大气科学学报2025，Vol.48Issue(6)：894-912,19.DOI:10.13878/j.cnki.dqkxxb.20240926001
典型和非典型大西洋尼诺对前冬ENSO的响应及其在春夏季的反馈
Response and feedback of Canonical and Non-canonical Atlantic Niños to ENSO in the preceding winter
摘要
Abstract
Inter-basin interactions between the tropical Atlantic and tropical Pacific Oceans play a pivotal role in shaping global climate variability on interannual timescales.Understanding the dynamical processes underlying these linkages is essential for improving seasonal climate prediction.The Atlantic Niño,the dominant mode of tropical Atlantic variability,exhibits two distinct forms:the Canonical Atlantic Niño(CA)and the Non-canonical Atlantic Niño(NCA).While the CA is well known to arise from the Bjerknes feedback,the mechanisms driving the NCA and its connections to preceding ENSO phases remain less clearly understood.This study systematically investigates the responses of CA and NCA to the preceding winter ENSO and their subsequent feedbacks during the ENSO decay phase,with the goals of(1)identifying the distinct physical processes through which La Niña and El Niño events trigger CA and NCA,respectively;(2)quantifying the feedback of CA and NCA on the deca-ying ENSO;and(3)evaluating the ability of CMIP6 climate models to reproduce these observed mechanisms.U-sing observational and reanalysis data spanning 1940-2022(ERA5 and SODA),interannual variability(periods≤ 9 years)was extracted through Fourier high-pass filtering.Composite,correlation,and regression analyses,along with Student's t-tests,were used to examine associated oceanic and atmospheric anomalies.La Niña-CA and El Niño-NCA events were identified based on the relationship between the winter(preceding December—February),Niño3.4 index and the summer(June—August)Atlantic Niño3 index(ATL3),with events selected when either index exceeded±0.5 standard deviations. The results show that a preceding winter La Niña induces westerly wind anomalies over the equatorial Atlan-tic via the Matsuno-Gill response,triggering downwelling Kelvin waves that suppress climatological upwelling and warm the eastern equatorial Atlantic.This warming reinforces low-level westerlies through the local Walker circulation,establishing a Bjerknes feedback that develops into a CA by early summer.In contrast,a preceding winter El Niño generates anticyclonic anomalies and warm SSTs in the tropical North Atlantic through the Pacific-North American teleconnection(PNA).The warm water is subducted and transported equatorward via mean me-ridional currents,leading to subsurface warming and the subsequent development of an NCA. Regarding feedback,the NCA significantly accelerates El Niño and promotes a phase transition to La Niña,whereas the CA exerts little influence on the decay of La Niña.During El Niño-NCA events,the Niño3.4 index decreases by 0.84 ℃ from April to August—significantly faster than during La Niña-CA or El Niño events.This rapid decay occurs through two pathways:1)warm SST anomalies in the tropical Indian Ocean and NCA generate eastward-propagating atmospheric Kelvin waves that produce easterly wind anomalies,moisture conver-gence,and enhanced convection over the Maritime Continent,thereby activating Bjerknes feedback in the Pacific;and 2)the Walker circulation response to the NCA enhances subsidence over the central-eastern Pacific,further favoring La Niña onset. The findings demonstrate that CA and NCA are triggered by distinct mechanisms linked to preceding ENSO phases and that the NCA plays a key role in facilitating the transition from El Niño to La Niña.Multi-model en-semble mean(MME)simulations from 48 CMIP6 models under PiControl experiments generally reproduce the observed response and feedback processes,supporting the robustness of these mechanisms.Nonetheless,model bia-ses persist,including underestimated ENSO decay rates and inter-model uncertainties in feedback strength.This study highlights the importance of accurately representing tropical inter-basin interactions in climate models to en-hance the predictability of ENSO and its global climate impacts,emphasizing the need to distinguish between CA and NCA in both observations and modeling efforts.关键词
典型大西洋尼诺/非典型大西洋尼诺/厄尔尼诺-南方涛动/响应/反馈Key words
Canonical Atlantic Niño/Non-canonical Atlantic Niño/El Niño-Southern Oscillation/response/feed-back引用本文复制引用
杨萌洲,袁潮霞,姜蕾杉,山形俊男..典型和非典型大西洋尼诺对前冬ENSO的响应及其在春夏季的反馈[J].大气科学学报,2025,48(6):894-912,19.基金项目
国家重点研发计划项目(2022YFF0801702) （2022YFF0801702）
国家自然科学基金基础科学中心项目(42088101) （42088101）
气象灾害教育部重点实验室&气象灾害预报预警与评估协同创新中心联合开放课题(KLME202504) 国家留学基金委对杨萌洲资助(CXXM2101180001) （KLME202504）
