東アジアにおける降水 d-excess 季節変動に関する再考察  [in Japanese] A reconsideration of Seasonal Variation in Precipitation Deuterium Excess Over East Asia  [in Japanese]

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Abstract

本研究では,過去の解釈の修正を念頭に置き,東アジア域での降水d-excessが冬季において高くなるメカニズムを考察した.気象庁のアメダス再統計値・NCEP/DOEの広域大気場の再解析データ・同位体大循環モデルを用いた解析から,日本海・太平洋北西部・黄海・東シナ海などを含む東アジアに隣接する海洋一帯(「東アジア海洋域」と定義)において,洋上大気の温度が海面水温に対して著しく低くなるため,実効相対湿度(海面水温で基準化した相対湿度)が下がる.そのため,大きな動的同位体分別によって高いd-excessを持つ水蒸気が大量に大気へ供給され,日本域・朝鮮半島・中国東部において,高いd-excessをもった降水がもたらされていることがわかった.冬季における太平洋起源の水蒸気のd-excessは日本海起源のそれと同様に高いことから,過去の解釈では可能とされていた日本における降水d-excessから水蒸気の起源が日本海か太平洋かを推定することは困難である.

This study investigates on the remarkable seasonal variations in deuterium excess (d-excess) in precipitation over large part of the East Asia. By using the AMeDAS (Automated Meteorological Data Acquisition System) re-statistic data provided by JMA (Japan Meteorological Agency), NCEP/DOE (National Centers of Environmental Prediction/Department of Energy) atmospheric reanalysis data, and an isotope-enabled atmospheric general circulation model, the followings are found: In winter season, the "East Asian Oceans," which include the Japan Sea, northwestern part of the Pacific Ocean, the Yellow Sea, and the East China Sea, are much warmer than the overlying surface air, and the effective relative humidity (vapor pressure normalized by saturated vapor pressure at sea surface temperature) becomes low; and evaporated vapor from East Asian Oceans, which have high d-excess due to the kinetic isotopic fractionation, causes d-excess-enriched precipitation over Japan, the Korean Peninsula, and the eastern part of China. Previously, precipitation over Japan has been believed decomposable its water vapor origin by using its d-excess because of the difference in d-excess of two distinctive sources, i.e., over the Japan Sea or the Pacific Ocean, but it is revealed difficult because of little difference in d-excess of the two origins due to the above mentioned processes.

Journal

  • JOURNAL OF JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

    JOURNAL OF JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 22(4), 262-276, 2009-07-05

    THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

References:  35

Cited by:  2

Codes

  • NII Article ID (NAID)
    10025316634
  • NII NACSIS-CAT ID (NCID)
    AN10088049
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    09151389
  • NDL Article ID
    10386296
  • NDL Source Classification
    ZM44(科学技術--地球科学--海洋・陸水・火山)
  • NDL Call No.
    Z15-619
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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