The Index Cycle: a Cross-Spectral Analysis of Zonal Index Data

摘要: Abstract In order to examine quantitatively the evidence for an index cycle, 21 years of daily 700-mb. zonal data western longitudes Northern Hemisphere were subjected cross-spectral analyses. The annual variation mean and standard deviation three indices (polar, temperate, subtropical) was removed by a standardizing procedure utilizing time-smoothed curves. variance (power) spectra individual indicated that their correlation structure can be closely approximated first-order Markov scheme. No found excess in range period (3 8 weeks) assigned cycle subjective means. cospectra all negative covariability among as would expected from circulation patterns characteristic index-cycle-like behavior, but none showed within interest. Coherence values, indicating degree relationship among...