Influence of Ice Crystal Aspect Ratio on the Evolution of Ice Size Spectra during Vapor Depositional Growth

2009 ◽  
Vol 66 (12) ◽  
pp. 3732-3743 ◽  
Author(s):  
Lindsay M. Sheridan ◽  
Jerry Y. Harrington ◽  
Dennis Lamb ◽  
Kara Sulia
Keyword(s):  
Aspect Ratio ◽  
Vapor Deposition ◽  
Crystal Size ◽  
Crystal Surface ◽  
Ice Crystals ◽  
Size Spectrum ◽  
Ice Crystal ◽  
Initial Size ◽  
Size Spectra ◽  
The Relationship

Abstract The relationship among aspect ratio, initial size, and the evolution of the size spectrum is explored for ice crystals growing by vapor deposition. Ice crystal evolution is modeled based on the growth of spheroids, and the ice size spectrum is predicted using a model that is Lagrangian in crystal size and aspect ratio. A dependence of crystal aspect ratio on initial size is discerned: more exaggerated shapes are shown to result when the initial crystals are small, whereas more isometric shapes are found to result from initially large crystals. This result is due to the nature of the vapor gradients in the vicinity of the crystal surface. The more rapid growth of the smaller crystals is shown to produce a period during which the size distribution narrows, followed by a broadening led by the initially smallest crystals. The degree of broadening is shown to depend strongly on the primary habit and hence temperature.

scholarly journals Triple-Moment Modal Parameterization for the Adaptive Growth Habit of Pristine Ice Crystals

2016 ◽  
Vol 73 (5) ◽  
pp. 2105-2122 ◽  
Author(s):  
Jen-Ping Chen ◽  
Tzu-Chin Tsai
Keyword(s):  
Aspect Ratio ◽  
Vapor Deposition ◽  
Growth Habit ◽  
Water Saturation ◽  
Ice Crystals ◽  
Size Spectrum ◽  
Crystal Shape ◽  
Ice Crystal ◽  
Aspect Ratios ◽  
Cloud Ice

Abstract A three-moment modal parameterization scheme was developed for describing variations in the shape of cloud ice crystals during growth by vapor deposition. The shape of ice crystals is represented using the volume-weighted aspect ratio, while the size spectrum of the crystal population is described using a three-parameter gamma function. Verified with binned spectral calculations, the proposed modal scheme performed quite accurately in the evolution of the mass and shape of cloud ice crystals growing under idealized conditions. The associated error is within 1% in mass after 1000 s of growth under water saturation. When the ventilation effect is taken into account, the error remains within 5%. Error with regard to the bulk aspect ratio is generally about 3%. A failure to take into account the ice crystal shape led to a 45% underestimation in mass growth. Using only two moments to describe the gamma distribution led to a 37% underestimation in mass and 28% underestimation in the bulk aspect ratio of the ice crystals. The proposed scheme is able to capture the shape memory effect and the gradual adaptation of ice crystal aspect ratios to a new growth habit regime.

scholarly journals Thin and subvisible cirrus and contrails in a subsaturated environment

2011 ◽  
Vol 11 (12) ◽  
pp. 5853-5865 ◽  
Author(s):  
M. Kübbeler ◽  
M. Hildebrandt ◽  
J. Meyer ◽  
C. Schiller ◽  
Th. Hamburger ◽  
...  
Keyword(s):  
Crystal Size ◽  
Life Time ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Size Spectra ◽  
Ice Clouds ◽  
Frontal Systems ◽  
Ice Crystal Size

Abstract. The frequency of occurrence of cirrus clouds and contrails, their life time, ice crystal size spectra and thus their radiative properties depend strongly on the ambient distribution of the relative humidity with respect to ice (RHice). Ice clouds do not form below a certain supersaturation and both cirrus and contrails need at least saturation conditions to persist over a longer period. Under subsaturated conditions, cirrus and contrails should dissipate. During the mid-latitude aircraft experiment CONCERT 2008 (CONtrail and Cirrus ExpeRimenT), RHice and ice crystals were measured in cirrus and contrails. Here, we present results from 2.3/1.7 h of observation in cirrus/contrails during 6 flights. Thin and subvisible cirrus with contrails embedded therein have been detected frequently in a subsaturated environment. Nevertheless, ice crystals up to radii of 50 μm and larger, but with low number densities were often observed inside the contrails as well as in the cirrus. Analysis of the meteorological situation indicates that the crystals in the contrails were entrained from the thin/subvisible cirrus clouds, which emerged in frontal systems with low updrafts. From model simulations of cirrus evaporation times it follows that such thin/subvisible cirrus can exist for time periods of a couple of hours and longer in a subsaturated environment and thus may represent a considerable part of the cirrus coverage.

