VARIATIONS OF SOME SEASONAL RAINFALL CHARACTERISTICS IN QUEENSLAND, AUSTRALIA - 1921-1987

Summer and winter indices of rainfall total, intensity, and contributi ons of rain-days of different intensities were developed from 70 stati ons in Queensland over the period 1921-1987. In both summer and winter , only a few days of relatively high intensity rainfall contribute mos t to the seasonal rainfall total. In wetter summers, although the numb ers of rain-days of different magnitude rainfall all increase, it is d ays with rainfall in excess of 50 mm day-1 that contribute most to the increased seasonal total. Year-to-year and longer time-scale variatio ns in seasonal rainfall totals are matched by similar variations in se condary rainfall characteristics, i.e. wetter years or periods are lik ely to have more rain-days and rainfall of greater intensity than drie r years or periods. Variations of the secondary rainfall characteristi cs show similar relationships with the Southern Oscillation as total r ainfall. The correlations with the SOI are, with one exception, insign ificant for the period, 1921-1950, of 'weak' SOI teleconnections. Only the date by which 15 per cent of the summer seasonal rainfall is accu mulated (representing pre-monsoon rainfall) has maintained a significa nt and stable relationship with the SOI over time. Rainfall in Queensl and is more closely linked with the number of tropical cyclones actual ly making landfall than the total number of cyclones in the region. Ev en in years when the large-scale circulation is not conducive to tropi cal cyclone activity, a single tropical cyclone crossing the coast can lead to substantial rainfall amounts.