Except for the seasons, nothing is thought to influence surface-level solar radiation and wind velocity patterns on timescales of up to about a decade as much as El Nine events. Here we report new information about Fl Nine events by illustratively showing that whenever the mean air temperature T at land-based Dar es Salaam station (6 degrees 53＇S, 39 degrees 12＇E) and the mean air temperature T-n over some off-shore equatorial islands in the Indian ocean have similar quasiregular periods, El Nine events take place at approximately regular frequency patterns. These frequency patterns, however, change whenever T-n and T acquire dissimilar periods. Finally we show that variations in the Southern Oscillation index (whose low negative values and high positive values coincide with Fl Nine and anti-El Nine events, respectively) were characterised by one particular amplitude-modulating state from 1954 up to about 1987. Moreover these variations switched into a different state about 1987 and have remained in that state ever since. These two states have different time-patterns of El Nine events.