HOW I LEARNED TO LOVE NORMAL-MODE ROSSBY–HAURWITZ WAVES

Several impor tant developments in the 1960s showed the way to using spectral analysis to identify and describe atmospheric waves predicted by theory. Among these waves were normal-mode Rossby–Haurwitz waves (NMRHWs). What follows is, first, a brief outline of how the influence of these developments on analyses of data collected during the Line Islands Experiment led to work on NMRHWs. Next, theoretical expectations of free NMRHWs as described by Kasahara and Kasahara and Puri in the early 1980s are discussed. Finally, spectral analyses of observed vorticity fields are presented for easy comparison with those expectations. The similarity between these relatively simple model predictions and observations is unique in meteorology, where complexity is the general rule. Readily available routines coded in NCAR Command Language (NCL) were used to isolate NMRHWs. It should be noted that, while these routines provide approximations to the theoretical predictions, open-access software for exact solutions has become available.