Appropriate application of the standardized precipitation index in arid locations and dry seasons
Appropriate application of the standardized precipitation index in arid locations and dry seasons
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DOI：
10.1002/joc.1371
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发表时间：
2007-01
期刊：
影响因子：
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通讯作者：
Hong-zhi Wu;M. Svoboda;M. Hayes;D. Wilhite;Fujiang Wen
中科院分区：
文献类型：
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作者：
Hong-zhi Wu;M. Svoboda;M. Hayes;D. Wilhite;Fujiang Wen
标准化降水指数（SPI）现已在世界范围内广泛用于研究和操作模式。对于干旱气候或具有明显旱季且零值常见的气候，短时间尺度上的 SPI 具有下限，指的是本研究中的非正态分布。在这些情况下，SPI 总是大于某个值，无法表明发生干旱。根据我们研究的全国统计数据表明，非正态率与当地降水气候密切相关。在美国东部，短时间尺度的SPI值可用于任何季节的旱涝监测和研究，而在美国西部，由于其明显的季节性降水分布，该指数的适当使用和解释变得复杂。所有干旱气候也是如此。从数学角度来看，非正态分布的 SPI 是由 SPI 构造中采用的混合分布所代表的高概率无雨情况引起的。从统计的角度来看，用于估计降水概率密度函数的2参数伽马模型以及干旱地区和时间的有限样本量也会降低SPI值的置信度。
The Standardized Precipitation Index (SPI) is now widely used throughout the world in both a research and an operational mode. For arid climates, or those with a distinct dry season where zero values are common, the SPI at short time scales is lower bounded, referring to non‐normally distributed in this study. In these cases, the SPI is always greater than a certain value and fails to indicate a drought occurrence. The nationwide statistics based on our study suggest that the non‐normality rates are closely related to local precipitation climates. In the eastern United States, SPI values at short time scales can be used in drought/flood monitoring and research in any season, while in the western United States, because of its distinct seasonal precipitation distribution, the appropriate usage and interpretation of this index becomes complicated. This would also be the case for all arid climates. From a mathematical point of view, the non‐normally distributed SPI is caused by a high probability of no‐rain cases represented in the mixed distribution that is employed in the SPI construction. From a statistical point of view, the 2‐parameter gamma model used to estimate the precipitation probability density function and the limited sample size in dry areas and times would also reduce the confidence of the SPI values.