The Poloidal Convection Model and Multi-Scale Moist Circulations

高大的积云在全球范围内产生了最多的暴雨。当空气从近地表上升到大气层的上层时，它们就形成了。为了给上升的、充满水分的空气腾出空间，冷干的空气被迫在云层周围向下移动。上升的空气在其内部形成可见的云滴和雨滴，但下降的空气在很大程度上是看不见的，可能会延伸到远离云核的地方。这种上升和下降的配对对云的行为的重要性得到了赞赏，但它没有得到很好的描述。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，并极大地简化了下降部分。该项目旨在通过将上升和下降的空气纳入一个框架来纠正这一点。通过这样做，将有可能第一次了解观察到的对流云的一些行为。例如，该项目旨在从数学上描述高大对流云如何通过其三维流动相互作用，从而描述单个云如何聚合形成暴雨、持久的天气系统，并更好地了解某些形状的云为什么以及何时增长，以及为什么其他形状的云不增长。这一认识随后将被纳入一个模型，以评估和预测全球降水模式和行为。该项目还将培训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。极面模型将与羽流模型进行对比。通过将对流的上升和下降与平稳变化的完整速度场相结合，该项目将开发云和环流的动力学方面的描述，例如平流和扩散如何影响环流的增减、成对的环流如何相互作用，以及上升气流中的局部潜热如何有助于回流环流的上升或下降。通过同时将极向环流的动力学方面结合到一个简单的模式中，将有可能解决长期存在的问题，如单个对流环流如何为像Madden Julian Oscillation这样的天气环流提供更高级别的支持。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.