( ( These clouds ) ( ( may ( produce ( ( precipitation , ) ( which ( is ( ( ( the ( primary route ) ) ( for water ) ) ( to ( ( return ( to ( ( the ( Earth 's ) ) surface ) ) ) ( within ( the ( water cycle ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS clouds)) (VP (MD may) (VP (VB produce) (NP (NP (NN precipitation)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (NP (NP (DT the) (JJ primary) (NN route)) (PP (IN for) (NP (NN water))) (S (VP (TO to) (VP (VB return) (PP (TO to) (NP (NP (DT the) (NN Earth) (POS 's)) (NN surface))) (PP (IN within) (NP (DT the) (NN water) (NN cycle))))))))))))) (. .)))
These clouds may produce precipitation , which is the primary  route for water to return to the Earth's surface within the water cycle.
(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))))))))))) (. .)))