Understanding the Warm Water Volume Precursor of ENSO Events and its Interdecadal Variation. Issue 3 (10th February 2018)

• Record Type: Journal Article
• Authors: Neske, S.; McGregor, S.
• Is Part Of: Geophysical research letters. Volume 45:Issue 3(2018)
• Page Start: 1577
• Page End: 1585
• Publication Date: 2018-02-10
• Subjects: ENSO -- warm water volume -- predictability -- precursor; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL076439
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: A wind forced ocean model is used to decompose the equatorial Pacific warm water volume (WWV) between 1980 and 2016 into two components: the (i) adjusted wind response, which is found by letting the model evolve unforced for three months, and (ii) instantaneous wind response, which are the instantaneous WWV changes due to Ekman transports. Our results suggest that roughly half of WWV variability is only as predictable as the winds that drive the instantaneous change. Separate examinations of pre‐2000 and post‐2000 periods reveal (i) nearly equal importance of instantaneous and adjusted responses for the pre‐2000 period and (ii) dominance of the instantaneous response during the post‐2000 period, which is most apparent during the recharged phase. This increasing instantaneous contribution prominence explains the post‐2000 reduction in WWV/El Niño‐Southern Oscillation sea surface temperature lead times (from six to nine months pre‐2000 down to three months post‐2000) and is consistent with the reduction in post‐2000 El Niño‐Southern Oscillation prediction skill. Key Points: Equatorial Pacific warm water volume is decomposed into instantaneous and adjusted contributions, caused by Ekman transport and wave dynamics, respectively Equatorial Pacific warm water volume changes are nearly equally driven by instantaneous and adjusted responses to winds for the period 1980–2016 The post‐2000 dominance of the instantaneous response explains the post‐2000 shortening in warm water volume/Niño3.4 sea surface temperature lead time