[M-IS06] Extreme Weather and Disasters in Southeast Asia

[MIS06-01] Understanding extremely pluvial winters over Yangtze–Huai River basin in China: Their complexity and tropical oceans influences

★Invited Papers

*Jiaying He^1,2,3, Jing-Jia Luo^1,2, Takeshi Doi³ (1.Nanjing University of information science and technology, 2.ICAR Institute for Climate and Application Research, 3.Japan Agency for Marine-Earth Science and Technology)

Keywords:Extremely precipitation, Model prediction/predictability, Tropical Oceans

In 2018/19 winter, the Yangtze–Huai River Basin (YHRB, one of the most developed areas in China) experienced an extremely pluvial condition with excessive and long-duration precipitation. Other three extremely pluvial winters during 1979/80–2018/19: 1997/98, 2002/03 and 1989/90 winters were also found. In 2018/19, 2002/03 and 1997/98 winters, similar low-level circulation pattern of anomalous southwesterlies (southeasterlies) over the southern (northern) YHRB was found. However, we found different tropical ocean states for the events. In 2018/19 winter, a combination of a moderate El Niño in the tropical Pacific and warm sea surface temperature (SST) anomalies in the tropical western Indian Ocean (IO) and Atlantic was seen. In 1997/98 winter, we found an extreme eastern Pacific El Niño with warm SST anomalies in the western tropical IO. In 2002/03 winter, a central Pacific El Niño occurred. In contrast, no significant warm SST anomalies were seen in 1989/90 winter. Based on coupled model numerical experiments, the tropical SST anomalies contributed almost half of the YHRB precipitation anomalies in 2018/19 and 1997/98 winters. In particular, the tropical IO warm SST anomalies induced anomalous anticyclones over the South China Sea and northeastern China, with moisture convergence over the YHRB. In 2002/03, the tropical Pacific SST anomalies contributed almost half of the YHRB precipitation anomalies, although its contribution could be reduced due to the inter-basin interactions. For 1989/90 winter, we discussed possible impacts of mid-high latitude wave trains. The results indicate the complexity and diverse potential predictability among the four extreme pluvial winters.