This study uses the non-hydrostatic regional climate model (NHRCM) to simulate and project rainfall and tropical cyclone (TC) activity over Vietnam. The simulated precipitation shows that climatic heavy rainfall centers are well captured in the seasonal march. In near and far future, the projected rainfall by NHRCM using outputs of the Meteorological Research Institute atmospheric general circulation model 3.2 with RCP8.5 scenario will clearly decrease in Northwest and Central Vietnam in June-August, while it will remarkably increase in Northeast and Central Vietnam in September-November. The model underestimates TC number and activity area in the first half of the TC season but slightly overestimates in the second half as compared to the best track. Projected TCs indicate a decrease in both TC number and activity area in near and far future. Moreover, the maximum TC number occurs one month late as compared to the present climate, whereas TC number remarkably decreases in July-August in far future. Rainfall induced by TCs increases in North Vietnam in the projected climate as compared to the baseline period. It also increases in mid-Central Vietnam in near future but decreases in southern Central Vietnam in near and far future. Conversely, non-TC rainfall is likely to decrease in North Vietnam in future and in mid-Central Vietnam in near future but increase in southern Central Vietnam in far future.

This article presents analyses of changes in the seasonal characteristics of the far future climate (2080-2099) across Vietnam as projected by the Non-Hydrostatic Regional Climate Model (NHRCM) in terms of the RCP 8.5 (Representative Concentration Pathways 8.5) scenario. The results show significant changes in seasonal rainfall in Vietnam compared with the 1982-2003 baseline period. Specifically, the June-August rainfall is projected to increase in South Central (SCVN), Central Highlands (CHVN), and South Vietnam (SVN), but to decrease by approximately 50% in North Central (NCVN) and off the Central coast. In the September-November season, the NHRCM detects an increase in rainfall of about 50% in North Vietnam (NVN) and CHVN. The increase and decrease in rainfall are due to the convergence and divergence of moisture flux that might be associated with the westward expansion of the Northwestern Pacific High Pressure in the far future.