The University of Tokyo · 환경과학
Tomoki Iwakiri 교수의 연구실은 기후변동성, 특히 엘니뇨-남중미열역동(ENSO)의 다년간 지속 현상인 다년간 라니냐 및 다년간 엘니뇨의 발생 메커니즘을 중심으로 연구를 진행하고 있습니다. 기후 모델링, 재분석 데이터 분석, 그리고 대기-오ceans 상호작용의 물리적 원리를 기반으로 한 이론적 프레임워크를 활용하여 ENSO의 주기성과 지속성의 기초를 규명하고 있습니다. 특히 열수위치, 에크먼 수송, 태평양 수렴-해방 과정 등 기후 시스템 내 핵심 메커니즘의 역할을 분석하고 있습니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
El Niño-Southern Oscillation (ENSO), characterized by anomalous sea surface temperature in the central-eastern equatorial Pacific, is a dominant interannual variability, impacting worldwide weather and socioeconomics. The ENSO cycle contains irregularity, in which La Niña often persists for more than two years, called "multi-year La Niña". Observational records show that multi-year La Niña tends to accompany strong El Niño in the preceding year, but their physical linkage remains unclear. Here w
Abstract La Niña persisted from 2020 to 2023, but its mechanisms are still unclear. In this study, atmosphere and ocean reanalysis and 100‐member initialized forecasts using a state‐of‐the‐art climate model were analyzed to identify factors contributing to the persistence of the first‐ to second‐year La Niña during 2020–2022. We found that North Pacific high pressure anomalies in the winter of 2020/2021 forced a negative phase of the Pacific meridional mode through the following spring, forming
La Niña is the negative phase of the El Niño-Southern Oscillation (ENSO) cycle. It occurs in the equatorial Pacific, and events known as multiyear La Niña often persists for more than two years. During a conventional La Niña event, the seasonal cycle of surface temperature over Japan is amplified (i.e., hotter summer and colder winter than normal years), but the influence of multiyear events on temperatures over Japan is unclear. In this study, we evaluate the teleconnection associated with mult
Abstract El Niño–Southern Oscillation (ENSO) events occasionally recur one after the other in the same polarity, called multiyear ENSO. However, the dynamical processes are not well understood. This study aims to elucidate the unified mechanisms of multiyear ENSO using observations, phase 6 of the Coupled Model Intercomparison Project (CMIP6) models, and the theoretical linear recharge oscillator (RO) model. We found that multiyear El Niño and La Niña events are roughly symmetric except for case
Abstract This study presents modeling evidence that the Indian Ocean Dipole (IOD) is enhanced in its frequency and amplitude under mid‐Holocene (8‐ka) conditions. This enhancement is identified in a global climate model simulation driven by the 8‐ka insolation, in which negative sea surface temperature anomalies grow more than the present‐day simulation in the eastern Indian Ocean. The mechanism of IOD amplification is explained in terms of a positive feedback among sea surface temperature, prec
Abstract Off‐equatorial wind stress curl anomalies that mainly drive geostrophic transport are essential for the phase transition of the El Niño‐Southern Oscillation (ENSO) induced by a recharge‐discharge process. The ENSO‐induced zonal wind stress anomaly also drives surface Ekman currents, which may counteract the geostrophic transport, but its effect on ENSO periodicity remains unclear in the recharge oscillator theory. Here, we extended an ENSO diagnostic framework, called the Bjerknes‐Wyrtk
Abstract Paleo proxy records have suggested that El Niño–Southern Oscillation (ENSO) variability during the mid-Holocene [8200 to 4200 years ago (8.2–4.2 ka)] was weaker than during the instrumental periods, but the mechanisms remain unclear. We examined processes of ENSO suppression using a coupled general circulation model (CGCM) that simulates ENSO amplitude and skewness under the present climate reasonably well. Two long simulations were performed: one using the preindustrial condition (CTRL
Removing CO<sub>2</sub> from the atmosphere is emerging as a viable strategy to mitigate global warming, yet the responses of the climate system to CO<sub>2</sub> reduction remain uncertain. One of the most uncertain aspects of El Niño behavior is the change in periodicity in response to CO<sub>2</sub> forcing [O. Alizadeh, <i>Earth-Sci. Rev.</i> <b>235</b>, 104246 (2022)]. In this study, we show that climate models consistently project an abrupt shortening of El Niño periodicity once CO<sub>2</
El Ni&#241;o&#8211;Southern Oscillation (ENSO) events occasionally recur one after the other in the same polarity, called multiyear ENSO. However, the dynamical processes are not well understood. This study aims to elucidate the unified mechanisms of multiyear ENSO using observations, CMIP6 models, and the theoretical linear recharge oscillator (RO) model. We found that multiyear El Ni&#241;o and La Ni&#241;a events are roughly symmetric except in some cases. The composite multiy
