From The Line Islands Experiment To Normal Mode Rossby-Haurwitz Waves

I will describe my introduction to Tropical Meteorology and data analysis working for Ed Zipser, Chief Scientist of the 1967 Line Islands Experiment. At the time, Yanai at Tokyo University and Wallace at the University of Washington and their colleagues were using spectrum analysis effectively to describe tropical disturbances. It was natural for us to apply their techniques to our Line Islands Data. That, in turn, led to using the same methods to diagnose long time series of tropical pressure and wind data that were being assembled by NCAR's Data Support Section.

Our spectral analyses revealed an eastward propagating, 45-day, disturbance that eventually was called the “MJO”. In addition, we found a westward, 5-day wave that had been seen by others and identified as a normal mode Rossby-Haurwitz wave. This opened the door for a career long interest in these normal modes.

I will relate theory of normal mode Rossby-Haurwitz waves as described by Kasahara (1980:JAS) and Kasahara and Puri (1981:MWR). Finally, comparisons of analyses based on ERA-Interim Data from a recent three year period (2010-2012). with Kasahara's work will be shown. The results, and that of others, support the existence of most of the theoretically predicted normal mode Rossby-Haurwitz waves discussed by Karahara.