The importance of air‐sea coupling in the simulation and prediction of the Madden‐Julian Oscillation (MJO) has been well established. However, it remains unclear how air‐sea coupling modulates the convection and related oceanic features on the subdaily scale. Based on a regional cloud‐permitting coupled model, we evaluated the impact of the air‐sea coupling on the convection during the convectively active phase of the MJO by varying the coupling frequency. The model successfully reproduced the atmospheric and oceanic variations observed by satellite and in situ measurements but with some quantitative biases. According to the sensitivity experiments, we found that stronger convection was mainly caused by the higher sea surface temperatures (SSTs) generated in high‐frequency coupled experiments, especially when the coupling frequency was 1 hr or shorter. A lower coupling frequency would generate the phase lags in the diurnal cycle of SST and related turbulent heat fluxes. Our analyses further demonstrated that the phase‐lagged diurnal cycle of SST suppressed deep convection through a decrease in daytime moistening in the lower troposphere. Meanwhile, in the upper ocean, the high‐frequency air‐sea coupling helped maintain the shallower mixed and isothermal layers by diurnal heating and cooling at the sea surface, which led to a higher mean SST. In contrast, the low‐frequency coupled experiments underestimated the SST and therefore convective activities. Overall, our results demonstrated that high‐frequency air‐sea coupling (1 hr or shorter) could improve the reproducibility of the intensity and temporal variation in both diurnal convection and upper ocean processes.

中文翻译：

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MJO通道期间海海耦合频率如何影响对流？

空气-海洋耦合在Madden-Julian涛动（MJO）的模拟和预测中的重要性已得到充分确立。但是，目前尚不清楚海海耦合如何在次日尺度上调节对流和相关海洋特征。基于区域允许云耦合模型，我们通过改变耦合频率来评估海气耦合对MJO对流活动阶段的对流影响。该模型成功地再现了通过卫星和原位测量观测到的大气和海洋变化，但存在一些定量偏差。根据敏感性实验，我们发现对流较强的原因主要是由高频耦合实验中产生的较高海表温度（SST）引起的，特别是当耦合频率为1小时或更短时。较低的耦合频率会在SST的昼夜周期和相关的湍流通量中产生相位滞后。我们的分析进一步表明，SST的相位滞后昼夜周期通过降低对流层下部白天的湿度来抑制深对流。同时，在上层海洋中，高频海海耦合通过海面的昼夜加热和冷却来帮助维持较浅的混合层和等温层，这导致平均海温升高。相反，低频耦合实验低估了海温，因此低估了对流活动。总体，