...程度分为五级，D0级为“异常干燥”(abnormally dry)，D2级为“严重干旱”(severe drought)，D3级为“极端干旱”(extreme drought)，D4级为“异常干旱”(exceptional drought)。
基于12个网页-相关网页
length of extreme drought period 极端干期长度
Extreme Drought Event 极端干旱事件
extreme drought period 极端干期长度
extreme drought and flood 异常旱涝
It was an extreme drought event that meet in one hundred years in warmer climate period,it persisted long time and disserved severely,and people’s life and wealth suffered bigness harm.
结果表明这是气候相对温暖期中100 a一遇的极端干旱事件。 它持续时间长、危害重,使群众生命财产遭受重大损失。
参考来源 - 1935～1937年川渝异常旱灾分析·2,447,543篇论文数据，部分数据来源于NoteExpress
Zhu said, "We experienced an extreme drought this year."
朱说：“我们今年经历了极度的旱灾。
The frequency of extreme drought in the dry period is much higher than that in the wet period.
在气候处于少雨时期，极端干旱频率远高于多雨时期。
The impacts of climate change hit hardest in Africa where extreme drought has intensified hunger and malnutrition in Chad.
气候使非洲生活变得更加艰苦，那里极度的干旱加剧了Chad（居民）的营养不良。
Scientists warn that without an agreement to reduce so-called green house gas emissions, global temperatures will continue to rise, with the catastrophic consequences of extreme weather events, the spread of drought and disease, and the extinction of plant and animal species.
VOA: standard.2009.12.09
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