P1.32 An observational study of changes in cloud microphysical properties through glaciogenic seeding by dry ice during the Japanese orographic snow cloud modification projects

Monday, 28 June 2010
Exhibit Hall (DoubleTree by Hilton Portland)
Narihiro Orikasa, MRI, Tsukuba, Ibaraki, Japan; and M. Murakami, A. Saito, H. Ohtake, A. Ikeda, and K. Yoshida

The determination of spacial and temporal distributions of supercooled liquid water and ice in orographic snow clouds is crucial for comprehensive understanding of the precipitation mechanisms, as well as for evaluation of the cloud seeding potentials. Airborne seeding experiments using dry ice pellets have been carried out under supercooled cloud conditons over the Mikuni Mountains of Japan since 1998. After seeding from cloud top, numerous tiny ice germs artificially generated during evaporation of the pellets in their fall appear in a seeding curtain (SC), and they gradually grow up by depletion of supercooled liquid water. Number concentrations of ice crystals measured by an OAP-2D imaging probe (such as 2DC) inside the SC present a striking contrast to ones outside the SC, which was defined by both 30 seconds prior to and 30 seconds subsequent to the SC as natural values. Based on classification of ice particle types, parameters on mean volume diameter, radar reflectivity, ice water content, shape factors and relative frequency of occurrence of each types were compared with inside and outside the SC. We present results of statistical analysis on those comparison as a function of elapsed time and a distance from a mountain ridge.
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