The Poloidal Convection Model and Multi-Scale Moist Circulations

高积云产生了全球大部分的暴雨。它们是空气从近地表上升到大气上层时形成的。为了给上升的、富含水分的空气腾出空间，凉爽、干燥的空气被迫在云层周围下降。上升的空气在其中形成可见的云滴和雨滴，但下降的空气在很大程度上是不可见的，并且可能延伸到远离多云核心的距离。这种上升和下降的配对对云的行为的重要性是赞赏的，但它没有很好地描述。目前对降雨对流云的模型和描述主要集中在云内上升的空气上，大大简化了下降部分。该项目旨在通过将上升和下降的空气结合在一个框架中来解决这个问题。通过这样做，将有可能第一次了解一些观测到的对流云的行为。例如，该项目旨在用数学方法描述高大的对流云是如何通过它们的三维流动相互作用的，因此，单个云是如何结合形成大雨、长期存在的天气系统的，并更好地理解某些形状的云为什么和何时会增长，而其他形状的云为什么不会增长。这一认识将被纳入评估和预测全球降水模式和行为的模式。该项目还将培养不同层次的学生进行跨学科研究。该项目将测试并进一步开发一种新的模型，该模型将任意对流环流描述为极向环流。极流模型将与羽流模型进行对比。通过将对流上升和下降与平滑变化的完整速度场相结合，该项目将对云和环流的动力学方面进行描述，例如平流和扩散如何影响环流的增长和衰减，环流对如何相互作用，以及上升气流中的局部潜热如何有助于向上或向下旋转环流。通过同时将极向环流的动力学方面整合到一个简单的模型中，将有可能解决长期存在的问题，如单个对流环流如何向马登朱利安涛动（Madden Julian Oscillation）这样的天气性对流环流升级。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Tall cumulus clouds produce most heavy rains globally. They form as air rises from near the surface to the upper reaches of the atmosphere. To make room for the ascending, moisture-laden air, cool, dry air is forced downward around the cloud. The ascending air forms visible cloud droplets and rain drops within it, but the descending air is largely invisible and may extend to distances far away from the cloudy core. The importance of this pairing of ascent and descent to the behavior of cloud is appreciated, but it is not well described. Current models and descriptions of raining convective clouds focus on the air that ascends inside the cloud and greatly simplify the descending portion. The project aims to remedy this by incorporating both ascending and descending air in one framework. By doing so, it will be possible to understand some observed behavior of convective clouds for the first time. For example, the project aims to mathematically describe how tall convective clouds interact with one another through their three-dimensional flow and thus how individual clouds coalesce to form heavily raining, long-lived weather systems and to better understand why and when certain shaped clouds grow and why others do not. This understanding will then be incorporated into a model to assess and forecast global precipitation patterns and behavior. The project will also train students at various levels in interdisciplinary research. The project will test and further develop a new model that describes an arbitrary convective circulation as poloidal. The poloidal model will be contrasted with a plume model. By coupling convective ascent and descent with a smoothly varying complete velocity field, the project will develop descriptions of dynamical aspects of clouds and circulation such as how advection and diffusion affect growth and decay of circulations, how pairs of circulations interact, and how localized latent heating within updrafts contributes to spinning up or down the return circulation. By simultaneously incorporating dynamical aspects of poloidal circulations into a simple model, it will be possible to address long standing questions like how individual convective circulations feed upscale to synoptic ones like the Madden Julian Oscillation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.