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[MZZ49-02] Effect of urbanization and vegetation on urban heat island intensity
Urbanization has progressed rapidly worldwide in recent decades and will accelerate as the world's population grows. Urbanization causes a decrease in vegetation and surface permeability, changes in albedo, etc. These changes in the surface environment cause the urban heat island. An assessment of the urban thermal environment is essential because the expansion of urbanization increases the intensity of the heat island. To evaluate the thermal environment in the city from satellite remote sensing, we quantified the effect of urbanization and vegetation on the surface temperature. This study estimated NDVI (normalized difference vegetation index) using Sentinel-2 satellite image data and surface temperature using Landsat-8 satellite image data. By spatially combining these two types of data, we investigated the relationship between the state of vegetation and the surface temperature. First, the NDVI images were obtained using the satellite image data of Sentinel-2 with a spatial resolution of 10 m. Next, the ground surface temperature images were made using the Landsat-8 satellite image data with a spatial resolution of 100 m. Finally, we got the average NDVI and surface temperature of spatial resolution of the 1 km × 1 km grid, respectively.
The two types of grid data were spatially combined to clarify the relationship with the distance from the city center. As an example, the analysis result of Washington, D.C., the capital of the United States, is shown. Here, we used each satellite image data of summer (June to August).
A negative correlation was found between the vegetation fraction and the surface temperature. The result suggests that the surface temperature tended to be lower in the fraction with more vegetation. In this study, we also simulated: a fully urban scenario (0% covered by vegetation), a scenario weighted by the fraction of the vegetation, and a fully vegetated scenario (100% covered by vegetation). The weighted scenario was affected by the vegetation fraction, and the farther away from the urban center, the lower the surface temperature became. The fully vegetation scenario showed a similar trend; the farther away from the urban center, the lower the surface temperature became except for points within 5 km of the center. On the other hand, the fully urban scenario was always maintained at a high value regardless of the distance from the urban center. These results indicate that vegetation in the urban environment plays an important role in regulating the surface temperature.
Reference
Impact of urbanization on US surface climate (2015)
Lahouari Bounoua, Ping Zhang, Georgy Mostovoy, Kurtis Thome1, Jeffrey Masek1, Marc Imhoff, Marshall Shepherd, Dale Quattrochi, Joseph Santanello, Julie Silva
Environmental Research Letters, Volume 10, Number 8
The two types of grid data were spatially combined to clarify the relationship with the distance from the city center. As an example, the analysis result of Washington, D.C., the capital of the United States, is shown. Here, we used each satellite image data of summer (June to August).
A negative correlation was found between the vegetation fraction and the surface temperature. The result suggests that the surface temperature tended to be lower in the fraction with more vegetation. In this study, we also simulated: a fully urban scenario (0% covered by vegetation), a scenario weighted by the fraction of the vegetation, and a fully vegetated scenario (100% covered by vegetation). The weighted scenario was affected by the vegetation fraction, and the farther away from the urban center, the lower the surface temperature became. The fully vegetation scenario showed a similar trend; the farther away from the urban center, the lower the surface temperature became except for points within 5 km of the center. On the other hand, the fully urban scenario was always maintained at a high value regardless of the distance from the urban center. These results indicate that vegetation in the urban environment plays an important role in regulating the surface temperature.
Reference
Impact of urbanization on US surface climate (2015)
Lahouari Bounoua, Ping Zhang, Georgy Mostovoy, Kurtis Thome1, Jeffrey Masek1, Marc Imhoff, Marshall Shepherd, Dale Quattrochi, Joseph Santanello, Julie Silva
Environmental Research Letters, Volume 10, Number 8