Abstract
Abstract. In situ single particle analysis of ice particle residuals (IPRs) and out-of-cloud aerosol particles was conducted by means of laser ablation mass spectrometry during the intensive INUIT-JFJ/CLACE campaign at the high alpine research station Jungfraujoch (3580 m a.s.l.) in January–February 2013. During the 4-week campaign more than 70 000 out-of-cloud aerosol particles and 595 IPRs were analyzed covering a particle size diameter range from 100 nm to 3 µm. The IPRs were sampled during 273 h while the station was covered by mixed-phase clouds at ambient temperatures between −27 and −6 °C. The identification of particle types is based on laboratory studies of different types of biological, mineral and anthropogenic aerosol particles. The outcome of these laboratory studies was characteristic marker peaks for each investigated particle type. These marker peaks were applied to the field data. In the sampled IPRs we identified a larger number fraction of primary aerosol particles, like soil dust (13 ± 5 %) and minerals (11 ± 5 %), in comparison to out-of-cloud aerosol particles (2.4 ± 0.4 and 0.4 ± 0.1 %, respectively). Additionally, anthropogenic aerosol particles, such as particles from industrial emissions and lead-containing particles, were found to be more abundant in the IPRs than in the out-of-cloud aerosol. In the out-of-cloud aerosol we identified a large fraction of aged particles (31 ± 5 %), including organic material and secondary inorganics, whereas this particle type was much less abundant (2.7 ± 1.3 %) in the IPRs. In a selected subset of the data where a direct comparison between out-of-cloud aerosol particles and IPRs in air masses with similar origin was possible, a pronounced enhancement of biological particles was found in the IPRs.
Highlights
Depending on their chemical and microphysical properties aerosol particles have a strong impact on the solar radiation budget, an influence on the lifetime of clouds and on precipitation
For the ice particle residuals (IPRs) data set, where the absolute number of particles is much lower, it was possible to do a more detailed inspection of the clusters: we inspected one cluster assigned to biological particles, where we found that 28 out of 76 were uncertain (37 %), and one cluster of the PAH/soot particle type, where 9 out of 23 spectra were uncertain (40 %)
For the identification of specific particle types the marker peaks that resulted from the laboratory studies were applied to the Jungfraujoch data
Summary
Depending on their chemical and microphysical properties aerosol particles have a strong impact on the solar radiation budget, an influence on the lifetime of clouds and on precipitation (direct and indirect effect; Lohmann and Feichter, 2005). In the midlatitudes the formation of precipitation occurs mainly via the ice phase. Ice formation can be initiated in the atmosphere either homogeneously or heterogeneously. Spontaneous freezing of cloud droplets at temperatures lower than −37 ◦C without any catalysts is called homogeneous freezing (Cantrell and Heymsfield, 2005). At temperatures > −37 ◦C only heterogeneous freezing can take place, with ice nucleation particles (INPs) playing the key role by initiating the freezing process. In mixedphase clouds, supercooled cloud droplets and ice crystals coexist at temperatures between −37 and 0 ◦C.
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