菲律宾以西海域的高温暖水与南海夏季风爆发

为了揭示高温暖水在中国南海（文中简称南海）夏季风爆发中所起的作用，依据欧洲中期天气预报中心发布的第5代全球大气海洋再分析资料，发现气候平均意义下印度洋—太平洋暖池中30℃以上高温暖水会在5月出现移位：5月上旬高温暖水出现在孟加拉湾中部，而到下旬消退并移位到南海南部。通过分析局地天气尺度的海洋-大气相互作用过程，揭示了上述高温暖水月内移位的物理机制：在孟加拉湾夏季风爆发后，逐渐增强的潜热释放和减少的短波辐射会导致孟加拉湾高温暖水的面积逐渐缩小；与此同时，在副热带高压影响下，南海菲律宾岛西南高温暖水出现，并因其面积逐渐增大，并与泰国湾的高温暖水共同构成了南海南部的高温暖水。研究发现南海季风爆发几乎都出现在上述高温暖水移位之后，因此孟加拉湾中部和南海南部海表温度的差由正转负可以作为南海季风爆发的先兆。

Effects of warm water west of the Philippines on the South China Sea summer monsoon onset

This study aims to reveal the impact of the Indo-Pacific warm pool on the onset of the South China Sea summer monsoon. Based on the fifth generation of global reanalysis data from the European Center for Medium-Range Weather Forecasts, it is found that the warmest Sea Surface Temperature (SST) above 30℃ over the Indo-Pacific warm pool shifts during May. The warmest water appears in the central Bay of Bengal in early May, then disappears and shifts to the southern part of the South China Sea in late May. Analysis of local ocean-atmosphere coupling at the synoptic scale reveals the underlying mechanism for the shift. After the onset of the Bengal summer monsoon, the gradually strengthening latent heat release and reduced short-wave radiation lead to gradual reduction in the area of warmest water in the Bay of Bengal. Meanwhile, under the influence of the subtropical high, warmer water appears and expands over southwest of the Philippine Islands, which, together with the warm water at the Gulf of Thailand, lead to warm water in the southern South China Sea. It is found that the summer monsoon onset in the South China Sea often follows the warmest water shift in the Indo-Pacific warm pool. Therefore, the transition of the SST difference between the central Bay of Bengal and the southern South China Sea from positive to negative can serve as a precursor for the onset of the South China Sea monsoon.