Rainfall drives atmospheric ice-nucleating particles in the coastal climate of southern Norway

Author(s): Franz Conen, Sabine Eckhardt, Hans Gundersen, Andreas Stohl, Karl Espen Yttri
Abstract: Ice-nucleating particles (INPs) active at modest supercooling (e.g. -8 °C; INP_-8/ can transform clouds from liquid to mixed phase, even at very small number concentrations (<10m^-3/. Over the course of 15 months, we found very similar patterns in weekly concentrations of INP_-8 in PM₁₀ (medianD1.7m^-3, maximumD10.1m^-3/ and weekly amounts of rainfall (medianD28 mm, maximum D153 mm) at Birkenes, southern Norway. Most INP_-8 were probably aerosolised locally by the impact of raindrops on plant, litter and soil surfaces. Major snowfall and heavy rain onto snow-covered ground were not mirrored by enhanced numbers of INP_-8. Further, transport model calculations for large (>4m^-3/ and small (<4m^-3/ numbers of INP_-8 revealed that potential source regions likely to provide precipitation to southern Norway were associated with large numbers of INP_-8. The proportion of land cover and land use type in potential source regions was similar for large and small numbers of INP_-8. In PM2:5 we found consistently about half as many INP_-8 as in PM₁₀. From mid-May to mid-September, INP_-8 correlated positively with the fungal spore markers arabitol and mannitol, suggesting that some fraction of INP_-8 during that period may consist of fungal spores. In the future, warmer winters with more rain instead of snow may enhance airborne concentrations of INP_-8 during the cold season in southern Norway and in other regions with a similar climate.
Organisation(s): Department of Meteorology and Geophysics
External organisation(s): Universität Basel, Norwegian Institute for Air Research
Journal: Atmospheric Chemistry and Physics
Volume: 17
Pages: 11065-11073
No. of pages: 9
ISSN: 1680-7316
DOI: https://doi.org/10.5194/acp-17-11065-2017
Publication date: 09-2017
Peer reviewed: Yes
Austrian Fields of Science 2012: 105206 Meteorology
ASJC Scopus subject areas: Atmospheric Science
Sustainable Development Goals: SDG 13 - Climate Action, SDG 15 - Life on Land
Portal url: https://ucrisportal.univie.ac.at/en/publications/2b509dc1-25e3-4fbf-a24f-a39ba490f65e

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