A Spatiotemporal Analysis of Historical Droughts in Korea

Abstract

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) rainy season follows. Summer droughts tend to be long (.200 days) because the dry season (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 they were caused by the consecutive shortage of summer rainfall for two or more years.

Application of the extreme learning machine algorithm for the prediction of monthly Effective Drought Index in eastern Australia

“…Based on the predicted values of the EDI, the severity and the duration of drought at the four sites were deduced following the approach of Kim et al (2011) where a drought month was identified when the monthly value of the EDI was negative (i.e. rainfall conditions were lower rainfall than the normal period).…”

“…Moreover, Dogan et al (2012) found the EDI to be very sensitive to subtle changes in rainfall, and showed the superiority of the EDI for continuous monitoring of short and long-term drought. The study of Byun et al (2008) also showed the ability of the EDI for prediction of future drought in Korea using periodicity analysis of long-term observed dataset and the study of Kim et al (2011) developed a spatio-temporal map using wavelet transformations for the Korean region. Despite a plethora of studies using the EDI for drought assessment in East Asia, to our best knowledge, no study on the prediction of the EDI has been conducted in Australia.…”

“…Despite a plethora of studies using the EDI for drought assessment in East Asia, to our best knowledge, no study on the prediction of the EDI has been conducted in Australia. In this context, the prediction of the EDI is a novel and an enlightening problem of interest, as this index can assist with the detection of actual drought onset and termination dates, and drought severity or intensity based on various water scarcity conditions (Byun et al, 2008;Byun and Wilhite, 1999;Dogan et al, 2012;Kim et al, , 2011Masinde, 2013;Morid et al, 2006;Pandey et al, 2008). The prediction of the EDI can also facilitate the measurement of short-term dry spells and long-term (or ongoing) drought events and more precisely, the detection of current usable water resources and precipitation return to normal for assessment of drought severity conditions (Dogan et al, 2012;Morid et al, 2006;Pandey et al, 2008).…”

A process-based typology of hydrological drought

“…To eliminate minor droughts, all drought events with a duration less than 15 days were excluded from the analysis (values up to 5 days are used by Hisdal et al, 2004;Birkel, 2005;Fleig et al, 2006;Van Loon et al, 2011a, but various studies showed that minor droughts can have durations up to 20 days; Hisdal, 2002;Fleig et al, 2005;Kaznowska and Banasik, 2011;Kim et al, 2011). Of the remaining drought events, a few were found to be not real drought events, but rather artefacts of the method used.…”

A study on the predictability of the transition day from the dry to the rainy season over South Korea

“…The EDI is a daily index that represents a continuous period and daily strength changes as objective values; it is an intensive measure that considers water accumulation with the weighting function of time passage. The merits of the EDI have been verified by many studies (Morid et al 2006;Pandey et al 2008;Lee and Byun 2009;Kim et al 2011;Lee et al 2012). The EDI is calculated using three equations:…”