Climatology of Low-Level Jets of Korea from Long-Term Rawinsonde Observations

Using long-term rawinsonde observation data collected from nine stations, we obtained the climatology of low-level jets (LLJs) over Korea, including occurrence frequency, altitude, wind direction, and wind speed. The characteristics (frequency, altitude, speed, direction) of LLJ occurrence on the Korean Peninsula show unique spatiotemporal variations. At stations located on the west coast (Baengnyeongdo and Heuksando), LLJ frequency was high from April to May (approximately 40%) and low in winter (approximately 15%). The station on the northeastern coast (Sokcho) displayed a double-peak pattern in LLJ frequency (approximately 30%), with peaks occurring from April to May and July to August. The inland areas (Gwangju and Osan) showed significantly lower LLJ occurrence frequencies than the coastal stations. In contrast, the southeastern coast (Pohang) and Jeju Island exhibited high occurrence frequencies (30–50%) throughout the year, unlike other stations where LLJs rarely occur even in winter. The altitude at which LLJs primarily occur is low (concentrated below 500 m) at the west coast stations and higher (evenly distributed up to 3 km) at the east coast stations. The wind directions of LLJs at the west coast and inland stations exhibited seasonal changes, being southerly in summer and northerly in winter, which were attributed to monsoon. In contrast, the east coast (Sokcho and Gangneung) consistently showed westerly wind LLJs throughout the year. LLJ wind speeds ranged from 13 to 20 m/s, with the strongest winds occurring in the northern part of the east coast (Sokcho and Gangneung).