gloominess vs ambiance

gloominess and ambiance both are nouns.

Word	Noun	Adjective	Verb	Adverb
gloominess	Yes	No	No	No
ambiance	Yes	No	No	No

As nouns, ambiance is a hypernym of gloominess; that is, ambiance is a word with a broader meaning than gloominess:

Other hypernyms of gloominess include ambience, atmosphere.

gloominess (noun)	ambiance (noun)
the quality of excessive mournfulness and uncheerfulness	the atmosphere of an environment
The property of having a frowning or scowling appearance.	a particular environment or surrounding influence
a feeling of melancholy apprehension
an atmosphere of depression and melancholy