08 May 2023
 | 08 May 2023
Status: this preprint is currently under review for the journal AMT.

Next-generation ice nucleating particle sampling on aircraft: Characterization of the High-volume flow aERosol particle filter sAmpler (HERA)

Sarah Grawe, Conrad Jentzsch, Jonas Schaefer, Heike Wex, and Frank Stratmann

Abstract. Atmospheric ice nucleating particle (INP) concentration data from the free troposphere are sparse, but urgently needed to understand vertical transport processes of INPs and their influence on cloud formation and properties. Here, we introduce the new High-volume flow aERosol particle filter sAmpler (HERA) which was specially developed for installation on research aircraft and subsequent offline INP analysis. HERA is a modular system constisting of a sampling unit and a powerful pump unit and has several features which were integrated specifically for INP sampling. Firstly, the pump unit enables sampling at flow rates exceeding 100 L min−1, which is well above typical flow rates of aircraft INP sampling systems described in the literature (~10 L min−1). Consequently, required sampling times to capture rare, high-temperature INPs (≥-15 °C) are reduced in comparison to other systems and potential source regions of INPs can be confined more precisely. Secondly, the sampling unit is designed as a seven-way valve, enabling switching between six filter holders and a bypass with one filter being sampled at a time. In contrast to other aircraft INP sampling systems, the valve position is controlled remotely via software so that manual filter changes in-flight are eliminated and the potential for sample contamination is decreased. This design is compatible with a high degree of automation, i.e., triggering filter changes depending on parameters like flight altitude, geographical location, temperature, or time. In addition to the design and principle of operation of HERA, this paper presents laboratory characterization experiments with size-selected test substances, i.e., SNOMAX® and Arizona Test Dust. The particles were sampled on filters with HERA, varying either particle diameter (300 nm to 800 nm) or flow rate (10 L min−1 to 100 L min−1) between experiments. The subsequent offline INP analysis showed good agreement with literature data and comparable sampling efficiencies for all investigated particle sizes and flow rates. Furthermore, the deposition efficiency of atmospheric INPs in HERA was compared to a straightforward filter sampler and good agreement was found. Finally, results from the first campaign of HERA on the High Altitude and LOng range research aircraft (HALO) demonstrate the functionality of the new system in the context of aircraft application.

Sarah Grawe et al.

Status: open (until 14 Jun 2023)

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  • RC1: 'Comment on amt-2023-88', Gabor Vali, 27 May 2023 reply

Sarah Grawe et al.

Sarah Grawe et al.


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Short summary
Measurements of Ice Nucleating Particle (INP) concentrations are valuable for the simulation of cloud properties. In recent years, filter sampling in combination with offline INP measurements has become increasingly popular. However, most sampling is ground-based and the vertical transport of INPs is not well quantified. The High-volume flow aERosol particle filter sAmpler (HERA) for application on aircraft was developed to expand the sparse dataset of INP concentrations at cloud-level.