Mapping the Heat: Surface Temperatures in the MAPC Region

Hot enough for ya? It probably depends on where you’re standing.

So far this summer, the weather station at Logan Airport has logged 3 days of air temperature above 90 degrees. Over the past 10 years, at least five days with highs above 90 degrees have been recorded at Logan each summer. As the climate changes over the coming decades, we can expect to endure more of these hot days and for hot days to string into longer heat waves. Such periods of high heat can be dangerous, even deadly, for our region’s most vulnerable residents, such as the elderly, those living alone, children, people with pre-existing health conditions, and the poor.

As you’ve surely noticed, some areas in the city feel much hotter than others. Black rooftops and paved surfaces can cause land surface temperature to rise far higher than the air temperature.  And those same surfaces can trap the heat in the city for longer, meaning that the night time air temperature does not lower enough to give residents a needed break from the heat.

Street trees, vegetation, rivers, and streams, on the other hand, contribute a cooling effect. Green infrastructure such as green or white roofs can further reduce the problem of high urban heat, which could in turn save lives.

A new set of maps created using satellite imagery shows the variation in land surface temperature across the MAPC region. The maps were created from two images taken in August of 2010, on a day when the Logan weather station logged a high of 92 degrees. In some spots on this map, the surface reaches 140 degrees—literally hot enough to fry an egg.  Clearly, the map shows that more urban areas are generally hotter than less densely populated areas. However, hot spots are not limited to the urban core. Suburban commercial centers with large black roofs and large parking lots, such as the complex along Route 9 in Framingham, also light up the map as hot spots.

The maps also reveal that even within the urban core, parks, greenways, and vegetated streetscapes contribute to cooler land surface temperatures. A quick comparison of the land surface temperature of the Back Bay portion of Commonwealth Avenue to the highly impervious sections of the same roadway that snake through Allston shows how much cooler a linear park can make a stretch of pavement. Incorporating parks and green spaces into the urban environment will only become more important as our region grows hotter.