Microscale dynamics and light scattering characteristics of ice crystals in contrails

凝结尾冰晶的微尺度动力学和光散射特性

• 批准号: 2593499
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2593499
• 关键词: Microscale; dynamics; light; scattering; characteristics

ContextUp until the COVID-19 pandemic, global aviation was forecasted to grow at a rate of 3 to 4% per annum. The industry has suffered more than most due to global travel restrictions and government financial support is being tied to environmental conditions, which is being called the 'green restart.' In 2019, CO2 emissions from the global aviation industry represented 3% of the total anthropogenic radiative forcing. However, aviation emissions including nitrogen oxide (NOx), sulphates and particulate matter (PM) also contribute to climate forcing. PM emitted by aircraft engines facilitate the formation of contrails, which are visible line shaped clouds that form behind aircraft you see in the sky. Contrails are made up of ice crystals and are formed when water vapour in the exhaust plume condenses onto soot particles (approximately 100 nm in diameter) to form liquid water droplets which then freeze as the plume cools. Contrails affect the earth's radiation balance and have a warming effect that is more significant than that of aviation's CO2 emissions, yet regulatory frameworks for reducing contrail impacts are held back by significant scientific uncertainties. Notwithstanding these uncertainties, tackling contrails presents an opportunity to significantly and rapidly reduce aviation's environmental footprint. Significant uncertainties in the climate effect of contrails remain, in part due to a lack of physical understanding of the microphysics of ice nucleation and its consequences on optical properties. The growth and shape of ice nucleates depends on the dynamics of PM surface properties: (i) PM tends to be hydrophobic, reducing ice nucleation, but sunlight and ozone oxidise PM surface that becomes hydrophilic, assisting ice formation; (ii) other atmospheric substances (hydrocarbons, SOx, NOx) may condense on PM and modify surface properties before water accumulates; (iii) PM porosity may be important, since water enters in pores and forms ice, which then assists ice growth; (iv) contrail ice particles could further absorb available water vapour in the atmosphere, thereby reducing the occurrence, coverage area and optical properties of natural cirrus, which could offset the net warming effect of contrails. The above behaviour may modify significantly the optical properties of ice crystals, which must be included in models to reduce uncertainties of estimates of contrail climate impact. Few studies have experimentally investigated the microphysics of ice nucleation on soot particles from aircraft engines, which are typically less than 100 nm in diameter.Aims and objectivesThe aim is to experimentally investigate the temporal evolution of the shape, size and light scattering properties of ice crystals that form on soot particles in conditions representative of cooling aircraft engine exhaust plumes. The student will perform controlled experiments by using suspended PM of variable composition and porosity in an ambient of different temperatures and gas compositions with variable residence times. The suspended particles will be illuminated by different spectral light characteristics to quantify the optical characteristics. The findings will be incorporated in models that evaluate the climate impact of aircraft contrails. The indirect forcing of contrails due to the effect on the optical properties of natural cirrus will be quantified by coupling an existing high-resolution contrail model with a general atmospheric circulation model, including aerosol-cloud interactions. This contributions of the project are that it will: (i) incorporate the interactions and feedbacks between contrails and natural cirrus for the first time; and (ii) more accurately quantify the impact of contrails on Earth's surface temperature with the inclusion of accurate optical properties, atmospheric processes and feedbacks. These modelling tools will be used to evaluate the potential for strategies to reduce the warming effect of contrails.

在COVID-19大流行之前，预计全球航空的情况将以每年3至4％的速度增长。由于全球旅行限制，该行业遭受的苦难比大多数人遭受的损失更大，政府的财政支持与环境条件有关，环境条件被称为“绿色重新启动”。 2019年，全球航空业的二氧化碳排放量占人为辐射强迫的总计3％。但是，包括氮（NOX），硫酸盐和颗粒物（PM）在内的航空排放也有助于气候强迫。飞机发动机散发的PM有助于形成关节尾尾，它们是可见的线形云层，在天空中看到的飞机后面形成。当水蒸气在排气羽流中的水蒸气凝结到烟灰颗粒（直径约为100 nm）上以形成液滴时，凝结物由冰晶体组成，并形成，然后将其冻结在羽状冷却时冻结。关节尾部会影响地球的辐射平衡，并具有比航空二氧化碳排放更重要的变暖作用，但要减少缩小尾尾影响的监管框架被严重的科学不确定性抑制了。尽管存在这些不确定性，但解决围栏还是有机会大幅度地减少航空的环境足迹。在捕捉片的气候效应中的显着不确定性仍然存在，部分原因是对冰核的微物理学及其对光学特性的影响缺乏物理上的理解。冰核的生长和形状取决于PM表面特性的动力学：（i）PM倾向于疏水，减少冰核，但是阳光和臭氧氧化PM表面会变成亲水，有助于冰形成； （ii）其他大气物质（碳氢化合物，SOX，NOX）可能会在PM上凝结，并在水积聚之前修改表面特性； （iii）PM孔隙率可能很重要，因为水进入毛孔并形成冰，从而有助于冰的生长； （iv）预口冰颗粒可以进一步吸收大气中的可用水蒸气，从而降低天然卷心的发生，覆盖面积和光学特性，从而抵消了关节尾部的净变暖效果。上述行为可能会显着修改冰晶的光学特性，必须将其包括在模型中，以减少估计估计气候气候影响的不确定性。很少有研究在实验中研究了飞机发动机的烟灰颗粒上的冰核的微物理学，这些烟灰颗粒的直径通常小于100 nm。iMS和Objectivesthe的目的是实验研究形状，大小和轻度散射特性的时间演化，这些冰晶的冰晶粒子在烟灰中形成了烟灰的颗粒，这些材料在烟灰中形成了烟灰，这些剂量是在烟灰中形成的，在烟灰中，在烟灰飞机上代表了冷却飞机的燃料式盘子。学生将在不同温度和气体成分的环境中使用可变成分和孔隙率的悬浮PM进行受控实验，并具有可变的停留时间。悬浮的颗粒将被不同的光谱光特性照亮，以量化光学特性。这些发现将纳入评估飞机围栏气候影响的模型中。由于对天然卷心的光学特性的影响而导致的间接强迫将通过将现有的高分辨率围栏模型与一般大气循环模型（包括气雾云相互作用）耦合来量化。该项目的这一贡献是：（i）首次结合关节和自然卷心的相互作用和反馈； （ii）更准确地量化了通过精确的光学特性，大气过程和反馈的方法，可以更量化预防片对地球表面温度的影响。这些建模工具将用于评估策略减少关节尾部变暖效果的潜力。