US Major Cities NDVI Summer Exposure Tracts 2000, 2010 and 2019

Normalized difference vegetation index (NDVI) was derived from Landsat satellite imagery captured every 16 days at a 30 m resolution downloaded from Google Earth Engine (GEE) between April and September for each of the three distinct time points (2000, 2010, and 2019) at the census tract level for metropolitan statistical areas containing a city with >500,000 residents (n = 37). The temporal range from April to September was used to identify the overall maximum greenness of an area and to minimize the amount of tracts missing NDVI due to cloud cover. We selected images with the least amount of cloud cover during the time period and all tracts within the study area were assigned a mean NDVI value using GEE.