This research clarified some statistical features of winter lightning activity in the coastal areas of Sea of Japan based on observational data obtained by Lightning Location System (LLS) in Tohoku district. Analysis of data indicated that during the cold season, the highest lightning frequency was displayed in the late autumn (Oct-Nov), when intensive lightning activity occurred in the coastal areas of Aomori and Akita prefectures. In the mid-winter season (Dec-Jan), the region of intense lightning activity moved southward to Yamagata and Niigata prefectures. Lightning frequency in the late winter season (Feb-Mar) was the lowest, with the region of intense lightning activity moving northward to Yamagata and Akita prefectures. An examination of ERA-interim reanalysis data revealed that during lightning days, Tohoku and Hokuriku districts were located near the southern part of the cyclone passing over Sea of Japan. Moreover, seasonal variation of lightning frequency patterns might be related to the prevailing wind direction in the study area. In the late autumn season, the prevailing surface wind direction over Sea of Japan was west to southwest, which created a strong wind convergence zone near the coastal areas of Aomori and Akita prefectures. However, the convergence zone moved southward when the wind direction changed northward in the mid-winter season. During the late winter season, the changes in wind patterns caused the convergence zone to be again formed near Aomori and Akita prefectures. These results are consistent with the changes in lightning frequency pattern.

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A total of 117 beachrock samples were collected from the Yaeyama Islands, southwestern Japan, in order to determine their formative period. They consist of 46 fossil shells, 36 calcarenite samples and 35 fossil corals, respectively. They were radiocarbon dated and their isotope fractionations （δ¹³C） were also analyzed. Then calibrated ages were calculated by computer program. The results are summarized as follows;
1. Beachrocks of the Yaeyama Islands have formed during the following seven stages:i.e. 5,560～5,260 cal BP, 5,020 cal BP, 4,700～4,660 cal BP, 4,360～4,050 cal BP, 3,810～3,710 cal BP, 3,530～500 cal BP, and recent time, respectively.
2. Figures of the maximum, minimum and the average δ¹³C values of 117 beachrock samples indicated 9.4‰, －4.95‰ and 2.97‰, respectively, however 80 samples were out of the range of marine organisms （δ¹³C:2‰～－2‰）.
3. Lagoon ecosystem of coral reef have been influenced by meteoric water that contained soluble calcium carbonate and carbon hydrate originated in Quaternary Ryukyu Limestone bed consisted of the islands.
4. Therefore calcium carbonate that cemented beach sediments had not only occupied from sea-water, but also it had derived from meteoric water. This process may be well understood by considering the post-depositional diagenesis.

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