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

在微物理模型中表示冰不仅对研究冰对云动力学和云寿命的影响很重要，而且对精确的定量降水预报也很重要。传统的微物理参数化人为地将冰分为云冰、雪和霰等类别。这些模型假设每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，冰晶的形状或习惯取决于温度，并随着冰在云层中的移动而演变。冰晶形状通过改变周围蒸汽场的梯度显著影响蒸汽生长速率。冰晶的形状也会影响旋转速率和下落速度。传统的模型无法捕捉到这种冰晶形状的敏感性。该项目将研究冰晶形状演变对不同云系统的影响。天气研究与预报（WRF）模式将进行模拟，以观察冰晶习惯演变如何影响地形降水、热带气旋动力学和降水以及飑线。二维建模框架还将用于探索混合相云中不断变化的冰晶形状对相分配的影响。最后，将研究如何通过进化冰晶形状来表示轻边缘冰晶，从而影响混合相云的稳定性。智力价值：这项研究提供了一个独特的机会来研究冰晶习惯的演变如何影响不同的云系统。目前，冰粒子形状演化对云演化的影响程度尚不清楚。利用新的微物理参数化方法，可以探索冰晶形状变化对云系统性质的影响。光照对混合相云的影响也将首次得到验证。更广泛的影响：模拟部分由冰晶形状决定的冰晶下落速度演变对定量降水预报至关重要。此外，卷云的性质和寿命对冰晶下落的速度非常敏感。卷云的辐射特性也取决于冰晶的形状，这意味着冰晶的形状可能对气候有重要影响。由于本研究中的微物理方法原则上可以用于任何建模框架，因此该研究有可能影响从业务预测到冰云气候研究的建模。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降水，使这项研究与社会相关。

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.