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首页> 外文期刊>Atmospheric chemistry and physics >Single particle analysis of ice crystal residuals observed in orographic wave clouds over Scandinavia during INTACC experiment
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Single particle analysis of ice crystal residuals observed in orographic wave clouds over Scandinavia during INTACC experiment

机译：在INTACC实验期间在斯堪的纳维亚半岛的地形波云中观察到的冰晶残留物的单颗粒分析

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Individual ice crystal residual particles collected over Scandinavia duringthe INTACC (INTeraction of Aerosol and Cold Clouds) experiment in October1999 were analyzed by Scanning Electron Microscopy (SEM) equipped withEnergy-Dispersive X-ray Analysis (EDX). Samples were collected onboard theBritish Met Office Hercules C-130 aircraft using a Counterflow VirtualImpactor (CVI). This study is based on six samples collected in orographicclouds. The main aim of this study is to characterize cloud residualelemental composition in conditions affected by different airmasses. Intotal 609 particles larger than 0.1 μm diameter were analyzed and theirelemental composition and morphology were determined. Thereafter ahierarchical cluster analysis was performed on the signal detected withSEM-EDX in order to identify the major particle classes and their abundance.A cluster containing mineral dust, represented by aluminosilicates, Fe-richand Si-rich particles, was the dominating class of particles, accounting forabout 57.5% of the particles analyzed, followed by low-Z particles,23.3% (presumably organic material) and sea salt (6.7%). Sulfur wasdetected often across all groups, indicating ageing and in-cloud processingof particles. A detailed inspection of samples individually unveiled arelationship between ice crystal residual composition and airmass origin.Cloud residual samples from clean airmasses (that is, trajectories confinedto the Atlantic and Arctic Oceans and/or with source altitude in the freetroposphere) were dominated primarily by low-Z and sea salt particles, whilecontinentally-influenced airmasses (with trajectories that originated ortraveled over continental areas and with source altitude in the continentalboundary layer) contained mainly mineral dust residuals. Comparison ofresidual composition for similar cloud ambient temperatures around –27°C revealed that supercooledclouds are more likely to persist in conditions where low-Z particles represent significant part of the analyzed cloudresidual particles. This indicates that organic material may be poor icenuclei, in contrast to polluted cases when ice crystal formation wasobserved at the same environmental conditions and when the cloud residualcomposition was dominated by mineral dust.The presented results suggest that the chemical composition of cloud nucleiand airmass origin have a strong impact on the ice formation throughheterogeneous nucleation in supercooled clouds.
机译：通过配备能量色散X射线分析（EDX）的扫描电子显微镜（SEM）分析了1999年10月在INTACC（气溶胶和冷云的相互作用）实验期间在斯堪的纳维亚各地收集的单个冰晶残留颗粒。使用逆流虚拟撞击器（CVI）在英国气象局Hercules C-130飞机上收集样品。这项研究基于在orographicclouds中收集的六个样本。这项研究的主要目的是表征在受不同气团影响的条件下云的残留元素组成。分析了总直径大于0.1μm的609个颗粒，并确定了其基本组成和形态。此后，对用SEM-EDX检测到的信号进行层次聚类分析，以识别主要的颗粒类别及其丰度。以矿物铝酸盐，富铁和富硅颗粒为代表的含有矿物粉尘的簇是主要的颗粒类别，占被分析颗粒的约57.5％，其次是低Z颗粒，占23.3％（可能是有机物质）和海盐（6.7％）。经常在所有组中检测到硫，这表明老化和云中颗粒的处理。单独揭露的样本的详细检查是冰晶残余成分与气团成因之间的关系。清洁气团（即，局限于大西洋和北冰洋的轨迹和/或自由对流层的源高度）中的云残留样本主要是由低Z和海盐颗粒虽然持续受到影响，但气团（其轨迹起源于或遍及大陆地区，并且源高度在大陆边界层中）主要包含矿物粉尘残留物。比较–27°C附近类似云朵环境温度下的残留成分，发现在低Z粒子占所分析云残留粒子的重要部分的条件下，过冷云更可能持续存在。这表明，与在相同环境条件下观察到冰晶形成且云残留成分以矿物粉尘为主的受污染情况相比，有机物质可能是不良的冰核。本研究结果表明云核气团起源的化学成分具有过冷云中的异质成核对冰的形成有很大影响。

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