Doctor of Philosophy

dissertationNumerical studies of sea and lake breezes are reviewed and gaps in our current understanding of these thermally-driven circulations are discussed. A numerical sensitivity study is conducted using large-eddy simulations to determine the dependence of sea- and lake-breeze speed and length scales to variations in the land-surface sensible heat flux, offshore background wind, initial atmospheric stability, and lake diameter. This study is the first to test the dependence of sea- and lake-breeze characteristics to variations in these geophysical variables using a three-dimensional large-eddy simulation capable of explicitly resolving boundary-layer turbulence and vertical motion near the sea-breeze front. This study provides new understanding on the sensitivity of sea and lake breezes to variations in the land-surface sensible heat flux, opposing background wind, and lake diameter as well as the complex interactions that occur among these geophysical variables. For the first time, the daytime life cycle of sea and lake breezes in the presence of variations in these variables is simulated, in contrast to many earlier studies that focused primarily on the mature midafternoon sea-breeze circulation. Significant spatial variability in the intensity and vertical structure of lake and sea breezes is noted in the large-eddy simulations. The critical value of an opposing wind at which a sea or lake breeze is destroyed by synoptic-scale pressure gradients is approximately 20% lower in this study than that documented in earlier numerical studies. The depth of sea and lake breezes has also been found to be highly sensitive to the magnitude of the opposing background wind. Finally, the results of this study show that lake breezes for small and medium-sized lakes evolve much differently than sea breezes during the afternoon due to a limited quantity of cool air over the lake

Idealized large-eddy simulations of sea and lake breezes: sensitivity to lake diameter, heat flux and stability

ManuscriptIdealized large-eddy simulations of lake and sea breezes are conducted to deter mine the sensitivity of these thermally-driven circulations to variations in the land-surface sensible heat flux and initial atmospheric stability. The lake-breeze and sea-breeze metrics of horizontal wind speed, horizontal extent, and depth are assessed. Modelled asymmetries about the coastline in the horizontal extent of the low-level onshore flow are found to vary as a function of the heat flux and stability. Small lake breezes develop similarly to sea breezes in the morning, but have a significantly weaker horizontal wind speed component and a smaller horizontal extent than sea breezes in the afternoon

Quantifying Methane Emissions in the Uintah Basin During Wintertime Stagnation Episodes

This study presents a meteorologically-based methodology for quantifying basin-scale methane (CH4) emissions in Utah’s Uintah Basin, which is home to over 9,000 active and producing oil and natural gas wells. Previous studies in oil and gas producing regions have often relied on intensive aircraft campaigns to estimate methane emissions. However, the high cost of airborne campaigns prevents their frequent undertaking, thus providing only daytime snapshots of emissions rather than more temporally-representative estimates over multiple days. Providing estimates of CH4 emissions from oil and natural gas production regions across the United States is important to inform leakage rates and emission mitigation efforts in order to curb the potential impacts of these emissions on global climate change and local air quality assessments. Here we introduce the Basin-constrained Emissions Estimate (BEE) method, which utilizes the confining topography of a basin and known depth of a pollution layer during multi-day wintertime cold-air pool episodes to relate point observations of CH4 to basin-scale CH4 emission rates. This study utilizes ground-based CH4 observations from three fixed sites to calculate daily increases in CH4, a laser ceilometer to estimate pollution layer depth, and a Lagrangian transport model to assess the spatial representativity of surface observations. BEE was applied to two cold-air pool episodes during the winter of 2015–2016 and yielded CH4 emission estimates between 44.60 +/– 9.66 × 103 and 61.82 +/– 19.76 × 103 kg CH4 hr–1, which are similar to the estimates proposed by previous studies performed in the Uintah Basin. The techniques used in this study could potentially be utilized in other deep basins worldwide

Environmental Refuges during Summertime Heat and Elevated Ozone Levels: A Preliminary Case Study of an Urban “Cool Zone” Building

