical shear zones associated with effects of steep upstream terrain, vertical mixing of horizontal momentum, and thermal circulation from the local sea breeze. In complex terrain, the added multi‐directional perturbations from the underlying roughness redistribute the statistical variations (measured by variances) in the three spatial dimensions. Isotropy, based on measured variances, was attained for both sites on the ridge. Isotropy also held true for the energy spectrum via Fourier analysis of the high temporal resolution data, but not for both sites. In general, local isotropy can be attained in cases of higher wind speeds and increased terrain relief. Measured spectral ratios did not converge to the limit suggested by the local isotropy hypothesis. These results identify contradictions in assessing the turbulence isotropy in both real space (statistically through variances) and Fourier space (through power spectrum analysis), which suggests caution in deriving or interpreting turbulence information for wind turbine design and selection. iii 2D‐LES experiments showed that turbulent kinetic energy (TKE) can attain long range memory of underlying terrain, which can then react accordingly with upcoming terrain. Under the high wind speed scenarios, which are suitable for wind farming, and over relatively complex terrain, the flow retained some aspects of terrain information at least 30H (H is the terrain height) upstream and downstream of the terrain. In general, as the turbulence field travels over new terrain it tends to increase in intensity downstream of that feature. The newly modified TKE field acquires geometric features from the underlying terrain; mainly these features register as amplifications in the wave structure of the field at wavelengths comparable to the height of the underlying terrain. The 2D‐LES sensitivity experiments identified key areas of high mean wind speed and turbulence in relation to terrain effects, all of which should be taken into consideration when thinking of locating a wind farm in such areas.

Thesis (Ph.D.)--York University, 2006. Graduate Programme in Earth and Space Science. / Typescript. Includes bibliographical references (leaves 271-296). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR19790

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics, 2000? / Copies of author's previously published articles inserted. Bibliography: p. 227-245.