Based on regional model simulations of two distinct cases of the southwest vortex (SWV), this study compares their thermal and dynamic features and the differences in the evolution between a steady SWV and an eastwardly propagating SWV. The main results are as follows: (1) the rainfall period and area are determined by the location and movement of the SWV. The pathway of SWV movement is largely controlled by large-scale circulation, especially the subtropical high, which may have a blocking effect on the SWV. Generally, a stable subtropical high extending to the west has a blocking effect that leads to a steady SWV without much movement, while the eastward and southward retreat of the subtropical high favors the eastward propagation of the SWV; (2) both of the SWV types exhibit a vertical structure of convergence, positive vorticity, vertical motion maxima and a divergence center sequentially from the lower to the upper atmosphere. The localized thermal conditions are more important in steady SWV than in the eastwardly propagating SWV, while dynamic effects dominate in the eastwardly propagating SWV; (3) the strength of the convective activity of the eastwardly propagating SWV is significantly greater than that of the steady SWV due to the increased atmospheric instability. The vertical velocity, vorticity, divergence and surrounding wind speed are much greater for the eastwardly propagating SWV than the steady SWV, which favors the increased strength and high-level development of the eastwardly propagating SWV.

中文翻译：

---

两类西南涡运动及垂直结构对比

本研究基于对西南涡 (SWV) 两种不同情况的区域模型模拟，比较了它们的热力和动力特征，以及稳定的 SWV 和向东传播的 SWV 之间演化的差异。主要结果如下： (1) 降雨周期和面积由西南涡的位置和运动决定。SWV运动路径主要受大尺度环流控制，尤其是副热带高压，可能对SWV有阻滞作用。一般情况下，稳定的向西延伸的副热带高压具有阻挡作用，导致稳定的 SWV 没有太多运动，而副热带高压向东和向南后退有利于 SWV 向东传播；(2) 两种 SWV 类型都表现出会聚的垂直结构，正涡度，垂直运动最大值和散度中心依次从低层到高层大气。局部热条件在稳定 SWV 中比在向东传播的 SWV 中更重要，而动态效应在向东传播的 SWV 中占主导地位；(3) 由于大气不稳定性增加，向东传播的SWV的对流活动强度明显大于稳定的SWV。向东传播的 SWV 的垂直速度、涡度、发散度和周围风速远大于稳定的 SWV，这有利于向东传播的 SWV 强度增加和高水平发展。局部热条件在稳定 SWV 中比在向东传播的 SWV 中更重要，而动态效应在向东传播的 SWV 中占主导地位；(3) 由于大气不稳定性增加，向东传播的SWV的对流活动强度明显大于稳定的SWV。向东传播的 SWV 的垂直速度、涡度、发散度和周围风速远大于稳定的 SWV，这有利于向东传播的 SWV 强度增加和高水平发展。局部热条件在稳定 SWV 中比在向东传播的 SWV 中更重要，而动态效应在向东传播的 SWV 中占主导地位；(3) 由于大气不稳定性增加，向东传播的SWV的对流活动强度明显大于稳定的SWV。向东传播的 SWV 的垂直速度、涡度、发散度和周围风速远大于稳定的 SWV，这有利于向东传播的 SWV 强度增加和高水平发展。