2:15 PM - 2:30 PM
[AAS03-02] Moisture sources of the record-breaking heavy rainfalls over Tohoku region in August 2022
Keywords:heavy rainfalls, moisture sources, Tohoku region, stationary front
Tohoku region (Aomori-ken, Akita-ken, and Iwate-ken) suffered record-breaking heavy rainfalls in early August 2022. Based on observations, three major events occurred on August 3rd, 8th~9th, and 11th, before the landing of the tropical storm Meari (No. 8). According to the early reports from the JMA, the major forcing of these events was the stationary front, and there were large amount of moisture transported from the East China Sea (ECS). However, it remains unclear whether the relatively small ECS could supply enough moisture for the continuous heavy rainfalls. On the other hand, unlike the summer Meiyu-Baiu front, this stationary front located at higher latitude, and therefore could unlikely be affected by the regular moisture-rich regions reported in previous studies, such as the Kuroshio and the subtropical western Pacific (WP) due to the blocking of the Japanese Archipelago. Thus, this study was motivated to identify and evaluate the moisture contributions and transport routes during the heavy rainfalls over Tohoku region.
In this study, moisture sources and transport routes were based on the Lagrangian air parcels that were backward traced 3 days. According to our results, the three major events did not share the same mechanisms and moisture sources (Figure). The moisture in the first event on August 3rd was transported mainly from the southern part of the Sea of Japan (JS) and the subtropical WP region south of Japan carried by the previously vanished Tropical storm Trases and the following migratory anticyclone. In the second event, the stationary front created a relatively stable moisture transport route which allowed the moisture from the ECS and the southeast China mainland entering the JS. During the last event on August 11th, due to the approaching tropical storm, the stationary front was disturbed and so was the moisture transport route from the ECS. On the other hand, as the front moved southward, the moisture from the Kuroshio region and the oceans south of Japan was allowed to be transported across the Japanese Archipelago. As a result, the contribution from the subtropical WP increased much compared to that in the second event.
During the meeting, the detailed results and further analyses would be presented.
In this study, moisture sources and transport routes were based on the Lagrangian air parcels that were backward traced 3 days. According to our results, the three major events did not share the same mechanisms and moisture sources (Figure). The moisture in the first event on August 3rd was transported mainly from the southern part of the Sea of Japan (JS) and the subtropical WP region south of Japan carried by the previously vanished Tropical storm Trases and the following migratory anticyclone. In the second event, the stationary front created a relatively stable moisture transport route which allowed the moisture from the ECS and the southeast China mainland entering the JS. During the last event on August 11th, due to the approaching tropical storm, the stationary front was disturbed and so was the moisture transport route from the ECS. On the other hand, as the front moved southward, the moisture from the Kuroshio region and the oceans south of Japan was allowed to be transported across the Japanese Archipelago. As a result, the contribution from the subtropical WP increased much compared to that in the second event.
During the meeting, the detailed results and further analyses would be presented.