17:15 〜 18:45
[AAS06-P06] 北半球夏季の東アジアにおける北西太平洋熱帯低気圧に関連する降水の増加傾向
キーワード：台風降水、東アジア―太平洋地域、極端天気、気候変動、太平洋十年変動
1. Introduction
The long-term variation in the intensity of TCs presents considerable scientific and administration challenges, particularly as these TC activities frequently result in substantial human casualties and extensive property damage. Over recent decades, there has been a notable escalation in the socio-economic damages caused by TCs on a global scale. Furthermore, TC-induced precipitation, a frequent cause of disasters like floods and landslides, is increasing under global climate change, particularly in the Northwest Pacific and North Atlantic regions. Given the significant threat that TCs pose to human safety and productive activities, there is a need for further practical assessment of the risks associated with TCs.
In East Asia (EA), the economic impact of TCs has notably risen during the TC season. Despite the significant TC effects in this region, targeted research on TC activity and associated precipitation over the entire EA continent remains limited. So, we are keenly interested in studying the changes in the Western North Pacific (WNP) basin's TC-related precipitation in the EA region during the summer season.
2. Data & Method
The TC frequency, trajectory, and other characteristics were obtained from the IBTrACS Project Version 4, focusing on the EA region. TC-related precipitation is identified from the CMORPH data and APHRODITE_MA V1101 data. The study covers a period from 1979 to 2021, focusing on the WNP basin during summer. For our observational analysis and to identify the scope of TC-related precipitation, we utilized ERA5 hourly and monthly reanalysis data. The sea surface temperature data were obtained from the COBE-SST2.
To provide a more comprehensive description and explanation of TC-related precipitation, we considered the precipitation within the main body of TC and distant rainfall connected to the TC through moisture channels. We defined these two types of precipitation as 'TC core precipitation' (TCP) and 'TC remote precipitation' (TRP), respectively. Here, we have chosen a fixed radius from the TC center for identifying TCP and an atmospheric river detection technique to identify TRP.
3. Results
The TC-related precipitation predominantly occurs in southern and southeastern China, extending across South Korea and Japan. Excluding Japan, the rainfall generally decreases from the coastal areas towards the inland. The rainfall pattern over the northern part of the Korean peninsula shows significant intensification, closely linked with the variation of TRP. Since the mid-1990s, the Pacific region has experienced a prolonged La Niña phase. This phenomenon, discussed as a climate shift, occurred between 1997 and 1999, accompanied by a notable entry into the PDO's negative phase by the end of 1998.
Interestingly, the characteristics of TCs over the WNP basin also exhibit similar transitional traits. Therefore, in this study, we define two distinct epochs based on the identified regime shifts: epoch1 (1979-1996) and epoch2 (1997-2021). Here, we observe a significant increasing trend in extreme TC rainfall during epoch2, which nearly doubled compared to epoch1 (As Figure shows). The findings indicate a significant negative correlation between TC-related precipitation and the PDO during epoch2. This connection can be attributed to the continentward and poleward trajectories of TCs influenced by the PDO. Our research identifies such a shift correlating with the intensified West Pacific subtropical high (WPSH) affected by the PDO.
In conclusion, this research provides insights into the long-term variability of TCs and their impacts, enhancing our understanding of climate change implications in the EA region. The study underscores the importance of considering both TCP and TRP in assessing the full scope of TC impacts, and we believe it will offer contributions to climate and disaster risk management strategies in the context of evolving TC dynamics.
The long-term variation in the intensity of TCs presents considerable scientific and administration challenges, particularly as these TC activities frequently result in substantial human casualties and extensive property damage. Over recent decades, there has been a notable escalation in the socio-economic damages caused by TCs on a global scale. Furthermore, TC-induced precipitation, a frequent cause of disasters like floods and landslides, is increasing under global climate change, particularly in the Northwest Pacific and North Atlantic regions. Given the significant threat that TCs pose to human safety and productive activities, there is a need for further practical assessment of the risks associated with TCs.
In East Asia (EA), the economic impact of TCs has notably risen during the TC season. Despite the significant TC effects in this region, targeted research on TC activity and associated precipitation over the entire EA continent remains limited. So, we are keenly interested in studying the changes in the Western North Pacific (WNP) basin's TC-related precipitation in the EA region during the summer season.
2. Data & Method
The TC frequency, trajectory, and other characteristics were obtained from the IBTrACS Project Version 4, focusing on the EA region. TC-related precipitation is identified from the CMORPH data and APHRODITE_MA V1101 data. The study covers a period from 1979 to 2021, focusing on the WNP basin during summer. For our observational analysis and to identify the scope of TC-related precipitation, we utilized ERA5 hourly and monthly reanalysis data. The sea surface temperature data were obtained from the COBE-SST2.
To provide a more comprehensive description and explanation of TC-related precipitation, we considered the precipitation within the main body of TC and distant rainfall connected to the TC through moisture channels. We defined these two types of precipitation as 'TC core precipitation' (TCP) and 'TC remote precipitation' (TRP), respectively. Here, we have chosen a fixed radius from the TC center for identifying TCP and an atmospheric river detection technique to identify TRP.
3. Results
The TC-related precipitation predominantly occurs in southern and southeastern China, extending across South Korea and Japan. Excluding Japan, the rainfall generally decreases from the coastal areas towards the inland. The rainfall pattern over the northern part of the Korean peninsula shows significant intensification, closely linked with the variation of TRP. Since the mid-1990s, the Pacific region has experienced a prolonged La Niña phase. This phenomenon, discussed as a climate shift, occurred between 1997 and 1999, accompanied by a notable entry into the PDO's negative phase by the end of 1998.
Interestingly, the characteristics of TCs over the WNP basin also exhibit similar transitional traits. Therefore, in this study, we define two distinct epochs based on the identified regime shifts: epoch1 (1979-1996) and epoch2 (1997-2021). Here, we observe a significant increasing trend in extreme TC rainfall during epoch2, which nearly doubled compared to epoch1 (As Figure shows). The findings indicate a significant negative correlation between TC-related precipitation and the PDO during epoch2. This connection can be attributed to the continentward and poleward trajectories of TCs influenced by the PDO. Our research identifies such a shift correlating with the intensified West Pacific subtropical high (WPSH) affected by the PDO.
In conclusion, this research provides insights into the long-term variability of TCs and their impacts, enhancing our understanding of climate change implications in the EA region. The study underscores the importance of considering both TCP and TRP in assessing the full scope of TC impacts, and we believe it will offer contributions to climate and disaster risk management strategies in the context of evolving TC dynamics.