( ( Air temperature ) ( ( decreases ( as ( ( altitude increases ) ( in ( the troposphere ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Air) (NN temperature)) (VP (VBZ decreases) (PP (IN as) (NP (NP (NN altitude) (NNS increases)) (PP (IN in) (NP (DT the) (NNP troposphere)))))) (. .)))
Air temperature decreases as altitude increases in the troposphere.
(ROOT (S (SBAR (IN As) (S (NP (DT the) (NN altitude)) (VP (VBZ decreases)))) (, ,) (NP (NP (DT the) (NN density)) (PP (IN of) (NP (NN air)))) (VP (VBZ decreases)) (. .)))