Dependence of Rainfall Variability on Mean Rainfall, Latitude, and the Southern Oscillation

The relationship between the relative variability of annual rainfall, the long-term mean annual rainfall, the latitude, and the correlation between annual rainfall and the Southern Oscillation Index is examined, using data from 974 stations. A nonlinear relationship between these variables accounts for 94% of the variance in annual rainfall variability. Relative variability typically increases as mean annual rainfall decreases, as latitude decreases, and as the effect of the Southern Oscillation increases. There is an interaction between latitude and the Southern Oscillation so that the effect of the Southern Oscillation on variability weakens as latitude increases.