Observational Studies of the Ultra-Long Waves in the Atmosphre (II)

Ultra-Long-Wave Energy Processes during the Stratospheric Sudden Warming

Abstract

In the previous paper [Iwashima (1973)], it has been shown that, by means of the time-filter method, the ultra-long wave in the atmosphere is generally separated into the two parts, i.e. travelling and quasi-stationary parts, and that the latter part of the ultra-long wave is usually associated with an amplitude-change.
In the present paper the energy equations for both parts of the wave are derived, and applied to an energetical study on the 1967/68 stratospheric sudden warming.
From an analysis before separating the wave into the travelling and quasi-stationary parts, it is shown that the energy processes are similar to the results obtained by Reed et al. (1963), Julian and Labitzke (1963), etc..
Separating the each ultra-long wave into the quasi-stationary part and the travelling one, we can obtain the respective energy processes. Some of the results are summarized as follows :
i) At the the warming stage, the kinetic energies of the quasi-stationary and travelling ultralong waves of wavenumber two [KS(2) and KT(2)] increase, and especially the increment of the former part is remarkable.
ii) The increase (or decrease) of KS(2) is mainly due to that of the energy transfer from the troposphere through the so-called pressure-interaction term of the quasi-stationary part of wavenumber two BGS(2).
iii) Increasing of KS(2) during the warming stage is also controlled by the energy transfer from the travelling waves of the various wavenumbers.
iv) The available potential energies of both parts of wavenumber one increase during the warming stage. These are mainly converted from the zonal available potential energy.