\label{fig:lifecycle}
Life cycle characteristics of PSA-like variability. The duration of all events is shown in panel (a), while the phase of events lasting more than 10 data times is shown in panel (b). Events that showed substantial eastward (defined as a linear phase gradient of greater than $0.25^{\circ}$E per data time) or westward (less than $-0.25^{\circ}$E per data time) propagation are colored red and blue respectively, otherwise gray shading is used. The intensity of the shading in panel (b) represents the amplitude of the PSA-like variability.
