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  Microphysical properties of synoptic-scale polar stratospheric clouds: in situ measurements of unexpectedly large HNO3-containing particles in the Arctic vortex

Molleker, S., Borrmann, S., Schlager, H., Luo, B., Frey, W., Klingebiel, M., et al. (2014). Microphysical properties of synoptic-scale polar stratospheric clouds: in situ measurements of unexpectedly large HNO3-containing particles in the Arctic vortex. Atmospheric Chemistry and Physics, 14(19), 10785-10801. doi:10.5194/acp-14-10785-2014.

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Molleker, S.1, Author           
Borrmann, S.1, Author           
Schlager, H.2, Author
Luo, B.2, Author
Frey, W.1, Author           
Klingebiel, M.2, Author
Weigel, R.2, Author
Ebert, M.2, Author
Mitev, V.2, Author
Matthey, R.2, Author
Woiwode, W.2, Author
Oelhaf, H.2, Author
Dörnbrack, A.2, Author
Stratmann, G.2, Author
Grooß, J.-U.2, Author
Günther, G.2, Author
Vogel, B.2, Author
Müller, R.2, Author
Krämer, M.2, Author
Meyer, J.2, Author
Cairo, F.2, Author more..
1Particle Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826291              
2external, ou_persistent22              


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 Abstract: In January 2010 and December 2011, synopticscale polar stratospheric cloud (PSC) fields were probed during seven flights of the high-altitude research aircraft M-55 Geophysica within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interaction) and the ESSenCe (ESSenCe: ESA Sounder Campaign) projects. Particle size distributions in a diameter range between 0.46 and 40 mu m were recorded by four different optical in situ instruments. Three of these particle instruments are based on the detection of forward-scattered light by single particles. The fourth instrument is a grayscale optical array imaging probe. Optical particle diameters of up to 35 mu m were detected with particle number densities and total particle volumes exceeding previous Arctic measurements. Also, gas-phase and particle-bound NOy was measured, as well as water vapor concentrations. The optical characteristics of the clouds were measured by the remote sensing lidar MAL (Miniature Aerosol Lidar) and by the in situ backscatter sonde MAS (Multiwavelength Aerosol Scatterometer), showing the synoptic scale of the encountered PSCs. The particle mode below 2 mu m in size diameter has been identified as supercooled ternary solution (STS) droplets. The PSC particles in the size range above 2 mu m in diameter are considered to consist of nitric acid hydrates, and the particles' high HNO3 content was confirmed by the NOy instrument. Assuming a particle composition of nitric acid trihydrate (NAT), the optically measured size distributions result in particle-phase HNO3 mixing ratios exceeding available stratospheric values. Therefore the measurement uncertainties concerning probable overestimations of measured particle sizes and volumes are discussed in detail. We hypothesize that either a strong asphericity or an alternate particle composition (e.g., water ice coated with NAT) could explain our observations. In particular, with respect to the denitrification by sedimentation of large HNO3-containing particles, generally considered to be NAT, our new measurements raise questions concerning composition, shape and nucleation pathways. Answering these would improve the numerical simulation of PSC microphysical processes like cloud particle formation, growth and denitrification, which is necessary for better predictions of future polar ozone losses, especially under changing global climate conditions. Generally, it seems that the occurrence of large NAT particles sometimes termed "NAT rocks" - are a regular feature of synoptic-scale PSCs in the Arctic.


 Dates: 2014
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: ISI: 000344164800025
DOI: 10.5194/acp-14-10785-2014
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Title: Atmospheric Chemistry and Physics
Source Genre: Journal
Publ. Info: Katlenburg-Lindau, Germany : European Geosciences Union
Pages: - Volume / Issue: 14 (19) Sequence Number: - Start / End Page: 10785 - 10801 Identifier: ISSN: 1680-7316
CoNE: https://pure.mpg.de/cone/journals/resource/111030403014016