Why ENSO Prediction Skill Declined Since 1999/2000?
Abstract
It is well known that of the El Niño-Southern Oscillation (ENSO) prediction skill declined since 1999/2000. In this talk, we will examine the potential factors resulting in the decline. It is noted that compared with 1979-99, the whole tropical Pacific climate system, including both the ocean and atmosphere, shifted to a lower variability regime after 1999/2000. Meanwhile, the frequency of ENSO became less regular and was closer to a white noise process. The lead time of equatorial Pacific subsurface ocean heat content to precede ENSO decreased remarkably, in addition to a reduction of maximum correlation between them. The weakening of the correlation and the shortening of the lead time posed more challenges for ENSO prediction, and is likely the reason behind the skill decrease in ENSO prediction after 2000.
Coincident with the changes of tropical Pacific climate variability, the mean states of the atmospheric and oceanic components also experienced physically coherent changes. Warm anomaly of sea surface temperature (SST) in the western Pacific and cold anomaly in the eastern Pacific resulted in an increased zonal SST gradient, which is linked to an enhancement of surface wind stress and strengthening of Walker circulation, as well as an increase in the thermocline slope. These changes were consistent with an increase (a decrease) in precipitation and an enhancement (a suppression) of the deep convection in the western (eastern) equatorial Pacific. Possible connections between the mean state and the ENSO variability and frequency changes in the tropical Pacific are also discussed.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC33I1478H
- Keywords:
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- 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 1627 Coupled models of the climate system;
- GLOBAL CHANGEDE: 4522 ENSO;
- OCEANOGRAPHY: PHYSICALDE: 4922 El Nino;
- PALEOCEANOGRAPHY