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Using high-speed holography to quantify secondary ice processes

使用高速全息术量化二次冰过程

基本信息

批准号：
NE/T001496/1
负责人：
Jonathan Crosier
金额：
$ 82.8万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT001496%2F1
关键词：
Using speed holography quantify secondary

项目摘要

Ice and mixed phase clouds have important effects in the atmosphere. They interact with incoming solar radiation and outgoing terrestrial radiation, and generate precipitation which impacts on the surface. Within these clouds, ice can form from one of two major pathways, i) primary ice formation and ii) secondary ice formation. Primary ice formation occurs when ice forms due the direct deposition of water from the gas to solid phase, or when liquid water freezes. Primary ice formation is mediated by aerosols which may, depending on their chemical composition, facilitate condensation, deposition, and freezing. Much research activity has and continues to focus on developing an understanding of the role of different aerosol types on these processes, with the ultimate goal of improving the accuracy of predicted cloud particle properties (number, size, and morphology). Despite these crucial advances in understanding primary ice formation, in-situ observations from research aircraft routinely highlight major discrepancies between the anticipated number density of ice particles in clouds versus that measured. These discrepancies have been reported for over 3 decades and have been the subject of much debate. Several theories have been developed to attempt to explain these discrepancies using variety of ambient datasets and laboratory studies. These theories, which typically involve particle collisions or freezing processes, act to increase the number of ice particle in clouds via fragmentation processes, and are termed ice-multiplication processes, or secondary ice processes. Unfortunately, the various secondary ice theories are highly uncertain, poorly quantified (if at all), and unverified by observations due to the difficulty of direct observation. Various studies which have attempted to assess the importance of these processes, despite the underlying uncertainty, show that there is large scope for impact of secondary ice on cloud evolution, precipitation formation, and lightning generation. We propose a collection of work to address the longstanding issue of secondary ice. The foundations for this project are based on the use of a new high-speed digital holographic microscope. This system provides the ability to provide high magnification imagery for entire 3-D volumes at high temporal resolution. When coupled with complementary apparatus (e.g. droplet generators, cold stages, environmental chambers), we will recreate and fully observe key microphysical processes of interest in the laboratory. The results of these laboratory experiments will be implemented in a series of numerical models to assess the impact of these processes on cloud properties, cloud lifetime, and precipitation formation.

冰和混合相云对大气有重要影响。它们与传入的太阳辐射和传出的地面辐射相互作用，并产生影响地表的降水。在这些云中，冰可以通过两种主要途径之一形成：i)初级冰形成和ii)次级冰形成。当水从气相直接沉积到固相而形成冰时，或者当液态水冻结时，就会发生初级冰的形成。初级冰的形成是由气溶胶介导的，根据其化学成分，气溶胶可能促进凝结、沉积和冻结。许多研究活动已经并将继续集中于加深对不同气溶胶类型在这些过程中的作用的理解，最终目标是提高预测云颗粒特性（数量、大小和形态）的准确性。尽管在了解初级冰形成方面取得了这些关键进展，但研究飞机的现场观测通常会突显云中冰粒的预期数密度与测量值之间的重大差异。这些差异已经被报道了 30 多年，并且一直是很多争论的主题。已经开发了几种理论来尝试使用各种环境数据集和实验室研究来解释这些差异。这些理论通常涉及粒子碰撞或冻结过程，通过破碎过程增加云中冰粒子的数量，被称为冰倍增过程或二次冰过程。不幸的是，各种次生冰理论具有高度不确定性，定量性较差（如果有的话），并且由于直接观察的困难而未经观察验证。尽管存在潜在的不确定性，但各种试图评估这些过程重要性的研究表明，次生冰对云演化、降水形成和闪电产生的影响范围很大。我们提出了一系列工作来解决长期存在的二次冰问题。该项目的基础是使用新型高速数字全息显微镜。该系统能够以高时间分辨率为整个 3D 体积提供高放大倍率图像。当与补充设备（例如液滴发生器、冷台、环境室）结合使用时，我们将在实验室中重现并充分观察感兴趣的关键微物理过程。这些实验室实验的结果将在一系列数值模型中实施，以评估这些过程对云特性、云寿命和降水形成的影响。