Rain day frequency and mean daily rainfall intensity as determinants of total rainfall over the eastern Orange free state

Abstract Summer rainfall totals over the eastern Orange Free State are described in terms of number of days of rain and of mean rainfall per rain day. Variations in rainfall may be considered to result from frequency changes in an objectively‐chosen subset of significant rain days. It is demonstrated, through the use of the equation y = αx exp (βx) (where x and y are the cumulative percentages of the number of rain days and of the rainfall respectively), that increases in mean rainfall per rain day result from an increased number of, and increased intensity of rain on, the heaviest rain days. Some implications of these findings for studies of atmospheric circulation changes and for weather modification are discussed.