This study aims to understand the nature of the tropical intraseasonal oscillations (ISOs) in an aquaplanet simulation performed using Geophysical Fluid Dynamics Laboratory's AM2.1 with a uniform sea surface temperature within the deep tropics. The simulated ISO resembles the observed Madden‐Julian Oscillation in that the spectral peak in precipitation appears at zonal wave number 1 and a period of ~60 days. Vertically integrated moist static energy budget of the simulated ISO shows that enhanced latent heat flux to the east of anomalously active convection causes eastward propagation of the ISO mode, which is weakly opposed by horizontal moisture advection. A series of mechanism denial experiments are conducted either by homogenizing select variables—surface wind stress, longwave radiative heating, and surface evaporation—with their zonal means from the control simulation or by suppressing free‐tropospheric moisture variation. Results of the mechanism denial experiments show that the simulated ISO disappears when the interactive surface evaporation is disabled, suggesting that the wind‐induced surface heat exchange (WISHE) mechanism is essential to the simulated ISO. Longwave cloud‐radiation feedbacks and moisture‐convection feedbacks affect horizontal scale and phase speed of the simulated ISO, respectively. Our results strongly suggest that the simulated ISO is the linear WISHE‐moisture mode of Fuchs and Raymond under horizontally uniform boundary conditions.

中文翻译：

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水行星模拟中的 WISHE-湿度模式

本研究旨在了解使用地球物理流体动力学实验室的 AM2.1 进行的水行星模拟中热带季节内振荡 (ISO) 的性质，该模拟在深热带地区具有均匀的海面温度。模拟的 ISO 类似于观测到的马登-朱利安振荡，降水的光谱峰值出现在纬向波数 1 处，周期约为 60 天。模拟 ISO 的垂直积分湿静态能量收支表明，异常活跃对流以东的潜热通量增强会导致 ISO 模式向东传播，而水平湿气平流对 ISO 模态的作用微弱。通过使用控制模拟中的纬向平均值均化选择变量（表面风应力、长波辐射加热和表面蒸发）或抑制自由对流层湿度变化来进行一系列机制否认实验。机制否认实验的结果表明，当交互式表面蒸发被禁用时，模拟的 ISO 消失，这表明风致表面热交换（WISHE）机制对于模拟的 ISO 至关重要。长波云辐射反馈和湿气对流反馈分别影响模拟 ISO 的水平尺度和相速度。我们的结果强烈表明，模拟的 ISO 是水平均匀边界条件下 Fuchs 和 Raymond 的线性 WISHE 湿度模式。