Eulerian Characteristics of the Meteorological Fields of an Explosive Cyclone Linked to a Tropopause Fold

The purpose of this paper is to present the Eulerian characteristics of meteorological fields regarding an explosive cyclone linked to a tropopause fold that occurred on January 1, 1997. The cyclone caused heavy snowfall and strong wind in the mid-region of the Korean Peninsula. The Eulerian characteristics of the meteorological conditions are examined using the atmospheric soundings at Osan and NCEP/NCAR reanalysis data. The present study mainly focuses on the temporal variation of both the thermal and dynamical tropopause, and the temporal changes of thermodynamic and kinematic variables. Temporal variation of tropopause is investigated based on WMO definitions of the thermal and dynamical tropopause. The analyzed variables include wind, water vapor content, temperature along with relative vorticity, and vertical air motion during the development of the explosive cyclone. The results suggest that the tropopause fold contributed to the development of the explosive cyclone, and that thermal tropopause acted as an interface, where there are significant changes in wind direction, water vapor mixing ratio, and temperature. An anomaly of static stability in the lower troposphere is found to be explicable by the transportation of stratospheric air through low-level tubes, suggested by Bithell et al. (1999). The present study suggests that the thermal tropopause is a critical interface, demarcating the layers of warm advection from the layers of cold advection during the fold of the tropopause. During the fold, the core region of cyclonic vorticity is found to be located above the dynamic tropopause.