Oxygen isotopic composition of winter precipitation in central Japan

The oxygen isotopic composition of the winter precipitation was observed in Tohkamachi, central Japan, in 1993/1994 and 1994/1995 winter. Synoptic met eorological conditions of winter precipitation in this area are classified as winter monsoons, cyclones positioned over the Sea of Japan, and cyclones located over the Pacific Ocean near Honshu (mam Japanese Island). The oxyg en isotopic composition of precipitation does not correlate with surface ai r temperature (r=0.012). A close relationship is instead observed between t emperature at the cloud top and the oxygen isotopic composition of precipit ation (r=0.662), and the mutual relationships are recognized for each weath er condition formed under that winter precipitation (r=0.772 for winter mon soon, 0.935 for cyclone positioned over the Pacific Ocean near Honshu). Win ter precipitation formed during the winter monsoon has a higher value of ox ygen isotopic composition than those formed when a cyclone is positioned ov er the Pacific Ocean near Honshu at the same temperature.