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The Urban Heat Island of New York City

Urban areas like New York City are big cities. Surrounding areas are aptly called the suburbs. The cities, unlike the suburbs, are usually comprised of large, tall buildings made of concrete and marble. These buildings are usually built close to each other with little to no space between them. The space is usually paved. The populations and population densities are usually high (Census 2021). In contrast to this, the suburban areas have smaller buildings and these are spaced apart. The space between these structures are usually green and dirt. The population and population densities are smaller compared to those of cities. One phenomenon which can be observed is that cities usually have higher temperatures compared to the surrounding suburban areas. This phenomenon is referred to as an Urban Heat Island (EPA 2023).

Our fact-finding field trip involved taking temperature readings of the air and different surfaces in Columbus Park in Brooklyn. The surfaces where the temperature was measured were pavement, cement, dirt, and grass. The measurements were taken at three distinct locations , for each surface type, and the average was then calculated. The initial plan was to measure the temperatures of these surfaces in both the sun and the shade, but the cloud cover was about 50% and covered our survey area. Therefore, all readings were taken in the shade. An infrared camera/ thermometer and a hand held infrared thermometer were used to measure the surface temperatures. In addition to the two previously mentioned instruments, a specialized room/ air temperature reader was used to measure the air temperature.

According to the EPA, there are two types of urban heat islands: atmospheric heat islands and surface heat islands. In our experiment, we did not collect sufficient data to model how the atmospheric temperatures would vary from cities to suburban areas. However, as mentioned before, the layout of the buildings in cities allows extraordinarily little space between these structures than they would in suburban areas. This allows for less movement of wind in cities and subsequently, less cooling by winds. In addition, the high populations and building structures of a big city like New York, translates to high energy consumption. These two factors combined can contribute to higher air (atmospheric) temperatures in the urban area than in the surrounding suburbs. However, since our data collection was limited, I can only theorize that the atmospheric temperatures in New York City are higher than that of the surrounding areas.

The data showed on October 17th, 2023 in Columbus Park , Brooklyn, the average temperature of the:

  1. pavement was 18.40 °C
  2. cement was 17.63 °C
  3. Dirt was 13.33 °C; and
  4. Grass was 13.00 °C.

This variation in temperature recordings can provide a model through which we can understand why Urban surface heat islands exist. As we can see, pavements and cement have a higher surface temperature while dirt and grass have a lower surface temperature. It logically follows that our cities will have higher surface temperatures than the suburbs since the surface of the cities are primarily made of pavement and cement.

Different surfaces absorb electromagnetic from the sun and that energy is absorbed by the different surfaces, in pavement and concrete, that energy is used to raise the temperature of the surface resulting in higher temperatures. The dirt absorbs some of that energy and reflects some of that energy. In grass, and plants, some of that energy is used in photosynthesis and less of that energy pool is available to raise the temperature of those surfaces (UC Berkeley 2020).

Based in these observations of surface temperatures, the most obvious recommendation to mitigate the effect of urban heat islands would be to build more green spaces. Here the plants can help by reducing the amount of the sun’s energy that is converted to heat by using photosynthesis to make food. Another recommendation would be to have dirt instead of pavement where possible.

Reference:

  1. US Census Bureau. (2021, December 16). Understanding population density. Census.gov. https://www.census.gov/newsroom/blogs/random-samplings/2015/03/understanding-population-density.html#:~:text=While%20the%20population%20density%20inside,neighborhoods%20within%20a%20single%20city.
  2. “Heat Island Effect | US EPA.” Learn About Heat Islands, Uniited States Environmental Protection Agency, 28 Aug. 2023, epa.gov/heatislands/learn-about-heat-islands.
  3. Absorption / reflection of sunlight – Understanding Global Change. (2020, September 11). Understanding Global Change. https://ugc.berkeley.edu/background-content/reflection-absorption-sunlight/#:~:text=Absorption%20of%20sunlight%20causes%20the,radiation%2C%20also%20known%20as%20heat.

 

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One Response

  1. I really like how you related the activity to Urban Heat Island (UHI) effect. Based on the definition, due to human activity, the temperature of high-population areas is significantly higher than in suburban areas. Especially in cities like New York, it contains a lot of factors like population, energy waste heat, low precipitation, building materials, less green areas, etc. Your activity data also agreed with this, the temperature of building materials is about 4 Celsius higher than grass or soil. So, in such a concrete forest, are there possible ways to alleviate the effect? The answer is yes.

    Two mainly used solutions:

    High albedo materials and pavements
    We know that the buildings and pavement absorb the short wave energy and reflect long wave energy. So, if we can use high albedo materials on the buildings and pavement, it will alleviate the UHI impact. For example, light color surface, or other high albedo material. In the experiment, “observed the effectiveness of albedo by using roofing materials of different albedo ranging from 0.20 to 0.60 and they found that the roof temperature dropped by 25C for 0.60 albedo compared to that of 0.20 albedo”. (Nuruzzaman, 2015)

    Green Roofs
    Green roofs play a role in lowering temperatures by absorbing heat and purifying the air. Plants leverage heat energy for their evapotranspiration process, contributing to a cooler environment. Furthermore, green roofs assist in prolonging the duration of runoff, thereby maintaining cooler temperatures in cities for an extended period.

    Reference

    https://www.epa.gov/heatislands

    Nuruzzaman, M. (2015). Urban heat island: causes, effects and mitigation measures-a review. International Journal of Environmental Monitoring and Analysis, 3(2), 67-73.
    https://www.researchgate.net/profile/Md-Nuruzzaman-12/publication/283507719_Urban_Heat_Island_Causes_Effects_and_Mitigation_Measures_-A_Review/links/563c573708ae34e98c485eb0/Urban-Heat-Island-Causes-Effects-and-Mitigation-Measures-A-Review.pdf

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