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Painting the town white? See what's behind LA's paint plans


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    Dr. Mario Picazo
    Meteorologist, PhD

    Tuesday, May 22, 2018, 5:04 PM - Heat has been on the rise in Los Angeles since the historical temperature record began. As the city grows and more buildings replace suburban and rural surfaces, the urban heat island effect continues to intensify. In 1878, the annual average temperature in downtown Los Angeles was about 17 degrees; today it is close to 21 degrees.

    Beyond modifications to the urban landscape, recent studies conducted by researchers from the Atmospheric and Oceanic Sciences Department at UCLA have shown that temperatures will continue to climb well above current levels in cities like Los Angeles if nothing is done to rein the greenhouse gas emissions that causes global warming. Inland areas of the Los Angeles Basin, especially those located in the valleys, will feel the heat more than others because of their distance from the Pacific Ocean, which normally helps moderate heat.

    Climate simulations for the later part of the century show how some parts of the greater Los Angeles area, like El Monte, Santa Clarita, and Riverside, could experience 100 to 150 days of extreme heat per year. In California, an extreme heat day is defined as a day between April and October where the maximum temperature exceeds the 98th historical percentile of maximum temperatures based on daily temperature data between 1961-1990. In Los Angeles, a day with temperatures 90 F (32 C) or higher is usually considered an extreme heat day, while a period of five consecutive days with such high temperatures becomes a heat wave.

    Because more of those days are expected to happen in the future, city officials have developed a plan to cope with the rising heat. The project involves painting the streets in white in some of the most heat-affected urban areas.

    To do so, they use a coating known as CoolSeal which is sprayed on roads to enhance the amount of solar radiation that is reflected (that is, raising the average albedo of the ground) thus allowing surfaces to absorb less heat. The common black asphalt is a good absorber of the Sun's rays and also a great emitter of infrared radiation, which the air above the surface in turn absorbs to become warmer. With the whiter, more reflective surfaces, a great portion of the solar energy is reflected back into the upper atmosphere, reducing road and consequently air temperatures considerably.

    Streets coated with CoolSeal stay and average 10 to 15 degrees cooler than the dark roads. The reduction of heat also keeps the surrounding buildings cooler, which means a considerable reduction in the air conditioning bill, especially during the summer months. The project aims to reduce overall city temperatures which will reduce energy consumption and the number of cases of heat related health issues.

    Major Garcetti is hoping to reduce the average temperature in Los Angeles by 3 degrees F in the next 20 years. The cost is about $40,000 per mile, but if heat is reduced as expected, air quality improves, and there is a cut back in heat-related deaths, it's worth every dollar.

    Watch below: What is an urban heat island?




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