clouding up vs clouding

clouding up and clouding both are nouns.

Word	Noun	Adjective	Verb	Adverb
clouding up	Yes	No	No	No
clouding	Yes	No	No	No

As nouns, clouding up and clouding are synonyms defined as:

clouding up and clouding: the process whereby water particles become visible in the sky

clouding up (noun)	clouding (noun)
the process whereby water particles become visible in the sky	the process whereby water particles become visible in the sky