Measurements of ice nucleating particles in remote locations of the atmosphere
Abstract
Clouds containing ice play a key role in precipitation formation and impact the Earth´s radiation budget. However, such clouds are very complex systems, which is why the knowledge on the formation, the concentration and the fate of ice crystals is still uncertain. In the absence of homogeneous freezing, the first formation of ice crystals is initiated by ice nucleating particles (INPs), and a better understanding of their sources and atmospheric concentration is needed. High-time resolution online INP instruments are desirable for such a purpose, but they require elaborate operation. Here we show ambient measurements from a long-term study with a continuous flow diffusion chamber (HINC; Horizontal Ice Nucleation Chamber), and furthermore present work from a newly developed expansion chamber (PINE; Portable Ice Nucleation Chamber).
During intensive field measurements at a free tropospheric site (Jungfraujoch, 3580 m a.s.l.), INPs were measured with HINC at 242 K relevant for the formation of mixed phase clouds. INP concentrations in the background free-troposphere show a reduced variability between 0.5 - 10 stdL-1, and without a clear seasonal trend. Only during Saharan dust events, and air masses influenced by marine origin and the local boundary layer, elevated INP concentrations were measured. While a common parameterization based on particle concentrations > 0.5 µm could at best describe ~50% of the measured INP concentrations, we find that the best estimator for INPs is the available aerosol surface area. The results from these field campaigns give insights into INP characteristics and are motivation for more measurements on a monitoring basis and at other remote atmospheric locations. A new type of INP counter is presented here, the PINE, an expansion chamber based on the design of the AIDA (Aerosol Interaction and Dynamics in the Atmosphere). The instrument can run continuously and semi-autonomously, and is able to quantify INP concentrations with a high time resolution of ~5 minutes. First tests and results from a field activity are presented, demonstrating PINE´s potential to monitor INPs.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A51D..01L
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES