Minimal Models for Investigating the Influence of Latent Heat Release on Midlatitude Dynamics

这项合作研究将针对中纬度地区天气系统科学中一些最具科学性和操作性的问题。为了区分湿润中纬度动力学的本质和非本质过程，一个由应用数学家和大气科学家组成的研究小组将提出和研究一组地球物理流体动力学问题。参与者将使用最小建模方法，并与观测数据进行比较，并在适当的情况下与综合物理数值计算的结果进行比较。其目的是分离基本的物理机制和降水对流在形成中纬度大气的一些典型结构中的作用。智力上的优点：将使用一个最小模式来研究具有降水对流的中纬度动力学。云微物理被包括在与凝结、自动转换和蒸发相关的时间尺度与问题中的所有其他相关时间尺度(平流、浮力、旋转和降雨)相比较小的限制中。简化的热力学基于以下设计原则：动量守恒定律、能量守恒定律、湿熵守恒定律和总水守恒定律都应该保留，但它们应该具有尽可能简单的非平凡形式。在这些假设下，全三维模型考虑了降水对流，同时大大减少了必要的闭合模型的数量。将进行三个主要的个例研究：(I)一个或多个斜压不稳定模(S)的演变，以研究潜热释放在中纬度闭塞过程中的作用；(Ii)存在低空对流的单急流的动力学，以阐明急流-对流反馈环及其饱和的机制；(Iii)具有对流的双急流动力学，作为极地和副热带急流偶尔合并以及随后发生极端降水事件的可能性的简化模式。数学建模的新发展将带给大气科学界，同时初级数学家将接触到大气科学中的关键开放问题。作为与两个社区分享新见解的一种方式，最小的模式将作为UW虚拟大气公开提供，其中包括探索降水对流对Eady斜压不稳定问题(UWVA：EADY)和涡旋和急流的非线性演变(UWVA：JET)的影响的教育/研究模块。这项研究可能会为与喷流叠加相关的极端天气提供有价值的见解，预计在全球变暖的世界中，这种极端天气会更加频繁。热带海面温度的轻微上升预计将导致北半球副热带急流普遍向北移动，从而增加副热带和极地急流叠加的可能性。更好地了解降水对流在中纬度涡旋和急流形成和演变中的作用，可能会提高在气候变暖时预报高影响天气的能力。

This collaborative research will target some of the most scientifically interesting and operationally relevant problems in weather systems science of the midlatitudes. To isolate essential vs. non-essential processes of moist midlatitude dynamics, a set of geophysical fluid dynamics problems will be formulated and investigated by a research team of applied mathematicians and atmospheric scientists. The participants will use a minimal modeling approach coupled with comparison to observational data, and when appropriate, to the results of comprehensive-physics numerical computations. The goal is to isolate the essential physical mechanisms and the role of precipitating convection in shaping some of the canonical structures of the midlatitude atmosphere.Intellectual Merit: A minimal model will be used to study midlatitude dynamics with precipitating convection. Cloud microphysics is included in the limit that the time scales associated with condensation, auto-conversion and evaporation are small compared to all other relevant time scales in the problem (advection, buoyancy, rotation, and rainfall). The simplified thermodynamics is based on the following design principle: the conservation laws for momentum, energy, moist entropy, and total water should all be retained, but they should have the simplest nontrivial form possible. Under these assumptions, the fully three-dimensional model accounts for precipitating convection while vastly reducing the number of necessary closure models. Three main case studies will be conducted: (i) evolution of one or more baroclinically unstable mode(s) to investigate the role of latent heat release in the midlatitude occlusion process, (ii) the dynamics of a single-jet in the presence of low-altitude convection to elucidate the mechanisms responsible for the jet-convection feedback loop and its saturation, and (iii) double jet dynamics with convection as a simplified model for the occasional merger of the polar and subtropical jets and the subsequent possibility of extreme precipitation events.Broader Impacts: A primary goal of the project is cross training of junior researchers in atmospheric science and mathematical modeling. New developments in mathematical modeling will be brought to the atmospheric sciences community, and simultaneously junior mathematicians will be exposed to key open problems in atmospheric science. As one way of sharing new insights with both communities, the minimal model will be made publicly available as the UW Virtual Atmosphere, with educational/research modules to explore the effects of precipitating convection on the Eady baroclinic instability problem (UWVA:Eady), and nonlinear evolution of eddies and jets (UWVA:Jet). The research is likely to provide valuable insights into extreme weather associated with jet superposition, anticipated to be more frequent in a globally warming world. Slight increases in tropical sea-surface temperatures are expected to lead to a general northward displacement of the Northern Hemisphere subtropical jet, and thus to an increased likelihood of subtropical and polar jet superposition. Better understanding of the role of precipitating convection in the formation and evolution of midlatitude eddies and jets will likely lead to improved ability to predict high-impact weather in a warmer climate.