Отражающее покрытие дорог в Аризоне охлаждает асфальт, но повышает температуру воздуха

Arizona Reduced Road Surface Heat Thanks To Reflective Coatings, But It Makes Ambient Air Even Hotter Climate change is here, and current EPA attitudes probably mean it's here to stay. And in towns like Phoenix, Arizona, where it already runs really hot, locals are experimenting with measures to keep the pavement a bit cooler, reports The Economic Times. Early efforts seem to be cooling down the pavement as intended, but with one unforeseen side effect: reflected heat makes the air above it even hotter. Phoenix is the fastest-growing city in the U.S., according to The New York Times. Covering 517 square miles, it's even larger than Los Angeles by area. The city has grown outward rather than upward, thanks to the open desert all around it making urban sprawl the path of least resistance. The large amount of paved areas — city streets, parking lots, highways — create one heck of a heat island, though, absorbing and retaining heat during the day, then radiating it at night, causing health problems and infrastructure issues. Even the Arizona DOT works mainly at night during the summer to beat the heat, according to NPR. That's why Phoenix, in partnership with Arizona State University, started its Cool Pavement Program in 2020, testing reflective coatings such as CoolSeal to see what effects they had on temperatures in and around road and parking lot surfaces. The results have been generally positive. Surface temperatures are between 12 and 10.5ºF lower than untreated pavement at noon and during the afternoon, respectively. Temperatures below the surface average 4.8ºF cooler, which helps the pavement last longer instead of degrading more quickly in the heat. Good for the road, but not for people While the reflection keeps the ground cooler, it doesn't make heat go away. Rather than absorbing into the ground, it heats the air just above it, raising air temperatures near the surface about 5.5ºF. What's good for infrastructure and mitigating heat island effects overall actually cooks pedestrians even more than untreated pavement. It's a bit like what happens to your body when you're out in the sun on a snowy mountain, or riding in a boat over water — you sunburn more easily because the sun doesn't just shine down on you as usual, but also reflects off the surface below you. That's an inconvenience you can avoid with more sunscreen, or simply getting away from the water. But when you're in a desert city during the summer, you can't avoid the heat indefinitely. At some point, you have to step outside your air-conditioned home, workplace, or car. And higher surface air temperatures during the day give people even less time to move between cooler environments. On the plus side, after sunset, nighttime temperatures six feet above treated surfaces were 0.5ºF cooler than untreated surfaces. After dark, pavement radiates the heat it collects during the day, keeping temperatures high into the night. This lower temperature indicates that treated pavement isn't absorbing as much heat, reducing overall heat island effects. It works, but at the cost of even higher surface air temperatures during the day. Is the trade-off worth it? Since modern cities are made for cars, not people, that answer is probably going to be yes.