The Horizontal Ice Nucleation Chamber (HINC): INP measurements at conditions relevant for mixed-phase clouds at the High Altitude Research Station Jungfraujoch

Abstract

Abstract. In this work we describe the Horizontal Ice Nucleation Chamber (HINC) as a new instrument to measure ambient ice-nucleating particle (INP) concentrations for conditions relevant to mixed-phase clouds. Laboratory verification and validation experiments confirm the accuracy of the thermodynamic conditions of temperature (T ) and relative humidity (RH) in HINC with uncertainties in T of ± 0.4 K and in RH with respect to water (RH w ) of ±1.5 %, which translates into an uncertainty in RH with respect to ice (RH i ) of ±3.0 % at T > 235 K. For further validation of HINC as a field instrument, two measurement campaigns were conducted in winters 2015 and 2016 at the High Altitude Research Station Jungfraujoch (JFJ; Switzerland, 3580 m a.s.l.) to sample ambient INPs. During winters 2015 and 2016 the site encountered free-tropospheric conditions 92 and 79 % of the time, respectively. We measured INP concentrations at 242 K at water-subsaturated conditions (RH w = 94 %), relevant for the formation of ice clouds, and in the watersupersaturated regime (RH w = 104 %) to represent ice formation occurring under mixed-phase cloud conditions. In winters 2015 and 2016 the median INP concentrations at RH w = 94 % was below the minimum detectable concentration. At RH w = 104 %, INP concentrations were an order of magnitude higher, with median concentrations in winter 2015 of 2.8 per standard liter (std L −1 ; normalized to standard T of 273 K and pressure, p, of 1013 hPa) and 4.7 std L −1 in winter 2016. The measurements are in agreement with previous winter measurements obtained with the Portable Ice Nucleation Chamber (PINC) of 2.2 std L −1 at the same location. During winter 2015, two events caused the INP concentrations at RH w = 104 % to significantly increase above the campaign average. First, an increase to 72.1 std L −1 was measured during an event influenced by marine air, arriving at the JFJ from the North Sea and the Norwegian Sea. The contribution from anthropogenic or other sources can thereby not be ruled out. Second, INP concentrations up to 146.2 std L −1 were observed during a Saharan dust event. To our knowledge this is the first time that a clear enrichment in ambient INP concentration in remote regions of the atmosphere is observed during a time of marine air mass influence, suggesting the importance of marine particles on ice nucleation in the free troposphere.

The Impact of Cloud Processing on the Ice Nucleation Abilities of Soot Particles at Cirrus Temperatures

“…HINC1 is a continuous flow diffusion chamber (CFDC), which has previously been described in Lacher et al. () and Mahrt et al. () and is based on the design detailed in Kanji and Abbatt ().…”

“…Within HINC1 the soot particles were processed by exposing the aerosols to fixed conditions of RH and T. HINC1 is a continuous flow diffusion chamber (CFDC), which has previously been described in Lacher et al (2017) and Mahrt et al (2018) and is based on the design detailed in Kanji and Abbatt (2009). In brief, two ice coated horizontally oriented parallel plates are individually cooled, so that a linear T profile between the two plates is created, establishing a RH profile across the chamber.…”

New type of evidence for secondary ice formation at around −15 °C in mixed-phase clouds

“…Independent rime samples were collected with a plexiglass impactor plate (Lacher et al, 2017) suspended on the railing of the terrace at Jungfraujoch for a few to several hours (∼ 1-13 h). In total, 30 samples of aggregated rime droplets were collected between 15 February and 11 March.…”

Background Free‐Tropospheric Ice Nucleating Particle Concentrations at Mixed‐Phase Cloud Conditions

“…Comparisons to INP concentrations were done using averages of the latter over the respective sampling period of the cloud water samples. Details are given in Boose, Kanji et al (2016) and Lacher et al (2017). Samples were analyzed for 23 different trace metal concentrations, with an inductively coupled plasma mass spectrometer (Agilent, 7500cx) as discussed in Zipori et al (2012) and Zipori et al (2015).…”

“…This results in a seasonal cycle of aerosol particle concentration and population, as well as air mass origins. In addition, the JFJ is regularly influenced by Saharan dust events (SDEs) transported within the FT (Collaud Coen et al, 2004), as well as air masses which originated in the marine boundary layer (Boose, Kanji, et al, 2016;Cui et al, 2011;Lacher et al, 2017).…”