การวิเคราะห์ภัยแล้งบริเวณภาคเหนือของประเทศไทยโดยใช้ดัชนีความแห้งแล้ง Standardized Precipitation Index (SPI)

Abstract

Abstract

This study aims to analyze the characteristics of spatial and temporal drought in northern Thailand during the years 1980-2017 (38 years), by analyzing the Standardized Precipitation Index (SPI). The data consists of monthly rainfall data from 31 observation stations of the Thai Meteorological Department (TMD) and gridded rainfall data from the Climatic Research Unit (CRU). The correlation coefficient between TMD monthly observed rainfall data and CRU gridded data is high with the range of 0.826-0.983, which indicates that the CRU data can be represented as the observation data. Therefore, in this study, the 78 grids of CRU precipitation data covering the northern region were used for calculating the SPI index in 2 different periods which is 3-month SPI index (SPI3) to analyze the early drought rainy season, and 6-month SPI index (SPI6) to analyze drought throughout the rainy season. From the analysis of SPI3 of July (Average of May-July) found that there were drought years ranging from severe drought to extreme drought (SPI3 ≤ -1.50) for 14 years. In 1987, there were affected areas of more than 25% and more than 75% in 2015. While the analysis of SPI6 of October (Average of May-October) found that there were drought years ranging from severe drought to extreme drought (SPI6 ≤ -1.50) for 15 years. In 1993, there were affected areas of more than 25% and more than 75% in 2015. In addition, it was found that drought in the northern region was associated with the El Nino phenomenon. The severe El Nino year has resulted in severe and extreme droughts, affecting almost the entire northern region.