Stable isotopic characteristic of Taiwan's precipitation: A case study of western Pacific monsoon region |
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| Authors: | Tsung-Ren Peng Chung-Ho Wang Chi-Chao Huang Li-Yuan Fei Chen-Tung Arthur Chen Jeen-Lian Hwong |
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| Institution: | 1. Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan;2. Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan;3. Central Geological Survey, Ministry of Economic Affairs, Taipei 23568, Taiwan;4. Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan;5. Lienhuachih Research Center, Taiwan Forestry Research Institute, P.O. Box 5, Yuchih, Nantou 55549, Taiwan;1. Key Laboratory of Western China''s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China;2. Department of Geological Sciences, University of Texas at San Antonio, San Antonio, TX 78249-0663, USA;1. UPMC Univ. Paris 06; Université Versailles St-Quentin, LATMOS-IPSL, Paris, France;2. UPMC Univ. Paris 06; UMR8539, CNRS/INSU, LMD-IPSL, Paris, France;3. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA;4. Spectroscopie de l''Atmosphère, Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles (ULB), Brussels, Belgium;1. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332, United States;2. Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, United States;3. Institute for Atmospheric and Climate Science, ETH Zürich, Universitätstrasse 16, 8092 Zürich, Switzerland;4. Gunung Mulu National Park, Sarawak, Malaysia;5. Institute of Biodiversity and Environmental Conservation, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Malaysia;1. Shanxi Normal University, School of Geographical Science, 1 Gongyuan Street, Linfen, Shanxi Province 041000, China;2. State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences (CAS), Urumqi, Xinjiang, China;3. Institute of International Rivers and Eco-security, Yunnan University, Kunming 650091, Yunnan, China |
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| Abstract: | The stable oxygen and hydrogen isotopic features of precipitation in Taiwan, an island located at the western Pacific monsoon area, are presented from nearly 3,500 samples collected during the past decade for 20 stations. Results demonstrate that moisture sources from diverse air masses with different isotopic signals are the main parameter in controlling the precipitation's isotope characteristics. The air mass from polar continental (Pc) region contributes the precipitation with high deuterium excess values (up to 23‰) and relatively enriched isotope compositions (e.g., ? 3.2‰ for δ18O) during the winter with prevailing northeasterly monsoon. By contrast, air masses from equatorial maritime (Em) and tropical maritime (Tm) supply the precipitation with low deuterium excess values (as low as about 7‰) and more depleted isotope values (e.g., ? 8.9‰ and ? 6.0‰ for δ18O of Tm and Em, respectively) during the summer with prevailing southwesterly monsoon. Thus seasonal differences in terms of δ18O, δD, and deuterium excess values are primarily influenced by the interactions among various precipitation sources. While these various air masses travel through Taiwan, secondary evaporation effects further modify the isotope characteristics of the inland precipitation, such as raindrop evaporation (reduces the deuterium excess of winter precipitation) and moisture recycling (increases the deuterium excess of summer precipitation). The semi-quantitative estimations in terms of evaluation for changes in the deuterium excess suggest that the raindrop evaporation fractions for winter precipitation range 7% to 15% and the proportions of recycling moisture in summer precipitation are less than 5%. Additionally, the isotopic altitude gradient in terms of δ18O for summer precipitation is ? 0.22‰/100 m, greater than ? 0.17‰/100 m of winter precipitation. The greater isotopic gradient in summer can be attributed to a higher temperature vs. altitude gradient relative to winter. The observed spatial and seasonal stable isotopic characteristics in Taiwan's precipitation not only contribute valuable information for regional monsoon research crossing the continent–ocean interface of East Asia, but also can serve as very useful database for local water resources management. |
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