Moist Atmospheric Adjustment

首席研究员将对潮湿大气调节过程进行理论研究。湿润大气调节被定义为湿润可压缩大气对规定的加热和/或润湿的响应。在任意形状的瞬时加热/润湿之后，大气通常会立即处于地转和流体静力不平衡的状态。湿润大气调整的研究描述了空气随后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。这些解决方案还将揭示云、阵风锋和其他由潮湿对流驱动的非流体静力环流的动力学。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。提出了大气对可压缩大气中蒸发冷却问题响应的原型模型。提出了一系列问题来检验可压缩性的全部影响，包括加热和润湿。理想的一维问题的线性和非线性解将使用拉格朗日技术和位涡守恒来获得最终的平衡状态。拉普拉斯和傅里叶变换技术将被用于解决线性时相关问题的解析和数值。将检查能量学，并评估声波和重力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。拟议的研究还将寻求开发一套节能的潮湿非弹性方程，这些方程与潮湿大气调节的声学成分一致，并且最好地捕捉湿度对布朗特-维萨拉频率的影响。这一理论研究的成功完成将增加人们对大气预报系统中常用的各种近似精度的认识。

The Principal Investigator will undertake a theoretical investigation of moist atmospheric adjustment processes. Moist atmospheric adjustment is defined as the response of a moist compressible atmosphere to a prescribed heating and/or moistening. Immediately after an instantaneous heating/moistening of arbitrary shape, the atmosphere will, in general, be in a state of geostrophic and hydrostatic imbalance. The study of moist 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 solutions will also shed light on the dynamics of clouds, gust fronts, 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 which can be propagated away; an addition of water must be conserved and can not be transformed (in the absence of phase changes) and propagated out of the system. A prototype model of the atmospheric response to the problem of evaporative cooling in a compressible atmosphere is presented in the proposal.A suite of problems are proposed to examine the full effects of compressibility that include heating and moistening. Linear and nonlinear solutions of idealized one-dimensional problems will use Lagrangian techniques and the conservation of potential vorticity to obtain the final state of balance. Laplace and Fourier transform techniques will be used to solve for the linear time-dependent problems analytically and numerically. The energetics will be examined and the partitioning of the energy between the acoustic and gravity 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.The proposed research will also seek to develop a set of moist anelastic equations that are energy conserving, that are consistent with the acoustic component of moist atmospheric adjustment, and that best capture the effect of moisture on the Brunt-Vaisala frequency.Successful completion of this theoretical study will increase knowledge of the accuracy of various approximations that are often employed in atmospheric forecast systems.