Articles | Volume 16, issue 13
Atmos. Chem. Phys., 16, 8341–8351, 2016

Special issue: BACCHUS – Impact of Biogenic versus Anthropogenic emissions...

Atmos. Chem. Phys., 16, 8341–8351, 2016

Research article 11 Jul 2016

Research article | 11 Jul 2016

Predicting abundance and variability of ice nucleating particles in precipitation at the high-altitude observatory Jungfraujoch

Emiliano Stopelli1, Franz Conen1, Cindy E. Morris2, Erik Herrmann3, Stephan Henne4, Martin Steinbacher4, and Christine Alewell1 Emiliano Stopelli et al.
  • 1Environmental Geosciences, University of Basel, 4056 Basel, Switzerland
  • 2INRA, UR 0407 Plant Pathology Research Unit, 84143 Montfavet, France
  • 3PSI, Laboratory of Atmospheric Chemistry, 5232 Villigen, Switzerland
  • 4Empa, Laboratory for Air Pollution/Environmental Technology, 8600 Dübendorf, Switzerland

Abstract. Nucleation of ice affects the properties of clouds and the formation of precipitation. Quantitative data on how ice nucleating particles (INPs) determine the distribution, occurrence and intensity of precipitation are still scarce. INPs active at −8 °C (INPs−8) were observed for 2 years in precipitation samples at the High-Altitude Research Station Jungfraujoch (Switzerland) at 3580 m a.s.l. Several environmental parameters were scanned for their capability to predict the observed abundance and variability of INPs−8. Those singularly presenting the best correlations with observed number of INPs−8 (residual fraction of water vapour, wind speed, air temperature, number of particles with diameter larger than 0.5 µm, season, and source region of particles) were implemented as potential predictor variables in statistical multiple linear regression models. These models were calibrated with 84 precipitation samples collected during the first year of observations; their predictive power was successively validated on the set of 15 precipitation samples collected during the second year. The model performing best in calibration and validation explains more than 75 % of the whole variability of INPs−8 in precipitation and indicates that a high abundance of INPs−8 is to be expected whenever high wind speed coincides with air masses having experienced little or no precipitation prior to sampling. Such conditions occur during frontal passages, often accompanied by precipitation. Therefore, the circumstances when INPs−8 could be sufficiently abundant to initiate the ice phase in clouds may frequently coincide with meteorological conditions favourable to the onset of precipitation events.

Short summary
Knowing the variability of ice nucleating particles (INPs) helps determining their role in the formation of precipitation. Here we describe and predict the concentrations of INPs active at −8 °C in precipitation samples collected at Jungfraujoch (CH, 3580 m a.s.l.). A high abundance of these INPs can be expected whenever a coincidence of high wind speed and first precipitation from an air mass occurs. This expands the set of conditions where such INPs could affect the onset of precipitation.
Final-revised paper