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Estimation of the Isotopic Composition and Origins of Winter Precipitation Over Japan Using a Regional Isotope Circulation Model
Author(s) -
Tanoue Masahiro,
Ichiyanagi Kimpei,
Yoshimura Kei,
Shimada Jun,
Hirabayashi Yukiko
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2017jd026751
Subject(s) - precipitation , extratropical cyclone , climatology , environmental science , humidity , pacific ocean , atmospheric sciences , oceanography , geology , geography , meteorology
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.