Wave Transience and Wave-Mean Flow Interaction Caused by the Interference of Stationary and Traveling Waves

Abstract

Madden and Labitzke reported an exceptionally large 18-day traveling wave 1 in the troposphere and lower stratosphere during January 1979. Observations from the LIMS instrument on Nimbus 7 indicate that during this period the regular westward phase regression extended upward as far as the lower. mesosphere. Alternate destructive and constructive interference between the transient wave and the time mean wave 1 resulted in large variations in wave amplitude with time. Analysis of the zonal wind deceleration during the minor sudden warming of that month indicates that this wave 1 transience was the primary cause of the warming. Prior to the large wave 1 amplitude growth immediately preceding the sudden warming (18-22 January), there were two other pulses of exceptionally large wave 1 amplitude (>2000 m peak amplitude) separated by about ten days. Thew earlier pulses were not associated with the traveling wave, which first appeared around 10 January. The change in the zonal wind associated with these first two pulses was much smaller. The amplitude growth during these earlier pulses did not persist as long, and was smaller in the lower stratosphere. Either of these factors may be the reason that these pulses did not cause strong wind deceleration.