Laboratory investigations of ice formation in the Earth's atmosphere

地球大气层冰形成的实验室研究

• 批准号: NE/D009308/1
• 负责人: Benjamin Murray
• 金额: $ 27.94万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD009308%2F1
• 关键词: Laboratory; investigations; ice; formation; Earth

Clouds that form in the Earth's atmosphere play an important role in the planet's climate. They can both reflect incoming light from the sun, thus cooling the planet, and insulate the surface of the planet by trapping heat. Clouds also alter the chemistry of the atmosphere by providing a medium in which, or on which, reactions can take place. The way in which clouds influence the atmosphere and climate depend, amongst other factors, on the physical properties of individual cloud droplets and ice crystals. However, processes such as ice formation in clouds, the central topic of this proposal, are very poorly understood. In fact our level of understanding of ice formation in clouds is so low that the Intergovernmental Panel on Climate Change (IPCC) does not include ice clouds in their most recent climate change assessment, even though ice nucleation undoubtedly has a significant impact on climate. The work described in this proposal will begin to address this paucity of basic scientific knowledge through a series of laboratory experiments. The laboratory experiments that are proposed here fall into two main categories. In the first set it is proposed to investigate the crystalline structure of ice (the arrangement of water molecules in ice) that forms under atmospheric conditions. In a recent major discovery it was found (Murray et al., Nature, v434, p202, 2005) that liquid water can freeze to ice with a crystal structure that was previously not expected to form in the Earth's lower atmosphere (altitude <50 km). Hexagonal ice is the 'normal' type of ice encountered in the atmosphere and its crystal structure gives rise to the hexagonal shape of snow flakes. The unusual type of ice that this proposal is concerned with is known as cubic ice and has some different physical properties to those of hexagonal ice, hence, cubic ice may strongly influence the way in which clouds form. It is proposed here to investigate the crystalline structure of ice when solution droplets of atmospherically relevant compositions freeze. The methodologies employed to do this are not typically applied to atmospheric science problems. If this proposal is successful, BJM will bring this novel and important methodology to the UK atmospheric science community. In the second set of experiments it is proposed to investigate the impact solid insoluble particles have on the formation of ice clouds in the atmosphere. It is well established that if a pure water droplet in the atmosphere is cooled, it will remain liquid until it reaches about -38oC. However, water often freezes at much higher temperatures than -38oC, because freezing is often induced by a solid object or particle. Only in the absence of solid surfaces can droplets stay liquid to very low temperature. The impact of solid particles on ice cloud formation is very poorly quantified, in part, because the ice initiating properties of common atmospheric particles are not well understood. Clearly, if we are to improve our understanding of ice clouds and their impact on climate, a detailed fundamental knowledge of the ice initiating properties of these particles is required. It is proposed here to develop a methodology capable of quantifying the ice forming properties of soot, mineral dust and proxies of meteoric particles when immersed in solution droplets of atmospheric relevance. This will be done with an optical microscope to measure ice formation in droplets with solid inclusions. The results from these ice initiation studies will be used to constrain ice formation in a numerical model in order to asses the impact of a particular particle type on the formation of clouds.

在地球大气层中形成的云对地球的气候起着重要作用。它们都可以反射来自太阳的光线，从而冷却行星，并通过捕获热量来隔离行星表面。云还通过提供一种介质来改变大气的化学性质，在这种介质中或在这种介质上可以发生反应。除其他因素外，云影响大气和气候的方式取决于单个云滴和冰晶的物理特性。然而，人们对这一提议的中心议题-云中冰的形成等过程知之甚少。事实上，我们对云中冰形成的理解水平非常低，以至于政府间气候变化专门委员会（IPCC）在其最新的气候变化评估中没有包括冰云，尽管冰成核无疑对气候有重大影响。本提案中所述的工作将开始通过一系列实验室实验来解决基础科学知识的缺乏问题。这里提出的实验室实验分为两大类。在第一组中，建议研究在大气条件下形成的冰的晶体结构（冰中水分子的排列）。在最近的一项重大发现中，发现了它（Murray等人，Nature，v434，p202，2005），液态水可以冻结成具有晶体结构的冰，这种晶体结构以前预计不会在地球的低层大气（海拔<50公里）中形成。冰是大气中遇到的“正常”类型的冰，其晶体结构导致雪花呈六边形。这个提议所涉及的不寻常的冰类型被称为立方冰，与六边形冰有一些不同的物理特性，因此，立方冰可能会强烈影响云的形成方式。这里建议研究冰的晶体结构时，大气相关的组合物的溶液液滴冻结。用于这样做的方法通常不适用于大气科学问题。如果这项提议获得成功，BJM将把这种新颖而重要的方法带到英国大气科学界。在第二组实验中，建议研究固体不溶性颗粒对大气中冰云形成的影响。众所周知，如果大气中的纯水液滴被冷却，它将保持液态，直到它达到约-38 ° C。然而，水通常在比-38 ° C高得多的温度下结冰，因为结冰通常是由固体物体或颗粒引起的。只有在没有固体表面的情况下，液滴才能在很低的温度下保持液态。固体颗粒对冰云形成的影响很难量化，部分原因是对普通大气颗粒的冰引发特性没有很好的了解。显然，如果我们要提高对冰云及其对气候影响的理解，就需要对这些粒子的冰引发特性有详细的基础知识。在这里，建议开发一种方法，能够量化的成冰性能的烟尘，矿物尘埃和代理的流星粒子时，沉浸在溶液液滴的大气相关性。这将用光学显微镜来测量具有固体内含物的液滴中的冰形成。这些冰的形成研究的结果将被用来限制冰的形成在一个数值模型，以评估一个特定的粒子类型对云的形成的影响。

项目成果

Heterogeneous freezing of water droplets containing kaolinite particles

• DOI: 10.5194/acp-11-4191-2011
• 发表时间: 2011-01-01
• 期刊: ATMOSPHERIC CHEMISTRY AND PHYSICS
• 影响因子: 6.3
• 作者: Murray, B. J.;Broadley, S. L.;Wills, R. H.
• 通讯作者: Wills, R. H.

Representing time-dependent freezing behaviour in immersion mode ice nucleation

• DOI: 10.5194/acp-14-8501-2014
• 发表时间: 2014-01-01
• 期刊: ATMOSPHERIC CHEMISTRY AND PHYSICS
• 影响因子: 6.3
• 作者: Herbert, R. J.;Murray, B. J.;Atkinson, J. D.
• 通讯作者: Atkinson, J. D.