scholarly journals Thin and subvisible cirrus and contrails in a subsaturated environment

2010 ◽  
Vol 10 (12) ◽  
pp. 31153-31186 ◽  
Author(s):  
M. Kübbeler ◽  
M. Hildebrandt ◽  
J. Meyer ◽  
C. Schiller ◽  
T. Hamburger ◽  
...  
Keyword(s):  
Crystal Size ◽  
Life Time ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Size Spectra ◽  
Ice Clouds ◽  
Frontal Systems ◽  
Ice Crystal Size

Abstract. The frequency of occurrence of cirrus clouds and contrails, their life time, ice crystal size spectra and thus their radiative properties depend strongly on the ambient distribution of the relative humidity with respect to ice (RHice). Ice clouds do not form below a certain supersaturation and both cirrus and contrails need at least saturation conditions to persist over a longer period. Under subsaturated conditions, cirrus and contrails should dissipate. During the mid-latitude aircraft experiment CONCERT 2008 (CONtrail and Cirrus ExpeRimenT), RHice and ice crystals were measured in cirrus and contrails. Here, we present results from 2.3/1.7 h of observation in cirrus/contrails during 6 flights. Thin and subvisible cirrus with contrails embedded therein have been detected frequently in a subsaturated environment. Nevertheless, ice crystals up to radii of 50 μm and larger, but with low number densities were often observed inside the contrails as well as in the cirrus. Analysis of the meteorological situation indicates that the crystals in the contrails were entrained from the thin/subvisible cirrus clouds, which emerged in frontal systems with low updrafts. From model simulations of cirrus evaporation times it follows that such thin/subvisible cirrus can exist for time periods of a couple of hours and longer in a subsaturated environment and thus may represent a considerable part of the cirrus coverage.

scholarly journals Characterization of Arctic mixed-phase cloud properties at small scale and coupling with satellite remote sensing

2017 ◽  
Author(s):  
Guillaume Mioche ◽  
Olivier Jourdan ◽  
Julien Delanoë ◽  
Christophe Gourbeyre ◽  
Guy Febvre ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Crystal Size ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Small Scale ◽  
Vertical Profiles ◽  
Liquid Droplets ◽  
Ice Crystal ◽  
High Concentration ◽  
Ice Crystal Size

Abstract. This study aims to characterize the microphysical and optical properties of ice crystals and supercooled liquid droplets within low-level Arctic mixed-phase clouds (MPC). We compiled and analyzed cloud in situ measurements from 4 airborne campaigns (18 flights, 71 vertical profiles in MPC) over the Greenland Sea and the Svalbard region. Cloud phase discrimination and representative vertical profiles of number, size, mass and shapes of ice crystals and liquid droplets are assessed. The results show that the liquid phase dominates the upper part of the MPC with high concentration of small droplets (120 cm−3, 15&tinsp;μm), and averaged LWC around 0.2 g m−3. The ice phase is found everywhere within the MPC layers, but dominates the properties in the lower part of the cloud and below where ice crystals precipitate down to the surface. The analysis of the ice crystal morphology highlights that irregulars and rimed are the main particle habit followed by stellars and plates. We hypothesize that riming and condensational growth processes (including the Wegener-Bergeron-Findeisein mechanism) are the main growth mechanisms involved in MPC. The differences observed in the vertical profiles of MPC properties from one campaign to another highlight that large values of LWC and high concentration of smaller droplets are possibly linked to polluted situations which lead to very low values of ice crystal size and IWC. On the contrary, clean situations with low temperatures exhibit larger values of ice crystal size and IWC. Several parameterizations relevant for remote sensing or modeling are also determined, such as IWC (and LWC) – extinction relationship, ice and liquid integrated water paths, ice concentration and liquid water fraction according to temperature. Finally, 4 flights collocated with active remote sensing observations from CALIPSO and CloudSat satellites are specifically analyzed to evaluate the cloud detection and cloud thermodynamical phase DARDAR retrievals. This comparison is valuable to assess the sub-pixel variability of the satellite measurements as well as their shortcomings/performance near the ground.

