AGS-PRF: Modeling Ice Crystal Habit Evolution from Vapor Growth and Riming--Investigating How Evolving Ice Particle Properties Impacts Clouds, Precipitation, and Phase Partitioning

在微物理模式中表示冰，不仅对于研究冰对云动力学和云寿命的影响，而且对于准确的定量降水预报都是重要的。传统的微物理参数化法人为地将冰分为云冰、雪和冰粒。这些模型假定每一种类型的冰晶大小随质量而变化，但它们没有考虑到冰晶形状的演变。在自然界中，冰晶的形状或习性取决于温度，并随着冰在云层中移动而演变。冰晶形状通过改变周围水汽场中的梯度显著影响水蒸气的生长速度。冰晶形状也影响成圈速度和下落速度。传统模式无法捕捉到冰晶形状的敏感性，本项目将研究冰晶形状演变对不同云系的影响。将使用天气研究和预报(WRF)模式进行模拟，以了解冰晶习性的演变如何影响地形降水、热带气旋动力学和降水以及咆哮线。还将使用一个二维模拟框架来探索冰晶形状演变对混合相云中相分配的影响。最后，我们将研究如何通过演化冰晶形状来表现轻边缘冰晶对混合相云稳定性的影响。智力价值：这项研究为研究冰晶习性演变如何影响不同的云系统提供了一个独特的机会。目前，冰粒形状演变对云演化的影响程度尚不清楚。利用新的微物理参数，可以探索演变中的冰晶形状对云系性质的影响。还可以首次研究光边缘如何影响混合相云。波及影响：模拟冰晶坠落速度的演变，部分由冰晶形状决定，对于定量降水预报至关重要。此外，卷云的性质和寿命对冰晶坠落的速度非常敏感。卷云的辐射特性也取决于冰晶形状，这意味着冰晶形状可能会对气候产生重要影响。由于这项研究中的微物理方法原则上可以用于任何建模框架，因此这项研究有可能影响从业务预报到冰云气候研究的各种建模。能够更准确地预测降水，特别是可能导致洪水的强降水或持续性降水，使这项研究具有社会意义。

Representing ice in microphysics models is important not only to study the effects of ice on cloud dynamics and cloud lifetime, but also for accurate quantitative precipitation forecasts. Traditional microphysics parameterizations artificially separate ice into categories such as cloud ice, snow, and graupel. These models assume that for each category ice crystal size varies with mass, but they do not account for ice crystal shape evolution. In nature, ice crystal shape, or habit, is temperature dependent and evolves as ice moves through a cloud. Ice crystal shape significantly affects vapor growth rates by varying the gradients in the encompassing vapor field. Ice crystal shape also influences riming rates and fall speed. Traditional models are not able to capture this ice crystal shape sensitivity.This project will study the impact of ice crystal shape evolution on different cloud systems. Simulations will be conducted using the Weather Research and Forecasting (WRF) model to look at how ice crystal habit evolution impacts orographic precipitation, tropical cyclone dynamics and precipitation, and squall lines. A 2-dimensional modeling framework will also be used to explore the effects of evolving ice crystal shape on phase partitioning in mixed-phase clouds. Finally, how representing lightly-rimed ice crystals, which is now possible by evolving ice crystal shape, impacts mixed-phase cloud stability will be studied. Intellectual Merit:The research provides a unique opportunity to study how ice crystal habit evolution impacts different cloud systems. At present, the degree to which ice particle shape evolution influences cloud evolution is unknown. With the new microphysics parameterization, the influence evolving ice crystal shape has on cloud system properties can be explored. How light riming affects mixed-phase clouds can also be examined for the first time.Broader Impacts:Modeling ice crystal fall speed evolution which is partially determined by ice crystal shape is crucial for quantitative precipitation forecasts. Also, cirrus cloud properties and lifetime are incredibly sensitive to ice crystal fall speeds. Cirrus cloud radiative properties depend on ice crystal shape as well, meaning ice crystal shape could have important influences on climate. Because the microphysical methods in this study can, in principle, be used in any modeling framework, the research has the potential to impact modeling ranging from operational forecasting through climate studies of ice clouds. Being able to more accurately forecast precipitation, especially heavy or persistent precipitation that could cause flooding in general makes this research relevant to society.