cloudlessness vs sunniness

cloudlessness and sunniness both are nouns.

Word	Noun	Adjective	Verb	Adverb
cloudlessness	Yes	No	No	No
sunniness	Yes	No	No	No

As nouns, sunniness is a hypernym of cloudlessness; that is, sunniness is a word with a broader meaning than cloudlessness:

cloudlessness: the lightness of a sunny day when there are no clouds in the sky
sunniness: lightness created by sunlight

cloudlessness (noun)	sunniness (noun)
the lightness of a sunny day when there are no clouds in the sky	lightness created by sunlight
	the quality of being cheerful and dispelling gloom