ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 48 Issue 9 > 2022,48(9):1090-1100. DOI:10.7519/j.issn.1000-0526.2022.040601 Prev Next
Causes of Persistent Precipitation over Southern China During February-March 2019 and the Relationship with MJO
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Abstract:
Based on the reanalysis data, the causes of persistent precipitation over southern China during February-March 2019 and the relationship with Madden-Julian Oscillation (MJO) are studied. This persistent precipitation can be divided into two episodes. During the first episode, the precipitation covered the whole southern China, during the second episode it mainly occurred in South China, with intensity stronger than the first. The large-scale circulation analyses show that during this precipitation event, the abnormal geopotential height over southern China and western Pacific was low in the west and high in the east, which was conducive to the occurrence of abnormal southerlies and moisture transport. During the first episode, moisture convergence and upward movement appeared obviously over the whole southern China; during the second episode, stronger moisture convergence and upward movement occurred only in South China. The diagnostic analyses of moisture budget show that the anomalous moisture flux divergence during the two episodes was primarily caused by the meridional moisture convergence, which contributed more than 70% to moisture flux divergence. By comparing the evolution of precipitation and MJO activity, we find that the variation of precipitation was closely related to the phase and amplitude of MJO. When the amplitude of MJO enhanced (weakened) obviously, the anomalous precipitation over southern China increased (decreased). The scale analyses of meridional moisture convergence suggest that the interaction between moisture and circulation at the low-frequency scale (longer than 90 days) and the intraseasonal scale (30-90 days) plays a decisive role in the meridional moisture convergence, especially low-frequency moisture convergence by intraseasonal meridional wind. Therefore, the MJO activity over the tropical region can play a significant role in the persistent precipitation over southern China through regulating the low-frequency moisture transport by the intraseasonal meridional wind.
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