Atmospheric Adjustment to Generalized Forcing

首席调查员将对大气对广义强迫的调整进行理论研究。大气调节被定义为潮湿的可压缩大气对规定的强迫的反应。在任意形状的瞬时强迫之后，大气总体上将处于地转和流体静力不平衡状态。大气调节的研究描述了大气随后达到地转和静水平衡状态的趋势。它是经典地转调整问题的推广，包括了可压缩性的影响，并考虑了非静力和潮湿过程。研究的作用力将是完全一般的，包括动量作用力、质量作用力、热作用力和水汽作用力。还将评估强迫的时间尺度的影响。因此，这项研究将提供对大气层基本工作原理的洞察。这些解决方案还将阐明云、中尺度对流系统和其他由湿对流驱动的非静力环流的动力学。虽然加热和增湿都相当于增加了气团的浮力，但有一个根本的区别。增加的热量可以转化为其他形式的能量，可以传播出去；增加的水必须守恒，不能(在没有相变的情况下)转化和传播到系统之外。将使用一组线性问题来检验可压缩性在对广义强迫的调整中的全部影响。利用初值和傅里叶变换技术对线性时变问题进行解析求解。我们将研究能量学，并评估声学、重力和兰姆模式之间的能量分配以及平衡的终态。这些解决方案为检验中尺度、云和预报模式的动力核心提供了一个基准。线性化调整问题的这些解析解将通过数值研究加以补充。这些数值研究将解决非线性对大气响应的影响，并使解决方案具有更现实的基态大气。这项研究还将开发一种消除声波和兰姆波的滞弹性模型。这种新的模型将是对现有模型的一个进步，因为它将节省质量、水分和能量。数值实验将证明这些滞弹性方程相对于完全可压缩方程的优点。因此，除了提供对大气动力学的洞察外，这项研究还将有助于对非静力模式进行基准测试和开发，这是数值天气预报模式的基础。

A theoretical investigation of atmospheric adjustment to generalized forcings will be carried out by the Principal Investigator. Atmospheric adjustment is defined as the response of a moist compressible atmosphere to a prescribed forcing. Immediately after an instantaneous forcing of arbitrary shape, the atmosphere will, in general, be in a state of geostrophic and hydrostatic imbalance. The study of atmospheric adjustment describes the subsequent tendency of the air to achieve a state of geostrophic and hydrostatic balance. It is an extension of the classic problem of geostrophic adjustment to include the effects of compressibility and to allow for nonhydrostatic and moist processes. The forcings studied will be completely general and include momentum, mass, thermal, and moisture forcings. The impact of the time scale of the forcing will also be assessed. Thus, the research will provide insight into the fundamental workings of the atmosphere. The solutions also will shed light on the dynamics of clouds, mesoscale convective systems, and other nonhydrostatic circulations driven by moist convection. Although both heating and moistening correspond to an addition of buoyancy to the air mass, there is a fundamental difference. An addition of heat can be transformed to other forms of energy that can be propagated away; an addition of water must be conserved and cannot be transformed (in the absence of phase changes) and propagated out of the system.A suite of linear problems will be used to examine the full effects of compressibility in the adjustment to generalized forcings. Initial value and Fourier transform techniques will be used to solve for the linear time-dependent problems analytically. The energetics will be examined and the partitioning of the energy between the acoustic, gravity, and Lamb modes and the balanced final state will be assessed. These solutions provide a benchmark to test the dynamical cores of mesoscale, cloud, and forecasting models.These analytic solutions of the linearized adjustment problem will be supplemented by numerical investigations. These numerical studies will address the effect of nonlinearities on the atmospheric response and enable solutions with a more realistic base-state atmosphere. The research also will develop an anelastic model that eliminates the acoustic and Lamb waves. This new model will be an advance over existing models in that it will conserve mass, moisture, and energy. Numerical experiments will document the merits of these anelastic equations in comparison to the fully compressible equations. Thus in addition to providing insight into the dynamics of the atmosphere the research will help to benchmark and develop nonhydrostatic models, which are the foundation for numerical weather forecast models.