( ( Maritime air ) ( ( mass ( ( An ( air mass ) ) ( that ( originates ( over ( the ocean ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Maritime) (NN air)) (VP (VBZ mass) (NP (NP (DT An) (NN air) (NN mass)) (SBAR (WHNP (WDT that)) (S (VP (VBZ originates) (PP (IN over) (NP (DT the) (NN ocean)))))))) (. .)))
Maritime air mass An air mass that originates over the ocean.
(ROOT (S (SBAR (IN If) (S (NP (DT an) (NN air) (NN mass)) (VP (VBZ forms) (PP (IN over) (NP (DT an) (NN ocean)))))) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (DT a) (JJ maritime) (NN air) (NN mass)))) (. .)))