Study on the classification and characteristics of cold surge in South Korea

Abstract This study examined the characteristics of cold surges in the Korean Peninsula over the last 45 years (1975–2019). During the period, there were 37 cases of cold surges affected by blocking (B_CS) and 129 cases of cold surges not influenced by blocking (nB_CS), indicating that most of the cold surges were nB_CS. The blocking that caused a cold surge over the Korean peninsula occurred mostly in the Okhotsk region and Ural region (OK_B and UR_B, respectively). In rare cases, blocking occurred simultaneously in the two regions called double blocking (DO_B), causing strong and long‐lasting cold surges. The nB_CS was related closely to the propagating wave‐train, hence the mean duration of nB_CS was shorter than the B_CS because the wave‐train propagated fast from the northwest to the southeast. Although the number of occurrences of B_CS was low, B_CS was stronger and lasted longer than nB_CS. In the case of cold surges affected by UR_B, referred to as UR_CS, their progression was slower compared to the cold surges affected by nB_CS because UR_B is slowing the atmospheric flow in the west. For cold surges affected by OK_B (OK_CS), the progression was slower than nB_CS and UR_CS because blocking was located downstream, slowing the propagating trough. Accordingly, the mean durations of nB_CS, UR_CS, and OK_CS were 2.7, 3.6, and 5.1 days, respectively, the mean of the temperature anomaly throughout the cold surge, was −3.8, −5.4, and −5.1°C, respectively. Overall, both the intensity and the progression speed of the cold surges differed according to the presence and location of blocking. A common characteristic of all types of cold surges was that they occur after the passage of the trough having a baroclinic structure. In addition, all types of cold surges were linked to an expansion of the Siberian high.