Rainfall variability and agriculture in the semi arid tropics, the Northern Territory, Australia

W. S. Mollah and I. M. Cook
Agricultural and forest meteorology, 79, 1-2, 39-60, 1996-03

Analyses of historical rainfall records for four sites for up to 103 seasons, 1888-1889 to 1990-1991 at Darwin and Katherine NT, address the three themes of climatic change, time scales and assessments of impacts on agriculture in marginal areas of the semi arid tropics. The mean for the period from 1951-1952 at Darwin represents a 10% increase over the mean for 1974-1975 and similarly at Katherine a 7% increase. Tightening the time scale to periods within seasons does not reveal similar changes, emphasising the higher variability of rainfall within seasons. Crops sown each season should recognise the timing of the occurrence of the sowing rains to minimise the risk to each landholder by seeking the best possible crop establishment. Drying conditions after each event limit the time over which soil conditions will remain suitable, so the area of crop sown will vary according to seasonal conditions.