丹波高地西南部の三峠断層系に発達する断層変位地形を調査し,第四紀後期における断層運動の諸性質について考察した.本断層系は三峠・周山・芹生・殿田・越畑の各活断層からなり,逆断層成分を伴う左ずれ運動によって特徴づけられる.左ずれ変位速度は0.18～0.66m/1,000年,縦ずれ変位速度は0.009～0.33m/1,000年である.縦ずれ変位の速度や横ずれ変位との割合は断層の走向と東西圧縮軸との会合角度によって支配されている.各断層には河谷の屈曲量(D)と断層より上流の河谷の長さ (L) との問にD=aLが成立しており,aは0.15～0.44の値をとる.三峠・殿田両断層を含む近畿地方の横ずれ断層にはS=(ユ～5)aの関係が認められる.左ずれ運動は50～60万年前頃から開始され,近畿地方の断層運動の活発化の時期と一致している.左ずれ運動以前には右ずれ運動が卓越していたことが推定される.

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西部太平洋の海面水温 (SST) 変動と東アジアの冬季モンスーンとの相互作用を通じて, SSTが熱源として大気循環場へ与える影響,および大気の熱的・力学的強制によって変動するSSTについて考察した.冬季モンスーンの強弱に対応して,西部太平洋のSSTの偏差分布は,日本付近の中緯度域と熱帯・亜熱帯域とでは,偏差が反転する対照的なパターンが形成される傾向にある.大気下層の熱収支解析と経験直交関数 (EOF) 解析から,SST偏差が反転する境界は,下層大気が非断熱加熱に対して鉛直移流でバランスするか水平移流でバランスするかの境界と一致していると推測される.熱帯・亜熱帯域のSSTの高温偏差は海洋大陸付近の活発な対流活動に寄与しているが,そのとき冬季モンスーンは活発で,中緯度域の低温偏差は大陸からの大規模なcold surgeに伴う大気-海洋熱交換による海洋の熱損失と海洋混合層内の水平移流効果によって形成されていると考えられる.また,東アジアの冬季モンスーンの強弱は海洋大陸上の積雲対流域を熱源とする松野-Gill型の双極子パターンの応答によって部分的に制御されていることがわかった.

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The purposes of this study are to clarify the regional difference of year-to-year changes of winter precipitation, and to investigate the type of disturbances contributing to winter precipitation and the relationships between the precipitation and the frequency of disturbances.
First, the correlation coefficients of the precipitation for winter during forty years from 1940/41 to 1979/80 at 46 stations (Fig. 1) were calculated (Figs. 2 and 3). The area indicating the correlation coefficients above a significant level was larger on the Pacific side than on the Japan Sea side. The stations included in the semi-climatic region of the Japan Sea side (Suzuki, 1962) had similar tendencies as the Pacific side. Since the stations on the Japan Sea side correlated only to the adjacent station, on the Japan Sea side was divided into four regions; the San-in region, the Hokuriku region, the Tohoku region and the southern part of Hokkaido. On the Pacific side, the similarity of fluctuations among stations was remarkable, so the regions were not distinctly separated, but overlapped with each other. Therefore, the region west of Kanto district, the region from Kinki district to Tohoku district and the region from Kanto district to Hokkaido were combined respectively as the area having the same tendency.
Daily precipitation was classified into four groups by use of synoptic charts according to the type of disturbances; Japan Sea Lows, Pacific Coast Lows, Coupled Lows and winter monsoons. The percentage ratio of the precipitation caused by lows to the total amount of winter precipitation, was calculated (Fig. 4). The same calculation was made for each type of low (Fig. 5). Moreover, the type of disturbances having a significant influence on winter precipitation and their distribution ratios were investigated for each station (Fig. 6). On the Pacific side, the disturbances contributing to winter precipitation were: Pacific Coast Lows and Coupled Lows in the south of Tohoku district, and Japan Sea Lows and Coupled Lows in Hokkaido. Though the region west of Kanto district and the Tohoku district had the same combination of disturbances, the contribution ratio between the two types of lows varied between the regions. On the Japan Sea side, likewise, the combination of disturbances and their order varied from station to station. The main causes of winter precipitation changed in accordance with the regional difference of year-to-year changes in precipitation.
Correlation coefficients between the frequencies of lows in and around the Japanese Islands and the winter precipitation were calculated (Figs. 7 and 9). The winter precipitation at the stations in which lows were the main causes depended on the frequency of lows. That is, the precipitation on the Pacific side from the Tohoku district to Kyushu was related to the frequency of Pacific Coast Lows, and the precipitation Hokkaido and on the Japan Sea side of Tohoku district was related to the frequency of Japan Sea Lows (Figs. 8 and 10).
We can conclude that the winter precipitation at each station mainly depends on the frequency of disturbances, and the regional differences of year-to-year changes in winter precipitation is due to the fact that the frequency of disturbances varies with regions.

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