Mesoscale Moisture Transport in Determining the Location of Daytime Convection Initiations Clustered in Time and Space Over Southern China
Mesoscale Moisture Transport in Determining the Location of Daytime Convection Initiations Clustered in Time and Space Over Southern China
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中尺度水汽输送在确定华南地区日间对流起始时空聚集位置中的应用
DOI：
10.1029/2021jd036098
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发表时间：
2022-05
期刊：
影响因子：
--
通讯作者：
Yu Du
中科院分区：
文献类型：
--
作者：
Chuying Mai;Yu Du
对流起始事件是指在时间和空间上成簇发生的一系列对流起始事件，由于其复杂的机制，其预测仍然是一个挑战。在本研究中，高分辨率的对流允许的模拟和观测进行了调查的非均匀不稳定的来源，白天的CI聚集在东北-西南方向的区域，在华南地区的辐合边界的提升不明显。在CI发生区，低层水汽显著增强，导致对流有效位能的不均匀性。中尺度反气旋式水汽通道是造成CI发生区水汽增强和不稳定的主要原因。白天非地转风的惯性振荡和中尺度高压扰动共同作用形成了中尺度水汽输送。敏感性实验进一步证实了所揭示的机制，中尺度反气旋输送是高度敏感的。水汽输送受中尺度气压扰动演变的影响，并控制CI的位置和形状。较强的中尺度气压扰动导致随后来自不同高压系统的中尺度反气旋气流向东输送水汽，因此CI发生在更远的东方数十至数百公里处。白天CI事件的气候特征还表明，在弱辐合条件下，各种中尺度水汽输送将水汽限制在CI事件区域内。
Convective initiation (CI) episodes are defined as a series of CIs that occur in clusters in time and space, and their prediction remains a challenge due to their complex mechanisms. In the present study, high-resolution convection-permitting simulations and observations were conducted to investigate the source of inhomogeneous instability for a cluster of daytime CIs gathering in a northeast-southwest oriented region in South China where the convergence boundary for lifting was not evident. In the region of the CI episode, low-level water vapor was enhanced significantly, which thus induced the heterogeneity of convective available potential energy. The enhanced moisture and instability in the CI episode region were caused by a mesoscale anticyclonic moisture channel. Mesoscale moisture transport formed under both the inertial oscillation of ageostrophic winds and the mesoscale high-pressure disturbances in the daytime. The revealed mechanism is further confirmed by sensitivity experiments, where mesoscale anticyclonic transport is highly sensitive. Water vapor transport was affected by the evolution of mesoscale pressure disturbances and dominated the location and shape of the CI episode. Stronger mesoscale pressure disturbances resulted in the subsequent mesoscale anticyclonic airflow coming from various high-pressure systems and conveying moisture farther east, and therefore, a CI episode occurred farther east by dozens to hundreds of kilometers. The climatology of the daytime CI episode also showed that the various mesoscale moisture transports confined moisture within the CI episode regions under weak convergence.
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