( ( ( Water vapor ) ( in ( the ( atmosphere forms ) ) ) ) ( ( clouds ( as ( it ( ( cools and ) condenses ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Water) (NNP vapor)) (PP (IN in) (NP (DT the) (NN atmosphere) (NNS forms)))) (VP (VBZ clouds) (SBAR (IN as) (S (NP (PRP it)) (VP (VP (VBZ cools)) (CC and) (VP (VBZ condenses)))))) (. .)))
Water vapor in the atmosphere forms clouds as it cools and condenses .
(ROOT (S (NP (NNP Water) (NN vapor)) (VP (MD must) (VP (VB lose) (NP (NN heat) (NN energy)) (SBAR (IN before) (S (NP (NNS clouds)) (VP (MD can) (VP (VB form))))))) (. .)))
Water vapor must lose heat energy before clouds can form.