As revealed by the empirical orthogonal function analysis (EOF), the dominant modes of northern hemispheric zonally-mean wind (u) in winter show two centers of opposite sign, one center located near 30?-35癗 and another near 55癗. The prominent modes of geopotential heights also show two centers, one is at 40癗 and another at 65癗. These two modes connected tightly. So, the zonal index can be defined as the difference in geopotential height between 40癗 and 65癗. This kind of zonal index correlate with westerly of 55癗 at 0.96. The anomalous variation of the westerly can impact the winter surface temperature and precipitation of China significantly. During the high-index years, most of China become warmer, and the precipitation in the mid-eastern China will increase. Correlation between the zonal index and the 160-station mean temperature and precipitation is 0.63 and 0.38 respectively.The Siberia High and Eastern Asia Trough that show the powerful control of winter climate of China, usually become weak during the high zonal index years.
GONG Dao-yi, WANG Shao-wu
. Structure of the Zonal-Mean Circulation Over the Northern Hemisphere and Its Impact on Climate of China in Winter[J]. SCIENTIA GEOGRAPHICA SINICA, 2001
, 21(2)
: 108
-112
.
DOI: 10.13249/j.cnki.sgs.2001.02.108
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