scholarly journals Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei

2009 ◽  
Vol 9 (16) ◽  
pp. 5933-5948 ◽  
Author(s):  
D. Barahona ◽  
A. Nenes
Keyword(s):  
Number Concentration ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Average Error ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Wide Range ◽  
Model Equations

Abstract. This study presents a comprehensive ice cloud formation parameterization that computes the ice crystal number, size distribution, and maximum supersaturation from precursor aerosol and ice nuclei. The parameterization provides an analytical solution of the cloud parcel model equations and accounts for the competition effects between homogeneous and heterogeneous freezing, and, between heterogeneous freezing in different modes. The diversity of heterogeneous nuclei is described through a nucleation spectrum function which is allowed to follow any form (i.e., derived from classical nucleation theory or from observations). The parameterization reproduces the predictions of a detailed numerical parcel model over a wide range of conditions, and several expressions for the nucleation spectrum. The average error in ice crystal number concentration was −2.0±8.5% for conditions of pure heterogeneous freezing, and, 4.7±21% when both homogeneous and heterogeneous freezing were active. The formulation presented is fast and free from requirements of numerical integration.

scholarly journals Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei

2009 ◽  
Vol 9 (3) ◽  
pp. 10957-11004 ◽  
Author(s):  
D. Barahona ◽  
A. Nenes
Keyword(s):  
Size Distribution ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Average Error ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Wide Range ◽  
Model Equations

Abstract. This study presents a comprehensive ice cloud formation parameterization that computes the ice crystal number, size distribution, and maximum supersaturation from precursor aerosol and ice nuclei with any size distribution and chemical composition. The parameterization provides an analytical solution of the cloud parcel model equations and accounts for the competition effects between homogeneous and heterogeneous freezing, and, between heterogeneous freezing in different modes. The diversity of heterogeneous nuclei is described through a nucleation spectrum function which is allowed to follow any form (i.e., derived from classical nucleation theory or from empirical observations). The parameterization reproduced the predictions of a detailed numerical parcel model over a wide range of conditions, and several expressions for the nucleation spectrum. The average error in ice crystal number concentration was −2.0±8.5% for conditions of pure heterogeneous freezing, and, 4.7±21% when both homogeneous and heterogeneous freezing were active. Apart from its rigor, excellent performance and versatility, the formulation is extremely fast and free from requirements of numerical integration.

scholarly journals Parameterizing the competition between homogeneous and heterogeneous freezing in cirrus cloud formation – monodisperse ice nuclei

2008 ◽  
Vol 8 (4) ◽  
pp. 15665-15698 ◽  
Author(s):  
D. Barahona ◽  
A. Nenes
Keyword(s):  
Number Concentration ◽  
Cloud Formation ◽  
Ice Formation ◽  
Average Error ◽  
Cirrus Cloud ◽  
Ice Crystal ◽  
Ice Nuclei ◽  
Wide Range ◽  
Homogeneous Freezing ◽  
Nuclei Number

Abstract. We present a parameterization of cirrus cloud formation that computes the ice crystal number and size distribution under the presence of homogeneous and heterogeneous freezing. The parameterization is very simple to apply and is derived from the analytical solution of the cloud parcel equations, assuming that the ice nuclei population is monodisperse and chemically homogeneous. In addition to the ice distribution, an analytical expression is provided for the limiting ice nuclei number concentration that suppresses ice formation from homogeneous freezing. The parameterization is evaluated against a detailed numerical parcel model, and reproduces numerical simulations over a wide range of conditions with an average error of 6±33%.

scholarly journals Parameterizing the competition between homogeneous and heterogeneous freezing in cirrus cloud formation – monodisperse ice nuclei

2009 ◽  
Vol 9 (2) ◽  
pp. 369-381 ◽  
Author(s):  
D. Barahona ◽  
A. Nenes
Keyword(s):  
Number Concentration ◽  
Cloud Formation ◽  
Ice Formation ◽  
Average Error ◽  
Cirrus Cloud ◽  
Ice Crystal ◽  
Ice Nuclei ◽  
Wide Range ◽  
Homogeneous Freezing ◽  
Nuclei Number

