AMPlifying the Simulation of Clouds and Precipitation

在天气和气候模式中，正确模拟云对于准确预测云和降雨至关重要。在大气模式中有两种常见的表示小尺度云过程的方法；这些被称为bin微物理方案和bulk微物理方案。批量方案是执行速度快的简单模型，而bin方案要复杂得多，但运行速度慢——实际上，太慢了，无法用于天气预报或气候预测。该项目将使用一种新的模型，称为任意力矩预测器（AMP），它受益于bin方案的准确性和灵活性，以改进批量方案。AMP就像一个镜头。它允许天气模型看到垃圾箱方案，就好像它是一个散装方案。通过改变视图，将有可能第一次理解如何最好地在模型中实现批量方案。这些结果有可能导致未来天气和气候模型设计和开发的重大转变。AMP像现有的批量方案一样预测云滴和雨滴的大小分布力矩，但过程参数化与bin方案使用的过程参数化相同。它的灵活性在于可以预测质量混合比和一个或两个附加的任意分布矩。这项工作将分为两个主要部分。1)将比较两种箱型方案和对应于每种箱型方案的两种版本的AMP对暖相层积云的大涡模拟，以评估整体方案的基本局限性。这样的直接比较箱和散装方案是不可能的以前。2)额外的模拟将使用具有预测矩的替代组合的AMP运行。模拟将根据现有的观测结果进行严格评估，以探索应使用非标准力矩组合来改进云和降水模拟的可能性。这种可能性是基于观测证据提出的，但尚未在3D模拟中得到验证。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。

Properly simulating clouds is critical for accurate prediction of clouds and rainfall in weather and climate models. There are two common ways in which small-scale cloud processes are represented in atmospheric models; these are known as bin microphysics schemes and bulk microphysics schemes. Bulk schemes are simple models that execute quickly while bin schemes are much more complex but run slowly – in fact, too slowly to be used in weather forecasting or climate prediction. This project will use a new model, called the Arbitrary Moment Predictor (AMP), which benefits from the accuracy and flexibility of bin schemes to improve bulk schemes. AMP acts as a lens. It allows a weather model to see a bin scheme as though it were a bulk scheme. By changing the view, it will become possible to understand how best to implement bulk schemes in models for the first time. The results have the potential to lead to a major shift in the design and development of future weather and climate models.AMP predicts size distribution moments of cloud droplets and rain drops like existing bulk schemes, but the process parameterizations are identical to those used by a bin scheme. It is flexible in that it can predict mass mixing ratio and one or two additional arbitrary distribution moments. There will be two major parts of the work. 1) Large eddy simulations of warm phase stratocumulus clouds with two bin schemes and with two versions of AMP corresponding to each bin scheme will be compared to assess fundamental limitations of bulk schemes. Such a direct comparison between bin and bulk schemes has not been possible before. 2) Additional simulations will be run using AMP with alternative combinations of predicted moments. Simulations will be rigorously assessed with available observations to explore the possibility that nonstandard moment combinations should be used to improve simulation of clouds and precipitation. Such a possibility has been suggested based on observational evidence but has not been tested in 3D simulations.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.