( M ( ( m ( ( Most ( local ( weather ( condition changes ) ) ) ) ( are ( caused ( by ( movement ( of ( air masses ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP M)) (VP (VBP m) (SBAR (S (NP (RBS Most) (JJ local) (NN weather) (NN condition) (NNS changes)) (VP (VBP are) (VP (VBN caused) (PP (IN by) (NP (NP (NN movement)) (PP (IN of) (NP (NN air) (NNS masses)))))))))) (. .)))
M m Most local weather condition changes are caused by movement of air masses.
(ROOT (S (NP (NP (DT The) (NN movement)) (PP (IN of) (NP (NP (DT an) (NN air) (NN mass)) (PP (IN over) (NP (NP (NN earth) (POS 's)) (NN surface)))))) (VP (VBZ causes) (NP (JJ local) (NN weather) (NNS changes))) (. .)))