Allen, Michael J., Sheridan, Scott C.

International Journal of Climatology

Published date July 20, 2015

Evaluating changes in season length, onset, and end dates across the United States (1948–2012)

  • States that as climatological studies utilize temporally and spatially static definitions of seasonal definitions, the understanding of seasonal change may be limited by the way in which seasons are defined
  • This research serves as a challenge to this perspective by examining the changes in seasons by incorporating variability into the way in which seasons are defined
  • Defines temporally and spatially variable seasons were defined based on thresholds of apparent temperature and upper-level circulation patterns for the period 1948–2012
  • Uses two apparent air temperature metrics (and 60 US surface stations) to define seasons that vary spatially and temporally
  • Observes late starts of autumn and winter since 1948 and earlier onsets of spring and summer
  • Finds that, for the individual stations, the largest shifts occurred along coasts and in larger, more urbanized environments
  • Finds that individual locations also showed increased variability in start date, and significant changes were found for all four seasons in the circulation approach
  • States that seasons have been shown to be important for a variety of processes including phenological responses and human adaptation to extreme temperature environments; and that the consideration of season variability may be appropriate for future climatological research