FACTOR-ANALYSIS OF REGIONAL CIRCULATION

Factor analysis of 500-mb geopotential height fields is used to identi fy atmospheric circulation regimes over the so-called third natural sy noptic region, which covers the east Pacific, North America, and the w est Atlantic in the Northern Hemisphere. Kendall rank correlation coef ficients are used to characterize the synoptic stability, or persisten ce, of atmospheric circulation patterns. Time series of stability asse ssments for various numbers of principal factors are analyzed. Circula tion stability over the region of interest is estimated quantitatively . A qualitative interpretation of flow features, depending on typical circulation structures, is given. The scenario for developing stable a nd unstable flows over the region under study is reconstructed.