Combined Effects of Blocking and AO on a Prolonged Snowstorm in Jeju Island

Abstract

An analysis of the snowstorm that occurred during January 23–25, 2016 in Jeju Island is presented. This event was considered part of the snowfall pattern that rarely occurs at Jeju Island due to the mild marine climate. In terms of diabatic heating, there are two factors encompassing convection and large-scale condensation. One heating factor was the convective instability due to cold advection at the upper level that was 1.7 times stronger than the continuous cold advection at the lower level. The other heating factor was the latent heat emitted by cloud developed by the instability. In the context of large-scale environment, the result of vertical temperature differential was due to the transition to the strong negative Arctic Oscillation (AO) in January 2016. Under the negative AO phase, blocking tilted to the southeast, compared to normal, occurred in the upper layers. Simultaneously, a trough with a core temperature of −45 °C was rapidly induced over the Korean Peninsula. In this study, the snowstorm occurred with a sea surface temperature 1–2 K higher than normal over the Yellow Sea, and cold advection to lower layers was persistent. Therefore, the snowstorm has not been resolved through consideration of the local instability. A maximum of 12 cm of fresh snow cover was recorded during this snowstorm, which persisted for 3 days due to the impact on its large-scale environment, which generated a strong vertical cold advection differential through the occurrence blocking during January 19–24, 2016, under the strong negative AO phase.