Quantifying the efficiency with which biological particles nucleate ice when immersed in supercooled water droplets

量化生物颗粒浸入过冷水滴时使冰成核的效率

• 批准号: NE/I013466/1
• 负责人: Benjamin Murray
• 金额: $ 43.65万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI013466%2F1
• 关键词: Quantifying; efficiency; biological; particles; nucleate

Clouds composed of both ice particles and supercooled liquid droplets, known as mixed phase clouds, exist at temperatures above ~-35oC and cover a large portion of the planet. These clouds impact climate by both simultaneously warming the planet by trapping outgoing infrared radiation and cooling the planet by reflecting incoming visible light from the sun back to space. It is becoming increasingly apparent that mixed phase clouds are very sensitive to the number and type of particles, known as aerosols, present in the atmosphere. A lot of work has been done in the past to understand the role of aerosols on clouds that are entirely composed of liquid droplets and the Intergovernmental Panel on Climate Change (IPCC) attempted to quantify this impact, albeit with large uncertainties. However, the role that aerosols play in ice formation, which dramatically alters the properties of a cloud, remains very uncertain and the IPCC were not in a position to assess this forcing despite evidence that the impact is very large. Aerosols that can catalyse ice particle formation are known as ice nuclei; however their identity, concentration, global distribution and the efficiency with which they nucleate ice are all poorly quantified at present. There is mounting evidence from field studies that biogenic particles, such as bacteria, pollen or fungal spores, nucleate ice in clouds. It has been known for some time that about 25% of insoluble aerosols can be of biogenic origin, but their role in cloud formation remains highly uncertain. In the past few years technological advancements in field equipment have led to the discovery that a major fraction of particles which can serve as ice nuclei in the atmosphere are of biogenic origin. In an aircraft campaign, it was found that a third of the ice crystals in a cloud over Wyoming contained biogenic material (Pratt et al., Nature Geosci, 2, 398. 2009). In a separate study biogenic material dominated the ice nuclei populations above -25oC in the Amazon (Prenni et al., Nature Geosci, 2, 402, 2009). Hoose (Nature Geosci, 2, 385, 2009) suggests that these discoveries may represent 'the tip of the iceberg'. Hence, it is clear that biogenic aerosols are strongly correlated with ice yet their proper treatment in cloud and climate models is missing and their ice nucleation properties are very poorly characterised with huge gaps in basic knowledge. Modelling studies give conflicting results, with some models suggesting a major impact on cloud formation while others suggest a marginal impact of biogenic ice nucleation. The difference in model results and the discrepancy with the field data suggests that the laboratory data on which the models are based is inadequate. In fact, in their global model Hoose et al. (J. Atm. Sci, doi: 10.1175/2010JAS3425.1, 2010) use a crude estimate of the ice nucleating ability of fungal spores since there is no suitable experimental data on which to base the parameterisation. Given fungal spores account for 23% of the primary emissions of organic aerosol globally, their assumption will lead to major uncertainties in the model. Lab data for ice nucleation by pollen and bacteria are also very poor. In short, there is a large amount of biogenic material in the atmosphere, but we do not know how it impacts clouds and climate due to the paucity of basic data. In order to address this paucity of information we propose a set of experiments in which we make use of a unique instrument which Murray developed during his NERC fellowship. This instrument has and is being used to measure the efficiency with which mineral dust particles nucleate ice in the immersion mode. This work has resulted in the first quantitative measurements of ice nucleation by clay minerals (Murray et al. Atm. Chem. Phys. Disc. 4, 115, 2010). We plan to apply the same rigorous and quantitative techniques to fungal spores, pollen, and bacteria for the first time.