Abstract. We present a parameterization of cirrus cloud formation that computes the ice crystal number and size distribution under the presence of homogeneous and heterogeneous freezing. The parameterization is very simple to apply and is derived from the analytical solution of the cloud parcel equations, assuming that the ice nuclei population is monodisperse and chemically homogeneous. In addition to the ice distribution, an analytical expression is provided for the limiting ice nuclei number concentration that suppresses ice formation from homogeneous freezing. The parameterization is evaluated against a detailed numerical parcel model, and reproduces numerical simulations over a wide range of conditions with an average error of 6±33%. The parameterization also compares favorably against other formulations that require some form of numerical integration.

scholarly journals An aerosol chamber investigation of the heterogeneous ice nucleating potential of refractory nanoparticles

2010 ◽  
Vol 10 (3) ◽  
pp. 1227-1247 ◽  
Author(s):  
R. W. Saunders ◽  
O. Möhler ◽  
M. Schnaiter ◽  
S. Benz ◽  
R. Wagner ◽  
...  
Keyword(s):  
Silicon Oxide ◽  
Cloud Model ◽  
Active Surface ◽  
Accommodation Coefficient ◽  
Contact Angles ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Ice Nuclei

Abstract. Nanoparticles of iron oxide (crystalline and amorphous), silicon oxide and magnesium oxide were investigated for their propensity to nucleate ice over the temperature range 180–250 K, using the AIDA chamber in Karlsruhe, Germany. All samples were observed to initiate ice formation via the deposition mode at threshold ice super-saturations (RHithresh) ranging from 105% to 140% for temperatures below 220 K. Approximately 10% of amorphous Fe2O3 particles (modal diameter = 30 nm) generated in situ from a photochemical aerosol reactor, led to ice nucleation at RHithresh = 140% at an initial chamber temperature of 182 K. Quantitative analysis using a singular hypothesis treatment provided a fitted function [ns(190 K)=10(3.33×sice)+8.16] for the variation in ice-active surface site density (ns:m−2) with ice saturation (sice) for Fe2O3 nanoparticles. This was implemented in an aerosol-cloud model to determine a predicted deposition (mass accommodation) coefficient for water vapour on ice of 0.1 at temperatures appropriate for the upper atmosphere. Classical nucleation theory was used to determine representative contact angles (θ) for the different particle compositions. For the in situ generated Fe2O3 particles, a slight inverse temperature dependence was observed with θ = 10.5° at 182 K, decreasing to 9.0° at 200 K (compared with 10.2° and 11.4° respectively for the SiO2 and MgO particle samples at the higher temperature). These observations indicate that such refractory nanoparticles are relatively efficient materials for the nucleation of ice under the conditions studied in the chamber which correspond to cirrus cloud formation in the upper troposphere. The results also show that Fe2O3 particles do not act as ice nuclei under conditions pertinent for tropospheric mixed phase clouds, which necessarily form above ~233 K. At the lower temperatures (<150 K) where noctilucent clouds form during summer months in the high latitude mesosphere, higher contact angles would be expected, which may reduce the effectiveness of these particles as ice nuclei in this part of the atmosphere.

scholarly journals Contact freezing: a review

2013 ◽  
Vol 13 (3) ◽  
pp. 7811-7869 ◽  
Author(s):  
L. A. Ladino ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Potential Role ◽  
Experimental Information ◽  
Cloud Formation ◽  
Ice Formation ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Quantitative Calculation ◽  
Ice Nuclei ◽  
Immersion Freezing ◽  
Reported Data

Abstract. This manuscript compiles both theoretical and experimental information on contact freezing with the aim to better understand this potentially important but still not well quantified heterogeneous freezing mode. There is no complete theory that describes contact freezing and how the energy barrier has to be overcome to nucleate an ice crystal by contact freezing. Experiments on contact freezing indicate that it can initiate ice formation at the highest temperatures. A difference in the freezing temperatures between contact and immersion freezing has been found using different instrumentation and different ice nuclei. There is a lack of data on collision rates in most of the reported data, which inhibits a quantitative calculation of the freezing efficiencies. Thus, new or modified instrumentation to study this heterogeneous freezing mode in the laboratory and in the field are needed. Important questions concerning contact freezing and its potential role for ice cloud formation and climate are also summarized.

