( You ( probably ( ( also ( know ( that ( ( air pressure ) ( decreases ( as ( ( the altitude ) increases ) ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (PRP You)) (ADVP (RB probably)) (VP (ADVP (RB also)) (VBP know) (SBAR (IN that) (S (NP (NN air) (NN pressure)) (VP (VBZ decreases) (SBAR (IN as) (S (NP (DT the) (NN altitude)) (VP (VBZ increases)))))))) (. .)))
You probably also know that air pressure decreases as the altitude increases.
(ROOT (S (NP (NNP Air)) (VP (VBP pressure) (SBAR (S (NP (PRP it)) (VP (VBZ decreases) (PP (IN as) (NP (NN altitude) (NNS increases))))))) (. .)))