Deep convection in the Indo-Pacific warm pool is vital in driving global atmospheric overturning circulations. Year-to-year variations in the strength and location of warm pool precipitation can lead to significant local and downstream hydroclimatic impacts, including floods and droughts. While the El Niño-Southern Oscillation (ENSO) is recognized as a key factor in modulating interannual precipitation variations in this region, atmospheric internal variability is often as important. Here, through targeted atmospheric model experiments, we identify an intrinsic low-frequency atmospheric mode in the warm pool region during the austral summer, and show that its impact on seasonal rainfall is comparable to ENSO. This mode resembles the horizontal structure of the Madden-Julian Oscillation (MJO), and may play a role in initiating ENSO as stochastic forcing. We show that this mode is not merely an episodic manifestation of MJO events but primarily arises from barotropic energy conversion aided by positive feedback between convection and circulation.

印度-太平洋暖池的深层对流对于驱动全球大气翻转环流至关重要。暖池降水的强度和位置的逐年变化可能会导致当地和下游的水文气候显着影响，包括洪水和干旱。虽然厄尔尼诺南方涛动 (ENSO) 被认为是调节该地区年际降水变化的关键因素，但大气内部变率通常也同样重要。在这里，通过有针对性的大气模式实验，我们识别了南半球夏季暖池地区固有的低频大气模式，并表明其对季节性降雨的影响与ENSO相当。这种模式类似于马登-朱利安振荡 (MJO) 的水平结构，并且可能在引发 ENSO 随机强迫方面发挥作用。我们表明，这种模式不仅仅是 MJO 事件的偶发性表现，而且主要是由对流和环流之间的正反馈辅助的正压能量转换产生的。