scholarly journals Contact freezing: a review of experimental studies

2013 ◽  
Vol 13 (19) ◽  
pp. 9745-9769 ◽  
Author(s):  
L. A. Ladino Moreno ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Qualitative Difference ◽  
Experimental Studies ◽  
Experimental Information ◽  
Cloud Formation ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Quantitative Calculation ◽  
Ice Nuclei ◽  
Immersion Freezing ◽  
Reported Data

Abstract. This manuscript compiles both theoretical and experimental information on contact freezing with the aim to better understand this potentially important but still not well quantified heterogeneous freezing mode. There is no complete theory that describes contact freezing and how the energy barrier has to be overcome to nucleate an ice crystal by contact freezing. Experiments on contact freezing conducted using the cold plate technique indicate that it can initiate ice formation at warmer temperatures than immersion freezing. Additionally, a qualitative difference in the freezing temperatures between contact and immersion freezing has been found using different instrumentation and different ice nuclei. There is a lack of data on collision rates in most of the reported data, which inhibits a quantitative calculation of the freezing efficiencies. Thus, new or modified instrumentation to study contact nucleation in the laboratory and in the field are needed to identify the conditions at which contact nucleation could occur in the atmosphere. Important questions concerning contact freezing and its potential role for ice cloud formation and climate are also summarized.

scholarly journals An aerosol chamber investigation of the heterogeneous ice nucleating potential of refractory nanoparticles

2009 ◽  
Vol 9 (6) ◽  
pp. 23271-23318 ◽  
Author(s):  
R. W. Saunders ◽  
O. Möhler ◽  
M. Schnaiter ◽  
S. Benz ◽  
R. Wagner ◽  
...  
Keyword(s):  
Silicon Oxide ◽  
Cloud Model ◽  
Active Surface ◽  
Accommodation Coefficient ◽  
Contact Angles ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Ice Nuclei

Abstract. Nanoparticles of iron oxide (crystalline and amorphous), silicon oxide and magnesium oxide were investigated for their propensity to nucleate ice over the temperature range 180–250 K, using the AIDA chamber in Karlsruhe, Germany. All samples were observed to initiate ice formation via the deposition mode at threshold ice super-saturations (RHi thresh) ranging from 105% to 140% for temperatures below 220 K. Approximately 10% of amorphous Fe2O3 particles (modal diameter = 30 nm) generated in situ from a photochemical aerosol reactor, led to ice nucleation at RHi thresh = 140% at an initial chamber temperature of 182 K. Quantitative analysis using a singular hypothesis treatment provided a fitted function [ns (190 K) = 10(3.33×sice)+8.16] for the variation in ice-active surface site density (ns: m−2) with ice saturation (sice) for Fe2O3 nanoparticles. This was implemented in an aerosol-cloud model to determine a predicted deposition (mass accommodation) coefficient for water vapour on ice of 0.1 at temperatures appropriate for the upper atmosphere. Classical nucleation theory was used to determine representative contact angles (θ) for the different particle compositions. For the in situ generated Fe2O3 particles, a slight inverse temperature dependence was observed with θ = 10.5° at 182 K, decreasing to 9.0° at 200 K (compared with 10.2° and 11.4°, respectively for the SiO2 and MgO particle samples at the higher temperature). These observations indicate that such refractory nanoparticles are relatively efficient materials for the nucleation of ice under the conditions studied in the chamber which correspond to cirrus cloud formation in the upper troposphere. The results also show that Fe2O3 particles do not act as ice nuclei under conditions pertinent for tropospheric mixed phase clouds, which necessarily form above ~233 K. At the lower temperatures (<150 K) where noctilucent clouds form during summer months in the high latitude mesosphere, higher contact angles would be expected, which may reduce the effectiveness of these particles as ice nuclei in this part of the atmosphere.

