( ( The ( vernal ( and ( autumnal equinoxes ) ) ) ) ( ( occur ( when ( ( the sun ) ( ( is directly ) ( above ( the equator ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ vernal) (CC and) (JJ autumnal) (NNS equinoxes)) (VP (VBP occur) (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NN sun)) (VP (VBZ is) (ADVP (RB directly)) (PP (IN above) (NP (DT the) (NN equator))))))) (. .)))
The vernal and autumnal equinoxes occur when the sun is directly above the equator.
(ROOT (S (NP (DT The) (NN sun)) (VP (VBZ is) (ADVP (RB directly)) (PP (IN over) (NP (DT the) (NN equator))) (PP (IN during))) (. .)))