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Roanoke one of 13 cities in national study of urban heat island effect

Roanoke one of 13 cities in national study of urban heat island effect


“Hot town, summer in the city, back of my neck getting dirty and gritty.”

The lyrics of the 1966 chart-topping hit song by The Lovin’ Spoonful captures the idea of urban heat island warming quite well, including “people looking half-dead, walking on the sidewalk, hotter than a matchhead.”

Urban heat island warming can be a potentially life-threatening matter, and not something only relegated to a major metropolis like New York or Los Angeles or a hotter one like Atlanta or Dallas.

Roanoke is the second smallest of 13 cities across the U.S. chosen to take part in a study of urban heat island warming this summer conducted by the National Integrated Health Information System in partnership with the National Oceanic Atmospheric Administration and CAPA Strategies LLC.

This past Monday, four two-person volunteer teams in automobiles and three cyclists covered routes at 6 a.m., 3 p.m. and 7 p.m. equipped with sensors to record temperatures in various parts of the city. The equipment will be sent to CAPA Strategies, which will analyze the data and provide the city a report of its urban heat signature, including a map showing the pattern of heat variation and suggested strategies for dealing with the heat.

Urban heat island warming refers to city areas warming to higher temperatures than surrounding rural areas because of the ability of concrete, asphalt and building materials to absorb heat more readily and hold that heat more intensely and for a longer time than trees, grass and soil in rural areas, radiating it back into the air of the city.

That heat is not evenly distributed within an urban environment. Roanoke’s participation in the study was inspired by a recent study the city of Richmond conducted with the Science Museum of Virginia, which found great disparities in temperature across different parts of the city in midsummer.

“They found variation in temperature of up to 16 degrees, and frequently the highest temperatures were in the poorest communities,” said Nell Boyle, sustainability outreach coordinator for the city of Roanoke.

Poorer parts of a city typically contain more housing that is not updated for modern temperature control and energy efficiency, with some lacking air-conditioning. In addition to heat stroke and heat exhaustion, people living in these areas are at a heightened risk of other diseases being worsened as their bodies cope with extreme heat.

“It will be interesting to see how much the temperature varies in the different parts of town,” Boyle said. “In the course of a year, excessive heat causes more deaths and health problems than all the natural disasters combined. Anything we can do to prevent that will directly help the members of our community.”

Other cities in the study include Austin, Texas; Burlington, Vermont; Cincinnati, Ohio; Detroit, Michigan; El Paso, Texas; Jackson, Mississippi; Las Cruces, New Mexico; Miami, Florida; New Orleans, Louisiana; Seattle, Washington and San Jose/Santa Clara, California.

Of those cities, only Burlington, Vermont, with under 50,000 people, is smaller in size than Roanoke, with just under 100,000 people in the central city of a larger metro area.

Monica Allen, director of public affairs for NOAA research, said Roanoke had three characteristics that made it a prime candidate for the study:

  • A highly urbanized core with old housing stock.
  • A population with high rates of health conditions such as COPD and asthma that can exacerbate heat stress effects.
  • The power loss experienced in a major heat wave following the June 29, 2012, derecho.

“Importantly, we are targeting cities of varying sizes, with varying urban structure, and in varying climates so that we can understand how the urban heat island effect changes under different conditions, and so we know what works best to manage that effect in different types of cities,” Allen said.

This is not the first time the Roanoke urban heat island has been studied.

In 2013 and 2014, utilizing both fixed-position sensors and mobile sensors mounted to automobiles, Virginia Tech collected temperature data across the city on several occasions. Technical studies have sprang from that data, combined with satellite sensing, on the effects of terrain and tree canopy on changes of temperature within the urban environment, and conversely, the effects or urban heat differences on seasonal changes in trees and other fauna.

One Tech study found warmer morning temperatures around Mill Mountain in the morning, with the pattern changing during the day as other parts of the city warmed with daytime heating.

“Both types are useful,” Allen said, referring to satellite and measured data, “but the air temperatures help us understand what it really feels like to be experiencing these temperatures as a human out for a walk, for example.”

Urban heat island warming appears to be a factor, along with higher dew points likely linked to more systemic global climate change, in Roanoke’s sharp rise in overnight and morning temperatures over the past few decades.

The Roanoke official weather sensor is located at the Roanoke-Blacksburg Regional Airport, which has become more surrounded by commercial properties with large buildings and parking lots in the past 30 years than it had been previously.

In a period of official weather data extending from 1912 to 2019, nine of the 10 warmest summers for average daily low temperature have occurred since 2005. July 2020 was the warmest month on record for average daily low temperature, at 70.8 degrees, and August 3 ended a record 19-day streak in which daily temperatures never dropped below 70 degrees in Roanoke.

Allen said there are three objectives after the study has been completed: inform the community of risk, produce science for decision-making, and teach how the science is done to inspire young scientists.

Boyle said the information from the study will be available for anyone who needs it.

“We will receive a report at the end of the study with recommendations for mitigation,” Boyle said. “The report will be shared with anyone who could benefit from it, such as the city planner, the city’s tree planting team and social services that have a cooling assistance program.

“We plan to collaborate with the Western Virginia Science Museum on outreach and education. It will go to any local agencies that can use the information about the vulnerable populations.”

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Since 2003, Kevin Myatt has penned the weekly Weather Journal column, and since 2006, the Weather Journal blog, which becomes particularly busy with snow. Kevin has edited a book on hurricanes and has helped lead Virginia Tech students on storm chases.

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