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Urban Heat Index

For Immediate Release


URBAN HEAT INDEX Heat’s Uneven Hold on City Neighborhoods

[Atlanta, Georgia, July 28, 2022] — It’s not always cool to be hot. That’s particularly true in some city neighborhoods around the country where heat stalls forming an even hotter pocket known as an urban heat island. Take, for example, the highly diverse and densely populated neighborhood of Alief in Southwest Houston. Alief’s nighttime temperatures in July average 82 degrees Fahrenheit, compared to the city’s overall average of 79.4 degrees. The higher temperatures can raise energy bills, levels of air pollution, and heat-related illnesses in a neighborhood already struggling with high asthma rates and energy burdens. That’s why Greenlink Analytics recently developed a new and novel data set examining Urban Heat Intensity for the country’s largest metro areas.

“Our Urban Heat Index translates a census tract’s temperatures into a severity score from 1 to 10 relative to other tracts in the city," says Sharanya Madhavan, lead data scientist for Greenlink’s Urban Heat Index project. “By looking at different temperatures, we can better understand the urban heat island effect, identify the neighborhoods disproportionately affected by heat, and begin to see the relationship between heat and other burdens.” The average Urban Heat Intensity score in Houston is 5.9. Alief’s is 10, meaning it has a high heat island effect and is disproportionately hotter than other neighborhoods around them. Here’s how we arrived at that number. Greenlink Analytics utilized satellite imagery to capture nighttime temperature for the 379 largest metropolitan areas in the United States down to the resolution of one square kilometer. Temperatures were analyzed for the hottest months of the year – May through August.

It’s the next step of scrutiny that sets the data apart. Greenlink analyzed temperature gaps from month to month to pinpoint the month with the largest heat disparities in each city. In Houston, it’s July. In Atlanta it’s May. In Denver it’s August. The goal was to assess the disparities in heat burdens, says Madhavan, since the data shows people having very different experiences related to heat within the same city and month. The month with the highest temperature differential was then converted to a heat intensity score using a percentile system. This allows each city to better understand how any neighborhood compares to others.

Urban heat islands form when cities cover land with buildings, concrete, asphalt, and other solid surfaces in population dense places. These hardscapes absorb the sun’s heat during the day and refract it at night, keeping the area hotter than normal. Low-income neighborhoods are frequently hotter than wealthier ones due to systemic differences in the way the communities are designed, developed, and maintained.

Relevant data is vital for addressing the disproportionate burden heat can cause. The Urban Heat Index data set will launch inside the Greenlink Equity Map the first week of August 2022.


 

For more information: Robynne Boyd, Communications Manager, Greenlink Analytics, (415) 516-7625, rboyd@greenlinkanalytics.org