Abstract: In order to study the features and causes of the drought disasters,the two drought events and their atmospheric circulation anomaly occurred in the northern China in summer of 1986 and 1997 is examined using daily stations precipitation data,daily monsoon monitoring index,daily subtropical high index,74 atmospheric circulation indices and NCEP/NCAR reanalysis data. The results show that,in comparison with 1986,the drought in 1997 had a longer duration,stronger disaster degree and larger range. The two Western Pacific Subtropical High (WPSH) evolutions showed a significant difference. This results display that the WPSH position is stronger and larger,in comparison with 1986,in addition to a shift to the west and south. This results in less water vapor transport from the tropical Indian Ocean and the South China Sea,and the sinking motion anomaly. Furthermore,the analysis of Pacific sea surface temperature showed that distribution of different equatorial and northwest Pacific SSTs affected different oscillation of the North-South and East-West of WPSH,thereby affecting the different arid region distribution in the two drought process.

Key words: drought event, circulation indices, atmospheric circulation, sea temperature anomaly, water vapor transport