No abstract

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 study determines the summer monsoon season over Southern Vietnam in 1981-2014 period by using observed daily rain-gauge data and reanalyzed daily 850 hPa wind data. The results show that the mean onset and retreat dates of summer monsoon over Southern Vietnam occur on May 15 and October 13, with standard deviations of 14.12 and 13.55 days, respectively. The results also show that the onset and retreat dates tend to precede in the recent years. In summer monsoon period, the values of RX1day and RX5day are high in Rach Gia and Ca Mau but low in Can Tho, CDD of all stations are low. In all stations, the values of extreme rainfall indices in 1998-2014 period are higher compared to those in 1981-1997 period.