Twentieth century changes in winter climatic regions (original) (raw)

The configuration of the northern hemispheric general atmospheric circulation system shifted from a zonal to a meridional pattern in the early 1950s. Winter climatic regions in the conterminous United States are developed for a ten year period dominated by zonal flow and a second decade of meridional flow using a combination of principal components factor analysis and a Euclidean distance clustering algorithm. The results demonstrate that regional patterns in the surface climatic data substantially changed as the circulation system shifted its basic configuration. The regional structures of the eastern United States and the Great Plains appeared to be particularly sensitive to the change in the upperlevel flow pattern. Many of the efforts to link shifts in climatic regions to circulation patterns have been carried out in the reconstruction of Holocene environments. Bryson, Baerreis, and Wendland [11 ] established spatial associations between climatic and biotic regions, and