Mechanism and Trend Change of Sudden Increase of Total Ozone in Seoul

The total ozone column values have been observed by numerous satellites including TOMS and OMI, and extensive network of ground-based measurements (Dobson & Brewer Spectrophotometer etc.), over long time period over the globe, in which statistical long-term trend or ozone recovery are analyzed. In March 14th, 2006, sudden increase of the total ozone values are observed in East Asia, where the mixing ratio of ozone in ozonesonde data at Sapporo (14th Mar, 2006) increased between 10 and 15km remarkably. In general, stratospheric ozone does not change that abruptly. However from late winter to early spring, sudden increase of total ozone values were observed over the North-east Eurasian Continent and the Sea of Ohotsuku. In the beginning of this periods, observed total ozone values increased by more than 40~50 DU, compared with previous day’s value, maintaining abnormal condition for a few days. This mechanism is not understood clearly but in previous studies, this effect occurred by secondary ozone peak that is caused by Stratosphere-Troposphere Exchange (STE). To explain this phenomenon, we select the highest 5% of total ozone values observed in Seoul since 1985 and analyze the back trajectory and NCEP/NCAR reanalysis data between 10~20km at the same time. In the events of sudden total ozone increase, air parcels of 10~15km altitudes came mostly from arctic region, which is statistically evident. These `arctic origin air’ are ozone-rich in mixing ratio thus results in the secondary ozone peak and ozone enhancements in Seoul. These enhancements were occurred several times in a month. Thus, it changes the average of total ozone and climatological values, which affects the trend of stratospheric ozone recovery. In this study, using the ozonesonde and total ozone data, we separate the total ozone and sudden enhancement of ozone in Upper troposphere/ Lower Stratosphere and examine the effect of these changes on the ozone recovery trend in Seoul.