A SPECTRAL STUDY OF THE WARMING EPOCH OF JANUARY–FEBRUARY 1958

Abstract

Contour and isotherm patterns of 100-, 50-, and 30-mb. charts have been subjected to harmonic analysis after the manner of Saltzman and Fleisher. The resulting wave-number statistics permit a detailed examination of the sudden warming and circulation breakdown that occurred in the Northern Hemisphere stratosphere in January?February 1958. The stratospheric warming epoch of January 1958 was preceded by a marked expansion in the ring of tropospheric westerlies. Thereafter in the stratosphere the kinetic energy of wave number 1 increased by nearly the same amount transferred to it by the zonal flow and the other waves. However a subsequent great increase in the kinetic energy of wave number 2 occurred simultaneously with a large transfer of kinetic energy from that wave to both the zonal flow and the other waves. This development of wave number 2 thus appears to have been baroclinic in nature. Correlation of daily spectral statistics for the stratosphere and troposphere show a number of significant interlevel relationships in the growth and decay of the longer cyclone waves.