Assessment of Drought Severity over South Korea using Standardized Precipitation Evapo-transpiration Index (SPEI)

Abstract

Drought is a non-negligible disaster of nature and it is mainly caused by rainfall shortage for a long time though there are many definitions of drought. 'Standard Precipitation Index' (SPI) that is widely used to express the level of meteorological drought intensity has a limit of not being able to consider the hydrological changes such as rainfall and evapotranspiration caused by climate change, because it does not consider the temperature-related variables other than the precipitation. Recently, however, 'Standardized Precipitation Evapotranspiration Index' (SPEI), a drought index of new concept which is similar to SPI but can reflect the effect of temperature variability as well as the rainfall change caused by climate variation, was developed. In this study, the changes of drought occurrence in South Korea were analyzed by applying SPEI for meteorological data (1973～2011) of 60 climate observatories under Korea Meteorological Administration (KMA). As the result of application, both of SPI and SPEI showed the trend of deepening drought in spring and winter and mitigating drought in summer for the entire nation, with SPI showing greater drought intensity than SPI. Also, SPI and SPEI with 12 months of duration showed that severe droughts with low frequency of around 6 years are generally being repeated.

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

“…During the past 30 years, Korea suffered from the severe drought damage at least once every 5-8 years [30,42]. In addition, moderate drought has happened annually in the regional and national area since 1990 [42].…”

“…A few studies have evaluated the drought using SPEI based on the Thornthwaite equation for calculating evapotranspiration [30]. The evapotranspiration is related to several factors, including temperature, precipitation, wind, humidity, etc.…”

Response to reviewer #2

“…Even though our findings from crop yields suggest the contrary due to the predominance of cereal croplands in northcentral regions of Spain, this can be attributed to episodes of abnormal extreme temperatures, such as the very low temperatures in early spring or warmer than usual temperatures in winter. These would affect the expected low evapotranspiration rates during the cold season (Fontana et al, 2015;Kolář et al, 2014). A recent study by Hernandez-Barrera et al (2016) demonstrated that during autumn and spring, precipitation deficit is the most influential climate factor affecting wheat growth, while an increase in the diurnal temperature range causes a reduction in wheat yield.…”

Analysis of Drought Characteristics using Time Series of Modified SPEI in South Korea from 1981 to 2010

“…During the past 30 years, Korea suffered from the severe drought damage at least once every 5-8 years (KRC, 2001; Kim et al, 2012). In addition, the moderate drought has been happened annually in the regional and national area, since 1990.…”

“…A few studies evaluated the drought using SPEI based on Thornthwaite equation for calculating evapotranspiration (Kim et al, 2012;Kim et al, 2013). The evapotranspiration is related to several factors such as temperature, precipitation, wind, and humidity etc.…”