Constraining the effects of volcanic eruptions on stratospheric aerosols and radiative forcing

该项目提案(VolARC)是DFG研究单位VolImpact(2820)第二阶段的五个科学提案之一，其第一阶段已于2019年春季开始。VolARC项目涉及火山对平流层气溶胶的影响及其对地球系统辐射平衡的影响的关键方面。在第一阶段工作的基础上，我们将解决三个科学目标：(1)巩固我们对火山喷发后平流层气溶胶参数演变的认识，并调查测量的平流层气溶胶数据集与模拟的平流层气溶胶数据集(即气溶胶消光剖面、气溶胶光学厚度和气溶胶颗粒尺寸分布)之间存在差异的原因。在这里，将特别关注了解火山喷发后平流层气溶胶粒子尺寸分布的时间变化。(2)估计模式分辨率和输送对平流层气溶胶演变的影响。为了大大加强第一阶段的工作，我们将采用涉及不同鸟巢的无缝模拟方法，以便能够一致地模拟从火山羽流的最初发展到全球和长期尺度的相关尺度上的所有过程。(3)研究肢体散射测量和太阳掩星测量对强烈火山喷发后平流层气溶胶的敏感性，以及它们监测可能的地球工程实验的能力。第一个方面是相关的，因为现有的极限体和掩星仪器对处于相对中等光学厚度的平流层气溶胶将变得不敏感。这是因为肢体几何体中的长倾斜路径。这些影响是众所周知的，但从未在系统的研究中进行过调查。鉴于硫化物注入平流层的潜在太阳辐射管理活动，第二个方面也非常重要。将利用全球卫星观测平流层气溶胶参数(主要在光谱范围内)和模式模拟与明确的平流层气溶胶微物理的协同作用来处理研究主题。我们将使用我们自己的算法从过去、现在和未来卫星仪器的测量中提取气溶胶参数，例如OMPS-LP、SAGE III和SCIAMACHY。模型模拟将主要基于ICON-ART，但也将使用MAECHAM-HAM来提供一些快速的模型比对数据。VolARC项目与VolImpact的其他四个项目有很好的联系，例如，通过将由多个VolImpact项目解决的主要科学主题。这些主题是：(1)气溶胶粒子尺寸分布；(2)火山水注入中层大气；(3)辐射强迫。此外，VolARC将协调整个研究单位的无缝模拟活动。

This project proposal (VolARC) is one of five scientific proposals for the second phase of the DFG research unit VolImpact (FOR 2820), whose first phase has started in spring 2019. The VolARC project deals with key aspects of volcanic effects on stratospheric aerosols and their impact on the radiative balance of the Earth system. Based on the work of phase I, we will address three science objectives: (1) Consolidating our understanding of the evolution of stratospheric aerosol parameters after volcanic eruptions and investigating the reasons for differences between measured and modelled stratospheric aerosol data sets (i.e. aerosol extinction profiles, aerosol optical depth and the aerosol particle size distribution). Here, a special focus will be on understanding the temporal variation of the stratospheric aerosol particle size distribution after volcanic eruptions.(2) Estimating the impact of model resolution and transport on stratospheric aerosol evolution. Significantly enhancing the work in phase I, we will employ a seamless simulation approach involving different nests in order to be able to consistently simulate all processes at their relevant scales, from the initial development of the volcanic plume up to global and long-term scales. (3) Investigating the sensitivity of limb-scatter and solar occultation measurements to stratospheric aerosols after strong volcanic eruptions as well as their capability to monitor possible geoengineering experiments. The first aspect is relevant, because current limb and occultation instruments will become insensitive to stratospheric aerosols already at relatively moderate aerosol optical depths. This is because of the long slant path in limb geometry. These effects are well known, but have never been investigated in a systematic study. The second aspect is also highly important in the light of potential solar radiation management activities based on the injection of sulfur compounds into the stratosphere. The research topics will be addressed by exploiting the synergy of global satellite observations of stratospheric aerosol parameters (mainly in the optical spectral range) and of model simulations with explicit stratospheric aerosol microphysics. We will employ our own algorithms to retrieve aerosol parameters from measurements with past, current and future satellite instruments, including, e.g. OMPS-LP, SAGE III and SCIAMACHY. The model simulations will be mainly based on ICON-ART, but MAECHAM-HAM will also be employed to provide some quick model intercomparison data. The VolARC project is well connected to the other four projects of VolImpact, for example via the overarching science topics that will be addressed by multiple VolImpact projects. These topics are: (1) the aerosol particle size distribution, (2) volcanic H2O injections into the middle atmosphere and (3) radiative forcing. In addition, VolARC will be coordinating the seamless simulation activities across the entire research unit.