Structures of Winter Monsoon Surges over the Far East Obtained from Empirical Orthogonal Function Analysis 1

Empirical Orthogonal Function analysis was applied to 4-6 day filtered wind and temperature data over eastern China, the East China Sea, southern Japan, the South China Sea, and the tropical western Pacific during the period 16 November 1970 through 15 March 1971. Eigen vector patterns for the first two modes indicate anomalous low-level northerly surges which tend to move progressively eastward across the China-East China Sea-Japan region. The combination of anomalous northerlies, below normal temperature, and abnormally strong descending motions results in a northward sensible heat flux and local kinetic energy generation below 700mb over this region. The outstanding features of the third eigen vector occur over the South China Sea where strong low-level northerly surges are contrasted with pronounced upper-level southerlies and much higher than normal temperature above 300mb. This region is also characterized by abnormal ascending motions and strong diabatic heating in the deep atmospheric layer from 850 to 200mb, perhaps reflecting pronounced convective activity. Flow patterns of the third eigen vector indicate the existence of a local Hadley cell with updrafts over the South China Sea and downdrafts near Japan.