Estimation of the Isotopic Composition and Origins of Winter Precipitation Over Japan Using a Regional Isotope Circulation Model. Issue 21 (11th November 2017)

• Record Type: Journal Article
• Authors: Tanoue, Masahiro; Ichiyanagi, Kimpei; Yoshimura, Kei; Shimada, Jun; Hirabayashi, Yukiko
• Is Part Of: Journal of geophysical research. Volume 122:Issue 21(2017)
• Page Start: 11, 621
• Page End: 11, 637
• Publication Date: 2017-11-11
• Subjects: isotopic composition of precipitation -- origins of precipitation -- regional isotope circulation model -- Japan -- East Asian Winter Monsoon; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2017JD026751
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The deuterium excess (d‐excess) of precipitation aids in identifying vapor source regions because it reflects humidity conditions in those regions. For Japan, studies have assumed that the Sea of Japan was the dominant source of winter precipitation when the d‐excess value in winter is >20‰ or higher than the average value in summer. Because this assumption is based on an interpretation that the high d‐excess value is due to an interaction between the continental winter monsoon (WM) and warm Sea of Japan, it may not be appropriate for winter precipitation due to extratropical cyclones (ECs). Here we clarify local patterns of isotopic composition and the origins of precipitation in WM and EC types over Japan using a regional isotope circulation model. The results indicate that the Sea of Japan made the highest contribution to precipitation on the Sea of Japan side in the WM type, whereas the Pacific Ocean is the dominant source of precipitation over Japan in the EC type. Because d‐excess values are higher in the WM type than the EC type, we can assume that the Sea of Japan is the dominant source of precipitation on the Sea of Japan side when the d‐excess value is high. In comparison, we cannot identify the source regions from d‐excess values alone for Honshu Island bordering the Pacific Ocean, because the difference in the d‐excess value between the WM and EC types is unclear. Moreover, WM variability can be estimated from observed d‐excess values due to their clear positive correlation. Key Points: The isotopic composition and origins of winter precipitation over Japan are clarified using a regional isotope circulation model The Sea of Japan contributes to winter precipitation with high deuterium excess on the Sea of Japan side of Japan Activity of the East Asian winter monsoon can be estimated from the observed deuterium excess of precipitation in the region Plain Language Summary: Understanding the dynamics of the origins of precipitation (i.e., vapor source regions) is useful for long‐term forecasting, understanding ocean‐atmosphere and land‐atmosphere feedback, and calibrating water isotope thermometers. We utilize a regional isotope circulation model and clarify local patterns of isotopic composition and the origins of precipitation in two typical winter precipitation types, winter monsoon (WM) and extratropical cyclones (ECs), over Japan. The results indicate that the Sea of Japan made the highest contribution to precipitation on the Sea of Japan side in the WM type, whereas the Pacific Ocean was the dominant source of precipitation over Japan in the EC type. Because deuterium excess (d‐excess) values are higher in the WM type than the EC type, we can assume that the Sea of Japan is the dominant source of precipitation on the Sea of Japan side when the d‐excess value is high. We also find that WM activity can be estimated from observed d‐excess values due to their clear positive correlation.