( ( The mesosphere ) ( ( ( extends ( from ( ( the ( upper limit ) ) ( of ( ( ( the stratosphere ) , ) ( ( ( ( around 80 ) kilometers ) ( -LRB- ( ( 50 miles ) -RRB- ) ) ) ( above ( sea level ) ) ) ) ) ) ) ) ( to ( ( ( the mesopause ) , ) ( its ( upper boundary ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN mesosphere)) (VP (VBZ extends) (PP (IN from) (NP (NP (DT the) (JJ upper) (NN limit)) (PP (IN of) (NP (NP (DT the) (NN stratosphere)) (, ,) (NP (NP (NP (QP (RB around) (CD 80)) (NNS kilometers)) (PRN (-LRB- -LRB-) (NP (CD 50) (NNS miles)) (-RRB- -RRB-))) (PP (IN above) (NP (NN sea) (NN level)))))))) (PP (TO to) (NP (NP (DT the) (NN mesopause)) (, ,) (NP (PRP$ its) (JJ upper) (NN boundary))))) (. .)))
The mesosphere extends from the upper limit of the stratosphere, around 80 kilometers (50 miles) above sea level to the mesopause, its upper boundary.
(ROOT (S (NP (DT The) (NN mesopause)) (VP (VBZ is) (PP (IN at) (NP (NP (DT the) (NN top)) (PP (IN of) (NP (DT the) (NN mesosphere)))))) (. .)))