scholarly journals Technical Note: A numerical test-bed for detailed ice nucleation studies in the AIDA cloud simulation chamber

2007 ◽  
Vol 7 (1) ◽  
pp. 243-256 ◽  
Author(s):  
R. J. Cotton ◽  
S. Benz ◽  
P. R. Field ◽  
O. Möhler ◽  
M. Schnaiter
Keyword(s):  
Numerical Test ◽  
Ice Nucleation ◽  
Technical Note ◽  
Ice Formation ◽  
Time Interval ◽  
Test Bed ◽  
Ice Particles ◽  
Temperature And Humidity ◽  
Chamber Temperature ◽  
Expansion Cooling

Abstract. The AIDA (Aerosol Interactions and Dynamics in the Atmosphere) aerosol and cloud chamber of Forschungszentrum Karlsruhe can be used to test the ice forming ability of aerosols. The AIDA chamber is extensively instrumented including pressure, temperature and humidity sensors, and optical particle counters. Expansion cooling using mechanical pumps leads to ice supersaturation conditions and possible ice formation. In order to describe the evolving chamber conditions during an expansion, a parcel model was modified to account for diabatic heat and moisture interactions with the chamber walls. Model results are shown for a series of expansions where the initial chamber temperature ranged from −20°C to −60°C and which used desert dust as ice forming nuclei. During each expansion, the initial formation of ice particles was clearly observed. For the colder expansions there were two clear ice nucleation episodes. In order to test the ability of the model to represent the changing chamber conditions and to give confidence in the observations of chamber temperature and humidity, and ice particle concentration and mean size, ice particles were simply added as a function of time so as to reproduce the observations of ice crystal concentration. The time interval and chamber conditions over which ice nucleation occurs is therefore accurately known, and enables the model to be used as a test bed for different representations of ice formation.

scholarly journals Technical note: A numerical test-bed for detailed ice nucleation studies in the AIDA cloud simulation chamber

2006 ◽  
Vol 6 (5) ◽  
pp. 9483-9516
Author(s):  
R. J. Cotton ◽  
S. Benz ◽  
P. R. Field ◽  
O. Möhler ◽  
M. Schnaiter
Keyword(s):  
Numerical Test ◽  
Ice Nucleation ◽  
Technical Note ◽  
Ice Formation ◽  
Time Interval ◽  
Test Bed ◽  
Ice Particles ◽  
Temperature And Humidity ◽  
Chamber Temperature ◽  
Expansion Cooling

Abstract. The AIDA (Aerosol Interactions and Dynamics in the Atmosphere) aerosol and cloud chamber of Forschungszentrum Karlsruhe can be used to test the ice forming ability of aerosols. The AIDA chamber is extensively instrumented including pressure, temperature and humidity sensors, and optical particle counters. Expansion cooling using mechanical pumps leads to ice supersaturation conditions and possible ice formation. In order to describe the evolving chamber conditions during an expansion, a detailed microphysics size-resolving parcel model was modified to account for diabatic heat and moisture interactions with the chamber walls. Model results are shown for a series of expansions where the initial chamber temperature ranged from −20°C to −60°C and which used desert dust as ice forming nuclei. During each expansion, the initial formation of ice particles was clearly observed. For the colder expansions there were two clear ice nucleation episodes. In order to test the ability of the model to represent the changing chamber conditions and to give confidence in the observations of chamber temperature and humidity, and ice particle concentration and mean size, ice particles were simply added as a function of time so as to reproduce the observations of ice crystal concentration. The time interval and chamber conditions over which ice nucleation occurs is therefore accurately known, and enables the model to be used as a test bed for different representations of ice formation.

