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MS-GWaM:大气模式的三维瞬态重力波参数化

发布时间:2024-05-08 打印

  Parametrizations for internal gravity waves in atmospheric models are traditionally subject to a number of simplifications. Most notably, they rely on both neglecting wave propagation and advection in the horizontal direction (single-column assumption) and an instantaneous balance in the vertical direction (steady-state assumption). While these simplifications are well justified to cover some essential dynamic effects and keep the computational effort small it has been shown that both mechanisms are potentially significant. In particular, the recently introduced Multiscale Gravity Wave Model (MS-GWaM) successfully applied ray tracing methods in a novel type of transient but columnar internal gravity wave parameterization (MS-GWaM-1D). We extend this concept to a three-dimensional version of the parameterization (MS-GWaM-3D) to simulate subgrid-scale non-orographic internal gravity waves. The resulting global wave model—implemented into the weather-forecast and climate code ICON—contains three-dimensional transient propagation with accurate flux calculations, a latitude-dependent background source, and convectively generated waves. MS-GWaM-3D helps reproducing expected temperature and wind patterns in the mesopause region in the climatological zonal mean state and thus proves a viable IGW parameterization. Analyzing the global wave action budget, we find that horizontal wave propagation is as important as vertical wave propagation. The corresponding wave refraction includes previously missing but well-known effects such as wave refraction into the polar jet streams. On a global scale, three-dimensional wave refraction leads to a horizontal flow-dependent redistribution of waves such that the structures of the zonal mean wave drag and consequently the zonal mean winds are modified.

  在大气模型中,内部重力波的参数化通常要经过一些简化。其中最值得注意的是,这些简化既忽略了水平方向上的波传播和平流(单柱假设),又忽略了垂直方向上的瞬时平衡(稳态假设)。虽然这些简化涵盖了一些基本的动态影响,并使计算工作量很小,但以上两种机制具有潜在的重要意义。最近提出的多尺度重力波模型(MS-GWaM)成功地将光线追踪方法应用于一种新型的瞬态柱状内重力波参数化(MS-GWaM- 1D)。我们将这一概念扩展到参数化的三维版本(MS-GWaM-3D),以模拟亚网格尺度的非地形内部重力波。由此产生的全球波模型(在天气预报和气候代码ICON中实现)包含具有精确通量计算的三维瞬态传播、依赖于纬度的背景源和对流产生的波。MS-GWaM-3D有助于在气候学纬向平均状态下再现中流层区域的预期温度和风型,证明了IGW参数化的可行性。分析全球波浪作用收支,我们发现水平波传播与垂直波传播同样重要。相应的波折射包括先前缺失但众所周知的效应,如波折射进入极地急流。在全球尺度上,三维波折射导致了依赖于水平流的波的再分布,从而改变了纬向平均波阻力的结构,从而改变了纬向平均风的结构。
 

  延伸阅读:https://doi.org/10.1175/JAS-D-23-0153.1(马杰编译)

  

 

  

 

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