Will the Hist...a Ni_a Event__Xianghui FANG.pdf

Will the Historic Southeasterly Wind over the Equatorial Pacificin March 2022 Trigger a Third-year La Nia Event?Xianghui FANG1,Fei ZHENG*2,3,Kexin LI2,Zeng-Zhen HU4,Hongli REN5,Jie WU6,Xingrong CHEN7,Weiren LAN8,Yuan YUAN6,Licheng FENG7,Qifa CAI8,and Jiang ZHU21Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences,Fudan University,Shanghai 200438,China2International Center for Climate and Environment Science(ICCES),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China3Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science&Technology,Nanjing 210044,China4Climate Prediction Center,NCEP/NWS/NOAA,College Park,MD 20740,USA5State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences,Beijing 100081,China6National Climate Center,Beijing 100081,China7National Marine Environmental Forecasting Center,Beijing 100081,China8Mailbox 5111,Beijing 100094,China(Received 25 May 2022;revised 15 June 2022;accepted 26 June 2022)ABSTRACTBased on the updates of the Climate Prediction Center and International Research Institute for Climate and Society(CPC/IRI)and the China Multi-Model Ensemble(CMME)El Nio-Southern Oscillation(ENSO)Outlook issued in April2022,La Nia is favored to continue through the boreal summer and fall,indicating a high possibility of a three-year LaNia(202023).It would be the first three-year La Nia since the 19982001 event,which is the only observed three-yearLa Nia event since 1980.By examining the status of airsea fields over the tropical Pacific in March 2022,it can be seenthat while the thermocline depths were near average,the southeasterly wind stress was at its strongest since 1980.Here,based on a quaternary linear regression model that includes various relevant airsea variables over the equatorial Pacific inMarch,we argue that the historic southeasterly winds over the equatorial Pacific are favorable for the emergence of thethird-year La Nia,and both the anomalous easterly and southerly wind stress components are important and contribute50%of the third-year La Nia growth,respectively.Additionally,the possible global climate impacts of this event arediscussed.Key words:El Nio-Southern Oscillation,three-year La Nia,strongest southeasterly wind,airsea interactionCitation:Fang,X.-H.,and Coauthors,2023:Will the historic southeasterly wind over the equatorial Pacific in March 2022trigger a third-year La Nia event?Adv.Atmos.Sci.,40(1),613,https:/doi.org/10.1007/s00376-022-2147-6.El Nio-Southern Oscillation(ENSO)is the largest interannual climate variability in the tropics.Although its evolutiontakes place in the tropical Pacific region,it has far-reaching impacts on climate and society around the world(McPhaden etal.,2006).Meanwhile,ENSO signals also provide very important information for other short-term climate predictions.There-fore,a successful ENSO forecast is of great importance.In fact,both statistical and physical forecast models could successfullypredict ENSO evolution with lead times of 6 to 12 months by the late 20th century(Latif et al.,1994).Despite this progress,the complexity of ENSO has always been an important obstacle restricting ENSO forecasting(Zheng et al.,2016;Timmermannet al.,2018;Fang and Xie,2020;Chen et al.,2022).ENSO exhibits a high degree of complexity both spatially and tempo-rally.For example,there are central Pacific(CP)and eastern Pacific(EP)types of El Nio(Ashok et al.,2007;Kao and Yu,*Corresponding author:Fei ZHENGEmail:ADVANCES IN ATMOSPHERIC SCIENCES,VOL.40,JANUARY 2023,613 News&Views Institute of Atmospheric Physics/Chinese Academy of Sciences,and Science Press and Springer-Verlag GmbH Germany,part of Springer Nature 20232009),there are differences in amplitude and spatial asymmetry between El Nio and La Nia(An and Jin,2004),and LaNia events can span two or three consecutive years(Hu et al.,2014;Zheng et al.,2015;DiNezio et al.,2017;Wu et al.,2021).These complexities undoubtedly bring significant challenges to simulating and predicting ENSO(DiNezio et al.,2017;Wu et al.,2021).By analyzing historical data,it has been noted that,compared with El Nio,the complexity of La Nia is morereflected in time than space.For example,of the 16 La Nias that have occurred from 1980 to the present,13 have lastedfor at least two years,and 19982001 was a three-year La Nia event.Recently,202122 has been officially identified as aLa Nia year,which makes 202022 a two-year La Nia event(Li et al.,2022).Furthermore,this La Nia did not quicklydecay after its peak.Instead,it persisted as a moderate La Nia and even recently rebounded.According to the latest ClimatePrediction Center and International Research Institute for Climate and Society(CPC/IRI)ENSO Outlook issued in April2022 (Fig.1a;http:/iri.columbia.edu/climate/ENSO/currentinfo/update.html),La Nia is favored to continue throughboreal summer(59%chance during JuneAugust 2022),with a 50%55%chance o