EXCITATION AND EVOLUTION OF THE QUASI-2-DAY WAVE OBSERVED IN UARS MLSTEMPERATURE-MEASUREMENTS/

The quasi-2-day wave is known as a strong and transient perturbation i n the middle and upper atmosphere that often occurs shortly after sols tice. The excitation mechanisms of this transient wave have been discu ssed for years, but no clear answer has yet been attained. In this pap er, propagating characteristics of the a-day wave are studied based on g-mon temperature measurements from the Microwave Limb Sounder onboar d the Upper Atmosphere Research Satellite. The studies are focused on the wave events that happened in January 1993 and in July-August 1993. The observations suggest that winter planetary waves could be respons ible far triggering the summer 2-day wave through long penetration int o the summer stratosphere. A connection is evident in the evolution of the wave amplitude between the summer 2-day wave generation and winte r wave penetration, The data also suggest that the enhancement of the wave amplitude is a manifestation of both a local unstable wave and a global normal-mode Rossby wave.