Public Research Seminar by Earth, Ocean and Atmospheric Sciences (EOAS) Thrust, HKUST (GZ) - Past and future variations of extreme rainfall over the Asian monsoon region under a changing climate: A process-oriented perspective

Asia, one of the world’s most densely populated regions, receives 50–80% of its annual rainfall during summer. However, the region is increasingly affected by extreme rainfall events, which often trigger floods and landslides, posing severe risks to human life and economic development. Despite growing concern, the physical mechanisms driving extreme rainfall variability remain incompletely understood, and the future projections differ substantially across global climate models. 

To address these challenges, Dr. Yujia You integrates high-resolution observations and climate model simulations to develop a process-oriented framework for understanding extreme rainfall in the Asian monsoon region. Her research focuses on heavy rain-producing weather systems and includes three key components: (1) By developing an automated, objective feature-tracking algorithm, the heavy rain-bearing low-pressure systems (LPSs) were identified, and their contributions to extreme rainfall were evaluated. LPSs that form on the downwind side of the Tibetan Plateau are found to be the dominant drivers of heavy rainfall across inland monsoon regions of China, with a significantly greater impact than tropical cyclones, whose influence is largely confined to coastal areas. (2) A genesis potential index was then constructed to link LPS activity to large-scale environmental variables. Environmental vorticity, relative humidity, and baroclinicity are key regulators of LPS activity, with declining baroclinicity emerging as the key driver of the observed long-term changes. (3) Given the critical importance of LPSs in generating extreme rainfall, the physical mechanisms by which internal variability and external forcing regulate extreme rainfall were evaluated, using Pakistan’s record-breaking heavy rainfall events in summer 2022 as a case study. The potential for improving climate models' ability to simulate LPSs and thereby constrain uncertainties in future extreme rainfall projections was also discussed.

Together, her research aims to advance our understanding of the physical mechanisms driving extreme rainfall variability in the Asian monsoon region and provides a foundation for better interpreting observed trends and more reliable future projections.