Influence of the mean circulation on gravity wave generation

重力波通过向上传输动量、能量和热量，代表了对流层和高层大气之间的主要耦合机制。理解和模拟中间层和低热层(MLT)对低层大气环流变化的动力反馈需要对低层大气中的GW源进行量化。这项研究的主要目的是研究对流层气流对GW的激发，以及MLT对与不同环流模式相关的这种强迫变化的交互响应。一种新的GW源参数化方案将被耦合到主流GW方案中，并在大气环流模式(GCM)中实施。这将是第一次明确地将GW产生与气象场联系起来的参数化，因此，能够捕捉对流层和MLT中不同环流模式之间的动态反馈。我们将探索与北大西洋涛动和北极涛动的不同阶段相关的GW强迫的变化。主要问题将是，通过GW耦合机制，对流层环流的自然可变性在多大程度上控制了MLT。

Gravity waves (GW) represent a major coupling mechanism between the troposphere and the upper atmosphere by transporting the momentum, energy, and heat upward. Understanding and modeling the dynamical feedback of the mesosphere and lower thermosphere (MLT) to variations of the circulation in the lower atmosphere require a quantification of GW sources in the lower atmosphere. The main objective of the proposed study is to investigate GW excitation by the flow in the troposphere and the interactive response of MLT to variations of this forcing associated with different circulation regimes. A novel parameterization of GW sources will be coupled to a mainstream GW scheme and implemented in general circulation models (GCM). This will be a first parameterization that explicitly links GW generation to meteorological fields, and, thus, able to capture dynamical feedbacks between varying circulation patterns in the troposphere and MLT. We shall explore changes in GW forcing associated the different phases of the North Atlantic Oscillation and Arctic Oscillation. The major question will be how much MLT is controlled by the natural variability of the tropospheric circulation via the GW coupling mechanism.