Journal Article

PreJuSER-20028

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Results and recommendations from an intercomparison of six Hygroscopicity-TDMA systems

Massling, A. ; Niedermeier, N. ; Henning, T. ; Fors, E. O. ; Swietlicki, E. ; Ehn, M.FZJ* ; Hämeri, K. ; Villani, P. ; Laj, P. ; Good, N. ; McFiggans, G. ; Wiedensohler, A.

2011
Copernicus Katlenburg-Lindau

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Please use a persistent id in citations: http://hdl.handle.net/2128/7419  doi:10.5194/amt-4-485-2011

Abstract: The performance of six custom-built Hygrocopicity-Tandem Differential Mobility Analyser (H-TDMA) systems was investigated in the frame of an international calibration and intercomparison workshop held in Leipzig, February 2006. The goal of the workshop was to harmonise H-TDMA measurements and develop recommendations for atmospheric measurements and their data evaluation. The H-TDMA systems were compared in terms of the sizing of dry particles, relative humidity (RH) uncertainty, and consistency in determination of number fractions of different hygroscopic particle groups. The experiments were performed in an air-conditioned laboratory using ammonium sulphate particles or an external mixture of ammonium sulphate and soot particles.The sizing of dry particles of the six H-TDMA systems was within 0.2 to 4.2% of the selected particle diameter depending on investigated size and individual system. Measurements of ammonium sulphate aerosol found deviations equivalent to 4.5% RH from the set point of 90% RH compared to results from previous experiments in the literature. Evaluation of the number fraction of particles within the clearly separated growth factor modes of a laboratory generated externally mixed aerosol was done. The data from the H-TDMAs was analysed with a single fitting routine to investigate differences caused by the different data evaluation procedures used for each H-TDMA. The differences between the H-TDMAs were reduced from +12/-13% to +8/-6% when the same analysis routine was applied. We conclude that a common data evaluation procedure to determine number fractions of externally mixed aerosols will improve the comparability of H-TDMA measurements.It is recommended to ensure proper calibration of all flow, temperature and RH sensors in the systems. It is most important to thermally insulate the aerosol humidification unit and the second DMA and to monitor these temperatures to an accuracy of 0.2 degrees C. For the correct determination of external mixtures, it is necessary to take into account size-dependent losses due to diffusion in the plumbing between the DMAs and in the aerosol humidification unit.

Keyword(s): J

Note: The H-TDMA calibration and intercomparison workshop held at the WMO-GAW World Calibration Centre for Aerosol Physics, Leipzig, Germany, was supported by the EU-projects ACCENT (GOCE-CT-2004-505337), EUSAAR (RII3-CT-2006-14 026140) and by the German Federal Environment Agency (FKZ: 351 01 046: GAW World Calibration Centre).

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Contributing Institute(s):

1. Troposphäre (IEK-8)

Research Program(s):

1. Atmosphäre und Klima (P23)

Appears in the scientific report 2012

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Database coverage:
; ; ; Current Contents - Social and Behavioral Sciences ; JCR ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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