Extreme Heat Relief Availability Agent Based Analysis of an ad-hoc Voluntary Cooling Center Network of Community and Public Organizations

The Phoenix area Heat Relief Network of cooling centers and water distribution stations was established in 2006 after an unusually large number of heat deaths in the area the previous year to provide more access to relief from dangerously hot weather. Data from 2006-2013 do not indicate a decline in the number of population-adjusted annual heat-related mortalities in Maricopa County, which is a compelling reason to look at ways to improve public health interventions for extreme heat including access to cooling centers. The Heat Relief Network is an ad-hoc voluntary network mainly comprised of non-profit and public community centers distributed across the Phoenix area with a variety of operating hours based on provision of primary services they offer in addition to heat relief. A study was initiated in summer 2014 to better understand cooling center usage, operation and facility variation by researchers from the Maricopa County Department of Public Health, Arizona Department of Health Services, and Arizona State University. Methods included visitor surveys, facility manager semi-structured interviews, and cooling center site survey.

We aimed to quantify cooling center accessibility from a spatial and temporal perspective compared to historical risk indicators and observed temperatures as a complement to the qualitative investigation. Comparison of 2013 cooling center availability with Phoenix meteorological data from 1988-2013 revealed potentially important gaps in cooling center availability relative to observed heat-index values. Analysis indicates that the heat index was greater than 105°F, a critical health threshold, on average nearly 24 evening hours (after 5pm) per year, 92% of which occurred from 5–7pm. In 2013 cooling centers were closed weekdays 69% before 5pm and 11% after 5pm, while on weekends were closed 11% before 5pm and 8% remained open after 5pm. Hence there is a large proportion of times during the evening and on weekends when the heat index historically exceeds dangerous levels of 105°F though very few Heat Relief Network cooling centers are available. In addition to these temporal gaps, there are spatial gaps in some areas of the city where there has historically been at higher risk of adverse heat-health events. The complex interaction of heat-health risk with available cooling centers in time and space requires an evaluation method that accounts for this variation.

This analysis presents a novel agent-based visualization framework of the Heat Relief Network temporal and spatial availability intersection with observed temperature and spatial heat vulnerability indicators to assess the dynamic, rather than static, heat health risk and cooling center relief availability evolution through time. This entails modeling the hourly availability of the cooling centers over the course of a year with a reasonable access radius. This will allow determination if there are areas with elevated heat risk indicators that would benefit from cooling center recruitment at times when existing cooling centers are unavailable. In addition, comparing cooling center availability and heat risk indicators with observed hourly heat index provides a measure of realized heat health risk by location at the hourly time scale. This approach allows a more accurate policy consideration of where additional cooling center recruitment and resource allocation could yield the most benefit by providing cooling centers at the times and places where risk is greatest but facilities are not locally available. This dynamic agent based visualization tool is planned to be used with in a participatory modeling exercise with cooling center managers to improve overall Heat Relief Network service delivery. Heat health risk in Maricopa County Phoenix, AZ is persistent rather than episodic, as is often the case in other large U.S. cities. This presents an opportunity to learn about extreme heat adaptation measures in Phoenix that may be useful to other regions of the U.S. in the future that may face health challenges associated with increasing temperatures.