City Tech and Partners Use NASA Environmental Data to Evaluate Urban Heat Interventions

In the face of climate change and extreme temperature events, urban planners and municipal officials must have access to better data and analytics to assess and respond to urban heat risks.

City structures absorb and hold on to heat longer, raising urban temperatures and making them difficult to cool. These urban heat islands – where buildings, concrete, and other development are significantly warmer than surrounding areas – pose immediate and long-term threats to human health and city infrastructure. High temperatures increase our demand for air conditioning and coolants, which in turn produces more greenhouse gases and air pollutants. Sudden heat events and the corresponding increased peak energy demand can lead to power outages. In addition to causing widespread discomfort, heat can worsen respiratory difficulties, inflict heat cramps and exhaustion, and contribute to heat-related deaths.

These risks are of greatest concern for vulnerable populations, including young children, the elderly, and people with underlying health conditions. Chicago’s 1995 heat wave killed more than 700 poor and elderly residents, and in Europe – where less than five percent of homes are equipped with air conditioning and cool air on public transit is a rarity – a 2003 heat wave was blamed for 15,000 deaths in France alone.

In addition to human risks, heat puts additional strain on city roads, buildings, and other physical structures, causing them to age faster and driving increased maintenance and repair costs. Recent examples of melted roads, buckled rails, and overstressed bridges test residents’ patience, challenge municipal budgets, and disrupt urban life. Many cities have implemented urban design changes, such as green spaces and reflective surfaces, to mitigate heat threats and cool buildings and the surrounding areas.

To-date, many assessments of urban heat mitigation efforts have anecdotal, at best. Most cities lack data to evaluate specific interventions and to inform future investments. With the right tools, public planners, property owners, and other urban stakeholders could better understand which interventions would be the most impactful at specific locations.

Collaborative solutions are critical to combining the best tools, technologies, and methods to address complex problems.

To address the growing threat of urban heat, City Tech Collaborative partnered with Microsoft, Esri, d3i Systems, and the City of Chicago to quantify cities’ heat reduction efforts.

The partnership combined unique technical expertise to build a new tool to inform local and regional urban heat planning efforts, with the goal of equipping urban planners and other stakeholders to deal with shocks and long-term stressors associated with extreme heat events. By aligning shared goals and incentives, this project drove rapid integration and testing of industry-leading capabilities:

• Microsoft Azure and other tools were critical for the management, security, and analyzation of climate data;
• More than 20,000 global cities use Esri’s ArcGIS mapping and spatial analytics software, which provided an essential platform to host urban heat island assessment data;
• d3i Systems’ expertise in supercomputer-based research using advanced models of Earth’s atmosphere, oceans, and land masses helped the team understand heat trends and the effect on the Earth’s surface;
• The Chicago Department of Planning and Development brought critical stakeholder feedback on solution design and usefulness; and
• City Tech convened, structured, and accelerated the collaboration on a new solution that would not have been possible for any single participant to have created alone.

City Tech and partners began the work with a simple question: do urban heat interventions such as parks and green spaces measurably reduce the surrounding areas’ temperature?

To answer this question, the team used existing NASA (National Aeronautics and Space Administration) Landsat data to analyze local heat trends and measure temperature changes over time. By focusing on specific locations where planners had installed heat-reducing green infrastructure, the team could evaluate the impact of these interventions. Using Chicago as a testbed for the new tool, solution participants assessed 26 parks and green spaces built since 1988. Five of these sites showed a statistically significant decrease in temperature of the surrounding area. One site experienced a statistically significant increase in temperature, and the remaining 20 sites were determined to have negligible change in temperature.

Although many factors – including new green infrastructure – contribute to ambient temperature, the team proved that it was possible to quantify temperature changes at specific locations over time. In analyzing NASA’s Landsat images, the team controlled for cloud cover and image quality; future tests could include additional control sites to understand the impact of material properties, vegetation density, and the intervention site’s surrounding environment.

This type of analysis demonstrates great promise for a commercially-viable urban heat island assessment tool. Equipped with this data for the first time, urban planners and municipal officials can understand whether or not the interventions are meeting their objectives, the significance of the interventions’ effects, and what types of interventions may be best-suited to a particular location.

For details on the Chicago case study, please see below.

Each successive heat wave reaffirms the need for cities to take action to address the rising threat of urban heat. City Tech, Microsoft, Esri, d3i Systems, and the City of Chicago successfully created a replicable, scalable study of urban heat spots over time and assessment of site-specific heat interventions. Using these findings, urban planners can focus their efforts on areas that are most vulnerable to shocks and long-term stressors associated with extreme heat events as well as understand which interventions achieved their goals of mitigating extreme heat. This new data is essential to inform how cities plan and implement future green spaces, cooling shelters, utility-sponsored programs for low-income customers, public health interventions, and weather-related emergency response to ensure that resources get to the communities and populations that need them most.

This collaboration highlights the opportunity to integrate this methodology into a commercially available visualization and planning tool accessible to municipal governments and other stakeholders. Although the COVID-19 pandemic has delayed efforts to integrate urban heat island assessment into the ArcGIS mapping and analytics platform for the time being, project participants are determined to expand access to this important capability in the near future.

For more information on City Tech’s Urban Heat Response Solution, please visit https://www.citytech.org/urban-heat-response.

The Urban Heat Response project used Chicago’s heat trends and interventions as a case study. Using imagery for summer months (i.e. June, July, and August) from NASA’s Landsat 5, 7, and 8, the team identified changes in macro- and micro-level hotspots from the 1980s to present and measured the statistical significance in temperature changes associated with locations where interventions – such as green roofs and parks – were implemented.

Overall findings of Chicago’s heat trends include:

• Macro-level hot spots have decreased most drastically on the south side Chicago and near the lakefront, with lesser reductions in the center of the city and on the far north side.
• Hot spots have persisted (and some have intensified) on the far northwest, west, and southwest sides of Chicago.
• The most significant microlevel hot spots are clustered in the far northwest side and southwest, particularly near Midway Airport.

The team analyzed a total of 26 intervention sites, neighborhoods, and census tracts as part of the study. Five locations showed a statistically significant decrease in land surface temperature:

• Millennium Park
• Stearns Quarry/Palmisano Park
• Steelworkers Park
• Park 540
• Park 566

One location, Census Tract #5608, showed a statistically significant increase in temperature.

About City Tech Collaborative (City Tech): City Tech is an urban solutions accelerator that tackles problems too big for any single sector or organization to solve alone. City Tech’s work uses IoT sensing networks, advanced analytics, and urban design to create scalable, market ready solutions. Current initiatives address advanced mobility, healthy cities, connected construction, and emerging growth opportunities. City Tech was born and raised in Chicago, and every city is a potential partner. Visit www.CityTech.org and follow us on Twitter and LinkedIn.