Developments concerning the physical and chemical characterization of ice nucleating aerosol particles with HALO: High volume flow aerosol particle sampling system, automated freezing array, and analytical methods

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The proposed project is based on and extents investigations to be carried out in the framework of DFG Transregional Collaborative Research Centre TR 172, entitled "ArctiC Amplification: Relevant Atmospheric and SurfaCe Processes, and Feedback Mechanisms" (AC)3, and here especially project B04 "Ship-based physical and chemical characteristics and sources of Arctic ice nucleating particles and cloud condensation nuclei". In TR 172, B04, the goal is to gain information (number concentration; chemical nature, mineral or organic; origin, local sources or long range transport) on Arctic ice nucleating particles (INP), by means of ship-borne measurements. However, these measurements can only be regarded as a first step, and measurements at different altitudes (inside the boundary layer and in the free troposphere) are mandatory to further increase our understanding of Arctic aerosol and cloud interactions in general, and Arctic cloud glaciation in particular. Therefore, activities carried out in TR 172 should be complemented by future INP-related measurements on board the research aircraft HALO. Specifically we are aiming at determining the number concentration of Arctic INP at higher altitudes, and finding indications concerning the INPs origin / sources by means of chemical particle composition analysis. To achieve this, in the framework of the present proposal we will focus on the development, testing and certification of a suitable high volume flow filter sampling system, for sub- and super-micron aerosol particles for operation on board the German research airplane HALO. The sampling system will mainly consist of an adapted version of the already existing (but not yet certified) "micrometre aerosol inlet" (MAI), and a still to be developed high volume flow filter sampler. Consideration of high volume flows (order 100 l/min) is required because of the expected low aerosol particle and INP number concentrations, and the resulting need for the collection of large air volumes. The first scientific application of the developed system is planned for the future ARCTIC-HALO campaign, foreseen for the second phase of TR 172 years (2020-2023), and will deal with the investigation of INP properties in the Arctic. However, after its successful development, the sampling system can be operated on other missions in which sampling of sub- and super-micron sized aerosol particles is required. For carrying out the planned works, we apply for one 75%, and one 50% PostDoc-positions for 3 years as well as the costs for adaptation and certification of the high volume aerosol inlet and the filter sampler. All other direct costs will be funded from the TROPOS internal budget.