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This paper is the first of a two-part study that investigates summer convective afternoon rainfall (CAR) activity over the East Asian continent through simulation and projection. We focus on the CAR activity over Taiwan in Part I. In Part II, the changes in CAR activity over South China and Luzon are examined. Using the WRF (Weather Research and Forecasting) model driven by two super-high resolution global climate models: HiRAM (High Resolution Atmospheric Model) and MRI (Meteorological Research Institute Atmospheric General Circulation Model), this study evaluates the performance of models (HiRAM, MRI, and WRF) used to simulate the summer CAR activity over Taiwan. The evaluations focus on the spatialtemporal variations in CAR activity during two time periods: the present-day (1979 - 2003, historical run) and the future (2075 - 2099, RCP8.5 scenario). For the present-day simulations, analyses indicate that both HiRAM and MRI cannot accurately simulate the temporal evolution of diurnal rainfall. This timing shift problem can be fixed after dynamical downscaling using WRF. The WRF dynamical downscaling approach also helps generate a more realistic CAR amount simulation over western Taiwan, where most residents live. In future projections all models predict that a significant decrease in CAR amount will occur over southwest Taiwan. This decrease in CAR amount is suggested due to the decrease in CAR frequency, not a change in the CAR rate. All models suggest that the cause of decrease in CAR frequency over southwest Taiwan is weaker local afternoon surface wind convergence and thermal instability to suppress CAR genesis. [ABSTRACT FROM AUTHOR]

This study is the second of a two-part investigation into summer convective afternoon rainfall (CAR) simulation and projection over the East Asian continents. In Part I, we examined the CAR activity over Taiwan. In this study we focus on CAR activity over South China and Luzon using the WRF (Weather Research and Forecasting Model) driven by HiRAM (High Resolution Atmospheric Model) (i.e., WRF-HiRAM). These examinations focus on two time-sliced simulations assuming the climate conditions at present (1979 - 2003, historical run) and at the end of the 21st century (2075 - 2099, RCP 8.5 scenario). The results show that WRF-HiRAM is capable of simulating the spatial-temporal variation in CAR activity over South China and Luzon close to the recorded observations. In the future projections, WRF-HiRAM predicts that CAR events over most of South China and eastern Luzon will become fewer but stronger. Conversely, CAR events over western Luzon will become more frequent and stronger. Analyses also indicate that the projected change in CAR amount over most of South China (except for the coastal regions) and Luzon will be dominated by the change in CAR rate, not the change in CAR frequency. As for the cause of change in CAR rate, WRF-HiRAM projects that atmospheric humidity over South China and Luzon will increase significantly in the future. This will lead to an increase in local CAR rate. In contrast, the projected change in CAR frequency over South China and Luzon is suggested to be greatly modulated by the change in daytime surface wind convergence and thermal instability. Examinations were also performed to document the characteristics and causes of the projected change in CAR activity extracted from HiRAM. [ABSTRACT FROM AUTHOR]