2013 Volume 122 Issue 4 Pages 666-681
Deuterium excess (d-excess), as well as δ18O and δD, can offer an opportunity to understand hydrological cycles. However, there have been few investigations on d-excess of precipitation within a broad area observation network, including high-latitude areas. This study presents spatiotemporal variations in d-excess of precipitation observed in the Japanese Alps region. Precipitation samples, collected monthly at 14 locations across the Japanese Alps region from July 2010 to June 2011, were sampled for isotopic analyses. Annual precipitation amount weighted mean values of d-excess ranged from 11.0 to 14.7‰, and a correlation with altitude was found. No correlation with longitude and latitude was observed. Monthly variations in d-excess indicated a tendency toward higher d-excess values during the winter months at all sampling points. Spatial distribution of d-excess in each month showed significant correlations of d-excess with altitude in summer months. In winter months, relatively high values of d-excess were observed in precipitation caused under winter-type synoptic pressure patterns. Thus, spatiotemporal variations in d-excess of precipitation over the Japanese Alps region can be characterized by the correlation with altitude in summer months and the influence of synoptic conditions on its spatial distribution in winter months.