Realistic initiation and dynamics of the Madden‐Julian Oscillation in a coarse resolution aquaplanet GCM
Realistic initiation and dynamics of the Madden‐Julian Oscillation in a coarse resolution aquaplanet GCM
复制标题
粗分辨率水生行星 GCM 中马登-朱利安振荡的真实启动和动力学
DOI：
10.1002/2013gl058187
复制
发表时间：
2013
影响因子：
5.2
通讯作者：
A. Majda
中科院分区：
文献类型：
--
作者：
R S Ajayamohan;B. Khouider;A. Majda
马登-朱利安振荡（MJO）的启动和传播的主要机制仍然存在广泛的争论。业务全球气候模式（GCMs）的能力，以正确地模拟MJO的底层积云参数化的不足，阻碍了。在这里，我们表明，一个粗分辨率的GCM，再加上一个简单的多云模式参数化模拟观察到的动态和物理结构的有组织的热带对流，模拟MJO在一个理想化的设置没有海洋动力学的aquaplanet。我们施加一个固定的非均匀海面温度复制印度洋/西太平洋暖池。这导致了一系列具有真实相速度、振幅和物理结构的MJO。每个MJO事件都在暖池上方的一个随机位置开始，有时在暖池东部边界附近死亡，有时在暖池之外的随机位置死亡。偶尔，MJO事件也会在最大加热中心失速。这让人想起这样一个事实，即在自然界中，一些MJO在海洋大陆上停滞，而另一些则到达太平洋中部和更远的地方。模式中的启动机制被认为是持续的间歇性对流事件与观测到的大尺度流型和内部热带动力相互作用的组合。大规模的流动模式与行星尺度的干开尔文波有关，这些干开尔文波是由之前的MJO事件触发的，并环绕地球仪，而暖池两侧的浓积云被认为迫使罗斯比环流，然后将水分引向赤道地区。
The main mechanisms for the initiation and propagation of the Madden‐Julian Oscillation (MJO) are still widely debated. The capacity of operational global climate models (GCMs) to correctly simulate the MJO is hindered by the inadequacy of the underlying cumulus parameterizations. Here we show that a coarse resolution GCM, coupled to a simple multicloud model parameterization mimicking the observed dynamics and physical structure of organized tropical convection, simulates the MJO in an idealized setting of an aquaplanet without ocean dynamics. We impose a fixed nonhomogeneous sea‐surface temperature replicating the Indian Ocean/Western Pacific warm pool. This results in a succession of MJOs with realistic phase speed, amplitude, and physical structure. Each MJO event is initiated at a somewhat random location over the warm pool and dies sometimes near the eastern boundary of the warm pool and sometimes at a random location way beyond the warm pool. Also occasionally the MJO events stall at the center of maximum heating. This is reminiscent of the fact that in nature some MJOs stall over the maritime continent while others reach the central Pacific Ocean and beyond. The initiation mechanism in the model is believed to be a combination of persistent intermittent convective events interacting with observed large‐scale flow patterns and internal tropical dynamics. The large‐scale flow patterns are associated with planetary‐scale dry Kelvin waves that are triggered by preceding MJO events and circle the globe, while congestus cloud decks on the flanks of the warm pool are believed to force Rossby gyres which then funnel moisture toward the equatorial region.