The combination of extreme heat waves and ozone pollution is a major health hazard for urban populations in the summertime, particularly for the most sensitive groups such as children, the elderly, the unsheltered, and those with pre-existing health conditions. The “Cool Zone Program”, operated by the Salt Lake County Aging and Adult Services, identifies areas in the county and Salt Lake City facilities where members of the public can escape the summer heat, hydrate, and learn about available programs. We measured indoor and outdoor temperature and ozone for a pilot study at a designated Cool Zone location during the 22 August–6 September 2019 period and found that the building provided substantial heat relief and protection from more than 75% of the outdoor ozone. We observed a nearly 35 min delay for the outdoor ozone to be reflected on the indoor readings, providing an action window for ventilation scheduling changes to protect against the highest ozone levels during the day. Our findings show that it is critical to re-think and formulate action plans to protect vulnerable populations from excessive heat and pollution events during the summer

The Feasibility of Monitoring Great Plains Playa Inundation with the Sentinel 2A/B Satellites for Ecological and Hydrological Applications

Playas are ecologically and hydrologically important ephemeral wetlands found in arid and semi-arid regions of the world. Urbanization, changes in agricultural land use and irrigation practices, and climate change all threaten playas. While variations in playa inundation on the Great Plains of North America have been previously analyzed by satellite using annual and decadal time scales, no study to our knowledge has monitored the Great Plains playa inundation area using sub-monthly time scales. Thousands of playas smaller than ~50 m in diameter, which were not previously identified by the Landsat satellite platform, can now be captured by higher resolution satellite data. In this preliminary study, we demonstrate monitoring spatial and temporal changes in the playa water inundation area on sub-monthly times scales between September 2018 and February 2019 over a region in West Texas, USA, using 10 m spatial resolution imagery from the Sentinel-2A/B satellites. We also demonstrate the feasibility and potential benefits of using the Sentinel-2A/B satellite retrievals, in combination with precipitation and evaporation data, to monitor playas for environmental, ecological, groundwater recharge, and hydrological applications

The Feasibility of Monitoring Great Plains Playa Inundation with the Sentinel 2A/B Satellites for Ecological and Hydrological Applications

Playas are ecologically and hydrologically important ephemeral wetlands found in arid and semi-arid regions of the world. Urbanization, changes in agricultural land use and irrigation practices, and climate change all threaten playas. While variations in playa inundation on the Great Plains of North America have been previously analyzed by satellite using annual and decadal time scales, no study to our knowledge has monitored the Great Plains playa inundation area using sub-monthly time scales. Thousands of playas smaller than ~50 m in diameter, which were not previously identified by the Landsat satellite platform, can now be captured by higher resolution satellite data. In this preliminary study, we demonstrate monitoring spatial and temporal changes in the playa water inundation area on sub-monthly times scales between September 2018 and February 2019 over a region in West Texas, USA, using 10 m spatial resolution imagery from the Sentinel-2A/B satellites. We also demonstrate the feasibility and potential benefits of using the Sentinel-2A/B satellite retrievals, in combination with precipitation and evaporation data, to monitor playas for environmental, ecological, groundwater recharge, and hydrological applications

Idle-Free Campaign Survey Results and Idling Reductions in an Elementary School

Air pollution near schools is particularly problematic. Pollution emissions from vehicle idling at or around schools may have significant effects on children’s health including increased rates of asthma and childhood leukemia. Outdoor pollution emissions from idling vehicles can also infiltrate into the schools resulting in health hazards both in school drop-off zones as well as inside nearby buildings. An Idle-Free Campaign was enacted at an elementary school to reduce idling among parents dropping off and picking up students. The campaign involved a focus group, surveys, informational events and materials, and vehicle counting efforts before and after the campaign. The surveys found that regardless of gender or level of education, parents were very concerned about air pollution concerns associated with idling and were willing to take steps to reduce their children’s exposure. Furthermore, the vehicle counting efforts showed a 17% reduction in idling vehicles and a 37% reduction in idling time following the anti-idling campaign. These findings show that a multi-pronged approach involving parents, teachers, staff, bus drivers, and delivery truck drivers, may be an effective tool to reduce idling at schools thus reducing children’s exposure