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Contrasting the Skills and Biases of Deterministic Predictions for the Two Types of El Niño

Authors:

Fei ZHENG1,2 and Jin-Yi YU3

1 International Center for Climate and Environment Science, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

2 Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China

3 Department of Earth System Science, University of California, Irvine, CA 92697-3100, USA

 

Abstract:

The tropical Pacific has begun to experience a new type of El Niño, which has occurred particularly frequently during the last decade, referred to as the central Pacific (CP) El Niño. Various coupled models with different degrees of complexity have been used to make real-time El Niño predictions, but high uncertainty still exists in their forecasts. It remains unknown as to how much of this uncertainty is specifically related to the new CP-type El Niño and how much is common to both this type and the conventional Eastern Pacific (EP)-type El Niño. In this study, the deterministic performance of an El Niño–Southern Oscillation (ENSO) ensemble prediction system is examined for the two types of El Niño. Ensemble hindcasts are run for the nine EP El Niño events and twelve CP El Niño events that have occurred since 1950. The results show that (1) the skill scores for the EP events are significantly better than those for the CP events, at all lead times; (2) the systematic forecast biases come mostly from the prediction of the CP events; and (3) the systematic error is characterized by an overly warm eastern Pacific during the spring season, indicating a stronger spring prediction barrier for the CP El Niño. Further improvements to coupled atmosphere–ocean models in terms of CP El Niño prediction should be recognized as a key and high-priority task for the climate prediction community.

 

Key words:

ENSO, EP El Niño, CP El Niño, prediction skill, systematic bias, spring prediction barrier

 


Citation:

Zheng, F.*, and J.-Y. Yu, 2017: Contrasting the skills and biases of deterministic predictions for the two types of El Niño. Adv. Atmos. Sci., 34(12), 1395–1403, doi: 10.1007/s00376-017-6324-y


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