( ( The ( first letter ) ) ( ( ( ( describes ( its ( moisture properties ) ) ) , ) ( with ( c ( used ( for ( ( ( ( continental ( air masses ) ) ( -LRB- ( dry -RRB- ) ) ) and ) ( m ( for ( ( maritime ( air masses ) ) ( -LRB- ( moist -RRB- ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ first) (NN letter)) (VP (VBZ describes) (NP (PRP$ its) (NN moisture) (NNS properties)) (, ,) (PP (IN with) (NP (NP (SYM c)) (VP (VBN used) (PP (IN for) (NP (NP (NP (JJ continental) (NN air) (NNS masses)) (PRN (-LRB- -LRB-) (ADJP (JJ dry)) (-RRB- -RRB-))) (CC and) (NP (NP (NN m)) (PP (IN for) (NP (NP (JJ maritime) (NN air) (NNS masses)) (PRN (-LRB- -LRB-) (NP (NN moist)) (-RRB- -RRB-))))))))))) (. .)))
The first letter describes its moisture properties, with c used for continental air masses (dry) and m for maritime air masses (moist).
(ROOT (S (NP (NP (CD One)) (PP (IN of) (NP (NP (DT the) (NNS properties)) (PP (IN of) (NP (DT an) (NN air) (NN mass)))))) (VP (VBZ is) (SBAR (IN that) (S (NP (DT an) (NN air) (NN mass)) (VP (VBZ has) (NP (NP (JJ similar) (NN temperature) (CC and) (NN moisture) (NNS properties)) (PP (IN throughout) (NP (PRP it)))))))) (. .)))
One of the properties of an air mass is that an air mass has similar temperature and moisture properties throughout it.