Fig. 4. Meridional wavenumber, l, plotted as a function of zonal wavenumber, k, for the 128-day cross-spectral estimate. Circles are for year 2, asterisks are for year 1. Error-bars show standard error based on computed limits of the cross-spectral phase. Also shown are l vs. k for 180- and 140-day Rossby waves at 22� 45'N, for a Rossby radius of 51 km.