( ( After ( air ( ( ( begins ( to cool ) ) and ) ( then ( becomes saturated ) ) ) ) ) ( , ( ( ( sublimation or ) condensation ) ( ( starts ( the ( cloud-forming process ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN After) (S (NP (NN air)) (VP (VP (VBZ begins) (S (VP (TO to) (VP (VB cool))))) (CC and) (VP (ADVP (RB then)) (VBZ becomes) (ADJP (JJ saturated)))))) (, ,) (NP (NN sublimation) (CC or) (NN condensation)) (VP (VBZ starts) (NP (DT the) (JJ cloud-forming) (NN process))) (. .)))
After air begins to cool and then becomes saturated, sublimation or condensation starts the cloud-forming process.
(ROOT (S (NP (NNP Condensation)) (VP (MD must) (VP (VB occur) (PP (IN for) (NP (NNS clouds))) (S (VP (TO to) (VP (VB form)))))) (. .)))