The Portable Ice Nucleation Experiment (PINE): a new commercially available instrument to advance atmospheric ice nucleation research

Description

We present our first laboratory test results of a new commercially available instrument, the so-called PINE. The PINE instrument was developed by the Bilfinger Noell company in technical collaboration with Karlsruhe Institute of Technology (KIT) and University of Leeds to advance online atmospheric ice nucleation research at high temperatures nominally above -15 °C, where “clear and significant research issues remain” (DeMott et al., 2011, Bull. Amer. Meteorol. Soc.). This portable expansion chamber is developed based on the design of the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber, which is a renowned chamber for studying ice clouds in a controlled setting with respect to both temperature and saturation, at KIT. A unique aspect of the PINE chamber includes its automated temperature-controlled operation (>-60 °C), minimum background particle concentration and its compact size, promising stand-alone operation even at remote locations with minimal on-site supervision. This system also simulates the close to reality atmospheric cloud parcel via expansion cooling without assuming the water supersaturation fields that other techniques assume. Using this instrument is critical to minimize error sources in high-temperature ice-nucleating particles (INP) observational data (i.e., temperatures above -15 °C). In this study, PINE sampled the same aerosol type from the AIDA chamber, and results were analyzed at same conditions. This allowed for a direct validation of PINE to AIDA. Accordingly, we have verified a minimum detection of INP concentration ≤0.2 L^-1 and high-temporal-resolution (a turn-over time of ~5 min for subsequent expansions) over a range of approx. 5 °C of a single expansion to provide immersion freezing data. The PINE instrument will be deployed at the ARM’s Southern Great Plains in Summer and Fall 2019 for online quantification of INP concentrations (i.e., the ARM Examining the Ice-nucleating Particles from SGP campaign). In addition, recently developed off-line INP extraction/detection techniques, the so-called West Texas Cryogenic Refrigerator Applied to Freezing Test (WT-CRAFT) system, has been improved for high-temperature application to cover the wide mixed-phase cloud temperature range, complementing the PINE chamber measurements. A combination of PINE and WT-CRAFT measurements provide accurate data as a basis for model parameterization.