Degree Discipline

States

Wildfire Influence on Rainfall Chemistry and Deposition in Texas during the 2011-2014 Drought

From 2011 to 2014, one of the most severe and intense droughts in Texas recorded history led to widespread wildfires across the state, with unknown effects on atmospheric nutrient and pollutant deposition. The objectives of this research were to: (1) characterize the frequency, magnitude, and spatiotemporal distribution of Texas wildfires (2011-2014); (2) identify smoke occurrence and source regions at eight Texas National Atmospheric Deposition Program (NADP) National Trends Network (NTN) sites (2011); and (3) quantify the influence of wildfire on weekly rainwater chemistry and deposition in 2011 at three NADP sites (Sonora, LBJ Grasslands, Attwater Prairie NWR). Data on large wildfires, smoke occurrence, and rainfall chemistry and deposition were coupled with principal component and back-trajectory analysis to address these objectives. Between 2011-2014, 72% of all wildfires occurred in 2011, accounting for 90% of the total area burned. In total, there were 17 extreme wildfires (i.e., in the 95th percentile of hectares burned), of which 11 occurred in 2011. Wildfire activity was concentrated in West Texas ecoregions and consumed primarily shrub/scrub and grassland/herbaceous land cover. Although West Texas experienced the most wildfires, smoke at the NADP locations in 2011, the "high-fire year," was more frequent in East Texas due to regional …
Date: August 2021
Creator: Williamson, Thomas
System: The UNT Digital Library
GIS-Based Analysis of Local Climate Zones in Denton, Texas (open access)

GIS-Based Analysis of Local Climate Zones in Denton, Texas

This study implemented a GIS-based analysis of local climate zones (LCZ) in Denton, TX with data sets from 2009, 2011, 2015, and 2016. The LCZ scheme enables evaluation of distinct regions' thermal characteristics with greater granularity than conventional urban-rural dichotomies. Further, the GIS-based approach to LCZ mapping allows use of high-resolution lidar data, the availability of which for the study area enabled estimation of geometric and surface cover parameters: height of roughness elements, sky-view factor, and building surface fraction. Pervious surface fraction was estimated from National Landcover Database impervious imagery. A regular grid was used to estimate per-cell mean values for each parameter, and with a decision-making algorithm (if/then statements) two maps were produced (2011 and 2015) and six LCZ identified in each: LCZ 6 (open low-rise), LCZ 8 (large low-rise), LCZ 9 (sparsely built), LCZ A (dense trees), LCZ B (scattered trees), and LCZ C (bush/scrub). Post-processing was carried out to ensure identified zones met the spatial minimum for qualification as LCZ. Landsat Collection 2 Level 2 surface temperature products from various seasons of 2011 and 2015 were acquired to examine LCZ thermal differentiability, and preliminary surface urban heat island intensity values were estimated. Particular attention was afforded to …
Date: December 2021
Creator: Michel, Daniel
System: The UNT Digital Library