Factors Controlling the Diversities of MJO Propagation and Intensity
Factors Controlling the Diversities of MJO Propagation and Intensity
复制标题
控制 MJO 传播和强度多样性的因素
DOI：
10.1175/jcli-d-20-0859.1
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发表时间：
2021
影响因子：
4.9
通讯作者：
Li, Tim
中科院分区：
文献类型：
--
作者：
Wang, Tianyi;Li, Tim
利用聚类分析方法探讨了麦登-朱利安振荡（MJO）在最大强度、纬向范围和相速度方面的多样性。地带性范围与相速显著相关。较长的地带性范围通常与较快的相位速度有关。纬向范围和纬向速度的变化与赤道太平洋独特的年际海温异常分布及其相关的水汽和环流模式有关。El Niño-like背景海温导致太平洋中部降水增强，使MJO以东形成更强的垂直翻转环流。这使得柱积分湿润静态能（MSE）倾向的东西不对称性更大，边界层水分领先更大，这是相速度更快的潜在原因。El Niño-like SSTA也有利于mjo进一步侵入太平洋，造成更大的纬向范围。强度变化与海洋大陆的年际海温和热带印度洋的背景水汽条件有关。观测到的在海洋大陆上空的温暖海温激发了印度洋上空一个下沉的局地Walker单体，这可能会减少背景湿度，减弱MJO强度。由于强度增长速度不同，强、弱事件的强度差异会被放大。强MJO强度增长较快的原因是较大的长波辐射加热和较大的地表潜热通量，两者都导致柱积分MSE的总时间变化率较大。
The diversity of the Madden–Julian oscillation (MJO) in terms of its maximum intensity, zonal extent, and phase speed was explored using a cluster analysis method. The zonal extent is found to be significantly correlated to the phase speed. A longer zonal extent is often associated with a faster phase speed. The diversities of zonal extent and speed are connected with distinctive interannual sea surface temperature anomaly (SSTA) distributions and associated moisture and circulation patterns over the equatorial Pacific. An El Niño–like background SSTA leads to enhanced precipitation over the central Pacific, allowing a stronger vertically overturning circulation to the east of the MJO. This promotes both a larger east–west asymmetry of column-integrated moist static energy (MSE) tendency and a greater boundary layer moisture leading, serving as potential causes of the faster phase speed. The El Niño–like SSTA also favors the MJOs intruding farther into the Pacific, causing a larger zonal extent. The intensity diversity is associated with the interannual SSTA over the Maritime Continent and background moisture condition over the tropical Indian Ocean. An observed warm SSTA over the Maritime Continent excites a local Walker cell with a subsidence over the Indian Ocean, which could decrease the background moisture, weakening the MJO intensity. The intensity difference between strong and weak events would be amplified due to distinct intensity growth speed. The faster intensity growth of a strong MJO is attributed to a greater longwave radiative heating and a greater surface latent heat flux, both of which contribute to a greater total time change rate of the column-integrated MSE.