A Spatiotemporal Analysis of Historical Droughts in Korea

The climatological characteristics of drought in South Korea were investigated using daily precipitation data for 1777‐2008. The effective drought index was used to quantify the drought intensity. As a result, five characteristics were discovered. First, South Korea can be divided into four drought subregions (the central, southern, and east coastal regions and Jeju Island) using hierarchical cluster analysis. Second, a map for longterm drought conditions in the four subregions is created that allows identification of the spatiotemporal distribution of droughts for the 231 yr at a glance. Third, droughts in South Korea have time scales that depend on the onset season. Spring (March‐May) droughts tend to be short (#200 days) because the summer (June‐September)rainyseasonfollows.Summerdroughtstendtobelong(.200days)becausethedryseason (October‐February) follows. In the dry season, droughts tend to be sustained or become severe rather than being initiated or relieved. Fourth, 5-, 14-, 34-, and 115-yr drought cycles were identified by spectral analysis. The 5-yr cycle was dominant in all of the regions, the 14-yr cycle was observed over the southern and east coastal regions, and the 34-yr cycle was observed over the central region. Fifth, the most extreme drought occurred in 1897‐1903 (return period: 233 yr) and was associated with the 115-yr drought cycle. After this drought, severe droughts (return period of .10 yr) occurred in 1927‐30, 1938‐40, 1942‐45, 1951‐52, 1967‐69, and 1994‐96; they were caused by the consecutive shortage of summer rainfall for two or more years.