Meteoric Influences on Stratospheric Aerosol and Clouds (MeteorStrat)

火山喷发的硫磺使平流层气溶胶层变亮，在全球平均地表温度趋势范围内引起强烈降温。平流层臭氧层保护我们免受有害的紫外线辐射，准确预测它将如何恢复依赖于平流层气溶胶和极地云的预测变化。metestrat项目解决了两个关键的知识空白，这两个空白限制了目前成分气候模型的预测能力，这两个空白都与持续供应进入高层大气的大气物质的影响有关。首先，最近的原位观测证实了20世纪90年代末的发现，即平流层气溶胶层中的大多数颗粒含有来自大气的难熔核，这对当前一代的相互作用平流层气溶胶模型提出了重大挑战。其次，极地平流层云为氟氯烃等化合物的排放提供了媒介，导致极地臭氧的损失，而极地平流层云是如何在北极形成的，这仍然是一个持续的不确定性，限制了模式对臭氧层如何恢复的预测的可信度。metestrat团队取得了两项突破性的研究成果，这两项研究成果独特地解决了平流层气溶胶和PSC科学中长期存在的问题。首先，我们的全球模式“大气烟雾相互作用实验”显示了来自地外物质的主要影响，大气夹杂物从根本上改变了硫颗粒的垂直分布，挑战了模式如何预测平流层气溶胶层的变化。其次，我们的实验室PSC冻结实验表明，不是烧蚀产生的烟雾颗粒（被发现是较差的NAT核），而是包含了非烧蚀的流星碎片颗粒，这可能解释了北极有多少NAT颗粒成核。这个项目建立在这些令人兴奋的研究发现的基础上，提出了两个假设，以解决评估宇宙尘埃如何影响平流层组成的总体目标。大气中硫酸颗粒更大，在平流层停留时间更短，这对模型如何预测火山增强引起的衰变具有重要影响B.固体硝酸psc在北极形成的机制最终可以通过提供优先NAT核的未烧蚀的大气碎片来解释。我们将结合我们国际领先的实验室和建模能力来验证这些假设。我们的工作计划涉及以下5个相关的科学问题：高纬度来源的大气硫粒子向低纬度延伸的距离有多远？它们在中纬度的丰度在不同季节和年份的变化有多大？更大的大气硫酸颗粒是否会影响更快的火山衰变时间尺度？如果是这样，对火山爆发导致的地表冷却有什么影响？3 .输入的未烧蚀“流星碎片”的源通量和大小分布是什么？烟尘或碎片如何转化为丛林层的流星硫颗粒？不同组成的流星碎片是如何促进NAT冻结的？与烟雾驱动的参数化相比，实验室发现的含义是什么？大气影响能否解释观测到的PSCs以及北极臭氧损失是如何加剧的？该项目的一个关键理念是收集现场和卫星测量数据集，以确保模型预测受到观测约束和校准，从而最大限度地提高对研究结果的信心。该项目将为英国地球系统模型提供模拟平流层未来变化的重要能力，特别是火山和潜在的平流层硫或粒子地球工程的影响。

Volcanic injections of sulphur brighten the stratospheric aerosol layer with major eruptions inducing periods of strong cooling within global mean surface temperature trends.The stratospheric ozone layer shields us from harmful UV radiation, and accurately predicting how it will recover relies on predicted changes in stratospheric aerosol and polar clouds.The MeteorStrat project addresses two key knowledge gaps that limit current predictive capability of composition-climate models, both associated with the effects from the continual supply of meteoric material entering the upper atmosphere.Firstly, recent in-situ observations have confirmed findings from the late 1990s that most particles in the stratospheric aerosol layer contain refractory core of meteoric origin, posing a major challenge to the current generation of interactive stratospheric aerosol models.Secondly, how the polar stratospheric clouds, that provide the medium by which emissions of compounds such as CFCs leads to polar ozone loss, form in the Arctic has remained a persistent uncertainty, limiting the confidence of model predictions for how the ozone layer will recover.The MeteorStrat team have made two breakthrough research findings that uniquely enable to address long-standing questions in stratospheric aerosol and PSC science.Firstly, our global model "meteoric smoke interaction experiments" show major effects from extra-terrestrial material, the meteoric inclusions radically altering the vertical distribution of sulphuric particles, challenging how models predict changes in the stratospheric aerosol layer. Secondly, our laboratory PSC freezing experiments reveal that rather than ablation-generated smoke particles (which were found to be poor NAT nuclei), it is an inclusion of non-ablated meteoric fragment particles that may explain how many NAT particles nucleate in the Arctic. This project builds on these exciting research findings with two hypotheses addressing the overarching aim to assess how cosmic dust influences the composition of the stratosphere.A. That meteoric-sulphuric particles are larger, with shorter stratospheric residence times, has important consequences for how models predict decay from volcanic enhancement B. The mechanism by which solid nitric acid PSCs form in the Arctic can finally be explained by the non-ablated meteoric fragments providing the preferential NAT nucleiWe will combine our internationally-leading laboratory and modelling capabilities to test these hypotheses. Our workplan addresses the following 5 related science questions: 1. How far do the high-latitude source meteoric-sulphuric particles extend to lower latitudes and how variable is their mid-latitude abundance across different seasons and years?2. Do the larger meteoric-sulphuric particles effect a faster volcanic decay timescale and if so what are the implications for the surface cooling attributed to volcanic eruptions?3. What is the source flux and size distribution of the non-ablated "meteoric fragment" input and how do smoke or fragments transform into Junge layer meteoric-sulphuric particles?4. How do the distinctly composed meteoric fragments facilitate NAT freezing and what are the implications of the laboratory findings compared to smoke-driven parameterizations?5. Can meteoric influence explain observed PSCs and how is Arctic ozone loss enhanced?A key philosophy of the project involves gathering in situ and satellite measurement datasets to ensure model predictions are observationally-constrained and calibrated to maximise confidence in research findings. The project will provide the UK Earth System Model with vital capability to simulate future changes to the stratosphere, in particular for the effects from volcanic and potential stratospheric sulphur or particle geoengineering.