scholarly journals Large surface radiative forcing from topographic blowing snow residuals measured in the High Arctic at Eureka

2009 ◽  
Vol 9 (6) ◽  
pp. 1847-1862 ◽  
Author(s):  
G. Lesins ◽  
L. Bourdages ◽  
T. J. Duck ◽  
J. R. Drummond ◽  
E. W. Eloranta ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Crystal Surface ◽  
Ice Crystals ◽  
The Arctic ◽  
High Mountain ◽  
Blowing Snow ◽  
Ice Crystal ◽  
North West

Abstract. Ice crystals, also known as diamond dust, are suspended in the boundary layer air under clear sky conditions during most of the Arctic winter in Northern Canada. Occasionally ice crystal events can produce significantly thick layers with optical depths in excess of 2.0 even in the absence of liquid water clouds. Four case studies of high optical depth ice crystal events at Eureka in the Nunavut Territory of Canada during the winter of 2006/07 are presented. They show that the measured ice crystal surface infrared downward radiative forcing ranged from 8 to 36 W m−2 in the wavelength band from 5.6 to 20 μm for 532 nm optical depths ranging from 0.2 to 1.7. MODIS infrared and visible images and the operational radiosonde wind profile were used to show that these high optical depth events were caused by surface snow being blown off 600 to 800 m high mountain ridges about 20 to 30 km North-West of Eureka and advected by the winds towards Eureka as they settled towards the ground within the highly stable boundary layer. This work presents the first study that demonstrates the important role that surrounding topography plays in determining the occurrence of high optical depth ice crystal events from residual blowing snow that becomes a source of boundary layer ice crystals distinct from the classical diamond dust phenomenon.

scholarly journals Observing cirrus halos to constrain in-situ measurements of ice crystal size

2007 ◽  
Vol 7 (1) ◽  
pp. 1295-1325 ◽  
Author(s):  
T. J. Garrett ◽  
M. B. Kimball ◽  
G. G. Mace ◽  
D. G. Baumgardner
Keyword(s):  
Crystal Size ◽  
In Situ Measurements ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Optical Extinction ◽  
Airborne Measurements ◽  
Ice Cloud ◽  
Ice Crystal Size ◽  
High Concentrations

Abstract. In this study, characteristic optical sizes of ice crystals in synoptic cirrus are determined using airborne measurements of ice crystal size distributions, optical extinction and water content. The measurements are compared with coincident visual observations of ice cloud optical phenomena, in particular the 22° and 46° halos. In general, the scattering profiles derived from the in-situ cloud probe measurements are consistent with the observed halo characteristics. It is argued that this implies that the measured ice crystals were small, probably with characteristic optical radii between 10 and 20 μm. There is a current contention that in-situ measurements of high concentrations of small ice crystals reflect artifacts from the shattering of large ice crystals on instrument inlets. Significant shattering cannot be entirely excluded using this approximate technique, but it is not indicated. On the basis of the in-situ measurements, a parameterization is provided that relates the optical effective radius of ice crystals to the temperature in mid-latitude synoptic cirrus.

scholarly journals Evaluating and constraining ice cloud parameterizations in CAM5 using aircraft measurements from the SPARTICUS campaign

2013 ◽  
Vol 13 (1) ◽  
pp. 1201-1246
Author(s):  
K. Zhang ◽  
X. Liu ◽  
M. Wang ◽  
J. M. Comstock ◽  
D. L. Mitchell ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vapor Deposition ◽  
Crystal Size ◽  
Model Simulation ◽  
Strong Dependence ◽  
Number Concentration ◽  
Aircraft Measurements ◽  
Ice Crystal ◽  
Ice Cloud ◽  
Ice Crystal Size

