Hydrometeorology Independent Researcher, Canberra, Australia.
Department of Spatial Sciences, Curtin University, Perth, Australia.
Sci Total Environ. 2018 Jan 1;610-611:691-702. doi: 10.1016/j.scitotenv.2017.08.109. Epub 2017 Aug 17.
Drought-like humanitarian crises in the Greater Horn of Africa (GHA) are increasing despite recent progress in drought monitoring and prediction efforts. Notwithstanding these efforts, there remain challenges stemming from uncertainty in drought prediction, and the inflexibility and limited buffering capacity of the recurrent impacted systems. The complexity of the interactions of ENSO, IOD, IPO and NAO, arguably remains the main source of uncertainty in drought prediction. To develop practical drought risk parameters that potentially can guide investment strategies and risk-informed planning, this study quantifies, drought characteristics that underpin drought impacts management. Drought characteristics that include probability of drought-year occurrences, durations, areal-extent and their trends over 11 decades (1903-2012) were derived from the Standardized Precipitation Index (SPI).Transient probability of drought-year occurrences, modelled on Beta distribution, across the region ranges from 10 to 40%, although most fall within 20-30%. For more than half of the drought events, durations of up to 4, 7, 14 and 24months for the 3-, 6-, 12- and 24-month timescales were evident, while 1 out of 10 events persisted for up to 18months for the short timescales, and up to 36months or more for the long timescales. Apparently, only drought areal-extent showed statistically significant trends of up to 3%, 1%, 3.7%, 2.4%, 0.7%, -0.3% and -0.6% per decade over Sudan, Eritrea, Ethiopia, Somalia, Kenya, Uganda and Tanzania, respectively. Since there is no evidence of significant changes in drought characteristics, the peculiarity of drought-like crises in the GHA can be attributed (at least in part) to unaccounted for systematic rainfall reduction. This highlights the importance of distinguishing drought impacts from those associated with new levels of aridity. In principle drought is a temporary phenomenon while aridity is permanent, a difference that managers and decision-makers should be more aware.
尽管在干旱监测和预测方面取得了进展，但非洲之角（GHA）地区仍出现了类似干旱的人道主义危机，且呈上升趋势。尽管做出了这些努力，但由于干旱预测的不确定性以及反复受影响系统的灵活性和有限的缓冲能力，仍然存在挑战。ENSO、IOD、IPO 和 NAO 的相互作用的复杂性，可以说是干旱预测不确定性的主要来源。为了制定实用的干旱风险参数，这些参数可能为投资策略和风险知情规划提供指导，本研究量化了支撑干旱影响管理的干旱特征。干旱特征包括干旱年份发生的概率、持续时间、面积范围及其在 11 个十年（1903-2012 年）内的趋势，这些都是从标准化降水指数（SPI）中得出的。该地区的干旱年份发生的暂态概率是基于 Beta 分布建模的，范围在 10%到 40%之间，尽管大多数都在 20%到 30%之间。在超过一半的干旱事件中，3、6、12 和 24 个月时间尺度的持续时间最长可达 4、7、14 和 24 个月，而在短时间尺度中，10 个事件中有 1 个持续时间最长可达 18 个月，而在长时间尺度中，持续时间最长可达 36 个月或更长时间。显然，只有干旱面积范围显示出高达 3%、1%、3.7%、2.4%、0.7%、-0.3%和-0.6%的每十年的统计显著趋势，分别在苏丹、厄立特里亚、埃塞俄比亚、索马里、肯尼亚、乌干达和坦桑尼亚。由于没有证据表明干旱特征发生了重大变化，因此可以将 GHA 类似干旱危机的特殊性（至少部分归因于）归因于未被考虑的系统性降雨减少。这凸显了区分干旱影响与与新的干旱程度相关的影响的重要性。原则上，干旱是一种暂时现象，而干旱是永久性的，管理者和决策者应该更加意识到这一区别。
