Developing an on-line parameterization approach for predicting the ambient organic aerosol hygroscopicity based on High- Resolution AMS measurements

大气气溶胶粒子的吸水能力（吸湿性）驱动了若干大气过程，例如粒子光散射、云滴形成、云凝结核（CCN）激活、改变水文循环以及云辐射强迫。尽管有机气溶胶在大气和气候中发挥着关键作用，但对于有机气溶胶对总体吸湿性的贡献，仍然存在很大的认识差距，有机气溶胶占亚微米颗粒质量浓度的较大部分。以下研究建议提出了一种有机气溶胶颗粒吸湿特性参数化的原始方法，使用基于高分辨率-飞行时间-气溶胶质谱仪（HR-ToF-AMS）测量的有机质谱分析的在线化学函数概念。该参数化的开发将基于加湿吸湿串联微分分析仪（HTDMA）和HR-ToF-AMS测量的组合，采用双重但互补的方法。为此，将对具有目标官能团的化合物和各种有机标准品的混合物进行密集的实验室筛选。与此同时，还将采用一种基于先前TROPOS实地活动的机器学习方法，该方法将两种仪器整合在一起。将对这两种方法进行比较，以便在研究中进行最终验证。然后，将在两个现场活动中验证这种参数化，每个活动都致力于一种特定类型的有机气溶胶：Melpitz（德国）的生物气溶胶为主的环境和SIRTA（法国）的城市气溶胶为主的环境，这两种仪器将在本项目中部署。将通过结合HR-ToF-AMS（有机和无机气溶胶）和蒸发仪（等效黑碳）的光学测量值来估计环境气溶胶在线吸湿性，然后与HTDMA测量的吸湿性进行比较。利用HR-ToF-AMS的高分辨率和单位质谱分辨率，以及在两个选定的现场站点存在气溶胶化学形态监测器（ACSM），该方法也将针对ACSM进行优化。因此，将为这两种仪器（HR-ToF-AMS和ACSM）开发一个自动程序，以便在气溶胶、云和痕量气体研究基础设施网络（ACTRIS）ACSM网络上进一步实施，为欧洲近实时和长期的散装气溶胶吸湿性测量提供一个独特的机会。

Several atmospheric processes are driven by water take-up ability (hygroscopicity) of the atmospheric aerosol particles such particle light scattering, cloud droplet formation, activation of cloud condensation nuclei (CCN), altering the hydrological cycle as well as the cloud radiative forcing. Despite its crucial role on the atmosphere and climate, there is still a large disparity of knowledge regarding the contribution of the organic aerosol, which constitutes a larger part of the sub-micrometer particle mass concentration, to the overall hygroscopicity. The following research proposal propounds an original approach of the parameterization of the hygroscopic properties of organic aerosol particles, using an online chemical function concept based on the organic mass spectra analysis from High Resolution-Time of Flight-Aerosol Mass Spectrometer (HR-ToF-AMS) measurements. The development of this parameterization will be based on a combination of Humidified Hygroscopic Tandem Differential Analyzer (HTDMA) and HR-ToF-AMS measurements in a dual, but complementary approach. For this, an intensive laboratory screening of chemical compounds with targeted functional groups and a mixture of varied organic standards will be conducted. Simultaneously, a machine learning approach based on previous TROPOS field campaigns, which integrated both the instruments will be carried out. Comparison between the two approaches will be made for final validation in the study. This parameterization will be then validated in two field campaigns each of them dedicated to a specific type of organic aerosol: a biogenic aerosol dominated environment at Melpitz (Germany) and an urban aerosol dominated environment at SIRTA (France), where both instruments will be deployed within this project. The ambient aerosol online hygroscopicity will be estimated by combining HR-ToF-AMS (organic and inorganic aerosol) and optical measurements from aethalometer (equivalent black carbon) and then be compared to the one measured by HTDMA. Taking the advantage of the High-resolution and Unit mass spectra resolution of the HR-ToF-AMS, and the presence of Aerosol Chemical Speciation Monitor (ACSM) at both selected field sites, where the method will be also optimized for the ACSM. Consequently, an automatic routine will be developed for both instruments (HR-ToF-AMS and ACSM) to be further implemented on the Aerosols, Clouds, and Trace gases Research Infrastructure Network (ACTRIS) ACSM network to provide a unique opportunity for a near-real-time and long-term bulk aerosol hygroscopicity measurement over Europe.