5:15 PM - 6:45 PM
[HTT16-P02] Oxygen and hydrogen stable isotope of precipitation and back-trajectory analysis for elucidating the origin of water vapor in Kyotanabe, Kyoto
Keywords:precipitation, oxygen and hydrogen stable isotope, back-trajectory analysis
Precipitation serves as one of the crucial sources of freshwater at the Earth's surface, influencing both ecological environments and urban development. Therefore, during the global variations in precipitation patterns, it is essential to elucidate the origin of water vapor condensing to precipitation.
In order to elucidate the origins of water vapor contributing to precipitation and the evaporation processes, the temporal variations in the oxygen and hydrogen stable isotope ratios of monthly precipitation samples collected from July 2019 to February 2021 and from June 2022 to October 2023 in Kyotanabe, Kyoto, Japan. To visualize the origin of air during precipitation, the HYSPLIT model was used to generate the back-trajectory at 850 hPa from October 2019 to October 2020 and from October 2022 to October 2023, and clustered by month.
The precipitation amount was higher from June to October and lower from November to February. An increasing trend in annual precipitation amount is observed, with an increase in the number of days with daily precipitation amount of 100 mm or more. The average annual temperature rose from 13.4℃ in 1985 to 16.3℃ in 2022, indicating a warming trend. From July 2019 to October 2023, the average monthly temperature during the spring season is clearly increased.
The temporal variations of the oxygen and hydrogen stable isotopic in precipitation show that δ18O and δ2H from June 2022 to October 2023 showed less variability than from July 2019 to February 2021. Except for August 2019, June and July 2020, August 2022 and April 2023, a correlation was observed between more increased precipitation and lower isotopic ratios, whereas no discernible relationship with temperature or seasonal variations was identified.
The back-trajectory analysis and variations in d-excess values for the origin of the water vapor that brings precipitation show that the influence of cold and dry air from the continent in winter, resulting in the relatively rapid evaporation of seawater from the west of Japan (the Yellow Sea, the East China Sea and the Sea of Japan), and bringing precipitation with high d-excess values to Kyotanabe. During the summer, warm and humid air from the Southeast Asian seas and the Pacific Ocean influence the slow evaporation at western and south-western seas of Japan and the Pacific Ocean. Therefore, the d-excess values of precipitation in Kyotanabe City were smaller and close to 10‰.
In order to elucidate the origins of water vapor contributing to precipitation and the evaporation processes, the temporal variations in the oxygen and hydrogen stable isotope ratios of monthly precipitation samples collected from July 2019 to February 2021 and from June 2022 to October 2023 in Kyotanabe, Kyoto, Japan. To visualize the origin of air during precipitation, the HYSPLIT model was used to generate the back-trajectory at 850 hPa from October 2019 to October 2020 and from October 2022 to October 2023, and clustered by month.
The precipitation amount was higher from June to October and lower from November to February. An increasing trend in annual precipitation amount is observed, with an increase in the number of days with daily precipitation amount of 100 mm or more. The average annual temperature rose from 13.4℃ in 1985 to 16.3℃ in 2022, indicating a warming trend. From July 2019 to October 2023, the average monthly temperature during the spring season is clearly increased.
The temporal variations of the oxygen and hydrogen stable isotopic in precipitation show that δ18O and δ2H from June 2022 to October 2023 showed less variability than from July 2019 to February 2021. Except for August 2019, June and July 2020, August 2022 and April 2023, a correlation was observed between more increased precipitation and lower isotopic ratios, whereas no discernible relationship with temperature or seasonal variations was identified.
The back-trajectory analysis and variations in d-excess values for the origin of the water vapor that brings precipitation show that the influence of cold and dry air from the continent in winter, resulting in the relatively rapid evaporation of seawater from the west of Japan (the Yellow Sea, the East China Sea and the Sea of Japan), and bringing precipitation with high d-excess values to Kyotanabe. During the summer, warm and humid air from the Southeast Asian seas and the Pacific Ocean influence the slow evaporation at western and south-western seas of Japan and the Pacific Ocean. Therefore, the d-excess values of precipitation in Kyotanabe City were smaller and close to 10‰.