A laboratory and model investigation of secondary ice production during to supercooled drop collisions with ice surfaces 

2021 ◽  
Author(s):  
Paul Connolly ◽  
Rachel James ◽  
Vaughan Phillips
Keyword(s):  
Laboratory Data ◽  
Ice Formation ◽  
Atmospheric Sciences ◽  
Ice Particles ◽  
Cold Room ◽  
Mode 2 ◽  
Rain Drops ◽  
Break Up ◽  
Ice Surfaces ◽  
Ice Production

<p>This work presents new laboratory data investigating collisions between supercooled drops and ice particles as a source of secondary ice particles in natural clouds. Furthermore we present numerical model simulations to put the laboratory measurements into context.</p><p>Secondary ice particles form during the breakup of freezing drops due to so-called “spherical freezing” (or Mode 1), where an ice shell forms around the freezing drop. This process has been studied and observed for drops in free-fall in laboratory experiments since the 1960s, and also more recently by Lauber et al. (2018) with a high-speed camera. Aircraft field measurements (Lawson et al. 2015) and lab data (Kolomeychuk et al. 1975) suggest that such a process is dependent on the size of drops, with larger drops being more effective at producing secondary ice.  Collision induced break-up of rain drops has been well studied with pioneering investigations in the mid-1980s, and numerous modelling studies showing that it is responsible for observed trimodal rain drop size distributions in the atmosphere, which can be well approximated by an exponential distribution.</p><p> </p><p>In mixed-phase clouds we know that rain-drops can collide with more massive ice particles. This, depending on the type of collision, may lead to the break-up of the supercooled drop (e.g. as hinted by Latham and Warwicker, 1980), potentially stimulating secondary ice formation (Phillips et al. 2018 - non-spherical, Mode 2).  There is a dearth of laboratory data investigating this mechanism.  This mechanism is the focus of the presentation.</p><p>Here we present the results of recent experiments where we make use of the University of Manchester (UoM) cold room facility. The UoM cold room facility consists of 3 stacked cold rooms that can be cooled to temperatures below -55 degC. A new facility has been built to study secondary ice production via Mode 2 fragmentation. We generate supercooled drops at the top of the cold rooms and allow them to interact with different ice surfaces near the bottom. This interaction is filmed with a new camera setup.</p><p>Our latest results will be presented at the conference.</p><p>References</p><p>Kolomeychuk, R. J., D. C. McKay, and J. V. Iribarne. 1975. “The Fragmentation and Electrification of Freezing Drops.” <em>Journal of the Atmospheric Sciences</em> 32 (5): 974–79. https://doi.org/10.1175/1520-0469(1975)032<0974>2.0.CO;2.</p><p>Latham, J., and R. Warwicker. 1980. “Charge Transfer Accompanying the Splashing of Supercooled Raindrops on Hailstones.” Quarterly Journal of the Royal Meteorological Society 106 (449): 559–68. https://doi.org/10.1002/qj.49710644912.</p><p>Lauber, Annika, Alexei Kiselev, Thomas Pander, Patricia Handmann, and Thomas Leisner. 2018. “Secondary Ice Formation during Freezing of Levitated Droplets.” Journal of the Atmospheric Sciences 75 (8): 2815–26. https://doi.org/10.1175/JAS-D-18-0052.1.</p><p>Lawson, R. Paul, Sarah Woods, and Hugh Morrison. 2015. “The Microphysics of Ice and Precipitation Development in Tropical Cumulus Clouds.” Journal of the Atmospheric Sciences 72 (6): 2429–45. https://doi.org/10.1175/JAS-D-14-0274.1.</p><p> </p><p> </p>

scholarly journals A new temperature- and humidity-dependent surface site density approach for deposition ice nucleation

2015 ◽  
Vol 15 (7) ◽  
pp. 3703-3717 ◽  
Author(s):  
I. Steinke ◽  
C. Hoose ◽  
O. Möhler ◽  
P. Connolly ◽  
T. Leisner
Keyword(s):  
Contact Angle ◽  
Relative Humidity ◽  
Active Surface ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Aerosol Size Distribution ◽  
Surface Site ◽  
Linear Behavior ◽  
Temperature And Humidity

