Analysis of Drought Intensity and Trends Using the Modified SPEI in South Korea from 1981 to 2010

The aim of this study is to analyze the characteristics of drought, such as intensity and trends, based on SPEI (Standardized Precipitation Evapotranspiration Index) at 8 stations in South Korea from 1981 to 2010. The traditional SPEI is based on the Thornthwaite equation for estimating evapotranspiration; SPEI_th. However, a standard of agricultural water management in Korea suggests the FAO Penman-Monteith equation; SPEI_pm. Therefore, we analyzed the intensity, variability, and trends of drought using SPEI_th and SPEI_pm, respectively, and compared the results. SPEI_pm showed slightly more intensive drought rather than SPEI_th except for Chuncheon and Gwangju. In 5 stations-excluding Cheoncheon, Gwangju and Jinju-the cumulative probability that SPEI_pm was below 1.5 was significantly increased from 1981-1995 to 1996-2010. In addition, the northwest and southwest regions had higher intensity of 1-month droughts, and the central and southwest regions had a higher intensity of 3-month droughts. According to the Mann-Kendall test, there was a decreasing trend of 1-month SPEI during the fall season and 3-month SPEI during winter season.