CARE2022 Hong Kong Conference

78 SESSION 1 Dealing with Excess Water Challenges 1. Sponge cities in China – advances and challenges Prof. Haifeng Jia (School of Environment, Tsinghua University, Beijing, CUHK) Oscillation (ENSO) and Madden-Julian Oscillation (MJO) may affect North America. It differs from Pacific/North American (PNA) teleconnection that is strongly influenced by ENSO-induced central Pacific precipitation anomalies. PNA features the anomalous Gulf of Alaska and Aleutian Low (High) during El Niño (La Niña). Thus, the Gulf of Alaska Low in ANA eminent during the 2021 La Niña is not a PNA response to the central Pacific heating associated with ENSO. Instead, the ANA teleconnection is coerced by the “wet Indiadry Philippines” dipolar heating resulting from the multi-scale interaction between the rapidly developing La Niña and the quasi-stationary MJO. Numerical experiments affirmed that the “wet India-dry Philippines” dipolar precipitation heating fortifies ANA teleconnection by generating two cross-Pacific wave trains. Indian heating induces a subtropical cross-Pacific wave train along the jet stream. In contrast, the Philippine heat source stimulates a midlatitude circum-Pacific wave train under November mean state. The combined effects of the dipolar heating during late Fall are demonstrated for the first time. The study of clustering extreme precipitation events provides a new perspective on examining future precipitation variability by emphasizing the clustering extreme precipitation events with escalated compound impact beyond their simple addition. Besides, the sequential clustering of extreme events might offer a predictability source because their favourable atmospheric precursors stem from the tropics associated with the rapid La Niña cooling. It also poses a question of whether there are ongoing changes in the routes of how the tropics and extratropics interact. 3. Accelerated intensification of extreme rainfall at urban scales Prof. Shaoming Shi, (Division of Environment and Sustainability, HKUST) Precipitation extremes can cause flooding and landslides, which bring substantial economic and societal losses. Under global warming, the intensity of precipitation events is expected to be generally strengthened, but quantitative prediction remains challenging, especially in tropical regions. This uncertainty is challenging for city authorities to make the most cost-benefit-and effectiveness decisions regarding climate adaptation. The challenges are rooted in the multiscale nature of convective weather systems and the limitation of computing resources for resolving all scales. 7 Workshop: Scholars’ Day Haifeng Jia, Tsinghua University A consequence of urbanisation is increased urban run-off that contribute to urban flooding all over the world. The traditional way to deal with urban run-off is to build concrete channels to carry the excess water away as quickly as possible. The new sponge city concept takes a completely different approach by ‘living with nature’ and requires fundamentally different design and implementation techniques. China’s approach has gained international attention. While the central government promote sponge city since 2013, local authorities have been responsible for implementation. The major challenges include insufficient knowledge, coordinating many disciplines and agencies for a project, how to quantify cost effectiveness, obtaining enough finance, and training of talent. 2. Clustering catastrophic weather events from India to China to Canada during COP27 Prof. Mengqian Lu (Department of Civil and Environmental Engineering, HKUST) The presentation explained a new phenomenon of extreme precipitation events that occurred in October-November 2021 that brought floods and blizzards across the world. Those events were connected to an intraseasonal/Asian/ North American (ANA) teleconnection (climate variability links between non-contiguous geographic regions) consisting of the South Asia High, East Asia Low, Okhotsk-Bering Sea High, Gulf of Alaska Low, and California High. The ANA teleconnection is a new route by which El Niño-Southern