Photolytic Inactivation of Ice-Forming Silver Iodide Nuclei

1951 ◽  
Vol 32 (4) ◽  
pp. 132-135 ◽  
Author(s):  
Edward C. Y. Inn
Keyword(s):  
Surface Structure ◽  
Silver Iodide ◽  
Chemical Nature ◽  
Ice Nucleation ◽  
Water Droplets ◽  
Ice Particles ◽  
Physico Chemical ◽  
Structure Sensitive ◽  
Photolytic Decomposition

Photolytic decomposition of silver-iodide crystals has been observed when the crystals were exposed to light of wave lengths less than 4300Å, as indicated by darkening of the exposed crystals. Qualitative observations indicate exposed silver iodide crystals undergo reversible photolysis, although the exact conditions under which this takes place is not well understood. When silver iodide nuclei were similarly exposed to light, the ability to form ice particles, when injected into a cloud of super-cooled water droplets, was found to be essentially destroyed. It is believed that, as a result of photolysis of the exposed silver iodide nuclei, the physico-chemical nature of surface of the nuclei has been altered to minimize effectively the surface-structure sensitive process of ice nucleation.

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.

scholarly journals Comparison of measured and calculated collision efficiencies at low temperatures

2015 ◽  
Vol 15 (23) ◽  
pp. 13759-13776 ◽  
Author(s):  
B. Nagare ◽  
C. Marcolli ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Silver Iodide ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Ice Nucleation ◽  
Brownian Diffusion ◽  
Water Droplets ◽  
Collision Efficiency ◽  
Contact Mode ◽  
Data Set ◽  
Temperature Range

Abstract. Interactions of atmospheric aerosols with clouds influence cloud properties and modify the aerosol life cycle. Aerosol particles act as cloud condensation nuclei and ice nucleating particles or become incorporated into cloud droplets by scavenging. For an accurate description of aerosol scavenging and ice nucleation in contact mode, collision efficiency between droplets and aerosol particles needs to be known. This study derives the collision rate from experimental contact freezing data obtained with the ETH CoLlision Ice Nucleation CHamber (CLINCH). Freely falling 80 μm diameter water droplets are exposed to an aerosol consisting of 200 and 400 nm diameter silver iodide particles of concentrations from 500 to 5000 and 500 to 2000 cm−3, respectively, which act as ice nucleating particles in contact mode. The experimental data used to derive collision efficiency are in a temperature range of 238–245 K, where each collision of silver iodide particles with droplets can be assumed to result in the freezing of the droplet. An upper and lower limit of collision efficiency is also estimated for 800 nm diameter kaolinite particles. The chamber is kept at ice saturation at a temperature range of 236 to 261 K, leading to the slow evaporation of water droplets giving rise to thermophoresis and diffusiophoresis. Droplets and particles bear charges inducing electrophoresis. The experimentally derived collision efficiency values of 0.13, 0.07 and 0.047–0.11 for 200, 400 and 800 nm particles are around 1 order of magnitude higher than theoretical formulations which include Brownian diffusion, impaction, interception, thermophoretic, diffusiophoretic and electric forces. This discrepancy is most probably due to uncertainties and inaccuracies in the description of thermophoretic and diffusiophoretic processes acting together. This is, to the authors' knowledge, the first data set of collision efficiencies acquired below 273 K. More such experiments with different droplet and particle diameters are needed to improve our understanding of collision processes acting together.

Physico-Chemical Nature of Bacteriolysis

Nature ◽  
1944 ◽  
Vol 153 (3875) ◽  
pp. 169-170 ◽  
Author(s):  
W. A. DORFMAN
Keyword(s):  
Chemical Nature ◽  
Physico Chemical

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.

Freezing of micrometer-sized liquid droplets of pure water evaporatively cooled in a vacuum

2018 ◽  
Vol 20 (45) ◽  
pp. 28435-28444 ◽  
Author(s):  
Kota Ando ◽  
Masashi Arakawa ◽  
Akira Terasaki
Keyword(s):  
Pure Water ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Liquid Droplets ◽  
Freezing Time ◽  
Water Droplets

The freezing time of pure-water droplets is measured in a vacuum and simulated by ice nucleation theory.

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