Found an inexpensive way to save the centers of megacities from overheating

Temperatures in cities are usually several degrees higher than in rural areas: this is a phenomenon

called the "urban heat island effect"(UHI). The city is usually 2-4 °C warmer. This is because urban infrastructure, especially sidewalks, absorbs a lot of heat compared to natural plant surfaces. 

Due to thermal pollution, local residents often buy air conditioners and waste water, and abnormally high temperatures pose a health threat. 

One way to reduce the temperature isuse the so-called gray infrastructure: for this you need to cover impermeable surfaces: walls, roofs and sidewalks with a special film or solution so that they do not heat up so much. 

Typical urban surfaces have solarreflection, or albedo of 0.20 units. This means that they reflect only 20% of sunlight and absorb up to 80%. But a special coating can be designed to reflect 30–50% or more. For example, Los Angeles already uses reflective surfaces on major streets, but on a global scale this can be expensive. 

The researchers used a computational modelfluid dynamics to find ways to reduce costs and increase the reflectivity of urban surfaces. Thus, the authors proposed applying a special coating to only half of the city. 

Selected surfaces, according to one ofauthors of the work Sushobhan Sena, should be located above the main wind direction. The barrier of cold surfaces will cool the warm air, and it, in turn, will spread to the rest of the city. This strategy, the authors believe, can save money and achieve the desired cooling effect. 

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