Exploring Uncertainty in Future Changes of Convective Afternoon Rainfall in Taiwan: The Influence of Sea Surface Temperature

The present study investigates the uncertainties in future projections of summer convective afternoon rainfall (CAR), a key meteorological feature in Taiwan that significantly contributes to over 40-50% of the total summer rainfall in Taiwan. The analyses employ a dynamical downscaling approach utilizing the Weather Research and Forecasting Model (WRF) and the High-Resolution Atmospheric Model (HiRAM). The projections were driven by four different sea surface temperature (SST) categories derived from CMIP5 model simulations under the Representative Concentration Pathway (RCP) 8.5 scenario. All projections indicate a consistent decrease in CAR frequency but an increase in intensity by the end of the 21st century. However, the extent of changes in CAR varies across four simulations with different degrees of Pacific SST warming. These variations in potential future changes in CAR frequency and intensity are linked to variations in daytime thermal instability, local inland wind convergence, and moisture flux convergence over Taiwan. The study further investigates the relationship between local thermodynamic conditions and projected large-scale atmospheric circulation patterns, emphasizing a decrease in East Asian monsoonal low and a decrease in subtropical Pacific high in the future. The study also clarifies the potential impact of ENSO on modulating the changes in CAR activities over Taiwan under global warming, where La Niña-like circulation patterns induce more CAR activities over Taiwan compared to El Niño-like circulation patterns. In summary, the study offers valuable insights into the potential implications of climate change on CAR events in Taiwan, highlighting the importance of understanding the underlying physical mechanisms of the factors governing CAR event characteristics.