scholarly journals An adsorption theory of heterogeneous nucleation of water vapour on nanoparticles

2015 ◽  
Vol 15 (15) ◽  
pp. 21883-21906
Author(s):  
A. Laaksonen ◽  
J. Malila
Keyword(s):  
Water Vapour ◽  
Heterogeneous Nucleation ◽  
Large Scale ◽  
Laboratory Data ◽  
Theoretical Description ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Scale Model ◽  
Adsorption Theory ◽  
Ice Cloud

Abstract. Heterogeneous nucleation of water vapour on insoluble nuclei is a phenomenon that can induce atmospheric water and ice cloud formation. However, modelling of the phenomenon is hampered by the fact that the predictive capability of the classical heterogeneous nucleation theory is rather poor. A reliable theoretical description of the influence of different types of water-insoluble nuclei in triggering the water condensation or ice deposition would help to decrease uncertainty in large scale model simulations. In this paper we extend a recently formulated adsorption theory of heterogeneous nucleation to be applicable to highly curved surfaces, and test the theory against laboratory data for water vapour nucleation on silica, titanium dioxide and silver oxide nanoparticles. We show that unlike the classical heterogeneous nucleation theory, the new theory is able to quantitatively predict the experimental results.

scholarly journals Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen

2012 ◽  
Vol 12 (5) ◽  
pp. 2541-2550 ◽  
Author(s):  
B. G. Pummer ◽  
H. Bauer ◽  
J. Bernardi ◽  
S. Bleicher ◽  
H. Grothe
Keyword(s):  
Radiative Forcing ◽  
Pollen Grains ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Distribution Area ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Nucleation Activity ◽  
Ice Nucleation Activity ◽  
The Impact

Abstract. The ice nucleation of bioaerosols (bacteria, pollen, spores, etc.) is a topic of growing interest, since their impact on ice cloud formation and thus on radiative forcing, an important parameter in global climate, is not yet fully understood. Here we show that pollen of different species strongly differ in their ice nucleation behaviour. The average freezing temperatures in laboratory experiments range from 240 to 255 K. As the most efficient nuclei (silver birch, Scots pine and common juniper pollen) have a distribution area up to the Northern timberline, their ice nucleation activity might be a cryoprotective mechanism. Far more intriguingly, it has turned out that water, which has been in contact with pollen and then been separated from the bodies, nucleates as good as the pollen grains themselves. The ice nuclei have to be easily-suspendable macromolecules located on the pollen. Once extracted, they can be distributed further through the atmosphere than the heavy pollen grains and so presumably augment the impact of pollen on ice cloud formation even in the upper troposphere. Our experiments lead to the conclusion that pollen ice nuclei, in contrast to bacterial and fungal ice nucleating proteins, are non-proteinaceous compounds.

scholarly journals Analysis of the effect of water activity on ice formation using a new thermodynamic framework

2014 ◽  
Vol 14 (14) ◽  
pp. 7665-7680 ◽  
Author(s):  
D. Barahona
Keyword(s):  
Water Activity ◽  
Nucleation Rate ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Solid Matrix ◽  
Effect Of Water ◽  
Thermodynamic Framework ◽  
New Framework

Abstract. In this work a new thermodynamic framework is developed and used to investigate the effect of water activity on the formation of ice within supercooled droplets. The new framework is based on a novel concept where the interface is assumed to be made of liquid molecules "trapped" by the solid matrix. It also accounts for the change in the composition of the liquid phase upon nucleation. Using this framework, new expressions are developed for the critical ice germ size and the nucleation work with explicit dependencies on temperature and water activity. However unlike previous approaches, the new model does not depend on the interfacial tension between liquid and ice. The thermodynamic framework is introduced within classical nucleation theory to study the effect of water activity on the ice nucleation rate. Comparison against experimental results shows that the new approach is able to reproduce the observed effect of water activity on the nucleation rate and the freezing temperature. It allows for the first time a phenomenological derivation of the constant shift in water activity between melting and nucleation. The new framework offers a consistent thermodynamic view of ice nucleation, simple enough to be applied in atmospheric models of cloud formation.

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