Northward Propagation, Initiation, and Termination of Boreal Summer Intraseasonal Oscillations in a Zonally Symmetric Model
Northward Propagation, Initiation, and Termination of Boreal Summer Intraseasonal Oscillations in a Zonally Symmetric Model
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纬向对称模型中北方夏季季节内振荡的向北传播、起始和终止
DOI：
10.1175/jas-d-18-0178.1
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发表时间：
2019
影响因子：
3.1
通讯作者：
M. D. L. Chevrotière
中科院分区：
文献类型：
--
作者：
Qiu Yang;B. Khouider;A. Majda;M. D. L. Chevrotière
本文使用一个简单的多层纬向对称模式，利用多云对流参数化并耦合到一个动力体大气边界层，模拟了夏季风槽中的北方夏季季内振荡（BSISO），并阐明了其产生、传播和终止的主要物理机制。在赤道附近开始的向北移动的降水事件在大约1°day - 1向北传播，并在20°N附近终止。与先前的发现不同，该模式中降水异常向北传播是由于正水分异常向北传播，这是由β效应引起的经向速度不对称造成的。从水分收支的角度看，平流构成了干燥空气偏压侵入对流中心，迫使新的对流事件在波扰北部形成，而水汽辐合则提供降水汇。BSISO事件是在赤道附近由Hadley单体下降分支和原位拥挤加热分别引起的第一次斜压辐散和第二次斜压辐合的竞争效应有利于对流增强时开始的。当第一斜压经向风的不对称性减弱和对流中心以北的负水汽梯度过大时，异常离开了强加的暖池域，这些降水事件往往在20°N附近终止和中途停止。
A simple multilayer zonally symmetric model, using a multicloud convective parameterization and coupled to a dynamical bulk atmospheric boundary layer, is used here to simulate boreal summer intraseasonal oscillations (BSISO) in the summer monsoon trough and elucidate the underlying main physical mechanisms responsible for their initiation, propagation, and termination. Northward-moving precipitating events initiated near the equator propagate northward at roughly 1° day−1 and terminate near 20°N. Unlike earlier findings, the northward propagation of precipitation anomalies in this model is due to the propagation of positive moisture anomalies in the northward direction, resulting from an asymmetry in the meridional velocity induced by the beta effect. From a moisture-budget perspective, advection constitutes a biased intrusion of dry air into the convection center, forcing new convection events to form north of the wave disturbance, while moisture convergence supplies the precipitation sink. The BSISO events are initiated near the equator when the competing effects between first-baroclinic divergence and second-baroclinic convergence, induced by the descending branch of the Hadley cell and in situ congestus heating, respectively, become favorable to convective intensification. The termination often near 20°N and halfway stalling of these precipitating events occur when the asymmetry in the first-baroclinic meridional winds weakens and when the negative moisture gradient to the north of the convection center becomes too strong as the anomaly exits the imposed warm pool domain.
影响因子：
8
作者：
G. Brunet;M. Shapiro;B. Hoskins;M. Moncrieff;R. Dole;G. Kiladis;B. Kirtman;A. Lorenc;Brian Mills;R. Morss;S. Polavarapu;D. Rogers;J. Schaake;J. Shukla
通讯作者：
G. Brunet;M. Shapiro;B. Hoskins;M. Moncrieff;R. Dole;G. Kiladis;B. Kirtman;A. Lorenc;Brian Mills;R. Morss;S. Polavarapu;D. Rogers;J. Schaake;J. Shukla