( ( Pollution levels ) ( ( ( are often ) ( reduced ( by ( ( ( atmospheric mixing ) , ) ( which ( depends ( on ( ( ( ( such ( weather conditions ) ) ( as temperature ) ) and ) ( ( the movement ) ( of ( ( ( high and ) low ) ( pressure systems ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Pollution) (NNS levels)) (VP (VBP are) (ADVP (RB often)) (VP (VBN reduced) (PP (IN by) (NP (NP (JJ atmospheric) (NNS mixing)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ depends) (PP (IN on) (NP (NP (NP (JJ such) (NN weather) (NNS conditions)) (PP (IN as) (NP (NN temperature)))) (CC and) (NP (NP (DT the) (NN movement)) (PP (IN of) (NP (ADJP (JJ high) (CC and) (JJ low)) (NN pressure) (NNS systems))))))))))))) (. .)))
Pollution levels are often reduced by atmospheric mixing, which depends on such weather conditions as temperature and the movement of high and low pressure systems.
(ROOT (S (NP (JJ Cloudy) (NNS conditions)) (VP (MD will) (ADVP (RBS most) (RB likely)) (VP (VB result) (PP (IN from) (NP (DT a) (JJ low-pressure) (NN weather) (NN system))))) (. .)))
Cloudy conditions will most likely result from a low-pressure weather system.