( ( Some clouds ) ( ( produce ( ( precipitation , ) ( such ( as ( ( ( ( rain or ) snow ) , ) ( which ( ( ( returns water ) back ) ( to ( ( Earth 's ) surface ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT Some) (NNS clouds)) (VP (VBP produce) (NP (NP (NN precipitation)) (, ,) (PP (JJ such) (IN as) (NP (NP (NN rain) (CC or) (NN snow)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ returns) (NP (NN water)) (PRT (RP back)) (PP (TO to) (NP (NP (NNP Earth) (POS 's)) (NN surface)))))))))) (. .)))
Some clouds produce precipitation, such as rain or snow, which returns water back to Earth's surface.
(ROOT (S (NP (NNP Precipitation)) (VP (VBP are) (NP (NP (DT a) (JJ natural) (NN process)) (SBAR (WHNP (WDT that)) (S (VP (VBZ allows) (NP (NN water)) (S (VP (TO to) (VP (VB return) (ADVP (RB again)) (PP (TO to) (NP (NP (DT the) (NN earth) (POS 's)) (NN surface))))))))))) (. .)))