Aerosols from the Asian monsoon in the upper troposphere: sources, evolution, impacts

每年6月至9月，在地中海至西太平洋的大片区域内，有一层在14-18公里高度的气溶胶负荷增强，即亚洲对流层顶气溶胶层（ATAL）。这些粒子的组成及其对这一敏感海拔区域辐射平衡的意义存在很大的不确定性。唯一一次从这一层深处进行的空中观测是在2017年加德满都的StratoClim运动期间获得的。利用地球物理学研究飞机上GLORIA红外光谱仪的数据，我们发现固体硝酸铵（AN）颗粒在气溶胶质量中占相当大的一部分。由于GLORIA在这些高度同时观测前体气体氨（NH3）的独特能力，我们发现AN气溶胶层是通过对流向对流层上层注入大量的表面NH3来补给的。研究还表明，固体AN粒子是大气中最有效的冰核之一。为了促进PHILEAS活动，我们建议共同努力进行大气模拟和观测，以更好地约束ATAL颗粒的组成、起源、影响和命运，特别是关于它们的演变以及它们对北半球对流层上层和平流层下层的影响。通过对东地中海和北太平洋受季风影响的气团的测量，我们将能够用处理过的气溶胶和微量气体含量分析空气，从而补充从季风深处进行的平流层观测。为了检测和量化流出物中可能较少的气溶胶和微量气体，我们建议通过利用最近才可用的光谱数据来改进GLORIA对NH3和AN等的数据检索。进一步，我们建议将GLORIA光谱的分析扩展到硫酸盐气溶胶及其前体气体SO2。在模拟方面，我们将进一步发展ICON-ART全球天气和气候模式系统，以模拟包括各种气溶胶类型（硝酸盐，铵，硫酸盐，有机物，灰尘）的ATAL，从而考虑到固体AN的高冰成核潜力。将进行模式运行，以获得2023年季风期间ATAL发展的全球概况，以及针对相关活动期间量身定制的气溶胶-云-辐射相互作用的详细云解析视图。除了对PHILEAS活动的直接分析之外，这项工作将为从以前和未来HALO活动以及卫星观测的机载GLORIA观测中改进气溶胶检索奠定基础。此外，它将使ICON-ART成为可能，ICON-ART是德国的一个中心气候模式系统，用于模拟气溶胶过程以及与ATAL相关的气溶胶/云相互作用。

Each year, from June till September, a layer of enhanced aerosol loading at 14–18 km altitude resides in a large area extending from the Mediterranean to the western Pacific - the Asian Tropopause Aerosol Layer (ATAL). There are large uncertainties about the composition of these particles as well as their significance for the radiative balance in this sensitive altitude region. The only airborne observations from deep inside this layer have been acquired during the StratoClim campaign based in Kathmandu in 2017. Based on data from the infrared spectrometer GLORIA on the research aircraft Geophysica, we discovered that solid ammonium nitrate (AN) particles account for a considerable part of the aerosol mass. Due to the unique capability of GLORIA to observe simultaneously the precursor gas ammonia (NH3) at these altitudes, we showed that the AN aerosol layer is fed by convection injecting large amounts of NH3 from the surface into the upper troposphere. It has also been demonstrated that solid AN particles count among the most efficient ice nuclei present in the atmosphere. Contributing to the PHILEAS campaign, we propose a common effort of atmospheric modelling and observations to better constrain the composition, origin, impacts and fate of ATAL particles - especially with regard to their evolution as well as their influence on the Northern Hemisphere upper troposphere and lower stratosphere. By acquiring measurements of monsoon-influenced air-masses over the eastern Mediterranean as well as outflow over the northern Pacific we will be able to analyse air with processed aerosol and trace-gas content, thereby complementing the StratoClim observations from deep inside the monsoon. To detect and quantify the likely smaller amounts of aerosol and trace gases in the outflow, we propose to improve the GLORIA data retrieval of NH3 and AN, amongst others, by utilizing spectroscopic data which has become available only recently. Further, we propose to expand the analysis of GLORIA spectra to sulfate aerosols as well as their precursor gas SO2. On the modelling side, we will further develop the ICON-ART global weather and climate model system for simulating the ATAL including various aerosol types (nitrate, ammonium, sulphate, organics, dust), thereby considering the high ice nucleating potential of solid AN. Model runs will be performed to achieve a global overview over the development of the ATAL during the time of the monsoon 2023, as well as detailed cloud resolving views on the aerosol-cloud-radiation interactions tailored to relevant campaign periods. Beyond the direct analysis of the PHILEAS campaign, this work will lay the foundation for improved aerosol retrieval from airborne GLORIA observations of previous and future HALO campaigns as well as satellite observations. Further it will enable ICON-ART, one of the central climate model systems in Germany on simulating aerosol processes as well as aerosol/cloud interactions connected to the ATAL.