Preprints
https://doi.org/10.5194/amt-2022-270
https://doi.org/10.5194/amt-2022-270
 
07 Oct 2022
07 Oct 2022
Status: this preprint is currently under review for the journal AMT.

Improved Counting Statistics of an Ultrafine DMPS System

Dominik Stolzenburg1,2,, Tiia Laurila1,, Pasi Aalto1, Joonas Vanhanen3, Tuukka Petäjä1, and Juha Kangasluoma1 Dominik Stolzenburg et al.
  • 1Institute for Atmospheric and Earth System Research / Physics, Faculty of Science, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
  • 2Institute for Materials Chemistry, Faculty of Technical Chemistry, Technical University of Vienna, 1060 Vienna, Austria
  • 3Airmodus Ltd., 00560 Helsinki, Finland
  • These authors contributed equally to this work.

Abstract. Differential mobility particle size spectrometers (DMPS) are widely used to measure the aerosol number size-distribution. Especially during new particle formation (NPF) the dynamics of the ultrafine size-distribution determine the significance of the newly formed particles within the atmospheric system. A precision quantification of the size-distribution and derived quantities such as new particle formation and growth rates is therefore essential. However, size-distribution measurements in the sub-10 nm range suffer from high particle losses and are often derived from only a few counts in the DMPS system, making them subject to very high counting uncertainties. Here we show that a CPC (modified Airmodus A20) with a significantly higher aerosol optics flow rate compared to conventional ultrafine CPCs can greatly enhance the counting statistics in that size-range. Using Monte Carlo uncertainty estimates, we show that the uncertainties of the derived formation and growth rates can be reduced from 10–20 % down to 1 % by deployment of the high statistics CPC on a strong NPF event day. For weaker events and hence lower number concentrations, the counting statistics can result in a complete breakdown of the growth rate estimate with relative uncertainties as high as 75 %, while the improved DMPS still provides reasonable results at 10 % relative accuracy. In addition, we show that other sources of uncertainty are present in CPC measurements, which might become more important when the uncertainty from the counting statistics is less dominant. Altogether, our study shows that the analysis of NPF events could be greatly improved by the availability of higher counting statistics in the used aerosol detector of DMPS systems.

Dominik Stolzenburg et al.

Status: open (until 27 Dec 2022)

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Dominik Stolzenburg et al.

Dominik Stolzenburg et al.

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Short summary
Size-distributions measurements of ultrafine particles are of special interest as they can be used to estimate the atmospheric signficance of new particle formation, a process which is thought to influence the global climate. Here we show that improved counting statistics in size-distribution measurements through the usage of higher sampling flows can significantly reduce the uncertainties in such calculations.