Abstract. A growing number of general circulation models are adapting interactive sulfur and aerosol schemes to improve the representation of relevant physical and chemical processes and associated feedbacks. They are motivated by investigations of climate response to major volcanic eruptions and potential solar geoengineering scenarios. However, uncertainties in these schemes are not well constrained. Stratospheric sulfate is modulated by emissions of sulfur-containing species of anthropogenic and natural origin, including volcanic activity. While the effects of volcanic eruptions have been studied in the framework of global model intercomparisons, the background conditions of the sulfur cycle have not been addressed in such a way. Here, we fill this gap by analyzing the distribution of the main sulfur species in nine global atmospheric aerosol models for a volcanically quiescent period. We use observational data to evaluate model results. Overall, models agree that the three dominant sulfur species in terms of burdens (sulfate aerosol, OCS, and SO2) make up about 98 % stratospheric sulfur and 95 % tropospheric sulfur. However, models vary considerably in the partitioning between these species. Models agree that anthropogenic emission of SO2 strongly affects the sulfate aerosol burden in the northern hemispheric troposphere, while its importance is very uncertain in other regions, where emissions are much lower. Sulfate aerosol is the main deposited species in all models, but the values deviate by a factor of 2. Additionally, the partitioning between wet and dry deposition fluxes is highly model dependent. Inter-model variability in the sulfur species is low in the tropics and increases towards the poles. Differences are largest in the dynamically active northern hemispheric extratropical region and could be attributed to the representation of the stratospheric circulation. The differences in the atmospheric sulfur budget among the models arise from the representation of both chemical and dynamical processes, whose interplay complicates the bias attribution. Several problematic points identified for individual models are related to the specifics of the chemistry schemes, model resolution, and representation of cross-tropopause transport in the extratropics. Further model intercomparison research is needed with a focus on the clarification of the reasons for biases, given the importance of this topic for the stratospheric aerosol injection studies.

中文翻译：

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多模型框架中全球大气背景硫收支分析

摘要。越来越多的大气环流模型正在采用交互式硫和气溶胶方案，以改善相关物理和化学过程以及相关反馈的表示。他们的动机是调查主要火山喷发的气候响应和潜在的太阳能地球工程情景。然而，这些方案的不确定性并没有得到很好的限制。平流层硫酸盐受到人为和自然来源的含硫物质（包括火山活动）的排放的调节。虽然在全球模型比较的框架下研究了火山喷发的影响，但硫循环的背景条件尚未以这种方式得到解决。在这里，我们通过分析火山静止期九个全球大气气溶胶模型中主要硫物质的分布来填补这一空白。我们使用观察数据来评估模型结果。总体而言，模型一致认为，就负荷而言，三种主要的硫物质（硫酸盐气溶胶、OCS 和 SO2）约占平流层硫的 98% 和对流层硫的 95%。然而，模型在这些物种之间的划分方面差异很大。模型一致认为，人为排放的二氧化硫强烈影响北半球对流层的硫酸盐气溶胶负荷，而其重要性在排放量低得多的其他地区则非常不确定。硫酸盐气溶胶是所有模型中的主要沉积物质，但其值偏差为 2 倍。此外，湿沉积通量和干沉积通量之间的划分高度依赖于模型。硫物质的模型间变异性在热带地区较低，向两极地区增加。动态活跃的北半球温带地区的差异最大，可能归因于平流层环流的表现。模型之间大气硫收支的差异源于化学和动力学过程的表示，它们的相互作用使偏差归因变得复杂。为各个模型确定的几个问题点与化学方案的细节、模型分辨率以及温带跨对流层顶传输的表示有关。鉴于该主题对于平流层气溶胶注入研究的重要性，需要进一步进行模型比较研究，重点是澄清偏差原因。