A STUDY OF THE ENERGETICS OF JANUARY 1959

Abstract

The energetics of the 500-, 100-, and 25-mb levels are computed on a daily and monthly basis during January 1959. On the average, during the month, zonal wave numbers 1 and 2 were dominant in the eddy kinetic and eddy available potential energy spectra at 25 and 100 mb; while at 500 mb, the emphasis was shifted to wave numbers 2 and 3. The dominance of the planetary scale over the synoptic scale at 500 mb was a manifestation of the persistence of a blocking circulation found during the month. The planetary scale tropospheric block had a direct influence on the stratospheric kinetic energy by initiating upward progression of planetary wave energy that in turn was partially absorbed by the stratospheric layers. A 10- to 12-day fluctuation in the blocking circulation was found to be followed by a pulsation of similar frequency in the eddy kinetic energy at 25 mb. Of the three pulses in the block, the second one had the largest amplitude and was followed by a stratospheric warming at 25 mb. The contour pattern at 25 mb during the warming phase was eccentric in character; whereas the other two eddy kinetic energy pulses, before and later, were characteristically of a bipolar nature. At 25 mb, in situ large-scale baroclinic processes contributed significantly to the occurrence and maintenance of the spectral energy maxima. At the same level, a nonnegligible influence of the large-scale kinetic energy mode was provided by the nonlinear wave energy transfers.