A Spectral Analysis of the Energetics of the Stratospheric Sudden Warming of Early 1957

Abstract

Abstract The spectral forms of tile energy equations for zonal and eddy kinetic energies and zonal and eddy available-potential energies are used to measure energy changes and energy conversions at 50 mb during the period 25 January–9 February 1957. The warming, which was of the bipolar type, could he divided into two phases, a first phase in which the meridional temperature gradient had its usual poleward direction at high latitudes and a second phase in which the gradient was reversed. During the first, or amplifying phase, the eddy energy increased and the energy of the zonal flow decreased, the decrease in zonal kinetic energy outweighing that of zonal available potential energy. The energy flow corresponded to that of a baroclinic instability. Zonal available-potential energy was transformed to eddy available-potential energy, eddy available-potential energy to eddy kinetic energy, and eddy kinetic energy to zonal kinetic energy. Indirect meridional circulations with descending motion in the middle l...