Analysis of Nimbus 3 SIRS Radiance Data: Traveling Planetary-Scale Waves in the Stratospheric Temperature Field

Abstract

Zonal harmonics of the radiances measured by the three central channels of the SIRS instrument on Nimbus 3, representing vertically averaged temperatures in the lower and middle stratosphere, were computed. The traveling components of the lowest zonal wave numbers were estimated by the quadrature-spectrum method of Deland for periods of 1?12 cycles/mo. The westward-traveling planetary-scale waves in the equatorial regions, previously described by Fritz, are approximately in phase with, and appear to be forced by, the westward-traveling planetary waves of middle latitudes. The traveling planetary waves are eastward traveling in high southern latitudes in winter, in contrast to an average slow westward motion in high northern latitudes in winter. The vertical structure of the traveling planetary-scale waves is remarkably uniform for all latitudes, with the temperature waves in the lower stratosphere (channels 6 and 7) lagging behind those in the middle stratosphere (channel 8) by approximately 2 days.