downward vs downwardly

downward is an adjective but downwardly is not an adjective.

Word	Noun	Adjective	Verb	Adverb
downward	No	Yes	No	Yes
downwardly	No	No	No	Yes

As adverbs, downward and downwardly are synonyms defined as:

downward and downwardly: spatially or metaphorically from a higher to a lower level or position

Other synonyms of downward include down, downwards.

downward (adjective)	downwardly (adjective)
extending or moving from a higher to a lower place
on or toward a surface regarded as a base

downward (adverb)	downwardly (adverb)
spatially or metaphorically from a higher to a lower level or position	spatially or metaphorically from a higher to a lower level or position