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- Creators: Arizona Board of Regents
The urban thermal environment varies not only from its rural surroundings but also within the urban area due to intra-urban differences in land-use and surface characteristics. Understanding the causes of this intra-urban variability is a first step in improving urban planning and development. Toward this end, a method for quantifying causes of spatial variability in the urban heat island has been developed. This paper presents the method as applied to a specific test case of Portland, Oregon. Vehicle temperature traverses were used to determine spatial differences in summertime ~2 m air temperature across the metropolitan area in the afternoon. A tree-structured regression model was used to quantify the land-use and surface characteristics that have the greatest influence on daytime UHI intensity. The most important urban characteristic separating warmer from cooler regions of the Portland metropolitan area was canopy cover. Roadway area density was also an important determinant of local UHI magnitudes. Specifically, the air above major arterial roads was found to be warmer on weekdays than weekends, possibly due to increased anthropogenic activity from the vehicle sector on weekdays. In general, warmer regions of the city were associated with industrial and commercial land-use. The downtown core, whilst warmer than the rural surroundings, was not the warmest part of the Portland metropolitan area. This is thought to be due in large part to local shading effects in the urban canyons.
As a result of three workshops within each community, the residents brought forth ideas that they want to see implemented to increase their thermal comfort and safety during extreme heat days. As depicted below, residents’ ideas intersected around similar concepts, but specific solutions varied across neighborhoods. For example, all neighborhoods would like to add shade to their pedestrian corridors but preferences for the location of shade improvements differed. Some neighborhoods prioritized routes to public transportation, others prioritized routes used by children on their way to school, and others wanted to see shaded rest stops in key places. Four overarching strategic themes emerged across all three neighborhoods: advocate and educate; improve comfort/ability to cope; improve safety; build capacity. These themes signal that there are serious heat safety challenges in residents’ day-to-day lives and that community, business, and decision-making sectors need to address those challenges.
Heat Action Plan elements are designed to be incorporated into other efforts to alleviate heat, to create climate-resilient cities, and to provide public health and safety. Heat Action Plan implementation partners are identified drawing from the Greater Phoenix region, and recommendations are given for supporting the transformation to a cooler city.
To scale this approach, project team members recommend a) continued engagement with and investments into these neighborhoods to implement change signaled by residents as vital, b) repeating the heat action planning process with community leaders in other neighborhoods, and c) working with cities, urban planners, and other stakeholders to institutionalize this process, supporting policies, and the use of proposed metrics for creating cooler communities.
Presentation by David Sailor, professor in the School of Geographical Sciences and Urban Planning and director of the Urban Climate Research Center at ASU. Sailer's presentation addresses how to define urban heat islands (UHI), and decisions about why and how to measure these complex ecosystems.
Ozone is a highly reactive compound that is harmful at very low concentrations as compared to other pollutants. One method of pollution control is the use of photocatalysis, specifically with titanium dioxide to induce ozone decomposition. An experiment was designed and executed in order to determine the rate of decomposition by coating concrete in 5% by weight titanium dioxide mixed with paint. The experiment was unsuccessful in inducing decomposition but gave important insight into the adsorptive properties of ozone over surfaces, particularly with bare concrete that had an adsorption of 22.51 ± 2.457 ppbv, which was much better than the coated samples. Further studies into the development of photocatalytic paint is needed in order to develop an effective urban ozone pollution control method to be implemented in major cities, particularly in the most polluted such as Los Angeles, California.
The City of Phoenix Street Transportation Department partnered with the Rob and Melani Walton Sustainability Solutions Service at Arizona State University (ASU) and researchers from various ASU schools to evaluate the effectiveness, performance, and community perception of the new pavement coating. The data collection and analysis occurred across multiple neighborhoods and at varying times across days and/or months over the course of one year (July 15, 2020–July 14, 2021), allowing the team to study the impacts of the surface treatment under various weather conditions.