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[AAS04-02] Interannual variations of moisture sources and isotopic composition of Meiyu-Baiu rainfall in Kyushu, southwestern Japan from 2004 to 2023
Keywords:Meiyu-Baiu rainfall, Extreme event, Moisture sources, Isotopic composition, Southwestern Japan, Interannual variations
Meiyu rainfall is an important climate phenomenon in East Asia, but its interannual variability in terms of frequency and intensity has amplified in recent decades. Moisture sources and isotopic composition of precipitation are crucial for understanding the effect of large-scale circulations on Meiyu-Baiu rainfall. The purpose of this study is to clarify the interannual variations of moisture sources and isotopic composition of the Meiyu-Baiu rainfall in Kyushu, southwestern Japan from 2004 to 2023.
A colored moisture analysis (CMA) with isotopic regional spectral model (isoRSM) was conducted to simulate the moisture sources and isotopic composition of Meiyu-Baiu rainfall in Kyushu from June 1 to July 31 during 2004-2023. The basic design for CMA was the same as that in Li et al. (2023), water origins were classified into three groups: Asian monsoon (AM) moisture, North Pacific subtropical high (NPSH) moisture, and local moisture. During the 20 Meiyu-Baiu seasons, a total 71 extreme rainfall events were selected for further event-based analysis.
During the 20 Meiyu-Baiu seasons, AM moisture was dominant, transported to Kyushu by the Asian monsoonal southwesterlies in the middle levels. Besides, the NPSH moisture was moderate, transported by the NPSH in the low levels. Regarding the isotopic characteristics, AM moisture showed lower δ2H and higher d-excess, due to more rainout and below-cloud evaporation during long-distance transport. These features are consistent with the results in Li et al. (2023).
For the interannual variability, the contribution of each major moisture to the total rainfall increased from the light Meiyu-Baiu seasons to the heavy seasons. Among the three moisture sources, the AM moisture exhibited the largest variability. The heavy Meiyu-Baiu seasons were characterized by enhancement of the AM and NPSH moisture and lower δ2H and higher d-excess. In addition, the western Pacific subtropical high expanded westward with the deepened East Asian mid-latitude trough on the east of the Tibetan Plateau. For the extreme rainfall events, extreme rainfall amount and extreme event number are positively corelated with total Meiyu-Baiu rainfall. Moisture source of extreme rainfall events are principally contributed from the AM moisture.
In this study, we systematically clarified the major moisture sources and their corresponding isotopic characteristics associated with large-scale circulations for heavy Meiyu-Baiu seasons and extreme rainfall events during 2004-2023. The study highlights importance of the AM moisture for extreme Meiyu-Baiu rainfall in East Asia.
A colored moisture analysis (CMA) with isotopic regional spectral model (isoRSM) was conducted to simulate the moisture sources and isotopic composition of Meiyu-Baiu rainfall in Kyushu from June 1 to July 31 during 2004-2023. The basic design for CMA was the same as that in Li et al. (2023), water origins were classified into three groups: Asian monsoon (AM) moisture, North Pacific subtropical high (NPSH) moisture, and local moisture. During the 20 Meiyu-Baiu seasons, a total 71 extreme rainfall events were selected for further event-based analysis.
During the 20 Meiyu-Baiu seasons, AM moisture was dominant, transported to Kyushu by the Asian monsoonal southwesterlies in the middle levels. Besides, the NPSH moisture was moderate, transported by the NPSH in the low levels. Regarding the isotopic characteristics, AM moisture showed lower δ2H and higher d-excess, due to more rainout and below-cloud evaporation during long-distance transport. These features are consistent with the results in Li et al. (2023).
For the interannual variability, the contribution of each major moisture to the total rainfall increased from the light Meiyu-Baiu seasons to the heavy seasons. Among the three moisture sources, the AM moisture exhibited the largest variability. The heavy Meiyu-Baiu seasons were characterized by enhancement of the AM and NPSH moisture and lower δ2H and higher d-excess. In addition, the western Pacific subtropical high expanded westward with the deepened East Asian mid-latitude trough on the east of the Tibetan Plateau. For the extreme rainfall events, extreme rainfall amount and extreme event number are positively corelated with total Meiyu-Baiu rainfall. Moisture source of extreme rainfall events are principally contributed from the AM moisture.
In this study, we systematically clarified the major moisture sources and their corresponding isotopic characteristics associated with large-scale circulations for heavy Meiyu-Baiu seasons and extreme rainfall events during 2004-2023. The study highlights importance of the AM moisture for extreme Meiyu-Baiu rainfall in East Asia.