5:15 PM - 7:15 PM
[ACG36-P08] The synoptic patterns affected by Tropical Pacific SST and extreme rainfall during the Baiu season
Keywords:Extreame rainfall, North Pacific High, ENSO, Interannual variation
El Niño-southern oscillation brings substantial impacts on weather worldwide. During El Niño decline from winter to summer, the North Pacific High (NPH) tends to extend westward to the south of Japan, which results in more-than-usual occurrence of atmospheric rivers around Japan. It is unclear, however, how this condition affects the frequency of extreme rainfall. Therefore, this study examines the relationship among NPH, Tropical Pacific sea surface temperature (SST), and the frequency of extreme rainfall based on the observational and reanalysis data.
We detected extreme rainfall events in June and July during 1976–2024 considering the Baiu season when massive water vapor transport occurs along the periphery of the NPH. The analysis domain was set to cover Kyushu region, southwestern Japan. The threshold of extreme rainfall is 80 mm/3hr based on the in-situ precipitation data of the Automated Meteorological Data Acquisition System (AMeDAS). Days with prevailing NPH close to Kyushu (NPH-pattern) was selected through the Self-Organizing Maps technique using JRA-3Q-based sea level pressure. It is found that the interannual variation in extreme rainfall is significantly correlated with the occurrence frequency of NPH-pattern. Additionally, this occurrence frequency is significantly correlated with the interannual variation in SST anomaly in the central Tropical Pacific from previous winter to spring. These results suggest that the SST anomaly in central Tropical Pacific affects the frequency of extreme rainfall in Kyushu region through the influence on the occurrence frequency of NPH-pattern.
We detected extreme rainfall events in June and July during 1976–2024 considering the Baiu season when massive water vapor transport occurs along the periphery of the NPH. The analysis domain was set to cover Kyushu region, southwestern Japan. The threshold of extreme rainfall is 80 mm/3hr based on the in-situ precipitation data of the Automated Meteorological Data Acquisition System (AMeDAS). Days with prevailing NPH close to Kyushu (NPH-pattern) was selected through the Self-Organizing Maps technique using JRA-3Q-based sea level pressure. It is found that the interannual variation in extreme rainfall is significantly correlated with the occurrence frequency of NPH-pattern. Additionally, this occurrence frequency is significantly correlated with the interannual variation in SST anomaly in the central Tropical Pacific from previous winter to spring. These results suggest that the SST anomaly in central Tropical Pacific affects the frequency of extreme rainfall in Kyushu region through the influence on the occurrence frequency of NPH-pattern.