Scale interaction between typhoons and the North Pacific subtropical high
and associated remote effects during the Baiu/Meiyu season
The interaction between typhoons and the North Pacific subtropical high and the associated remote impact on East Asian and North Pacific anomalous weather
during the Baiu/Meiyu season have been investigated using the Japanese long-term Reanalysis project data aided by the Japan Meteorological Agency Climate Data
Assimilation System. The typhoons that appeared in July have been categorized into two primary tracks, the Hainan Island course (HC) and the Okinawa Island course (OC).
A typhoon gives rise to negative absolute vorticity advection along its eastern periphery, which locally reinforces the western ridge of the North Pacific
subtropical high, whereas the resultant anomalous high stimulates the westward (northward) migration of the HC (OC) typhoon through its combination with
the background flow. A combined effect of the typhoon and its induced anomalous anticyclonic circulation increases the transportation of moisture into
the Baiu/Meiyu frontal zone in the vicinity of Japan. Over the East China Sea and the Sea of Japan, northward or northeastward moisture flux is pronounced
along the western periphery of the typhoon-induced anticyclonic circulation anomaly in the HC category, triggering heavy rainfall on central Japan's Sea of Japan coast.
Similar remote effects also operate in the OC category, which is responsible for the occurrence of extremely heavy rainfall along the Pacific coast of western Japan.
When an OC typhoon approaches the Asian jet, it is capable of giving rise to anticyclonic vorticity within the jet, leading to the downstream development of
stationary Rossby wave packets via the North Pacific waveguide.
台風と太平洋高気圧との相互作用と梅雨期の台風の遠隔影響について、長期再解析並びに気象庁気候データ同化システムのデータを用いて調査した。
７月に発生した台風を二つの主経路、海南コース(HC)と沖縄コース(OC)、に分類した。台風はその東側に沿って負の絶対渦度移流を生じさせるため、北太平洋高気圧西端のリッジを
強化する一方、誘起された高気圧性循環は背景場の流れと複合することで、HCコース（OCコース）の台風の西進（北進）を促す。また、台風と台風が誘起した高気圧性循環の複合効果により、
日本付近の梅雨前線帯への水蒸気輸送が強化される（下図参照）。東シナ海から日本海にかけて、HCコースの台風が誘起した高気圧性循環の西縁に沿って北（東）向きの水蒸気フラックスが卓越し、
中部日本の日本海側で梅雨末期の大雨をもたらす要因となる。同様な遠隔影響はOCコースの台風でもみられ、西日本の太平洋沿岸の極端な大雨の発生要因の一つとなっている。OCコースの台風が中緯度のアジアジェットに
接近すると、ジェット内に高気圧性渦度を生成することで、北太平洋の導波管に沿う定常ロスビー波束の下流へのエネルギー伝播を生じさせている。
*Please refer to the following manuscript.
*詳細は下記論文を参照してください。
Hirata, H., and R. Kawamura (2014):
Scale interaction between typhoons and the North Pacific subtropical high and associated remote effects during the Baiu/Meiyu season. Journal of Geophysical Research: Atmospheres, 119, doi:10.1002/2013JD021430
