Sky luminance distribution is the basis of daylighting

and the reference sky classification is a prerequisite for determining the distribution of the sky luminance. Combining with the daylighting observation data of 1 minute in IDMP daylighting observation stations in Chongqing

by analyzing meteorological parameters affecting the sky brightness distribution

the meteorological parameters

such as the cloud cover

surface conditions on the sun

and the horizon to the zenith luminance gradient

are identified as key factors exerting influence on reference sky classification. On this basis

the reference sky is divided into six types.