soberness vs sombreness

soberness and sombreness both are nouns.

Word	Noun	Adjective	Verb	Adverb
soberness	Yes	No	No	No
sombreness	Yes	No	No	No

As nouns, soberness and sombreness are synonyms defined as:

Other synonyms of soberness include graveness, gravity, sobriety, somberness.

soberness (noun)	sombreness (noun)
a manner that is serious and solemn	a manner that is serious and solemn
the state of being sober and not intoxicated by alcohol	a feeling of melancholy apprehension
	a state of partial or total darkness