Ground-based measurements of immersion freezing in the eastern Mediterranean

Ardon‐Dryer, Karin; Levin, Zev

doi:10.5194/acp-14-5217-2014

Cited by 58 publications

(68 citation statements)

References 91 publications

(101 reference statements)

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“…In the CRAFT system, droplets were placed on a semi-solid hydrophobic surface (a thin Vaseline layer). It is expected that the Vaseline coating on a cold stage can play a key role in preventing the influence of frost growth related to freezing of neighboring droplets as well as water vapor deposition on the surface of the substrate3435. On the other hand, many other studies have employed solid hydrophobic substrates; for example, 96-well microtiter plates in the CSU-IS924 and hydrophobized glass/silicon substrates in the BINARY25, NIPI2627, FRIDGE3033 and NC State-CS828.…”

Section: Discussionmentioning

confidence: 99%

An improved approach for measuring immersion freezing in large droplets over a wide temperature range

Tobo

2016

Sci Rep

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Immersion freezing (ice nucleation by particles immersed in supercooled water) is a key process for forming ice in mixed-phase clouds. Immersion freezing experiments with particles in microliter-sized (millimeter-sized) water droplets are often applied to detecting very small numbers of ice nucleating particles (INPs). However, the application of such large droplets remains confined to the detection of INPs active at temperatures much higher than the homogeneous freezing limit, because of artifacts related to freezing of water droplets without added INPs at temperatures of −25 °C or higher on a supporting substrate. Here I report a method for measuring immersion freezing in super-microliter-sized droplets over a wide temperature range. To reduce possible artifacts, droplets are pipetted onto a thin layer of Vaseline and cooled in a clean booth. In the Cryogenic Refrigerator Applied to Freezing Test (CRAFT) system, freezing of pure (Milli-Q) water droplets are limited at temperatures above −30 °C. An intercomparison of various techniques for immersion freezing experiments with reference particles (Snomax and illite NX) demonstrates that despite the use of relatively large droplets, the CRAFT setup allows for evaluating the immersion freezing activity of the particles over almost the entire temperature range (about −30 °C to 0 °C) relevant for mixed-phase cloud formation.

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Section: Discussionmentioning

confidence: 99%

An improved approach for measuring immersion freezing in large droplets over a wide temperature range

Tobo

2016

Sci Rep

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“…This limits filter sampling techniques with subsequent ice nucleation experiments to quantify purely FT INP concentrations, because the time scale of temporal changes in FT INP concentrations may at times limit the effectiveness for sampling bulk volumes. These methods have their greatest benefits for assessing the most efficient INPs through collection over long sample periods (e.g., Ardon‐Dryer & Levin, ; Bigg, ; Bingemer et al, ; Conen et al, ; Knopf et al, ; Mason, Chou et al, ; Santachiara et al, ). INP sampling with high temporal resolution on the order of minutes is achieved with online techniques such as Continuous Flow Diffusion Chambers (CFDCs; Rogers, ), which determine INP concentrations at a set temperature and supersaturation condition (Chou et al, ; DeMott et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…To date, however, CFDCs cannot be operated autonomously and need a human interface, resulting in high temporal resolution measurements of INP concentrations being limited to single‐field campaigns. A handful ambient INP measurements under FT conditions do exist (Ardon‐Dryer & Levin, ; Bigg, ; Boose, Kanji et al, ; Boose, Sierau et al, ; Conen et al, ; DeMott, Sassen, et al, ; DeMott et al, ; Field et al, ; Lacher et al, ; Mason, Si, et al, ; Prenni et al, ; Richardson et al, ; Rogers et al, ; Schrod et al, ; Stith et al, ). These studies find that in the temperature range 238–243 K, INP concentrations span several orders of magnitude, from <1 to several hundred INPs per standard liter of air (per stdL, given at standard conditions of T = 273.15 K and pressure = 1,013 hPa).…”

Section: Introductionmentioning

confidence: 99%

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

Lacher¹,

DeMott

Levin

et al. 2018

JGR Atmospheres

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Clouds containing ice are vital for precipitation formation and are important in determining the Earth's radiative budget. However, primary formation of ice in clouds is not fully understood. In the presence of ice nucleating particles (INPs), the phase change to ice is promoted, but identification and quantification of INPs in a natural environment remains challenging because of their low numbers. In this paper, we quantify INP number concentrations in the free troposphere (FT) as measured at the High Altitude Research Station Jungfraujoch (JFJ), during the winter, spring, and summer of the years 2014–2017. INPs were measured at conditions relevant for mixed‐phase cloud formation at T = 241/242 K. To date, this is the longest timeline of semiregular measurements akin to online INP monitoring at this site and sampling conditions. We find that INP concentrations in the background FT are on average capped at 10/stdL (liter of air at standard conditions [T = 273 K and p = 1013 hPa]) with an interquartile range of 0.4–9.6/stdL, as compared to measurements during times when other air mass origins (e.g., Sahara or marine boundary layer) prevailed. Elevated concentrations were measured in the field campaigns of 2016, which might be due to enhanced influence from Saharan dust and marine boundary layer air arriving at the JFJ. The upper limit of INP concentrations in the background FT is supported by measurements performed at similar conditions, but at different locations in the FT, where we find INP concentrations to be below 13/stdL most of the time.

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“…Several studies exist from airborne platforms (e.g., Bigg, 1967;Rogers et al, 1998;Prenni et al, 2009;DeMott et al, 2010;Avramov et al, 2011;Schrod et al, 2017) and ground-based observations (e.g., DeMott et al, 2003b;Chou et al, 2011;Ardon-Dryer and Levin, 2014;Mason et al, 2016;Boose et al, 2016a, b) quantifying the number concentration of INPs and identifying their potential sources. Typically, filter sampling with subsequent offline freezing methods, and online measurements with continuous-flow-diffusion chambers (CFDCs) are used as INP measurement techniques.…”

Section: Introductionmentioning

confidence: 99%

“…Typically, filter sampling with subsequent offline freezing methods, and online measurements with continuous-flow-diffusion chambers (CFDCs) are used as INP measurement techniques. For filter sampling, aerosols are collected for a certain time and known air volume, after which the collected particulate is cooled and exposed to controlled temperature and RH conditions (e.g., Bigg, 1967;Santachiara et al, 2010;Conen et al, 2011;Bingemer et al, 2012;Ardon-Dryer and Levin, 2014;Knopf et al, 2014;Mason et al, 2015). Filter techniques observe the onset freezing temperature of a sample with a very large number of particles resulting in a very sensitive detection limit.…”

Section: Introductionmentioning

confidence: 99%

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

Lacher¹,

Lohmann²,

Boose

et al. 2017

Atmos. Chem. Phys.

112

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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.

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Ground-based measurements of immersion freezing in the eastern Mediterranean

Cited by 58 publications

References 91 publications

An improved approach for measuring immersion freezing in large droplets over a wide temperature range

An improved approach for measuring immersion freezing in large droplets over a wide temperature range

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

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

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