Instrument artifacts lead to uncertainties in parameterizations of cloud condensation nucleation

Autor: J. A. Mirrielees, S. D. Brooks
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Atmospheric Measurement Techniques, Vol 11, Pp 6389-6407 (2018)
Druh dokumentu: article
ISSN: 1867-1381
1867-8548
DOI: 10.5194/amt-11-6389-2018
Popis: The concentrations of cloud condensation nuclei (CCN) modulate cloud properties, rainfall location and intensity, and climate forcings. This work assesses uncertainties in CCN measurements and the apparent hygroscopicity parameter (κapp), which is widely used to represent CCN populations in climate models. CCN measurements require accurate operation of three instruments: the CCN instrument, the differential mobility analyzer (DMA), and the condensation particle counter (CPC). Assessment of DMA operation showed that varying the ratio of aerosol to sheath flow from 0.05 to 0.30 resulted in discrepancies between the κapp values calculated from CCN measurements and the literature value. Discrepancies were found to increase from  sheath flow) than predicted. For the CPC instrument, undercounting occurred at high concentrations, resulting in calculated κapp lower than the literature values. Lastly, undercounting by CCN instruments at high concentration was also assessed, taking the effect of supersaturation on counting efficiency into account. Under recommended operating conditions, the combined DMA, CPC, and CCN uncertainties in κapp are 1.2 % or less for 25 to 200 nm diameter aerosols.
Databáze: Directory of Open Access Journals
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