THE NORTH CENTRAL TEXAS URBAN HEAT ISLAND MAGNITUDE AND ITS RELATION TO SEVERE AND EXTREME DROUGHT

Abstract

This study focuses on how summer droughts affect the urban heat island (UHI) in Dallas-Fort Worth (DFW). The nocturnal UHI has been computed by comparing downtown temperature observations to rural temperature measurements under the condition that wind speed is less than 2 m/s, a cloudless sky, and no precipitation. To understand the combined effects of long-term climate change and UHI, trends of temperature anomalies from 1902 - 2019 for Waco and 1900 – 2019 DFW from NOAA COOP were determined relative to a baseline of 1951-1980. The differing trends of these temperature anomalies have been influenced by the UHI (which is larger in the DFW metropolitan area than in Waco) and the higher continentality of the DFW sites. The NOAA Palmer Drought Severity Index (PDSI) was investigated for Climate Zone 3 in Texas and used to isolate years of extreme-severe drought during the month of July and correlated to the UHI magnitude estimates from NOAA COOP and Texas Commission for Environmental Quality (TCEQ). The findings suggest a statistically significant correlation between an increase in the PDSI and the UHI magnitude for the most current decade from 2011 to 2020, in agreement with the study from Winguth and Kelp (2013) for the previous decade. The reduced latent heat flux under drought conditions can lead increase of the UHI. Under wet conditions the UHI magnitude is below 3°C. The most extreme daily UHImag of 5.6°C occurred during the severe drought in July of 2011. Population change appears to influence anthropogenic heat flux in the DFW area, however, land surface changes attribute to latent and sensible heat fluxes that affect the UHI magnitude.