Evaluation Rainfall Characteristics over Vietnam Simulated by the Non–Hydrostatic Regional Climate Model – NHRCM during the 1981–2001 period
This study aims to evaluating characteristics of rainfall simulated by Non–Hydrostatic Regional Climate Model (NHRCM) over seven sub–regions of Vietnam during the 1981–2001 period. Features such as seasonal cycle of monthly average daily rainfall, maximum daily rainfall, and frequencies at different thresholds are compared with observations. Statistical evaluations of errors and correlation coefficient are also examined to see the differences between model results and observations. The results show that NHRCM captured well the seasonal cycle of the simulated monthly average daily rainfall, but magnitudes are underestimated in all sub–regions except South Central Vietnam (N1). Generally, underestimations of the simulated daily rainfall are observed in almost all months and sub–regions, higher differences are found in rainy months and the most underestimation of rainfall is observed in South Vietnam (N3). Correlation coefficients over 0.6 are found in North West Vietnam (B1) and South Vietnam (N3). Monthly absolute maxima of the observed daily rainfall are found in North Central (B4) in transition months when the model usually underestimated significantly. In addition, NHRCM tends to simulate cases with rainfall amounts below 16 mm/day or above 50 mm/day with higher frequencies compared with the observations. In contrast, frequencies detected by NHRCM seem to be lower than those of the observations for rainfall amount in 16 – 50 mm/day, especially in sub–regions N2 and N3. These results are supportive for applying the Regional Climate Model in simulating rainfall characteristics over Vietnam, especially for Non–Hydrostatic version.