Dynamic and thermodynamic mechanisms of Miocene South Asian summer monsoon rainfall enhancement driven by African topography evolution

The evolution of African topography has recently been proposed as a key driver of the multi-stage Miocene development of the South Asian summer monsoon (SASM); however, the dynamic and thermodynamic mechanisms underlying this linkage remain poorly understood. Here, we use the fully coupled EC-Earth3 model together with moisture budget diagnostics and moist static energy (MSE) analysis to quantify the pathways through which African dynamic topography modulated SASM rainfall. Our results show that enhanced SASM precipitation during the Early and Middle Miocene relative to the preindustrial period is primarily driven by the positive contribution of dynamic moisture advection associated with anomalous vertical motion. The MSE budget further reveals that this anomalous ascent is mainly governed by the latent-heat-induced moist enthalpy advection by the mean zonal winds. These findings provide valuable insights into the coupled dynamic–thermodynamic mechanisms through which African tectonic processes shaped monsoon rainfall on geological time scales. 非洲地形演化是驱动地质时期南亚夏季风变化的关键因素.本研究利用EC-Earth3全耦合地球系统模式, 结合大气三型环流分解,水汽收支与湿静力能诊断, 探讨了中新世非洲地形对南亚季风降水的调控机制.结果表明, 早,中中新世南亚季风降水的显著增强主要由异常上升运动驱动, 而该垂直运动受平均纬向风输送的湿焓平流控制, 其中潜热分量贡献占主导.这主要是由于中新世非洲地形的演化通过改变阿拉伯海区域的大气环流和水汽条件, 将大量潜热输送至南亚, 最终导致季风降水增加.