Abstract. Deposition nucleation experiments with Arizona Test Dust (ATD) as a surrogate for mineral dusts were conducted at the AIDA cloud chamber at temperatures between 220 and 250 K. The influence of the aerosol size distribution and the cooling rate on the ice nucleation efficiencies was investigated. Ice nucleation active surface site (INAS) densities were calculated to quantify the ice nucleation efficiency as a function of temperature, humidity and the aerosol surface area concentration. Additionally, a contact angle parameterization according to classical nucleation theory was fitted to the experimental data in order to relate the ice nucleation efficiencies to contact angle distributions. From this study it can be concluded that the INAS density formulation is a very useful tool to describe the temperature- and humidity-dependent ice nucleation efficiency of ATD particles. Deposition nucleation on ATD particles can be described by a temperature- and relative-humidity-dependent INAS density function ns(T, Sice) with ns(xtherm) = 1.88 ×105 · exp(0.2659 · xtherm) [m−2] , (1) where the temperature- and saturation-dependent function xtherm is defined as xtherm = −(T−273.2)+(Sice−1) ×100, (2) with the saturation ratio with respect to ice Sice >1 and within a temperature range between 226 and 250 K. For lower temperatures, xtherm deviates from a linear behavior with temperature and relative humidity over ice. Also, two different approaches for describing the time dependence of deposition nucleation initiated by ATD particles are proposed. Box model estimates suggest that the time-dependent contribution is only relevant for small cooling rates and low number fractions of ice-active particles.

scholarly journals Small ice particles at slightly supercooled temperatures in tropical maritime convection

2020 ◽  
Vol 20 (6) ◽  
pp. 3895-3904
Author(s):  
Gary Lloyd ◽  
Thomas Choularton ◽  
Keith Bower ◽  
Jonathan Crosier ◽  
Martin Gallagher ◽  
...  
Keyword(s):  
Ice Nucleation ◽  
Dust Particles ◽  
Cumulus Clouds ◽  
Desert Dust ◽  
Ice Nuclei ◽  
Production Processes ◽  
Ice Particles ◽  
Small Crystals ◽  
Vapour Diffusion ◽  
Very High

Abstract. In this paper we show that the origin of the ice phase in tropical cumulus clouds over the sea may occur by primary ice nucleation of small crystals at temperatures just between 0 and −5 ∘C. This was made possible through use of a holographic instrument able to image cloud particles at very high resolution and small size (6 µm). The environment in which the observations were conducted was notable for the presence of desert dust advected over the ocean from the Sahara. However, there is no laboratory evidence to suggest that these dust particles can act as ice nuclei at temperatures warmer than about −10 ∘C, the zone in which the first ice was observed in these clouds. The small ice particles were observed to grow rapidly by vapour diffusion, riming, and possibly through collisions with supercooled raindrops, causing these to freeze and potentially shatter. This in turn leads to the further production of secondary ice in these clouds. Hence, although the numbers of primary ice particles are small, they are very effective in initiating the rapid glaciation of the cloud, altering the dynamics and precipitation production processes.

scholarly journals Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

2019 ◽  
Author(s):  
Nsikanabasi Silas Umo ◽  
Robert Wagner ◽  
Romy Ullrich ◽  
Alexei Kiselev ◽  
Harald Saathoff ◽  
...  
Keyword(s):  
Fly Ash ◽  
Significant Role ◽  
Coal Fly Ash ◽  
Aerosol Particles ◽  
Ice Nucleation ◽  
Temperature Cycling ◽  
Cloud Formation ◽  
Ice Formation ◽  
Nucleation Activity ◽  
Ice Nucleation Activity

