日本財団 図書館


AIR-SEA INTERACTION PROCESSES

 

Long-term studies of air/sea temperatures at Oki-no-Tori Sima

 

Iwao Nakano*, Hidetoshi Fujimori* and Junichi Kimura**

* Japan Marine Science and Technology Center (JAMSTEC)

**Shin-Nippon Meteorogical & Oceanographical Consultant Co., Ltd. (METOCEAN)

 

Abstract

 

Time series of the air and sea temperatures at Oki-no-Tori Sima (20.42°N 136.07°E) showed specific season-to-season and year-to-year variations. The monthly mean air temperature of March in 1993 was 0.5℃ lower than those in 1994 and subsequent years. The monthly mean air and sea temperatures of March had a good correlation with the time when the high SST zone between 25℃ and 26℃ was triggered to move northward and passed over the Oki-no-Tori Sima. The timing was determined by the SST distribution in the North-West Pacific Ocean in March. This high SST zone finally reached to the Japan Sea and Pacific coast line of the mainland of Japan in August. It was coinciding with the summer of Japan. The SST in the Sea of Japan was a good index to the summer of Japan. If the SST was low, we had a cold summer as in 1993. If the SST was high, we had an intense heat summer as in 1994. In addition, the north limit of the northward movement of the high SST zone in the Sea of Japan had a relation with the time when the zone was triggered to move northward.

 

Introduction

 

Oki-no-Tori Sima is the southernmost place in Japan at the location of 20.42。?, 136.07。? near the boundary of Tropics in the central part of the Philippine Sea as shown in Fig.1. It is a sinking coral reef with no significant land mass. This natural condition makes it possible to observe the pure oceanic weather. The climatology of the Western North Pacific showed that SST and Air temperature at Oki-no-Tori-Sima is heated up by the Tropical sunshine and cooled down by the Winter Monsoon. Oki-no-Tori Sima is just located at the south limit of the Winter Monsoon. The weather at Oki-no-Tori-Sima is sensitive to the conditions of Winter Monsoon and Tropical SST.

In 1940's, a weather station and light house was built. But after the end of World War II , they were abandoned and ruined. In 1987 Ministry of Construction conducted an inspection of Oki-no-Tori Sima. After that inspection, observation was restarted. The tidal and sea temperature observation at Oki-no-Tori Sima (Sato, 1994) has been conducted by Hydrographic Department of Marine Safety Agency since 1987. The weather and wave observaion has been carried out by the Ministry of Construction since 1988. On the other hand, in 1988. Japan Marine Science and Technology Center started a weather and wave observation on the foothold of the ruined weather station in order to develop a self-supplied weather and wave observation system. In 1992, JAMSTEC moved the weather and wave observation system to and around the Self Elevation Platform. In 1993, JAMSTEC resumed the weather observation at the top of the leg of the Self Elevation Platform. These observation systems are maintained once a year.

Combined data observed by tree organizations covers 1987 to 1997. These data allow us to evaluate the characteristics of the weather and to compare these data with the weather data in Japan. After these analyses, we found that some relation existed in the air and sea temperatures at Oki-no-Tori-Sima and the summer condition in Japan.

 

 

 

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