著者

野元 世紀 杜明 遠 上野 健一

出版者

The Association of Japanese Geographers

雑誌

Geographical review of Japan, Series B (ISSN:02896001)

巻号頁・発行日

vol.62, no.2, pp.137-148, 1989-12-31 (Released:2008-12-25)

参考文献数

9

被引用文献数

2 1

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雲南省西双版納の景洪,劾養盆地で1986年~87年, 88年~89年の寒霧季,冷気湖と霧の観測を行なった。盆地大気下層の気温プロファイルは霧形成時に大きく変化する。霧形成時に気温の逆転層,すなわち冷気湖が発達する。しかし下層の逆転は霧形成時に消滅し,不安定なプロファイルが形成される。 逆転層や不安定大気の発達は盆地内の地形環境に強く影響される。そのため両盆地における夜間の気温プロファイルの変化は異なる。霧の発達は気温のプロファイルに関係するので霧のラィフサィクルについても両盆地で差が見られた。さらに冷気湖の発達や霧の形成にメソスケールの循環系の関学が示唆された。

著者

野元 世紀

出版者

The Association of Japanese Geographers

雑誌

地理学評論 (ISSN:00167444)

巻号頁・発行日

vol.48, no.6, pp.424-437, 1975-06-01 (Released:2008-12-24)

参考文献数

25

被引用文献数

5 3

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In Central Japan, orographically and thermally induced anticyclones, cyclones and fronts appear very frequently in winter. Takayama High is one of such local anticyclones, which is formed either thermally on clear nights by long wave radiation or mechanically by upper winds. In the latter cases, it usually accompanies Matsumoto Low simultaneously. In the thermal cases, cold air cooled by radiation in the mountaineous region flows down along large valleys and produces local discontinuity lines on the Hokuriku coasts of the Sea of Japan and on the southern coast of Boso Peninsular. On this account, the Takayama High has been studied mainly in relation to the Hokuriku Front, which brings heavy snowfalls in the Hokuriku region. A local cyclone, Suruga-wan Low, is frequently formed when the winter monsoon becomes weaker. The previous studies made it clear that a winter maximum and a summer minimum of its appearance are caused by the thermal effects of water and air temperatures of the Suruga Bay and its vicinity. It has already been stated that the origins of the local front, Boso Front, are closely related to (1) the local high in thermal cases and (2) the convergence of two or more currents branched off topographically from the same Pc air mass with a local cyclone on the Sagami Bay or the Suruga Bay. The purpose of this paper is to clarify their synoptic climatological features. The results are as follows; i) On the meso-scale charts, the occurrence of the Takayama High is 12.3 days per month on an average from December to February, the Suruga-wan Low 9.8 days and the Boso Front 21.3 days. The frequencies of occurrence of the Takayama. High are found most frequently in December, but those of the Suruga-wan Low are in Febuary and the Boso Front in January. This is accounted for by the fact that each of them corresponds with different synoptic pressure patterns. ii) Most frequently the Takayama High persists for 18—20 hours, forming at 17—19h and disappearing at 10—12h on the next day. The shape of the Takayama High is influenced by the direction of upper winds (Fig. 1 (a) (b)) and the differences of the pressure gradient from the center have a close relation to the differences of the direction. In general, it is very difficult to define the size of a local anticyclone, but if the Takayama High is defined by the outermost closed isobar, the areas of the Takayama High of the W—SW type are about 3 times as large as the one of the NW type (Fig. 2 and 4). The maximum of the area of W—SW type Takayama High is 39.1×103km2, and the one of NW type is 9.1×103km2. iii) In the case of the Takayama High of the W—SW type, a local cyclone is formed from time to time in the Matsumoto district by orographical effects. When a Matsumoto Low is formed, strong southerly wind blows and air temperature becomes higher in the district. An indicator of the relative intensity of the Matsumoto Low, ΔP (the difference of sea level pressure at Takayama minus Matsumoto) is obviously related to the W—SW upper wind (mainly 850—700mb); The stronger the wind of these levels is, the greater ΔP occurs simultaneously (Fig. 5). Furthermore, ΔP is related clearly to the temperture of these levels, when 700mb temperature is above -13°C. It seems that warm strong wind, whichh is observed in association with the Matsumoto Low, is caused by a föhn effect. This is verified by facts that ΔT (the difference of air temperature at Matsumoto minus its vicinity) has a relation to the temperature of the height of the mountain-tops (about 700mb) (Fig. 9) and to the wind direction of the levels, and also by the distributions of air temperature, wind (Fig. 8) and relative humidity at the surface level.