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Application of a climate departure index to the study of freeze dates and growing season length in the south‐eastern United States
Author(s) -
Suckling Philip W.
Publication year - 1989
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.3370090405
Subject(s) - climatology , growing season , geography , spring (device) , climate change , period (music) , environmental science , climatic variability , physical geography , index (typography) , ecology , biology , geology , mechanical engineering , physics , world wide web , computer science , acoustics , engineering
A climate departure index ( CDI ) is utilized to study the variability of last spring‐freeze dates, first autumn‐freeze dates, and growing season length in the south‐eastern United States for the period 1911–1986. The CDI is useful for determining how ‘normal’ or ‘unusual’ a particular year is compared to the long‐term situation for the region under consideration. This study shows that when distinct long‐term climatic trends exist for the climatic element under study, the CDI should be calculated using residuals from a trend line rather than simply comparing individual yearly values to the long‐term average. With respect to last spring‐freeze and first autumn‐freeze dates and growing season length in south‐eastern United States, the CDI analysis illustrates that a period of rather ‘normal’ conditions occurred during the late 1950s to early 1970s. Slightly higher CDI values for the 1980s, which implies a greater occurrence of extreme events (i.e. greater climatic variability), is not unprecedented given the high CDI values earlier in the century. The decade of the 1940s especially experienced a greater frequency of unusual last spring‐freeze dates and first‐autumn‐freeze dates (either extra early or late) as well as larger variations in growing season length.