Geographia Technica, Vol 15, Issue 2, 2020, pp. 47-56
A COMPREHENSIVE GRID-BASED RAINFALL CHARACTERISTICS IN THE CENTRAL PLAIN RIVER BASIN OF THAILAND
Weerayuth PRATOOMCHAI 
, Sarintip TANTANEE , Chaiwat EKKAWATPANIT
ABSTRACT: Eight rainfall indicators were used to analyze the 5 min. × 5 min. grid-based rainfall characteristics in the central plain region of Thailand. The non-parametric statistics called Mann-Kendall test was applied to 32-year (1980-2011) time series data, statically significant (p-value ≤ 0.05) and Kendall’s tau correlation maps were considered for informative examination. Annual rainfall showed increasing trend in the upper basin and statically increasing by 35.8% of the whole basin. A number of rainy days (RD) and number of consecutive wet days (CWD) showed increasing by 70.2% and 57.9% of the basin for RD and CWD, respectively, while a number of consecutive dry days (CDD) exhibited decreasing trend over 85.0% of the study area even only 13.8% satisfied at 95% statically significant. The simple daily rainfall intensity (SDRI), heavy rainy days (HRD), max. 1-day, and max. 3-day demonstrated upward trends. The findings suggest that the region is shifting towards wetter condition. The explicit results of rainfall characteristics maps are expected to facilitate and allow various users to make better water resources management and overcome reluctant interpretation rainfall changes/trends for areas lacking of measured data as well as baseline information for climate change study.
Keywords: Chao Phraya River basin; Mann-Kendall test; rainfall indices; trend analysis
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