urban heat

Monitoring urban heat islands

More than 60 million people in the US are under an excessive heat warning or heat advisory, and meteorologists say hot temperatures are likely to persist across large sections of the country for the entire Summer. Heat waves are also enveloping Europe - a clear effect of climate change and global warming.

Cities are generally warmer than rural areas, and it is increasingly important for local administrations to map the hottest neighborhoods, monitor key indicators of heat-related health risks, take action and protect vulnerable citizens and communities. However, many cities lack weather station networks that can monitor heat islands comprehensively, so they look for alternative solutions to reliably collect and correlate data about atmospheric and surface urban heat.

Several systems have been used over time for this purpose, including satellite tracking. In the 1990’s, LANDSAT TM satellite data and GIS software were used to map micro urban heat islands in Dallas, Texas, suggesting heat exposure to be significantly higher in low-income, densely populated neighborhoods. More recent research projects had similar findings: the poorest areas tend to be significantly hotter than the richest in 76% of urban US counties.

An alternative monitoring and data collection system was piloted in France by a team of researchers from the University of Toulouse. Supervised by meteorology researcher Eva Marques, their approach leverages temperature sensors in connected cars to map urban heat.

After a first experiment in the city of Toulouse, the team created temperature maps in several western European cities using a database comprising millions of car sensor measurements that manufacturers had collected for insurance purposes from 2016 to 2018. The researchers found they could reliably estimate temperature variations for spaces as small as 200 by 200 meters with fine-grained data collected at 10-second intervals. Their method proved to be effective in assessing urban heat at street level – and highly beneficial even in small cities that lack weather station networks, but nonetheless need to have reliable heat monitoring.

Crowdsourcing data is a new hope to produce and share maps with these municipalities in the years to come,” said Marques. The challenge is ensuring data consistency and quality while scaling-up pilot projects. A robust architecture for data management and analysis is also crucial, and some cities are now planning to integrate urban heat islands monitoring in new or existing smart IoT infrastructures.