{"title":"Changes in El Niño characteristics and air–sea feedback mechanisms under progressive global warming","authors":"Min-Hua Shen, Jia-Yuh Yu","doi":"10.1007/s44195-023-00051-5","DOIUrl":null,"url":null,"abstract":"Abstract In this study, we investigate the potential changes of El Niño characteristics, including intensity, frequency and CP/EP El Niño ratio, under progressive global warming based on the 140-year CMIP6 model simulation outputs with the 1pctCO2 experiment. Major air-sea feedback mechanisms attributing to the changes are also examined. The CMIP6 ensemble means project a slight enhancement of El Niño intensity by about 2% and a modest increase of El Niño frequency by about 4% from the first to the second 70-year periods. It is found that these small changes result from the opposite response to global warming between CP and EP El Niño, i.e., the intensity of EP El Niño is projected to weaken by nearly 4.6% while the intensity of CP El Niño is projected to increase by about 4.5%. Since CP El Niño occurs more frequently than EP El Niño in CMIP6 simulations, this leads to a slight enhancement of the total El Niño intensity if these two types of El Niño were not separated. A similar situation occurs in projecting the future change of El Niño frequency, i.e., the frequency of EP El Niño is projected to decrease by about 1.4% while the frequency of CP El Niño is projected to increase by about 2%, thereby leading to a modest increase of the total El Niño frequency. By comparing the variance explained by key air-sea feedback mechanism between the two 70-year periods, we also note that the increased CP/EP ratio can be explained by the enhanced role played by the SF (seasonal footprinting) mechanism in a warmer atmosphere. Our study also points out that, as long as a climate model can correctly produce the intensity (variance) of major air-sea feedback mechanisms, the relationship between changes in El Niño characteristics and changes in feedback mechanisms can be physically robust.","PeriodicalId":22259,"journal":{"name":"Terrestrial, Atmospheric and Oceanic Sciences","volume":null,"pages":null},"PeriodicalIF":0.8000,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Terrestrial, Atmospheric and Oceanic Sciences","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1007/s44195-023-00051-5","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Abstract In this study, we investigate the potential changes of El Niño characteristics, including intensity, frequency and CP/EP El Niño ratio, under progressive global warming based on the 140-year CMIP6 model simulation outputs with the 1pctCO2 experiment. Major air-sea feedback mechanisms attributing to the changes are also examined. The CMIP6 ensemble means project a slight enhancement of El Niño intensity by about 2% and a modest increase of El Niño frequency by about 4% from the first to the second 70-year periods. It is found that these small changes result from the opposite response to global warming between CP and EP El Niño, i.e., the intensity of EP El Niño is projected to weaken by nearly 4.6% while the intensity of CP El Niño is projected to increase by about 4.5%. Since CP El Niño occurs more frequently than EP El Niño in CMIP6 simulations, this leads to a slight enhancement of the total El Niño intensity if these two types of El Niño were not separated. A similar situation occurs in projecting the future change of El Niño frequency, i.e., the frequency of EP El Niño is projected to decrease by about 1.4% while the frequency of CP El Niño is projected to increase by about 2%, thereby leading to a modest increase of the total El Niño frequency. By comparing the variance explained by key air-sea feedback mechanism between the two 70-year periods, we also note that the increased CP/EP ratio can be explained by the enhanced role played by the SF (seasonal footprinting) mechanism in a warmer atmosphere. Our study also points out that, as long as a climate model can correctly produce the intensity (variance) of major air-sea feedback mechanisms, the relationship between changes in El Niño characteristics and changes in feedback mechanisms can be physically robust.
基于CMIP6模式140年模拟结果和1pctCO2实验,研究了全球变暖条件下El Niño的强度、频率和CP/EP比值的潜在变化。还研究了导致这些变化的主要海气反馈机制。CMIP6总体意味着预估El Niño强度在第一个到第二个70年周期中略有增强约2%,El Niño频率在第一个到第二个70年周期中略有增加约4%。研究发现,这些微小的变化是由CP和EP El Niño对全球变暖的相反响应引起的,EP El Niño的强度预计减弱了近4.6%,而CP El Niño的强度预计增加了约4.5%。由于在CMIP6模拟中,CP El Niño比EP El Niño发生的频率更高,如果不将这两种类型的El Niño分开,则会导致El Niño的总强度略有增强。在预测El Niño未来频率变化时也出现了类似的情况,即EP El Niño的频率预计将下降约1.4%,而CP El Niño的频率预计将增加约2%,从而导致El Niño总频率适度增加。通过比较两个70年周期间主要海气反馈机制解释的差异,我们还注意到CP/EP比值的增加可以解释为大气变暖中SF(季节性足迹)机制作用的增强。我们的研究还指出,只要气候模式能够正确地产生主要海气反馈机制的强度(方差),El Niño特征变化与反馈机制变化之间的关系在物理上是稳健的。
期刊介绍:
The major publication of the Chinese Geoscience Union (located in Taipei) since 1990, the journal of Terrestrial, Atmospheric and Oceanic Sciences (TAO) publishes bi-monthly scientific research articles, notes, correspondences and reviews in all disciplines of the Earth sciences. It is the amalgamation of the following journals:
Papers in Meteorological Research (published by the Meteorological Society of the ROC) since Vol. 12, No. 2
Bulletin of Geophysics (published by the Institute of Geophysics, National Central University) since No. 27
Acta Oceanographica Taiwanica (published by the Institute of Oceanography, National Taiwan University) since Vol. 42.