Determination of climatological seasons for the East Coast of the U.S. using an air mass-based classification

This paper discusses the application of a year-round synoptic classification procedure to define climatolog~cal seasons based upon the frequency occuiience of seasonal air masses The classification is developed through air inass 'seed day identification and discriminant function analysis, and assigns each day to 1 of 18 ail mass types for each of 14 stations along the East Coast of the United States Unlike the 'astronomical definitlon of seasons, which divides a year into 4 equal p e i ~o d s , the length of wlnter ranges fiom about 1'4 mo in Mlami, Florida to more than 4 mo in Portland, hdaine as determined by air mass frequencies The suminer extends more than 5 mo in Flonda, whlle it only lasts 3 mo in Maine In the mld-Atlantic region, there ale 2 longer seasons (summer and wlntei, about 4 mo edch) and 2 shorter seasons (spnny and fall, about 2 mo each) The seasonal definitlon proposed here more closely corresponds to phenological responses than do t r a d ~t ~o n a l def~nitions The lnforination can be applied to numerous environmentdl assessment problems, including animal demographics and habitat distnbutions, plant phenology and subsequent pollen release, m~gration and hibernation patterns, human health and psychological iesponses to climate, and agncultural p l a n n ~n g activities KEY WORDS Climatological seasons Synoptic climatology Spatial synoptic classif~cation Air masses Discriminant function analysis