It is well-known that among many other positive environmental impacts, the urban greenery has positive effect on city’s micro climate and can help to reduce the temperature.
To visualize the relation between lower temperatures and urban greenery in Barcelona, two types of data were used:
The vegetation cover based on the NDVI index: available from Open Data BCN website.
The land surface temperature (LST) after atmospheric correction: retrieved from the thermal infrared imagery collected by the multispectral scanner of Landsat 8 satellite, 6th of July 2019, at 10:30 UTC when the temperature in Barcelona was 26ºC.
The estimated LST reaches a maximum temperature of 56.1ºC and a minimum of 27.3ºC (the spectator might consider the temperature too high, however we are referring to the land surface temperature not the air temperature). The highest temperatures are mainly concentrated in the industrial and commercial areas of the city. On the contrary, the parts with lower temperatures coincide with the vegetated areas of the city: especially corresponding to parks and gardens, but also avenues of trees and inner gardens of blocks.
This map has been created by Carla Garcia-Lozano, Anna Peliova and Josep Sitjar from the Service of Geographic Information Systems and Remote Sensing (SIGTE) of the Universitat de Girona.
The visualization presented here shows how the areas with the lowest land surface temperature (LST) clearly coincide with the vegetated areas. By modifying the transparency of the vegetation cover layer you can see how this phenomenon happens even in the main wooded avenues. Likewise, the average LST and vegetation coverage layers shows how the most vegetated neighbourhoods are also the coolest ones.
The relationship between land surface temperatures (LST) and plant cover (NDVI) is very high, with an inversely proportional trend between the variables (R = -0.69), which means that the parts with lower temperatures coincide with the vegetated areas of the city.