Combined Effect of ENSO and AO on Winter Temperatures of the Korean Peninsula on Subseasonal Time Scales

The combined effect of the El Nino-Southern Oscillation (ENSO) and Arctic Oscillation (AO) on the variability of boreal winter (December-February) temperature over South Korea is examined at the subseasonal time scale using subseasonal-to-seasonal (S2S) hindcast data. Daily hindcast data from the European Centre for Medium-Range Weather Forecasts (ECMWF) database is used. We selected the following six composite cases using a threshold of +/- 0.5 for each index: El Nino and positive AO (EP), El Milo and negative AO (EN), La Nina and positive AO (LP), La Nina and negative AO (LN), positive AO only (PA), and negative AO only (NA). Results from reanalysis data suggest the possibility of using these two climate factors as predictors for 1-month prediction of South Korea up to 4 weeks in advance. Thus, we confirmed that the ENSO plays a statistically significant role in strengthening (weakening) the AO influences on the temperature anomalies in the in phase (out of phase). For example, there is a significant increase (decrease) in mean temperature anomalies through positive (negative) geopotential height (GPH) anomalies and warm (cold) temperature advection over South Korea in the EP (LN) case. The ECMWF S2S hindcast demonstrated an acceptable ability to reproduce circulation patterns over East Asia up to 3 weeks in advance, and sufficiently predicted weekly mean temperature anomalies over South Korea in EP, LN, and PA cases.

Automated summary

The study found that El Nino and Arctic Oscillation have impacts on winter temperatures in South Korea, internal climate factors can predict temperatures in advance, and in specific cases, they can influence temperature anomalies.