Characteristics of Gridded Rainfall Data for Thailand from 1981–2017
We used a spatially interpolated gridded dataset produced by the Thai Meteorological Department (TMD) to explore long-term rainfall trends. We placed data from 1981–2017 into a 0.5° grid using the Kriging method. Long-term trends in maximum daily and monthly rainfall, and total annual rainfall, were analyzed using the nonparametric Mann–Kendall trend test. Chumphon, Lamphun, Nakhon, Sawan, and Buriram provinces exhibited significant positive trends in the annual maximum daily rainfall (p<0.05, p<0.01). The coastal area of Chachoengsao Province exhibited a significant negative trend (p<0.05). January rainfall showed a negative trend throughout Thailand. Annual rainfall showed a positive trend in many regions, especially in northern, northeastern, and southern areas. The eastern region exhibited a negative trend but statistical significance was not attained. The 10-, 30-, 50-, and 100-year daily rainfall probabilities were estimated using the Generalized Extreme Value method. The eastern side of the southern region exhibited remarkably high rainfall.
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