Quasiperiodicity
{{Short description|Mathematical notion of recurrence with unpredictable period}}
Quasiperiodicity is the property of a system that displays irregular periodicity. Periodic behavior is defined as recurring at regular intervals, such as "every 24 hours".[http://www.merriam-webster.com/dictionary/periodicity Periodicity – Definition and More from the Free Merriam-Webster Dictionary] Quasiperiodic behavior is almost but not quite periodic.[http://www.merriam-webster.com/dictionary/quasiperiodic Quasiperiodic – Definition and More from the Free Merriam-Webster Dictionary] The term used to denote oscillations that appear to follow a regular pattern but which do not have a fixed period. The term thus used does not have a precise definition and should not be confused with more strictly defined mathematical concepts such as an almost periodic function or a quasiperiodic function.
Climatology
Climate oscillations that appear to follow a regular pattern but which do not have a fixed period are called quasiperiodic.[http://dev.unisdr.org/english/library/catalogue/v.php?id=1975 Not Found – UNISDR]{{dead link|date=July 2016 |bot=InternetArchiveBot |fix-attempted=yes }}The meteorological glossary: 2d ed. 1930. Meteorological Office, Great Britain. "Certain phenomena which recur more or less regularly but without the exactness of truly periodic phenomena are termed quasi-periodic."
Within a dynamical system such as the ocean-atmosphere system, oscillations may occur regularly when they are forced by a regular external forcing: for example, the familiar winter-summer cycle is forced by variations in sunlight from the (very close to perfectly) periodic motion of the Earth around the Sun. Or, like the recent ice age cycles, they may be less regular but still locked by external forcing. However, when the system contains the potential for an oscillation, but there is no strong external forcing to be phase-locked to, the "period" is likely to be irregular.
The canonical example of quasiperiodicity in climatology is El Niño–Southern Oscillation (ENSO). ENSO is highly consequential for wheat cultivation in Australia. Models to predict and thereby assist adaptation to ENSO have a large potential benefit to Australian wheat farmers.
{{cite journal|year=2021|issue=1|volume=3|publisher=Oxford University Press (OUP) (The Annals of Botany Company (AoB))|first11=Scott|first10=Fred|first9=Tim|first8=Yash|first7=Ben|first6=Kenton|first5=Yifan|first4=Karine|first3=Pablo|first2=Yan|first1=Andries|last11=Chapman|last10=Roosta|last9=Neale|last8=Dang|last7=Biddulph|last6=Porker|last5=Zhang|last4=Chenu|last3=Tejada|last2=Zhao|last1=Potgieter|title=Evolution and application of digital technologies to predict crop type and crop phenology in agriculture|journal=in silico Plants|issn=2517-5025|doi=10.1093/insilicoplants/diab017|doi-access=free|hdl=11343/280690|hdl-access=free}}
This review cites this study:
{{cite journal|year=2018|issue=3|volume=6|first3=Karine|first2=Scott|first1=Bangyou|last3=Chenu|last2=Chapman|last1=Zheng|page=77|doi=10.3390/cli6030077|id=CK ORCID [https://orcid.org/0000-0001-7273-2057 0000-0001-7273-2057]|journal=Climate|title=The Value of Tactical Adaptation to El Niño–Southern Oscillation for East Australian Wheat|bibcode=2018Clim....6...77Z|doi-access=free}}
In the modern era, it has a "period" somewhere between four and twelve years and a peak spectral density around five years.{{cn|date=January 2023}}
See also
References
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