update definition

Co-Authored-By: Cliff Hansen <[email protected]>
Co-Authored-By: Echedey Luis <[email protected]>

Author: 3 people

pvlib/data/variables_style_rules.csv

@@ -11,7 +11,7 @@ ghi;global horizontal irradiance
 ghi_extra;horizontal irradiance at top of atmosphere (extraterrestrial)
 gri;ground-reflected irradiance
 ape;average photon energy
-aoi;angle of incidence between ±90°
+aoi;angle of incidence. Angle between the surface normal vector and the vector pointing towards the sun's centre
 aoi_projection;cos(aoi)
 airmass;airmass
 airmass_relative;relative airmass