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Understanding Land Surface Temperature Dynamics


Using LP DAAC data to understand land surface temperature dynamics. Presented by the LP DAAC. Using MODIS and ASTER Land Surface Temperature data, distributed by the Land Processes Distributed Active Archive Center, or LP DAAC, we can understand various temperature related processes and how things like development, elevation, and land cover impact the land surface temperature of an area. Using LP DAAC data we can observe land surface temperatures at the global scale. Europe experienced a deadly heatwave during the summer of 2003, observed here using MODIS Data. This data allows us to see warmer temperatures in larger cities such as Milan, Paris, and Barcelona compared to the rural areas surrounding them. This phenomena is called the Urban Heat Island, or UHI effect, or when an urban area is significantly warmer than nearby rural areas due to human infrastructure and activities. Understanding the UHI effect is important in cities with densely built up regions of impervious surfaces, such as streets and parking lots that absorb and store the sun’s energy. The heat absorbed by concrete, asphalt, and other building materials during the day is reradiated back into the atmosphere at night, leading to warmer nighttime temperatures in cities. During heatwaves the UHI effect is exacerbated and can be deadly, as the area does not receive relief from the hot temperatures at night and can last for a week or longer. Land surface temperatures are also affected by elevation. In this mosaic of five ASTER Surface Kinetic Temperature scenes, we see how temperature changes from the warm Mediterranean Sea, to the cooler, forested Apennine Mountains. The low-lying Po River Valley is hot, seen here in shades of red —as is the city of Milan, due to UHI-induced higher temperatures. As we move past Milan, the temperatures decrease with increasing elevation up into the Alps. In addition to urban areas and elevation, vegetation is another factor that influences land surface temperature. Areas with dense vegetation tend to have lower land surface temperature. The darker green areas indicate dense forests stretching from the Northeast down through the Appalachian Mountains, compared with the less dense row-crops of the Midwest in lighter green. Switching to land surface temperature, the forested regions appear cooler and agricultural regions and cities appear warmer. Notice the hotspots over cities such as New York City, Toronto, Columbus, and Chicago. On a smaller scale, urban parks and other green spaces in cities help mitigate UHIs. Here we see Manhattan and the surrounding areas. On a hot summer day, the ASTER surface kinetic temperature layer shows Central Park in yellow, indicating a cooler surface amid a sea of hot, densely built-up areas. Land Surface Temperature data gives scientists a resource to understand land surface temperature dynamics. This information can be used to help monitor and mitigate the intensity of UHIs by informing local decision makers on the benefits of features such as urban green spaces, which ultimately help improve the living conditions of Earth’s billions of urban inhabitants. For more information about the LP DAAC’s Land Remote Sensing Data products please visit the LP DAAC’s website at lpdaac.usgs.gov

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