Abstract
In order to confirm the increase of natural ice nucleus count around the 28th day after a meteor shower, measurements of natural ice nuclei were made with an improved filter paper technique at sufficiently separated two or more sites. The measurements were made continuously for the two periods of more than ten days in May and November, 1962 and January-February, 1963.
It was found that the concentration of ice nuclei increased at each site around the same day, that is, the 28th day after major meteor showers. Other increase by local source was seldom found during the periods.
From 1960 to 1964, the time variation of all the concentration of measured ice nuclei during the several days around the 28th day after a meteor shower was examined by a mixing cloud chamber or filter paper technique. Almost always the ice nuclei showed unusual increase during the 27th to 29th day after the meteor shower. From the statistical examination, it was recognized that the increment of precipitation amount occurs for the period of the ice nucleus increase following the major meteor shower.
