Forced gravity waves and the tropospheric response to convection
Forced gravity waves and the tropospheric response to convection
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DOI：
10.1002/qj.3278
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发表时间：
2018-04
影响因子：
8.9
通讯作者：
O. Halliday;S. Griffiths;D. Parker;A. Stirling;S. Vosper
中科院分区：
文献类型：
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作者：
O. Halliday;S. Griffiths;D. Parker;A. Stirling;S. Vosper
我们目前的理论工作，旨在提高我们的深对流层环境的中尺度影响，通过强迫重力波的理解。从线性的、流体静力学的、非旋转的、不可压缩的方程组中，我们找到了分层大气中规定加热的二维解析解，当区域盖足够高时，分层大气从对流层向上辐射。我们询问的空间和时间的敏感性的垂直速度和潜在的温度不同的加热功能，考虑到近场和远程响应稳定和脉冲加热。我们发现中尺度对流层对对流的响应显著依赖于重力波的向上辐射特性，而重力波的向上辐射特性又依赖于源的时空结构和假定的层结。我们发现，当从被困（即低盖）移动到向上辐射（即高盖）解决方案时，对流层平均垂直速度减少了50%，但是，即使有最大的向上辐射，我们仍然观察到加热结束后4小时远场的对流层垂直速度。我们量化了与将10 km宽的加热粗化到100 km网格（以大气环流模式（GCM）的方式）相关的误差，观察到垂直速度减少了20%。这些结果对低分辨率数值模型中对流参数化的影响被量化，并且表明，由于补偿沉降向邻近区域转移的错误率，网格框上加热的平滑导致显著的网格框内趋势。此外，我们探索了一个简单的时间相关的加热参数化，最大限度地减少在父GCM网格框中的错误，虽然在附近的错误增加的代价。
We present theoretical work directed toward improving our understanding of the mesoscale influence of deep convection on its tropospheric environment through forced gravity waves. From the linear, hydrostatic, non‐rotating, incompressible equations, we find a two‐dimensional analytical solution to prescribed heating in a stratified atmosphere, which is upwardly radiating from the troposphere when the domain lid is sufficiently high. We interrogate the spatial and temporal sensitivity of both the vertical velocity and potential temperature to different heating functions, considering both the near‐field and remote responses to steady and pulsed heating. We find that the mesoscale tropospheric response to convection is significantly dependent on the upward radiation characteristics of the gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and the assumed stratification. We find a 50% reduction in tropospherically averaged vertical velocity when moving from a trapped (i.e. low lid) to upwardly radiating (i.e. high lid) solution but, even with maximal upward radiation, we still observe significant tropospheric vertical velocities in the far‐field 4 h after heating ends. We quantify the errors associated with coarsening a 10 km‐wide heating to a 100 km grid (in the way a general circulation model (GCM) would), observing a 20% reduction in vertical velocity. The implications of these results for the parametrization of convection in low‐resolution numerical models are quantified, and it is shown that the smoothing of heating over a grid box leads to significant in‐grid‐box tendencies, due to the erroneous rate of transfer of compensating subsidence to neighbouring regions. Further, we explore a simple time‐dependent heating parametrization that minimizes error in a parent GCM grid box, albeit at the expense of increased error in the neighbourhood.