Observation of Quasi-2-Day Convective Disturbances in the Equatorial Indian Ocean during DYNAMO
Observation of Quasi-2-Day Convective Disturbances in the Equatorial Indian Ocean during DYNAMO
复制标题
DOI：
10.1175/jas-d-17-0351.1
复制
发表时间：
2018-08
影响因子：
3.1
通讯作者：
Hungjui Yu;Richard H. Johnson;P. Ciesielski;H. Kuo
中科院分区：
文献类型：
--
作者：
Hungjui Yu;Richard H. Johnson;P. Ciesielski;H. Kuo
本研究考察了 2011 年 10 月中旬至下旬马登-朱利安涛动动力学 (DYNAMO) 现场活动期间在印度洋中部甘岛上空发现的向西传播的对流扰动，其发生间隔为准 2 天。大气探测、卫星和雷达数据被用来开发七种此类扰动的组合。合成和谱分析表明，1）准2日对流事件包括向西传播的日对流扰动，相速为10-12 m s−1，其振幅在甘经附近~1000 km的纬向尺度上的准2日时间尺度上调制； 2）准2日对流扰动的云生命周期显示出明显的热带云种群演化模式——从浅层到深层再到层状对流； 3) 中尺度对流系统发展和边界层调制的时间尺度对于确定准2日对流事件的周期性具有重要作用; 4) 在一些准 2 天的事件中，有证据表明云系统沿着 Yamada 等人提出的路线反向传播（向西和向东）。基于这些发现，结合了先前对西太平洋和印度洋这一现象的研究概念，对 DYNAMO 期间观察到的准 2 天扰动的机制提出了解释。
This study examines the westward-propagating convective disturbances with quasi-2-day intervals of occurrence identified over Gan Island in the central Indian Ocean from mid- to late October 2011 during the Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign. Atmospheric sounding, satellite, and radar data are used to develop a composite of seven such disturbances. Composites and spectral analyses reveal that 1) the quasi-2-day convective events comprise westward-propagating diurnal convective disturbances with phase speeds of 10–12 m s−1 whose amplitudes are modulated on a quasi-2-day time scale on a zonal scale of ~1000 km near the longitudes of Gan; 2) the cloud life cycle of quasi-2-day convective disturbances shows a distinct pattern of tropical cloud population evolution—from shallow to deep to stratiform convection; 3) the time scales of mesoscale convective system development and boundary layer modulation play essential roles in determining the periodicity of the quasi-2-day convective events; and 4) in some of the quasi-2-day events there is evidence of counterpropagating (westward and eastward) cloud systems along the lines proposed by Yamada et al. Based on these findings, an interpretation is proposed for the mechanisms for the quasi-2-day disturbances observed during DYNAMO that combines concepts from prior studies of this phenomenon over the western Pacific and Indian Oceans.