Volcanic impacts on atmospheric dynamics (VolDyn)

关于平流层和对流层动力学对火山气溶胶云的响应有大量的科学文献。由于观测到的大喷发数量较少，并且由于系统内部的大变异性，仍然存在一些悬而未决的问题，但一个总的情况已经出现，特别是涉及平流层经向翻转环流的加速，平流层涡旋的加强以及对流层对这种平流层异常的响应。然而，我们对中间层的反应知之甚少。在皮纳图博火山爆发后，通过对极地中间层云（PMC）的观测和激光雷达的直接观测，有间接的温度异常迹象，但对可能导致这种情况的潜在机制知之甚少。我们的项目旨在填补这一知识空白。在VolDyn的第一阶段，我们还表明，在皮纳图博火山喷发后不久开始观测的卤素掩星实验（HALOE）卫星仪器表明，上层中层温度正异常可能与火山喷发有关。高层大气二十面体非流体静力（UA-ICON）环流模式的首次模拟表明，夏季半球平流层环流异常对中间层动力学有明显的影响。我们目前正在分析半球间的耦合过程。在VolDyn的第二阶段，我们将继续使用UA-ICON系统地探索中间层扰动对喷发特征的敏感性，如喷发硫质量、喷发纬度或喷发季节。此外，由于中间层异常可能对平流层环流异常的细节很敏感，我们希望尽可能真实地模拟历史上的皮纳图博火山喷发（卫星时代最大的火山事件）及其对平流层的影响。我们的目标不仅是对现有的观测结果进行定性的比较，而且还要进行定量的比较——这对于坦博拉火山或喀拉喀托火山等其他历史喷发来说是不可能的。为了将皮纳图博火山喷发的模拟结果与观测结果进行比较，我们将使用几乎所有包含皮纳图博火山喷发日期或喷发后几个月的现有中间层温度数据集。这些数据包括来自HALOE和风成像干涉仪（WINDII）等星载仪器的数据，以及来自桌山、上普罗旺斯、霍恩培ßenberg和伍珀塔尔等地面站的数据。最后，除了环流异常外，水汽异常也可能对观测到的PMC信号有贡献。为了理解这一点，我们想在进一步的模式模拟中分析火山水蒸气向极地夏季中间层顶的输送。

There is a large body of scientific literature on the response of stratospheric and troposphericdynamics to volcanic aerosol clouds. Due to the small number of well observed large eruptions and due to the large internal variability of the system, there are still some open questions, but a general picture has emerged which involves in particular an acceleration of the stratospheric meridional overturning circulation, the strengthening of stratospheric vortices and tropospheric responses to this stratospheric anomaly. Much less is known, however, about the mesospheric response. There are indirect indications of temperature anomalies from observations of polar mesospheric clouds (PMC) and direct ones from Lidar observations after the Pinatubo eruption, but little is known about potential mechanisms which may have contributed to this. Our project intends to fill this knowledge gap. In phase I of VolDyn we showed that also the Halogen Occultation Experiment (HALOE) satellite instrument, that started observing shortly after the Pinatubo eruption, indicates a positive upper mesospheric temperature anomaly possibly related to the eruption. First simulations with the upper atmosphere icosahedral non-hydrostatic (UA-ICON) general circulation model have shown for the summer hemisphere a clear influence of stratospheric circulation anomalies on mesospheric dynamics. We are currently analyzing interhemispheric coupling processes.In phase II of VolDyn we will continue using UA-ICON to systematically explore the sensitivity of the mesospheric perturbation to the characteristics of an eruption, such as the emitted sulfur mass, the eruption latitude, or the eruption season.Moreover, as mesospheric anomalies are likely sensitive to specifics of stratospheric circulation anomalies, we want to simulate the historic Pinatubo eruption (the largest volcanic event in the satellite era) and its effects up to the mesosphere as realistically as possible using a nudging approach for the stratosphere. Our aim is to not only make a qualitative but also a quantitative comparison with existing observations – something that is not possible for other historic eruptions such as those of Tambora or Krakatau. To compare the simulation results for the Pinatubo run with observations, we will use virtually all available mesospheric temperature data sets that contain the date of the Pinatubo eruption or the immediate months afterwards. These include data from satellite-borne instruments such as HALOE and the wind imaging interferometer (WINDII), and data from ground-based stations such as Table Mountain, Haute Provence, Hohenpeißenberg, and Wuppertal.Finally, not only circulation but also water vapor anomalies may contribute to the observed PMC signals. To understand this, we want to analyse the transport of volcanic water vapour to the polar summer mesopause in further model simulations.