Can Eurasia Experience a Cold Winter under a Third-Year La Nina in 2022/23?

The Northern Hemisphere(NH)often experiences frequent cold air outbreaks and heavy snowfalls during La Nina winters.In 2022,a third-year La Nina event has exceeded both the oceanic and atmospheric thresholds since spring and is predicted to reach its mature phase in December 2022.Under such a significant global climate signal,whether the Eurasian Continent will experience a tough cold winter should not be assumed,despite the direct influence of mid-to high-latitude,large-scale atmospheric circulations upon frequent Eurasian cold extremes,whose teleconnection physically operates by favoring Arctic air invasions into Eurasia as a consequence of the reduction of the meridional background temperature gradient in the NH.In the 2022/23 winter,as indicated by the seasonal predictions from various climate models and statistical approaches developed at the Institute of Atmospheric Physics,abnormal warming will very likely cover most parts of Europe under the control of the North Atlantic Oscillation and the anomalous anticyclone near the Ural Mountains,despite the cooling effects of La Nina.At the same time,the possibility of frequent cold conditions in mid-latitude Asia is also recognized for this upcoming winter,in accordance with the tendency for cold air invasions to be triggered by the synergistic effect of a warm Arctic and a cold tropical Pacific on the hemispheric scale.However,how the future climate will evolve in the 2022/23 winter is still subject to some uncertainty,mostly in terms of unpredictable internal atmospheric variability.Consequently,the status of the mid-to high-latitude atmospheric circulation should be timely updated by medium-term numerical weather forecasts and sub-seasonal-to-seasonal prediction for the necessary date information and early warnings.

A transformer-based coupled ocean-atmosphere model for ENSO studies

The El Nino-Southern Oscillation (ENSO) is the strongest interannual anomalies affecting weather and climate worldwide. As has been well recognized, ENSO originates from the coupling between the ocean and atmosphere in the tropical Pacific, characterized by a coherent evolution of subsurface temperature anomalies that profoundly impact sea surface temperature (SST) and surface wind fields.

A multi-model prediction system for ENSO

The El Niño and Southern Oscillation(ENSO)is the primary source of predictability for seasonal climate prediction.To improve the ENSO prediction skill,we established a multi-model ensemble(MME)prediction system,which consists of 5 dynamical coupled models with various complexities,parameterizations,resolutions,initializations and ensemble strategies,to account for the uncertainties as sufficiently as possible.Our results demonstrated the superiority of the MME over individual models,with dramatically reduced the root mean square error and improved the anomaly correlation skill,which can compete with,or even exceed the skill of the North American Multi-Model Ensemble.In addition,the MME suffered less from the spring predictability barrier and offered more reliable probabilistic prediction.The real-time MME prediction adequately captured the latest successive La Niña events and the secondary cooling trend six months ahead.Our MME prediction has,since April 2022,forecasted the possible occurrence of a third-year La Niña event.Overall,our MME prediction system offers better skill for both deterministic and probabilistic ENSO prediction than all participating models.These improvements are probably due to the complementary contributions of multiple models to provide additive predictive information,as well as the large ensemble size that covers a more reasonable uncertainty distribution.