Graduation Semester and Year
Spring 2025
Language
English
Document Type
Thesis
Degree Name
Master of Science in Earth and Environmental Science
Department
Earth and Environmental Sciences
First Advisor
Arne Winguth
Abstract
The Dallas-Fort Worth metroplex in North Central Texas is the 4th largest and fastest growing region in the United States. In this study, the response of the urban microclimate and ozone levels to drought conditions will be assessed. The urban heat island (UHI), defined as the temperature difference between an urban and rural weather station, was filtered for low wind speeds (≤ 3 m s-1). An in-depth analysis of the UHI at 1200 CST was done from 2008-2023 to identify trends. A significant correlation exists between the Palmer drought severity index and the UHI at 1200 CST, indicating the impact that soil moisture has on the warming rates and temperature. During dry years, the UHI tended to be <1°C and >1°C during wet years. It was determined that the basis for this phenomenon is the influence that soil moisture and land cover have on the thermal admittance and surface roughness properties of urban and rural regions. During years of extreme drought, the UHI at 1200 CST decreased by at least 2°C relative to the previous year. An analysis of the maximum daily 8-hour average (MDA8) of temperature, nitrogen dioxide (NO2), and ozone (O3) was done to assess the influence the parameters have on each other. 19% of the variability of O3 was due to temperature whereas 41% was attributed to NO2, indicating that NO2 is more influential on the formation of O3. Additionally, NO2 and O3 concentrations were lower in moist years. Possible explanations include increased northward-directed water vapor transport from the Gulf of Mexico linked to a strong lower-level jet and Bermuda high pressure system and local reactions with water vapor that promote a sink for NO2 and O3. It was also determined that monthly MDA8 O3 concentrations in July from 2008-2023 did not exceed the 70 ppb attainment standard set forth by the Environmental Protection Agency.
Keywords
Urban Heat Island, Land Cover, Soil Moisture
Disciplines
Earth Sciences | Environmental Sciences | Physical Sciences and Mathematics
License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Sumner, Patrick, "Assessing the Dallas-Fort Worth Urban Microclimate and Surface Ozone Variability Under Differing Drought Conditions" (2025). Earth & Environmental Sciences Theses. 216.
https://mavmatrix.uta.edu/ees_theses/216