5:15 PM - 7:15 PM
[ACG36-P15] Decadal modulation of Indian Ocean basin-scale warming effects on East Asian summer climate
Keywords:Indian Ocean basin warming, Northwestern Pacific subtropical high, Decadal climate variability, Asian summer monsoon
Global climate variability and change can control a favorable background that impacts on the statistics on regional and local phenomena, such as heavy rainfall and temperature extremes. For example, the interannual variability in the summertime heavy daily rainfall potential in East Asia is closely linked to large-scale horizontal moisture transport anomalies due to changes in the subtropical high in the northwestern Pacific. The enhanced subtropical high is usually accompanied by basin-scale warming in the Indian Ocean following the wintertime El Niño events, and its low-frequency modulations may be influenced by the sea surface temperatures (SSTs) over the northern Indian Ocean and the tropical Pacific Ocean.
To assess the factors potentially contributing to the low-frequency modulations, we conducted sensitivity experiments using an atmospheric model. We focused on the SST differences between the first and second halves of the past four decades, in the background states, the basin-scale warming anomalies in the Indian Ocean, and the accompanying anomalies in the tropical Pacific Ocean. The response of the subtropical high in the northwestern Pacific to the basin-scale warming of the Indian Ocean is enhanced under the recent warmer background state particularly over the Indian and western Pacific Oceans. The different spatial patterns of the accompanying SST anomalies in the tropical Pacific, likely related to the so-called El Niño diversity, also contribute to the modulation by modifying tropical and subtropical atmospheric responses in the western Pacific.
To assess the factors potentially contributing to the low-frequency modulations, we conducted sensitivity experiments using an atmospheric model. We focused on the SST differences between the first and second halves of the past four decades, in the background states, the basin-scale warming anomalies in the Indian Ocean, and the accompanying anomalies in the tropical Pacific Ocean. The response of the subtropical high in the northwestern Pacific to the basin-scale warming of the Indian Ocean is enhanced under the recent warmer background state particularly over the Indian and western Pacific Oceans. The different spatial patterns of the accompanying SST anomalies in the tropical Pacific, likely related to the so-called El Niño diversity, also contribute to the modulation by modifying tropical and subtropical atmospheric responses in the western Pacific.