過去研究指出，降冰輻射效應（falling-ice radiative effects，簡稱 FIREs）會影響模式中熱帶太平洋背景平均態的模擬，並可能進一步影響中太平洋型聖嬰的演變。由於聖嬰衰退過程也可能受到印度洋偶極與印度洋全洋盆模態相關回饋的影響，本研究使用 Community Earth System Model version 1 with the Community Atmosphere Model version 5（簡稱 CESM1-CAM5）進行的兩組敏感度實驗，分別為納入 FIREs 的 Snow 實驗，以及未納入 FIREs 的 NoSnow 實驗，以探討 FIREs 對聖嬰衰退、印度洋響應及後續印太交互作用的影響。 結果顯示，在未納入 FIREs 的 NoSnow 實驗中，東太平洋背景平均態較暖，且背景東風應力較弱，使聖嬰發展期間的海氣耦合區域向中東太平洋延伸。此一東移可能使延遲振盪機制中的負回饋作用較晚發生，造成聖嬰衰退較慢。較慢衰退的太平洋暖異常進一步使聖嬰相關的大氣橋作用維持至衰退年，促進東印度洋冷卻與正印度洋偶極結構的發展。隨著正印度洋偶極於冬季減弱，印度洋響應逐漸轉變為正印度洋全洋盆模態，並可能透過大氣凱爾文波在西太平洋誘發東風異常，有利於赤道太平洋降溫及後續類反聖嬰冷異常的增強。整體而言，本研究指出 FIREs 可能不僅影響熱帶太平洋背景平均態，也會透過調節聖嬰衰退、印度洋響應與印太回饋過程，進一步影響聖嬰－南方振盪相位轉換。;Previous studies have shown that falling-ice radiative effects (FIREs) can influence the simulation of the tropical Pacific background mean state and may further affect the evolution of Central Pacific (CP) El Niño. Because El Niño decay may also be influenced by feedbacks associated with the Indian Ocean Dipole (IOD) and the Indian Ocean Basin mode (IOB)， this study uses the Snow and NoSnow sensitivity experiments conducted with the Community Earth System Model version 1 with the Community Atmosphere Model version 5 (CESM1-CAM5) to investigate the impacts of FIREs on El Niño decay， the Indian Ocean response， and subsequent Indo-Pacific interactions. The results show that， in the NoSnow experiment， where FIREs are excluded， the eastern Pacific background mean state is warmer and the background easterly wind stress is weaker. These background conditions allow the air–sea coupling region during El Niño development to extend farther into the central-to-eastern Pacific. This eastward extension may delay the negative feedback associated with the Delayed Oscillator mechanism， leading to slower El Niño decay. The more slowly decaying Pacific warm SSTAs further maintain the El Niño-related atmospheric bridge effect into the decay year， promoting eastern Indian Ocean cooling and the development of a positive IOD pattern. As the positive IOD weakens in winter， the Indian Ocean response gradually transitions into a positive IOB pattern， which may induce easterly wind anomalies over the western Pacific through atmospheric Kelvin waves. This process may favor equatorial Pacific cooling and the subsequent strengthening of La Niña-like cold anomalies. Overall， this study suggests that FIREs may influence not only the tropical Pacific background mean state， but also the El Niño–Southern Oscillation (ENSO) phase transition by modulating El Niño decay， the Indian Ocean response， and Indo-Pacific feedback processes.
