This is also a good ref on Hovmoller diagrams

Fedorov, Alexey V, and Jaclyn N Brown. “Equatorial Waves.” In Ocean Currents, Ed. J. H. Steele, S. A. Thorpe, and K. K. Turekian. Elsevier Science, 2010.

This diagram is an idealized version of what would happen if the standing wave was closer to a pure sine wave without harmonics. From Federov, on the left is their ocean response to oscillatory winds in a shallow-water model, shown as a Hovmoller diagram of the thermocline depth anomalies on the equator. On the right is my simple LTE model with a single forcing cycle.


So Hovmoller is essentially plotting the spatiotemporal standing wave as a surface countour plot