热带中间层顶区域平均纬向风半年振荡的不对称性研究

Semi-annual oscillation (SAO) is one of the most dominant oscillations in the equatorial middle atmosphere and believed to have important influence on the circulations of stratosphere, mesosphere and lower thermosphere. The variations and physical mechanisms of SAO are not very clear yet. So nearly 20 years satellite-based wind observations (including HRDI/UARS and TIDI/TIMED data sets) would be used for the research of SAO in the mean zonal wind in the tropical mesopause region. The attention should be specially focused on the seasonal and equatorial asymmetries in the mesopause SAO. Inter-annual variations of mesopause SAO and their relationships with stratospheric quasi-biennial oscillation (QBO) will be also included. In order to better understand the mechanisms in the SAO asymmetries, the Whole Atmosphere Community Climate Model (WACCM) simulations will be analyzed for quantifying the forcing terms and their contributions to mesopause SAO. Spatial and temporal distributions of forcing terms will be analyzed to understand and interpret the cause of asymmetries in the tropical mesopause SAO. This study will largely improve our understanding in the prevailing structures of middle atmosphere.

半年振荡是热带中层大气中显著的周期振荡，对平流层、中间层和低热层大气环流产生重要影响，但关于半年振荡的变化特征以及物理机制还缺乏进一步研究。项目拟综合利用近20年的卫星风场观测数据（包括HRDI/UARS和TIDI/TIMED）考察热带中间层顶区域平均纬向风半年振荡系统的季节不对称性和赤道不对称性，研究半年振荡的年际变化特征以及与平流层准两年振荡的关系。结合最新的大气环流模式WACCM的模拟结果，计算各种强迫因子对中间顶区域纬向风半年振荡形成的贡献，分析这些强迫因子的时空分布特征，解释半年振荡季节不对称性和赤道不对称性的原因，提高对中层大气盛行模态的理解。

中间层定区域半年振荡SAO是中层大气中除平流层振荡QBO之外最重要的周期性变化之一，对中层大气环流的动力学特性有重要影响。利用美国TIMED卫星搭载的多普勒干涉仪TIDI在中间层顶区域的水平风场观测数据针对80-105 km区域平均纬向风的半年振荡进行系统的研究，包括振幅和相位的特征。并且将TIDI最新分析结果与历史上其它观测资料所得结果进行对比分析，并分析原因。 分析了平均纬向风半年振荡SAO的季节不对称性（第一次半年振荡强于第二次半年振荡）特征，分析半年振荡的赤道不对称性（振幅空间分布偏向于南半球），并讨论了与平流层QBO的可能联系。