The stratosphere–troposphere exchange of ozone and aerosols over Korea

Abstract

Vertical profiles of ozone, partial pressure, and meteorological parameter are obtained from ozonesondes and rawinsondes launched at Pohang (36.03°N, 129.40°E) in Korea. Stratosphere–troposphere exchanges (STE) of ozone and aerosols associated with the upper trough/surface high pressure system have been analyzed by TOMS data, and reanalyzed data of NCEP/NCAR and meteorological mesoscale model such as potential temperature, geopotential height, potential vorticity, and ageostrophic and vertical wind velocity. The secondary ozone peak in the upper troposphere over Pohang corresponded to the central axis of the jet stream near the tropopause, and then an enhancement of ozone in the upper troposphere was observed when the jet stream with a cut-off low was located over Korea. The maximum flux of ozone by STE over Korea occurs in wintertime and springtime. It was estimated that the downward fluxes observed in winter and spring for the period of 5 yr (1995–1998) at Pohang were the source of −7.72×10 7 ozone molecules/cm 2 s between 100 and 300 hPa, and 5.72×10 7 ozone molecules/cm 2 s between 300 and 500 hPa. The annual average flux during the period also was presented as a decrease of 3×10 7 ozone molecules/cm 2 s between 100 and 500 hPa. It indicates that ozone flux is decreasing in the lower stratosphere and increasing in the troposphere. The gradients of potential temperature and isentropic potential vorticity near the upper troposphere in east Asia sloped steeply like the frontal zone between the polar and the subtropical jet core. Therefore, it was regarded that ozone and aerosols of the upper level over east Asia penetrated into the lower level or the ground over Korea because of the downstream due to tropopause folding near the jet streams and the sinking of surface high pressure. In particular, yellow-sand occurring in springtime in east Asia was determined by the distribution of weather systems associated with STE. The results of observation and modeling indicate that the enhancements of ozone and aerosols in springtime occur in the advection and the downward motion due to the upper trough/cut-off low and the high surface pressure.