Abstract. Ice-nucleating particles (INPs), which are precursors for ice formation in clouds, can alter the microphysical and optical properties of clouds, hence, impacting the cloud lifetimes and hydrological cycles. However, the mechanisms with which these INPs nucleate ice when exposed to different atmospheric conditions are still unclear for some particles. Recently, some INPs with pores or permanent surface defects of regular or irregular geometries have been reported to initiate ice formation at cirrus temperatures via the liquid phase in a two-step process, involving the condensation and freezing of supercooled water inside these pores. This mechanism has therefore been labelled as pore condensation and freezing (PCF). The PCF mechanism allows formation and stabilization of ice germs in the particle without the formation of macroscopic ice. Coal fly ash (CFA) aerosol particles are known to nucleate ice in the immersion freezing mode and may play a significant role in cloud formation. In our current ice nucleation experiments with CFA particles, which we conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) aerosol and cloud simulation chamber at the Karlsruhe Institute of Technology, Germany, we partly observed a strong increase in the ice-active fraction for experiments performed at temperatures just below the homogeneous freezing of pure water, which could be related to the PCF mechanism. To further investigate the potential of CFA particles undergoing PCF mechanism, we performed a series of temperature-cycling experiments in AIDA. The temperature-cycling experiments involve exposing CFA particles to lower temperatures (down to ~ 228 K), then warming them up to higher temperatures (238 K–273 K) before investigating their ice nucleation properties. For the first time, we report the enhancement of the ice nucleation activity of the CFA particles for temperatures up to 263 K, from which we conclude that it is most likely due to the PCF mechanism. This indicates that ice germs formed in the CFA particles’ pores during cooling remains in the pores during the warming and induces ice crystallization as soon as the pre-activated particles experience ice-supersaturated conditions at warmer temperatures; hence, showing an enhancement in their ice-nucleating ability compared to the scenario where the CFA particles are directly probed at warmer temperatures without temporary cooling. The enhancement in the ice nucleation ability showed a positive correlation with the specific surface area and porosity of the particles. On the one hand, the PCF mechanism could be the prevalent nucleation mode for intrinsic ice formation at cirrus temperatures rather than the previously acclaimed deposition mode. On the other, the PCF mechanism can also play a significant role in mixed-phase cloud formation in a case where the CFA particles are injected from higher altitudes and then transported to lower altitudes after being exposed to lower temperatures.

THE ICE NUCLEATION BEHAVIOR OF AMINO-ACID PARTICLES

1966 ◽  
Vol 44 (10) ◽  
pp. 2431-2445 ◽  
Author(s):  
J. Maybank ◽  
N. Barthakur
Keyword(s):  
Amino Acid ◽  
Liquid Phase ◽  
Water Saturation ◽  
Ice Nucleation ◽  
Cloud Chamber ◽  
Airborne Particles ◽  
Ice Formation ◽  
Vapor Pressures ◽  
Nucleation Behavior ◽  
Threshold Temperatures

The problem of whether ice nucleation takes place more readily from the vapor directly to the solid, or via an intermediate liquid phase has been studied for several of the more efficient amino-acid nucleators. It has been shown that the threshold temperatures observed in cloud chamber tests are in fact those of the material acting as freezing nuclei (i.e. via the liquid phase), and any discrepancies between such tests and trials with bulk water may be accounted for satisfactorily by partial destruction of the nucleus surface by the water. Investigations on ice formation about airborne particles and on macroscopic amino-acid crystals have shown that for certain of these substances a transition in behavior takes place around −20 °C. Below this temperature, ice formation no longer requires saturation conditions with respect to supercooled water and so the particles may be considered to act by converting the vapor directly to ice, and can, therefore, be designated sublimation nuclei.The major obstacle in the way of airborne particles acting as freezing nuclei has been the requirement that they act first as condensation centers. Under the conditions prevailing in supercooled clouds with vapor pressures equal to, or barely exceeding that of water saturation, condensation is unlikely on the somewhat hydrophobic surfaces of amino-acid particles. It has been shown, however, by using a radioactive tracer in small water droplets that droplet–particle collisions can occur. While not efficient, this process would permit a few particles in a cloud chamber experiment to act as freezing nuclei, thereby establishing the potential activity of the material itself.

