Long-term Characteristics of Seasonal Rainfall at Katherine,Northern Territory

Rainfall at Katherine, Northern Territory, is concentrated into a few months, mainly December-March. For the 101 seasons, 1888–89 to 1988–89, the average rainfall is 947 mm and it is relatively reliable with a coefficient of variation of 24 per cent. Within this period use of the 15 seasons moving average shows two major spans of seasons in which average seasonal rainfall has increased and two others of decreasing average seasonal rainfall Also, the rain-causing mechanisms that operate in the region produce markedly more variable rainfall within seasons. This paper characterises the types of growing seasons at Katherine on the basis of the proportion of the seasonal total that falls within each of the seventeen fortnightly periods from 9 October to 3 June. Overall, 31 different groups of seasons are identified with 13 groups consisting of a single season. Conversely, the largest group contains 35 seasons. The analyses identify groups of seasons in which rainfall has occurred early or late in the season and others which have featured dry spells or wet spells in the core of the season. This variability helps to explain some of the challenges for farming systems research and for the development of sustainable farming systems.