TY - JOUR
T1 - Role of the climatological intertropical convergence zone in the seasonal footprinting mechanism of El Niño-Southern Oscillation
AU - Park, Jae Heung
AU - Sung, Mi Kyung
AU - Yang, Young Min
AU - Zhao, Jiuwei
AU - An, Soon Il
AU - Kug, Jong Seong
N1 - Publisher Copyright:
© 2021 American Meteorological Society. All rights reserved.
PY - 2021/7/1
Y1 - 2021/7/1
N2 - The North Pacific Oscillation (NPO), a primary atmospheric mode over the North Pacific Ocean in boreal winter, is known to trigger El Niño-Southern Oscillation (ENSO) in the following winter, the process of which is recognized as the seasonal footprinting mechanism (SFM). On the basis of the analysis of model simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), we found that the SFM acts differently among models, and the correlation between the NPO and subsequent ENSO events, called the SFM efficiency, depends on the background mean state of the model. That is, SFM efficiency becomes stronger as the climatological position of the Pacific intertropical convergence zone (ITCZ) moves poleward, representing an intensification of the northern branch of the ITCZ. When the Pacific ITCZ is located poleward, the wind-evaporation-sea surface temperature (SST) feedback becomes stronger as the precipitation response to the SST anomaly is stronger in higher latitudes than that in lower latitudes. In addition, such active ocean- atmosphere interactions enhance NPO variability, favoring the SFM to operate efficiently and trigger an ENSO event. Consistent with the model results, the observed SFM efficiency increased during the decades in which the northern branch of the climatological ITCZ was intensified, supporting the importance of the tropical mean state of precipitation around the Pacific ITCZ.
AB - The North Pacific Oscillation (NPO), a primary atmospheric mode over the North Pacific Ocean in boreal winter, is known to trigger El Niño-Southern Oscillation (ENSO) in the following winter, the process of which is recognized as the seasonal footprinting mechanism (SFM). On the basis of the analysis of model simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), we found that the SFM acts differently among models, and the correlation between the NPO and subsequent ENSO events, called the SFM efficiency, depends on the background mean state of the model. That is, SFM efficiency becomes stronger as the climatological position of the Pacific intertropical convergence zone (ITCZ) moves poleward, representing an intensification of the northern branch of the ITCZ. When the Pacific ITCZ is located poleward, the wind-evaporation-sea surface temperature (SST) feedback becomes stronger as the precipitation response to the SST anomaly is stronger in higher latitudes than that in lower latitudes. In addition, such active ocean- atmosphere interactions enhance NPO variability, favoring the SFM to operate efficiently and trigger an ENSO event. Consistent with the model results, the observed SFM efficiency increased during the decades in which the northern branch of the climatological ITCZ was intensified, supporting the importance of the tropical mean state of precipitation around the Pacific ITCZ.
KW - El Niño
KW - Intertropical convergence zone
KW - North Pacific Oscillation
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U2 - 10.1175/JCLI-D-20-0809.1
DO - 10.1175/JCLI-D-20-0809.1
M3 - Article
AN - SCOPUS:85106897833
SN - 0894-8755
VL - 34
SP - 5243
EP - 5256
JO - Journal of Climate
JF - Journal of Climate
IS - 13
ER -