谱模式SAMIL对南亚季风区大气季节内振荡向北传播的模拟

基于与NCEP资料结果的比较，研究了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室发展的大气环流模式SAMIL对夏季南亚季风区季节内振荡（ISO）向北传播特征的模拟，并结合目前对ISO北传机制的理解对模拟结果进行了分析讨论。SAMIL在夏季南亚地区模拟出相当强度的季节内振荡的活动，并且模拟的ISO也表现出与NCEP资料相似的从赤道向北传播的特征，但传播的速度要慢于NCEP资料的结果。模拟的北传ISO具有与NCEP资料相似的结构特征，涡度和水汽场明显的呈经向不对称，涡度和水汽的正异常位于ISO对流的北面，最大的上升运动和最强的行星边界层辐合也位于ISO对流的北面。ISO 结构的经向不对称性正是模式模拟的ISO具有向北传播特征的原因；而模式对夏季南亚季风区高低层风场和行星边界层水汽的合理模拟起了关键的作用。同时，根据关于ISO北传机理的已有研究，模式的结果也表明南亚地区夏季风场的垂直结构是那里ISO向北传播的重要机制。

GCM Simulation of the Northward Propagating Intraseasonal Oscillation in the South Asian Summer Monsoon Region

The northward propagating intraseasonal oscillation(ISO) in the South Asian summer monsoon region simulated by general circulation model SAMIL developed in the State Key Laboratory for Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG),Institute of Atmospheric Physics(IAP),Chinese Academy of Sciences is examined and compared with that from NCEP reanalysis data.SAMIL simulates this oscillation with comparable strength in the South Asia region,and northward propagation of this oscillation from the equator is also simulated though the propagation is slightly slower than that from observations.The simulated northward propagating ISO shows similar vertical structure to observations.The vorticity and the specific humidity fields are obviously meridionally asymmetric with the positive vorticity and specific humidity anomalies lying over the north of the ISO convective center.The maximum ascending motion and convergence in the planetary boundary layer also lie over the north of the ISO convection center.Reasonable simulation of this meridional asymmetric structure leads to well simulation of the northward propagating ISO for the SAMIL model.Key factors associated with the good performance in simulating northward propagating ISO are the reasonable simulations of summer wind fields in South Asian and distribution of specific humidity in the planetary boundary layer.Meanwhile,the modeling result also suggests that the vertical structure of summer winds in South Asian plays a key role in the northward propagation of ISO there,which is consistent with previous studies.