<Notes>Distribution of Monthly Rainfall in Northeast Thailand

Abstract

The distribution in space and in time of monthly rainfall in Northeast Thailand is investigated in this paper, using daily data at 56 stations, each having at least 20 years of continuous record. It was found that monthly rainfall sequences at all stations in this region have six significant harmonics corresponding to six periods : 12, 6, 4, 3, 2.4 and 2 months. At a station, the rainfall sequence in a month can be considered to be independent and can be fitted by the leakage law. Moreover, during the months of April through September, monthly rainfall in the region has a general pattern of increasing values towards the eastern and northeastern sections, while during the months of October to January, it has a general pattern of decreasing values towards these sections. Finally, an assessment of water availability for irrigation is made using the distribution of monthly rainfall and the potential evapotranspiration.