Abstract. This study uses aircraft measurements of relative humidity and ice crystal size distribution collected in synoptic cirrus during the SPARTICUS (Small PARTicles In CirrUS) field campaign to evaluate and constrain ice cloud parameterizations in the Community Atmosphere Model version 5. The probability density function (PDF) of ice crystal number concentration (Ni) derived from high frequency (1 Hz) measurements features a strong dependence on ambient temperature. As temperature decreases from −35 °C to −62 °C, the peak in the PDF shifts from 10–20 L−1 to 200–1000 L−1, while the ice crystal number concentration shows a factor of 6–7 increase. Model simulations are performed with two different in-situ ice nucleation schemes. One of the schemes can reproduce a clear increase of Ni with decreasing temperature, by using either an observation based ice nuclei spectrum or a classical theory based spectrum with a relatively low (5–10%) maximum freezing ratio for dust aerosols. The simulation with the other scheme, which assumes a high maximum freezing ratio (100%), shows much weaker temperature dependence of Ni. Simulations are also performed to test empirical parameters related to water vapor deposition and the auto-conversion of ice crystals to snow. Results show that a value between 0.05 and 0.1 for the water vapor deposition coefficient and 250 μm for the critical ice crystal size can produce good agreements between model simulation and the SPARTICUS measurements in terms of ice crystal number concentration and effective radius. The climate impact of perturbing these parameters is also discussed.

scholarly journals Bacterial Ice Crystal Controlling Proteins

Scientifica ◽  
2014 ◽  
Vol 2014 ◽  
pp. 1-20 ◽  
Author(s):  
Janet S. H. Lorv ◽  
David R. Rose ◽  
Bernard R. Glick
Keyword(s):  
Freezing Tolerance ◽  
Crystal Surface ◽  
Molecular Size ◽  
Ice Nucleation ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Freezing Damage ◽  
Ice Binding ◽  
Protein Classes ◽  
Ice Nucleation Proteins

Across the world, many ice active bacteria utilize ice crystal controlling proteins for aid in freezing tolerance at subzero temperatures. Ice crystal controlling proteins include both antifreeze and ice nucleation proteins. Antifreeze proteins minimize freezing damage by inhibiting growth of large ice crystals, while ice nucleation proteins induce formation of embryonic ice crystals. Although both protein classes have differing functions, these proteins use the same ice binding mechanisms. Rather than direct binding, it is probable that these protein classes create an ice surface prior to ice crystal surface adsorption. Function is differentiated by molecular size of the protein. This paper reviews the similar and different aspects of bacterial antifreeze and ice nucleation proteins, the role of these proteins in freezing tolerance, prevalence of these proteins in psychrophiles, and current mechanisms of protein-ice interactions.

scholarly journals Supersaturation Variability and Cirrus Ice Crystal Size Distributions

2014 ◽  
Vol 71 (8) ◽  
pp. 2905-2926 ◽  
Author(s):  
B. Kärcher ◽  
A. Dörnbrack ◽  
I. Sölch
Keyword(s):  
Crystal Size ◽  
Ice Crystals ◽  
Future Research ◽  
Small Scale ◽  
Size Distributions ◽  
Ice Crystal ◽  
Tropical Tropopause ◽  
Crystal Size Distributions ◽  
Mass Fluxes ◽  
Ice Crystal Size

Abstract Small-scale dynamical variability affects atmospheric supersaturation and therefore the development of ice clouds via uptake of water vapor on ice crystals. This variability and its implications for ice growth are difficult to capture experimentally and theoretically. By interpreting supersaturation as a stochastic variable, the authors examine the average temporal behavior of, and the link between, supersaturation fluctuations and ice crystal size distributions in upper-tropospheric cirrus clouds. The authors classify cirrus types according to their ability to dampen supersaturation fluctuations owing to depositional growth of cloud ice and study how size distributions in them respond to supersaturation variability, investigating the possibility of the occurrence of ice-supersaturated states within cirrus. Typical time scales for growth and damping impacts on supersaturation are minutes and minutes to hours, respectively, and are highly variable among cirrus types and within single clouds. Transient deviations from saturated equilibrium states can occur depending on the ice crystal number concentration and size and on the strength of the small-scale dynamical forcing. Supersaturation preferentially occurs in cloud regions with few small ice crystals. The authors demonstrate that supersaturation fluctuations in very thin tropical tropopause cirrus create long-lived supersaturated states. Furthermore, they potentially generate few large ice crystals, broadening size distributions, and significantly enhance water mass fluxes due to sedimentation. Although not studied here, they may also allow new ice crystals to nucleate. Implications of these findings for those clouds to dehydrate air entering the lower stratosphere are discussed and future research needs are outlined.

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