Preprints
https://doi.org/10.5194/amt-2021-189
https://doi.org/10.5194/amt-2021-189

  21 Jul 2021

21 Jul 2021

Review status: this preprint is currently under review for the journal AMT.

Calibration and evaluation of broad supersaturation scanning (BS2) cloud condensation nuclei counter for rapid measurement of particle hygroscopicity and CCN activity

Najin Kim1, Yafang Cheng2, Nan Ma3, Mira L. Pöhlker1, Thomas Klimach1, Thomas F. Mentel4, Ovid O. Krüger1, Ulrich Pöschl1, and Hang Su1 Najin Kim et al.
  • 1Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, 55128, Germany
  • 2Minerva Research Group, Max Planck Institute for Chemistry, Mainz, 55128, Germany
  • 3Center for Air Pollution and Climate Change Research (APCC), Institute for Environmental and Climate Research (ECI), Jinan University, Guangzhou, 511443, China
  • 4Institute of Energy and Climate Research, IEK-8: Troposhere, Forschungzentrum Jülich GmbH, Jülich, 52425, Germany

Abstract. For understanding and assessing aerosol-cloud interactions and their impact on climate, reliable measurement data of aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity are required. The CCN activity of aerosol particles can be determined by scanning particle size and supersaturation (S) in CCN measurements. Compared to the existing differential mobility analyzer (DMA)-CCN activity measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of S simultaneously, can measure the CCN activity with a high time-resolution. Based on a monotonic relation between the activation supersaturation of aerosol particles (Saerosol) and the activated fraction (Fact) of the BS2-CCN measurement, we can derive κ, a single hygroscopicity parameter, directly. Here, we describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve (FactSaerosol). For calibration, size-resolved CCN measurements with ammonium sulfate and sodium chloride particles are performed under the three different thermal gradient (dT) conditions (dT = 6, 8, and 10 K). We point out key processes that can affect the calibration curve and thereby need to be considered as follows: First, the shape of the calibration curve is primarily influenced by Smax, the maximum S in the activation tube. We need to determine appropriate Smax depending on particle size and κ to be investigated. To minimize the effect of multiply charged particles, small geometric mean diameter (𝐷𝑔) and 𝜎𝑔 geometric standard deviation (𝜎𝑔) in number size distribution are recommended when generating the calibration aerosols. Last, Fact is affected by particle number concentration and has a decreasing rate of 0.02/100 cm−3 due to the water consumption in the activation tube. For evaluating the BS2-CCN system, inter-comparison experiments between typical DMA-CCN and BS2-CCN measurement were performed with the laboratory-generated aerosol mixture and ambient aerosols. Good agreements of κ values between DMA-CCN and BS2-CCN measurements for both experiments show that the BS2-CCN system can measure CCN activity well compared to the existing measurement, and can measure a broad range of hygroscopicity distribution with a high time-resolution (~1 second vs. few minutes for a standard CCN activity measurement). As the hygroscopicity can be used as a proxy for the chemical composition, our method can also serve as a complementary approach for fast and size-resolved detection/estimation of aerosol chemical composition.

Najin Kim et al.

Status: open (until 25 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Najin Kim et al.

Viewed

Total article views: 161 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
123 34 4 161 10 1 3
  • HTML: 123
  • PDF: 34
  • XML: 4
  • Total: 161
  • Supplement: 10
  • BibTeX: 1
  • EndNote: 3
Views and downloads (calculated since 21 Jul 2021)
Cumulative views and downloads (calculated since 21 Jul 2021)

Viewed (geographical distribution)

Total article views: 156 (including HTML, PDF, and XML) Thereof 156 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 29 Jul 2021
Download
Short summary
Broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of supersaturation simultaneously, can measure a broad range of CCN activity distribution with a high-time resolution. We describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve. For evaluating the BS2-CCN system, inter-comparison experiments between typical DMA-CCN and BS2-CCN measurement were performed.