Packing Characteristics and Its Effect on Heat Transfer Characteristics in Melting of Granular Packed Bed Subject to Horizonal Forced Convection

2002 ◽  
Author(s):  
Y. L. Hao ◽  
Y.-X. Tao
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Melting Process ◽  
Packed Bed ◽  
Time Interval ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Ice Particles ◽  
Different Types ◽  
Series Of Experiments

A series of experiments are conducted to investigate the characteristics and its effect on the melting and heat of a packed bed consisting of melting ice particles to horizontal forced convection. The volumes and situations of the melting ganular packed beds are by the visualization observations and measurements digital camcorders within the range of Re = 71 ~ 2291, Gr/Re2 = 1.48×10−5 ~ 17.32, and Ste = 0.0444 ~ 0.385, respectively. The mass of ice particles is measured at the time interval during the melting process. Two types of pattern can be found under the different conditions. The different types of heat transfer characteristics emerge in type of packing pattern. The correlations for each type of pattern are obtained based on the experimental results.

scholarly journals Experimental investigation of homogeneous freezing of sulphuric acid particles in the aerosol chamber AIDA

2003 ◽  
Vol 3 (1) ◽  
pp. 211-223 ◽  
Author(s):  
O. Möhler ◽  
O. Stetzer ◽  
S. Schaefers ◽  
C. Linke ◽  
M. Schnaiter ◽  
...  
Keyword(s):  
Ice Formation ◽  
Data Set ◽  
Aerosol Analysis ◽  
Expansion Time ◽  
Aerosol Chamber ◽  
Mechanical Pump ◽  
Expansion Cooling ◽  
Homogeneous Freezing ◽  
Physical And Chemical ◽  
Good Agreement

Abstract. The homogeneous freezing of supercooled H2SO4/H2O solution droplets was investigated in the aerosol chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) of Forschungszentrum Karlsruhe. 24 freezing experiments were performed at temperatures between 189 and 235 K with aerosol particles in the diameter range 0.05 to 1 µm. Individual experiments started at homogeneous temperatures and ice saturation ratios between 0.9 and 0.95. Cloud cooling rates up to -2.8 K min-1 were simulated dynamically in the chamber by expansion cooling using a mechanical pump. Depending on the cooling rate and starting temperature, freezing threshold relative humidities were exceeded after expansion time periods between about 1 and 10 min. The onset of ice formation was measured with three independent methods showing good agreement among each other. Ice saturation ratios measured at the onset of ice formation increased from about 1.4 at 231 K  to about 1.75 at 189 K. The experimental data set including thermodynamic parameters as well as physical and chemical aerosol analysis provides a good basis for microphysical model applications.

Ice nucleation by cellulose and its potential contribution to ice formation in clouds

2015 ◽  
Vol 8 (4) ◽  
pp. 273-277 ◽  
Author(s):  
N. Hiranuma ◽  
O. Möhler ◽  
K. Yamashita ◽  
T. Tajiri ◽  
A. Saito ◽  
...  
Keyword(s):  
Ice Nucleation ◽  
Ice Formation ◽  
Potential Contribution

scholarly journals Dependence of homogeneous crystal nucleation in water droplets on their radii and its implication for modeling the formation of ice particles in cirrus clouds

2017 ◽  
Vol 19 (30) ◽  
pp. 20075-20081 ◽  
Author(s):  
Yuri S. Djikaev ◽  
Eli Ruckenstein
Keyword(s):  
Nucleation Rate ◽  
Ice Nucleation ◽  
Cirrus Clouds ◽  
Crystal Nucleation ◽  
Water Droplets ◽  
Ice Particles ◽  
Homogeneous Crystal

Dependence of the ice-nucleation-rate in water droplets on their radii and temperature is determined by taking into account volume-based and surface-stimulated modes.

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