Remote and In-situ Investigations of a Medium City Urban Heat Island

Cities and urban areas around the world often experience elevated land surface and air temperatures compared to their more rural surroundings, and this is called the urban heat island (UHI) effect. Globally, there has been much research that documents and examines the UHI effects of large cities, but comparatively little work has been done regarding the UHI effects of small and medium cities. This work presents what is possibly the first-ever in-depth analysis of the UHI at the medium city of Augusta, Georgia within the Augusta, Georgia-South Carolina Metropolitan Statistical Area (MSA). The area is home to more than 615,000 people. We use two approaches to capture and analyze the spatiotemporal variability in temperature and UHI effects over Augusta: (1) surface (or skin) UHI, describing elevated land surface temperatures, is investigated via satellite remote sensing methods using Landsat imagery from 2019-2021, and (2) canopy layer UHI, describing elevated temperatures in the near-surface to building height layer of the atmosphere. Data collections involving the second approach used in-situ vehicle traverses and sounding flights based on a rotary unmanned aerial vehicle system (UAS). Both the ground vehicle and UAS were equipped with identical, low-cost Raspberry Pi-based sensor units that recorded temperature, pressure, and relative humidity. The payload of the UAS was complemented with a radiometric thermal imager. Data acquisition in Augusta happened during summer 2023 and collections were conducted during morning, midday, afternoon and evening, with priority given to clear days and days with Landsat satellite overpass over the region. A statistical hotspot analysis of the satellite-derived UHI reveals localized areas of hot and cold within the study area, allowing for fine-scale analysis of the anatomy of the surface UHI that found peak surface UHI values of up to 15°C. This analysis informed route delineation and collections using the ground vehicle, in support of identification and characterization of areas with specific patterns of temperature and their contribution to UHI in Augusta. Vertical profiles of temperature and relative humidity collected at multiple sampling locations around the MSA contribute to the understanding of UHI as a 3D phenomenon and confirm the potential of integrative/collaborative approaches for more complete characterization of UHI associated with medium cities.