由冰粒和过冷液滴组成的云，被称为混合相云，存在于温度高于-35 ° C的地方，覆盖了地球的大部分地区。这些云通过捕获向外辐射的红外辐射使地球变暖，并通过将来自太阳的可见光反射回太空使地球冷却，从而影响气候。越来越明显的是，混合相云对大气中存在的称为气溶胶的颗粒的数量和类型非常敏感。过去已经做了很多工作来了解气溶胶对完全由液滴组成的云的作用，政府间气候变化专门委员会（IPCC）试图量化这种影响，尽管存在很大的不确定性。然而，气溶胶在冰形成中所发挥的作用（它极大地改变了云的性质）仍然非常不确定，尽管有证据表明影响非常大，但IPCC无法评估这种强迫。能够催化冰粒形成的气溶胶被称为冰核;然而，目前对它们的身份、浓度、全球分布以及它们使冰成核的效率都缺乏量化。越来越多的实地研究证据表明，生物粒子，如细菌、花粉或真菌孢子，会在云中形成冰核。一段时间以来，人们已经知道大约25%的不溶性气溶胶可以是生物来源的，但它们在云形成中的作用仍然非常不确定。在过去几年中，由于现场设备的技术进步，人们发现，大气中可作为冰核的粒子的主要部分是生物起源的。在一次飞机运动中，人们发现怀俄明州上空云层中三分之一的冰晶含有生物源物质（Pratt等人，Nature Geosci，2，398. 2009年）。在一项单独的研究中，生物源物质在亚马逊河温度高于-25 ° C的冰核种群中占主导地位（Prenni等人，Nature Geosci，2，402，2009）。Hoose（Nature Geosci，2，385，2009）认为这些发现可能代表了“冰山的尖端”。因此，很明显，生物气溶胶与冰有很强的相关性，但它们在云和气候模型中的适当处理却缺失，而且它们的冰成核特性非常差，基础知识存在巨大差距。模拟研究给出了相互矛盾的结果，一些模型表明对云的形成有重大影响，而另一些模型则认为生物冰成核的影响很小。模型结果的差异和与实地数据的差异表明，模型所依据的实验室数据是不够的。事实上，在他们的全球模型中，Hoose等人（J. Atm.科学，doi：10.1175/2010JAS3425.1，2010）使用真菌孢子的冰成核能力的粗略估计，因为没有合适的实验数据作为参数化的基础。鉴于真菌孢子占全球有机气溶胶主要排放量的23%，他们的假设将导致模型中的重大不确定性。花粉和细菌形成冰核的实验室数据也非常少。简而言之，大气中有大量的生物物质，但由于缺乏基本数据，我们不知道它如何影响云和气候。为了解决这种信息的缺乏，我们提出了一套实验中，我们利用一种独特的仪器，穆雷在他的NERC奖学金。该仪器已经并正在用于测量矿物粉尘颗粒在浸没模式下成核成冰的效率。这项工作导致了粘土矿物对冰成核的第一次定量测量（Murray等人，Atm.化学物理光盘4，115，2010）。我们计划首次将同样严格的定量技术应用于真菌孢子、花粉和细菌。

项目成果

Sensitivity of liquid clouds to homogenous freezing parameterizations.

• DOI: 10.1002/2014gl062729
• 发表时间: 2015-03-16
• 期刊: GEOPHYSICAL RESEARCH LETTERS
• 影响因子: 5.2
• 作者: Herbert, Ross J.;Murray, Benjamin J.;Dobbie, Steven J.;Koop, Thomas
• 通讯作者: Koop, Thomas

The Fifth International Workshop on Ice Nucleation phase 2 (FIN-02): Laboratory intercomparison of ice nucleation measurements

第五届国际冰核研讨会第二阶段（FIN-02）：冰核测量的实验室比对

• DOI: 10.5194/amt-2018-191
• 发表时间: 2018
• 作者: DeMott P

Not all feldspars are equal: a survey of ice nucleating properties across the feldspar group of minerals

• DOI: 10.5194/acp-16-10927-2016
• 发表时间: 2016-09-05
• 期刊: ATMOSPHERIC CHEMISTRY AND PHYSICS
• 影响因子: 6.3
• 作者: Harrison, Alexander D.;Whale, Thomas F.;Murray, Benjamin J.
• 通讯作者: Murray, Benjamin J.

Not all feldspar is equal: a survey of ice nucleating properties across the feldspar group of minerals

并非所有长石都是平等的：对长石矿物组的冰成核特性的调查

• DOI: 10.5194/acp-2016-136
• 发表时间: 2016
• 作者: Harrison A

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.