報告書番号

T00017

タイトル（和文）

地球温暖化に伴う東アジアの気候変化 -NCAR-CSM/RegCM2.5を用いてシミュレートされた現状気候およびCO2倍増気候の評価-

タイトル（英文）

Climate change in and around Japan due to global warming. - Evaluation of present and 2CO2 climates simulated with the NCAR-CSM/RegCM2.5 nesting system -

概要 （図表や脚注は「報告書全文」に掲載しております）

NCAR-CSMを用いたCO2漸増実験結果を側方・下方境界条件として，RegCM2.5により東アジアの現状の気候およびCO2倍増時の気候をシミュレートした。RegCMの結果はCSMと比べて海面気圧や気温の分布で差は小さかったが，冬季のわが国の日本海側における降水量や梅雨期の降水帯を良く再現し，RegCMの必要性を示した。現状気候の再現結果において，シベリア高気圧，北太平洋高気圧の過少／過大評価，オホーツク海の低温バイアスのほか，春季，秋季の気候の特徴が約１ヶ月早く始まるなど，主としてCSMのバイアスに起因するバイアスの存在が明らかにされた。CO2倍増に伴うオホーツク海を中心とした冬季の温度上昇や北太平洋高気圧の発達傾向などが示されたが，ほとんどが現状気候のバイアスを補償する方向に働いており，バイアスの絶対値を越えない。今後の気候変化予測には全球気候モデルの精度向上が最も重要である。

概要 （英文）

In this study, present and 2CO2 climates for East Asia are simulated with the RegCM2.5 using the outputs of the CO2 transient run from NCAR-CSM as lateral and surface boundary conditions. Although the simulated geographical distribution patterns of sea level pressure and temperature are similar between RegCM and CSM, RegCM reproduced more realistic climate features such as wintertime precipitation along the Japan Sea side of Japan and precipitation zones in the early summer rainy season. These results indicate the availability of RegCM for the prediction of local climate change. Through the evaluation of a simulated present climate, significant biases are found such as underprediction of the Siberian High in winter, overprediction of the North Pacific High (NPH) in summer, and cold bias over the Okhotsk Sea in winter, as well as the earlier progress of seasonal features both in spring and autumn. These are mainly due to the biases reproduced by the CSM in the CO2 transient run. For a 2CO2 climate, some climate change features such as wintertime warming over the Okhotsk Sea and the development of NPH toward the southwest are found. However, most of the climate changes, including these changes, occur over the bias region, and their magnitudes do not necessarily exceed the bias of the simulated present climate. Therefore, these climate change features must be examined through the careful comparison with the results from the additional simulations or those from other model systems. The most important point for the prediction of regional climate change is the improvement of the performance of global climate models to represent the present climate.

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