( Troposphere-stratosphere ( exchange . ) )
(ROOT (NP (JJ Troposphere-stratosphere) (NN exchange) (. .)))
Troposphere-stratosphere exchange.
(ROOT (S (NP (DT The) (NN stratosphere)) (VP (VBZ is) (NP (NP (DT the) (NN layer)) (PP (IN above) (NP (DT the) (NNP troposphere))))) (. .)))