Large-scale sea surface temperature forcing contributed to the 2013–2017 record-breaking meteorological drought in Korea

Abstract This study examined the contribution of the Pacific Decadal Oscillation (PDO) to the record-breaking 2013–2017 drought in Korea. The meteorological drought signal, measured by the Standardized Precipitation Index (SPI), in 2013 and 2016 co-occurred with a heat wave. The positive phase of the PDO during the mid-2010s was responsible for the precipitation deficit, particularly in 2014, 2015, and 2017, resulting in a five years of meteorological drought. The enhanced atmospheric heating anomalies over the subtropical central Pacific, induced by the in-situ PDO-related sea surface temperature (SST) warming, led to a low-atmospheric cyclonic flow centered over the mid-latitude Pacific. The northerly wind anomalies at the western edge of this low-level cyclonic flow were responsible for the horizontal negative advection of moist energy, which contributed to the decreased precipitation and the resultant negative SPI over Korea in 2014, 2015, and 2017. The large-ensemble simulation supported the observational findings that the composited SST anomalies during the five years of persistent drought exhibited prominent and persistent SST warming over the subtropical central Pacific, along with large-scale cyclonic flow over the North Pacific. The findings of this study imply that the SST anomalies over the North Pacific and subtropical central Pacific can be a predictable source to potentially increase the forecast ability of the multi-year Korea droughts.