Atmospheric Adjustment to Generalized Forcing

首席研究员将对广义强迫的大气调整进行理论研究。大气调整被定义为潮湿的可压缩大气对规定强迫的响应。在一个任意形状的瞬时强迫之后，大气一般会立即处于地转和流体静力不平衡的状态。大气平差的研究描述了随后空气达到地转和静水平衡状态的趋势。它是地转调整的经典问题的延伸，包括可压缩性的影响，并允许非流体静力和潮湿过程。所研究的强迫将完全是一般的，包括动量、质量、热量和水分强迫。还将评估强迫的时间尺度的影响。因此，这项研究将对大气的基本运作提供深入的了解。这些解决方案还将揭示云的动力学、中尺度对流系统和其他由潮湿对流驱动的非流体静力环流。虽然加热和润湿都对应于对气团的浮力的增加，但它们有一个根本的区别。增加的热量可以转化为其他形式的能量，这些能量可以传播出去；添加的水必须被保存，不能被转化（在没有相变的情况下）并传播出系统。一组线性问题将用于检验可压缩性对广义力调整的全部影响。初值和傅里叶变换技术将用于解析求解线性时变问题。将检查能量学，并评估声波、重力和兰姆模式之间的能量分配以及平衡的最终状态。这些解决方案为测试中尺度、云和预报模型的动力核心提供了基准。这些线性化平差问题的解析解将得到数值研究的补充。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。该研究还将开发一种消除声波和兰姆波的非弹性模型。这种新模型将是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非弹性方程与完全可压缩方程的优点。因此，除了提供对大气动力学的深入了解之外，这项研究还将有助于建立基准和开发非流体静力模型，这是数值天气预报模型的基础。

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.