Periodic Variability in the Large-Scale Southern Hemisphere Atmospheric Circulation
Periodic Variability in the Large-Scale Southern Hemisphere Atmospheric Circulation
复制标题
南半球大范围大气环流的周期性变化
作者：
D. Thompson;E. Barnes
可预测的行为很少有内部强迫的大尺度大气环流模式表现出周期性行为，而且这种行为集中在热带地区。识别这些周期性过程对于理解天气动力学很重要。汤普森和巴恩斯(第641页)报告说，在南半球的大气环流中发现了20到30天的周期。这种振荡可能会在中纬度南半球的大部分地区引发大规模的气候变化。南半球的大尺度大气环流在大约20至30天的时间尺度上振荡。气候系统中的周期性行为不仅对天气预报，而且对于理解和解释驱动气候变异性的物理过程具有重要意义。在这里，我们证明了南半球大尺度大气环流在大约20-30天的时间尺度上表现出明显的周期性。这种周期性与南半球斜压环模有关，并出现在涡动热通量、涡动能和降水的半球平均中。观测和理论分析表明，这种振荡是温带外斜压性、热波通量和辐射衰减之间的反馈作用的结果。这种振荡在推动中纬度南半球大部分地区的大范围气候变化方面发挥了潜在的深远作用。
Predictable Behavior Few internally forced large-scale atmospheric circulation patterns exhibit periodic behavior, and those that do are centered in the tropics. Identifying these periodic processes is important for understanding the dynamics of weather. Thompson and Barnes (p. 641) report the discovery of a 20- to 30-day periodicity in the atmospheric circulation in the Southern Hemisphere. The oscillation could potentially drive large-scale climate variability throughout much of the mid-latitude Southern Hemisphere. Large-scale atmospheric circulation in the Southern Hemisphere oscillates on a time scale of roughly 20 to 30 days. Periodic behavior in the climate system has important implications not only for weather prediction but also for understanding and interpreting the physical processes that drive climate variability. Here we demonstrate that the large-scale Southern Hemisphere atmospheric circulation exhibits marked periodicity on time scales of approximately 20 to 30 days. The periodicity is tied to the Southern Hemisphere baroclinic annular mode and emerges in hemispheric-scale averages of the eddy fluxes of heat, the eddy kinetic energy, and precipitation. Observational and theoretical analyses suggest that the oscillation results from feedbacks between the extratropical baroclinicity, the wave fluxes of heat, and radiative damping. The oscillation plays a potentially profound role in driving large-scale climate variability throughout much of the mid-latitude Southern Hemisphere.