Classification, seasonality and persistence of low-frequency atmospheric circulation patterns

Abstract

Orthogonally rotated principle component analysis (RPCA) of Northern Hemisphere 1-month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability. The analysis is detailed and comprehensive, in that 1) a high resolution, approximately equal-area 358-point grid is used for the virtually maximum possible 35-yr period of record, 2) a positive bias in the NMC data base in the early 1950s in the subtropics is largely eliminated for the first time, and 3) homogeneous, separate analyses of each month of the year are carried out, detailing the month-to-month changes in the dominant circulation patterns. The conclusion from all considerations is that the RPCA method provides a physically meaningful, as well as statistically stable product with the simplicity of teleconnection patterns but with pattern choice and depiction superior to those of the teleconnection method. -from Authors