INTeRnal waves In angular momeNtum StratifICation (INTRINSIC)

该项目将使用一个简化模型和一个数值模型来研究具有曲线形状的水密度的“快速”变化如何改变海洋表面边界层内重力内波的传播和命运。研究人员将确定IGW能量在弯曲的细微尺度锋面内是增加还是减少。他们将检验一个新的假设，即参数次谐不稳定最初由Thomas和Taylor(2014)提出，用于地转流，在弯曲的反气旋锋面内上升。这项研究使用了精细模拟的层次结构，其中分析和理想化的数值模式(最不复杂)被用来提供信息和促进对现实模拟(最复杂)的分析。目前对IGW在锋面内传播的理解假设为地转平衡。虽然对于中尺度锋面(水平尺度为50-200公里)是准确的，但由于锋面弯曲，亚中尺度锋面(水平尺度为0.1-10公里)内的流体块往往经历显著的向心加速。密度、涡度和绝对角动量守恒的组合原理对流体团的运动产生了深刻的影响，并修正了IGW色散关系。这项拟议的研究通过考察这些守恒定律在半分析性、理想化和现实化的细尺度数值模拟中的综合影响，促进了科学界对IGW的理解。这项研究的预期结果包括更好地理解曲线前锋在IGW动力学中的作用，并描述分析模型的限制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project will use a simplified model and a numerical model to examine how a 'rapid' change in water density that has a curved shape, a 'curved front', modifies the propagation and fate of internal gravity waves (IGW) within the ocean surface boundary layer. The investigators will determine if IGW energy increases or decreases within fine-scale fronts that are curved. They will test a new hypothesis that parametric subharmonic instability, initially proposed by Thomas and Taylor (2014) for geostrophic flow, is elevated within curved anticyclonic fronts. The research uses a hierarchy of fine-scale simulations, whereby analytical and idealized numerical models (least complex) are used to inform and facilitate analysis of realistic simulations (most complex).Present understanding of IGW propagation within fronts assumes a geostrophic balance. Although accurate for mesoscale fronts (horizontal scales of 50-200 km), fluid parcels within submesoscale fronts (horizontal scales of 0.1-10 km) often experience pronounced centripetal accelerations owing to frontal curvature. The combined principles of density, vorticity, and absolute angular momentum conservation have a profound influence on fluid parcel motion and modify the IGW dispersion relation. The proposed study advances the scientific community’s understanding of IGWs by examining the combined effects of these conservation laws in the context of semi-analytical, idealized and realistic fine-scale, numerical simulations heavily informed by observations. The expected outcomes of this research include improved understanding of the role of curved fronts on IGW dynamics and delineation of the limits of an analytical model.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.