Characteristic analysis of East Asia atmospheric circulation in summers of abnormal years of the Western Pacific Warm Pool

Based on NCEP/NCAR reanalyzed data, a composite analysis of East Asia atmospheric circulation in summer of SST abnormity years of the Western Pacific Warm Pool is made. In comparison with the average conditions in climate, the results show that when the Warm Pool SST is positive, a strong anticyclone deviation circulation occurs in the lower troposphere over the Western Pacific Ocean along with positive SST anomalies of the Warm Pool, going against development of the westerly over the south of the South China Sea and the equatorial Pacific Ocean, and weakening the intensity of tropical summer monsoon; a deviation flow over the area between the west of the South China Sea and the eastern part of the Indo-China peninsula turns to the China's mainland, the southerly boosting up and the subtropical summer monsoon becoming stronger; in the middle and lower troposphere, the position of the ridge line of the west Pacific subtropical high goes southward, and bounded approximately by 400 hPa, the intensity of subtropical high strengthens in the lower troposphere and weakens in the upper troposphere. When the Warm Pool SST is negative, the situations are basically opposite to the above, the intensity or variation extent is smaller than that in the warm abnormal years. In addition, the ascending branch of the Walker circulation moves westward largely in the warm abnormal years, but shift eastward in the cold abnormal years.