15:30 〜 15:45
[ACG33-06] Western Pacific teleconnection-induced East Asian warm winter during El Niño: Role of the Indian Ocean warming
キーワード：エルニーニョ、インド洋、テレコネクション、冬季東アジア
The winter East Asian climate tends to get warm in major El Niño events, but some cold winters were also observed despite the remote forcing from El Niño. Using the database for Policy Decision-making for Future climate change (d4PDF) large ensemble simulations, the present study investigates a mechanism for the warm and cold East Asian winters during El Niño with a focus on atmospheric teleconnections triggered by anomalous sea surface temperature (SST) patterns in the tropical Indo-Pacific.
Our results show that the Western Pacific (WP) teleconnection pattern plays a primary role in the warm winters in East Asia. The WP patterns tend to appear in years when both El Niño and the Indian Ocean dipole mode (IOD) develop in autumn. In those years, the tropical Indian Ocean (TIO) strongly warms in the following winter, forming a distinct zonal contrast in precipitation anomalies over the tropical Indo-Pacific through a reduced Walker circulation. The Rossby wave source anomalies show that the WP pattern is related to a weakened local Hadley circulation associated with suppressed (enhanced) convection over the western Pacific (western TIO). By contrast, the WP patterns do not dominate in cold winters due to the absence of strong TIO warming. The present study proposes feedback that promotes excitation of the WP pattern through the Hadley and the Walker circulations modulated by the tropical Indo-Pacific interbasin interaction.
Our results show that the Western Pacific (WP) teleconnection pattern plays a primary role in the warm winters in East Asia. The WP patterns tend to appear in years when both El Niño and the Indian Ocean dipole mode (IOD) develop in autumn. In those years, the tropical Indian Ocean (TIO) strongly warms in the following winter, forming a distinct zonal contrast in precipitation anomalies over the tropical Indo-Pacific through a reduced Walker circulation. The Rossby wave source anomalies show that the WP pattern is related to a weakened local Hadley circulation associated with suppressed (enhanced) convection over the western Pacific (western TIO). By contrast, the WP patterns do not dominate in cold winters due to the absence of strong TIO warming. The present study proposes feedback that promotes excitation of the WP pattern through the Hadley and the Walker circulations modulated by the tropical Indo-Pacific interbasin interaction.