By using the precipitation data of Seoul that is holding a remarkably long term, the historical drought events have been summarized, of them the longest drought period finds out for 25 months between 1900y and 1902y. The droughts are gradually intensified and frequent in the 20th century even though the precipitation is increased in the 20th century.
Seasonal drought in Korea has been investigated by using ST1. As the results, 1) most droughts and severe droughts are shown in summer because precipitation is mainly concentrated in summer. 2) The drought periodicity is extended to 8-year periodicity in comparison with 4-year periodicity in the 1970's and its fluctuation is bigger than past. These characteristics are detected through ST2 by three periods. One is 1777-2005 in Seoul station; another is 1942-2005.