Analysis of the Dynamical Forcing of Persistent Anomaly Life Cycles in a General Circulation Model

对持续性大气流动异常的研究发现，高频瞬变涡旋在维持大气流动异常以防止其向下传播方面起着重要作用。这些瞬变涡旋如何影响异常模式的开始和衰变，仍然是个问题。例如，异常的出现往往与(天气尺度扰动)风暴的上游加强有关，但尚不清楚这种加强是在背景环境中发生的，相对于大尺度涡旋而言是中性的还是稳定的，还是作为大尺度不稳定的结果。已经发展了一种诊断技术，它可以根据低频和高频瞬变涡旋过程来检查缓慢变化的大尺度流动的强迫。它已被应用于一个两层大气环流模式的永久1月份资料。结果表明，低频过程通常决定了异常的局部增减，尽管并不总是如此。根据这一奖项，主要研究人员将把这种诊断技术应用于一个复杂的模式--国家大气研究中心的社区气候模式--的输出，并将结果与之前的研究结果进行比较。这项研究将加深我们对季节内气候变化原因的理解。

Investigations of persistent atmospheric flow anomalies have found that high frequency transient eddies play an important role in maintaining anomalies against downstream propagation. The precise way in which these transient eddies affect the onset and decay of the anomalous patterns remains a question. For example, the onset of anomalies is often associated the upstream intensification of synoptic-scale disturbance )storms), but it is not clear whether this intensification occurs in a background environment neutral or stable with respect to large-scale eddies or as a consequence of large-scale instability. A diagnostic technique has been developed that allows examination of the forcing of the slowly-varying large-scale flow in terms of both low frequency and high-frequency transient eddy processes. It has been applied to perpetual January data from a two level general circulation model. Results indicate that the low frequency processes typically, thought not always, determine the local growth or decay of anomalies. Under this award, the principal investigators will apply this diagnostic technique to the output form a sophisticated model, the Community Climate Model of the National Center for Atmospheric Research, and compare the results with those of the previous study. This research will enhance our understanding of the causes of intraseasonal climate variability.