Diffuse Horizontal Irradiance is the amount of radiation received per unit area by a surface that does not arrive on a direct path from the sun, but has been scattered by molecules and particles in the atmoshere. Basically, it is the illumination that comes from clouds and the blue sky.

If you are interested in more detailed information on the DIF values for any location worldwide, please see our Solar GIS Data Layer, Solar Time-series, and Solar Site Climate Variability Analysis products.