Examination and Analysis of Ice Nucleating Propertiesof Several AgI Pyrotechnic Nucleants
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Abstract:
AgI pyrotechnic nucleants are important seeding agents used in cold cloud seeding operation of weather modification. Currently, several kinds of AgI pyrotechnic nucleants are being used in weather modification operation in China, and their differences in ice nucleating properties need to be evaluated through the uniform test method. In this study, seven kinds of AgI pyrotechnic nucleants, numbered from 1 to 7, were tested in an 1m3 isothermal cloud chamber, and their ice nucleating properties including ice nucleation effectiveness and nucleation rate are compared. The results show that the orders of the ice nuclei numbers calculated by the pyrotechnic nucleant per a gram are in the range of 1010(-8 ℃) to 1013(-18 ℃), and the variation of ice nucleation effectiveness versus temperature can be expressed reasonably by the exponential function. In the low temperature section (≤-16 ℃), high ice nucleation effectiveness can be achieved by various AgI pyrotechnic nucleants. The differences in nucleation effectiveness among those AgI pyrotechnic nucleants in low temperature section are smaller than those in high temperature section (>-16 ℃). In the high temperature section, No.3, No.4 and No.7 samples of pyrotechnic nucleants show higher ice nucleation effectiveness than other four pyrotechnic nucleants. The nucleation rates of all pyrotechnic nucleants are also not the same. The time of 90% AgI ice nuclei grown into ice crystals are in the range of 78 to 18 minutes for various pyrotechnic nucleants when the temperature is at-8 ℃, and the slow nucleation processes such as contactfreezing nucleation may be the main nucleation mechanism of AgI ice nuclei produced by all AgI pyrotechnic nucleants at this temperature.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.