Time-course of oxygen stable isotopic ratios (i.e., δ^18O) as well as seasonal variation of δ^18O has been examined to investigate the characteristics, sources and the passing route of precipitations in Niigata Pr...Time-course of oxygen stable isotopic ratios (i.e., δ^18O) as well as seasonal variation of δ^18O has been examined to investigate the characteristics, sources and the passing route of precipitations in Niigata Prefecture. The precipitation samples have been mainly collected with a filtrating bulk sampler at the rooftop of Niigata University. Furthermore, backward trajectories analyses have been also conducted for these samples taken sequentially for a short period. Consequently, the following features have been mainly clarified for the precipitations in Niigata Prefecture: (1) the δ^18O values varied between -14.57%o and -3.86%0 in the precipitations of Niigata University; (2) as for the comparison among sampling points, the mean value of δ^18O at seaside spots (i.e., Niigata City: -6.93%0) is larger than that of inland spots (Sanjyo City: -8.68%0); (3) δ^18O value was generally small in the rainy or typhoon season, and relatively large in summer; (4) decreasing δ^18O content with time is a predominant feature of sequentially sampled rainfalls as predicted by Rayleigh models of atmospheric vapor condensation.展开更多
文摘Time-course of oxygen stable isotopic ratios (i.e., δ^18O) as well as seasonal variation of δ^18O has been examined to investigate the characteristics, sources and the passing route of precipitations in Niigata Prefecture. The precipitation samples have been mainly collected with a filtrating bulk sampler at the rooftop of Niigata University. Furthermore, backward trajectories analyses have been also conducted for these samples taken sequentially for a short period. Consequently, the following features have been mainly clarified for the precipitations in Niigata Prefecture: (1) the δ^18O values varied between -14.57%o and -3.86%0 in the precipitations of Niigata University; (2) as for the comparison among sampling points, the mean value of δ^18O at seaside spots (i.e., Niigata City: -6.93%0) is larger than that of inland spots (Sanjyo City: -8.68%0); (3) δ^18O value was generally small in the rainy or typhoon season, and relatively large in summer; (4) decreasing δ^18O content with time is a predominant feature of sequentially sampled rainfalls as predicted by Rayleigh models of atmospheric vapor condensation.