Reflectivity Optimization Map (2.0)
### Search or click anywhere on the map
Reflective Earth uses satellite data to calculate how much sunlight is reflected back to space from the selected area and how much theoretically could be reflected. Choose more than one area to understand the reflectivity of different surfaces nearby.
### Choose actions you can take to make a difference
You can reduce heat in your building and substantially cut your energy bills by increasing the reflectivity of your building and surrounding areas. You can also save lives* by advocating for changes in a neighborhood or a city’s reflectivity. Click the “What Can you Do” button to learn more. The more people use the map, the more options we’ll be able to show.
### Download the Data
You can download data for the areas you’ve selected to share with your neighbors, with property owners, and with local officials. Ask them to join you in taking action to cool surfaces and make your community more resilient to extreme heat.
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About the Reflectivity Optimization map
The Reflectivity Optimization Map shows estimates of surface reflectivity (%) and reflected outgoing solar radiation (watts per square meter). The surface reflectivity estimates are based on Sentinel-2 satellite imagery from the European Space Agency (ESA) and the reflected outgoing solar radiation estimates are based on atmospheric data from the European Center for Medium Range Weather Forecasts (ECMWF). The map and underlying data were developed by the Reflective Earth team in partnership with the World Resources Institute and the Cool Roof team at Google.
Reflectivity (albedo) data is estimated from Sentinel-2 multi-spectral satellite imagery provided by the European Space Agency via Google Earth Engine. Data values represent weighted averages of six bands (B2, B3, B4, B8, B11, B12) during relatively cloud free conditions (cloud probability less than 30%) over time (presently the year 2021). The albedo number is computed from the values of the six bands using weights originated by Bonafoni et al. (2020). Sentinel-2 imagery bands range in spatial resolution from 10 meters to 60 meters. The displayed pixels are 10 meter squares. Because some of the original data has resolution lower than 10 meters and because the original data is orthorectified to fixed 10 meter pixels, there is some bleed over of albedo values from each pixel area to adjoining pixels.
The potential amount of sunlight that could be reflected by the surface back to space is estimated using 30 years of hourly ERA5 reanalysis data – about 1 Terabyte – from the European Centre for Medium-range Weather Forecasts (ECMWF) Copernicus Climate Change Service (C3S). ERA5 is based on a state-of-the-art weather model that includes the effects of elevation, clouds, aerosols, and greenhouse gasses. The potential value displayed on the map pixel represents the maximum amount of sunlight that could be reflected back to space by a Lambertian square meter of surface area averaged over a year using a novel model for solar energy that makes it to space from the Earth surface. A peer-reviewed journal article describing the work is available at Environmental Research Communications.
