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

对持续大气流动异常的研究发现，高频瞬态涡流在维持异常不受下游传播的影响方面起着重要作用。这些瞬态涡流影响异常模式的发生和衰减的精确方式仍然是一个问题。例如，异常的发生通常与天气尺度扰动（风暴）的上游强化有关，但尚不清楚这种强化是发生在大尺度涡旋中性或稳定的背景环境中，还是作为大尺度不稳定的结果。已经开发了一种诊断技术，可以根据低频和高频瞬态涡流过程来检查缓慢变化的大尺度流动的强迫。该方法已应用于两层大气环流模式的1月份永久数据。结果表明，低频过程通常（但并非总是）决定了异常的局部增长或衰减。根据该合同，主要研究人员将把这种诊断技术应用于一个复杂模型的输出，即国家大气研究中心的社区气候模型，并将结果与之前的研究结果进行比较。这项研究将增强我们对季节内气候变率的原因的理解。

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.