Year-to-year variability in rainfall has long been recognised as a major issue in managing livestock enterprises across Australia’s grazing lands. Extension products documenting rainfall variability have been developed over the last 30 years and have been keenly sought by producers and their advisors. This paper describes multi-year rainfall variability from 1889 to 2020 and provides the basis for classifying the 131 years of rainfall into 18 discrete Wet (7), Average (2) and Dry (9) periods as presented in the ‘Queensland’s Extended Wet and Dry Periods’ poster. The classification was consistent with: analysis of fluctuations and trends in the long-term time series of reported livestock numbers; drought declarations for government assistance; and documented periods of pasture resource degradation and recovery. Rainfall during the nine Wet and Average periods was +18% above the long-term average annual rainfall (LTAAR), in contrast to the Dry periods with −17% below LTAAR. Wet periods (including Average) were on average 7 years in duration, ranging from 5 to 9 years. Dry periods were on average 8 years in duration and ranged from 5 to 13 years. Detailed analysis of the effects of the El Niño Southern Oscillation (ENSO) phenomenon indicated that: (a) the Wet/Dry periods were dominated by different frequencies and amounts of rainfall in La Niña/El Niño years; (b) rainfall in ENSO neutral years was generally above and below average rainfall for the Wet or Dry periods respectively; (c) the frequency of ENSO year-types was less important than the overall rainfall surplus (or deficit) in La Niña (or El Niño) years within the Wet (or Dry) periods respectively; and (d) the timing of Wet and Dry periods was correlated with indices of quasi-decadal and inter-decadal variability in components (sea surface temperatures and atmospheric pressures) of the global climate system. Climatic risk assessment systems for grazing management at multi-year timescales are yet to be developed.

长期以来，降雨量的逐年变化一直被认为是管理澳大利亚牧场畜牧企业的一个主要问题。在过去 30 年中开发了记录降雨变化的推广产品，并受到生产者及其顾问的热切追捧。本文描述了从 1889 年到 2020 年的多年降雨变化，并为将 131 年的降雨量分为 18 个离散的湿 (7)、平均 (2) 和干 (9) 时段提供了基础，如“昆士兰的扩展湿和干旱时期的海报。分类符合： 分析报告的牲畜数量的长期时间序列的波动和趋势；政府援助的干旱声明；并记录了牧场资源退化和恢复的时期。九个湿润期和平均期的降雨量比长期平均年降雨量 (LTAAR) 高 18%，而干旱期的降雨量比 LTAAR 低 -17%。湿润期（包括平均）平均持续 7 年，从 5 年到 9 年不等。干旱期平均持续 8 年，从 5 年到 13 年不等。对厄尔尼诺南方涛动（ENSO）现象影响的详细分析表明：（a）在拉尼娜/厄尔尼诺年中，干湿期主要由不同频率和降雨量主导；(b) ENSO 中性年的降雨量通常分别高于和低于湿季或干季的平均降雨量；(c) 在湿（或干）期内，ENSO 年份类型的频率不如拉尼娜（或厄尔尼诺）年的总体降雨盈余（或亏缺）重要；(d) 干湿期的时间与全球气候系统组成部分（海面温度和大气压力）的准年代际和年代际变化指数相关。用于多年时间尺度放牧管理的气候风险评估系统尚待开发。