Development and characterization of an ice-selecting pumped counterflow virtual impactor (IS-PCVI) to study ice crystal residuals
Name
Cziczo_Development and characterization.pdf
Size
1.81 MB
Format
Adobe PDF
Checksum (MD5)
c9a51850e3fccd42ac1ddb10a982716b
Author(s)
Hiranuma, Naruki
Möhler, Ottmar
Kulkarni, Gourihar
Schnaiter, Martin
Vogt, Steffen
Vochezer, Paul
Järvinen, Emma
Wagner, Robert
Bell, David M.
Wilson, Jacqueline
Date Issued
August 2016
Journal
Atmospheric Measurement Techniques
Publisher
Copernicus GmbH
Citation
Hiranuma, Naruki et al. “Development and Characterization of an Ice-Selecting Pumped Counterflow Virtual Impactor (IS-PCVI) to Study Ice Crystal Residuals.” Atmospheric Measurement Techniques 9.8 (2016): 3817–3836.
Version
Final published version
Abstract
Separation of particles that play a role in cloud activation and ice nucleation from interstitial aerosols has become necessary to further understand aerosol-cloud interactions. The pumped counterflow virtual impactor (PCVI), which uses a vacuum pump to accelerate the particles and increase their momentum, provides an accessible option for dynamic and inertial separation of cloud elements. However, the use of a traditional PCVI to extract large cloud hydrometeors is difficult mainly due to its small cut-size diameters (< 5 µm). Here, for the first time we describe a development of an ice-selecting PCVI (IS-PCVI) to separate ice in controlled mixed-phase cloud system based on the particle inertia with the cut-off diameter ≥ 10 µm. We also present its laboratory application demonstrating the use of the impactor under a wide range of temperature and humidity conditions. The computational fluid dynamics simulations were initially carried out to guide the design of the IS-PCVI. After fabrication, a series of validation laboratory experiments were performed coupled with the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) expansion cloud simulation chamber. In the AIDA chamber, test aerosol particles were exposed to the ice supersaturation conditions (i.e., RHice > 100 %), where a mixture of droplets and ice crystals was formed during the expansion experiment. In parallel, the flow conditions of the IS-PCVI were actively controlled, such that it separated ice crystals from a mixture of ice crystals and cloud droplets, which were of diameter ≥ 10 µm. These large ice crystals were passed through the heated evaporation section to remove the water content. Afterwards, the residuals were characterized with a suite of online and offline instruments downstream of the IS-PCVI. These results were used to assess the optimized operating parameters of the device in terms of (1) the critical cut-size diameter, (2) the transmission efficiency and (3) the counterflow-to-input flow ratio. Particle losses were characterized by comparing the residual number concentration to the rejected interstitial particle number concentration. Overall results suggest that the IS-PCVI enables inertial separation of particles with a volume-equivalent particle size in the range of ~ 10–30 µm in diameter with small inadvertent intrusion (~ 5 %) of unwanted particles.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Terms of Use
Creative Commons Attribution 3.0 License
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.5194/amt-9-3817-2016
